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

A preparation method for a positive electrode active material, characterized by comprising:

• mixing a first raw material comprising a nickel source and a manganese source with a complexing agent and a precipitating agent to perform a co-precipitation reaction to prepare a precursor, optionally, the first raw material further comprising an M1 source, wherein a reaction temperature of the co-precipitation reaction is 65° C. to 80° C.;
• and
• mixing the precursor with a lithium source for calcination to prepare the positive electrode active material;
• or
• mixing the precursor with a lithium source for calcination and then performing mixing with an M2 source for calcination to prepare the positive electrode active material,
• the positive electrode active material having the following general formula:
• wherein M1 and M2 each independently comprise one or a plurality of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, or Nb, 0.8≤a≤1.2, 0.55≤x<1, 0<y≤0.25, and 0≤z≤0.2, the positive electrode active material is present in a form of secondary particles formed by aggregation of primary particles, the secondary particles comprise secondary pores formed by spaces between the primary particles, the secondary pores have an inner diameter of 0.1 μm to 2 μm, and the primary particles have a substantially spherical shape, and
• wherein at least some of the primary particles further comprise primary pores therein, and the primary pores have an inner diameter of 0.05 μm to 0.6 μm.