JPH10188971A - Unsintered nickel electrode for alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unsintered nickel pole with the usage factor of active material being less decreased after overdischarge. SOLUTION: In an unsintered nickel pole for an alkaline storage battery, cobalt compound powder is added to active material powder formed of nickel hydroxide particles or nickel hydroxide mainly contained solid solution particles or composite particle powder with cobalt compound layers formed on the surfaces of nickel hydroxide particles or nickel hydroxide mainly contained solid solution particles in used as active material powder. To the active material powder, at least one type of element selected out of ruthenium, rhodium, palladium, iridium, boron, gallium and scandium is added in simple substance or compound configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a non-sintered nickel electrode used as a positive electrode of an alkaline storage battery.

[0002]

2. Description of the Related Art As a positive electrode of an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, a nickel powder is sintered on a substrate such as a perforated steel plate. A sintered nickel electrode impregnated with an active material (nickel hydroxide) is well known.

In order to increase the amount of active material to be filled in a sintered nickel electrode, it is necessary to use a sintered substrate having high porosity. However, since the bond between the nickel particles due to sintering is weak, if the porosity of the sintered substrate is increased, the nickel particles are likely to fall off the sintered substrate. Therefore, in practice, the porosity of the sintered substrate cannot be made larger than 80%, and therefore, the sintered nickel electrode has a problem that the amount of the active material that can be filled is small. Further, generally, since the pore size of the sintered body of nickel powder is as small as 10 μm or less,
There is also a problem that the filling of the active material into the sintered substrate must be performed by a solution impregnation method in which a complicated impregnation step needs to be repeated several times.

[0004] For these reasons, non-sintered nickel electrodes have been proposed in recent years. A non-sintered nickel electrode is made of a kneaded material (paste or slurry) of an active material (nickel hydroxide) and a binder (aqueous methylcellulose solution) with a high porosity substrate (foamed metal plated with an alkali-resistant metal). It is produced by filling into. In the case of the non-sintered nickel electrode, a substrate having a high porosity can be used (a substrate having a porosity of 95% or more can be used). Filling the substrate is easy.

However, because of the use of a binder and the difficulty in forming a sufficient conductive network,
The non-sintered nickel electrode has a lower active material utilization rate than the sintered nickel electrode.

[0006] As a non-sintered nickel electrode which solves this drawback, a nickel hydroxide powder to which cobalt hydroxide powder is added (see JP-A-61-74261) and a method in which the surface of nickel hydroxide particles is water Cobalt oxide layer and β-C
One coated with an oOOH layer has been previously proposed (Japanese Patent Application Laid-Open No. 62-234867 and Japanese Patent Publication No. 8-24041).
Reference). In each case, the conductivity between nickel hydroxide particles is enhanced by the addition or coating of cobalt hydroxide.

[0007] However, these conventional non-sintered nickel electrodes have a problem in that, when overdischarged, the active material utilization after that is greatly reduced.

The present invention has been made to solve this problem, and an object of the present invention is to provide a non-sintered nickel electrode for an alkaline storage battery in which a reduction in the active material utilization rate is small even after overdischarging. And

[0009]

The non-sintered nickel electrode for an alkaline storage battery according to the present invention is characterized in that an active material powder comprising nickel hydroxide particles or solid solution particles containing nickel hydroxide as a main component is used. In a non-sintered nickel electrode for an alkaline storage battery to which a cobalt compound powder is added, together with the cobalt compound powder, ruthenium,
At least one element selected from rhodium, palladium, iridium, boron, gallium, and scandium is added in the form of a simple substance or a compound.

In the non-sintered nickel electrode for an alkaline storage battery according to the second aspect of the present invention, a layer of a cobalt compound is formed on surfaces of nickel hydroxide particles or solid solution particles containing nickel hydroxide as a main component. In the non-sintered nickel electrode for an alkaline storage battery using the composite particle powder as an active material powder, the composite particle powder contains at least one element selected from ruthenium, rhodium, palladium, iridium, boron, gallium, and scandium. Is added in the form of a simple substance or a compound.

