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
A positive electrode active material and a preparation method thereof, a positive electrode plate, a lithium-ion secondary battery, and a battery module, battery pack, and apparatus containing such lithium-ion secondary battery are provided. The positive electrode active material includes matrix particles and a coating layer covering an exterior surface of the matrix particle, where the matrix particle includes a lithium nickel cobalt manganese oxide, and the coating layer includes an oxide of element M 1 ; the matrix particle is doped with element M 2 and element M 3 , element M 2 in the matrix particle is uniformly distributed, and element M 3 in the matrix particle has a decreasing concentration from the exterior surface to a core of the matrix particle; and element M 1 and element M 3 are each independently selected from one or more of Mg, Al, Ca, Ba, Ti, Zr, Zn, 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.
1. A positive electrode active material, comprising a matrix particle and a coating layer covering an exterior surface of the matrix particle, wherein the matrix particle comprises a lithium nickel cobalt manganese oxide, and the coating layer has a thickness T ranging from 0.001 μm to 0.032 μm and comprises an oxide of element M 1 ;
the matrix particle is doped with element M 2 and element M 3 , relative deviation of a local mass concentration of element M 2 in the matrix particle is 20% or below, and element M 3 in the matrix particle has a decreasing concentration from the exterior surface to a core of the matrix particle; and
element M 1 is selected from the group consisting of Mg, Al, Ca, Ba, Ti, Zr, Zn, B, and any combinations thereof,
element M 2 is selected from the group consisting of Si, Ge, Se, Ru, Rh, Pd, Sb, Te, Ta, W, Mo, Nb, and any combinations thereof,
element M 3 is selected from the group consisting of Al, Ca, Ba, Zr, Zn, B, and any combinations thereof;
and wherein the lithium nickel cobalt manganese oxide is a compound represented by chemical formula 1:
Li 1+α [Ni x Co y Mn z M 2 b M 3 d ]O 2-p X p chemical formula 1
in chemical formula 1, X is selected from the group consisting of F, Cl, Br, S, and any combinations thereof, 0.7≤x<0.9, 0<y<0.3, 0<z<0.3, −0.1≤α≤0.2, 0<b≤0.1, 0<d≤0.1, 0≤p≤0.1, and x+y+z+b+d=1.
2. The positive electrode active material according to claim 1 , wherein a concentration ratio of element M 1 to element M 3 is 0.1:1 to 20:1; and
both a concentration of element M 1 and a concentration of element M 3 are concentrations in the positive electrode active material, measured in ppm,
wherein the concentrations of element M 1 and element M 3 in the positive electrode active material are the mass ratios of the respective element in the positive electrode active material to the positive electrode active material in part per million and are measured as described in the description.
3. The positive electrode active material according to claim 1 , wherein the matrix particle is doped with element X of 100 ppm to 5000 ppm, element X is selected from the group consisting of F, Cl, Br, S, and any combinations thereof, and a concentration of element X is a concentration in the positive electrode active material; and
element X has a decreasing concentration in the direction from the exterior surface to the core of the matrix particle,
wherein the concentration of element X in the positive electrode active material is the mass ratio of the respective element in the positive electrode active material to the positive electrode active material in part per million and is measured as described in the description.
4. The positive electrode active material according to claim 1 , wherein element M 1 is the same as element M 3 .
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 3000 ppm;
a concentration of element M 2 ranges from 100 ppm to 5000 ppm; and
a concentration of element M 3 ranges from 100 ppm to 3000 ppm;
wherein the concentrations of element M 1 , element M 2 and element M 3 in the positive electrode active material are the mass ratios of the respective element in the positive electrode active material to the positive electrode active material in part per million and are measured as described in the description.
6. The positive electrode active material according to claim 1 , wherein a volume average particle size D v 50 of the positive electrode active material ranges from 8 μm to 20 μm.
7. The positive electrode active material according to claim 1 , wherein the thickness T of the coating layer and an average particle size D of the positive electrode active material satisfy: 0.002≤T/ D ≤0.031.
