JPS60263420A - Energy storing device - 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] Industrial Field of Application The present invention is directed to an electric double layer consisting of a pair of polarizable electrodes and an electrolytic solution or a polarizable electrode and a non-polarizable electrode. The present invention relates to a storage device.

Conventional Structure and its Problems Conventionally, an electric double layer capacitor consisting of a pair of polarizable electrodes and an electrolyte has the basic structure shown in FIG. That is, a pair of polarizable electrodes 1 and 2, a separator 3 existing between them, and a current collecting layer 4 of each polarizable electrode 1 and 2,
6, and activated carbon powder, activated carbon fiber, etc. are used as typical polarizable electrodes.

Figure 2 shows a specific example of the electric double layer capacitor devised by the present inventors, which includes a woven fabric 6.7 made of activated carbon fibers and aluminum formed on one side of the activated carbon fiber woven fabric 6, 70 by plasma spraying. Current collecting layers 8, 9 and separator 1o
It is a flat capacitor consisting of a metal case 11, 12 which also serves as positive and negative electrodes, and an insulating gasket 13, and uses a mixed solution of pro, pyrene carbonate, and tetraethylammonium barchlorate as the electrolyte.

On the other hand, the basic structure of a conventional capacitor or battery consisting of a polarizable electrode, a non-polarizable electrode, and an electrolytic solution is shown in FIG. That is, it is composed of a polarizable electrode 2o, its current collecting layer 21, a separator 22, and a non-polarizable electrode 23. In this case as well, a typical polarizable electrode is activated carbon or a twisted non-polarized electrode. As the polarizable electrode, metals such as lithium, their oxides, chalcogenides, etc. are used.

FIG. 4 shows another example of this capacitor, which uses an activated carbon fiber woven fabric 30 for the positive electrode, lithium metal pellets 31 for the negative electrode, and is composed of a separator 32, cases 33 and 34, and a gasket ring 35. The electrolyte used is a mixture of lithium chloride and propylene carbonate.

Considering the withstand voltage of these capacitors and batteries, the maximum operating voltage is determined as described below.

First, in a capacitor using a pair of activated carbon fibers as polarizable electrodes as shown in Figure 2, the surfaces of the positive and negative electrodes (
Due to the polarization of the tetraethylammonium perchlorate ion represented by formula 1), an electric double layer is formed between the tetraethylammonium ion (+) and the tetraethylammonium chlorate ion (-).

(C2H6)4NCt04→(C2H6)4N++Ct
o4- (Formula 1) The voltage that can be applied to cause this reaction is the positive electrode.

Both negative electrodes are determined by the decomposition voltage of the electrolyte.

FIG. 5 shows the voltage-current curves of the anode and cathode when a propylene carbonate and tetraethylammonium barchlorate-based electrolyte is used and conventional cellulose-based activated carbon is used for the positive and negative electrodes. -2 at the negative electrode as shown in this figure
, 5V, +2 at the positive electrode. Decomposition of the electrolyte begins near OV, and the system as a whole can only obtain a usable withstand voltage of 4.6V at most.

In practice, the working withstand voltage is even lower due to the metal used for current collection, the anodic dissolution of the case material metal, film formation, dissolution reaction current, etc., but this will control the working withstanding voltage. The biggest factor is the decomposition voltage of the electrolyte. By the way, the decomposition reaction due to the anode and cathode reactions of the electrolyte is as follows:
It is largely related to the properties of the electrode material, and in particular when activated carbon is used as a polarizable electrode, the functional groups present on its surface greatly influence the decomposition voltage. The conventionally used activated carbon electrode has a positive electrode,
Since the same properties were used for both negative electrodes, the withstand voltage was at most 2 to 2.5V.

Next, a capacitor with a polarizable electrode-non-polarizable electrode system will be described. In this type of capacitor, an electric double layer formation reaction occurs at the positive electrode due to the polarization of the electrolytic solution, which is the same as that in the above-mentioned capacitor, and at the negative electrode, for example, precipitation and dissolution reactions of lithium ions occur. (Formula 2) is the positive and negative electrode reactions when charging this capacitor.

