DD229539A5 - SEKUNDAERELECTRO ENERGY STORAGE DEVICE AND ELECTRODE DAFUER - Google Patents

Abstract

The invention relates to the use of a carbonaceous material in conjunction with a collecting electrode as an electrode for secondary electric energy storage devices. The aim and the object of the invention are to design the electrodes of a material chosen as being suitable in such a way that damage to the electrodes due to repeated electrical charging and discharging cycles is largely ruled out and thus the life of the electrodes is prolonged. The electrode consists of an electrode body of an electrically conductive carbonaceous material having a skeletal orientation at least at or near the surface and a current collector electrically connected thereto, the carbonaceous material having an elastic modulus greater than 6.9 GPa and a physically dimensional Change of less than 5% during repeated electrical charge and discharge cycles. At least one of the electrodes described is part of each cell housed in a housing of a secondary electric energy storage device. Fig. 1

Description

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Field of application of the invention

The invention relates to the use of a carbonaceous material in conjunction with a collecting electrode as an electrode for secondary electric energy storage devices. The carbonaceous material of the electrode is stable in the presence of an electrolyte system containing anions such as perchlorates, hexafluororates and the like under ambient or normal operating temperatures when using the electrode.

Characteristic of the known technical solutions

Various patents and technical literature describe electrical energy storage devices using a carbonaceous material such as carbon or graphite as the electrode material. Of course, one of the earliest of these devices is the Laclanche battery of 1866, wherein carbon in a ZN / NH ₄ Cl / MnO ₂ primary battery was used as the collector electrode. Since then, carbon has been widely used as a component of the electrode in primary batteries, primary fuel cells, secondary fuel cells, secondary batteries and capacitors. The function of the carbon or graphite in these above-mentioned devices was primarily that of a current collector or as a reactive material to form new compounds with fluorine having different structures and properties than the original carbon / graphite, and more recently as semiconductor materials , which form salts with ions of the electrolyte. These prior art devices can be subdivided as follows:

Primary batteries as described in Colman et al., U.S. Patent No. 2,597,451, Panasonic Lithium Battery Literature and U.S. Patent Nos. 4,271,242, 3,700,502 and 4,224,389; Fuel cells as disclosed in Japanese Publication No. 54-082043; Secondary fuel cells with limited reloadability, as described in Dey et al, US Pat. No. 4,073,025, a rechargeable fuel cell using activated (large surface area) graphite; Rechargeable secondary batteries (accumulators) as described in Hart, US Patent 4251568 using graphite as a current collector and in Bennion, US Patent 3844837 and 4009323 and capacitors as in Bu'therus et al, US Patent 3,700,975 or DE-PS 3231243 using high surface area carbon (graphite). Some of these devices also use ionizable salts that are dissolved in a non-conductive solvent.

The carbonaceous materials described in the patents and in the literature are materials that are graphitized and carbonated until the materials become electrically conductive. These materials are derived from polyacetylenes, polyphenylene polyacrylonitriles and petrol pitch heated to "carbonize and / or graphitize" the precursor material to give it some degree of electrical conductivity Techniques used are graphites such as RPG (pyrolytic graphite reinforced), R-1 nuclear reactor grade graphite, PGCP (pyrolytic graphite carbon paper) and a material containing expanded and densified graphite and the like.

The doping of similar carbonaceous materials has also been described in Chemical and Engineering News, Vol.60 No. 16, p.29 to 33.19.04.1982, "Conducting Polymers R & D Continues to Grow"; Journal Electrochem Society, Electrochemical Science, 118 , No. 12, pp. 1886-1890, December 1971; and Chemical and Engineering News, 59, No. 41, p.34 to 35, 12, 110, 1981, "Polymer Cell Offers More Power, Less Weight".

The problems encountered with these cells are that they do not have a long life since the electrode made of this carbonaceous material is susceptible to degradation when subjected to repeated electrical charging and discharging cycles.

For example, U.S. Patent No. 3,844,837 (Bennion et al) describes a battery using nuclear grade graphite impregnated with splinters of LiO ₂ as the positive electrode and copper as the negative electrode in a LiCF ₃ SO ₃ dimethyl sulfite (DMSU) electrolyte. The graphite electrode was made from grade R-1 graphite nuclear and was described as flaky after nine cycles of electrical charging and discharging. The patentees also tested graphite fabric and found it unsatisfactory. Various other graphites were used with similarly unsatisfactory results, with the best results being obtained with pyrolytic graphite, which failed after 33 cycles. Dey et al, using high surface area carbon or graphite material in whose pores the chemical reaction takes place, is generally believed to have low conductivity because of the lack of continuity of the carbon surface. Furthermore, it is believed that these materials do not maintain the dimensional stability and structural integrity necessary for the reversible formation of carbon complexes necessary for the long rechargeable cycle life of secondary batteries.

