JPS6325694B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an electric double layer capacitor that utilizes an electric double layer formed by the interface between a polarizable electrode and an electrolyte, and includes a plurality of elements composed of carbon fiber and metal spraying. This invention relates to small, large-capacity electric double layer capacitors that are individually laminated. Conventional Structures and Problems Conventional electric double layer capacitors are roughly divided into two types based on the shape of their polarizable electrodes. The first one uses activated carbon powder as a polarizable electrode and has the following manufacturing process. That is, as shown in FIG. 1, graphite, carbon black, activated carbon, etc., and a binder such as tetrafluoroethylene/polyvinylpyrrolidone are placed on a net-like current collector 1 such as an expanded metal made of aluminum metal. Polarizable electrode 2
It is rolled and supported. A separator 3 impregnated with an electrolytic solution, a current collector 1, and a polarizable electrode 2 are wound together and sealed in a cylindrical aluminum case 4. The second type uses a cloth, paper, or felt material made of activated carbon fibers as the polarizable electrode 5. A current collector 6 is formed on the electrode 5 by plasma spraying or the like, and an electrolytic solution is applied. For example, as shown in FIG. 2, the housing is housed in a flat aluminum case 8 via a separator 7 impregnated with . Note that 9 in the figure is an insulator seal packing. The latter of the above two types of electric double layer capacitors was invented by the present inventors (Japanese Patent Application Laid-Open No.
55-99714), which was realized by combining the characteristics of activated carbon fibers such as a large specific surface area and mechanical strength with metal spray layer formation technology, and provides a small and large capacity electric double layer capacitor. It is. OBJECTS OF THE INVENTION An object of the present invention is to further develop the second type described above and provide an electric double layer capacitor that is smaller in size, has a larger capacity, and has excellent reliability. Structure of the invention The present invention stacks a plurality of unit capacitor elements,
For example, a metal sprayed layer is formed on the end face to take out the entire electrode. DESCRIPTION OF EMBODIMENTS The electric double layer capacitor of the present invention is roughly divided into the following two types. That is, a first type in which a unit capacitor element is a combination of two polarizable electrodes and a separator, and a second type in which a unit capacitor element is a combination of one polarizable electrode, a separator, and a non-polarizable electrode. It is divided into those of FIG. 3 shows the basic structure of the first type, which includes a metal layer 11 on a cloth, paper, or felt 10 made of carbon fiber or activated carbon fiber, and a separator 12 impregnated with an electrolytic solution sandwiched between the metal layer 11. , this structure A is taken as a unit capacitor element. At this time, the metal layer 11 functions as a collector electrode, and the carbon fiber layer 10 functions as a polarizable electrode. As shown in the figure, n unit capacitor elements are stacked alternately, and metal layers 13 and 14 are provided on both end faces B and B' to form collective electrodes, respectively. At this time, it is preferable to provide insulation between adjacent unit capacitor elements A and A by using a spacer 15 or the like. There are various methods of forming the metal layers 13 and 14, but plasma spraying, arc spraying, etc. are suitable. FIG. 4 shows the basic structure of the second type, in which a combination B consists of a metal layer 21 on a cloth, paper, or felt 20 made of carbon fiber or activated carbon fiber, and a separator 22 impregnated with an electrolyte. Becomes a unit capacitor element. N unit capacitor elements are stacked alternately as shown in the figure, and two metal layers are placed on both end surfaces C and C.
3 and 24 are provided, each serving as a collective electrode. In an electric double layer capacitor with such a configuration, the metal layer 2
1 functions as a collector electrode, and the carbon fiber layer 20 functions as a polarizable electrode. The metal layers 21 facing each other with the separator 22 in between function as opposing non-polarizable electrodes of the carbon fiber layer 20 and constitute individual unit capacitor elements. These electrode configurations are realized by a combination of activated carbon fibers used as polarizable electrodes and sprayed metal layers used as current collecting electrodes. Next, the activated carbon fibers and the sprayed metal layer used in the present invention will be described in detail. As a polarizable electrode of an electric double layer capacitor,
Activated carbon is generally used in large numbers because of its large specific surface area and chemical stability. The activated carbon fiber used in the present invention is made by combining activated carbon fibers with a specific surface area of 1000 to 2000 m ² /gr into cloth, paper, or felt, and its properties were compared with that of conventional coconut shell-based granular activated carbon. are shown in Table 1 below.

