JP2003045422A - Alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline storage battery having high utilization factor in a positive electrode, high recoverability in high temperature storage, and high cycle characteristics in a high temperature atmosphere. SOLUTION: This alkaline storage battery has a non-sintered positive electrode using nickel hydroxide as an active material; a negative electrode using a hydrogen storage alloy as an active material; a separator; and an electrolyte, and the nickel hydroxide in which part of nickel in the nickel hydroxide on the particle surface is made trivalent and the particle surface is covered with cobalt oxide containing sodium is used, and at least a cobalt compound and an yttrium group element compound are added to the positive electrode, and the cobalt compound and the yttrium group element compound are oxidized with an alkali aqueous solution before constituting the alkaline storage battery. The valence of the cobalt oxide containing sodium is preferably 2.6-3.1, and as the yttrium group element, yttrium, ytterbium, and erbium are preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery, and more particularly to an alkaline storage battery having a high positive electrode utilization rate, a high recovery rate in high temperature storage, and excellent cycle characteristics in a high temperature atmosphere.

[0002]

2. Description of the Related Art As a positive electrode for an alkaline storage battery, a sintered positive electrode in which nickel powder is impregnated into pores in a sintered substrate of nickel and filled with an active material, and nickel hydroxide as an active material are used as a binder. , Prepare a positive electrode mixture-containing paste by dispersing it in water or a solvent together with a thickener, apply it to a conductive base material made of a metal porous body such as a metal foam serving as a current collector, fill it, and dry it. There is a non-sintered positive electrode manufactured through the process. In the former sintered type positive electrode, since the conductivity of the sintered substrate is high, the utilization rate of the active material is excellent, but it is difficult to increase the porosity of the sintered substrate.
Since it is not possible to increase the filling amount of nickel hydroxide, it is difficult to achieve high capacity, and since the binding force between nickel particles is weak, the active material drops off when a sintered substrate with high porosity is used. There was a problem that it was easy to do.

Therefore, the latter non-sintered positive electrode has been proposed as a positive electrode for a hydride secondary battery. In this non-sintered positive electrode, the packing density of nickel hydroxide as an active material can be increased. Although it has the advantage that it can be produced and is easy to manufacture, it has a problem that since the distance between the nickel hydroxide and the base material is long, the conductivity is low and the utilization rate of the active material is low.

Therefore, in the non-sintered positive electrode, metallic cobalt or a cobalt compound such as cobalt monoxide or cobalt hydroxide is added as a conduction aid to the positive electrode in order to increase the utilization factor and achieve a high capacity. Is proposed.
These cobalt-based additives are oxidized in an alkaline electrolyte during charging and become higher-order cobalt oxides such as cobalt oxyhydroxide to form a conductive network that electrically connects particles of nickel hydroxide. It is known.

However, since the above cobalt-based additive is difficult to be uniformly dispersed in the positive electrode and is unevenly distributed, the network formed from it tends to be non-uniform and it is difficult to secure good conductivity. Further, since a network is formed on the entire positive electrode, increasing the addition amount of the cobalt-based additive decreases the filling amount of nickel hydroxide. Therefore, recently, without reducing the filling amount of nickel hydroxide, in order to form a uniform conductive network, instead of cobalt or a cobalt compound as an additive as described above, or together with the additive,
It has been proposed to use nickel hydroxide whose particle surface is coated with a cobalt compound such as cobalt hydroxide in advance (Japanese Patent Laid-Open No. 234867/1987 and Japanese Patent Laid-Open No. 62/34867).
-234868, JP-A-4-4698, etc.). Further, for the purpose of further increasing the capacity and improving the reliability, it is also possible to coat the nickel hydroxide particle surface with a higher-order cobalt compound by mixing an alkaline solution, a cobalt compound, and nickel hydroxide and heat-treating them. An attempt has been made (Japanese Patent Laid-Open No. 8-148145).

[0006]

However, the non-sintered positive electrode using the heat-treated nickel hydroxide as an active material as described above is excellent in the utilization factor and the reduction resistance of the conductive network at high temperature storage. However, in a cycle test under a high temperature atmosphere, there is a problem that more gas is generated from the positive electrode than at room temperature, the charging efficiency is lowered and the utilization rate of the active material is deteriorated. That is, since the charging potential of nickel hydroxide is close to the oxygen generation potential, a competitive reaction between oxygen generation and the charging reaction occurs at the end of charging, which hinders the charging of nickel hydroxide and becomes noticeable in a high temperature atmosphere. In a high temperature atmosphere, there is a problem that the charging efficiency is reduced and, as a result, the utilization rate of nickel hydroxide is also reduced.

Therefore, in order to improve the charging efficiency, lithium hydroxide, sodium hydroxide or the like is added to the electrolytic solution, or calcium hydroxide, calcium oxide,
Add zinc oxide, cadmium hydroxide, etc., or add Sr, Sc, Al, Ga, Ti, Zr, N to nickel hydroxide.
b, Bi, Mo, Ag, Sn, Sb, V, Cr, Mn,
It has been proposed to form a solid solution of Fe, Cu, etc. (Japanese Patent Laid-Open Nos. 10-40948 and 10-149821.
Issue). However, addition of calcium hydroxide or calcium oxide to the positive electrode is liable to cause lumps (lumps) during preparation of the positive electrode mixture-containing paste, and therefore, there is a problem that a uniform paste cannot be prepared.
In addition, there is a problem that addition of zinc oxide or the like to the positive electrode lowers the high rate discharge characteristics and the utilization rate of the positive electrode at low temperature and high rate discharge, and the solid solution of a metal element such as Sr in nickel hydroxide has physical properties. Since there is a large change, there is a problem in that it is difficult from a manufacturing point of view.

