▎ 摘　　要

NOVELTY - Secondary battery comprises positive electrode active material which has first region and second region provided inside the first region. The first region and the second region are chosen from lithium, oxygen, first transition metal, second transition metal, and/or third transition metal, respectively. The first transition metal is nickel. The second transition metal is cobalt. The third transition metal is manganese. The concentration of nickel is higher in the first region than in the second region. USE - The secondary battery is useful in electronic device and vehicle (claimed) such as hybrid vehicle, electric vehicle and plug-in hybrid vehicle. ADVANTAGE - The secondary battery is provided with positive electrode active material that has high charge/discharge capacity, high charge/discharge voltage with less deterioration, is safe or reliable, suitable for electricity storage device that is not susceptible to deterioration and has long-life, and extends the one-charge mileage with almost no change in the total weight of the vehicle equipped with the secondary battery of the same weight.