Positive electrode active material for alkaline storage battery, positive electrode for alkaline storage battery, alkaline storage battery, and method for manufacturing positive electrode active material for alkaline storage battery

Abstract

There are provided a positive electrode active material for an alkaline storage battery, a positive electrode for an alkaline storage battery, and an alkaline storage battery each of which has an excellent output characteristics and also has an excellent self-discharge characteristic and an excellent cycle lifetime characteristic. The positive electrode active material for an alkaline storage battery according to the present invention has nickel hydroxide particles each containing at least magnesium in a solid solution state and a cobalt compound layer coating the surface of each of the nickel hydroxide particles. Among them, the cobalt compound layer contains cobalt having an average valence of not less than 2.6 and not more than 3.0 and also contains sodium at a proportion of less than 0.10 wt % to the total weight of the cobalt compound layer. The positive electrode active material for an alkaline storage battery according to the present invention has a conductivity smaller than 1.0×10 −5 S/cm in a state pressurized at 39.2 MPa.

1 - 15 . (canceled) 
     
     
         16 . A method for manufacturing a positive electrode active material for an alkaline storage battery having nickel hydroxide particles and a cobalt compound layer coating each of the nickel hydroxide particles, the method comprising:
 a cobalt compound layer forming step of forming the cobalt compound layer on a surface of each of the nickel hydroxide particles by supplying an aqueous solution containing cobalt ions into an aqueous solution containing nickel hydroxide particles, while supplying an aqueous sodium hydroxide solution into the aqueous solution containing the nickel hydroxide particles to maintain the pH thereof in a range of 11.5 to 13.5 and also supplying air thereinto.   
     
     
         17 . The method for manufacturing a positive electrode active material for an alkaline storage battery according to  claim 16 , wherein the cobalt compound layer forming step includes adjusting a concentration of oxygen dissolved in the aqueous solution containing the nickel hydroxide particles to a value of not less than 1.0 mg/l and not more than 1.5×10 mg/l by using the air supplied into the aqueous solution containing the nickel hydroxide particles.