MXPA99003228A

MXPA99003228A - Multi-electrode double layer capacitor

Info

Publication number: MXPA99003228A
Application number: MXPA/A/1999/003228A
Authority: MX
Inventors: Joseph Farahmandi C; M Dispennette John; Blank Edward; C Kolb Alan
Original assignee: Maxwell Energy Products Inc
Priority date: 1996-10-07
Filing date: 1999-04-07
Publication date: 2000-09-04

Abstract

A single cell, multi-electrode high performance double layer capacitor includes first (Stack A) and second (Stack B) flat stacks of interleaved electrodes (141) adapted to be housed in a closeable two-part capacitor case (Fig. 12) which includes only a single electrolyte seal (154, 156, 158). Each electrode stack has a plurality of electrodes connected in parallel, with the electrodes of one stack being interleaved with the electrodes of the other stack to form an interleaved stack (141), and with the electrodes of each stack being electrically connected to respective capacitor terminals. A porous separator sleeve (140) is inserted over the electrodes of one stack (Stack B) before interleaving to prevent electrical shorts between the electrodes. The electrodes are made by folding a compressible, low resistance, aluminum-impregnated carbon cloth (136), made from activated carbon fibers, around a current collector foil (132), with a tab (133) of the foils of each electrode of each stack being connected in parallel. The parallel-connected tabs (135, 142) are then connected to the respective capacitor terminals. The height of the interleaved stack is somewhat greater than the inside height of the closed capacitor case, thereby requiring compression of the interleaved electrode stack when placed inside of the case, and thereby maintaining the interleaved electrode stack under modest constant pressure. The closed capacitor case is filled with an electrolytic solution and sealed. A preferred electrolytic solution is made by dissolving an appropriate salt into acetonitrile (CH3CN). In one embodiment, the two parts of the capacitor case (150, 152) are conductive and function as the capacitor terminals.

Description

MULTIPLE ELECTRODE CAPACITOR, DOUBLE LAYER BACKGROUND OF THE INVENTION The present invention relates in general to a double-layer electric capacitor, and more particularly to a high-performance, double-layer capacitor made with aluminum-impregnated, low-resistance carbon cloth electrodes, and a high performance electrolyte solution Dual layer capacitors, also referred to as electrochemical capacitors, are energy storage devices that can store more energy per unit weight and unit volume than traditional capacitors. In addition, they usually supply stored energy at a higher power rating than rechargeable batteries. The double layer capacitors consist of two porous electrodes that are isolated from the electrical contact, by means of a porous separator. Both the separator and the electrodes are impregnated with an electrolytic solution. This allows the ionic current to flow between the electrodes through the separator, at the same time that the separator prevents an electric or electronic current (Opposite to an ionic current) short in the cell.

Attached to the back of each of the active electrodes, there is a current collector sheet. One purpose of the current collector plate is to reduce the ohmic losses in the double layer capacitor. If these current collector plates are not porous, they can also be used as part of the capacitor seal. The double-layer capacitors store electrostatic energy in a polarized liquid layer that forms when there is a potential between two electrodes submerged in an electrolyte. When the potential is applied through the electrodes, a double layer of positive and negative charges is formed at the electrode-electrolyte interface (hence the name "double-layer" capacitor), by polarization of the electrolyte ions due to the separation of the charge under the applied electric field, and also due to the dipole orientation and the alignment of the electrolyte molecules over the entire surface of the electrodes. The use of carbon electrodes in electrochemical capacitors with high power and high density, represents a significant advantage in this technology, because the coal has a low density, and the carbon electrodes can be manufactured with very high surface areas. The manufacture of double-layer capacitors with carbon electrodes has been known in the art for some time, as evidenced by US Patents 2,800,616 (Becker) and 3,648,126 (Boss et al.). A major problem in many carbon electrode capacitors, including double layer capacitors, is that capacitor performance is often limited due to the high internal resistance of the carbon electrodes. This high internal resistance can be due to several factors, including the high resistance to contact of the internal carbon-carbon contacts, and the resistance to contact of the electrodes with a current collector. This high resistance translates into large ohmic losses in the capacitor during the charging and discharging phases, whose losses also adversely affect the capacitor's RC time resistance (resistance X capacitance), and interfere with its capacity to charge and / or download efficiently in a short period of time. Accordingly, there is a need in the art to lower the internal resistance, and consequently, the time constant, of the double layer capacitors. During the recent years, different electrode manufacturing techniques have been disclosed. For example, the Yoshida et al. Patent (U.S. Patent 5,150,283) discloses a method for connecting a carbon electrode to a current collector by depositing coal dust and other electrical conductivity improving agents on a aluminum substrate. Another related approach to reducing the internal resistance of carbon electrodes is disclosed in the United States patent 4, 597, 028 (Yoshida et al.), Which teaches that the incorporation of metals, such as aluminum, into carbon fiber electrodes can be accomplished through the weaving of metal fibers into carbon fiber preforms. Still another approach to reducing the strength of a carbon electrode is taught in U.S. Patent 4,562,511 (Nishino et al.), Wherein the carbon fiber is immersed in an aqueous solution to form a layer of a metal oxide. conductor, and preferably a transition metal oxide, in the pores of the carbon fibers. Nishino et al. Also disclose the formation of metal oxides, such as tin oxide or indium oxide by vapor deposition. Still another related approach to achieve low resistance is disclosed in U.S. Patents 5,102,745; 5,304,330 and 5,080,963 (Tatarchuk et al.). The Tatarchuk et al. Patents demonstrate that metal fibers can be intermixed with a carbon preform, and can be sintered to create a structurally stable conductive matrix, which can be used as an electrode. The Tatarchuk et al. Patents also teach a process that reduces electrical resistance at the electrode, by reducing the number of carbon-carbon contacts, through which the current must flow to reach the metal conductor. This approach works well if stainless steel or nickel fibers such as metal are used. However, applicants have learned that this approach has not been successful when using aluminum fibers, due to the formation of aluminum carbide during sintering or heating of the electrode. Another area of concern in the manufacture of double layer capacitors refers to the method for connecting the current collector sheet to the electrode. This is important, because the interface between the electrode and the current collector plate is another source of internal resistance of the double layer capacitor, and this internal resistance must be kept as low as possible. U.S. Patent 4,562,511 (Nishino et al.) Suggests the plasma spraying of molten metals, such as aluminum on one side of a polarizable electrode, to form a current collecting layer on the surface of the electrode. Alternative techniques for bonding and / or forming the current collector are also considered in the Nishino et al. '511 patent, including arc spraying, vacuum deposition, sputtering, non-electrolytic plating, and the use of conductive paints. The patents of Tatarchuk et al. Cited above (U.S. Patents 5,102,745; 5,304,330 and 5,080,963) show the binding of a metal foil current collector to the electrode by sintering bond of the metal foil to the electrode element. U.S. Patent 5,142,451 (Kurabayashi et al.) Discloses a method for linking the current collector to the electrode surface by a hot curing process that causes the material of the current collectors to enter the pores of the elements of electrode. Still another related technique with respect to the method for making and adhering stream collecting sheets, can be found in U.S. Patents 5,065,286; 5,072,335; 5,072,336; 5,072,337 and 5,121,301 all issued to Kurabayashi et al. The dual-layer bipolar capacitors shown in Figures 1 to 3, and the electrodes used therein, are described in International Publication No. W096 / 11486 (U.S. Patent 5,621,607). Referring to Figure 1, there is illustrated a single-cell, high-performance, double-layer capacitor 10, which includes a cell holder 11, a pair of aluminum / carbon composite electrodes 12 and 14, an electronic separator 18. , an electrolyte 20, a pair of current collector plates 22 and 24, and electrical conductors 28 and 29, which extend from the current collector plates 22 and 24. The pair of aluminum / carbon composite electrodes 12 and 14 is formed from a porous carbon cloth preform or a carbon paper preform that is impregnated with molten aluminum. The porosity of the aluminum / carbon composite electrodes 12 and 14 is specifically controlled during the impregnation process, to subsequently allow a sufficient quantity of the electrolyte 20 to be introduced into the double layer capacitor 10, and to penetrate the pores of carbon fibers. The pair of current collector sheets 22 and 24 in the form of thin layers of aluminum foil, are attached to the back of each electrode aluminum / carbon composite 12 and 14. An electronic separator 18 is placed between the opposed aluminum / carbon composite electrodes 12 and 14. The electronic separator 18 is preferably made of a highly porous material that acts as an electronic insulator between the electrodes aluminum / carbon compounds 12 and 14. The electronic separator 18 ensures that the opposing electrodes 12 and 14 are never in contact with one another. The contact between the electrodes would result in a short circuit and rapid depletion of the charges stored in the electrodes. The porous nature of the electronic separator 18 allows the movement of the ions in the electrolyte 20. The preferred electronic separator 18 is a porous polypropylene or polyethylene sheet approximately 0.025"millimeters (0.001 inches) thick. Polyethylene can be initially soaked in the electrolyte 20 before being inserted between the aluminum / carbon composite electrodes 12 and 14. The cell holder 11 can be a pair of top and bottom covers that are clamped together, and it is an advantage to minimize the weight of the packing element. Packed double layer capacitors are normally expected to weigh no more than 25 percent more than the unpacked double layer capacitor. The electrical conductors 28 and 29 extend from the current collector sheets 22 and 24 through the cell holder 11, and are adapted to be connected to an electrical circuit. An aluminum / bipolar carbon composite electrode 30 is used, as shown in Figure 2A, in combination with the end portions shown in Figures 2B and 2C, in a series stack of these electrodes to form a double layer capacitor high performance bipolar 40, as shown in Figure 3. The aluminum / carbon composite electrode 30 (Figure 2A) comprises a separate polarized aluminum / carbon composite body with a non-porous stream collecting foil 36. Attached to a surface 37 of the current collector plate 36, there is a charged electrode 32 for a first electrode. Attached to the opposite surface 38 of the current collector sheet 36, there is an oppositely charged electrode 34. These electrode structures are stacked as shown in Figure 3, with a series of the bipolar capacitors shown in Figure 2A placed between the two end portions shown in Figures 2B and 2C to form a bipolar double layer capacitor 40. In Figure 3, the first electrode 34 can be a negative electrode for a first capacitor cell "A", so that the adjacent electrode from cell "A", that is, electrode 42, becomes oppositely charged, that is, it becomes a positive electrode. The charge of the electrode 42 is carried forward to a first electrode 44 of the cell "B", that is, the electrode 44 of the cell "B" becomes positively charged in relation to the electrode 34. This causes the lower electrode 42 of cell "B" becomes oppositely charged, that is, negatively charged in relation to electrode 44 of cell "B". The series stack of bipolar double layer capacitors is high performance 40, therefore, it includes a plurality of cells (A, B, C and D) that are connected in series. Each cell includes a pair of porous electrodes composed of carbon impregnated with aluminum. Cell "A" includes electrodes 34 and 42 facing each other, with an ionically conductive spacer 46 disposed therebetween. Cells "B" and "C" include electrodes 44 and 42 facing each other, with an ionically conductive spacer 46 disposed therebetween. Cell "D" includes electrodes 44 and 32 facing each other, with an ionically conductive spacer 46 disposed therebetween. The internal non-porous current collectors 48 are placed between the adjacent cells, joining two polarized electrodes 42 and 44. The external current collector sheets 49 are placed at each end of the stack. Sufficient electrolyte 50 is introduced into each cell to saturate the composite electrodes 32, 34, 42 or 44 and the separator 46 inside each cell.

