JPH02234355A - Manufacture of hydrogen absorbing electrode - Google Patents

Abstract

PURPOSE:To manufacture an electrode in a simple process by applying a paste mixture containing a hydrogen-absorbing alloy powder, a polymer latex, and an alkali-resistant conductive powder to a conductive core and drying at a temperature lower than the melting point of the alkali-resistant polymer. CONSTITUTION:After a paste mixture containing a hydrogen-absorbing alloy powder, an alkali-resistant polymer powder-dispersed polymer latex, and an alkali-resistant metal or carbonic conductive powder is applied to a conductive core body, the applied paste mixture is dried at a temperature lower than the melting point of the alkali-resistant polymer contained in the latex to give a hydrogen-absorbing electrode plate. In this case, since the latex granules work as a firm binder binding the hydrogen-absorbing alloy grains, without the electrode active mass being supported on three-dimensional skeleton of a cellular nickel, an electrode with high strength is obtained. By this method, a hydrogen-absorbing electrode with high strength is obtained by extremely simple processes wherein a paste mixture is applied on a conductive core body and drying the paste.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a water cable storage electrode used in alkaline batteries.
This is related to the method of delivery. Conventional technologies and their problems Hydrogen storage electrodes use hydrogen storage alloys that reversibly store and release hydrogen. The operating potential of a hydrogen storage electrode is almost the same as that of a cadmium electrode, and its discharge capacity per unit volume is significantly larger than that of a cadmium electrode. Therefore, when this electrode is used as the negative electrode of an alkaline storage battery, it is possible to obtain an alkaline storage battery that operates at approximately the same voltage as when cadmium is used as the negative electrode, and has a discharge capacity that is significantly larger than when cadmium is used as the negative electrode. Are known. Conventionally, hydrogen storage electrodes have been manufactured mainly by sintering a hydrogen storage alloy and metal, or by using a paste containing a hydrogen storage alloy and a polymer binder. Electrodes manufactured using the former method are advantageous in that they have high strength because the hydrogen storage alloy and metal are strongly bonded, but they require long-term baking at high temperatures when manufacturing the electrodes. It has the disadvantage of requiring a connection. On the other hand, the latter method using paste (hereinafter referred to as the "paste method") is advantageous in that electrodes can be manufactured in a shorter time than the former method. The following methods are available for manufacturing paste-type hydrogen storage electrodes. That is, as described in Japanese Utility Model Publication No. 57-34678, there is a method in which a foamed metal is filled with a paste-like mixture containing hydrogen storage alloy powder and an alkali-resistant polymer binder. In this method, a fluororesin in the form of a dispersion or methylcellulose in the form of a solution is used as a polymeric binder. The paste is then dried to develop the binding strength of these polymers. The inventor attempted to produce a hydrogen storage alloy using this method and discovered the following drawbacks. That is, when a fluororesin is used as a binder, the fluororesin is easily deformed into fibers by kneading, so the m-fibers become entangled with each other while the paste is kneaded, increasing the viscosity of the paste as a whole. This has the disadvantage that it becomes difficult to control the viscosity of the paste, resulting in uneven application of the paste.
Furthermore, when the fluororesin fibers are filled with the paste into the nickel foam, they become entangled with the framework that forms the porous nickel foam, making it difficult to fill the nickel foam with the paste. Additionally, when a water-soluble polymer such as methylcellulose is used as a binder, a film of this polymer is formed on the surface of the hydrogen storage alloy when the paste is dried, and the hydrogen storage alloy and alkaline electrolyte are bonded together. contact is inhibited. the result,
There is a disadvantage that the amount of hydrogen storage alloy that does not participate in the charge/discharge reaction of the t-electrode increases, and the discharge capacity of the hydrogen storage electrode decreases. Furthermore, this method has the disadvantage that when filling the foamed metal with a paste-like mixture, the paste must be kneaded with a rubber spatula, which requires complicated operations to manufacture the electrodes. Means for Solving the Problems The present invention can be manufactured with simpler operations than conventional paste-type hydrogen storage electrodes, and the weight distribution of the hydrogen storage alloy is uniform, and hydrogen in the alloy can be easily discharged. The aim is to solve the above-mentioned problems by obtaining a paste-type hydrogen storage electrode with a large discharge capacity. Specifically, the present invention comprises a hydrogen storage alloy powder, a polymer latex in which particles of an alkali-resistant polymer that maintain a spherical shape without becoming fibrous during kneading are dispersed, and a metal or carbonaceous alkali-resistant conductive powder. After applying a paste-like mixture containing the above to a conductive core, the applied paste-like mixture is dried at a temperature lower than the melting point of the alkali-resistant polymer contained in the latex to obtain a hydrogen storage electrode plate. .

