JPH04286108A - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To minimize internal resistance to withheld a large current of charge/ discharge in terms of an electric double layer capacity submerged in a dielectric solution after an activated coal layer is formed on a metal foil to manufacture an electrode foil and a positive electrode, a separator, a negative electrode, and a separator are laminated in that order. CONSTITUTION:When an attempt is made to form an activated coal layer on a collector 3 made of an aluminum foil to manufacture an electrode foil, the activated coal layer is formed so that the collector 3 may be partially exposed. The collector 3 and a separator 5 are alternately laminated and coiled. Then, the exposed collector 3 is crushed to a flattened state. The flattened portion is used as an extraction terminal 6, which reduces the internal resistance of an electric double layer capacitor to an extremely small extent.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor having an improved lead terminal structure.

0002

BACKGROUND OF THE INVENTION The lead-out conductor portion of a conventional wound type electric double layer capacitor has a structure in which a thin metal rod or thin plate is bonded to a current collector. Normally, there is one lead-out conductor per current collector, and even in a long current collector for a large-capacity electric double layer capacitor, the number of lead-out conductors is several.

0003

[Problems to be Solved by the Invention] The electric double layer capacitor having such a structure has the following problems.

That is, in the above structure, the ratio of the cross-sectional area of the lead-out conductor to the area of the electrode is small, and the distance from the electrode to the lead-out conductor becomes long. Therefore, when charging and discharging, electrons must travel long distances, resulting in a large resistance value. As a result, the internal resistance becomes high, and when charging and discharging at a large current, a large amount of electrons flow through the thin lead-out conductor, causing the lead-out conductor to generate heat, which has an adverse effect on the life of the capacitor. When the internal resistance is high, the voltage effectively applied to the capacitor becomes low due to the voltage drop caused by the internal resistance, and the capacitance of the capacitor becomes small.

Furthermore, since the lead conductor is bonded to a current collector made of thin metal foil, the strength of the portion of the current collector to which the lead wire is bonded is reduced, reducing reliability.

The present invention aims to solve the above-mentioned conventional problems, and provides a highly efficient and reliable electric double layer capacitor with low resistance loss in the lead conductor and no decrease in strength due to lead conductor joints. The purpose is to

[0007]

[Means for Solving the Problems] In order to achieve the above object, the electric double layer capacitor of the present invention includes activated carbon in a part of the current collector when forming an activated carbon layer on the current collector to make an electrode foil. After leaving the exposed surface without forming a layer, stack the electrode foil for the positive electrode, the separator, the electrode foil for the negative electrode, and the separator in this order and wind them. The electric body part is flattened and the flat part is used as a lead-out terminal.

[0008]

[Operation] According to the above-mentioned means, by using the end of the current collector itself as a lead-out terminal, a large cross section of the current collector can be used as a lead-out conductor, whereas wires were conventionally used as lead-out conductors. As a result, the ratio of the cross-sectional area of the lead conductor to the area of the electrode becomes extremely large, and the distance traveled by electrons when charging and discharging the capacitor becomes shorter, reducing the internal resistance value and increasing the The voltage drop becomes extremely small, and the capacitor capacity can be increased with the same electrode area.

Furthermore, since the resistance value in the lead conductor is small, there is no heat generation in the lead conductor, and there is no physical joint between the current collector and the lead conductor, so the strength of the lead conductor portion is dramatically improved.

As a result, a highly reliable electric double layer capacitor with low loss can be produced.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 2 shows the electrode configuration of an electric double layer capacitor. In FIG. 2, 1 is an electrode foil that becomes a positive electrode, 2 is an electrode foil that is a negative electrode, 3 is a current collector that constitutes the electrode foils 1 and 2, 4 is an activated carbon layer formed on the current collector 3, and 5
is a separator.

In this embodiment, an etched aluminum foil is used as the current collector 3, and as an example, the aluminum foil is used for the positive electrode 1 with a size of 30 mm in length and 70 mm in width.
For the negative electrode 2, the current collector 3 was cut into 30 mm long x 60 mm wide. An electrode of activated carbon layer 4 was formed to a position 13 mm vertically from one end of these current collectors to produce an electrode foil. This activated carbon electrode uses powdered activated carbon (specific surface area: 2500
mm 2 /g, average particle size 2 μm) was mixed with a binder and applied to the current collector 3. The electrode foils thus produced are stacked one on top of the other in the order of separator 5, positive electrode 1, separator 5, and negative electrode 2 from the bottom. At this time, the activated carbon layer 4 of the positive electrode 1 and the activated carbon layer 4 of the negative electrode 2 face each other with the separator 5 in between, and the exposed part of the current collector 3 of the positive electrode 1 and the current collector 3 of the negative electrode 2
The exposed parts are arranged in opposite directions so that they do not overlap. Thereafter, the stacked electrode foils with the separator 5 in between are wound laterally to form a rod-shaped capacitor element as shown in FIG. In FIG. 3, 5 is a separator whose lateral dimension is sufficiently longer than the electrode foil, so that the electrode part of the activated carbon layer 4 does not appear on the surface of the rod-shaped capacitor element, and the separator 5 is placed on the surface of the rod-shaped capacitor element. exposed in strips. Activated carbon layers 4 are formed on both sides of the separator 5 exposed in a band shape.
The current collector 3 on which is not formed is exposed.

