FR2556138A1 - DEVICE FOR STORING SECONDARY ELECTRIC ENERGY, AND ELECTRODE FOR THIS DEVICE - Google Patents

Abstract

ELECTRODE INTENDED TO BE USED IN AN ELECTRICAL ENERGY STORAGE DEVICE INCLUDING AN ELECTRODE BODY MADE OF ELECTRICALLY CONDUCTIVE CARBON MATERIAL, HAVING A SKELETAL ORIENTATION, AT LEAST AT OR NEAR AND NEAR ITS SURFACE, CURRENT COLLECTOR ELECTRICALLY ASSOCIATED WITH THIS ELECTRODE. CARBON MATERIAL HAS A YOUNG MODULE OF MORE THAN 6.9 GPA AND IS VARIED IN ITS PHYSICAL DIMENSIONS OF LESS THAN 5 DURING REPEATED ELECTRIC CHARGE AND DISCHARGE CYCLES. THE FIGURE SHOWS THE HIGH SPEED POWER DISCHARGE OF A SECONDARY ELECTRIC ENERGY STORAGE DEVICE INCLUDING AN ELECTRODE ACCORDING TO THE INVENTION.

Description

DEVICE FOR STORING SECONDARY ELECTRIC ENERGY, AND

ELECTRODE FOR THIS DEVICE.

  The invention resides in the use of a carbonaceous material together with an electron collector as an electrode for secondary electrical energy storage devices. The carbonaceous material of the electrode is stable in the presence of an electrolyte system containing

  anions such as perchlorates, hexafluoroarsenias,

  and the like, under ambient or normal temperature conditions of the electrode. In other words, the carbonaceous material does not expand or contract irreversibly appreciably during the deep electric charging and discharging cycles, such as those that can be performed in the operation of a battery.

  secondary electrical energy storage device.

  Numerous patents and a large technical literature describe electrical energy storage devices using a carbonaceous material such as carbon or graphite as electrode material. Of course, one of the oldest of these devices is the Leclanchée battery

  of 1866, in which carbon was used as a

  electron generator in a Zn / NH4C1 / MnO2 primary cell. Since then, carbon has been used extensively as a constituent

  of the electrode in the primary cells, the fuel cells

  primary cells, secondary fuel cells, secondary batteries and capacitors. The function of carbon or graphite, in these devices mentioned above, is essentially that of a current collector or that of a reactive material to form, with fluorine,

  new compounds that possess structures and properties

  different from those of the original carbon or graphite,

  and most recently they have been used as semi-

  conductors forming salts with the ions of the electrolyte.

  These devices of the prior art can be arranged in different categories: primary batteries such as the one

  which is described by Coleman et al. in the United States Patent

  United States of America N 2,597,451, in the documentation

  "Panasonic Lithium Battery", and in US patents

  United States of America Nos. 4,271,242, 3,700,502 and 4,224,389; fuel cells, as described in Japanese Patent Publication No. 54-082043; and secondary fuel cells, with limited reloadability, such as that described by Dey et al. in U.S. Patent 4,037,025, which is a rechargeable fuel cell utilizing activated graphite (high surface area); rechargeable secondary batteries (accumulators) such as that described by Hart in U.S. Patent No. 4,251,568, using graphite as a current collector, and by Bennion in patents

  United States of America Nos. 3,844,837 and 4,009,323, and

  densifiers such as that described by Butherus et al. in U.S. Patent No. 3,700,975 or in German Patent No. 3,231,243 using a high surface area carbon (graphite). Some of these devices also use ionizable salts dissolved in a

non-conductive solvent.

  The carbonaceous materials which are described in the patents and in the literature are graphitized materials

  or carbonized to become electrically conductive.

  These materials are derived from polyacetylenes, polyphenylenes, polyacrylonitriles, and petroleum pitch, which have been heated to tarbonize and / or graphize the material.

  precursor so as to acquire some degree ------------

  electrical conductivity. Some of the graphites which are used in the prior art literature are graphites such as RPG (reinforced pyrolytic graphite), R-1 (graphite grade for nuclear reactors), PGCP (pyrolytic graphite carbon paper) and "GRAFOIL" (Trade Mark of Union Carbide Corporation)

  comprising expanded and compressed graphite, and the like.

  Doping of similar carbonaceous materials also

  has been reported in "Chemical and Engineering News", Volume 60, No. 16, pages 29-33, April 19, 1982, in an article entitled "Conducting Polymers R & D Continues to Grow"; in "Journal Electrochemical Society, Electrochemical Science", 118, No. 12, pages 1886-1890, December 1971; and in "Chemical & Engineering News", 59, NI 41, pages 34-35, October 12, 1981, in an article entitled "Polymer Cell Offers More Power,

Less Weight ".

  The problems posed by the batteries thus described are that they do not have a long life, given

  that the electrode made of such a carbonaceous material is susceptible

  tible to degrade when subjected to cycles

  repeated charging and discharging.

  For example, U.S. Patent No. 3,844,837 (Bennion et al.) Discloses a battery using a nuclear grade graphite impregnated with Li 2 O flakes as a positive electrode and copper as a negative electrode.

  in an electrolyte LiCF3SO3-Dimethyl Sulfite (DMSU).

