JPS58669B2 - battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of a liquid battery using a liquid cathode active material, and by using a metal foam that is easy to process as a cathode current collector, it is lightweight and has excellent polarization characteristics. The purpose of this invention is to provide a battery that has good current density and can operate at high current density.

The hydrogen generation reaction from water is as follows.

H2O+e-→1/2H2↑+0H- E=-0.826V (however, PH14) If the above reaction is a positive electrode reaction, the theoretical potential is -0.8
The reaction potential is 26 V, which is not a very noble reaction, but if a substance with a base reaction potential, such as Li, Na, Mg, etc., is combined as the negative electrode active material, it can be put to practical use.

Conventionally, this type of battery has a negative electrode 1 and a net-like or corrugated positive electrode current collector 2 arranged in a battery case 3 with a separator 4 interposed therebetween, as shown in FIG. In addition to providing an inlet 5 and an electrolyte outlet 6, a negative electrode lead wire 7 and a positive electrode lead wire 8 are attached to a negative electrode 1 and a net-like or corrugated positive electrode current collector 2, respectively. It is operated by circulating it as an electrolyte.

For this reason, in this type of liquid battery, before use, the negative electrode active material 1
The battery is made up of accessories such as a mesh or corrugated positive electrode current collector 2 and a battery case 3, and is operated by injecting water during use, resulting in a lightweight battery.

Furthermore, when used underwater, for example as a torpedo battery, it has the advantage that there is no need to carry water with it.

However, on the other hand, the biggest drawback of this type of battery is that the hydrogen generation reaction has relatively large polarization, and when a large current density is used, the electrode potential decreases significantly.

The problem of polarization can be avoided by lowering the current density of the positive electrode, but
Since active substances such as Li and Na are used as the negative electrode active material, the negative electrode active material often reacts directly with water, resulting in a decrease in the utilization rate of the negative electrode active material, so do not lower the current density too much. is not desirable.

The present invention uses a metal foam with a large pore size, an average pore size of 0.3 to 2 mm, as a positive electrode current collector instead of the conventional net-like or corrugated positive electrode current collector, which has the disadvantage of large polarization. This is an attempt to solve the problem.

In FIG. 2 showing one embodiment of the present invention, 9 is an open-cell metal foam positive electrode current collector.

Also, other numbers are the same as in FIG.

In particular, in a battery using Li or Na as the negative electrode 1, the reaction product film on the surface of the negative electrode 1 acts as a separator, so the separator 4 is not necessary.

The metal foam used in the present invention will be described below.

That is, the foam has a porosity of 80 to 98%, the pores are spherical and all communicate, it has a three-dimensional network structure, and the skeleton is hollow, so it is extremely lightweight.

Such a porous body is made by imparting conductivity to the surface of a spongy polyurethane resin foam by electroless plating, plating it with the required metal to a thickness of about 15 μm by electrolytic plating, and then heating it in a hydrogen atmosphere furnace. It is obtained by carbonizing and removing the polyurethane resin.

Next, conditions to be met by the metal foam used as a positive electrode current collector in the present invention will be listed.

1) The material must have a low overvoltage due to electromotive reaction.

2) Stable with electrolyte and not corroded.

3) Open cells, allowing electrolyte, gas, etc. to freely pass through the foam.

4) Be mechanically strong.

Metal foams made of materials that satisfy the above conditions include iron, nickel, and the like.

Of these, iron is the cheapest and most practical material because it is easy to process.

Foams with an average pore diameter of about 0.3 to 2 mm and a skeleton thickness of about 0.2 to 1 mm are easy to handle and have good properties.

Furthermore, if the characteristics are not sufficient with iron alone, performance can be further improved by coating with a suitable catalyst such as platinum black, Raney nickel, or Raney silver.

On the other hand, the positive electrode electromotive reaction of this type of battery using hydrogen peroxide as a liquid positive electrode active material is considered as follows.

H2O2→H++HO2− H02−+H2O+2e−→3OH− OH−+H+→H2O As a total reaction, H2O2+2e−→2OH E=+0.878V As described above, the reaction potential of this reaction is significantly nobler than that of water, and theoretically There will be no gas generation.

However, in this type of battery that uses hydrogen peroxide as a liquid cathode active material, batteries that use a conventional mesh or corrugated cathode current collector have the disadvantages of using water as a liquid cathode active material, as described above. It has the disadvantage that gas is generated which theoretically would not be generated.

On the other hand, in the battery according to the present invention in which hydrogen peroxide is used as the positive electrode active material and a metal foam is used as the positive electrode current collector, no gas generation is observed.

When using a non-aqueous solution as the liquid cathode active material, the electrolyte is prepared by dissolving lithium perchlorate, sodium, magnesium, etc. at a rate of about 1 mol/l in propylene carbonate, and thionyl chloride is added to this as the cathode active material. A high voltage of about 3V can be obtained by using a liquid cathode active material in which an oxidizing agent such as sulfur disulfide is dissolved.

However, when a non-aqueous solution is used, it is difficult to handle and can only be used at a relatively low current density, making it inferior to an aqueous solution.

The effects of the positive electrode current collector made of the metal foam of the present invention are as follows.

1) Since a metal foam is used as the positive electrode current collector, it is possible to obtain several times to several tens of times the surface area with the same volume compared to net-like or corrugated positive electrode current collectors, so the current density per surface area can be reduced. If it is discharged at the same value as the conventional product, it is possible to increase the apparent current density even if the volume is the same.

In addition, since the foam has a larger pore diameter than a porous plate such as a porous carbon plate, the active material and electrolyte flow through it, and reactants are quickly supplied and products are removed. Can be used widely from the surface to the inside of the foam.

2) The weight can be reduced to 1/2 to 115 times that of a net-like or corrugated positive electrode current collector having the same ability.

3) It can be processed into the desired shape simply by pressing, and it is easy to create any shape.

As described above, the present invention can significantly improve performance and reduce weight in a liquid battery comprising a liquid cathode active material using an aqueous solution or a non-aqueous solution, and exhibits particularly excellent effects when an aqueous solution is used. It is also possible to reduce costs,
Its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a conventional battery using water as a liquid positive electrode active material, and FIG. 2 is a vertical cross-sectional view of a battery according to the present invention using water as a liquid positive electrode active material. 1... Negative electrode, 3... Battery case, 4...
・Separator, 5... Electrolyte inlet, 6...
... Electrolyte outlet, 7 ... Negative electrode lead wire, 8 ...
. . . Positive electrode lead wire, 9 . . . Metal foam positive electrode current collector.

Claims (1)

[Claims] 1. A metal foam with an average pore diameter of 0.3 to 2 mm is used as a current collector for the liquid cathode active material flowing in the container, and Li,
A liquid battery made of negative electrode active materials such as Na and Mg. 2. The liquid battery according to claim 1, wherein water is the liquid cathode active material. 3. The liquid battery according to claim 1, wherein hydrogen peroxide is the liquid cathode active material.