CH663688A5 - ELECTRODE FOR USE IN AN ELECTRICITY STORAGE DEVICE. - Google Patents

Description

The invention consists of an electrode for use in an electrical energy storage device, an electrode comprising an electrode body of an electrically conductive carbonaceous material 25, having a structure oriented, at least at the surface, and an associated current collector electrically with it, wherein said carbonaceous material has a Young's modulus higher than 6.9 GPa and undergoes a physical dimension variation of less than 5% during the 30 cycle of repeated electric charge and discharge.

The carbonaceous material of the electrode in question has proved stable in the presence of an electrolytic system containing anions such as perchlorates, hexafluoro-arsenates and the like, under ambient or normal operating temperatures of use of the electrode. 35 In other words, the carbonaceous material does not swell or contract irreversibly in an appreciable manner during forced charging and discharging cycles, such as those that can be performed during the operation of a secondary electrical energy storage device, in which i.e. energy is stored inside the electrode material without dissolving it in the electrolyte.

The carbonaceous material of the electrode in question, in fact, can function indifferently as a positive or negative electrode, has a high duration and the ability to charge and discharge 45 rapidly an extraordinarily high number of times.

Number of patents and technical literature describe electrical energy storage devices using a carbonaceous material such as carbon or graphite as an electrode material. Of course, one of these previous devices was the 1866 Leclanché battery, in which carbon was used as an electron collector in a primary Zn / NH4C1 / Mn02 battery.

Until then, carbon has been used extensively as an electrode component in primary batteries, primary fuel cells, secondary fuel cells, secondary batteries and secondary capacitors. The function of carbon or graphite in such aforementioned devices has been mainly that of a current collector or as a reactive material to form new compounds with fluorine, which have structures and properties other than those of the original carbon / graphite and, more recently, as semi-conductive materials that form salts with electrolyte ions.

These prior art devices can be classified as: primary batteries, as described in the Tunisian sta-65 patent no. 2 597 451 to Coleman et al., In technical publications of the Panasonic Lithium Battery literature, and in US patents no. 4 271 242, 3 700 502 and 4 224 389; fuel cells as in the Japanese patent publication

3

663 688

. 54-082 043; and secondary fuel cells, with limited recharge rate as described in U.S. Pat. 337 025 in the name of Dey et al., The activated graphite folding rechargeable fuel cell (high surface area); batteries: rechargeable waves (accumulators) as described in the US short no. 4 251 568 to Hart employing graphite and current collector, and in U.S. patents no. 344 837 and 4 009 323 in the name of Bennion, and capacitors such as • 1 U.S. Pat. 3 700 975 in the name of Butherus et al., Or German preventive no. 3 231 243 using high surface carbon (graphite). Some of these devices use ionizable salts dissolved in a non-conductive solvent.

The carbonaceous materials described in the patents and literature of the art are graphitized or carbonized materials until the materials do not become electrically conductive. These aterials are derived from polyacetylenes, polyphenylenes, polyacrylate-iryls and petroleum pitch and have been heated to "carbonize or graphitize" the precursor material to impart a certain degree of electrical conductivity. Some of the graphites used has previous technical literature are graphites such as RPG einforced Pyrolytic Graphite or Reinforced Pyrolytic Graphite) aphite Rl of the type for nuclear reactors, PGCP (Pyrolytic Gra-ite Carbon or Carcta Pyrolytic Graphite Carbon) and GRA-JIL (a trademark of Union Carbide Corpora-n factory) comprising compressed and expanded graphite and the like. Characteristics of similar carbonaceous materials have been reported in Chemical and Engineering News, Volume 60, 3. 16, pp. 29-33, 10 April 1982 in an article entitled "onducting Polymers R '& D Continues to Grow»; Journal ectrochem Society, Electrochemical Science, 118, No. 12, pp. 86-1890, December 1971; and Chemical & Engineering News ,, No. 41, pp. 34-35, 12 October 1981 entitled "Polymer Cell fers More Power, Less Weight".

The problems relating to these cells are that they are not long lasting, since the electrode made of such a carbon pig is susceptible to degradation when subjected to repeated charging and discharging cycles.

For example, U.S. Pat. No. 3 844 837 (in the name of nnion et al.) Describes a battery using a nuclear graphite impregnated with LiìO chips as a sitive electrode and copper as a negative electrode in a LiCF3S03-dimethyl sulfite electrolyte (DMSU). The graphite electrode is prepared from an R-1 nuclear graphite produced by the Great Lakes Carbon Company) and has been reported

swelling and contraction of the electrode body and that this swelling and contraction increases with each cycle of electric charge and discharge which deforms the graphite plates which are thrown due to the stresses associated with swelling 5 and contraction. In conducting these experiments during the development of the present invention, it was confirmed that this flaking of the graphite plates occurred when the aforementioned graphite materials were subjected to repeated charging and discharging cycles.

10 The electrode according to the invention differs from those according to the prior art in that it is able to withstand more than 100 charging and discharging cycles in complete safety and can also reach 500 charging and discharging cycles with a discharge capacity greater than 150 Coulombs per gram of carbonaceous material of the electrode, without appreciable damage.

