METHOD FOR FORMING POSITIVE ELECTRODE ACTIVE MATERIAL

A method for forming a positive electrode active material of a lithium ion secondary battery is provided. In the method for forming a positive electrode active material, a first container that includes a mixture of lithium oxide, fluoride, and a magnesium compound and fluoride that is outside the first container are provided in a heating furnace, and the heating furnace is heated at a temperature higher than or equal to a temperature at which the fluoride is volatilized or sublimated. It is further preferable that the fluoride be lithium fluoride and the magnesium compound be magnesium fluoride.