JPS61203616A - Electric doule-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 This invention relates to an electric double layer capacitor using activated carbon as a polarizable electrode.

BACKGROUND OF THE INVENTION Conventionally, the electrode bodies of electric double layer capacitors using this type of electrolyte have been made by press-molding activated carbon particles or kneading them with a suitable binder and coating them on the entire metal current collector. In addition, when activated carbon fibers are used, a method is known in which a sprayed aluminum layer is formed on the activated carbon fibers, and the electrode body is made by spot welding the electrode case made of strong stainless steel as the case material and the sprayed aluminum layer. Ta.

Problems to be solved by the invention In electric double layer capacitors with such a current collector,
When an organic electrolyte is used, propylene carbonate, r-butyrolactone, N-N-dimethylformamide, and acetonitrile are used as the solvent for the electrolyte, but in these electrolytes, stainless steel is completely polarized when anodically polarized. It dissolved without forming any passivity.

The potential at which the current starts flowing due to this dissolution is 2.3 to 264 V, which is determined by the decomposition potential of the solvent on the cathode side, and is higher than the oxidation potential of activated carbon or the decomposition potential of the electrolyte in the electrolyte using these organic solvents. Therefore, when the entire current collector is made of stainless steel, the anode potential is limited by the dissolution potential of stainless steel, and 3V, which is an electrochemically stable potential region determined by the polarized electrode and electrolyte, can be effectively used. I couldn't do it. For example, if a voltage higher than the voltage at which leakage current starts to increase is applied, a large amount of iron, nickel, etc. will be detected in the negative activated carbon electrode, causing the stainless steel to dissolve and iron ions to migrate from the anode to the cathode. It has been confirmed that

As described above, stainless steel is not effective as a current collector in order to effectively use 3V, which is the electrochemically stable range determined by the activated carbon polarizable electrode and electrolyte, and it is possible to use 3V. In order to obtain an electric double layer capacitor with a high withstand voltage, when anode polarization is performed in the solvent used, a reactive current flows at a potential equal to or higher than that of activated carbon, which is a polarizable electrode. It was necessary to use a material for the entire current collector that was strong enough to be used as a case material. However, if a metal such as titanium is used as an all-metal current collector that forms a passive state even in these electrolytes, the withstand voltage will be lower than when stainless steel is used as the current collector, as shown in Figure 3. In the case of propylene carbonate and tetraethylammonium barchlorate based electrolytes, the region where the reaction current flows is expanded to the extent of O and SV. However, in this case, there was a problem that the increase in internal resistance was large and the voltage drop when using an electric double layer capacitor was large, making it impractical.

The present invention solves these drawbacks and provides an electric double layer capacitor having a withstand voltage of 3V or more.

Means for solving the problems and the technical means of the present invention for solving the above problems is that when the above-mentioned electric double layer capacitor is used, at least the polarizable electrode of the metal case serving as an anode and the electrolyte are It is coated with titanium nitride and titanium carbide.

action The effect of this technical means is as follows.

In other words, stainless steel causes a dissolution reaction when it comes into contact with an electrolyte and becomes anode polarized, but if the contact surface with the electrolyte is made of titanium nitride or titanium carbide, it becomes the same polarized electrode as an activated carbon electrode, so even if %3V is applied. An electrochemically stable electric double layer capacitor can be obtained. Furthermore, since no oxide film is formed due to voltage application, there is no increase in the internal resistance of the product as would be the case when titanium is used.

In this case, since the current collector also serves as a case material, it must have sufficient strength as a case material. However, if titanium nitride or titanium carbide is used as a case material, it is hard and brittle and does not have sufficient workability. Therefore, under these restrictive conditions, it is appropriate to use a material such as stainless steel that has no problem in electrical contact as an external terminal and has strength as a case material, and a composite material of titanium nitride and titanium carbide.

Example The present invention will be explained below using specific examples.

