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

A secondary battery, comprising positive electrode plate, negative electrode plate positive electrode active material, and electrolyte;

• the electrolyte conduct ions between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate comprising positive electrode active material, the positive electrode active material comprises:
• (i) secondary particles, wherein the secondary particles are formed by aggregating primary particles, and the secondary particles further comprise an M1 element, the M1 element comprises a transition metal element other than iron, and a mass content of the M1 element is X1 based on a total mass of the secondary particles;
• and
• (ii) single-crystal or quasi-single-crystal particles, wherein the single-crystal or quasi-single-crystal particles comprise an Ma element, the Ma element comprises a transition metal element other than iron, and a mass content of the Ma element is X2 based on a total mass of the single-crystal or quasi-single-crystal particles, wherein X2 is less than X1;
• wherein an average particle size of the secondary particles is r, an average particle size of the single-crystal or quasi-single-crystal particles is R2, and 2≤r/R2≤30.