Positive electrode Cn+Cto4-→Cn+・ClO2-+e (Formula 2) %Formula % The voltage used in this system is determined by the Li solution deposition potential for the negative electrode, and the decomposition voltage of the electrolytic solution for the positive electrode, as in the case of the capacitor. Determined by In this case as well, the decomposition voltage of the electrolyte is controlled by the functional groups on the surface of the activated carbon, and by using activated carbon having a more aggressive potential, a higher anodic decomposition voltage of 1=7 I −1 can be obtained. Conventionally, the activated carbon used in this system had a hardness of 3 to 3.2 cm for the entire system.

Purpose of the Invention The purpose of the present invention is to obtain energy storage devices such as capacitors and batteries that have a high withstand voltage. The object of the present invention is to obtain high-voltage capacitors and batteries by making the positive and negative electrode decomposition reaction voltages more anodic and cathodic, respectively.

Structure of the Invention To achieve this object, the present invention basically consists of a pair of polarizable electrodes and an electrolyte, or a polarizable electrode, a non-polarizable electrode, and an electrolyte, and the positive electrode is heated to a high oxidation potential. and the negative electrode has a lower oxidation potential.

ζ According to the present invention, the difference in the decomposition voltage of the electrolyte (positive,
This increases the difference in negative electrode decomposition voltage, making it possible to obtain energy storage devices such as capacitors and batteries that have a high usable withstand voltage.

Description of Examples As stated in the previous section, even if the same electrolyte is used, the decomposition voltage of the electrolyte differs depending on the nature of the activated carbon polarizable electrode. FIG. 6 is an enlarged schematic diagram of the surface of activated carbon, which shows that in addition to the carbon element, the surface also contains carboxyl groups 40. Phenolic hydroxyl group 41° carbonyl group 42. Quinone group 43
There are functional groups such as These functional groups promote or prevent decomposition of the electrolyte when activated carbon is polarized positively and negatively. In other words, carboxyl groups and phenolic hydroxyl groups have the function of increasing the electrolyte decomposition voltage during anode polarization, and when cathode polarization, they are themselves reduced and promote electrolyte decomposition, making the decomposition voltage more noble. I end up. On the other hand, carbonyl groups, quinone groups, etc. act to prevent decomposition of the electrolyte by 9/·-7 when the cathode is polarized, and when the anode is polarized, they are also oxidized and promote oxidation of the electrolyte, resulting in The anodic decomposition voltage becomes more base.

Based on the above, in order to improve the withstand voltage of the entire capacitor/battery system, activated carbon with many acidic functional groups (carboxyl groups, phenolic hydroxyl groups) should be used for the positive electrode, and neutral or basic carbon should be used for the negative electrode. Functional groups (carbonyl group,
It can be seen that it is effective to use activated carbon having a large number of quinone groups.

The following two methods can be considered for producing activated carbon having these functional groups. In other words, at the time of carbonization and activation of raw materials,
There are two methods: a method in which the reaction atmosphere is an oxidizing but reducing atmosphere; and a method in which carbonized and activated carbon materials and activated carbon materials are treated in an oxidizing but reducing atmosphere.

As the oxidizing atmosphere, o2. These methods include carbonization, activation, and post-treatment in an oxidizing gas such as CO2 and N2O, and a method in which the generated carbon and activated carbon are treated with an oxidizing acid such as HNO3.

10 beds Further, as the reducing atmosphere, N2. Hydrocarbons, c.

There are methods of carbonization, activation, and post-treatment in reducing gases such as N2, Ar, etc., and methods of carbonization, activation, and post-treatment in reducing gases such as N2, Ar, etc., and methods of carbonizing, activating, and post-treating the generated carbon and activated carbon in reducing acids such as HCl and NaOH.

This method involves treatment with an alkali such as KOH.

7a and 7b show an example of a carbon electrode in FIG. 7a suitable as a positive electrode and an example of a carbon electrode in FIG. 7 suitable as a negative electrode. .

Note that even when a non-polarizable electrode such as Li is used as the negative electrode, activated carbon having many acidic functional groups provides a higher working voltage as described above.

Next, a specific example will be described.

(Example-1) Activated carbon fibers obtained by carbonizing and activating phenolic resin fibers at high temperatures in N2-N20 gas were used as positive electrodes, and activated carbon fibers obtained by carbonizing and activating the same raw material fibers at high temperatures in hydrocarbon gas. A capacitor was constructed using activated carbon fibers as a negative electrode.

