JP3253476B2 - Non-sintered nickel electrode for alkaline storage batteries - Google Patents

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 as a positive electrode of an alkaline battery typified by a nickel-hydrogen storage battery and a nickel-cadmium storage battery, an active material used therefor, and a method for producing the same. It is about.

[0002]

2. Description of the Related Art Conventionally, as a nickel electrode for an alkaline battery, a so-called sintered electrode plate is used in which a substrate obtained by sintering nickel powder on a perforated steel plate as a core metal is impregnated with an active material. It has been known. In this electrode plate, the bonding between the nickel powders is weak, and when the substrate has a high porosity, the nickel powder falls off. Therefore, in practice, the porosity of the substrate is limited to about 80%. .

Further, since a core metal such as a perforated steel plate is required, the packing density of the active material is generally reduced. Furthermore, since the pores of the nickel powder formed by sintering are as small as 10 μm or less, there is a problem that the method of filling the active material is limited to a solution impregnation method in which complicated steps are repeated several times. .

[0004] As an attempt to improve these problems, for example, an alkali-resistant metal fiber sintered body without using a metal core, or a carbon fiber non-woven fabric or the like is plated with an alkali-resistant metal to obtain a conductive core. A so-called paste type electrode plate in which the active material powder is filled in a paste form has been developed. Even with this electrode plate, the utilization rate of the active material was lower than that of the sintered electrode plate, and there was a problem in practical use.

As a countermeasure against this, there is known a technique in which cobalt is present on the surface of an active material. In particular,
The cobalt compound is dissolved in the alkaline electrolyte to form divalent HCoO ²⁻ on the surface of the active material. As this changes into a conductive CoOOH compound at a noble potential,
The active material surface must be coated with a cobalt compound. For example, JP-A-62-234867 and JP-A-62-23
As disclosed in Japanese Patent No. 7667, a method of coating the surface of nickel hydroxide particles with cobalt hydroxide,
As disclosed in Japanese Unexamined Patent Publication, a method has been proposed in which the surface of nickel hydroxide particles is coated with a solid solution of nickel hydroxide and cobalt hydroxide.

However, in the nickel hydroxide particles as the active material produced by the above-described method, the cobalt coating the surface is diffused into the nickel hydroxide particles as the battery cycle progresses. . As a result, it is not possible to maintain the conductivity of the electrode surface, which is the effect of adding cobalt, over a long period of the cycle, and there is a problem that the capacity is reduced as the cycle proceeds.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is intended to suppress the diffusion of cobalt into nickel hydroxide particles, and to provide an effect of adding cobalt over a long period of the cycle. It is intended to propose an active material in which is exhibited.

It is another object of the present invention to provide a non-sintered nickel electrode for an alkaline battery using this active material, which has high performance, is stable and has high productivity. As a result, an alkaline storage battery having excellent cycle characteristics can be provided.

Furthermore, the present invention proposes such an active material and a method for producing a non-sintered nickel electrode using the same.

[0010]

According to the present invention, there is provided a non-sintered nickel electrode for an alkaline storage battery, wherein the nickel electrode comprises an active material comprising particles mainly composed of nickel hydroxide and a mixed precipitate containing manganese and cobalt. An electrode, wherein the particles are coated with the mixed precipitate.

The non-sintered nickel electrode active material used in the alkaline storage battery of the present invention is an active material comprising particles mainly composed of nickel hydroxide and a mixed precipitate containing manganese and cobalt. Particles are coated with the mixed precipitate.

The method for producing an active material for a non-sintered nickel electrode used in an alkaline storage battery according to the present invention comprises the steps of: mixing particles mainly composed of nickel hydroxide in a mixed solution comprising a manganese salt solution and a cobalt salt solution. The particles are immersed and neutralized, and the particles are coated with a mixed precipitate of manganese and cobalt.

Further, in the method for producing a non-sintered nickel electrode for an alkaline storage battery according to the present invention, the method comprises immersing particles mainly composed of nickel hydroxide in a mixed solution comprising a manganese salt solution and a cobalt salt solution. The active material is obtained by coating the particles with a mixed precipitate composed of manganese and cobalt, and the active material is filled in a conductive core.

