JPH10321482A - Electrical double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further increase the energy density of an electrical double layer capacitor. SOLUTION: Tubular carbon fibers 18 called carbon nano-tubes are used for polarizable electrodes 12 and 13. Since the tubular carbon fibers 18 have outside diameters of 1-500 nm, the surface area per unit volume of tubular carbon fiber groups can be increased further as compared with the case where activated carbon particles are used for the polarizable electrodes and, in its turn, the energy density of an electrical double layer electrode can be increased further.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric double layer capacitor.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing an example of a conventional electric double layer capacitor. In this electric double layer capacitor, a large number of activated carbon particles (electrodes) and polarizable electrodes 2 and 3 composed of an electrolyte solution are provided on both sides of a porous separator 1 having ion permeability and non-electron conductivity. Current-collecting electrodes 4 and 5 having non-ion permeability and electron conductivity are provided, and a frame-like gasket 6 made of insulating rubber or the like is provided between each of the surroundings of both surfaces of the separator 1 and the current-collecting electrodes 4 and 5. 7 is provided. in this case,
Activated carbon particles are used as the electrodes of the polarizable electrodes 2 and 3 because the particle diameter is as small as about 10 to 50 μm. Therefore, the surface area per unit volume of the activated carbon particles can be increased, and the energy density can be reduced. This is because it can be made larger.

[0003]

However, in such a conventional electric double layer capacitor, even though the activated carbon particle diameter is as small as about 10 to 50 μm, the surface area per unit volume of the activated carbon particle group is limited. Because there is
There was a problem that the energy density was limited. An object of the present invention is to further increase the surface area per unit volume of the polarizable electrode.

[0004]

According to the present invention, a large number of minute conductive tubes are used as electrodes of a polarizable electrode. The invention according to claim 4 uses a tubular carbon fiber having an outer diameter of about 1 to 500 nm as the conductive tube.

According to the present invention, since the minute conductive tube is used as the electrode of the polarizable electrode, the surface area per unit volume of the conductive tube group is made smaller than when the activated carbon particles are used as the electrode of the polarizable electrode. It can be even larger.

[0006]

FIG. 1A is a sectional view of an electric double layer capacitor according to a first embodiment of the present invention, and FIG. 1B is a schematic enlarged sectional view thereof.
In this electric double layer capacitor, polarizable electrodes 12 and 13 are provided on both sides of a separator 11, and current collecting electrodes 14 and 15 are provided on both sides thereof. Frame-shaped gasket 1 between
6, 17 are provided. The polarizable electrodes 12 and 13 are composed of a large number of minute tubular carbon fibers (conductive tubes) 18 and an electrolyte solution 19. In this case, the tubular carbon fiber 18 is made of what is called a carbon nanotube. The separator 11 can be omitted when there is no possibility that the tubular carbon fibers 18 in the polarizable electrodes 12 and 13 on both sides are in direct contact with each other.

Here, a method of forming the tubular carbon fibers 18 called carbon nanotubes will be described.
For example, in a glass container in which an inert gas such as He or Ar of about 100 to 500 Torr is sealed, a DC arc discharge is generated between two carbon rod electrodes arranged in the glass container, so that the carbon of the negative electrode is reduced. When a carbon deposit is grown on the surface of the rod electrode, and the grown carbon deposit is raked, a tubular carbon fiber 18 is obtained. The outer diameter of the tubular carbon fiber 18 thus obtained is 1 to 5
It is about 00 nm, and the length is about 0.05 to 500 μm. As a method of incorporating the tubular carbon fiber 18, a paste obtained by mixing the tubular carbon fiber 18 and the electrolyte solution 19 is mixed with the separator 11 or the current collecting electrode 1.
There is a method of applying to 4 and 15.

