JPH08329938A - Nickel electrode for alkaline storage battery and alkaline storage battery - Google Patents

Abstract

PURPOSE: To provide a nickel electrode for an alkaline storage battery with high discharging performance, and high charging efficiency at high temperature by containing zinc or cobalt and copper in a solid solution state in the crystal of nickel hydroxide of a main active material. CONSTITUTION: In a nickel electrode having an active material whose main component is nickel hydroxide, zinc and/or cobalt and copper are contained in a solid solution state in the crystal of the nickel hydroxide. When zinc, cobalt, and copper are contained, about 1-5wt.% zinc, about 1-6wt.% cobalt, and about 0.1-5wt.% copper are preferable, when zinc and copper are contained, about 1-5wt.% zinc and about 1-3wt.% copper are preferable, and when cobalt and copper are contained, about 1-5wt.% cobalt and about 1-3.wt% copper are preferable. A high-performance alkaline storage battery in which the swelling of the electrode is sufficiently suppressed to lengthen the life, and environmentally harmful cadmium is not used is obtained.

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 such as a nickel metal hydride battery, a nickel zinc battery, a nickel cadmium battery, a nickel iron battery and the like, and an alkaline storage battery provided with the nickel electrode. Is.

[0002]

2. Description of the Related Art As high energy density batteries for electric vehicles, nickel metal hydride batteries and nickel zinc batteries using a pasted nickel electrode for the positive electrode have been developed. It is required that the charging efficiency is long and the charging efficiency at high temperature is high.

As a method for improving the performance of nickel electrodes to meet such demands, it is known that adding a solid solution of a different element to nickel hydroxide as an active material is effective. For example, Group II elements such as zinc and cadmium and Group Ib elements are added in order to suppress the formation of γ-NiOOH, which is the cause of swelling of the nickel electrode, and prolong the life. In addition, in order to increase the oxygen overvoltage and improve the charging efficiency at high temperature, cobalt having the action of making the oxidation potential of the nickel electrode base is added, or zinc oxide having the action of making the oxygen generation potential noble, Such as cadmium oxide
I am mixing group II element compounds. Even if these elements are added in combination, the action of each element is exhibited.

[0004]

When cobalt is added, the oxygen overvoltage increases in proportion to the addition amount.
Since the discharge voltage is also reduced, the addition amount is limited. In addition, cobalt is a rare element and therefore expensive. II
When the group element compound is added, there is almost no effect in the high temperature region of 45 ° C. or higher, and the charging efficiency is significantly reduced. On the other hand, the use of cadmium is regulated from the environmental aspect.

As described above, in order to put a nickel electrode for an electric vehicle into practical use, it is necessary to effectively suppress electrode swelling, improve charging efficiency at high temperatures, and not cause environmental deterioration. However, from the above-mentioned circumstances, no other effective nickel electrode has been found as a conventional nickel electrode that has been put into practical use, other than the one in which zinc and cobalt are added as a solid solution to nickel hydroxide. Moreover, even with the nickel electrode, the charging efficiency at high temperature is about 70 to 80% at 50 ° C., and further improvement is desired.

The present invention provides a nickel electrode for an alkaline storage battery, which has excellent discharge performance, can sufficiently suppress electrode swelling, has sufficiently high charging efficiency at high temperatures, and does not cause environmental deterioration.
Another object of the present invention is to provide an alkaline storage battery including the nickel electrode.

[0007]

In order to achieve the above object, the nickel electrode for an alkaline storage battery according to claim 1 of the present invention is a nickel electrode having an active material mainly composed of nickel hydroxide. It is characterized in that nickel contains at least one of zinc and cobalt and copper in a solid solution state in its crystal.

According to a second aspect of the present invention, in the nickel electrode according to the first aspect, both zinc and cobalt and copper are contained. In addition, in the invention described in claim 2, the content of each component is preferably as follows. That is, zinc: 1 to 5% by weight, cobalt: 1 to 6% by weight, copper: 0.
1-5% by weight.

According to a third aspect of the present invention, the nickel electrode according to the first aspect contains zinc and copper. In addition, in the invention described in claim 3, the content of each component is preferably as follows. That is, zinc: 1 to 5% by weight, copper: 1 to 3% by weight.

