JPH09115509A - Alkaline storage battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain oxidation of a hydrogen storage alloy negative electrode and the degradation by componental dissolution by containing hydrogen storage alloy and a prescribed compound in the negative electrode. SOLUTION: An alkaline storage battery is composed of a postive electrode mainly composed of a metallic oxide, a negative electrode mainly composed of hydrogen storage alloy, a separator and alkaline electrolyte. Hydrogen storage alloy and a strontium compound or the hydrogen storage alloy and a nuobium compound are contained in this negative electrode. Then, oxidation of the hydrogen storage alloy negative electrode and the degradation by componental dissolution are sufficiently restrained even at high temperature time or the like more than when strontium or niobium whose dissolving quantity in alkaline electrolyte is a trace quantity is contained, and a long service life and highly reliable alkaline storage battery whose perserving characteristic is enhanced while keeping highly efficient discharge performance still high, can be formed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an alkaline storage battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art A nickel-hydrogen storage battery using nickel hydroxide for the positive electrode, a hydrogen storage alloy for the negative electrode, and an alkaline aqueous solution for the electrolyte has recently attracted attention as a battery having a large energy density and containing no heavy metals such as lead and cadmium. ing. In the alkaline storage battery having the hydrogen storage alloy as the negative electrode, the performance deteriorates due to the oxidation of the hydrogen storage alloy powder forming the negative electrode and the dissolution of a part of the component metals by repeating the charge / discharge cycle.

As a countermeasure therefor, for example, in Japanese Unexamined Patent Publication (Kokai) No. 3-280362, alkaline earth metal ions such as strontium and barium are added to an alkaline electrolyte so that the alkaline earth metal ions form water molecules. It is disclosed that even if the addition amount is very small, the high-rate discharge characteristic is kept high and the storage characteristic is improved in order to strongly supplement it as hydration water.

Further, in JP-A-1-265453, by using a hydrogen storage alloy containing an alkaline earth metal as its composition as a negative electrode, it is possible to suppress the solidification between the alloy particles and to improve the cycle characteristics and A method of improving high rate discharge characteristics is disclosed.

Further, Japanese Patent Publication No. 58-36661 discloses that
It has been disclosed that niobium can be used as one of the component metals substituting for Fe in the Ti-Fe-based hydrogen storage alloy, and if the amount of substitution is within the optimum range, hydrogen storage / release characteristics are improved. There is.

[0006]

However, in the above-mentioned conventional method of adding alkaline earth metal ions such as strontium and barium to the alkaline electrolyte, the amount of strontium dissolved in the alkaline electrolyte is very small. However, when the constituent elements of the hydrogen storage alloy are violently oxidized and eluted, the suppressing effect is small, and especially when the life shortening of the charge / discharge cycle at a high temperature is remarkable, there is a problem that the suppressing effect is insufficient. there were.

Further, even in the conventional method of incorporating strontium or niobium into the composition of the hydrogen storage alloy, the effect of suppressing the severe oxidation and dissolution of the alloy at high temperature is insufficient.

An object of the present invention is to solve the above problems and to provide a highly reliable alkaline storage battery having a long life by suppressing the oxidation of the hydrogen storage alloy negative electrode and the deterioration due to the dissolution of the components. .

[0009]

In order to achieve the above object, the alkaline storage battery of the present invention comprises a positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator, and an alkaline electrolyte. The negative electrode comprises a hydrogen storage alloy and at least one selected from a strontium compound and a niobium compound.

Further, a paste made of a powder of a hydrogen storage alloy is applied to or filled in a conductive substrate, immersed in a solution containing strontium hydroxide or a strontium salt or niobate, and then a solution containing strontium salt or niobate. The soaked product is soaked in an alkali, washed with water, and then dried.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Strontium has a specific gravity of 1.30.
Trace amount (10 ^-2mol /
Dissolve (about l). Therefore, with the above configuration, hydrogen
Strontium compound mixed with occlusion alloy powder is electrolyte
It dissolves in a very small amount in the
Strontium is redeposited and a film is formed. Arca
The film of strontium hydroxide in the electrolyte solution absorbs hydrogen.
Suppresses the deterioration and deterioration of the alloy by suppressing the oxidation and melting of the alloy
Therefore, the high temperature life cycle is improved.

It should be noted that strontium in the alloy composition cannot be dissolved and precipitated in an alkaline electrolyte as described above, and the amount of strontium contained in the method of adding strontium to the electrolyte is very small. Cannot be demonstrated.

