Positive active material, positive electrode plate and lithium-ion secondary battery

A positive active material, comprising active material bulk particles and a coating layer of an oxide containing N element,

• wherein an surface of the active material bulk particles is doped with M element to form a doped layer, and the content of the M element is 400 ppm to 3000 ppm, and the content of the M element gradually decreases from an outer surface of the active material bulk particles towards a core direction;
• wherein the content of the N element in the coating layer is 100 ppm to 2000 ppm;
• wherein the M element and the N element are each independently selected from one or more of Mg, Ca, Ce, Ti, Zr, Al, Zn, and B;
• and
• wherein the content of the M element and the content of the N element are based on the positive active material;
• and wherein the average content of the N element per unit volume of the coating layer is greater than the average content of the M element per unit volume of the doped layer.