JP2951940B2 - Electrode for alkaline storage battery, method for producing the same, and alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode for an alkaline storage battery and a method for producing the same, and more particularly to an alkaline storage battery using this electrode as a positive electrode.

[0002]

2. Description of the Related Art Generally, a porous sintered substrate constituting an electrode for an alkaline storage battery is prepared by slurrying a metal powder such as nickel together with a resin component serving as a thickener on a metal plate such as iron serving as a core material. After being applied and dried, it is manufactured by heat treatment in a reducing atmosphere containing hydrogen and sintering. For the alkaline storage battery electrode, the porous sintered substrate obtained in this way is immersed in a nickel nitrate solution, and the holes of the substrate are filled with nickel hydroxide as an active material by a chemical or electrochemical method. Manufactured.

A method of filling a chemical active material is called a chemical impregnation method, in which a porous sintered substrate is immersed in a high-concentration nickel nitrate solution, dried, and then immersed in an alkaline solution to form pores in the pores. This is done by changing the nitrate to nickel hydroxide. In this case, a sufficient amount of nickel hydroxide cannot be obtained by one operation, so that several operations are usually repeated.

On the other hand, a method of electrochemically filling an active material is called an electrodeposition impregnation method, and is carried out by subjecting a porous sintered substrate to cathodic electrolysis in a highly concentrated nickel nitrate solution. As a result of the electrolysis, the nitrate of nickel nitrate existing in the pores of the porous sintered substrate is reduced as shown in the following reaction formula (1) to generate ammonium ions, and the pH is increased. As shown in ()), nickel hydroxide precipitates in the pores. NO ₃ ⁻ + 9H ⁺ + 8e ⁻ → NH ₄ OH + 2H ₂ O (1) Ni ²⁺ + 2OH ⁻ → Ni (OH) ₂ (2)

However, since the nickel nitrate solution is highly corrosive, the nickel sintered body portion in the porous sintered substrate is corroded in the chemical impregnation and electrodeposition impregnation steps, the electrode plate becomes brittle, and the cycle characteristics deteriorate. There are issues. Then, the following technology is disclosed in order to prevent corrosion of the nickel sintered body.

For example, Japanese Patent Application Laid-Open No. 48-100267 describes a technique for forming a protective film on the surface of a nickel sintered body. The publication discloses nickel silicate, nickel phosphate, and nickel carbonate as substances constituting the protective film. Further, JP 59-7 8 4 57 discloses, by passing the gas containing oxygen, a technique for forming a nickel oxide film on the surface of the sintered nickel body is described. Also, JP-A-62-61271,
JP-A-63-128555 and JP-A-4-75
No. 255 describes a technique for forming a cobalt oxide film as a protective film of a nickel sintered body. This cobalt oxide film is formed by thermal decomposition of a cobalt salt.

[0007]

The protective coating on the surface of the nickel sintered body according to the above prior art has high corrosion resistance and is effective in preventing corrosion. However, since the conductivity of the protective film itself is low, there is a problem that the utilization rate of the active material is reduced. In particular, in the case of the electrodeposition impregnation method, nickel hydroxide does not precipitate on the protective film having low conductivity, and nickel hydroxide precipitates on the exposed portion of the nickel where the protective film is broken. This is because the protective coating is damaged when the porous sintered substrate is transported or collected. Electrolytic efficiency (efficiency of nickel hydroxide deposition relative to input charge)
There is also a problem that is reduced.

In order to solve the above-mentioned conventional problems, the present invention provides an electrode for an alkaline storage battery having a high utilization rate of an active material and excellent corrosion resistance, and an alkaline storage battery using this electrode and having good cycle characteristics. The purpose is to do.
In addition, the alkaline storage battery has a small amount of corrosion of the porous sintered substrate in the active material filling step, has a good electric field efficiency when the electrodeposition impregnation method is applied, and can evenly fill the active material in the substrate pores. It is an object of the present invention to provide a method for manufacturing an electrode for use.

[0009]

In order to achieve the above object, a film containing a compound containing cobalt and nickel is formed as the protective film. This compound is composed of at least one selected from an oxide containing cobalt and nickel and a hydroxide containing cobalt and nickel. However, the hydroxide has a feature that the average value of the oxidation numbers of the metal elements in the hydroxide (hereinafter referred to as “average oxidation number”) is larger than + II.

