Positive electrode active material, method for preparation thereof, positive electrode plate, lithium-ion secondary battery and related battery module, battery pack and apparatus
The present application discloses a positive electrode active material including a lithium nickel cobalt manganese oxide, the molar content of nickel in the lithium nickel cobalt manganese oxide accounts for 60%-90% of the total molar content of nickel, cobalt and manganese, and the lithium nickel cobalt manganese oxide has a layered crystal structure of a space group R 3 m; a transition metal layer of the lithium nickel cobalt manganese oxide includes a doping element, and the local mass concentration of the doping element in particles of the positive electrode active material has a relative deviation of 20% or less; and in a differential scanning calorimetry spectrum of the positive electrode active material in a 78% delithiation state, an initial exothermic temperature of a main exothermic peak is 200° C. or more, and an integral area of the main exothermic peak is 100 J/g or less.
1. A positive electrode active material, comprising a lithium nickel cobalt manganese oxide, wherein the molar content of nickel in the lithium nickel cobalt manganese oxide is 60%-90% of the total molar content of nickel, cobalt and manganese, and the lithium nickel cobalt manganese oxide has a layered crystal structure of a space group R 3 m;
a transition metal layer of the lithium nickel cobalt manganese oxide comprises a doping element, and the local mass concentration of the doping element in particles of the positive electrode active material has a relative deviation of 20% or less; and
in a differential scanning calorimetry spectrum of the positive electrode active material in a 78% delithiation state, an initial exothermic temperature of a main exothermic peak is 200° C. or more, and an integral area of the main exothermic peak is 100 J/g or less.
2. The positive electrode active material according to claim 1 , wherein
a half-peak width of the main exothermic peak is 30° C. or less; or
a peak temperature of the main exothermic peak is 230° C. or more.
3. The positive electrode active material according to claim 1 , wherein the local mass concentration of the doping element in the particles of the positive electrode active material has a relative deviation of 15% or less.
4. The positive electrode active material according to claim 1 , wherein when the positive electrode active material is in the 78% delithiation state, the doping element has a valence of greater than +3.
5. The positive electrode active material according to claim 1 , wherein the doping element comprises one or more of Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W.
6. The positive electrode active material according to claim 1 , wherein the positive electrode active material has a true density ρ true satisfying: 4.6 g/cm 3 ≤ρ true ≤4.9 g/cm 3 .
7. The positive electrode active material according to claim 1 , wherein the positive electrode active material has a true doping concentration ω satisfying: 2300 μg/cm 3 ≤ω≤49500 μg/cm 3 .
8. The positive electrode active material according to claim 1 , wherein the mass concentration of the doping element in the positive electrode active material has a deviation ε<50%, relative to an average mass concentration of the doping element in the particles of the positive electrode active material.
9. The positive electrode active material according to claim 1 , wherein the positive electrode active material further satisfies one or more of the following (1)-(4):
(1) the positive electrode active material has a volume average particle size D v 50 of 5 μm to 20 μm;
(2) the positive electrode active material has a specific surface area of 0.2 m 2 /g to 1.5 m 2 /g;
(3) the positive electrode active material has a tap density of 2.3 g/cm 3 to 2.8 g/cm 3 ; and
(4) the positive electrode active material has a compacted density of 3.1 g/cm 3 -3.8 g/cm 3 under a pressure of 5 tons (equivalent to 49 kN).
10. The positive electrode active material according to claim 1 , wherein the lithium nickel cobalt manganese oxide satisfies a chemical formula Li 1+a [Ni x Co y Mn z M b ]O 2 , wherein M is the doping element, M is selected from one or more of Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W, 0.7≤x≤0.9, 0<y<0.3, 0<z<0.3, 0≤a<0.2, 0<b<0.3, and x+y+z+b=1; or
the lithium nickel cobalt manganese oxide satisfies a chemical formula Li 1+c [Ni r−d Co s M nt M′ d ]O 2 , wherein M′ is the doping element, M′ is selected from one or more of Al, Si, Ti, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Te, and W, 0.7≤r−d≤0.9, 0<s<0.3, 0<t<0.3, 0≤c<0.2, 0<d<0.3, and r+s+t=1.
11. A positive electrode plate, comprising a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to claim 1 .
12. The positive electrode active material according to claim 1 , wherein when the positive electrode active material is in the 78% delithiation state, the doping element has a valence selected from one or more of +4, +5, +6, +7, and +8.
13. The positive electrode active material according to claim 1 , wherein the positive electrode active material has a true doping concentration ω satisfying: 3000 μg/cm 3 ≤ω≤35000 μg/cm 3 .
14. The positive electrode active material according to claim 1 , wherein the positive electrode active material has a true doping concentration ω satisfying: 14810 μg/cm 3 ≤ω≤36710 μg/cm 3 .
15. The positive electrode active material according to claim 1 , wherein the mass concentration of the doping element in the positive electrode active material has a deviation ε≤30%, relative to an average mass concentration of the doping element in the particles of the positive electrode active material.