JPH06196364A - Manufacture of coin-shaped electric double layer capacitor - Google Patents

Abstract

PURPOSE:To obtain a coin-shaped electric double layer capacitor having large discharge capacity and small internal resistance with little dispersion in performance by making sufficient contact with a case and a cover of a polar electrode. CONSTITUTION:A collector net 3 of stainless steel is welded to the respective internal surfaces of a metal case in the shape of a flat container 11 and a cover. The collector 3 is set on a press-molding metal mold 10 while keeping its surface upward, and a power electrode agent made of a mixture of activated powder, acetylene black and a teflon binder (binding agent) is piled up, and this power electrode agent is press-molded into a pellet shape while pressure putting this powder electrode agent into a pellet shape for being pressure put inside the surface of the collector 3 so as to manufacture a polar electrode 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a coin type electric double layer capacitor.

[0002]

2. Description of the Related Art A coin-type electric double-layer capacitor has a flat container-like metal case that constitutes one of the electrodes, and has polarizable electrodes stacked above and below the separator via a separator. After the liquid is filled, the metal cover that constitutes the other electrode is fitted to the case via the sealing gasket,
The inside is sealed by crimping the case. This capacitor stores the positive and negative electric charges taken in through the case and the cover during charging in each activated carbon electrode, and gradually releases the electric charges stored during the discharging through the case and the cover, so that it takes time to charge. It can be used in the same usage form as a kind of secondary battery without taking any cost.

[0003]

However, this coin-type electric double layer capacitor has the drawbacks that the discharge capacity is small, the internal resistance is high, and the variation in performance is large in practical use.

The reason for this is that the polarizable electrode is preliminarily molded into a predetermined shape and is housed in the case, and the contact between the case and the cover depends only on the caulking pressure, so that the contact of this portion is made. This is because the resistance is high and the current collection efficiency is reduced, and the polarizable electrode is not fixed to the case and the cover, so that the variation in performance becomes large.

On the other hand, a collector such as an expanded metal is arranged on the inner surfaces of the case and the cover, and a polarizable electrode which is molded and dried in a predetermined shape in advance is placed on top of the collector, so that the case and the cover are electrically charged. There are some that get a physical connection. However, even in this case, only the effect of digging into the current collector by the caulking pressure of the case can be obtained, so that satisfactory performance cannot be obtained.

The present invention has been made to solve the above problems, and its purpose is to make the contact between the polarizable electrode and the case and the cover sufficient, which results in a large discharge capacity, a small internal resistance, and performance. The present invention provides a method for manufacturing a coin-type electric double layer capacitor in which the variation of the above is minimized.

[0007]

In order to achieve the above object, in the present invention, a metal having a rough surface such as a metal net is provided on each inner surface of a flat container-shaped metal case and a cover which constitute a current collector of both electrodes. The current collector is welded and set in a mold with the surface of the current collector facing upward, and a powder electrode agent comprising a mixture of activated carbon powder and a binder is deposited on the current collector, The powder electrode material is press-molded into a predetermined shape and pressed into the surface of the metal current collector.

[0008]

According to the above construction, the metal current collector having a roughened surface is welded to each inner surface of the case and the cover, the powder electrode material is molded into a predetermined shape, and at the same time, the current collector is pressed by a pressure. It bites into and crimps to provide good electrical contact to the case and cover.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. First, as shown in FIGS. 1 (a) and 1 (b),
A stainless steel collector 3 is welded to the inner surfaces of the flat container-shaped metal case 1 and the cover 2. Although the shape of the current collector 3 is a net shape in the figure, it may be either a shape in which a large number of protrusions are formed or a plate shape having a rough surface made of a porous body.

As the welding method, any of resistance welding, ultrasonic welding and laser welding can be adopted. In the case of resistance welding, the contact resistance between the current collector 3 and the case 1 and the cover 2 is determined depending on the number of spot welding spots, so the optimum number of spot welding points is determined according to the dimensions.

Next, polarizable electrodes 4 are provided on the inner surfaces of the case 1 and cover 2 as follows.

For example, as shown in FIG. 2A, a press mold 10 for providing a polarizable electrode 4 on a case 1 is used, and a current collector 3 is placed on a lower mold 12 of the press mold 10. The case 1 is set with the surface facing upward, and then the die 14 is lowered to surround the periphery of the current collector 3. In this state, a required amount of the powder electrode agent is charged into the cavity formed inside the die 14, and then the punch 16 is lowered to mold the powder electrode agent, and at the same time, the powder electrode agent is made to dig into the uneven surface of the current collector 3. To fix.

