JPS6055A - Manufacture of silver oxide battery - Google Patents

Abstract

PURPOSE:To stabilize internal resistance by reducing the surface of granulated silver oxide powder by spraying reducing solution in hot fluidized air, and forming a positive mix of silver oxide battery with a mixture of the reduced silver oxide and graphite. CONSTITUTION:Granulated silver oxide powder is fluidized in hot fluidized air, and the surface of the powder is reduced by 2-7wt% of the total silver oxide by spraying reducing solution. 1-3wt% graphite is mixed with this silver oxide powder and the mixture is molded in a pellet to form a positive mix 1. The pellet is pressed in a positive case 3, and combined with a negative electrode 6 mainly comprising amalgamated zinc powder, a separator 4, and an absorbing material 4 to form a silver oxide battery. By uniformly convering the surface of granulated silver oxide with metallic silver and mixing with graphite, breakage of silver network is prevented and closed circuit voltage is improved.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a method for producing a silver oxide battery, particularly a method for producing a positive electrode active material, in which a reduced narrow side of granular oxide particles is mixed with graphite. By using the obtained material as a positive electrode active material, the internal resistance of the battery is stabilized, and the closed circuit voltage characteristics are also stable (-), thereby providing a silver oxide battery with excellent properties.

Conventional configurations and their problems Conventionally, the following proposals have been made for the purpose of stabilizing the internal resistance of silver oxide batteries. That is,
Silver oxide powder is reduced to form a metallic silver layer on the particle surface (-
By forming the battery into a positive electrode active material using six-pressure molding, the internal resistance of the battery can be stabilized using the network of the metallic silver layer. 1~gashi,
This proposal still has the following shortcomings. The drawback is that after reducing the silver oxide powder to form a metallic silver layer on the surface of the particles, the metallic silver layer formed on the surface of the particles is destroyed when the particles are press-molded into pellets. be.

In addition, when pressure molding into pellets, silver oxide and metallic silver formed on the particle surface adhere to the mold, and when the pellet is taken out from the mold, slippage occurs between the pellet and the mold. However, there were problems such as cracking and chipping of the pellets.

Furthermore, when the pellets are filled into the positive electrode case and subjected to secondary pressurization, the metallic silver layer formed on the surface of the silver oxide powder particles is violently destroyed, so that the metallic silver layer does not cause enough distortion. This resulted in variations in the circular resistance of the battery and variations in the closed circuit voltage characteristics. Further, the method for reducing the silver oxide powder here was a method in which the silver oxide powder was immersed in a reducing solution to reduce the surface of the silver oxide particles to form a metal layer. However, with such a reduction method, it is difficult to uniformly reduce the surface of silver oxide particles.
Furthermore, the shape of the particles and the metallic silver layer on the surface of the particles may be destroyed due to the stirring method used to immerse the silver oxide in the reducing solution.

Purpose of the Invention The present invention solves the conventional problems described above by modifying the reduction method of the positive electrode active material and further mixing graphite, thereby stabilizing the internal resistance and closed circuit voltage characteristics of the silver oxide battery. The purpose is to simplify the manufacturing process of positive electrodes and improve productivity.

Structure of the Invention In order to achieve the above object, the present invention aims to reduce the particle surface by reducing the particle surface by reducing the particle surface by spraying a reducing solution onto the silver oxide in the fluidized state in a fluidized state in heated fluidized air. This is characterized in that it is mixed with graphite and used as a positive electrode mixture (-).

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail. FIG. 1 is a half-sectional view of a silver oxide battery in an example of the present invention.

1 is a positive electrode mixture according to the present invention, which is made by pressure molding a mixture of granular silver oxide particles whose surfaces have been reduced with a reducing solution and graphite. Reference numeral 2 denotes a positive electrode ring having an angular cross-section, which serves to protect the shoulder of the positive electrode mixture and to absorb sealing pressure. 3 is a positive electrode case that also serves as a positive electrode terminal, 4 is a separator made of a microporous film made of polyethylene and cellophane, 6 is an electrolyte-impregnated material made of nylon nonwoven fabric or cellulose or conoton, etc., and 6 is a negative electrode made of zinc hydrate. It consists of powder, a thickening agent such as carboxymethyl cellulose, and an alkaline electrolyte. 7 is a sealing plate which also serves as a negative electrode terminal, and 8 is a sealing robber king, which is generally made of nylon 66°11 or the like. In a battery having such a configuration, when the positive electrode mixture 1 reduces the surface of the granular silver oxide particles using a reducing solution,
Silver oxide particles are made into a fluidized state in heated fluidized air, the surface is reduced by spraying a reducing solution onto the fluidized silver oxide particles, and at the same time, a metallic silver layer is formed on the surface of the granular silver oxide particles. Using. The amount of silver oxide reduced is 2 to 7 percent by weight of the total amount of silver oxide, and a reducing solution corresponding to a reduction of 2 to 7 percent by weight is sprayed. A mixture of a positive electrode active material whose surface is made of metallic silver and graphite is molded into pellets and used. Hereinafter, a method for producing a positive electrode active material, which is a feature of the present invention, will be explained in detail. Granular silver oxide is placed in a fluidized tank 11 shown in FIG. 2, and dry air is blown upward from the blowing port 12 at the bottom of the tank to stir the granular silver oxide. Separately from this, a reducing solution such as hydrazine is weighed in advance so that the amount of silver oxide reduced is 2 to 7% by weight, and diluted with a solvent such as methyl alcohol. A reducing solution 13 such as L-hydrazine diluted with a solvent such as methyl alcohol is sprayed into the fluidized tank through a nozzle 14. The sprayed reducing solution comes into contact with the surface of the granular silver oxide which is being stirred by dry air in the fluidized tank, reducing the surface layer and reducing the surface of the granular silver oxide. Silverizes metal. Because dry air is blown up in the fluidized tank,
Drying is performed simultaneously with the reduction reaction, and a positive electrode active material whose surface layer is uniformly covered with metallic silver can be obtained in a short time.

