JPS612265A - Alkaline battery - Google Patents

Abstract

PURPOSE:To provide an alkaline battery having good storage life by forming a polyvinyl pyrrolidone film on the surface of positive mix to prevent breakdown of positive mix molding or movement of positive mix particles toward a negative electrode. CONSTITUTION:A solution prepared by dissolving polyvinyl pyrrolidone in a solvent is applied on the surface, which is to be in contact with a separator 4, of a positive mix molding 2, and dried to form a film 3 of polyvinyl pyrrolidone. The film 3 of polyvinyl pyrrolidone prevents breakdown of positive mix molding 2 or movement of positive mix particles toward a negative electrode. Since the polyvinyl pyrrolidone film swells by contacting alkaline electrolyte, electrolyte exists near the positive mix, and no battery reaction is disturbed.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to alkaline batteries.

[Background technology]

The positive electrode mixture for alkaline manganese batteries, which are commonly used as alkaline dry batteries, is made by extrusion after mixing fine manganese dioxide powder, fine graphite powder, and a binder such as sodium polyacrylate or carboxymethyl cellulose. It has been used by pulverizing it into a granular mixture, which is then pressure-molded into a ring shape.

In this way, since the positive electrode mixture is a pressed compact of fine powder,
Electric +! When L is stored for a long period of time or when vibrations are applied, its fine powder components are liberated from the molded body, pass through the separator mesh, and migrate to the negative electrode side, causing a decrease in discharge capacity and eventually causing the negative and positive electrodes to separate. There was a problem of 4- causing an internal short circuit.

In order to prevent such particle collapse of the positive electrode mixture as much as possible, a viscous binder such as sodium polyacrylate or carboxymethyl cellulose is added to the positive electrode mixture.
Despite this, sufficient effects cannot be obtained, and the current situation is that low discharge capacity F and internal short circuits occur due to particle collapse as described above.

Therefore, a water-soluble binder solution such as sodium polyacrylate or carboxymethyl cellulose as described above is applied to the inner circumferential surface of the positive electrode mixture that is likely to cause particle collapse, that is, the surface of the positive electrode mixture that contacts the separator and faces the negative electrode. It has been proposed to dry the positive electrode mixture to form a film of sodium polyacrylate or carboxymethylcellulose on the surface of the positive electrode mixture to prevent particle collapse on the surface of the positive electrode mixture. The function of preventing particle disintegration due to elution is degraded, and satisfactory results are not obtained.

[Purpose of the invention]

The present invention solves the above-mentioned drawbacks of the prior art, and aims to provide an alkaline battery with excellent long-term storage stability by preventing particle collapse of the positive electrode mixture and migration of the positive electrode mixture particles to the negative electrode side. Objective i [Summary of the Invention] The present invention applies a solution of polyvinylpyrrolidone dissolved in a solvent to one surface of the positive electrode mixture in contact with the separator, dries it to form a polyvinylpyrrolidone film on the surface of the positive electrode mixture, and The polyvinylpyrrolidone coating prevents particle disintegration of the positive electrode mixture and migration of the positive electrode mixture particles to the negative electrode side, and prevents performance deterioration and internal short circuits due to particle disintegration during storage, thereby achieving the above objectives. It is something.

The polyvinylpyrrolidone used in the present invention is a water-soluble polymer and slightly dissolves in weak alkaline solutions, but it dissolves in a very small amount and swells in strong alkaline aqueous solutions such as those used as electrolytes in alkaline batteries. It also has excellent oxidation resistance, and is chemically stable against strong oxidizing substances such as manganese dioxide, which is a positive electrode active material.

As mentioned above, polyvinylpyrrolidone is a water-soluble polymer and dissolves in water, but it is also soluble in alcohols such as methyl alcohol, ethyl alcohol, and butyl alcohol, and is also soluble in alcohols such as methylene chloride, chloroform, etc. It is also soluble in halogenated hydrocarbons. Furthermore, it has the unique property of being soluble in ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatic hydrocarbons such as toluene and xylene using alcohol as a co-solvent.

Polyvinylvinylpyrrolidone also has excellent film-forming ability, and when polyvinylpyrrolidone is dissolved in the above-mentioned solvent and dried, a transparent, glossy and durable film is formed.