Furthermore, the electrode according to the present invention has the precious property of being able to be charged and recharged either positively or negatively in a partial or total way without damage.

20 All this is the result of the considerations made after long studies and tests, considerations that are set out below.

According to a first aspect, the present invention must provide an electrode comprising an electronic body of electrically conductive carbonaceous material having a structure 25 oriented at least at the surface, and a current collector associated electrically with it and undergo a physical dimensional variation of less than 5 % during the repeated electric charge and discharge cycle.

According to another aspect, the invention must allow 30 to realize an electrical energy storage device comprising a housing having an electrically non-conductive internal surface and an external surface impermeable to humidity, or laminar or laminated body and having at least one cell arranged in said housing, each cell 35 comprising at least one pair of non-mutual contact electroconductive electrodes, said housing containing a substantially non-aqueous electrolyte, wherein at least one of the electrodes of each cell is an electrode according to the invention.

«The electrodes must be able to be separated from each other by a certain distance, by means of an ion permeable material.

Physical properties

The electrically conductive carbonaceous material of the electro which it undergoes scaling after nine cycles of charging and discharging 45 must have the following criteria relating to the physical properties: ttric. Patent holders also tried a fabric of. (1) a Young's modulus greater than 6.9 GPa, preferably ifite and have concluded that it is unsatisfactory. variable from 69 GPa to 380 GPa preferably from 138

Various other graphites were used with results similar to 311 GPa.

nsatisfactory the best results having been obtained from (2) A aspect ratio higher than 100: 1. By pyrolytic graphite ratio which failed after 33 cycles. Dey et 50 of shape means in the present context the ratio between length and diameter 1 / d of a fibrous or filament strand of a carbon and graphite material with a high surface, within the pores of which the imic reaction occurs, but this material is of low conductance due to the continuity of the coal surface. Furthermore, it is believed that these materials do not maintain the desired stability and structural integrity necessary for the resilient formation of carbon complexes required for a long duration: secondary battery recharge cycles.

Experiments carried out during the development of the present inaction included the use of GRAFOIL electrodes (factory arch) which failed following the first electric recharge and of RPG (Super Temperature) graphite which were also defective. It was found that more than 20% of the positive electrode made of RPG graphite was found in the form of flakes, chips and dust after only 27 charge and discharge electric cycles.

It should be noted that the prior art identifies disintegration and damage to the electrode as the result of carbonaceous material, or the relationship between length and depth when the carbonaceous material is formed as a flat sheet.

55 (3) The structural and mechanical integrity of the carbonaceous material in any shape it can be manufactured (woven, knitted, or non-woven from continuous filament or flaky fibers or from a film) should be such that it does not require the presence of a support such as a plate

60 pressure (facial films or net) to keep the carbonaceous material in the desired leaf or plate shape, during at least 100 charge / discharge cycles.

(4) A surface area of at least 0.1 m2 / g but less than that associated with activated absorbent carbon, suitably

65 less than 50 m2 / g preferably less than 10 m2 / g and more preferably less than 5 m2 / g.

(5) Sufficient integrity of the shape of the carbonaceous material to allow the carbonaceous material to retain its salty

663 68S

4

plate or sheet type rubber when it has dimensions greater than one square inch (6.45 cm2) up to dimensions greater than 144 square inches (930 cm2) without support other than a metal frame of the current collector forming the edge portion of the electrode.

(6) The electrode of the present invention must be substantially free of water down to a degree lower than 100 ppm. Preferably, the water content should be less than 20 ppm. and more preferably less than 10 ppm. The device according to the invention must be able to operate with a water content of up to 300 ppm, but will have a somewhat reduced cycle duration. - Furthermore, it should be borne in mind that if the level of the water content has become onerous, then the device must be able to be disassembled, dried and reassembled in this dry or anhydrous state without substantial damage to its ability to operate continuously.

Performance criteria

(7) The carbonaceous material of an electrode must be able to withstand more than 100 charge and discharge cycles without any appreciable damage due to the flaking of the carbonaceous material. Preferably, no appreciable damage should occur after more than 500 electric charge and discharge cycles, with a discharge capacity greater than 150 coulombs per gram of carbon material of an electrode.

(8) The coulometric (coulombic) efficiency of the carbonaceous material: of the electrode must be greater than 70%, preferably greater than 80% and preferably greater than 90%.

(9) The carbonaceous material of the electrode must be able to withstand electrical discharges greater than 70% of its charge capacity for at least 100 charge and discharge cycles and preferably greater than 80% for more than 500 charge and discharge cycles .

Therefore, the carbonaceous material of an electrode having its own physical ages previously described must preferably be able to withstand discharge and electric recharge for more than 100 cycles with a discharge capacity greater than 150 coulombs per gram of carbonaceous material in an electrode and with a coulometric efficiency greater than 70% without any irreversible change in size (dimensional change less than about 5%).

Usually, the carbonaceous material will be obtained by heating a precursor material to a temperature above 850 ° C until it becomes electrically conductive. Starting materials carbon precursors capable of forming the portion of electrically oriented carbon material conducting the electrode can be formed from pitch (oil or carbon tar), polyacetylene, polyacrylonitrile, poly-phenylene, SARAN (trademark) and similar. The carbon precursor starting material will have to have some degree of structural orientation, i.e. many of these materials either have substantial concentrations of oriented benze-noide structural fractions or fractions which are capable of conversion, following heating, to a structural orientation like benze -noid and equivalent, at or near the surface due to the structural orientation of the starting material.

