JP3363670B2 - Non-sintered nickel electrode for alkaline storage battery, method for producing the same, and alkaline storage battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nickel electrode for an alkaline storage battery, and more particularly to a method for manufacturing a nickel electrode used in an alkaline storage battery such as a metal hydride storage battery or a nickel-cadmium storage battery.

[0002]

2. Description of the Related Art As a method for producing a nickel hydroxide electrode for an alkaline storage battery, a porous nickel sintered substrate as an active material holder is dipped in an acidic nickel salt impregnating solution such as nickel nitrate to form nickel salt in the holes of the substrate. After the impregnation with the nickel salt, the nickel salt is converted into nickel hydroxide in an alkali and the active material filling operation is repeated to produce a nickel hydroxide electrode. There is a non-sintering method in which a nickel hydroxide electrode is manufactured by mixing the binder with an aqueous solution in which the binder is dissolved and directly filling the foamed nickel as an active material slurry.

According to the method (1), the nickel sintered substrate cannot be filled with a desired active material unless it is repeated several times, because a sufficient amount of the active material cannot be obtained with one operation. Can not. In order to increase the filling efficiency of the active material and to simplify the manufacturing process, a high-temperature high-concentration nickel nitrate aqueous solution is used as the impregnation liquid, and the desired amount of active material is obtained with a small number of impregnations. There is a problem of severe corrosion. Also, to prevent the corrosion of the sintered substrate,
A method for producing oxidation resistant nickel oxide on the surface of a sintered substrate has been proposed, but nickel oxide has a problem that conductivity is poor and conductivity between the active material and the substrate is significantly impaired. . Therefore, in JP-A-63-216268, cobalt hydroxide is generated on the surface of a porous nickel sintered substrate for the purpose of preventing corrosion of the sintered substrate and improving the conductivity between the active material and the substrate. Then, it is disclosed that after the substrate is heat-treated in the presence of alkali and oxygen, the substrate is subjected to an active material filling operation involving impregnation with an acidic nickel salt. However, according to this method, even if the conductivity between the active material and the substrate is improved, the conductivity between the nickel hydroxide particles as the active material is not sufficiently improved. Further, the sintering method is complicated in terms of the method of manufacturing the substrate, filling of the active material, and the like. Further, in the sintering method, the porosity of the substrate is smaller than that in the non-sintering method, the amount of the active material filled is limited, and there is also a limit in increasing the capacity.

In the method (1), the utilization rate of nickel hydroxide is slightly lower than that in the sintering method, and it is effective to add high-order cobalt having high conductivity in order to improve the utilization rate. Therefore, in JP-A-1-200555, in order to improve the utilization rate of nickel hydroxide, cobalt hydroxide is formed on the surface of the active material made of nickel hydroxide, and heat treatment is performed in the presence of alkali. It is disclosed that a highly conductive high-order cobalt oxide such as CoOOH or Co ₂ O ₃ is formed on the surface of the nickel hydroxide active material.

[0005]

However, in the method described in JP-A-1-200555, although the utilization factor of the active material is improved, there is a problem that the capacity is remarkably reduced when it is over-discharged. It was

The present invention has been made in view of the above problems, and an object of the present invention is to improve the utilization rate of an active material and prevent a decrease in capacity when over-discharged.

[0007]

Means for Solving the Problems In order to solve the above problems, the present invention relates to the presence of oxygen and an alkali on the surface of nickel hydroxide particles to which one or more of zinc, cadmium, magnesium or calcium is added in a solid solution state. Heat treatment under
It is characterized in that it comprises an active material having a layer of a cobalt compound having a crystal structure in which the crystal structure is disordered and which is larger than divalent.

Further, a non-sintered nickel electrode having an active material having a layer of a cobalt compound having a disordered crystal structure and having a valence greater than 2 is formed on the surface of nickel hydroxide particles to which zinc or the like is added in a solid solution state. There are the following two methods for manufacturing.

A mixture of nickel hydroxide powder containing one or more of zinc, cadmium, magnesium or calcium added in a solid solution and metallic cobalt or a cobalt compound is heat treated in the presence of oxygen and an alkali to form an active material. It is characterized in that the active material is retained on the active material holder.

An aqueous solution adjusted to pH 8.0 to 12.0 by adding an aqueous solution of cobalt sulfate or cobalt nitrate to nickel hydroxide powder to which one or more kinds of zinc, cadmium, magnesium or calcium are added in a solid solution state. It is characterized in that after being neutralized in the medium, it is heat-treated in the presence of oxygen and an alkali to obtain an active material, and the active material is held by an active material holder.

