JPS6313333B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a small-sized, large-capacity wet type electric double layer capacitor. (Structure of conventional example and its problems) Fig. 1 shows the structure of a conventional coin-type electric double layer capacitor, in which a conductive electrode 2 is formed on a polarizable electrode body 1; They are made to face each other with a separator 3 in between, are impregnated with an electrolytic solution, and are sealed using a gasket 4 and a case 5. In addition, in the case where 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 1 with the conductive electrode 2
It is possible to punch out a circular shape with a desired diameter,
A coin-type electric double layer capacitor has been 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 The third model is more efficient than the one shown in the diagram.
Even with the pattern shown in the figure, it is not possible to obtain a usage efficiency of 91% or higher. This poses a major problem in terms of reducing the cost of double layer capacitors. (Object of the Invention) An object of the present invention is to improve the utilization efficiency of raw materials in a flat electric double layer capacitor. (Structure of the Invention) The present invention effectively punches regular hexagonal polarizable electrode bodies from a sheet-like polarizable electrode body having conductive electrodes, and arranges both poles by facing each other through a separator. 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 the electric double layer capacitor will be briefly explained. FIG. 4 shows a model of the basic principle of an electric double layer capacitor, in which activated carbon fiber 7 is used as a polarizable electrode body, and 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 placed parallel to the electrolyte and an electric field is applied, charges are accumulated at the interface, and if the charges accumulated at this interface can be taken out,
It becomes an electric double layer capacitor. Here, when 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 center, and φ is the double layer potential, equation (1) holds true. η=d/4πδφ (1) From equation (1), it can be seen that the amount of charge accumulated at the interface is proportional to the double layer formation area. That is, in a coin-shaped double layer capacitor, 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 n circles each with a radius of 1 cm vertically and horizontally, we will need a rectangular original sheet with a width of 2 nm and a height of √3(n-1) + 2 cm, and the total area of the ^two circles punched out from it is n. ²・πcm ² . Here, if the utilization efficiency is E ₁ , becomes. Here, if n is set to infinity, Therefore, it is impossible to obtain a utilization efficiency of 90.69% or more. 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 cm, we need n + (n + 1) × 0.5 cm for the length and √3 ncm for the width, and the total area of the n ² regular hexagons punched from there is ,

[Formula]. Here, if the utilization efficiency is E ₂ , then Then, when n is set to infinity So, the larger n is, the more the usage efficiency is 100
It can be seen that it approaches %. For example, when n=100, the utilization efficiencies in FIGS. 3 and 5 are 90.55% and 99.66%, respectively. (Example 1) FIGS. 6a and 6b 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 is a cross-sectional view of the configuration, 1 is a polarizable electrode body, 2 is a conductive electrode, 3 is a separator, 4 is a gasket, and 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. Then 10 per side
mm regular hexagonal electrodes are punched out or cut in the pattern shown in Fig. 5, and an organic electrolyte in which tetraethylammonium perchlorate is dissolved in propylene carbonate is used as the electrolyte.
The sealed casing constitutes the capacitor of the present invention. 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 make 10,000 capacitors as described above with the amount required when punching out electrodes in a circle with a diameter of 20 mm in the pattern shown in Figure 3, and the amount is shown in Table 1. show.

[Table] Table 1 shows that using regular hexagonal electrodes can reduce raw material costs by as much as 25%, and this cost reduction increases as the production volume increases. Furthermore, the area ratio between the electrodes having a regular hexagonal shape (10 mm on a side) and a circular shape (radius 10 mm) is about 82.7% of the latter. Therefore, the capacity value is reduced to about 82.7% of the conventional value, but the raw material activated carbon fiber is 75.2% of the conventional value.
It can be seen that this method is only necessary and can greatly contribute to cost reduction. Table 2 shows the characteristics of the capacitor of the present invention together with the conventional example.

[Table] (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. According to Table 3, when an inorganic electrolyte such as dilute sulfuric acid is used, the breakdown voltage cannot reach the 2V value of an organic electrolyte system, and the limit is 1.2V, which is the decomposition voltage of water, but a large capacity value can be obtained. is,
Furthermore, impedance can be reduced, making it suitable for strong discharge applications.

[Table] (Example 3) Figure 7 shows a case where a capacitor having a structure in which two polarizable electrode bodies 1 are laminated is assembled in the same system as in Example 1, where 2 is a conductive electrode, 3 is a conductive electrode, and 3 is a conductive electrode. indicates a separator, which is the same as in each of the previous figures. Its characteristics are shown in Table 4.

[Table] 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 is close to 100% in mass production, and the electrode area is is 82.7%, but the cost is
75.2%, which can greatly contribute to reducing the cost of small, large-capacity double-layer capacitors.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of a conventional coin-shaped electric double layer capacitor, Figures 2 and 3 are diagrams showing the punching pattern of a polarizable electrode body, and Figure 4 is a model of the basic principle of an electric double layer capacitor. 5 is a diagram showing the polarizable electrode body pattern of the present invention, FIG. 6 is a diagram showing the configuration of an embodiment of the electric double layer capacitor of the present invention, and FIG. 7 is a diagram showing the structure of an embodiment of the electric double layer capacitor of the present invention. It is a figure which shows another Example. 1... Polarizable electrode body, 2... Conductive electrode, 3...
... Separator, 4 ... Gasket, 5 ... Case, 6 ... Sheet-shaped polarizable electrode body, 7 ... Activated carbon fiber, 8 ... Aluminum electrode, 9 ... Organic electrolyte.

Claims (1)

[Scope of Claims] 1. A regular hexagonal polarizable electrode body is formed from a sheet-like polarizable electrode body having a conductive electrode, and both electrodes are arranged so as to face each other with a separator interposed therebetween. What is claimed is: 1. An electric double layer capacitor characterized by having a structure in which a sealed casing is formed after injection. 2. The electric double layer capacitor according to claim 1, characterized in that activated carbon fiber is used as the polarizable electrode body. 3. The conductive electrode according to claims 1 and 2, characterized in that a metal layer of aluminum, copper, etc. is formed on the polarizable electrode body by either thermal spraying or vapor deposition. Electric double layer capacitor. 4. Claims 1 and 2, characterized in that, as the conductive electrode, a conductive resin layer is formed on the polarizable electrode body by any one of a screen printing method, a spray method, and a dip method. electric double layer capacitor.