Active polymer latex is obtained by dispersing monomers in water using a surfactant, etc., and polymerizing the monomers (this reaction is called emulsion polymerization), in which fine particles of polymers are dispersed in water. This is what we are doing. Polymers obtained by emulsion polymerization include polyethylene. Polyvinylidene chloride, polyvinyl chloride. Polyvinyl acetate, polyethylene, polypropylene. Polymethyl methacrylate, polyurethane. Polymers such as chloroprene, polytetrafluoroethylene, and diethylene-butadiene copolymers. Vinylidene chloride-vinyl chloride copolymer, acrylonitrile-butadiene copolymer. There are many types of cobolima such as acrylonitrile-styrene copolymer and vinyl chloride-vinyl acetate copolymer. The particles that make up these polymer latexes are extremely small, submicron in size. The present invention utilizes the characteristics of this polymer latex, as described below. The inventor discovered the following about this polymer latex. In other words, when this polymer latex is mixed with hydrogen storage alloy powder to create a paste-like mixture and this is dried, water in the gaps between the hydrogen storage alloy and latex particles is lost as the drying progresses. ．． During this drying process, if water remains in the gaps between the latex oval particles and the hydrogen storage alloy particles, a large capillary force acts on this water. Therefore, the latex particles interposed between the particles of the hydrogen storage alloy are significantly compressed and deformed even when the drying temperature is much lower than the melting point of the latex polymer. As a result, the latex particles act as a strong binder between the hydrogen storage alloy particles. In the present invention, this phenomenon is utilized to obtain a hydrogen storage alloy. That is, hydrogen storage alloy powder, polymer latex in which fine particles of alkali-resistant polymer are dispersed, metallic nickel, and graphite. A paste mixture containing a metal or carbonaceous alkali-resistant conductive powder such as acetylene black is applied to a nickel-plated steel plate with perforations,
It is applied to an alkali-resistant conductive core such as Expanded Metal made by Metal Nigel, and the applied material is dried at a temperature lower than the melting point of the alkali-resistant polymer. In this way, a highly strong hydrogen storage single pole can be obtained by simply applying a paste-like mixture to a conductive core and drying it. Therefore, according to the present invention, an electrode with high strength can be obtained without supporting the active material by a three-dimensional skeleton of foamed nickel unlike conventional paste-type electrodes. In the present invention, the paste-like mixture is dried at a temperature lower than the melting point of the polymer. The reason is as follows. In other words, when the temperature becomes higher than the melting point of the polymer, the polymer flows and a polymer film is formed on the surface of the hydrogen storage alloy, inhibiting the contact between the hydrogen storage alloy and the alkaline electrolyte, resulting in charging. The amount of hydrogen storage alloy involved in discharge decreases, resulting in the disadvantage that the discharge capacity of the t-electrode decreases.

