JPS594114A - 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 The present invention relates to an electric double layer capacitor, and more specifically, it uses carbon fiber as a polarizable electrode,
This invention relates to an electric double layer capacitor using a conductive material sprayed directly onto a polarizable electrode as a current collector.

By taking advantage of the features of the present invention, a small coin-shaped large capacity capacitor can be realized using a simple manufacturing method.

Conventionally, as shown in FIG. 1, an electric double layer capacitor is made of an expanded metal or punched metal with an aluminum phase added thereto as a current collector 1, and a polarizable electrode 2 is placed on the surface of the current collector 1. A base material 4 containing activated carbon powder as a main component and a binder such as a fluororesin is supported by a molding press or rolling roller 5, and a row of current collectors 1 and polarizable electrodes 2 are wound through a separator 3. Turn,
Those in which electrolyte was injected were common.

However, in an electric double layer capacitor with such a structure of current collector and polarizability, the metal current collector 1 and the active carbon electrode 2
The contact force with the metal net is weak and polarization occurs due to the current collector metal net? I
3: +; a has fallen off, is (has been scraped off or rolled up) =
Due to the stress caused by this, the contact force between the two becomes weaker during use, resulting in a gradual increase in the internal resistance of the electric double layer capacitor and a tendency for the capacitance to gradually decrease.

Unfortunately, when rolling a polarized 1-I electric rod made of activated carbon powder and binder onto a current collector metal, the application efficiency is poor, and the polarization external electric current (uneven application of J, and capacity variation due to rolling are also improved). This has been raised as something that should be done.

In order to solve these structural defects, for example, the metal surface of the current collector may be roughened using plastin ink to increase the contact strength with the polarizable electrode, or activated carbon powder may be coated with methyl cellulose. Various attempts have been made, such as adding a binder to strengthen the bonding force between activated carbons, but although all of them have shown slight improvements in properties, there are still many unsatisfactory points.

In order to solve these drawbacks, the present invention uses carbon fiber as a polarizable electrode instead of the conventional activated carbon paste, and an electric double layer having a conductor layer formed by thermal spraying on the carbon fiber as a current collector. It is a capacitor. More specifically, the present invention relates to a coin-shaped flat electric double layer gear puncture that takes advantage of the current collector-polarizable electrode structure having high mechanical strength.

First, the carbon fiber used in the present invention will be explained.

The properties required for a polarizable electrode are: (1) large surface area per unit weight, (2) low electrical resistance, (2) high mechanical strength, and (2) high chemical resistance. The activated carbon fibers described below have the characteristics of ■, ■, and ■ that conventional activated carbon powder has.
In addition to the above properties, it also has the mechanical strength needed as an electrode, making it an extremely effective material. There are four types of activated carbon fibers that meet this requirement: pheno-JV type (cured novolac fiber), rayon type, Aku IJ) type, and pinch type. The method of forming carbon fibers or activated carbon fibers using these raw material fibers is as shown in FIG.

That is, there is a method in which raw material fibers are directly carbonized and activated, and a method in which carbon fibers are once made into carbon fibers and then activated. Generally, after the carbon fiber M1 has been formed, activation is performed at a temperature of 700 to 800° C. in a mixed gas atmosphere consisting of water vapor and nitrogen. The surface area, electrical resistance, and flexibility of carbon fibers are inversely proportional, so as carbon fibers are activated to activated carbon fibers, the surface area increases, the carbonization yield decreases, and the electrical resistance and flexibility deteriorate. . The carbonization yield of the fiber used as a polarizable electrode of an electric double layer capacitor is preferably about 10 to 80%, although it varies depending on the type of raw material fiber. In some cases, the material loses its flexibility and cannot withstand the mechanical strength during current collection processing. On the other hand, if the carbonization yield is 80 mm or more, the electrical resistance, flexibility, and carbon fiber strength are excellent, but the surface area becomes small and the electric capacity per unit volume decreases by 7 mm, which is not preferable.

Table 1 shows the characteristics of various carbon fines.

Below Margin As is clear from Table 1, acrylic and pinch type materials are generally somewhat flexible and have a slightly smaller surface area.

Although rayon-based fibers have a similar surface area, they are delicate and brittle, and carbon fibers in the form of rayon are still popular.
It is difficult to make paper, and it is possible to make paper-like paper, but there are problems with 1niJ chemical resistance and water resistance.However, phenolic carbon fiber is made from cured novolac fiber. Because it is infusible and has low heat shrinkage, there is no need to make the raw material fibers unsubstituted in advance, and woven or nonwoven fabrics can be activated carbonized as they are. It is particularly excellent as a polarizable electrode for capacitors.

However, paper making using phenol/I/thread carbon carbon fiber material has a number of advantages, especially the special phenol-based carbon fiber used as a binder using phenolic carbon fiber as raw material (1) Phenol-based paper manufactured by Kynor Co., Ltd. Paper made using fiber (trade name) has excellent flexibility, electrical resistance, water resistance, and chemical resistance.
Winding strength and processing accuracy.

Feature 10 that is extremely superior in many aspects such as electric capacity and cost
・＼－゛It is recognized that the person has 艮.

Next, we will discuss the current collecting electrode used in the misfire.

The current collecting electrode used in the present invention is a conductive layer directly formed on a polarizable electrode by plasma spraying or arc spraying. This conductor material includes Al, Ni+Cu, which are electrochemically stable with respect to the electrolyte.