In the present invention, the mixed precipitate is
The range is 2% by weight to 26% by weight, particularly preferably 3% by weight to 25% by weight, based on the weight of the active material.

In the present invention, manganese is
In the mixed precipitate, in terms of metal relative to cobalt, 0.
It is added so as to be in a range of 5% by weight to 50% by weight.

In the production method of the present invention, manganese sulfate and manganese nitrate are used as manganese salts, and cobalt sulfate and cobalt nitrate can be used as cobalt salts. By using such sulfates and nitrates, an active material and a nickel electrode can be efficiently provided without contamination of impurities.

[0017]

The surface of nickel hydroxide particles or particles mainly composed of nickel hydroxide is coated with a mixed precipitate containing manganese and cobalt. As a result, even if the number of cycles of the battery advances, it is possible to prevent cobalt added to the surface of the active material from diffusing into the particles. Therefore, the effect of adding cobalt can be exhibited over a long period of time, and a decrease in battery capacity due to the progress of the cycle can be prevented.

Although the reason for this is not clear, at least a portion of the mixed precipitate containing manganese and cobalt is a mixed crystal of manganese hydroxide and cobalt hydroxide. With this mixed crystal, the crystal structure of the mixed crystal is maintained even when the number of cycles of the battery advances. As a result, it is estimated that diffusion of cobalt into nickel hydroxide as an active material is suppressed.

The addition of less than 0.5% by weight of manganese in terms of metal relative to cobalt in the mixed precipitate formed on the active material cannot suppress the diffusion of cobalt into the nickel hydroxide particles. Therefore, a decrease in battery capacity is observed as the cycle progresses. On the other hand, when manganese is added in an amount exceeding 50% by weight, the conductivity of the active material surface is reduced, so that a sufficient discharge capacity, that is, a battery capacity cannot be obtained.

On the other hand, if the amount of the mixed precipitate is less than 3% by weight based on the total weight of the active material, the effect of coating the cobalt is not sufficient, and the conductivity of the electrode cannot be increased. On the other hand, if the coating exceeds 25% by weight, the ratio of nickel hydroxide in the active material decreases, and a sufficient battery capacity cannot be obtained.

[0021]

【Example】

(Example 1) [Preparation of active material] 1000 ml of an aqueous solution in which cobalt sulfate (16.8 g) and manganese sulfate (2.8 g) were dissolved was prepared. Ni (OH) ₂ which is nickel hydroxide particles is added to this aqueous solution.
Add powder (100 g) and stir. At the same time, 1M
An aqueous solution of sodium hydroxide was added dropwise to perform neutralization. The pH at this time was adjusted to 12 and maintained. The stirring time is one hour. Thereafter, the nickel hydroxide particles having the mixed precipitate formed on the surface were washed with water, and then dried under vacuum to obtain an active material of the present invention.

In this active material, cobalt hydroxide and manganese hydroxide are precipitated as mixed precipitates formed on the surface of the active material. This mixed precipitate is 10% by weight based on the weight of the active material. And in the mixed precipitate:
10% by weight of manganese in terms of metal based on cobalt
It contains.

A glass electrode pH meter with automatic temperature compensation is used for pH measurement during the preparation of the active material. [Preparation of Electrode] A paste was obtained by kneading 80% by weight of the active material obtained in the above-mentioned preparation of the active material and 20% by weight of an aqueous solution of methylcellulose (containing 1% by weight) as a binder or a thickener. This paste was filled in a conductive core which was a porous body made of nickel-plated foamed metal (porosity 95%, average particle size 200 μm). The conductive core filled with the paste was dried and molded to obtain a non-sintered nickel electrode. [Preparation of Battery] The non-sintered nickel electrode obtained as described above is used as a positive electrode, and a known paste-type cadmium electrode, a separator made of nylon non-woven fabric, an alkaline electrolyte, a metal battery container, and a metal lid are used. Were combined to produce a nickel-cadmium battery according to the present invention. The composition of the alkaline electrolyte used here was KOH: NaOH: LiOH =
8: 1: 1 (specific gravity = 1.285).

