JP2003077470A - Manufacturing method of nickel electrode material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of obtaining a nickel electrode material in which the discharge reserve can be reduced and a high utilization rate of the active material can be obtained. SOLUTION: This is a manufacturing method of a nickel electrode material that comprises an oxidation treatment process in which a positive electrode active material, in which a covering layer made of a lower-grade cobalt compound is formed on the surface of the positive electrode active material particles made of nickel hydroxide solid solution, is wetted in a water solution of an oxidizer and an alkaline water solution of 30-40 wt.%, and heated at a temperature of 70-120 deg.C in the wet condition.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode material used for a nickel electrode of an alkaline storage battery. 2. Description of the Related Art In recent years, with the spread of portable devices such as portable telephones, notebook computers, and handy video cameras, alkaline storage batteries have been required to be extended in operating time, and high capacity is strongly desired. ing. In particular, a nickel-metal hydride battery has a nickel electrode having a positive electrode active material containing nickel hydroxide as a main component, a negative electrode containing a hydrogen storage alloy as a main material,
And is rapidly spreading as a secondary battery having high capacity and high reliability. There are two types of nickel electrodes for alkaline storage batteries: sintered electrodes and non-sintered electrodes. Sintered electrodes are
A porous nickel sintered substrate as an active material holder is immersed in an aqueous solution of an acidic nickel salt such as nickel nitrate to impregnate the nickel salt in the holes of the substrate, and then the nickel salt is hydroxylated in an alkali. It is obtained by repeatedly performing a filling operation of changing to nickel. However,
In the case of the sintered electrode, it is difficult to increase the porosity of the substrate to about 80% or more, so that the amount of the filled active material cannot be increased, and there is a limit to increasing the capacity. On the other hand, non-sintered electrodes are prepared by dissolving a binder such as carboxymethyl cellulose in water in nickel hydroxide particles formed from an aqueous solution of an acidic nickel salt such as nickel sulfate and an aqueous solution of sodium hydroxide. A paste is prepared by adding a viscous liquid, and the paste is porosity 95%.
It is obtained by directly filling the above foam substrate or fiber substrate. According to the non-sintered electrode, a higher capacity can be expected. [0005] Since nickel hydroxide itself has poor conductivity, non-sintered electrodes generally have an oxidation number of cobalt such as cobalt hydroxide in order to improve current collection between active material particles. Is a divalent cobalt compound. The divalent cobalt compound does not have conductivity by itself, but is electrochemically oxidized by initial charging in the battery to become a higher-order cobalt compound having conductivity,
It effectively functions as a conductive network.
In particular, if a positive electrode material in which the surface of a positive electrode active material made of nickel hydroxide is coated with cobalt hydroxide is used, a conductive network is more easily formed, and the utilization rate of the densely packed active material is greatly increased. Can be increased. Note that the higher-order cobalt compound is a cobalt compound having an oxidation number of cobalt of 2 or more, and specifically, is considered to be cobalt oxyhydroxide (CoOOH). The oxidation of cobalt hydroxide by the initial charge is an irreversible reaction and is not reduced at the time of discharging, so that the negative electrode active material corresponding to the irreversible component remains without being discharged. The amount of electricity remaining without being discharged is called a discharge reserve. When the discharge reserve is generated, the uncharged capacity of the negative electrode, that is, the charge reserve is reduced at the end of charging, the generation of hydrogen gas is promoted, the internal pressure of the battery is increased, and the cycle life is shortened. [0007] In the nickel-metal hydride storage battery, a discharge reserve is also generated by corrosion of the negative electrode alloy. Further, an irreversible product generated in the oxidation-reduction of nickel hydroxide, which is a positive electrode active material, also generates a discharge reserve. Therefore, if the discharge reserve can be reduced, the internal pressure of the battery at the end of charging decreases, the cycle life improves,
