Supercapacitors-101-a-home-inventors-handbook

Supercapacitors 101 - A Home Inventors Handbook by Robert Murray-Smith Copyright 2013 Robert Murray-Smith Smashwords Edition

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Contents Introduction History Current Commercial Activity Basic Principles Current Research Principles Of Operation Capacitor Construction Applications Design Considerations Future Directions Of The Technology Conclusion FAQ

This book is best used in conjunction with the youtube videos found at youtube.com/user/RobertMurraySmith where I will be happy to answer any questions

you may have. The electrochemical supercapacitor is an emerging technology that promises to play an important role in meeting the demands of electronic devices and systems both now and in the future. This book traces the history of the development of the technology, and explores the principles and theory of operation as well as giving some guidance on the methods for producing the materials required to construct a supercapacitor . The use of supercapacitors in applications such as pulse power, backup sources, and others has many advantages over alternative technologies and until recently was well beyond the scope of the home experimenter. However, with the help of this book it is now possible for everyone to become involved in this exciting field of energy development.

Introduction

Electrochemical capacitors are currently called by a number of names: supercapacitor , ultracapacitor, or electrochemical double-layer capacitor. The list of different names is almost as large as the number of manufacturers, and since the technology is only currently beginning to find itself a market a universal term does not seem to have been agreed upon as yet. The term ‘supercapacitor ’ finds itself in common usage, being the tradename of the first commercial devices made by Nippon Electric Company (NEC), but ‘ultracapacitor’ is also commonly used, originating from devices made by the Pinnacle Research Institute (PRI) for the US military. While electrostatic capacitors have been used as energy storage elements for nearly a century, low capacitance values have traditionally limited them to low- power applications as components in analogue circuits, or at most as short-term memory backup supplies. Recent developments in manufacturing techniques have changed this, however, and with the ability to construct materials of high surface-area and electrodes of low resistance has come the ability to store more energy in the form of

electric charge. This has combined with an understanding of the charge transfer processes that occur in the electric double-layer to make high-power electrochemical capacitors possible. Supercapacitors therefore represent a new breed of technology that occupies a niche amongst other energy storage devices that was previously vacant. They have the ability to store greater amounts of energy than conventional capacitors, and are able to deliver more power than batteries.

Besides bridging the gap between capacitors and batteries, supercapacitors also possess a number of desirable qualities that make them an attractive energy storage option. The mechanisms by which Supercapacitors store and release charge are completely reversible, so they are extremely efficient and can withstand a large number of charge/discharge cycles. They can store or release energy very quickly, and can operate over a wide range of temperatures. Supercapacitors have only very recently begun to make themselves known as a viable energy storage alternative, and while most electrical engineers may be aware of the technology it is probable that few possess an understanding of the processes involved and the applications that are possible. Ignorance of the full capabilities of Supercapacitors will most likely lead to more conventional alternatives being selected instead. In these electrochemical capacitors, the electrolyte is the conductive connection between the two electrodes. This distinguishes them from electrolytic capacitors, in which the electrolyte is the cathode and thus forms the second electrode. Supercapacitors are polarized and must operate with the correct polarity in the same way that batteries are polarized. Polarity is controlled by design with asymmetric electrodes, or, for symmetric electrodes, by a potential applied during manufacture. To think of supercapacitors as a single thing is a bit of a mistake. Supercapacitors actually divide into three main types. Those that store their charge electrostatically like ordinary capacitors, those that store their charge electrochemically like ordinary

batteries and the hybrid type that exist somewhere in between. This relationship is shown diagrammatically below.

The three types are differentiated by their electrode design. Double-layer capacitors – with carbon electrodes or derivates with much higher static double-layer capacitance than the faradaic pseudocapacitance Pseudocapacitors – with electrodes out of metal oxides or conducting polymers with much higher faradaic pseudocapacitance than than the static double-layer capacitance Hybrid capacitors – capacitors with special electrodes that exhibit both significant

History The storage of electrical charge in the interface between a metal and an electrolytic solution has been studied by chemists since the nineteenth century, but the practical use of double-layer capacitors only began in 1957, when a patent was placed by General Electric for an electrolytic capacitor using porous carbon electrodes. Although the patent admits that “it is not positively known exactly what takes place when the devices… are used as energy storing devices,” it was believed that energy was being stored in the pores of the carbon, and it was noted that the capacitor exhibited an “exceptionally high capacitance.” Later, in 1966, The Standard Oil Company, Cleveland, Ohio (SOHIO) patented a device that stored energy in the double- layer interface. At this time SOHIO acknowledged that “the ‘double-layer’ at the interface behaves like a capacitor of relatively high specific capacity.” SOHIO went on to patent a disc-shaped capacitor in 1970 utilising a carbon paste soaked in an electrolyte. By 1971, however, a subsequent lack of sales led SOHIO to abandon further development and license the technology to NEC. NEC went on the produce

the first commercially successful double-layer capacitors under the name “supercapacitor .” These low voltage devices had a high internal resistance and were thus primarily designed for memory backup applications, finding their way into various consumer appliances. By the 1980’s a number of companies were producing electrochemical capacitors. Matsushita Electric Industrial Co., (otherwise known as Panasonic in the Western world), had developed the “Gold capacitor” since 1978. Like those produced by NEC, these devices were also intended for use in memory backup applications. By 1987 ELNA had begun producing their own double-layer capacitor under the name “Dynacap”. The first high-power double-layer capacitors were developed by PRI. The “PRI Ultracapacitor,” developed from 1982, incorporated metal-oxide electrodes and was designed for military applications such as laser weaponry and missile guidance systems. News of these devices triggered a study by the United States Department of Energy (DoE) in the context of hybrid electric vehicles, and by 1992 the DoE Ultracapacitor Development Program was underway at Maxwell Laboratories.

capacitor patented by general electric

electrolytic energy storage device patented by SOHIO

capacitor patented by SOHIO In 2005 aerospace systems and controls company Diehl Luftfahrt Elektronik GmbH chose supercapacitors to power emergency actuation systems for doors and evacuation slides in airliners, including the Airbus 380 jumbo jet. In 2005, the market reached between US $272 million and $400 million. As of 2007 solid state micrometer-scale electric double-layer capacitors based on advanced superionic conductors were employed for low-voltage electronics such as deep-sub-voltage nanoelectronics and related technologies (the 22 nm technological node of CMOS and beyond). As of 2010 multi-voltage 5.3 W SUPERCAPACITOR power supply for medical equipment produced a total of 55 F of capacitance, charged in about 150 seconds and ran for about 60 seconds. The circuit used switch-mode voltage regulators followed by linear regulators for clean and stable power, reducing efficiency to about 70%. The developers recommended a buck-boost best handles the widely varying voltage across a supercapacitor buck-boost.

Current Commercial Activity Quite a few companies around the world currently manufacture Supercapacitors in a commercial capacity. NEC and Panasonic in Japan have been producing SUPERCAPACITOR components since the 1980’s. In the U.S.A Epcos, ELNA, AVX, and Cooper produce components, while Evans and Maxwell produce integrated modules that include voltage balancing circuitry. Kold Ban International markets a supercapacitor module designed specifically for starting engines in cold weather. CapXX in Australia offers a range of components, as does Ness Capacitor Co. in Korea. In Canada, Tavrima manufactures a range of modules. ESMA in Russia sells a wide variety of SUPERCAPACITOR modules for applications in power quality, electric vehicles, and for starting engines.

Basic Principles To understand how supercapacitors work, it is helpful to understand how capacitors in general work. Capacitors are circuit components that store electric charges. They store their energy in electric fields, which are created by the interaction between the capacitor's two conducting surfaces. These surfaces have equal and opposite charges, with one surface collecting positive charges and the other collecting negative charges. These two surfaces, which are usually plates called "electrodes," are always electrically separate from one another. The plates are separated by an insulator (also called a "dielectric"), which helps to give the capacitor its high capacitance because it polarizes the material's molecules. As the plates are conductors, the positive and negatives charges are stored on their surfaces; however, since they have equal and opposite charges, the capacitor's net charge is zero.

What allows the capacitor to hold its charge is a property called "capacitance." Capacitance (C), measured in Farads (F), is the ratio of the magnitude of the charge on the plates (Q) to the magnitude of the voltage between the plates (V). Thus, C = Q/ V. Farads are coulombs/volt; one Farad is when one coulomb causes a potential difference of one volt across the plates. Capacitance is proportional to the surface area of the plates (in other words, it is proportional to the size of the electric field) and inversely proportional to the magnitude of the distance between the plates. Capacitance also varies based on the type of insulator. The closer together the plates are without actually touching, the greater the capacitor's capacitance. The relationship between capacitance and surface area is what makes supercapacitors different in their design and function from traditional capacitors. The plates in supercapacitors are not separated by insulators in the same way as those of capacitors. Capacitors use dielectrics to increase their capacitance by allowing their plates to get very close to one another. However, the practical limitations on the surface area of the plates and the distance between the plates reduce capacitors' ability to have the same high levels of capacitance found in supercapacitors . Supercapacitors solve this problem by using a new technology that allows them to have enormous surface area relative to the distance between the plates.

Comparison of different types of capacitor. Left: "normal" capacitor, middle: electrolytic, right: electric double-layer capacitor. Note that despite appearing to be separated in the image, the carbon "islands" at each electrode in the rightmost image form a continuously connected foam in 3D. At the moment most supercapacitors use activated carbon. When two pieces of activated carbon are immersed into a liquid electrolyte, they form an amazingly effective capacitor. The success of this method is primarily due to the carbon's large surface area-to-volume ratio, a product of the many microscopic nodules that cover its surface. Supercapacitors are made by coating two metal foil electrodes with this activated carbon, separating them with a thin piece of paper, and immersing the carbon-coated plates (the foil electrodes) into a liquid electrolyte. The carbon on the negative plate collects electrons, which then attract positive ions from the electrolyte into the pores of the carbon. The carbon on the positive plate collects positive charges, which then attract negative ions from the electrolyte. The thin piece of paper keeps the

two plates from touching, which keeps the current from flowing between the two plates, allowing the positive and negative ions to move freely within their respective plates. This creates two layers of charge, making the supercapacitor look like two capacitors in a series; this is the double-layer mechanism that gives supercapacitors their name of "Electric Double-Layer Capacitors (EDLC)." This design means that the charges on each plate of the supercapacitor can be incredibly close to one another while still maintaining the carbon's large surface area, giving supercapacitors their high capacitance.

Current Research Research is currently being conducted at a number of institutions in the interests of improving both the energy and power densities of SUPERCAPACITOR technology. Activated carbons are the most commonly used electrode material in commercial supercapacitors at present, and a good deal of research is interested in determining the factors that contribute to the specific capacitance and series resistance in such materials. The Université Henri Poincaré-Nancy in France has performed research on the correlation between the porous electrode structure and series resistance. Other work done by another French laboratory at the Conservatoire National de Arts et Métiers confirms the impact of pore size distribution on specific capacitance.

TEM image of an activated carbon electrode

Nanotubular carbons have been explored recently, and a number of academic institutions such as the Poznan University of Technology, Poland, and Sungkyunkwan University in Korea have constructed electrodes that demonstrate a higher specific capacitance than that achievable by activated carbons. Studies at the Chinese Academy of Science have taken this a step further and shown that activated carbon nanotubes have an even higher specific capacitance than normal carbon nanotubes. Considerable interest has also been shown in conducting polymer materials, and research suggests that high specific capacitances should be attainable.

