JPH02195646A - Separator for alkaline cell - Google Patents

Abstract

PURPOSE:To prevent a discharge abnormality and the deterioration of the high load discharge capacity by superposing and winding a cellophane and a nonwoven fabric, making them into a cylindrical form, and forming dots or perforation cuttings to penetrate from the front side to the rear side of the whole surface of the cellophane. CONSTITUTION:A gel-form zinc negative electrode 5 and a positive electrode composite 6 mainly of manganese dioxide are filled concentrically surrounding the periphery of a collector rod 4, and a generator element is composed under the condition to partition both electrodes by a cylindrical separator 7. The separator 7 is composed by labelling a cellophane 8 and a nonwoven fabric 9 through a paste material, superposing them two or three folds to form in a cylindrical form, and labelling a lid 7a at the bottom. On the whole surface of the cellophane 8, cuttings to penetrate from the front side to the rear side of the cellophane 8 are formed beforehand. As a result, a penetrating phenomenon to the separator 7 can be perfectly prevented by the presence of the membrane of the cellophane 8 even though crystals are generated by an abnormal condition. By forming the cuttings to the cellophane 8, the electrolyte filled inside the separator 7 is absorbed to the inside of the positive electrode composite rapidly through the cuttings, and the increase of the inner resistance and the influence to the high load discharge capacity are restricted.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a low mercury alkaline battery using a zinc alloy powder containing lead, aluminum, indium, etc. as a negative electrode active material, and particularly relates to a low mercury alkaline battery using a zinc alloy powder containing lead, aluminum, indium, etc. The present invention relates to an improvement in a separator that separates a mixture from a mixture.

(Prior Art) Since mercury, which causes zinc to freeze, is a type of pollutant, various zinc alloys are currently being developed to reduce the mercury content.

Among them, zinc alloys containing lead, aluminum, indium, etc. are attracting attention because they can suppress gas generation and are effective materials for reducing freezing, with a degree of freezing of 1.5
% or less is used as negative electrode zinc.

However, in the case of a low mercury alkaline battery using the zinc alloy as a negative electrode active material, there is a problem in that the discharge performance rapidly deteriorates at a certain load resistance.

This phenomenon occurs specifically during light load discharge, but after disassembling and examining the inside of these batteries with degraded discharge performance, it was found that internal short circuits were caused by discharge products. .

The causes are thought to be lead, aluminum,
When a low-fragility zinc alloy containing indium etc. is discharged with a specific current, a unique conductive lead oxide or lead hydroxide crystal grows, which penetrates the separator, resulting in a short circuit phenomenon. It is thought that it may cause

Therefore, as a countermeasure, changing the composition of the zinc alloy,
There are two methods to solve the problem, such as adding additives that have the effect of suppressing the growth of peculiar crystals, and a physical method, which suppresses crystal growth and prevents internal short circuits by making the fibers that make up the separator denser. There is a way to seal it.

This invention attempts to prevent the internal short circuit phenomenon by devising the latter separator.

However, in order to increase the fiber density of nonwoven fabrics, it was necessary to solve the following problems.

(Problem to be solved by the invention) It is possible to stably produce a nonwoven fabric with a fiber density as high as necessary while maintaining various properties such as electrolyte retention rate and liquid absorption rate required by alkaline battery separators. There are many technical and economical difficulties in manufacturing it, and it has not yet been fully put into practical use.

Therefore, in order to obtain the same effect as increasing the fiber density of a nonwoven fabric, it is necessary to increase the thickness of the nonwoven fabric or increase the number of times it is wrapped, which results in an increase in the thickness of the separator. Put it away.

Furthermore, as the thickness of the separator increases, the amount of negative electrode active material and positive electrode mixture to be filled decreases, resulting in a significant reduction in general performance such as discharge performance and storability.

In addition, cellophane has been considered as a separator material instead of the nonwoven fabric, but cellophane alone has a slow electrolyte absorption rate, and the electrolyte filled inside the separator is quickly absorbed into the positive electrode mixture. As a result, the current value immediately after battery assembly becomes unstable, and cellophane itself has a high ion permeation resistance, which increases internal resistance and reduces high-load continuous discharge characteristics, which limits its use. Ta.

Furthermore, it has been proposed to use cellophane wrapped around the non-woven fabric, but when injecting electrolyte with both layers wrapped, the cellophane gets wrinkled and the injection cylinder is At present, it has not been put into practical use because it is difficult to insert and problems arise due to differences in liquid retention rate and liquid absorption rate between the two.