8. A preparation method for a positive electrode active material, comprising:
(a) mixing a nickel-cobalt-manganese ternary material precursor, a lithium source, and an element M 2 precursor, and performing sintering treatment, to obtain a substrate particle uniformly doped with element M 2 ;
(b) mixing the substrate particle with a modifying-element precursor, and performing sintering treatment, to cause a modifying element to dope the substrate particle at a decreasing concentration from an exterior surface to a core of the substrate particle, to obtain a matrix particle, wherein the modifying element is element M 3 or a combination of element M 3 and element X; and
(c) mixing the matrix particle with an element M 1 precursor, and performing sintering treatment, to form an element M 1 -containing oxide coating layer having a thickness T ranging from 0.001 μm to 0.032 μm on an exterior surface of the matrix particle, so as to obtain a positive electrode active material, wherein
relative deviation of a local mass concentration of element M 2 in the matrix particle is 20% or below, element M 1 is selected from the group consisting of Mg, Al, Ca, Ba, Ti, Zr, Zn, B, and any combinations thereof, element M 2 is selected from the group consisting of Si, Ge, Se, Ru, Rh, Pd, Sb, Te, Ta, W, Mo, Nb, and any combinations thereof, element M 3 is selected from the group consisting of Al, Ca, Ba, Zr, Zn, B, and any combinations thereof, and element X is selected from the group consisting of F, Cl, Br, S, and any combinations thereof; and
wherein the matrix particle comprises a lithium nickel cobalt manganese oxide which is a compound represented by chemical formula 1:
Li 1+α [Ni x Co y Mn z M 2 b M 3 d ]O 2-p X p chemical formula 1
in chemical formula 1, X is selected from one or more of F, Cl, Br, and S, 0.7≤x<0.9, 0<y<0.3, 0<z<0.3, −0.1≤α≤0.2, 0<b≤0.1, 0<d≤0.1, 0≤p≤0.1, and x+y+z+b+d=1.
9. The preparation method according to claim 8 , wherein the method further satisfies at least one of the following:
a temperature for the sintering treatment in step (a) is 600° C. to 1000° C.;
a temperature for the sintering treatment in step (b) is 600° C. to 950° C.; and
a temperature for the sintering treatment in step (C) is 150° C. to 500° C.
10. A positive electrode plate, comprising a positive electrode current collector and a positive electrode active substance layer disposed on the positive electrode current collector, wherein the positive electrode active substance layer comprises the positive electrode active material according to claim 1 .
11. A lithium-ion secondary battery, comprising the positive electrode plate according to claim 10 .
12. The positive electrode active material according to claim 4 , wherein element M 1 and element M 3 are selected from the group consisting of Ti, B, Zr, and a combination thereof.
13. The positive electrode active material according to claim 1 , wherein when the positive electrode active material is in a 78% delithiated state, an average valence of element M 2 is α; when the positive electrode active material is in an 11% delithiated state, an average valence of element M 2 is β; and αand βsatisfy: α>β>+3.
14. The positive electrode active material according to claim 1 , wherein ω 1 is a percentage of a sum of mass of elements M 1 , M 3 , and X within a thickness range of ⅕ of a particle size of the matrix particle of the positive electrode active material in a direction from an exterior surface of the matrix particle to a core of the matrix particle, relative to a total mass of the elements M 1 , M 3 , and X in the matrix particle, and ω 1 is from 40% to 62%.
15. The positive electrode active material according to claim 14 , wherein ω 1 is from 50% to 62%.
16. The positive electrode active material according to claim 1 , wherein ω 2 is a percentage of a sum of mass of elements M 1 , M 3 , and X within a thickness range of ⅔ of a particle size of the matrix particle of the positive electrode active material in a direction from an exterior surface of the matrix particle to a core of the matrix particle, relative to a total mass of the elements M 1 , M 3 , and X in the matrix particle, and ω 2 is from 80% to 97%.
17. The positive electrode active material according to claim 16 , wherein ω 2 is from 90% to 97%.
18. The preparation method according to claim 8 , wherein element M 1 is the same as element M 3 , and element M 1 and element M 3 are selected from the group consisting of Ti, B, Zr, and a combination thereof.