JPH10106900A - Electrode for electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for an electric double layer capacitor wherein corrosion of an aluminum collector does not progress when the electric double layer capacitor is used at a comparatively high temperature. SOLUTION: An electrode for an electric double layer capacitor is formed by spreading paste on an aluminum collector 10, which paste is obtained by mixing active carbon 12, carbon powder 14 and aluminum powder 24 and kneading them together with binder. When water is subjected to electrolysis in the electrolytic solution, proton-rich water 22 is generated. In the case that the water 22 is moved toward a negative electrode 18 by the effect of an electric field, protons react with the previously added aluminum powder 24 and are consumed, so that corrosion of the aluminum collector 10 which is to be caused by protons can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in an electrode used for an electric double layer capacitor, and more particularly to an improvement in corrosion resistance at high temperatures.

[0002]

2. Description of the Related Art An electrode for an electric double layer capacitor is formed by kneading activated carbon and carbon powder as a conductive material with a binder, coating the mixture on an aluminum current collector, and firing. FIG. 3 shows an example of such an electrode for an electric double layer capacitor.

In FIG. 3, an active carbon 12 and a carbon powder 14 are carried on a aluminum current collector 10 by a binder (not shown) to form a positive electrode 16 and a negative electrode 18. A separator 20 is provided between the positive electrode 16 and the negative electrode 18, and the positive and negative electrodes 16, 18 and the separator 20 are impregnated with an electrolytic solution.

If water is present in the electrolytic solution, it is electrolyzed at the time of charging / discharging of the electric double layer capacitor and becomes a gas, which increases the internal resistance to lower the capacitance, or a case (vessel) due to an increase in internal pressure. ) Causes problems such as blistering. Therefore, it is desirable to remove as much moisture as possible when assembling the electric double layer capacitor. However, it is extremely difficult to completely remove water from the assembled electric double layer capacitor because of the large adsorption power of the activated carbon 12 in the electrode. A countermeasure for such residual moisture is disclosed in JP-A-7-22295.

The above-mentioned publication discloses a method of applying a predetermined voltage to assemble an electric double layer capacitor and closing the case to electrolyze and remove residual moisture. In this way, water is forcibly removed by electrolysis.

[0006]

However, according to the above-described conventional method, oxygen gas is generated, but hydrogen gas is hardly generated due to potential. Therefore, protons (hydrogen ions, H ⁺ ). When protons remain in the electrolytic solution, proton-rich water 2 containing a large amount of the protons
2 is attracted toward the negative electrode 18 by the electric field between the positive electrode 16 and the negative electrode 18, reaches the aluminum current collector 10 of the negative electrode 18, and corrodes the same.

That is, as shown in FIG. 3, oxygen gas (O ₂ ) is generated by electrolysis, and simultaneously generated proton-rich water 22 moves to the negative electrode 18 side. At this time, the aluminum current collector 10 of the negative electrode 18 reacts with the protons (H ⁺ ) in the proton-rich water 22 to be dissolved as aluminum ions (Al ³⁺ ), and the corrosion of the aluminum current collector 10 proceeds. When the aluminum current collector 10 is corroded in this way, there is a problem that the internal resistance of the electrode is increased and the capacity of the electric double layer capacitor is reduced.

Further, such a corrosion reaction is accelerated when the temperature rises. For example, when an electric double layer capacitor is used at a temperature of 45 ° C. to 50 ° C., the life of the aluminum current collector 10 of the negative electrode 18 is further shortened. There was also the problem of becoming.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an electrode for an electric double layer capacitor in which corrosion of an aluminum current collector does not progress even when the electric double layer capacitor is used at a relatively high temperature. Is to provide.

[0010]

To achieve the above object, the present invention relates to an electrode for an electric double layer capacitor having a current collector and an active material, wherein the active material reacts with hydrogen ions. Alternatively, any of substances which absorb hydrogen ions is added.

[0011] Further, as the substance reacting with the hydrogen ions, one or more metals selected from aluminum, iron and copper are used.

[0012] Further, as the substance absorbing hydrogen ions, one or more metals selected from titanium, ruthenium and iridium are used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of an electrode for an electric double layer capacitor according to the present invention. The same elements as those in the conventional example shown in FIG. Omitted.

In FIG. 1, an activated carbon 12 and a carbon powder 14 as a conductive material are kneaded together with a substance which easily reacts with protons or a substance which electrochemically absorbs protons and a binder (not shown) to form a paste. To form an active material according to the present invention. The substance that easily reacts with the proton or the substance that electrochemically absorbs the proton is replaced with a part of the carbon powder 14 as the conductive material.

As a substance which easily reacts with protons, for example, there are aluminum, iron, copper and the like. Further, as a substance that electrochemically absorbs protons, for example, titanium,
There are ruthenium and iridium.

FIG. 1 shows an example in which aluminum is used as the above-mentioned substance.