Although it has been proposed to add a ytterbium compound, a yttrium compound, a rare earth compound, etc. to the positive electrode (Japanese Patent Laid-Open Nos. 9-265981 and 10-106556), addition of these compounds is proposed. Has an effect on charging efficiency at high temperature, but these compounds are difficult to dissolve in an alkaline aqueous solution, and when the conductive network of cobalt is formed in the battery, they are unevenly distributed, so that effect is sufficiently exerted. It is considered that they have not done it. Further, when the above compound is unevenly distributed,
There was a problem that a non-uniform conductive network was formed when the conductive network was formed by the cobalt compound in the battery, resulting in poor utilization and cycle characteristics.

The present invention solves the problems of the prior art as described above, has a high utilization factor of the positive electrode and a high recovery rate at high temperature storage, and improves the charging efficiency in a high temperature atmosphere to improve the charging efficiency in a high temperature atmosphere. It is an object of the present invention to provide an alkaline storage battery having excellent cycle characteristics in.

[0010]

The present invention provides an alkaline storage battery having a non-sintered positive electrode having nickel hydroxide as an active material, a negative electrode having a hydrogen storage alloy as an active material, a separator and an electrolytic solution. Nickel oxide is composed of nickel hydroxide on the surface of the particles, in which a part of nickel is trivalent, and the surface of the particles is coated with a cobalt oxide containing sodium. The positive electrode contains at least a cobalt compound and a yttrium group element compound. The above problem is solved by adding and oxidizing the cobalt compound and the yttrium group element compound with an aqueous alkali solution.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, in the present invention, a part of nickel in nickel hydroxide on the particle surface is composed of trivalent nickel, and the particle surface is coated with a cobalt oxide containing sodium. Using nickel hydroxide as a positive electrode active material, at least a cobalt compound and a yttrium group element compound are added to the positive electrode, and the cobalt compound and the yttrium group element compound are oxidized by an alkaline aqueous solution, so that the positive electrode can be used. Rate and recovery rate at high temperature storage, and the reason why cycle characteristics in high temperature atmosphere are improved will be described in detail.

When the surface of nickel hydroxide particles is coated with a cobalt compound, nickel hydroxide, cobalt hydroxide and an alkaline aqueous solution are mixed at a certain ratio and dried in air with stirring to obtain a particle surface. Higher order cobalt compounds can be coated. By coating with this cobalt compound, the utilization rate of the positive electrode and the recovery rate at high temperature storage can be improved. However, in a high-temperature atmosphere, the positive electrode swells due to the oxygen gas generated from the positive electrode during charging, or the conductive network of the cobalt compound collapses due to the hydrogen gas generated from the negative electrode, which reduces the current collection effect and improves cycle characteristics. become worse.

Therefore, the inventors of the present invention, when coating the surface of the nickel hydroxide particles with a higher-order cobalt compound, the nickel in the nickel hydroxide on the surface of the nickel hydroxide particles (hereinafter referred to as the nickel hydroxide particles). By simplifying “nickel in nickel hydroxide” on the surface to “trivalent” part of “nickel” and coating the particle surface of the trivalent nickel hydroxide with cobalt oxide containing sodium It was found that the cycle characteristics can be improved in a high temperature atmosphere. Further, in the production of the positive electrode, cobalt hydroxide, cobalt compounds such as cobalt oxide and yttrium, yttrium group element compounds such as ytterbium are added to the nickel hydroxide, and the positive electrode is oxidized using an alkaline aqueous solution. The cycle characteristics in the high temperature atmosphere could be further improved.

First, in order to make part of the nickel on the surface of the nickel hydroxide particles trivalent, nickel hydroxide and an alkaline aqueous solution to which an oxidizing agent such as hydrogen peroxide is added at a fixed ratio are mixed and the mixture is decompressed under reduced pressure. By drying, a part of nickel on the surface of nickel hydroxide particles can be made trivalent.
Then, after the drying, a certain amount of cobalt hydroxide and an aqueous solution of sodium hydroxide are added to and mixed with the nickel hydroxide, and the particles of nickel hydroxide are coated with a cobalt oxide containing sodium by drying. can do. If the surface of the nickel hydroxide particles is coated with a high-order cobalt compound without partially changing the nickel on the surface of the nickel hydroxide particles to trivalent, the adhesion between the cobalt compound and nickel hydroxide Was insufficient, and the conductive network of the cobalt compound was likely to collapse due to gas generation in a high-temperature atmosphere, but due to the fact that part of the nickel on the nickel hydroxide particle surface became trivalent,
The adhesion with the cobalt oxide is improved, and the contact with the alkaline electrolyte in the battery further improves the adhesion.