Note that 16 is an exhaust port.

The mixture of the positive electrode active material and graphite obtained by this method is press-molded into a pellet shape, then filled into a positive electrode case and subjected to secondary pressurization. A positive electrode using a mixture of the positive electrode active material obtained by the above manufacturing method and graphite is press-molded into a pellet shape,
When secondary pressure is applied in the positive electrode case, the network of metallic silver layer formed at the interface of granular silver oxide is destroyed;
If graphite is mixed in an amount of at least 1% by weight based on the total weight of silver oxide, it is possible to cover the destroyed portions of the network of the metallic silver layer and obtain sufficient conductivity.

In addition, due to the slipperiness of graphite, when press-molded into pellets,
Silver oxide and metallic silver formed on the particle surface do not adhere to the mold, and when the pellet is taken out of the mold, there is good slippage between the pellet and the mold.
Problems such as cracking and chipping of conventional pellets can also be solved.

If the amount of graphite added exceeds 3% by weight of the total amount of silver oxide, the bulk of the positive electrode mixture increases, making it impossible to obtain a high-density positive electrode, which is disadvantageous. Furthermore, various studies were conducted regarding the amount of reduction of granular silver oxide, and in order to obtain excellent internal resistance and closed circuit voltage characteristics as a battery,
It is necessary to reduce at least 2% by weight of the total weight of silver oxide; conversely, if the amount of reduction exceeds 7% by weight, the effective amount of silver oxide added as an active material will be reduced, which is disadvantageous.

Hereinafter, specific examples according to the present invention will be explained. The configuration conditions of the positive electrode according to the manufacturing method of the present invention used here are as follows.

1. Reduction amount: 6% by weight of the total amount of silver oxide.

2 Added amount of graphite: 2% by weight of the total amount of silver oxide.

In a battery using the positive electrode manufactured under the above configuration conditions, the amount of A1 reduction and the amount of graphite added were each 51iffi of the total amount of silver oxide.
B1: A battery using 6% and 4% by weight as the positive electrode; 01: A battery using 1% and 2% by weight as the positive electrode. B1 A battery using the same 8 weight percent and 2 weight percent as the positive electrode.E1 A battery using conventional silver oxide powder immersed in a reducing solution to reduce the surface of the silver oxide particles and form a metallic silver layer as the positive electrode. The battery used was F. The amount of silver oxide reduced in Battery F was 5% by weight of the total amount of silver oxide. Batteries A, B, and C manufactured under the above conditions
The number of pellet cracks, initial closing voltage, and discharge capacity of ,D,F,,F are shown in the following table. The battery size used in the comparative test here was a silver oxide battery R8721SW with a diameter of 7.9 mm and a height of 2.1 mm.

The measurement conditions for each item shown in the previous table are as follows.

Pellet cracking: Number of pellets cracked during production of n=60.

Closed circuit voltage: After being left in each temperature condition for 16 hours, the lowest voltage was measured at 2Ω for 5 seconds, and the average value of n-6.

Discharge capacity: Calculated from the discharge time to the final voltage of 1.4μ with a constant resistance discharge of 30Ω at 20°C.
Average value of n=5.

From the above results, batteries B, D, and F had the problem of pellet cracking, and batteries C and E had a small capacity.

In addition to the effects of the invention, the battery obtained by the manufacturing method of the invention has no pellet cracking, has a large discharge capacity, and has a sufficient closed circuit voltage.

[Brief explanation of the drawing]

11...Fluidization tank, 12...Heating (~tai no inlet), 13...Reducing solution, 14...
··spray nozzle.

Claims (3)

[Claims] (1) Granular silver oxide is brought into a fluidized state in heated fluidized air, and a reducing solution is sprayed onto the silver oxide to reduce the particle surface. A mixture of this and graphite is used as a positive electrode mixture. A method for manufacturing a silver oxide battery, characterized in that it is used. (2) The method for producing a silver oxide battery according to claim 1, wherein the metallic silver obtained by reduction is 2 to 7 weight percent of the total amount of silver oxide. (3) The method for producing a silver oxide battery according to claim 1, wherein the amount of graphite added is 1 to 3 weight percent.