The positive electrode active material for a secondary battery, a positive electrode for a secondary battery, a secondary battery, and the positive electrode active material manufacturing method for a secondary battery

The long life of the secondary battery. Further, suppressing the resistance increase at the time of saving the secondary battery at high temperatures. In addition, to suppress the resistance increase in charge-discharge cycle. Lithium manganate, a positive electrode active material comprising a lithium nickelate, are used. Lithium manganate is a compound compound of spinel structure or a portion of an existing site Mn or O of the compound is substituted with other elements represented by the following formula (1). (However, in the above formula (1), x is 0.15 ≦ x ≦ 0.24.)