POSITIVE ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE MATERIAL, BATTERY, AND METHOD FOR PRODUCING POSITIVE ELECTRODE ACTIVE MATERIAL

The positive electrode active material of the present disclosure includes a complex oxide represented by a formula (1): LiNiMeO as a main component and contains water in an amount of 2.9 ppm by mass or more and 44.7 ppm by mass or less. Here, x satisfies 0.5 ≤ x ≤ 1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.