As described above, a small amount of water contained in the electrolytic solution is electrolyzed during charging and discharging of the electric double layer capacitor, oxygen is generated as a gas, and the remaining protons are not electrolyzed. The water is mixed into the water and becomes proton-rich water 22. This proton-rich water 22
It moves toward the negative electrode 18 by the action of the electric field,
During this movement, the aluminum powder 24 added to the positive electrode 16 and the negative electrode 18 reacts with the proton, and the proton is consumed. Thus, protons are consumed by the aluminum powder 24 in the positive electrode 16 and the negative electrode 18, and the negative electrode 1
Since all protons in the proton-rich water 22 disappear before reaching the anode 8, the aluminum current collector 10 of the anode 18
Can be prevented from being corroded.

In the embodiment shown in FIG. 1, an example is shown in which the aluminum powder 24 is added instead of a part of the carbon powder 14, but all the carbon powder 14 is added to the aluminum powder 24. It can also be replaced. This is because the aluminum powder 24 itself has high conductivity and can also function as a conductive material.

Further, even if a substance which easily reacts with other protons is used in place of the aluminum powder 24, protons are consumed by the same action as described above. Further, when a substance that electrochemically absorbs protons is used instead of the aluminum powder 24, the protons are consumed not by a chemical reaction but by electrochemical absorption. Corrosion of the current collector 10 can be prevented.

The amount of such an aluminum powder 24 or other substance which reacts easily with protons or a substance which electrochemically absorbs protons is usually determined in consideration of the amount of water mixed in the electrolytic solution. It is necessary that 0.1% or more be present in the electrode excluding the aluminum current collector 10. Further, it is possible to add about 10% at the maximum in consideration of the amount of the conductive material usually added to the electrode.

In FIG. 1, since the proton-rich water 22 moves toward the negative electrode 18 by the action of an electric field, the aluminum powder 24 may be added only to the negative electrode 18.

FIG. 2 is a sectional view of a negative electrode 18 of another embodiment of the electrode for an electric double layer capacitor according to the present invention.

In FIG. 2, an active material 26 is applied to the aluminum current collector 10 as in the prior art, and aluminum powder is partially added as a conductive material to the outside of the electrode, that is, on the surface side, or only aluminum powder is used as the conductive material. Is added to form an aluminum-added layer 28. As described above, since a cross-sectional view of the negative electrode 18 is shown in FIG.
The surface on which 8 is formed is closer to the positive electrode 16. Therefore, when proton-rich water 22 is generated on the positive electrode 16 side and attracted to the negative electrode 18 by the action of an electric field, the aluminum powder 24 in the aluminum-added layer 28 formed on the surface of the negative electrode 18 and the proton-rich water 22 The protons react with the protons and are consumed. Thereby, corrosion of the aluminum current collector 10 of the negative electrode 18 can be prevented.

The aluminum-added layer 28 may be formed by laminating a plurality of layers in which the amount of the aluminum powder 24 added is sequentially changed. As described above, according to the configuration in which the aluminum-added layer 28 is formed only on the surface side of the negative electrode 18, corrosion of the aluminum current collector 10 on the negative electrode 18 side can be prevented, and the addition amount of the aluminum powder 24 can be reduced. It is also possible to prevent the electric double layer capacitor from becoming heavy.

In each of the above embodiments, the addition of the aluminum powder 24 can prevent corrosion of the aluminum current collector 10 of the negative electrode 18, so that water in the activated carbon is forcibly removed during the manufacture of the electric double layer capacitor. There is no need, and the manufacture of the electric double layer capacitor can be facilitated.

[0027]

As described above, according to the present invention,
Since a substance that reacts with hydrogen ions or a substance that absorbs hydrogen ions is added to the electrodes, protons generated by electrolysis of a small amount of water present in the electrolyte solution or activated carbon react with these substances or It is absorbed and does not reach the negative electrode side. As a result, corrosion of the aluminum current collector on the negative electrode side by protons can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of an electrode for an electric double layer capacitor according to the present invention.

FIG. 2 is a sectional view of another embodiment of the electrode for an electric double layer capacitor according to the present invention.

FIG. 3 is an explanatory view of corrosion of a negative electrode side aluminum current collector of an electrode for an electric double layer capacitor in the related art.

[Explanation of symbols]

Reference Signs List 10 aluminum current collector, 12 activated carbon, 14 carbon powder, 16 positive electrode, 18 negative electrode, 20 separator, 22
Proton-rich water, 24 aluminum powder, 26
Active material, 28 aluminum added layer.

Claims (3)

[Claims] 1. An electrode for an electric double layer capacitor having a current collector and an active material, wherein either a material that reacts with hydrogen ions or a material that absorbs hydrogen ions is added to the active material. An electrode for an electric double layer capacitor. 2. The electrode for an electric double layer capacitor according to claim 1, wherein one or more metals selected from aluminum, iron, and copper are used as the substance that reacts with the hydrogen ions. Electrode for electric double layer capacitor. 3. The electrode for an electric double layer capacitor according to claim 1, wherein the substance that absorbs hydrogen ions is selected from the group consisting of titanium, ruthenium, and iridium.
An electrode for an electric double layer capacitor, wherein the above metal is used.