POSITIVE ELECTRODE ACTIVE MATERIAL, ELECTRODE, AND BATTERY

A positive electrode active material includes secondary particles. Each of the secondary particles includes primary particles. Each of the primary particles includes an olivine-type phosphate compound. A cross section of the secondary particle consists of a central portion and an outer peripheral portion. A relationship of “0.8≤φ2/φ1” is satisfied. “φ1” represents a porosity of the central portion. “φ2” represents a porosity of the outer peripheral portion.