Also in the niobium compound, the niobium compound mixed in the hydrogen-absorbing alloy powder becomes niobate ions in the alkaline electrolyte to form a complex compound on the surface of the alloy, which suppresses oxidation and dissolution of the alloy. . However, in niobium in the alloy composition, since the metal niobium is in a passive state in all pH regions, the above effect cannot be obtained.

Further, since the strontium compound and the niobium compound are distributed in a high dispersion throughout the negative electrode and enter the gap portion in the negative electrode, the resistance between the alloys is not lowered.
The strontium hydroxide film and the niobium complex compound are formed uniformly on the entire surface of the negative electrode alloy. Therefore, the effect of suppressing the oxidation and dissolution of the hydrogen storage alloy acts on the entire negative electrode alloy, and the effect of suppressing the deterioration of the high temperature life cycle characteristics is further enhanced.

[0015]

【Example】

 (Example 1) Commercially available Mm (Misch Metal Misch
 metal: consists of a mixture of rare earth elements,
The composition of Mm is La 31, Ce 48, Nd in% by weight.
15, Pr 5, and others 1. ), Ni, Co,
Weigh a sample composed of Al and Mn to a certain composition ratio
Amount, mix, heat melt by arc melting, CaCu
_FiveType crystal structure and composition is MmNi_3.5Co_0.75Al
_0.3Mn_0.4Was used as a hydrogen storage alloy for the negative electrode. This alloy
Grind with a ball mill to an average particle size of about 20 μm
Was. Hydrogen absorption of strontium hydroxide in this alloy powder
It was added at a ratio of 1% by weight with respect to the amount of gold. Further carbo
Pace by adding 1% by weight aqueous solution of xymethylcellulose
To form a foamed nickel porous body with a porosity of 95%
It is filled in a conductive substrate consisting of
By pressing, a hydrogen storage alloy electrode was prepared. This electrode
As the negative electrode, a well-known metal foam nickel type positive electrode
Swirl-shaped separator made of sulfonated ropylene non-woven fabric
Configure an electrode group, insert it into a metal case, and
Injection using aqueous potassium chloride solution (specific gravity 1.30) as electrolyte
After that, it was sealed. In this way the sealed alkali
A storage battery was produced and designated as battery A, which is an example of the present invention.

Next, as a first conventional example, a battery constructed in the same manner as the above example without adding strontium hydroxide to a hydrogen storage alloy was designated as a conventional battery B.

Next, in the above-mentioned conventional example, a battery using a solution prepared by dissolving strontium hydroxide to a saturated amount in an aqueous solution of potassium hydroxide (specific gravity 1.30) as an electrolytic solution is referred to as a battery C according to a second conventional example. did.

Next, as a third conventional example, strontium was added to the composition of the hydrogen storage alloy, and the alloy composition was changed to MmNi.
A hydrogen storage alloy with _3.5 Co _0.75 Al _0.3 Mn _0.4 Sr _0.05 was obtained, and this was used as a negative electrode, and a battery configured in the same manner as the second conventional example was used as a conventional battery D.

A charge / discharge cycle test at a high temperature was performed on each of the above-mentioned various batteries. Regarding the cycle characteristics, a cycle of charging at a current equivalent to ⅓ CmA at 65 ° C. for 4.5 hours and then performing a complete discharge at a current equivalent to 1 CmA was repeated to evaluate the capacity change due to the cycle.

FIG. 1 is a diagram showing the relationship between the capacity retention rate and the number of charge / discharge cycles when the capacity of the first cycle is 100. In the figure, A indicates the battery of the present invention, and B, C, and D indicate conventional batteries. As is clear from this figure, in the battery using the negative electrode in which strontium hydroxide was added to the hydrogen storage alloy powder of the present invention, in the battery B in which strontium hydroxide was not added to the hydrogen storage alloy which is the conventional example, and in the electrolytic solution, The charge-discharge cycle characteristics at high temperature are significantly improved as compared with the battery C in which only strontium is added and the battery D in which strontium is added in the hydrogen storage alloy composition. The effect of strontium hydroxide was the same when strontium oxide was added.

(Example 2) The cycle life of the battery was examined by changing the amount of strontium hydroxide added to the hydrogen storage alloy produced in Example 1 in various ways.

The amount of strontium hydroxide added is 0.01 to 2.
Vary between 5% by weight. Otherwise, a sealed alkaline storage battery was prepared in the same manner as in Example 1, and a charge / discharge cycle test was conducted. FIG. 2 shows 500 when the capacity in the first cycle is 100, depending on the amount of strontium hydroxide added.
It is a figure showing the relationship of the capacity maintenance rate of the cycle. As is clear from this figure, when the amount of strontium hydroxide added was 0.05 to 2.0% by weight, the charge-discharge cycle characteristics were improved. If the amount added is outside this range, the resistance between alloy particles will increase and discharge will not be sufficient, and if the amount added is too small, the formation of a strontium hydroxide film on the alloy surface will not be sufficient, so the cycle It is presumed that the effect of suppressing the shortening of the life is reduced.

