JPS5925169A - Manufacture of negative pole for alkaline primary battery - Google Patents

Abstract

PURPOSE:To improve storage reliability of alkaline primary battery through uniform mixture of gelation agent powder and hardening zinc powder and formation of stable gelated negative pole without separation of electrolyte by using an alakali metal chloride of polyaclyric acid of specific grain size as the gelation agent. CONSTITUTION:A uniformly mixed negative pole black mix can be obtained by sufficiently mixing the powder, which has been obtained after it has been smashed or by adjusting the polymerization condition so that the grain size of polyaclyric potassium in the neutral degree of 90% or more is ranged from 100- 300, with the hardening zinc powder as the geletion agent. The stable gelerated negative pole can be obtained by injecting potassium hydroxide electrolyte to such black mix. Accordingly, an alkaline primary battery having outstanding storage reliability, namely, assuring excellency in open voltage, discharging capacity and liquid lead resistivity can be obtained even after the use of a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a negative electrode for an alkaline secondary battery in which the negative electrode active material is zinc hydrate powder and the electrolyte is an aqueous alkali hydroxide solution. be.

Structures of conventional examples and their problems Alkaline secondary batteries that use zinc hydrate powder as the negative electrode active material include alkaline manganese batteries that use manganese dioxide as the positive electrode, daffodil batteries that use mercuric oxide as the positive electrode, There are silver oxide batteries that use divalent silver oxide. These alkaline rechargeable batteries are manufactured as power sources for consumer devices such as cameras, calculators, electronic watches, and hearing aids, but with the rapid diversification and increase in production of these consumer devices in recent years, the need for these batteries has significantly increased. is increasing and various sizes are being produced. These batteries usually last for 14-14 hours after being loaded into the equipment and used as the power source.

In addition to the above, since the battery may be used for a long period of time, such as nearly two years, it must have excellent storage reliability, that is, the static and dynamic characteristics such as the battery's inherent electric power L+-, discharge capacity, etc. can be maintained for a long time. It is important that the solution is stable even after storage and that the electrolyte solution does not become a secondary solution during use or storage. In particular, it must be completely excellent in liquid resistance. In other words, if the electrolyte leaks during use, it will corrode and damage the equipment as it is a highly concentrated alkaline water bath solution.
This is because, in the worst case, the entire device may become unusable.

For this reason, various measures have been considered in the past in order to stabilize the leakage resistance. For example, in these batteries, the opening of the case containing all the power generating elements such as positive and negative electrode active materials is
Seallogasukesoto 9th seal board.

These are sealed with a so-called molded sealing plate that integrates these, and the opening end of the case is curled inward to seal it. Selection of individual materials for directly involved components 1. Methods for improving dimensional accuracy and 7)
A method for optimizing the dimensional balance between the constituent materials, and a low molecular weight polyamide resin for part or all of the gas sealing material.

asphalt pitch, chlorosulfonated polyethylene,
These methods include a method of dissolving polybutene or the like in an organic solvent to form a viscous solution and applying it to the sealing portion, and a method of setting appropriate curling conditions for the case.

Measures to improve the structural conditions directly related to the sealing of these batteries are effective in stabilizing/degrading leakage resistance, but in addition, the positive and negative electrode active materials, which are the power generation elements of these batteries, If the method of filling the electrolyte, separator, and liquid-containing material, especially the conditions for filling the negative electrode into the sealing plate consisting of the negative electrode active material Yonghwa lead and the negative electrode electrolyte, are not suitable, the direct sealing conditions may not be suitable. However, the leakage resistance is stable and good.

Traditionally, the negative electrode of this type of battery has been made by mixing zinc hydrate powder with gelling agent powder that completely gels an alkaline electrolyte, and placing a certain amount of the mixed negative electrode into a sealing plate filled with the negative electrode. An alkaline electrolyte was injected to serve as a negative electrode. As the gelling agent, single substances or mixtures of sodium alginate, starch or starch derivatives such as acrylonidonyl grafted starch, or sodium salt of carboxymethyl cellulose have been used. However, since all of these gelling agents are natural polymers or derivatives thereof,
The alkaline electrolyte gels, but during long-term storage, the alkaline electrolyte decomposes and causes a decrease in viscosity, causing electrolytic g
Because it is difficult to maintain a gel-like state, the battery characteristics after long-term storage, especially the open circuit voltage and discharge capacity, deteriorated.