FE-SEM image of carbon nanotubes Metal-oxides have always been an attractive electrode material due to their low resistance and high specific capacitance, but their excessive cost has generally ruled them out as a commercially viable option. Traditionally a strong sulphuric acid has been used as an electrolyte with metal-oxide electrodes in order to increase the ion mobility, and hence the rate of charge and discharge. This limits, however, the choice of electrode materials because most become unstable and corrode in a strongly acidic electrolyte. Research at the University of Texas, USA, has therefore focused on the possibility of using a milder, potassium chloride aqueous electrolyte for use with metal-oxides. The work suggests that the replacement is indeed possible, and should widen the availability of possible electrode materials. Manganese-oxide, a cheaper alternative to ruthenium-oxide, has been confirmed as a good electrode candidate by the Imperial College, London. The most promising results seem to lie in the use of hybrid configurations, which consist of activated carbons and conducting polymers or metal-oxides. Studies at the University of Bologna, Italy have resulted in a supercapacitor that has a positive activated carbon electrode and a negative polymer electrode that outperforms configurations solely using activated carbon. Work at the National Cheng Kung University in Taiwan indicates that high specific capacitance can be achieved by the deposition of conducting polymers onto activated carbon. Frackowiak et al. at the Poznan University of Technology have demonstrated an increase in specific capacitance of carbon nanotubes coated with a polymer. Also of interest is the study of solid-state supercapacitors being conducted at the University of Twente in The Netherlands, in which yttria-stabilised zirconia is used instead of a liquid electrolyte. Future research

Activated carbons currently dominate the market as an electrode material, but progress in the development of conducting polymers and metal oxides is continuing at a steady rate. The exploitation of pseudocapacitive effects to enhance double-layer capacitance seems to be a prevalent goal amongst current researchers, and offers a good chance of developing the next generation of high- power, high-energy supercapacitors .

Principles Of Operation Supercapacitors are able to be developed as energy storage devices based on an understanding of the physical processes that take place.

Basic principles Electrochemical capacitors operate on principles similar to those of conventional electrostatic capacitors. A conventional capacitor stores energy in the form of electrical charge, and a typical device consists of two conducting materials separated by a dielectric. When an electric potential is applied across the conductors electrons begin to flow and charge accumulates on each conductor. When the potential is removed the conducting plates remain charged until they are brought into contact again, in which case the energy is discharged. The amount of charge that can be stored in relation to the strength of the applied potential is known as the capacitance, and is a measure of a capacitor’s energy storage capability.

an electrostatic capacitor

An EDLC Supercapacitors store electrical charge in a similar manner, but charge does not accumulate on two conductors separated by a dielectric. Instead the charge accumulates at the interface between the surface of a conductor and an electrolytic solution. The accumulated charge hence forms an electric double-layer, the separation of each layer being of the order of a few Angstroms. An estimate of the capacitance can be obtained from the double-layer model proposed by Helmholtz in 1853, in which the double-layer consisted of two charge monolayers. One layer forms on the charged electrode, and the other layer is comprised of ions in the electrolyte Supercapacitor devices consist of two electrodes to allow a potential to be applied across the cell, and there are therefore two double-layers present, one at each electrode/electrolyte interface. An ion-permeable separator is placed between the electrodes in order to prevent electrical contact, but still allows ions from the electrolyte to pass through. The electrodes are made of high effective surface-area materials such as porous carbon or carbon aerogels in order to maximise the surfacearea of the double-layer. High energy densities are therefore achievable in Supercapacitors due to their high specific capacitance, attained because of a high

electrode/electrolyte interface surface-area and a small charge layer separation of atomic dimensions.

Construction of a supercapacitor with stacked electrodes 1.Positive electrode, 2.Negative electrode, 3.Separator In addition to the capacitance that arises from the separation of charge in the doublelayer, a contribution to capacitance can be made from reactions that can occur on the surface of the electrode. The charge required to facilitate these reactions is dependent on the potential, resulting in a Faradaic ‘pseudocapacitance’. The electric double-layer The understanding of the electrical processes that occur at the boundary between a solid conductor and an electrolyte has developed gradually. Various models have been developed over the years to explain the phenomena observed by chemical scientists. Helmholtz’s double layer When Helmholtz first coined the phrase “double layer” in 1853, he envisioned two layers of charge at the interface between two dissimilar metals. Later, in 1879, he compared this metal/metal interface with a metal/aqueous solution interface. In this model, the interface consisted of a layer of electrons at the surface of the electrode, and a monolayer of ions in the electrolyte. In surface science it is often useful to work in terms of differential capacitance. The Gouy-Chapman model In the early 1900’s, Gouy considered observations that capacitance was not a constant and that it depended on the applied potential and the ionic concentration. To account for this behaviour Gouy proposed that thermal motion kept the ions from accumulating on the surface of the electrode, instead forming a diffuse space charge.

To formulate this model the Poisson equation was used to relate potential to charge density, and the Boltzmann equation was used to determine the distribution of ions. Ions were thus considered as point charges with no volume

Helmholtz double layer model

Gouy-Chapman diffuse model Stern and Grahame In 1924, Stern modified the Gouy-Chapman model by including a compact layer as well as Gouy’s diffuse layer. The compact Stern layer consisted of a layer of specifically adsorbed ions. Grahame divided the Stern layer into two regions. He denoted the closest approach of the diffuse ions to the electrode surface as the outer Helmholtz plane (this is sometimes referred to as the Gouy plane). The layer of adsorbed ions at the electrode surface was designated as being the inner Helmholtz plane.

Grahame combined the capacitance resulting from the Stern layer and that resulting from the diffuse layer. This model has not been significantly improved upon since its formulation, but any capacitive effects that may result from dipoles interacting with the charged electrode surface are not considered in this model.

Stern-Grahame model The current model In 1963 Bockris, Devanathan and Muller proposed a model that included the action of the solvent] They suggested that a layer of water was present within the inner Helmholtz plane at the surface of the electrode. The dipoles of these molecules would have a fixed alignment because of the charge in the electrode. Some of the water molecules would be displaced by specifically adsorbed ions. Other layers of water would follow the first, but the dipoles in these layers would not be as fixed as those in the first layer.

a double layer model including the layer of solvents Pseudocapacitance Pseudocapacitance arises from reversible Faradaic reactions occurring at the electrode, and is denoted as ‘pseudo’-capacitance in order to differentiate it from electrostatic capacitance. The charge transfer that takes places in these reactions is voltage dependent, so a capacitive phenomenon occurs. There are two types of reactions that can involve a charge transfer that is voltage dependent. Redox reactions In a redox reaction two things are involved an oxidant and a reductant. The reversible reduction oxidation reaction is what gives rise to the ability for charge transfer. Adsorption of ions The deposition of ions to form a monolayer on the electrode substrate is a reversible process that results in a Faradaic charge transfer, and hence gives rise to pseudocapacitance in a similar manner to that demonstrated in redox reactions. Summary The high values of specific capacitance attainable through SUPERCAPACITOR technology are a result of double-layer capacitance, and often pseudocapacitance. Double-layer capacitance offers good charge storage capabilities thanks to possessing high surface-area materials as electrodes, and the fact that charge separation occurs at atomic dimensions. Pseudocapacitance that arises from redox or ion sorption reactions further improves the achievable capacitance.

Capacitor Construction A wide variety of SUPERCAPACITOR materials and processes for cell construction currently exist. This chapter covers the properties of various available materials and describes the aspects of each alternative that have a significant impact on device performance. Electrode Materials Selection of electrode materials plays a crucial role in determining the electrical properties of a supercapacitor . Double-layer charge storage is a surface process, and the surface characteristics of the electrode greatly influence the capacitance of the cell. Carbon is the most widely used electrode material, but considerable research is being conducted into metal-oxides and conducting polymers. Carbon Carbon has been utilised as a high surface area electrode material ever since development of the electrochemical capacitor began. Today, it is still an attractive option because of its low cost, availability, and long history of use. Carbon electrodes can take a number of manufactured forms such as foams, fibres, and nanotubes. One might expect the specific capacitance to be directly proportional to the carbon electrode’s surface area, however this is not always the case. Often, a type of carbon with a lower surface area will have a higher specific capacitance than a type with a larger surface area. This is because the actual double-layer capacitance varies depending on the process used to prepare the carbon. Treatment of activated carbon materials influences the porous structure of the electrode surface, and it is the accessibility of the pores to the electrolyte that is important. The mobility of the ions within the pores is different to the mobility of ions in the bulk of the electrolytic solution, and is greatly influenced by pore size. If the pores are too small to allow easy access to electrolyte ions they will not contribute to double-layer capacitance. The pore size must therefore be chosen to suit the electrolyte and thereby ensure that the pore size distribution is optimal based upon the size of the ions. In the next figure the effect of pore diameter on specific capacitance is clearly demonstrated, with smaller pores becoming completely inaccessible to the ions at high frequencies. The conductivity of the electrode is of great concern to the power density of an EDLC. Conductivity is inversely proportional to particle size, so a material of higher surface area and is therefore made of smaller particles develops an increased resistance. Power density is thus improved with the use of activated carbons with more large pores, though this will limit energy storage due to reduced surface area. The use of binding material also affects conductivity, and power performance is improved with a decreased percentage of binder. Pseudocapacitive effects are often found to occur on the surface of activated carbons. The level of pseudocapacitance can be enhanced by treatment of the carbon to increase surface functionality. As an example, Frackowiak sites the work of Miller in which the capacitance of activated carbon was enhanced by treatment with ruthenium oxides.

Besides activated carbons, electrodes can also be formed from carbon aerogels. Aerogels are a suspension of carbon nanoparticles within a gel, and have a high surface-area, good conductivity, and may be used without binding material. Particle size is controlled by the preparation process, and smaller particles result in a larger accessible pore surface-area. Nanotubes Nanotubes offer a new possibility for carbon electrodes, but are still being researched. Preliminary results suggest that higher capacitance is achieved by tangled networks with an open central canal.

tangled network of carbon nanotubes Conducting Polymers Conducting polymers store and release charge through redox processes. When oxidation occurs, (also referred to as ‘doping’), ions are transferred to the polymer backbone. When reduction occurs (‘dedoping’) the ions are released back into the solution (Fig. 3.4). Charging in conducting polymer films therefore takes place throughout the bulk volume of the film, and not just on the surface as is the case with carbon. This offers the opportunity of achieving high levels of specific capacitance.

charging process of conductive polymer electrodes Work at the Los Alamos National Laboratory has reported prototype polymer film capacitors with an energy density of 39 Wh/kg and a power density of 35 kW/kg. The two peaks in the voltammetry plot demonstrate that the charging process is predominately due to redox reactions, and only occurs within a narrow range of voltages in this particular case. While long-term stability is expected to be a problem due to the phenomenon of swelling and shrinking in conducting polymers, some research has demonstrated stability over thousands of cycles. Metal-Oxides Metal-oxides present an attractive alternative as an electrode material because of high specific capacitance and low resistance, possibly making it easier to construct highenergy, high-power Supercapacitors . Extensive research into ruthenium-oxides has been conducted for military applications, where cost is presumably less of an issue than it is for commercial ventures. The US Army Research Lab has assembled prototype cells with an energy density of 8.5 Wh/kg and a power density of 6 kW/kg. Academic institutions have focused on searching for other, cheaper, materials to use instead of ruthenium-oxides, but the selection has traditionally been limited by the use of concentrated sulfuric acid as an electrolyte. It was believed high capacitance and fast charging was largely a result of H sorption, so a strong acid was therefore necessary to provide good proton conductivity. This resulted in a narrow range of possible electrode materials, however, since most metal-oxides break down quickly in acidic solutions. Milder aqueous solutions such as potassium chloride have therefore been considered for use with metal-oxides such as manganese-oxides. Although manganese- oxide electrodes currently appear to possess lower specific capacitances than ruthenium-oxides, the lower cost and milder electrolyte may be enough of an advantage to make them a viable alternative.

