POSITIVE ACTIVE MATERIAL, POSITIVE ELECTRODE PLATE, ELECTROCHEMICAL ENERGY STORAGE APPARATUS, AND APPARATUS

1 . A positive active material comprising secondary particles, wherein,

the secondary particles have a formula of Li x Ni y Co z M k Me p O r A m , wherein 0.85≤x≤1.15, 0<y<1, 0<z<1, 0<k<1, 0≤p≤0.1, 1≤r≤2, 0≤m≤1, m+r≤2, M is one or two selected from Mn and Al, Me is one or more selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and A is one or more selected from N, F, S, and Cl,

a particle size D v 10 of the secondary particles is 2.5 μm to 8 μm, wherein D v 10 is a corresponding particle size when a cumulative volume distribution percentage of the positive active material reaches 10%.

2 . A positive active material according to claim 1 , wherein a particle size D n 10 of the positive active material is 0.5 μm to 3 μm, and D n 10 is a corresponding particle size when a cumulative number distribution percentage of the positive active material reaches 10%.

3 . A positive active material according to claim 2 , wherein D n 10 and D v 10 further satisfy 1≤D n 10×D v 10≤20.

4 . The positive active material according to claim 1 , wherein D v 10 is 3 μm to 6 μm.

5 . The positive active material according to claim 1 , wherein a particle size D v 50 is 5 μm to 18 μm, and D v 50 is a corresponding particle size when the cumulative volume distribution percentage of the positive active material reaches 50%.

6 . The positive active material according to claim 1 , wherein a particle size D v 90 of the positive active material is 10 μm to 30 μm, and D v 90 is a corresponding particle size when the cumulative volume distribution percentage of the positive active material reaches 90%.

7 . The positive active material according to claim 1 , wherein an actual specific surface area BET 2 of the positive active material is 0.1 m 2 /g to 0.8 m 2 /g.

8 . The positive active material according to claim 1 , a theoretical specific surface area BET 1 of the positive active material and an actual specific surface area BET 2 of the positive active material satisfy: 0.8≤(BET 2 −BET 1 )/BET 1 ≤5.5, wherein

BET 1 =6/(ρ× D v 50);

ρ is an actual density of the positive active material, measured in g/cm 3 ; and

D v 50 is a corresponding particle size when the cumulative volume distribution percentage of the positive active material reaches 50%, measured in m.

9 . The positive active material according to claim 1 , further comprising a coating layer disposed on a surface of at least one of the secondary particles, and the coating layer comprises a coating element selected from the group consisting of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, P, and any combinations thereof.

10 . The positive active material according to claim 1 , wherein in the Li x Ni y Co z M k Me p O r A m , 0.50≤y≤0.90, 0.05≤z≤0.2, 0.05≤k≤0.4, and 0≤p≤0.05.

11 . A method for preparing a positive active material, the method comprising:

mixing a ternary material precursor comprising Ni, Co, and M, a Li-containing compound, and a compound containing a doping element Me to form a precursor mixture;

sintering the precursor mixture to form secondary particles;

performing graded screening of the secondary particles; and

obtaining the secondary particles having a particle size D v 10 from 2.5 μm to 8 μm, wherein D v 10 is a corresponding particle size when a cumulative volume distribution percentage of the positive active material reaches 10%,

wherein the secondary particles have a formular of Li x Ni y Co z M k Me p O r or Li x Ni y Co z M k Me p O r , 0.85≤x≤1.15, 0<y<1, 0<z<1, 0<k<1, 0≤p≤0.1, 1≤r≤2, M is one or two selected from Mn and Al, Me is one or more selected from Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb.

12 . The method according to claim 11 , wherein,

the ternary material precursor is selected from the group consisting of: Ni 1/3 Co 1/3 Mn 1/3 (OH) 2 , Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , Ni 0.5 Co 0.25 Mn 0.25 (OH) 2 , Ni 0.55 Co 0.15 Mn 0.3 (OH) 2 , Ni 0.55 Co 0.1 Mn 0.35 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.4 (OH) 2 , Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 , Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.07 (OH) 2 , 0.9Ni 0.8 Co 0.2 (OH) 2 ·0.1Al 2 (OH) 3 , 0.9Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 ·0.1Al 2 (OH) 3 , and any combinations thereof; and

the Li-containing compound is selected from the group consisting of LiOH·H 2 O, LiGH, Li 2 CO 3 , Li 2 O, and any combinations thereof.

13 . The method according to claim 11 , wherein the sintering is performed at a temperature of 700° C. to 800° C. under an oxygen concentration of 20% or more.

14 . The method according to claim 11 , wherein the performing graded screening of the secondary particles further comprises:

subjecting the secondary particles into an air flow classifier having a nozzle;

causing the secondary particles to be ejected from the nozzle with an air flow;

collecting the secondary particles using a collector placed at a distance from the nozzle, wherein the secondary particles ejected from the nozzle fly toward the collector and are separated by particle size; and

wherein the distance between the collector and the nozzle is adjusted to collect the secondary particles with D v 10 from 2.5 μm to 8 μm.

15 . The method according to claim 11 , wherein the performing graded screening of the secondary particles further comprises:

sifting the secondary particles using a sieve, wherein the sieve has a mesh value from 200 to 1000.

16 . The method according to claim 11 , further comprising adding a compound containing a doping element to the precursor mixture, wherein,

the compound containing a doping element A is selected from the group consisting of LiF, NaCl, Na 2 S, Li 3 N, and any combinations thereof, and the doping element A is selected from the group consisting of N, F, S, Cl, and any combinations thereof; and

the positive active material is Li x Ni y Co z M k Me p O r A m , 1<r≤2, 0<m≤1, m+r≤2.

17 . A method for preparing a positive active material, the method comprising:

mixing a ternary material precursor comprising Ni, Co, and M, a Li-containing compound, and a compound containing a doping element Me to form a precursor mixture;

sintering the precursor mixture to form secondary particles;

mixing the secondary particles with a compound containing a coating element to form a mixture;

sintering the mixture to form the positive active material, wherein the positive active material comprises a coating layer on a surface of at least one of the secondary particles, and the coating layer comprises the coating element;

performing graded screening of the positive active material; and

obtaining the positive active material having a particle size D v 10 from 2.5 μm to 8 μm, wherein D v 10 is a corresponding particle size when a cumulative volume distribution percentage of the positive active material reaches 10%.

18 . The method according to claim 17 , wherein,

the compound containing the coating element is selected from the group consisting of an oxide containing the coating element, a nitrate containing the coating element, a phosphate containing the coating element, a carbonate containing the coating element, and any combinations thereof; and

the coating element is selected from the group consisting of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, P, and any combinations thereof.

19 . The method according to claim 18 , wherein the compound containing the coating element accounts for 0.01% to 0.5%, based on a total mass of the positive active material.

20 . The method according to claim 17 , wherein sintering the mixture is performed at a temperature from 200° C. to 700° C.