In addition, in the present invention, polyethylene, polyvinylidene chloride, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene can be used as the polymer latex. Polymethyl methacrylate. The base is kneaded, such as polymers such as roloprene, copolymer such as styrene-butadiene copolymer, chloride and nylidene-vinyl chloride copolymer, acrylonitrile-butadiene copolymer, and acrylonitrile-styrene copolymer. When preparing this, we use a dispersion of an alkali-resistant polymer that maintains its spherical shape and does not easily form into fibers. Also, latex containing dispersed polymers, such as fluorocarbon resins such as polytetrafluoroethylene, which easily become fibers due to cross-wires, is not used. Therefore, in the present invention, the latex particles do not become fibrous when the paste is kneaded, and a stable viscosity of the paste is obtained, so that the above-mentioned disadvantages do not occur and stable working conditions can be achieved.
This is advantageous in that it allows you to obtain -. Furthermore, in the present invention, a metal or carbonaceous alkali-resistant conductive powder is added to the paste mixture. Its purpose is
The objective is to improve the conductivity between the f4 pole boron storage alloy powder and the conductive core to facilitate the discharge of hydride from the hydrogen storage alloy. That is, the inventor manufactured a hydrogen absorbing R electrode by the method of the present invention by changing the amount of alkaline conductive powder added, and as a result of charging and discharging this electrode in an alkaline electrolyte, the conductive powder was It has been found that in the absence of additives, it is easy to charge this electrode, but it is extremely difficult to discharge it. The reason why such a phenomenon occurs is not clear, but it is thought to be as follows. In other words, since the hydrogen storage alloy is a metal in the discharged state, it has extremely good electronic conductivity, so it can be easily charged without using conductive powder. However, as charging progresses, metal hydrides with poor electronic conductivity are formed. Next, when discharging, if conductive powder is not used, the electrical resistance of the metal hydride, which is the charge product, is large, so the metal hydride located far from the conductive core will collect current. It becomes difficult and the electrode discharge becomes difficult. On the other hand, when a conductive powder is used, the metal hydride has good current collection properties, making it easier to discharge the electrode. In the method of the present invention, a punched metal or an expanded metal that does not form a three-dimensional network is used for the conductive core, so the use of an alkali-resistant conductive powder makes it possible to discharge the electrode. In the case of conventional electrodes in which foamed nickel is filled with a hydrogen storage alloy, the skeleton acts as a three-dimensional current collector network, so it is not necessarily necessary to use conductive powder, but in the case of electrodes such as those described above, The problem of requiring complicated operations for production remains unsolved. EXAMPLE Hereinafter, the present invention will be explained in detail using a preferred example of a real vagina. Experiment 1 First, we used the hydrogen storage electrode of the present invention, which uses a polymer latex in which alkali-resistant polymer particles that maintain a spherical shape when kneading the paste are dispersed, and the hydrogen storage electrode of the present invention, which uses a polymer latex in which particles of an alkali-resistant polymer that maintain a spherical shape when kneaded, and a polymer latex that does not maintain a spherical shape during kneading but turn into fibers. The superiority of the hydrogen storage electrode according to the present invention will be explained by showing an example of manufacturing a comparative hydrogen storage electrode using a polymer latex with particles dispersed therein and a comparison hydrogen storage electrode using a water-soluble polymer as a binder. I will explain specifically.
[Hydrogen storage electrode Al (Example of the present invention)] A hydrogen storage electrode Al according to the present invention was prepared as follows. The hydrogen storage alloy was manufactured by mixing metallic titanium powder and metallic nickel powder at an atomic ratio of 2:1 and melting this mixture using an arc melting furnace in an argon atmosphere.
In order to make the composition of the base metal ingot obtained by melting uniform,
After cooling, the mixture was turned over and redissolved, which was repeated three times. Next, the thus obtained intermetallic compound Ti2 old alloy ingot was crushed in a mortar made of cemented carbide.
Then, 100 parts by weight of this hydrogen storage alloy powder that has passed through a 100 mesh sieve is mixed with 20 parts by weight of artificial Kurofune powder (manufactured by LON7A, trade name: [850-200), and water is added to this mixture. Kneaded. Polyethylene resin (melting point 110''
C) Polymer latex in which fine particles are dispersed (Sanyo Chemical Co., Ltd.)
20 parts by weight of this latex was added and kneaded using Permarin PI {), manufactured by Co., Ltd., to obtain a paste-like kneaded product. This mixture is then applied to a thickness of 0.5 mm with perforations.
The coating was applied to a conductive core made of a 20 micron thick nickel plated steel plate of 0.09 nus, and the thickness of the coating was adjusted using a doctor blade.

