JPS62136761A - Manufacture of nickel electrode for alkaline battery - Google Patents

Abstract

PURPOSE:To secure such an electrode that is very high in capacity, by regulating a grid diameter and a means space diameter of a spongy Ni porous body, and the form and grain size of Ni(OH2) powder or a main active material. CONSTITUTION:Mean grain size of spherical powder of Ni(OH)2 is set to a range of 5-25mu, while mean space diameter of a spongy Ni porous body before this powder is filled up is set to be 10-50 times over the mean grain size of the Ni(OH)2, and a grid diameter is selected to a range of 30-70mu. Paste consisting of the Ni(OH)2 as a main body is filled in this porous body, producing an Ni electrode after being compressed by pressure. This method is more simplified than the conventional sintered type Ni electrode, and on top of very high in capacity, a discharge rate characteristic and a cycle life characteristic are also almost equal to that electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing nickel electrodes for alkaline batteries.

Conventional technology Nickel electrodes used in alkaline batteries are usually made by filling a porous nickel sintered substrate with active materials such as nickel hydroxide or cobalt hydroxide by means such as electrolysis or chemical impregnation. something is being used. Recently, a sponge-like porous nickel body has been filled with an active material paste mainly composed of nickel hydroxide. Nickel electrodes with high capacity have also been proposed.

The conventional active material filling process of sintered nickel electrodes is impregnation 9 alkali treatment, such as chemical impregnation method.

Many processes such as washing with water and drying were required, and in order to obtain a high-capacity electrode, these processes had to be repeated several times, making it extremely complicated.On the other hand, sponge Porous nickel body (porosity: 90-9
5%) allows selection of large pore diameters, which allows paste-like active material to be directly filled into the porous body, and allows for high capacity with a simple process of just pressurizing after filling. It is possible to manufacture nickel electrodes with

In addition, regarding the characteristics of the electrode, in terms of capacity, the capacity per unit volume of the conventional sintered nickel electrode is 370 to 450 m2.
While it is about Ah/cA, 480-520m
It has become possible to obtain a high capacity on the order of Ah/tri, and to obtain discharge characteristics at large currents that are equivalent to those of the sintered type.

Problems to be Solved by the Invention However, simply selecting an arbitrary sponge-like porous nickel material or selecting a shape of nickel hydroxide with a particle size of 9 will result in problems such as capacity per unit volume, lifespan, high rate discharge, and use of active materials. It is far inferior to sintered electrodes in terms of rate and characteristics.

As a result of study, the present inventors found that by regulating the lattice diameter and average space diameter of the sponge-like porous nickel material, and the shape and particle diameter of the nickel hydroxide powder, which is a living substance, the present inventors found that it is inferior to the sintered type in each characteristic. It has been found that electrodes with extremely high capacitance can be obtained.

As a means to solve the problem, the present invention is to fill a sponge-like porous nickel body with a three-dimensionally continuous structure with active material powder mainly composed of nickel hydroxide in the form of a paste, and then pressurize and compress the powder. In the method for manufacturing a nickel electrode, the nickel hydroxide powder has a spherical shape and an average particle size of 6.
~25μ, the average space diameter of the sponge-like porous nickel material is 10~50 times the average particle size of the nickel hydroxide powder, and the lattice diameter (thickness) is 30~70μ.

Function: In the method of directly filling a sponge-like porous nickel body with active material powder in the form of a paste, the particle structure (shape) of the nickel hydroxide powder, which is a living substance, may have a large effect on the filling characteristics. be. Therefore, we made an active material paste using nickel hydroxide with a spherical particle structure as shown in Figure 1 and nickel hydroxide with a nodular particle structure as shown in Figure 2. A nickel electrode was prepared by filling a nickel porous body and drying and pressurizing the material.The filling capacity densities of the nickel electrodes were compared, and the results shown in Table 1 were obtained.

Table 1 As is clear from Table 1, those using nickel hydroxide having a spherical particle structure have a higher filling capacity density. In other words, an electrode with high capacity can be obtained. The first reason for this is that, as shown in Figure 1, spherical nickel hydroxide has a smooth surface, so when filling the active material, the surfaces of the powder particles can easily fit inside the porous body. Secondly, when the powder is press-molded after filling, large gaps are created between the powder particles in the case of nodular nickel hydroxide, whereas in the case of spherical nickel hydroxide, the active material is This is thought to be because the nickel hydroxide powder particles are arranged densely and the gaps become smaller since they are not spherical. The above phenomenon is the same regardless of the particle size of the nickel hydroxide.When we investigated the relationship between the average particle size and utilization rate of zero-order spherical nickel hydroxide powder, we found the results shown in Figure 3. Obtained. It was found that at a high rate discharge of about 30 μm, the utilization rate varies depending on the particle size, and the optimum average particle size is 5 to 25 μm. FIG. 4 shows the results of investigating the cycle life characteristics of spherical nickel hydroxide having such an average particle diameter filled as an active material paste into sponge-like nickel porous bodies with different average space diameters. The average space diameter of the sponge-like porous nickel material is 1 of the average particle diameter of nickel hydroxide.
It was found that electrodes using sponge-like porous nickel materials with a ratio of less than 0 times and more than 50 times deteriorated significantly. Analysis of the cause revealed that in electrodes where the average space diameter of the sponge-like porous material is less than 10 times the average particle size of nickel hydroxide, the lattice of the sponge-like porous nickel material may break down in places due to the expansion of the active material due to repeated charging and discharging. In contrast, in electrodes with an average space diameter of 5Q times or more the average particle size of nickel hydroxide, the active material fell off and deteriorated. In addition, when the average space diameter of the sponge-like nickel porous body was in the range of 10 to 5 times the particle size of nickel hydroxide, no difference in the filling capacity density was observed. In addition, when examining the lattice diameter of the sponge-like porous nickel material, 30
If it is less than 30μ, there is a risk that the porous material will be deformed due to lack of strength during filling, and if it is more than 30μ, there will be no significant difference in conductivity,
Above μ, there was a strong tendency for the filling capacity density to decrease.

