JPH0260072A - Alkaline storage battery - Google Patents

Abstract

PURPOSE:To prevent short circuit caused by repeating charge-discharge cycles and to prevent drop in capacity by forming a no active material filling part at the end of an electrode adjacent to the current collecting plate of a counter electrode in a paste type electrode. CONSTITUTION:Part to be a current collecting plate welding part 1a or a no active material filling part 1c of a substrate is previously masked with an adhesive tape. Paste prepared by mixing an active material with water and carboxymethylcellulose is filled in the substrate, and dried, then this substrate is pressed and cut to form an active material filling part 1b and to obtain a paste type nickel electrode 1. The electrode 1 and a sintered cadmium electrode 2 having the same width as the electrode 1 are spirally wound with shifted by 2mm each other/through a separator 3 to form an electrode group. A negative current collecting plate 5 is brought into contact with the bottom of the electrode group and welded, then they are inserted into a battery can 7, welded, and an electrolyte is poured, then a sealing plate is welded to form an alkaline storage battery. Discharge capacity almost same as that in the initial stage is kept even after 200 cycles of charge-discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to alkaline storage batteries such as nickel-cadmium batteries and nickel-metal hydride batteries having a hydrogen storage alloy as a negative electrode.

[Conventional technology]

Conventionally, the mainstream current collection method for alkaline storage batteries for general use has been to collect the positive electrode with a tab and the negative electrode with pressure contact to the can, but for rapid charging and rapid discharging applications, the positive and negative electrodes are connected through a separator. After winding or laminating to form an electrode group,
A method is becoming mainstream in which two current collector plates are welded several times from above and below to form current collectors for positive and negative electrodes, respectively.

Traditionally, the sintering method was the mainstream method used for this purpose, but in recent years, with the aim of lower cost and higher capacity,
A paste-type electrode using a three-dimensional network porous material as a substrate and filling it with an active material has been developed and is now in practical use.

[Problem to be solved by the invention]

Paste electrodes using a three-dimensional porous network as a substrate have the inherent advantages of low cost and high capacity, as well as rapid charging and discharging performance.

However, if this type of electrode is used in combination with a method in which current collector plates are welded and attached from above and below after the electrode group is formed, a short circuit will occur. This is because in a paste type electrode having a three-dimensional network porous material as a substrate, the active material tends to fall off from the substrate during repeated charging and discharging. In the above current collection method, the positive and negative electrodes are wound or stacked with their current collecting plates offset from each other so that they do not touch other electrodes, but the difference is only 1 to several meters in actual batteries.
If the active material falls off from the electrode substrate,
The fallen active material grows like a dendrite on the edge of the substrate.
Easily causes contact short circuit with the current collector plate of the counter electrode. If the counter electrode collects current by pressure welding inside the battery can, it is possible to prevent this type of problem by inserting an insulating plate into the bottom of the can in advance, but in the case of current collection using a current collector plate, ,
Inserting an insulating plate between the electrode and the counter electrode current collector plate is extremely difficult due to its structure, and these circumstances led to a combination of a paste-type electrode using a three-dimensional network porous material as a substrate and a current collection method using a current collector plate. This has hindered the practical application of alkaline storage batteries.

The present invention has been made in order to solve the above-mentioned conventional problems, and aims to provide an alkaline storage battery that has excellent rapid charging and discharging performance and long life performance, and has a high capacity at low cost.

[Means to solve the problem]

In the present invention, after forming an electrode group by winding or stacking a paste-type N electrode with a three-dimensional network porous material as a substrate via a counter electrode and a separator, current collector plates are welded and attached from above and below to collect current. In this type of alkaline storage battery, a paste-type electrode with a three-dimensional porous network substrate as a substrate has a plain part, which is not filled with active material and has almost the same thickness as the electrode, at the end of the electrode that is close to the current collector plate of the counter electrode. This is an alkaline storage battery characterized by having:

Examples of the three-dimensional network porous body include sponge-like nickel, felt-like nickel, and sintered bodies of nickel fibers. The active material to be filled in the substrate is nickel hydroxide for the positive electrode, cadmium oxide for the negative electrode, or a paste of hydrogen storage alloy powder.