The alkaline aqueous solution used for the above purpose is preferably a sodium hydroxide aqueous solution having a concentration of 20 to 50% by weight, the oxidizing agent is hydrogen peroxide, etc., and the addition amount of the oxidizing agent is preferably 1 to 10% by weight. . That is, when the addition amount of the oxidizing agent is 1% by weight or more, a part of nickel on the surface of the nickel hydroxide particles can be made trivalent without lowering the productivity, and the amount of nickel added to the alkaline aqueous solution can be increased. By adjusting the addition amount of the oxidizing agent to 10% by weight or less,
It is possible to prevent the oxidation of nickel hydroxide from progressing too rapidly and to obtain the desired nickel hydroxide in a uniform state. That is, by adjusting the amount of the oxidizing agent added to the alkaline aqueous solution to 1 to 10% by weight, nickel hydroxide in which a part of the nickel on the particle surface becomes trivalent can be uniformly formed without lowering the productivity. Can be obtained at

The amount of the oxidizing agent-added alkaline aqueous solution to which the oxidizing agent is added is preferably 3 to 10 parts by weight based on 100 parts by weight of nickel hydroxide. Within this range, the reaction can be completed within an appropriate drying time. The degree of vacuum during drying is 133 Pa to 66.5 kPa.
The range of is preferable. Since nickel hydroxide has pores on the surface, the surface of nickel hydroxide can be oxidized by allowing the above-mentioned oxidizing agent-added alkaline aqueous solution to penetrate into the pores by setting an appropriate degree of vacuum. At that time, the degree of vacuum is 13
When it is in the range of 3 Pa to 66.5 kPa, it is possible to prevent the powder of nickel hydroxide from scattering at the time of drying and to sufficiently infiltrate the pores of nickel hydroxide into the alkaline aqueous solution containing the oxidizing agent. . And, the concentration during the drying is preferably 40 to 120 ° C. Within this range, the thermal decomposition of nickel hydroxide can be prevented and the surface of nickel hydroxide can be made trivalent without taking too long to dry.

After the above-mentioned drying, cobalt hydroxide and an aqueous solution of sodium hydroxide are added to nickel hydroxide and dried while mixing. At that time, the concentration of sodium hydroxide in sodium hydroxide is preferably 20 to 50% by weight,
Further, cobalt hydroxide and the sodium hydroxide aqueous solution are added in an amount of 2 to 8 parts by weight of cobalt hydroxide and 20 to 50% by weight of the above with respect to 100 parts by weight of nickel hydroxide.
2 to 20 parts by weight is preferable. By setting the addition amount of cobalt hydroxide to 2 to 8 parts by weight with respect to 100 parts by weight of nickel hydroxide as described above, while achieving uniform coating with cobalt hydroxide,
A required amount of nickel hydroxide can be secured by suppressing a decrease in the amount of nickel hydroxide due to an excessive amount of cobalt hydroxide coated. Also, the concentration of sodium hydroxide is 20 to
By adjusting the amount of the sodium hydroxide aqueous solution to 50% by weight and the addition amount of the aqueous sodium hydroxide solution to the range of 2 to 20 parts by weight with respect to 100 parts by weight of nickel hydroxide, the reaction of cobalt hydroxide can be performed without taking too long time for drying. It is possible to suppress the sudden occurrence and achieve a uniform coating of cobalt oxide containing sodium.

Here, the nickel hydroxide whose particle surface is coated with cobalt oxide particles containing sodium is preferably a solid solution of cobalt and zinc. This is because the precipitation form of the cobalt oxide is affected by the composition, crystallinity, and pore structure of nickel hydroxide, and when nickel hydroxide in which cobalt and zinc are in solid solution is used, the particle surface is coated. This is because variations in the thickness of the cobalt oxide particles are reduced, the coverage rate of nickel hydroxide on the particle surface is increased, and the utilization rate of the positive electrode is improved.

The amount of cobalt and zinc dissolved in nickel hydroxide is 0.5 to 2% by weight (0.5 to 2% of cobalt based on 100 parts by weight of nickel hydroxide).
Parts by weight) and 0.5 to 5% by weight (ratio of zinc to 0.5 to 5 parts by weight with respect to 100 parts by weight of nickel hydroxide). Further, nickel hydroxide is preferably particles having a fine pore structure, and particularly preferably particles having a peak value of pore radius of 0.8 nm or less. The pore radius was 1. 1 g of a sample of 1 g at 80 ° C. by the nitrogen adsorption method (Yuasa Ionics, Autosoap 1).
What pre-treated by vacuum suction to 33 Pa or less was measured, and nitrogen gas was adsorbed to a relative pressure (P / P ₀ ) of 0.995 or more at a measurement pore size of 0.1 to 10 nm (MP + BJH method) and a measurement time of 120 minutes. It is expressed by the value when measured on the desorption side after