(Example 3) 1% by weight of carboxymethyl cellulose was added to the hydrogen storage alloy powder prepared in Example 1.
Add an aqueous solution to make a paste, which has a porosity of about 95%.
Was filled in the foamed nickel porous body. This was dried and pressed into a predetermined thickness to obtain a hydrogen storage electrode. This hydrogen storage alloy electrode was immersed in a hot aqueous solution of strontium hydroxide having a concentration of 1 mol / l at 90 ° C. for about 1 minute, and then at 100 ° C.
For 30 minutes. By this immersion, the strontium hydroxide is dispersed in the gaps of the entire alloy in the negative electrode plate. A sealed alkaline storage battery was prepared in the same manner as in Example 1 except that this was used as a negative electrode. This was designated as Battery E according to an example of the present invention, and a charge / discharge cycle test was conducted. FIG.
Is a battery E manufactured by the manufacturing method of this example and a battery A manufactured by the manufacturing method of Example 1 with a capacity of 1 cycle.
It is a figure showing the relationship between a capacity maintenance rate and the number of charge / discharge cycles when it is set to 00. From this result, by using the production method of the present invention, by distributing the strontium compound in a high dispersion throughout the negative electrode, the film formation of strontium hydroxide is performed on the entire negative electrode alloy surface, resulting in a decrease in charge-discharge cycle life at high temperature. The effect of suppressing is further improved.
The effect of strontium hydroxide was the same as in the case of adding a strontium salt such as strontium acetate, but in that case, it is necessary to remove anions by the steps of alkali immersion, washing with water and drying.

Example 4 Niobium oxide was added to the hydrogen storage alloy powder prepared in Example 1 in place of strontium hydroxide at a ratio of 2% by weight based on the amount of hydrogen storage alloy.
Further, a 1 wt% aqueous solution of carboxymethyl cellulose was added to form a paste, which was filled into a conductive substrate made of a foamed nickel porous body having a porosity of 95%, which was dried and then pressed to a predetermined thickness to obtain a hydrogen storage alloy. An electrode was prepared. This electrode is used as a negative electrode, and a known foamed metal nickel positive electrode and a separator made of sulfonated polypropylene non-woven fabric constitute a spiral electrode group, which is inserted into a metal case to form an aqueous potassium hydroxide solution (specific gravity 1.30). ) Was injected as an electrolytic solution, and then a sealing was performed. In this way, an AA size sealed alkaline storage battery was obtained, and a battery F that was an example of the present invention was obtained.

Next, as a first conventional example, a battery constructed in the same manner as the above example without adding niobium oxide to the hydrogen storage alloy is referred to as a conventional battery G.

Next, as a second conventional example, an alloy in which niobium was added to the composition of a hydrogen storage alloy was prepared to prepare MmNi _3.5 Co.
_A hydrogen storage alloy of _0.75 Al _0.3 Mn _0.4 Nb _0.05 was obtained, and this was used as a negative electrode, and a battery configured in the same manner as in the above-described embodiment was used as a conventional battery H.

A charge / discharge cycle test at a high temperature was conducted on each of the above-mentioned various batteries. Regarding the cycle characteristics, a cycle of charging at a current equivalent to ⅓ CmA at 65 ° C. for 4.5 hours and then performing a complete discharge at a current equivalent to 1 CmA was repeated to evaluate the capacity change due to the cycle.

FIG. 4 is a diagram showing the relationship between the capacity retention rate and the number of charge / discharge cycles when the capacity of the first cycle is 100. In the figure, F shows the batteries G and H of the present invention, and conventional batteries. As is clear from this figure, in the battery using the negative electrode in which niobium oxide was added to the hydrogen storage alloy powder of the present invention, compared with the battery in which niobium was added in the hydrogen storage alloy composition of the conventional example, the temperature was significantly higher. It can be seen that the charge / discharge cycle characteristics are improved.

(Embodiment 5) The cycle life of the battery was examined by changing the amount of niobium oxide added to the hydrogen storage alloy produced in Embodiment 4 in various ways.