Metal-oxide electrodes can only be used with aqueous electrolytes, thereby limiting the achievable cell voltage. Gains in power density from lower resistance are therefore often offset by losses due to the lower operating voltage. Hybrid And Composite Configurations Hybrid electrode configurations show considerable potential, consisting of two different electrodes made of different materials. Composite electrodes consist of one type of material incorporated into another within the same electrode. In the course of research into polymer electrodes at the University of Bologna it was found that a sufficiently high polymer concentration could not be realised in the negative electrode. The positive polymer electrode was successfully constructed, however, and an activated carbon was used as the negative electrode. This hybrid configuration resulted in a supercapacitor that outperformed a cell comprised of two carbon electrodes. Also of interest are the results of experiments into depositing polymers onto carbon substrates to form composite electrodes. Carbon nanotubes coated with conducting polymers have yielded particularly good results, with high specific capacitances of 180 F/g being reported. The improved levels of energy storage are a result of the charging taking place largely throughout the bulk of the material, along the surface of the nanotubes and along the backbone of the polymer. The pseudocapacitance arising from the redox processes in the polymer further enhances the capacitive gains.

A carbon nanotube coated in polypyrrole Electrolytes The choice of electrolyte in a supercapacitor is as important as the choice of electrode material. The attainable cell voltage of a supercapacitor will depend on the breakdown voltage of the electrolyte, and hence the possible energy density (which is dependent on voltage) will be limited by the electrolyte. Power density is dependent on the cell’s ESR, which is strongly dependent on electrolyte conductivity. There are currently two types of electrolyte in use in Supercapacitors: organic and aqueous.

Organic electrolytes are the most commonly used in commercial devices, due to their higher dissociation voltage. Cells using an organic electrolyte can usually achieve voltages in the range of 2 – 2.5 V. The resistivity of organic electrolytes is relatively high, however, limiting cell power. Aqueous electrolytes have a lower breakdown voltage, typically 1 V, but have better conductivity than organic electrolytes. The capacitance of a supercapacitor is greatly influenced by the choice of electrolyte. The ability to store charge is dependent on the accessibility of the ions to the porous surface-area, so ion size and pore size must be optimal. The best pore size distribution in the electrode depends upon the size of the ions in the electrolyte, so both electrode and electrolyte must be chosen together. Separator The separator prevents the occurrence of electrical contact between the two electrodes, but it is ion-permeable, allowing ionic charge transfer to take place. Polymer or paper separators can be used with organic electrolytes, and ceramic or glass fibre separators are often used with aqueous electrolytes. For best supercapacitor performance the separator should have a high electrical resistance, a high ionic conductance, and a low thickness. Supercapacitor Construction The functional components of a supercapacitor crucial to its operation are the electrodes, electrolyte, and separator. The surface properties of the electrode material have a significant impact on specific capacitance, as do the chemical properties if pseudocapacitance is exhibited. While activated carbon is currently the most commonly used material, conducting polymers present a possible future alternative. Metal-oxides may also become viable one day. The choice of electrolyte has a significant impact on achievable power, as well as influencing specific capacitance. Aqueous electrolytes have better conductivity than organic electrolytes, but have a low breakdown voltage. The properties of the separator also have an impact on cell performance. A supercapacitor cell basically consists of two electrodes, a separator, and an electrolyte. The electrodes are made up of a metallic collector, which is the high conducting part, and of an active material, which is the high surface area part. The two electrodes are separated by a membrane, the separator, which allows the mobility of the charged ions but forbids the electronic conductance. This composite is rolled or folded into a cylindrical or rectangular shape and stacked in a container. Then the system is kept with an electrolyte. The electrolyte may be of solid state, organic or aqueous type, depending on the application power requirement. The working voltage of supercapacitor is determined by the decomposition voltage of the electrolyte and depends mainly on the environmental temperature, the current intensity and the required lifetime. In general, Supercapacitors improve storage density through the use of a nanoporous material, typically activated charcoal, in place of the conventional insulating dielectric

barrier. Activated charcoal is an extremely porous, "spongy" form of carbon with an extraordinarily high specific surface area—a common approximation is that 1 gram (a pencil-eraser-sized amount) has a surface area of roughly 250 square metres (2,700 sq ft)—about the size of a tennis court. It is typically a powder made up of extremely fine but very "rough" particles, which, in bulk, form a low-density heap with many holes. As the surface area of such a material is many times greater than a traditional material like aluminum, many more charge carriers (ions or radicals from the electrolyte) can be stored in a given volume. As carbon is not a good insulator (vs. the excellent insulators used in conventional devices), in general Supercapacitors are limited to low potentials on the order of 2 to 3 V and thus are "stacked" (connected in series) to supply higher voltages. Activated charcoal is not the "perfect" material for this application. The charge carriers it provides are far larger than the holes left in the charcoal, which are too small to accept them, limiting the storage. The mismatch is exacerbated when the carbon is surrounded by solvent molecules. As of 2010 virtually all commercial supercapacitors use powdered activated carbon made from coconut shells. Higher performance devices are available, at a significant cost increase, based on synthetic carbon precursors that are activated with potassium hydroxide.

Closer look at the structure of a supercapacitor The capacitance value of an supercapacitor is determined by two main things:

Double-layer capacitance – electrostatic storage of the electrical energy achieved by separation of charge in a Helmholtz double layer at the interface between the surface of a conductor electrode and an electrolytic solution electrolyte. The separation of charge distance in a double-layer is on the order of a few Angstroms (0.3–0.8 nm) and is static in origin. Pseudocapacitance – Electrochemical storage of the electrical energy, achieved by redox reactions electrosorbtion or intercalation on the surface of the electroder by specifically adsorpted ions that results in a reversible faradaic charge-transfer on the electrode. Principle charge storage of different capacitor types. Basically, supercapacitors are constructed from the following 5 components; A current collector - a metallic backing sheet - this is not necessary in some types. A high surface area electrode material An electrolyte A separator A case The components are layered up and formed into the desired shape, charged with an initial voltage and you are ready to go. All the components, with the possible exception of the case, are the subject of much research and study. This is because the all the components and the interaction between them intimately affect the supercapacitors performance. However, perhaps the material that has received the most attention is the electrode material. Electrode Materials When thinking of an electrode material what you are looking for is a material that is: conductive has a high surface area will form a double layer exhibits some pseudocapacitance current materials that are being looked at are:

Graphene. This is the wonder material that everybody is excited about. But, truth be told it is only one of the many materials suitable for supercapacitors and not the best at that. However the method is first to produce graphene oxide and the reduce the oxied by burning it in a lightsscribe dvd player to form the reduced graphene oxide coating Making graphene oxide

Oxidation of graphite is carried out by mixing H2SO4:H3PO4 (320:80 mL), graphite flakes, and KMnO4 (18 g) using a magnetic stirrer. After adding all the materials slowly, the one-pot mixture is left for 3 days to allow the oxidation of graphite. The colour of the mixture changes from dark purplish green to dark brown. Later, H2O2 solution is added to stop the oxidation process, and the colour of the mixture changes to bright yellow, indicating a high oxidation level of graphite. The graphite oxide formed is washed three times with 1 M of HCl aqueous solution and repeatedly with deionized water until a pH of 4–5 is achieved. The washing process is carried out using simple decantation of supernatant via a let it settle technique. During the washing process with deionized water, the graphite oxide experienced exfoliation, which resulted in the thickening of the graphene solution, forming a GO gel. Light scribe method

The GO has to be dispersed in water and this is done by sonicating. The dispersed solution is then drop cast onto a substrate and placed in a light scribe device and 'burnt' for a minimum of 6 times. The resultant lightscribed graphene doesn't need any binders or adhesive to hold it to the substrate and no backing collector plate is needed. If you want to use graphene with another form of reduction then some form of activation is necessary for example the reduced graphene can be activated by soaking in 30% KOH solution then annealing at 800 degrees centigrade for and hour or the material can be doped for example with tin oxide. To do this Dried GO is exfoliated in distilled water with ultrasonic treatment to form a colloidal suspension. Subsequently, 38% HCl and SnCl2 and urea are added, then the mixture is continually stirred at 60◦Cfor 6 h. The product is rinsed completely with distilled water and dried at room temperature under vacuum the ratio of GO to water to HCL to SNCl2 to Urea is: 10:20:0.15:0.22:0.1 Activated carbon. Activated carbon isn't all that hard to make, just tedious. Charcoal is made from heating wood in a low-oxygen environment. The heat drives off all the moisture and hydrocarbons (wood gas) in the wood, leaving just carbon (charcoal). To activate the charcoal, you treat it with acid or calcium chloride and heat it again.

Looking on YouTube will reveal half-a-dozen or so videos on making your own charcoal cooker. The common features are: 1. being able to seal up the container so that air doesn't get into the oven (otherwise the wood burns, not chars), and 2. a small hole or tube to allow the wood gas to escape so you don't have a pressure bomb. If you're making activated charcoal, in the end you're going to want to grind the result into a powder, so start with small pieces of wood coconut shells are the best and are what is used in high quality activated carbon filters and capacitors. Put the wood into your cooker, seal it up, and light a fire underneath it. As it heats, you'll see steam/wood gas come out of the small hole. After the steam starts coming out, cook the wood for at least 4 hours -- you'll have to experiment to see how long it will take depending on the amount of wood, etc. After 4 or 5 hours, take the cooker off the heat and let it cool naturally. You'll want to make sure it's thoroughly cool before opening it because otherwise the char inside will burst into flame when the oxygen hits it. After it's cooled and you've opened it up to expose the charcoal, test a few pieces to make sure they've charred all the way through. If not, you can still use that batch for burning but not for making into activated charcoal; and remember to cook it longer next time. Get some battery acid and using a glass pan, plastic or rubber tongs, rubber gloves, goggles, and all the other safety equipment you can muster, pour the acid into the glass pan. Then carefully place each piece of charcoal into the acid and let it soak for four or five minutes. Remove each piece from the acid, let it drain a bit, then put it back into the cooker. If you are using calcium chloride (this is the desiccant found in cheap dehumidifier salts) then make up a saturated solution and dip the charcoal in that instead. When all the pieces have been treated, seal the cooker back up, put it back on the heat, and cook the charcoal for another 4 hours or so. Let the cooker cool, open it up, grind up the pieces, and you've got activated carbon. To use activated carbon you will need a binder - sugar solution will do - and a backing collector plate. Smear your sugar carbon mix onto the backing plate as evenly as possible and then heat it to 230 degrees centigrade until the sugar has carbonised and the mix is dry. Hydrothermal Carbonisation Hydrothermal carbonisation (HTC) is one of the more exciting prospects for supercapacitors as it opens up a whole new world of possibilities. The concept of hydrothermal carbonization (HTC) was initially introduced by Friedrich Bergius in 1913. He described the hydrothermal transformation of cellulose into coal like materials and developed the Bergius process in which coal is liquefied to yield biofuels. He was awarded the Nobel Prize in chemistry in 1931 together with Carl Bosch, in recognition of their contributions to the invention and development of

chemical high-pressure methods. Nowadays the focus of HTC has shifted somewhat from the production of biofuels to the carbonization of biomass to yield functional carbon materials particularly for superapacitors.