The method for forming the electrode group differs depending on the shape of the battery, and is mainly performed by winding in the case of a cylindrical battery, and by lamination in the case of a prismatic battery. The width of the plain area is at least 1/11
Approximately 111 is necessary, but if it is too large, the amount of active material filled will decrease accordingly. In addition, the height is approximately the same thickness as the electrode, so that it touches the separator and does not allow the fallen active material to pass through.

[For production]

A particular problem with the active material falling off from the three-dimensional network porous substrate is the falling off at the end of the electrode near the current collector plate of the counter electrode, and this type of failure is directly caused in other parts. It cannot be the cause. Therefore, the problem can be solved by preventing the dendrite-like active material from falling off at the ends. In the present invention, by providing a plain portion at the end that is approximately the same thickness as the electrode and is not filled with active material, the active material that would normally fall off from the substrate due to repeated charging and discharging is suppressed by the plain portion. Since it is held within the substrate, it is possible to effectively prevent 'fri' contact between the current collector plate of the counter electrode and the active material. Retaining the fallen active material in the uncoated area of the substrate not only prevents short circuits but also prevents a decrease in capacity due to falling off.

(Example) The effects of the present invention will be explained in detail below.In Fig. 1, as a three-dimensional network porous body serving as a substrate, nickel short m
On this substrate using a sintered body of fiber, a portion that would become the welded portion 1a of the current collector plate or the uncoated portion 1C was masked in advance with adhesive tape. This was filled with an active material consisting of 85 parts by weight of nickel hydroxide, 10 parts by weight of cobal powder, and 5 parts by weight of cobalt hydroxide, made into a paste with water and carboxymethyl cellulose, and then dried. ,Pressurization,
A filling portion 1b was formed through cutting, and a paste-type nickel electrode 1 was created. Note that tape-shaped nickel was welded to the welded portion 1a with the positive electrode current collector plate 4. In Figure 2,
Sintered cadmium electrodes 2 of the same size as this paste-like nickel electrode 1 are shifted by 2rIun from each other through a separator 3 to form a wound electrode group, and then a negative electrode current collector plate 5 is attached from below by welding. After that, it is inserted into the battery can 7 and welded, and through injection of liquid and welding sealing with the sealing plate 6, the S
A C size alkaline storage battery A was created. As a comparative example, an alkaline storage battery B was prepared in the same manner as in the example except that the uncoated portion on the sintered body of 1 tft 1 nickel short substrate was filled with active material paste without masking.
50 each, and for these storage batteries, 1c・1
A cyclic charge/discharge test consisting of 50% charge/LC discharge was conducted.

The results are shown in FIG. Battery B according to the comparative example is 25~
While all internal short circuits occurred during 100 cycles, battery A according to the present invention maintained almost the same discharge capacity as the initial stage even after 200 cycles of charging and discharging.

〔Effect of the invention〕

As detailed above, the alkaline storage battery of the present invention using a paste-type electrode having a plain portion not filled with active material at the end close to the current collector plate of the counter electrode has the advantage of not causing short circuits due to repeated charging and discharging. It has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a front view of a paste-type nickel positive electrode according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of the same alkaline storage battery. FIG. 3 is a diagram showing changes in discharge capacity of alkaline storage batteries according to Examples and Comparative Examples as the alkaline storage batteries undergo charge/discharge cycles. A is an example battery of the present invention, and B is a conventional comparative example battery.

Claims (1)

[Claims] An alkaline method in which current is collected by welding a current collector plate from above and below after forming an electrode group by winding or stacking a paste electrode with a three-dimensional network porous material as a substrate via a counter electrode and a separator. 1. An alkaline storage battery characterized in that the paste type electrode has a plain portion not filled with an active material at an end of the electrode close to a current collector plate of a counter electrode.