KR0154399B1 - Manufacturing method of metal hydrogen electrode for nickel/metadhydrogen battery - Google Patents

Abstract

The present invention relates to a method for producing a metal hydrogen electrode for nickel / metal hydride batteries, which is pulverized to -325 # by adsorption and desorption of hydrogen to a hydrogen storage alloy prepared in an arc melting furnace or a high temperature induction melting furnace, and then 1 to 20 wt.%. Mix with expanded graphite. When mixing, 5 to 20 wt. The reason for removing oxygen is to prevent oxidation of the electrode. The mixed powder is coated on a nickel network of about 20 to 24 #, dried, and pressed to form an electrode at a pressure of ^{1 to 10} ton / cm ² .

The present invention improves the processability of the electrode by mixing the expanded graphite with a hydrogen storage alloy powder and compression molding to nickel network to produce a metal hydrogen electrode, preventing dropping by the micronization of the hydrogen storage alloy to improve the stability and life of the electrode It has the effect of increasing the electrode capacity by extending, reducing the amount of the conductive material and the binder, and also has the advantage of reducing the manufacturing cost by simplifying the electrode manufacturing equipment because of the excellent workability of the electrode.

Description

Manufacturing method of metal hydrogen electrode for nickel / metal hydrogen storage battery

1 is a process diagram schematically showing a manufacturing process of a metal hydrogen electrode according to the present invention.

2 is a graph showing the electrode capacity and life test results for the metal hydrogen electrode of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal hydrogen electrode for a nickel / metal hydrogen battery, and in particular, a hydrogen resistance alloy powder and expanded graphite are mixed and pressed into a nickel network to prepare a metal hydrogen electrode, thereby producing a metal hydrogen electrode. The present invention relates to a method for manufacturing a metal hydrogen electrode for a nickel / metal hydride battery, which improves, prevents dropping due to micronization, prolongs the stability and life of the electrode, and increases the electrode capacity by reducing the amount of the conductive material and the binder. .

Conventional method of manufacturing a typical metal hydrogen electrode is a method mainly used by the OBC of the United States, the method of compression molding and sintering the V-Ti-Zr-Ni-based alloy powder, and mixing the conductive material or Mm-based alloy powder After encapsulation (microencapsulation), there is a method of preparing the electrode by a paste by mixing the binder. (大角 泰 章, ソ-タ と 鹽 素, 10, 343 (1990), T, Sakai et al., J. Electrochem Soc. 134, 558 (1987), MA Fetcenko, US Pat. 5,096,667, US Pat. 5,104,617 (1992).

The manufacturing method of sintering by compression molding in the manufacturing method of the metal hydrogen electrode has the advantage that the electrode capacity is high because the electrode is manufactured without a conductive material or a binder, but a special high-pressure compression molding device and a sintering device are required, which leads to equipment problems. In addition, as the electrode is manufactured without a binder, handling of the electrode is difficult, and the electrode active material is dropped due to the micronization of the electrode by repeating the charge / discharge cycle.

In addition, the method of manufacturing the electrode by the paste method has the advantage of increasing the life of the electrode by easy handling of the electrode and less dropping of the electrode active material, but has the disadvantage of reducing the electrode capacity due to the addition of excessive conductive and binder materials. .

The object of the present invention devised in view of the above problems is that the expanded graphite, which can be used as a binder at the same time as the workability and excellent in electrical conductivity, can also be used as a conductive material, is mixed with hydrogen storage alloy powder and pressed into nickel network. In order to improve the processability of the electrode by manufacturing a metal hydrogen electrode, to prevent dropping by the micronization of the hydrogen storage alloy to extend the stability and life of the electrode, and to increase the electrode capacity by reducing the amount of the conductive material and the binder. A method of manufacturing a metal hydrogen electrode is provided.

The object of the present invention is to uniformly mix the hydrogen storage alloy powder and expanded graphite with water or alcohol, apply the mixed powder to a nickel network, and then dry and press molding for nickel / metal hydrogen storage battery. It is achieved by providing a method for producing a metal hydrogen electrode.

Hereinafter, with reference to the manufacturing process of Figure 1 of the accompanying drawings will be described in more detail the present invention.

First, hydrogen is adsorbed and desorbed to -325 # in a hydrogen storage alloy prepared in an arc melting furnace or a high temperature induction melting furnace, and then mixed with 1 to 20 wt.% Of expanded graphite. When mixing, 5 to 20 wt.% Of oxygen-depleted water, alcohol and the like are added for uniform mixing. The reason for removing oxygen is to prevent oxidation of the electrode. The mixed powder is applied to a nickel network of about 20 to 24 #, dried, and press-molded at a pressure of ^{1 to 10} ton / cm ² to prepare an electrode. In general, expanded graphite is thermally and chemically stable and has excellent processability, and is used for sealing gaskets, mechanical joints, valves, etc., and graphite is chemically treated with an expansion material (acid or chlorine compound) and then heat treated (800 to 1100 ° C.). (See US Pat. No. 3,440,181 (1969)).