In addition, the capacity of the battery can be increased. In view of this, Japanese Patent Application Laid-Open No. 8-148146 discloses that a higher cobalt compound is unevenly distributed on the surface of nickel hydroxide particles in advance, thereby suppressing generation of a discharge reserve due to oxidation due to initial charging. However,
As described above, since the cause of the discharge reserve is not only the irreversible capacity of cobalt hydroxide, this alone is not sufficient. Further, in order to reduce the discharge reserve, attempts have been made to oxidize a part of nickel hydroxide which is a positive electrode active material. For example, Japanese Patent Application Laid-Open No. 2000-223119 discloses a method in which a high-order cobalt compound is retained on the surface of nickel hydroxide particles and nickel hydroxide is partially oxidized in an aqueous alkaline solution. However, when the above-mentioned method is performed in a high-concentration aqueous alkaline solution,
Part of the nickel hydroxide is γ-nickel oxyhydroxide (γ
—NiOOH), which reduces the tap density of the particles and may be contrary to the increase in capacity. Conversely, when the reaction is carried out in a low-concentration aqueous alkaline solution, inactive nickel oxide is produced as a by-product, and the activity of nickel hydroxide itself is impaired, and the active material utilization rate may be reduced. An object of the present invention is to provide a manufacturing method capable of obtaining a nickel electrode material capable of reducing a discharge reserve and obtaining a high active material utilization rate. Means for Solving the Problems The invention according to claim 1 is:
A positive electrode in which a coating layer made of a low-order cobalt compound having an oxidation number of cobalt of 2 or less is formed on the surface of positive electrode active material particles made of nickel hydroxide or a solid solution of nickel hydroxide in which dissimilar elements are dissolved. The material is wetted with an aqueous solution of an oxidizing agent and a 30 to 40% by weight alkaline aqueous solution, or with a 30 to 40% by weight alkaline aqueous solution containing an oxidizing agent. A nickel electrode material, comprising an oxidation treatment step of heating at a temperature. According to the first aspect of the present invention, the concentration of the aqueous alkali solution is 30 to 40% by weight, and the heating temperature is 7%.
Since the temperature is 0 to 120 ° C., the solubility of the low-order cobalt compound in the aqueous alkali solution is maintained high, and the oxidation reaction proceeds smoothly. Therefore, the low-order cobalt compound is oxidized,
The oxidation number of cobalt changes to a higher-order cobalt compound larger than divalent, and a part of nickel hydroxide is oxidized. In addition, since the oxidation treatment is performed in a wet state,
The treatment with the alkaline aqueous solution having the above concentration suppresses the formation of inactive nickel oxide, and thus does not impair the activity of nickel hydroxide itself, and also suppresses the formation of γ-NiOOH. Is prevented from decreasing. Therefore, according to the first aspect of the present invention, nickel hydroxide as a positive electrode active material is partially oxidized, the coating layer is made of a high-order cobalt compound, and the tap density is high. Thus, a nickel electrode material in which the activity of the positive electrode active material is not impaired is obtained. When such a nickel electrode material is used for a nickel electrode, and eventually for a nickel-metal hydride battery, the following effects (1) to (3) are exhibited. (1) Since a part of nickel hydroxide of the positive electrode active material is oxidized, generation of irreversible electricity by initial charging after battery assembly is prevented. In addition, since the coating layer is made of a higher-order cobalt compound, generation of irreversible electricity by initial charging after battery assembly is prevented. Therefore, in the battery using this nickel electrode material, the discharge reserve is sufficiently reduced. Since the discharge reserve can be reduced,
The capacity of the negative electrode can be substantially increased, and therefore the capacity can be increased while maintaining the same size of the battery, or the size can be reduced while maintaining the same capacity of the battery. Therefore, both miniaturization and high capacity can be achieved. Further, since the discharge reserve can be reduced, the charge reserve can be increased, and therefore, the gas generated at the time of overcharge can be effectively absorbed by the charge reserve.
