JPS61224270A - Manufacture of cadmium negative electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To give an adequate mechanical strength and improve performance of an electrode such as active substance utilization rate, by spreading a solution of a salt of monoatonic cation of a high polymer carboxylic acid over the surface, after soaking a solution of a metallic salt of diatomic or more, in the pores of a dried body of a metallic core spread with a specified paste, and then drying up it. CONSTITUTION:An active substance such as cadmium oxide, an electric conductor, an antialkaline short fiber, and a binder such as an organic paste or synthetic resin powder are mixed and kneaded together with a dispersion medium of water or an organic solvent to make up a paste. The paste is spread over a metallic core and dried up to form a dried body which has numerous pores remained after the dispersion medium evaporates. The pores of the body is soaked with a solution of a metallic salt of diatomic or more. Then a solution of a salt of monoatomic cation of a high polymer carboxylic acid is spread over the surface. In such a way, a membrane of a gel of solution of a high polymer carboxylic acid is formed over the electrode plate, and then dried up. Now a high polymer carboxylic acid salt is concentrated only over the surface of the electrode plate, causing to make the surface contain a large amount of binder to have a high strength, while the inner part of the plate contains little binder, resulting in a high porous property without losing a good active substance utilization rate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a cadmium negative electrode plate of the PACE 1 type for use in alkaline storage batteries such as nickel-cadmium storage batteries and silver-cadmium storage batteries.

Problems to be solved by conventional technology/inventions Conventional PACE 1-type cadmium negative electrode plates used in alkaline storage batteries such as nickel-cadmium storage batteries are easier to manufacture and have lower energy density than sintered cadmium negative electrode plates. However, it has the disadvantage that mechanical strength and plate performance such as active material utilization rate conflict with each other. That is,
Conventional paste-type cadmium negative electrode plates are made into a paste by kneading an active material such as cadmium oxide, a conductive material, alkali-resistant short fibers, and an adhesive such as an organic glue or synthetic resin powder with a dispersant consisting of an organic solvent or water. This paste is applied to a metal core and dried to form a dried product, which is manufactured and is widely put into practical use. However, in the sintered cadmium square plate, the active material powder is held in the pores of the TEPCO body skeleton, which has a strong three-dimensional network structure formed by sintering the metal nickel powder. In paste-type cadmium negative electrode plates, adhesives such as organic glues and synthetic resin powders, which have lower mechanical strength than sintered metal nickel powders, bind between particles of active material powder, or the binder itself The active material powder is held by forming a skeleton of a three-dimensional network structure. Therefore, for example, when manufacturing a cylindrical sealed nickel-cadmium crystal battery, in step 1, the negative electrode plate is wound together with the positive electrode plate and the hybarator to produce an electrode plate group, which is then stored in a battery container. When an assembly process is required, strong bending and frictional forces are applied to the negative electrode plate, but with the sintered cadmium negative electrode plate, there was no problem because the mechanical strength of the electrode plate was sufficiently high. However, in paste-type cadmium negative electrode plates, when using a binding agent necessary to obtain sufficient mechanical strength similar to that of sintered-type cadmium negative electrode plates, the electrolyte necessary for charging and discharging the electrode plate is occupied. The active material utilization rate may decrease because the pores in the electrode plate are blocked by the binder, the surface of the active material is covered with the binder, or when the battery is overcharged, the positive electrode The binder is oxidized by the oxygen generated from the plate and a large number of carbonate radicals are formed, resulting in a decrease in the discharge voltage and deterioration of the electrode plate performance. This means that the high energy density, which is an advantage, cannot be sufficiently obtained. On the other hand, if the amount of binder is reduced so as not to deteriorate the electrode plate performance, the mechanical strength of the electrode plate will be reduced and the active material will fall off during the battery assembly process, resulting in poor product yield. Therefore, conventional paste-type cadmium negative electrode plates had to sacrifice either mechanical strength or electrode plate performance11). Therefore, a paste-type cadmium negative electrode plate that maintains its advantage of high energy density and has high mechanical strength so that the active material does not fall off during the battery assembly process has been desired.