Experiments conducted in the course of development of the present invention included the use of a material containing expanded and densified graphite which failed at the first electrical charge and also the use of RPG (Super Temp) graphite electrodes which also failed. It was found that an amount of more than 20% of the positive electrode of RPG graphite in the form of flakes, chips and powder was lost after only 27 electrical charging and discharging cycles.

It is noted that the prior art has found the degradation and damage of the electrode as a result of expansion and contraction of the electrode body, and that this expansion and shrinkage grows with each electrical charge and discharge cycle, which distorts the graphite platelets due to stress from spreading and shrinking. In carrying out these experiments in the course of development of the present invention, it was confirmed that this flaking of the graphite flakes occurs when the above-mentioned graphite materials are repeatedly subjected to electric charging and discharging cycles.

Object of the invention

The object of the invention is to extend the life of secondary electric energy storage device, in particular the electrodes used therein.

Explanation of the essence of the invention

The invention is based on the object consisting of a suitably chosen as selected material electrodes in such a way that damage to the electrodes due to repeated electrical charging and discharge cycles is largely excluded

 In a first aspect, the present invention provides an electrode for use in a secondary

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An electro-energy storage device comprising an electrode body of electrically conductive carbonaceous material having a skeletal orientation at least at or near the surface and a current collector electrically connected thereto, said carbonaceous material having a modulus of elasticity greater than 6.9GPa ( 1,000,000 psi) and a physical dimensional change of less than 5% during repeated electrical charging and discharging cycles.

In another aspect, the invention provides a secondary electro-energy storage device comprising a housing having an electrically non-conductive inner surface and a moisture-impervious outer surface or laminar body and at least one cell mounted within that housing, each cell being at least one A pair of electrically conductive electrodes which are electrically insulated from each other, wherein the housing contains a substantially non-aqueous electrolyte, wherein at least one of the electrodes of each cell is an electrode according to the invention.

In a further aspect, the invention resides in a secondary electro-energy storage device consisting of a housing having an electrically nonconductive inner surface and a moisture-impermeable outer surface or lamellar body and having at least one cell mounted in that housing, each one Cell consists of at least one pair of electrically conductive electrodes, which are electrically insulated from each other, wherein the housing contains a substantially non-aqueous electrolyte, wherein each of the electrodes of each cell is an electrode, as claimed in the items 2 or 3, and wherein each of the electrodes has the freedom of choice of polarity in recharging and the ability to be partially and / or totally polarized without damage.

The electrodes may be separated by a distance or by a non-electrically conductive, ion-permeable material.

Preferably, the electrically conductive carbonaceous material of the electrode should have the following physical property criteria:

(1) Young's modulus greater than 6.9GPa (1,000,000 psi), preferably 69GPa (10,000,000 psi) to 380 GPa (55,000,000 psi), more preferably 138 to 311 GPa (20,000,000 to 45,000,000 psi) ,

(2) An aspect ratio greater than 100: 1. The aspect ratio is defined herein as the ratio of length to diameter l / d of a fibrous strand or strand of carbonaceous material or as the ratio of length to depth when the carbonaceous material is planar Surface is formed.

(3) The structural and mechanical integrity of the carbonaceous material, in whatever form it is processed (woven, knitted or unwoven, from continuous thread or staple fibers or a film), must be such as to limit the presence of a carrier, such as e.g. As a press plate (flat sheets or mesh) is not required to keep the carbonaceous material in the desired surface or plate-like shapes when it undergoes at least 100 charging / discharging cycles.

(4) A surface area of at least 0.1 m ² / g but less than one better bonds with activated absorbent carbon less than 50m ² / g, preferably less than 10m ² / and more preferably less than 5m ² / g.

(5) Enough integrity of the carbonaceous material form to enable the carbonaceous material to retain its plate-like or sheet-like shape when larger than 2.5 cm ² (1 inch ² ) to greater than 930 cm ² ( 144inch ² ), without a support other than the metallic pantograph frame forming the edge portion of the electrode.

(6) The secondary electric energy storage device to which the electrode of the invention is applied should be substantially anhydrous to the amount of less than 100 ppm. Preferably, the water content should be less than 20ppm, and more preferably less than 10ppm. The device of the invention may be operated with a water content of up to 300 ppm, but will then have an approximately reduced cycle life. Furthermore, it should be understood that if the water content level becomes troublesome, the device may be disassembled, dried and reassembled without significant damage to its continued operability.

(7) The carbonaceous material of an electrode should be able to withstand more than 100 charging and discharging electric cycles without substantial damage to the carbonaceous material peeling. Preferably, no significant damage should occur after more than 500 electrical charge and discharge cycles, with a discharge capacity greater than 150 coulombs per gram of carbonaceous material of an electrode.

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

(9) The carbonaceous material of the electrode should be capable of withstanding high electric discharges of more than 70% of the electric charge capacity for at least 100 cycles of electric charge and discharge, and more preferably more than 80% for more than 500 electric charge and discharge cycles.

Accordingly, the carbonaceous material of an electrode having the above-described physical properties should preferably have electric 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 coulometric efficiency of more than 70% without im substantial irreversible change in dimensions (dimensional change of less than about 5%) can withstand.