Examples of preferred carbonaceous precursor materials which exhibit a similar structural orientation upon heating are complexes of multifilamentary or monoforming threads, or fibers, prepared from petroleum or polyacrylonitrile pitch. These multi or mono filamentary «threads» or fibers are easily converted into textile threads or threads which can then be manufactured in a fabric type product. A technique for producing suitable monofilament fibers is illustrated in U.S. Pat. 4 005 183 wherein the fibers are formed in a file which is then woven to obtain a fabric. The fabric is then subjected to a temperature, usually higher than 1000 ° C, sufficient to carbonize the fabric to make the material 5 electrically conductive carbon and so as to impart to the material the characteristics of physical properties described above in paragraphs (1) to ( 6). Such a fabric, in association with an electron collector, is particularly suitable for use as an electrode in the secondary electrical energy storage device according to the present invention.

Advantageously, the carbonaceous precursor material will be in the form of a fiber, continuous filament thread (s), consisting of a filament or continuous filaments or in the form of a non-continuous fiber cable (thread) which can be formed into 15 complexes such as complex woven, nonwoven or knitted fabrics, or the staple fibers per se can be layered to form an element of fabric, flat, paper or felt type. However, acceptable results can be obtained when threads made of short fibers, 20 to 1 to 10 cm long, are woven into a cloth-like product [provided that these short fibers still have the required physical properties when heat treated previously mentioned in points (1) to (6)]. It should of course be borne in mind that although it is advantageous to form the precursor material preferably in a stabilized state (such as that which is obtained by oxidation), in the desired shape (woven or felt mesh) before carbonization, this realization can be carried out after carbonization if the module is less than about 380 GPa and preferably less than about 269 GPa for machine manufacturing. It should of course be borne in mind that the carbonaceous material may be formed from a film precursor.

The degree of carbonization and / or graphitization does not seem to be a controlling factor in the performance of the material 35 as an electronic element in an electrical energy storage device except for the fact that it must be sufficient to make the material sufficiently electrically conductive, and sufficient to provide the aforementioned physical and mechanical properties under the intended conditions of use. Carbonaceous materials having carbonization of about 90% are indicated in the technical literature of the art as partially carbonized. Carbonaceous materials having carbonization from 91 to 98% are indicated in the literature as carbonized material, while re-material having a carbonization greater than 45 98% are called graphitized. It has surprisingly been found that carbonaceous materials having a carbonization degree of 90 to 99% have proved unsatisfactory as electrode materials, unless the carbonaceous material has the dimensional stability required during the charge and discharge cycles. For example, the RPG and GRAFOIL graphites, although they have the required degree of carbonization, the required electrical conductivity and surface area, do not have the required physical properties of Young's modulus and aspect ratio and therefore have not been successful.

55 Examples of embodiments of rechargeable and reversible polarity storage cells of electricity prepared by aligning electrodes according to the invention and further various examples of embodiment of the electrode according to the invention will be described with reference to the drawings enclosed in which 60 :

the graph of fig. 1 shows the voltage at the terminals with respect to the discharge in coulombs per gram of fiber, for a 0.9 ohm cell for various discharge speeds ranging from 6 hours to 3/4 of an hour;

"5 fig. 2 shows the data for a 0.7 ohm cell;

fig. 3 shows the comparison of the two cells for the highest discharge rate (speed corresponding to 3A per hour);

fig. 4 shows the power determinations with electrode

5

663 688

from 10 cm x 10 cm for the state of charge carried out at levels of 247 coulombs per gram (72% charge) and 224 coulombs per gram (65% charge);

fig. 5 shows the voltage trace of a discharge with a maximum power rating of 40 seconds.

A rechargeable and reversible polarity electric energy storage device is now described, i.e. a cell prepared by at least aligning a pair of electrodes according to the invention, made up of the carbon material previously described and its associated electron collector (which are electrically conductive) in a housing. The housing has a non-conductive internal surface, impervious to moisture. The electrodes are immersed in a non-aqueous fluid (the water being present in an amount lower than about 100 ppm) contained in said housing.

The fluid itself is capable of forming, or contains dissolved in it, at least one ionizable metal salt. Each electrode consists of the heat-treated carbonaceous material, as previously specified, associated with an electron collector which is preferably isolated from contact with the electrolytic fluid.

The device may be constructed without the polarity reversal capability by aligning the aforementioned electrically conductive carbon fiber assembly, such as a fabric, and its electrode collector as an alternating positive electrode; on a negative electrode which can be made of a metal, such as lithium, or from a metal alloy, by immersing the electrodes in a substantially non-aqueous fluid, fluid capable of forming or containing, at least one ionizable soluble metal salt dissolved in it to provide electrolyte ions.

