JPH11273671A - Non-sintered positive electrode for alkaline storage battery and alkaline storage battery using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide high energy density, excellent over-discharge resistance, etc., well-balanced battery characteristics over a wide temperature range, and particularly to minimize capacity deterioration when charge / discharge cycles are repeated at high temperatures. Provide an alkaline storage battery. SOLUTION: Nickel hydroxide solid solution particles having a coating layer of cobalt oxide having a valence higher than 3.0 and 0.1 to 0.1 parts by weight of the nickel hydroxide solid solution particles coated with the cobalt oxide. A positive electrode mixed with 5.0 parts by weight of metal yttrium powder or yttrium oxide powder is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintered positive electrode for an alkaline storage battery and an alkaline storage battery using the same.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for alkaline storage batteries to have higher capacities with the spread of portable devices. In particular, a nickel-hydrogen storage battery is a secondary battery including a positive electrode mainly composed of nickel hydroxide and a negative electrode mainly composed of a hydrogen storage alloy, and has been widely used as a high capacity and high reliability secondary battery.

Hereinafter, the positive electrode for an alkaline storage battery will be described.

[0004] Positive electrodes for alkaline storage batteries are roughly classified into two types: a sintered type and a non-sintered type. The former has a porosity of 80 obtained by sintering a core material such as punched metal and nickel powder.
% Nickel sintered substrate is impregnated with a nickel salt solution such as an aqueous solution of nickel nitrate, and then impregnated with an alkaline aqueous solution to produce nickel hydroxide in the porous nickel sintered substrate. It is. Since it is difficult for this positive electrode to further increase the porosity of the substrate,
The amount of nickel hydroxide cannot be increased, and there is a limit to increasing the capacity.

[0005] As the latter non-sintered type positive electrode, for example, as disclosed in Japanese Patent Application Laid-Open No. 50-36935, a three-dimensionally continuous foamed nickel substrate having a porosity of about 95% is formed on a nickel hydroxide substrate. One that retains particles has been proposed and is now widely used as the positive electrode of high capacity alkaline storage batteries. In this non-sintered positive electrode, spherical nickel hydroxide particles having a large bulk density are used from the viewpoint of increasing the capacity. Further, in order to improve the discharge characteristics, charge acceptability, and life characteristics, it is common to use the above-mentioned nickel hydroxide particles by partially dissolving metal ions such as cobalt, cadmium, and zinc.

As the conductive agent to be held on the foamed nickel substrate together with such nickel hydroxide particles, divalent cobalt oxide (for example, Japanese Patent Publication No. 7-77129) and yttrium oxide (for example, −
No. 28992) has been proposed.

The function of the divalent cobalt oxide is as follows. Usually, the size of the holes of the foamed nickel substrate is provided sufficiently larger than the particle size of the nickel hydroxide to be filled therein. Therefore, the charge / discharge reaction proceeds smoothly in the nickel hydroxide particles near the substrate skeleton where the current collection is maintained, but the reaction of the nickel hydroxide particles separated from the skeleton does not sufficiently proceed. Therefore, in many cases, a divalent cobalt oxide such as cobalt hydroxide or cobalt monoxide is added as a conductive agent. Although these divalent cobalt oxides have no conductivity per se, they are electrochemically oxidized into β-cobalt oxyhydroxide having conductivity during initial charging in a battery, and this is converted to nickel hydroxide particles. It functions as a conductive network connecting the substrate and the substrate skeleton. Due to the presence of the conductive network, the utilization rate of the active material filled at high density can be significantly increased in the non-sintered positive electrode, and the capacity can be increased as compared with the sintered positive electrode.

[0008] On the other hand, yttrium oxide has the function of greatly improving the charge acceptability of the positive electrode at high temperatures, although the reason is not clear. As another attempt to improve the decrease in the positive electrode charge acceptability at a high temperature (which is caused by the fact that the oxygen generation reaction is likely to occur as a side reaction of the charge), Japanese Patent Application Laid-Open No. H4-21222 discloses another attempt.
As described in JP-A-69-69, a method is known in which the composition of an alkaline electrolyte is a three-component mixed system of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

However, even in the non-sintered type positive electrode having the above-described structure and the alkaline storage battery using the same, the current collection performance of the conductive network by cobalt is not perfect, so that the utilization rate of the nickel hydroxide particles is limited. There was an upper limit. Furthermore, the above-mentioned positive electrode has a drawback that if the battery is left in an over-discharged or short-circuited state, or if it is stored for a long time or at a high temperature, the capacity of the positive electrode is reduced by subsequent charge and discharge. This is because, in the electrochemical cobalt oxidation reaction in the battery as described above, divalent cobalt oxide is completely converted to β.
-It is because it cannot be changed to cobalt oxyhydroxide, and the function of the conductive network is likely to be reduced.