  The graphite electrode is made of nuclear grade R-1 graphite (sold by the Great Lakes Carbon Company) and is known to be peeled after 9 cycles of electric charge and discharge. The patentees also tried a graphite cloth and came to the conclusion that it was unsatisfactory. Several other graphites have been used with unsatisfactory results, the best results being obtained with pyrolytic graphite which no longer worked after 33 cycles. Dey et al. use a carbon or a graphitic material with a high specific surface area in the pores of which a chemical reaction takes place, but it is generally believed that these materials have a low conductance due to the lack of continuity of the carbon surface. Moreover, it is believed that such materials do not retain the dimensional stability and structural integrity that are necessary for the reversible formation of the carbon complexes that are required for

  long cycle life of rechargeable batteries

  Daires. Experiments that have been conducted during the development of the present invention included the use of "GRAFOIL" (registered trademark) which did not work.

  from the first electrical charge, and graphing electrodes

  you "RPG" ("Super Temp") that did not work either.

  It has been found that more than 20% of electricity

  Positive trode made of graphite "RPG" was lost in the form of scales, flakes and powder after only

  27 cycles of charging and discharging.

  It should be noted that the prior art identifies disintegration and deterioration of the electrode as a result of expansion and contraction of the electrode body, and that expansion expansion increases with each charge and discharge cycle. electric,

  which deforms the graphite platelets, which

  slow under the effect of stress resulting from expansion and contraction. In carrying out these experiments during the development of the present invention, it was confirmed that such flaking of the graphite platelets occurred when the aforementioned graphite-based materials were subjected to repeated charge cycles.

and electric discharge.

  In a first aspect, the present invention provides an electrode for use in a secondary electrical energy storage device, comprising an electrode body made of carbonaceous material.

  conductor of electricity, having a skeletal orientation

  at least at or near the surface, and a current collector associated therewith electrically, said carbonaceous material having a Young's modulus of more than 6.9 GPa (1,000,000 psi), and undergoing a physical dimension change of less than 5% during repeated cycles

  electric charge and discharge.

  In another aspect, the invention proposes a dis-

  positive secondary electrical energy storage device, comprising a housing having a non-electrically conductive inner surface and an exterior surface or moisture impermeable laminate body and having at least one battery disposed in said housing, each cell comprising at least one a pair of electrically conductive electrodes which are electrically insulated from contact with each other, said housing containing a substantially non-aqueous electrolyte, at least one of

  each stack being an electrode according to the invention.

  In yet another aspect, the invention resides in a secondary electrical energy storage device comprising a housing having a non-electrically conductive interior surface and an impermeable outer surface or laminate body, and having a at least one battery disposed in said housing, each cell comprising at least one pair of electrically conductive electrodes which are electrically insulated from contact with each other, said housing containing a substantially non-aqueous electrolyte, each of electrodes of each cell being an electrode comprising an electrode body made of an electrically conductive carbonaceous material, having

  skeletal orientation, at least at or near the

  of the surface, and an associated electrical current collector

  triply to this electrode, said carbonaceous material having

  a Young's modulus of more than 6.9 GPa (1,000,000 psi) and

  a variation in physical dimensions of less than

  5% during repeated charging and discharging cycles.

  preferably the carbonaceous material having a Young's modulus of 6.9 GPa to 380 GPa (1,000,000 to 55,000,000 psi) and

  derived from a precursor material which is a polyacrylonitrile

  or a pitch, more preferably the carbonaceous material having a Young's modulus of 69 GPa to 380 GPa (10,000,000 to 55,000,000 psi), and each of said electrodes having the

  freedom of choice of polarity when charging and

  study to be polarized in the opposite direction, partiellemer.t

  and / or totally, without inconvenience.

  The electrodes can be separated from each other by a distance or by a material

  ion permeable and non-conductive electricity.

  Physical Properties Preferably, the electrically conductive carbon material of the electrode must have the following physical property criteria: (1) Young's modulus of more than 1,000,000 psi 6.9 GPa (1,000,000 psi) preferably 69 GPa (10,000,000 psi to 380-GPa (55,000,000 psi), or more preferably 138 GPa to 311 GPa)

(20,000,000 to 45,000,000 psi).

  (2) Aspect ratio of more than 100: 1. The aspect ratio is defined here as the ratio of the length to the diameter l / d of a fibrous or filamentary strand of the carbonaceous material, or as the ratio of the length to the depth when the carbonaceous material is put under the

form of a flat sheet.

  (3) The structural and mechanical integrity of the carbonaceous material, irrespective of its manufacturing form (woven, knitted or non-woven from a continuous filament or short fibers or film), shall be such that it does not require the presence of a support such as a pressure plate (surface films or mesh) to maintain the carbonaceous material in the desired forms of the sheet or plate type over at least 100 cycles of charge and

discharge.

  (4) Specific surface area of at least 0.1 m2 / g, but less than that associated with activated carbon adsorption; this specific surface should be less than 50 m 2 / g, preferably less than 10 m 2 / g,

  or, even better, less than 5 m 2 / g.

  (5) Sufficient integrity of the shape of the carbonaceous material to allow the carbonaceous material to retain its plate-like or sheet-like shape when its size is more than 6,45 cm2 (1 in 2) to more than 930 cm 2 (144 inch2) without bracket other than a metal frame of the collector

  current forming the marginal part of the electrode.

  (6) The secondary electrical energy storage device, in which the electrode of this invention is used, should be substantially free of water, within the limit of less than 100 ppm. Preferably, the water content should be less than 20 ppm, or more preferably less than 10 ppm. The device of the invention can operate with a water content of up to 300 ppm, but it then has a somewhat reduced cyclical life. Moreover, it goes without saying that, if the water content becomes too high, the device can be disassembled, dried and reassembled in this state.

  dry without significant damage for the continuation of its operation.