Further, the alkaline storage battery of the present invention comprises zinc,
Oxygen is added to the surface of nickel hydroxide particles to which one or more of cadmium, magnesium or calcium is added in a solid solution state.
And a nickel electrode provided with an active material having a layer of a cobalt compound having a crystal structure disturbed by a heat treatment in the presence of an alkali and having a disordered crystal structure, and an alkaline electrolyte,
It is characterized by having a separator mainly composed of a non-woven fabric of polyolefin resin fiber and a negative electrode provided with an MmNi ₅ type hydrogen storage alloy.

[0012]

[Function] By forming a layer of a cobalt compound such as cobalt hydroxide on the surface of nickel hydroxide particles and performing heat treatment in the coexistence of oxygen and alkali, a higher order cobalt oxide layer having a crystal structure that is larger than divalent Are obtained on the surface of the nickel hydroxide particles. The higher order cobalt oxide layer having a disordered crystal structure larger than divalent has extremely high conductivity, and therefore the utilization factor of the active material is remarkably improved. Further, the higher cobalt oxide layer having one or more of zinc, cadmium, magnesium or calcium in a solid solution state in the nickel hydroxide and having a crystal structure disordered and having a higher degree than divalent nickel hydroxide particles is nickel hydroxide particles. When it is formed on the surface, it is possible to suppress a decrease in capacity when over-discharging while maintaining a high utilization rate.

As a method for producing an active material having a layer of a cobalt compound having a larger crystallographically disordered divalent compound on the surface of nickel hydroxide particles to which one or more kinds of zinc, cadmium, magnesium or calcium are added in a solid solution state Is a method of heat-treating a mixture of nickel hydroxide powder to which zinc or the like is added in a solid solution state and metallic cobalt or a cobalt compound in the presence of oxygen and an alkali. This method has a feature that the manufacturing method is easy because the powders are mixed together. In this method, the metal cobalt or cobalt compound is preferably mixed in an amount of 5 mol% or more and 14 mol% or less with respect to nickel hydroxide. This is required in order to sufficiently form the highly conductive high-order cobalt oxide layer on the surface of the nickel hydroxide particles, at least 5 mol% with respect to nickel hydroxide. Further, in order to minimize the influence on the capacity due to the decrease in the amount of nickel hydroxide, it is necessary to make it 14 mol% or less.

On the other hand, as another production method, an aqueous solution of cobalt sulfate or cobalt nitrate is added to nickel hydroxide powder containing one or more of zinc, cadmium, magnesium or calcium added in a solid solution state to obtain a pH of 8.0 to 8.0. 1
After neutralizing in an aqueous solution adjusted to 2.0, there is a method of heat treatment in the presence of oxygen and alkali. in this way,
Disordered crystal structure on the surface of the nickel hydroxide powder particles
It has the feature that it can coat a layer of cobalt compound, which is larger than the valence, more uniformly. Further, when the pH value of the aqueous solution at the time of neutralization becomes less than 8.0, the cobalt compound layer cannot be sufficiently formed on the surface of the nickel hydroxide particles, and
If the pH value exceeds 12.0, the cobalt compound layer cannot be uniformly coated on the surface of the nickel hydroxide particles, so that the utilization rate of the active material decreases. Therefore, the pH
It is necessary to neutralize in an aqueous solution adjusted to 8.0 to 12.0.

The alkali used when cobalt hydroxide is formed on the surface of nickel hydroxide particles and heat-treated in the coexistence of oxygen and alkali is converted into an alkali aqueous solution having a concentration of 15 to 40% by weight. Since the solubility is high and the viscosity of the alkaline solution is low, the permeability to the active material is good and the utilization rate of the active material is improved. Further, when lithium ions are contained in the alkali, the effect of suppressing the capacity decrease at the time of over-discharge is further enhanced.

In the heat treatment, the heating temperature is 50 to 15
When the temperature is 0 ° C., the solubility of cobalt hydroxide in alkali is large, and since nickel hydroxide does not change to nickel oxide which is not the active material, the utilization rate of the active material is further improved.

Zinc free of nickel hydroxide active material,
When one or more zinc compounds, cadmium or cadmium compounds are present, the oxygen generation potential during charging shifts to a noble value and the charge acceptability at high temperatures is improved.

[0018]

【Example】

<Experiment 1 (Overdischarge characteristics)> [Example 1] (Production of positive electrode) An aqueous solution of nickel sulfate, an aqueous solution of zinc sulfate of 2 mol% with respect to nickel sulfate, and an aqueous solution of sodium hydroxide were adjusted to pH with ammonia water. While adding gradually, nickel hydroxide powder containing 2 mol% of solid solution zinc was deposited.