[0010] That is, the first alkaline storage battery electrode of the present invention is an alkaline storage battery electrode filled with active material in the porous substrate containing nickel hydroxide, the active material
On the surface of the porous substrate to be filled, cobalt and hydroxide (Note that the average oxidation number + greater than II) containing an oxide and cobalt and nickel containing nickel comprises at least one selected from, 1S / characterized in that a coating layer having a conductivity of not less than cm is formed.
The second alkaline storage battery electrode of the present invention is an alkaline storage battery electrode filled with active material containing nickel hydroxide to the porous substrate, the porous filling the active material
A coating layer comprising an oxide containing cobalt and nickel and having a molar ratio of cobalt to nickel of 6: 4 to 8: 2 on the surface of the quality substrate .

With such a configuration, it is possible to realize an electrode for an alkaline storage battery having a high utilization rate of the active material and excellent in corrosion resistance. In addition, by using this electrode as a positive electrode, an alkaline storage battery having good cycle characteristics can be provided.

Further, a first method for producing an electrode for an alkaline storage battery of the present invention is a method for producing an electrode for an alkaline storage battery in which a porous substrate is filled with an active material containing nickel hydroxide. Before filling the active material, the surface of the porous substrate is selected from an oxide containing cobalt and nickel and a hydroxide containing cobalt and nickel (however, the average oxidation number is larger than + II). It consists of at least one, characterized in that it comprises a step of forming a coating layer having a conductivity of more than 1S / cm. Also,
A second method for producing an electrode for an alkaline storage battery of the present invention is a method for producing an electrode for an alkaline storage battery in which a porous substrate is filled with an active material containing nickel hydroxide, wherein the porous substrate is filled with the active material. Forming a coating layer made of an oxide containing cobalt and nickel and having a molar ratio of cobalt to nickel of 6: 4 to 8: 2 on the surface of the porous substrate. Features.

With this configuration, the amount of corrosion of the porous sintered substrate in the active material filling step can be reduced. Further, the electrolytic efficiency in the electrodeposition impregnation method is good, and the active material can be evenly filled in the pores of the porous sintered substrate.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described. The electrode for an alkaline storage battery of the present invention,
An interface between the active material, nickel hydroxide, and the porous sintered substrate is provided with a coating layer having excellent conductivity and corrosion resistance. According to one embodiment of the present invention, the coating layer includes an oxide containing cobalt and nickel. According to another aspect of the present invention, the coating layer includes a hydroxide containing cobalt and nickel and having an average oxidation number greater than two. This coating layer is 1 S / cm or more, preferably 10 S / cm.
It has a high conductivity as described above. Such high conductivity improves the utilization of the active material.

It is preferable that the coating layer contains an oxide containing cobalt and nickel. An oxide containing cobalt and nickel has higher conductivity and corrosion resistance than a hydroxide containing cobalt and nickel. Therefore, the utilization factor and cycle characteristics of the active material can be further improved.

On the other hand, a hydroxide containing cobalt and nickel and having an average oxidation number higher than divalent is slightly inferior in corrosion resistance to an oxide containing cobalt and nickel. This is effective in preventing corrosion of the porous sintered substrate in the filling step. In addition, this hydroxide has an advantage in the production method that it can be produced at a relatively low temperature.

It is preferable that the coating layer contains cobalt and nickel in a molar ratio of 6: 4 to 8: 2. With such a molar ratio, an electrode having particularly high conductivity and a high utilization rate of the active material can be obtained.

In the method for producing an electrode for an alkaline storage battery according to the present invention, the above-described coating layer is formed before the porous substrate is filled with nickel hydroxide as an active material. This coating layer can be formed by bringing the porous substrate into contact with a solution containing cobalt and nickel and then heating.