The individual carbon electrode structures 32, 34, 42 and / or 44 are manufactured from a carbon fabric preform or from a carbon paper preform, which is impregnated with molten aluminum. The porosity of the electrode structures 32, 34, 42 and / or 44 is controlled during the impregnation process, to allow a sufficient quantity of the electrolyte 50 to be introduced subsequently into the capacitor cell, and to penetrate the pores of the fibers of coal. Coated aluminum impregnated electrodes 32, 34, 42 and / or 44 are porous, and have aluminum impregnated inside the activated carbon fibers, such that the equivalent series resistance of each electrode, when used in a 2.3 to 3.0 volt cell, is about 1.5 O cm2 or less, and the capacitance of each composite electrode 42 and 44 is about 30 F / g or greater. A large capacitance is achieved by the large surface area of the activated carbon fibers, and the very small separation distance between the layers of the capacitor. Internal current collector sheets 48 of each bipolar electrode are preferably non-porous layers of aluminum foil designed to maintain the spacing between adjacent cells of electrolyte 50. External flow collector sheets 49 are non-porous, and can be use as part of the external seal of the capacitor. An electronic separator 46, preferably a porous polypropylene or polyethylene sheet, is placed between the opposing electrode structures inside each internal cell of the capacitor. A porous carbon fiber fabric preform, or a carbon fiber paper preform that is of a suitable activated carbon fiber material, such as a carbon fiber felt or other porous activated carbon fiber substrate is used. , to manufacture the carbon electrode structure. Aluminum is impregnated deep into the interstices of the carbon fiber bundles inside the carbon cloth, and the result of this impregnation with aluminum of the fibrous carbon bundles is a low resistance current path between the activated carbon elements inside. of the electrode. Despite this low resistance current path, the electrode structure remains porous, so that a non-aqueous electrolyte forms and infiltrates the interstices and pores of the activated carbon fiber bundles. A manufacturing process is disclosed wherein a carbon fiber electrode preform is made from carbon fiber, using high surface area carbon, ie, carbon fibers having a surface area of approximately 500 to 3000 m2 / gram, and a diameter of approximately 8 to 10 microns. The impregnation of the carbon fiber fabric with molten aluminum is carried out using a plasma spray technique. The plasma spray technique is controlled to make the aluminum penetrate into the carbon fiber cloth preform, by adjusting the electric current to the spray unit, the temperature and pressure of the molten aluminum, the distance of the plasma spray unit from the carbon fiber preform, sweeping of the plasma spray unit, and ambient air flow during the spraying process. There is a continuing need for better double-layer capacitors; therefore, improvements are sought on the subject matter of International Publication Number W096 / ll, 486. These improved double layer capacitors need to supply large amounts of useful energy at very high power output and energy density evaluations within a relatively short period of time. These improved double layer capacitors must also have a relatively low internal resistance, and yet they must be capable of producing a relatively high operating voltage. In addition, it can also be seen that improvements are needed in the techniques and methods for manufacturing double-layer capacitor electrodes, in order to lower the internal resistance of the double layer capacitor, and maximize the operating voltage. Since the capacitor's energy density increases with the square of the operating voltage, the higher operating voltages translate directly into significantly higher energy densities, and as a result, higher power output evaluations. There, it can easily be seen that better techniques and methods are needed to lower the internal resistance of the electrodes used inside a double layer capacitor, and increase the operating voltage. Compendium of the Invention The present invention solves the above and other needs, by providing a high perance double layer capacitor having multiple electrodes, wherein the multiple electrodes are made of activated carbon that is impregnated in volume with aluminum, in order to significantly reduce the internal resistance of the electrode, by decreasing the resistance to contact between activated carbon elements. More particularly, the high perance double layer capacitor of the present invention includes at least one pair of carbon electrodes impregnated with aluminum, each ed by the impregnation in volume of an activated carbon pre (i.e. carbon cloth) with aluminum, or other suitable metal, example, titanium, each electrode being separated from the other by a porous separator, and both electrodes being saturated with a high-perance electrolytic solution. In accordance with one aspect of the invention, a high-perance double-layer capacitor is provided which is made as a single-cell multi-electrode capacitor. "A single cell" means that only one electrolyte solution seal is required, even when using multiple aluminum impregnated carbon electrodes connected in parallel. This double-layer capacitor with multiple electrodes and a single cell, in one embodiment, includes first and second flat batteries of composite electrodes adapted to be housed in a two-part, enclosed capacitor enclosure. Conveniently, the enclosure represents the only capacitor component that must be sealed to prevent electrolyte leakage. Each electrode stack has a plurality of aluminum impregnated carbon electrodes connected in parallel, the electrodes of one stack interconnecting with the electrodes of the other stack to an interleaved stack, and the electrodes of each stack electrically connecting to the respective terminals of the battery. capacitor. A porous separating jacket is inserted over the electrodes of a stack be being inserted, to prevent electrical shorts between the electrodes when they are interspersed. In an alternative embodiment, the electrodes and the separator can be coiled spirally instead of being interleaved in flat stacks. The electrodes are preferably made by folding a carbon cloth impregnated with very low strength, compressible metal (the activated carbon fiber fabric being made) around a current collector sheet. In the flat cell mode, the current collector sheets of each respective stack are connected in parallel with each other, and with the respective terminal of the capacitor. In the spirally coiled mode, the current collector sheet of each electrode is connected to the respective terminal of the capacitor. The preferred metal impregnated in the carbon fabric comprises aluminum, although other metals, example, titanium, can also be used. the flat stack mode, the height of the non-confined interleaved stack, by design, is a little greater than the internal height of the closed capacitor enclosure, thus requiring a slight compression of the interposed stack of electrodes when Place inside the enclosure. This slight compression conveniently keeps the electrode stack interspersed under a modest constant pressure, for example, 10 psi (0.7 Kg / cm2) while remaining inside the enclosure. In the spiral wound mode, the winding of the electrodes requires a light radial compression, in order to fit inside the closed enclosure of the capacitor. In any mode, modest pressure helps to ensure low resistance to contact between the current collector sheets and the electrodes of the carbon cloth impregnated with aluminum. The closed capacitor enclosure is filled with an appropriate electrolytic solution and sealed. A preferred electrolytic solution is made by dissolving a selected salt in acetonitrile (CH3CN). In accordance with another aspect of the invention, the two parts of the capacitor enclosure can be conductive, and can be isolated from one another when the capacitor enclosure is assembled, thereby allowing each half of the enclosure to function as the terminal of the capacitor. capacitor. A high performance double layer capacitor embodiment made as described herein, exhibits a capacitance of approximately 2400 Farad, an energy density in the range of 2.9 to 3.5 W-hr / kg at an operating voltage of 2.3 volts, an evaluation of power of approximately 1000 W / kg at a discharge of 400 amperes, an electrode resistance of approximately 0.8 milliohms (itiO), and a time constant of approximately 2 seconds. These operating parameters, for the knowledge of the applicants, represent a significant and notable advance over what had been available up to now in the double layer capacitor technique. In accordance with yet another aspect of the invention, the flat stack capacitor design lends itself to upward scaling or scaling down the multiple electrodes, in order to meet the needs of a particular dual layer capacitor application. Therefore, by simply increasing or decreasing the size and number of the composite electrodes that are used inside the interleaved electrode stack, and by making the appropriate scale changes in the physical parameters (size, weight, volume) of the capacitor, It is possible to provide a high performance double layer capacitor that is tailored to a specific application. With this capacitor, the door is opened in this way to a wide variety of applications, where relatively large amounts of energy must be stored and recovered from a compact storage device, in a relatively short period of time. A similar scale can also easily be achieved using the spiral wound mode. The present invention also relates to improved methods for manufacturing a high performance double layer capacitor. These methods include, for example, impregnating molten aluminum in a commercially available carbon fabric comprising a woven fabric of activated carbon fibers. The transverse strength of the carbon cloth is dramatically reduced, for example, by a factor of fifty, by impregnating molten aluminum deep into the skein of fiber bundles. The carbon cloth impregnated with aluminum serves as the key component of each electrode inside the double-layer capacitor. The electrical contact is made with the impregnated carbon cloth in the manner of a sheet current collector that makes contact with the impregnated side of the fabric on both sides of the sheet, i.e. the impregnated cloth is folded around the current collector of sheet, in such a way that both sides of the sheet current collector make contact with the impregnated side of the folded fabric. The contact resistance between the sheet current collector and the carbon cloth is reduced by applying pressure to the impregnated fabric before being assembled inside the capacitor, to soften the ridges and valleys on the impregnated surface, thereby increasing the Surface area that makes contact with the sheet current collector. The large surface area provided by the carbon cloth of each composite electrode used with the invention, it can be multiplied many times by inserting a large number of these composite electrodes, for example, 54 electrodes. The interleaved aluminum impregnated electrodes are separated by a suitable porous spacer that provides electrical insulation between the electrodes, and yet they allow the ions of an electrolyte solution to pass easily through them. The sheet current collectors of the alternating electrodes, for example, the sheet current collectors of 27 electrodes, are electrically connected in parallel, and connected to a suitable terminal of the capacitor. In a similar manner, the sheet current collectors of the remaining electrodes are also electrically connected in parallel, and connected to the other terminal of the capacitor. The interleaved electrode stack is then sealed in a suitable capacitor enclosure, the enclosure of which keeps the stack interposed under a modest pressure to reduce contact resistance. The interior of the enclosure is then evacuated and dried, and filled with a highly conductive non-aqueous electrolytic solution made of a suitable solvent mixed with a specified salt. In accordance with the foregoing, it is a feature of the present invention to provide a high performance double layer capacitor, and a method for manufacturing this capacitor, having a relatively high energy density of more than about 3.4 -hr / kg, to an operating voltage of 2.3 volts. It is another feature of the invention to provide an improved double layer capacitor having a maximum usable power density greater than about 1000 W / kg. It is a further feature of the invention to provide an improved double layer capacitor having a low internal resistance, in combination with a high capacitance, such that the characteristic RC time constant of the capacitor remains at a value allowing relatively fast times loading / unloading For example, in one embodiment, the resistance of the capacitor is less than about 0.9 mO, while the capacitance is at least 2350 Farads, thus enabling the capacitor charge and discharge to occur (at a zero impedance load, or short) at a time constant of approximately 2 seconds. Another important feature of the invention is the identified use of advanced non-aqueous electrolytic solutions, which allow higher capacitor operating voltages. For example, a preferred electrolytic solution is mixed, using an acetonitrile solvent (CH3CN), and a suitable salt, whose electrolyte allows a nominal operating voltage of 2.3 volts, with peak voltages up to 3.0 volts or higher. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other aspects, features, and advantages of the present invention will become clearer from the following more particular description thereof, presented in conjunction with the following drawings, in which: Figure 1 is a sectional view of a single-cell, high-performance double-layer capacitor, shown in International Publication Number W096 / 11468. Figure 2 is a sectional representation of an aluminum / bipolar carbon composite electrode described in International Publication Number W096 / 11468. Figure 2B illustrates an upper portion of a bipolar stack that would use the composite electrode of Figure 2A. Figure 2C illustrates a lower portion of a bipolar stack that would use the composite electrode of Figure 2A. Figure 3 is a sectional representation of a bipolar pile in series of double-layer capacitors of bipolar high-performance type, of the type shown in Figure 2A. Figure 4A schematically shows a basic double layer capacitor made in accordance with the present invention. Figure 4B conceptually illustrates the activated carbon fibers that are part of the carbon cloth used in the electrodes of the double layer capacitor, and additionally helps to illustrate the way in which a double layer capacitor can reach-a large surface area and, therefore, a large capacitance. Figure 5 shows the equivalent circuit diagram of the basic double layer capacitor of Figures 4A and 4B. Figure 6 shows the equivalent circuit diagram of a multi-electrode double-layer capacitor made in accordance with a preferred embodiment of the present invention. Figure 7 is a simplified equivalent electrical equivalent circuit illustrating the role of the capacitor's internal resistance, Rz, to efficiently supply energy to a load. Figures 8A and 8B schematically show a technique that can be used to plasma spray an activated carbon cloth with aluminum, thereby impregnating the aluminum in the skeins of the carbon fiber bundles of the fabric, as illustrated in FIGS. Figures 9A and 9B. Figure 9A shows a schematic representation of a side sectional view of the carbon cloth, and illustrates the manner in which a plurality of fiber bundles are woven to form the carbon cloth. Figure 9B conceptually illustrates a cross-sectional view of an individual fiber bundle of the carbon fabric, and further conceptually illustrates a preferred penetration of the aluminum deep into the skein of the fiber bundle. Figures 10A-10F illustrate a preferred method for manufacturing an electrode stack for use in a dual-electrode multi-layer capacitor. Figure HA illustrates the manner in which the individual electrodes of two electrode stacks are interspersed, made as illustrated in Figures 10A-10F, a stack of which has a porous spacer placed on each electrode as shown in Figure 10F. , to form an electrode assembly. Figure 11B illustrates the electrode assembly of Figure HA, after it is wrapped with a suitable spacer material to form an electrode pack. Figure 11C illustrates an alternative spiral wound configuration of the electrode assembly. Figure 12 is a part-separated view of a preferred "clam shell" double layer capacitor, illustrating the manner in which the electrode package of Figure 11B is placed inside the upper and lower conductive covers, which covers They seal hermetically to each other to finish the capacitor assembly. Figures 13A, 13B and 13C illustrate top, end and end sectional views, respectively, of a capacitor enclosure. alternative that can use, either, a conductive enclosure or a non-conductive enclosure, that has capacitor terminals at each end of the enclosure. Figures 14A and 14B are a flow diagram illustrating the method for manufacturing and assembling the preferred "clam shell" double layer capacitor shown in Figures 10A to 12. Figure 15 illustrates the current and voltage waveforms. associated with the test of a double layer capacitor made in accordance with Figures 14A and 14B. Figures 16A and 16B show current-voltage graphs of the double-layer capacitor made in accordance with the present invention, and further illustrate the working voltage that can be obtained with this design for two different levels of impurities (water) in the solution electrolyte The corresponding reference characters indicate corresponding components through the different views of the drawings. Detailed Description of the Invention The following description of the best mode currently contemplated for practicing the invention, should not be taken in a limiting sense, but is merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. DOUBLE-LAYER CAPACITOR, MULTIPLE ELECTRODES, ONLY ONE CELL At this point, a more detailed description of a single-cell multi-layer dual-layer capacitor will be presented, in conjunction with a more detailed description of Figures 4A to 16B. A key feature of this capacitor, as will become clearer from the following description, is the use of multiple electrodes (or, in the preferred embodiment, a "flat stack" of electrodes) connected in parallel within a package of capacitor, which requires only a single electrolyte seal. Because only an electrolyte seal is required, it is appropriate to refer to this capacitor as a "single cell" capacitor, since it is the electrolyte seal that normally defines what a cell comprises. This multi-electrode, single-cell, double-layer capacitor configuration represents the best mode for practicing the invention today. However, it is emphasized that the invention is not intended to be limited to this mode or modality. Rather, it is contemplated that the invention extends to all double layer capacitors using low resistance carbon electrodes in conjunction with aluminum of the type described herein, regardless of the specific configuration of electrodes that may eventually be used to manufacture the capacitor, and independently of the electrolytic solution of high specific conductivity that is used. These electrode configurations may include, for example, multiple electrodes connected in parallel in a single cell (as more fully described herein); a pair of electrodes configured in a spiral pattern in a single cell; electrodes connected in series in stacked cells; or other electrode configurations. Turning to Figure 4A, a schematic representation of a double layer, single-cell, two-electrode capacitor 60, made in accordance with the present invention is illustrated. The capacitor includes two separate aluminum impregnated carbon electrodes 62 and 64, electrically separated by a porous separator 66. The electrodes 62 and 64, as explained in greater detail below, comprise a relatively dense tissue of activated carbon fibers, forming a carbon cloth, where molten aluminum has been impregnated. The electrode 62 is in contact with a current collector sheet 68, which sheet 68 in turn is connected to a first electrical terminal 70 of the capacitor 60. In a similar manner, the electrode 64 is in contact with another current collector sheet 72. , whose foil 72 is connected to a second electrical terminal 74 of the capacitor 60. The region between the electrodes 62 and 64, as well as all the spaces and voids available inside the electrodes 62 and 64, are filled with a highly non-aqueous electrolytic solution. conductive 76. The ions of the electrolytic solution 76 are free to pass through the pores or holes 65 of the separator 66; however, the separator 66 prevents the electrode 62 from contacting physically, and consequently, an electrical short, with the electrode 64. A preferred spacer, for example, is polypropylene. The polypropylene includes pore openings of rectangular shape having dimensions of the order of 0.04 per 0.12 microns. This pore size prevents the fibers of the carbon cloth, which have a diameter of the order of 8 to 10 microns, from being introduced through the pores. Another suitable separating material is polyethylene. The polyethylene generally has pore sizes of the order of 0.1 microns in diameter or less, thus also preventing the introduction of carbon fibers having a minimum diameter of 8 microns through them. In operation, when an electrical potential is applied through the terminals 70 and 74, and, consequently, through the series connected electrodes 62 and 64, a polarized liquid layer is formed in each electrode submerged in electrolyte. It is these polarized liquid layers that store electrostatic energy, and function as the double layer capacitor - that is, they function as two capacitors in series. More particularly, as illustrated conceptually in Figure 4A by the symbols "+" and "-" (representing the electrical charge at the electrode-electrolyte interface of each electrode 'which is immersed in the electrolyte), when a voltage is applied across the electrodes, for example, when the electrode 62 is positively charged in relation to the electrode 64, a double layer is formed (symbolically illustrated by the two layers "+" / - "shown in the Figure 4A) by the polarization of the electrolyte ions, due to the charge separation under the applied electric field, and also due to the bipolo orientation and the alignment of the electrolyte molecules over the entire surface of the electrodes. energy in the capacitor according to the following relationships: C = kcA / d (1) and E = CV2 / 2 (2) where C is the capacitance, kc is the effective dielectric constant of the double layer, d is the distance from know ration between the layers, A is the surface area of the electrodes that is immersed in the electrolytic solution, V is the voltage applied through the electrodes, and E is the energy stored in the capacitor. In a double layer capacitor, the separation distance d is measured so small that it is measured in Armstrongs, while the surface area "A", that is, the surface area "A" per gram of electrode material, can be very big. Therefore, as can be seen in Equation (1), when d is very small, and A is very large, the capacitance will be very large. The surface area "A" is large due to the configuration of the electrodes, each electrode comprising a bundle of activated carbon fiber bundles to form a carbon cloth. The activated carbon fibers do not have a smooth surface, but are chopped with numerous holes and pores 80, as suggested by Figure 4B. That is, Figure 4B conceptually illustrates a small section of an activated carbon fiber 78, which has numerous pinholes or holes 80 therein. The fiber 78, as indicated above, normally has a diameter of the order of 8 to 10 microns; although the bites or holes of the activated carbon fiber have a typical size of approximately 40 Armstrongs. The fiber 78 is immersed in an electrolytic solution 76. Each bite or orifice 80 significantly increases the surface area of the fiber that is exposed to the electrolytic solution 76. Because there are a large number of fibers 80 in each bundle, and because there are several beams inside the fabric that forms the carbon cloth, the result is a three-dimensional electrode structure that allows the electrolyte to penetrate into the fiber tissue, and makes contact with all, or almost all, of the surface area of the fibers, thus dramatically increasing the surface area "A" of the electrode, on which the double layer of charged molecules is formed. By way of example, a suitable carbon cloth that can be used to make the electrodes of the present invention, is commercially available from Spectracorp, of Lawrence, Massachusetts, as the "Carbon Fabric 2225" part number. The diameter of the carbon fibers of this fabric, such as fibers 76 and 78 shown in Figure 4B, is the order of 8 microns (8x10 ~ 6 meters); while the total thickness of the carbon cloth is approximately 0.53 millimeters (mm). The average diameter of the pores in activated carbon fibers is about 44 Armstrongs, and the pore / void volume is about 1.2 milliliters / gram. It should be noted that the pore / void volume results from three different types of voids or pores in the fabric: (1) the pores or pitting in the individual activated carbon fibers (such as the pores 80 shown in Figure 4B, which cover most of the surface area of the activated carbon fibers), (2) the space between the fibers that form a carbon bundle (whose space, for the purposes of the present invention, when seen in a cross section, as in Figure 9B is referred to as the "skein" of the fiber bundle); and (3) the gaps between the bundles of fibers that are woven to form the fabric. This pore volume results in a total surface area of the carbon cloth of approximately 2,500 mV gram. Due to the volume of pores / voids in the fabric, the fabric is a little spongy and, therefore, compressible. The density of the fabric is usually about 0.3 grams / cm 3, resulting in an effective area / theoretical volume unit of about 750 m2 / cm 3. With this area / volume unit, therefore, it is possible, see Equation (1), to achieve the capacitances of the order of 6 F / cm3. However, achieving high capacitance is only a part of the invention. For this high capacitance to be of practical use, it must be able to store and discharge energy in a relatively fast period of time. The charge / discharge time of a capacitor, as described more fully below, is regulated by the capacitor's internal resistance. The lower the internal resistance, the shorter the charge / discharge time. The internal resistance of the basic double layer capacitor 60 illustrated in Figure 4A is formed of several components, as illustrated in the equivalent circuit diagram of the capacitor 60 shown in Figure 5. As seen in Figure 5, the resistance inner of the double layer capacitor 60 includes a contact resistance, Rc, which represents all the resistance in the current path between the capacitor terminal 70 to the electrode 62 (shown in Figure 5 as the capacitor upper sheet Cl), or all the resistance in the current path between the capacitor terminal 74 and the electrode 64 (shown in Figure 5 as the lower sheet of the capacitor C2). As seen further in Figure 5, the internal resistance of the capacitor 60 also includes an electrode resistance, REL, which represents the resistance inside the electrode 62 (or inside the electrode 64), between the surface of the carbon cloth used for making the electrode and all the individual activated carbon fibers used inside the carbon cloth, i.e., REL represents the internal contact resistance between the carbon fibers inside the electrode. Additionally, a resistance of electrolytic solution, RES, in relation to the electrolytic solution 76; and a resistance of the separator, RSEP, in relation to the porous separator 66. Any energy stored inside the capacitor 60, must enter or leave the capacitor by means of an electric current flowing through Rc, REL, RES and RSEP. Therefore, it is seen that, in order to achieve practical loading / unloading times, the values of Rc, RE, RES and RSEP, which in combination with the capacitance C define the time constant tc of the capacitor, must be Keep as low as possible. The resistance of the separator, RSEP, is a function of the porosity and the thickness of the separator. A preferred spacer material is polypropylene, having a thickness of approximately 0.001 inches (0.025 millimeters). An alternative spacer material is polyethylene, which also has a thickness of approximately 0.001 inches (0.025 millimeters). Polypropylene inherently has larger pores than polyethylene, due to the manner in which polypropylene is constructed. Polypropylene typically exhibits a porosity of 25 to 40 percent; while polyethylene exhibits a porosity of 40 to 60 percent. Consequently, polyethylene inherently demonstrates a lower separating strength than polypropylene, simply because it has a higher porosity, ie, there are more pores or openings through which electrolyte ions can flow, even when the holes are on average smaller. The resistance of the electrolytic solution is determined by the conductivity of the particular electrolytic solution that is used. In the selection of the type of electrolytic solution to be used, several issues must be considered. Aqueous electrolytic solutions generally have a higher conductivity than non-aqueous solutions (e.g., by a factor of 10). However, aqueous solutions limit the working voltage of the capacitor cell to about 0.5 to 1.0 volts. Because the energy stored in the cell is a function of the square of the voltage, see Equation (2) above, it is probably better to use high-energy applications using a non-aqueous electrolyte, which allows cell voltages of the order of 2.0 to 3.0 volts. As indicated above, the preferred electrolyte for use with the double layer capacitor described herein is made of a mixture of acetonitrile (CH3CN) and a suitable salt, the mixture of which exhibits a conductivity of the order of 50 ohm "1. However, it should be emphasized that the invention described herein contemplates the use of alternative electrolytic solutions, particularly non-aqueous (or organic) electrolytic solutions, other than the solution made of acetonitrile described above For example, various electrolyte solutions are disclosed. alternatives in the aforementioned U.S. Patent Application, Serial Number 08 / 319,493, filed 07/10/94, Rc contact resistance, in combination with the REL electrode resistance, represent a significant source of resistance internal capacitor 60. A high resistance of the electrode has been an important block in the development of capacit double layer, high energy density, commercially viable. A key feature of the present invention is to provide a double layer capacitor having a very low electrode resistance in combination with a high energy density. A main objective of the present invention is to reduce Rc + REL to a value that is small compared to RSEP- For that purpose, much of the following discussion focuses on fabrication and assembly techniques that reduce electrode resistance, REL, as well as the contact resistance, Rc. To further illustrate the significant role that the resistance of the REL electrode has in the operation of the multi-layer dual-layer capacitor of the present invention, reference is now made to Figure 6. Figure 6 shows the equivalent circuit diagram of a single-cell, multi-electrode, double-layer capacitor 90 connected in parallel, made in accordance with a preferred embodiment of the present invention. . The only difference between Figure 6 and Figure 5 is that Figure 5 shows a double layer capacitor (corresponding to that shown in Figure 4A), which uses only two electrodes 62 and 64. In contrast, the double capacitor The preferred embodiment of the present invention uses a large number of electrodes, for example, 54 electrodes, configured in a flat stack interspersed within a single cell. Accordingly, in the equivalent circuit diagram of the capacitor 90 shown in FIG. 6, the multiple electrodes are shown connected in parallel in two rows of n electrodes. A first stack, Battery A, is represented by the capacitances ClA, C2A, C3A, ... CnA. A second battery, Battery B, is similarly represented by the capacitances ClB, C2B, C3B, ... CnB. The effective electrode resistance, REL, therefore, is a combination of all the individual resistors that make contact with the multiple electrodes of the n capacitances. In a similar way, the resistance of the electrolytic solution, RES, is represented as a combination of all the individual resistors that are connected to each of the n capacitors. The capacitors of Battery A are connected to the capacitors of Battery B, through the parallel combination of all the resistances of the electrolytic solution, RES, and a resistance of the separator, Rc. The total resistor Rz of the capacitor, based on the model shown in Figure 6, and further based on a "clam shell" capacitor design, as described below in relation to Figure 12, can be expressed as: Rz = 2RC + 2REL + 2RES + RSEP ~ 800 μO A simplified circuit illustrating the use of a capacitor as a power source to supply power to a load, RL, is shown in Figure 7. In Figure 7, all are included. capacitor resistors associated with both Battery A and Battery B, including the contact resistance Rc associated with both terminals, and also including the resistance of the electrolytic solution RES and the resistance of the separator_RSEP (if it is not low enough to be neglected), in the capacitance resistance Rz. The total resistance Rt of the power supply circuit of the electrode 7 is: Rt = Rz + RL (3) The total time constant t of the power supply circuit is, therefore: t = RTC, (4) while the time constant tc of only the capacitor is: tc = RZC (5) The voltage developed through the load VL is: VL = V0 (RL / RT) = V0 (l-Rc / Rt) (6) and the power supplied to the load is: P = IVL = -IV0 (1-RC / RT) = IV0 (1-CRC / CRT) (7) or P = IV0 (l-tc / t (8) The expression (l-tc / t) represents the evaluation of efficiency S of the power supply circuit, that is, S = (l-tc / t) (9) The degree to which the power source (in this case the capacitor was charged up to a voltage of V0) can efficiently supply power to the load, RL, therefore, depends a lot on the RC time constant characteristic of the capacitor tc. The RC time constant characteristic of the capacitor, in turn, is directly related to the resistance of the capacitor, Rz. In order to achieve an efficient power supply circuit using the double layer capacitor C, therefore, it can be seen that the resistance of the capacitor, Rz, must be minimized, so that a time constant can be realized low capacitor tc. Conveniently, the present invention provides a multi-electrode double-layer capacitor of the type shown in the equivalent circuit of Figure 6 which, when configured substantially as described below in connection with Figures 9A-12, has specifications of operation as stipulated in Table 1. This configuration (i.e., the configuration shown in Figure 12) may be referred to herein as UC3000. Significantly, a capacitor that operates in accordance with the specifications shown in Table 1, exhibits a time constant tc of about 2 seconds. This time constant means that, at an output voltage V0 of for example 2.3 volts, and an output current of 400 amperes (which means that the RT value would be approximately 55 to 60 milliohms (mO)), the capacitor it can function as an efficient energy storage device, with an evaluation of efficiency S greater than approximately 0.80, and more than approximately 0.9 in an output current of 200 amperes. In addition, the energy density achieved is in the range of 2.9 to 3.5 W-hr / kg, and the power rating is greater than 1000 W / kg (at 400 amperes). This operation in a double-layer capacitor of a single cell, for the knowledge of the applicants, had never been achieved before.