In the construction of a preferred embodiment of the aforementioned device, conventional porous separators of glass fiber, polymeric materials or compounds of polymeric materials are to be and are preferably used to separate the positive and negative electrodes from each other. Preferably, a non-woven polypropylene oil is used as a separator since it has the desired degree of porosity and at the same time has a tortuous path sufficient to prevent arboreal fibers from penetrating through it, thus preventing electrical corcircuitation . The porous separators also act advantageously as stiffening elements or supports for the electrodes.

Energy storage devices which are contained in fluid tight housings are generally known in the art. Such housings can be suitably used in the present invention provided that the housing material is electrically non-conductive and impermeable to gases and / or moisture (water or water vapor).

The materials that are found to be chemically comipatibi-. as housing material include polyvinylchloride, joliethylene, poylipropylene, polytrifluorethylene and related related perfluorinated polymers, instant hardening polymers (ISP), but fast-curing reactive urethane mixture, the frames, a coating or metal plating. with a non-conductive olymeric material such as an epoxide, for example DER * (trademark of The Dow Chemical Company) 331 or with DERAKANE * ZETABON * (trademark of the Dow Chemical Company) and / or glass or os -metal, fluoride or the like. Housing materials which have not proven suitable in the preferred propylene-carbonate system include acrylic resins, polycarbonate and ny-) n. Acrylic resins crack, and polycarbonates both repole and become extremely brittle, while nylon (except for aramides) is chemically reactive.

In addition to being compatible, a housing material must also have an absolute barrier of less than 0.2 g of: 0 / yard / foot2 (2.15 g of H20 / yard / m2) against the transmission of vapor of water from the external environment to the housing.

No thermoplastic material currently known offers alone this absolute barrier against humidity with a thickness that would be useful for housing a battery. Currently only metals, for example aluminum or mild steel, present an absolute barrier against humidity with sheet-like thicknesses. Aluminum foil having a thickness greater than 0.0015 inches (0.038 mm) has proved essentially impermeable to the transmission of water vapor. It has also been found that when laminated to other materials, sub-tile aluminum foil in the order of 0.00035 inches (0.009 mm) can provide adequate protection against the transmission of water vapor. Suitable housings made of metal-plastic laminate, epoxy-CED coated metal (cathodic electro-deposited) or metal with an internal coating of plastic or glass meet the requirements of both chemical compatibility and the ability to act as a barrier to moisture. Most of the battery cells built so far have been tested either in a dry box having a water level below 5 ppm, or in a glass cell or in a double-walled housing, with the 20 space between the walls filled with an activated molecular sieve, for example zeolite 5A.

The electrolytic fluid preferably consists of a non-conductive, chemically stable, non-aqueous solvent for ionizable salt or salts in which the ionizable salt is dissolved in the solvent. It is possible to use as a solvent those compounds which are generally known in the art such as for example compounds having oxygen, sulfur and / or nitrogen atoms bonded to carbon atoms in an electrochemically non-reactive state. Preferably, it is possible to use nitriles such as acetonitrile; 30-m starches and dimethylformamide, ethers such as tetrahydrofuran, sulfur compounds such as dimethylsulphite, and other compounds such as propylene carbonate. It should of course be borne in mind that the solvent itself can be ionizable under conditions of use sufficient to supply the necessary ions in the solvent. Therefore, the ionizable salt must be at least partially soluble and ionizable either when it is dissolved and passes into solution in the solvent or upon liquefaction. Although it should be borne in mind that slightly soluble salts are suitable, it will be understood that the electric cycling capacity in charge and discharge can be adversely affected by the low concentration of these salts in solution.

Ionizable salts which can be used in the practical implementation of the present invention are those taught in the prior art and include salts of the most active metals, such as for example, the salts of alkaline metals, preferably lithium, sodium or "potassium, or mixtures of these , containing stable anions such as perchlorate (C104 =), tetrafluoroborate (BF4 =), hexa-fluoroarseniate (AsF6 =), hexafluoroantimonate (SbF6 =) or hexa-fluorophosphate (PFô =).

so The electrolyte (solvent and salt) must be substantially free of water, i.e. it must contain less than 100 ppm of water, preferably less than 20 ppm of water and more preferably less than 10 ppm of water. Of course, the electrolyte can be made so as to have more than the desired quantity of water 55 and dried, for example, on molecular sieves of activated zeolite 5A. These agents can also be combined in the finished battery to ensure that the low water level requirement is maintained. The electrolyte must also be such as to allow ions (anions and cations) of the ionizable salt to move freely through the solvent, when the electric potential of the charge and discharge moves the ions to and from their respective poles (electrodes).

The electrode, when constructed in the form of a fabric or sheet, includes an electron collector conductively associated with at least one of the edges of the carbon or sheet fibers. The edge (s) are / are preferably further protected with a material to isolate the collector and to substantially protect the electron collector from contact with the

663 688

6

fluid and its electrolyte ions. The protective material must of course not be affected by the electrolyte fluid or ions.