Usually, the carbonaceous material is obtained by heating a precursor material to a temperature above 85O ⁰ C until it is electrically conductive. Carbonaceous precursor starting materials that can form the electrically conductive oriented portion of the plastic-containing material electrode can be formed from pitch (petroleum or coal tar), polyacetylene, polyacrylonitrile, polyphenylene, and the like. The carbonaceous precursor starting material should have skeletal orientation to some extent, ie, many of these materials have either a substantial content of aligned benzen-like structural portions or portions which upon heating can be converted to benzene-like or equivalent skeletal orientation at or near the surface because of Skeletal orientation of the starting material.

Exemplary of preferred carbonaceous precursor materials that exhibit this skeletal orientation on heating are microstructure of multistrand filaments or fibers made from petrol pitch or polyacrylonitrile. Such multiple or

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Thread strands or fibers are easily processed into threads or yarns, which are then processed into a fabric-like product. One technique for making suitable single filament fibers is disclosed in U.S. Patent No. 4,005,183 where the fibers are made into a yarn which is then woven into a fabric. The tissue temperature is then subjected, usually about 1 000 ⁰ C, which is sufficient to carbonize the tissue to make the carbonaceous material is electrically conductive and so the material having the physical properties described here (in (1) to 6). Such a fabric, in conjunction with a collecting electrode, is particularly suitable for use as an electrode in the secondary electric energy storage device of the present invention.

Preferably, the carbonaceous precursor material is in the form of a continuous hair fiber, a filament (s) formed of continuous filaments or discontinuous fiber strand (yarn) which can be made into a structure such as woven, unwoven or knitted structure, or the staple fibers can be piled up on their own to form a fabric, a paper-like or felt-like planar part. However, acceptable results are obtained when yarns of short fibers of 1 to 10 cm in length are woven into a fabric-like product (provided that the short fibers still have the required physical properties mentioned in (1) to (6) above) have, if they are heat treated). It will be understood that, although it is advantageous to bring the precursor material preferably in a stabilized state (as obtained by oxidation) into the desired shape (knit, woven or felted) from the carbonation, this embodiment also applies after carbonation can be made when the modulus of elasticity is below about 380GPa (55,000,000 psi), and preferably below about 269GPa (39,000,000 psi) for bulk processing. It is understood that the carbonaceous material can be formed from a film precursor.

The degree of carbonation and / or graphitization does not appear to be a factor to be controlled in the operation of the material as an electrode element in the electrical storage device, except that it must be sufficient to render the material sufficiently electrically conductive and sufficient to provide the above-mentioned physical mechanical properties under the specified conditions of use. Carbonaceous materials with about 90% carbonization are referred to in the literature as partially carbonated. Carbon-containing materials with 91 to 98% carbonization are referred to in the literature as carbonized material, while materials with a carbonization of more than 98% are referred to as graphitized. It has surprisingly been found that carbonaceous materials with a degree of carbonation of 90 to 99% failed as electrode materials when the carbonaceous material does not have the requisite dimensional stability during electrical charging and discharging cycles. For example, RPG graphite and a material containing expanded and densified graphite do not have the required physical properties of modulus of elasticity and aspect ratio, and therefore fail even though they have the required degree of carbonation, electrical conductivity and surface area. According to the invention, a rechargeable and polarity reversible electric storage device can be manufactured by aligning at least one pair of collecting electrodes made of the above-described carbonaceous material and the corresponding collecting electrode (which is electrically conductive) in a housing. The housing has a non-conductive interior surface and is impermeable to moisture. The electrodes are immersed in a non-aqueous liquid (with water present in an amount of less than about 100 ppm) contained in the housing. The liquid itself must be able to form an ionizable metal salt or contains dissolved therein at least one ionizable metal salt. Each electrode is made of the carbonaceous heat-treated material of the present invention connected to a collecting electrode which is preferably insulated from contact with the electrolyte liquid.

The secondary electric energy storage device according to the invention can be manufactured without the possibility of reversing the polarity by aligning the above-mentioned electrically conductive carbonaceous fiber structure, e.g. As a fabric and its collecting electrode as a positive electrode alternating with a negative electrode, which may be formed of a metal such as lithium or a metal alloy and immersing the electrodes in a substantially non-aqueous liquid, wherein the liquid itself form at least one ionizable soluble metal salt or at least one ionizable soluble metal salt dissolved therein to provide electrolyte ions.

In producing a preferred embodiment of the secondary electric energy storage device of the present invention, conventional porous separators made of fiberglass, polymer materials or composite polymer materials may be used, and are preferably used to separate the positive and negative electrodes from each other. Most preferably, a nonwoven polypropylene sheet is used as a separator because it has the desired degree of porosity yet has a sufficiently entangled web to prevent carbonaceous fibers from penetrating it, thereby preventing shorting. (Advantageously, the porous separators also serve as reinforcement or support for the electrodes.)