The internal pressure rise can be suppressed, and the charge / discharge cycle life can be improved. (2) Since the tap density is high, the current collector can be filled with the electrode material at high density. Therefore, high capacity can be achieved. (3) Since the activity of the positive electrode active material is maintained without being impaired, the utilization rate of the active material can be improved. Further, according to the first aspect of the present invention, since the treatment is performed in a wet state, the amount of the aqueous solution used for the treatment can be reduced as compared with the immersion treatment. Therefore, manufacturing costs are reduced. The different elements to be dissolved are cobalt,
One or more of zinc, magnesium, cadmium, aluminum, and manganese are preferred. When cobalt is dissolved, the charging potential of the nickel electrode material can be shifted to the base side, and the potential difference between the charging potential and the oxygen generation potential can be set large, so that the charging efficiency of the battery at high temperatures can be improved. When any of zinc, magnesium, and cadmium is dissolved, it is possible to suppress generation of γ-NiOOH, particularly at the end of charging, and to suppress swelling of the nickel electrode. Prevention to improve the charge / discharge cycle life. For example, the production of positive electrode active material particles comprising a solid solution of nickel hydroxide in which zinc and cobalt are dissolved is performed as follows. An aqueous solution of ammonium sulfate is added to a mixed aqueous solution of nickel sulfate, zinc sulfate, and cobalt sulfate, and the pH is further adjusted to an alkaline side to generate an ammine complex ion of nickel, zinc, and cobalt. While stirring and supplying to the aqueous sodium hydroxide solution, the pH of the reaction bath was adjusted to 11
１３13 and the temperature is maintained at 40-50 ° C. Thereby, nickel hydroxide solid solution particles in which zinc hydroxide and cobalt hydroxide are dissolved, that is, positive electrode active material particles are generated. When zinc sulfate and cobalt sulfate are omitted, positive electrode active material particles composed of nickel hydroxide are generated. The formation of the coating layer made of a low-order cobalt compound is performed as follows. The aqueous solution of sodium hydroxide is added to the reaction bath while the positive electrode active material particles are immersed and stirred in the aqueous solution of cobalt sulfate in the reaction bath, and the pH is maintained at 11 to 13. Thereby, a coating layer made of cobalt hydroxide is formed on the surfaces of the positive electrode active material particles. That is, positive electrode material particles are generated. Examples of the low-order cobalt compound include simple cobalt, cobalt monoxide, and cobalt hydroxide. In particular, cobalt hydroxide is preferable because cobalt oxyhydroxide is easily generated. As the alkaline aqueous solution, it is preferable to use an aqueous solution in which at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide is dissolved. As the oxidizing agent, potassium peroxodisulfate (K ₂ S ₂ O ₈ ) and sodium peroxodisulfate (N
a ₂ S ₂ O ₈ ), ammonium peroxodisulfate ((N
H ₄ ) ₂ S ₂ O ₈ ) and sodium hypochlorite (Na
It is preferable to use at least one of OCI). Since these oxidizing agents can oxidize divalent cobalt and divalent nickel, not only low-order cobalt compounds but also nickel hydroxide are reliably oxidized. DESCRIPTION OF THE PREFERRED EMBODIMENTS << Production of Nickel Electrode Material >> (Example 1) [Production of Positive Electrode Active Material] An aqueous solution of ammonium sulfate was added to a mixed aqueous solution comprising nickel sulfate, zinc sulfate and cobalt sulfate. In addition, by further adjusting the pH to the alkaline side, nickel, zinc, and an ammine complex ion of cobalt are generated, and this aqueous solution is supplied to the aqueous sodium hydroxide solution in the reaction bath while stirring,
The pH of the reaction bath was maintained at 11-13 and the temperature at 40-50 ° C. As a result, nickel hydroxide solid solution particles in which zinc hydroxide and cobalt hydroxide were dissolved, that is, positive electrode active material particles were produced. The contents of nickel, zinc, and cobalt in the positive electrode active material were 58% by weight and 3, respectively.
7% by weight and 1.2% by weight. [Formation of Positive Electrode Material (Coating with Cobalt Hydroxide)] Next, an aqueous solution of sodium hydroxide was added to the reaction bath while the positive electrode active material particles were immersed and stirred in an aqueous solution of cobalt sulfate in the reaction bath. pH 11-13 was maintained.
As a result, a coating layer made of cobalt hydroxide was formed on the surfaces of the positive electrode active material particles. That is, positive electrode material particles were generated. The content ratio of the coating layer made of cobalt hydroxide in this positive electrode material was 7% by weight. [Oxidation treatment step] 100 g of positive electrode material particles
70 ml of a 10% by weight aqueous solution of sodium hypochlorite (NaClO) and a 30% by weight aqueous solution of sodium hydroxide 1
0 ml was sprayed, thereby bringing the positive electrode material particles into a wet state, and then heated at a temperature of 70 ° C. in that state.