In recent years, as a means for improving the imperfectness of the conductive network due to such cobalt, Japanese Patent Application Laid-Open No.
In JP-A-48145 and JP-A-8-148146, cobalt hydroxide in a positive electrode active material is heat-treated (oxidized) in the presence of an aqueous alkali solution and oxygen (air) outside a battery to disturb the crystal structure. A technique for modifying cobalt oxide having a valence larger than divalent is disclosed.
As a content similar to this, the improvement of cobalt oxide having a cobalt valence of 2.5 to 2.93 in JP-A-9-147905 is further described in JP-A-9-259888.
In the publication, characteristics of a battery using β-cobalt oxyhydroxide prepared by a similar method are shown.

Further, Japanese Patent Application Laid-Open No. Hei 8-148146 discloses the above.
According to the report, a similar heat treatment was performed with a coating layer of cobalt hydroxide.
Nickel solid solution particles (hereinafter referred to as Co (OH)_Two
(Referred to as coated Ni particles). this
In the case, Co (OH) _TwoMaking coated Ni particles
To improve the dispersibility of cobalt
There is an advantage that the amount of cobalt used can be reduced.
On the other hand, in Japanese Patent Application Laid-Open No. 9-73900,
Co (OH) containing alkaline aqueous solution_Two
The coated Ni particles are allowed to flow in a fluidized
Alternatively, a method of heating while dispersing is disclosed.
When such a treatment is performed, the occurrence of particle agglomeration due to agglomeration, etc.
There is an advantage that trouble can be reduced.

The above-mentioned techniques, which have been filed and published in recent years, basically allow the cobalt oxidation reaction (which does not proceed satisfactorily under normal conditions) occurring at the initial charge of the battery to be sufficiently performed outside the battery. It is of the gist. Accordingly, it is possible to improve a defect caused by the imperfectness of the conductive network due to the aforementioned cobalt.

However, in the positive electrode active material for an alkaline storage battery (nickel hydroxide solid solution particles having an oxidized cobalt type coating layer) described in the above publication, the oxidation state of the cobalt species forming the coating layer is still incomplete. Hard to say
There was room for improvement. This is because the progress of oxidation of cobalt hydroxide in the coexistence of alkali is greatly affected not only by the ambient temperature and the concentration of the coexisting alkaline aqueous solution, but also by the amount of ambient moisture and oxygen, and without these controls. This is because it cannot be oxidized to a sufficiently high-order state. From a detailed experiment and analysis focusing on this, it was found that Japanese Patent Application
In 272341, the cobalt species forming the coating layer by optimally controlling the oxidation conditions have a valence of 3.
The point that it is oxidized to γ-cobalt oxyhydroxide higher than 0, and the utilization rate and the overdischarge resistance of the positive electrode using this active material are determined by using an active material with insufficient cobalt oxidation. It is shown that it is dramatically improved compared to the case. At the same time, in the specification of the application, an efficient production method was also presented.

[0014]

[Problems to be solved by the invention]
The inventors of the present invention used nickel hydroxide particles coated with an oxide having a valence of a cobalt species higher than 3.0 as a cathode active material to form a coating layer as described above, While the characteristics of the battery can be greatly improved, it has been found that the capacity decrease when the charge / discharge cycle is repeated at a high temperature is larger than that of the conventional positive electrode. There are several reasons for this, and the exact mechanism has not been determined at this time. However, one of the causes is the alteration of the cobalt species accompanying the charge / discharge cycle at a high temperature as described below.

That is, when a battery using the above-mentioned positive electrode active material is discharged at a high temperature (for example, 40 ° C.) until the battery voltage becomes about 0.8 V, a coating layer of active material particles is formed at the end of discharge. Some of the cobalt oxides undergo a discharge reaction (reduction). This is due to the fact that the internal resistance of the battery is low at high temperatures, so that the positive electrode is easily discharged, and the valence and conductivity of the cobalt oxide are extremely high.