  Performance criteria (7) The carbon material of an electrode shall be capable of withstanding more than 100 charge cycles and

  electric shock without appreciable damage due to

  the carbonaceous matter. Preferably, no appreciable damage should occur after more than 500 electric charge and discharge cycles, with a capacity of

  discharge of more than 150 coulombs per gram of carbonaceous material

born of an electrode.

  (8) The coulometric (coulombic) yield of the carbonaceous material of the electrode should be greater than 70%, preferably greater than 80% or more preferably greater than 90%. (9) The carbonaceous material of the electrode shall be capable of withstanding electrical discharges at depth representing more than 70% of its electrical load capacity for at least 100 cycles of electric charge and discharge, and, preferably, more 80% for more than

  500 cycles of charging and discharging.

  As a result, the carbon material of an electrode,

  possessing the physical properties described above.

  above, should preferably be able to withstand electrical discharge and recharge of more than 100 cycles at a discharge capacity of more than 150 coulombs per gram of carbonaceous material in an electrode, and with a yield of

  more than 70%, without any irreversible changes

  sible importance of its dimensions (variation of

less than about 5%).

  Usually, the carbonaceous material will be obtained by heating a precursor material to a higher temperature

  at 850 C until it becomes electrically conductive.

  Carbon precursor starting materials capable of forming the electrically conductive oriented carbonaceous material portion of the electrode may be formed from pitch (petroleum or coal tar), polyacetylene, polyacrylonitrile, polyphenylene, "SARAN" (registered trademark), and similar materials. The carbonaceous precursor starting material should have a certain degree of skeletal orientation, i.e., many of these materials, or contain substantial concentrations of oriented benzenoid structural parts, or portions thereof. which may, by heating, assume a benzene or equivalent skeletal orientation at or near their surface as a result of the orientation

  skeletal of the starting material.

  Examples of preferred carbon precursor materials that exhibit this skeletal orientation

  by heating are sets of strands or multi-fibers

  or monofilaments, which are prepared from

  oil or polyacrylonitrile. These fibers or multi-strands

  or monofilaments are easily converted into yarns or yarns which can then be made into a fabric-like product. A suitable monofilament fiber production technique is described in U.S. Patent No. 4,005,183, wherein the fibers are formed into a film which is then woven into a web. This fabric is then exposed to a temperature, usually greater than 1000 C, sufficient to carbonize the fabric in order to render the carbonaceous material electrically conductive, and so as to give this material the physical property characteristics which have been achieved. described

  above in subsections (1) to (6). Such a canvas,

  connected to an electron collector, is particularly suitable

  good for use as an electrode in the

  secondary electrical energy storage system of the present invention. It is advantageous for the carbonaceous precursor material to be in the form of a continuous filament fiber, continuous filament yarn (s) or non-continuous fiber tow (yarn) which the they can be in the form of assemblies such as woven, non-woven or knitted assemblies, or the short fibers themselves can be layered to form a web or flat element of the paper type or of the type felt. However, acceptable results are obtained by weaving yarns made of short fibers, having a length of 1 to 10 cm,

  in a fabric-type product (provided that these fibers are

  They still have, after heat treatment, the

  required physical properties mentioned above.

  in paragraphs (1) to (6). It goes without saying of course

  that, although it is advantageous to put the material

  slider preferably in a stabilized state (such as that obtained by oxidation), in the desired form (knitted, woven or felt) before carbonization, such a construction can be performed after carbonization if the module is less than about 380 GPa ( 55,000,000 psi) and preferably

  less than about 269 GPa (39,000,000 psi) for the manufacture

  machine cation. It goes without saying that the material

  carbonaceous can be formed from a film precursor.

  Degree of carbonization and / or graphitization

  does not seem to be a major factor in the performance

  the material as an electrode element in an electrical energy storage device, except that this degree must be sufficient to render the material sufficiently electrically conductive, and also sufficient to give the aforementioned physical and mechanical properties under the conditions of use indicated. Carbonaceous materials whose degree of carbonization is about 90%

  are said in the literature partially carbonized.

  The carbonaceous materials whose degree of carbonization is 91 to 98% are called in the literature carbonized materials, while the materials whose degree of

  carbonization and more than 98% are called graphitized.

  It has surprisingly been found that carbonaceous materials, whose degree of carbonization was 90 to 99%,

  did not give satisfactory results as

  electrodes, unless the carbonaceous material has

  the dimensional stability required during successive cycles of

  electrical charge and discharge. For example, graphite "RPG" and "GRAFOIL", although having the degree of

  carbonization, the electrical conductivity and the specific surface

  required properties do not have the physical properties required for Young's modulus and the ratio of

  in appearance, and therefore did not give satisfaction.

  According to the invention, a rechargeable electrical energy storage device can be prepared and

  reversible polarity by aligning at least one pair of electrodes

  trodes, made of the carbonaceous material described above, and its associated electron collector (which is electrically conductive) in a housing. This housing has a surface

  non-conductive interior and is impervious to moisture.

  The electrodes are immersed in a non-aqueous fluid (the water being present in a proportion of less than about 100 ppm) which 1 1 is contained in said housing. The fluid itself must be capable of forming, or must contain in solution, at least one ionizable metal salt. Each electrode is formed of the thermally treated carbonaceous material according to the present invention associated with an electron collector which is preferably insulated against contact with the

electrolyte fluid.

