JPH0480513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a nickel positive electrode for batteries and a method for manufacturing the same, and more specifically, it is applied to a non-sintered nickel positive electrode for alkaline batteries.

Conventional structure and its problems Traditionally, non-sintered nickel positive electrodes used in alkaline battery nickel positive electrodes, that is, positive electrodes that directly use nickel hydroxide powder as the active material, have been developed through a neutralization reaction between nickel sulfate and alkali. A powder obtained by drying and solidifying the precipitated nickel hydroxide lumps and then pulverizing this is used. The shape of the particles in this case has a fractured surface through the pulverization process, so that they are in the form of rice grains as a whole, but they are relatively flat and have an angular shape.

In addition, the average particle diameter is widely distributed from 1 to 200 μm through pulverization, and this is used as an active material to make pocket-type nickel positive electrodes, foamed metal-type nickel positive electrodes (active material filled in a three-dimensional network sponge-like substrate, or When used in coatings), there were the following problems.

In the pocket-type nickel positive electrode, since fine particles are mixed in, there is a risk that the active material particles may fall out from the pores of the metal pocket, which has many pores. Similar problems exist in foamed metal nickel positive electrodes, and when a paste-like mixture is used as the active material, variations in particle shape and particle size affect the stability of the paste properties, such as fluidity. It is difficult to obtain constant fluidity, and there is a risk that the amount filled into the support or electrode substrate may become unstable due to filling properties.

In other words, the fine powder obtained by pulverization has a fractured surface and its particle shape is irregular.
As the particle size becomes smaller, the non-surface area increases relatively. For this reason, the liquid (kneading solution) that is adsorbed on the particle surface
Since the amount of adsorbed liquid increases and the amount of adsorbed liquid varies depending on the particle size, it is difficult to maintain constant fluidity as a paste. When filling a paste into a substrate made of foamed metal, using nickel hydroxide powder with a small particle size makes it easier to fill the paste, but the powder content in the paste decreases and the energy density as a positive electrode decreases. It doesn't increase.

Purpose of the Invention The present invention aims to suppress the falling off of a mixture mainly composed of nickel hydroxide powder used in a non-sintered nickel positive electrode from a substrate or support, and to prevent the mixture from falling off a substrate or support in the form of a paste. The purpose of the present invention is to provide a nickel positive electrode that prevents instability of paste fluidity, has good filling properties, and has a high energy density, and a method for manufacturing the same.

Structure of the Invention The present invention mainly consists of nickel hydroxide powder, which has a particle shape of spherical, almost spherical, egg-shaped, or a combination of these, and has a narrow particle size distribution, and which is mixed with a conductive material, etc. It is characterized by the use of a mixture. This mixture is then applied to a non-sintered nickel positive electrode such as a foamed metal type or a pocket type.

In the case of the former foamed metal type electrode, as shown in FIG. 1A, it is composed of a powder 1 mainly containing an active material and a foamed metal 2 as a metal substrate for holding the powder. In addition, the latter uses a metal pocket 3 having a large number of micropores 4 as a support instead of foam metal,
This is filled with a powder mixture consisting mainly of active material powder.

The active material powder 6 to be filled into the metal substrate or support is replaced with the conventional pulverized powder, which is mainly composed of planes, has angular shapes, and has many variations in particle size, as shown in FIG. 2A. As shown in Figure 2B, it is spherical, almost spherical, egg-shaped, or an aggregate of these, and the average particle size is 1 to 1.
There is little variation within 100 μm.

The spherical, almost spherical, egg-shaped, or aggregation of these shapes all have curved surfaces, are rounded overall, and have a small specific surface area.

Furthermore, even when the paste is prepared with a mixing solution or other additives, the dispersion state in the paste is good and the paste has good fluidity.When this paste is filled or applied to a metal substrate, the active material powder becomes clogged. This allows for high energy consumption of the electrode plate.

Description of Examples Example 1 A concentration of approximately
While 1N nickel sulfate aqueous solution is introduced, flaky NaOH powder is added and the pH is adjusted under stirring.
to about 11 and the temperature to about 40℃. Each particle is continuously added from both sides of the stirring tank, and the particles are slowly matured into spherical, almost spherical, or egg-shaped particles, or particles that have grown large by aggregation of these, or particles whose corners have been shaved off by stirring and become spherical or almost spherical. Alternatively, only the egg-shaped particles are taken out to obtain nickel hydroxide powder. The average particle size of the powder here is 1~
It was 100 μm.