According to a fourth aspect of the present invention, the nickel electrode according to the first aspect contains cobalt and copper.
In the invention of claim 4, the content of each component is
The following is preferable. That is, cobalt: 1-5
% By weight, copper: 1-3% by weight.

The alkaline storage battery according to claim 5 is an alkaline storage battery provided with a nickel electrode having an active material mainly composed of nickel hydroxide, wherein nickel hydroxide is contained in the crystal of at least one of zinc and cobalt and copper. And is contained in a solid solution state.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Nickel electrode, test cell shown below,
And the alkaline storage battery was produced.

Nickel Electrode (1) Preparation of Nickel Hydroxide Powder First, nickel hydroxide powder containing zinc, cobalt, and copper in a solid solution state was prepared as follows. That is,
A predetermined amount of zinc sulfate, cobalt sulfate, and copper sulfate were added to nickel sulfate to prepare an aqueous solution, and ammonium sulfate was added to this aqueous solution to form an ammine complex of nickel, zinc, cobalt, and copper, respectively. An aqueous sodium hydroxide solution was added dropwise thereto with vigorous stirring, and the alkalinity was adjusted to pH 11 to 13 to precipitate nickel hydroxide.

Here, a nickel hydroxide powder containing 3% by weight of zinc, 5% by weight of cobalt and 1% by weight of copper in a solid solution was obtained. This nickel hydroxide powder was a spherical powder having the following physical properties. That is, tap density:
2.0-2.1 g / ml, BET specific surface area: 7-17 m
² / g, pore volume determined from adsorption isotherm (desorption side) by the nitrogen adsorption method: 0.01 to 0.03 ml / g.
Therefore, the density was higher than that of the nickel hydroxide powder obtained by the conventional method. The physical properties of the nickel hydroxide powder obtained by the conventional method are as follows: tap density: about 1.6 g / ml, pore volume:
It was about 0.14 ml / g. The conventional method is a method in which an aqueous solution of sodium hydroxide is dropped into an aqueous solution of nickel sulfate with vigorous stirring to precipitate nickel hydroxide.

(2) Preparation of Electrode Next, the nickel hydroxide powder thus obtained was mixed with 10% by weight of cobalt monoxide powder, which is a conductive network preparation agent, and a thickening solution of carboxymethyl cellulose was added to form a paste. Then, this predetermined amount was filled in a nickel metal porous substrate having a porosity of about 95%, dried and pressed to produce a nickel electrode. The obtained nickel electrode had a capacity density of about 600 mAh / ml, and a nickel electrode (about 50 mm) prepared in the same manner using the nickel hydroxide powder obtained by the conventional method.
0 mAh / ml), a higher capacity density was exhibited.

Test Cell An open cell was constructed by using the nickel electrode as a positive electrode, the hydrogen storage alloy electrode as a negative electrode, and a separator interposed. The electrolytic solution used was a 6 mol / l potassium hydroxide aqueous solution.

Alkaline storage battery The nickel electrode is used as a positive electrode, the hydrogen storage alloy electrode, the zinc electrode, the iron electrode, or the cadmium electrode is used as a negative electrode, and the separator is made of polypropylene nonwoven fabric and is wound or laminated, for example, hydroxylated. An alkaline electrolyte such as an aqueous potassium solution was poured to prepare a cylindrical or prismatic battery.

(Embodiment 2) Zinc sulfate and copper sulfate were used as compounds added to nickel sulfate, and nickel hydroxide powder containing zinc and copper in a solid solution was obtained in the same manner as in Embodiment 1 except that nickel nickel powder was further added. An electrode was produced to construct a test cell and an alkaline storage battery. The negative electrode of the cell was a cadmium electrode.

Here, a nickel hydroxide powder containing 3% by weight of zinc and 3% by weight of copper in a solid solution was obtained. This nickel hydroxide powder was a spherical or egg-like powder having the following physical properties. That is, tap density: 2.1 g / m
1, BET specific surface area: 10 m ² / g, pore volume obtained from adsorption isotherm (desorption side) by nitrogen adsorption method: 0.03 m
It was 1 / g. Therefore, the density was higher than that of the nickel hydroxide powder obtained by the conventional method.