Example 1 As shown in Figure 1, a cloth made of phenolic activated carbon fiber (
A polarizable electrode 1 having a thickness of O, Sn and a specific surface area of 2oood/gr) with a conductive electrode formed on one side has a diameter of 2α.
A disk shape is cut out using a punching die to obtain an electrode body. After impregnating this electrode body with an electrolyte solution containing 10 wt% of propylene carbonate and tetraethylammonium tetrafluoroboret, the electrode body is stacked with a separator 2 interposed between them, and the inner surface is coated with titanium nitride (thickness 10 μm).
Then, a stainless steel case 3 coated with only the anode side or both electrodes is placed between the cases 3, and a gasket 4 is placed on the open end of the case 3, and the entire seal is sealed by caulking. 5 is a film of titanium nitride and titanium carbide.

This titanium nitride coating was performed using the CV-N method (ahθm1ca
The inner surface of the stainless steel case 3 is coated by reacting carbon tetrachloride with ammonia at a high temperature of 111Qo to 1400'C using a 1T&per Deposition).

Table 1 shows various characteristics of the electric double layer capacitor according to the present invention. Similarly, Table 1 shows, for comparison, the characteristics of a prototype with a structure in which the inner surface of the stainless steel case is not coated with titanium nitride or titanium carbide.

(The following is a blank space) Example 2 As shown in Fig. 1, activated carbon particles from palm are kneaded with a binder made of polyfluorocarbon, molded, and then cut out into a disk shape with a diameter of 2α using a punching die to obtain polarizable electrode 1. . This electrode body is impregnated with an electrolytic solution containing 10 wt% of tetraethylammonium tetrafluoroborate in propylene carbonate, and then stacked on top of each other with a separator 2' interposed between them, and this is then covered with a stainless steel case whose inner surface is coated with titanium carbide. 3, place the gasket 4 on the open end of the case 3, and seal it by caulking.
Do the following.

Table 1 shows various characteristics of the electric double layer capacitor according to the present invention.

Example 3 As shown in Figure 2, an acrylic activated carbon fiber cloth (thickness 0
．． A polarizable electrode 1 having a diameter of 5 M'l and a specific surface area of 5 ood/fir was punched out into a disc shape with a diameter of 2α using a punching die.
Obtain an anode electrode body.

A non-polarizable electrode 6 having a diameter of 2 (7), for example lithium, is placed on this electrode body as a cathode electrode body, with a separator 2 interposed between each electrode body, to form a - set of electrode bodies.

After this set of electrode bodies is impregnated with electrolytic a made by adding 10 wt% of lithium fluoroporate to propylene carbonate, it is sandwiched between stainless steel cases 3 whose inner surfaces are fully coated with titanium nitride, and the case 3 has an opening. Place a gasket on the end and seal it by caulking.

Table 2 shows various characteristics of the electric double layer capacitor according to the present invention. Similarly, Table 2 shows, for comparison, the characteristics of a prototype with a structure in which the inner surface of the stainless steel case is not coated with titanium carbide or titanium nitride.

(Hereinafter referred to as "Kinshiro") Effects of the Invention As described above, this invention utilizes the fact that titanium nitride and titanium carbide coatings have the same properties as polarizable electrodes to create a high-withstand voltage electric secondary battery with a withstand voltage of 3V or more. A multilayer capacitor can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the electric double layer capacitor of the present invention, FIG. 2 is a sectional view showing another embodiment of the present invention,
FIG. 3 is a characteristic diagram showing the potential-current characteristics of an electric double layer capacitor when titanium and stainless steel are used as current collectors. 1... Polarizable electrode, 2... Separator, 3... Case, 6... Titanium nitride,
Titanium carbide film, 6...Non-polarizable electrode.

Claims (3)

[Claims] (1) An element is created by arranging a polarizable electrode made of activated carbon fiber or activated carbon powder, etc. with a counter electrode via an electrolyte, and this element is housed in a pair of metal cases, and the metal case is It is constructed by bringing a polarizable electrode and a counter electrode into electrical contact with each other, and is characterized in that the surface of the metal case on the side that becomes the anode, which comes into contact with the polarizable electrode and the electrolyte, is coated with titanium nitride or titanium carbide. Electric double layer capacitor. (2) The electric double layer capacitor according to claim 1, wherein a polarizable electrode made of activated carbon fiber or activated carbon powder is used as the counter electrode. (3) The electric double layer capacitor according to claim 1, wherein a non-polarizable electrode is used as the counter electrode, and the counter electrode is used as a cathode.