Next, 2 mixed powders of nickel hydroxide powder to which zinc was added in a solid solution state of 2 mol% and cobalt hydroxide powder of 10 mol% with respect to the nickel hydroxide were prepared.
5% by weight aqueous sodium hydroxide solution was added, then
The active material a _{1 of the} present invention was produced by heating at 100 ° C. in air, washing with water and drying.

The active material a ₁ 100 produced in this way
50 parts by weight of an aqueous solution in which 0.2% by weight of methyl cellulose was dissolved was mixed with parts by weight to prepare a slurry liquid.
The slurry liquid is filled in a foam nickel having a porosity of 95% (thickness: about 1.6 mm), held, and dried. Then, it was rolled to prepare a nickel electrode A ₁ of the invention having a thickness of about 0.6 mm.

(Preparation of Negative Electrode) Alloy components of misch metal (Mm; mixture of rare earth elements), nickel, cobalt,
A predetermined amount of aluminum and manganese were weighed and mixed so that the respective addition ratios were 1: 3.6: 0.6: 0.2: 0.6. Then, this mixture is induction-heated and melted in a high-frequency induction furnace in an argon gas atmosphere, and then the alloy melt is cooled by a roll method to obtain Mm _1.0 Ni _3.6.
An ingot of hydrogen storage alloy represented by Co _0.6 Al _0.2 Mn _0.6 was produced. Next, this hydrogen storage alloy ingot was mechanically crushed to obtain a hydrogen storage alloy powder having an average particle diameter of about 100 μm.

Thereafter, a binder such as polyethylene oxide and an appropriate amount of water were added to the hydrogen storage alloy powder and mixed to prepare a hydrogen storage alloy paste. This hydrogen storage alloy paste was applied to punching metal and rolled to prepare a hydrogen storage alloy negative electrode having a thickness of about 0.4 mm.

(Preparation of Battery) Then, the nickel electrode A _{1 of the} present invention, the hydrogen storage alloy electrode, and the separator mainly composed of a nonwoven fabric of polyolefin resin fiber are cut into predetermined dimensions, respectively, and the nickel electrode and the hydrogen storage alloy electrode are cut. After winding and through the separator and inserting into the battery case, inject alkaline electrolyte to obtain a nominal capacity of 1200mA.
A nickel-hydrogen storage battery (A ₁ ) of H was produced.

The battery of the present invention (A ₂ ) was prepared in the same manner as in Example 1 except that the aqueous zinc sulfate solution in Example 1 was replaced with an aqueous cadmium sulfate solution and 2 mol% of cadmium was added to nickel hydroxide powder as a solid solution. Was produced.

The battery of the present invention (A ₃ ) was prepared in the same manner as in Example 1 except that the zinc sulfate aqueous solution in Example 1 was replaced with a magnesium nitrate aqueous solution and magnesium was added to nickel hydroxide powder in a solid solution state of 2 mol%. Was produced.

The battery of the present invention (A ₄ ) was prepared in the same manner as in Example 1 except that the aqueous solution of zinc sulfate in Example 1 was replaced with an aqueous solution of calcium nitrate and calcium was added to nickel hydroxide powder in a solid solution state of 2 mol%. Was produced.

Instead of the 2 mol% zinc sulfate aqueous solution in Example 1, 1 mol% zinc sulfate aqueous solution and 1 mol%
A battery (A ₅ ) of the present invention was produced in the same manner as in Example 1 except that 1 mol% of zinc and 1 mol% of cadmium were added to the nickel hydroxide powder in a solid solution using the aqueous cadmium sulfate solution.

Instead of 10 mol% of cobalt hydroxide in Example 1, 10 mol% of nickel hydroxide was used.
A battery (A ₆ ) of the present invention was produced in the same manner as in Example 1 except that the metal cobalt powder of 1 was mixed.

The mixed powder of nickel hydroxide powder and cobalt hydroxide powder was replaced with the 25 wt% sodium hydroxide aqueous solution in Example 1, and the same molar number as the 25 wt% sodium hydroxide aqueous solution was used. Example 1 except that a mixed solution of sodium and lithium hydroxide (molar ratio of sodium hydroxide and lithium hydroxide was 9: 1) was added.
A battery (A ₇ ) of the present invention was produced in the same manner as in.

[Example 2] A 2 mol% zinc sulfate aqueous solution and a sodium hydroxide aqueous solution were gradually added to nickel sulfate while adjusting the pH with ammonia water to form a 2 mol% solid solution of zinc. The nickel hydroxide powder added in the state was deposited.