TABLE 1 UC3000 Performance Specifications Parameter Value Units Capacitance 2, 300 Farads Tolerance ± 10 or Nominal Voltage 2. .3 Volts Nominal Power 6, 000 Joules ESR * 650 μO (* ESR = Series Resistance of the Electrode) Aluminum Enclosure Style machined in two pieces. Electrical Connection Each half of the enclosure is of opposite polarity. The electrical connection is through the surface contact of the enclosure. Enclosure Dimensions 2.28 X 2.62 X5.80 inches 57.9 X 66.4 X 147 mm Enclosure Weight 200 g Total Weight 600 g ~ Internal Volume 375 cm3 Electrolyte: Organic Impregnant (solvent + salt) solvent: Acetonitrile (CH3CN) Salt: Ammonium tetrafluoroborate tetraethyl (CH3CH2) 4N + BF4 Salt / solvent ratio: 303.8 g / liter Turning now to Figures 8A-14B, the basic technique used in the manufacture of a double layer capacitor in accordance with the present invention will be described. Figures 14A and 14B are a flow diagram illustrating the main steps in this process; although Figures 8A-12 illustrate the individual steps of the process. Accordingly, in the description of the assembly and manufacturing process that follows, reference will be made to the specific blocks or tables of the flow chart of Figures 14A and 14B, to identify the particular steps, while making reference to the respective figures of Figures 8A-12 to illustrate the step that is being taken. With reference first to block 200 of Figure 14A, and with reference also to Figures 8A and 8B, an initial step to be made in the manufacture of a capacitor 90 (Figure 6) in accordance with the present invention, is to spray a suitable carbon cloth 92 with plasma (FIG. 8A) with an aluminum plasma spray 94, so that the aluminum is impregnated deeply into the skein of the fibers of the carbon cloth. The carbon cloth 92 to be sprayed is preferably a commercially available fabric, such as the part number "Carbon Fabric 2225" obtained in Spectracorp, previously described. Of course, other suitable carbon fabrics can also be used. As seen in Figures 8A and 8B, the carbon cloth 92 is normally obtained on a roll 96. The roll is usually about 36 inches (91.44 centimeters) wide. A length of carbon cloth 92 is removed from the roll 96, and stopped in a suitable frame 98. The frame includes a backing mesh 93. The frame is placed in front of a plasma roll nozzle 100. The frame 98 exhibits a " window "of the fabric, which has the approximate dimensions of 2.31 inches (0.91 centimeters) by 34.25 inches (13.48 centimeters), to the plasma spray 94. The plasma rolling nozzle is controlled by an XY 102 controller, to provide a pattern of spray desired on the carbon cloth. The aluminum plasma spray 94 is formed by feeding two aluminum wires 104 and 106 from respective rolls of aluminum wire into the nozzle 100 at a controlled rate. The tips of the wires stop inside the nozzle at a specified separation distance. An electric power source 108 causes an electric current to flow through the wires, and an arc through the tips of the wires. The electric arc causes the aluminum to melt and vaporize. When the aluminum is melted and vaporized, it leaves the nozzle 100 in a plasma stream by compressed air, provided by the air compressor 110. As the aluminum is spent and carried into the plasma stream 94, it is introduced. additional aluminum wire 104, 106 in the nozzle 100, to maintain the desired gap for the electric arc. In this way, an aluminum source is continuously introduced into the nozzle, so that a constant stream of vaporized aluminum can be directed towards the carbon cloth. The vaporized stream of aluminum is sprayed on and into the carbon cloth 92, following a spray pattern up and back, as shown in Figure 8B. The backing mesh 93, which has mesh openings of the order of 0.25 square inches (1.61 square centimeters), allows the plasma to flow to continue through the fabric, in order to optimize the volume impregnation with aluminum. The internal dimensions of the frame 18 are approximately 2.3 inches (0.91 centimeters) in height by 32 inches (13.48 centimeters) in width. The aluminum wires 104, 106 are preferably 99.5 percent pure aluminum, with a diameter of approximately 0.16 centimeters. In operation, all of the operating equipment shown in Figure 8A, for example, the nozzle 100, the XY controller 102, the frame 98, and the wires 104, 106, are placed in a plasma spray chamber (to confine the vaporized aluminum). The air in the chamber dries. An extraction fan 112 maintains a constant flow of air through the chamber in the direction away from the nozzle 100. The cloth 92 is manually held in the frame 98, and a single spray pattern is performed. Only one side of the cloth is sprayed. Once sprayed, the fabric is released from the frame. Then a new stretch of non-sprayed carbon cloth 92 is advanced into the frame for the next strip of carbon cloth to be sprayed. During the plasma spray process, the electric current used to vaporize the aluminum is 60"to 65 amps, at an arc voltage of approximately 26 volts. The compressed air is maintained at a pressure of approximately 50 psi (3.52 Kg / cm2). The distance between the tip of the nozzle 100 and the fabric is 20 inches (7.87 centimeters). The complete spray pattern is traversed at a constant speed over a period of about 45 seconds. The nozzle is adjusted in such a way that the stream of vaporized aluminum covers the fabric as evenly as possible with minimal overlap. Once the aluminum spraying process has been completed, an aluminum layer is present on the front side of the fabric, and there should be a slight visual pattern of the backing mesh 93 visible on the back side of the fabric. This pattern provides visual verification that at least some aluminum has penetrated all the way through the fabric, to optimize the impregnation in volume during the spraying process. All the equipment referenced in Figure 8A is conventional. The details and manner of operating this equipment are known to those skilled in the art.