The amount of niobium oxide added was varied between 0.1 and 4.0% by weight in terms of niobium with respect to the hydrogen storage alloy. Otherwise, a sealed alkaline storage battery was produced in the same manner as in Example 4, and a charge / discharge cycle test was performed. Figure 4
Depending on the amount of niobium oxide added, the capacity of the first cycle should be 10
It is a figure showing the relationship of the capacity maintenance rate of the 500th cycle when it is set to 0. As is clear from this figure, the charge / discharge cycle characteristics were improved when the amount of niobium oxide added was 0.5 to 3.0% by weight.

(Example 6) 1 wt% of carboxymethyl cellulose was added to the hydrogen storage alloy powder prepared in Example 4.
Add an aqueous solution to make a paste, which has a porosity of about 95%.
Was filled in the foamed nickel porous body. This was dried and then pressed to a predetermined thickness to form a hydrogen storage electrode. This hydrogen storage alloy electrode was immersed in an aqueous sodium niobate solution having a concentration of 1 mol / l for about 1 minute, and then dried at 100 ° C. for 30 minutes. By this immersion, niobic acid is dispersed in the gaps of the entire alloy in the negative electrode plate. A sealed alkaline storage battery was produced in the same manner as in Example 1 except that this was used as a negative electrode. This was designated as Battery I and subjected to a charge / discharge cycle test. FIG. 6 shows the relationship between the capacity retention rate and the number of charge / discharge cycles in the case where the battery I manufactured by the manufacturing method of this example and the battery F manufactured by the manufacturing method of Example 4 have a capacity of 100 in the first cycle. It is a figure showing. From this result, by using the production method of the present invention and distributing the niobate in a high dispersion throughout the negative electrode, the effect of suppressing the reduction of the charge / discharge cycle life at high temperature is improved.

[0032]

As described above, according to the alkaline storage battery of the present invention, by adding at least one selected from the strontium compound and the niobium compound to the hydrogen storage alloy powder, the deterioration of the alloy is suppressed and the high temperature Life cycle is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing charge / discharge cycle characteristics of an alkaline storage battery of Example 1 of the present invention and a conventional example battery.

FIG. 2 is a diagram showing the amount of strontium hydroxide added and the charge / discharge cycle characteristics in the alkaline storage battery of Example 2 of the present invention.

FIG. 3 is a diagram showing charge / discharge cycle characteristics of an alkaline storage battery of Example 3 of the present invention and a conventional example battery.

FIG. 4 is a diagram showing charge / discharge cycle characteristics of an alkaline storage battery of Example 3 of the present invention and a conventional example battery.

FIG. 5 is a diagram showing the amount of niobium oxide added and the charge / discharge cycle characteristics in the alkaline storage battery of Example 3 of the present invention.

FIG. 6 is a diagram showing charge / discharge cycle characteristics of an alkaline storage battery of Example 3 of the present invention and a conventional example battery.

Claims (8)

[Claims] 1. An alkaline storage battery comprising a positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator and an alkaline electrolyte, wherein the negative electrode is a hydrogen storage alloy and a strontium compound or niobium. An alkaline storage battery containing at least one selected from compounds. 2. The strontium compound is at least one selected from strontium oxide, strontium hydroxide and strontium salt.
The alkaline storage battery according to the above. 3. The alkaline storage battery according to claim 1, wherein the strontium compound is added in an amount of 0.05 to 2.0% by weight in terms of strontium with respect to the amount of hydrogen storage alloy. 4. The alkaline storage battery according to claim 1, wherein the niobium compound is at least one selected from niobium oxide and niobate. 5. A hydrogen storage alloy containing a niobium compound,
The alkaline storage battery according to claim 1, wherein 0.5 to 3.0% by weight in terms of niobium is added. 6. A method of manufacturing an alkaline storage battery comprising a positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator, and an alkaline electrolyte, which comprises a powder of the hydrogen storage alloy. Apply the paste to the conductive substrate,
Alternatively, a method for manufacturing an alkaline storage battery is characterized in that it is filled, immersed in a solution containing strontium hydroxide, and then dried. 7. A method of manufacturing an alkaline storage battery comprising a positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator, and an alkaline electrolyte, which comprises a powder of the hydrogen storage alloy. Apply the paste to the conductive substrate,
Alternatively, a method for manufacturing an alkaline storage battery is characterized in that it is filled, immersed in a solution containing a strontium salt, then immersed in an alkali, washed with water, and dried. 8. An alkaline storage battery comprising a positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator and an alkaline electrolyte, wherein a paste of the powder of the hydrogen storage alloy is a conductive substrate. A method for manufacturing an alkaline storage battery, comprising: immersing the electrode plate coated or filled with the above in a solution containing an alkali metal salt of niobate, and then drying.