The valence of the cobalt oxide containing sodium which coats the surface of the nickel hydroxide particles is preferably 2.6 to 3.1 in terms of cobalt. The above valence is 2.
By setting the ratio to 6 or more, it is possible to prevent the battery from being easily reduced when stored at high temperature, maintain the high temperature storage property properly, and set the valence to 3.1 or less,
It is possible to prevent the amount of oxidized nickel from increasing, and to appropriately maintain the high utilization rate of the positive electrode. In addition, the valence in terms of cobalt of the cobalt oxide containing sodium which coat | covers the obtained nickel hydroxide particle surface was measured as follows. That is, 0.25 g of the sample is 0.025
Immerse in 100 ml of mol / l Mohr's salt (containing 10 wt% CH ₃ COOH), stir for 1 hour, then
10 ml of mol / l sulfuric acid was added, and 0.025 mol
Trivalent cobalt is quantified by titrating with a 1 / l potassium permanganate aqueous solution. At that time, since the value of trivalent nickel may be superimposed on the measurement result, the amount of trivalent nickel is obtained in advance for the positive electrode before the treatment, and the trivalent nickel content is determined from the measured value. Subtract the amount to obtain the amount of trivalent cobalt. Further, the total amount of cobalt in the positive electrode is obtained in advance by atomic absorption spectrometry, and the amount of trivalent cobalt is subtracted from the amount to obtain the amount of divalent cobalt.

When a positive electrode mixture-containing paste is prepared using nickel hydroxide in which a part of nickel on the particle surface is made trivalent as described above and the particle surface is coated with cobalt oxide containing sodium, Add a cobalt compound into the paste. The cobalt compound added as the conductive additive is preferably composed of cobalt having a valence of 2 or more, and for example, cobalt monoxide, cobalt hydroxide or the like is preferable. Only one of these may be used, or both may be used in combination. Furthermore, it is preferable that a metal conductive auxiliary agent such as nickel as well as cobalt is not included, except for a metal derived from a metal conductive base material. In the present invention, the cobalt compound is 0.5 to 5% by weight of cobalt with respect to the weight of nickel hydroxide (that is, 0.1 wt% of cobalt in the cobalt compound is 100 parts by weight of nickel hydroxide). 5 to 5 parts by weight) is preferable. By setting the addition amount of the cobalt compound in this range, it is possible to further increase the conductivity without significantly reducing the filling amount of the positive electrode active material, and it is possible to achieve a further higher capacity and at high temperature. The alkaline storage battery having excellent cycle characteristics can be obtained. It should be noted that the amount of the cobalt compound added is less than the general amount of 6 to 20% (as the weight of cobalt) which is the general amount of the conventional cobalt-based conductive additive, and the cost of expensive cobalt material is reduced. You can

Further, in order to further improve the cycle characteristics in a high temperature atmosphere, a yttrium group element compound having a high oxygen generation overvoltage is added to the positive electrode. The yttrium group element compound is preferably a ytterbium compound, an yttrium compound, an erbium compound or the like, and the addition amount thereof is preferably 0.0006 to 0.05 mol in terms of the number of moles of the yttrium element with respect to 100 g of nickel hydroxide. This is because by setting the addition amount of the yttrium group element compound in the above range, it is possible to improve the cycle characteristics in a high temperature atmosphere while preventing the reaction resistance from increasing and decreasing the utilization rate of the positive electrode. Is.

The yttrium group elements in the yttrium group compound are Sc, Y, Eu, Gd, Tb and D.
y, Ho, Er, Tm, Yb, Lu, where Sc is scandium, Y is yttrium, Eu is europium, Gd is gadolinium, Tb is terbium, and D is
y is dysprosium, Ho is holmium, Er is erbium, Tm is thulium, Yb is ytterbium, L
u is ruthenium. Examples of the yttrium group element compound include oxides and hydroxides of the yttrium group element compound.

In the present invention, in producing a non-sintered positive electrode, it is necessary to first prepare a positive electrode mixture-containing paste, and the positive electrode mixture-containing paste is prepared by nickel on the surface of the particles. Of a positive electrode active material made of nickel hydroxide whose part is trivalent and whose surface is coated with a cobalt oxide containing sodium, a cobalt compound, a yttrium group element compound, for example, a thickener such as carboxymethyl cellulose, for example, polytetrahydrofuran. It is carried out by mixing a binder such as fluoroethylene in the presence of water or a solvent.

The non-sintered positive electrode is prepared by applying the positive electrode mixture-containing paste prepared as described above to a conductive base material made of a metal porous material such as nickel foam, filling and drying the positive electrode. It is manufactured by forming a mixture layer and performing a pressure molding process. That is, volatile components such as water and solvent contained in the positive electrode mixture-containing paste are removed by the above-mentioned drying, and a part of the positive electrode mixture is filled in the pores of the porous conductive base material. At the same time, a thin layer of the positive electrode mixture is formed on the surface of the conductive base material, and the non-sintered positive electrode is manufactured by way of the step of press-molding this positive electrode mixture layer. In the present invention, the cobalt compound and the yttrium group element compound are described as being added to the positive electrode, but as is clear from the above description, this is the cobalt compound or the yttrium group element compound in the positive electrode mixture. Means that is added.

Further, as described above, in order to utilize the cobalt compound and the yttrium group element compound added to the positive electrode, the oxidation treatment with the alkaline aqueous solution is performed. The oxidation treatment with the alkaline aqueous solution is carried out by immersing the positive electrode manufactured as described above in the alkaline aqueous solution and subjecting it to heat treatment. Explaining this by taking the case of using ytterbium oxide as an yttrium group element compound as an example, the positive electrode is immersed in an alkaline aqueous solution and subjected to heat treatment, whereby the cobalt compound is changed to a higher cobalt compound, and the conductivity increases. A network is formed. On the other hand, ytterbium oxide is dissolved in an alkaline aqueous solution to become ytterbium hydroxide, which is taken into the conductive network when the conductive network is formed by the cobalt compound and coats the surface of nickel hydroxide particles with the cobalt compound. As a result, the oxygen generation voltage becomes high, the oxygen generation at the end of charging is delayed, and it becomes easy to accept the nickel hydroxide charge, so that the cycle characteristics in a high temperature atmosphere are further improved.