Thereafter, the positive electrode material particles were washed with water and dried. The positive electrode material thus obtained was used as the nickel electrode material of Example 1. The average oxidation number of nickel and cobalt in the nickel electrode material was 2.20. This average oxidation number was determined by the following method. [Method of Obtaining Average Oxidation Number] First, a predetermined amount of positive electrode material particles and ferrous ammonium sulfate (Fe (NH ₄ ) ₂ (SO ₄ )
₂ ) is dissolved in a 20% by volume aqueous acetic acid solution, and redox titration is performed using a potassium permanganate solution. Then, from the obtained titration values, the amounts of nickel and cobalt having two or more valences are obtained, and the average oxidation number of nickel and cobalt is calculated from the values and the total amount of nickel and cobalt contained in a predetermined amount of the cathode material. Ask. {Preparation of Nickel Electrode} A nickel electrode material, a 0.6% by weight CMC (carboxymethylcellulose) solution, and a 40% by weight PTFE (polytetrafluoroethylene) were mixed at a weight ratio of 76.7: 22.9: The mixture was mixed at 0.4 to obtain an electrode material paste. Then, the electrode material paste is filled in a porous nickel foam substrate, dried, and then rolled to obtain an electrode material packing density of 2.6 g / cc.
A nickel electrode having a positive electrode capacity of 1450 mAh was produced. {Preparation of Alkaline Storage Battery} Nickel electrode and composition formula Mm _1.0 Ni _4.0 Co _0.7 Mn _0.3
Al _0. A negative electrode composed mainly of a hydrogen storage alloy represented by No. ₃ is spirally wound through a 100-μm-thick polypropylene nonwoven fabric, inserted into a battery case, and subjected to electrolysis comprising an aqueous solution of potassium hydroxide and lithium hydroxide. The solution was injected and sealed, thereby producing an AA-size nickel-metal hydride storage battery having a theoretical capacity of 1450 mAh. Comparative Example 1 In the same manner as in Example 1, a positive electrode active material and further a positive electrode material were produced, and the subsequent oxidation treatment step was omitted. The obtained positive electrode material was used as a nickel electrode material of Comparative Example 1. Comparative Example 2 A positive electrode active material and further a positive electrode material were produced in the same manner as in Example 1. Then, in the subsequent oxidation treatment step, the use of the aqueous sodium hydroxide solution was omitted, and the other conditions were the same as in Example 1. That is, in the oxidation treatment step, the wet state was achieved only with the aqueous solution of sodium hypochlorite. The obtained positive electrode material was used as a nickel electrode material of Comparative Example 2. Comparative Example 3 In the same manner as in Example 1, a positive electrode active material and further a positive electrode material were produced. Then, in the subsequent oxidation treatment step, the use of the sodium hypochlorite aqueous solution was omitted, and the other conditions were the same as in Example 1. That is, in the oxidation treatment step, a wet state was obtained only with the aqueous sodium hydroxide solution. The obtained positive electrode material was used as a nickel electrode material of Comparative Example 3. Comparative Example 4 In the same manner as in Example 1, a positive electrode active material and further a positive electrode material were produced. Then, in the subsequent oxidation treatment step, the positive electrode material was immersed in 400 g of a mixed solution composed of 350 g of a 10% by weight aqueous solution of sodium hypochlorite and 50 g of a 30% by weight aqueous solution of sodium hydroxide. Heat treatment at a temperature of Thereafter, the positive electrode material particles were washed with water and dried. That is, in the oxidation treatment step, the immersion state was used instead of the wet state.