(Embodiment 3) A nickel hydroxide powder containing cobalt and copper in a solid solution state was obtained in the same manner as in Embodiment 1 except that the compounds added to nickel sulfate were cobalt sulfate and copper sulfate. An electrode was produced to construct a test cell and an alkaline storage battery. The negative electrode of the cell was a cadmium electrode.

Here, a nickel hydroxide powder containing 5% by weight of cobalt and 5% by weight of copper in a solid solution was obtained. This nickel hydroxide powder was a spherical powder having the following physical properties. That is, tap density: 2.0 to 2.1 g
/ Ml, BET specific surface area: 10 to 30 m ² / g, pore volume obtained from adsorption isotherm (desorption side) by nitrogen adsorption method:
It was 0.01-0.05 ml / g. Therefore, the density was higher than that of the nickel hydroxide powder obtained by the conventional method.

Comparative Example 1 Nickel hydroxide powder was obtained in the same manner as in Example 1 except that nothing was added to nickel sulfate, and a nickel electrode was prepared to form a test cell.

(Comparative form 2) The compound added to nickel sulfate was only zinc sulfate, and the other conditions were the same as in the first embodiment.
A nickel hydroxide powder containing zinc in a solid solution state was obtained, a nickel electrode was further prepared, and a test cell was constructed. Here, a nickel hydroxide powder containing 3% by weight of zinc in a solid solution state was obtained.

(Comparative Example 3) A nickel hydroxide powder containing cobalt in a solid solution state was obtained in the same manner as in Example 1 except that the compound added to nickel sulfate was only cobalt sulfate, and a nickel electrode was prepared. , A test cell was constructed. Here, a nickel hydroxide powder containing 3% by weight of cobalt in a solid solution state was obtained.

(Comparative Example 4) A nickel hydroxide powder containing copper in a solid solution state was obtained in the same manner as in Example 1 except that the compound added to nickel sulfate was only copper sulfate, and a nickel electrode was prepared. , A test cell was constructed. Here, a nickel hydroxide powder containing 3% by weight of copper in a solid solution state was obtained.

(Comparative Example 5) Zinc sulfate and cobalt sulfate were used as compounds added to nickel sulfate, and nickel hydroxide powder containing zinc and cobalt in a solid solution state was obtained in the same manner as in Example 1 except that nickel nickel powder was further added. An electrode was prepared and a test cell was constructed. Here, a nickel hydroxide powder containing 3% by weight of zinc and 5% by weight of cobalt in a solid solution state was obtained.

(Performance Test and Conclusion) For the nickel electrodes of Embodiments 1 to 3 and Comparative Embodiments 1 to 5, the active material utilization rate, charging efficiency at high temperature, and electrode swelling degree were examined.

(1) Utilization rate of active material Generally, when the crystallinity of nickel hydroxide is low, the utilization rate of active material is high. Therefore, with respect to nickel hydroxide, the full width at half maximum of the X-ray diffraction line (001) plane was examined. It is known that the full width at half maximum is a measure of the crystallinity, and generally, the larger the half width is, the smaller the crystallinity is.

In Comparative Example 5, the full width at half maximum of the nickel hydroxide powder was 0.4 degrees, and the nickel electrode active material utilization rate was 85%. On the other hand, in Embodiment 1, the full width at half maximum of the nickel hydroxide powder was 0.9 degree, and the active material utilization rate of the nickel electrode was 98%. Therefore, the coexistence of copper in a solid solution state suppresses the crystallinity of the nickel hydroxide powder of the first embodiment. That is, copper has the effect of suppressing crystallization and improving the utilization rate of the active material.

The nickel electrodes of Embodiments 2 and 3 also showed a high active material utilization rate of 98 to 99%.

FIG. 1 shows the discharge performance of the nickel electrode of Embodiment 2 and the nickel electrode of Comparative Embodiment 5 in which the cobalt content is 3% by weight. The charging / discharging conditions were that charging was performed at a rate of 0.1 C up to 150% of the reference capacity, and discharging was performed at a rate of 0.2 C with respect to the mercury oxide reference electrode.
I decided to go up to V. The charge / discharge temperature was 20 ° C.
As can be seen from FIG. 1, in the nickel electrode of Embodiment 2, no decrease in discharge voltage was observed as in the nickel electrode of Comparative Embodiment 5, and good discharge performance was exhibited.

