POSITIVE ELECTRODE ACTIVE MATERIAL AND PREPARATION METHOD THEREOF, POSITIVE ELECTRODE PLATE, LITHIUM-ION SECONDARY BATTERY, AND BATTERY MODULE, BATTERY PACK, AND APPARATUS CONTAINING SUCH LITHIUM-ION SECONDARY BATTERY

1 . A positive electrode active material, comprising bulk particles and an element M 1 -containing oxide coating layer applied on an exterior surface of each of the bulk particles, wherein the bulk particle comprises a nickel-containing lithium composite oxide;

bulk phases of the bulk particles are uniformly doped with element M 2 ; and

a surface layer of the bulk particle is an exterior doped layer doped with element M 3 ,

wherein element M 1 and element M 3 each are independently selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B, and element M 2 comprises one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W.

2 . The positive electrode active material according to claim 1 , wherein

when the positive electrode active material is in a 78% delithiated state, element M 2 has a valence higher than +3, optionally one or more of +4, +5, +6, +7, and +8; or

when the positive electrode active material is in a 78% delithiated state, element M 2 has more than two different valence states, and element M 2 in the highest valence state has one or more valences of +4, +5, +6, +7, and +8.

3 . The positive electrode active material according to claim 1 , wherein a relative deviation of local mass concentration of element M 2 in the bulk particles is less than 35%, optionally less than 30%, and further optionally less than 20%.

4 . The positive electrode active material according to claim 1 , wherein a deviation s of the concentration of element M 2 in the positive electrode active material with respect to an average mass concentration of element M 2 in the bulk particles satisfies ε<50%; optionally ε≤30%; and optionally ε≤20%.

5 . The positive electrode active material according to claim 1 , wherein in the positive electrode active material,

a concentration of element M 1 ranges from 100 ppm to 2000 ppm, and optionally from 1000 ppm to 1500 ppm;

a concentration of element M 2 ranges from 500 ppm to 5000 ppm, and optionally from 2500 ppm to 3500 ppm; and

a concentration of element M 3 ranges from 400 ppm to 3000 ppm, and optionally from 2000 ppm to 2500 ppm.

6 . The positive electrode active material according to claim 1 , wherein element M 3 in the bulk particle has a mass concentration gradient decreasing from the exterior surface to the core of the bulk particle; and optionally, a mass concentration of element M 3 in the exterior doped layer is less than a mass concentration of element M 1 in the coating layer.

7 . The positive electrode active material according to claim 1 , wherein element M 1 and element M 3 are the same, and are both element L, wherein element L has a mass concentration gradient decreasing from the exterior surface to the core of the particle of the positive electrode active material, and element L is one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B.

8 . The positive electrode active material according to claim 1 , wherein a ratio of a sum of the concentration of element M 1 and the concentration of element M 3 in the positive electrode active material to a volume average particle size D*50 of the positive electrode active material ranges from 25 ppm/μm to 1000 ppm/μm, optionally from 200 ppm/μm to 700 ppm/μm, and further optionally from 400 ppm/μm to 550 ppm/pun.

9 . The positive electrode active material according to claim 1 , wherein

a thickness of the exterior doped layer is 10% to 30% of the bulk particle size, and optionally 15% to 25% of the bulk particle size; or

a thickness of the coating layer ranges from 1 nm to 200 nm, optionally from 50 nm to 160 nm, and further optionally from 90 nm to 120 nm.

10 . The positive electrode active material according to claim 1 , wherein the positive electrode active material further satisfies one or more of the following requirements (1) to (3):

(1) a volume average particle size D v 50 of the positive electrode active material ranges from 3 μm to 20 μm, optionally from 5 μm to 11 μm, and further optionally from 6 μm to 8 μm;

(2) a specific surface area of the positive electrode active material is 0.2 m 2 /g to 1.5 m 2 /g, and optionally 0.3 m 2 /g to 1 m 2 /g; or

(3) a tap density of the positive electrode active material optionally ranges from 2.3 g/m 3 to 2.8 g/m 3 , and optionally from 2.4 g/m 3 to 2.7 g/m 3 .

11 . The positive electrode active material according to claim 1 , wherein the nickel-containing lithium composite oxide is a compound represented by formula 1,

Li 1+a [Ni x Co y Mn z M 2 b M 3 d ]O 2-p X p   formula 1

in the formula 1, X is selected from one or more of F, N, P, and S, 0.5≤x<1, 0≤y<0.3, 0≤z<0.3, −0.2<a<0.2, 0<b<0.2, 0<d<0.2, 0≤p<0.2, x+y+z+b+d=1, and element M 2 and element M 3 each are defined according to claim 1 .

12 . A lithium-ion secondary battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active substance layer disposed on the positive electrode current collector, and the positive electrode active substance layer comprises the positive electrode active material according to claim 1 .

13 . A preparation method of a positive electrode active material, comprising:

(a) providing a mixture, wherein the mixture comprises a nickel-containing transition metal source, a lithium source, and a precursor of element M 2 ;

(b) subjecting the mixture to a sintering treatment to obtain matrix particles uniformly doped with element M 2 ;

(c) mixing the matrix particles and a precursor of element M 3 and subjecting the resulting mixture to a sintering treatment to make element M 3 dope a surface layer of the matrix particle to form an exterior doped layer, so as to obtain bulk particles; and

(d) mixing the bulk particles and a precursor of element M 1 and subjecting the resulting mixture to a sintering treatment to form an element M 1 -containing oxide coating layer on exterior surfaces of the bulk particles, so as to obtain the positive electrode active material,

wherein element M 1 and element M 3 each are independently selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B, and element M 2 includes one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W.

14 . The method according to claim 13 , wherein the method further satisfies at least one of the following:

a sintering temperature in step (b) ranges from 600° C. to 1000° C., optionally from 600° C. to 900° C., and further optionally from 650° C. to 850° C.;

a sintering temperature in step (c) ranges from 400° C. to 750° C., and optionally from 450° C. to 700° C.; or

a sintering temperature in step (d) ranges from 100° C. to 500° C., and optionally from 200° C. to 450° C.