JPH0482164A - Electrode plate for battery - Google Patents

Abstract

PURPOSE:To prevent breakage of a substrate and lowering of battery performance in winding the battery in a spiral shape by using a sponge-like metal porous body with a metal skeleton steppedly increasing in thickness in the thickness direction, and locating the thickened metal skeleton of the substrate on the outer peripheral side in forming a spiral electrode body. CONSTITUTION:A conductive coating maternal dispersed with graphite powders is coated on a foaming urethane resin thus providing conductivity to the foaming urethane resin. Ni is coated on the resin by electroplating. In this case, the thickness of the Ni coating film is steppedly changed, thereby forming a substrate. Subsequently, an electrode plate using the substrate is assembled to a Cd anode plate and a separator, which is wound in such a manner that the thickened skeleton of the electrode plate using the substrate is located on the outside with respect to the winding center, thus forming a battery.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to an electrode plate in which the substrate is a sponge-like porous metal material having a three-dimensional continuous structure, and the pores are filled with an active material. It is.

(b) Prior Art Conventionally, sintered electrode plates have been widely used as nickel electrode plates for sealed nickel-cadmium batteries and the like. This sintered electrode plate uses a substrate with a porosity of 75 to 80% obtained by sintering nickel powder in a reducing atmosphere. moreover,
This substrate was immersed in a nickel salt aqueous solution and then treated with an alkaline aqueous solution to turn the nickel salt into an active material and obtain a sintered electrode plate. The sintered electrode plate obtained by this method has strong mechanical strength, excellent high-rate discharge characteristics, and long life.

However, since the pore diameter of the sintered electrode plate is small, in order to fill it with a predetermined amount of active material, the number of impregnations must be increased. Therefore, there is a drawback that the manufacturing process becomes complicated and the cost becomes high.

In order to solve these drawbacks, a method has been proposed in which a sponge-like porous metal material having a continuous three-dimensional structure is used as a substrate. Since this sponge-like metal porous body has a larger pore diameter than that of a sintered substrate, it is possible to directly fill the active material in the form of a paste, thereby simplifying the process. Furthermore, since the porosity is 95% or more, which is higher than that of a sintered electrode plate, a large amount of active material can be filled and a high capacity can be achieved.

In JP-A-56-102076, a sponge-like metal sheet is used as a substrate, and by making the lattice diameter near the surface of the sheet larger than the internal lattice diameter, a sheet having the same lattice diameter near one surface and at the center can be obtained. It has been proposed that the active material can be packed more densely than when using the active material.

However, the electrode plate obtained by filling a sponge-like metal sheet with an active material has a large lattice diameter and low porosity near the surface, making it difficult to fill with the active material. Furthermore, when used while being carried around in a spiral like a cylindrical sealed nickel-cadmium battery, although it has high porosity, its skeleton is thin, so its strength is weak and it may break when being carried. Furthermore, even if the metal skeleton is not completely broken, there are often deep cracks in the metal skeleton, which lowers the conductivity and increases deterioration, especially during high rate discharge.

In order to solve this drawback, Japanese Patent Application Laid-Open No. 59-207560
In the publication, after a sponge-like porous metal material is filled with an active material, grooves are formed at appropriate intervals in the Jj direction perpendicular to the winding direction during battery construction using a press to prevent the electrode plates from being cut. A method has been proposed.

However, in the method of forming the creases by pressing as described above, the volume of the grooves in the crease portions is not utilized. Therefore, the energy density of the electrode decreases. Furthermore, the process equipment becomes complicated.

(c) Problems to be Solved by the Invention The present invention seeks to provide an electrode plate that uses a sponge-like porous metal material as a substrate and can prevent breakage of the substrate and deterioration of battery performance when it is carried in a spiral manner. It is something.

(d) Means for Solving the Problems The electrode plate of the present invention has a three-dimensional continuous structure, uses a sponge-like porous metal material as a substrate, and has the porous portions filled with an active material. The substrate is a sponge-like metal porous body in which the metal skeleton is gradually thickened in the thickness direction, and the thicker metal skeleton of the substrate is located on the outer circumferential side when forming the spiral electrode body.