The battery using the mixed precipitate of cobalt and manganese, that is, the active material coated with the mixed crystal, was designated as Battery A of the present invention. Comparative Example 1 As a comparative example, 1000 ml of an aqueous cobalt solution in which cobalt sulfate (18.5 g) is dissolved is prepared. Ni (OH) ₂ powder (100 g), which is the nickel hydroxide particles used above, was charged into the aqueous cobalt solution with stirring. A 1M aqueous solution of sodium hydroxide was added dropwise to neutralize the solution. The pH at this time was adjusted to 12 and maintained. This stirring and mixing takes one hour. At this time, the deposit composed of the cobalt compound, that is, the cobalt hydroxide is 10% by weight based on the weight of the active material.

Thereafter, a precipitate of nickel hydroxide particles coated with cobalt hydroxide is obtained, washed with water and dried.
The active material of Comparative Example 1 was obtained. Then, a comparative battery X was produced in the same manner as in Example 1 described above.

The comparative example 1 is a method close to the technique disclosed in Japanese Patent Application Laid-Open No. 622-234867 in that nickel hydroxide particles coated with cobalt hydroxide are used. Comparative Example 2 1000 ml of an aqueous solution in which cobalt sulfate (16.7 g) and nickel sulfate (1.85 g) were dissolved was prepared. In the same manner as above, nickel hydroxide particles Ni
(OH) ₂ powder (100 g) was charged with stirring. And
A 1M aqueous solution of sodium hydroxide was added dropwise to neutralize the solution. The pH at this time was adjusted to 12 and maintained. This mixing and stirring required one hour. The surface precipitate at this time is 10% by weight based on the weight of the active material. In addition, nickel is contained at 10% by weight in terms of metal with respect to cobalt therein.

Thereafter, a precipitate of nickel hydroxide particles coated with cobalt hydroxide and nickel hydroxide is obtained,
After washing with water and drying, an active material as Comparative Example 2 was obtained.

Using this active material, a comparative battery Y was produced in the same manner as in Example 1 described above.

The comparative example 2 uses a nickel hydroxide particle coated with a solid solution of cobalt hydroxide and nickel hydroxide, and is a method close to the technique disclosed in JP-A-3-62457. It is. [Test Conditions of Battery] Using the battery A of the present invention, the comparative battery X, and the comparative battery Y thus obtained, the cycle characteristics of the batteries were compared. The experiment conditions at this time were as follows:
The current is charged to a depth of 160%, and 1C discharging (1.0 V cut) is repeated. And each battery capacity was measured.

FIG. 1 shows the results. The horizontal axis in FIG. 1 indicates the number of cycles, and the vertical axis indicates the battery capacity. The battery capacity is indicated by an index with the discharge capacity at the first cycle as 100. Thus, in the comparative battery X and the comparative battery Y,
It can be understood that the battery capacity of the battery A of the present invention is hardly deteriorated while the battery capacity is reduced with the progress of the cycle number.

The reason why the difference in cycle characteristics is observed is that in the battery A of the present invention, cobalt added to the surface of the active material is prevented from diffusing into the nickel hydroxide particles. As a result, the effect of adding cobalt can be exhibited for a long period of time, and a decrease in battery capacity due to the progress of the cycle is prevented.

In the first embodiment, nickel hydroxide particles containing no zinc, cobalt, cadmium, calcium, magnesium, manganese or the like are used as a starting material. As a matter of course, when a mixed precipitate of cobalt and manganese is formed using an active material mainly composed of nickel hydroxide in which zinc, cobalt, cadmium, magnesium, calcium, manganese, etc. are dissolved therein. However, the same effect can be obtained. (Example 2) In Example 2, the amount of manganese and cobalt, which are elements forming a mixed precipitate, was examined. The active material used here was prepared in accordance with [Production of active material] in Example 1 above. That is, the amount of cobalt added in the mixed precipitate is changed by adjusting the amounts of the cobalt salt and the manganese salt dissolved in water. Here, the weight ratio of the mixed precipitate to the weight of the active material is fixed at 10% by weight.

The specific amount of addition of manganese relative to cobalt in the mixed precipitate formed on the surface of the active material is 0.10% by weight, 0.25% by weight, 0.5% by weight,
1% by weight, 5% by weight, 10% by weight, 25% by weight, 35% by weight,
50%, 55% and 60% by weight. The amount of manganese added is based on the amount of cobalt in the mixed precipitate in terms of metal.