As the alkaline aqueous solution used in the above-mentioned oxidation treatment, for example, potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, a mixed aqueous solution thereof and the like are preferable. The concentration of this alkaline aqueous solution is preferably 5 to 50% by weight, and particularly preferably 20 to 50% by weight. By increasing the concentration of the alkaline aqueous solution to 5% by weight or more, the solubility of the yttrium group element compound or the cobalt compound is enhanced to facilitate the formation of a conductive network, and by setting it to 50% by weight or less, the positive electrode is caused by the increase in the viscosity of the alkaline aqueous solution. This is because it is possible to prevent poor penetration into the precursor. The temperature of the oxidation treatment with the alkaline aqueous solution is preferably 35 to 100 ° C, particularly preferably 50 to 90 ° C,
Immersion time is 0.2-2.4 hours, especially 0.25-1.2
Time is preferred. By setting the temperature during the oxidation treatment with the alkaline aqueous solution to 35 ° C. or higher and the immersion time to 0.2 hours or longer, the cobalt compound and the yttrium group element compound can be sufficiently dissolved, and the temperature is 100 ° C.
This is because the cobalt compound or the yttrium group element compound can be dissolved in a short time without deteriorating the characteristics by setting the following or by setting the immersion time to 2.4 hours or less. Further, it is preferable to heat and ripen after the immersion treatment in the above alkaline aqueous solution. In this ripening treatment, the temperature is 35 to 110 ° C., particularly 60 to 110 ° C.
C. is preferred, and the aging time is preferably 0.2 to 2.4 hours, particularly preferably 0.5 to 2.4 hours. That is, the aging temperature is 3
By setting the aging temperature to 5 ° C. or more and the aging time to 0.2 hours or more, the oxidization process is properly advanced and the aging temperature is set to 11
By setting the temperature to 0 ° C. or lower and the aging time to 2.4 hours or shorter, it is possible to prevent the oxidation from proceeding too much.

The present inventor has conducted further studies in assembling an alkaline storage battery using the above-mentioned non-sintered positive electrode that has been subjected to oxidation treatment. As a result, potassium hydroxide was the main constituent, lithium hydroxide and sodium hydroxide were the main constituents. It was found that when an alkaline aqueous solution containing any one or more of zinc oxide is used as the electrolytic solution, the charging efficiency at high temperature can be further improved. The content of lithium hydroxide or sodium hydroxide in the alkaline electrolyte is preferably 1 to 10% by weight, and 2 to
It is more preferably 6% by weight. That is, the effect is appropriately expressed by setting this concentration, and
It is possible to prevent deterioration of low-temperature characteristics due to too much.
When zinc oxide is contained, its amount is preferably 1 to 6% by weight, more preferably 2.5 to 5.5% by weight. That is, by setting this concentration, it is possible to appropriately exhibit the effect and to prevent the deterioration of the low temperature characteristics due to the excessive amount.

In contrast to the positive electrode manufactured as described above, a hydrogen storage alloy electrode is used for the negative electrode and an alkaline aqueous solution is used for the electrolytic solution, but these structures may be the same as those of the conventional one. For example, as the hydrogen storage alloy that is the active material of the hydrogen storage alloy electrode that constitutes the negative electrode, for example, rare earth-Ni-based, Laves-based, Mg-Ni-based, V-
Various hydrogen storage alloys such as Ti-Ni series are listed,
Among them, a rare earth-Ni based hydrogen storage alloy using misch metal is preferable. In particular, Ni, Co, Mn, and Al are contained, and the ratios of Ni, Co, Mn, and Al to the misch metal (Mm) 1 are 3.4 in atomic ratio, respectively.
~ 4.3, 0.2-0.7, 0.1-0.5, 0.1
A rare earth-Ni based hydrogen storage alloy in the range of 0.4 is preferable. That is, the cobalt oxide forming the conductive network formed on the positive electrode is easily reduced by the hydrogen gas generated by the corrosion of the hydrogen storage alloy of the negative electrode or the eluted ions, and therefore the conductive network is destroyed. However, since the hydrogen storage alloy having the above composition has a relatively large capacity and little corrosion, it is particularly preferably used in the present invention.

In the alkaline storage battery of the present invention, for example, a separator made of the above-mentioned positive electrode and negative electrode and a nylon non-woven fabric or a polyolefin-based non-woven fabric for separating them is loaded in a battery can and injected as an electrolytic solution of an alkaline aqueous solution. After that, it is manufactured by going through a sealing process.

[0031]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples illustrated in the embodiments. In the following, "parts" means "parts by weight", and "%" indicating concentration, solid solution amount, etc. is "% by weight" unless otherwise specified. Prior to the description of the examples, Reference Example 1 shows a production example of nickel hydroxide used as a positive electrode active material in Examples, and Comparative Reference Example 1 shows a production example of nickel hydroxide used as a positive electrode active material in Comparative Examples. Indicate.