As described above, the outer diameter of the tubular carbon fibers 18 used as the electrodes of the polarizable electrodes 12 and 13 is 1 to 50.
Since the length is about 0 nm and the length is about 0.05 to 500 μm, the surface area per unit volume of the group of tubular carbon fibers 18 can be further increased as compared with the case where activated carbon particles are used as electrodes of the polarizable electrode. As a result, the energy density can be further increased. In this case, in order to increase the surface area per unit volume of the group of tubular carbon fibers 18, the outer diameter of the tubular carbon fibers 18 is preferably as small as possible, for example, 1 to 100.
About nm is preferable. By the way, the tubular carbon fiber 1
8 is literally a tube, so that not only its outer peripheral surface but also its inner peripheral surface can function as an electrode surface. On the other hand, considering that the tubular carbon fiber 18 is crushed, it is not so preferable that the tubular carbon fiber 18 is too long. Therefore, the length of the tubular carbon fiber 18 is preferably, for example, about 0.05 to 10 μm.

Here, the case of the charged state of the electric double layer capacitor will be briefly described with reference to FIG. When charging is performed using the current collecting electrode 14 as a negative electrode and the current collecting electrode 15 as a positive electrode, the positive ions in both electrolyte solutions 19 and 22 cause the tubular carbon fibers 1 of the polarizable electrode 12 on the negative electrode side to be charged.
Thus, the negative ions in the electrolyte solutions 19 and 22 are adsorbed on the surface of the tubular carbon fiber 18 of the polarizable electrode 13 on the positive electrode side.

FIG. 2 is a sectional view of an electric double layer capacitor according to a second embodiment of the present invention. This electric double layer capacitor has a first collector electrode 14 provided with a first polarizable electrode 12 composed of a large number of minute conductive tubes and an electrolyte solution on an upper surface, a separator 11, and a large number of separators on a lower surface. A second current collecting electrode 15 provided with a second polarizable electrode 14 made of a minute conductive tube and an electrolyte solution is placed in this order with a gasket 16 between them.
17 to form one electric double layer capacitor unit 21, a plurality (four in FIG. 2) of the electric double layer capacitor units 21 are stacked, It is housed in a cylindrical or cylindrical insulating cylinder 22 made of insulating resin, and the insulating cylinder 22 is covered with a positive electrode case 23 and a negative electrode case 24 made of aluminum, stainless steel, or the like, and a positive electrode case located inside. 2
3 and a spacer 25 made of an insulating resin is provided between the side wall of the negative electrode case 24 and the side wall of the negative electrode case 24 located outside. In this case, the lower surface of the first current collecting electrode 14 of the lowermost electric double layer capacitor unit 21 is
The upper surface of the second current collecting electrode 15 of the uppermost electric double layer capacitor unit 21 is in close contact with the upper inner surface of the positive electrode case 23. Therefore, this electric double layer capacitor has a structure in which a plurality of electric double layer capacitor units 21 are connected in series.

By the way, the current collecting electrodes 14 and 15 have thicknesses of 30
When the separator 11 is formed of a resin film having a thickness of about 30 μm and the thickness of the polarizable electrode 12 is set to about 5 μm, the thickness of one electric double layer capacitor unit 21 is reduced. It can be about 100 μm. Even if ten electric double layer capacitor units 21 are stacked to form an electric double layer capacitor as shown in FIG. 2, the thickness (excluding the thickness of the two cases 22 and 23) is reduced. The thickness can be considerably reduced to about 1 mm.