【table】

[Table] Among these, the coconut shell-based activated carbon powder is used as the first type of powder paste polarizable electrode and has a surface area of 700 to 800 m ² /gr.
On the other hand, phenol-based, rayon-based, and acrylic-based activated carbons can be produced using activated carbon. The fibers can be used in the form of cloth, paper, or felt.
Also, the surface area of the product obtained by this method is 1000~
2000m ² /gr, which is more than double that of coconut shell-based activated carbon powder, and if its wide specific surface area can be used effectively, a very large capacity can be obtained in a small volume. Furthermore, among these activated carbon fibers, acrylic and pitch fibers are generally somewhat flexible and have a slightly small surface area. Furthermore, although rayon-based fibers have a large surface area, their fibers are brittle, and although felt-like carbon fibers are popular, they are difficult to make into paper, and paper-like forms are possible, but they have problems with chemical resistance and water resistance. be. On the other hand, phenolic carbon fibers are made from cured novolac fibers, and since the cured novolac fibers are infusible and have low heat shrinkage, there is no need to make the raw material fibers infusible beforehand, and the phenolic carbon fibers can be woven into fabrics. It is particularly excellent as a polarizable electrode for electric double layer capacitors because it can be activated carbonized as it is and is strong and flexible. In addition, paper making using phenolic carbon fiber as a raw material has a number of advantages.In particular, paper is made using phenolic carbon fiber as a raw material and special Kynol (trade name of phenolic fiber manufactured by Nippon Kynor Co., Ltd.) as a binder. It was recognized that the resulting product has extremely excellent characteristics in many aspects such as flexibility, electrical resistance, water resistance, chemical resistance, winding strength, processing accuracy, electric capacity, and cost. Next, the sprayed metal layer that makes the electrode structure of the present invention possible will be described. The metal current collecting layer used in the present invention can be formed by plasma spraying,
Preferably, it is formed by arc spraying or the like. As a metal current collecting layer, for example, a metal foil may be sandwiched between activated carbon fibers and a separator, a metal vapor-deposited film,
Various constituent materials are possible, such as applying conductive paint, but each has advantages and disadvantages when considering the strength of the constituent body, chemical stability against electrolyte, man-hours during manufacturing, thickness control, cost, etc. On the other hand, the thermal sprayed metal layer can of course be formed on any surface of the activated carbon fiber, but the adhesive strength between the activated carbon fiber and the metal layer is extremely strong, and the formed metal layer can be formed on the activated carbon fiber. It can be used as a reinforcing material, and it is very easy to stack unit capacitors. The metal used here is preferably an element that is stable to the electrolyte, such as Al, Zn, Cu, or Ni. Next, the electrode extraction section will be described. As mentioned above, in order to further take out the electrodes of the entire capacitor from the end face of the collector electrode of the unit capacitor group of the present invention,
There are two metal layers. (13, 14 in Figure 3,
23 and 24 in Figure 4) This metal electrode layer is formed so that every other unit capacitor is taken out from the same side electrode, and it is necessary to form it so that the electrodes of adjacent unit capacitors do not come into contact with each other. There is. In order to achieve this objective, it is preferable to form these current collecting electrodes by a plasma spraying method. FIG. 6 shows how metal powder 3 is applied to a stacked unit capacitor group 30 using a plasma spray gun 31.
2 is shown being sprayed. In this case, an insulating spacer 35 or the like as described in the description of FIG. 3 may be provided so that the electrodes 33 and 34 of adjacent unit capacitors are not electrically connected. Only the electrodes indicated by diagonal lines in the same direction in FIG.
It is formed so as to be in contact with the collective thermal spray electrode 36. The specific way to take out the leads is for the face bonding type without leads as shown in Figure 7a (in the same figure, 40 is the capacitor body, 4
1 is a thermal spray electrode. ), as shown in Figure 7b,
The metal lead wire 42 is held on the end face of the capacitor during the formation of the thermal sprayed layer 43 and is embedded in the thermal sprayed layer 43, as shown in FIG. A conceivable example is one in which the lead wire 46 is bonded. All of these are used by being placed in a case made of resin, metal, ceramic, etc., or by being dipped in resin. Furthermore, as shown in FIG. 7d, it is also possible to seal the exterior cases 52 and 53, which are in contact with the sprayed layer 51 via spot-welded leads 50 with a gasket 54, and place them in a coin-shaped battery case. In addition, in the same figure, 55 is an insulating spacer. Next, more specific embodiments of the present invention will be described. (Example 1) Activated carbon fiber (manufactured by Nippon Kynol Co., Ltd., specific surface area
2000m ² /gr) by plasma spraying on one side.
Form a 5 μm aluminum conductive layer. This was cut into 5 mm square pieces and 10 sheets were stacked together with a separator as shown in Figures 3 and 4. However, the separator used in this example is made of a polyethylene film with a thickness of 10 μm, and the separator is coated with an electrolyte solution containing 30% by weight of propylene carbonate, 50% by weight of γ-butyrolactone, and 20% by weight of tetramethylammonium verchlorate. Impregnate as. Aluminum sprayed layers (thickness: 10 μm) are formed on opposing end faces of such a laminated structure by plasma spraying, and electrodes are taken out.
Figure 7d shows the laminated capacitor made in this way.
Seal the housing using the method shown in , and measure the characteristics. Table 2 shows the characteristics of the electric double layer capacitor obtained in this example in comparison with those of a conventional activated carbon powder type and a single layer of activated carbon fiber.

