JPS5940284B2 - electric double layer capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to increasing the current that can be passed through an electric double layer capacitor and reducing leakage current, that is, improving potential storage ability.

Conventionally, this type of solid-state device that utilizes the electric double layer capacitance formed at the interface between a polarizable electrode and a solid electrolyte uses Rb 1g4 I 5 and N841g 4 I in the electrolyte.
5.

A silver ion conductive solid electrolyte such as 93S■, 8g6I4WO3, etc. is used, and the polarizable electrode is made of carbon or (Ag
2S)0.69・(Ag1.7Te)0.285・
(A74P207) 0.025 was used, and Ag was used for the counter electrode.

That is, since conventional electric double layer capacitors were composed of Ag and silver salt, they had the disadvantage of being expensive.

Therefore, the present inventors previously used a molded mixture of Cu2S and solid electrolyte for the working electrode, counter electrode, and reference electrode, and placed halogen (tJ-copper and halogenated N,
We have filed a patent application for an electric double layer capacitor with a structure in which a copper ion conductive solid electrolyte made of a reactant with N'methylhexamethylenetetramine or halogenated Nmethyltriethylenediamine is interposed.

This uses a solid electrolyte with Cu+ ion conductivity as the electrolyte, and there are problems associated with it, such as the use of Ag as a counter electrode.
If only Cu was used instead of Cu, the reversibility would be poor, leading to premature shortening, which was solved by using Cu2S, thereby reducing the price.

However, the ionic conductivity of such electrolytes is 115~10 v/Cm at room temperature compared to that of silver salts.
1/10, and the current that can be passed is smaller by that much.
In addition, it had the disadvantage that cupric halogenide, which has electron conductivity, redeposited, and its potential holding ability was worse than that of a capacitor made of silver salt.

The present invention solves these problems by changing the electrolyte, and the electric double layer capacitor of the present invention will be explained below with reference to the drawings of FIGS. 1 to 6.

Fig. 1 shows the internal structure of an electric double layer capacitor according to an embodiment of the present invention in which the element body has a diameter of 15mm. It is constructed by press-molding 1 g of a mixture containing 80 wt of Cu2S.

Reference numeral 2 denotes a current collector for this counter electrode 1, which is made of a copper foil of about 30 μm and is interposed between the aluminum case 3 and the counter electrode 1.

Furthermore, silver paste is applied to the aluminum case 3 side of the current collector 2 to reduce contact resistance.

4 is a working electrode, which is made of a mixture 0.4 having the same composition as the counter electrode 1.
A solid electrolyte layer 5 formed by press-molding 1 g of electrolyte is interposed between the working electrode 4 and the counter electrode 1.

6 is 1 g of a mixture having the same composition as the counter electrode 1 and the working electrode 4.
A solid electrolyte layer 7 similar to the solid electrolyte layer described above is interposed between the reference electrode 6 and the working electrode 4.

8 is a current collector of this reference electrode, and a 100-mesh copper net is used.

In addition to individually pelletizing these molded products and stacking them on top of each other, the mixture of counter electrode 1 is first placed in a cylindrical press mold,
After temporarily pressing at a pressure of 100 Ky/c, i, the solid electrolyte layer 5 and the powder of the working electrode 4 were sequentially added and the temporary pressing was repeated, and then the gold-plated copper wire 9 was press-fitted into the end of the working electrode 4. After that, the solid electrolyte layer 7 and the powder of the reference electrode 6 are added, and the temporary pressing is repeated.Finally, the copper net 8, which has a circular part cut out, is placed so that the cut part is the press-fitting part of the copper wire 9 of the working electrode 4. The element body may be molded by placing it on the reference electrode 6 so as to face it upward and pressing the entire element with a pressure of 4 ton/crA.

In this case, a part of the solid electrolyte layer 7 and the reference electrode 6 are cut out, a part of the copper wire 9 is dug out, and a lead wire 10 is soldered to the tip part, and a lead wire 11 is attached to the current collector 8. are connected with silver paste, and placed on a current collector 2 made of copper foil pasted with silver paste on the inner bottom surface of an aluminum case with a lead wire 12 connected to the outer bottom surface, and then a rubber backing 13 and an insulating resin lid. The finished product can be obtained by inserting the body 14 into the opening of the aluminum case 3 and sealing it by curling the upper edge 3a of the aluminum case 3 inward.

In addition, when the molded products are overlapped, a part of the reference electrode 6 and the solid electrolyte layer 7 is cut out in advance.

Here, the electrolyte powder used in the present invention is prepared as follows.

Cupric halides and alkali halides (the alkali ions are Rb+ and Ni+) were heated at 140°C for 2 hours to remove excess moisture and halogen.

