POSITIVE ELECTRODE ACTIVE MATERIAL AND PREPARATION METHOD THEREOF, POSITIVE ELECTRODE PLATE, LITHIUM-ION SECONDARY BATTERY, AND APPARATUS CONTAINING SUCH LITHIUM-ION SECONDARY BATTERY
This application discloses a positive electrode active material, including secondary particles and a coating layer applied on an exterior surface of each of the secondary particles, where the secondary particle includes a lithium transition metal oxide that contains a doping element M 1 , the coating layer includes an oxide of element M 2 , M 1 is selected from one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W, and M 2 is selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B; a relative deviation of local mass concentration of element M 1 in the secondary particle is less than 20%; and the secondary particle from the core to the exterior surface of the particle includes a plurality of layers of primary particles arranged along radial direction of the secondary particle.
1 . A positive electrode active material, comprising secondary particles and a coating layer applied on an exterior surface of each one of the secondary particles, wherein the secondary particle comprises a lithium transition metal oxide, the coating layer comprises an oxide of element M 2 , and the positive electrode active material satisfies a chemical formula (1):
Li 1+a [Ni x Co y Mn z M 1 b M 2 c ]O 2−d X d chemical formula (1)
wherein in the chemical formula (1), M 1 is an element doped in a transition metal site of the lithium transition metal oxide, M 1 is selected from one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W, X is an element doped in an oxygen site of the lithium transition metal oxide, X is selected from one or more of F, Cl, Br, I, S, N, and P, M 2 is an element of the coating layer, M 2 is selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B, 0.5≤x<1, 0<y≤0.3, 0≤z≤0.3, −0.1<a<0.2, 0<b<0.3, 0<c<0.3, 0≤d<0.2, 0<b+c<0.3, and x+y+z+b=1;
a relative deviation of local mass concentration of element M 1 in the secondary particle is less than 20%; and
each one of the secondary particles has a core and an exterior surface and comprises a plurality of layers of primary particles arranged along a radial direction of the secondary particle from the core to the exterior surface, and a number of primary particles contained in the outermost layer of the plurality of layers ranges from 5 per μm 2 to 50 per μm 2 .
2 . The positive electrode active material according to claim 1 , wherein a deviation ε of a concentration of element M 1 in the positive electrode active material with respect to an average mass concentration of element M 1 in the secondary particles satisfies ε<50.
3 . The positive electrode active material according to claim 1 , wherein a specific surface area of the positive electrode active material ranges from 0.1 m 2 /g to 1.5 m 2 /g.
4 . The positive electrode active material according to claim 1 , wherein a compacted density of the positive electrode active material under a pressure of 5 tons is more than 3.0 g/cm 3 .
5 . The positive electrode active material according to claim 1 , wherein a volume median particle size D v 50 of the positive electrode active material ranges from 3 μm to 25 μm.
6 . The positive electrode active material according to claim 1 , wherein a length of the primary particle ranges from 100 nm to 1000 nm, and a width of the primary particle ranges 50 nm to 400 nm.
7 . The positive electrode active material according to claim 1 , wherein an aspect ratio of the primary particle ranges from 2 to 20.
8 . The positive electrode active material according to claim 1 , wherein a concentration of element M 1 in the positive electrode active material ranges from 200 ppm to 8000 ppm; and
a total concentration of element M 1 and element M 2 in the positive electrode active material ranges from 1000 ppm to 12000 ppm.
9 . The positive electrode active material according to claim 1 , wherein
when the positive electrode active material is in a 78% delithiated state, element M 1 has a valence higher than +3; or
when the positive electrode active material is in a 78% delithiated state, element M 1 has more than two different valence states, and element M 1 in the highest valence state has one or more valences of +4, +5, +6, +7, and +8.
10 . A preparation method of a positive electrode active material, comprising steps of:
(a) providing a mixture, wherein the mixture comprises a precursor of a positive electrode active material, a lithium source, a precursor of element M 1 , and optionally a precursor of element X;
(b) subjecting the mixture to a sintering treatment to obtain secondary particles; and
(c) mixing the secondary particles and a precursor of element M 2 to obtain a resulting mixture and subjecting the resulting mixture to a sintering treatment to obtain the positive electrode active material;
wherein the positive electrode active material comprises secondary particles and a coating layer applied on an exterior surface of each of the secondary particles, the secondary particle comprises a lithium transition metal oxide, the coating layer comprises an oxide of element M 2 , and the positive electrode active material satisfies a chemical formula (1),
Li 1+a [Ni x Co y Mn z M 1 b M 2 c ]O 2−d X d chemical formula (1)
wherein in the chemical formula (1), M 1 is an element doped in a transition metal site of the lithium transition metal oxide, M 1 is selected from one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W, X is an element doped in an oxygen site of the lithium transition metal oxide, X is selected from one or more of F, Cl, Br, I, S, N, and P, M 2 is an element of the coating layer, M 2 is selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B, 0.5≤x<1, 0<y≤0.3, 0≤z≤0.3, −0.1<a<0.2, 0<b<0.3, 0<c<0.3, 0≤d<0.2, 0<b+c<0.3, and x+y+z+b=1;
a relative deviation of local mass concentration of element M 1 in the secondary particle is less than 20%; and
each one of the secondary particles has a core and an exterior surface and comprises a plurality of layers of primary particles arranged along a radial direction of the secondary particle from the core to the exterior surface, and a number of primary particles contained in the outermost layer of the plurality of layers ranges from 5 per μm 2 to 50 per μm 2 .