Energy storage devices contained in liquid tight housings are well known in the art. Such housings may be suitably employed in the present invention as long as the housing material is electrically nonconductive and impermeable to gases and / or moisture (water or water vapor). The materials found to be chemically compatible as the housing material include polyvinyl chloride, polyethylene, polypropylene, polytrifluoroethylene and related perfluorinated polymers, instant cured polymers (ISP), a fast-setting reactive urethane blend, the aramids, a metal coated with a non-conductive polymeric material such as an epoxy resin and / or glass or a metal oxide, fluoride or the like.

Housing materials found to be unsuitable in the preferred propylene carbonate system include acrylic, polycarbonate, and nylon. Acrylic resin derivatives get hairline cracks and polycarbonates get both hairline cracks and are also extremely brittle, while nylon (except the aramids) is chemically reactive.

Also, to be compatible, the housing material must also have an absolute barrier of less than 0.02 grams H ₂ O / yr / ft ² (0.2 grams H ₂ O / yr / fr ² ) versus the permeability of water vapor from the outside environment represent the housing. No currently known thermoplastic material alone provides this absolute barrier to moisture at a thickness suitable for a battery case. Currently only metals, z. As aluminum or mild steel an absolute barrier against moisture in film thickness. Aluminum foils greater than 0.038 mm (0.0015 inch) thick were substantially impermeable to water vapor. It has also been shown that aluminum foil, which is only 0.009 mm (0.00035 inch) thick, when coated on other materials. a corresponding protection aßaen Wassfirriamnfnfurnhlässinkfiit «creates

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Metal-plastic laminate housings, CED epoxy-coated metal (cathodic electroplated), or metal with an inner plastic or glass insert currently meet the requirements for both chemical compatibility and moisture barrier capability. Most of the cells and batteries produced to date have either been placed in a protective chamber with an H ₂ O content of less than 5 ppm, a glass cell, or a double-walled housing in which the gap between the walls with an activated molecular sieve, e.g. B. 5 A zeolite, filled, tested. The electrolyte liquid is preferably a nonconductive, chemically stable, non-aqueous ionizable salt solvent in which the ionizable salt is dissolved in the solvent. It is possible to use as solvents the compounds which are well known in the art, such as e.g. B. Compounds containing oxygen, sulfur and / or nitrogen atoms bonded to carbon atoms in an electrochemically non-reactive state. Preference is given to using nitriles, such as acetonitrile; Amides such as dimethylformamide; Ethers, such as tetrahydrofuran; Sulfur compounds such as dimethylsulfite; and other compounds such as propylene carbonate. It will of course be understood that the solvent itself may be sufficiently ionizable under the conditions of use to provide the necessary ions in the solvent. Therefore, the ionizable salt must be at least partially soluble and ionizable, either when it is dissolved and goes into the solvent or liquefied. Although it is to be understood that sparingly soluble salts are applicable, it will be appreciated that the low concentration of these salts in solution may adversely affect the rate of electrical charge and discharge.

Ionizable salts that can be used in the practice of the invention are those taught in the art and include salts of the more active metals, such as, e.g. The alkali salts, preferably of lithium, sodium or potassium or mixtures thereof, the stable anions such as perchlorate (CIO ₄ -), tetrafluororbotate (BF ₄ -), hexafluoroarsenate (AsF ₆ -), hexafluoroantimonate (SbF ₆ -) or Hexafluorophosphate (PF ₆ -) included.

The electrolyte (solvent and kit) must be substantially anhydrous, i. it should contain less than 100ppm of water, preferably less than 20ppm of water, and most preferably less than 10ppm of water. Of course, the electrolyte may be composed to have more than the desired amount of water and to be dried, e.g. B. on activated zeolite 5 A molecular sieves. Such means may also be mixed into the finished battery to ensure that the low water content requirement is obtained. The electrolyte should also be such that ions (anions and cations) of the ionizable salt are free to move through the solvent as the electrical potential of charge and discharge moves the ions to and from their respective poles (electrodes).

The electrode, when formed as a web or sheet, includes a collecting electrode conductively connected to at least one of the edges of the carbonaceous fibers or the sheet. the edge (s) is preferably further protected by a material to insulate the collector and substantially protect the collecting electrode from contact with the liquid and its electrolyte ions. The protective material must of course be unaffected by the liquid or electrolyte ions.

The current collector is in close association with the carbonaceous material of the electrode along at least one edge, and preferably at all four edges, when the carbonaceous material is in the form of an assembly such as a planar fabric, sheet or felt. It is also conceivable that the electrode may be formed in other shapes, such as in the form of a cylindrical or tubular bundle of fibers, threads or yarns in which the ends of the bundle are provided with a current collector. It will also be understood that an electrode in the form of a planar body of fabric, sheet or felt may be rolled up with a porous separator between the layers of carbonaceous material such that the opposite edges of the coiled material are bonded to a current collector. Although copper has been used as a current collector, any electrically conductive metal or alloy may be used, such as a metal substrate. As silver, gold, platinum, cobalt, palladium and alloys thereof. Likewise, although electroplating has been used, bonding of a metal or metal alloy to the carbonaceous material, any other coating technique (including melt applications) or electroless deposition methods may be used as long as the edges or ends of the electrode including the majority of the fiber ends at the edges of the carbonaceous material can be wetted by the metal to an extent sufficient to provide substantially low resistance electrical contact and current path.

