Abstract: To provide a positive electrode active material of a lithium ion battery which has a large discharge capacity, excellent cycle characteristics, and suppressed gas generation. Resolution Means: A lithium metal composite oxide powder for use in a positive electrode active material for a lithium ion battery, the powder thereof having a composition of LiaNibCocAldO2 (wherein, a=0.8 to 1.2, b=0.7 to 0.95, c=0.02 to 0.2, d=0.005 to 0.1, and b+c+d=1) treated with an aqueous solution of an organic metal salt and soluble aluminum salt, and not causing volume expansion due to gas generation.

Abstract: A lithium metal composite oxide powder for use in a positive electrode active material for a lithium ion battery has a composition of LiaNibCocAldO2 (wherein, a=0.8 to 1.2, b=0.7 to 0.95, c=0.02 to 0.2, d=0.005 to 0.1, and b+c+d=1). The powder has been treated with an aqueous solution of an organic metal salt and soluble aluminum salt and does not cause volume expansion due to gas generation. A positive electrode active material with the lithium metal composite oxide powder has a large discharge capacity, excellent cycle characteristics, and suppressed gas generation.

Abstract: To provide a positive electrode active material of a lithium ion battery which has a large discharge capacity, excellent cycle characteristics, and suppressed gas generation. Resolution Means: A lithium metal composite oxide powder for use in a positive electrode active material for a lithium ion battery, the powder thereof having a composition of LiaNibCocAldO2 (wherein, a=0.8 to 1.2, b=0.7 to 0.95, c=0.02 to 0.2, d=0.005 to 0.1, and b+c+d 1) treated with an aqueous solution of an organic metal salt and soluble aluminum salt, and not causing volume expansion due to gas generation.