11t, , ``Phenolic activated carbon fibers were immersed in 1 m01e/l of HNO3 for 10 hours, washed with water, dried activated carbon fibers were used as the positive electrode, and the same activated carbon fibers were immersed in 0.5 mole/l of HCl for 6 hours. A capacitor was constructed using the washed and dried activated carbon fiber as a negative electrode.

(Example 3) A capacitor was constructed using activated carbon fibers obtained by carbonizing and activating phenolic resin fibers in N2-N20 gas at high temperatures as a positive electrode and metal lithium pellets as a negative electrode.

(Example 4) Activated carbon fiber obtained by carbonizing and activating phenolic activated carbon fiber in N2-CO2 gas at high temperature was used as the positive electrode, and the activated carbon fiber treated in H2 atmosphere at high temperature was used as the negative electrode. Constructed a capacitor.

(Example-6) The same positive electrode as in Example-4 was used under vacuum at high temperature ('10
'torr) was used as a negative electrode to construct a capacitor.

Each electrode is punched in order of 12 diameters, and one side is coated with a plasma sprayed aluminum coating. In Example 3, the electrolyte was LICLO4 and all others were tetraethylammonium hachloride! Used for layer liquid. The structure of the capacitor is shown in FIG. 2, and Table 1 shows the capacitor characteristics along with the conventional example.

Table 1: Effects of the Invention As described above, according to the present invention, by using an electrode with a high oxidation potential as the positive electrode and an electrode with a low oxidation potential as the negative electrode, it is possible to obtain a capacitor or battery with a high working voltage. I can do it. These electrodes can be obtained by various processing methods, carbonization and activation methods as shown in the text, and depending on how the obtained activated carbons are combined, an energy storage device with high withstand voltage can be obtained.

[Brief explanation of drawings]

14 Page 7 ゛Figure 1 is a basic configuration diagram of a capacitor consisting of a pair of polarizable electrodes, Figure 2 is a sectional view showing a specific example of the configuration of the capacitor in Figure 1, and Figure 3 is a diagram showing the configuration of a polarizable electrode and a non-polarized electrode. A basic configuration diagram of a capacitor consisting of polarizable electrodes, Figure 4 is a sectional view showing a specific example of the configuration of the capacitor in Figure 3, and Figure 6 shows a mixture of tetraethylammonium verchlorate and glopyrene carbonate used as an electrolyte. FIG. 6 is a schematic diagram showing the functional groups on the activated carbon surface, and FIG. 7 is a positive electrode of the present invention. FIG. 2 is a schematic structural diagram of an activated carbon material for a capacitor or battery suitable for a negative electrode. 1.2.20...Polarizable electrode, 6,7.30.
...Activated carbon fiber woven fabric, 23...Non-polarizable electrode, 31...Lithium metal pellet. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3, 36 34. 97 Figure 5 Figure 6 Figure 7

Claims (6)

[Claims] (1) Basically composed of a pair of polarizable electrodes and an electrolyte, or a polarizable electrode, a non-polarized electrode, and an electrolyte, with the positive electrode having a high oxidation potential and the negative electrode having a lower oxidation potential. An energy storage device characterized by: (2) The electrode with a high oxidation potential is a carboxyl group. Activated carbon or carbon material has many acidic functional groups such as phenolic hydroxyl groups, and the electrode with a lower oxidation potential is activated carbon or carbon material that has many neutral functional groups such as carbonyl groups and quinone groups, and basic functional groups. The energy storage device according to claim 1, characterized in that it is a material. (3) The non-polarizable electrode is lithium, sodium, potassium, iron, nickel, aluminum, or titanium. The energy storage device according to claim 2f, wherein the energy storage device is tantalum metal or an oxide or chalcogenide of these metals. (4) The energy storage device according to claim 2, wherein the activated carbon or the carbon material is activated carbon fibers, carbon fibers, cloth 2 paper, or felt made of the activated carbon fibers. (5) Activated carbon fibers and carbon fibers are phenolic resin fibers, cellulose fibers, and polyacrylate fibers. 5. The energy storage device according to claim 4, wherein each of the pitch systems consists of one or more pitch systems. (6) The electrolytic solution contains at least one of metal perchlorate, BF-salt, PF4-salt, tetraethylammonium barchloret+a acid, and KOH constituting the non-polarizable electrode. An energy storage device according to claim 1.