For this reason, attempts have been made to use powders of synthetic water-soluble polymers such as potassium polyacrylate or sodium polyacrylate as gelling agents that are stable in alkaline electrolytes. Alkali metal salts of polyacrylic acid are usually prepared by neutralizing acrylic acid with an alkali hydroxide such as sodium hydroxide.
The alkali metal salt of polyacrylic acid produced by either an aqueous solution polymerization method in which this neutralized salt is polymerized in an aqueous solution or a precipitation polymerization method in which it is dispersed and polymerized in an organic solvent such as methyl alcohol, is In the aqueous solution polymerization method, it is in the form of a lump, and in the precipitation polymerization method, it is in the form of a fine powder. Therefore, the above-mentioned negative electrode manufacturing method is used, that is, the permanent lead powder and the gelling agent are completely mixed, and then the alkali 114. In the method of injecting a solution and making it into a negative electrode, is it better than the 80-200% zinc hydrate powder normally used in alkaline rechargeable batteries? i-
It was difficult to mix polyacrylic acid uniformly. In other words, previous 1. [2] Using a gelling agent such as potassium polyacrylate, that is, alkaline 71J,
For the purpose of completely gelatinizing the solution, the amount of zinc hydrate is usually 3~
The alkali metal salt of polyacrylic acid produced by the aqueous solution polymerization method is in the form of lumps, so mixing itself is difficult, and the precipitation polymerization method is difficult. The alkali metal salt of polyacrylic acid obtained can be uniformly mixed with the glazing zinc powder up to less than 3%, but beyond that, some of the alkali metal salt of polyacrylic acid may be mixed into the glazing zinc powder. It was completely separated from the powder and could not be mixed. U7 The negative electrode mixed with an alkali metal salt of polyacrylic acid at a mixing ratio of less than 3% with respect to the zinc hydrate powder is sealed [
(Even if the electrolyte was injected into the cell after filling, the electrolyte of 1st grade, which did not gel, remained, which was inconvenient in the battery manufacturing process.

Purpose of the Invention The present invention solves the above-mentioned disadvantages (a). Therefore, by completely improving the gelling agent, the mixing of the gelling agent powder and the zinc hydride powder is made uniform, and free The objective is to create a stable gel-like negative electrode without electrolyte and to improve the storage reliability of alkaline rechargeable batteries.

Structure of the invention The present invention has a neutralization degree of 90% or more and a particle size of 100 to 30%.
A gel-like negative electrode is obtained by injecting an electrolytic solution consisting of an aqueous potassium hydroxide solution into a negative electrode mixture of a powder of polyacrylic i'tJ7lium having a particle size of 0 and a frozen zinc powder. .

As a result of various studies on the particle size of alkali metal salt powder of polyacrylic acid used as a gelling agent, the present inventors found that
When mixed with ~200 Menoshiko's frozen fIF lead powder,
It has been found that when the particle size of the gelling agent powder is within the range of ioo to 300 meters/-, it can be uniformly mixed with the zinc hydride powder by shaking at about 10% by weight.

On the other hand, in a comparison of alkali metal salts of polyacrylic acid, potassium hydroxide is used as a neutralizing agent in the above-mentioned production method, and potassium polyacrylate has a degree of neutralization of 90% or more. When used as a gelling agent in alkaline rechargeable batteries that use potassium hydroxide as an electrolyte, other alkali metal salts of polyacrylic acid, such as sodium polyacrylate and lithium polyacrylate, can be used as a gelling agent. It has been found that the open circuit voltage of the battery is higher and the battery is stable even after storage than when using potassium polyacrylate with a degree of neutralization of less than 90 percent.

In this way, the powder obtained by adjusting the pulverization or polymerization conditions so that the particle size of potassium polyacrylate having a degree of neutralization of 90% or more falls within the range of 100 to 300 is mixed with the frozen zinc powder as a gelling agent. As a result, a negative electrode mixture in which the two are sufficiently evenly mixed is obtained, and by injecting potassium hydroxide electrolyte into this, a stable gel-like negative electrode is obtained.
It is possible to obtain an alkaline cell with excellent storage reliability, that is, excellent open circuit voltage, discharge capacity, and leakage resistance even during long-term storage.

Even if the lumpy potassium polyacrylate obtained by the aqueous solution polymerization method is mechanically crushed and sieved, if the polymerization conditions are adjusted, the fine powder becomes secondary particles, so-called granule-like powder. By sieving, particles of a predetermined size can be obtained.

The potassium polyacrylate powder of 100 to 300 mesosi obtained in this way has a molecular weight of 80 to
It can be mixed uniformly within a weight ratio of 3 to 10% with respect to 200 horns of frozen zinc powder. It can be filled in a uniformly mixed state on the size sealing plate.

However, if the particle size of potassium polyacrylate powder is less than 10 mesonko, large particles of potassium polyacrylate will separate when mixed with zinc hydride powder. teeth,
Fine powder of potassium polyacrylate separates when filling the sealing plate.

In a battery using the mixed negative electrode of potassium polyacrylate powder and zinc chloride powder obtained in this way, even after long-term storage, the kelizing agent, that is, potassium polyacrylate, is not affected by the alkaline electrolyte and does not decompose. It is possible to maintain a gel-like state without causing any oxidation, making it a stable negative electrode, and it is possible to make the open circuit voltage of the battery high and stable at the initial stage and after storage, thereby achieving excellent storage reliability. It is possible to have one.