The obtained positive electrode material was used as a nickel electrode material of Comparative Example 4. Comparative Example 5 In the same manner as in Example 1, a positive electrode active material and further a positive electrode material were produced. Then, in the subsequent oxidation treatment step, an aqueous solution of potassium permanganate (KMnO ₄ ) was used instead of the aqueous solution of sodium hypochlorite, and the other conditions were the same as in Example 1. That is, in the oxidation treatment step, potassium permanganate was used as the oxidizing agent. The obtained positive electrode material was used as a nickel electrode material of Comparative Example 5. Comparative Example 6 In the same manner as in Example 1, a positive electrode active material and further a positive electrode material were produced. Then, in the subsequent oxidation treatment step, 100 g of the positive electrode material particles
The coated cobalt hydroxide is oxidized by heating at 120 ° C. by moistening with 20 g of a 0% by weight aqueous sodium hydroxide solution, and then the positive electrode material particles are converted into a 15% by weight aqueous sodium hydroxide solution in a reaction bath. Charge, bath temperature 6
While stirring at 0 ° C., 10 m of sodium hypochlorite solution
was added to the reaction bath to oxidize nickel hydroxide in the positive electrode active material. Thereafter, the positive electrode material particles were washed with water and dried. The obtained positive electrode material was used as a nickel electrode material of Comparative Example 6. Comparative Example 7 A 30% by weight aqueous sodium hydroxide solution was used in place of the 15% by weight aqueous sodium hydroxide solution of Comparative Example 6, and the other conditions were the same as in Comparative Example 6. The obtained positive electrode material was used as a nickel electrode material of Comparative Example 7. Then, using the nickel electrode materials of Comparative Examples 1 to 7, in the same manner as in Example 1, a nickel electrode and eventually a nickel-metal hydride storage battery were produced. When the nickel electrode materials of Comparative Examples 4 and 7 were used, the positive electrode capacity was set to 1250 mAh. (Measurement of Tap Density) The tap densities of the nickel electrode materials of Example 1 and Comparative Examples 1 to 7 were measured. Tap density, specifically, after a predetermined amount of electrode material particles are put into a measuring cylinder and the operation of dropping from a height of about 10 cm is repeated 100 to 200 times, the volume occupied by the electrode material particles is measured. Sought. Table 1 shows the results. In Table 1, relative values are shown with the tap density of Example 1 as 100. (Measurement of Active Material Utilization) The active material utilization was measured for the batteries using the nickel electrode materials of Example 1 and Comparative Examples 1 to 7. Specifically, the measurement was performed as follows. That is, at 20 ° C., a charging current of 1
After charging at 45mA (0.1C) for 15 hours, 290m
The battery was discharged at A (0.2 C), and was terminated at a battery voltage of 1.0 V. The discharge capacity at the end of this time was obtained, and from the obtained capacity and 1450 mAh, which is the nominal capacity of the battery, was obtained by the following equation. Table 1 shows the results. (Active material utilization rate) = 100 × (discharge capacity of 0.2 C discharge) / positive electrode filling capacity (Measurement of utilization rate after overdischarge) Using nickel electrode materials of Example 1 and Comparative Examples 1 to 7 The utilization rate after overdischarge was measured for the batteries that had been discharged. Specifically, the measurement was performed as follows. That is, the battery was repeatedly subjected to 0.1 C charge and 0.2 C discharge for 3 cycles, then externally short-circuited through a 4Ω resistor and left at 60 ° C. for 3 days. After overdischarge, remove the resistor and at 20 ° C,
After charging for 15 hours at a charging current of 145 mA (0.1 C), discharging at 290 mA (0.2 C),
The discharge was terminated at V. The discharge capacity at the end of this time was obtained, and from the obtained capacity and 1450 mAh, which is the nominal capacity of the battery, was obtained by the following equation. Table 1 shows the results. (Utilization rate after overdischarge) = 100 × (discharge capacity after overdischarge) / positive capacity of positive electrode (Measurement of Cycle Characteristics) For the batteries using the nickel electrode materials of Example 1 and Comparative Example 3, the cycle characteristics of the active material utilization were measured. The result is shown in FIG. The active material utilization was measured in the same manner as described above. (Study) As can be seen from Table 1, Example 1
Has a higher active material utilization rate than Comparative Examples 1, 2, and 5, and a higher utilization rate after overdischarge. In addition, Example 1 has a higher active material utilization rate than Comparative Example 6. This is considered to be because in Comparative Example 6, the concentration of the aqueous alkali solution used in the oxidation treatment of the nickel hydroxide was low, so that an inactive nickel oxide was generated. Example 1 has a higher tap density than Comparative Examples 4 and 7. This is because γ-NiOOH was generated in Comparative Example 4 because the concentration of the aqueous alkaline solution was high, and in Comparative Example 7 because the concentration of the aqueous alkaline solution used in the oxidation treatment of nickel hydroxide was high. It is believed that there is. In the batteries using the nickel electrode materials of Comparative Examples 4 and 7 having a low tap density, a predetermined amount of the electrode material could not be filled, and the capacity was reduced. Also, as can be seen from FIG.
