2. DESCRIPTION OF RELATED ART Carbon is used as an active material for battery electrodes for many different structures ranging from soft, amorphous carbon to hard, crystal and graphite and in many different forms such as powders and fibers.

Traditionally, these carbons have been bound or pasted to a metal substrate to provide an electrical path from the active material to the battery terminals.

The materials used to bind the carbon to the metal typically interfere with the electrochemistry, add resistance to the electrode, and increase the weight of the electrode. Metal current collectors can contribute as much as half of the weight of a battery electrode.

Previously, carbonaceous materials were used as an active material in negative electrode for absorbing and discharging lithium ions. In these uses, the carbonaceous material has a layered structure more disordered than graphite and has hexagonal net phases with selected orientation. These materials, therefore, included both a graphite-like layered structured part and a turbulence layered structured part. In U. S. Patent 5,244,757 to Takami, et al. there are specific parameters relating to the graphite-like layered structure of the carbonaceous material. This patent, along with all of the prior art, is limited because the carbon material is formed into a fiber having fine

structures in either a lamella type or Brooks-Taylor orientation.

U. S. Patent 5,677,084 to Tsukamoto, et al. discloses carbon fibers that are used in carbonaceous material in the form of a unidirectional arranged body in combination with electrically conductive fibers or foil. A problem disclosed in the prior art is the concern that proper conductivity occurs. In order to overcome this problem the carbon particles or fibers were attached to a matting or adhered to an electro conducting foil, such as a metal foil to the entire carbonaceous area. This provided sufficient conductivity, thereby enabling proper conductivity of the carbon material.

U. S. Patents 5,862,035 and 6,094,788 both to Farahmandi, et al. disclose a double layer capacitor which utilizes aluminum which is impregnated into a commercially available carbon cloth made up of bundles of active carbon fibers. As with the above prior art, the Farahmandi, et al. patents require the aluminum to ensure proper conductivity of the carbon material and cover the entire carbonaceous area.

Numerous patents and technical literature describe electrical energy storage devices utilizing carbonaceous material such as carbon or graphite as an electrode material. The function of the carbon or graphite in the prior art has been primarily that of a current collector, or as a reactive material to form new compounds, or as an additive to a metal or ceramic material for the storage (doping/de-doping and/or intercalation/deintercalation) of lithium ions in a lithium ion secondary battery. Lithium ion secondary batteries concern the shuttling of the lithium ions from one electrode to the other (cathodes and anodes) with no direct use of anions that may be present in the system for energy storage. The carbon materials used in dual graphite systems are chosen with different requirements than seen in much of the prior art. U. S.

Patent 5,993,997 to Fujimoto, et al. for instance, describes the use of a carbon compound material capable of occluding and discharging lithium (or

doping/de-doping) which is then shuttled to the negative electrode composed mainly of a carbon material that intercalates and deintercalates the lithium in opposition to the reaction occurring at the opposite electrode. This patent is typical of the prior art. The dual graphite energy storage system is very different. The graphites chosen for dual graphite systems are used strictly to intercalate and deintercalate both cations and anions at two different electrodes. The ions are strictly drawn out of the electrolyte solution for intercalation, and never from one electrode to the other. The cations migrate and intercalate into one electrode at the same time the anions migrate and intercalate into the other electrode. The reverse process also occurs simultaneously. This explains why many skilled in the art refer to this technology as dual intercalating. The carbonaceous materials used in dual graphite systems require a unique selection process that is inherent with the technology since the requirements are interdependent. Additionally, the results of individual half-cells do not predict the final result of a completed dual graphite cell. All components in the dual graphite technology depend on the other components, including the cation intercalating carbon fiber, the anion intercalating carbon fiber, the ionizable salt and its concentration, and the solvent.

The prior art describing dual graphite energy storage devices is limited.

U. S. Patent 4,865,931 and U. S. Patent 4,830,938 to McCullough, et al. describe a dual graphite energy storage system in which the carbonaceous material has a Young's modulus of greater than 1 MSI but less than 75MSI.

