JPS6035510A - Electric double layer capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a small-sized, large-capacity wet electric double layer capacitor.

(Conventional structure and its problems) FIG. 1 shows the structure of a conventional coin-type electric double layer capacitor, in which a polarizable electrode body IK4 conductive electrode 2 is formed,
The polarizable electrode bodies 1 are opposed to each other with a separator 3 in between, impregnated with an electrolytic solution, and sealed using a gasket 4 and a case 5. In addition, when activated carbon fiber is used as the polarizable electrode body 1 and a metal layer such as aluminum or titanium or a conductive resin layer is formed as the conductive electrode 2, the polarizable electrode body 1 having the conductive electrode 2 is desired. It was possible to punch out a circular shape with a diameter of , and a coin-shaped electric double layer capacitor was realized. However, FIGS. 2 and 3 show the punching patterns of the polarizable electrode body, and when the circular polarizable electrode body 1 is punched out from the sheet-like polarizable electrode body 6, the number of punches is very large and the second Even with the pattern shown in FIG. 3, which is more efficient than the one shown in the figure, it is not possible to obtain a utilization efficiency of 91% or more. This poses a major problem in terms of reducing the cost of double layer capacitors.

(Objective of the Invention) An object of the present invention is to improve the utilization efficiency of raw materials in a coil type electric double layer capacitor.

(Structure of the Invention) The present invention effectively punches out regular hexagonal polarizable electrode bodies from a T-shaped polarizable electrode body having conductive electrodes, and arranges both poles by facing each other through a separator. death,
It has a structure in which the electrolyte is injected and then the casing is sealed.

(Description of Examples) Before describing specific examples, the operating principle of an electric double layer capacitor will be briefly explained.

Figure 4 shows a model of the basic principle of an electric double layer capacitor, using activated carbon fiber 7 as a polarizable electrode body.
Aluminum 8 is used as a conductive electrode having current collecting ability. Further, an organic electrolyte 9 in which tetraethylammonium perchlorate is dissolved in propylene carbonate is used as the electrolyte.

In this way, when activated carbon fibers are arranged parallel to an electrolytic solution and an electric field is applied, charges are accumulated at the interface, and if the charges accumulated at this interface can be extracted, an electric double layer capacitor is formed.

Here, η is the amount of charge per unit area, d is the dielectric constant of the medium, δ is the average distance from the solid surface to the ion at J sima, φ
When is the double layer potential, the equation (]) holds true.

η=Tφ (1) From equation (1), it can be seen that the amount of charge that can be accumulated at the interface is proportional to the area where the double layer is formed.

That is, in a coin-shaped double-layered case, making the electrode circular allows the electrode area to be maximized within the case.

However, when circular shapes are continuously punched out from the raw material sheet-like polarizable electrode, the utilization efficiency is not good.

Next, through specific calculations, we will clarify how the shape of the punching pattern affects the efficiency of raw material utilization.

First, consider the case where a circle is packed in the closest density as shown in FIG.

If we punch out a circle with a radius of 10 by n pieces vertically and horizontally, then the horizontal part is 2ncy + and the vertical part is JT (n -1) + zcz o
A rectangular shape is required, and the total area of n2 circles punched from it is n2·π2. Letting the utilization efficiency be El, it becomes as follows. If n is set to infinity, then 90.
It is not possible to obtain a utilization efficiency of more than 69%.

Next, consider the case where regular hexagons are closest packed as the polarizable electrode body of the present invention as shown in FIG.

If we punch out n pieces vertically and horizontally from a regular hexagon with a side of 1-, the length will be 1 + (n4-] )X0.5 (-'a, the width) n tx, and the regular hexagons to be punched from there will be When E2 is 02 squares, the following equation is obtained, and when n is set to infinity, it can be seen that the larger n is, the closer the utilization efficiency is to 100. For example, when n = Zoo, the utilization efficiency in Figures 3 and 5 is 90, respectively.
55% and 9966%.

(Example 1) FIGS. 6(a) and 6(b) are plan views of a polarizable electrode body and a separator of an embodiment of the electric double layer capacitor of the present invention,
(C) shows a cross-sectional view of its configuration, where 1 is a polarizable electric frame, 2
is a conductive electrode, 3 is a separator, 4 is a conductive electrode,
5 is a case.