Utilizing the properties of polyvinylpyrrolidone as described in the present invention, a solution of polyvinylpyrrolidone dissolved in a solvent is applied to the surface of the positive electrode mixture in contact with the separator, and dried to form a film of polyvinylpyrrolidone on the surface of the positive electrode mixture. The polyvinylpyrrolidone coating prevents particle disintegration of the positive electrode mixture and migration of the positive electrode mixture particles to the negative electrode side, thereby providing an alkaline battery with excellent long-term storage stability.

Polyvinylpyrrolidone has 4 types ranging from low molecular weight to high molecular weight.
It is divided into grades and is commercially available in powder form. Specific examples of commercially available products include Zeilal Aniline &
Fillem (General Aniline)
&Fi1m Corp, ) or Badische
Aniline and Soda Company (Badische A)
PVPK-15 (average molecular weight 10,0
00), -PVPK-30 (average molecular weight 40
,000), P V P K -60 (average molecular weight 1
60.000>, PVPK-90 (average molecular weight 360,000), and the like. When these are made into a solution, the higher the molecular weight, the higher the viscosity, but the viscosity of low molecular weight ones can be increased by increasing the amount used, and there are large differences between them and high molecular weight ones in terms of other properties. There isn't.

Polyvinylvinyl pyrrolidone solution is prepared by dissolving polyvinylpyrrolidone in the above-mentioned solvent, and the concentration at this time varies depending on the molecular weight of polyvinylpyrrolidone and the type of container, but it is usually 2 to 15% by volume. be done.

The polyvinylpyrrolidone solution is applied to the surface of the positive electrode mixture in contact with the separator, that is, the inner peripheral surface of the ring-shaped positive electrode mixture in a cylindrical alkaline battery, and the upper surface of the positive electrode mixture in a button-shaped alkaline battery. As a specific application method, a polyvinylpyrrolidone solution is usually applied by spraying, or 1. A method is adopted in which the solution is injected into the hollow part of a ring-shaped positive electrode mixture housed in a positive electrode can and the excess solution is sucked out.

Drying is usually carried out at a temperature of about 40 to 80°C.

It is difficult to accurately measure the thickness of the polyvinylvinylpyrrolidone film, but if the polyvinylpyrrolidone solution is injected into the hollow part of the ring-shaped positive electrode mixture and immediately sucked out and dried to form a film, it is about 3 to 30 pm. The thickness will be
Even such a thin film can sufficiently exhibit its effect.

Since the polyvinylpyrrolidone film swells upon contact with the alkaline electrolyte, the electrolyte can be present near the positive electrode mixture without interfering with battery reactions.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 The alkaline manganese battery shown in FIG. 2 was produced as shown below.

A granular mixture consisting of 40 parts by weight of manganese dioxide, 4 parts by weight of graphite, 0.2 parts by weight of sodium polyacrylate and 1.8 parts by weight of water was pressurized and formed into a ring shape.
They were stacked and loaded into an LRG type positive electrode can 1. A core rod is inserted into the hollow part of the stacked ring-shaped positive electrode mixture, and a punch slidably attached to the outer periphery of the core rod is lowered to pressurize the positive electrode mixture from above to transfer the positive electrode mixture to the positive electrode can 1.
It was crimped on the inner surface of the

After crimping, pull up the punch, and then pull out the core rod, add 10 parts by weight of polyvinylpyrrolidone (PVPK-90 mentioned above) to 200 parts by weight of ethyl aluminum into the hollow part of the ring-shaped positive electrode mixture 2. An alcoholic solution of dissolved polyvinylpyrrolidone was injected into the positive electrode mixture 2 until it slightly exceeded one end.

Immediately after injection, the excess polyvinylpyrrolidone solution is sucked out using a vacuum pump, and the entire battery is placed in a hot air drying oven at 60°C for 5 minutes to evaporate the alcohol. A coating 3 of polyvinyl vinyl chloride was formed on the surface. Next, after bending the opening of the positive electrode can 1 and forming a groove near the opening end, vinylon
A separator 4 made of rayon mixed paper and vinylon paper is inserted, and then an electrolytic solution consisting of a 35% by weight potassium hydroxide aqueous solution in which zinc oxide is dissolved is injected into the hollow part of the separator 4 to separate the separator 4 and the positive electrode mixture. 3 was absorbed.