Next, this coating was dried using hot air at 75°C.

Then, press the electrode with a roll at room temperature to make the electrode thickness about 0.
71HI and cut into a size of aonnx 401111 to obtain a hydrogen storage electrode.

[Water cable storage electric iFi! B] (Comparative example) Hydrogen storage battery according to the present invention [! Instead of the polymer latex in A in which fine particles of polyethylene resin are dispersed, there is a polymer latex in which fine particles of ethylene trough, which is a polymer that turns into fibers during kneading, are dispersed (manufactured by Daikin Corporation). A hydrogen storage electrode B of a comparative example was manufactured under the same conditions as the hydrogen storage electrode A according to the present invention, except that a product named: Boliflon Disversion D-1 was used. [Hydrogen storage electrode C] (Educational example) In the hydrogen storage tiA according to the present invention, instead of adding and kneading 20 parts by weight of polymer latex in which fine particles of polyethylene resin are dispersed, methylcellulose (Shin-Etsu), which is a water-soluble polymer, is used. Manufactured by Kagaku Co., Ltd. Product name Nimetrose 3M-
4000) was added, mixed and dispersed, heated to 70°C to dissolve the methylcellulose, and then cooled to room temperature to obtain a paste-like mixture.
In addition, a hydrogen storage electric fiC as a comparative example was fabricated using QgkPI- in the same manner as the hydrogen storage monopole A according to the present invention. Table 1 shows the average value and standard deviation of the water cord storage alloy contained in each of these electrodes. From Table 1, it can be seen that the standard deviation of the weight of the hydrogen-absorbing brother IA gold contained in the hydrogen-absorbing electrode 4ffiA according to the present invention and the hydrogen-absorbing electrode C of the comparative example is significantly smaller than that of the hydrogen-absorbing electrode iB of the comparative example. Therefore, it can be seen that the distribution of hydrogen storage alloy weight 1 contained in these electrodes A and C is more uniform than in electrode B. Next, 1 each of the above-mentioned hydrogen storage batteries iA, B and C
By using one sheet as the negative electrode and two sintered nickel hydroxide electrodes as the positive electrode, the discharge of the battery is limited by the capacity of the negative electrode.
We manufactured different types of alkaline storage batteries. We then investigated the effect of the type of binder used in the hydrogen storage electrode on the discharge performance of the negative electrode in the battery configuration. For the negative electrode, for any of the three types of electrodes mentioned above, approximately 5.
An electrode containing 2 g of hydrogen storage alloy was chosen. The positive nickel hydroxide electrode was manufactured as follows. That is, using a sintered nickel substrate with a porosity of approximately 85%, vacuum impregnation was repeated six times using the usual vacuum impregnation method to co-inject nickel hydroxide and cobalt hydroxide into the pores of this sintered substrate. Then, a sintered nickel hydroxide electrode was manufactured.