Next, an aqueous solution of cobalt sulfate and an aqueous solution of sodium hydroxide were added to nickel hydroxide powder to which zinc was added in a solid solution state of 2 mol%, and the addition amount was adjusted.
In an alkaline aqueous solution maintained at a pH of 10, the surface of the particles of the nickel hydroxide powder is 10 m against the nickel hydroxide.
Cobalt compound layer of ol% was coated. Then, the nickel hydroxide powder coated with a cobalt compound layer on its surface was added with a 25 wt% sodium hydroxide aqueous solution, and then heat-treated in air at 100 ° C., washed with water and dried to obtain the active material b of the present invention. ₁ was produced. Other than the above, a battery (B ₁ ) of the present invention was produced in the same manner as in Example 1.

The same procedure as in Example 2 was repeated except that the zinc sulfate aqueous solution in Example 2 was replaced with a cadmium sulfate aqueous solution, and nickel hydroxide powder was added to the nickel hydroxide powder in a 2 mol% solid solution state. A battery (B ₂ ) of the present invention was produced.

The same procedure as in Example 2 was repeated except that the aqueous solution of zinc sulfate in Example 2 was replaced with an aqueous solution of magnesium nitrate, and nickel hydroxide powder was used in which 2 mol% of magnesium hydroxide was added in a solid solution state. The battery of the present invention (B ₃ ) was produced.

The same procedure as in Example 2 was repeated except that the aqueous zinc sulfate solution in Example 2 was replaced with an aqueous calcium nitrate solution, and nickel hydroxide powder was used in which 2 mol% of calcium was added in a solid solution state to nickel hydroxide powder. A battery of the present invention (B ₄ ) was produced.

The 2 mol% zinc sulfate aqueous solution in Example 2 was replaced with a 1 mol% zinc sulfate aqueous solution and a 1 mol% cadmium sulfate aqueous solution, and 1 mol% zinc and 1 mol% cadmium were added in solid solution to nickel hydroxide powder. Example 2 except that nickel hydroxide powder was used
A battery of the present invention (B ₅ ) was produced in the same manner as in.

Comparative Example A comparative battery (C ₁ ) was prepared in the same manner as in Example 1, except that zinc sulfate or the like was not added to nickel sulfate.

A comparative battery (C ₆ ) was prepared in the same manner as in Example 1 except that 2% by weight of zinc oxide was added to nickel sulfate in a free state. .

A comparative battery (D ₁ ) was prepared in the same manner as in Example 2, except that zinc sulfate or the like was not added to nickel sulfate.

A comparative battery (D ₆ ) was prepared in the same manner as in Example 2, except that 2% by weight of zinc oxide was added in a free state to nickel sulfate. .

The batteries of the present invention (A ₁ ) to (A ₇ ),
(B ₁ ) to (B ₅ ) and comparative batteries (C ₁ ), (C ₆ ), (D
_{For 1} ) and (D ₆ ), the discharge capacity at the first cycle and the discharge capacity at the fifth cycle when over-discharging was performed for five cycles were measured, and the discharge capacity at the fifth cycle with respect to the discharge capacity at the first cycle was measured. Was calculated and the results are shown in Table 1. The test conditions at this time were 1 C current (1200 m
Charging is performed in A), the charging is stopped when the value of −ΔV (voltage drop amount after the charging voltage reaches the maximum value) of 10 mV is detected, the charging is stopped for 1 hour, and then the discharging is performed with a current of 1C. The discharge was stopped when the discharge cutoff voltage reached 1V.

Regarding over-discharge, after the charge and discharge,
Further, it was carried out under the condition that it was forcibly discharged at a current of 0.05 C (60 mA) for 16 hours.

[0042]

[Table 1]

As is clear from Table 1, the battery of the present invention (A
_{1) ~ (A 7),} (B 1) ~ (B 5) is zinc in the nickel hydroxide active material, cadmium, comparative battery without added any magnesium or calcium _{(C 1), (D 1} ) And comparative batteries with zinc added in the free state (C ₆ ), (D ₆ ).
Compared with the above, it was possible to suppress the decrease in capacity when over-discharged.

Further, in the battery (A ₇ ) of the present invention using an alkali containing lithium ions, it was possible to suppress the decrease in capacity when further discharged. From the above, it is important to add zinc, cadmium, magnesium or calcium in a solid solution state to the nickel active material. It can be seen that the addition of an alkaline solution containing lithium ions and heat treatment can further suppress the decrease in capacity when overdischarged. <Experiment 2 (Measurement of Utilization Rate of Active Material)> When the nickel hydroxide electrode of Example 1 was prepared, a mixed powder of nickel hydroxide powder and 10 mol% of cobalt hydroxide was hydrated. Comparative electrode C ₂ was prepared in the same manner except that the aqueous sodium solution was not added, that is, the heating treatment was performed in the air at 100 ° C. in the absence of alkali.

