JPH07153465A - Unsintered positive electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide an unsintered positive electrode plate for an alkaline storage battery using nickel hydroxide as the main constituent of an active material and having a high and stable utilization factor of the active material by adding a specific compound to the active material. CONSTITUTION:In this unsintered positive electrode plate for an alkaline storage battery using nickel hydroxide as the main constituent of an active material, a compound expressed by CoOx (0<-x<1) of 10wt.% is added to the active material, for example. Cobalt oxide (CoO) is heat-treated in the hydrogen atmosphere to obtain this compound, for example.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nickel hydroxide positive electrode plate for alkaline storage batteries.

[0002]

2. Description of the Related Art Conventionally, in an alkaline storage battery for a nickel / cadmium storage battery or a nickel / hydrogen storage battery, a positive electrode plate is made by sintering nickel powder into a punching metal or the like, and a porous substrate is used to hold the active material. Formula nickel positive plates have been used. Such a sintered nickel positive electrode plate has the following problems.

First, when the porous substrate has a high porosity,
Since the strength becomes weak, it is difficult to obtain a porosity of 90% or more. Therefore, there is a limit in increasing the porosity of the substrate in order to increase the filling amount of the active material. Further, the sintered positive electrode plate has a problem that a complicated process is required to hold the active material on the sintered substrate.

As a positive electrode plate for improving the above problems of the sintered positive electrode plate, a positive electrode plate capable of achieving high energy density and having a simple manufacturing process is prepared. The non-sintered positive electrode plate directly held by the active material holder is used. In the non-sintered positive electrode plate, various attempts have been conventionally made to improve the utilization rate of the active material in order to increase the energy density.

As an example thereof, a positive electrode plate in which metallic cobalt powder is added as an additive to an active material (JP-A-59-59).
No. 128766), a positive electrode plate in which metallic cobalt and a cobalt compound are added to an active material (JP-A-53-51).
449 and Japanese Patent Laid-Open No. 2-216763). In these positive electrode plates, the cobalt species added to the active material are once dissolved in the electrolytic solution and uniformly dispersed on the nickel hydroxide surface to connect the active material-active material and the active material-current collector. In the form described above, the deposit turns into cobalt oxyhydroxide by the first charge, and a network of cobalt oxyhydroxide is formed.

This cobalt oxyhydroxide has a high conductivity, and the formed network improves the conductivity between the active material and the active material and between the active material and the current collector, and as a result, the utilization rate of the active material is improved. . JP-A-53-5144 described above
Among the cobalt compounds described in Japanese Patent Laid-Open No. 9-216716 and Japanese Patent Laid-Open No. 216763/1990, cobalt oxide (CoO) is known to have a high effect of improving the utilization rate.

[0007]

However, the above-mentioned positive electrode plate has the following problems. First, when metallic cobalt is added as an additive, metallic cobalt is less likely to be dissolved in the electrolyte, so that a sufficiently conductive network is less likely to be formed. Therefore, there is a problem that the effect of improving the utilization rate of the active material is low.

On the other hand, cobalt oxide (CoO) is easily dissolved in the electrolytic solution and forms a uniform network between the active material and the active material and between the active material and the current collector.
It is an additive with a high effect of improving the utilization rate of the active material. However, it is easily oxidized in the air, and when manufacturing the positive electrode plate,
There is a problem that it deteriorates during storage and the effect as an additive decreases.

The present invention has been made to solve the above problems, and provides a non-sintered positive electrode plate for an alkaline storage battery, which has a high utilization rate of an active material and a stable utilization rate. With the goal.

[0010]

In order to achieve the above object, the present invention provides a non-sintered positive electrode plate for an alkaline storage battery containing nickel hydroxide as a main component of an active material, wherein CoO _{x is} added to the active material. The compound represented by (0 <x <1) is added.

[0011]

The function of CoO _x (0 <
x <1) is not cobalt oxide but a compound having both properties of metallic cobalt and cobalt oxide. This CoO _x (0 <x <1) has a metallic cobalt-like property with respect to oxygen and is unlikely to be oxidized by oxygen.

In addition to this, conventional cobalt oxide (Co
Like O), it is easily dissolved in the electrolytic solution, covers the surface of nickel hydroxide, and enhances the conductivity between the active material and the active material and between the active material and the current collector. As a result, the utilization rate of the active material is increased. It can be effectively improved.

[0013]

【Example】

(Example 1) First, Ni (OH) ₂ powder 9 as an active material was used.
0% by weight and 10% by weight of CoO _0.7 powder (particle size: 1.5 μm) as an additive for improving the utilization rate of the active material were mixed.

Next, to the mixed powder of the above-mentioned active material and the additive, 50% of a 1% by weight HPC aqueous solution as a binder is added.
% By weight and kneaded to prepare a paste. This paste was held on a nickel sponge, dried, and then rolled to produce a non-sintered positive electrode plate. The additive CoO _0.7 used in this positive electrode plate was prepared as follows. (Method for Producing CoO _0.7 ) By subjecting cobalt oxide (CoO) to heat treatment in a hydrogen atmosphere, the additive CoO _0.7 of the above-described example was produced.