  We can build the storage device

  secondary electrical energy of the invention, without any

  reverse polarity, aligning the above-mentioned

  electrically conductive carbon fibers, such as a cloth, and its electron collector as a positive electrode alternating with a negative electrode which may be made of a metal, such as lithium, or a metal alloy, and dipping the electrodes in a substantially non-aqueous, fluid fluid which is itself

  capable of forming, or which contains, at least one metal salt

  ionizable soluble in solution to give electrolyte ions. In the construction of a preferred embodiment of the secondary electrical energy storage device of the present invention, conventional porous separators made of glass fibers, polymeric materials, or composites can be used and preferably used. of polymeric materials, to separate the positive and negative electrodes from one another. It is best to use a non-woven polypropylene sheet as a separator, since it has the desired degree of porosity and yet offers a winding path to prevent the carbon fibers from penetrating it, thus preventing a

  electrical short-circuit. Porous separators behave

  also, advantageously, as stiffeners

  or supports for the electrodes.

  Energy storage devices that are contained in fluid-tight housings are generally known in the art. Such housings can be suitably used in the present invention as long as the housing material is not electrically conductive and impermeable to gases and / or moisture (water or water vapor). Materials that have been found to be chemically compatible as housing materials include polyvinyl chloride, polyethylene, polypropylene,

  polytrifluorethylene and the perfluorinated polymers corre-

  a so-called "instant curing" (ISP) polymer, a rapidly solidifying mixture of reactive urethanes, the aramids, a metal coated with a non-conductive polymeric material such as an epoxy resin, for example the polymer sold under the commercial designation "DER" by the Company "The Dow Chemical Company", or the material sold under the trade name "DERAKANE" by the Company "The

  Dow Chemical Company ", of the material sold under the name

  "ZETABON" by the company "The Dow Chemical Company" and / or glass, or a metal oxide, a metal flower or a similar compound. Housing materials that have not been found suitable in the preferred composition of propylene carbonate include acrylic resins, polycarbonates and nylon. Acrylic resins crack and polycarbonates crack and, in addition, become extremely fragile,

  while nylon (with the exception of aramids) is chemically

responsive.

  A dwelling must not only be compatible, but also offer an absolute barrier, corresponding to less than 2.15 g of water per year and pwm2 (about 0.2 g of water per year per foot2), the transmission of water vapor since

  the external environment of housing. No thermo

  Currently known plastic alone provides this absolute barrier to moisture in a thickness that is usable for a battery housing. At present only metals, for example aluminum or mild steel, offer an absolute barrier to moisture in thicknesses corresponding to thin sheets. Aluminum foil having a thickness of more than 0.038 mm (0.0015 inches) has been shown to be substantially impermeable to water vapor transmission. It has also been shown that, laminated with other materials, an aluminum foil as thin as 0.009 mm (0.00035 inches) could provide sufficient protection against the transmission of water vapor. Suitable housings made of a metal-plastic laminate, a cathodically electrodeposited epoxy resin-coated metal (CED), or a metal bearing

  an inner lining of plastic or glass, filled with

  currently complying with the requirements of chemical compatibility and moisture screen formation. Most of the batteries and batteries that have been built to date have been tested either in a "dry box" with a water content of less than 5 ppm, a glass cell or a double-walled housing whose space The electrolyte fluid is preferably composed of a non-aqueous, chemically stable and non-conductive solvent for the salt (s). ) ionizable (s), the ionizable salt being dissolved in the solvent. As solvents, the compounds which are generally known in the art can be used such as, for example, compounds having oxygen, sulfur and / or nitrogen atoms bound to carbon atoms in an electrochemically non-reactive state. . Preferably, nitriles such as acetonitrile can be used; amides such as dimethylformamide; ethers such as tetrahydrofuran; sulfur compounds such as sulphite

  dy-ethyl and other compounds such as propylene carbonate.

  It must, of course, be understood that the solvent itself can be ionized

  under conditions of use sufficient to provide the

  in the solvent. Thus, the ionizable salt must be at least partially soluble and ionizable, either when it is dissolved and goes into solution in the solvent or by liquefaction. Although it is understood that slightly soluble salts are usable, it will be appreciated that the low concentration of these salts in solution may have an adverse effect on the speed of the charge and

of the electric shock.

  Ionizable salts which can be used in the practice of the invention are those taught in the prior art, and include the salts of the more active metals, such as, for example, the alkali metal salts, preferably lithium, of sodium or potassium, or mixtures thereof containing stable anions such as

  perchlorate anions (C104 =), tetrafluoroborate (BF4 =), hexa

  fluoroarsenate (AsF6 =), hexafluoroantimoniate (SbF6 =) or

hexafluorophosphate (PF6 =).

  The electrolyte (solvent and salt) must be substantially free of water, that is to say it must contain less than ppm of water, preferably less than 20 ppm water, or better still less than 10 ppm. ppm of water. Of course, the electrolyte can be prepared with a greater amount of water than the desired amount and dried, for example, over an activated zeolite 5A molecular sieve. Such agents can also be combined in the finished battery to guarantee the requirement of low water content is met. The electrolyte must also be such as to allow the ions (anions and cations) of the ion-sand salt to move freely in the solvent, as the electric charge and discharge potential brings the ions closer to and away from their ions. respective

(Electrodes).