The crystal structures of charged and discharged carbon anodes have been extensively studied in the prior art for typical secondary batteries unlike the dual graphite technology. The prior art discusses the ability of carbon fiber to dope/de-dope or intercalate/deintercalate lithium for use in electrochemical cells, however the references do not include the specifics required for use with anion use. Of special interest is the work reviewed by

Matsumura, et al., in which the group investigates the explanations for high discharge capacities for lithium ion cells beyond 372 mAh/g, that do not fit the typical models as theorized for carbons by those familiar with the art. They use a model to describe how carbons allow for several types of interactions with lithium to be possible, where lithium is intercalated between the graphitic layers and doped at the edges of the layers. Where Lc is the crystalline thickness and the interlayer spacing is d (002), the surface of the crystallite is proportional to 1/ ( (Lc/d002) +1), and relates in a linear fashion to lithium discharge capacity in mAh/g, allowing for C>6Li where capacity increases with small crystallite size Lc and large interlayer distance when La crystallite size is smaller than 100angstroms. However, the relationship of anion discharge capacity in dual graphite cells is not like that of lithium cells.

With regard to the use of a carbon foam material or a carbon mat in which the fibers are thermally fused to each other, U. S. Patent 5,145,732 to Kyutoku, et al. discloses the use of a carbon felt material however the material is referred to as a thermal insulator, expressing that the material is not principally conductive nor principally one of continuous carbon structure, and in addition the material is impregnated with a resin. Other prior art references disclose the use of a carbon aerogel for use in a battery.

Additionally, U. S. Patent 5,932,185, refers to the use of carbon foams as electrodes where the thickness of the electrode is less than 40 mils.

It would therefore be useful to develop a new carbon material that has proper conductivity without requiring the addition of a metal in order to function properly.

SUMMARY OF THE INVENTION The present invention provides a carbon material for use in a dual graphite battery. The carbon material includes a carbonaceous material having a Young's modulus of greater than 75MSI. Also provided by the present invention is a conductive carbon material for use in an energy storage system, wherein the carbon material includes a carbonaceous material selected from the group consisting essentially of a single conductive fiber, a multiplicity of conductive fibers, conductive fibers formed into a cloth, a carbon foam and a carbon mat in which the fibers are thermally fused together. Included in the invention is a carbon material or fiber having a crystallite surface calculated by 1/ [ (Lc/d002) +1] of less than or equal to 0.025 for anion intercalation, and a method for making stabilized unidirectional cloth by affixing a webbing to a carbonaceous material.

DESCRIPTION OF THE DRAWINGS Other advantages of the present invention are readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein : Figure 1 is a graph comparing the degree of graphitization of the carbon fiber tested as the as the anion intercalation/deintercalation fiber versus the anion fiber discharge capacity measured in mAh/g ; Figure 2 is a graph depicting the crystallite surface (as calculated by 1/ ( (Lc/d002) +1)) versus the anion discharge capacity for various types of carbon fibers ; and Figure 3 is a schematic representation of various types of continuous

carbon fibers that can be used in dual graphite cells and batteries from a top view ; (3) (a) shows a woven material ; (3) (b) shows a unidirectional material ; (3) (c) shows a biaxial braid material; (3) (d) shows a triaxial braid material ; and (3) (e) shows an end result of a carbon foam or a carbon mat in which fibers are thermally fused to each other.

DETAILED DESCRIPTION OF THE INVENTION Generally, the present invention provides a carbon material for use in a dual graphite battery. The carbon material is made of a carbonaceous material having a Young's modulus greater than 75MSI.

The terminology used to describe a dual graphite cell during a galvanostatic cycle is different than that of a typical battery. Since a dual graphite cell incorporates the intercalation and deintercalation of both an anion and a cation, the terminology generally employed by those in the battery art of"anode"and"cathode"do not translate well in the dual graphite technology, as the electrode polarities are clearly switched between charge and discharge of the cell. The terminology employed by those familiar in the art of the dual graphite technology, more clearly delineates the electrodes, and is very simplistic. Electrodes are simply referred to as"cation electrode", which denotes the electrode that intercalates and deintercalates the cation (i. e. Li) ; and"anion electrode", which denotes the electrode that intercalates and deintercalates the anions (i. e. BF4). This terminology eliminates the confusion that can occur during dual graphite battery discussions when the state of charge or discharge is not being specified.

The present invention uses a conductive carbon/graphite material consisting of one or more of the following : (1) a single conductive fiber ;

(2) a multiplicity of conductive fibers ; (3) a multiplicty of conductive fibers formed into a cloth form such as a woven fabric, unidirectional mat, biaxial braid, triaxial braid ; (4) a carbon foam ; and, (5) a carbon mat in which the fibers are thermally fused to each other.