Reference Example 1 The oxidation treatment of the positive electrode active material was performed using a granulator dryer [Fukae Powtech Co., Ltd .: FMD-10J type (trade name)]. That is, 1 part of cobalt and 4% of zinc were solid-dissolved, and 100 parts of nickel hydroxide particles having a peak value of pore radius of 0.7 nm were added to 5 parts of 30% aqueous sodium hydroxide solution containing 5% of hydrogen peroxide. The mixture was mixed for 10 minutes and dried at 100 ° C. under a vacuum degree of 13.3 kPa for 30 minutes to make part of nickel on the surface of the nickel hydroxide particles trivalent. Then, 6 parts of cobalt hydroxide and 10 parts of 40% sodium hydroxide aqueous solution were added, and the mixture was stirred in air at 110 ° C. for 4 hours.
Drying was performed for 0 minutes to produce nickel hydroxide in which the surface of particles was coated with a cobalt compound.

Comparative Reference Example 1 As in Reference Example 1, 1% cobalt and solid solution zinc were added,
6 parts of cobalt hydroxide and 10 parts of 40% aqueous sodium hydroxide solution were added to 100 parts of nickel hydroxide particles having a peak value of pore radius of 0.7 nm, and the mixture was dried in air at 110 ° C. for 40 minutes while stirring. I went. That is, Comparative Reference Example 1 was the same as Reference Example 1 except that the addition of the hydrogen peroxide-added sodium hydroxide aqueous solution and the drying at 100 ° C. and the vacuum degree of 13.3 kPa, which were performed in Reference Example 1, were not performed. Was carried out to produce nickel hydroxide having the particle surface coated with a cobalt compound.

The nickel hydroxide coated with the cobalt compound in Reference Example 1 and Comparative Reference Example 1 was subjected to surface analysis by ESCA (X-ray photoelectron spectroscopy). That is, PHI5500MC (trade name) manufactured by ULVAC, Inc. was used as an X-ray source, MgKα400W, and an analysis region of φ800 μm was analyzed under the measurement conditions of a photoelectron emission angle of 45 deg. FIG. 1 shows the state of cobalt, and FIG. 2 shows the state of nickel. Regarding cobalt, as shown in FIG. 1, in both Reference Example 1 and Comparative Reference Example 1, a broad peak showing the form of an oxide or a hydroxide is observed in the vicinity of 785 eV to 788 eV. However, regarding nickel, as shown in FIG. 2, the peak of trivalent at 857 eV is seen in Reference Example 1, but divalent in Comparative Reference Example 1 not oxidized with hydrogen peroxide. The state (855 eV) is shown. That is, as in Reference Example 1, when a part of nickel on the surface of nickel hydroxide particles is made trivalent by previously performing an oxidation treatment with an oxidizing agent (hydrogen peroxide), Higher order cobalt oxides can be coated. In addition, chemical analysis showed that sodium was sample 1
It was confirmed that 2% was mixed with g. Further, the valence of the cobalt oxide of Reference Example 1 was 2.9 in terms of cobalt, and the valence of the cobalt oxide of Comparative Reference Example 1 was 2.5 in terms of cobalt.

Example 1 A part of nickel on the surface of particles produced in Reference Example 1 was made trivalent, and the surface of the particles was coated with cobalt oxide containing sodium. 2 parts, ytterbium oxide powder 3 parts (0.0
075 mol, 0.015 mol as ytterbium with respect to 100 g of nickel hydroxide) 10 parts by weight of 2% carboxymethyl cellulose aqueous solution, 3 parts of 60% polytetrafluoroethylene dispersion are added and mixed to prepare a paste containing positive electrode mixture. Was prepared. The obtained positive electrode mixture-containing paste is applied to and filled in a porous conductive substrate made of nickel foam (the positive electrode mixture-containing paste is applied to the substrate so that the positive electrode mixture is contained in the pores of the substrate. Fill a part of the paste containing the agent), 8
After being dried at 0 ° C. for 1 hour to form a positive electrode mixture layer, it was pressure-molded at 1 ton / cm ² to form a sheet, which contained 30% of potassium hydroxide and 2% of lithium hydroxide.
After immersing in an alkaline aqueous solution heated to ℃ for 0.5 hours, after immersing in an alkaline aqueous solution containing air for 95 hours in air at 95 ℃, washed with hot water at 70 ℃ for 0.7 hours, After drying at 85 ℃ for 1 hour, the theoretical capacity is 650m.
A non-sintered positive electrode of Ah was obtained.

The negative electrode was manufactured as follows. That is, commercially available samples of Mm (containing La, Ce, Nd and Pr), Ni, Co, Mn and Al (all having a purity of 99% by weight or more) were treated with MmNi _3.9 Co _0.6 Mn _0.36 A
It was heated and melted in a high frequency melting furnace so that a composition of 1 _0.25 was obtained to obtain a hydrogen storage alloy. By mechanically crushing this hydrogen storage alloy, hydrogen storage alloy powder having an average particle diameter of 35 μm was obtained. To 100 parts of this hydrogen storage alloy powder, 1 part of carbonyl nickel powder, 10 parts of 5% poly-N-vinylacetamide aqueous solution and 1.7 parts of 40% styrene-2-ethylhexyl acrylate copolymer were added and mixed, A negative electrode mixture-containing paste was prepared. This negative electrode mixture-containing paste is applied to a base material made of punching metal, filled and dried to form a negative electrode mixture layer, which is then pressure-molded and then cut into a predetermined size to form a sheet-shaped negative electrode. It was made.