Activated carbon fiber is used as the polarizable electrode body 1, and a conductive electrode 2 is formed on the surface of the activated carbon fiber by spraying aluminum by a plasma spraying method. Thereafter, regular hexagonal electrodes with 10 sides on each side were punched out or cut in the pattern shown in Figure 5, and an organic electrolyte solution containing tetraethylammonium perfluorate dissolved in propylene carbonate was used as the electrolyte solution. The capacitor of the present invention is constructed by sealing the capacitor.

Note that the separator 3 is less expensive than the polarizable electrode body 1 and the like, and is circular in order to prevent short circuits.

Here, we compared the amount of raw activated carbon fiber required to create 10,000 capacitors as described above with the amount required when punching out circular electrodes with a diameter of 201111 mm in the pattern shown in Figure 3. Shown in 1.

Table 1 can be reduced by as much as 25 yen, and this cost reduction increases as the production volume increases.

Furthermore, the area ratio between the electrodes having a regular hexagonal shape (X side 10 cut) and a circular electrode shape (radius 1k) is approximately 827% of the latter.
becomes. Therefore, although the capacity value is reduced to about 827% of the conventional value, only 752 units of the raw material activated carbon fiber is required compared to the conventional one, which can greatly contribute to cost reduction.

Table 2 shows the characteristics of the capacitor of the present invention together with the conventional example.

Table 2 (Example 2) Table 3 shows the characteristics when the structure was similar to that of Example 1 and dilute sulfuric acid was used as the electrolyte. Table: When using an inorganic electrolyte such as dilute sulfuric acid, the breakdown voltage cannot reach the 2V value of an organic electrolyte system, and the limit is 1 or 2V, which is the water decomposition voltage, but large capacity It is possible to obtain a high value and also reduce impedance, making it suitable for strong discharge applications.

Table 3 (Example 3) Figure 7 shows a polarizable electrode body 1 in the same system as in Example 1.
This figure shows a case where a capacitor having a structure in which two layers are laminated is assembled, and 2 is a conductive electrode and 3 is a separator, which is the same as in the previous figures.

Its characteristics are shown in Table 4.

Table 4 Comparing Tables 4 and 2, it can be seen that the capacitance value increases in proportion to the amount of polarizable electrode body. The impedance is controlled by the internal resistance of the electrolyte, and there is not much difference between Tables 2 and 4.

(Effects of the Invention) As explained above, according to the present invention, since the polarizable electrode body is made into a regular hexagon, the utilization efficiency of raw materials approaches 100% in mass production, and the electrode area is reduced compared to the conventional one. ,
However, the cost is 75.2%, which can greatly contribute to reducing the cost of small-sized, large-capacity double layer capacitors.

[Brief explanation of the drawings] Fig. 1 shows the structure of a conventional coin-shaped electric double layer capacitor, Figs. 2 and 3 show punching patterns of polarizable electrode bodies, Fig. 4 is an explanatory diagram showing the basic principle of an electric double layer capacitor as a model, FIG. 5 is a diagram showing a polarizable electrode body pattern of the present invention, and FIG. The figure shown in FIG. 7 is a diagram showing another embodiment of the present invention. l...Polarizable electrode body, 2...
... Conductive electrode, 3 ... Separator, 4 ... Gasket, 5 ...
・・・・・・Case, 6 concave curves, sea I shape polarizable electrode body, 7 curves, activated carbon fibers, 8・・・・・・・・・
Aluminum electrode, 9... Organic electrolyte. Patent Applicant: Matsushita Electric Industrial Co., Ltd. (;P Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 (b) (C)

Claims (4)

[Claims] (1) A regular hexagonal polarizable electrode body is formed from a sheet-like polarizable electrode body having conductive electrodes, these are placed facing each other with a separator in between, and both electrodes are arranged, and an electrolyte is poured into the body. An electric double layer capacitor characterized by having a sealed casing structure. (2) The electric double layer capacitor according to claim (1), characterized in that activated carbon fiber is used as the polarizable electrode body. (3) Claim (1) characterized in that a metal layer such as aluminum or copper is formed on a polarizable electrode body as a conductive electrode by either a thermal spraying method or a vapor deposition method.
The electric double layer capacitor described in Items 1 and 2). (4) As a conductive electrode, a conductive resin layer is formed on a polarizable electrode body by any one of a screen printing method, a spray method, and a dip method. The electric double layer capacitor according to item (2).