A mixture of 20 g of nickel powder and 5 g of cobalt powder per 100 g of this powder is kneaded with 70 c.c. of water to form a paste. This is sucked up with a pump with good adhesion, and a substrate made of foam metal (1.3 mm thick,
After drying, it was pressurized to a thickness of about 0.7 mm, which was immersed in a suspension containing 1.2 wt% fluororesin and dried again. A
Obtain a nickel positive electrode as shown in .

Example 2 A mixture of nickel hydroxide powder and graphite obtained in the same manner as in Example 1 was filled into a nickel pocket with a thickness of about 0.1 mm and having many micropores of about 20 μm, and as shown in FIG. 1B. Obtain a pocket-type nickel positive electrode as shown in . Note that 5 in the figure indicates a space formed within the electrode. Next, the nickel positive electrode obtained in the same manner as in Example 1 was cut into pieces of 40 x 55 mm, and the amount of active material filled (total weight - weight of the substrate) was analyzed.
We investigated 350 electrode plates.

The results are shown in Figure 3a. For comparison, a powder obtained by pulverizing a conventionally used lump is used, and the result is shown in b. As a result, when the nickel hydroxide powder of the present invention is used, the particle shape is spherical, almost spherical, egg-shaped, or a combination of these, all of which are round, and the specific surface area is small, and the paste can be adjusted. Even when the paste is mixed, the amount of mixing solution adsorbed on the particle surface is small, the powder is well dispersed in the paste, and the paste has good fluidity.

Therefore, the variation in the amount of active material filled in the paste state on the substrate is much smaller than before.
It was found that a large amount of active material can be filled or coated per unit volume, and the energy density of the electrode plate can be increased.

In addition, when used in a pocket-type electrode, when we applied 5G vibration in a width of 1 cm on the left and right sides and measured the weight of the falling off material, we found that with conventional powder, 5 g of fallen material fell out in 10 minutes per 100 g filled amount, but with the present invention. When using powder from
The extent of this was extremely small.

Effects of the Invention As is clear from the above results, the non-sintered electrode of the present invention using the nickel hydroxide powder having a spherical, almost spherical, or egg-shaped particle shape or an aggregate thereof as an active material has the following effects: Handling during electrode production is extremely stable, and the filling capacity of the active material to the substrate or support can be made uniform.

In addition, particle shapes that are spherical, almost spherical, egg-shaped, or a combination of these may also be used in the early reaction bath.
It can be easily and appropriately obtained by stirring and neutralizing nickel salt and alkali while controlling the pH and temperature.

[Brief explanation of the drawing]

Figure 1A is a schematic diagram showing a foamed metal type nickel positive electrode according to the present invention, Figure 2B is a schematic cross-sectional view of a pocket type nickel positive electrode, Figure 2A is a schematic diagram of a conventionally used nickel hydroxide powder, and Figure 2B is a schematic diagram of a nickel hydroxide powder used conventionally. 3 is a schematic diagram of spherical nickel hydroxide powder in the present invention.
The figure shows the distribution of the active material filling amount when the electrode obtained in the example of the present invention is cut into 44×55 mm. 1...Mixed powder mainly composed of nickel hydroxide,
2...foamed metal, 3...metal pocket, 4...
...Micropore, 5...Space, 6...Active material.

Claims (1)

[Claims] 1. A nickel positive electrode in which a powder mixture mainly composed of nickel hydroxide powder is filled or applied in a dry state or paste state into a metal substrate or support, the particle shape of the nickel hydroxide powder used. A nickel positive electrode for batteries is spherical, almost spherical, egg-shaped, or a combination of these, and its surface is mainly composed of curved surfaces. 2 The average particle size of the nickel powder used is 1~
A nickel positive electrode for a battery according to claim 1 having a thickness in the range of 100 μm. 3 Flow or inject the nickel salt aqueous solution and alkali into the reaction tank, and bring it to the specified pH while stirring.
A powder mixture or paste mainly composed of nickel hydroxide powder is maintained at a certain temperature and the particle shape is grown into a spherical, almost spherical, egg-like shape, or an aggregate of these through reaction aging, and the surface is mainly composed of curved surfaces. A method for manufacturing a nickel positive electrode for batteries, which is prepared and filled or coated onto a metal substrate or support.