Subsequently, charging is performed.
A charging reaction (oxidation) of the discharged cobalt oxide occurs. However, the capacity at which the cobalt oxide is charged at this time is slightly smaller than the capacity discharged. That is,
When charge and discharge are performed at a high temperature, the valence of the cobalt oxide forming the coating layer is slightly reduced. When such a charge / discharge cycle is repeated, the above phenomena are accumulated, and the cobalt oxide of the coating layer has a lower valence and is thermodynamically stable CoHO ₂ or Co ₃ O ₄ ( In each case, the structure approaches an oxide having poor conductivity. As a result, the cobalt conductive network of the positive electrode cannot function satisfactorily, and the capacity decreases as a positive electrode or as a battery.

Therefore, as a simple attempt to improve the above-mentioned capacity reduction, the oxygen overvoltage at the time of charging can be reduced by changing the composition of the alkaline electrolyte to a ternary mixed system of potassium hydroxide, sodium hydroxide and lithium hydroxide. It is presumed that a method of changing this to improve the charging efficiency of the coating layer with respect to the cobalt oxide is effective. In fact, if such an attempt is made, it is possible to somewhat alleviate the capacity deterioration accompanying the charge / discharge cycle at a high temperature. On the other hand, however, in such an electrolytic solution, the electric conductivity of the solution at a low temperature (for example, 0 ° C.) is low, so that the discharge performance at a low temperature must be significantly reduced. That is, the balance of the battery characteristics with respect to the operating temperature is impaired.

The present invention solves the above-described problems, and maintains the excellent characteristics of a cobalt oxide having an oxidation valence higher than 3.0 which forms the coating layer of the active material. ,
It is a main object of the present invention to provide an alkaline storage battery having an excellent balance of battery characteristics in a wide temperature range and having a small capacity deterioration even when a charge and discharge cycle is repeated at a high temperature.

[0019]

According to the present invention, there is provided a non-sintered positive electrode for an alkaline storage battery according to the present invention, which comprises a nickel hydroxide solid solution having a coating layer of cobalt oxide having a valence higher than 3.0. 0.1 to 5.0 with respect to the amount of particles and the nickel hydroxide solid solution particles coated with the cobalt oxide.
It is composed of a mixture of parts by weight of metal yttrium powder or yttrium oxide powder. According to the above, since the conductivity of cobalt oxide having a higher valence than 3.0 is very high, a positive electrode having a high utilization rate and excellent overdischarge resistance can be obtained.

Further, the capacity deterioration when the charge / discharge cycle is repeated at a high temperature is greatly improved by the action of metal yttrium or yttrium oxide. The adsorption of the metal yttrium or the yttrium oxide on the surface of the cobalt oxide increases the oxygen overpotential in high temperature charging. As a result, the charging efficiency of the cobalt oxide is improved,
Even during high-temperature charging, the cobalt oxide is oxidized to a high oxidation state. Therefore, it is possible to suppress a decrease in the valence of the cobalt oxide (a decrease in conductivity) due to accumulation of charge / discharge cycles. In particular, by combining the positive electrode having the above structure with an alkaline electrolyte having excellent conductivity at a low temperature to form a battery, a cobalt oxide having a higher valence than 3.0 which forms a coating layer of an active material is formed. It is possible to provide an alkaline storage battery having excellent balance of battery characteristics in a wide temperature range while maintaining excellent characteristics of the above, and having less capacity deterioration even when charge / discharge cycles are repeated at a high temperature.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is characterized in that nickel hydroxide solid solution particles having a coating layer of cobalt oxide having a higher valence than 3.0 are coated with the cobalt oxide. A non-sintered positive electrode for an alkaline storage battery, comprising 0.1 to 5.0 parts by weight of a mixture of nickel yttrium hydroxide solid solution particles and metal yttrium powder or yttrium oxide powder.

According to a second aspect of the present invention, there is provided nickel hydroxide solid solution particles having a cobalt oxide coating layer higher than 3.0 valence, and nickel hydroxide solid solution particles coated with the cobalt oxide. A positive electrode comprising a foamed nickel porous substrate filled with a mixture of metal yttrium powder or yttrium oxide powder in an amount of 0.1 to 5.0 parts by weight,
An alkaline storage battery including a negative electrode, a separator, and an alkaline electrolyte.