The object of the present invention is to solve the problems encountered when constructing a separator by wrapping nonwoven fabric and cellophane, and to provide a separator for alkaline batteries that does not have crystal penetration and has low ion penetration resistance.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides
In an alkaline battery in which the following zinc alloy powder is used as a negative electrode active material, and the negative electrode active material and the positive electrode mixture are separated through a cylindrical separator, the separator is formed by wrapping cellophane and nonwoven fabric in a cylindrical shape. The gist is that the entire surface of the cellophane has dots or perforation-like cuts that pass through the front and back sides of the cellophane.

The LR6 type alkaline battery according to the present invention has a first
The general structure is shown in the figure.

This alkaline battery is manufactured by caulking the inner periphery of the upper opening of a bottomed cylindrical battery case 1 to the peripheral flange of a negative electrode terminal plate 2 via a sealing gasket 3 by drawing or curling, thereby sealing the inside of the battery. are doing.

Inside the battery is a current collector rod 4 whose upper end passes through the center of the sealing gasket 3 and is electrically connected to the negative terminal plate 2;
A gelled zinc negative electrode 5 is arranged around the outer periphery of the current collector rod 4.
, and a positive electrode mixture 6 mainly composed of manganese dioxide are filled concentrically and separated by a cylindrical separator 7 to constitute a power generation element.

The gelled zinc negative electrode 5 is made by mixing and dispersing a negative electrode active material containing zinc alloy powder in a gelled alkaline electrolyte,
More specifically, it is made by adding a trace amount of lead-aluminum-indium to zinc, and its degree of freezing is 1.5%.

The gel electrolyte has a composition consisting of a potassium hydroxide solution and a gelling agent such as CMC, and the frozen zinc alloy powder is mixed and dispersed in this gel electrolyte.

As shown in FIG. 2, the separator 7 is made by pasting together cellophane 8 and a nonwoven fabric 9 through a paste, and
It is formed into a cylindrical shape by being rolled up in layers, and a lid 7a is attached to the bottom.

Note that the two may be simply overlapped to form a cylindrical shape.

The layered structure may be a two-layered structure of cellophane 8 and a nonwoven fabric 9 as shown in the figure, or a three-layered structure in which both sides of cellophane 8 are sandwiched with nonwoven fabric 9 as shown in FIG.

The nonwoven fabric 9 is made of vinylon and a binder,
Alternatively, vinylon and cellulose fibers with a binder added are used.

Cellophane 8 is obtained by coagulating the viscose liquid in a coagulation tank, then regenerating cellulose in a cellulose regeneration bath, desulfurizing it, washing it with water, and drying it.

This thickness is determined by the concentration and flow rate of the viscose liquid, but if the thickness exceeds 30 μm, it will lead to an increase in internal resistance, and if the thickness is less than 15 μm, stable production is difficult due to the manufacturing technology. It is desirable that the range is 15 to 30 μm.

Cuts passing through the front and back of the cellophane 8 are previously formed on the entire surface of the obtained cellophane 8.

The cut is formed by passing the original cellophane 8 between rolls provided with a plurality of blades at a predetermined length and interval, thereby forming cuts of a predetermined length and interval. Note that the cut may be a point instead of a perforation.

If the length of the cuts is too long, the cuts will open or overlap in the wound state, making it impossible to achieve the intended objectives of preventing crystal growth, improving the electrolyte absorption rate, and reducing ion permeation resistance.

Furthermore, if the formation density is low, the rate of absorption of the electrolyte into the mixture will be low.

Therefore, the length should be 10 degrees or less, and if the cut is a point, it is desirable that there be 3 or more points in 1c-.

The nonwoven fabric 9 is made by mixing vinylon and pulp with a polyvinyl alcohol binder and has a thickness of 80 to 200 μm.
A normal non-woven fabric of m may be used.

As the glue used for bonding, for example, a polyvinyl alcohol aqueous solution, CMC, and a polysodium acrylate aqueous solution are used.

(Function) Even if crystals are formed due to a peculiar phenomenon, penetration into the separator can be completely prevented by the interposition of the cellophane film.

By forming cuts in the cellophane, the electrolytic solution filled inside the separator is quickly absorbed into the positive electrode mixture through each cut, thereby minimizing the increase in internal resistance and the effect on high-load discharge characteristics.