Next, the hollow part of the separator 4 in the positive electrode can 1 is filled with a negative electrode material 5 made of pasty zinc, and then a synthetic resin sealing body 8 equipped with a negative electrode lead rod 6 and a washer 7 is inserted into the opening of the positive electrode can 1. The opening of the positive electrode can 1 was sealed by radially tightening the portion beyond the groove of the positive electrode can 1 to bring it into close contact with the sealing body 8. Thereafter, the exterior was applied by a conventional method to produce an LR6 type alkaline manganese battery as shown in FIG. In Fig. 2, 9 is a leaf spring, 1O is a negative terminal plate, 11 is an insulating ring, 12.13 is a resin chip, -B, 1
4 is a positive terminal plate, 15 is a metal exterior can, and 16 is an insulating ring.

Comparative Example 1 An LR6 type battery was manufactured in the same manner as in Example 1 except that a polyvinylpyrrolidone film was not formed on the inner peripheral surface of the positive electrode mixture.

Comparative Example 2 Instead of the polyvinylpyrrolidone coating, a 5% aqueous sodium polyacrylate solution was applied to the inner circumferential surface of the positive electrode mixture in the same manner as in Example 1, dried, and coated on the inner circumferential surface of the positive electrode mixture. An LR6 type battery was manufactured in the same manner as in Example 1 except that a film of polyacrylic acid and thorium was formed.

Comparative Example 3 Instead of polyvinylpyrrolidone coating, polystyrene 1
A toluene y8 solution of polystyrene dissolved in 200 parts by weight of toluene is applied to the inner circumferential surface of the positive electrode mixture in the same manner as in Example 1, dried, and polystyrene is applied to the inner circumferential surface of the positive electrode mixture. L was the same as in Example 1 except that a film of
An R6 type battery was manufactured.

The battery of Example 1 and the battery cans 500 of Comparative Examples 1 to 3
After each battery was stored at 45°C for a certain period of time, a vibration test was conducted to determine the number of internally short-circuited batteries, and the results are shown in Table 1. The conditions for the vibration test are an amplitude of 1.5
inm, a vibration frequency of 50 H2, a vibration time of 60 minutes, and two vibration directions: the axial direction of the battery and the direction perpendicular to the axial direction.

In addition, the battery of Example 1 and the battery cans 10 of Comparative Examples 1 to 3
The short-circuit current was measured at 0 and after storage at 45° C. for a predetermined period of time, and the results are shown in Table 2.

Furthermore, 10Ω continuous discharge (final voltage 0.9 V)'L for the battery of Example 1 and the batteries of Comparative Examples 1 to 3.

The discharge duration was measured, and the results are shown in Table 3 as an index, with the initial discharge duration of the battery of Comparative Example 1 set as 100.

Table 1 Number of internal short circuits Table 2 Short circuit current (A) Table 3 Discharge duration As shown in Tables 1 to 3, the battery of Example 1 of the present invention did not have internal short circuits during storage. , and the discharge duration decreased little due to storage. This is considered to be due to the fact that the polyvinylpyrrolidone coating prevented particle collapse of the positive electrode mixture and migration of the positive electrode mixture particles to the negative electrode side. Furthermore, the battery of Example 1 of the present invention had a high short circuit current, and no decrease in battery reaction due to the formation of the polyvinylpyrrolidone film was observed. The battery of Comparative Example 2 in which a film of sodium polyacrylate was formed on the inner peripheral surface of the positive electrode mixture had good initial characteristics, but the performance deteriorated significantly during storage. In the battery of Comparative Example 3 in which the inner peripheral surface was formed with a diameter of 6.7 mm, the polystyrene coating hindered the battery reaction, and a decrease in short circuit current and a decrease in discharge duration due to an increase in internal resistance were observed.

[One Prefecture of Invention] As explained above, according to the present invention, migration of positive electrode mixture particles to the negative electrode side was prevented, and Nagamachi storage stability was improved.

[Brief explanation of the drawing]

1, 1 and 2 are diagrams showing an alkaline battery according to the present invention, and FIG. 1 is a cross-sectional view showing a state in which a polyvinylpyrrolidone film is formed on the inner peripheral surface of the positive electrode mixture during manufacturing, FIG. 2 is a partial sectional view showing the state after manufacture. 2... Positive electrode mixture, 3... Polyvinylpyrrolidone coating, 4... Separator No. 10 Figure 2

Claims (1)

[Claims] (1) An alkaline battery characterized in that a solution prepared by dissolving polyvinylpyrrolidone in a solvent is applied to the surface of the positive electrode mixture 2 in contact with the separator 4 and dried to form a coating 3 of polyvinylpyrrolidone.