When the nickel hydroxide electrode of Example 1 was prepared, the same procedure was followed except that a mixed powder of nickel hydroxide powder and 10 mol% of cobalt hydroxide with respect to the nickel hydroxide was oxidized with H ₂ O _2. A comparative electrode C ₃ was produced.

In preparing the nickel hydroxide electrode of Example 1, cobalt hydroxide alone was added to a 25% by weight aqueous solution of sodium hydroxide, and then heat treated in air at 100 ° C. to mix with nickel hydroxide. A comparative electrode C ₄ was prepared in the same manner except for the above.

In producing the nickel hydroxide active material of Example 1, an aqueous sodium hydroxide solution was not added to the mixed powder of nickel hydroxide powder and 10 mol% of cobalt hydroxide with respect to the nickel hydroxide, and A comparative electrode C ₅ was prepared in the same manner except that it was not heat-treated in air.

When the nickel hydroxide active material of Example 2 was prepared, an aqueous solution of cobalt sulfate and an aqueous solution of sodium hydroxide were added to nickel hydroxide powder to form a cobalt hydroxide layer on the surface of nickel hydroxide. Comparative electrode D ₂ was prepared in the same manner except that the aqueous sodium hydroxide solution was not added to and the heat treatment was not performed in air.

The utilization ratio of the active material was measured for the electrodes A ₁ and B _{1 of the} present invention and the reference electrodes C ₂ , C ₃ , C ₄ , C ₅ and D ₂ and the results are shown in Table 2.

As a test method at this time, using a Ni plate as a counter electrode, charging was performed for 24 hours at a charging current of 0.1 C (120 mA) in a potassium hydroxide solution of about 25% by weight of an open system, and 1/3 C was used. Discharge was performed at a current of (400 mA), and the discharge was stopped when the discharge cutoff voltage for the Ni plate reached −0.8V.

[0051]

[Table 2]

As is apparent from Table 2, the electrodes A ₁ and B ₁ of the present invention are the reference electrodes C ₂ and H ₂ O ₂ which are oxidized only in air.
The utilization efficiency is remarkably higher than that of the reference electrode C ₃ oxidized with an oxidizing agent such as C, the reference electrode C ₄ obtained by alone oxidizing cobalt hydroxide, and the reference electrodes C ₅ and D ₂ not oxidized at all. Recognize. In addition, the comparison electrodes C ₂ , C ₃ , C ₄
Has a low utilization rate as compared with the non-oxidized reference electrodes C ₅ and D ₂ . It can be said that when oxidized in the absence of an alkali, a high-order cobalt oxide layer having a poor conductivity, which is higher than divalent, is generated, which rather lowers the utilization rate.

From the above, it is important to heat-treat nickel hydroxide having a cobalt hydroxide layer formed on the surface thereof in the presence of oxygen and alkali.

FIG. 1 shows the results of X-ray diffraction analysis of cobalt hydroxide which was heat-treated in the presence of oxygen and alkali and those which were not treated at all.

Here, FIG. 1A shows cobalt hydroxide,
It shows the X-ray diffraction of the material that was heat-treated in the coexistence of oxygen and alkali.

Further, FIG. 1 (b) shows X-ray diffraction of cobalt hydroxide which was not subjected to any heat treatment in the coexistence of oxygen and alkali.

As is clear from FIG. 1, the X-ray diffraction peak of (a) almost disappears from the X-ray diffraction peak of (b). In particular, the disappearance of X-ray diffraction peaks near 19 degrees and 38 degrees is remarkable.

From this, it is understood that the crystal structure of cobalt oxide is disturbed by the heat treatment in the presence of oxygen and alkali.

<Experiment 3 (capacity measurement per unit amount of active material)
In the preparation of the nickel hydroxide active material in Example 1, the capacity of the nickel hydroxide active material per unit amount of active material was prepared by mixing the nickel hydroxide powder with various amounts of cobalt hydroxide powder mixed. The results are shown in Table 3 and FIG.

The test method at this time was the same as in Experiment 2.

[0061]

[Table 3]

As is clear from Table 3 and FIG. 2, when nickel hydroxide powder and cobalt hydroxide powder were mixed as in the manufacturing method of Example 1, the amount of cobalt hydroxide added was nickel hydroxide. On the other hand, it is preferably 5 to 14 mol%. This is because if the amount of cobalt hydroxide is less than 5 mol% with respect to nickel hydroxide, the amount of cobalt hydroxide is too small to form a highly conductive high-order cobalt oxide layer. Further, it is considered that in the range of more than 14 mol%, the decrease in the amount of nickel hydroxide as the active material has a larger effect on the capacity than the effect of the heat treatment in the coexistence of oxygen and alkali.

