JPH09259878A - Non-sintered nickel electrode for alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Ni electrode improved in utilizing efficiency of active material by using a power formed of a composite particle constituted by forming a conductive layer formed of a specified Li-contained Co compound on the surface of nickel hydroxide particle as the active material. SOLUTION: A powder formed of a composite particle constituted by forming a conductive layer formed of a Li-contained Co compound in which the ratio of Li weight calculated in terms of atom is 0.1-10wt.% to the total weight of the Li-contained Co compound on the surface of nickel hydroxide particle or particle mainly composed of nickel hydroxide. This powder is preferably formed by heating a powder formed of the composite particle constituted by forming a Co compound (e.g. cobalt hydroxide) on the surface of nickel hydroxide or a particle mainly composed of nickel hydroxide particle at 50-200 deg.C in the state where an aqueous solution of lithium hydroxide is added thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintered nickel electrode used in alkaline storage batteries such as nickel-hydrogen storage batteries and nickel-cadmium storage batteries. The present invention relates to improvement of active material powder for the purpose of providing a nickel electrode.

[0002]

2. Description of the Related Art Conventionally, as a nickel electrode of an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, a sintered substrate obtained by sintering nickel powder on a perforated steel plate is impregnated with an active material (nickel hydroxide). Sintered nickel electrodes formed by this method are well known.

[0003] In order to increase the packing density of the active material in the sintered nickel electrode, it is necessary to use a sintered substrate having a high porosity. However, the bond between the nickel particles due to sintering is weak, and if the porosity of the sintered substrate is increased, the nickel powder will easily fall off from the sintered substrate. Therefore, practically, the porosity of the sintered substrate cannot be made higher than 80%, and therefore, the sintered nickel electrode has a problem that the filling amount of the active material is small. In addition, since the pore size of a sintered body of nickel powder is generally as small as 10 μm or less, it is necessary to fill the substrate (sintered body) with the active material by a solution impregnation method in which a complicated impregnation step is repeated several times. There is also a problem.

Under these circumstances, a non-sintered nickel electrode has recently been proposed. A non-sintered nickel electrode is a substrate with a high porosity (paste metal plated with alkali-resistant metal, etc.) that is a kneaded material (paste) of an active material (nickel hydroxide) and a binder solution (methyl cellulose solution, etc.). It is made by directly filling the. In the non-sintered nickel electrode, since a substrate having a high porosity can be used (a substrate having a porosity of 95% or more can be used), the packing density of the active material can be increased and the active material can be increased. It becomes possible to easily fill the substrate with.

However, in a non-sintered nickel electrode, when a substrate having a high porosity is used to increase the packing density of the active material, the current collecting ability of the substrate becomes worse than that of the sintered nickel electrode. , The active material utilization rate decreases.

Therefore, in order to improve the conductivity of the non-sintered nickel electrode, a powder composed of composite particles obtained by coating the surface of nickel hydroxide particles with cobalt hydroxide may be used as the active material powder (Japanese Patent Laid-Open No. 62-62-62). No. 234867), a powder composed of composite particles in which the surface of particles containing nickel hydroxide as a main component is coated with cobalt oxyhydroxide may be used.
3-78965).

However, as a result of a study by the present inventors,
Even with these improvements, it was found that it is difficult to obtain a non-sintered nickel electrode having a sufficiently high utilization rate of the active material.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a non-sintered nickel electrode for an alkaline storage battery having a high utilization ratio of an active material. To provide.

[0009]

In order to achieve the above object, the non-sintered nickel electrode for alkaline storage batteries of the present invention comprises:
A powder composed of composite particles formed by forming a conductive layer composed of a lithium-containing cobalt compound on the surface of nickel hydroxide particles or particles containing nickel hydroxide as a main component, wherein the lithium is used as the active material. In the contained cobalt compound, the ratio of the lithium weight converted into atoms, that is, the lithium content is 0.1 wt% to 10 wt% with respect to the total weight of the lithium-containing cobalt compound.

If the lithium content is out of this range, a conductive agent having a sufficiently high conductivity cannot be obtained. The lithium content is calculated by the following formula.

Lithium content (% by weight) = (weight of lithium in terms of atom / total weight of lithium-containing cobalt compound) × 100 As particles having nickel hydroxide as a main component, cobalt, zinc, cadmium, calcium Examples thereof include those in which an element having an action of suppressing expansion of the nickel electrode such as manganese and magnesium is dissolved in nickel hydroxide.