The positive electrode and the negative electrode were spirally wound with a nylon non-woven separator interposed therebetween, and the spirally wound electrode body was inserted into a battery can.
%, Sodium hydroxide 4%, lithium hydroxide 2% and zinc oxide 3% were injected and sealed to produce a AAA alkaline storage battery.

The structure of the alkaline storage battery will be described with reference to FIG. 3. Reference numeral 1 is the positive electrode and 2 is the negative electrode. In FIG. 3, the positive electrode 1 and the negative electrode 2 are described in detail. However, the base material and the like are omitted and shown as a single structure. The positive electrode 1 and the negative electrode 2 are superposed on each other with the separator 3 interposed therebetween, and are spirally wound and inserted into the battery can 5 as the spirally wound electrode body 4, and the insulator 14 is arranged on the upper portion thereof. Has been done. In addition, the insulator 13 is provided on the bottom of the battery can 5 prior to the insertion of the electrode body 4.
Is provided.

The annular gasket 6 is made of nylon 66, and the battery lid 7 is composed of a terminal plate 8, a sealing plate 9 and a metal spring 10 and a valve body 11 which are arranged in an internal space formed by them. The opening of 5 is sealed by the battery lid 7 or the like. That is, after inserting the electrode body 4, the insulator 13, the insulator 14 and the like into the battery can 5, an annular groove 5a is formed in the vicinity of the open end of the battery can 5 so that the bottom portion projects inward. The annular gasket 6 and the battery lid 7 are arranged in the opening of the battery can 5 by supporting the lower portion of the annular gasket 6 with the inner peripheral side protruding portion of the groove 5a, and the portion of the battery can 5 beyond the groove 5a is placed inside. It is tightened in one direction to seal the opening of the battery can 5. The terminal plate 8 is provided with a gas discharge port 8a, the sealing plate 9 is provided with a gas detection port 9a, and a metal spring 10 and a valve body 11 are arranged between the terminal plate 8 and the sealing plate 9. ing. Then, the outer peripheral portion of the sealing plate 9 is bent to sandwich the outer peripheral portion of the terminal plate 8 to fix the terminal plate 8 and the sealing plate 9.

This battery has a metal spring 1 under normal circumstances.
Since the valve body 11 closes the gas detection port 9a by the pressing force of 0, the inside of the battery is kept in a sealed state, but when gas is generated inside the battery and the pressure inside the battery rises abnormally. , The metal spring 10 contracts to form a gap between the valve body 11 and the gas detection port 9a, and the gas inside the battery passes through the gas detection port 9a and the gas discharge port 8a and is discharged to the outside of the battery. As a result, when the battery internal pressure decreases and the battery internal pressure returns to normal, the metal spring 10 restores to the original state,
The pressing force causes the valve element 11 to close the gas detection port 9a again to keep the inside of the battery in a sealed structure.

The positive electrode lead body 12 is made of a nickel ribbon, one end of which is spot-welded to the conductive base material of the positive electrode 1, the other end is spot-welded to the lower end of the sealing plate 9, and the terminal plate 8 is By contact with the sealing plate 9, it can function as a positive electrode terminal. The conductive base material is exposed on the outer surface side of the outermost peripheral portion of the negative electrode 2, and the base material contacts the inner wall of the battery can 5, whereby the battery can 5 functions as a negative electrode terminal.

Example 2 Ytterbium oxide was added in an amount of 4 parts (0.01 mol, 0.02 mol of ytterbium to 100 g of nickel hydroxide), and the temperature of the positive electrode when immersed in an alkaline aqueous solution was 88 ° C. Immersion time 0.65 hours, 95 ℃
Example 1 except that the aging time in air was 1 hour.
An alkaline storage battery was prepared in the same manner as in.

Example 3 Yttrium oxide was replaced by 1.5 instead of ytterbium oxide.
(0.006 mol, 0.012 mol of yttrium with respect to 100 g of nickel hydroxide) was added,
An alkaline storage battery was prepared in the same manner as in Example 1.

Example 4 The same procedure as in Example 1 was repeated except that 2.3 parts of erbium oxide (0.006 mol, 0.012 mol of erbium per 100 g of nickel hydroxide) was added in place of ytterbium oxide. A storage battery was produced.

Comparative Example 1 An alkaline storage battery was produced in the same manner as in Example 1 except that nickel hydroxide having the surface of the particles prepared in Comparative Reference Example 1 coated with cobalt oxide was used.

Comparative Example 2 An alkaline storage battery was prepared in the same manner as in Example 1 except that ytterbium oxide was not added and the oxidation treatment with the alkaline aqueous solution was not performed.

Comparative Example 3 An alkaline storage battery was produced in the same manner as in Comparative Example 1 except that ytterbium oxide was not added and the oxidation treatment with an alkaline aqueous solution was not performed.