A battery is manufactured using each of these active materials,
B ₁ , B ₂ , B ₃ , B ₄ , B ₅ , B ₆ , B ₇ , B ₈ , B
_9, and a B _10, B _11. Then, a cycle test of the battery was performed under the same conditions as the test conditions of the battery described above.

FIG. 2 shows the result. In FIG.
The horizontal axis represents the number of cycles (times), and the vertical axis represents the discharge capacity of each battery. Here, the discharge capacity of the battery is indicated by an index with the discharge capacity at the first cycle being 100.

From FIG. 2, it can be seen that the amount of manganese added to cobalt is 0.5% by weight or more in terms of metal, and the batteries B ₃ to
In B _11, it can be seen that the good cycle characteristics can be obtained.

Next, Table 1 shows the amount of manganese added in each battery and the discharge capacity of each battery.

[0038]

[Table 1]

In Table 1, the discharge capacity at the 300th cycle is shown as the discharge capacity of the battery. This value, manganese amount i.e. content relative cobalt, the discharge capacity of the battery B ₄ is 10 wt% in terms of metal is indicated by the index 100. From Table 1, the battery B _10, B ₁₁ manganese amount exceeds 50%, it can be seen that the discharge capacity of the battery is reduced.

As described above, the amount of manganese to be added is determined with respect to cobalt in the mixed precipitate formed on the surface of the active material.
It can be said that it is preferably added in the range of 0.5% by weight to 50% by weight in terms of metal. (Example 3) In Example 3, the weight ratio of the mixed precipitate to the weight of the active material and the battery characteristics were examined.

Each active material was prepared in [Preparation of Active Material] in Example 1 above. That is, the weight ratio of the mixed precipitate to the active material is changed by adjusting the amounts of the cobalt salt and the manganese salt used. Here, the amount of manganese added to cobalt in the mixed precipitate is fixed at 10% by weight in terms of metal.

The specific weight ratio of each mixed precipitate is 0%, 2%, 3%, 5%, 10%, 15%, 20%, 25%, 26% %, 28% by weight, and 30% by weight. Batteries made using each of these active materials were respectively referred to as C ₁ , C ₂ , C ₃ , C ₄ , C ₅ , C ₆ ,
C ₇ , C ₈ , C ₉ , C ₁₀ , and C ₁₁ were used. Then, a cycle test of the battery was performed under the same conditions as the test conditions of the battery described above.

FIG. 3 shows the result. In FIG.
The horizontal axis represents the weight ratio of the mixed precipitate to the weight of the active material, and the vertical axis relatively shows the discharge capacity of the battery. This discharge capacity is based on a battery prepared using an active material in which the weight ratio of the mixed precipitate to each active material is 10% by weight. Represents.

[0044] From FIG. 3, the ratio of the mixture precipitates with respect to the weight of the active material, 2 wt% to 26 cell C ₂ is in the range of weight%
In -C _9, it can be understood that the improvement of the discharge capacity is attained.

Further, it can be seen that particularly good discharge capacities are obtained in the batteries C _{3 to} C ₈ in the range of 3% to 25% by weight.

From the above, it is preferable that the mixed precipitate is added in the range of 2% by weight to 26% by weight based on the weight of the active material, and it is most preferable that the mixed precipitate be 3% by weight to 25% by weight. I can understand.

[0047]

As described above, according to the present invention, in the active material, diffusion of cobalt into the nickel hydroxide particles can be suppressed, and the effect of adding cobalt over a long period of the cycle can be exhibited. Further, a non-sintered nickel electrode using such an active material can maintain a high capacity for a long period of the cycle.

According to the manufacturing method of the present invention, such an active material and a non-sintered nickel electrode can be efficiently manufactured without contamination.

As a result, it is possible to provide an alkaline storage battery which exhibits an effect of adding cobalt over a long period of time and can maintain a high capacity and has excellent cycle characteristics.
Its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a cycle characteristic diagram of a battery.

FIG. 2 is a cycle characteristic diagram of a battery.

FIG. 3 is a diagram illustrating a relationship between a weight ratio of a mixed precipitate to an active material and a battery capacity.

