Positive electrode active material and preparation method therefor, battery cell, and electric device

A preparation method for a positive electrode active material, comprising the following steps:

• providing a precursor for a lithium-containing phosphate;
• grinding the precursor for the lithium-containing phosphate and a carbon source;
• and
• increasing the temperature of a ground material to a first temperature T1 at a first rate in a protective gas atmosphere, maintaining the temperature at the first temperature T1 for a first time t1, then increasing the temperature to a second temperature T2 at a second rate, and maintaining the temperature at the second temperature T2 for a second time t2, so as to obtain a positive electrode active material,
• wherein the positive electrode active material comprises a lithium-containing phosphate, and an X-ray diffraction pattern of the positive electrode active material tested in a fully charged state satisfies:
• there is a (311) crystal plane peak in a range of 35° to 36° and a (011) crystal plane peak in a range of 20° to 21°, and the ratio of a peak intensity I311 of the (311) crystal plane peak to a peak intensity I011 of the (011) crystal plane peak satisfies I311/O011≥0.008.