JP2874052B2 - Method for producing porous substrate for battery electrode and electrode using the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sponge-like porous metal substrate for a battery electrode, and an electrode using the same.

2. Description of the Related Art In recent years, various batteries have been used in various electronic devices using batteries as power sources, particularly in the field of portable devices. Among them, cylindrical alkaline storage batteries, which have a wide range of use and are excellent in cost performance, occupy the mainstream. Conventionally, as a substrate holding the active material, a sintered type has been generally used for the positive electrode, and a sintered type or perforated steel plate has been generally used for the negative electrode. However, in recent efforts to increase the capacity, a sponge-like porous metal substrate having a large volume for holding the active material has been used as an active material holding substrate.

Problems to be Solved by the Invention As described above, an electrode plate using a sponge-like porous metal body as a substrate has an advantage that a high capacity density can be obtained, but because the amount of metal is smaller than that of a sintered substrate, There is a drawback that the strength against bending when winding the electrode plate is poor. Therefore, when winding an electrode plate using a sponge-like metal porous body, as shown in JP-B-58-34902, the major diameter of the substantially weight-proof space formed by the tension during the manufacturing process of the sponge-like metal porous body It has been proposed to wind the electrode in a direction perpendicular to the direction to allow a margin for the elongation on the outer periphery and prevent the electrode plate from breaking during winding. However, it has been difficult to always obtain a constant hole shape for various hole shapes due to variations in the production of the foamed polymer base material, and there has been a problem that strain remains on the substrate due to tension.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem and to obtain an electrode plate having uniform and excellent electrode winding properties.

Means for Solving the Problems In order to achieve the above object, the present invention peels a block of a foamed polymer base material around an axis in which bubbles generated during the production of a foamed polymer mainly escape, and performs the following steps. A method for obtaining a sponge-like porous metal substrate, and an electrode in which the substrate is filled with an active material, wherein the electrode has the same direction as the direction in which bubbles are released during the production of the foamed polymer and the axial direction of the winding as an electrode plate. It is characterized by the following.

According to this, the direction in which bubbles generated at the time of polymer foaming are parallel and constant with respect to the width direction of the peeled foamed polymer thin film, and the pore shape and size also in the long direction of the thin film. The variation in is reduced. In the electrode filled with the active material in this substrate, if the direction in which air bubbles escape and the axial direction of winding are the same, the strength of the electrode against bending during winding can be maintained, and therefore, the discharge characteristics are excellent. ,
A battery with less variation can be obtained.

Examples Hereinafter, examples of the present invention will be described.

In the block 1 of the foamed polymer shown in FIG. 1, a direction (a direction in the figure) through which the air bubbles generated in the production process mainly escape is found, and the foamed polymer block having a thickness of 1.5 Peel with mm. Nickel is vacuum-deposited on the peeled strip-shaped thin film 2 at about 100 g / m ² , followed by nickel plating of about 500 g / m ^{2 in} an aqueous nickel sulfate solution, and then the foamed polymer substrate is burned at about 400 ° C. The sponge-like porous nickel substrate is obtained by removing and subjecting to a reduction treatment at about 900 ° C. in hydrogen gas.
On this substrate, nickel hydroxide 90% by weight, cobalt powder 7
% Of cadmium hydroxide and 3% by weight of water, and filled with an active material paste prepared by adding water.
Press molding to 0.8mm. Then, as shown in FIG. 2A, an electrode plate 3 having a width of 37 mm and a length of 90 mm at right angles is obtained in parallel with the direction in which the air bubbles escape, and a current collecting lead is attached to the electrode plate 3 to form a positive electrode plate 4 (the present invention). Production method A). As a production method B for comparison, from the electrode obtained in the same manner as the production method A, as shown in B in FIG. Get.

Next, the foamed polymer block 1 is peeled around a direction perpendicular to the direction shown in FIG. 1a (b in FIG. 1) as an axis. As shown in C in the figure, 37 mm in width parallel to the axis,
It is processed into a 90 mm length in the perpendicular direction to obtain a positive electrode plate (Comparative Manufacturing Method C).

Further, as a comparative manufacturing method D, as shown in D in FIG. 3, the electrode obtained in the same manner as the manufacturing method C was processed into a width of 37 mm in a direction perpendicular to the axis and a length of 90 mm in a parallel direction. Thus, a positive electrode plate 4 is obtained.

These electrode plates are wound around a negative electrode together with cadmium and nylon separators to obtain an AA cylindrical nickel-cadmium storage battery using potassium hydroxide as an electrolyte.

Twenty batteries were prepared according to the respective manufacturing methods, charged at 80 mA for 15 hours, discharged at 800 mA to 1.0 V, and compared in capacity. The result is shown in FIG.

In the case of the production method A of the present invention, the discharge capacity is 800 m
Ah or more, and the variation is smaller than that by other manufacturing methods.

 This is considered to be due to the following reasons.

The bubbles generated during the production of the foamed polymer block usually escape mainly upward, but form a tunnel-like cavity in that direction. Therefore, a large number of these cavities are arranged in almost the same direction in the formed foamed polymer. When peeling is performed in this direction as an axis, the above-mentioned cavities are always arranged almost uniformly in the width direction in the obtained band of the foamed polymer. However, if the axis of the peeling is perpendicular to the direction in which the bubbles mainly escape, the direction of the resulting band will not be constant and the cavity will be cut at various angles. The state filled with the active material is a state in which the tunnel-shaped cavity is filled with the active material.
Just because the electrode plate is wound along this cavity, the rod-shaped active material that is clogged in the cavity, so to speak, does not break, but when it is wound around the axis perpendicular to the cavity, the rod-shaped active material becomes Because of the bending direction, a problem of remarkable cracking or cutting of the electrode plate occurs. As a result, the discharge characteristics of the battery deteriorate.

Effects of the Invention As described above, according to the present invention, there is little variation in the properties of the sponge-like metal porous body, and the electrode filled with the active material also has excellent winding characteristics, and thus has excellent discharge characteristics and variation. It is possible to provide an electrode having a small number of electrodes.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the direction of peeling and the peeling direction of bubbles generated during the production of a block of foamed polymer and its production, and FIG. 2 is a diagram showing a positive electrode plate according to production method A and comparative production method B of the present invention. FIG. 3 is a diagram showing positive electrode plates according to comparative manufacturing methods C and D, and FIG. 4 is a diagram showing a comparison of discharge characteristics of batteries by each manufacturing method.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/80

Claims (2)

(57) [Claims] 1. A block of foamed polymer is cut out (peeled) into a thin film, and a conductive film is formed thereon by means of vapor deposition, plating, coating or the like singly or in combination. In the step of producing a sponge-like porous metal substrate having a three-dimensional structure for a battery electrode by burning and removing and subsequently reducing, the peeling direction is mainly changed by bubbles generated during the production of a foamed polymer as a base material. A method for producing a porous substrate for a battery electrode, comprising obtaining a sponge-like porous metal substrate using a thin-film polymer peeled about an exit direction as an axis. 2. A battery electrode according to claim 1, wherein the porous substrate is filled with an active material, wherein the direction in which the air bubbles escape is the same as the axial direction of the electrode plate winding.