(2) Charging efficiency at high temperature As for charging efficiency, charging / discharging under predetermined conditions is performed at 20 ° C, 40 ° C, 5 ° C.
The discharge capacity was measured at 0 ° C. and 60 ° C., and the discharge capacity at 20 ° C. was evaluated as a percentage. The charging / discharging conditions were the same as the charging / discharging conditions in (1) above. Furthermore, the oxygen generation potential, the average oxidation potential, and the potential difference (η value) between the two potentials were determined. Table 1 shows the results.

[0033]

[Table 1]

Generally, the charging efficiency of the nickel electrode is improved as the η value, which is a measure of the oxygen overvoltage, is larger because the oxidation reaction of nickel hydroxide as the active material proceeds without generating oxygen. The large η value of the nickel electrode of Embodiment 1 is due to the large shift of the oxidation potential to base, which is based on the action of cobalt added as a solid solution. Therefore, as shown in Table 1, the nickel electrodes of Embodiment 1 and Comparative Embodiment 5 both have large η.
The value shows the charging efficiency at 40 to 50 ° C. But,
The nickel electrode of the first embodiment is 6
High charging efficiency at 0 ° C.

Therefore, in order to see the result in more detail regarding the charging efficiency at high temperature, the following test was conducted. That is, the contents of zinc, cobalt, and copper were varied within the range of 5% by weight to prepare nickel hydroxide powders having different η values, and the charging efficiency of the nickel electrode using them was measured. The nickel hydroxide powder and the nickel electrode were manufactured in the same manner as in the first embodiment. FIG. 2 shows the relationship between the charging efficiency of those nickel electrodes and the η value at 20 ° C. As can be seen from FIG. 2, regarding the charging efficiency at 45 ° C., there is almost no difference between the nickel electrode of Embodiment 1 and the nickel electrode of Comparative Example 5, and the charging efficiency depends solely on the η value. There is. However, regarding the charging efficiency at 60 ° C., the nickel electrode of Embodiment 1 is higher than the nickel electrode of Comparative Form 5 even if the η value is the same. As described above, the nickel electrode of Embodiment 1 has improved charging efficiency at 60 ° C. as compared with Comparative Embodiment 5, and has high charging efficiency at high temperature.

With respect to the nickel electrode in which the content of copper was changed in the second embodiment, the nickel electrode in which the contents of zinc and copper were changed in the second and fourth comparison examples, and the nickel electrode of the first comparison example, 40 ° C. I checked the charging efficiency. The charging / discharging conditions were the same as the charging / discharging conditions in (1) above. The result is shown in FIG. As can be seen from FIG. 3, copper has an effect of improving the charging efficiency at high temperature, and the effect is increased by using it in combination with zinc. Addition amount of copper is 1-3
Weight percent is preferred.

Nickel electrode of Embodiment 3 and Comparative Embodiment 1
Of the nickel electrode of Comparative Example 4 and the copper content of Comparative Example 4 are 1
The relationship between the charging / discharging temperature and the charging efficiency was examined for the nickel electrode in the case of weight% and in the range of 3 to 5% by weight. FIG. 4 shows the results. As you can see from Figure 4,
By using copper in combination with cobalt, the charging efficiency at high temperatures is significantly improved.

(3) Electrode swelling degree γ-NiOOH which is a cause of electrode swelling (change in electrode thickness)
Was investigated. It is said that it is necessary to add 3% by weight or more of zinc to nickel hydroxide as a solid solution in order to effectively suppress the production of γ-NiOOH. Therefore, the production rates of γ-NiOOH of the nickel electrodes of Example 1 and Comparative Example 2 were measured as follows. That is, the γ-NiOOH powder generated when overcharged at a charge rate of 0.5 C at a low temperature of 5 ° C. was measured by an X-ray diffraction peak. As a result, it was 7% for the nickel electrode of Comparative Example 2, but was 6% for the nickel electrode of Embodiment 1. That is, even in the nickel electrode of the first embodiment, γ-NiO
Generation of OH was suppressed.