In the above positive electrode, when a positive electrode mixed with a metal yttrium powder or an yttrium oxide powder less than 0.1 part by weight based on the amount of the nickel hydroxide solid solution particles is used, the oxygen overvoltage of cobalt during charging at a high temperature is increased. Cannot be sufficiently increased, so that the capacity deterioration when the charge / discharge cycle is repeated at a high temperature is not significantly improved. Further, in the above positive electrode, even when a positive electrode mixed with a metal yttrium powder or an yttrium oxide powder in an amount of more than 5.0 parts by weight based on the amount of the solid solution particles of nickel hydroxide is used, the oxygen overvoltage of cobalt in charging at a high temperature. The effect of increasing the saturation is saturated, and there is not much improvement effect of the capacity deterioration when the charge and discharge cycle is repeated at a high temperature, and the amount of nickel hydroxide particles that determines the cathode capacity is relatively reduced. However, a positive electrode having a high energy density cannot be obtained.

According to a third aspect of the present invention, an optimum composition of the alkaline electrolyte for the alkaline storage battery is defined. The electrolyte mainly contains potassium hydroxide and further contains a small amount of lithium hydroxide. The concentration of potassium hydroxide was 7.0 to 8.0 normal, and the concentration of lithium hydroxide was 0.5 to 1.0 normal.

When considering the balance of battery characteristics with respect to temperature, in the above-mentioned alkaline storage battery, the characteristics at high temperatures can be made sufficiently excellent by the action of yttrium or yttrium oxide. Therefore, it is preferable to select an alkaline electrolyte accompanying the composition having a composition that sufficiently brings out the discharge characteristics at a low temperature. From this viewpoint, an electrolytic solution mainly containing potassium hydroxide having excellent electric conductivity at a low temperature and further containing lithium hydroxide having an effect of improving the utilization factor of the positive electrode is suitable.

In this case, the concentration of the alkaline species is limited by the common ion effect in accordance with the concentration of potassium hydroxide having high solubility, so that the solubility limit of lithium hydroxide having low solubility is restricted. According to the results of studies by the inventors, the best battery characteristics were obtained when the potassium hydroxide concentration was adjusted to 7.0 to 8.0 normal and the lithium hydroxide concentration was adjusted to 0.5 to 1.0 normal. Turned out to be.
When the potassium hydroxide concentration is lower than 7.0 normal, the solubility limit concentration of lithium hydroxide can be higher than 1.0 normal, but such an electrolytic solution can ensure sufficient low-temperature discharge performance. Can not. If the concentration of potassium hydroxide is higher than 8.0N, the solubility limit of lithium hydroxide is limited to less than 0.5N. Can not. From the above, those having a concentration in the above range are most suitable.

The invention according to claim 4 is characterized in that the coating layer of cobalt oxide has a thickness of 0.2 μm or less and further covers the entire surface of the particles. When the thickness of the coating layer is too small, the conductive network is insufficient and the current collection from the hydroxide particles cannot be sufficiently maintained. On the other hand, if it is excessively large, the amount of nickel hydroxide particles that determine the capacity of the positive electrode is relatively reduced, so that a positive electrode having a high energy density cannot be obtained. It is most preferable that the thickness of the coating layer is within the above range and that the entire surface of the particles is coated in order to maximize the current collecting ability from the nickel hydroxide particles.

[0028]

Embodiments of the present invention will be described below in detail.

(Preparation of Positive Electrode) Nickel hydroxide solid solution particles serving as the base particles of the active material were synthesized by the following well-known method. That is, an aqueous solution containing nickel sulfate as a main component and containing predetermined amounts of cobalt sulfate and zinc sulfate,
A method was used in which sodium hydroxide was gradually added dropwise while adjusting the solution pH with aqueous ammonia to precipitate spherical nickel hydroxide solid solution particles. The precipitated nickel hydroxide solid solution particles were washed with water and dried to obtain mother particles. The average particle size of the nickel hydroxide solid solution particles was 10 μm.

The above-mentioned nickel hydroxide solid solution particles are charged into an aqueous solution of cobalt sulfate, and an aqueous solution of sodium hydroxide is gradually added thereto. The mixture is stirred at 35 ° C. while maintaining the pH at 12 to maintain the surface of the solid solution particles. Co (OH) ₂ -coated Ni particles were produced by depositing cobalt hydroxide. Here, regarding the coating amount of cobalt hydroxide, Co (OH)
₂ The ratio of the weight of the coating layer to the total weight of the coated Ni particles was adjusted to be 5.0% by weight. The prepared Co (O
H) The ₂ coated Ni particles were washed with water and then vacuum dried.
In the particles, the thickness of the coating layer was about 0.1 μm.
It was confirmed by electron microscope observation that the entire surface of the particles was coated with m.

