JPH1186881A - Alkaline dry battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a possibility of causing liquid leakage due to heat generation by a large electric current flow, when an alkaline dry battery is externally short-circuited erroneously, as well as to prevent the deterioration of an ordinary general discharge characteristic. SOLUTION: Thermoplastic resin powder, for example, low density polyethylene having a melting point of not more than 130 deg.C is arranged in a layer shape at least in one place among an interface between a hollow cylindrical positive electrode mix 2 and a bottomed cylindrical separator 3 of an alkaline dry battery, an interface between the bottomed cylindrical separator 3 and a gel-like zinc negative electrode 4 and the inside of the bottomed cylindrical separator. If the battery is heated abnormally, a thermoplastic resin softens and melts, and controls heat generation by cutting off electric current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery with improved safety.

[0002]

2. Description of the Related Art Alkaline batteries are superior in high current characteristics to manganese batteries and are often used for relatively high current applications. As a result, applications for higher currents than before have been expanded. In order to meet such needs, it is desired that the battery performance also has a large current characteristic.

[0003]

However, if the high current characteristic is simply improved, a large current will flow when an external short circuit occurs accidentally, and heat will be generated within a short time, resulting in softening of the sealing body or boiling of the electrolyte. There is a risk of liquid leakage, which is very dangerous.
In a lithium battery or the like, there is a type in which a porous polyethylene film is used as a separator, and holes are closed due to melting of the polyethylene film at the time of abnormal heat generation due to an external short circuit, thereby interrupting current and controlling the heat generation temperature. However, in the case of an alkaline dry battery, when a porous polyethylene film is used, there is a problem in that general discharge characteristics are significantly reduced due to an increase in internal resistance.

[0004] The present invention has been made in view of the above circumstances, without reducing the discharge performance for general use,
It is an object of the present invention to provide a safe alkaline dry battery with no liquid leakage by interrupting an excessively flowing current when abnormal heat is generated due to an external short circuit and controlling heat generation.

[0005]

That is, the present invention relates to a bottomed cylindrical positive electrode can serving also as a positive electrode terminal, a hollow cylindrical positive electrode mixture disposed in the positive electrode can, and a bottomed cylindrical separator. And a gelled zinc negative electrode filled into the hollow portion of the positive electrode mixture through
The thermoplastic resin powder having a temperature of 0 ° C. or less is mixed with the interface between the hollow cylindrical positive electrode mixture and the bottomed cylindrical separator, the interface between the bottomed cylindrical separator and the gelled zinc negative electrode, and It is characterized in that it is disposed in a layered manner at least at one position in the inside of the bottom cylindrical separator.

Generally, nylon 66 or polypropylene is used for an insulating gasket of an alkaline dry battery. The heat distortion temperature at 4.6 kg / cm ² is 240 ° C. for nylon 66 and 90 to 1 for polypropylene.
15 ° C. The heat distortion temperature at 18.6 kg / cm ² is reduced to 70 ° C. even for nylon 66. On the other hand, since the boiling point of the 40% KOH aqueous solution is 135 ° C.,
When the temperature of the battery rises to 135 ° C. or higher, the electrolytic solution boils, and the insulating gasket is deformed under the influence of the rise of the internal gas pressure due to the boiling of the electrolytic solution and the temperature, which may cause liquid leakage.

In the present invention, a thermoplastic resin is disposed at a predetermined position, and the thermoplastic resin has excellent insulating properties and a characteristic of melting and softening at a certain temperature. Therefore, by utilizing this characteristic, temperature control at the time of abnormal heat generation can be performed, and the maximum heat generation temperature can be controlled according to the melting point. That is, since the thermoplastic resin powder having a melting point of 130 ° C. or less is disposed at the predetermined position, when the battery abnormally generates heat and reaches a temperature equal to or higher than the melting point of the thermoplastic resin, the thermoplastic resin softens and melts. Then, the active material powder comes into close contact with the nearby active material powder or closes the holes of the separator, and as a result, current is cut off, so that heat generation can be controlled.