The size of this electrode is 40 false vlx 40Ix 0.
It is 85nn, and this electric [! The total amount of nickel hydroxide and cobalt hydroxide filled in one sheet is 2,
It was 4g. ! The content of cobalt hydroxide was approximately 95% in molar ratio to the total amount of nickel hydroxide and cobalt hydroxide. Next, hydrogen storage electricity! f! A flooded type test battery made in an open type using a large amount of 5.8Hκ011 electrolyte, with one electrode as a negative electrode, two nickel hydroxide electrodes as a positive electrode, and a nylon nonwoven fabric as a separator. was produced. The discharge capacity of the positive electrode used in this battery is 1. It is 39nAh. The size of the battery case is 45
A piece made of acrylic resin with a size of 45 x 3 nm was used. In this way, the hydrogen storage battery according to the present invention! Ii! A, a battery manufactured using hydrogen storage electrodes B and C of comparative example,
These batteries, referred to as batteries A, B, and C, respectively, were heated at 25°C.
In, 0. Charged for 20 hours with a current of 0858,
．． 1 with a current of 085A. Table 2 shows the discharge capacity at the third cycle when a charge/discharge test was conducted under the condition of discharging to OV. Table 2 From Table 2, the discharge capacity of battery A and battery B is
It can be seen that it is significantly larger than . From these test results, it was found that in the case of the present invention, which uses a polymer latex in which particles of an alkali-resistant polymer are dispersed, which maintain a spherical shape during kneading, when using a polymer latex in which particles of alkali-resistant polymer, which form into fibers when mixed, are dispersed. The weight distribution of the hydrogen-absorbing alloy contained in the electrode is uniform compared to the case where a water-soluble polymer is used.
Moreover, it is clear that a hydrogen storage electrode that has two characteristics of large discharge capacity can be obtained.

Experiment 2 Next, we will show the results of tests with varying amounts of metal or carbonaceous alkali-resistant conductive powders, and show that the addition of these conductive powders is an essential elliptical requirement of the present invention. Explain that. Produce a hydrogen-absorbing pole as follows. That is, as a hydrogen storage alloy, ■
12Ni instead of LaNl*. s CO2. s was used. Carbonyl nickel powder (manufactured by INCO, trade name: Type) is used as an alkali-resistant conductive powder.
255) Yota C, t Artificial graphite powder (manufactured by LONZA,
WfJ crystal name: LN50-200) f was used, and the mixing ratio of the hydrogen storage alloy powder and the conductive powder was varied over a wide range while keeping the total of the hydrogen storage alloy and the alkali-resistant conductive powder at a constant value of 110 parts by weight. changed. Then, as a polymer latex in which particles of an alkali-resistant polymer that maintain a spherical shape during kneading are dispersed, a polymer latex in which fine particles of an acrylonitrile-styrene copolymer are dispersed (manufactured by Asahi Kasei Co., Ltd., product name: Bolitron A) is used. -65) was used. Other conditions were as follows: Hydrogen storage electrode A of the present invention in Experiment 1
I made it the same as Here, electrodes using carbonyl nickel powder and artificial black bell pepper powder as conductive powders are referred to as electrode D and electrode E, respectively. The songs using these electrodes as negative electrodes were created in Experiment 1.
A test battery was manufactured with the same configuration as battery A in . A battery using electrode D is called battery D, electric fl! A battery using E is called battery E. Experiment 1 using these batteries
A charge/discharge cycle test was conducted under the same energizing conditions, and
The discharge capacity at the 1st cycle was measured. In addition, the amount of hydrogen remaining in the water cable storage alloy without being discharged at the 10th cycle was measured. The results are shown in FIG.