  The electrode, when constructed as a fabric or sheet, has an electron collector that is conductively associated with at least one of the edges of the carbon fibers or sheet. The edge (s) is (are) preferably protected by a material used to isolate the collector and to protect it to a large extent from its contact with the fluid and with the ions of his electrolyte. The fluid or ions of the electrolyte must not, of course, act on the protective material. The current collector is in intimate contact with the carbon material of the electrode, at least along one of its edges and preferably on each of its four edges, when the carbonaceous material is in the form of a set such that a canvas, a sheet or a felt flat. It is also envisaged that the electrode may be constructed in other forms, for example, in the form of a cylindrical or tubular bundle of fibers, wires or yarns, the ends of which are provided with a current collector . It is also evident that an electrode in the form of a plane body of web, sheet or felt can be wound with a porous separator between the layers of the carbonaceous material, and with the opposite edges of the wound material connected to a current collector. Although copper metal has been used as a current collector, it is also possible to

  use any metal or alloy conducting the electri-

  tricity, such as for example silver, gold, platinum, cobalt, palladium, and their alloys. Similarly, although electroplating was used to fix a metal

  or a metal alloy to the carbonaceous material, it can be used

  other coating techniques (including the application of

  melting baths) or non-galvanic deposition methods as long as the edges or ends of the electrode, including most of the ends of the fibers at the edges of the carbonaceous material, are wetted by the metal to a sufficient extent to ensure contact

  electrical and a current path substantially weak.

  Collectors that are made of a non-noble metal, such as copper, nickel, silver or alloys of these same metals, must be protected from the electrolyte, and are therefore preferably coated with synthetic resinous material or an oxide, fluoride or similar compound which will not be attacked by the electrolyte or undergo appreciable degradation under

operating a battery.

  The electrodes of the present invention, made of the electrically conductive carbonaceous material and its current collector, can be used as positive electrodes in secondary energy storage devices. No appreciable damage is observed for the electrode itself or for the electrolyte, i.e. for the solvent and the ionizable salt, when carrying out repeated charges at a capacity of more than 150 coulombs per gram of active carbonaceous material, and deep discharges, that is to say more than 80% of the total electrode capacity, at charging and

discharge more or less large.

  Alternatively, the electrodes of the invention, made of electrically conductive carbonaceous material and its current collector, can also be used both as positive electrodes and as negative electrodes in an accumulator (secondary cell) with characteristics similar favorable operating

  to those described above.

  A surface area of at least 0.5 m 2 per gram and a low resistivity of less than 0.05 ohm / cm 2 of the carbonaceous material used for the electrode of the invention are desirable properties. Thus, a battery constructed with the carbon electrodes of the invention has an extremely low internal resistance and a very high corresponding coulometric efficiency, which

  is usually greater than 80%.

  During the boundary search period of the present invention, it was found that initial current densities, under load, of greater than 15.5 to 31 mA / cm 2 (1CO at 200 mA / in 2) could result in damage for

  the carbonaceous material of the electrode.

EXAMPLE 1

  A pair of electrodes each having an area of 71 cm 2 (11 in 2) was prepared from a "Panex (Trade Mark) PWB-6" web (fabric that had been heat treated at a temperature greater than 1000 ° C). by the manufacturer to make it conductive electricity) purchased from the Company "Stackpole Fibers Industry Company". This fabric was woven from a polyacrylonitrile precursor (PAN) in which the yarn was made from non-continuous filaments (short fibers) having an average length of about 5 cm (2 inches) and a diameter of 7 to 8 micrometers and an aspect ratio of about 700: 1. This canvas had been treated by the manufacturer after weaving. The edges of the thermally treated fabric were coated with copper by electrolytic deposition to form a current collector. We have

  welded wire to one end of the coated edges

  copper. Each of the four edges of each electrode (current collector and connecting wire) was coated with an amine curable epoxy resin, "DER (Trade Mark) 331", manufactured by The Dow Chemical Company, to isolate the metal from the corrosive effects of the electrolyte in

  the conditions of use. We plunged the pair of electro-

  in an electrolyte comprising a 15% solution of LiC104 in propylene carbonate contained in a polyvinyl chloride (PVC) housing. The electrodes were separated

  by a distance of less than 0.6 cm (0.25 inches). We have

  assigned to the assembly of the electrodes in the housing in a dry box. The housing was sealed while in the dry box, leaving the metal wires of the housing protruding. The water content of the thus assembled housing was less than 10 ppm. The fibers had a Young's modulus of about 230 GPa (33,000,000 psi) and a surface-to-weight ratio of 0.6 to 1.0 m 2 / g. It was determined that the total electrical capacitance of the active carbonaceous material of the electrode was about

C coulombs / g.

  The cell thus prepared was electrically charged to a maximum voltage of 5.3 volts, preventing the current density from exceeding 5.4 mA / cm 2 (35 milliamps per square inch) of electrode active area. The battery was electrically charged and discharged 1250 times over a period of 11 months and showed a coulometric efficiency of more than 90%, with a discharge capacity of more than 1%. We then removed the battery and examined each one

  electrodes in a microscope with magnification 1000.

  Insofar as they were measurable, the fibers had the same diameter as the fibers of the same batch that had not been used in the pile. The stack was reassembled and the tests continued in the same manner as described above. The battery has, to date, completed more than 2800 charge and discharge cycles over a period of 23 months without decreasing its coulometric efficiency, and

  still has a coulometric yield of more than 90%.

EXAMPLE 2

  Six electrodes similar to the electrodes of Example 1 were prepared and mounted in a three-cell unit such that each of the three pairs of electrodes

  was hermetically sealed in pockets (bags) of poly-

  ethylene separated. The electrodes were mounted in series. The three-cell unit was operated in the same manner as in Example 1, except that the voltage was about 16 volts. The initial idle voltage was about 13.5 volts. After 228 electric charge and discharge cycles, during which the discharge was performed to a depth of more than 78% of the total capacitance, the cells were removed and the electrodes removed from their pockets and examined.

  the fibers for signs of possible deterioration

  ration, that is to say scaling and dilation and excessive contractions of the fibers. This examination revealed no detectable variation in fiber diameter with respect to the fibers measured in the same batch of fabric that had not been

  used to prepare the electrode of this example.

