Positive electrode active material, lithium ion secondary battery, and method of producing positive electrode active material

A method of producing a positive electrode active material comprising:

• preparing a precursor using a coprecipitation method;
• preparing a mixture by mixing the precursor and a lithium compound;
• preparing a sintered product by heating the mixture;
• and
• disintegrating the sintered product to produce the positive electrode active material,
• wherein the precursor includes secondary particles, the secondary particles include a plurality of primary particles, and the primary particles are a composite metal hydroxide,
• wherein, when the mixture is heated, the primary particles become a lithium-containing composite metal oxide, and an electron conducting oxide is precipitated at at least a part of a grain boundary between the primary particles, and
• wherein the electron conducting oxide has a perovskite structure that is represented by Formula (I):
• ACox1Mx2O3, wherein in the formula, A is at least one of La and Sr, M is at least one of Mn and Ni, and x1 and x2 satisfy 0<x1≤1, 0≤x2≤1, and 0.6≤x1+x2≤1.