The following are examples and comparative examples in which a metal hydrogen electrode was manufactured using the manufacturing method of the present invention and the battery performance was tested, thereby making the present invention more clearly understood.

Example 1

MmNi _3.5 Co _0.8 Mn _0.4 Al _0.3 ground with -325 # and 1 g of hydrogen storage alloy powder were mixed at a ratio of 0.1 g of expanded graphite and 0.1 g of alcohol, and applied to a 20 # nickel screen. The electrode A is manufactured by pressing at a pressure of cm ² .

Comparative Example 1

0.1 g of copper powder (-10 μm) and 0.05 g of 60% PTFE suspension were mixed with 1 g of the hydrogen storage alloy powder as in Example 1, applied to a 20 # nickel screen, dried, and pressed at a pressure of 5 ton / cm ² . To prepare electrode A '. Further, the same hydrogen storage alloy powder was microencapsulated in a ratio of 10wt.%, Mixed with a ratio of 0.05g of 60% PTFE suspension to 1g of this powder, applied to a 20 # nickel screen, dried, and then dried at 5 ton / cm ² . Prepare electrode A under pressure.

Example 2

B was prepared in the same manner as in Example 1 with respect to V ₁₅ Ti ₁₅ Zr ₂₁ Ni ₂₉ Cr ₅ Co ₆ Mn ₈ hydrogen storage alloy powder pulverized to -325 #.

Comparative Example 2

The same hydrogen storage alloy powder as in Example 2 was applied to a 20 # nickel screen, and then pressed at a pressure of 10 ton / cm ² to prepare electrode B '.

Figure 2 shows the results of the battery performance test on the electrode prepared under the above conditions in 30% KOH + 1M LiOH solution.

As can be seen from these results, in the case of MmNi _3.5 Co _0.8 Mn _0.4 Al _0.3 alloy electrode, the capacity of the electrode produced by the method of the present invention is about 250mAh / g including expanded graphite, Comparative Example prepared by the conventional method In the electrode 1, an increase in capacity of about 15 to 20 mAh / g was shown compared to the capacity of 230 mAh / g and 235 mAh / g of the electrodes A 'and A including the conductive material and the binder. In addition, the life test results up to 200 times showed that the electrode life was longer than that of the electrode A ', and that the electrode life was almost the same as the electrode A', indicating that the electrode life was excellent. This can increase the electrode capacity because the amount of the conductive material can be reduced by using expanded graphite, and also to increase the life of the electrode by preventing dropping by the micronization of the hydrogen storage alloy.

In the case of the V ₁₅ Ti ₁₅ Zr ₂₁ Ni ₂₉ Cr ₅ Co ₆ Mn ₈ alloy electrode, the capacity of the electrode manufactured by the paste method of the present invention was about 320 mAh / g including expanded graphite. It was slightly lower than the electrode capacity of 330mAh / g of B ', it can be seen that the electrode life was much better. This is because the portion of the hydrogen storage alloy of the electrode active material is lowered as the expanded graphite is used, resulting in a slight decrease in the electrode capacity. On the other hand, since the expanded graphite holds the active material, the electrode is prevented from falling off due to the micronization of the hydrogen storage alloy. It is a much longer lifespan.

As described above, in the present invention, the expanded graphite is mixed with a hydrogen storage alloy powder and press-molded into a nickel network to prepare a metal hydrogen electrode, thereby improving the workability of the electrode and preventing dropping due to micronization of the hydrogen storage alloy. Prolonging the stability and life of the electrode, there is an effect of increasing the electrode capacity by reducing the amount of the conductive material and the binder.

In addition, since the processability of the electrode is excellent, there is an advantage that the electrode manufacturing equipment is simplified to reduce the manufacturing cost.

Claims (4)

A method of manufacturing a metal hydrogen electrode for a nickel / metal hydride battery, characterized in that the hydrogen storage alloy powder and expanded graphite are uniformly mixed with water or alcohol, and the mixed powder is applied to a nickel network, followed by drying. The method of manufacturing a metal hydrogen electrode for a nickel / metal hydride battery according to claim 1, wherein the amount of said expanded graphite is 1 to 20 wt.%. The method of manufacturing a metal hydrogen electrode for nickel / metal hydride batteries according to claim 1, wherein the water or alcohol is one in which oxygen is removed and the amount thereof is 5 to 20 wt.%. The method of manufacturing a metal hydrogen electrode for nickel / metal hydride batteries according to claim 1, wherein the nickel network is 20 to 24 #, and the compression molding pressure is 1 to 10 ton / cm ² .