The purpose of spraying the carbon cloth with aluminum is to reduce the transverse resistance through the fabric 92. The measured data of the series resistance of the electrode (ESR), taken ~ before and after the plasma spray, and with Different amounts of aluminum are summarized in Table 2.

TABLE 2 Capacitance Density ESR of Capacitor Aluminum (mg / cm3) (F / g) (O-cm2) 0 (not sprayed) 115 52.0 157 > 130 1,509 209 > 140 1,299 250 147 1.26 410 144 1.08 509 130 1,308 The data in Table 2 were taken using electrodes that were 2500 m2 / gram, cut up to 5.1 centimeters in diameter, and that contained approximately 0.2 grams of carbon. The density of carbon in the non-sprayed fabric was 0.26 grams / cm3. As seen from the data in Table 2, the strength of a carbon cloth that has been sprayed with aluminum plasma reduces the strength of the fabric by up to a factor of 50. This dramatic reduction in strength, which is caused by a decrease in the volume resistivity of the electrode structure, has direct influence on the resistance of the electrode, REL, and consequently, significantly improves the capacity of the capacitor to exhibit a low time constant. As seen further from the data in Table 2, the reduction of the resistance of the electrode through the impregnation of aluminum, is a process that must be optimized in order to produce the lowest resistance for an amount of aluminum desired. If there is too little aluminum, the resistance remains too high. If there is too much aluminum, the electrode weight is increased enough to degrade the energy density. If there is too much aluminum, the electrolyte is also blocked, and can not penetrate into the carbon fabric to make contact with the entire surface area of the fibers, thus effectively decreasing the available surface area. It is significant that the aluminum spray 94 which is directed towards the carbon cloth 92 (Figure 8A), does much more than just coat the surface of the carbon cloth with aluminum. Although aluminum certainly coats the surface, it also penetrates the fabric, and therefore, impregnates the fabric with aluminum. The meaning of impregnating the fabric with aluminum will be better illustrated with reference to Figures 9A and 9B. Figure 9A shows a schematic representation of a side sectional view of the carbon cloth 92. As seen in Figure 9A, the carbon cloth 92 is formed of a plurality of fiber bundles 120, which are woven to form the fabric of coal. For simplicity, only four fiber bundles 120 are shown in Figure 9A. Each fiber bundle 120 is formed of many carbon fibers 122, as best seen in Figure 9B, which conceptually illustrates a cross-sectional view of one of a single fiber bundle 120. The axial strength of the individual carbon fibers 122 is very low, but the transverse resistance through a carbon beam 120 is relatively high. It is this transverse resistance, that is, the resistance from the point "A" on one side of the fabric 92, to the point "B" on the other side of the fabric, which should be lowered in order to reduce the resistance of the fabric. REL electrode. The plasma spray of the carbon cloth 92, with an aluminum spray 94, conveniently causes the aluminum to flow into the skein 126 of the beam 120, as shown in Figure 9B. This penetration, or impregnation, into the skein of the fiber bundle 120, therefore reduces the contact resistance between the individual fibers 122. The resultant low transverse contact resistance, together with the intrinsic low axial resistance of the fibers, then allows a very low resistance path is made completely across the width of the fabric 92, that is, it provides a very low transverse resistance through the electrode structure. When the aluminum spray 94 hits the fabric 92, not only impregnates the skein 122 of the fiber bundle 120 with aluminum, as described above, but also forms an aluminum layer 124 on the sprayed surface of the fabric. In addition, some of the aluminum fills some of the voids 128 between the fiber bundles. The aluminum layer 124 helps to make good electrical contact (low resistance) with the sheet current collectors 68 and 72 (Figure 4A). That is, the aluminum layer 124 serves to lower the contact resistance, Rc. The presence of aluminum in the voids 128 between the fiber bundles adds weight to the electrode and, therefore, must be minimized after achieving adequate volume resistivity and a low characteristic RC time constant. The ideal impregnation depth of the aluminum in the skein 126 of the bundles of carbon fibers 120 has not yet been quantified. However, it is believed that the impregnation pattern, when viewed in cross section, is similar to that illustrated in Figure 9, which fills approximately 2/3 to 3/4 of the available skein volume at the point where it is exposed. the beam on the surface of the fabric. The weight of the aluminum retained on or within the carbon fabric is maintained between about 42 and 53 percent, for example, at 48 percent, of the total weight of the carbon cloth plus the aluminum, or about 15 percent. percent of the total weight, including the electrolyte. Returning to Figure 14A, it is seen that, after the carbon cloth has been sprayed and impregnated with aluminum (block 200), the impregnated carbon cloth is previously cut into strips having dimensions greater than 2 by 10 inches (0.8 by 3.9 centimeters) (block 202). Pre-cut impregnated carbon cloth strips are then cut with die (block 204), to have more accurate dimensions of 2x10 inches (0.8 by 3.9 centimeters), and the corners of the strip are rounded to have a radius of approximately 0.03 inches (0.76 millimeters). The die cut strips are then pressed in a mechanical press, to be subjected to a pressure of at least about 1500 psi, and preferably of about 1600 psi (112.7 kg / cm2). The carbon cloth 92 is a little spongy, so that the application of this pressure serves to compress the fabric of the fiber bundles 120, in order to make the fabric thinner by about 15 to 20 percent. This reduction in the thickness of the fabric directly results in a reduction in the thickness of the electrode structure, when assembled, and in a reduction in the strength of the electrode structure. Applying the pressure to the impregnated carbon cloth strips softens the sprayed side of the fabric (softens the valleys and ridges), so that there is more surface area of the sprayed aluminum layer 124 that can make contact with the collecting sheets of current 132, in order to reduce the contact resistance Rc of the assembled capacitor. Still with reference to Figure 14A, in a path parallel to the preparation of the impregnated carbon cloth strips, the sheet current collectors are also prepared. A first step in the preparation of the sheet current collectors is to previously cut aluminum sheet to an approximate desired dimension (block 208), and then die-cut the aluminum sheet to the precise dimension (block 210). The preferred aluminum foil used for the current collector has a thickness of approximately 0.002 inches (0.05 millimeters). The sheet is cut to a shape "substantially as shown in Figure 10 A. This shape includes a blade end 132, and a tongue end 133. The tongue end 133 and the blade end 132, therefore, comprise a current collector sheet 130 (sometimes referred to as the current collector sheet) The current collector sheet 130 is approximately 10 inches (25.4 centimeters) long.Pallet end 132 is approximately 6 inches (15.2 centimeters) in length. long, and the tongue end 133 is approximately 4 inches (10.2 centimeters) long. The blade end 132 has a width of approximately 2 inches (5.08 centimeters), and the tongue end has a width of approximately 1 inch (2.54 centimeters). Two stacks 134 of 27 current collector sheets are assembled (block 212, FIG. 14A), as illustrated in FIG. 10B. In each stack, the tongue ends 133 of the twenty-seven collecting sheets 130 are bonded together, using any suitable bonding technique, such as sintering or ultrasonic welding, thereby forming a solid tongue end 135, 142, wherein each collector sheet is electrically and mechanically connected in a secure manner to each of the other collector sheets of the stack, In contrast, the blade ends of the collector sheets 130 of the stack remain disconnected. Figure 14A, it is seen that, in addition to the preparation of the impregnated carbon fabrics (blocks 200-206), and to the preparation of the aluminum current collector sheets (blocks 208-212), the shirts must also be prepared Insulators 140 (Figure 10F) These insulating sleeves 140 function as the separator -66 (Figure 4) in the double layer capacitor.The sleeves are made by previously cutting a suitable insulating material / separator (block 214), such as polypropylene or polyethylene, in strips. One material suitable for use as the separator is Celguard 2400, commercially available from Hoechst Celanese of Charlotte, NC, USA, which is a polypropylene material approximately 0.001 inches (0.025 centimeters) thick, with generally rectangular pores of average size. of approximately 0.04 x 0.12 microns. The Celguard (or other separator material) is formed into shirts or tubes (block 216, Figure 14A), which have a size that allows the shirts to slide comfortably over a current collector sheet 130 having a strip of impregnated carbon cloth 136 folded around it, as shown in Figure 10F. The edges of the Celguard can be securely linked to one another in order to form the shirt through the use of any suitable sealing technique, such as thermal bonding, as is known in the art. Once the current collector sheets 130, the aluminum impregnated carbon cloth strips 136, and the separator sleeves 140 have been formed or otherwise fabricated, an electrode package can be assembled (block 218, FIG. 14A ). This electrode package assembly involves wrapping or surrounding each of the sheet vanes 132 of each electrode stack with the impregnated carbon cloth strips 136 in the manner illustrated in Figures 10C, 10D and 10E. As seen in these figures, the fabric strips 136 are folded into a central fold line 137, with the sprayed side of the fabric placed against both sides of the pallet end 132 of the collecting sheets 130. Each of the collecting sheets of each of the two stacks of collecting sheets has a folded strip of cloth 136 placed on it in this manner, with the exception of the uppermost collecting sheet of a pile, and the lowermost collecting sheet of the other pile, the sheets of which they have half a strip of cloth 136 placed on the side of the collecting sheet that faces the inside of the pile. The separator jackets 140 are then placed on the combination of the carbon cloth strip 136 and the blade end 132 of each of the collecting sheets 130 of one of the two collector sheet stacks, for example, the "B" Stack. . The "sheets" of the two stacks of sheets (wherein one "sheet" comprises the collecting sheet and its accompanying charcoal cloth strip), with one separating / insulating jacket 140 inserted on each sheet, and the other not having any separator / insulation shirt, are then interleaved with one another as illustrated in Figure HA, to form an interleaved electrode assembly 141. The completed electrode assembly 141 includes a first electrode stack, for example, 54 electrodes. Each electrode is formed of a current collector sheet 130 which is surrounded by a strip of carbon cloth impregnated with aluminum 136. Each strip of carbon cloth is separated and electrically insulated from an adjacent carbon cloth strip by the separating material 140. Alternating electrodes are connected electrically in parallel by the linked tabs 135 (Battery A) or 142 (Battery B) of the respective current collector plates. An alternating electrode assembly 141 'which can be used in a spiral wound embodiment of the invention is illustrated in Figure 11C. In Figure 11C, two elongated current collector sheets 136 'are wound together in spiral, each having a tab portion 133' which is connected to the appropriate terminals of the capacitor 70 and 74, and each having a non-woven fabric. carbon impregnated with corresponding elongate aluminum 136 'folded over it, such that a sprayed side 138' of the fabric faces the sheet 132 '. An insulating or separating jacket 140 'is placed on one of the film / cloth electrodes of the wound assembly, to prevent the electrodes from shorting one another when they are wound together. The length and width of the current collector sheets 132 'and the corresponding aluminum impregnated carbon cloth electrodes 136' of the spiral wound electrode assembly 141 ', of the embodiment shown in Figure 11C, can be selected as such. so that approximately the same electrode area is reached that is achieved using the interleaved flat stack assembly 141 shown in Figure 11A, or to achieve a desired performance criterion. One