The current collector intimately contacts the carbon material of the electrode at least along one edge and preferably on all four edges thereof when the carbon material is in the form of a complex such as a flat fabric, sheet or felt. It has also been found that the electrode can be constructed in other forms such as in the form of a cylindrical or tubular bundle of fibers, threads or textile threads in which the ends of the bundle are equipped with a current collector. It is also evident that an electrode in the form of a flat body of fabric, sheet or felt can be rolled up with a porous separator between the layers of the carbon material, and with the opposite edges of the rolled material, connected to a current collector. Although metallic copper has been used as a current collector, any metal or electrically conductive alloy such as silver, gold, platinum, cobalt, palladium and their alloys can be used. Similarly, although electroplating has been employed in connecting a metal or metal alloy to the carbonaceous material, other coating techniques (including fusion applications) or non-galvanic deposition methods may be employed, provided that the edges or ends of the electrode, including a majority of the ends of the fibers at the edges of the carbonaceous material, are wetted by the metal sufficient to provide an electrical contact and its substantially low resistance current path.

Collectors made of a non-noble metal, such as copper, nickel, silver or alloys of these metals must be protected by the electrolyte and therefore are preferably coated with a synthetic resin material or an oxide, fluoride or the like, which will not be attacked by the electrolyte, nor will it undergo any significant degradation in the operating conditions of a cell.

Electrodes according to the present invention made from the electrically conductive carbonaceous material and its current collector can be used as a positive electrode in a secondary energy storage device. No substantial damage to the electrode itself or to the electrolyte, ie solvent and ionizable salt, is observed in undergoing repeated charges with a capacity greater than 150 coulombs per gram of active carbon material, and high discharges, up to a "depth" greater than 80% of the total electrode capacity with high speeds or slow charging. ca / download.

Alternatively, electrodes according to the invention made up of the electrically conductive carbon material and its current collector can also be used as both positive and negative electrodes in an accumulator (secondary battery) with advantageous operating characteristics similar to those which have been previously described.

A surface area of at least 0.5 m2 per gram and a low resistivity of less than 0.005 ohm / cm of the carbonaceous material used for the electrode of the invention constitute desirable properties. Therefore, a battery constructed with the carbon electrodes of the invention has an extremely low internal resistance and an extremely high corresponding coulometric efficiency which is usually higher than 80%.

During the period of study relating to the limits of the present invention, it has been found that initial current densities under load greater than 100 to 200 mA / square inch (15.5 to 31 mA / cm2) can result in material damage carbonaceous electrode.

Example 1

A pair of electrodes each having an area of 11 square inches (71 cm2) were prepared from a tissue of

Panex (Trademark) PWB-6 (a fabric that had been heat treated at a temperature greater than 1000 ° C by the manufacturer, which made this electrically conductive fabric) purchased from the Stackpole Fibers Industry Company. The woven fabric was woven from a polyacrylonitrile (PAN) precursor in which the yarn was made from non-continuous filaments (staple fibers) having an average length of about 2 inches (5 cm) and a diameter between 7 and 8 microns, and a aspect ratio of about 700: 1. The fabric was heat treated by the manufacturer after weaving. The edges of the heat treated fabric were coated with copper by electroplating to provide a current collector. A metal wire was soldered to one end of the copper-clad or coated edges. All four edges of each electrode (colis current reader and wire connector) were coated with an amine DER (trademark) 331 hardening epoxy resin, manufactured by The Dow Chemical Company, to isolate the metal from the effects corrosive of the electrolyte under the conditions of use. The pair of electrodes was immersed in an electrolyte comprising a 15% solution of LYCIO 4 in propylene carbonate contained in a polyvinyl chloride (PVC) housing. The electrodes were spaced less than 0.25 inches (0.6 cm) apart. The electrode assembly in the housing was supported in a dry box. 25 The housing was sealed while it was in the dry box with the metal wires coming out of the housing. The water content in the mounted housing was less than 10 ppm. The fibers had a Young's modulus of about 33,000,000 psi (230 GPa) and a ratio between area and weight between 0.6 and 1.0 30 m2 / g. The total electrical capacity of the active carbon material of the electrode was about 250 coulombs / gram.

The cell thus prepared was electrically charged to a; maximum voltage of 5.3 volts with limited current so as not to exceed 35 milliamperes per square inch (5.4 mil-35 liamperes / cm2) of the electrode's facial area. The cell was electrically charged and discharged for 1250 cycles within a period of 11 months and had a coulometric efficiency or efficiency of over 90%, conducted with a discharge capacity greater than 85% .- The cell was therefore disassembled and the fibers from each 40 of the tissue electrodes were examined under a microscope with 1000-fold magnification. As far as measurable, the fibers had the same diameter as the fibers from the same batch that had not been used in the cell. The cell was reassembled and the test was continued in the same 45 mode which was previously described. The cell has so far completed over 2800 charge and discharge cycles within a period of 23 months without reducing coulometric efficiency, and it still has a coulometric efficiency of over 90%.

50 Example 2

Six electrodes similar to the electrodes of Example 1 were prepared and connected in a three cell unit, so that each of the three pairs of electrodes was sealed in separate polyethylene pockets (bags). The electrodes had connected in 55 series. The three-cell units were operated in the same way as in Example 1 except for the fact that the voltage was about 16 volts. The initial open circuit voltage was around 13.5 Volts. After 228 charge and discharge cycles during which the discharge was conducted with a deep discharge "or greater than 78% of the total capacity, the cells were disassembled and the electrodes were removed from their pockets and the fibers examined to determine signs deterioration, i.e. excessive flaking and swelling and contraction of the fibers. The examination showed no detectable variation in the diameter of the fibers with respect to fibers measured in the same batch of fabric that had not been used to prepare the electrode of this example. Measurements were conducted with a laser interferometer.

