JPS60216452A - Paste type positive-electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To obtain a positive-electrode plate with high performance at a low cost by cobalt-plating a porous substrate made of sintered alkali-resistant metal fibers and filling it with an active material made of nickel hydroxide. CONSTITUTION:Alkali-resistant metal fibers obtained by cutting Fe, Ni, etc. are sintered to form a porous substrate. After this porous substrate is cobalt-plated, it is filled with a positive-electrode active material mainly composed of nickel hydroxide, and it is dried and thickness-adjusted to form a paste type positive- electrode plate for alkaline storage battery. Thereby, it can be filled with the active material at a high density, and the utilization factor of the active material can be improved. Accordingly, a positive-electrode plate with a high energy density can be obtained at a low cost.

Description

[Detailed Description of the Invention] The present invention relates to a positive electrode plate for alkaline storage batteries, particularly a paste-type nickel plate, and an object of the present invention is to provide a high-performance, low-cost, and highly productive nickel positive electrode plate for conventional alkaline storage batteries. As a nickel positive electrode plate, a sintered type electrode plate is well known in which a porous substrate made by sintering nickel powder into a perforated steel plate or a nickel net is filled with a nickel active material.

This porous substrate is made by simply sintering nickel powder onto a perforated steel plate or nickel net, and the bond between the nickel powder particles is weak, causing them to fall off when the porosity is high. 80-degree charcoal is the limit.

In addition, these porous substrates have a weak bond between the nickel powder particles, so they always require a core metal such as a perforated steel plate or nickel net, which has the disadvantage that the active material filling charge per unit volume decreases by the volume of the core metal. are doing.

Furthermore, since the pores of the porous material are as small as 10 μm or less, the filling method is limited to a solution impregnation method that involves repeated complicated steps.

In an attempt to improve these shortcomings, a so-called paste filling method has been carried out, in which a solid active material is directly filled into a nickel-plated iron fiber sintered body without a core, a nickel fiber sintered body, etc. . In addition, there is a pocket type electrode plate that is filled with TtJ' contacting solid active material, but this type has a structure in which a perforated copper plate is processed to create a pocket part and the active material is filled in the pocket part. The volume occupied by the perforated steel plate in the pocket portion is large, and the packing density per unit volume is quite low.

Hitherto, as methods for manufacturing metal fibers, there have been inexpensive methods such as a cutting method or a method in which metal powder is processed and sintered into a fiber form.

In the cutting method, a gold lj of several wire diameters is passed onto a fixed tool.
When cutting fibers by moving the 4 wires,
There are two types of so-called chatter vibration cutting that utilize self-excited vibration in turning. The diameter of the metal fiber is 4μ
The thinner the fiber diameter, the greater the surface area and the higher the utilization rate of the active material. on the other hand.

As the fiber diameter increases, the surface area decreases and the active material utilization rate definitely decreases, so fibers with a diameter of 50 μm or more have little merit. Pore distribution of the substrate that is easy to fill with practical active materials,
When considering tensile strength and active material utilization rate, it is desirable to have a thickness of about 4 to 50 μm. A porous substrate is obtained by uniformly distributing the fibers by air lading or other methods and then sintering them in a high-temperature reducing atmosphere of about 1000°C.

For the porous substrate, the fiber amount, sintering temperature, time, etc.
By doing so, it is possible to obtain a material with a porosity of 85 to 98 and a strength for eastern use. Note that when this porous substrate is made of iron fiber, 10 to 20% nickel plating is required to prevent corrosion in an alkaline electrolyte.

Conventionally, when these porous substrates are filled with an active material whose main component is hydroxide, the active material utilization rate is lower than that of, for example, a sintered electrode plate. The present invention has been made to improve this point, and focuses on the fact that the utilization of active materials can be improved by pre-plating cobalt on a porous substrate. According to the present invention, a porous substrate is first plated with cobalt of about 1 to 2 μm, and the cobalt-plated porous substrate is coated with nickel monohydroxide as a main component, a small amount of cadmium hydroxide, and nickel monohydroxide as a main component. In this method, an active material containing cobalt hydroxide in a eutectic state is filled in a slurry form with a solvent such as water, dried, and the thickness is adjusted to form a positive electrode plate. A dormitory embodiment of the present invention will be described in detail below.