Although the chemical structure of the lithium-containing cobalt compound constituting the conductive layer is not clear at present, since the active material of the present invention has extremely high conductivity,
It is speculated that this is not a simple mixture of a cobalt compound (cobalt oxyhydroxide, etc.) and lithium, but an intercalation compound in which lithium is incorporated into the crystal of the cobalt compound.

The active material powder according to the present invention is, for example, a powder composed of nickel hydroxide particles or composite particles formed by forming a cobalt compound layer on the surface of particles containing nickel hydroxide as a main component. It can be produced by heat treatment at 50 ° C. to 200 ° C. in a state where an aqueous lithium solution is added. The cobalt compound layer may be in the form of cobalt hydroxide or cobalt oxide,
For example, nickel hydroxide is added to a cobalt sulfate aqueous solution, a sodium hydroxide aqueous solution is added, and a cobalt compound is chemically deposited on the surface of the nickel hydroxide particles. The cobalt compound layer can also be formed on the surface of nickel hydroxide particles by a mechanical charge method in which nickel hydroxide powder is kneaded with cobalt oxide, cobalt hydroxide or metallic cobalt. Instead of the powder composed of the composite particles, a powder composed of nickel hydroxide particles or particles containing nickel hydroxide as a main component, and a mixed powder such as cobalt hydroxide powder, cobalt monoxide powder or metal cobalt powder is used. However, since the conductive layer (coating) is not easily formed by this method, the former is preferable.

In the present invention, the heat treatment temperature is 50.degree.
It is regulated at 200 ℃. This is because if the heat treatment temperature is out of this range, it becomes difficult to form a conductive layer having high conductivity. This is considered due to the following reasons.

That is, the conductive layer in the present invention is formed by the following reaction route when, for example, cobalt hydroxide is used as a starting material.

[0016]

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However, when the heat treatment temperature is lower than 50 ° C., the reaction from CoHO ₂ to the Li-containing cobalt compound is difficult to proceed sufficiently, so that a large amount of CoHO ₂ having low conductivity is produced. On the other hand, when the heating temperature exceeds 200 ° C., a large amount of tricobalt tetroxide (Co ₃ O ₄ ) having low conductivity is generated. It is considered that these are the reasons why it becomes difficult to form a conductive layer having high conductivity when the heat treatment temperature deviates from 50 ° C to 200 ° C.

The heat treatment time varies depending on the amount and concentration of the lithium hydroxide aqueous solution, the heat treatment temperature, etc., but is generally 0.5 to 10 hours.

The lithium content of the lithium-containing cobalt compound is regulated to 0.1% by weight to 10% by weight. If the lithium content is out of this range, a conductive layer having a sufficiently high conductivity cannot be formed, and it becomes impossible to obtain a non-sintered nickel electrode having an extremely high utilization ratio of the active material.

The composite particles composing the active material powder according to the present invention include the lithium-containing cobalt compound in the composite particles, based on the weight of the nickel hydroxide particles or the particles containing nickel hydroxide as the main component. 1% by weight based on the weight of cobalt atom converted from cobalt of
It is characterized by containing 10% by weight. In this specification, this value is the content of the lithium-containing cobalt compound. This value was calculated as follows.

