Positive electrode active material, positive electrode sheet, secondary battery, and electric device

The embodiment of the invention relates to a positive active material, a positive pole piece, a secondary battery and an electric device. The positive electrode active material comprises a first active material and a second active material; the first active material comprises a compound with a molecular formula of Li < 1 + x > Fe < 1-y > A < y > P < 1-z > Q < z > O < 4 > and a modified compound thereof; and the second active substance comprises a compound with the molecular formula of LihNijCokM1dM2eOfRg and a modified compound of the compound. According to the embodiment of the invention, the capacity exertion and cycle performance of the secondary battery can be improved.