Subsequently, Co (OH) ₂ -coated Ni particles
An appropriate amount of a 5% by weight aqueous solution of potassium hydroxide was impregnated, put into a drying apparatus having a microwave heating function, heated, and guided to complete drying while sending oxygen. By this operation, the cobalt hydroxide coating layer on the surface of the particles was oxidized to a higher state exceeding 3.0 valence, and turned to blue. This was sufficiently washed with water and dried under vacuum to obtain Co-oxidized active material particles.

Next, 1.0 part by weight of Y ₂ O ₃ , 0.1 part by weight of carboxymethylcellulose (CMC) as a thickener and 100 parts by weight of the thus obtained Co-oxidized active material particles were added. An active material slurry was prepared by adding and mixing and dispersing 0.2 parts by weight of polytetrafluoroethylene (PTFE) as a binder and an appropriate amount of pure water. This active material slurry was filled in a known foamed nickel foam substrate having a thickness of 1.4 mm, dried in a drier at 80 ° C., rolled to about 0.7 mm by a roll press, and further reduced to a predetermined size. This was cut into a nickel positive electrode (hereinafter referred to as positive electrode X). Also, a nickel positive electrode (hereinafter referred to as positive electrode Y) was prepared in the same manner as above except that Y ₂ O ₃ was not added to the Co-oxidized active material particles.

(Preparation of Batteries) The following two types of alkaline electrolytes were prepared for use in battery construction.

A: KOH concentration is 7.1N, LiOH
A mixed aqueous solution of potassium hydroxide and lithium hydroxide having a concentration of 0.9 normal.

B: KOH concentration of 5.1N, LiOH
And a mixed aqueous solution of potassium hydroxide, lithium hydroxide and sodium hydroxide, wherein the concentration of NaOH is 1.5N and the concentration of NaOH is 0.7N.

The two types of nickel positive electrodes X and Y produced above
A negative electrode mainly composed of a hydrogen storage alloy, a polypropylene non-woven fabric separator subjected to a hydrophilic treatment, an electrolyte A,
B, using a known method, 4/3 AAA (L-AA)
A) A nickel-hydrogen storage battery having a size and a nominal capacity of 800 mAh was manufactured. X-A, X-
B, YA, and YB.

(High Temperature Cycle Life Test) These four types of batteries XA, XB, YA, and YB were subjected to
A test in which charging at a charge rate of 1 CmA and -ΔV control (cutoff voltage of 5 mV) and discharging at 40 ° C., a discharge rate of 1 CmA and a cut voltage of 0.8 V were repeated 500 cycles was performed, and a change in battery capacity was measured. For battery capacity,
The discharge capacity up to 1.0 V was read. The results of FIG. 1 were obtained by plotting the number of charge / discharge cycles on the horizontal axis and the battery capacity (indexed with the first XA cycle having the highest value being 100) on the vertical axis. The following can be seen from FIG.

First, in XA and XB using the positive electrode X, the capacity of the battery is less deteriorated than in YA and YB using the positive electrode Y. The reason for this is that the action of yttrium oxide in the positive electrode X improves the charging efficiency of the cobalt oxide and increases its oxidation valency, thereby lowering the valence of the cobalt oxide (accumulation of conductivity) due to accumulation of charge / discharge cycles. It is presumed that the decrease in the property) was suppressed.

Further, the battery capacity deterioration of the battery XB using the electrolyte B is smaller than that of the battery XA using the electrolyte A, and similarly, the capacity deterioration of the battery YB is smaller than that of the battery YA. Few. This is because the electrolytic solution B has a higher content of lithium hydroxide having an effect of improving the positive electrode utilization rate.

(Low-temperature cycle life test) The four batteries prepared in the same manner as above were charged at 0 ° C. and at a charge rate of 1 Cm.
A, 500 cycles of a test in which charging under −ΔV control (10 mV cut-off voltage) and discharging at 0 ° C., a discharge rate of 1 CmA and a cut voltage of 0.8 V were performed for 500 cycles, and the battery capacity (discharge capacity up to 1.0 V) Was measured. The results in FIG. 2 were obtained by plotting the number of charge / discharge cycles on the horizontal axis and the battery capacity (indexed with the first XA cycle having the highest value being 100) on the vertical axis. The following can be seen from FIG.

Compared with XA and YA using the electrolytic solution A,
XB and YB using the electrolyte B have smaller battery capacities. The reason is considered as follows.