As the solution for immersing the porous substrate, the molar ratio of cobalt to nickel is adjusted to 6: 4 to adjust the molar ratio of cobalt to nickel in the coating layer.
A solution containing 8: 2 is preferable. Examples of the cobalt salt or nickel salt contained in the solution include inorganic acid salts such as nitrate, chloride and sulfate, or organic acids such as acetate, formate, oxalate, citrate and 2-ethylhexane salt. Salt can be used, but the pyrolysis temperature is low,
Inexpensive nitrates are preferred. Further, the solvent is not limited to water, and an organic solvent such as alcohol may be used depending on the type of solute to be used.

The concentration of the total amount of cobalt and nickel is preferably 0.01 M (mol / L) or more.

Further, in order to form the coating layer, it is preferable that the porous substrate is brought into contact with a solution containing cobalt and nickel and then with the alkaline solution. This is because if the element is heated after being brought into contact with the alkaline solution, metal elements such as cobalt and nickel can be oxidized by dissolved oxygen contained in the alkaline solution. Sodium hydroxide, potassium hydroxide, lithium hydroxide and the like can be used as the alkaline solution. In this case, it is preferable to heat the porous substrate at a temperature of 120 ° C. or higher.

Upon contact with an alkaline solution, salts containing cobalt and nickel are chemically replaced with hydroxides. By substituting such salts with hydroxides, it is possible to suppress the generation of decomposition products of highly corrosive inorganic or organic acids when these salts are thermally decomposed. Therefore, the heat treatment equipment can be easily designed.

Further, in order to form a coating layer, the porous substrate may be brought into contact with a solution containing cobalt and nickel, then brought into contact with an alkaline solution, and further washed with water. By contacting with an alkaline solution, salts containing cobalt and nickel are chemically replaced with hydroxides. At this time, an inorganic acid salt or an organic acid salt is produced as a by-product, and such a by-product is removed together with an excess alkali component in a water washing step. Therefore, by bringing the porous substrate into contact with the alkaline solution as described above and further washing with water, it is possible to suppress the generation of a highly corrosive inorganic acid or organic acid decomposition product and an alkali mist during heating. Therefore, the heat treatment equipment can be easily designed.

In order to form a coating layer made of the above oxide, it is preferable to heat the porous substrate at a temperature of 250 ° C. or higher.

As the porous sintered substrate used in the present invention, a conventionally used porous sintered substrate can be used without any particular limitation. The method for filling the active material in the present invention is preferably a chemical impregnation method, an electrodeposition impregnation method, or a combined impregnation method of the electrodeposition impregnation method and the chemical impregnation method.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below based on examples. First, carbonyl nickel powder was slurried with a thickener consisting of methyl cellulose and water, and applied to a 60-μm thick nickel-plated porous steel sheet. This nickel-plated porous steel sheet is
At about 1000 ° C in a reducing atmosphere containing hydrogen.
To produce a porous sintered substrate. The thickness of the nickel sintered body layer of the porous sintered substrate is about 30 per side.
0 μm and had a porosity of about 80%.

Next, a coating layer made of an oxide or hydroxide containing cobalt and nickel was formed on the porous sintered substrate by the following three methods.

(First Coating Layer Forming Method) The above substrate is immersed in an aqueous solution of cobalt nitrate and nickel nitrate for 3 minutes, and then heat-treated at a predetermined temperature in air for 10 minutes.
A coating layer group (1) was formed.

(Second Coating Layer Forming Method) The above substrate was immersed in an aqueous solution in which cobalt nitrate and nickel nitrate were dissolved for 3 minutes, and then vacuum dried at 80 ° C. for 60 minutes. next,
After being immersed in a 6.5 M aqueous sodium hydroxide solution for 30 minutes, it was heat-treated at a predetermined temperature in air for 10 minutes to form a coating layer group (2).

(Third Method for Forming Coating Layer) The above substrate was immersed in an aqueous solution in which cobalt nitrate and nickel nitrate were dissolved for 3 minutes, and then dried in vacuum at 80 ° C. for 60 minutes. next,
After being immersed in a 6.5 M sodium hydroxide aqueous solution for 30 minutes, running water washing was performed for 30 minutes. In addition, one in the air
Heat treatment was performed at a predetermined temperature for 0 minutes to form a coating layer group (3). In each of the above methods, aqueous solutions having different molar ratios of cobalt nitrate and nickel nitrate were used.