Each of the alkaline storage batteries of Examples 1 to 4 and Comparative Examples 1 to 3 was stored at 70 ° C. for 6 hours, and then charged at 25 ° C. and 0.1 C (70 mA) for 12 hours to obtain 0. The charge / discharge cycle of discharging to 1.0 V at 2 C (140 mA) was repeated until the discharge capacity became constant, and then the utilization rate of the positive electrode was examined. The results are shown in Table 1.

The utilization factor of the above positive electrode is 0.
The discharge capacity was measured when the battery was charged at 25 C (160 mA) for 6 hours and discharged to 1.0 V at 0.2 C (130 mA) after 1 hour of rest, and calculated as a ratio to the theoretical capacity of the positive electrode. The results are shown in Table 1.

Further, the discharged battery was stored at 80 ° C. for 14 days, and then the battery was charged at 25 ° C. and 1 C (650 mA) for 1.2 hours, and after 20 minutes of rest, 1 C (650 m).
Three cycles of discharging to 1.0 V in A) were performed, and the discharge capacity at the high temperature storage was obtained by dividing the discharge capacity at the third cycle by the initial discharge capacity. The results are shown in Table 1.

Furthermore, the battery was placed in an environment of 45 ° C.
At a current value of (650 mA), the battery is charged under the charge cut condition of -ΔV = 10 mV, and the battery voltage is 1 V at 1 C (650 mA).
By repeating the charging / discharging cycle of discharging until the discharge capacity drops to 400 mAh, the cycle number in the high temperature atmosphere was evaluated by examining the number of cycles until the discharge capacity dropped to 400 mAh. The results of examining the number of cycles are shown in Table 1.

[0052]

[Table 1]

As shown in Table 1, the batteries of Examples 1 to 4 and Comparative Example 1 in which the positive electrode was oxidized with an alkaline aqueous solution were compared with the batteries of Comparative Examples 2 to 3 in which the positive electrode was not oxidized. Therefore, the utilization rate of the positive electrode was high. In addition, the batteries of Examples 1 to 4 using nickel hydroxide whose particle surface was coated with cobalt oxide containing sodium as an active material,
The recovery rate at high temperature storage was higher than that of the battery of Comparative Example 1 in which nickel hydroxide without such coating was used as an active material.

Further, nickel hydroxide having a part of nickel on the surface of particles made trivalent and the surface of the particles coated with cobalt oxide containing sodium was used as an active material, and a yttrium group element compound and cobalt hydroxide were used for the positive electrode. The batteries of Examples 1 to 4 added and subjected to oxidation treatment of the positive electrode were 3
Compared to the battery of Comparative Example 1 using nickel hydroxide containing no valent nickel as an active material and the batteries of Comparative Examples 2 to 3 in which the yttrium group element compound was not added and the positive electrode was not oxidized. The cycle characteristics in the atmosphere of 45 ° C were excellent.

[0055]

As described above, according to the present invention,
It is possible to provide an alkaline storage battery having a high utilization factor of the positive electrode and a high recovery rate at high temperature storage, and excellent cycle characteristics in a high temperature atmosphere.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a nickel hydroxide prepared in Reference Example 1 in which a part of nickel on the surface of the particle is trivalent and the surface of the particle is coated with cobalt oxide containing sodium, and a surface of the particle prepared in Comparative Reference Example 1 is cobalt. It is a figure which shows the state of the binding energy of cobalt in the surface analysis by ESCA of nickel hydroxide coated with the oxide.

FIG. 2 is a graph showing nickel hydroxide obtained by coating a part of nickel on the surface of particles produced in Reference Example 1 with trivalence and coating the surface of the particles with cobalt oxide containing sodium, and the surface of particles produced by Comparative Reference Example 1 with cobalt. It is a figure which shows the state of the binding energy of nickel in the surface analysis by ESCA of nickel hydroxide coat | covered with the oxide.

FIG. 3 is a cross-sectional view schematically showing an example of the alkaline storage battery according to the present invention.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 separator

Continued front page    F-term (reference) 5H028 EE04 EE05 HH01                 5H050 AA05 AA07 AA08 BA11 CA03                       CB16 DA09 EA01 EA12 GA15                       GA22 HA01 HA02

Claims (4)

[Claims] 1. An alkaline storage battery comprising a non-sintered positive electrode having nickel hydroxide as an active material, a negative electrode having a hydrogen storage alloy as an active material, a separator, and an electrolytic solution, wherein the nickel hydroxide is a hydroxide of a particle surface. A part of nickel in nickel is made trivalent and the particle surface is coated with cobalt oxide containing sodium. At least a cobalt compound and a yttrium group element compound are added to the positive electrode, and the cobalt compound and yttrium are added. The alkaline storage battery is characterized in that the group element compound is oxidized in an alkaline aqueous solution. 2. The alkaline storage battery according to claim 1, wherein the valence of the cobalt oxide containing sodium is 2.6 to 3.1 in terms of cobalt. 3. The alkali according to claim 1, wherein the amount of the yttrium group element compound added is 0.0006 to 0.05 mol in terms of the number of moles of the yttrium group element with respect to 100 g of nickel hydroxide. Storage battery. 4. The alkaline storage battery according to claim 1, wherein the yttrium group element is yttrium, ytterbium or erbium.