Content of lithium-containing cobalt compound (% by weight) = (weight of cobalt converted to atoms in lithium-containing cobalt compound / weight of nickel hydroxide particles or particles having nickel hydroxide as a main component) × 100 When the content of the lithium-containing cobalt compound is less than 1% by weight, the conductivity of the active material powder is not sufficiently improved, and thus a sufficient electrode capacity cannot be obtained. On the other hand, the same content
If the amount exceeds 10% by weight, the amount of nickel hydroxide as the active material decreases, so that sufficient electrode capacity cannot be obtained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limited to the following Examples, and is appropriately modified and implemented within the scope not changing the gist thereof. Is possible. (Preliminary Experiment 1) Cobalt hydroxide and 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt% lithium hydroxide aqueous solution, The mixture was mixed at a weight ratio of 1:10 and heat-treated at 80 ° C. for 8 hours. After the heat treatment, it was washed with water and dried at 60 ° C. to prepare a lithium-containing cobalt compound. When the lithium content of this lithium-containing cobalt compound was analyzed by atomic absorption spectrometry, it was 0.05% by weight, 0.1% by weight, 0.5% by weight, 1% by weight, 5% by weight, 10% by weight, 12% by weight, 15% by weight in order. Met. The lithium content of the lithium-containing cobalt compound shown below is
It is a value estimated from the concentration of the used lithium hydroxide aqueous solution based on the above analysis results. (Example 1) Aqueous solution in which 13.1 g of cobalt sulfate was dissolved in water
To 1000 ml, add 100 g of nickel hydroxide powder, and then add 1M sodium hydroxide aqueous solution dropwise while stirring until the pH of the solution becomes 11, then continue stirring, and when the pH of the solution drops slightly, add 1M water. An aqueous solution of sodium oxide was appropriately added dropwise to maintain the pH of the solution at 11, and the reaction was carried out for 1 hour. A pH-controlled glass electrode was used to monitor the pH.
Then, the precipitate was filtered off and washed with water to obtain a powder composed of composite particles obtained by coating the surface of nickel hydroxide with cobalt hydroxide. Then, this powder was mixed with a 4% by weight aqueous lithium hydroxide solution at a weight ratio of 1:10, heat-treated at 80 ° C. for 8 hours, washed with water, and dried at 60 ° C. to form nickel hydroxide particles on the surface. An active material powder composed of composite particles formed by forming a conductive layer composed of a lithium-containing cobalt compound was obtained. When the content of the lithium-containing cobalt compound in the composite particles was analyzed by an atomic absorption method, it was 5% by weight. The lithium content of this lithium-containing cobalt compound is 1% by weight (estimated value from preliminary experiment 1).

100 of the above active material powder (average particle size 10 μm)
By weight, 20 parts by weight of a 1% by weight methylcellulose aqueous solution as a binder was kneaded to prepare a paste. This paste was applied to a nickel-plated foam metal (porosity
A non-sintered nickel electrode A1 according to the present invention was produced by filling a porous substrate having 95% and an average pore diameter of 200 μm), drying and pressing. (Comparative Example 1) A powder composed of composite particles obtained by coating the surface of nickel hydroxide particles with cobalt hydroxide, which was obtained in the middle of the process for producing the active material powder of Example 1, was used as it was as the active material powder. A non-sintered nickel electrode (reference electrode) B1 was produced in the same manner as in Example 1 except that the above was used as.

The method adopted here is similar to the technique described in Japanese Patent Laid-Open No. 62-234867 which is a prior art. (Comparative Example 2) A powder composed of composite particles obtained by coating the surface of nickel hydroxide particles with cobalt hydroxide, obtained in the middle of the step of producing the active material powder of Example 1,
By reacting with 30 wt% hydrogen peroxide solution heated to ℃, cobalt hydroxide on the surface was oxidized and converted into β-CoOOH. A non-sintered nickel electrode (reference electrode) B2 was produced in the same manner as in Example 1 except that this powder was used as the active material powder.

The method adopted here is similar to the technique described in Japanese Patent Laid-Open No. 3-78965, which is a prior art. [Preparation of alkaline storage battery] The non-sintered nickel electrode (positive electrode) described above, a conventionally known paste type cadmium electrode (negative electrode) having a larger electrochemical capacity than this positive electrode, polyamide nonwoven fabric (separator), 30% by weight hydroxylated An AA size alkaline storage battery was produced using a potassium aqueous solution (alkali electrolyte solution), a metal battery can, a metal battery lid, and the like. <Non-sintered nickel electrode active material utilization rate> About 25% of the above alkaline storage battery was charged at 0.1C and 160%
10 cycles of charging and discharging with 1 C as a cycle of discharging to 1.0 V at 1 ° C. were performed to obtain the positive electrode active material utilization rate at the 10th cycle defined by the following formula.

Utilization rate of active material (%) = {discharge capacity (mAh) at 10th cycle / (amount of nickel hydroxide (g) × 288 (mAh /
g))} × 100 The results are shown in Table 1. The active material utilization rate in Table 1 is an index when the active material utilization rate of the non-sintered nickel electrode A1 is 100.