FIG. 1 shows the molar ratio between cobalt and nickel contained in the coating layer formed on the porous sintered substrate and the cobalt in the nitrate aqueous solution used in the first to third coating layer forming methods. And the molar ratio of nickel to nickel. As is clear from FIG. 1, the molar ratio between cobalt and nickel in the formed coating layer was almost equal to the molar ratio between cobalt and nickel in the aqueous nitrate solution.

The molar ratio between cobalt and nickel in the coating layer was measured according to the following procedure. The porous sintered substrate after the film formation was immersed in a 50% by weight acetic acid aqueous solution at 80 ° C. for 5 minutes, and the amounts of cobalt and nickel dissolved in the acetic acid aqueous solution were measured by a high-frequency plasma emission spectrometer. And the molar ratio of nickel to nickel were calculated.

Further, the coating layers were formed on the ceramic substrate by the first to third coating layer forming methods, and the composition analysis and the conductivity measurement of each coating layer were performed . The composition analysis of the coating layer was performed by an X-ray diffractometer, and the conductivity was measured by a sheet resistance measuring device.

From the results of X-ray analysis, it was confirmed that a complex hydroxide containing cobalt and nickel was formed by heat treatment at a relatively low temperature according to each of the above methods. In addition, the composite hydroxide was found to have a tendency that the oxidation number of the metal contained in the hydroxide was increased as the heat treatment temperature was increased. When the heat treatment temperature was further increased, generation of an oxide containing cobalt and nickel was confirmed. In particular, from the coating layer formed by the heat treatment at 250 ° C. or higher, only the diffraction peak attributed to the oxide was observed.

Further, according to the second method for forming a coating layer, it has been confirmed that compared to other methods for forming a coating layer, a hydroxide and an oxide having a high oxidation number are generated by heat treatment at a relatively low temperature. Was done. This is due to the oxidizing effect of dissolved oxygen present in the alkaline solution. However, in the first and third methods for forming a coating layer, if the oxygen concentration in the atmosphere during the heat treatment for forming the coating film is increased, oxidation can be performed at a low temperature as in the second method for forming a coating layer.

FIG. 2 shows the effect of the molar ratio of cobalt and nickel on the conductivity of the coating layer. The heat treatment temperature at the time of forming the coating layer was 140 ° C. or 250 ° C. As shown in FIG. 2, in any of the first to third coating layer forming methods, the molar ratio of cobalt to nickel is 6: 4.
~ 8: 2, high conductivity could be obtained.

At a heat treatment temperature of 140 ° C., the conductivity of the coating layer group (2) is relatively high. X-ray analysis showed that the coating layer group (2) at a heat treatment temperature of 140 ° C. contained a relatively large number of hydroxides having a high oxidation number.
At a heat treatment temperature of 250 ° C., the coating layer groups (1) to
The X-ray diffraction pattern of (3) was similar. Therefore, it is considered that there is a strong correlation between the conductivity of the coating layer and the crystal structure.

FIG. 3 shows the effect of the heat treatment temperature during the formation of the coating layer on the conductivity of the coating layer. The molar ratio between cobalt and nickel in the aqueous nitrate solution used for forming the coating layer was 7: 3. There was a tendency for the conductivity to increase with an increase in the heat treatment temperature, and the heat treatment at 250 ° C. or higher showed a substantially constant maximum value for the conductivity of any of the coating layer groups. However, in the coating layer group (2), the conductivity tended to be improved from a relatively low temperature range, and the conductivity became 10 S / cm or more by the heat treatment at 120 ° C. or more.

From the results of X-ray analysis, it has been confirmed that a composite hydroxide layer of cobalt and nickel having a high oxidation number is formed by increasing the heat treatment temperature. Therefore, it is considered that the composite hydroxide layer of cobalt and nickel having a high oxidation number contributes to improvement in conductivity.

From the coating layer formed by the heat treatment at 250 ° C. or higher, only diffraction peaks attributable to Co ₂ NiO ₄ were obtained. Therefore, when the results shown in FIG. 2 are taken into consideration, the conductivity higher than 10 S / cm is determined by Co ₂ N.
This is considered to be due to the generation of iO ₄ . In addition,
In the coating layer group (2), a composite hydroxide of cobalt and nickel having a high oxidation number and C
The generation of o ₂ NiO ₄ was confirmed.

