JPS60149115A - 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 Field of Industrial Application The present invention relates to an electric double layer capacitor that utilizes an electric double layer formed at the interface between a polarizable electrode and an electrolyte.

Conventional structure and its problems The basic structure of an electric double layer capacitor using activated carbon as a polarizable electrode is as shown in FIG. An electrolytic solution is impregnated between a pair of polarizable electrodes, and a separator is used to prevent a short circuit.

Conventionally, there are the following three types of configurations of this type of electric double layer capacitor, and their configurations and problems will be summarized.

The first one uses a punched aluminum metal as the current collector 4, as shown in FIG. Form-press the polarizable electrode material or
Alternatively, it is supported by a rolling roller, a pair of current collectors and polarizable electrodes are wound around the separator 3, and an electrolytic solution is injected. The activated carbon powder used here is generally 1
It is difficult to have a specific surface area of oooonX7y or more. In such a polarizable electrode, the amount of activated carbon per unit volume is reduced by the fluororesin or the like, and the double layer capacity is also reduced. Furthermore, in the polarizable electrode manufactured using the above-mentioned current collector, the metal current collector and the activated carbon electrode are basically only in physical contact;
In particular, when a polarizable electrode is spirally wound to form a spiral structure, the activated carbon electrode layer on the outside of the current collector and the activated carbon electrode layer on the inside of the current collector have opposite stresses, so the current collector and activated carbon electrode There were disadvantages such as the contact became weaker, the internal resistance of the electric double layer capacitor gradually increased, and the utilization efficiency of the activated carbon electrode layer gradually decreased.

As shown in FIG. 3, the second electrode is a polarizable electrode 6 made of cloth 9 mainly composed of activated carbon fibers, such as paper or felt, and a metal layer 6 made of aluminum or titanium as a current collector 6. The pair of polarizable electrodes can be constructed by a thermal spraying method, vapor deposition method, etc., and after injecting an electrolytic solution, the pair of polarizable electrodes can be constructed into a coin shape with an exterior case 7 and a gasket 8 via a separator 3.

In addition, this kind of device has a polarizable electrode 5 having a metal layer 6.
This is an advantageous method in which activated carbon fibers can be wound into a superstructure and configured into any desired shape, such as having the configuration described in the first configuration, and activated carbon fibers have sufficient strength during processing. Unlike the case where a binder is used, a binder is not required, and therefore the capacity per unit volume is also increased.

However, the disadvantage of this method is that the activated carbon fibers are expensive and the fiber diameter is as small as about 3 to 12 mφ, so it is currently extremely difficult to reduce the electrical resistance. Therefore, it has the disadvantage that a large current cannot be extracted during discharge.

The third method is to activate carbonize glassy carbon and use it for polarizable electrodes. However, this method makes it difficult to synthesize glassy carbon, and it is still difficult to obtain a material with a large specific surface area even after activated carbonization. Furthermore, the first.
It is also extremely difficult to process into the configuration mentioned in 2.

Purpose of the Invention The purpose of the present invention is to obtain an electric double layer carbon material with a simple manufacturing process and low manufacturing cost by using a strong and polarizable electrode with a large specific surface area in place of the conventional activated carbon powder. It is something.

Structure of the Invention In order to achieve this object, the present invention provides at least a carbon porous body obtained by carbonizing a molded body made of phenol formaldehyde resin, resol resin, polyvinyl alcohol, and starch, or an activated carbon porous body obtained by carbonizing and activated carbonizing. This was used as a polarizable electrode on one side.

Description of Examples Before describing specific examples, the activated carbonized porous body of the present invention will be described.

First, a method for manufacturing the activated carbon porous body used in the polarizable electrode of the present invention will be described. In order to make an activated carbon porous body,
First, a porous body of phenol resin must be prepared. Generally, novolac resins and resol resins are known as phenol formaldehyde resins. Novolac resins are produced by reacting phenol and formalin using an acid catalyst such as oxalic acid under conditions in which there is an excess of phenol, such that the molar ratio of phenol to formaldehyde is, for example, 0.7 to 0.9. The novolac resin is mainly composed of trimers to pentamers of phenol bonded mainly through methylene groups, and contains almost no free methylol groups.