The powder electrode agent is composed of a mixture of activated carbon powder, acetylene black, and Teflon binder (binder). The powder electrode agent is bound to each other by the binder according to the pressing pressure, and the pelletized polarizable electrode 4 is formed. While being molded, it is pressed into a rough surface such as a net of the current collector 3 to be integrated. Similarly, the polarizable electrode 4 is integrally formed inside the cover 2 by press molding.

After the completion of molding, an electrolytic solution is poured into each polarizable electrode. As the electrolytic solution, a solution obtained by dissolving (Et) ₄ NBF ₄ in PC is used. Next, as shown in FIG. 3, a separator 5 is arranged in the middle of both polarizable electrodes 4, and a cover 2 is fitted to a case 1 via a sealing gasket 6,
If you crimp the opening of case 1, they will be insulated from each other.
The coin-type electric double layer capacitor sealed inside is completed. Any polarity may be used, but it is customary to use the case 1 side as a positive electrode and the cover 2 side as a negative electrode.

Next, the performance of the coin type electric double layer capacitor obtained by the above manufacturing method was investigated.

When a case with a diameter of 24 mm and an inner surface of the cover 2 are spot-welded with four current collectors made of stainless steel net with a diameter of 16 mm. Only two spot-welded current collectors are provided. A polarizable electrode having a length of 1.25 mm was formed by press molding as described above, and the internal resistance and discharge capacity of 10 samples obtained thereby were measured, and the following average values were obtained. … Internal resistance 1.1 (Ω) Discharge capacity 12.3
(C) ... Internal resistance 3.0 (Ω) Discharge capacity 10.1
(C) ... Internal resistance 7.2 (Ω) Discharge capacity 3.3
(C) Further, FIG. 4 shows variations in internal resistance and discharge capacity.

As is clear from this result, the sample of has a minimum internal resistance and an extremely high discharge capacity,
From the result shown in FIG. 4, the variation of both is extremely small,
The performance is average.

On the other hand, the sample (1) has a small variation in both the internal resistance and the discharge capacity and shows an averaged performance, but the internal resistance is slightly higher and the discharge capacity is smaller than that of the current collector. This is due to insufficient welding.

However, the sample (1) had an extremely large internal resistance, a small discharge capacity, and an extremely large variation in performance, and had the same tendency as in the past, and the effect of press molding was not exhibited.

Therefore, by welding the current collector to the case and the cover with an appropriate welding strength and molding the polarizable electrode on this surface with an appropriate pressing strength, the internal resistance is about 1 as compared with the conventional type. It is concluded that the discharge capacity is reduced to / 7 and the discharge capacity is improved to about 4 times.

[0021]

As described above in detail with reference to the embodiments, in the method of manufacturing the coin type electric double layer capacitor according to the present invention, the metal current collector having the roughened surface is provided on the inner surfaces of the case and the cover. Since the powder electrode material is formed into a predetermined shape by press molding and at the same time it is pressed into the current collector by pressurization to obtain good electrical contact with the case and cover, In comparison, it is possible to reduce the internal resistance and improve the discharge capacity, and it is possible to provide a coin-type electric double-layer capacitor having small variations in performance.

[Brief description of drawings]

1A and 1B are cross-sectional views showing a state in which a current collector is welded to a case and a cover.

2 (a) and 2 (b) are explanatory views showing a press forming process of a polarizable electrode.

FIG. 3 is a cross-sectional view showing a completed state of a coin type electric double layer capacitor.

FIG. 4 is a graph showing variations in resistance and capacitance of samples to which the manufacturing method of the present invention is applied.

[Explanation of symbols]

 1 Case 2 Cover 3 Current Collector 4 Polarizing Electrode 5 Separator 6 Sealing Gasket 10 Press Mold 12 Lower Die 14 Die 16 Punch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Nakamura 5-36-11 Shinbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. (72) Inventor Tatsuya Yamazaki 5-36-11 Shinbashi, Minato-ku, Tokyo Fuji Electrochemical Co., Ltd.

Claims (1)

[Claims] 1. A metal current collector having a roughened surface, such as a metal net, is welded to each inner surface of a flat container-shaped metal case and a cover forming current collectors of both electrodes, and the surface of the current collector is fixed to the inner surface. Set on the upper side in a mold, deposit a powder electrode agent composed of a mixture of activated carbon powder and a binder on the current collector, press-mold the powder electrode agent into a predetermined shape, and press the metal current collector. A method for producing a coin-type electric double layer capacitor, characterized by being press-fitted into the surface of a body.