[0027]

[Table 1]

As shown in Table 1, the non-sintered nickel electrode A
1 has a higher active material utilization rate than the non-sintered nickel electrodes B1 and B2. <Relationship between lithium content of lithium-containing cobalt compound and utilization rate of active material> 1% by weight, 2% by weight, 3% by weight, 5% by weight, 6% by weight, 7% by weight as a lithium hydroxide aqueous solution at the time of heat treatment Alternatively, a lithium-containing cobalt compound was produced in the same manner as in Example 1 except that an 8 wt% lithium hydroxide aqueous solution was used. The lithium content of these lithium-containing compounds is 0.05 wt%, 0.1 wt%,
0.5% by weight, 5% by weight, 10% by weight, 12% by weight, 15% by weight
Met. Next, non-sintered nickel electrodes A to G were produced in the same manner as in Example 1 except that these lithium-containing cobalt compounds were used, respectively, and then alkaline storage batteries were produced.

The prepared alkaline storage battery was charged and discharged under the same conditions as above for 10 cycles, and the active material utilization rate of the non-sintered nickel electrode at the 10th cycle was determined to obtain the lithium content rate and the active material utilization rate. I investigated the relationship. The results are shown in Table 2 and FIG. FIG. 1 is a graph showing the relationship between the lithium content of the lithium-containing cobalt compound (conductive layer) and the active material. In FIG. 1, the horizontal axis represents the lithium content (% by weight) of the lithium-containing cobalt compound, and the vertical axis represents the utilization rate of the active material. Note that FIG. 1 also shows the results for the non-sintered nickel electrode A1 (lithium content 1% by weight) produced in the previous Example 1. The active material utilization rate on the vertical axis of FIG. 1 is relatively expressed by an index when the active material utilization rate of the non-sintered nickel electrode A1 is 100.

[0030]

[Table 2]

As shown in Table 2 and FIG. 1, it can be seen that when the lithium content of the lithium-containing cobalt compound is 0.1 to 10% by weight, a non-sintered nickel electrode having an extremely high utilization rate of the active material can be obtained. . <Relationship between Lithium-Containing Cobalt Content of Composite Particles and Active Material Utilization> In the same manner as in Example 1 except that the concentration of the cobalt sulfate aqueous solution was changed, the lithium-containing cobalt compound (conductive layer) was converted into cobalt atoms. 0.5% by weight, 1% by weight, 10% by weight, 12% by weight or 15% by weight of active material powder was prepared. Both powders have a lithium content of 1 in the lithium-containing cobalt compound.
Adjusted to wt%. Next, non-sintered nickel electrodes a to e were produced in the same manner as in Example 1 except that these active material powders were used, respectively, and then alkaline storage batteries were produced.

The alkaline storage battery thus prepared was subjected to 10 cycles of charge and discharge under the same conditions as those described above, and the active material utilization rate of the non-sintered nickel electrode at the 10th cycle was determined. The relationship between the rate and the active material utilization rate was investigated. The results are shown in Table 3. Table 3 also shows the results for the non-sintered nickel electrode A1 (content of lithium-containing cobalt compound: 5% by weight) produced in Example 1 above. The active material utilization rate in Table 3 is an index when the active material utilization rate of the non-sintered nickel electrode A1 is 100.

[0033]

[Table 3]

From Table 3, it can be seen that a non-sintered nickel electrode having a high utilization rate of the active material can be obtained when the content of the lithium-containing cobalt compound in the composite particles is 1% by weight or more.

FIG. 2 shows the relationship between the content of the lithium-containing cobalt compound in the composite particles and the battery capacity. In FIG. 2, the content rate (% by weight) of the lithium-containing cobalt compound is plotted on the horizontal axis, and the battery capacity is plotted on the vertical axis. The battery capacity in Fig. 2 is the battery capacity of the nickel-cadmium storage battery using the non-sintered nickel electrode A1.
It is expressed as an index relative to 100.

From FIG. 2, when the content of the lithium-containing cobalt compound in the composite particles exceeds 10% by weight, the amount of nickel hydroxide as the active material decreases, and the battery capacity sharply decreases. I understand. When the results of Table 3 and FIG. 2 are combined, in order to obtain a non-sintered nickel electrode having a high utilization rate of the active material and a large capacity, the content rate of the lithium-containing cobalt compound in the composite particles is 1% by weight. It can be seen that it is preferable to set the content to ˜10% by weight. (Experiment 3) The following experiment was conducted as a preliminary experiment 2. That is, cobalt hydroxide and a 4 wt% lithium hydroxide aqueous solution were mixed at a weight ratio of 1:10, and the mixture was mixed at 45 ° C, 50 ° C, 60 ° C, 10 ° C.
8 at 0 ℃, 150 ℃, 200 ℃, 220 ℃ or 250 ℃
Heat treatment was performed for a time. After the heat treatment, it was washed with water and dried at 60 ° C. to prepare a lithium-containing cobalt compound. When the lithium content of this lithium-containing cobalt compound was analyzed by an atomic absorption method, it was 0.01% by weight (45 ° C.), 1
Weight% (50 ° C), 1% by weight (60 ° C), 1% by weight (100 ° C), 1
% By weight (150 ° C), 1% by weight (200 ° C), 0.05% by weight (220
C) and 0.02% by weight (250 ° C).