overview of the HTC process In simple terms, HTC is a mimic of natural coalification on a timescale of hours and days, rather than millions of years. The process has the advantage of being very simple to carry out and also being rather insensitive to small deviations in concentration, temperature or reaction time. Basically a precursor is placed in a sealed container, the so-called autoclave, using water as an environmentally benign solvent. This also eliminates the need for energy-consuming drying of the precursor which is a great disadvantage for processes such as pyrolysis of biomass. The autoclave can then be heated to the desired temperature (above 100 °C, generally 180 °C-200 °C) where pressure due to evaporation of liquid water is built up. This pressure is self-generated and not externally applied. From a thermodynamic point of view, HTC is an exothermic process and. After about 16 – 18 h of reaction time the HTC process yields a carbon material which is comprised of nano- to micrometer sized spherical particles ideal for supercapacitor electrodes. All kinds of things can be hydrothermally carbonised from sugar to corn starch. Some reports include HTC of prawn shells, cuttlefish bones, rice grains, oak leaves and orange peels. The beauty of HTC of carbonisation as a process is that HTC doesn't destroy the nanostructure of the originating material. What this means is that HTC offers a huge range of possibilities for the home inventor. HTC At Home A simple autoclave can easily be constructed from pipe fittings. You will need the cold iron fittings found at any plumbers merchant. you need three things Pipe nipple 2 end caps to fit yellow PTFE tape wind the tape around the pipe nipple screw threads. screw on one end cap. Fill the pipe with the material you wish to carbonise. Screw on the other end cap. Then, place in the oven at 220 degree centigrade and leave for anywhere between 8 and 22 hours

The actual time and temperature will need experimenting with but HTC is really an extraordinarily simple method. Carbon Fibre Electrodes. There has been recent work utilising 125gsm weave off the shelf carbon fibre in supercapacitors . It becomes usable once the fabric has been coated with carbon nanoparticles. There are two simple methods to do this. The first is to pass the fibre through an ethanol flame where the fibre is positioned at the midpoint of the flame and held there for 30 seconds. The second and easier method is to paint the fabric with India ink. Carbon Nanotubes Carbon nanotubes can be synthesised by dissolving one mole of citric acid in 4 moles of ethylene glycol and stirring it at 50 degrees centrigrade until it becomes clear. After that heat the solution to 135 degrees centigrade for 5 hours when it will form a gel. The gel is charred at 300 degrees centigrade for 2 hours. This is then ground into a powder and heated for 8 hours at 400 degrees centigrade. The resulting carbon nanotubes can be dispersed in ethanol. Carbon nanotubes can also be made in an ordinary microwave oven by sealing 30% by weight of iron(II)acetate with 70% by weight graphite in a glass vessel and microwaving at 700 watts for 30 minutes. The iron acetate decomposes to zerovalent iron evaporates and coats the glassv essel the carbon from the graphite is then catalytically grown as nanotubes from the iron seeds. An ink is relatively easy to make from this by taking 10 mg·mL–1 SDBS surfactant and dissolving it in deionized(DI) water with the help of bath sonication. The carbon nanotubes are then dispersed in the surfactant solution to a concentration of 1.6 mg·mL–1. After bath sonication for 5 min, the CNT dispersion was probe-sonicated for 30 min at 200 W. This ink has been used by Milan University to make cotton conductive.

Basic test cell Electrolytes

Once you have formed you choice of material you can back it onto a metal foil as a current collector and place a separator of either paper or recycled seperator or bought in stock and give thought to the electrolyte. These can be aqueous, non aqueous or solid. Non-Aqueous Electrolyte Systems The use of non-aqueous electrolytes for electrochemical capacitors is, in principle, preferred since higher operating voltages can be utilized due to the larger decomposition limits of such electrolyte solutions. common types of blended electrolytes

Gel Polymer electrolytes The gel polymer electrolytes continue to attract attention since their introduction by M. Armand. So far various systems have been extensively investigated in high-energy lithium-ion batteries, electric double-layer supercapacitors , fuel cells, and chemical sensors. The operating voltage is about 4 V and conductivity up to 10 mS/cm. In principle the gel polymer electrolyte can be classified as the two-phase system composed of ionically conducting medium entrapped in host polymer matrix. The most important ionic conductors are proton and lithium based electrolytes. The first one are known for their high conductivity with the H donors originating from e.g. sulphuric or phosphoric acid. In the second group mobile Li+ species are provided by dissolution of lithium perchlorates, fluorophosphates or fluoroborates in aprotic solvents. Furthermore the sodium, potassium or ammonium based electrolytes are known. Among others acetonitrile, propylene and ethylene carbonates are the most common choices of aprotic solvents. The polymer matrix, based on poly(propylene), poly(vinylidene difluoride), poly(tetrafluoroethylene), poly(ethylene oxide) (PEO), polyaniline (PANI), poly(methyl methacrylate) (PMMA), ensures desired mechanical properties resulting in self-standing gel polymer electrolyte. Gel polymer electrolytes have several advantages: - volatile organic solvent is not incorporated

- supercapacitors can be made of any size and shape and - light weight and high energy density battery can be made. Ionic Liquid Electrolytes Covalent supercapacitor electrolyte technology is based on a family of salts known as hydrophobic ionic liquids (IL). These materials posses a unique set of physical, chemical and electrochemical properties that strongly favor their use as electrolytes in supercapacitors . IL technology is based on the judicious pairing of delocalized heterocyclic organic cations and charge stabilized organic and inorganic anions. Properties of the ionic liquid: - ion concentration from 4 M to 6 M 0C to 400 C - wide working temperature, from -90 - non-flammable with low toxicity - non-corrosive to electrode and packing components at elevated temperatures - isothermal stabilities approaching 300 C with no measurable vapor pressure The viscosities of IL are minimally two orders of magnitude greater than those of most common molecular solvents. Aqueous electrolytes 2 moles per litre of Lithium sulphate. Sulfates combine the advantages of electrochemical stability with low cost and among the sulfates, lithium sulfate has the advantage of a higher solubility in water, as compared to the less expensive sodium and potassium salts and is non toxic. Pottasium hydroxide, phosphoric acid and sulphuric acid all make good electrolytes. Making PolyVinyl Alcohol from white glue White glue or polyvinyl acetate can be converted into gel glue or polyvinyl alcohol through a base induced hydrolysis reaction. Polyvinyl acetate, sodium hydroxide and ethanol are combined, heated and stirred for 30 minutes. The base induced hydrolysis reaction yields polyvinyl alcohol and sodium acetate. The overall reaction is summarized in the reaction scheme below: It shows that upon addition of our base, sodium hydroxide, the polyvinyl acetate is broken into two parts. The red atoms signify the parts of the sodium hydroxide that have been added to the two products of this reaction.

Materials 1. Ring Stand 2. Flask Clamp 3. Erlenmeyer Flask (250 ml) 4. Sodium Hydroxide 5. White Glue 6. Ethanol 7. Hot Plate 8. Glass Stir Rod 9. Heating Mantle 10. pH paper 11. Graduated cylinder (100 ml) Procedure 1. Pour 50 ml of white glue using the graduations of the Erlenmeyer flask as a guide. 2. Weigh out 2.32 g of sodium hydroxide and add it to the white glue in the Erlenmeyer flask. 3. Measure 50 ml of ethanol using the graduated cylinder and add it to the white glue and sodium hydroxide in the Erlenmeyer flask. 4. Place the heating mantle onto the base of the ring stand and then place the Erlenmeyer flask on top of the heating mantle and

secure the flask by using the flask clamp to attach it to the ring stand. 5. Turn on the heating mantle and use the glass stir rod to stir the white glue, sodium hydroxide and ethanol as the mixture is heated for approximately 30 minutes.

6. Once the solution has been heated for 30 minutes, make sure that the solution is free of any unreacted white glue or sodium hydroxide and turn off the heating mantle. 7. Dip the glass stir rod into the solution and touch the pH paper in order to determine the pH of your gel glue. If you don't have a flask - use a jam jar. PVA Solid Electrolyte A PVA solid electrolyte is a a gelled polymer. They can be made from 1g of polyvinyl alcohol (PVA), 10g of distilled water, and .8g of 85% phosphoric acid or it can be made from 5g white glue (polyvinyl acetate) and 1g of 85% phosphoric acid. You heat the PVA or white glue and stir in the water. Once fluid you add the acid and keep stirring until the solution goes clear. Once this happens you are ready to go.

Applications Electrochemical supercapacitors are still relatively new devices that have yet to experience widespread use. This has originally been due to their limited power and energy capabilities, and they therefore only saw use in low-power, low-energy applications such as for memory backup. Recently, however, significant advances have been made in improving both energy and power density, and new applications for Supercapacitors are being developed at an increasing rate. The following are a number of possible applications for the SUPERCAPACITOR as an energy storage element. Memory Backup Supercapacitors have long been in use as short-term backup supplies in consumer appliances. Many appliances now incorporate digital components with memory, and even a very brief interruption in the power supply would otherwise cause a loss of stored information. In such situations a supercapacitor can act as the power supply for a short period, thereby retaining data.

The common alternative to the supercapacitor in this application is the battery. Batteries do not generally have a long product lifetime, and therefore need to be replaced regularly. Today’s consumer appliances are also cheap to the extent that a battery could cost up to 20% of the price of the appliance. Supercapacitors are therefore a good choice as backup power supply due to their long lifetime. Electric Vehicles The prospect of the use of Supercapacitors in electric vehicles has drawn much attention to the technology, appealing to the energy-conscious because of their energy efficiency and because of the possibility of recuperating energy lost during braking. Many of the current power sources being considered for use in electric vehicles (EVs) do not meet the power requirements of vehicle acceleration. Fuel cells are promising due to their extremely high energy density, but they are currently limited in their power specifications. Both the power and energy requirements of an EV can therefore be satisfied with a combination of fuel cell and supercapacitor technology. A combined power source configuration allows the high-energy density device such as a fuel cell to provide the average load requirements. Peak load requirements that result from accelerating or climbing up hills can be met by the high-power device such as a supercapacitor bank. The utilisation of supercapacitors also makes regenerative braking possible. Because the SUPERCAPACITOR bank can be recharged it is possible to store some of the energy of an already moving vehicle, and therefore increase the fuel efficiency of the EV.