All of these carbon fiber forms are equally effective in that they are all conductive, light in weight, and deliver good cell capacity. These forms can be used in any combination, but the preferred embodiment uses the same form for the anion and cation intercalating fiber with in the same cell in order to provide the cell with the best cell compression, etc. The difference between the forms is the number of terminal connections required to ensure full utilization of the material.

Energy storage, especially in dual graphite systems, is greatly enhanced by the proper selection of carbon materials. Increasing the energy capacity of the anion intercalating electrode means that less volume and weight of carbonaceous material is required to achieve more energy storage.

This in turn increases the entire energy storage device's energy density giving the device more energy per weight and volume. In addition, less total carbonaceous material in the device reduces the total cost of the device.

Through the understanding of the relationship between the carbon's degree of graphitization, crystallite surface and intercalation capacity, greatly improved energy storage is achieved.

In addition, it is shown in the current invention that the degree of graphitization and/or carbonization is an important factor in the performance of the material as an electrode element. Greatly improved energy storage, greater than 100mAh/g anion discharge capacity, is achieved by optimizing the carbon for the anion intercalating electrode (or what would traditionally be

referred to as the cathode in electrochemical cells) through optimizing its degree of graphitization. Previous efforts to increase energy storage, which was no greater than 100mAh/g, were focused on aspect ratio and surface area. Figure (1) shows a clear representation of this. Carbonaceous materials having about 90 percent carbonization, are referred to in the literature as partially carbonized. Carbonaceous materials having from 91 to 98 percent carbonization are referred to in the literature as a carbonized material, while materials having a carbonization of greater than 98 percent are referred to as graphitized. The present invention uses the term carbon fiber or material to describe all levels of carbonization described above for simplicity.

Figure (2) clearly shows the relationship of anion discharge capacity is opposite that of lithium as described by Matsumura, et al. patent.

Accordingly, the anion preferentially stores/intercalates in the d002 spacing of the graphite, versus the surfaces or edges of the crystal structure of the carbon fiber. Therefore, capacity is linked more closely to La than it is to Lc.

Carbon fibers most preferred for anion intercalation/deintercalation electrodes have a crystallite surface calculated by 1/ ( (Lc/d002) +1) of less than or equal to 0.025.

The present invention provides a method for the use of continuous carbon fiber, not formed electrodes with binders as seen in much of the prior art (such as the reference by Steel, J. A. and Dahn, J. R.). The present invention also provides for the use of a non-aqueous electrolyte, unlike some of the prior art references such as the reference by Noel, M. and Santhanam, R. Additionally, all tests performed on the fibers of the present invention were done in a dual graphite cell where the anode and cathode were both carbon fibers unlike the majority of the prior art (such as the reference by Santhanam, R. and Noel, M.). A noble metal is only used occasionally as a reference electrode, but not as a counter or working electrode in the present

invention. Through extensive testing, it has been proven that the results of individual half-cells do not predict the final result of a completed dual graphite cell. All components in the dual graphite technology depend on the other components, including the cation intercalating carbon fiber, the anion intercalating carbon fiber, the ionizable salt and its concentration, and the solvent.

Of extreme importance, in any application using carbon/graphite materials, is the contact between every individual fiber piece being carried completely to the exterior of the device, or to the central area of thermal or electrical collection. Electrically and thermally conductive bonds must, therefore, occur between every individual fiber and the metal, then in turn every individual fiber to the other fibers in the bundle (tow), every fiber bundle to every other fiber bundle in the cloth formation used, and finally to the entire metal substrate in order to obtain 100% utilization of all carbon/graphite in the system where a cloth is used. This fact translates to required penetration and uniform bond formation with all portions of the carbon/graphite.

The present invention is applicable to a wide variety of conductive materials. For example, the present invention is applicable to various forms and grades of carbon and graphite particularly graphite fibers, formed from coal tar or petroleum pitches which are heat treated to graphitize to some degree the carbonaceous matter. In addition, the present application is applicable to the various polymers which on heating to above about 800C lose their non-carbon or substantially lose their non-carbon elements yielding a graphite like material (a material having substantial polyaromatic configurations or conjugated double bond structures) which results in the structure becoming conductive and are in part at least graphitic in form.