As the solid solution particles containing nickel hydroxide as a main component, at least one element selected from cobalt, zinc, cadmium, calcium, manganese, magnesium, bismuth, aluminum and yttrium is dissolved in nickel hydroxide. An example is shown below. By using such solid solution particles, swelling of nickel hydroxide during a charge / discharge cycle can be suppressed.

Examples of the cobalt compound include a sodium hydroxide-containing cobalt compound prepared by adding an aqueous solution of sodium hydroxide to cobalt hydroxide, β-CoOOH, and β-CoOOH, and performing a heat treatment in the presence of oxygen. The heat treatment temperature when synthesizing the sodium-containing cobalt compound is preferably from 50 to 200 ° C. When the heat treatment temperature is lower than 50 ° C., the sodium-containing cobalt compound having a high electric conductivity is not sufficiently formed, while when the heat treatment temperature exceeds 200 ° C., tricobalt tetroxide having a low electric conductivity is used. Co ₃ O ₄ ) is produced. The heat treatment time varies depending on the amount and concentration of the aqueous sodium hydroxide used, the heat treatment temperature, and the like, but is generally 0.5 to 10 hours.

RuO ₂ is used as a ruthenium compound, Rh ₂ O ₃ is used as a rhodium compound, PdO is used as a palladium compound, and IrO ₂ is used as an iridium compound.
And Ir ₂ O ₃ , B ₂ O ₃ as a boron compound,
Ga ₂ O ₃ , Ga (OH) ₃ and GaF ₃ are used as gallium compounds, and Sc ₂ O ₃ is used as scandium compounds.
And ScF ₃ are each exemplified.

The amount of at least one element selected from ruthenium, rhodium, palladium, iridium, boron, gallium and scandium is 0.05 to 5 parts by weight based on 100 parts by weight of nickel hydroxide in the active material powder. Regulated by weight. When the addition amount is less than 0.05 part by weight, it is difficult to sufficiently suppress the decrease in the utilization rate of the active material after overdischarge, while when the addition amount exceeds 5 parts by weight, the amount of the active material becomes To decrease the electrode capacity.

In the electrode of the present invention, the active material utilization rate hardly decreases even when overdischarge occurs. The reason is presumed as follows. That is, at the time of discharging, β-CoOOH (cobalt hydroxide becomes β-CoOOH after charging) is reduced to cobalt hydroxide. When ruthenium or the like is not added to the active material powder, over-discharge causes the generated cobalt hydroxide and nickel hydroxide to have similar crystal structures, so that cobalt hydroxide diffuses into the active material particles. In addition, the amount of cobalt hydroxide adhering to the surface of the active material particles is reduced, the conductivity between the active material particles is reduced, and the utilization rate of the active material is reduced. On the other hand, in the case of the electrode of the present invention in which an additive such as ruthenium is added to the active material powder, the additive suppresses internal diffusion of cobalt hydroxide during overdischarge, so that the active material utilization rate decreases. It becomes difficult to do.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention may be practiced by appropriately changing the gist of the invention. Is possible.

(Experiment 1) In this experiment, the rate of decrease in discharge capacity after overdischarge in the case where an element such as ruthenium was added was compared with that in the case where no element was added.