The present invention aims to solve the problems of the prior art as described above.

Means to solve problems The present invention uses an active material such as oxidizing power Domiu 11, 1! Electrical materials.

Short LJ fibers and a binder are kneaded together with a dispersant made of water or an organic solvent to form a paste, and this paste is applied to a metal core and dried.
The above-mentioned problem is solved by impregnating the surface with a solution of a metal salt having a higher valence and then applying a solution of a monovalent cation of a polymeric carboxylic acid to the surface and drying it.

Effect When a paste-type cadmium negative electrode plate with a small amount of binder and low mechanical strength is used in one culm of the above-mentioned J-Una battery assembly, the active material falls off when the plate is bent strongly. It occurs when cracks form on the surface of the electrode plate, or when the surface of the electrode plate is scraped when the plate is rubbed strongly.

Therefore, in order to prevent the active material from falling off during the N pond assembly process, it is sufficient to increase the mechanical strength of the surface of the paste-type cadmium negative electrode plate. This is achieved by optimizing the distribution of the adhesive.

That is, an active material such as cadmium oxide, a conductive material, an alkali-resistant short IIM, and an adhesive such as an organic glue or a synthetic resin powder are kneaded together with a dispersant made of water or an organic solvent to form a paste. The dried material formed by coating on a metal core and drying has multiple pores that remain after the dispersant evaporates, so a solution of a divalent or higher metal salt is impregnated into these pores. .

Next, when a solution of a salt of a monovalent cation of a polymeric carboxylic acid is applied to the surface of the groove, the solution of a salt of a polymeric carboxylic acid becomes 2
The monovalent cation of the polymeric carboxylic acid salt is 21iIIIi.
The polymeric carboxylic acid is substituted by the above metal ions, and the divalent or higher valence metal ions combine with the valence and the corresponding carboxyl group, so the polymeric carboxylic acid is crosslinked by the divalent or higher valence metal ions and forms a three-dimensional network structure. is formed, and the polymeric carboxylic acid solution turns into a gel. This kind of gelation is caused by the above-mentioned 2
Occurs at the contact point of different solutions, that is, the surface of the electrode plate,
Once gelation occurs, the diffusion rate of the polymer carboxylate becomes extremely low, so that the diffusion of the polymer carboxylate into the interior of the electrode plate is reliably suppressed.

When a gel film of a solution of polymer carboxylate is formed on the surface of the electrode plate in this way and then dried, the polymer carboxylate is localized only on the surface of the electrode plate and acts as a binder for the active material. It acts as. As a result, the surface of the electrode plate has a large amount of binder and has high strength, while the inside of the electrode plate has a small amount of binder and maintains high porosity, reducing the active material utilization rate. ! A charcoal root that is often used! Since the cadmium negative electrode plate of the Pace 1 to 4-7 type is inferior in both mechanical strength and electrode plate performance by 1↓, a cadmium negative electrode plate of the 4-7 type is used.

In addition, as a metal ion in the salt of a divalent or higher metal, C, 1!1. ZnP+, △+ ++, M[+2
4-, C,,2'1 etc. can be used, but c
d'' is the active material of the cadmium negative electrode plate, Cd (Ol
-1) It is particularly suitable because it is converted to 2. In addition, both inorganic and organic anions can be used as J3 anions in salts of divalent or higher metals, but low-molecular-weight carboxylic acids such as formate ions and acetate ions have a negative impact on battery performance even if used relatively frequently. This is particularly suitable since it has little influence. The m of a solution of a salt of a metal with a valence of 2 or more is 0, O
If it is 1 mol/1 or more, it is sufficient to gel a solution of a monovalent cation salt of a polymeric carboxylic acid. In addition, as a salt of a monovalent cation of a polymeric carboxylic acid, sodium alginate, sodium salt of carboxymethylcellulose, sodium polyacrylate, etc. are suitable, and if the concentration of the solution is 0.1 weight valent or more, it is suitable for the electrode plate. This is sufficient to increase the strength.