[Explanation of symbols]

 A: Battery of the present invention X, Y: Comparative battery

──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuhiko Niiyama 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Mamoru Kimoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Koji Nishio, inventor 2-5-5-Keihanhondori, Moriguchi-shi, Osaka Pref. Sanyo Electric Co., Ltd. No. 5 Sanyo Electric Co., Ltd. (56) References JP-A-5-121073 (JP, A) JP-A-8-227710 (JP, A) JP-A-5-21064 (JP, A) JP-A-8 −96807 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/32 H01M 4/52

Claims (16)

(57) [Claims] 1. A nickel electrode using an active material comprising particles mainly composed of nickel hydroxide and a mixed precipitate containing manganese and cobalt, wherein the particles are coated with the mixed precipitate. A non-sintered nickel electrode for alkaline storage batteries. 2. The non-sintered nickel electrode for an alkaline storage battery according to claim 1, wherein the mixed precipitate is in a range of 2% by weight to 26% by weight based on the weight of the active material. . 3. The non-sintered nickel electrode for an alkaline storage battery according to claim 1, wherein the mixed precipitate is in a range of 3% by weight to 25% by weight based on the weight of the active material. . 4. The method according to claim 1, wherein the manganese content is 0.5% by weight to 50% by metal conversion with respect to the cobalt in the mixed precipitate.
The non-sintered nickel electrode for an alkaline storage battery according to claim 1, wherein the non-sintered nickel electrode is added in a range of weight%. 5. An active material comprising particles mainly composed of nickel hydroxide and a mixed precipitate containing manganese and cobalt, wherein the particles are coated with the mixed precipitate. Active material for non-sintered nickel electrodes used for storage batteries. 6. The non-sintered nickel used for an alkaline storage battery according to claim 5, wherein the mixed precipitate is in a range of 2% by weight to 26% by weight based on the weight of the active material. Extremely active material. 7. The non-sintered nickel used in an alkaline storage battery according to claim 5, wherein the mixed precipitate is in a range of 3% by weight to 25% by weight based on the weight of the active material. Extremely active material. 8. The manganese is present in the mixed precipitate in an amount of 0.5% by weight to 50% by weight as a metal relative to the cobalt.
The active material for a non-sintered nickel electrode used in an alkaline storage battery according to claim 5, wherein the active material is added in a range of weight%. 9. Particles mainly composed of nickel hydroxide are immersed in a mixed solution composed of a manganese salt solution and a cobalt salt solution, neutralized, and the particles are mixed with a mixed precipitate composed of manganese and cobalt. A method for producing an active material for a non-sintered nickel electrode used for an alkaline storage battery, characterized by being coated. 10. The non-sintered nickel used in an alkaline storage battery according to claim 9, wherein the mixed precipitate is in a range of 2% by weight to 26% by weight based on the weight of the active material. A method for producing an electrode active material. 11. The non-sintered nickel used in an alkaline storage battery according to claim 9, wherein the mixed precipitate is in a range of 3% by weight to 25% by weight based on the weight of the active material. A method for producing an electrode active material. 12. The manganese is used in an amount of 0.5% by weight to 5% by weight in terms of metal relative to the cobalt in the mixed precipitate.
10. The composition according to claim 9, wherein the addition is in the range of 0% by weight.
A method for producing an active material for a non-sintered nickel electrode used in the alkaline storage battery according to the above. 13. Particles mainly composed of nickel hydroxide,
It is immersed in a mixed solution composed of a manganese salt solution and a cobalt salt solution, neutralized, and obtains an active material in which the particles are coated with a mixed precipitate composed of manganese and cobalt. A method for producing a non-sintered nickel electrode for an alkaline storage battery, characterized by filling. 14. The non-sintered nickel electrode for an alkaline storage battery according to claim 13, wherein the mixed precipitate is in a range of 2% by weight to 26% by weight based on the weight of the active material. Manufacturing method. 15. The non-sintered nickel electrode for an alkaline storage battery according to claim 13, wherein the mixed precipitate is in a range of 3% by weight to 25% by weight based on the weight of the active material. Manufacturing method. 16. The manganese may be present in an amount of 0.5% by weight to 5% by weight in terms of metal relative to the cobalt in the mixed precipitate.
2. The composition according to claim 1, wherein the addition is in the range of 0% by weight.
4. The method for producing a non-sintered nickel electrode for an alkaline storage battery according to item 3.