FIGS. 4 and 5 show the results of a corrosion resistance test of a porous sintered substrate on which a coating layer was formed by the first to third coating layer forming methods.

In the corrosion resistance test, the porous sintered substrate was
The sample was immersed in an aqueous solution of nickel nitrate having a pH of 1.0 or 4.5 M and maintained at a temperature of 4.5 ° C. for 60 minutes, washed with water, dried, and the corrosion dissolution rate was calculated from the weight change of the porous sintered substrate before and after the test. did.

FIG. 4 shows the effect of the molar ratio of cobalt and nickel on the corrosion dissolution rate of the porous sintered substrate. As shown in FIG. 4, the heat treatment temperature at the time of forming the coating layer was 140 ° C. or 250 ° C. When the molar ratio of cobalt to nickel was in the range of 10: 0 to 2: 8, no influence of the above molar ratio on corrosion resistance was observed.

FIG. 5 shows the influence of the heat treatment temperature during the formation of the coating layer on the corrosion dissolution rate of the porous sintered substrate having the coating layer formed thereon. The molar ratio between cobalt and nickel in the aqueous nitrate solution used for forming the coating layer was 7: 3. FIG.
As shown in the above, it is recognized that the corrosion resistance tends to improve with an increase in the heat treatment temperature.
The corrosion dissolution rate was less than 1%. Further, in the second method for forming a coating layer, the corrosion resistance was improved from a relatively low temperature region.

Also in this case, it is considered that the hydroxide layer having a high average oxidation number formed with an increase in the heat treatment temperature contributes to the improvement of the corrosion resistance. Also in this case,
It is considered that Co ₂ NiO ₄ formed by a heat treatment at 250 ° C. or higher achieves high corrosion resistance of 1% or less in corrosion dissolution rate by the above-described measurement method. In this case, according to the second coating layer forming method, the corrosion dissolution rate was reduced to 2% or less by the heat treatment at 120 ° C. or higher.

FIG. 6 shows the effect of the total concentration of cobalt and nickel in the aqueous nitrate solution during the formation of the coating layer on the corrosion dissolution rate of the porous sintered substrate. The conditions for forming the film on the porous sintered substrate were such that the molar ratio of cobalt and nickel in the aqueous nitric acid solution was constant at 7: 3, and the heat treatment temperature was 250 ° C.
And As shown in FIG. 6, when the total concentration of cobalt and nickel in the nitrate aqueous solution was 0.01 M or more, good corrosion resistance was obtained.

As described above, on the surface of the porous sintered substrate,
By forming a coating layer containing at least one of an oxide containing cobalt and nickel, and a hydroxide containing cobalt and nickel and having an average oxidation number larger than two, corrosion resistance to nitrate is improved, Furthermore, an electrode for an alkaline storage battery having good conductivity was able to be manufactured. Since the conductivity is good, it can be expected that the electrolysis efficiency in the electrodeposition step for filling the active material is good, and the pores of the sintered substrate are uniformly filled with the active material. Therefore, if this electrode is used as a positive electrode, an alkaline storage battery having good corrosion resistance and cycle characteristics can be manufactured.

In order to confirm this effect, an alkaline storage battery was manufactured using the above-mentioned electrode for an alkaline storage battery, and the battery capacity was measured and the cycle characteristics were examined.

Hereinafter, a method for producing an alkaline storage battery will be described. First, a coating layer was formed on the surface of the porous sintered substrate by the second coating layer forming method. By changing the molar ratio of cobalt and nickel in the aqueous nitrate solution, coating layers having different compositions were formed on the respective porous sintered substrates. The heat treatment temperature for forming the coating layer was 140 ° C. or 250 ° C.
Also, for comparison, untreated (no coating layer is formed)
A porous sintered substrate was produced.