In addition, in the preparation of the nickel hydroxide active material in Example 2, the capacity measurement results per unit active material amount of the nickel hydroxide active material prepared by changing the addition amount of the cobalt sulfate aqueous solution are shown in Table 4. And shown in FIG.

The test method at this time was the same as in Experiment 2.

[0065]

[Table 4]

As is clear from Table 4 and FIG. 3, when the aqueous solution of cobalt sulfate and the alkaline solution were added to the nickel hydroxide powder as in the production method of Example 2, the amount of cobalt hydroxide added was 3 to 1 for nickel hydroxide
It is preferably 4 mol%. This is 3 mol%
If it is less than 1, the formation of the highly conductive cobalt oxide layer is insufficient due to the small amount of cobalt compound.
Further, it is considered that in the range of more than 14 mol%, the decrease in the amount of nickel hydroxide as the active material has a greater effect on the capacity than the effect of the heat treatment in the coexistence of oxygen and alkali. <Experiment 4 (Relationship between Alkali Concentration and Utilization Rate)> In the production of the nickel electrode in Example 1, a mixed powder of nickel hydroxide powder and cobalt hydroxide powder was added with an aqueous sodium hydroxide solution of various concentrations and heated. Table 5 and FIG. 4 show the values of the utilization rates of the nickel hydroxide electrodes produced by the treatment.

The test method at this time was the same as the test method of Experiment 2.

[0068]

[Table 5]

As is clear from Table 5 and FIG. 4, the concentration range of the alkaline aqueous solution is preferably 15 to 40% by weight.

It is considered that when the sodium hydroxide concentration was less than 15% by weight, the solubility of cobalt hydroxide was low and no effect was observed.

The sodium hydroxide concentration is 40% by weight.
It is considered that when the value exceeds the above range, the viscosity of the aqueous sodium hydroxide solution becomes high, so that the permeability to the active material is lowered and the effect is not recognized.

Further, in the preparation of the nickel electrode in Example 2, a nickel compound powder was coated with a cobalt compound layer by adding an aqueous solution of a cobalt sulfate salt and an aqueous solution of sodium hydroxide to the nickel hydroxide powder. Table 6 and FIG. 5 show the values of the utilization rates of nickel hydroxide electrodes prepared by adding various concentrations of aqueous sodium hydroxide solution and heat treatment.

The test method at this time was the same as the test method of Experiment 2.

[0074]

[Table 6]

As is clear from Table 6 and FIG. 5, the concentration range of the alkaline aqueous solution is preferably 15 to 40% by weight.

It is considered that when the sodium hydroxide concentration was less than 15% by weight, the solubility of cobalt hydroxide was low and no effect was observed.

The sodium hydroxide concentration is 40% by weight.
It is considered that when the value exceeds the above range, the viscosity of the aqueous sodium hydroxide solution becomes high, so that the permeability to the active material is lowered and the effect is not recognized.

With respect to the alkaline species, the same effect was observed with an aqueous solution of potassium hydroxide. In addition, LiO in an aqueous solution of sodium hydroxide or potassium hydroxide
Similar effects were observed even if H was contained. <Experiment 5 (Relationship between heating temperature and utilization rate)> In the production of the nickel electrode in Example 1, a mixed hydroxide of nickel hydroxide powder and cobalt hydroxide powder was heat-treated at various temperatures to produce a hydroxide. The values of the utilization rate of the nickel electrode are shown in Table 7 and FIG. All other conditions were the same as in Example 1.

The test method at this time was the same as in Experiment 2.

[0080]

[Table 7]

As is clear from Table 7 and FIG. 6, the heating temperature is preferably in the range of 50 ° C to 150 ° C.

When the heating temperature is less than 50 ° C.,
It is considered that the solubility of cobalt hydroxide in alkali was low and no effect was observed. Also, the heating temperature is 150 ℃
It is considered that when the content exceeds the range, the crystal structure of nickel hydroxide itself also changes, and the utilization rate is lowered.

Further, in the preparation of the nickel electrode in Example 2, the nickel hydroxide surface was coated with a cobalt compound layer by adding an aqueous solution of cobalt sulfate and an aqueous solution of sodium hydroxide to the nickel hydroxide powder. Table 8 and FIG. 7 show the values of the utilization rate produced by heat-treating the above. All other conditions were the same as in Example 2.

The test method at this time was the same as the test method of Experiment 2.

[0085]

[Table 8]

As is clear from Table 8 and FIG. 7, the heating temperature is preferably in the range of 50 ° C to 150 ° C.