Consumers made of a non-noble metal such as copper, nickel, silver or alloys of these metals must be previously protected from the electrolyte and therefore are preferably coated with a synthetic resinous material or an oxide, fluoride or the like that is not attacked by the electrolyte or undergoes any substantial degradation reaction in the operating conditions of the cell.

Electrodes of the present invention made of the electrically conductive carbonaceous material and its current collector can be used as a positive electrode in a secondary energy storage device. Significant damage to the electrode itself or to the electrolyte, d. H. the solvent or ionizable salt is not observed when repeating charges at a capacity greater than 150 coulombs per gram of active carbonaceous material and discharges greater than 80% of the total capacity of the electrode at fast or slow charge / discharge rates. Discharge is subjected.

Alternatively, the electrodes of the invention made of the electrically conductive carbonaceous material and its current collector can also be used both as positive and as negative electrodes in a secondary battery having similar favorable operating characteristics as described herein. A surface area of at least 0.5m ² / g and a low resistivity of less than 0.05 ohm / cm of the carbonaceous material used for the electrode of the invention are desirable properties. Therefore, a battery made with electrodes according to the invention with the plastic-containing material has an extremely low internal resistance and a very high corresponding coulometric efficiency, which is usually greater than 80%.

During the research period beyond the limits of the present invention, it has been found that upon charge initial current densities in excess of 15.5 to 31 mA / cm ² (100 to 200 mA / in ² ) can result in damage to the carbonaceous material of the electrode.

embodiments

The invention will be explained in more detail below by exemplary embodiments. In the accompanying drawing: Fig. 1: the graph of terminal voltage vs. discharge for an O, 90hm cell at various

Discharge rates; Fig. 2 is a graph of terminal voltage vs. discharge for an O, 70hm cell at various discharge rates;

Fig. 3: the comparison of a 0.7 ohm cell with a 0.9 ohm cell for a discharge rate of 45 minutes; FIG. 4 is a graph showing the maximum power of a battery cell against the state of the charge and FIG. the graphical representation of the voltage curve of a 40-second discharge with maximum power. In a first embodiment, a pair of electrodes, each with an area of 71 cm ² (11 in ² ), were made of a PWB-6 fabric (a fabric that was heat treated at a temperature above 1000 ^° C., which made the fabric electroconductive, The fabric was woven from a polyacrylonitrile (PAN) precursor in which the yarn is made of non-continuous fibers (staple fibers) having an average length of about 5cm (2 inches) and a diameter of 7 to 8 / xm and an aspect ratio of The fabric was heat treated after weaving The edges of the heat treated fabric were electroplated with copper to create a current collector A wire was soldered to one end of the copper coated edges. Current collectors and line connectors) were coated with a curable amine epoxy resin to protect the metal from the corrosive effects of the electrolyte under use isolate conditions. The pair of electrodes were immersed in an electrolyte consisting of a 15% solution of LiCIO ₄ in propylene carbonate contained in a polyvinyl chloride (PVC) housing. The electrodes were less than 0.6 cm (0.25 inches) apart. The installation of the electrodes in the housing was carried out in a protective chamber. The housing was sealed while it was in the protective chamber with the wires extending from the housing. The water content in the assembled housing was less than 10 ppm. The fibers had a modulus of elasticity of about 230GPa (33000000 psi) and an area to weight ratio of 0.6 to 1.0 m ² / g. The total electrical capacitance of the active carbonaceous material of the electrode was determined to be 250Coulomb / g.

The cell thus prepared was electrically charged with a maximum voltage of 5.3VoIt, the current being limited to not exceed 5.4mA / cm ² (35mA / inch ² ) electrode surface area. The cell was electrically charged and discharged over a period of 11 months in 1,250 cycles and exhibited a coulometric efficiency of greater than 90%, with a discharge capacity greater than 85%. The cell was then disassembled, and the fibers from each tissue electrode were examined under a microscope at 10,000x magnification. As far as it was measurable, the fibers had the same diameter as the fibers of the same delivery that had not been used in the cell. The cell was reassembled and testing was continued in the same manner as previously described. So far, the cell has completed over 2,800 charge and discharge cycles over a 23-month period, with no reduction in coulometric efficiency. It still has a coulometric efficiency of more than 90%. In a second embodiment, six electrodes, similar to the electrodes of Example 1, were prepared and connected in a three-cell unit such that each of the three pairs of electrodes was terminated in separate polyethylene compartments (pockets). The electrodes were connected in series. The tri-cell unit was operated in the same manner as in Example 1 except that the voltage was about 16 volts. The starting voltage of the open circuit was about 13.5 volts. After 228 electrical charge and discharge cycles during which the discharge was performed at a high discharge of greater than 78% of the total capacitance, the cells were disassembled. The electrodes were removed from their compartments and the fibers were inspected for signs of destruction, ie scaling and extraordinary expansion and shrinkage of the fibers. The study showed no detectable change in fiber diameter of fibers measured in the same furnish of tissue that had not been used to make the electrodes of the example. The measurements were carried out with a laser interferometer.