advantage of the spiral wound assembly 141 'is that it is somewhat easier to assemble and manufacture than the interleaved flat stack assembly 141. An advantage of the interleaved flat stack assembly 141, however, is that the sheet strength Current collectors may be lower (because they use many short parallel current collectors, as opposed to a long current collector). Additionally, the interleaved flat stack assembly 141 lends itself to more efficient use in a rectangular shaped enclosure, while the spiral wound assembly 141 'is more suitable for use in a cylindrical shaped enclosure. Depending on the application for which the capacitor is going to be used, a rectangular enclosure may be more beneficial than a cylindrical enclosure. Returning to a description of the interleaved flat stack assembly 141 (Figure HA), after the two electrode stacks have been interleaved to form the assembly 141, the entire assembly is wrapped in a suitable insulating material 144, such as Celguard. The insulating material 144 can be held in place with a suitable tape 146, which is also tightly wrapped around the assembly 141, thereby forming a pack of wrapped flat stack electrodes 143. The tabs of the current collector 135 and 142 are extend from each end of pack 143. Once the flat cell electrode pack 144 has been manufactured, the final mechanical assembly of the capacitor can be performed. This mechanical assembly is illustrated in Figure 12, the figure of which shows a separate view in parts of physical components of the preferred double-layer capacitor. These components include a lower conductive cover 150, and an upper conductive cover 15'4. One of the tabs, for example, the tab "135, of the electrode pack 143, is linked to the interior of the lower cover 150 at the location 160. The other tab, for example, the tab 142, of the electrode pack 143, it is connected to the interior of the upper cover 152, in a corresponding location. This bond (block 224, FIG. 14A) can be achieved using any suitable bonding technique, such as spot welding, ultrasonic welding, or the like. Of course, the link must be a low resistance link, having a resistance no greater than about 5 μO, so that the low resistance of the global electrode REL of the capacitor can be maintained. Once the tabs of the electrode pack 143 have been linked to the respective upper and lower conductive covers, the capacitor enclosure assembly is closed (block 226, FIG. 14A), attaching and sealing the upper cover 152 to the lower cover 150. , using any suitable bonding / sealing technique. Note that the upper and lower covers, in combination, comprise the enclosure of the capacitor assembly. A preferred technique for closing the capacitor enclosure, shown in Figure 12, uses screws 164, in combination with insulating nylon bushings 162, to securely secure a flange 153 of the upper cover 152 to a corresponding flange 151 of the lower cover 150. To ensure a good seal when the tabs of the upper and lower covers are joined together, an O-ring 154 fits inside a slot around the periphery of the flange 153, and another O-ring 156 fits inside a slot. similarly around the periphery of the flange 151. In addition, a polypropylene package 158 electrically insulates the two covers one from the other. Because, like the clam shells, the capacitor enclosure is closed by holding the upper cover 152 attached to the lower cover 150, the packing configuration illustrated in FIGS. 10A-12 is sometimes referred to by the applicants as the assembly. "clam shell" or the design of "clam shell". An important feature of the "clam shell" assembly shown in Figure 12 is that the electrode package 143, in its wrapped and interleaved form, has dimensions a little larger than the internal dimensions of the upper and lower covers. However, because the carbon cloth is a little spongy, it is compressed enough to fit inside the closed top and bottom covers. Accordingly, package 143 remains slightly compressed when placed inside of, and held within, the upper and lower covers. This results in the electrode package 143 being maintained under a constant modest pressure of approximately 10 psi (0.7 Kg / cm2) when the top cover 152 and the bottom cover 150 are mechanically joined together. This modest continuous pressure also serves to lower the contact and electrode resistance of the electrode assembly, because it keeps the current collector sheets 130 in firm mechanical contact with the sprayed side of the respective impregnated carbon cloth strips 136. The arrows 121 symbolically represent that the electrode assembly 141 is maintained under a constant modest pressure, "P", applied in a direction such as to force or compress the electrodes in contact with the current collecting sheets (see Figure 11B). For the spiral wound assembly 141 ', shown in Figure 11C, the constant modest pressure "P" is applied in a radial direction, as illustrated by arrows 121'. Although the modest pressure is about 10 psi (0.7 Kg / cm2), in practice, the pressure can vary anywhere from about 5 to 18 psi (0.35 to 1.27 tKg / cm2). The structural design of the upper and lower covers (or other capacitor enclosure), which does not comprise a pressure vessel by itself, is nevertheless designed to withstand an internal pressure of up to approximately 20 psi (1.4 Kg / cm2). An important component needed to complete the capacitor assembly, is a means to fill the closed assembly with a suitable electrolytic solution, and then permanently seal the assembly. For this purpose, a seal plug 168 is threadably received in a filling hole 167 located at one end of the lower cover 150, as seen in Figure 12. An O 166 ring package with the cap 168 is used. , in order to effect the seal. A similar filling hole (not shown) is located at the other end of the upper cover 152. The use of two filling holes facilitates the movement of the gases influenced in and out of the closed assembly. Referring again to Figure 14A, once the enclosure assembly has been closed (block 226), it is tested to determine if there are electrical shorts. This test is performed simply by measuring the resistance between these two covers, Figure 12, each of which is conductive, and they function as the electrical terminals of the capacitor. In an ideal capacitor, this resistance (for a "dry" assembly - no electrolyte is yet introduced into the enclosure) must be infinite. A low resistance measurement, for example, of only a few ohms, between the upper and lower covers of the dry closed assembly, indicates that an electrical short has occurred inside the assembly. In practice, a dry resistance of at least 20 MO is acceptable to pass this electric shorts gate. Still with reference to Figure 14A, it is noted that a previously made step before bonding the foil tabs to the enclosure covers (block 224) comprises forming or otherwise fabricating the lower cover 150 and the upper cover 152 (block 220). ). In the currently used mode, the covers are each machined from a solid block of aluminum. The outer dimensions of the closed assembly, including flanges 151 and 153, are 2.25 inches (5.72 centimeters) high by 2.62 inches (6.65 centimeters) wide, and 5.6 inches (14.2 centimeters) long. The body of the enclosure (not including the eyelashes) has a width of approximately 2.18 inches (5.54 centimeters), which means that the eyelashes 151 and 153 extend outward from the body of the enclosure by approximately 0.22 inches (0.56 centimeters). As indicated above in Table 1, the internal volume of the capacitor enclosure is approximately 375 cm 3, and the enclosure weight is approximately 200 grams. As indicated above, for the clam shell configuration shown in Figure 12, the top and bottom covers function as the two terminals of the capacitor. It is contemplated that covers made using compacted and / or compressed copper clad aluminum, relatively inexpensive, as opposed to the more expensive machined aluminum blocks, may be used in the future. Copper-clad aluminum is preferred for this purpose, as opposed to aluminum, because it provides lower external contact resistance when several of the capacitors are stacked together. The use of stamped and / or compressed materials to form the covers of the capacitor assembly conveniently reduces the weight of the enclosure to approximately 100 grams, and increases the energy density from approximately 2.9 W-hr / kg to approximately 3.5 W-hr / kg . It should also be noted that alternative packaging schemes can be used with the invention. For example, a double-ended capacitor design, shown in Figures 13A, 13B and 13C, can be used. The double ended configuration shown in Figures 13A, 13B and 13C includes an elongated capacitor enclosure 170, having a generally square cross section, having a terminal 172 at each end of the pack. The terminal 172 preferably includes a threaded hole 173, to which a threaded screw can be attached. The material of the enclosure 170 can be conductive or non-conductive. If he is a driver, the terminals are electrically isolated from the enclosure by 176 and 178. The terminal 172 is attached to each end of the double ended assembly using a nut 174. A caster and / or packing 176 can be used with the nut 174, to securely secure the terminal in place, and provide electrical isolation of the enclosure when necessary. An insulating package 178 is used on the interior of the enclosure to seal the terminal 172 and prevent leaks. During the assembly of the double ended design, the tabs 135 and 142 of the flat stack internal electrode pack 143 (Figure 11B) are linked to the inside of the terminals at each end of the enclosure 170. Note that a stopper is provided seal 166 and packing 168 on at least one end of the double ended capacitor, as shown in Figure 13B. Preferably, a seal plug is provided at both ends of the capacitor, to facilitate the filling of the assembly with the electrolytic solution. The main advantage of the double ended configuration shown in Figures 13A, 13B and 13C, is that the cover material does not need to be conductive (although it can be), but it can be a suitable non-conductive material of light weight, such as plastic . The total weight of the double-ended capacitor enclosure shown in Figures 13A, 13B and 13C, therefore, can be made significantly smaller than the weight of the capacitor enclosure for the capacitor configuration shown in Figure 12. The weight of the Enclosure is important, because it contributes directly to the capacitor's energy density. Because some alternative packaging schemes may include terminals, as illustrated above in relation to Figures 13A, 13B and 13C, the flow chart of Figure 14A includes the step of installing the terminals on the enclosure, if such terminals (block 222). Passing immediately to Figure 14B, once the capacitor has been assembled as shown in Figure 12 (or in Figures 13A, 13B or 13C), and tested for electrical shorts (block 228, Figure 14A) , seal the assembly of the enclosure (block 232), as required, or make it sealable, using a seal plug 168 and a packing 166. Then the sealable enclosure is evacuated, and the internal components are completely dried (block 234) . This drying process normally takes place over a period of two or three days, and comprises joining a vacuum pump to the closed assembly, by means of the filling orifice 167 (Figure 12), and maintaining a constant negative pressure of approximately 10"6. Torr for a specified period of time, for example, 48 to 72 hours.When dry, the assembly is tested for leaks (block 236.) This leak test can be done using any suitable technique, * as In this field, a preferred leak test includes spraying an inert gas, for example, helium (He), on and around the enclosure while it is still connected to the vacuum pump, and while a negative pressure is still inside. If there is a leak, the negative pressure inside the room sucks the He gas through the leak, and then the He gas can be detected in the flow of the output stream of the vacuum pump. pass If the leakage test is successful, then the enclosure is ready to be impregnated, through the fill hole, with a prescribed amount of a specified electrolyte solution (block 248). The electrolyte solution is mixed by dissolving a selected salt in a prescribed solvent. Accordingly, to prepare the solution, the solvent is prepared (block 238), and the specified salt is procured (block 240). As indicated above, the preferred solvent is an organic solvent of acetonitrile (CH3CN). The preferred salt is tetraethyl ammonium tetrafluoroborate, or (CH3CH2) 4N + BF4 ~. The electrolyte solution is mixed (block 242) by first drying the salt for at least 12 hours, and then dissolving the dry salt in the solvent. The proportion of the salt to the solvent is 303.8 grams / liter, which produces 1.4 moles / liter.