When the heating temperature is less than 50 ° C.,
It is considered that the solubility of cobalt hydroxide in alkali was low and no effect was observed. Also, the heating temperature is 150 ℃
It is considered that when the content exceeds the range, the crystal structure of nickel hydroxide itself also changes, and the utilization rate is lowered. <Experiment 6 (Charging temperature characteristics at high temperature)> In place of 100 parts by weight of the active material a ₁ in the production of the positive electrode of Example 1, 4 parts by weight of zinc oxide was added to 100 parts by weight of the active material a _1. A battery (A ₈ ) of the present invention was produced in the same manner as in Example 1.

The 2 mol% zinc sulfate aqueous solution in Example 1 was replaced with a 6 mol% zinc sulfate aqueous solution, and zinc was added to the nickel hydroxide powder in a 6 mol% solid solution state, that is, in the battery (A ₈ ) of the present invention. A battery (A ₉ ) of the present invention was produced in the same manner as in Example 1 except that the amount of zinc contained in the positive electrode was the same.

Battery of the present invention (A ₈ ) and battery of the present invention (A ₉ ).
Then, the discharge capacity at the time of charging at 40 ° C. and 60 ° C. was measured, and the ratio to the discharge capacity at the time of charging at 25 ° C. was obtained. The results are shown in Table 9. The discharge capacity when charged at 25 ° C. was set to 100%.

The test conditions at this time were as follows: charging was performed at 25 ° C., 40 ° C. and 60 ° C. with a current of 0.1 C (120 mA) for 16 hours, and after resting at 25 ° C. for 3 hours, 1 C (12
Discharging was performed with a current of 00 mA), and the discharge was terminated when the discharge termination voltage reached 1V.

[0091]

[Table 9]

In place of 100 parts by weight of the active material b ₁ in the production of the positive electrode of Example 2, 4 parts by weight of 100 parts by weight of the active material b ₁ were used.
A battery (B ₆ ) of the present invention was produced in the same manner as in Example 2 except that zinc oxide in an amount of part by weight was added.

The 2 mol% zinc sulfate aqueous solution in Example 2 was replaced with a 6 mol% zinc sulfate aqueous solution, and zinc was added to the nickel hydroxide powder in a 6 mol% solid solution state, that is, in the battery (B ₆ ) of the present invention. A battery (B ₇ ) of the present invention was produced in the same manner as in Example 1 except that the amount of zinc contained in the positive electrode was the same.

Battery of the present invention (B ₆ ) and battery of the present invention (B ₇ ).
Was measured for the discharge capacity at the time of charging at 40 ° C. and 60 ° C., and the ratio to the discharge capacity at the time of charging at 25 ° C. was obtained. The results are shown in Table 10. 25
The discharge capacity when charged at 100C was set to 100%.

The test condition at this time is 25 as in the above.
0.1C current at 120 ℃, 40 ℃ and 60 ℃ (120m
The battery was charged in A) for 16 hours, rested at 25 ° C. for 3 hours, then discharged at a current of 1 C (1200 mA), and stopped when the discharge cutoff voltage reached 1V.

[0096]

[Table 10]

As is clear from Tables 9 and 10, the batteries (A ₈ ) and (B ₆ ) of the present invention have improved charging temperature characteristics at higher temperatures than the batteries (A ₉ ) and (B ₇ ) of the present invention. . This is considered to be because the presence of nickel hydroxide and zinc oxide in a free state caused the oxygen generation potential during charging to shift to a noble level, thus improving charge acceptability at high temperatures.

The same effect was obtained by holding at least one of zinc, a zinc compound, cadmium, and a cadmium compound, in addition to holding only zinc oxide in a free state. <Experiment 7 (Relationship between pH and Utilization Rate)> In the production of the nickel electrode in Example 2, the utilization rate of nickel hydroxide powder when the pH values of the aqueous solution of cobalt sulfate and the aqueous solution of sodium hydroxide were variously changed. The values are shown in Table 11 and FIG. All other conditions were the same as in Example 2.

The test method at this time was the same as in Experiment 2.

[0100]

[Table 11]

As is clear from Table 11 and FIG.
The value of is preferably in the range of 8 to 12.0. It does not form as a complete cobalt compound at pH below 8.

If the pH exceeds 12.0, the surface of nickel hydroxide cannot be uniformly coated.

In this example, after forming a cobalt hydroxide layer on the surface of nickel hydroxide powder in which zinc or the like is solid-dissolved, an aqueous sodium hydroxide solution is added and heat treatment is performed in air. It should not be limited to this, and the same effect was observed by spraying an aqueous sodium hydroxide solution in a mist state and heating it in the air.