In Figure 1, curves (A) and (B) show the relationship between the discharge capacity of batteries D and E and the weight of the hydrogen storage alloy of the negative electrode when the mixing ratio of hydrogen storage alloy powder and conductive powder is changed, respectively. It represents the relationship between the ratio and the weight ratio of the conductive powder to the total of the hydrogen storage alloy and the conductive powder. Curves (c) and (d) are the ratio of the amount of undischarged hydrogen contained in the negative electrode water storage alloy of batteries D and E, respectively, converted into discharge capacity and the weight of the negative electrode hydrogen storage alloy. represents the relationship between the weight ratio of the conductive powder to the total of the hydrogen storage alloy and the conductive powder. From the curves (A) and (B) in Figure 1, batteries D and E
In both cases, it can be seen that if no conductive powder is added, the battery can hardly be discharged. and,
When the amount of conductive powder added is small, the ratio between the discharge capacity of the battery and the weight of the water storage alloy increases as the amount of added conductive powder increases. It can be seen that when it becomes larger than the same level as , it becomes almost constant. Considering curves (A), (B), (C), and (C) together, we can see that the hydrogen storage alloy cannot discharge when no conductive powder is added, and when the amount of conductive powder added is small, hydrogen It can be seen that the main cause of the phenomenon in which the discharge capacity of the storage alloy is small is that hydrogen, which is difficult to discharge, remains in the hydrogen storage alloy.

Therefore, in the present invention, it is clear that a high discharge capacity can be obtained by adding metal or carbonaceous alkali-resistant conductive powder such as nickel or graphite.

<Experiment 3> Finally, we will show the discharge performance of the hydrogen storage electrode when the drying temperature of the paste-like mixture is changed, and show that the present invention can make the drying temperature of the paste-like mixture lower than the melting point of the alkali-resistant polymer. Explain that this is an essential requirement. The negative electrode plate was made of the aforementioned polymer latex (manufactured by Sanyo Kasei Co., Ltd., trade name: Permarin) in which particles of polyethylene (melting point 110°C) were dispersed as an alkali-resistant polymer that maintained a spherical shape during mixing in the electrolyte [zD in Experiment 2]. PM), 100 parts by weight of hydrogen storage alloy, 40 parts by weight of carbonyl nickel powder, and the conditions were the same as for electrode D, except that the drying temperature was varied from 60°C to 160°C. We created the water cable occlusion electric test F.

Next, except for using electrode F, the conditions were set to In! A battery F, which was the same as battery A, was manufactured. Then, a charge/discharge cycle test was conducted under the same current conditions as in Actual @1, and the discharge capacity at the 10th cycle was investigated. Figure 2 shows the relationship between the discharge capacity and the drying temperature of the paste mixture in this case. From Figure 2, the drying temperature is the melting point of the polymer contained in the latex.
It can be seen that the discharge capacity does not decrease when the temperature is lower than 10°C. It has been found that when using other polymers with different melting points, it is also suitable to dry at a temperature lower than the melting point of the polymer.

Effects of the Invention As described above, the present invention enables manufacturing with simpler operations than conventional paste-type hydrogen storage electrodes, has a uniform weight distribution of the hydrogen storage alloy, and furthermore, the hydrogen storage electrode in the alloy can be easily discharged. It is possible to obtain a hydrogen storage electrode that is easy to use and has a large discharge capacity.

[Brief explanation of drawings]

Figure 1 shows the discharge capacity of an alkaline battery using a water cable storage electrode as the negative electrode, the ratio of the capacity for undischarged hydrogen to the weight of the hydrogen storage alloy, and the electrical conductivity relative to the sum of the water cable storage alloy and conductive powder. It is a diagram showing the relationship with the weight ratio of powder.
In the figure, (a) and (b) represent the actual discharged capacity, and (c) and (d) represent the undischarged hydrogen capacity. FIG. 2 is a diagram showing the relationship between the ratio of the discharge capacity of an alkaline storage battery using a hydrogen storage electrode as the negative electrode and the weight of the hydrogen storage alloy, and the drying temperature of the paste mixture.

Claims (1)

[Claims] 1. A paste-like mixture containing a hydrogen storage alloy powder, a polymer latex in which particles of an alkali-resistant polymer that maintain a spherical shape during kneading are dispersed, and a metal or carbonaceous alkali-resistant conductive powder is mixed into a conductive core. A method for producing a hydrogen storage electrode, which comprises applying the paste mixture to the latex and then drying the applied paste mixture at a temperature lower than the melting point of the alkali-resistant polymer contained in the latex.