7

663 688

Example 3 duto with the trade name of Panox (trademark of

Various flat sheets were cut from a fabric woven at the factory) and it was a non-conductive carbon fiber with a starting from thread made of a monofilament precursor fiber with a shape ratio greater than 250: 1, made in a thread and essentially continuous. prepared from oil pitch. the woven fabric, as reported, had not been heated to a The fibers were manufactured by The Union Carbide Company and s temperature above 400 ° C. The fabric has been treated with sales under the trade name of Thornel (Mar-heat at a temperature of about 1000 ° C for a period of factory time). The thread of the precursor fiber tow with a sufficient time to make the fabric electroconductive. The tissue of about 800: 1 shape was woven to obtain a heat treated fabric had a Young's modulus of 23,000,000 suto and then heat treated at a higher temperature of psi (160 GPa) and a surface area of about 1 m2 / gm. Two at 2000 ° C. Each of the flat sheets had an area of the dimensional tissue samples each having a width of 2 inches (5 sions of approximately 1 square foot (930 cm2). The fiber had a cm) on one side and an area of 4 inches (26 cm2) were cut Young's modulus of 45,000,000 psi (315 GPa) and an area on- from the heat-treated fabric and the four edges of each fabric-of about 1 m2 / gram after heat treatment . The toes were plated with metallic copper to form a collet sheet were plated with metallic copper along the four current pads for the electrode. A wire was soldered to one of such that all the fibers were electrically connected to the edge of the current collector of each electrode. The joint is for forming a collector frame of electrons. A solder wire and the copper current collector were coated insulated copper was attached to a collector edge close to with a vinylester resin coating composition of a corner by solder and the solder joint and Derakane type ( trademark). A composite sheet of copper collector was coated with nonwoven, polygropropylene vinyl ester, Celgard (trademark) 5511 of the DERAKANE type (trademark of The 20 was positioned between the two electrodes and the electrodes were inserted in Dow Chemical Company). Each pair of sheets was enclosed in a plastic pocket (wrapper). This complex was designed parallel to each other with the metal wires welded in place in a dry box, in which the water content was at opposite ends of the coupled edges and kept less than 20 ppm of the electrolytic solution. A wallpaper by means of a composite sheet of non-woven polypropylene 10% by weight solution of LYCIO4 in a 5-thousandths of an inch thick carbon-perforated and fibrous solution of propylene was used to fill the fine wrapper. 0.1 mm). A polyethylene pocket (bag) having dimensions that the two electrodes were not immersed in the electrolyte solution - approximately 1 square foot (930 cm2) was used as a container. The metal wires from each electrode were connected to a cell holder. Three cells were assembled into a two-way bipolar switch, one terminal of which was dry-collected by arranging a pair of carbon fiber sheets at a 5.3 volts electrical voltage source. The other aio and their separator in each of the three pockets and filling 30 terminal was connected to a resistive electrical load of 10 each pocket with about 500 grams of an electrolyte constituted ohms. The cell was forced to discharge in a pushed or deep way a solution of 15% by weight of LÌCIO4 in carbonate of product up to over 80% of its total charge and made to work Chilean. The electrolyte level in the pocket has been determined for over 800 cycles of electric charge and discharge with an efficiency "adorning 21 grams of active fiber per electrode (the area of the Echoulometric greater than 80%. The capacity of this cell was exposed to the electrolyte). The remainder of the carbon fibers 35 approximately 70% of that of the PAN example (Example 1) on one ii each electrode extended out of the solution or was total electrode weight basis.

jerto by means of the Derakane resin frame (trademark of It has been found that cells built according to the present invention

"abbrica) / metallic copper. have an internal resistance which, on average, is less than

The complex of cells in a dry box maintained the 0.038 ohm / square foot (0.41 ohm / m2) of the facial area of the water content at less than 20 ppm of electrolyte solution - 40 the electrode in a cell with six electrodes. This value, originally-: a. Each pocket was sealed, while it was in the case measured as less than 1 ohm, it included the dry ad-a wires, so as to allow the ends of the metal wires leading to the charging system, having a length of about 6 apple trees extend through the seal at tri ends. After measuring the resistance of the lead wires 0 affixed to the sealed edge. The three cells thus prepared were conductors and following subsequent re-measurement of the resistance placed in a transparent plastic box is the total metal wires of the system from charge, it was calculated that the resistance was not connected in series . A certain amount of bulk sieves of the accumulator (secondary battery) was actually zeolite olars activated -5A (to absorb moisture) was 0.038 ohm / square foot (0.41 ohm / m2).

junta on the top of the cells, and the complex has been removed A confirmation of the data of the previous examples has been carried out on dry boxes The end metal wires of the two plates by a collaborator in a two-electrode cell made at the end of the three series of cells were connected to terminals starting from «Thornel» fabric, VCB-45 having a form of ìali extending through a lid for the box, and the 45,000,000 psi (315 GPa) co-Young, a surface area of 1 lerchio was quickly sealed to the box itself. m2 / g and an aspect ratio greater than 10,000: 1, in which