  Measurements were made with a laser interferometer.

EXAMPLE 3

  Several flat sheets were cut from a woven fabric from a yarn of a substantially continuous monofilament precursor fiber obtained from petroleum pitch. The fibers were manufactured by The Union Carbide Company and sold under the

  trade name "Thornel" (registered trademark). The spun yarns

  eg precursor fibers, with an aspect ratio of 800: 1

  approximately, had been woven into a canvas and then treated with

  mically at a temperature of over 2000 C. Leaves

  planes each had an area of about 930 cm2 (1 foot2).

  The fibers had a Young's modulus of 315 GPa (45,000,000

  psi) and a surface area of about 1m2 / g after treatment.

  thermal energy. The copper-metal sheets were coated

  along their four edges so that all the fibers are electrically connected and form an electron collector frame. An insulated copper wire was attached to one of the collector edges, near an angle, by welding, and the solder joint and the copper collector were coated with the material sold by The Dow Chemical Company. Company "under the trademark" DERAKANE ", a trademark of a curable vinyl ester resin. The sheets of each pair were aligned parallel to each other with the wires welded at the opposite ends of the complementary edges, and were separated by a perforated fibrous nonwoven polypropylene composite sheet having a thickness of about 0.1 mm (5 millipouces). . A polyethylene bag (bag) having an area of about 930 cm 2 (1 ft 2) was used as the battery container. Three stacks were assembled in a dry box by placing a pair of the carbon fiber sheets and their separator in each of three pockets, and each bag was filled with about 500 grams of an electrolyte consisting of a 15% solution. by weight of LiC104 in propylene carbonate. The level of electrolyte in the pocket was determined so that 21 g of active fiber per

  electrode (the surface of the electrode exposed to the electrolyte).

  The rest of the carbon fibers of each electrode protruded from the solution or was covered by the chassis of

  resin "DERAKANE" (registered trademark) / metallic copper.

  The assembly of the batteries in a dry box made it possible to maintain the water content at less than 20 ppm of the electrolyte solution. Each pouch was welded while it was in the dry box, so as to allow the ends of the welded wires to pass through the weld joint at the opposite ends of the welded edge. The three cells thus prepared were placed in a transparent plastic box and the wires were connected in series. A certain amount of 5 A molecular sieve of activated zeolite (to absorb moisture) was added to the top of the cells, and the entire dry box was removed. The end wires of the two end plates of the series of three cells were connected to terminals through a cover of the box, and the cover was quickly sealed to the box. The assembly was charged to a potential of 15 to 16 volts, and with an intensity of 1.8 to 2 A, for 45 minutes. The device was then discharged into a 12-volt automotive headlamp consuming an average intensity of 2.0 to 2.5 A. The device was discharged at 90% of its capacity in 30 minutes. More than 850 times the electric charge and discharge cycles were performed. The stack was then disassembled and the fibers were examined under 1000 microscope magnification, and no detectable signs of expansion or deterioration under the effect of chipping were found. The device accepted an electrical charge and a deep discharge at 90% capacity for each cycle.

EXAMPLE 4

  A "PAN" fabric (precursor fiber) from the company "R.K. Textile, Ltd.", Heaton Moor, United Kingdom, has been obtained. This fabric was sold under the trade name "Panox" and consisted of a non-conductive carbon fiber having an aspect ratio of more than 250: 1 in the form of yarn and woven fabric, and believed to be not heated to a temperature of more than 400 C. This fabric was heat treated at a temperature of about 1000 C for a time sufficient to make it conductive electricity. The thermally treated fabric had a Young's modulus of 160 GPa (23,000,000 psi) and a specific surface area of about 1 m2 / g. Two fabric samples each 5 cm (2 inches) wide on one side and 26 cm 2 (4 inches 2) in this thermally treated fabric were cut, and the four edges of each metallic copper fabric were coated. to form a current collector for the electrode.

  angles of the current collector of each electrode.

  The solder and the copper current collector have been coated with an ester resin coating composition.

  vinylic "DERAKANE" (registered trademark). A sheet was

  the nonwoven polypropylene composite, "CELGARD (registered trademark) 5511", between the two electrodes, and introduced

  the electrodes in a pocket (envelope) of plastic material

  tick. This set was placed in a dry box in which the water content was maintained at less than 20 ppm of the electrolyte solution. A weight percent solution of LiC104 in a solution of propylene carbonate was used to fill the envelope until both

  electrodes are immersed in the electrolyte solution.

  The wires of each electrode were connected to a two-pole bipolar switch, one of whose terminals was

  connected to a voltage source of 5.3 volts.

  The other terminal was connected to an electrical resistance of ohms. The cell was discharged deep to more than% of its total charge and operated over 800 charge and discharge cycles with a coulometric efficiency of over 80%. The capacity of this cell, relative to the total weight of the electrode, represented

  about 70% of that of Example "PAN" (Example 1).

  It has been found that batteries constructed in accordance

  In accordance with the present invention, there was an internal resistance which was, on average, less than 0.41 ohm / m 2 (0.038 ohm per square foot) of the useful area of the electrode in a six-electrode cell. This value, originally measured at less than 1 ohm, included the connection wires to the charging device, approximately 6 meters long. By measuring the resistance of the connecting wires and then remeasuring the total resistance of the device from the load, it was calculated that the resistance of the accumulator

* (secondary battery) itself was 0.41 ohm / m2 (0.0038 ohm / ft2).