In a third embodiment, a plurality of planar sheets were woven from a woven fabric woven from yarn made from a substantially continuous filament precursor fiber of petrol pitch. The precursor fiber tow having an aspect ratio of about 800: 1 was woven into a fabric and then heat treated at a temperature greater than 2000 ° C. The planar leaves each had a dimension of about 930 cm ² area (1 ft ² ). The fiber had a modulus of elasticity of 315GPa (45000000 psi) and a surface area of about 1 m ² / g after the heat treatment. The sheets were coated with copper along their four edges so that all the fibers were electrically connected to form a collection electrode frame. An insulated copper wire was fixed to one edge of the collector near the corner by soldering, and the soldering seam and the copper attaching electrode were coated with a curable vinyl ester resin. Each pair of blades were aligned parallel to each other with the soldered wires at opposite ends of the stops and separated by perforated nonwoven fibrous polypropylene composite sheets having a thickness of 0.1 mm (5 mils). A polyethylene compartment (bag) about 930 cm ² (1 ft ² ) in size was used as a cell container. Three cells were assembled in a protective chamber by placing a pair of the carbon fiber sheets and their separator in each of the three compartments and filling each compartment with about 500 g of an electrolyte of a 15% by weight solution of LiCIO ₄ in propylene carbonate. The electrolyte level in the compartment was determined to provide 21 grams of active fiber per electrode (the area of the electrode exposed to the electrolyte). The remainder of the carbon fibers of each electrode extended out of the solution or was covered by the resin / copper frame.

The construction of the lines in a protective chamber kept the water content at less than 20 ppm electrolyte solution. Each compartment in the protection chamber has been sealed in a manner to extend the ends of the solder wire through the gasket at opposite ends of the sealed edges. The three cells thus treated were placed in a clear plastic container and the wires were connected in series. A quantity of activated zeolite 5 A molecular sieves (to absorb the moisture) was added over the top of the cells and the assembly was removed from the protection chamber. The end wires of the two end plates of the three cell series were connected to terminals extending through a cover or cover plate for the container, and the cover was quickly sealed to the container.

The assembly was charged at a voltage of 15 to 16 volts and at a current of 1.8 to 2 amperes for 45 minutes. Thereafter, the device was discharged through a 12VoIt headlamp, which took an average current of 2.0 to 2.5 amps. The device was discharged for 30 minutes to 90% of its capacity. The electric charging and discharging cycles were performed over 850 times. The cell was then disassembled and the fibers were examined under a microscope at 1 000X magnification and showed no detectable signs of dilation or destruction due to desquamation. The device assumed an electrical charge and high discharge at 90% capacity for each cycle.

In a fourth embodiment, a fabric based on PAN (precursor fiber) was used. The fabric was a non-conductive carbon fiber with an aspect ratio greater than 250: 1, which was fabricated into yarn and woven fabric and was not heated to a temperature in excess of 400 ^° C. The fabric was heat treated at a temperature in excess of 1000 ° C for a time sufficient to render the fabric electrically conductive. The heat-treated fabric had a modulus of elasticity of 150GPa (23000000 psi) and a surface area of about 1 m ² / g. Two samples of tissue, each 5 cm (2 inches) wide on one side and 26 cm ² (4 inches ² ) in area, were cut from the heat treated tissue and the four edges of each tissue were covered with copper to form a current collector for the To form electrode. A wire was soldered to one corner of the current collector of each electrode. The solder seam and the copper pantograph were coated with a vinyl ester resin coating composition. A nonwoven polypropylene composite sheet was placed between the two electrodes and the electrodes were placed in a plastic box (envelope). This assembly was placed in a protective chamber wherein the water content was maintained at less than 20 ppm electrolyte solution. A 10% by weight solution of LiCIO ₄ in a propylene carbonate solution was used to fill the envelope until the two electrodes were submerged in the electrolyte solution. The wires from each electrode were connected to a double pole, a switch, to each of which a terminal was connected to a power source of 5.3 volts. The other terminal was connected to an electrical resistance line of 10 ohms. The cell was highly discharged to more than 80% of its total charge and operated in more than 800 electrical charge and discharge cycles with a coulometric efficiency greater than 80%. The capacity of this cell was about 70% of that of the PAN example (Example 1) based on the weight of the total electrode.

It was found that cells which were produced according to the present invention, have an internal resistance, the average less than 0,35Ohm per m ² (0,038Ohm / ft ²⁾ electrode surface in a six-electrode cell is. This value, which was originally measured to be less than 1 ohm, included the lead wires to the charge system, about 6 meters in length. When measuring the resistance of the wires and then measuring the total resistance of the system of the charge, the resistance of the secondary battery was accurately calculated as 0.35 ohms / m ² (0.038 ohms / ft ² ).