The complex was loaded to a potential comprised between scun tissue had a size of 15.2 cm X 15.2 cm. Bor-5 and 16 volts and with a current of between 1.8 and 2 amperes and copper copper were plated around all four edges> for 45 minutes. Subsequently the device was discharged 55 of the tissues to form the current collector. The collector through a current-absorbing 12 volt automobile headlight was then coated with DERAKANE (average manufacturer's mark between 2.0 and 2.5 amperes. The device is brica) 470-36.1 collector edges of current had a discharge discharged at 90% of its capacity in 30 minutes. Cycles of about 2.6 cm in length, leaving areas of aric carbonaceous material and electrical discharge were conducted over 850 times. I activate it about 10 cm x 10 cm. The area of 100 cm2 of each she was then disassembled and the fibers were examined under an electrode containing about 6 g of carbon fiber. 0 a microscope with a magnification of 1000 times and not avoided. The electrodes were separated by placing an electrode in an enzyme with significant signs of swelling or deterioration with a heat-sealed bag of micro-pore polypropylene film, due to scaling. The device accepted an electric charge sa «Celgard» (trademark) 5511.

a discharge pushed to 90% of the capacity for each cycle. The electrode and separator assembly has been arranged in

65 a polyethylene bag, the bag was filled with an Example 4 dry electrolyte consisting of 15% by weight of LÌCIO4 in paper

A PAN base fabric (precursor fiber) was obtained from propylene bonate (about 100 cc) and the complex was crushed by R.K. Textile, Ltd., Heaton Moor, U.K. The fabric was vented between two plastic edge pressure plates

663 688

8

many sides of the bag containing the electrolyte. The thickness of the copper current collector coated with DERAKANE prevented the fibrous portion of the two electrodes from being compressed at a minimum mutual separation distance. In subsequent tests, a spacer plate dilOcm X 10 cm was inserted between the edge pressure plates to more closely compress the electrode-separator combination together. This reduced the cell resistance from about 0.9 ohm to about 0.7 ohm.

Discharge data for varying discharge rates were taken for two of the cell configurations previously described. In one case (0.9 ohm cell) the separation of the electrodes was limited by the epoxy coating on the current collector to approximately 4 mm. In the other case (0.7 ohm cells), the electrodes were brought together at the center with only the porous polypropylene separator between them (less than 1 mm).

The graph of fig. 1 shows the voltage at the terminals with respect to the discharge in coulombs per gram of fiber, for the 0.9 ohm cell for various discharge speeds ranging from 6 hours to 3/4 of an hour.

These discharges correspond to a so-called first plateau (2 volt cut). If it is assumed that the total capacity of the first plateau is 180 coulombs per gram for the 2 volt cutting voltage, then the values on the abscissas can be replaced with "% discharge"; with 180 coulombs / g «equivalent to 100% discharge».

The total energy recovered after 3 hours under constant load is almost the same as at 6 hours. Due to the high discharge rate of V4, inefficiencies are generated and inefficiencies occur due to the resistance of the cell and the polarization of the electrodes.

The electrode current densities corresponding to these discharge rates are:

Speed

Average current density

(Hours)

with constant load (ma / cm2)

6

0.5

3

1.0

1.5

2.0

0.75

4.0

The "coulombs per gram of fiber" are based on the weight of the. active carbon material of only one electrode.

Fig. 2 shows the data for the 0.7 ohm cell. Obviously more energy is available for the cell with the lowest resistance. Fig. 3 shows the comparison of the two cells for the highest discharge rate (speed corresponding to 3/4 hours).

A metallic lithium reference electrode was inserted into the cell to determine which electrode was polarizing. The voltage drops between each electrode and the reference electrode were determined during charging and discharging and following opening of the circuit.

After opening the circuit, the voltages between the negative electrode and the reference electrode were generally less than 100 mv and varied only slightly over time. The voltage, when measured between the positive electrode and the reference electrode, varied with time, decreasing after each charge and increasing after each discharge.

5 The maximum power capacity of a battery cell for different charging stages was determined by pulsing discharge of the cell onto loads that supplied voltages to the terminals of half the open circuit voltage. The "pulses" were 10 seconds long and the power was calculated as the 10 average power within 10 seconds.

The cell was first loaded at 344 coulombs per gram of active carbonaceous material into an electrode. This was assumed to be a 100% state of charge. The maximum absorbed current of the 10 cm x 10 cm electrode cell for the 100% charge state was between 2.5 and 3.0 amperes. Subsequent potency determinations were performed at levels of 247 coulombs per gram (72% charge) and 224 coulombs per gram (65% charge). Fig. 4 shows the results.

The maximum power from this cell was approximately 0.48 20 watts per gram of fiber for a 100% charge state, decreasing to about 0.31 watts per gram of fiber for a 72% charge state. The power capacities decrease rapidly after which the voltage drops and polarization occurs. . An impulse discharge of more than 10 seconds does not necessarily reduce the final power in large quantities. Fig. 5 shows the voltage trace of a discharge with a maximum power rating of 40 seconds. After the first 10 seconds, the voltage drop is small.