Complete connection to all carbon/graphite is essential to obtain full utilization of the material in any use. This keeps the amount of the relatively

expensive materials to a minimum, which translates to lower product costs and waste. For a battery, this also translates to the ability to obtain higher energy densities by using only the stoichiometric amount of materials required for the system to function. In the case of a dual graphite energy storage device, poor utilization of the carbon material leads to overall loss in cell capacity.

Carbon/graphite fibers, and their various forms, have the least amount of resistance in the axial direction, or along the length of the fiber. Electrical and thermal energy is carried more efficiently along the length of a fiber than it is between fibers that are only in direct physical contact with each other, even when these fibers are held under pressure or with binders. Binders themselves, though often called conductive, are not as conductive as the fiber itself. Fibers that have only surface contacts with each other, have a large increased resistance between them due to these factors. For these reasons, it is preferential to utilize all fibers in a manner that takes advantage of the low resistance axial direction. For this reason, continuous fibers are often preferential to any form of carbon powder, chopped fibers, felt type mats, mesocarbon microbeads, etc.

An advantage to the use of the different carbon/graphite forms can be seen. Those forms that require the lowest number of connection sites have the least amount of collector area that must be accommodated in an end use.

In applications where weight and or space is a critical factor, the least amount of collector weight and area used by the collector is typically an important consideration, since it is this collector that generally contributes the most in terms of weight, space, and often cost. Specifically in a battery, the reduced amount of collector translates to improved energy density of the end products, which in turn provides more possible end uses, and lower costs.

Carbon/graphite powders, chopped fibers, felt type mats, mesocarbon

microbeads, etc., requ re an individual contact individual contact every piece every carbon/graphite to the collector. This often means that the collector has a large surface area, and thus uses a great deal of space, adds extra weight and costs to the end product. Continuous fibers of various forms are often preferred. For example, a woven cloth contains continuous fibers that run in two directions that are perpendicular to each other. This means that the woven cloth has fiber ends exposed on four sides. The woven cloth then requires at least two edges of collection to utilize all carbon/graphite materials in the cloth, and thus takes more space and weight for current collection than for instance a unidirectional cloth, but less than is required for a graphite powder which would have one entire side of the material coated as a collector and would require a binder. Unidirectional cloths, or braids such as biaxial or triaxial, contain continuous fibers that run in essentially one direction. The fibers start and then end with only two edges of exposed fiber ends ; these then require only one edge of collection. A carbon/graphite foam, or mat of thermally bonded fibers, requires only one point of collection to attach all carbon/graphite together, since the material is fused together creating essentially one continuous fiber. Figure (3) depicts these various carbon forms schematically.

The present invention includes the method and use of a unidirectional carbon fiber material. U. S. Patent 5,677,084 refers to the use of a sheet of unidirectionally arranged carbon fibers ; however, this prior art reference requires the fibers to be placed on a metal foil sheet, or the fibers are pasted and coated with a resin, that is in contact with the entire fiber surface. Figure (3) (b) shows carbon fibers laying in a parallel arrangement. This fabric can be held in place by using a cross-stitch, or outer stitch, or with a web mat.

The present invention reduces weight, maintains cloth shape and improves handling of these unidirectional carbon fibers. The unidirectional carbon fibers may be sprayed or covered with either polypropylene, polyethylene, or Teflon or glass, or combinations thereof that are stable in the battery

environment, in a webbing/mat which covers the fiber surface on top and/or bottom, and extends beyond the carbon fiber in the perpendicular direction so that in the case of the fiber sandwich, the top and bottom covers are melted together and to the carbon fabric.

In the case of the carbon fiber being covered with the webbing/mat the melting provides a stabilized fabric by melting the webbing/mat onto the carbon fiber. The mat can also be woven, but due to cost is more effectively a random or nonwoven. The mat can be applied directly to the fibers as they are oriented off a spool and then the fiber and polymer and/or glass mat can be run through a hot roller or other heat source such as IR lamps. Several other processing options also exist with the same end product formed. The end result is a stable and easily handled cloth.

The unidirectional carbon fiber cloths can be of any size or shape, as determined by the end use. The material can be used as a battery electrode and separator pair where two sandwiches are placed adjacent to one another where the carbon acts as electrodes and the polymer as a separator.

Optionally, a thinner mat can be applied to the carbon and an additional layer of separator material is placed between the carbon/polymer sandwiches.