The porous sintered substrate on which the coating layer was formed and the untreated porous sintered substrate were filled with the active material by a chemical impregnation method. The porous sintered substrate was immersed in a mixed aqueous solution of 4.5 M nickel nitrate and 0.1 M cobalt nitrate maintained at 80 ° C. for 3 minutes, dried at 80 ° C. for 90 minutes, and then dried at 80 ° C., 6. The filling operation of dipping in a 5M aqueous solution of sodium hydroxide was repeated seven times to prepare an electrode for an alkaline storage battery.

Next, the capacity manufactured under the same conditions is sufficiently large.
Hydrogen storage alloy based negative electrode (MmNi _3.55Mn_0.4Al_0.3
Co_0.75) And separator (polypropylene non-woven fabric)
Alkaline electrolyte (potassium hydroxide) and the above alkaline storage
Nominal 1.3Ah by combining with a pond electrode under the same conditions
Was manufactured.

12A for each of the alkaline storage batteries produced
Charging / 12 A discharging was performed, and capacity measurement was performed. Also,
The cycle characteristics were examined by repeating the 12A charge / 12A discharge cycle. At this time, the 12A charging was performed for 6 minutes, and the 12A discharging was terminated when the voltage reached 0.8V.

FIGS. 7 and 8 show the capacity of the alkaline storage battery at the third and 500th cycles.
The alkaline storage batteries (A) to (F) shown in FIG.
FIG. 8 shows an example in which the alkaline storage batteries (G) to (M) use electrodes whose heat treatment temperature is set to 250 ° C. FIG. on the other hand,
An alkaline storage battery using a positive electrode without a coating layer is shown as an alkaline storage battery (N).

As shown in FIGS. 7 and 8, a large battery capacity was obtained in the porous sintered substrate having the coating layer in which the molar ratio of cobalt to nickel was in the range of 6: 4 to 8: 2. In addition, in the alkaline storage battery using the electrode heat-treated at 250 ° C., a larger battery capacity was obtained.
Thus, it was confirmed that a large battery capacity could be obtained by adjusting the molar ratio between cobalt and nickel so that the conductivity of the coating layer was improved.

The effect of the molar ratio of cobalt to nickel on the capacity reduction due to the cycle was hardly recognized. On the other hand, in an alkaline storage battery using an electrode having a heat treatment temperature of 250 ° C., the decrease in capacity was smaller than when the heat treatment temperature was 110 ° C. From the comparison with the results described above, it is considered that the cycle characteristics of the alkaline storage battery are improved by improving the corrosion resistance of the coating layer.
In addition, the capacity of the alkaline storage battery (N) having no coating layer produced for comparison dropped to about 65% after 500 cycles.

As described above, by using the above electrode as the positive electrode, an alkaline storage battery having a high utilization rate of the active material and excellent cycle characteristics was realized.

Next, the effect on the electrodeposition step was confirmed.
First, by the second coating layer forming method, coating layers having different compositions were formed on the porous sintered substrate while changing the molar ratio of cobalt and nickel in the nitrate aqueous solution. The heat treatment temperature for forming the coating layer was 250 ° C.

The porous sintered substrate on which the coating layer was formed was 90
By immersing in a 4.5 M nickel nitrate aqueous solution at a temperature of 450 ° C. and performing cathodic electrolysis, nickel hydroxide was electrodeposited and filled.

In order to confirm how the nickel hydroxide clogs the porous sintered substrate after the electrodeposition, a cross section of the porous sintered substrate was observed with an electron microscope. As a result, when the molar ratio of cobalt to nickel is in the range of 6: 4 to 8: 2, nickel hydroxide is used from the central portion close to the nickel-plated porous steel plate serving as the core material of the porous sintered substrate to the surface. It was evenly packed. On the other hand, when the molar ratio is out of this range, as in the case of the porous sintered substrate having the nickel oxide layer formed on the surface, the nickel hydroxide is large in the vicinity of the surface, and the inside thereof is not uniformly filled.

The electrolysis efficiency at the time of electrodeposition also becomes high when the molar ratio of cobalt to nickel in the coating layer is in the range of 6: 4 to 8: 2, and the effect of the conductivity of the porous sintered substrate is reduced. Appeared. Furthermore, no corrosion occurred in any of the porous sintered substrates in the electrodeposition step, indicating high corrosion resistance.