11 . The method according to claim 10 , wherein
an atmosphere for the sintering treatment in step (b) contains oxygen; and
a percentage of oxygen in the sintering atmosphere ranges from 80% to 100%.
12 . The method according to claim 11 , wherein a percentage of oxygen in the atmosphere for the sintering treatment in step (b) ranges from 80% to 100%.
13 . The method according to claim 10 , wherein a temperature for the sintering treatment in step (c) ranges from 500° C. to 1000° C.
14 . The method according to claim 10 , wherein a duration for the sintering treatment ranges from 5 hours to 35 hours.
15 . The method according to claim 10 , wherein steps (a) and (b) further comprise:
dividing the precursor of element M 1 into L batches for doping, wherein L ranges from 2 to 5,
mixing the precursor of the positive electrode active material, the lithium source, and a first batch of the precursor of element M 1 and performing a first sintering treatment;
when L is 2, the method further comprises mixing a product of the first sintering treatment with a second batch of the precursor of element M 1 and performing a second sintering treatment to obtain the secondary particles;
when L is 3, the method further comprises mixing a product of the first sintering treatment with a second batch of the precursor of element M 1 and performing a second sintering treatment, and mixing a product of the second sintering treatment with a third batch of the precursor of element M 1 and performing a third sintering treatment to obtain the secondary particles;
when L is 4, the method further comprises mixing a product of the first sintering treatment with a second batch of the precursor of element M 1 and performing a second sintering treatment, mixing a product of the second sintering treatment with a third batch of the precursor of element M 1 and performing a third sintering treatment, and mixing a product of the third sintering treatment with a fourth batch of the precursor of element M 1 and performing a fourth sintering treatment to obtain the secondary particles; and
when L is 5, the method further comprises mixing a product of the first sintering treatment with a second batch of the precursor of element M 1 and performing a second sintering treatment, mixing a product of the second sintering treatment with a third batch of the precursor of element M 1 and performing a third sintering treatment, mixing a product of the third sintering treatment with a fourth batch of the precursor of element M 1 and performing a fourth sintering treatment, and mixing a product of the fourth sintering treatment with a fifth batch of the precursor of element M 1 and performing a fifth sintering treatment to obtain the secondary particles.
16 . The method according to claim 15 , wherein
the precursor of element M 1 into 2 batches comprising a first batch and a second batch; and
a mass ratio of the first batch to the second batch is a ratio of 40/60 to 60/40.
17 . The method according to claim 12 , wherein
a temperature for each sintering treatment of steps (b) and (c) ranges from 500° C. to 1000° C.; and
a duration for each sintering treatment ranges from 2 hours to 25 hours.
18 . The method according to claim 10 , wherein
an atmosphere for the sintering treatment in step (c) contains oxygen;
a temperature for the sintering treatment in step (c) ranges from 200° C. to 700° C.; and
a duration for the sintering treatment ranges from 2 hours to 10 hours.
19 . The method according to claim 10 , wherein the mixture of step (a) comprises the precursor of element M 1 , and in the chemical formula (1) of the positive electrode active material in step (c), 0<d<0.2.
20 . 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 a positive electrode active material,
wherein the positive electrode active material comprises secondary particles and a coating layer applied on an exterior surface of each of the secondary particles, wherein the secondary particle comprises a lithium transition metal oxide, the coating layer comprises an oxide of element M 2 , and the positive electrode active material satisfies a chemical formula (1):
Li 1+a [Ni x Co y Mn z M 1 b M 2 c ]O 2−d X d chemical formula (1)
wherein in the chemical formula (1), M 1 is an element doped in a transition metal site of the lithium transition metal oxide, M 1 is selected from one or more of Si, Ti, Cr, Mo, V, Ge, Se, Zr, Nb, Ru, Rh, Pd, Sb, Te, Ce, and W, X is an element doped in an oxygen site of the lithium transition metal oxide, X is selected from one or more of F, Cl, Br, I, S, N, and P, M 2 is an element of the coating layer, M 2 is selected from one or more of Mg, Al, Ca, Ce, Ti, Zr, Zn, Y, and B, 0.5≤x<1, 0<y≤0.3, 0≤z≤0.3, −0.1<a<0.2, 0<b<0.3, 0<c<0.3, 0≤d<0.2, 0<b+c<0.3, and x+y+z+b=1;
a relative deviation of local mass concentration of element M 1 in the secondary particle is less than 20%; and
each one of the secondary particles has a core and an exterior surface and comprises a plurality of layers of primary particles arranged along a radial direction of the secondary particle from the core to the exterior surface, and a number of primary particles contained in the outermost layer of the plurality of layers ranges from 5 per μm 2 to 50 per μm 2 .