Due to the cut, there is no wrinkles caused by the shrinkage of the cellophane itself during injection.

(Effects of the Invention) As described above, according to the alkaline battery using the alkaline battery separator according to the present invention, it is possible to prevent discharge abnormalities under special discharge conditions when using low flux zinc alloy powder, and at the same time , it is possible to prevent deterioration of high load discharge performance.

Further, there is no problem during injection into the cylinder due to wrinkles, which was a manufacturing defect when cellophane is used, and injection workability is improved.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings. However, this invention is not limited only to the following examples.

Example 1 below. Example 2. LR6 type batteries having the configurations of Comparative Examples 1 to 3 were manufactured respectively, and their performance was comparatively measured. As a result, the results shown in Tables 1 to 4 below were obtained.

Example 1 A piece of cellophane with a thickness of 20 μm was perforated with alternating lengths, pitches, and intervals in the width direction. A nonwoven fabric was pasted on both sides, and this three-layer structure was rolled in a single layer to form a cylindrical shape and used as a separator to assemble an LR6 type alkaline battery as shown in FIG.

The nonwoven fabric is 65% vinylon and 20% linter pulp.
% and a polyvinyl alcohol binder of 15% and a thickness of 140 μm.

The zinc alloy powder used for the gelled zinc negative electrode filled inside the separator is a zinc alloy powder with a freezing rate of 1.0%, and its composition is 5001)9 heavy lead.

500pp aluminum, 200pp indium,
The balance is zinc.

Example 2: 10 points per CD on 20 μm thick cellophane with a diameter of 0
．． A dot size process of 0.05 to 0.1 mm is performed, and the above-mentioned first
The same nonwoven fabric as in the example was laminated in a three-layer structure in a sandwich state, and the three-layer structure was wrapped in a single layer to form a separator, and an LR6 type alkaline battery was assembled using this.

Note that the other configurations are the same as those of the first embodiment.

Comparative Example 1 The above-mentioned cellophane was made into a three-layer structure together with a non-woven fabric without cutting, and this was wrapped in layers to form a separator, and an LR6 type alkaline battery was assembled using this. Other configurations are as described in 1. This is the same as the second embodiment.

Comparative Example 2 A separator was constructed by wrapping a commonly used nonwoven fabric in three layers, and an LR6 type alkaline battery was assembled using the separator.

Incidentally, the zinc alloy powder to be filled inside the negative electrode is the same as the above-mentioned No. 1. The same zinc alloy powder as in the second example with a viscosity of 1.0% was used.

Comparative Example 3 In a commonly used alkaline battery, powdered zinc with a freezing rate of 3.0% was used as a gelled zinc negative electrode.

Table 1 (Number of abnormalities occurring during 3,9-fold 5M/D discharge) Table 3゜ (Short circuit current after 1 month of assembly) Table 2 (Short circuit current after 30 minutes of assembly) Table 4゜ (Discharge during 1Ω continuous discharge) Characteristics) *For discharge performance, Comparative Example 3. The initial performance was set as 100 and expressed as an index.

As is clear from the results shown in the three tables above, Example 1,
In the alkaline battery No. 2, there is no discharge abnormality under special discharge conditions, and there is little deterioration in high-load discharge performance.

In addition, the short circuit current value immediately after assembly was sufficient, suggesting that the internal electrolyte was quickly absorbed into the positive electrode mixture through the separator and that the increase in internal resistance after storage was small.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an LR6 type alkaline battery applied to the present invention, FIG. 2 is an enlarged sectional view showing the layer structure of the separator, and FIG. 3 is an enlarged sectional view showing another layer structure of the separator. . 5... Gel-like zinc negative electrode 6... Positive electrode mixture 7... Separator 8... Cellophane 9... Nonwoven fabric

Claims (1)

[Claims] (1) In an alkaline battery in which a zinc alloy powder with a degree of viscosity of 1.5% or less is used as a negative electrode active material, and the negative electrode active material and the positive electrode mixture are separated through a cylindrical separator, the separator is made of cellophane. an alkaline battery, which is formed into a cylindrical shape by overlapping and rolling a nonwoven fabric, and wherein the entire surface of the cellophane is formed with dots or perforation-like cuts that pass through the front and back sides of the cellophane. separator.