From the above results, in the manufacturing method of nickel electrodes in which a sponge-like porous nickel body is filled with an active material mainly composed of aquacultured nickel in paste form and then compressed under pressure, the shape of the particles of nickel hydroxide powder is is spherical, and its average particle size is 6 to 25 μm, and the average space diameter within the sponge-like porous nickel body is 10 to 100 μm of the average particle size of the nickel hydroxide powder.
50 times, and the grating diameter was preferably 30 to 70 μm.Examples: Specific examples of the present invention will be described below.

To 100 parts by weight of nickel hydroxide, 10 parts by weight of nickel metal powder, 5 parts by weight of cobalt metal powder, and 5 parts by weight of cadmium hydroxide powder were added and mixed, and water and carboxymethyl cellulose were added to this and kneaded. The paste was made into a paste, filled into a sponge-like porous nickel material with an average space diameter of 3o○μ and a lattice diameter of about 50μ, and compressed under pressure to form a paste with a thickness of about 0.0μ.
A nickel electrode of about 78 mm was obtained. The nickel hydroxide used here was spherical nickel hydroxide A with an average particle size of 15μ, spherical nickel hydroxide B with an average particle size of 35μ, and spherical nickel hydroxide B with an average particle size of 15μ.
Nodular nickel hydroxide C.

For comparison, a normal sintered nickel electrode was also prepared. By combining these A-D electrodes with paste-type cadmium electrodes that have sufficient capacity for nickel electrodes,
A KR-3C sized sealed alkaline storage battery was prototyped and subjected to battery capacity tests, discharge rate characteristics tests, and cycle life characteristics tests.

Battery capacity test is 150mA at 20°C ambient temperature.
The battery capacity was evaluated by charging at a current of 16 hours and then discharging at 300 mA. In addition, the discharge rate characteristic test was performed at 20
After charging at 150 mA for 16 hours in an atmosphere of °C, the capacity when discharging at a current equivalent to 10 and 3 C of each battery capacity was evaluated as a ratio to the battery capacity determined in a battery capacity test. In addition, the cycle life test was conducted at 500 mA at 20°C.
After charging for 4.5 hours with a constant resistance equivalent to 1500mA
The battery is discharged in minutes, and the battery voltage in the first cycle is 1,
○The total time to reach V is 100, and the discharge time is 1
The life span was defined as the time when the deterioration reached 80% or less of the number of cycles, and the evaluation was made based on the number of cycles. Table 2 shows the results of various characteristic tests.

Table 2 In Table 2, batteries A, B, and C have an average space diameter of 300μ.

This battery uses a nickel electrode made by filling a sponge-like porous nickel material with a lattice diameter of 50 μm with an active material paste of spherical nickel hydroxide with an average particle size of 16 μm, and the battery is of the normal sintering type. It uses nickel electrodes. As is clear from Table 2, the battery using the nickel electrode according to the present invention not only has an extremely high capacity, but also has the discharge rate and life characteristics of the sintered type.
This is almost as good as when using a 17 Kel electrode.

Effects of the Invention As described above, the nickel electrode according to the present invention is not only easier to manufacture than the conventional sintered nickel electrode and has an extremely high capacity, but also has almost the same characteristics. It has great industrial value.

[Brief explanation of drawings]

Figure 1 shows the particle structure of spherical nickel hydroxide at a magnification of 10
Figure 2 is an electron micrograph at 1000x magnification showing the particle structure of nodular nickel hydroxide.
Figure 3 shows the utilization rate of nickel electrodes with different average particle diameters of spherical aqueous nickel powder, and Figure 4 shows the charging to the end of life when the average cubic capacity of a sponge-like porous nickel body is changed. It is a figure showing the number of times of discharge. Name of agent: Patent attorney Toshio Nakao and 1 other person/
■ Figure 2 Figure 3 Nik 4th addition: Nogaru's Chikari-kyo'fk (p
Figure 4

Claims (1)

[Claims] A method for producing a nickel electrode in which a three-dimensionally continuous sponge-like porous nickel body is filled with an active material mainly composed of nickel hydroxide in the form of a paste, and then compressed under pressure,
The nickel hydroxide powder is spherical and has an average particle size of 5
~25μ, and the average space diameter of the sponge-like porous nickel material before filling with the active material is 10μ of the average particle size of nickel hydroxide.
A method for producing a nickel electrode for an alkaline battery, characterized in that the nickel electrode is 50 times larger and has a lattice diameter of 30 to 70μ.