For comparison, an untreated porous sintered substrate was electrodeposited. Untreated porous sintered substrates have high electrolysis efficiency due to good conductivity, and nickel hydroxide is uniformly filled, but has low corrosion resistance. My body parts are weakened.

In the above embodiment, the negative electrode was used to store hydrogen.
MmNi as a gold-based negative electrode_3.55Mn _0.4Al_0.3Co_0.75
But is not limited to this, Mg_TwoNi, TiMn
_1.5Etc. can also be used. Also, with separator
Polyamide nonwoven instead of polypropylene nonwoven
Or the like may be used. As the alkaline electrolyte, hydroxylated
Sodium hydroxide etc. can be used instead of potassium
it can. In addition, alkaline electrolytes are
Lithium hydroxide or the like may be added.

The alkaline storage battery manufactured in the above embodiment is
Although it is a nickel-hydrogen battery, the present invention is not limited to this, and may be applied to other alkaline storage batteries such as a nickel-cadmium battery.

[0064]

As described above, according to the electrode for an alkaline storage battery of the present invention, the porous material for filling the active material is used.
The oxide containing cobalt and nickel and the average oxidation number containing cobalt and nickel are +
At least either one selected from a large hydroxide than II
Forming a coating layer having a conductivity of 1 S / cm or more or an oxide layer containing cobalt and nickel and having a molar ratio of cobalt to nickel of 6: 4 to 8: 2. Thereby, both the utilization rate of the active material and the corrosion resistance can be increased. The alkaline storage battery of the present invention using this electrode as a positive electrode has improved battery capacity as well as cycle characteristics.

Further, according to the method for producing an electrode for an alkaline storage battery of the present invention, before the porous substrate is filled with the active material,
By performing the step of forming the coating layer on the surface of the porous substrate, the amount of corrosion of the porous sintered substrate in the active material filling step is small, and the electrolytic efficiency in the electrodeposition impregnation method is good, and the active material is Can be evenly filled in the pores of the porous substrate.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the molar ratio of cobalt and nickel in a nitrate aqueous solution and the molar ratio of cobalt and nickel in a coating layer formed on a porous sintered substrate in one embodiment of the present invention. It is.

FIG. 2 is a diagram showing the effect of the molar ratio of cobalt and nickel on the conductivity of the coating layer in one embodiment of the present invention.

FIG. 3 is a diagram showing the influence of a heat treatment temperature during film formation on the conductivity of the film layer in one embodiment of the present invention.

FIG. 4 is a diagram showing the influence of the molar ratio of cobalt and nickel on the corrosion dissolution rate of the porous sintered substrate in one embodiment of the present invention.

FIG. 5 is a diagram showing the influence of a heat treatment temperature during film formation on the corrosion dissolution rate of a porous sintered substrate in one embodiment of the present invention.

FIG. 6 is a diagram showing the effect of nitrate aqueous solution concentration on the corrosion dissolution rate of a porous sintered substrate in one embodiment of the present invention.

FIG. 7 is a diagram showing a change in capacity between an alkaline storage battery according to an embodiment of the present invention and a conventional alkaline storage battery.

FIG. 8 is a diagram showing a change in capacity between an alkaline storage battery according to an embodiment of the present invention and a conventional alkaline storage battery.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masakazu Tanahashi 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Yoshiki Murakami 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co. (72) Inventor Osamu Kaida 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Masayoshi Maruta 1006 Odaka Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-151972 (JP, A) JP-A-63-216268 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/66 H01M 4/80 H01M 4/24 -4/26

Claims (19)