  Confirmation of the data of the above examples was made by a collaborator in a two-electrode stack made of Thornel cloth, VCB-45, having a Young's modulus of 315 GPa (45,000,000 psi), one surface specificity of 1 m2 / g and an aspect ratio of more than 10,000: 1, in

  which each fabric had a dimension of 15.2 cm x 15.2 cm.

  Copper edges were placed around each of the four

  hang the canvases to form the current collector.

  The current collector of "DERAKANE" (registered trademark) 470-36 "was then coated, the edges of the current collector were approximately 2.6 cm wide, leaving areas of active carbon material about 10 cm long. x 10 cm The useful surface of 100 cm2 of each electrode contained about

6 grams of carbon fiber.

  The electrodes were separated by placing one of the electrodes in a heat-sealed bag of polypropylene film

  microporous "Celgard" (registered trademark) 5511.

  The assembly formed by the electrodes and the separator was placed in a polyethylene bag, this bag was filled with a dry electrolyte of 15% by weight LiC104 in propylene carbonate (about 100 cm3) and compressed. the assembly between two pressure plates with plastic edges that supported the 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 too close to each other by compression. In subsequent tests, a 10 cm x 10 cm spacer plate was introduced between the plates of

  pressure to compress more closely together -

  combination formed by the electrodes and the separator. This lowered the battery resistance from about 0.9 ohm to about

0.7 ohm.

  The discharge data was taken at various discharge rates for two of the above described configurations of the stack. In one case (0.9 ohm cell), the separation of the electrodes was limited to about 4 mm by the epoxy resin coating of the current collector. In the other case (0.7 ohm battery), the electrodes were compressed against each other in the center, with only the porous polypropylene separator between them (minus

of 1 mm).

  In the diagram of Figure 1, the curves show the terminal voltage as a function of the discharge, in coulombs per gram of fiber, for the 0.9 ohm stack with several discharge rates ranging from 6 hours to 3 hours. 4 hours. These discharges correspond to what we

  calls a first step (2 volts cut-off voltage).

  Assuming that the total capacitance corresponding to the first step is 180 coulombs per gram for the 2 volts cut-off voltage, the x-axis values can be replaced by "discharge percentage", 180 coulombs / g

  equivalent to "100% discharge".

  The total energy recovered at a corresponding speed

  at 3 hours of discharge, at constant load, is almost the same as for the speed corresponding to 6 hours. At the fast discharge rate of 3/4 of an hour, deficiencies are created and occur under the effect of the resistance of the battery and the polarization of the electrodes. The electrode current densities corresponding to these discharge rates are: Speed Current Density (in hours) Constant Load Average (in mA / cm2)

6 0.5

3 1.0

1.5 2.0

0.75 4.0

  The number of "coulombs per gram of fiber" is based on the weight of the active carbonaceous material of a

electrode only.

  The curves in Figure 2 show the results obtained with the 0.7 ohm stack. It is obvious that more energy is available for the battery with the lowest resistance. The curves in Figure 3 compare the two batteries at the speed of

  highest discharge (3/4 of an hour).

  A lithium metal reference electrode was introduced into the cell to determine which electrode was polarizing. The voltage drops between each electrode and the reference electrode were determined during

  charge and discharge and when opening the circuit.

  At the opening of the circuit, the voltages between the negative electrode and the reference electrode were generally less than 100 mV and changed only slightly with time. The voltage, measured between the positive electrode and the reference electrode, varied with time, decreasing after each charge and increasing

after each discharge.

  The maximum power capabilities of a battery cell at different stages of the charge were determined by pulsing the cell at loads that gave terminal voltages representing half of the no-load voltage. The "pulses" were 10 seconds long and

  the power was calculated on average over these 10 seconds.

  The element was first loaded at 344 coulombs per gram of active carbonaceous material in an electrode. We took this as a 100% state of charge. The maximum current drawn from the 10 cm x 10 cm electrode element for a 100% charge state was 2.5 to 3.0 amperes. Subsequent power determinations were made at 247 coulombs per gram (72% charge) and 224 coulombs per gram (65% charge). The curve of Figure 4 shows

The obtained results.

  The maximum power drawn from this element was about 0.48 watts per gram of fiber at a 100% charge state, and dropped to about 0.31 watts per gram of fiber at a 72% charge state. The power capacity drops quickly after that as the voltage drops and the polarization begins. A pulsed discharge of more than 10 seconds does not necessarily reduce much the final power. The curve in Figure 5 shows the voltage trace of a power discharge at a maximum speed of 40 seconds. After the first 10 seconds, the fall

voltage is low.

EXAMPLE 5

  A three-cell battery was constructed from twelve plates, four per cell, of fiber

  "Thornel" brand described in Example 3. Each plate had a

  approximately 30.5 cm x 30.5 cm or 930 cm2 (12 inches x 12 inches) or

  144 inches 2), and had been coated with copper on each side.

  Copper plating along the edges was coated with "DERAKANE" (Trade Mark), the trade name for a curable vinyl ester resin. The plates had an active area of about 852 cm2 (132 inches). The four plates of each element were assembled with a lightweight polypropylene scrim separator perforated between each plate. The pairs of plates of each element were connected in parallel so that in charge-discharge the plates were alternately +, -, +, -,. The four plates

  and their separators were contained in a bag of poly-

  propylene, 33 cm x 33 cm (13 inches x 13 inches) which contained approximately 600 cc of an electrolyte solution

  of 15% by weight of LiC104 in propylene carbonate.