The concentration of potassium hydroxide, which is considered to largely depend on the low-temperature discharge characteristics, of the electrolyte solution A is 7.1
By setting the concentration in the range of 7.0 to 8.0, high electric conductivity is ensured even at a low temperature. Therefore, X
With -A and YA, sufficient low-temperature discharge performance can be obtained. On the other hand, the electrolyte B had a lithium hydroxide concentration as high as 1.5N, so that the potassium hydroxide concentration had to be as low as 5.1N. Poor electrical conductivity. Therefore, sufficient low-temperature discharge performance cannot be obtained with XB and YB.

Based on the above results, it is XA that exhibits excellent battery performance in two characteristics, high temperature and low temperature cycle life. The reason why the capacity deterioration upon repeated charge / discharge cycles at high temperature is reduced is that, in the positive electrode X, the charge efficiency of cobalt oxide is improved by the action of yttrium oxide, and This is because a decrease in valence (decrease in conductivity) is suppressed. In addition, by using the electrolyte solution A, the electric conductivity of the solution at a low temperature is kept high, and the low-temperature discharge characteristics are improved.

The above effect is not limited to the case where 1.0 part by weight of Y ₂ O ₃ is mixed with 100 parts by weight of the above-mentioned Co-oxidized active material particles. .0
Even if a positive electrode mixed with parts by weight of metal yttrium powder or yttrium oxide particles is used, the electrolytic solution is not limited to the case of using the composition in the example, and the concentration of potassium hydroxide is 7. It was confirmed by another experiment that the same results were obtained if the concentration was 0 to 8.0 normal and the concentration of lithium hydroxide was 0.5 to 1.0 normal.

Further, in the present embodiment, when producing Co (OH) ₂ -coated Ni particles, a coating layer was formed by utilizing a chemical reaction in an aqueous solution. It is not limited to those described. A method of mixing nickel hydroxide solid solution particles and cobalt hydroxide powder and coating the particle surface with cobalt hydroxide using a shear force or an impact force during mechanical mixing (mechanical mixing method) or the like to use Co (OH) The positive electrode of the present invention can be produced also as _2- coated Ni particles. In oxidizing the Co (OH) ₂ -coated Ni particles, a high-concentration aqueous solution of potassium hydroxide was used, but the same effect can be obtained by using a high-concentration aqueous solution of sodium hydroxide. Alkali wet Co
As a heating method for oxidizing (OH) ₂ coated Ni particles,
Although the method is described in which heating is performed while oxygen is supplied in a dryer having a microwave heating function, the method is not limited to this.

[0046]

As described above, the use of the positive electrode of the present invention provides a high energy density, excellent overdischarge resistance, etc., and a good balance of battery characteristics over a wide temperature range. It is possible to provide an alkaline storage battery with less capacity deterioration when the discharge cycle is repeated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in battery capacity according to the number of charge / discharge cycles at 40 ° C. of each battery used in Examples.

FIG. 2 is a diagram showing a change in battery capacity according to the number of charge / discharge cycles at 0 ° C. of each battery used in Examples.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshitaka Namizu 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Koji Yuasa 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Inside

Claims (4)

[Claims] 1. A nickel hydroxide solid solution particle having a coating layer of cobalt oxide having a valence higher than 3.0 and a nickel hydroxide solid solution particle coated with the cobalt oxide. A non-sintered positive electrode for an alkaline storage battery, comprising 1 to 5.0 parts by weight of a mixture of a metal yttrium powder or a yttrium oxide powder. 2. Nickel hydroxide solid solution particles having a coating layer of cobalt oxide having a higher valence than 3.0, and 0.1 to 5.0% by weight based on the amount of said nickel hydroxide solid solution particles. An alkaline storage battery comprising a positive electrode, a negative electrode, a separator, and an alkaline electrolyte, wherein a mixture of a metallic yttrium powder or a yttrium oxide powder is filled in a porous nickel foam substrate. 3. The alkaline electrolyte is mainly composed of potassium hydroxide, and contains a small amount of lithium hydroxide. The concentration of potassium hydroxide is 7.0 to 8.0N, and the concentration of lithium hydroxide is The concentration is 0.5 to 1.0 normal.
The alkaline storage battery according to the above. 4. The coating layer of cobalt oxide having a thickness of 0.2 μm or less and covers the entire surface of the particles.
The alkaline storage battery according to the above.