Block diagram of electric car with supercapacitors The power flow of the fuel cell is a smooth function, with the fast acceleration requirements being powered by the supercapacitors . The recharging of the supercapacitors during braking periods can also be done. It was found in tests that the fuel consumption was 6.1 L/100 km without regenerative braking, and 5.3 L/100 km with regenerative braking, amounting to a saving of 15%]. In addition to their applications within EVs, supercapacitors could also be used to maximise the efficiency of internal combustion engines (ICEs) in hybrid vehicles (HEVs). 42 V electrical systems are being proposed due to the increasing power demand in luxury vehicles, and alternatives to various devices such as the starter motor will become viable. Within a 42 V vehicle one such option will be the integrated starter alternator (ISA), an electrical machine that can replace both the

starter motor and the alternator. The implementation of an ISA can provide greater generating ability and creates the possibility of start-stop operation of the ICE. The ISA can start the ICE quickly and easily, so when the vehicle has stopped for an extended period of time the ICE can be turned off rather than unnecessarily burning fuel. A supercapacitor bank within this configuration provides the power for engine cranking, and is kept charged by a battery. The battery is not required to provide the power for starting the ICE and only has to charge the supercapacitors . Battery lifetime is thus lengthened. Power Quality Supercapacitors can be used as the energy storage device for systems designed to improve the reliability and quality of power distribution. Static condensers (Statcons) and dynamic voltage restorers (DVRs) are systems that aim to inject or absorb power from a distribution line in order to compensate for voltage fluctuations. As a result, such systems require a DC energy storage device of some sort from which energy can be drawn and in which energy can be stored. The length of voltage disturbance that can be effectively compensated for will depend on the energy density of the DC storage device. The vast majority of voltage perturbations on the distribution bus are short-lived, most not lasting more than ten cycles [48]. The limited storage capability of the supercapacitor is therefore not a problem. The storage device must also be able to respond quickly to voltage disturbances, so the SUPERCAPACITOR has the advantage of possessing a fast discharge time. Batteries are not generally suitable for short-duration, fast-response applications such as the Statcon or DVR, and if the battery is drained considerably, as may well occur in this situation, the device lifetime will be shortened considerably. Battery Improvement An increasing number of portable electronic devices such as laptops and mobile phones incorporate batteries as power supplies. Many such devices draw high-power, pulsed currents (Fig. 5.7), and current profiles consisting of short, high-current bursts result in a reduction of battery performance. Using supercapacitors in combination with a battery is therefore an optimal solution. A supercapacitor can relieve the battery of the most severe load demands by meeting the peak power requirements, and allowing the battery to supply the average load. The reduction in pulsed current drawn from the battery results in an extended battery lifetime. Many electronic devices also include premature shutdown circuitry. These devices will power-down upon the detection of a low voltage, preventing loss of data. A noisy supply voltage can sometimes trigger these shutdown circuits. The supercapacitor will help prevent premature shutdowns by reducing the severity of voltage transients. Electromechanical Actuators Electromechanical actuators can perform thrust vector control for the launch of space vehicles, or can act as flood-control actuators on submarines. Most actuation systems

demand pulsed currents with high peak power requirements but fairly moderate average power requirements. While a supercapacitor bank on its own is unlikely to be able to store enough energy, a battery combined with a supercapacitor can be designed to meet both average and peak load requirements. Trying to meet both requirements with a battery alone results in an oversized configuration, which is undesirable in space applications in which weight must be kept to a minimum. By designing a hybrid power source consisting of a battery and a supercapacitor bank weight savings of 60% can be made over using a battery alone. Adjustable-Speed Drive ‘Ride-Through’ Adjustable-speed drives (ASDs) are commonly used in industrial applications because of their efficiency, but they are often susceptible to power fluctuations and interruptions. Disruptions in industrial settings are usually highly undesirable, and downtime of a machine that is part of a continuously running process can equate to significant monetary losses. The ability to design adjustable-speed drives that can ‘ride-through’ power supply disturbances is therefore a valuable one. In order for an ASD to ride-through a disturbance at full-power, an energy storage device is needed to act as a backup power source. A number of options are available, with batteries and flywheel systems being able to provide ride-through for up to an hour. The major disadvantages of batteries and flywheel systems are their size and maintenance requirements, but batteries are currently a cheap option. Fuel cells can store a large amount of energy but can not respond quickly. SMES systems can provide reasonable ride-through capabilities, but require sophisticated cooling systems. Supercapacitors can respond quickly to voltage fluctuations, have a long lifetime, require no maintenance, and can be easily be monitored due to the fact that their state of charge is dependent on the voltage. The choice of energy storage option will largely depend upon the power requirement and the desired ride-through time. It is obvious that supercapacitors are an advantageous choice for ride-through times of up to 5 seconds and up to a rating of 100 kVA. Portable Power Supplies Supercapacitors are well suited to act as rechargeable stand-alone power sources for portable electronic equipment with moderate energy demands. Most devices presently using battery power supplies have long recharge times and need to be charged overnight. This has come to be accepted as a limitation of the current technology, but supercapacitors offer the opportunity to create devices that can be recharged quickly, perhaps in just a few seconds. Repeated charging and discharging can be performed without significant losses in efficiency. By using the latest light-emitting diodes (LEDs) it would therefore be possible to create a highly efficient and quickly rechargeable safety light. The need to constantly replace the batteries of handheld remote controls could be eliminated. Remote Power From Renewable Sources Remote power supplies that derive their energy from intermittent sources such as wind or solar radiation require energy storage to ensure that energy is available at all times. Under such circumstances Supercapacitors have a number of advantages over the commonly chosen battery.

Photovoltaic (PV) power supplies cycle every day, and this continuous cycling has a detrimental effect on batteries resulting in their needing to be replaced every 3-7 years. Contrarily, Supercapacitors are able to withstand a large number of charge and discharge cycles without suffering significant losses in performance, and thus only need to be replaced every 20 years, which is the lifetime of the PV panels. Lifecycle costs are therefore reduced through the elimination of frequent maintenance requirements. Energy efficiency is always of primary concern in renewable power generation, and supercapacitors demonstrate a higher charging efficiency than batteries. A lead-acid battery, for example, can lose up to 30% of the energy during charging. Supercapacitors , on the other hand, may only lose 10%. The ability to operate efficiently of a wider range of temperatures is also an advantage of using supercapacitors . Some remote stations may be located in cold climates and if batteries are used for energy storage the temperature will have to be maintained at close to room temperature by auxiliary systems, representing additional cost and energy consumption. The major shortcoming of supercapacitor technology for application in intermittent renewable energy sources is limited energy density. This results in the capital costs of achieving energy storage equal to that of batteries in being excessive, and Supercapacitors are hence rarely chosen as an option. A study by Telstra Research Laboratories emphasises the reduced life-cycle costs of network termination units powered by PV panels and supercapacitors , and concludes that while present prices exclude their use the capital costs can be expected to decrease significantly in the coming years. Summary Of Supercapacitor Applications The supercapacitor is still a young technology that has yet to experience widespread implementation. It does, however, enjoy a great amount of attention with regards to its potential application in a number of areas. A traditionally high ESR has previously limited Supercapacitors to memory backup applications, and they have been used in such settings for many years. Recent reductions in ESR have improved the power capabilities of supercapacitors , however, and they are now well suited to pulsed-current applications such as mobile phones and electrical actuators. They can also perform a load-levelling function when used in combination with batteries, providing peak power in devices such as laptops, reducing power demands on the battery and therefore extending battery lifetime. Supercapacitors can be used in a similar manner in EVs, providing power for acceleration and allowing a primary power source such as a fuel cell to supply the average power. When used in EVs supercapacitors also allow for energy to be recuperated during braking, improving the efficiency of the vehicle. Supercapacitors can also be used on their own to provide the energy needed by power quality systems that ensure reliable and disturbance-free power distribution. Supercapacitors then supply the energy needed to inject power into the distribution line and thus compensate for any voltage fluctuations. They can also be used to design systems that grant adjustable-speed drives the ability to ride-through temporary power

supply disturbances. Such applications are vital in industrial settings, and can prevent material and financial losses that could occur due to machine downtime. In portable devices like torches and remote controls Supercapacitors could be recharged very quickly and would probably not need to be replaced within the lifetime of the product. As the energy storage device for a remote PV or wind turbine system the supercapacitor would offer high energy efficiency, wide operating temperature range, and greatly reduced maintenance requirements in comparison to lead-acid batteries. Their energy density is still quite limited, however, and the capital costs generally exclude them as a viable option. Reduced costs could make supercapacitors an attractive alternative in the future. In order to use supercapacitors in any application there are a number of design hurdles that need to be overcome. The following chapter therefore considers various design considerations that must be taken into account when making use of Supercapacitors .

Design Considerations Using supercapacitors as energy storage devices in any application entails consideration of a number of factors. Firstly, an EDLC’s terminal voltage decays as it is being discharged. Secondly, individual cell voltage is usually limited to a few volts, so if high voltages are required a number of cells must be connected in series. This does, however, lead to an increase in total ESR. Finally, if a series connection of cells is required, care must be taken to ensure that local over-voltages can not occur. Voltage Decay The voltage across the terminal of a supercapacitor is directly dependent on the amount of charge remaining in it, so while it is being discharged the voltage will decay. The DC requirements of the load must therefore be considered, and two options to ensure that they are met can be taken. If the load can function over a range of voltages then the Supercapacitors can be sized to allow for the voltage decay. By assuming a simple RC equivalent circuit consisting of a capacitance and ESR the voltage drop that will occur over a given time can be estimated. If a constant DC voltage output must be supplied, a DC-DC converter should be used. Switched-mode topologies are able to maintain a constant DC output for a certain range of input voltages. Supercapacitor Bank Sizing A large number of applications will require voltage levels much higher than that which can be achieved by a single supercapacitor . It is therefore often necessary to connect a number of supercapacitors in series in order to supply the required DC voltage. The total bank voltage is then simply the product of individual cell voltage and the number of cells in the series. Voltage Balancing

Variations in the individual capacitance values of Supercapacitors connected in series result in the total voltage being unevenly distributed throughout the bank. This means that the local voltage across each supercapacitor in the array will not be equal. It is therefore possible for a local voltage greater than the EDLC’s rated voltage to occur, and the cell could be deteriorated. Measures are thus required to ensure that local over-voltages can not occur. The simplest method of limiting individual cell voltage is to connect a resistor across each supercapacitor [60]. The major disadvantage of such a solution is the power lost through the resistors. A more efficient, but still reasonably simple solution is to connect zener diodes across each capacitor. Power losses are then less because current will only flow through the diodes when an over-voltage occurs. Summary Of Design With Supercapacitors The problems of using Supercapacitors to provide a DC voltage are therefore overcome through a number of methods. Supercapacitor banks can be sized to ensure a maximum acceptable voltage drop over a certain period of time. Alternatively, DCDC converters can be used to maintain a constant DC voltage. Voltage limitations of individual Supercapacitors can be overcome by connecting multiple Supercapacitors in series, while the total resistance of the array can be reduced by a greater number of parallel connections. In such an array, supercapacitors with different capacitance values will see different voltages at their terminals. In the interests of avoiding local over-voltages that could destroy the Supercapacitors efforts must be made to keep the voltages balanced. While resistors or zener diodes can be used to perform this function, the most efficient means is to implement active balancing circuitry that incorporates a buck-boost converter for each supercapacitor pair. This will require a large amount of additional components, however. Household Power Generation The following example is a system proposed by Nergaard et al. at the Virginia Polytechnic Institute and State University. The system is designed to supply an average household with the normal 240 V AC supply that it is accustomed to, powered by a 48 V fuel cell and using supercapacitors for energy storage. The fuel cell represents a clean and renewable method of power generation, and combined with supercapacitor technology it makes environmentally sustainable remote power generation a possibility. The general design of the system is shown below, and utilises a fuel cell for main power generation, and a supercapacitor bank (referred to by Nergaard et al. as ultracapacitors) for meeting peak power requirements. The power electronics indicated by the dashed-line box consists of a DC-DC converter and an inverter, and serves to convert the DC voltage supplied by the fuel cell into the 240 V AC supply that will be used by the house.