  This level of electrolyte in each bag was sufficient to give about 37 grams of active fiber per electrode plate. The battery was initially charged over a period of 1000 minutes at a capacity of 7.9 amperes / hour at a potential of 14-16 volts. The element was then discharged over a period of 200 minutes in a 12-volt automotive headlamp with an average capacity of 6.2 amps, representing a discharge depth of more than 1%. Charging was done in 800 minutes. An average coulometric yield of about 90% was observed during repeated charge and discharge cycles.

Claims (22)

  An electrode for use in a secondary electrical energy storage device, comprising an electrode body made of an electrically conductive carbonaceous material, having a skeletal orientation, at least at or near the surface, and a current collector electrically associated with this electrode, characterized in that said carbonaceous material has a Young's modulus of more than 6.9 GPa (1,000,000 psi) and undergoes a variation of its physical dimensions of less than 5% during repeated charge cycles and electric discharge.   2. Electrode according to claim 1, characterized in that the set of carbonaceous material has a Young's modulus of 6.9 GPa to 380 GPa (1,000,000 to 55,000,000 psi) and that the carbonaceous material derives from 'a precursor material   which is a polyacrylonitrile or a pitch.   3. Electrode according to claim 2, characterized in that the carbonaceous material has a Young's modulus of 69 GPa   at 380 GPa (10,000,000 to 55,000,000 psi).   4. Electrode according to claim 2, characterized in that the carbonaceous material has a Young's modulus of   138 GPa to 311 GPa (20,000,000 to 45,000,000 psi).   Electrode according to one of claims 1 to 4,   characterized by the fact that the carbonaceous material has a   specific surface area from 0.1 to 50 m2 / g.   6. Electrode according to claim 5, characterized in that the carbonaceous material has a specific surface area from 0.1 to 10 m 2 / g.   7. Electrode according to claim 6, characterized in that the carbonaceous material has a specific surface area from 0.1 to 5 m2 / g.   Electrode according to one of claims 1 to 7,   characterized by the fact that the carbonaceous material has a ratio   aspect ratio (1 / d) or an equivalent ratio of more than 100 to 1.   9. Electrode according to one of claims 1 to 8,   characterized by the fact that the carbonaceous material has a   autonomous structural grit in dimensions ranging from   6.45 cm2 to more than 930 cm2 (1 to more than 144 inches2).   10. Electrode according to one of claims 1 to 9,   characterized in that the carbonaceous material is in the form of a web, a film, a paper, or a   sheet of paper type or felt type, or other sets.   11. Electrode according to one of claims 1 to 9,   characterized in that the carbonaceous material is in the form of a web or felt-like web or sheet comprising a set of at least one tow of continuous filaments, or short fibers of which the length is 1 to cm (at 4 inches).   Electrode according to one of claims 1 to 9,   characterized in that the carbonaceous material is a woven or knitted fabric made of a set of continuous filament tow, or   short fibers having a length of 1 to 10 cm (at 4 inches).   Electrode according to one of claims 1 to 9,   characterized in that the carbonaceous material is in the form of a web or felt-like web or sheet formed from a tow of continuous filaments or short fibers.   Electrode according to one of claims 1 to 13,   characterized by the fact that the electron collector is an electrically conductive metal which is plated on at least one of the edges of the carbonaceous material, and that said plated edge is coated with a non-conductive and non-reactive protective material.   15. Electrode according to one of claims 1 to 14,   characterized in that the carbonaceous material is capable of supporting more than 100 electric discharge cycles at a discharge depth of more than 70% and with a coulometric yield of more than 70% without any appreciable damage   for the structural integrity of the material.   16. Electrical energy storage device se-   condenser comprising a housing having a non-electrically conductive inner surface and an outer surface or a moisture impermeable laminate body and having at least one battery disposed in said housing, each battery   comprising a pair of electrically conductive electrodes   which are electrically insulated from mutual contact, said housing containing a substantially non-aqueous electrolyte,   characterized in that at least one of the electrodes of each   that battery is an electrode as defined in one of the Claims 1 to 15   17. Device according to claim 16, characterized in that the electrolyte comprises a non-aqueous solvent,   chemically stable and non-conductive and an ionizable salt dis- under in this solvent.   18. Device according to one of claims 16 and   17, characterized in that the solvent of the electrolyte is   selected from compounds having oxygen atoms,   and / or nitrogen which are bonded to carbon atoms in an electrochemically non-reactive state, and that said salt is an alkali metal salt.   19. Device according to claim 18, characterized in that the solvent of the electrolyte is propylene carbonate and the alkali metal salt is the perchlorate of lithium.   20. A secondary electrical energy storage device comprising a housing having a non-electrically conductive inner surface and an exterior surface or moisture impermeable laminate and having at least one battery disposed in said housing, each cell comprising minus a pair of electrically conductive electrodes that are electrically isolated from a contact   mutually, said housing containing a sensitive electrolyte-   non-aqueous, characterized in that each of the electrodes of each cell is an electrode as defined   in one of claims 1 to 15.   21. Device according to claim 20, characterized   the fact that each electrode of a battery has the freedom of choice of its polarity upon recharging, and the property of being polarized in the opposite direction, partially and / or totally without inconvenience.   22. Device according to one of the referendications 20 and 21, characterized in that it has a power density   of more than 0.31 watt per gram of   active positive bone for a pulse period of 40 sec- condes at full load.