30 Example 5

A three cell battery was constructed from twelve plates, four per cell, of the Thornel type fiber described in Example 3. Each plate was approximately 12 inches x 12 inches (144 square inches or 930 35 cm2) in size. , and had been copper-plated on each edge. The copper plating along the edges was coated with a polymerizable vinyl ester resin of the Derakane type (trademark). The plates had an active area of approximately 132 square inches (852 cm2). The four plates of each cell were assembled with a perforated mesh separator of polypropylene between each plate. Pairs of plates in each cell were connected in parallel, so that after charging / discharging the plates were alternately +, -, +, -. The four plates and the gold separators were contained in a lipropylene polka dot bag having dimensions of 13 inches x 13 inches (33 cm X 33'cm) which contained about 600 cc of an electrolytic solution of 15% by weight of LÌCIO4 in carbonate of propylene. This level of electrolyte in each bag was sufficient to provide about 37 grams of active fibers per electrode plate. 50 The battery was initially charged within a period of 1000 minutes at a capacity of 7.9 amperes per hour with a potential of 14-16 volts. The cell was then discharged within a period of 200 minutes through a 12 volt car headlight, emitting an average capacity of 6.2 amperes per hour, representing a depth of discharge greater than 80%. Charging was accomplished within a period of 800 minutes. An average of coulometric efficiency of approximately 90% under charge-discharge cycling was observed.

v

1 sheet of drawings

Claims (20)

663 688 1. Electrode for use in an electrical energy storage device, an electrode comprising an electrode body of an electrically conductive carbonaceous material having a structure, oriented at least at the surface, and a current collector electrically associated with it, wherein said carbonaceous material has a Young's modulus greater than 6.9 GPa and undergoes a physical size variation of less than 5% during the repeated electric charge and discharge cycle. 2. The electrode according to claim 1, wherein said complex of carbonaceous material has a Young's modulus ranging from 6.9 GPa up to 380 GPa and wherein said carbonaceous material is a derivative of a polyacrylonitrile or pitch. 2 Electrode according to claim 2, wherein the carbonaceous material has a Young modulus ranging from 69 GPa up to 380 GPa. 4. The electrode according to claim 2, wherein the carbonaceous material has a Young modulus ranging from 138 GPa to 311 GPa. The electrolytic solvent is selected from compounds having oxygen, sulfur and / or nitrogen atoms bonded to carbon atoms in an electrochemically non-reactive state wherein said salt is an alkaline metal salt. 5. Electrode according to claims 1 to 4 wherein said carbonaceous material has a surface area of 0.1 to 50 mVg. 6. The electrode according to claim 5, wherein the carbonaceous material has a surface area of 0.1 to 10 m2 / g; 7. The electrode according to claim 6, wherein the carbonaceous material has a surface area of 0.1 to 5 m2 / g. 8. The electrode according to claims 1 to 7, wherein the component part or parts of said carbonaceous material have a. relationship between the. length «1» and diameter or depth «d» 1 / d greater than 100: 1. 9. Electrode according to claims 1 to 8 wherein said electrode body has a surface starting from 6.45 cm2. 10 t and electrolytic is propylene carbonate and the alkali metal salt is lithium perchlorate. 20. The storage device according to claim 16, wherein all the electrodes of each cell are electrodes according to one of claims 1 to 5. 15. A device according to claims 16.20, having a maximum power greater than 0.31 watts per gram of active positive carbon electrode for a pulse period of 40 seconds at full charge. 10. Electrode according to claims 1 to 9, wherein said carbonaceous material is in the form of a fabric, film, sheet or felt. 11. The electrode according to claims 1 to 9, wherein said carbonaceous material is in the form of a fabric or felt or sheet comprising a complex of continuous filaments or staple fiber yarns having a length of 1 to 10 cm. 12. Electrode according to claims 1 to 9, wherein said carbonaceous material is a knitted fabric consisting of a complex of continuous filaments or staple fiber yarns having a length varying from 1 to 10 cm. 13. Electrode according to any one of claims 1 to 9, wherein said carbonaceous material is a felt or sheet type fabric obtained from a complex of continuous filaments or staple fiber yarns. Electrode according to one of claims 1 to 13 wherein said electron collector is an electrically conductive metal intimately adhering to at least one edge of said carbonaceous material, and wherein said metal coating is covered with a non-conductive and non-reactive protective material . Electrode according to one of claims 1 to 14 wherein said carbonaceous material is able to withstand more than 100 electric discharge cycles with a discharge degree greater than 70% of the charging capacity and with a coulometric efficiency greater than 70% without appreciable damage to the structural integrity of the material. 16. Electric energy storage device comprising a housing having an electrically non-conductive inner surface and an outer surface impervious to moisture, or laminar or laminated body having at least one cell arranged in said housing, each cell comprising at least one pair of electrically conductive electrodes not in mutual contact, said housing containing a substantially non-aqueous electrolyte, wherein at least one of the electrodes of each cell is an electrode according to one of claims 1 to 15. 17. The device of claim 16 wherein the electrolyte comprises a non-aqueous, non-conductive solvent, chemically stable and an ionizable twig dissolved in it. 18. Device according to claims 16 and 17 wherein the 19. The device of claim 18 wherein the solvent 20