The HY.POWER Electric Car Increasing concerns about vehicle emissions have spurred a great deal of research effort into the development of electric vehicles. Major problems have been encountered, however, due to the limited capabilities of battery technology. Despite this, new methods of energy storage and power generation have recently brought researchers closer to their goals, and the next example presents a prototype EV built at the Paul Scherrer Institute (PSI) in Switzerland. The car is based on the Volkswagen Bora, with an electric motor driving the front wheels. The primary power source is a 48 kW fuel cell weighing 185 kg and is located in the trunk. Fuel takes the form of compressed hydrogen stored in two 25 L tanks. The supplementary power source consists of two supercapacitor modules, each consisting of 2 parallel strings of 70 supercapacitors in series. The individual Supercapacitors are 1500 F, 2.5 V components. The bank was designed to meet the vehicle’s requirement of 360 V, and had a total ESR of 110 m?. The maximum energy storage of the module is 360 Wh. A number of power electronics modules are required in order to manage the various DC requirements of the energy sources and electric motor.

The HY.POWER electric vehicle is an example of just how feasible the construction of a car powered with renewable energy has become. It can reach top speeds of up to 136 km/h, and can accelerate from 0 to 100 km/h in 12.5 seconds. Since the fuel is in the form of compressed hydrogen, the only emissions present are water. A supplementary form of energy storage such as a supercapacitor module not only allows for peak power demands to be met, but also greatly improves vehicle efficiency through regenerative braking.

Future Directions Of The Technology Research and development efforts into SUPERCAPACITOR technology have been steadily gathering momentum since the 1970’s. This rate of progress is likely to continue as concerns about energy efficiency and sustainable development increase. The emission-free electric car has long been the dream of many of those concerned about retarding the progress of environmental degradation, and the potential use of Supercapacitors in EVs should continue to draw new attention to the technology. The available energy and power of SUPERCAPACITOR devices greatly depends upon the materials used, and significant research is directed at ways of improving the electrode and electrolyte materials. Greater understanding of the charging processes in the electric double-layer has led to a clear recognition of the crucial factors that must be addressed by electrode and electrolyte materials. New methods of carbon activation and new polymer and metal-oxide materials are continuously being developed, and improved electrolytes will result in increased cell voltages. Supercapacitors will become a more competitive energy storage option as interest in the technology grows and production levels are increased. Awareness of the possible applications and advantages of Supercapacitors will gradually spread amongst the engineering and scientific community, and demand should increase. Manufacturers will then be able to produce cheaper devices by producing them in larger quantities and employing automated production lines. Greater availability and more competitive prices combined with improved energy and power performance will lead to widespread adoption of supercapacitors as energy storage devices. While the technology is still in its infancy and is invisible to the public consciousness it is likely that supercapacitors will one day be as ubiquitous as the battery is today. Established companies such as NEC and Panasonic have the advantages of existing manufacturing capabilities and other commercial product lines which can support the development of new Supercapacitors . New companies that do not possess manufacturing capabilities from the outset may find difficulty in obtaining the large amount of capital required, given that the market is still relatively undeveloped. It is therefore likely that most new companies will form joint ventures with larger companies that already possess manufacturing capabilities, which was the direction taken by PRI in its joint venture with Westinghouse.

Conclusion Armed with a basic understanding of SUPERCAPACITOR performance, construction techniques, synthesis methods and design issues, it is hoped that the reader will be better equipped to build their own supercapacitor . Possible applications of SUPERCAPACITOR technology have also been described to illustrate the wide range of possibilities that exist, and may perhaps even encourage the formation of ideas about new ways that supercapacitors could be used effectively. It is apparent that the state of the SUPERCAPACITOR as an energy storage solution is still very much in the early stages of development. The physical processes that occur during charge transfer and the implications that they have for SUPERCAPACITOR performance are only just being fully understood and

quantified. It is for this reason that current cost evaluations usually rule out supercapacitors as a viable alternative to batteries, a mature technology that has been widely available for many decades. The handful of applications described in this survey therefore represents only a small selection of the possible uses of SUPERCAPACITOR energy storage as the technology stands today. Because of the advantages of charging efficiency, long lifetime, fast response, and wide operating temperature range, it is tempting to try and apply Supercapacitors to any application that requires energy storage. The limitations of the current technology must be fully appreciated, however, and it is important to realise that supercapacitors are only useful within a finite range of energy and power requirements. Outside of these boundaries other alternatives are likely to be the better solution. Nevertheless, commercial SUPERCAPACITOR devices have been available for many years now, and their quantity and performance has been steadily increasing. Both improvements in performance and the demand for better devices support each other in a mutually sustaining cycle. As devices of greater energy density and higher power become available, more new applications are formulated and demand will become greater. Increased levels of interest in the technology then lead to increased research and development efforts, which in turn will result in better devices being manufactured, and so the cycle continues. An established market will make it easier for new companies to enter the arena, and costs will drop as manufacturing quantities and demand both increase. The most important thing to remember about supercapacitor technology is that it is a new and different technology in its own right. There may exist some similarities between SUPERCAPACITOR operation and the operation of electrostatic capacitors, but there are fundamental differences that result from the different physical processes involved and these must be appreciated. Problems may be encountered if systems are designed based on the assumption that Supercapacitors behave like normal capacitors. Equivalent circuit models are therefore a useful tool to design engineers, and simulations based on these can provide good estimates on how a supercapacitor bank will behave in certain applications. Supercapacitors are, at any rate, a part of the new wave of advanced energy storage devices that will further the push towards greater energy efficiency and more sustainable alternatives. They will be a useful tool with which to engineer highly efficient electrical and electronic systems, and as the state of the technology advances they will become progressively more commonplace.

FAQ Solid electrolyte for supercapacitors This is a bout converting white glue (PVAc) to the yellow polyvinyl alcohol (PVA) needed to make solid electrolytes for supercapacitors . Once you have converted the PVAc to PVA all you do is add phosphoric acid and you have a solid electrolyte for supercapacitors Q and A

Heartrent Quick question, you said that the reaction also produces sodium acetate; how do you separate the sodium acetate and any unreacted ethanol from the polyvinyl alcohol? I assume you distill it or something? Robert Murray-Smith Polyvinyl alcohol (PVA) is pretty tough to dissolve in cold water. So you dissolve it in hot let it cool and the PVA will precipitate out. Of course some will stay in solution so you get losses but the precipitate is pretty pure and if you do it twice you get a nice purity. Again you will get losses but it is a standard purification procedure. in reply to Heartrent Eric Bélistan now i will began to understand chimic reaction. Thank you for your job. Suggestion : create a free compagny for free energy regards, Eric Robert Murray-Smith HIya mate, Thanks for your comment - i am glad i could help and as for the free comapny - I am thinking of doing exactly that with a few friends of mine in reply to Eric Bélistan mwm2929 Ah, since both are water soluable... if you are ever in Houston, Texas, please let me know. I would like to shake your hand. Robert Murray-Smith Yes they are but solubility for PVA depends on temperature - more than the solubility of sodium acetate. I mean all solubility depend on temp. It's just that PVA's solubility difference is so marked you can use it as a property for refinement. Lol - next time I am in Texas i'll let you know. in reply to mwm2929 Dan Murphy Man ... I cant help thinking, blending graphene with EVA or Poly Propalene in a fluid bed reactor could/would/may? be extruded, drawn down to a ultra thin film & bonded into High Density chains.. . or maybe the Linear low densities might be able to bleed out the electrons like a resister?? oh dam I need some sleep... my head hurts.. I cant quit thinking about this... lol

Robert Murray-Smith Dissolve in hot water. When you cool it most of the PVA will drop out of solution in reply to mwm2929 mwm2929 Is there a good way to extract the sodium acetate for use as a hand warmer without damaging the PVA? How to make supercapacitors at home part 5 - Hydrothermal Carbonisation There's not actually that much to supercapacitors - it's two electrodes held apart by a seperator and filled up with an electrolyte. So, obviously the electrode material and electrolye have a huge impact on the quality of the supercapacitor . There is in fact only so much you can do by slapping a conductive past onto a strip of metal. The next step in developing high performace capacitors is to give the paste some benficial structure. Hydrothermal carbonisation lets you use natures complex structures as templates for building your own high performance supercapacitors . What's more - it's not restricted to supercapacitors - batteries will benefit from this as well and it's easy to do. Q and A Retinalism RMS! I'm with Dan above, (as much as that's a potential worry), I'm keen to try some of your ideas for my "Off-Grid" and EV exploits. Quick charge acceptance and load current delivery are my goals, so I'll be prototyping your methods shortly. Do you happen to have these documented for quick reference? Your efforts are appreciated, last time I learned this much in less than a hour was watching science guru Prof. Julius Sumner Miller. :) (Subscribed!) Robert Murray-Smith Hiya mate - thanks for your kind comments - I am putting together a supercapacitors book right now which will have all the info in it. I'm sorry to have to sell the books but the money will help the research. Anyhow the thing should be ready next week Cheers mate, Rob. in reply to Retinalism Dan Murphy Ha! Never thought I have a man crush! Your videos are amazing. Robert Murray-Smith

Lol cheers mate in reply to Dan Murphy caru83 Thank you for sharing all this! Does hydrothermalized carbon need activation or is it activated already? Robert Murray-Smith it depends on your precursor. Activation is about creating an open pore structure in the carbon material. If you HTC something with this structure you are ready to go. If you HTC something with a dense structure you will need to activate. in reply to caru83 caru83 Thank you, this was not clear to me. Would a temperature controlled (eg. nichrome around the vessel with a temp sensor) rig be benificial? Also, do you talk in °F or °C when referring to temperatures? BTW, congrats for your graphene speaker now in public domain! in reply to Robert Murray-Smith Robert Murray-Smith Absolutely it would. I am talking in centigrade and glad you liked the speaker lol in reply to caru83 caru83 This is very interesting, I am now starting experiment with making classic AC supercaps, but this is a fascinating matter, as I read 150F/g-200F/g is already achievable with HTC. One thing that I still cannot figure out is about the HT carbon porosity: does it mantain porosity even if after HTC the carbon is ground or powderized? Also, do you have any clue what happens if you try to activate HT carbon? Maybe even more pores are created bringing to even higher specific capacitance? in reply to Robert Murray-Smith Robert Murray-Smith HTC is currently outstripping graphene - something not a lot of people appreciate in the made rush to capitalise on graphene. The interesting stuff is in biotemplating. Processing to a powder would give an overall reduction in porosity. You would process the raw material and HTC it after finalizing the shape. I don't know about

your activation question - I guess you would do it if your HTC material was insufficiently porous. in reply to caru83 caru83 I got it. So for example one could try a mix of chitine and leaves... I look forward for your prototype! Good luck with it, I hope you are on something great! :) in reply to Robert Murray-Smith rakshith malige cant wait for the next video in the series! whiterynostl I too would love to see you make a hydrogen cell. whiterynostl Fascinating! You sir are a great teacher. Im very glad I stumbled upon your channel. Hope to see many more videos from you. Good day!! Venturestarx I'll have a cute video of a rough reduction from the good old microwave In the next day or two. It seems that as long as you keep the substrate cool enough to not damage it, all works well. :) Robert Murray-Smith I look forward to seeing it in reply to Venturestarx sk8pkl wow!!! reaalllyy great info sir. I love your videos. So much better than school! Robert Murray-Smith Cheers mate in reply to sk8pkl SiliconM4trix Another great video! A couple questions. * How would the results from hydro-thermal carbonization (in this application) differ from a simpler pyrolysis reaction?