Confirmation of the data of the above examples was obtained for a Thornel fabric two-electrode cell, VCB-45, having a modulus of elasticity of 315 GPa (45000000 psi) surface area of 1 m ² / g and an aspect ratio greater than 10000: 1, wherein each fabric has a Dimension of 15.2cm χ 15.2cm had. Copper edges were coated around all four edges of the fabric to form the current collector. The current collector was then coated with a curable vinyl ester resin. The pantograph edges were about 2.6 cm wide and gave areas of active carbonaceous material of about 10 cm χ 10 cm. The 100 cm ^{2 area of} each electrode contained about 6 grams of carbon fiber. The electrodes were separated by introduction into a microporous polypropylene film.

The structure of the electrodes and separator was placed in a polyethylene bag, the pocket has been filled with a dry electrolyte of 15wt .-% LiClO ₄ in propylene carbonate (about 100 cm ³⁾ and the assembly was compressed between two plastic edge-pressing plates, the sides of the Pocket, which held the electrolyte supported. The thickness of the vinyl ester resin coated copper current collector kept the fibrous portion of the two electrodes from being pressed together at a minimum separation distance. In later runs, a 10cm x 10cm spacer plate was inserted between the edge press plates to more densely compress the electrode-separator combination. This lowered the cell resistance from about 0.9 ohms to about 0.7 ohms.

Discharge data at different discharge rates was recorded for two of the above-described performances of the cell. In one case (0.9 ohm cell) the electrode separation was limited by the epoxy coating on the current collector to approximately 4mm. In the other case (0.7 ohm cells), the electrodes were pressed in the middle against each other so that only the porous polypropylene separator was between them (less than 1 mm). In Figure 2, the curves show the terminal voltage versus discharge, Coulomb per gram of fiber for the 0.9 ohm cell at different discharge rates in the range of 6 hours to ³ hours. These discharges correspond to a so-called first plateau (2VoIt suppression). Assuming that the total capacity of the first plateau is 180 coulombs per gram to the 2VoIt suppression voltage, the abscissa values can be replaced by "percent unloading";"180 coulombs / gram", which corresponds to "100% unloading".

The total energy recovered at a 3 hour constant charge rate is almost the same as the 6 hour rate. Fast discharge at ³ A hours of speed produces poor effects due to cell resistance and electrode polarization. The electrode current densities corresponding to these discharge rates are:

Speed Average current density

(Hours) at constant charge (mA / cm ² )

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 active carbonaceous material of only one electrode.

Figure 2 shows the data for the O, 70hm cell. Obviously, more energy is available for the cell with the lower resistance. Fig. 3 shows the comparison of the two cells at the higher discharge speed ( ³ A hours of speed).

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

When opening the circuit, the voltages between the negative electrode and the reference electrode were generally less than 10 ohmV and changed only slightly over time. The voltage, when measured between the positive electrode and the reference electrode, changed with time, decreasing after each charge and increasing after each discharge.

The maximum performance in a battery cell at different charge levels was determined by cell discharge discharges at charges giving terminal voltage V2 of open circuit voltage. The "bumps" were 10 seconds long and the power was calculated as the average power over the 10 seconds.

The cell was first charged to 344 coulombs per gram of active carbonaceous material in an electrode. This was taken as a 100% condition of charge. The maximum current drawn from the 10cm χ 10cm electrode cell at 100% state of charge was 2.5 to 3.0 amps. Subsequent performance determinations were made at charges of 247 coulombs per gram (72% charge) and 223 coulombs per gram (65% charge). 4 shows the results.

The maximum power of this cell was about 0.48 watts per gram of fiber at 100% state of charge, which dropped to about 0.31 watts per gram of fiber at 72% state of charge. The performance then dropped off quickly as the tension subsided and polarization began. A burst discharge of more than 10 seconds does not reduce the final performance very much. Fig. 5 shows the voltage curve of a 40 second discharge with maximum power. After the first 10 seconds, the voltage drop is low.

In a fifth embodiment, a three cell battery was fabricated from 12 plates, four per cell, of the filament precursor fiber as described in Example 3. Each plate had a dimension of approximately 930 cm ² (12 inches χ 12 inches, 144 inches ² ) and was copper-plated on each edge. The copper coating along the edges was coated with curable vinyl ester resin. The plates had an active area of about 852 cm ² (132 inches ² ). The four plates of each cell were assembled with a perforated polypropylene scrim separator between each plate.

Pairs of plates in each cell were connected in parallel so that at charge / discharge the plates were alternately +, -, +, -. The four plates and their separators were contained in a polypropylene bag having a size of 33cm 33cm χ (13inch χ 13inch) containing about 600cm ³ electrolytic solution of 15wt .-% LiClO ₄ in propylene carbonate.