The positive electrode plate produced in this manner is described below in (a).
It is called a positive electrode plate. (Comparative Example 1) A positive electrode plate was produced in the same manner as in Example 1 except that cobalt oxide (CoO 2 particle size of 1.5 μm) was used as an additive instead of CoO _0.7 . The positive electrode plate thus manufactured is hereinafter referred to as a (x ₁ ) positive electrode plate. Comparative Example 2 A positive electrode plate was produced in the same manner as in Example 1 except that metallic cobalt (particle size: 1.5 μm) was used as the additive instead of CoO _0.7 .

The positive electrode plate thus produced is hereinafter referred to as a (x ₂ ) positive electrode plate. (Comparative Example 3) As an additive, cobalt oxide (CoO) and metallic cobalt were used instead of CoO _0.7 , and the amount of addition was 90% by weight of the active material Ni (OH) _{2 and} cobalt oxide ( A positive electrode plate was produced in the same manner as in the above-mentioned example except that 7% by weight of CoO) and 3% by weight of metallic cobalt were used.

The positive electrode plate thus manufactured is hereinafter referred to as (x ₃ ) positive electrode plate. (Experiment 1) The above (a) positive electrode plate, (x ₁ ) positive electrode plate to (x
₃ ) The electrode plate utilization rate was measured using the positive electrode plate, and the results are shown in Table 1. Prior to this experiment, a cell for use rate measurement using the positive electrode plate was prepared.

An electrode group was prepared by using each positive electrode plate, a sintered cadmium electrode, and a separator, and the electrode plate group was immersed in a 30% by weight aqueous solution of potassium hydroxide to prepare a measuring cell. Each of the measurement cells prepared in this manner is as follows: (a) a cell using a positive electrode plate (A) cell, and (x ₁ ) to (x ₃ ) a positive electrode plate, respectively (X ₁ ) to They are referred to as (X ₃ ) cells in order.

As the experimental conditions, the measurement was carried out under the following charging / discharging conditions. Charge: 0.1 C (VS theoretical capacity) × 16 h Discharge: 1/4 C (VS theoretical capacity) Discharge to 0 V The electrode plate utilization rate was calculated based on the formula (1) shown below. Electrode plate utilization rate = (measured discharge capacity / theoretical capacity) × 100 (1) However, Table 1 shows the values when the utilization rate of the (X ₂ ) cell is 100. .

[0020]

[Table 1]

As is clear from Table 1, C is used as an additive.
electrode plates utilization when using oO _0.7 is the same as the electrode plate utilization in the case of using a cobalt oxide (CoO), CoO _0.7 was used in this example, a high effect of improving the utilization compound You can say that. (Experiment 2) Next, the storage performance of the additive was examined. The results are shown in Table 2.

As the experimental conditions, the additive, CoO _0.7 used in the examples, and the cobalt oxide (C used in the comparative examples,
oO) and metallic cobalt in an atmosphere of 40 degrees each
After leaving it for a week, a positive electrode plate was produced in the same manner as described above, and the cell production and the utilization rate were measured in the same manner as in Experiment 1. However, the results in Table 2 are values when the result of the utilization rate of the (X ₂ ) cell in Experiment 1 is set to 100, and for comparison, Experiment 1
The results are re-listed as the data of utilization rate before storage.

[0023]

[Table 2]

As is apparent from Table 2, C is used as an additive.
It can be seen that the cell (A) using oO _0.7 has a high utilization rate even after storage, which is the same as that before storage, and a stable utilization rate can be obtained. Regarding the (X ₁ ) cell, it seems that the metallic cobalt added is not deteriorated and the utilization factor does not decrease after storage, but the utilization factor itself is low.

With respect to the (X ₂ ) (X ₃ ) cells, since cobalt oxide (CoO), which is easily oxidized, is used as an additive, oxidation occurs during storage, resulting in a decrease in utilization rate after storage. It seems to be. From the results of Experiments 1 and 2 described above, it was revealed that CoO _0.7 is an excellent additive having a high effect of improving the electrode plate utilization rate and a good storage performance. (Other matters) The additive used in the above examples is CoO.
_Although it is _0.7 , it is not limited to this composition as long as it is CoO _x (0 <x <1).

[0026]

As described above, according to the present invention,
Similar to cobalt oxide (CoO), CoO _x (0 <x <1) is a compound that has a high effect of improving the utilization rate of the electrode plate and is hard to react with oxygen. By using such a compound as an additive, it was possible to provide a non-sintered positive electrode plate for an alkaline storage battery, which has a high utilization rate of the active material and a stable utilization rate.

Claims (1)

[Claims] 1. In a non-sintered positive electrode plate for an alkaline storage battery containing nickel hydroxide as a main component of an active material, a compound represented by CoO _x (0 <x <1) is added to the active material. A non-sintered positive electrode plate for an alkaline storage battery characterized by the above.