* Also, I know the frequency range of conventional microwave ovens will highly excite carbon ions (especially as a gas, but also in a substrate). Do you think this may play a part in speeding up the reaction? (although the water is taking most of the heat) Robert Murray-Smith Pyrolysis tends to destroy the structure whereas HTC preserves it. I think you are absolutely right iro carbon excitation. in reply to SiliconM4trix Rick S i love your down to earth approach to chemistry. I wish you had a book or a DVD series on generalized approaches to chemistry. I took two semesters in college and loved it but felt like i don't know how to make anything really. can we make bucky balls and how do we play with them? practical application ideas are hard to ask about when we don't know processes. how about info on hydrogen generators for cars, or is this a scam? Robert Murray-Smith One of the great things about the net is how easy it is to get info - when I was younger if I wanted this kind of info I had to go 250 miles to a specialist library - now I can just sit here and find out anything. However, there is a lot of rubbish mixed in and the hard job now isn't finding the info but telling good from bad. Hydrogen generators are like that. There is a lot of good work out there - but, a lot of scams. If hydrogen generation is your interest I can give you some pointers. in reply to Rick S Joseph Richardson I'm in a America where temperature is in Fahrenheit and pressure is in PSIG so I sometimes get confused because you don't always specify units. I'm a little concerned because I believe you are quoting temperature in Celsius. The pressure for water at 180 C is 130 PSIG and for 220 C it is 320 PSIG. Even though the pipe is rated for 35 PSIG I'm not surprised it handles 130 PSIG. I wouldn't want to push it further, though. By some chance are the temperatures you quote actually Fahrenheit? Robert Murray-Smith Pressure is a pain. All kinds of things are used to measure it and nobody sticks to the same units. If you read papers from around the world like I do you are forever converting from one to another - it gets pretty tiresome to be honest. Actually the rating was in bar which is approx 500 psi - if i said bar - i was just confused. I was using centigrade because that is pretty standard here in Europe - though i sometimes use kelvins but hardly ever farenheit. in reply to Joseph Richardson

Robert Murray-Smith Personally, I would be very surprised if a 35 pipe psi coped with 4 to 5 times it rating. However, I take your point. What people have to realize when doing this sort of stuff is that it is inherently dangerous. You are working with toxic chemicals in explosive situations. This is no problem if you take appropriate measures - check out my reply to jimboot2 to see what i actually did when testing this idea. I also wouldn't use the pipe over a long period of time as it will corrode and weaken in reply to Joseph Richardson Robert Murray-Smith Of course, I am an experienced chemist - so, I am able to judge the danger of an experimental situation to a fair degree - even then I use a belt, braces and a bit of string to hold up my trousers. I would expect any serious experimenter to do the same and that is who I am addressing myself to. Luckily - here in England we have a concept of personal responsibility. Which basically means if you are foolhardy enough to do any of this without the proper precautions and you blow your hands off in reply to Joseph Richardson Robert Murray-Smith continued from below - well, that's your problem. If you want to do this you have to familiarize yourself with what are the proper precautions. And seriously - the proper precautions are little more than common sense - sadly lacking in some people I know. But thanks for raising the safety issue and I know I have gone on a bit but it has it has given me a chance to warn others to be safe - wear gloves, wear glasses and for God's sake don't drink the acid! in reply to Joseph Richardson jimboot2 Really loving your vids can't wait for the next installment.thanks! Ps don't blow up :) Robert Murray-Smith Cheers mate - i'll try not to. Actually when i do some of these things i take ridiculous precautions. When I was first testing the autoclave idea i had no idea if it would blow up or not - so I dragged the oven outside and surrounded it with sandbags - seriously! - It was a real anticlimax - nothing blew up! How disappointing is that. However this stuff can be dangerous particularly if you deviate too much from what i am suggesting - like chucking a load of acid in there to see what happens! in reply to jimboot2 overunitydotcom I think with good lampblack powder you are also in the 5 to 10 Ohms / cm range for electrical conductivity, so it is much easier just to buy good lampblack powder,,,,

Looking forward to see your next graphene experiments and the building of the supercap. Many thanks for your interesting videos. Now also your sound and video quality is very good ! ;) Regards, Stefan. Robert Murray-Smith Amazing what a decent camera will do! The acetylene black I have as a comparator has a rated resistance of 0.035 ohms per centimetre when compressed to 6.3 bar. But mixed with a little water and painted on a bit of glossy card it reads190 ohms when I stick my ohmmeter on it. My material read 5 when I do the same thing. My fault I should have been more full in my explanation but even being short it took 16 mins to cover the material and that is a lifetime for some viewers. in reply to overunitydotcom Robert Murray-Smith And you aright it easier to buy lampblack. But you can also buy supercaps and that' s got to be the easiest of all,and if that is what you want to do go right ahead and do it. But, also if that is what you want to do perhaps you are missing the point of what this channel is about and it may not be the best place for you Regards Rob. in reply to overunitydotcom FoulFiend113 One question about ultra capacitors. Do you control the energy release via a resistor, to avoid dangerous instantaneous electrical energy release? Robert Murray-Smith I'm not much of an electrician I'm afraid. I'm more about the chemistry and physics of the device and it's architecture. in reply to FoulFiend113 FoulFiend113 Same here ;) What size of electrical storage are you looking to attain with the super capacitors you are developing? in reply to Robert Murray-Smith Robert Murray-Smith

An order of magnitude better than current Li batteries in reply to FoulFiend113 MisterBlex Hello Robert, sorry to keep bugging you about this, but I still want to know if the Improved Hummers methode had worked for you and if you obtainde GO that can be sonic bathed and burned, as that method is still the most available to me. If it did, I beg of you, please describe the reactions that take place in there, as I'm having a hard time understanding them, and if you can, what should I do with the light brown solution after adding water and letting it precipitate. Thank you and keep it up. Robert Murray-Smith It's no problem - send you e-mail to my e-mail and I will write out a better process for you in reply to MisterBlex spturks what happened to your graphene super cap? ever finish it ? Robert Murray-Smith Yep. Ididn't post as Eric Goeken has a really nice procedure posted on his channel that is basically the same and I rant to finish the chitin super cap before posting a vid about them as a comparison in reply to spturks softilol 12:21 very interesting Robert Murray-Smith Cheers in reply to softilol fuba44 Hello Robert, and thank you for a very informative video. But for us with a short attention span, what does making thermal hydrocarbons have to do with the graphen you made earlier. Maybe a video that could provide the big picture is in order? Robert Murray-Smith Done one - I tried to make it short but it turned out longer than this one. It's kind of hard to tackle this subject in a short way it's kind of a bit complicated for that - sorry. But,hopefully the next vid helps with the overview

in reply to fuba44 FoulFiend113 altering the chemical nature of carbon, to attain better electrical properties... in reply to fuba44 Raymond Earle Hi Robert. Glad your back. Will answer your email now. Carbonizing? Does that include Sunday lunch. LOL. Great video. Robert Murray-Smith Cool lol How to make supercapacitors at home part 3 - alternative sources Another poor audio - soory - another early video - here we are looking at places to get materials for a supercapacitor if you don't want to go to the trouble of extracting chitin. From these materials and a bit of activated carbon (a shoe insert - oder eaters!) and a little phosphoric acid and you would be well on your way to making a supercapacitor . It wouldn't be new as this is pretty much what they make them from at the moment - but you would certainly be able to make one! Q and A Gilbert S Robert the sounds quality has greatly improved.... Thank you Robert Murray-Smith New camera, new mic - I have been spending my pocket money lol. in reply to Gilbert S unionaerolabs i wonder if this lithium can be used to make tritium with neutrons from a fusor Robert Murray-Smith I hadn't thought about that - but now you mention it - it has me wondering! in reply to unionaerolabs MisterBlex Hello mate, i very much like your exhiliration when you start explaining things, and i really like your "home" approach to procuring reactants and making things. What I would like to know is if you have any update on the Graphene and GO, as I really

want to reproduce the experiment, considering that Graphene is such an amazing material, not only as a supercapacitor , but also for hardness and, if you didn't know, you can filther water with it, and it will let only water molecules through. Robert Murray-Smith Hiya mate - there's a lot to say on this! first thanks very much. second - I have acouple of things running with the graphene but as you can appreciate the experiments take quite a long time each and i tend to post only on success - though i have been modifying that of late - because so many people have asked. Anyhow - I have developed what i think is an even easier approach to producing graphene dirctly by coating sand with a monolayer of sucrose and pyrolising it with mild temperature. in reply to MisterBlex Robert Murray-Smith (there will be a few posts here i think - the limit is 500 characters per post) so the pyrolosis is at 200 in the prescence of sulphuric acid and then the carbonised sand is graphetised in a microwave. And that is where i have got to. I think sonication my well cleave the graphite off the sand as graphene. Anyway when I have finished it i'll post. I am investigating supercaps with structured nanofoams because - although graphene is good - nanofoams are better - and a friend of mine asked me. in reply to MisterBlex Seshu Kanuri When you pyrolize Sucrose, you get Charcoal, not Graphite. in reply to Robert Murray-Smith Robert Murray-Smith You do indeed unless you then heat the produced carbon to its graphetization temperature in which case you get graphite. I like to keep a polite tone to the posts it might have been better if you had phrased that as a question rather than a statement particularly as you hadn't read the post properly or understood it before you said something that was just wrong. I hate to slap you down but please, think it through reply to Seshu Kanuri Robert Murray-Smith to look into it and see. I did get a post from a guy that set me thinking that it might be an idea to pyrolise carbon sources on copper nanopartices as a route to graphene synthesis - now that's an interesting idea. Anyway - I am still working away on the graphene and will post as things happen. But i am pleased you find it useful. in reply to MisterBlex sk8pkl

I cant wait to see the capacitor all built up :D! Robert Murray-Smith Cheers mate - i'm on it. in reply to sk8pkl overunitydotcom Well done, but shouldn´t you be more careful with the Lithium metal roll as it could explode or at least ignite , if you put water on it ? So if you have wet hands you could get a burn from it ? Robert Murray-Smith I guess I tend to be a little blase - it's mostly because I know what I am doing and so do it automatically. But you are right - if you are new to this material proper precautions need to be taken - Lithium is not that much of a problem as it form an oxide coating pretty quickly - but if in water it forms a soluble hydroxide and so the reaction goes run away. And what we are talking about is such a small amount that the heat of reaction and amount of reactants are in such small amounts. in reply to overunitydotcom Robert Murray-Smith That very little can happen here. But you are quite right - due care should be taken. If you are unsure - wear gloves and eye protection and for god's sake don't go licking it! - this may sound a little facetious - but i assure you it's not meant to be. People have been hospitaised for tasting (would you believe it!) Anyway - thanks for pointing this out. How to make supercapacitors at home part 1 - introduction There is quite a lot of information to go through on how to make supercaps so I thought i'd break it up into smaller sections to make the videos more watchable. This one is a sort of introduction with details on the architechture of a device and what I am planning to do - the more practical videos I will up load as I make them and the supercapacitor - I hope you enjoy it. Q and A softilol Make a solar panel covered aeroplane, made out of graphene ( both panels and plane structure), put supercapacitor bateries in it and electo engine that props the plane and EUREKA ! :D Solar panel cars with supercapacitor bateries will come sooner or later anyway... my bet is 15 years. Robert Murray-Smith

