| abstract |
The invention provides a positive electrode active material having excellent high-temperature storage characteristics and cycle characteristics, a positive electrode, and a lithium ion secondary battery using the same. The positive electrode active material (for lithium ion secondary battery) is characterized by being Li a M b (PO 4 ) c The compound has crystal water (M contains at least one selected from Fe, Mn, Co, Ni, VO and V, and a is more than or equal to 1 and less than or equal to 4, b is more than or equal to 1 and less than or equal to 2, and c is more than or equal to 1 and less than or equal to 3). |