Zn, etc. The amount of adhesion due to "melting" is 0.05m
1i'/ctfr~500 mg/ca is suitable. If it is below this range, the electrical resistance will be high and it will not function as an electrode. In addition, if there are many "this range",
If the electrode is too thick and rough, it will easily peel off or fall off from the carbon fiber rod, or cracks will occur, conversely weakening the mechanical strength. The polarizable carbon fiber electrode with the above-mentioned appropriate amount of current-collecting thermal spray layer has not only such mechanical strength and properties unique to activated carbon, but also is much easier to handle during manufacturing than when using the conventional paste method. As a result, a coin-shaped flat plate electric double layer capacitor as described below can be easily provided.

Below, as a specific example, Fig. 3 and Fig. 4 are shown as 11.
Coin-shaped board 71j: A triple layer capacitor will be explained as an example.

As shown in the figure, phenolic activated carbon fiber (thickness Q, 3
1. II, surface area 2 ooon? / qr) i was,
Aku IJ/Shin activated carbon fiber (thickness 0.3 dl, surface area 800 m"/qr) 5 μm thick Al on the surface of 10)
gj 11 is formed by the Puchsma spraying method. This two-layer structure 12 is punched out into a disk shape with a diameter of 2 or 1 using a punching die to obtain a two-layer structure 13. Separator: 1-30 wt% propylene carbonate, 70 wt% γ-butyrolactone
A two-layer structure 13 is made of a material 14 impregnated with a mixed electrolyte of t strips.
Then use the scissors and attach this to the two aluminum cases 16
．． 16 with scissors, and gasket 17 with 1[1.

Table 2 shows various characteristics of the electric double layer capacitor according to the present invention. For comparison, Table 2 also shows two types of carbon fiber polarized electrodes with the same shape, one without a thermally sprayed electric material, and one with activated carbon paste applied on a conventional bunched metal collector electrode. The characteristics of the prototype are shown below.

(Table 2) As shown in the results of the above examples, the electric double layer capacitor of the present invention has a capacity per medium volume that is two to three times that of a conventional activated carbon powder base, and has a low internal resistance. -1: Even in a high two-component load life test at 70°C and 1000 hr, the activated carbon paste type showed a large capacitance change due to base l-not (I separation) from the collector electrode. In the capacitor of the present invention, the initial value is kept stable over time.

Furthermore, a flat capacitor using a polarization t'l: electrode that does not have a metal spray layer on the surface of activated carbon fibers has a larger capacity and a smaller internal resistance than an activated carbon paste method. However, p(
Since the pile is larger than that of the capacitor of the present invention, current collection is not completely achieved, so the initial characteristics are inferior to that of the capacitor of the present invention. In terms of long-term reliability, although it has stronger mechanical strength than activated carbon base, it is not reinforced with a sprayed layer, so the ends of activated carbon fibers may fall off.

Cutting may occur, and high temperature loads may be fatal
・A slight decrease in capacity is observed.

As described above, the electric double layer capacitor of the present invention has excellent characteristics, and from the viewpoint of manufacturing, polarizable electrodes can be formed by simple operations such as punching, and activated carbon does not fall off during manufacturing. Capacity variation also becomes extremely small.

According to the present invention, high performance and high capacity.

A small-sized, large-capacity flat plate capacitor can be obtained by a simple manufacturing method, has a 14-sided angle, and can be manufactured with characteristic variations kept to a minimum.

[Brief explanation of the drawing]

Figure 1 (a) is a diagram showing the configuration of a conventional electric double layer capacitor, Figures 1 (b) and (C) are the same. FIG. 3 is a diagram showing an example of the method for manufacturing an electric double layer capacitor according to the present invention, and FIG. 4 is a diagram showing the structure of an electric triple layer capacitor according to the present invention. 1o...Activated carbon fiber stack, 11...A1 layer, 12゜13...Two-layer structure, 16.15.
····Case. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 (5ff 10 /4 \ l//

Claims (1)

[Scope of Claims] (1) A polarizable electrode mainly composed of carbon fibers or activated carbon fibers, a metal electrode formed thereon, and a polarizable electrode provided on the other side of the polarizable electrode +i< An electric double layer capacitor comprising an electrolyte. (2) A metal electrode formed on one side of the polarizable electrode is in contact with the first electrode, which also serves as a half section of the exterior case, and the other side of the polarizable electrode is placed through a separator impregnated with an electrolyte,
2. The electric double layer capacitor according to claim 1, wherein the second electrode, which also serves as the other half of the outer case, is opposed to the second electrode. (3) Two polarizable electrodes face each other with the respective metal electrodes formed on the outside, and a separator impregnated with electrolyte is interposed between the two polarizable electrodes, and One of the metal electrodes formed on the polar electrodes is in contact with a first electrode that also serves as a half section of the outer case, and the other electrode is in contact with a second electrode that also serves as the other half section of the outer case. (4) The electric double layer gapacitor according to claim 1, characterized in that the first electrode and the second electrode are connected to each other via a gasket! The electric double layer capacitor according to item 2, item 3. (6) The sprayed metal is Al, Ni, Cu, and Zn.
The electric double layer capacitor according to claim 6, characterized in that the electric double layer capacitor comprises at least one kind selected from the group consisting of: (a) The electric double layer capacitor according to claim 1, wherein the weight of the sprayed metal per unit area of the polarized tIA electrode surface is in the range of 0.06 to 500 m'i/ca. (8) The commercial air double capacitor according to claim 1, characterized in that the carbon fibers are made of phenolic activated carbon fibers.