JPH01241812A - Electric double-layer capacitor - Google Patents

Abstract

PURPOSE:To prevent deterioration of a capacitance and an increase in internal resistance by containing at least one kind of low melting point ingredient selected from silicate, borate, phosphate, germanate, tellurite, aluminate, vanadate, and halide in a polarizable electrode having carbon as a main ingredient. CONSTITUTION:Salts such as silicate must be ingredients having a low melting point. That is, those having a melting point of below 1000 deg.C are suitable since they act effectively as binders of carbonicingredients forming an electrode. For carbon used in a polarizable electrode, one of or both of activated charcoal fibers or activated charcoal of grain size of 0.1-200mu, in particular, 0.5-20mu or carbon black are used. These carbons and particles of low melting point and preferably of a diameter of 0.1-20mu are added in the range of contents of 5-50wt.%, preferably 10-30wt.%, and are mixed by a wet or dry method. This mixture is pressurized and molded to a predetermined shape of an electrode. Then, the electrode is heated at a predetermined temperature, and a part or all of the low melting point ingredients are melted and solidified.

Description

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

[Prior art] The electrodes of electric double layer capacitors are mainly made of carbonaceous material, and conventionally, powdered activated carbon, for example, is used, which is kneaded into a slurry using an electrolyte such as sulfuric acid, and then pressurized with a press. (U.S. Pat. No. 3,288,64)
No. 1).

Additionally, to improve cracking and fracture resistance, powdered activated carbon may be combined with a sufficient amount of electrolyte to give a paste consistency and optionally a fluoropolymer binder such as polytetrafluoroethylene. A carphone paste electrode made of a mixture has been proposed (Japanese Patent Publication No. 53-7025, Japanese Patent Publication No. 55-70
-41015).

Further, as a carbon material, an electrode with high mechanical strength using activated carbon fiber is known (Japanese Patent Publication No. 15138/1983). Furthermore, in order to obtain as small a volume as possible, electrodes using pulverized activated carbon fibers or special binders have been proposed (Japanese Patent Application Laid-Open No. 612620?, fil-28207).
No. 8).

Further, JP-A No. 82-40011 describes that activated carbon fibers, ceramic fibers, and glass fibers are dispersed and mixed to form a paper.

[Problems to be Solved by the Invention] However, the electrodes typified by US Pat. There is.

In addition, carbon paste electrodes, such as those typified by Japanese Patent Publication No. 53-7025, are flexible and have crack resistance and fracture resistance, but they lack shape retention, and special measures are required to supplement their strength. It has the disadvantage that it requires a cell with a specific structure.

In addition, since the electrodes typified by Tokkosho [(0-15138) use fibrous activated carbon, they not only have a smaller specific surface area than powder, but also have a larger porosity and less loss in the space. Since it is large, it has a drawback that it is disadvantageous when the smallest possible volume is required for a given capacity.

Furthermore, the electrodes typified by JP-A No. 81-2 [1207] still have the drawback that the effect of improving the specific surface area is small and the mechanical strength of the original activated carbon fibers is impaired.

Furthermore, the electrode disclosed in Japanese Patent Application Laid-Open No. 62-40011 does not necessarily have sufficient mechanical strength and has a drawback in terms of reliability.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned drawbacks, and includes silicate, borate, phosphate, An object of the present invention is to provide an electric double layer capacitor characterized by containing at least one low melting point component selected from germanates, tellurites, aluminates, vanadates, and halides.

It is necessary that the salts such as silicates used in the present invention have a low melting point. That is, those having a melting point of 1000° C. or less are suitable because they act effectively as a binder for the carbonaceous components constituting the electrode.

In the present invention, the carbon material used for the polarizable electrode is activated carbon fiber or particle size of 0.1 to 200 μl, especially 0.5 to 20 μl.
Either or both of JL's activated carbon and carbon black are used. These carbonaceous materials and the low melting point components preferably have a diameter of 0.1 to 20 Ji.

The content of particles is 5 to 50% by weight, preferably 10 to 30% by weight.
It is added in a range of % by weight and mixed using a wet or dry method.

This mixture is pressure molded into a predetermined electrode shape, and then the electrode is heated at a predetermined temperature to melt and solidify part or all of the low melting point components. This operation can also be performed after placing the molded electrode in a storage case made of stainless steel or the like.

It is also possible to first heat the pressure-molded electrode to melt and solidify part or all of the low melting point component, and then press or adhere it to the current collector or storage case. As the pressure bonding or adhesion method, that is, the current collecting method, various conventionally known methods can be employed. For example, a method of bonding using a carbon-based conductive adhesive can be preferably employed.