[0008] Among thermoplastic resins, low-density polyethylene (hereinafter referred to as LDPE) has a melting point of about 105 to 120 ° C and a boiling point of an electrolyte of 135 ° C, and is therefore a preferred material in the present invention. The average particle size of the LDPE powder is preferably from 20 to 200 μm. LD is less than 20μm
The dense PE layer increases the internal resistance of the battery,
If the thickness exceeds μm, it is considered that the thickness of the LDPE powder layer increases and the filling amount of the gelled zinc negative electrode decreases, which adversely affects general discharge characteristics. The amount of adhesion at that time is 10
About 100 g / m ² is preferable. If it is less than 10 g / m ² , the effect of interrupting the current cannot be expected because it is too small, and if it is 100 g / m ² or more, the thickness of the LDPE powder layer increases, the filling amount of the gelled zinc negative electrode decreases, and the internal resistance increases. Adversely affect general discharge characteristics.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an alkaline dry battery according to the present invention, JIS standard LR6 type (AA).
FIG. 2 is a cross-sectional view of a (type) alkaline dry battery.

In FIG. 1, reference numeral 1 denotes a bottomed cylindrical metal can also serving as a positive electrode terminal, and three positive electrode mixtures 2 formed into a cylindrical shape by pressure are separately filled in the metal can. . The positive electrode mixture 2 is obtained by mixing a manganese dioxide powder and a carbon powder and pressing the mixture into a hollow cylinder at a predetermined pressure using a molding die. In the hollow portion of the positive electrode mixture 2, a bottomed cylindrical separator 3 made of a nonwoven fabric of acetalized polyvinyl alcohol fiber is disposed. Outside the bottomed cylindrical separator 3, a thermoplastic resin powder layer 4 is provided.

A gel zinc negative electrode 5 made of non-melonized zinc alloy powder, an alkaline electrolyte and polyacrylic acid as a gelling agent is filled through the separator. In the gelled zinc negative electrode 5, a negative electrode current collector rod 6 made of brass is mounted so that its tip is inserted into the gelled negative electrode 5. An insulating gasket 7 made of a double annular polyamide resin is provided on the outer periphery of the upper part of the negative electrode current collecting rod 6 and the inner peripheral surface of the upper part of the metal can 1. A ring-shaped metal plate 8 is disposed between the double annular portions of the insulating gasket 7, and a cap-shaped metal sealing plate 9 serving also as a negative electrode terminal is provided on the head of the current collecting rod 6 on the metal plate 8. It is arranged to abut. And
The inside edge of the metal can 1 is sealed by the gasket 7 and the metal sealing plate 9 by bending the opening edge of the metal can 1 inward.

(Examples 1 to 9) The separator 3 of the alkaline dry battery shown in FIG. 1 was slightly moistened with water, and LDPE powders having an average particle diameter of 20 μm, 100 μm and 200 μm were coated on the outside thereof at 10 g / m ² and 50 g, respectively. / M ^{2 and} 10
The LDPE powder layer 4 was adhered so as to be 0 g / m ² , and dried. This separator was placed in the hollow cylindrical positive electrode mixture 2 and filled with a gelled zinc negative electrode to produce a LR6 (AA) alkaline dry battery according to JIS. The main physical properties of the LDPE powder used are as follows:
Melting point: 105 ° C., density: 0.918 g / cm ³ , melt flow rate: 20 g / 10 min.

Comparative Example 1 The procedure of Examples 1 to 9 was repeated except that a separator to which no LDPE powder was attached was used.
A JIS standard LR6 (AA) alkaline dry battery was produced.

(Comparative Examples 2 to 4) A separator having an average particle size of 1
0 μm LDPE powder was added to 10 g / m ² , 50 g / m ²
JIS standard LR6 type (AA type) in the same manner as in Examples 1 to 9 except that it was adhered so as to be 100 g / m ^2.
An alkaline battery was prepared.

(Comparative Examples 5 to 10) Same as Examples 1 to 9 except that LDPE powder having an average particle size of 20 μm, 100 μm and 200 μm was attached to a separator so as to be 5 g / m ^{2 and} 150 g / m ^2. And JIS standard L
An R6 type (AA) alkaline battery was prepared.

(Comparative Examples 11 to 13) LDPE powder having an average particle diameter of 300 μm was placed on a separator at 10 g / m ² and 50 g.
A JIS standard LR6 (AA) alkaline dry battery was produced in the same manner as in Examples 1 to 9, except that the battery was adhered so as to be 100 g / m ² and 100 g / m ² .