(e) When an electrode plate made of a sponge-like metal porous material with a uniform skeleton thickness in the thickness direction of the working substrate is actually carried around and observed, it is found that it has fractures and cracks. Furthermore, many breaks and cracks were observed on the outer surface of the agitated electrode plate. When winding, this is the side that is closer to the winding core (inner side) than the side that is farther away from the core (outer side).
The above phenomenon occurs because the tensile stress on the electrode plate is stronger.

In order to prevent this, the entire skeleton may be made thicker, but this would reduce the pore diameter of the porous portion and reduce the amount of active material filled, resulting in a decrease in the energy density of the electrode plate.

However, according to the configuration of the present invention, the outer metal skeleton, which is easy to break, is thick, so that the electrode plate is prevented from breaking.

Furthermore, in the present invention, the metal skeleton is partly thicker and the volume occupied by the substrate relative to the electrode plate is also slightly increased, so the amount of active material filled is slightly smaller. It is easy to fill the active material. As a battery, there is no reduction in discharge capacity due to breakage or cracking of the electrode plates, so the discharge capacity increases.

Furthermore, the effect of the present invention becomes greater as the thickness of the electrode plate increases.

(f) Example A conductive paint containing graphite powder dispersed in an organic glue was applied to the foamed urethane resin to impart electrical conductivity to the foamed urethane resin. Next, a metallic nickel film was electrodeposited on this conductive foamed urethane resin using a nickel plating bath. During this electrodeposition, a nickel plate serving as a counter electrode is placed on only one side of the foamed urethane resin, and the current density is intentionally decreased (increased) in stages in the thickness direction of the foamed urethane resin to form a nickel coating. Substrate a was prepared by changing the thickness of the substrate in stages. As a comparison board, a board was prepared in which the nickel film was uniformly plated to a thickness of 10 μm.

Next, N i (OH), 90% by weight, metallic Co
Add 50% by weight of water, a small amount of glue, and Teflon to the active material powder mixed with 0% by weight, stir to make it uniform, make a paste, fill it into the above substrates a and b, dry it, and press it with a roller press. It was rolled into a completed electrode plate. The basis weight and amount of active material of substrates a and b are the same.

Next, combine the electrode plate using substrate a, the cadmium cathode plate, and the separator, and turn the electrode plate using substrate a so that the thicker skeleton is on the outside of the winding core, and the nominal capacity is 650 mA/fl. A battery (A) of the present invention was prepared.

A comparative battery (B) was prepared under the same conditions as in Section 1 except that a substrate was used in the same manner.

The internal resistances of 500 batteries of the present invention (A) and comparative batteries (B) were each measured, and the results of the short circuit occurrence rate are shown in Table 1.

Table 1 Next, the present invention battery (A) and the comparative battery (B) were tested at 0. IC(6
After charging for 16 hours with a current of 5 mA), the IC (650
Table 2 shows the battery capacity when discharged at a current of 4C (2600mA).

Table 2 Table 1.2 shows that the battery of the present invention has a lower short circuit occurrence rate due to rupture of the metal skeleton during rotation of the electrode plate, compared to the comparative battery.
Moreover, it can be seen that there is no decrease in conductivity due to cracks, etc., and deterioration during high rate discharge is also small.

(G) Effects of the Invention As described above, the electrode plate of the present invention suppresses the breakage of the substrate, does not reduce conductivity due to cracks, etc., and prevents deterioration of battery performance. The value is extremely great.

Claims (1)

[Claims] (1) In an electrode plate in which a sponge-like metal porous body having a three-dimensional continuous structure is used as a substrate and the porous portions are filled with an active material, the metal skeleton as the substrate is made thicker in stages in the thickness direction. 1. An electrode plate for a battery using a sponge-like metal porous body, and characterized in that the thicker side of the metal skeleton of the substrate is located on the outer peripheral side when forming a spiral electrode body.