[Table] As is clear from Table 2, the electric double layer capacitor according to the present invention has a very large capacity per unit volume, a small internal resistance per unit capacity, and a small change in capacity during high temperature load life. It is becoming. Effects of the Invention As described above, the present invention utilizes activated carbon fibers and metal spraying technology to realize an electric double layer capacitor that has excellent advantages such as a very large capacity per unit volume. The industrial value is very large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional electric double layer capacitor, FIG. 2 is a diagram showing another example of a conventional electric double layer capacitor, and FIG. 3 is a diagram showing an example of an electric double layer capacitor according to the present invention. , FIG. 4 is a diagram showing another example of the electric double layer capacitor according to the present invention, FIG. 5 is a diagram showing the manufacturing process of activated carbon fiber used in the main part of the present invention, and FIG. 6 is a diagram showing another example of the present invention. Figure 7a, which shows the method for forming the current collecting electrode, which is the main part of the
b, c and d are diagrams each showing a configuration example of an electric double layer capacitor according to the present invention. 1,6... Current collector, 2,5... Polarizable electrode, 10,
20...Carbon fiber layer, 11, 13, 14, 21, 2
3, 24... Metal layer, 43, 44, 51... Sprayed layer.

Claims (1)

[Claims] 1. Consisting of a pair of polarizable electrodes made of carbon fiber or activated carbon fiber that face each other with a separator impregnated with an electrolytic solution interposed therebetween, the side of the pair of polarizable electrodes facing the separator and is a stack of multiple unit capacitor elements with a current collector provided on the opposite side,
Further, electrodes for external extraction formed by either plasma spraying or arc spraying are provided on both end faces of the laminate of the unit capacitor elements, and the pair of current collectors provided in the unit capacitor elements are connected to the outside. An electric double layer capacitor characterized by being electrically connected to respective extraction electrodes. 2 The current collector and the external electrode are made of Al, Ni,
The electric double layer capacitor according to claim 1, characterized in that the electric double layer capacitor is made of at least one member selected from the group consisting of Zn and Cu. 3. The electric double layer capacitor according to claim 1, wherein the carbon fibers are made of phenolic carbon fibers. 4. A unit capacitor element in which a polarizable electrode made of carbon fiber or activated carbon fiber is provided with a current collector on one side and a separator impregnated with an electrolyte on the other side, the current collector and the separator being adjacent to each other. In this way, a plurality of unit capacitor elements are laminated, and external extraction electrodes formed by either plasma spraying or arc spraying are provided on both end faces of the stack of unit capacitor elements, and a plurality of unit capacitor elements are laminated. An electric double layer capacitor characterized in that the current collectors are alternately connected to external extraction electrodes on both end faces of the laminate.