JPH027509A - Electric double-layer capacitor - Google Patents

Abstract

PURPOSE:To avoid the damage of a porous separator caused by a pressure applied at the time of sea]ling and make it easy to predetermine the pressure by employing carbon paste composed of powder active carbon and electrolyte solution and graphitized carbon added to it as the material of an electrode. CONSTITUTION:A conductive sheet is punched out, placed on an unvulcanized nonconductive annular sheet concentrically and bonded to it by compression to form a recess. The recess is filled with a paste electrode 3a made of paste composed of powder active carbon, sulfuric acid and 20-80-wt.% of carbon graphitized by a thermal treatment to form a paste-filled sheet. A pair of the paste-filled sheets are coupled concentrically with a porous separator 5 between and with the respective carbon paste electrodes 3a facing each other and then a pressure is applied from the top and bottom and the coupled sheets are held in a high temperature atmosphere to form a basic cell 1a. The basic cells 1a are laminated to form a laminated unit 6. Then the unit 6 is housed in a metallic package case 8 and a mechanical pressure is applied to it. While this state is maintained, the top end of the package case 8 is caulked and sealed to obtain an electric double-layer capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric double layer capacitor, and more particularly to a carbon paste electrode for an electric double layer capacitor.

[Conventional technology]

Generally, the elements of electric double layer capacitors (hereinafter referred to as basic cells) using carbon paste electrodes are separated through a porous separator 5 that is ion permeable and non-electron conductive, as shown in FIG. An ion-impermeable conductive separator 2 is arranged through a pair of carbon paste electrodes 3b made of powdered activated carbon and an electrolyte solution, and the conductive separator 2 is arranged around the pair of carbon paste electrodes.
It has a structure consisting of a non-conductive gasket 4 provided to hold the carbon paste electrode 3b interposed therebetween and to isolate it from the outside world. The carbon paste electrode 3b serving as the electrode of the basic cell 1b has conventionally been made of a mixture of powdered activated carbon and an electrolyte solution.

Furthermore, as shown in FIG. 6, the electric double layer capacitor is constructed by combining a laminate 6 in which a required number of basic cells 1b are stacked according to the voltage used, a metal exterior case 8, a surface of the basic cells 1b, and a metal laminate 6. It has a structure in which it is cased with an insulating case 7 to prevent short circuit with the exterior case 8, and the first and second electrode plates 9 are used as electrodes.

The electric double layer capacitor is manufactured by applying pressure of 1 to 100 kg/cm" from above and below to the laminate 6 of the basic cell 1b in order to reduce the contact resistance within the carbon paste electrode 3b, and while maintaining this pressure, the opening of the outer case 8 is opened. The edges are folded inward and caulked to seal.

[Problem to be solved by the invention]

In the conventional electric double layer capacitor mentioned above, the contact resistance of the powdered activated carbon is large, so the pressure at the time of caulking is increased to reduce the equal series resistance (hereinafter referred to as ESR) of the electric double layer capacitor. If the pressure at the time of sealing is increased too much, the porous separator 5 will be torn, so it is very difficult to set the pressure.

It is an object of the present invention to provide an electric double layer capacitor that can obtain a small ESR even if the pressure is low during caulking and sealing, and as a result, the porous separator will not be damaged, and the pressure can be easily set. It is in.

[Means for Solving the Problems] The electric double layer capacitor of the present invention is an electric double layer capacitor whose electrode is a mixture of powdered activated carbon and an electrolyte solution, in which graphitized carbon is added to the powdered activated carbon. Constructed as a feature.

The amount of graphitized carbon added is 20 to 80
The object of the present invention can be achieved by setting the amount to % by weight.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 3 is a longitudinal sectional view of a basic cell of an electric double layer capacitor according to an embodiment of the present invention, and FIG. 4 is a longitudinal sectional view of an electric double layer capacitor comprising the basic cell of FIG. 3.

First, as shown in FIG. 3, an unvulcanized non-conductive sheet with a thickness of 0.5 mm is punched concentrically with an inner diameter of 6 mm and an outer diameter of 11 mm to form the ring-shaped sheet described above.

