JP2558501B

PURPOSE:To obtain a lithium secondary battery whose capacity deterioration caused by charge-discharge cycles is low by synthesizing a specific transition metal oxide in an atmosphere of a specified oxygen concentration. CONSTITUTION:A transition metal oxide as shown in LixMyO2 (M is Co or a solid solution of Co and a first transition metal, x is 0.8-1.2, y is 0.8-1.2) used as a positive active material is synthesized by heating a Li source reacting material and an M source reacting material in an atmosphere of 1-10% oxygen concentration. Since oxidizing activity of LixMyO2 obtained is weak, oxidation reaction or polymerization reaction of an electrolyte by the positive active material is retarded, capacity deterioration is decreased, and reversibility is increased. A lithium secondary battery whose capacity deterioration caused by charge-discharge cycles is low is obtained.