Positive electrode active material precursor, positive electrode active material, preparation method and secondary battery

The invention provides a positive electrode active material precursor, a positive electrode active material, a preparation method and a secondary battery, the preparation method comprises the following steps: S1, preparing a metal salt aqueous solution and a precipitant aqueous solution, S2, preparing a metal salt aqueous solution and a precipitant aqueous solution, the preparation method comprises the following steps: S1, preparing a precipitant aqueous solution, mixing the precipitant aqueous solution and the metal salt aqueous solution at a shearing speed of 10000 r/min or above, and carrying out a co-precipitation reaction, and S3, after the reaction is finished, carrying out washing and drying so as to obtain the positive electrode active material precursor. According to the preparation method provided by the invention, the positive electrode active material precursor which is regular in morphology, small in particle size, narrow in particle size distribution, single in crystal phase, high in purity, uniform in element distribution and high in batch stability and consistency can be obtained, so that the electrochemical performance of the positive electrode active material and a secondary battery can be improved.