Description of examples The present invention will be explained in detail below.

The drawing shows a button-type alkaline manganese battery.

1 is a metal sealing plate that also serves as a negative electrode terminal, and is made of a crat plate made of copper, stainless steel, and nickel plywood, and has copper on the inside. 2 is a sealing gasket for completely insulating the positive and negative electrodes and sealing the opening, and is made of polyamide resin or the like. Reference numeral 3 is a cylindrical metal case with a bottom, which is made of iron coated with Ninokerumenogi on its entire surface, and at its inner bottom, a mixture 4 of mixed powder of manganese dioxide and graphite previously formed into a tablet shape is added together with a positive electrode ring 6. It is crimped. 6 is a separator film made of a porous synthetic resin film, such as a porous polyglopylene film or a cellophane film.

7 is an electrolyte-impregnated material composed of a woven fabric or a non-woven fabric such as Konoton, viscose rayon, fluoropylene resin, or polyamide resin.

8 is a negative electrode, which is made of a mixture of zinc hydrate powder and potassium acrylate powder, which is impregnated with an electrolytic solution. To explain in more detail, zinc hydrate powder with a particle size of 80 to 200 mm is uniformly mixed in a powder mill of potassium polyacrylate obtained by an aqueous solution method or precipitation polymerization method and adjusted to a particle size of 100 to 300 mm. A certain amount of the electrolyte was filled into a sealing plate, and the entire potassium hydroxide electrolyte was poured into this to form a negative electrode.

The present invention uses potassium polyacrylate with a degree of neutralization of 90% or more with adjusted particle size, instead of the powder of a natural water-soluble polymer used as the gelling agent for the negative electrode. All the powder is used, and it does not separate from the frozen zinc powder.
Potassium polyacrylate having a mixed i11 ratio of hydration side chains to hydration side chains, which is necessary for gelation of an alkaline electrolyte, can be uniformly mixed, and the injected alkaline electrolyte quickly gels. However, if the ratio of sodium polyacrylate to the weight of zinc hydride is in the range of 3 to 10%, alkaline electrolytic Klf: In order to quickly gel the electrolyte after injection, it is necessary to polymerize potassium polyacrylate. degree is 8
000 or more is appropriate.

A battery of JIS product number LR44 was constructed as described above. Here, the electrolyte has a potassium hydroxide concentration of 40% by weight.
, a zinc oxide concentration of 6% by weight was used, and as a gelling agent, potassium polyacrylate with a degree of neutralization of 95% by an aqueous solution polymerization method and an average degree of polymerization of 20,000 to 30,000 was used.

This battery is called iA, and the gelling agent is sodium alginate, sodium salt of carboquine methylcellulose, and the degree of neutralization is 95.
%, and all batteries using sodium polyacrylate with an average degree of polymerization of 20,000 to 30,000 are designated as BC and D, respectively. In addition, the mixing ratio of frozen zinc and gelling agent was 96:4 by weight.

Table 1 compares the open circuit voltages of these batteries initially, after storage for 6 months and 1 year at room temperature, and after storage for 1 month at 60"C - and when loaded with a 16Ω resistor at 20°C. Table 2 shows a comparison of the discharge duration until reaching 1.OV when discharged as follows.The open circuit voltage is 60,
The discharge test was expressed as the average value of 5 samples.

Further, Table 3 shows a comparison of the number of leaking batteries in 60 samples when left in an environment with a temperature of 45° C. and a relative humidity of 90%.

As is clear from Table 1, Table 2, Table 3, and Tables 1 to 3, the gelling agent using potassium polyacrylate replaces the conventionally used sodium salt of sodium alginate or carboxymethylcellulose. It can be seen that the open circuit voltage and discharge time after storage are stable compared to those made of sodium polyacrylate, and the open circuit voltage is higher than that of sodium polyacrylate, and the leakage resistance is particularly stable.

In addition, although the example was explained using an alkaline manganese battery,
Other alkaline batteries such as silver oxide batteries and mercury batteries have similar effects.

Even potassium polyacrylate produced by precipitation polymerization has the same effect.

Effects of the Invention According to the present invention, an alkaline secondary battery with excellent storage reliability can be obtained.

[Brief explanation of the drawing]

The drawing is a cross-sectional side view of a main part of a button-type alkaline manganese battery according to an embodiment of the present invention. 4...Positive electrode, 6...Separator, Y...
...Liquid-containing material, 8...Negative electrode.

Claims (1)

[Claims] Neutralization degree 90 with particle size in the range of 100 to 300 grains
A negative electrode for an alkaline secondary battery, which is made by injecting a potassium hydroxide electrolyte into a negative electrode mixture prepared by mixing potassium polyacrylate powder of % or more and lead oxide powder to form a gel-like negative electrode. manufacturing method.