Positive electrode sheet, secondary battery, battery module, battery pack and electrical apparatus
A positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical apparatus are described. The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector and having a single-layer or multi-layer structure. When the positive electrode film layer is of the single-layer structure, at least one positive electrode film layer comprises both a first positive electrode active material and a second positive electrode active material with a chemical formula of Li a A x Mn 1-y R y P 1-z C z O 4-n D n ; and/or, when the positive electrode film layer is of the multi-layer structure, at least one layer of the at least one positive electrode film layer includes both a first and second positive electrode active material. The secondary battery made of the positive electrode sheet has high energy density and high battery cell rate performance.
1 . A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer comprising a first layer of a first positive electrode active material on the current collector and a second layer on the first layer, the second layer comprising a second positive electrode active material;
wherein the first positive active material comprises particles selected from one or more compounds of formula: Li a A x Mn 1-y R y P 1-z C z O 4-n D n ;
wherein,
A comprises one or more elements selected from the group consisting of Na, K, Mg, Nb Mo, W, Zn and Al,
R comprises one or more elements selected from the group consisting of Mg, Ti, Zr, V, Nb, Fe, Co, Ni, Ga, Ge, Sn and Sb,
C comprises one or more elements selected from the group consisting of B (boron), S, Si and N,
D comprises one or more elements selected from the group consisting of S, F, Cl and Br,
a is selected from a range of 0.9 to 1.1, x is selected from a range of 0.001 to 0.1, y is selected from a range of 0.001 to 0.5, z is selected from a range of 0.001 to 0.1, and n is selected from a range of 0.001 to 0.1;
the second positive electrode active material comprises particles selected from the group consisting of one or more of LiNi b Co c Mn (1-b-c) O 2 , LiNi b COAl (1-b-c) O 2 and LiCoO 2 ; wherein b is independently selected from 0.3-0.9, and a sum of b and c is independently selected from 0.3-0.9.
2 . The positive electrode sheet according to claim 1 wherein the first active material comprises Li 0.998 Mg 0.005 Mn 0.6 Fe 0.35 V 0.05 P 0.999 S 0.001 O 3.999 F 0.001 and the second active material comprises LiNi 0.5 Mn 0.3 Co 0.2 O 2 .
3 . The positive electrode sheet according to claim 1 wherein the positive electrode sheet comprises the current collector, the first positive electrode film layer comprising the particles of the first active material comprises Li a A x Mn 1-y R y P 1- C z O 4n D n where the surface is further coated with carbon, and
the second active layer comprising the second active material comprises LiNi b Co c Mn (1-b-c) O 2 .
4 . The positive electrode sheet according to claim 1 , wherein a mass ratio of the first positive active material in the positive electrode film to the second positive active material in the positive electrode film layer is 1:7 to 7:1.
5 . The positive electrode sheet according to claim 1 , wherein in the first positive electrode active material,
A is selected from the group consisting of Mg and Nb, and/or
R is selected from at least two elements selected from the group consisting of Mg, Ti, Zr, V, Nb, Fe, Co, Ni, Ga, Ge, Sn and Sb;
C is S, and/or;
D is F.
6 . The positive electrode sheet according to claim 1 , wherein in the first positive electrode active material,
A is selected from the group consisting of Mg or Nb, and/or,
R is at least two elements selected from the group consisting of Mg, Ti, V, Fe, and Co,
C is S, and/or,
D is F.
7 . The positive electrode sheet according to claim 1 , wherein in the first positive electrode active material, x is selected from a range of 0.001-0.005; and/or, y is selected from a range of 0.01 to 0.5; and/or, z is selected from a range of 0.001 to 0.005; and/or, n is selected from a range of 0.001 to 0.005; and/or, a ratio of (1−y) to y is selected from 1-4; and/or, a ratio of a to x is selected from 9-1100.
8 . The positive electrode sheet according to claim 1 , wherein a lattice change rate of the first positive electrode active material is about 2.2 to 8%.
9 . The positive electrode sheet according to claim 1 , wherein a Li/Mn antisite defect concentration of the first positive electrode active material is about 0.4 to 2%.
10 . The positive electrode sheet according to claim 1 , wherein surface oxygen valence of the first positive electrode active material is about −1.82 to 1.98.
11 . The positive electrode sheet according to claim 1 , wherein a compacted density of the first positive electrode active material at 3T is 2.0 g/cm 3 or more.
12 . The positive electrode sheet according to claim 1 , wherein a surface of the particles of first positive electrode active material is further coated with carbon.
13 . The positive electrode sheet according to claim 1 , wherein in the second positive electrode active material,
a ratio of b to (1-b-c) to c in LiNi b Co c Mn (1-b-c) O 2 is 5:2:3 or 3:1:1 or 8:1:1; or,
a ratio of b to c to (1-b-c) in LiNi b Co c Al (1-b-c) O 2 is 5:2:3 or 3:1:1 or 8:1:1.
14 . The positive electrode sheet according to claim 1 , wherein a sum of mass of the first positive electrode active material and the second positive electrode active material accounts for 88%-98.7% of the mass of the positive electrode sheet.
15 . A secondary battery, comprising the positive electrode sheet according to claim 1 .
16 . A battery module, comprising the secondary battery according to claim 15 .
17 . A battery pack, comprising the battery module according to claim 16 .
18 . An electrical apparatus, comprising at least one of the secondary battery according to claim 15 .