Therefore, it itself does not have self-crosslinking properties and has thermoplasticity. Yet, besides this kind of novolak resin.

A cured novolac resin having a relatively high condensation product in which 7 to 10 phenol groups are bonded with styrene groups can be used in the material of the present invention.

The resol resin is a highly reactive resin whose main component is a phenol compound having a relatively large amount of methylol groups. These phenolic resins are suitable as raw materials for the present invention.

Furthermore, conventional cured phenolic resins have an excessively high three-dimensional crosslinking density, making them harder and more brittle than necessary. Therefore, the crosslinking density was controlled to be sufficient and optimal for the development of the properties of the cured phenolic resin (the network of the net 7-copolymer is large), and it has "stretchability" and "stickiness" compared to the cured product of the resol resin. Those with excellent properties are most suitable as raw materials for the present invention.

Next, a method for producing an activated carbon porous body will be described by giving an example.

To produce porous phenolic resin, a formalization reaction of polyvinyl alcohol (poval) is used.

Below is one example.

(1) Prepare a 15-20% polyvinyl alcohol aqueous solution, mix a considerable amount of the above-mentioned phenol resin (for example, granular phenol resin manufactured by Kanebo Co., Ltd., trade name 6 Bell Pearl) with the desired porosity; Mix in something that can be removed in the last step as a pore agent, such as potato starch.

(2) Add formalin and sulfuric acid as a reaction catalyst to the mixed solution, stir thoroughly, and pour the reaction solution containing many bubbles into a mold at the initial stage of the formalization reaction.

(3) When reacted for 10 to 40 hours at room temperature to 50°C, a water-insoluble foam having a degree of formalization of 60 to 70% is produced.

(4) In order to heat-fuse the phenolic resin, 150
Heat to ~180°C.

(5) If the resulting foam is thoroughly washed with water to completely remove starch and acid, a porous phenolic resin material with open cells can be obtained.

The number, size, etc. of bubbles in the porous body vary depending on the mass of the pore agent, the viscosity of the formalin additive mixture, the reaction conditions, and the degree of formalization.

The phenolic resin porous body produced in this manner is less brittle and stronger than conventional cured resol resins because the network polymer has a large network.

Next, a method for carbonizing and activating the phenolic resin porous body produced in this manner will be described.

First, carbonization proceeds by applying a temperature of 800 to 1000° C. to the above-mentioned material in an inert gas atmosphere such as nitrogen gas or in a vacuum. When conventional phenolic resins are carbonized, they become extremely brittle, but when the resin and porous body manufacturing method of the present invention is used, mechanical strength not found in conventional products can be obtained.

Furthermore, we will discuss the activation method. Although it is possible to activate the carbonized material to make it activated carbon, it is more efficient to carbonize and activate the activated carbon porous body with good properties. For activation, the phenolic resin porous body is heated at 800 to 1000°C in a nitrogen and water vapor atmosphere. ■After treating the porous material with a catalyst such as sodium hydroxide or zinc chloride, SOO under nitrogen atmosphere or nitrogen or oxygen atmosphere
Heat at 1000°C. This is done using methods such as

The activated carbon porous body obtained in this way has a specific surface area of
2200. m7f (BET method), it has an unprecedentedly large specific surface area and is strong.

(Example 1) A coin-shaped electric double layer capacitor shown in FIG. 3 was prototyped using activated carbon porous bodies having various specific surface areas, pore diameters, and porosity for the anode and cathode of polarizable electrodes. A conductive resin containing carbon particles as conductive particles was used for the conductive electrode.