Once mixed, the electrolyte is tested to determine if it has impurities (block 244). It is important that the amount of water in the electrolyte be reduced to less than 20 ppm (part per million), preferably less than about 15 ppm. If the level of impurities, for example, water, in the electrolyte, exceeds 20 ppm, the operating voltage of the capacitor can be adversely affected. For example, when the amount of water in the electrolyte reaches a level of 40 ppm, the useful working voltage of the capacitor is reduced to approximately 70 percent of what it has when the water in the electrolyte is only 14 ppm, as shown in Figures 16A and 16B. Accordingly, it is seen that it is important that impurities, particularly water, are removed from the electrolyte before the electrolyte is impregnated in the closed-room assembly. (It is observed that some additives can be added to the electrolyte, for example, to improve its operation or to improve the operating life of the capacitor, but water should be avoided). The water content of the solution is measured using a coulometric titrant, as is known in the art. A representative titrator that can be used for this purpose is the. LC3000 titrator available in EM Science Aquastar. Unfortunately, there may already be some water inside the enclosure assembly, despite attempts to completely dry the interior of the assembly. For example, water can be trapped in the carbon fibers of the carbon cloth.

This trapped water can be released into the electrolyte, thus becoming an impurity within the electrolyte, as soon as the electrolyte free of impurities in the enclosure assembly is impregnated. To remove this water (or similar impurities) from the carbon, it is contemplated that the closed assembly is flooded with a suitable solvent, for example, acetonitrile, the electrolytic solution, or other water removing material, before filling the assembly with the electrolyte. By having a filling hole at each end of the closed assembly, it becomes possible to flood the inside of the closed assembly. It is also contemplated that the carbon cloth, before being impregnated with aluminum, and / or after being impregnated with aluminum, but before being assembled in the electrode piles, can also be flooded or cleaned with a suitable material (e.g. of water or additives that seek and remove water), selected to remove impurities, especially water. If the electrolyte solution passes the impurity test successfully (block 244), it is also tested for its conductivity (block 246). The conductivity test is performed using a conventional conductance meter that measures the conductance using an alternating current signal. The conductance of the solution must be at least 55 to 58 milliohms / cm at 22 ° C. Once the electrolyte solution has been mixed and tested to determine if it has impurities and conductivity, it is impregnated in the closed-room assembly (block 248, Figure 14B). The preferred impregnation is done by placing the electrode enclosure in such a way that one filling hole is on the bottom, and another on the top, and then the enclosure is filled with the electrolyte under pressure from the bottom to the top , in such a way that no gases present in the room are caught in it. The amount of electrolyte solution to be impregnated in the enclosure, for the clam shell enclosure design shown in Figure 12, is 200 milliliters (or 205 grams). After the prescribed amount of electrolytic solution has been impregnated in the enclosed space, the plugs 168 are inserted into the filling holes 167, to finally seal the enclosure (block 250, Figure 14B). Then, final electrical tests of the capacitor are made (block 262), to test whether the capacitor meets its specified operating criteria. In general, acceptance tests include charging the capacitor up to its specified working voltage, Vw, for six hours, and then allowing the capacitor to self-discharge for a period of fourteen hours. The voltage drop that occurs during this fourteen-hour self-discharge period provides a measure of the equivalent parallel resistance of the capacitor, which must be at least 200 ohms, preferably over 350-400Ω, for example, when minus 360 O. (A self-discharge resistance of 200 O corresponds to a self-discharge time constant of at least 5.8 days). Additional acceptance tests that can be performed include subjecting the capacitor of a constant current cycle test to determine the cycle capacitance and the continuous state series resistance. This test is performed by applying a biphasic current of 100 amperes and / or 200 amperes to the capacitor, as shown in Figure 15. The voltage waveform resulting from the application of the current is measured. From the current and voltage waveforms, which includes the time measurements, a large number of parameters are determined to characterize the capacitor. These parameters include the load capacitance, Carriba; Discharge capacitance Cabajo; the capacitance of half discharge, I 2A AND the resistance of continuous state, R8. In order to meet the desired performance criteria currently imposed, these values must be: Cabajo > 2200 Farad, C1 2 > I down for approximately 150 Farads; R8 < 1 milliohm, Carriba / Cabajo > 0.98; And Cabaj0 / Carriba < l .05 For the first group of single-cell multi-electrode double-layer capacitors, which have been made in accordance with the present invention, ie, using the clam shell design shown in Figure 12, the test data of acceptance are as shown in Table 3. The final acceptance tests also include tests of alternating current impedance. The extremely low impedance of the double-layer capacitor makes alternating current impedance measurements difficult using standard equipment and techniques. The key parameter to be measured is the initial resistance, R0. This resistance affects the peak power that the capacitor can supply. It is measured at 1000 Hz using a Solatron 1250 Frequency Response Analyzer, and a Pot-niostat PARC 273. R0 must be approximately half the R8 value, or approximately 0.45 mO. TABLE 3 Parameter Value _ Standard Deviation '' down 2422 f 44.6 f R_ 0.908 mO 0.058 mO ^ aarrrriibbaa '' ^^ down 1.01 R.parallel 387 O 53 O As described above, therefore, it is seen that the single-cell, multi-electrode double-layer capacitor provided by the present invention represents a significant advance in the double-layer capacitor technique. The use of carbon cloth impregnated with aluminum, folded around a sheet of current collector sheet, forms "an" efficient electrode structure that provides very low electrode resistance. By connecting a large number, for example, twenty-seven, of these electrodes in parallel in a first electrode stack, and intercalating the electrodes of the first electrode stack with a second electrode stack, wherein each electrode is further surrounded by a sleeve of suitable separating / insulating electrode, and then by packing this package of electrodes interspersed within a sealed enclosure that holds the electrode package under modest pressure, and then by further impregnating the sealed enclosure with a prescribed amount of highly conductive non-aqueous electrolyte , a double-layer capacitor that exhibits capacitance values greater than 2200 Farads is realized, at a nominal working voltage of approximately 2.3 volts, an electrode resistance of approximately 0.8 mO, a time constant of approximately 2 seconds, a energy density in the range of 2.9 to 3.5 W-hr / kg, and a power rating of more than 1000 W / kg a a discharge of 400 amps. Conveniently, these operating parameters can be further improved when the capacitor is operated at a higher voltage, for example, 2.7 volts, or even 3.0 volts (which can easily be done once all the impurities in the capacitor are removed). electrolytic solution), and reduce the weight of the enclosure. For example, at an operating voltage of 2.0 volts, the energy density rises "to 5.9 W-hr / kg.In addition, when using a polyethylene separator material, instead of a polypropylene separator, the effective resistance of the electrode, allowing the capacitor time constant to be reduced up to about 1.5 seconds.Although the invention described above has been described by means of the specific modalities and applications thereof, those skilled in the art could make the same numerous modifications and variations without departing from the scope of the invention stipulated in the claims.