Nu, +, N(CH3) (selected from 10) as a raw material, the powder has an atomic ratio of A:Cu:I:C/=
4:16 Near: 13 (A is Rb, NH4,
N (selected from G(3)4) and molded tablets were placed in a deaerated container and heated to 200 ml.
It was prepared by heating at °C for 17 hours and then grinding.

The fact that the heated substance is a completely new substance is shown in Figure 2a.
.

This can be seen from the X-ray diffraction of the sample before and after heating shown in b.

Incidentally, Fig. 2 a r b uses Rb as the type of alkali, but K is used as the type of alkali.

The crystal structures using NH,,N(CH3)4 after heating reaction are almost similar, and the interplanar spacing is N(CH3)4.
It is slightly narrower at K, and slightly narrower at K.

The conductivities of these electrolytes were measured at AC IKHz, and the results were as shown in FIG.

In addition, in Fig. 3, A is for using Rb, B is for using K, C is for using NH4, and D is for N(CH3)4.
E is the best CuBr among the conventional examples.
and CuBr37 with N-methyltriethylenediamine bromide
．． 5 mo1% mixed reactant value.

In addition, we used Cu for the cathode electrode and PT for the anode electrode, and applied a voltage below the decomposition voltage to find the current-voltage relationship. %)) All samples showed behavior that matched well with the .

In this equation, l is the distance between the electrodes, R is the gas constant, and E
is the applied voltage, 1 is the current flowing, T is the absolute temperature, and F is the Faraday constant.

By the way, the electrical conductivity σ in the alternating current obtained above is the total conductivity, which is considered to be the sum of the ionic conductivity σion and the electronic conductivity σe.

The rate at which the current carries electrons, that is, the electron transference number te, is t
Since Q=σe/σ, insert the measured value into the above equation and get σe
All samples show an order of 10'v/Cm (te is about 1O-7), indicating that ionic conduction is the main factor.

FIG. 4 shows the potential change when the current applied is 50 mA at room temperature, and the symbols in FIG. 4 are the same as those in FIG. 3.

As is clear from Fig. 4, in the case of conventional electrolyte (
Characteristics E), and those of the present invention (characteristics A, B
, C, and D), but when the applied current is large, such as 50 mA, the potential no longer changes linearly when the current is applied, and when the current is stopped, the potential starts to fluctuate.

This is considered to be because polarization other than normal charging or discharging of the electric double layer is occurring.

This means that the application of this element, for example as a timing integration element, uses the linear relationship between the amount of electricity supplied and the potential.

Alternatively, this may be a hindrance to applications that utilize potential memory for electronic channel selection, etc., and this means that the present invention can increase the usable current value.

In Fig. 5, the potential of the working electrode is set to 50 mV by applying current.

It shows the potential change when the current supply is stopped after setting Q mV to -40 mV.

Note that the temperature was kept constant at 60°C.

Further, FIG. 6 shows the change in potential after being left for 24 hours when the potential of the active electrode was set to 50 mV.

From FIG. 6, it can be seen that while the conventional electrolyte (characteristic E) has a considerably poor potential retention at high temperatures, the electrolyte of the present invention (characteristics A, B, C, and D) significantly improves the potential retention. is recognized.

As described above, according to the present invention, not only can the current used in conventional elements be increased to the entire potential range, but also
It is an extremely excellent material that can significantly improve potential retention at high temperatures.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the internal structure of an electric double layer capacitor according to an embodiment of the present invention, and FIG. 2a is a cross-sectional view. b is a diagram showing changes in components before and after the reaction during the production of the solid electrolyte of the present invention, FIG. 3 is a diagram showing changes in electrical conductivity depending on temperature between the conventional electrolyte and the electrolyte of the present invention, and FIG. 50
Figure 5 shows the change in potential holding capacity when rnA (large current) is energized and at rest. Figure 5 shows the change in potential holding capacity when left at a temperature of 60°C. Figure 6 shows the change in potential holding capacity when the rnA (large current) is energized and at rest. FIG. 3 is a diagram showing changes in potential holding ability due to temperature.

Claims (1)

[Scope of Claims] 1. An electric double layer capacitor in which the working electrode and the counter electrode are made of a molded mixture of Cu2S and a solid electrolyte, and a Cu + ion conductive solid electrolyte is interposed between these electrodes, wherein the solid electrolyte As CuCl0Cu+ ion 115 to Rb+. An electric double layer capacitor characterized in that it is substituted with a cation selected from NR4+ (R is H or an alkyl group) and in which 7/20 of C1- ions are replaced with I- ions.