Next, a conductive sheet is punched out to a diameter of 111IIIll, placed concentrically on the ring-shaped sheet, and pressed to form a recess. This recess is filled with a paste electrode 3a containing a mixture of 30% by weight sulfuric acid, powdered activated carbon, and carbon graphitized by heat treatment at 1300 to 1500'C for 30 minutes to obtain a paste-filled sheet.

Next, the pair of paste-filled sheets are made of polypropylene with a thickness of 2 mm in the direction in which the carbon paste electrodes 3a face each other.
4 kg/cm2
Pressure was applied from above and below, and while this pressure was maintained, it was left in an atmosphere at a temperature of 5°C for 125 min for 3 hours to create conductivity between the unvulcanized non-conductive sheets and between the unvulcanized non-conductive sheets. The basic cell 1a of the example of the present invention was obtained by closely adhering the plastic sheets.

Next, as shown in FIG. 4, eight basic cells 1a of the present invention are stacked in series to form a laminate 6, and then a metal exterior case 8 is formed.
A mechanical pressure of 30 kg/cm'' was applied to the laminate 6, and while this state was maintained, the upper end of the outer case 8 was caulked and sealed to obtain an electric double layer capacitor with an operating voltage of 5V.

Figure 1 shows the amount of graphitized carbon added and the E of 40 electric double layer capacitors when the mechanical pressure (hereinafter referred to as caulking pressure) applied when caulking and sealing the laminate 6 is 30/Ω.
The relationship with the average value of SH is shown. The horizontal axis in FIG. 1 is the weight percent of graphitized carbon relative to powdered activated carbon. The vertical axis is the ESR of the electric double layer capacitor. When the amount of graphitized carbon added is increased to 80% by weight, the ESR of the electric double layer capacitor decreases to about 1/3 of that of a conventional capacitor. As is clear from FIG. 1, the effect of graphitized carbon is significant when the amount added is 20 to 80%.

Figure 2 shows the results of 40 electric double layer capacitors when the crimping pressure was changed for electric double layer capacitors made in the same manner as described above by adding 50% by weight of graphitized carbon to powdered activated carbon in a carbon paste electrode. It shows the change in the average value of ESH. In FIG. 2, curve A is according to the present invention, and curve B is conventional. Same ESR as before by adding graphitized carbon
We were able to obtain an electric double layer capacitor with a lower crimping pressure than before.

〔Effect of the invention〕

As explained above, the present invention can reduce the caulking pressure and ESR of electric double layer capacitors by using a carbon paste electrode in which graphitized carbon is added to powdered activated carbon and an electrolyte solution. As a result, it is an object of the present invention to provide an electric double layer capacitor in which the porous separator is not damaged due to pressure during sealing, and the pressure can be easily set.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the amount of graphitized carbon added and the ESR of the electric double layer capacitor obtained by the present invention, and FIG. 2 is a graph showing the relationship between the amount of graphitized carbon added and the ESR of the electric double layer capacitor obtained by the present invention. A graph showing the relationship between caulking pressure and ESR for capacitors and conventional electric double layer capacitors. Figure 3 is a vertical cross-sectional view of a basic cell of an electric double layer capacitor with an improved carbon paste electrode according to an embodiment of the present invention. , FIG. 4 is a vertical cross-sectional view of an electric double layer capacitor consisting of the basic cell shown in FIG. 3, tE÷, FIG. FIG. 6 is a longitudinal sectional view of an electric double layer capacitor made of the conventional basic cell shown in FIG. 5; 1a... Basic cell of the present invention, 1b... Conventional basic cell, 2... Conductive separator, 3a... Carbon paste electrode added with graphitized carbon, 3b...
Conventional carbon paste electrode, 4... Non-conductive gasket, 5... Porous separator, 6... Laminate, 7
...Insulation case, 8...Metal exterior case, 9...
First and second electrodes.

Claims (2)

[Claims] (1) An electric double layer capacitor whose electrode is a mixture of powdered activated carbon and an electrolyte solution, characterized in that graphitized carbon is added to the powdered activated carbon. (2) The electric double layer capacitor according to claim 1, wherein the amount of graphitized carbon added is 20 to 80% by weight based on powdered activated carbon.