Example Examples of the present invention will be described in detail below.

Dissolve 0.82% of polyvinyl alcohol in 45cc of ethylene glycol, and add a 1mm length of vinyl chloride-acrylonitrile copolymer to it. 0.5 g of l fiber is added and stirred to make a paste, and cadmium oxide 1009 and carbonyl nickel powder 153 are added and kneaded to form a paste. This paste was applied to a nickel-plated porous iron plate with holes of 2.5ml in diameter and a thickness of 0.5ml.
It is applied to a metal core of 0.09 mm in thickness to a thickness of 1.3III11, and dried by evaporating the ethylene glycol with hot air at about 120°C. After drying, the dried body was immersed in a cadmium acetate aqueous solution of 0.3 mol/ml to impregnate the pores of the dried body with this aqueous solution, and then the excess liquid film adhering to the surface was gently removed using the circular n side of a glass rod. It is removed by wiping, and then roll-coated with an aqueous solution of sodium salt of carboxymethyl cellulose of 1% by weight or more, and dried by evaporating the moisture with hot air at about 90°C. The electrode plate Δ according to the present invention was manufactured by press-molding it to a thickness of 0.6+am after drying. For comparison, a conventional electrode plate B was manufactured by applying the same paste as the electrode plate A to a metal core, drying it, and then press-molding it. In addition, a paste made by mixing polyvinyl alcohol to 45 cc of ethylene glycol in the paste for electrode plate A was applied to the metal core, dried, and then press-molded. Manufactured.

The paste-type cadmium negative electrode plate manufactured in this way was cut into pieces of 270Il1m in height and 36+1111cm in width, and wound together with a sintered nickel hydroxide positive electrode plate and a separator made of polyamide nonwoven fabric to form a cylindrical sealed nickel-cadmium plate. The table below shows a comparison of the results of measuring the amount of active material falling off the negative electrode plate when the storage battery was manufactured.

As is clear from the above table, the electrode plate A according to the present invention has a significantly lower amount of active material falling off than the electrode plate B manufactured by the conventional method in which the binder is less released, and the electrode plate manufactured by the conventional method in which the amount of binder is large. Board C
It can be seen that the horizontal plate strength is almost the same.

In addition, the above paste type cadmium negative electrode plate was used as 40III.
IIX 40111 and used it as a test electrode, and two sintered nickel hydroxide positive electrode plates of the same size as the test electrode were used as counter electrodes. A test battery was constructed using the electrode as a reference electrode, and the theoretical capacity of the test electrode was 0.47Ah, and when charging and discharging were repeated at a 5-hour rate, the mercury oxide electrode standard reached O■. The figure shows the active material utilization rate during discharge.

As can be seen from the figure, the electrode plate A according to the present invention has a higher active material utilization rate than the electrode plate C manufactured by the conventional method in which a large amount of binder is released, and has almost the same activity as the electrode plate B manufactured by the conventional method in which the amount of binder is small. It can be seen that the material utilization rate is high.

EFFECTS OF THE INVENTION As described above, the present invention provides 1q of paste-type cadmium negative electrode plates for alkaline storage batteries that have sufficient mechanical strength and good plate performance such as active material utilization. 1

[Brief explanation of drawings]

The figure is a characteristic diagram showing a comparison of active material utilization rates during discharge of paste-type cadmium negative electrode plates obtained by the manufacturing method of the present invention and the conventional manufacturing method. Cycle Atsushi (times)

Claims (1)

[Claims] A dried product made by kneading an active material such as cadmium oxide, a conductive material, short fibers, and a binder with a dispersant consisting of an organic solvent or water to form a paste, and applying this paste to a metal core and drying it. A cadmium negative electrode plate for an alkaline storage battery, characterized in that the pores of the plate are impregnated with a solution of a salt of a divalent metal or higher, and then a solution of a salt of a monovalent cation of a polymeric carboxylic acid is applied to the surface and dried. manufacturing method.