Although FIG. 2 shows a case where a plurality of electric double layer capacitor units 21 are connected in series, for example, the electric double layer capacitor units 21 may be connected in parallel as in a third embodiment of the present invention shown in FIG. Can also. In this case, the electric double layer capacitor unit 21 has a planar rectangular shape,
The left end portion of the first current collecting electrode 14 is bent to be along the left end surfaces of the separator 11 and the gaskets 16 and 17,
The right end of the second current collecting electrode 15 is bent so as to be along the right end surfaces of the separator 11 and the gaskets 16 and 17. A spacer 3 made of an insulating resin sheet is interposed between each of the four electric double layer capacitor units 21.
1 is interposed. A substantially L-shaped negative electrode is provided on the left bent portion of the first current collecting electrode 14 of the four electric double layer capacitor units 21 and on the lower surface of the first current collecting electrode 14 of the lowermost electric double layer capacitor unit 21. The plate 32 is in close contact. The right end bent portion of the second current collecting electrode 15 of the four electric double layer capacitor units 21 and the upper surface of the twelfth current collecting electrode 15 of the uppermost electric double layer capacitor unit 21 are partially partially L-shaped. The positive electrode plate 33 is closely contacted.
An insulating member 34 made of a mold resin is provided around a portion of each of the negative electrode plate 32 and the positive electrode plate 33 except for the respective end portions and around the four electric double layer capacitor units 21. A case 35 is provided. Thus, this electric double layer capacitor has a structure in which four electric double layer capacitor units 21 are connected in parallel.

Although FIGS. 2 and 3 show a case where a plurality of electric double layer capacitor units 21 are stacked, the present invention is not limited to this. For example, although not shown, a long first current collecting electrode provided with a plurality of minute conductive tubes and a first polarizable electrode composed of an electrolyte solution on one surface, and a long separator And a long second current collecting electrode provided on the other surface with a second polarizable electrode comprising a large number of minute conductive tubes and an electrolyte solution,
A long spacer made of an insulating resin sheet may be laminated in this order, and the laminated structure may be wound into a roll. In this case, the electrolyte solution was formed by winding the first and second current collecting electrodes to which the conductive tube was attached, the separator, and the spacer in a roll shape, and the wound thing was stored in an insulating case. Later, the conductive tube may be soaked into the conductive tube.

In the above description, as an example, a case where a paste obtained by mixing tubular carbon fibers and an electrolyte solution is applied to the first and second current collecting electrodes 14 and 15 to a thickness of about 5 μm. Although described, the present invention is not limited to this. For example, a large number of tubular carbon fibers may be arranged in close contact with each other in a single layer on each of the opposing surfaces of the current collecting electrodes 14 and 15. Further, a large number of tubular carbon fibers may be arranged in a single layer on each of the facing surfaces of the current collecting electrodes 14 and 15, for example, every other one.

[0015]

As described above, according to the present invention, since the minute conductive tube is used as the electrode of the polarizable electrode, the surface area per unit volume of the conductive tube group can be reduced by the electrode of the polarizable electrode. Can be made even larger than in the case of using activated carbon particles, and the energy density can be made even larger.

[Brief description of the drawings]

FIG. 1A is a sectional view of an electric double layer capacitor according to a first embodiment of the present invention, and FIG. 1B is a schematic enlarged sectional view thereof.

FIG. 2 is a sectional view of an electric double layer capacitor according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an electric double layer capacitor according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a conventional electric double layer capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Separator 12, 13 minutes Polarity electrode 14, 15 Current collecting electrode 18 Tubular carbon fiber 19 Electrolyte solution

Claims (4)

[Claims] 1. A polarizable electrode comprising a large number of minute conductive tubes and having electrodes arranged so as not to contact each other is disposed on each of the opposing surfaces of a pair of opposing current collecting electrodes. An electric double layer capacitor comprising at least one electric double layer capacitor unit. 2. A plurality of electric double layer capacitor units are stacked so that current collecting electrodes are in contact with each other, and a plurality of said electric double layer capacitor units are connected in series. 2. The electric double layer capacitor according to 1. 3. The electric device according to claim 1, wherein a plurality of said electric double layer capacitor units are stacked via an insulating spacer, and a plurality of said electric double layer capacitor units are connected in parallel. Double layer capacitor. 4. The conductive tube has an outer diameter of 1 to 500 n.
The electric double layer capacitor according to any one of claims 1 to 3, wherein the electric double layer capacitor is made of about m tubular carbon fibers.