The lithium content of the lithium-containing cobalt compound used below is a value estimated from the heat treatment temperature in the above analysis result.

By the way, in the production of the lithium-containing cobalt compound, the heat treatment temperature is 45 ° C., 50 ° C., 60 ° C., 10 ° C.
A lithium-containing cobalt compound was prepared in the same manner as in Experiment 1 except that the temperature was 0 ° C., 150 ° C., 200 ° C., 220 ° C. or 250 ° C., that is, a 4 wt% lithium hydroxide aqueous solution was used. The lithium content of these lithium-containing cobalt compounds was 0.01% by weight, 1% by weight, 1% by weight, 1% by weight, 1% by weight, 1% by weight, 0.05% by weight from the estimated value in the above preliminary experiment 2.
It will be 0.02% by weight. Then, in Experiment 1 except that these lithium-containing cobalt compounds were used respectively.
In the same manner as above, alkaline storage batteries T1 to T8 were sequentially manufactured.

Each of these alkaline storage batteries T1 to T8 was charged and discharged under the same conditions as in Experiment 1 for 10 cycles to obtain the active material utilization rate of the positive electrode at the 10th cycle, and to determine the heat treatment temperature and the active material utilization rate. I investigated the relationship. This result
As shown in FIG. FIG. 3 shows the relationship between the heat treatment temperature and the active material utilization rate when synthesizing a lithium-containing cobalt compound. In FIG. 3, the heat treatment temperature (° C.) is plotted on the horizontal axis, and the active material utilization rate is plotted on the vertical axis. It should be noted that FIG. 3 also shows the results for the alkaline storage battery A1 manufactured in Experiment 1 above. Further, the active material utilization rate on the vertical axis of FIG. 3 is relatively represented by an index when the active material utilization rate of the alkaline storage battery A1 is 100.

As shown in FIG. 3, alkaline storage batteries A1 and T
50 to 20 because the active material utilization rate of 2 to T6 is extremely high
It can be seen that the lithium-containing cobalt compound (conducting agent of the present invention) produced by heat treatment at 0 ° C. has extremely high electric conductivity.

[0041]

As described above, according to the present invention, it is possible to provide a non-sintered nickel electrode for an alkaline storage battery, which has a high utilization factor of an active material and a high conductivity, and which can provide a battery having a large battery capacity. The industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the lithium content of a lithium-containing cobalt compound (conductive layer) and the active material utilization rate.

FIG. 2 is a graph showing the relationship between the lithium-containing cobalt compound of the composite particles and the battery capacity.

FIG. 3 is a graph showing a relationship between a heat treatment temperature when synthesizing a lithium-containing cobalt compound and an active material utilization rate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kozo Nogami 2-5-5, Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. No. 5 Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. An alkaline storage battery using, as an active material, powder of composite particles formed by forming a conductive layer of a lithium-containing cobalt compound on the surface of nickel hydroxide particles or particles containing nickel hydroxide as a main component. A non-sintered nickel electrode for use in the lithium-containing cobalt compound, wherein the ratio of lithium weight converted to atoms is 0.1 wt% to 10 wt% with respect to the total weight of the lithium-containing cobalt compound. A non-sintered nickel electrode for alkaline storage batteries. 2. A powder composed of composite particles in which a cobalt compound layer is formed on the surface of nickel hydroxide particles or particles containing nickel hydroxide as a main component, and a lithium hydroxide aqueous solution is added thereto. 50 ℃ ~ 200 with added
The non-sintered nickel electrode for an alkaline storage battery according to claim 1, which is produced by heat treatment at ℃. 3. In the composite particles, the weight of cobalt in the lithium-containing cobalt compound is 1 weight of cobalt with respect to the weight of nickel hydroxide particles or particles containing nickel hydroxide as a main component. % To 10% by weight of the non-sintered nickel electrode for alkaline storage batteries according to claim 1.