After distributing the nickel fibers obtained by the chatter vibration cutting method using the air lading method, the fibers were sintered at 1050° C. for about 30 minutes in a reducing atmosphere to obtain a porous substrate with a thickness of 2n1 and a porosity of 95%. Thereafter, cobalt plating with a thickness of 1 to 2 μm was applied in a plating bath consisting of ammonium cobalt acetate, ammonium acetate, acetic acid, formalin, cadmium sulfate, etc. .

This cobalt-plated porous body is coated with 9 nickel hydroxide.
Approximately 10% by weight of nickel powder is added to a eutectic material consisting of 4 mol% of cobalt hydroxide, 5 mol% of cobalt hydroxide, and 1 mol% of cadmium hydroxide, and mixed well, and further mixed with approximately 40% by weight of water and approximately 2% by weight of nickel powder. After adding carboxymethyl cellulose and filling the slurry, dry 1 thickness 19tf1
A 0.7n positive electrode plate was obtained. The packing density of the active material is approximately 1
．． There is 89/cc engineering. This positive electrode plate was cut into 4 x 4 cm pieces, charged and discharged in a potassium hydroxide electrolyte, and the energy density t<''h/cc) was measured.For comparison, a piece of the same size but not plated with cobalt was measured. The energy density (mAh7-) of the positive electrode plate was determined.

Table I shows potassium hydroxide with a specific gravity of 1.24.
．． A comparison of 1,000 energy densities (mAh/cc) is shown when the battery was charged with a current of 1.011 for 15 hours and then discharged to OV VS ``9/Hp□ with a current of 0.20.

6-Table 1 From Table 1, the active material utilization rate is improved by coating the surface of the fiber porous body with Copal F plating.

A similar tendency was observed no matter what type of fibrous porous material was used. From this, it is presumed that the contact surface between the fibrous porous material and the active material plays an important role in improving the active material utilization rate. That is, cobalt is Co-+HOOO,→002 in the alkaline electrolyte in the anode direction.
Since it has the property of dissolving once with 0s and precipitating, it is presumed that the active material utilization rate is improved because it has the effect of completely connecting the current collector surface and the active material. The metal fiber positive electrode plate of the present invention has an energy density that is approximately 40% higher than that of a conventional nickel powder sintered electrode plate. This is due to the fact that high-density packing of the active material is possible without the need for a metal core and the use of a highly porous substrate, and also because the active material utilization rate is higher than that of conventional metal fiber positive electrode plates. It is.

Nowadays, when batteries are required to be made more compact, the present invention makes it possible to manufacture a nickel positive electrode plate with high energy density and at low cost, and its industrial value is extremely great.

Applicant Yuasa Battery Co., Ltd.

Claims (1)

[Claims] 1) For an alkaline storage battery, characterized in that a porous substrate formed by sintering alkali-resistant metal fibers is coated with cobalt and filled with a positive electrode active material mainly composed of nickel hydroxide. Paste type 2) The paste type electrode plate for an alkaline storage battery according to claim 1, wherein the alkali-resistant metal fibers are fibers obtained by cutting ridge lines. 3) The alkali-resistant gold I14IIm fiber is a fiber obtained by chatter vibration cutting of an iron ingot.4) The alkali-resistant metal fiber is a fiber obtained by chatter vibration cutting of a nickel ingot. A paste-type positive electrode plate for an alkaline storage battery according to claim 1. 5) Paste-type positive electrode plate 0 for alkaline storage batteries according to claim 1, in which the alkali-resistant metal fibers are processed from nickel powder or dichelic oxide powder.