JPS63261817A - Electric double-layer capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an electric double layer capacitor.

Conventional technology This type of electric double layer capacitor uses polarizable electrodes and an electrolyte (
It is a capacitor with large capacitance that utilizes an electric double layer formed at the interface with liquid) and is mainly used as a backup for volatile semiconductor memory (e.g. RAM, random access memory) during power outages. This is what is being done.

Conventional electric double layer capacitors of this type have a so-called disc-shaped (coin-shaped or button-shaped) structure, as shown in Figure 2, and are composed of graphite, activated carbon, carbon black, and some binder. An electrolytic solution (not shown) is impregnated between carbon electrodes 1 made of carbon powder material, or carbon electrodes supported on a net made of Furuminiram or stainless steel, or carbon fibers, especially activated carbon fiber cloth. It is sealed by a metal case 3 that serves as a current collector and an exterior material, a metal lid 4, and a sealing body 6 that serves as an insulator and a sealing member, with a separator 2 interposed therebetween. especially,
In the case of a carbon electrode made of activated carbon fiber cloth, an aluminum layer is formed by plasma spraying or the like on the surface that contacts the metal case and metal lid in order to improve current collection.

Such conventional electric double layer capacitors are often used for power outage backup of RAM, and since the operating voltage of this RAM is usually about 5V, the electric double layer capacitor must also have a withstand voltage of 5V or more. The withstand voltage of an electric double layer capacitor largely depends on the electrolyte used.9 When a non-aqueous electrolyte is used, it is about 3V, whereas when an aqueous electrolyte is used, it is only 0. It is about 8v.

Therefore, in order to make the working voltage of an electric double layer capacitor 5V or higher, 2 to 3 capacitors are connected in series when a non-aqueous electrolyte is used, and 6 to 7 capacitors are connected in series when an aqueous electrolyte is used. There is. By the way, when using a non-aqueous electrolyte, it is necessary to remove sufficient moisture from the material constituting the capacitor element. The reason for this is that if water is present as an impurity, it can only be used at a voltage below 1.23 V, which is its theoretical decomposition voltage. Furthermore, the sealing body can withstand non-aqueous organic solvents,
In addition, it is necessary to use a material with low moisture permeability.

For these reasons, a molded polypropylene resin has been used as a sealing body for conventional electric double layer capacitors.

Problems to be Solved by the Invention The greatest use of such conventional electric double layer capacitors is for bank-up of semiconductor memories during power outages. Therefore, its use is not the main function of the 7E handset 2; but its purpose is to improve functionality, and there is a strong desire to make it lighter, thinner, and smaller.

Activated carbon fiber cloth has conventionally been used as an electrode to achieve large capacitance. Currently, the surface area of this type of activated carbon has reached 2Q0~2600m14. Moreover, since the pore size needs to be large enough for the electrolyte to wet, the effective surface area is 30
It is thought to be around %. As described above, since the capacitance is the amount of activated carbon used minus the weight, the design of the capacitor can be determined by the diameter and thickness of the electrode.

Therefore, to double the capacitance, either increase the diameter by ~.7 times or double the thickness. Here, increasing the diameter by one block is limited by the installation area of the capacitor,
The thickness is similarly limited by the height of the capacitor. But for the diameter, the metal lid.

Compared to cases that require new molds to be made, there are many manufacturing advantages such as the thickness can be adjusted by simply modifying the existing mold.

However, it is necessary to solve the most difficult problem, which is the manufacture of the electrodes. This means that in order to obtain a thicker activated carbon fiber cloth, about 2 to 3 times as much raw material fiber cloth is required, and it is not easy to activate carbonize this.

The present invention is intended to solve these conventional problems, and it is an object of the present invention to obtain a large capacitance without changing the diameter.

As a means to solve the problem, the present invention involves forming a deep aluminum layer in the thickness direction on a carbon electrode such as activated carbon by plasma spraying, making the sprayed layer near the separator porous, and applying an electrolyte to this layer. The element is constructed by impregnating the material with the following materials, and by stacking two sheets of these.

According to the structure of the present invention, the electrode, the separator,
Each part of the metal lid and case is in good contact,
A large capacitance can be obtained without changing the diameter.

Embodiment Next, an embodiment of the present invention will be described. First, as shown in FIG. 1, an activated carbon fiber cloth 11 was used as a polarizable electrode. Is it thickness O, elf, weight 125g/rr? .

Surface area 2000n? /g, and four of these were made to have a diameter of 6 mm to prepare a metal case 16 with an outer diameter of 11 mm, a corresponding metal lid 15, and a sealing body 14. The metal case 16, which has a negative potential, is made of stainless steel 5US3.
The inner surface of the metal lid 1S with 04 as a plus is made of aluminum, and the outer surface is made of SUS 304, and both are clad and integrated. The separator 13 is a nonwoven fabric made of polypropylene fiber, and has a thickness of 35 mm and a basis weight of 5.
0g/rr? It is a porous sheet. The sealing body 14 is a polypropylene furnace.

It is a resin molded product.

Table 1 shows the electrical characteristics of each material and structure of conventional products 1 and 2, reference example, and invention products 1 and 2, such as capacitance, internal resistance,
Leakage current (value after 30 minutes of application of 3V) is listed.

Inventive product 1.2 has an aluminum layer formed on the above electrode by plasma spraying, and the separator side is made porous; reference example is a product in which only an aluminum layer is sprayed but not made porous; and conventional product 1. .2 is the one in which no aluminum layer was formed.

(The following is a blank space) Effects of the Invention As described above, the present invention has better electrical characteristics (larger capacitance, smaller internal resistance, smaller leakage current) than the conventional one. This uses conventional electrodes, slightly changes the state of the aluminum layer, and makes the separator less dense and
It becomes possible to realize this by increasing the thickness, and it becomes possible to standardize electrode materials and manufacturing equipment, and its industrial value is great.

[Brief explanation of drawings]

Figure 1 is a sectional view of the electric double layer capacitor of the present invention, Figure 2 is a sectional view of the electric double layer capacitor of the present invention.
The figure is a cross-sectional view of a conventional product. 11...Carbon electrode, 13...Separator, 16...Metal lid, 16...Metal case. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 15 Losses, J.A.2 Figure 2

Claims (2)

[Claims] (1) Form an aluminum layer deep in the thickness direction on a carbon electrode such as graphite, carbon black, or activated carbon by plasma spraying, make the sprayed layer near the separator porous, and impregnate it with electrolyte to form an element. An electric double layer capacitor is made by stacking two of these. (2) Claim 1 in which the activated carbon is an activated carbon fiber cloth
Electric double layer capacitor described in section.