(57) [Claims] 1. An electrode for an alkaline storage battery in which a porous substrate is filled with an active material containing nickel hydroxide, wherein the active material is
An oxide containing cobalt and nickel and a hydroxide containing cobalt and nickel (however, the average oxidation number of metal elements in the hydroxide is more than + II) At least one selected from
From it, the alkaline storage battery electrode, wherein a coating layer having a conductivity of more than 1S / cm is formed. 2. The electrode for an alkaline storage battery according to claim 1, wherein the coating layer contains cobalt and nickel in a molar ratio of 6: 4 to 8: 2. 3. An electrode for an alkaline storage battery in which a porous substrate is filled with an active material containing nickel hydroxide, wherein the active material is
The surface of the porous substrate to be filled with cobalt contains cobalt and nickel, and the molar ratio of cobalt to nickel is 6: 4.
An electrode for an alkaline storage battery, wherein a coating layer made of an oxide having a thickness of 8 to 2 is formed. 4. The electrode for an alkaline storage battery according to claim 1, wherein the coating layer has a conductivity of 10 S / cm or more. 5. The electrode for an alkaline storage battery according to claim 1, wherein the coating layer contains Co ₂ NiO ₄ . 6. A method for producing an electrode for an alkaline storage battery in which a porous substrate is filled with an active material containing nickel hydroxide, wherein the surface of the porous substrate is filled before the porous substrate is filled with the active material. , the hydroxide containing the oxide and cobalt and nickel containing cobalt and nickel (Note that the average value of the oxidation number of the metal elements in the hydroxide is greater than + II) comprises at least one selected from, 1S
A method for producing an electrode for an alkaline storage battery, comprising a step of forming a coating layer having a conductivity of at least / cm. 7. A method of manufacturing an electrode for an alkaline storage battery in which a porous substrate is filled with an active material containing nickel hydroxide, wherein the surface of the porous substrate is filled before the porous substrate is filled with the active material. Forming a coating layer made of an oxide containing cobalt and nickel and having a molar ratio of cobalt to nickel of 6: 4 to 8: 2. . 8. The method for producing an electrode for an alkaline storage battery according to claim 6, wherein the step of forming the coating layer includes a step of heating the porous substrate after bringing the porous substrate into contact with a solution containing cobalt and nickel. Method. 9. The method for producing an electrode for an alkaline storage battery according to claim 8, wherein the solution containing cobalt and nickel contains cobalt and nickel in a molar ratio of 6: 4 to 8: 2. 10. The method for producing an electrode for an alkaline storage battery according to claim 8, wherein the solution containing cobalt and nickel contains a nitrate of cobalt and a nitrate of nickel. 11. The solution containing cobalt and nickel has a concentration of 0.01 M of the total amount of cobalt and nickel.
The method for producing an electrode for an alkaline storage battery according to claim 8, which is the above. 12. The step of forming the coating layer comprises: contacting the porous substrate with a solution containing cobalt and nickel; contacting the porous substrate with an alkaline solution; The method for producing an electrode for an alkaline storage battery according to claim 6 or 7, further comprising the step of heating. 13. The method for producing an electrode for an alkaline storage battery according to claim 12, wherein the porous substrate is heated at a temperature of 120 ° C. or higher. 14. The step of forming the coating layer includes the steps of: contacting the porous substrate with a solution containing cobalt and nickel; contacting the porous substrate with an alkaline solution; 8. The method according to claim 6, further comprising the steps of: washing with water; and heating the porous substrate.
4. The method for producing an electrode for an alkaline storage battery according to item 1. 15. The method for producing an electrode for an alkaline storage battery according to claim 8, wherein the porous substrate is heated at a temperature of 250 ° C. or higher. 16. An alkaline storage battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte, wherein the positive electrode includes an active material containing nickel hydroxide on a porous substrate. The porous material being filled and filling the active material
At least one selected from an oxide containing cobalt and nickel and a hydroxide containing cobalt and nickel (however, the average oxidation number of metal elements in the hydroxide is larger than + II) on the surface of the porous substrate. It consists of one, 1S / cm
An alkaline storage battery comprising an electrode on which a coating layer having the above conductivity is formed. 17. The alkaline storage battery according to claim 16, wherein the coating layer contains cobalt and nickel in a molar ratio of 6: 4 to 8: 2. 18. An alkaline storage battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte, wherein the positive electrode includes an active material containing nickel hydroxide on a porous substrate. The porous material being filled and filling the active material
An electrode on the surface of the porous substrate, on which a coating layer made of an oxide containing cobalt and nickel and having a molar ratio of cobalt to nickel of 6: 4 to 8: 2 is provided. Alkaline storage battery. 19. The alkaline storage battery according to claim 16, wherein said coating layer contains Co ₂ NiO ₄ .