JPS6252447B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electric double layer capacitor, and its purpose is to improve the connection strength with external leads by optimizing the shape, opening degree, and thickness range of the expanded metal used as a metal current collector. An object of the present invention is to provide an electric double layer capacitor that has good contact with electrodes without weakening the internal resistance and has low internal resistance. Conventionally, as shown in FIGS. 1 and 2, electric double layer capacitors include a polarizable electrode body 2 configured by supporting a carbon electrode 2b on a current collector 2a to which a lead wire 1 is connected, and a separator 3. The element is constructed by winding the material with the material interposed between the materials, and is characterized by an extremely large capacitance of Farad (F) class. The polarizable electrode body 2 of this type of electric double layer capacitor is formed by molding and pressing carbon powder, which has a large specific surface area and good conductivity, as a polarizable electrode material on a current collector made of expanded metal, or Carbon powder was made into a rubber-like electrode material and produced by rolling it around a rolling roller. However, in the past, this expanded metal had not been investigated in depth, but as efforts were made to improve the characteristics of electric double layer capacitors, it became necessary to study this current collector, especially in terms of reducing internal resistance. That is, in the electrode body manufactured using such a current collector, since this polarizable electrode material is a powder, contact resistance with the current collector becomes a problem. On the other hand, in order to use this capacitor, it is necessary to pull out the external lead (mainly a metal plate or metal rod) from the current collector, so the strength of the connection between the current collector and the external lead becomes an issue. It's here. These two problems, that is, the contact between the polarizable electrode material and the current collector, and the connection between the current collector and the external lead, are greatly affected by the shape of the holes in the expanded metal used as the current collector. has come to light. In other words, when the pore size is small, there is less penetration of the polarizable electrode material into the current collector, and when it is large, the connection method uses needle caulking, so the metal flesh of the external lead and the expanded metal are Since there is less entanglement with the metal part, the connection strength between the current collector (expanded metal) and the external lead becomes weaker. However, only the short width (SW) and long width (LW) of conventional expanded metal are specified, and little consideration has been given to the degree of opening, other perforation conditions, and shape. In other words, priority is given to the strength of the connection between the current collector and the external lead, which tends to result in smaller pores, resulting in the disadvantage of increasing the internal resistance of the electric double layer capacitor element. . The present invention relates to adapting the processing conditions for the through-hole shape of expanded metal in response to the above-mentioned reduction in internal resistance. In addition, the expanded metal referred to in the present invention is
As shown in Figures 3a and b, multiple SWs and LWs are constructed by making multiple cuts in a smooth thin plate at regular intervals and pulling the thin plate in the direction of widening the cuts.
It is a metal plate having a hexagonal through hole A. In addition, the opening degree measurement value is obtained by irradiating white light from above the expanded metal, measuring the illuminance at that time and the illuminance when the expanded metal is removed, and expressing the ratio as a percentage. This is the value. The details of the present invention will be explained below. In the embodiment described here, the DC capacitance of the electric double layer capacitor is 10F, and the size is 12.5 mm × 34 mm.
belongs to. In the present invention, valve metals (Al, Ti, Zr, Nb, Ta, Mo, W) are suitable as the current collector material. The present inventors used high-purity Al foil in terms of cost, workability, performance, etc., and adopted a thickness of 95 μm based on network workability, strength, and element diameter. This Al foil is SW=0.25~1.25mm, LW=0.5~2.5mm, the opening degree is 15~70%, and the net thickness after processing is 0.2~0.45.
Al expanded metals with various processing conditions in the mm range were made, and after degreasing, they were used as current collectors. By the way, when applying the conventional product to these conditions, SW = 1.0mm, LW = 2.0mm, opening degree 30%
It is. The above Al expanded metal was mixed with 10 parts of powdered activated carbon, 1.5 parts of acetylene black, and 2 parts of polyvinylpyrrolidone (PVP) as a binder.
A thin electrode was produced by applying the mixture to a rolling roller together with a rubber-like carbon electrode consisting of 1 part and 3 parts of tetrafluoroethylene resin dispersion. And 23×65mm, 23×
The electrodes were cut to 80 mm, and an Al lead rod was attached to each by caulking. A porous film was sandwiched between two electrodes having the above dimensions as a separator, and wound into a spiral shape using a winder. To this, 0.7Mol of electrolyte was added to a mixed solvent consisting of γ-butyrolactone (7 parts) and propylene carbonate (3 parts).
It was impregnated with a solution of tetraethylammonium perchlorate, placed in an Al case, and sealed. First, Table 1 shows the relationship between the shapes of SW and LW, lead caulking strength, and electrode adhesion. by the way,
As mentioned on the previous page, the SW and LW of expanded metal are determined by the notches (LW) at regular intervals using multiple chevron blades and the feed pitch (SW). The inventors have previously determined the SW/LW shown in Table 1.
In addition to the above conditions, expanded metals were made and examined under many combinations of conditions, and one of the results was that the SW/LW ratio of 1/2 was close to the appropriate value. However, although the SW/LW ratio may not be the optimal value, it can be said to be the optimal value in a comprehensive evaluation including industrial management.
Next, we set SW=0.75mm and LW=1.5mm and examined the opening degree and thickness, and Table 2 shows the results. Further, FIG. 4 shows the relationship between the internal resistance and tensile strength of the electric double layer capacitor element manufactured under the conditions shown in Table 2. Also, SW=0.75mm, LW=1.5mm,
Table 3 shows the thickness determined by setting the opening degree to 45% to 55%. In Tables 1 to 3, ◯ means good, △ means usable, and × means unusable.

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[Table] From the above results, when considering the workability, strength, and characteristics of the current collector for electric double layer capacitors, the suitable range of processing conditions for the Al expanded metal is 0.5 to 1.0 mm for SW and 0.5 to 1.0 mm for LW. 1.5~2.0mm,
Opening degree 40~65%, net thickness/original plate thickness 2.5~
It was 4.0 times higher. In this way, by adapting the processing conditions for expanded metal, which has not been studied much in the past due to connection strength, it is possible to improve the adhesion of electrodes without changing the conventional connection strength, and to improve the internal structure of the product. This made it possible to reduce resistance and variation. In other words, by specifying and optimizing processing conditions such as opening degree and thickness from the conventional simple SW and LW specifications, it is possible to reduce the absolute value and variation of internal resistance that has never been seen before, and to increase the opening degree from 30% to 50%. %, the elongation rate of the plate length can be increased from 1.3 times
1.7 times, the actual amount used is also smaller and costs can be reduced. As a result of these improvements, improvements can be made in all aspects of workability, characteristics, and price, and the value is extremely great.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a general electric double layer capacitor element, Figure 2 is a perspective view of a polarizable electrode body of the same element, Figures 3a and b are enlarged views of expanded metal, and Figure 4 is a perspective view of a polarizable electrode body of the element. 2 is a diagram showing the relationship between internal resistance and tensile strength of electric double layer capacitor elements manufactured under the conditions shown in Table 2. FIG. 2... Polarizable electrode, 2a... Current collector, 2b...
carbon electrode.

Claims (1)

[Claims] 1. In an electric double layer capacitor that uses an electric double layer formed at the interface between a polarizable electrode and an electrolyte, the short width of the through hole is used as a current collector for the polarizable electrode body.
0.5~1.0mm, long width 1.0~2.0mm, and opening degree
An electric double layer capacitor characterized by using expanded metal with a thickness ratio of 40 to 65% and a thickness ratio of 2.5 to 4.0 times the original plate thickness.