Claims

CLAIMS 1. A double-layer capacitor, comprising a capacitor box having a first part and a second part, capable of clamping together to form a sealed capacitor box, the first part having a first capacitor terminal associated with it , and the second part having a second capacitor terminal associated therewith; a pair of electrodes separated by a porous separator within said sealed capacitor box, each of the electrodes of the pair of electrodes being respectively coupled to the first or second capacitor terminals; and a non-aqueous electrolytic solution within the sealed capacitor box, whereby the pair of electrodes is saturated and immersed within the electrolytic solution, and wherein the double layer capacitor is characterized by: a first stack of electrodes comprising a plurality of electrodes, each electrode of the first stack of electrodes comprising a current collector sheet and a compressible carbon cloth impregnated with aluminum, in direct physical contact with the current collector sheet, and where the current collector sheet of each electrode is connected electrically to the first capacitor terminal, whereby the electrodes of the first stack are all connected in parallel to the first capacitor terminal via their respective current collector plates; a second stack of electrodes comprising a plurality of electrodes, each electrode of the second stack of electrodes comprising a current collecting sheet and a compressible carbon cloth impregnated with aluminum, in direct physical contact with the current collecting sheet, and where the sheet The current collector of each electrode is electrically connected to the second capacitor terminal, whereby the electrodes of the second stack of electrodes are all connected in parallel to the second capacitor terminal via their respective current collector plates; and a porous separating sleeve positioned around each of the electrodes of the second stack, the separating sleeve having pores therein through which the ions can easily pass; the electrodes of the first and second stacks being interlocked with each other to form a stack of flat, interlaced electrodes, in which the adjacent electrodes are prevented from electrically contacting each other by means of the porous separating sleeve; and the stacking of flat, interlaced electrodes, being maintained under a constant pressure of between about 0.35 and 1.27 kg / cm2 within the sealed capacitor box. The double-layer capacitor of claim 1, characterized in that the first and second parts of the capacitor box are made of a conductive material, and where the capacitor box includes an electrical insulator to prevent them. first and second parts electrically short each other when the first and second parts are clamped together to form the sealed capacitor box, and further where the first capacitor terminal comprises the first part of the capacitor box and the second terminal of the capacitor box. Capacitor comprises the second part of the capacitor box. The double-layer capacitor of claim 1 or 2, wherein each current collector sheet of each electrode of the first and second electrode stacks has a tongue portion and a fin portion, and wherein the impregnated carbon cloth is placed in contact with the fin portion of each current collector sheet of each stack of electrodes, and further where the tab portion of the current collector sheet of each electrode in the first stack of electrodes is bonded to the other tab portions of the current collector sheets used within the first stack of electrodes and to form a first linked tab portion that is connected to the first capacitor terminal, and also where the tab portion of the current collector sheet of each electrode in the second stack of electrodes is linked to the other tab portions of the current collector sheets used within the second stack of electrodes to form a second portion of linked tongue which is connected to the second capacitor terminal. 4. The double layer capacitor of claim 3, wherein the first and second parts of the capacitor box are made of aluminum and collectively weigh no more than 200 g. The double layer capacitor of claim 3, wherein the first and second parts of the capacitor box are made of copper-clad aluminum and collectively weigh no more than 100 g. The double layer capacitor of claim 1, wherein the first and second parts of the capacitor box are made of a non-conductive material, and further where the first capacitor terminal comprises a first feed terminal therethrough that is mounts in the first part of the capacitor box, and wherein the second capacitor terminal comprises a second feed terminal therethrough mounted in the second part of the capacitor box. The double layer capacitor of claim 6, wherein the first and second through-feed terminals are located at opposite ends of the capacitor box. The double layer capacitor of claim 1, wherein the capacitor box includes two sealable fill holes located at opposite ends of the capacitor box. The double layer capacitor of claim 1, wherein the impregnable, compressible carbon fabric comprises a carbon cloth made of activated carbon fibers arranged in woven bundles to form the carbon cloth, and further where the aluminum is impregnated in the spaces between the activated carbon fibers within each bundle of carbon fibers to reduce the transverse electrical resistance of the carbon cloth. The double layer capacitor of claim 9, wherein the carbon cloth impregnated with aluminum is pressed to reduce the thickness of the fabric impregnated with aluminum by about 15% before placing it in contact with the current collector sheets of the stacks of first and second electrodes. 11. The double layer capacitor of the claim 10, wherein the carbon cloth impregnated with pressed aluminum of most electrodes in the stack of flat, interlaced electrodes is bent so as to make contact with both sides of its respective current collector sheet. 12. The double layer capacitor of the claim 11, where the carbon cloth that is impregnated with aluminum exhibits a weight per area, before impregnation, of 130 to 135 g / m2, and is 0.50"to" 0.55 mm in thickness, and has a volume of pores of 1.0 to 1.5 ml / g. 13. The double layer capacitor of the claim 12, where the weight of the aluminum impregnated in the carbon fabric comprises no more than about 53% of the total weight of the carbon cloth impregnated with aluminum. The double layer capacitor of claim 13, wherein the transverse strength of the carbon cloth impregnated with aluminum is reduced by a factor of at least 50 after impregnation, compared to the transverse strength of the carbon cloth before of impregnation. 15. The double layer capacitor of the claim 14, where the capacitor box has an internal volume of no more than 375 cm3, a total weight of not more than 600 g, and where the stacking of flat electrodes, interlaced, includes at least 50 electrodes, 25 electrodes in each of the first and second electrode stacks. 16. The double layer capacitor of the claim 15, where the capacitor exhibits a capacitance of 230 Farades ± 10% at a nominal voltage of 2.3 volts. 17. The double layer capacitor of the claim 16, where the capacitor also exhibits an energy density of between about 3.4 and 3.5 W-hr / kg, a rated power capacity of around 1,000 W / kg at a 400 amp discharge, a total electrode resistance of less about 0.8 milliohms, and a time constant no greater than about 2 seconds. 18. The double layer capacitor of claim 1, wherein the electrolytic solution is characterized as containing a solution of 300 to 305 g of tetraethylammonium tetrafluoroborate (CH3CH2) 4N + BF4 ~ per liter of acetonitrile (CH3CN). 19. The double layer capacitor of claim 1, wherein the porous separating sleeve is made of a polypropylene sheet having a thickness of at least 0.025 mm and generally rectangular pores having an average pore size of about 0.04 by 0.12 μm. 20. A double layer capacitor having a sealable capacitor box, in which are first and second terminal means and an electrode assembly inside the case including first and second electrodes, and a non-aqueous electrolyte sealed within said box, said double-layer capacitor characterized in that: the first electrode comprises a first current collector plate and a first compressible carbon fabric, impregnated with a prescribed metal, in direct physical contact with the first current collector plate, and where the first current collector sheet is electrically connected to the first terminal means; the second electrode comprises a second current collecting sheet and a second compressible carbon fabric, impregnated with the prescribed metal, in direct physical contact with the second current collecting sheet, and where the second current collecting sheet is electrically connected to the second terminal means; a porous separating sleeve positioned around the second electrode; and the first and second electrodes being positioned with each other, but preventing the first electrode from contacting electrically with the second electrode by means of the porous separating sleeve. The double layer capacitor of claim 20, characterized in that the porous separating sleeve is made of either: (1) a polypropylene sheet having a thickness of at least 0.025 mm, generally rectangular pores having an average pore size of around 0.04 by 0.12 μm, and a porosity of 25 to 40%, or (2) a polyethylene sheet having a thickness of at least 0.025 mm, a pore diameter of less than 0.5 μm, and a porosity of 40-60%. 22. The double layer capacitor of claim 20 or 21, characterized in that the first and second electrodes are pressed together with a pressure of between 0.35 and 1.27 kg / cm2 inside the closed box. 23. The double layer capacitor of claim 20, 21 or 22, characterized in that the electrolyte comprises a solution containing 300 to 305 g of tetraethylammonium tetrafluoroborate (CH3C? 2) 4N + BF4 ~ per liter of acetonitrile (CH3CN). 24. The double layer capacitor of the claim 23, characterized in that the metal that is impregnated in the open spaces of the fibers of carbon fibers comprises aluminum or titanium. 25. The double layer capacitor of the claim 24, characterized in that the carbon cloth that is impregnated with aluminum or titanium exhibits a weight per area, before impregnation, of 130 to 135 g / m2 and a thickness of 0.50 to 0.55 mm, and has a pore volume of 1.0. at 1.5 ml / g. 26. The double-layer capacitor of claim 24, characterized in that the impregnable, compressible carbon fabric comprises a carbon fabric made of activated carbon fibers arranged in woven bundles to form the carbon cloth, and furthermore where the Aluminum is impregnated in the spaces between the activated carbon fibers within each bundle of carbon fibers to reduce the transverse electrical resistance of the carbon cloth 27. A method of making a double-layer capacitor, which comprises: (a) ) impregnate carbon cloth with a metal by means of spraying the metal, while in a fluid or vaporized form, the carbon cloth being woven from activated carbon fibers into bundles of carbon fibers with spaces or voids between fibers individual carbon fibers within a bundle so that it is believed to have metal in the spaces; (b) form a plurality of current collector sheets, each sheet having a tab portion and a fin portion; (c) linking the tongue portions of the half of the plurality of current collector sheets together, to create an electrical interconnection, thereby forming a first stack of sheets; (d) linking the tongue portions of the other half of the plurality of current collector sheets together, to create an electrical interconnection, thereby forming a second stack of sheets; (e) forming stacks of first and second electrodes by placing carbon cloth impregnated against the fin portion of each of the current collector sheets of the first and second sheet stacks, with the sprayed side of the impregnated carbon cloth placed against the current collector sheet; (f) placing a porous separating sleeve over each of the electrodes of the second stack of electrodes, which electrodes each comprise a current collecting sheet and its associated impregnated carbon cloth; (g) interleaving the electrodes of the first and second electrode stacks, so that each spacer sleeve functions as an electrical insulator between adjacent electrodes and prevents adjacent electrodes from electrically shorting each other to form a stack of interlaced electrodes; alternating electrode current collector plates in the stacking of interlaced electrodes being connected in parallel; (h) compressing the stack of interlaced electrodes to force the sprayed side of the impregnated carbon cloth against the current collector sheets of each stack, thereby reducing the contact resistance between the current collector sheets and the associated impregnated carbon cloth , respective; e (i) saturating the stack of interlaced electrodes with non-aqueous electrolyte so that the interlaced electrode stacks are immersed within the electrolyte. Summary A dual-layer, single-cell, high-performance, single-layer capacitor includes flat (A-stacking) and second (B-stacking) interlocking electrodes (141), adapted to be housed in a two-part capacitor box , capable of being closed (Figure 12), which includes a single "" electrolyte seal (154, 156, 158). Each stack of electrodes has a plurality of electrodes connected in parallel, the electrodes of one stack being interlocked with the electrodes of the other stack to form an interlaced stack (141), and with the electrodes of each stack being electrically connected to the respective terminals of the stack. capacitor. A porous separating sleeve (140) is inserted over the electrodes of a stack (stack B) before interlacing to prevent electrical shorts between the electrodes. The electrodes are made by folding a carbon cloth (136) impregnated with aluminum, low resistance, compressible, made of activated carbon fibers, around a current collector sheet (132) with a tab (133) of the sheets of each electrode of each stack connected in parallel. The tabs connected in parallel (135, 142) are then connected to the respective terminals of the capacitor. The height of the interlaced stack is somewhat greater than the internal height of the closed capacitor box, thereby requiring compression of the stacking of interlocking electrodes when placed inside the box, and thereby keeping the stack of electrodes interlaced under a modest constant pressure. The closed capacitor box is filled with electrolytic and sealed solution. A preferred electrolytic solution is made by dissolving an appropriate salt in acetonitrile (CH3CN). In one embodiment, the two parts of the capacitor box (150, 152) are conductive and functional as the capacitor terminals.