In addition, fluororesin such as PTFE is added to the already mentioned electrode composition.
It is also possible to use it by adding up to 20% by weight.

It is also possible to add and mix the glassy substance to the carbon fine powder in the form of a paste rather than a powder.

In the case of activated carbon fibers, it is also possible to knead them using a doctor blade method or the like. In this case, the solvents used for pasting include aliphatic hydrocarbons such as n-hexane and n-hebutane, aromatic hydrocarbons such as aromatic naphtha and turpentine, alcohols such as ethanol and phthanol, ketones, esters, polyesters, etc. All alcohols, cellulose, etc. can be used.

The electrolytic solution used in combination with the polarizable electrode of the present invention is not particularly limited, and various conventionally known or well-known electrolytes can be employed. Among such electrolytes, solvents such as propylene carbonate, γ-futhyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, and sulfolane are preferably used as the organic electrolyte. Examples of solutes in the electrolyte include alkali metal groups, tetraalkylammonium salts, and tetraalkylphosphonium salts such as perchloric acid, hexafluorophosphoric acid, tetrafluoroboric acid, and perfluoroalkylsulfonic acid. , these solutes are added to the above solvent at a concentration of 0.1 to 3.0 mol/
An electrolytic solution in which a concentration of parent solvent, preferably 0.5 to 1.5 mol/volume solvent, is dissolved is preferably used.

[Example] Next, examples and comparative examples of the present invention will be described.

A unit cell of a coin-shaped electric double layer capacitor (diameter 20 mm) is common to the examples and comparative examples of the present invention.
, thickness 2.0 mm) was produced in the following manner. First, to 80% by weight of activated carbon powder (specific surface area: 2000 m2/g), 10% by weight of carphone flak, and 10% by weight of low melting point component powder of various compositions with an average particle size of 1p were added, wet kneaded, and then pressure molded. and a disc-shaped electrode (diameter 15 mm, thickness 0
．． 7mm). These electrodes are each placed in a stainless steel cap and heated under vacuum at a predetermined temperature to be fixed.

After storing the separator, 0.5mo in the unit cell
After injecting an electrolytic solution prepared by dissolving 1 liter of tetraethylphosphonium tetrafluoroporate in 1 liter of propylene carbonate to fully impregnate the electrodes and separator with the electrolyte, seal the cap and the end of the can through the cassette. death,
It completely stopped.

After measuring the initial capacitance and internal resistance when applying a voltage of 2.8 V using the unit cell of the electric double layer capacitor thus prepared, the cell was subsequently applied with a voltage of 2.8 V.
The capacity was measured after storage for 1000 hours at 70°C without applying a voltage of 100°C, and the rate of deterioration (%) from the initial capacity was calculated. Internal resistance was also measured in the same way.

Note that the internal resistance is calculated using the AC two-terminal method (frequency lk It z
).

In Comparative Example 1, the above electrolyte was kneaded with 90% by weight of the above activated carbon powder and 10% by weight of carphone flak, and then pressure molded.
The same procedure as in Example was carried out except that an electrode (5Il]I11 diameter, 0.7 mm thickness) was used for integral sealing.

Comparative Example 2 was the same as the example except that a phenolic activated carbon fiber cloth (15 m + n diameter, 0.7 mm thickness) with aluminum sprayed on one side was placed on the side that contacted the gap case with the aluminum surface and fixed by spot welding. I went to

The results of Examples 1 to 9 and Comparative Examples 1 to 2 are shown in Table 1.

[Effects of the Invention] According to the present invention, an electric double layer capacitor having excellent long-term reliability with little capacity deterioration and little increase in internal resistance even after a high-temperature load test can be produced.

Claims (6)

[Claims] 1. At least one selected from silicates, borates, phosphates, germanates, tellurites, aluminates, vanadates, and halides is contained in a polarizable electrode mainly composed of carbonaceous material. An electric double layer capacitor characterized by containing one type of low melting point component. 2. The electric double layer capacitor according to claim 1, wherein the low melting point component has a melting point of 1000°C or less. 3. The electric double layer capacitor according to claim 1, wherein the low melting point component is added in the form of particles having a diameter of 0.1 to 20 microns. 4. The electric double layer capacitor according to claim 1, wherein the carbonaceous material is at least one selected from activated carbon powder, carbon black, and activated carbon fiber. 5. The electric double layer capacitor according to claim 1, wherein the polarizable electrode contains at least one of activated carbon powder and carbon black, and a fluororesin. 6. The electric double layer capacitor according to claim 1, wherein the content of the low melting point component is 5 to 50% by weight.