This level of electrolyte in each pocket was sufficient to provide about 37 grams of active fibers per electrode plate. The battery was initially charged for a period of 1,000 minutes to a capacity of 7.9 amp hours at a voltage of 14 to 16 volts. The cell was then discharged over a period of 200 minutes through a 12VoIt car headlamp, which had an average capacity of 6.2 light hours, which corresponds to a discharge height of more than 80%. The recharging was carried out over a period of 800 minutes. An average coulometric efficiency of approximately 90% was observed in the charge-discharge cycling.

Claims (22)

-2- 702 Invention claim: An electrode for use in a secondary electric energy storage device, characterized in that it consists of an electrode body of an electrically conductive carbonaceous material having a skeletal orientation at least at or near the surface and a current collector electrically connected thereto, wherein the carbonaceous material has a modulus of elasticity greater than 6.9 GPa and undergoes a physical dimensional change of less than 5% during repeated electrical charge and discharge cycles. The electrode of item 1, characterized in that the carbonaceous material structure has a modulus of elasticity of from 6.9 GPa to 380 GPa, and in that the carbonaceous material is derived from a precursor material selected from polyacrylonitrile or pitch. 3. The electrode according to item 2, characterized in that the carbonaceous material has a modulus of elasticity of 69 GPa to 380 GPa. 4. The electrode according to item 2, characterized in that the carbonaceous material has a modulus of elasticity of 138 GPa to 315 GPa. 5. An electrode according to any one of items 1 to 4, characterized in that the carbonaceous material has a surface area of 0.1 to 50m ² / gram. 6. The electrode of item 5, characterized in that the carbonaceous material has a surface area of 0.1 to 10 m ² / gram. 7. The electrode according to item 5, characterized in that the carbonaceous material has a surface area of 0.1 to 5 m ² / gram. 8. An electrode according to any one of items 1 to 7, characterized in that the carbonaceous material has an aspect ratio or equivalence ratio of. has more than 100: 1. 9. An electrode according to any one of items 1 to 8, characterized in that the carbonaceous material has an independent structural integrity in the range of 2.54 cm ² to more than 930 cm ² . 10. An electrode according to any one of items 1 to 9, characterized in that the carbonaceous material in the form of a tissue, a film, a paper, a paper-like or fiizähnlichen planar sheet or other structure is present. Electrode according to any one of items 1 to 9, characterized in that the carbonaceous material is in the form of a woven fabric or a felt-like fabric or sheet consisting of a structure of at least one yarn thread of continuous filament or staple fibers of 1 to 1 length 10 centimeters. 12. An electrode according to any one of items 1 to 9, characterized in that the carbonaceous material is a woven or knitted fabric is a structure of yarn of continuous yarn or staple fibers having a length of 1 to 10cm. 13. An electrode according to any one of items 1 to 9, characterized in that the carbonaceous material is a fabric or a felt-like fabric or sheet, which is made of a structural cable made of continuous filaments or staple fibers. 14. An electrode according to any one of items 1 to 13, characterized in that the collecting electrode is an electrically conductive metal which is plated on at least one edge of the carbonaceous material and wherein the plated edge is coated with a non-conductive, non-reactive protective material. An electrode according to any one of items 1 to 14, characterized in that the carbonaceous material can withstand more than 100 electrical discharge cycles of greater than 70% discharge height with a coulometric efficiency greater than 70% without appreciable damage to the structural integrity of the material. 16. A secondary electric energy storage device, characterized in that it consists of a housing with an electrically non-conductive inner surface and a moisture-impermeable outer surface or a laminar body and at least one cell which is mounted in this housing, each cell of a pair of electrically conductive electrodes which are electrically insulated from each other, wherein the housing contains a substantially non-aqueous electrolyte, wherein at least one of the electrodes of each cell is an electrode according to any one of items 1 to 15. 17. The device according to item 16, characterized in that the electrolyte contains a non-conductive, chemically stable, non-aqueous solvent and an ionizable salt dissolved therein. 18. Device according to pt 16 or 17, characterized in that the electrolyte solvent is selected from compounds containing oxygen, sulfur and / or nitrogen atoms bound to carbon atoms in electrochemically non-reactive state, and that the salt is an alkali metal. 19. Device according to item 18, characterized in that the electrolyte solvent is propylene carbonate. and the alkali salt lithium perchlorate. Secondary electric energy storage device, characterized in that it consists of a housing having an electrically non-conductive inner surface and a moisture-impermeable outer surface or a fin body and at least one cell, which is located in the housing, each cell of at least one pair electrically conductive electrodes which are electrically insulated from each other, wherein the housing contains a substantially non-aqueous electrolyte, wherein each of the electrodes of each cell is an electrode according to any one of items 1 to 15. 21. The device according to item 20, characterized in that each electrode of a cell has the freedom of choice of polarity in the recharging and the ability to be polarized partially and / or completely opposite without damage. 22. Device according to item 20 or 21, characterized in that it has a maximum power density of more than 0.31 watts per gram of active carbon positive electrode over a burst period of 40 seconds at full charge. For this 3 pages drawings