Nickel hydroxide powder 1 having an average particle size of 10 μm
00 parts by weight, 5 parts by weight of cobalt hydroxide powder, ruthenium oxide (RuO ₂ ), rhodium oxide (Rh ₂ O ₃ ),
Palladium oxide (PdO), iridium oxide (Ir
O ₂ ), boron oxide (B ₂ O ₃ ), gallium oxide (Ga
₂ O ₃ ), scandium oxide (Sc ₂ O ₃ ), gallium (Ga), gallium hydroxide (Ga (OH) ₃ ), gallium fluoride (GaF ₃ ), scandium fluoride (Sc
And F ₃₎ or trioxide iridium (Ir ₂ O _3), respectively 2 parts by weight in terms of an element and a 1 wt% aqueous solution of methyl cellulose 20 parts by weight, was kneaded to prepare a paste. These pastes are filled in a porous substrate made of nickel-plated foamed metal (porosity: 95%; average pore diameter: 200 μm), dried, and press-molded. Electrodes) a to l were prepared.

Further, 100 parts by weight of nickel hydroxide powder having an average particle size of 10 μm, 5 parts by weight of cobalt hydroxide powder,
A paste was prepared by kneading 20 parts by weight of a 1% by weight aqueous solution of methylcellulose to prepare a paste, and the paste was nickel-plated into a foamed metal (porosity: 95%; average pore diameter: 20%).
A non-sintered nickel electrode (comparative electrode) x was prepared by filling a porous substrate having a thickness of 0 μm), drying and pressing. This comparative electrode is a conventionally known electrode disclosed in JP-A-61-74261.

Each of the above-mentioned non-sintered nickel electrodes (positive electrodes), known paste-type cadmium electrodes (negative electrodes), polyamide nonwoven fabric (separator), 30% by weight potassium hydroxide aqueous solution (electrolyte solution), metal battery cans, Using a battery lid,
AA size nickel-cadmium alkaline storage battery A ~
L (using the electrodes a to l of the present invention in order) and X (comparative electrode x
Was used. The electrochemical capacity ratio between the positive electrode and the negative electrode was set to 1: 1.8 so that the battery capacity was limited by the positive electrode capacity.

For each of these batteries, at 0.1 C
After charging 0%, the process of discharging to 1.0 V at 1 C is one step.
10 charge / discharge cycles were performed, and the discharge capacity D1 at the 10th cycle of each battery was determined. Next, each battery was charged 160% at 0.1 C, connected to a resistance of 5Ω, and maintained at a temperature of 70 ° C. for 7 days to be over-discharged. After overdischarge, after charging 160% at 0.1C,
Discharge to 1.0 V at 1C, and discharge capacity D2 after overdischarge
I asked. By substituting the discharge capacities D1 and D2 into the following formula, the capacity retention rate (%) after overdischarge of each battery was obtained. Table 1 shows the results. The larger the value of the capacity retention ratio after overdischarge, the smaller the decrease in the active material utilization rate after overdischarge.

Capacity retention after overdischarge (%) = (D2 / D
1) x 100

[0023]

[Table 1]

As shown in Table 1, the alkaline storage batteries A to L
Has a higher capacity retention ratio after overdischarge than the alkaline storage battery X. From this fact, it is understood that a non-sintered nickel electrode with a small decrease in the active material utilization rate after overdischarge can be obtained by adding an additive specified in the present invention such as ruthenium.

<Experiment 2> In this experiment, the relationship between the amount of the additive to nickel hydroxide and the utilization rate of the active material after overdischarge was examined, taking as an example the case of adding ruthenium oxide.

The addition amount of ruthenium oxide in terms of ruthenium element per 100 parts by weight of nickel hydroxide powder is 2
Parts by weight, 0.01 parts by weight, 0.05 parts by weight,
0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 3 parts by weight, 5 parts by weight
Experiment 1 except that the weight parts were 6 parts by weight or 7 parts by weight.
In the same manner as in the above, non-sintered nickel electrodes m to u were produced in order. Next, alkaline storage batteries MU were sequentially manufactured using each non-sintered nickel electrode, and the capacity retention ratio after overdischarge of each battery was determined in the same manner as in Experiment 1. Table 2 shows the results. Table 2 also shows data on alkaline storage battery A (addition amount of ruthenium oxide in terms of ruthenium element: 2 parts by weight).