[0014] With the capacitor element thus manufactured, the current collectors 3 exposed on both sides are then flattened to form lead-out terminals 6, as shown in FIG. In FIG. 1, 7 is a metal or resin case of the capacitor, and the capacitor element, on which lead terminals 6 are formed at both ends in a later process, is impregnated with an electrolytic solution containing propylene carbonate as the main solvent.
Only both lead terminals 6 are exposed and enclosed in a case 7, completing an electric double layer capacitor.

In this embodiment, a polypropylene film is used as the separator. (Example 2) The structure was the same as in Example 1, except that fibrous activated carbon (specific surface area: 2000 mm2/g, fiber diameter: 2 μm, fiber length: 5 μm) was used instead of powdered activated carbon.

In Example 1, powdered activated carbon was used, and in this example (Example 2), fibrous activated carbon was used.
Chopped pieces may also be used.

(Example 3) The structure was the same as in Example 1, and acetylene black was added to activated carbon as a conductivity imparting agent.

(Example 4) The structure was the same as in Example 1, but an aluminum net foil was used as the current collector.

In Example 1, aluminum foil was used as the current collector, and in this example (Example 4), aluminum net foil was used, but other metal plates or punched metal may also be used as the current collector. .

(Comparative Example) As a comparative example with the above four types of examples, a positive electrode of 13 mm in length x 70 mm in width and a positive electrode of 13 mm in length x 70 mm in width were used.
An activated carbon electrode is formed on a current collector made by joining a metal rod as a lead conductor to a 60 mm wide negative electrode, and each electrode foil is wound up between separators, impregnated with an electrolytic solution containing propylene carbonate as the main solvent, and electrically A double layer capacitor was manufactured.

Table 1 shows a comparison of the characteristics and performance of the electric double layer capacitor of this comparative example and the electric double layer capacitors of Examples 1 to 4.

[0022]

[Table 1]

According to (Table 1), the electric double layer capacitors according to the four embodiments of the present invention have larger capacitances with the same electrode foil area and lower internal resistance values than the electric double layer capacitors of the comparative examples. It can be seen that the voltage has become significantly smaller and the voltage holding time has become much longer.

[0024]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, by directly using a part of the current collector as a lead-out terminal, it is possible to increase the capacitance with the same electrode foil area. As a result, the voltage holding time can be extended. Furthermore, since the internal resistance value can be significantly reduced, it can withstand charging and discharging of large currents. Furthermore, the mounting strength of the lead terminals is dramatically improved, making it possible to realize high-performance and highly reliable electric double-layer capacitors.

[Brief explanation of the drawing]

[Fig. 1] A perspective view showing the shape of an embodiment of the electric double layer capacitor of the present invention before being enclosed in a case.

FIG. 2 is a perspective view showing the laminated state of electrodes and separators in an embodiment of the electric double layer capacitor of the present invention.

[
FIG. 3 is a perspective view showing a capacitor element before extraction terminal processing in an embodiment of the electric double layer capacitor of the present invention

[Explanation of symbols]

3 Current collector 4 Activated carbon layer 5 Separator 6 Output terminal

Claims (4)

[Claims] Claim 1: A pair of positive and negative current collectors, an activated carbon layer forming an electrode formed on the pair of current collectors, and a portion where the pair of positive and negative activated carbon layers are overlapped so as to face each other. An electric double layer capacitor is composed of an electrolyte and separators stacked alternately with activated carbon layer parts, and the activated carbon layer is formed on the current collector so that at least a part of the current collector is exposed. An electric double layer capacitor with a structure in which the exposed part on the electric body is used as a lead-out terminal. 2. The electric double layer capacitor according to claim 1, wherein the activated carbon layer comprises powdered, fibrous or chopped activated carbon and a binder. 3. The electric double layer capacitor according to claim 1, wherein the activated carbon layer contains a conductivity imparting agent. 4. The electric double layer capacitor according to claim 1, wherein the current collector is a metal plate, foil, net or punched metal.