With respect to the nickel electrode having a changed copper content in Embodiment 2, the nickel electrode having a changed copper content in Comparative Embodiment 4, and the nickel electrode of Comparative Embodiment 1, the production rate of γ-NiOOH. I checked. FIG. 5 shows the result. As can be seen from FIG. 5, copper has γ-N
It has an action of suppressing iOOH production, and its action becomes remarkable by using it in combination with zinc.

Nickel electrode of Embodiment 3 and Comparative Embodiment 4
In the above, the relationship between the electrode swelling and the production rate of γ-NiOOH was examined for the nickel electrode having a copper content of 1, 3, 5 wt% and the nickel electrode of Comparative Example 1. FIG. 6 shows the result. As can be seen from FIG. 6, copper has γ-N
It has an effect of suppressing the production of iOOH, and this effect is exhibited without being inhibited even when used in combination with cobalt. It should be noted that the addition of copper in excess of 5 wt% is excessive for suppressing the production of γ-NiOOH.

(4) Conclusion Zinc added in a solid solution state to nickel hydroxide, which is an active material, has a conventionally known effect. That is, it suppresses the generation of low-density γ-NiOOH which causes the swelling of the nickel electrode.

Similarly, the cobalt added in a solid solution state is
It has a conventionally known effect. That is, the oxygen overvoltage of the nickel electrode is increased to improve the charging efficiency at high temperature.

Copper, which is also added in a solid solution state, exhibits the following actions (1) to (3). Even if copper is used in combination with zinc or cobalt, the action of zinc or cobalt is not hindered. It suppresses the crystallization of nickel hydroxide and improves the utilization rate of the active material. Incidentally, the active material utilization rate of nickel hydroxide generally has a correlation with the crystallinity, and the higher the crystallinity, that is, the higher the crystallinity, the lower the active material utilization rate tends to be. The oxygen overvoltage of the nickel electrode is increased to improve the charging efficiency at high temperature. This effect becomes remarkable when used in combination with zinc or cobalt. It suppresses the generation of γ-NiOOH and suppresses electrode swelling. This effect becomes greater when used in combination with zinc.

As described above, in the nickel electrode of Embodiment 1, in addition to the γ-NiOOH production suppressing effect of zinc and the charging efficiency improving effect of cobalt at 40 to 50 ° C., the active material utilization improving effect of copper and the high temperature In this case, the charging efficiency improving effect and the γ-NiOOH production suppressing effect are exhibited. In particular, the effect of copper for improving charging efficiency at high temperatures is increased by using it in combination with zinc and cobalt, and the effect of suppressing γ-NiOOH production is increased by using it in combination with zinc.

In the nickel electrode of the second embodiment, in addition to the effect of suppressing the production of γ-NiOOH by zinc, the effect of using copper to improve the utilization rate of the active material, the effect of improving the charging efficiency at high temperatures, and
-The effect of suppressing NiOOH production is exhibited. In particular, the effect of improving the charging efficiency at high temperature and the effect of suppressing the production of γ-NiOOH by copper are increased by using together with zinc.

In the nickel electrode of the third embodiment, in addition to the charging efficiency improving effect of cobalt at 40 to 50 ° C., the active material utilization improving effect of copper, the charging efficiency improving effect at high temperature, and the γ-NiOOH production suppressing effect. Is being demonstrated. In particular, the effect of improving the charging efficiency of copper at high temperature is increased by using it in combination with cobalt.

Therefore, all of the nickel electrodes of Embodiments 1 to 3 are excellent in discharge performance, can suppress the swelling of the electrodes by suppressing the production of γ-NiOOH, and have a sufficiently high charging efficiency at high temperatures. In addition, since cadmium is not contained in the nickel electrode, it does not cause environmental deterioration.

In addition, the alkaline storage batteries of Embodiments 1 to 3 have the following functions and. That is, good performance is exerted on the basis of the above action of the nickel electrode. Since the nickel electrode does not contain cadmium,
Cadmium does not interfere with the battery reaction,
Provide a stable battery system. That is, in a battery, it is known that, when the battery is charged and discharged for a long period of time, the element added to the nickel electrode is partially eluted into the electrolytic solution, which adversely affects the negative electrode depending on the kind of the element. In particular, when a nickel electrode to which cadmium is added as an electrode swelling inhibitor is used in a nickel metal hydride battery, the eluted cadmium is deposited on the surface of the hydrogen storage alloy electrode, which is the negative electrode, and inhibits the reaction.