I have a friend working on this - the cars that is - prototypes will be sooner than that I think - the world is getting greener lol in reply to softilol angelohori thank you for posting you help us a lot Robert Murray-Smith thanks, that's good to know. in reply to angelohori sceptic33 i´m a bit confused... if graphite oxide conducts electricty too, how come the thin unscribed layer left between the LSG electrodes doesn´t short out the cap? Robert Murray-Smith The graphite oxide has about 40% oxide 'trash' between the layers that is the real insulator. You can remove this by washing the graphite oxide in NaOH this will result in a conductive material - not very conductive - that is true - but conductive nevertheless in reply to sceptic33 sceptic33 so the GO doesn´t conduct electricity?.. i guess the carbon layers themselves must conduct fine but are isolated from each other and the lsg by the covering layer of oxygen... if you wash out the oxide aren´t you just left with graphite again? check out vorbeck if you haven´t already... in reply to Robert Murray-Smith Robert Murray-Smith No, the graphite is oxidised into graphite oxide - it's just there is also a lot of 'trash' left over that is carried around on the surface of the graphene plates and that is what is insulating. in reply to sceptic33 Dan Avila Thank you so much for making these videos and putting in all the time you do for the common man. They are really helping me in my self-studies. Robert Murray-Smith

I am really pleased to hear that - that is my main motivation for doing this. in reply to Dan Avila Mongrel Shark Great video! I learned a lot. Just curious why you are not going down the simple graphene and dvd burner path? I was envisioning painting graphene all over some cling wrap and lasering it. Then roll it up to make it smaller.. Sounds like you are going to get a better cap, but is there any easy(er) way? Good to see the audio problem is resolved :) Robert Murray-Smith The graphene isn't a dead duck. Particularly as I want it for so many other projects I have in mind. It's just a friend of mine was interested in supercaps. To my mind, although graphene has been used in supercaps it's not the best material. I think a mesoporous nitrogen doped conductive carbon framework is far more promising here particularly for pseudocapacitance. So, while I am mulling over the graphene I thought I would look into this - mostly to help my friend. in reply to Mongrel Shark Mongrel Shark Great if you can find a better way. or eliminate a possibility. I was just looking forward to the graphene because it sounds so easy. Why have you not put it on a dvd and put in burner yet? Is there something I am missing? in reply to Robert Murray-Smith Robert Murray-Smith I have a limited budget to do this stuff on and i just spent quite a bit of it on a new camera! - now i have to wait for my birthday to get a sonic bath. That's in june by the way, and I need the sonic bath before i can proceed with the graphene. All a bit silly I know - but such is life - and plenty of other things to be getting on with. I will do it. It's just a matter of time. in reply to Mongrel Shark Mongrel Shark No worries. I know what its like not having the right kit to do something. I like the idea of a better super cap too. These experiments are very interesting too. Whats the sonic bath for? I thought it was just paint on thin and laser it to set, once you had the graphene? Or is the trick to get the Graphene really thin before you laser it? in reply to Robert Murray-Smith Robert Murray-Smith

Essentially what i have made is graphite oxide. It won't become graphene oxide until I sonicate it. The difference being the thickness of the layers. You could make graphene straight from graphite but the problem is cleaving it down to few or single layer graphene. The reason people make graphite oxide is that the van der waals forces between the layers in graphite oxide is so much weaker than the forces between the layers of graphite that it can be cloven down to single layers much more easily. in reply to Mongrel Shark Mongrel Shark So the advantage of graphene is that it has smaller layers, and thus more surface area? If I got some ultrasonic transducers, could I make a sonic thingamejig? in reply to Robert Murray-Smith Robert Murray-Smith That's about right - but as to making one it's probably not worth the effort - a friend of mine - Eric Goeken - has posted a vid where he uses a sonic bath to disperse the graphene - the bath he used cost $30 I think - he gives full details on his youtube channel - I am buying one this weekend! - though they are £40 here in the UK in reply to Mongrel Shark Mongrel Shark I can get an ultrasonic cleaning tub here in that price range. The transducers are $30 too, so your right, not worth it. in reply to Robert Murray-Smith Robert Murray-Smith I agree, unless of course you want the fun of just making one. Did you know for example salt doped cement is piezoelectric and I did contemplate making one using this material but there were way more interesting things to be getting on with in reply to Mongrel Shark Mongrel Shark Thats an interesting one! Any suggestions for salt/cement electrodes? I've seen a few ally neg-carbon pos ones with salt cement in a drink can. I think the ally decays over time though. in reply to Robert Murray-Smith Robert Murray-Smith Since coming across it i haven't really thought about it - just though you might find it interesting - though now you mention it a graphite intercalated compound foil

electrode does seem like a good solution given it's chemical inertness and high conductivity. in reply to Mongrel Shark onthecuttingedge2005 conductive and non conductive spray paint. Robert Murray-Smith This would certainly form a capacitor - just not a very good one - well - no better than aluminum plates on polypropylene. And the idea here is to construct a super capacitor - not just a capacitor. The main difference isn't in the materials but in the nanostructure and therefore the operating principle - hope this helps - rob. in reply to onthecuttingedge2005 SixB0w Great video! finally someone who really explains this capacitor types. Robert Murray-Smith thanks mate. in reply to SixB0w Laurens Bulthuis Since you want to use salt as the standard solution.. how about using calcium as an anode and ferrite as a cathode? Stlll wondering what happens if you put a good semi conducting crystal (or a compound of different crystals) between them. Robert Murray-Smith You are moving more towards a battery there. And I agree that would be interesting. I'll look into it after I have finished the caps project. Cheers in reply to Laurens Bulthuis flashboyonly S P L

E N D I D Keep going like this. 1 LIKE from me for this video amd the ideea you have. Robert Murray-Smith Cheers mate! in reply to flashboyonly harpbloke fascinating. and cuttle fish, mighty stuff. looking forward to watching/learning. thanks. Robert Murray-Smith lol - did you know cuttlefish bones are one of the main exports of india - they will be pleased if this works! in reply to harpbloke sk8pkl THis iiisss verryy interresting sir And I cant wait for the next videos, but may I ask if you know about hydride? IT has something to do with hybrid hydrogen metal alloys. When you heat those alloys up, they release their hydrogen... violently. it dosent explode, but it has a pretty impressing hydrolic, pneumatic force. + its the best way to compress hydrogen. I know it has nothing to do with capacitors, but I asked you 3 times about hydride and i got no awnsers so I ask again lol. thx for awnsr Robert Murray-Smith I posted a reply three days ago on your main youtube page under the comments link. I just checked and it is there! But - i do know about hydrides - what is it that you are interested in? let me know and i will try and help in reply to sk8pkl sk8pkl oh I'm sorry I did'nt look there =P... welll I'll tell you why im intressted in hydride. I would like to make myself an electrical power plant that works on compressed hydrogen flow comming from heated hydride container or hydrogen nickel container. you compress hydrogen in nickel by electrolisis and then you release it using the heat

from the sun to run a generator. I thought it could be reaalllyy intresting to have such a powerplant. horizon technology already build those, but you know... =P. in reply to Robert Murray-Smith Robert Murray-Smith i'l give it a little thought and get back to you on this - i do remember there being an interesting system using aluminium wire to generate hydrogen - I can't remember the details - but it was played around with by a couple of car companies until they abandoned it. I can't remember why. But that might be interesting to you and a lot easier than hydride manufacture and control - but i will look into that for you too. in reply to sk8pkl sk8pkl oohhhh interresting indeed. I will have a look to that of course. thanks alot :)... They probably abandon the idea because of the petrol companies. Just like the horizon tech car. They cant sell those cars, they say, because the society isnt ready to have those kind of cars. It's their words my friend.... but it dosent stop us from building something similar to produce electricity. We just have to build this up and shut our mouths xD... anyways, it would be to save money, not make some. in reply to Robert Murray-Smith Robert Murray-Smith For the aluminum wire as fuel you want European patent Publication N° 0055134A1or US patent 4702894 - they are calling it the Cornish hydrogen generator so a youtube search should get a lot of good info - hope this helps - Rob. in reply to sk8pkl sk8pkl oh wow thanks alot :). in reply to Robert Murray-Smith Robert Murray-Smith No probs mate in reply to sk8pkl overunitydotcom What is Kaiton??? Good to see that you have fixed your audio problem. Now only the fan makes still some noise.

Better use lampblack instead of activated carbon cause it is more conductive. Well looking forward how you will make it with graphene and how much better this version will be ... Robert Murray-Smith It's chitin. Chitin is a polysaccharide and the second most abundant biopolymer. It's found in insect body casings, crab shells, prawn shells, squid and cuttle fish bones and fungi cell walls. I like the lamp black idea and i will probably use it if that's ok - But the hydrothermic carbonisation process I am going to use in the second part maintains the original structure of the base material and structure is important in supercaps so i am hoping for an improvement there. in reply to overunitydotcom snappyboy1 If we knew a lot about super capacitors we would be using them to power our flying cars. You are the leader in the graphine field. Institutions with way more resources are behind you working by yourself. Whatever problems you encounter, you will solve. Good luck. Robert Murray-Smith thanks mate! in reply to snappyboy1 Joseph Richardson The part where you talked about carbonizing cuttlefish bones reminded me of an article I read about using carbonized poultry feathers for hydrogen storage. My local farm supply store shows me that it is 80% protein, 1% fat, 4% fiber, 6% ash. I've often wondered whether it would be good for supercapacitors . I haven't tried it. Robert Murray-Smith Feathers are mostly keratin - a protein, Chitin is a polysaccharide. It would certainly be interesting to carbonise the keratin and compare it to the chitin. But the hydrothermic carbonisation process I am going to use maintains the original structure of the base material and structure is important in supercaps. I'm not sure what the nanostructure of feathers is. But again, it would be an interesting investigation. in reply to Joseph Richardson TheMajorLim very interesting. Robert Murray-Smith

cheers! in reply to TheMajorLim RimstarOrg Sorry to hear the graphene approach hasn't worked out yet, especially after all your efforts. Thanks for trying anyway. Looking forward to watching your supercapacitor efforts. Robert Murray-Smith The graphene isn't a dead duck. Particularly as I want it for so many other projects I have in mind. It's just a friend of mine was interested in supercaps. To my mind, although graphene has been used in supercaps it's not the best material. I think a mesoporous nitrogen doped conductive carbon framework is far more promising here particularly for pseudocapacitance. So, while I am mulling over the graphene I thought I would look into this - mostly to help my friend. in reply to RimstarOrg

#### About The Author I'm primarily interested in free energy but i tend to write whatever takes my interest so there's a whole mix of music, art, science, invention and making. Really just whatever i happen to be working on at the moment. Now I have decided to share it and I hope you like what you read and maybe got something from it you can catch up on some of the latest things I am working on on youtube by typing in my name - hope to hear from you sometime - cheers!