Has better cycle characteristics than Comparative Example 3. This is because, according to the nickel electrode material of Example 1, since nickel hydroxide is oxidized, the discharge reserve can be reduced, and therefore, the decrease in the charge reserve can be suppressed and the internal pressure characteristics can be improved. ,it is conceivable that. (Study on Relationship between Concentration of Alkaline Aqueous Solution and Utilization Rate of Active Material) A nickel electrode was prepared in the same manner as in Example 1 except that the concentration of the aqueous sodium hydroxide solution in the oxidation treatment step of Example 1 was variously set. A nickel-metal hydride storage battery was manufactured in the same manner as described above using the nickel electrode material, and the active material utilization was measured in the same manner as described above.
The set concentrations were 10, 20, 30, and 30% by weight.
40 and 50. The result is shown in FIG. As can be seen from FIG. 2, the concentration of the aqueous sodium hydroxide solution, that is, the alkali concentration is preferably 30 to 40% by weight. When the content is less than 30% by weight, it is considered that the solubility of cobalt hydroxide in the aqueous alkali solution was low, and no treatment effect was observed. If the amount exceeds 40% by weight, it is considered that the viscosity of the aqueous solution of sodium hydroxide increases, and the penetration of sodium hydroxide into the positive electrode active material decreases, so that no treatment effect was observed. With respect to the kind of alkali, the same action and effect were observed for potassium hydroxide aqueous solution. In addition, the same effect was also obtained in the case where an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide contained lithium hydroxide. (Examination of Relationship between Heating Temperature and Active Material Utilization) The heating temperature in the oxidation treatment step of Example 1 was set variously, and otherwise the same as in Example 1 to obtain a nickel electrode material. Using the electrode material, a nickel-metal hydride storage battery was manufactured in the same manner as described above, and the active material utilization was measured in the same manner as described above. The set heating temperature is 45
° C, 70 ° C, 95 ° C, 120 ° C, and 145 ° C. The result is shown in FIG. As can be seen from FIG.
120 ° C. is preferred. If the temperature is lower than 70 ° C., it is considered that the solubility of cobalt hydroxide in the aqueous alkali solution was low, and no treatment effect was observed. On the other hand, when the temperature exceeds 120 ° C., it is considered that the vaporization of water in the treatment aqueous solution in the oxidation treatment step becomes remarkable, the viscosity of the treatment aqueous solution is improved and the oxidation reaction is suppressed, and therefore, the active material utilization rate is reduced. Can be In the examples and comparative examples described above, two types of aqueous solutions, an aqueous solution of an oxidizing agent and an aqueous alkaline solution, are used as the aqueous solution used for the treatment. Various types of aqueous solutions may be used. According to the first aspect of the present invention, it is possible to obtain a nickel electrode material capable of reducing a discharge reserve and obtaining a high active material utilization rate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the relationship between the charge / discharge cycle and the active material utilization rate in Example 1 and Comparative Example 3. FIG. 2 is a diagram showing the relationship between the concentration of an aqueous solution of sodium hydroxide and the utilization rate of an active material in the production method of the present invention. FIG. 3 is a diagram showing a relationship between a heating temperature and an active material utilization rate in the production method of the present invention.

Continuation of front page    (72) Inventor Seijiro Ochiai             2-3-21 Kosobe-cho, Takatsuki-shi, Osaka             In the formula company Yuasa Corporation (72) Inventor Mitsuhiro Kodama             2-3-21 Kosobe-cho, Takatsuki-shi, Osaka             In the formula company Yuasa Corporation (72) Inventor Masaharu Watada             2-3-21 Kosobe-cho, Takatsuki-shi, Osaka             In the formula company Yuasa Corporation (72) Inventor Masahiko Oshitani             2-3-21 Kosobe-cho, Takatsuki-shi, Osaka             In the formula company Yuasa Corporation F term (reference) 5H028 BB05 BB10 EE05 EE10 HH01                       HH08                 5H050 AA02 AA08 CA03 CA04 CB16                       DA02 GA02 GA15 GA22 HA01                       HA14

Claims (1)

Claims: 1. A low-order cobalt compound having a cobalt oxidation number of 2 or less on the surface of positive electrode active material particles composed of nickel hydroxide or a solid solution of nickel hydroxide in which dissimilar elements are dissolved. The positive electrode material on which the coating layer made of is formed is wetted with an aqueous solution of an oxidizing agent and a 30 to 40% by weight alkaline aqueous solution, or with a 30 to 40% by weight alkaline aqueous solution containing an oxidizing agent. , 70-1 in the wet state
A method for producing a nickel electrode material, comprising: an oxidation treatment step of heating at a temperature of 20 ° C.