Table 1 shows the relationship between the specific surface area and storage capacity of the activated carbon porous material of such a capacitor. In principle, this capacitor is
It can be seen that since the double layer capacitance accumulated at the interface between the polarizable electrode and the electrolyte is utilized, the double layer formation area and amount increase almost proportionally.

In this example, the weight of the polarizable electrode is 6011 Ig,
As the electrolyte, an organic electrolyte containing propylene carbonate as a solvent and tetraethylammonium perchlorate as a solute was used. In this example, the specific surface area is 2000 m79
By using the activated carbon porous body described above, an electric double layer capacitor with extremely large capacity can be obtained.

(Example 2) A coin-shaped capacitor similar to Example 1 was produced. In Example 1, a conductive resin having carbon particles as conductive particles was used for the conductive electrode, but in this example, aluminum was formed on the surface of the activated carbon porous body by plasma spraying. When the plasma spraying method is used, the bond between the activated carbon porous body and aluminum becomes strong and the contact resistance can be reduced, and since the electrode is an aluminum metal conductive electrode, the conductivity is better than that of Example 1. Table 2 shows various properties when an activated carbon porous body with a specific surface area of 2000 m7W is used.

Table 2 also shows the characteristics of capacitors obtained by performing aluminum arc spraying instead of plasma spraying. In either plasma or arc, a capacitor with lower impedance than the capacitor shown in Example 1 can be obtained.

The following blank space (Example 3) An activated carbon porous material with a specific surface area of 2000 m7'j similar to that used in Example 1 was used for the anode and cathode polarizable electrodes, and the solute and solvent systems as shown in Table 3 were prepared. organic electrolyte, as well as sodium hydroxide.

A capacitor was constructed using sulfuric acid as an electrolyte. Its properties are shown in Table 3. Good capacitor characteristics can be obtained with either electrolyte. With an organic electrolyte system, the withstand voltage can be raised to about 2V, but the impedance is larger than that of water.

Blank space below (Example 4) The specific surface area of the cathode of the polarizable electrode is 2oootti'/y
A coin-type electric double layer capacitor shown in FIG. 3 was constructed using the activated carbon porous body using gold and lithium as an anode and interposing a polypropylene separator.

The electrolyte used was lithium chlorate dissolved in propylene carbonate. Table 4 shows various custom orders when the electrode is 14 mmφ. Even if a non-polarizable electrode such as lithium is used as an anode, a capacitor with good characteristics can be produced.

Table 4 Effects of the Invention As described above, the present invention uses a porous activated carbon material that has higher strength and a higher specific surface area than conventional polarizable electrodes, so it is easy to process and has a small size and large capacity. An electric double 1-capacitor can be obtained.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of an electric double layer capacitor, Fig. 2 is a perspective view showing an example of the main parts of a conventional electric double layer capacitor, and Fig. 3 is a half-sectional front view showing a coin-shaped electric double layer capacitor. It is. 1...Activated carbon layer, 2...Collector electrode, 3.
...Separator.

Claims (4)

[Claims] (1) Phenol-formaldehyde resin and resol 411 A porous carbon material obtained by carbonizing a molded product consisting of fat, polyvinyl alcohol, and starch, or a porous activated carbon material obtained by carbonization activation and activated carbonization is used for at least one polarizable electrode. Characteristic electric double layer capacitor. (2) The electric double layer capacitor according to claim 1, characterized in that a porous carbon material is used as a polarizable electrode as a cathode, and an alkali metal or alkaline earth metal is used as a non-polarizable electrode as an anode. . (3) The hole diameter of the carbon porous material used as a polarizable electrode is 5~
2. The electric double layer capacitor according to claim 1, wherein the electric double layer capacitor has a thickness of 200 μm and a porosity of 40 to 86%. (4) The electric double layer capacitor according to claim 1, wherein an aqueous electrolyte such as sodium hydroxide or sulfuric acid is used as the electrolyte. (■ As an electrolytic solution, perchlorate is used as a solute, and propylene carbonate and gamma butyrlactone are used as a solvent.) Multilayer capacitor.