(Comparative Example 14) In the same manner as in Examples 1 to 9 except that a porous polyethylene film was used for the separator,
A JIS standard LR6 (AA) alkaline dry battery was produced.

A liquid leakage test and a discharge test were performed on each of the LR6 alkaline dry batteries prepared as described above.
The results are shown in Table 1. In the liquid leakage test, 100 batteries were externally short-circuited for 24 hours and then left for one week to visually measure the number of liquid leakages generated. In the discharge test, a 10Ω battery was subjected to a 2Ω continuous discharge test, and the ratio was expressed as a ratio when the average value of the duration up to the voltage of 0.9 V in Comparative Example 1 was 100%.

[0019]

[Table 1]

From Table 1, it can be seen that the batteries of Examples 1 to 9 did not cause leakage in the liquid leakage test and had a 2Ω continuous discharge characteristic of LDPE.
A good result was obtained, which was comparable to that of Comparative Example 1 to which no powder was attached.

In the batteries of Comparative Examples 5, 7, and 9 in which the amount of the LDPE powder attached was 5 g / m ² , the number of leaks occurring one week after the external short-circuit test was five, and no effect was exhibited. Also, L
Comparative Example 6 in which the amount of DPE powder attached was 150 g / m ² .
In the batteries of Nos. 8 and 10, the 2Ω continuous discharge characteristics were reduced by 12 to 20% as compared with Comparative Example 1 in which the LDPE powder was not attached, indicating that the 2Ω continuous discharge characteristics were adversely affected.

The batteries of Comparative Examples 2 to 4 in which the average particle diameter of the LDPE powder is smaller than those in Examples 1 to 9 and Comparative Examples 11 to 13 in which the average particle diameter of the LDPE powder is larger than those in Examples 1 to 9
In each of the batteries, the decrease in the continuous discharge characteristic of 2Ω was 10 to 3 times.
It is as large as 7%, which also has an adverse effect. further,
In the battery of Comparative Example 14 using the porous polyethylene film as the separator, the 2Ω continuous discharge characteristic was reduced by 50%.

In the above embodiment, the thermoplastic resin powder layer is provided at the interface between the positive electrode mixture and the separator. However, the thermoplastic resin powder is provided at the interface between the separator and the gelled zinc negative electrode and inside the separator. A JIS standard LR6 (AA) alkaline dry battery having the same specifications as the above embodiment was prepared and subjected to the same test, and the same result as the above embodiment was obtained.

[0024]

As described above, in the alkaline dry battery of the present invention, abnormal heat generation at the time of external short circuit can be controlled without sacrificing the general discharge performance. Can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an alkaline dry battery showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal can, 2 ... Positive electrode mixture, 3 ... Separator, 4 ... Thermoplastic resin powder layer, 5 ... Gel zinc negative electrode, 6 ... Negative current collector rod, 7 ... Insulating gasket, 8 ... Ring-shaped metal plate, 9 …
Metal sealing plate.

Claims (3)

[Claims] 1. A bottomed cylindrical positive electrode can also serving as a positive electrode terminal,
In an alkaline dry battery including a hollow cylindrical positive electrode mixture disposed in the positive electrode can and a gelled zinc negative electrode filled in a hollow portion of the positive electrode mixture via a bottomed cylindrical separator, the melting point is The thermoplastic resin powder having a temperature of 130 ° C. or less is mixed with the interface between the hollow cylindrical positive electrode mixture and the bottomed cylindrical separator, the interface between the bottomed cylindrical separator and the gelled zinc negative electrode, and An alkaline dry battery, wherein the alkaline dry battery is provided in a layered manner at least at one location inside a bottom cylindrical separator. 2. The thermoplastic resin powder has an average particle diameter of 20 to 20.
^2. The alkaline dry battery according to claim 1, wherein the alkaline dry battery is a low-density polyethylene powder having a thickness of 200 [mu] m, and has an adhesion amount of 10 to 100 g / m < ² >. 3. The alkaline dry battery according to claim 1, wherein said thermoplastic resin is a low density polyethylene.