[0027]

[Table 2]

As shown in Table 2, the alkaline storage batteries M and T
Has a lower capacity retention ratio after overdischarge than the alkaline storage batteries N to S and A. In addition, the alkaline storage battery U has a high utilization rate of active material after overdischarge, as high as the alkaline storage batteries N to S and A.
The discharge capacity D1 is low. From this fact, in order to obtain a non-sintered nickel electrode having a large electrode capacity and a small decrease in the active material utilization after overdischarge, it is necessary to add ruthenium oxide in terms of ruthenium element to 100 parts by weight of nickel hydroxide powder. It is understood that the amount is preferably 0.05 to 5 parts by weight.

In Experiment 2, the case where ruthenium oxide was added was examined, but when other elements or compounds specified in the present invention were added, the addition amount in terms of those elements was 0.05 to 5 parts by weight. Was confirmed to be preferable.

In Experiments 1 and 2 described above, nickel hydroxide powder was used as the active material powder. However, the nickel hydroxide particles contained cobalt, zinc, cadmium, calcium,
It was confirmed that the same result as described above was obtained also when a solid solution particle powder in which at least one element selected from manganese, magnesium, bismuth, aluminum and yttrium was dissolved was used.

In the above Experiments 1 and 2, nickel hydroxide powder was used as the active material powder and cobalt hydroxide powder was used as the conductive agent.
The same result as described above can be obtained even when a composite particle powder in which a layer of a cobalt compound as a conductive layer is formed on the surface of nickel hydroxide particles or solid solution particles containing nickel hydroxide as a main component is used. confirmed.

[0032]

According to the present invention, there is provided a non-sintered nickel electrode with a small decrease in the active material utilization after overdischarge.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mutsumi Yano 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kozo Nogami 2-5-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Ikuro Yonezu 2-5-5 Keihanhondori 2-chome, Moriguchi-shi, Osaka Prefecture (72) Inventor Koji Nishio 2 Keihanhondori, Moriguchi-shi, Osaka 5-5, Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. A non-sintered nickel electrode for an alkaline storage battery in which a cobalt compound powder is added to an active material powder comprising nickel hydroxide particles or solid solution particles containing nickel hydroxide as a main component. Non-sintering type for alkaline storage batteries, characterized in that at least one element selected from ruthenium, rhodium, palladium, iridium, boron, gallium and scandium is added in a form of a simple substance or a compound together with the powder of Nickel pole. 2. A non-sintered nickel electrode for an alkaline storage battery using, as an active material powder, a composite particle powder having a cobalt compound layer formed on the surface of nickel hydroxide particles or solid solution particles containing nickel hydroxide as a main component. In the alkaline storage battery, wherein at least one element selected from ruthenium, rhodium, palladium, iridium, boron, gallium, and scandium is added to the composite particle powder in the form of a simple substance or a compound. For non-sintered nickel electrode. (3) at least one element selected from ruthenium, rhodium, palladium, iridium, boron, gallium and scandium, in the form of a simple substance or a compound;
For 100 parts by weight of nickel hydroxide in the active material powder,
The non-sintered nickel electrode for an alkaline storage battery according to claim 1, wherein 0.05 to 5 parts by weight is added. 4. A solid solution particle comprising nickel hydroxide as a main component, wherein cobalt hydroxide, zinc, cadmium,
The non-sintered nickel electrode for an alkaline storage battery according to any one of claims 1 to 3, wherein at least one element selected from the group consisting of calcium, manganese, magnesium, bismuth, aluminum and yttrium is dissolved. 5. The method according to claim 1, wherein the cobalt compound is cobalt hydroxide or β.
-CoOOH or β-CoOOH by adding an aqueous solution of sodium hydroxide, in the presence of oxygen at 50 to 200 ° C.
The non-sintered nickel electrode for an alkaline storage battery according to any one of claims 1 to 4, which is a sodium-containing cobalt compound produced by a heat treatment.