[0049]

According to the nickel electrode of claim 1,
In addition to the effect of at least one of zinc and copper, copper can improve the utilization rate of the active material, improve the charging efficiency at high temperature, and further suppress the swelling of electrodes. Therefore, the nickel electrode according to claim 1 has excellent discharge performance, and
NiOOH generation can be suppressed and electrode swelling can be suppressed sufficiently,
Charging efficiency at high temperature is sufficiently high. In addition, since cadmium is not contained in the nickel electrode, it does not cause environmental deterioration.

According to the second aspect of the present invention, the production of γ-NiOOH can be suppressed by zinc, and the cobalt content of 40-
The charging efficiency at 50 ° C. can be improved, and in addition, the effect of claim 1 can be exhibited by copper. In particular, when used in combination with zinc and cobalt, copper can remarkably improve the charging efficiency at high temperatures, and remarkably suppress the production of γ-NiOOH.

According to the invention of claim 3, the production of γ-NiOOH can be suppressed by zinc, and in addition, the effect of claim 1 can be exhibited by copper. In particular, when used in combination with zinc, copper can remarkably improve the charging efficiency at high temperatures and remarkably suppress the production of γ-NiOOH.

According to the invention of claim 4, cobalt can improve the charging efficiency at 40 to 50 ° C., and in addition, copper can exert the effect of claim 1. In particular, when used in combination with cobalt, copper can significantly improve charging efficiency at high temperatures.

According to the alkaline storage battery of claim 5,
The effects described in claims 1 to 4 can be exhibited. Further, since cadmium is not contained in the nickel electrode, it is possible to prevent the cell reaction from being hindered by cadmium and to provide a stable cell system.

[Brief description of drawings]

FIG. 1 is a diagram showing discharge performance between a nickel electrode of Embodiment 2 and a nickel electrode in which a cobalt content in Comparative Embodiment 5 is 3% by weight.

FIG. 2 is a diagram showing a relationship between a charging efficiency of a nickel electrode having nickel hydroxide powders having different η values and a η value at 20 ° C. in Embodiment 1 and Comparative Embodiment 5.

FIG. 3 is a diagram showing a nickel electrode having a changed copper content in Embodiment 2, a nickel electrode having a changed content of zinc and copper in Comparative Embodiments 2 and 4 and a nickel electrode of Comparative Embodiment 1; FIG. 5 is a diagram showing the relationship between the amount of copper added and the charging efficiency at 40 ° C.

FIG. 4 shows a nickel electrode according to a third embodiment, a nickel electrode according to a first comparative example, and a nickel electrode according to a fourth comparative example in which the copper content is 1% by weight and 3 to 5% by weight. It is a figure which shows the relationship between charging / discharging temperature and charging efficiency.

FIG. 5 shows the amount of copper added with respect to the nickel electrode of Embodiment 2 in which the content of copper is changed, the nickel electrode of Embodiment 4 in which the content of copper is changed, and the nickel electrode of Comparison 1. It is a figure which shows the relationship with the production rate of (gamma) -NiOOH.

FIG. 6 shows the electrode swelling and γ-NiOOH of the nickel electrode of Embodiment 3, the nickel electrode of Comparative Embodiment 4 having a copper content of 1, 3, 5 wt%, and the nickel electrode of Comparative Embodiment 1. It is a figure which shows the relationship with a production rate.

Claims (5)

[Claims] 1. A nickel electrode having an active material mainly composed of nickel hydroxide, wherein the nickel hydroxide contains at least one of zinc and cobalt and copper in a solid solution state in the crystal thereof. Characteristic nickel electrode for alkaline storage battery. 2. The nickel electrode for an alkaline storage battery according to claim 1, which contains both zinc and cobalt and copper. 3. The nickel electrode for an alkaline storage battery according to claim 1, which contains zinc and copper. 4. The composition according to claim 1, which contains cobalt and copper.
The nickel electrode for an alkaline storage battery described. 5. In an alkaline storage battery provided with a nickel electrode having an active material mainly composed of nickel hydroxide, nickel hydroxide contains at least one of zinc and cobalt and copper in a solid solution state in its crystal. Alkaline storage battery characterized by having.