Although the sodium hydroxide aqueous solution is used in this embodiment, an alkali such as potassium hydroxide aqueous solution may be used.

[0105]

As described above, according to the present invention,
A high capacity and a high utilization rate per unit weight of the active material can be obtained, and since the capacity decrease upon overdischarge can be suppressed, the alkaline storage battery provided with the electrode of the present invention has a large capacity and excellent stability. And its industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of an active material of the present invention and a comparative active material.

FIG. 2 is a graph showing the relationship between the capacity per unit amount of active material and the cobalt hydroxide concentration in Example 1.

FIG. 3 is a relationship diagram of the capacity per unit active material amount and the cobalt hydroxide concentration in Example 2.

FIG. 4 is a relationship diagram between the concentration of sodium hydroxide aqueous solution and the utilization rate in the method for producing a nickel electrode of Example 1.

FIG. 5 is a relationship diagram between sodium hydroxide aqueous solution concentration and utilization rate in the method for manufacturing a nickel electrode of Example 2.

FIG. 6 is a relationship diagram between a heating temperature and a utilization rate in the manufacturing method of the nickel electrode of Example 1.

FIG. 7 is a relationship diagram between a heating temperature and a utilization rate in the method for manufacturing a nickel electrode of Example 2.

FIG. 8 is a relationship diagram between the pH value and the utilization rate of the aqueous sodium hydroxide solution in the method for producing a nickel electrode of Example 2.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshitaka Baba 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP-A-1-200555 (JP, A) JP HEI 6-140036 (JP, A) JP HEI 3-78965 (JP, A) HEI 2-109261 (JP, A) HEI 5-21064 (JP, A) JP-B HEI 6-38336 (JP , B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/24-4/52

Claims (13)

(57) [Claims] 1. The surface of nickel hydroxide particles to which one or more kinds of zinc, cadmium, magnesium or calcium are added in a solid solution state is heat treated in the presence of oxygen and alkali.
A non-sintered nickel electrode for an alkaline storage battery, comprising an active material having a layer of a cobalt compound having a crystal structure in which the crystal structure is disordered and which is larger than divalent. 2. A mixture of nickel hydroxide powder to which one or more of zinc, cadmium, magnesium or calcium is added in a solid solution and metallic cobalt or cobalt compound powder is heat treated in the presence of oxygen and alkali. A method for producing a non-sintered nickel electrode for an alkaline storage battery, which comprises obtaining an active material and holding the active material on an active material holder. 3. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 2, wherein the metallic cobalt or cobalt compound is 5 to 14 mol% with respect to nickel hydroxide. 4. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 2, wherein the alkali is an alkaline solution having a concentration of 15 to 40% by weight. 5. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 2, wherein the alkali contains lithium ions. 6. The temperature during the heat treatment is 50 to 150.
The temperature is in ° C. The method for manufacturing a non-sintered nickel electrode for an alkaline storage battery according to claim 2. 7. The non-sintering type for alkaline storage batteries according to claim 2, wherein the active material holder holds the active material and one or more of zinc, a zinc compound, cadmium or a cadmium compound. Manufacturing method of nickel electrode. 8. Nickel hydroxide powder prepared by adding one or more of zinc, cadmium, magnesium or calcium in a solid solution state is added to an aqueous solution of cobalt sulfate or cobalt nitrate, and pH is 8.0 to 12.0. Non-sintered type for alkaline storage batteries, characterized in that after being neutralized in an aqueous solution adjusted to, heat treatment is carried out in the coexistence of oxygen and alkali to obtain an active material, and the active material is held by an active material holder. Manufacturing method of nickel electrode. 9. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 8, wherein the cobalt salt is 3 to 14 mol% with respect to nickel hydroxide. 10. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 8, wherein the alkali is an alkaline solution having a concentration of 15 to 40% by weight. 11. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 8, wherein the heating temperature is 50 to 150 ° C. 12. The active material-supporting body, the active material,
The method for producing a non-sintered nickel electrode for an alkaline storage battery according to claim 8, wherein one or more of zinc, a zinc compound, cadmium or a cadmium compound is held. 13. The surface of nickel hydroxide particles to which one or more kinds of zinc, cadmium, magnesium or calcium are added in a solid solution state is heat treated in the presence of oxygen and alkali.
A nickel electrode having an active material having a layer of a cobalt compound having a disordered crystal structure larger than that of a divalent compound obtained by an alkaline electrolyte, a separator mainly composed of a non-woven fabric of a polyolefin resin fiber, and an MmNi ₅ system An alkaline storage battery comprising: a negative electrode having a hydrogen storage alloy.