A positive active material, comprising active material bulk particles and a coating layer of an oxide containing N element, wherein the 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 the outer surface of the active material bulk particles towards the 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; 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;wherein the positive active material is a lithium transition metal oxide having a layered structure, and the lithium transition metal oxide having a layer structure is a compound represented by the formula, Li 1+a [Ni x Co y Mn z A d M b N e]O 2-e X e wherein A is selected from one or more of Mg, Ca, Ce, Ti, Zr, Al, Zn and B, and X is selected from one or more of S, N, F, Cl, Br and I; wherein 0<x<1, 0≤y<0.3, 0 ≤ z<0.3, 0<a<0.2, 0<b<0.2, 0<c<0.1, 0≤d<0.2, 0≤e≤0.2, x+y+z+b+d+c=1, preferably, 0.6 < x < 1; wherein the thickness of the doped layer is from 10% to 30% of the average particle diameter of the active material bulk particles; and/or wherein the thickness of the coating layer is from 0.001 μm to 0.2 μm. wherein the 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 the outer surface of the active material bulk particles towards the 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; 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;wherein the positive active material is a lithium transition metal oxide having a layered structure, and the lithium transition metal oxide having a layer structure is a compound represented by the formula, Li 1+a [Ni x Co y Mn z A d M b N e]O 2-e X e wherein A is selected from one or more of Mg, Ca, Ce, Ti, Zr, Al, Zn and B, and X is selected from one or more of S, N, F, Cl, Br and I; wherein 0<x<1, 0≤y<0.3, 0 ≤ z<0.3, 0<a<0.2, 0<b<0.2, 0<c<0.1, 0≤d<0.2, 0≤e≤0.2, x+y+z+b+d+c=1, preferably, 0.6 < x < 1; wherein the thickness of the doped layer is from 10% to 30% of the average particle diameter of the active material bulk particles; and/or wherein the thickness of the coating layer is from 0.001 μm to 0.2 μm. 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;wherein the positive active material is a lithium transition metal oxide having a layered structure, and the lithium transition metal oxide having a layer structure is a compound represented by the formula, Li 1+a [Ni x Co y Mn z A d M b N e]O 2-e X e wherein A is selected from one or more of Mg, Ca, Ce, Ti, Zr, Al, Zn and B, and X is selected from one or more of S, N, F, Cl, Br and I; wherein 0<x<1, 0≤y<0.3, 0 ≤ z<0.3, 0<a<0.2, 0<b<0.2, 0<c<0.1, 0≤d<0.2, 0≤e≤0.2, x+y+z+b+d+c=1, preferably, 0.6 < x < 1; wherein the thickness of the doped layer is from 10% to 30% of the average particle diameter of the active material bulk particles; and/or wherein the thickness of the coating layer is from 0.001 μm to 0.2 μm.