The nature of the dual graphite system is not as restricted by electrode thickness as found in similar technologies. As such, thicker electrodes can be used than those described in the prior art, and the electrode thickness is limited only by the cell design and intended use. Figure (3) (e) shows a material in which the end result is a mat or foam of carbon that is essentially all one fiber. Carbon foams and thermally fused felts are being produced using various different methods and in various degrees of graphitization. The foam/fused felt has a structure similar to a sponge with a portion of the volume consisting of solid carbon while the remainder is void. Since the individual strands of carbon are inherently connected to each other, an entire

piece of carbon foam/fused felt acts as a single piece of carbon. Therefore, by connecting to a single atom of the carbon, you connect to all of the atoms in the structure. This is particularly useful with electrical current in batteries where the carbon material can act as both the active material for energy storage and as the current collector for electric current. The amount of metal needed in a typical electrode can constitute as much as half of the weight, whereas carbon foam/fused mat reduces it to virtually nothing.

Although particular embodiments of the present invention have been described in the foregoing description, it will be understood by those skilled in the art that the invention is capable of numerous modifications, substitutions and rearrangements without departing from the spirit or essential attributes of the invention.

The invention presented specifies the various types, and forms, of carbonaceous materials that are optimal for the use in dual graphite cells, which are incorporated to form dual graphite batteries. The dual graphite energy storage device is different from all other batteries. The dual graphite cell functions strictly on the intercalation and deintercalation of anions and cations, where no electrochemical reactions are required for energy storage and use.

The carbonaceous materials used in dual graphite cells, and/or batteries, have requirements specific to this technology. Improved anion intercalation and deintercalation capacity is seen as the degree of graphitization of the carbon fiber increases. Exact electrode capacities differ depending upon the supporting electrolyte used, and depending upon the cation intercalation/deintercalation fiber used.

Various forms of the carbon fiber electrodes can be used in a dual graphite cell or battery, however those requiring the least amount of current

collector are preferable. The dual graphite cell or battery obtains increasing levels of energy density as the continuous carbon fiber to current collector area ratio increases. This means that the order of preferred materials are: a carbon mat (in which the fibers are thermally fused to each other) and a carbon foam, a multiplicity of conductive fibers formed into a cloth form (such as a woven fabric, unidirectional mat, biaxial braid, triaxial braid), a multiplicity of conductive fibers, and a single conductive fiber.

EXAMPLE 1 A dual graphite cell was built through the following steps.

Unidirectional carbon cloth, of the design previously described, was cut to the desired size. Current collectors were placed upon one edge of each electrode. A thin layer of a typical battery separator was placed between the two electrodes. The electrodes were placed in an air and watertight package.

The package void space was filled with a typical battery electrolyte. Upon charge and discharge the dual graphite cell repeatably achieved 180mAh/g of both anion and cation capacity.

EXAMPLE 2 Experimentally, graphite foam was used from various sources to make electrodes for cation intercalation and for anion intercalation in a dual graphite battery. Electrically conductive carbon ink was used to join the foam to a metal strip, and the metal was then coated to protect it from corrosion in the electrolyte. The foam materials for the two electrodes were in a one to one weight ratio. A thin layer of a typical battery separator was placed between the two electrodes. The electrodes were placed in an airtight and watertight package. The package void space was filled with a typical battery electrolyte.

In at least one of the carbon foams tested the following data was achieved : >228 perchlorate capacity mAh/g and >228 lithium capacity mAh/g.

Throughout this application various publications are referenced by author and year. Full citations for the publications are listed below. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.

The invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

REFERENCES US Patent Documents 4,725,422 4,830,938 4,865,931 5,145,732 5,244,757 5,527,643 5,741,472 5,626,977 5,677,084 5,773,167 5,862,035 5,898,564 5,932,185 5,993,997 6,094,788 Other References Matsumura, Y., et al., Interactions between disordered carbon and lithium in lithium ion rechargeable batteries, Carbon, Vol. 33 (No. 10), 1995, p1457- 1462.

Noel, M. and Santhanam, R., Electrochemistry of graphite intercalation compounds, Journal of Power Sources, Vol. 72,1998, p53-65.

Santhanam, R. and Noel, M., Influence of polymeric binder on the stability and intercalation/de-intercalation behaviour of graphite electrodes in non- aqueous solvents, Journal of Power Sources, Vol. 63,1996, p1-6.

Steel, J. A. and Dahn, J. R., Electrochemical intercalation of PF6 into graphite, Journal of The Electrochemical Society, Vol. 147 (No. 3), 2000, p892-898.