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EP-4270575-B1 - POSITIVE ELECTRODE PLATE, SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK AND ELECTRIC DEVICE

EP4270575B1EP 4270575 B1EP4270575 B1EP 4270575B1EP-4270575-B1

Inventors

  • ZHOU, XIANG
  • LIU, JIANG
  • LI, Baiqing
  • JIANG, Yao
  • LIU, XIAOMEI

Dates

Publication Date
20260513
Application Date
20220304

Claims (15)

  1. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector; the positive electrode film layer is of a single-layer structure or a multi-layer structure; when the positive electrode film layer is of a single-layer structure, at least one of the positive electrode film layers comprises both a first positive electrode active material having a core-shell structure and a second positive electrode active material; and/or, when the positive electrode film layer is of a multi-layer structure, at least one layer of at least one of the positive electrode film layers comprises both a first positive electrode active material having a core-shell structure and a second positive electrode active material; the first positive electrode active material comprises an inner core, a first coating layer covering the inner core and a second coating layer covering the first coating layer; wherein the inner core comprises Li 1+x Mn 1-y A y P 1-z R z O 4 , the first coating layer comprises pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the second coating layer comprises carbon element; wherein, A is selected from one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; R is selected from one or more elements of B, Si, N and S; x is selected from any value in the range of -0.100-0.100; y is selected from any value in the range of 0.001-0.500; z is selected from any value in the range of 0.001-0.100; M and X are independently selected from one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; and the second positive electrode active material is selected from one or more of LiNi a Co b Mn (1-a-b) O 2 , LiNi a Co b Al (1-a-b) O 2 and LiCoO 2 ; wherein a is independently selected from any value in the range of 0.3-0.9 (optionally 0.33-0.8), and the sum of a and b is independently selected from any value in the range of 0.3-0.9 (optionally 0.66-0.9).
  2. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector; at least one of the positive electrode film layers is of a multi-layer structure, and any positive electrode film layer having a multi-layer structure respectively comprises a first positive electrode active material having a core-shell structure and a second positive electrode active material in different layers; the first positive electrode active material comprises an inner core, a first coating layer covering the inner core and a second coating layer covering the first coating layer; wherein the inner core comprises Li 1+x Mn 1-y A y P 1-z R z O 4 , the first coating layer comprises pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the second coating layer comprises carbon element; wherein, A is selected from one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; R is selected from one or more elements of B, Si, N and S; x is selected from -0.100-0.100; y is selected from 0.001-0.500; z is selected from 0.001-0.100; M and X are independently selected from one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; the second positive electrode active material is selected from one or more of LiNi a Co b Mn (1-a-b) O 2 , LiNi a Co b Al (1-a-b) O 2 and LiCoO 2 ; wherein a is independently selected from any value in the range of 0.3-0.9 (optionally 0.33-0.8), and the sum of a and b is independently selected from any value in the range of 0.3-0.9 (optionally 0.66-0.9); and optionally, any of the positive electrode film layers having a multi-layer structure respectively comprises the first positive electrode active material and the second positive electrode active material in adjacent layers.
  3. A positive electrode sheet, comprising a positive electrode current collector as well as a positive electrode film layer A and a positive electrode film layer B respectively provided on both surfaces of the positive electrode current collector; the positive electrode film layer A and the positive electrode film layer B are each independently of a single-layer structure or a multi-layer structure; at least one layer of the positive electrode film layer A comprises a first positive electrode active material having a core-shell structure, while at least one layer of the positive electrode film layer B comprises a second positive electrode active material; the first positive electrode active material comprises an inner core, a first coating layer covering the inner core and a second coating layer covering the first coating layer; wherein the inner core comprises Li 1+x Mn 1-y A y P 1-z R z O 4 , the first coating layer comprises pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the second coating layer comprises carbon element; wherein, A is selected from one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; R is selected from one or more elements of B, Si, N and S; x is selected from -0.100-0.100; y is selected from 0.001-0.500; z is selected from 0.001-0.100; M and X are independently selected from one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; and the second positive electrode active material is selected from one or more of LiNi a Co b Mn (1-a-b) O 2 , LiNi a Co b Al (1-a-b) O 2 and LiCoO 2 ; wherein a is independently selected from any value in the range of 0.3-0.9 (optionally 0.33-0.8), and the sum of a and b is independently selected from any value in the range of 0.3-0.9 (optionally 0.66-0.9).
  4. The positive electrode sheet according to any one of claims 1 to 3, wherein the mass ratio of the first active material to the second active material is 1:7-7:1, and optionally 1:4-4:1.
  5. The positive electrode sheet according to any one of claims 1 to 4, wherein in the first positive electrode active material, A is selected from one or more elements of Zn, Fe, Ti, V, Ni, Co and Mg; and/or, A is selected from at least two elements of Fe, Ti, V, Ni, Co and Mg; and/or, x is selected from any value in the range of -0.100-0.006; and/or, y is selected from any value in the range of 0.1-0.4; and/or, M and X are independently selected from one or more elements of Li and Fe; and/or, the ratio of y to 1-y is selected from 1:10 to 10:1, optionally 1:4 to 1:1; and/or, the ratio of z to 1-z is selected from 1:999 to 1:9, and optionally 1:499 to 1:249.
  6. The positive electrode sheet according to any one of claims 1 to 5, wherein in the first positive electrode active material, the phosphate in the first coating layer has an interplanar spacing of 0.345-0.358nm and an included angle of crystallographic direction (111) of 24.25°-26.45°; and the pyrophosphate in the first coating layer has an interplanar spacing of 0.293-0.326nm and an included angle of crystallographic direction (111) of 26.41°-32.57°.
  7. The positive electrode sheet according to any one of claims 1 to 6, wherein in the first positive electrode active material, the coating amount of the first coating layer is greater than 0 wt% and less than or equal to 7 wt%, and optionally 4-5.6 wt%, based on the weight of the inner core.
  8. The positive electrode sheet according to any one of claims 1 to 7, wherein in the first positive electrode active material, the weight ratio of the pyrophosphate to phosphate in the first coating layer is 1:3 to 3:1, and optionally 1:3 to 1:1.
  9. The positive electrode sheet according to any one of claims 1 to 8, wherein in the first positive electrode active material, the crystallinities of the pyrophosphate and phosphate are each independently 10% to 100%, and optionally 50% to 100%.
  10. The positive electrode sheet according to any one of claims 1 to 9, wherein in the first positive electrode active material, the coating amount of the second coating layer is greater than 0 wt% and less than or equal to 6 wt%, and optionally 3-5 wt%, based on the weight of the inner core.
  11. The positive electrode sheet according to any one of claims 1 to 10, wherein the concentration of Li/Mn antisite defects in the first positive electrode active material is 4% or less, and optionally 2% or less.
  12. The positive electrode sheet according to any one of claims 1 to 11, wherein the lattice change rate of the first positive electrode active material is 6% or less, and optionally 4% or less; and/or wherein the surface oxygen valence state of the first positive electrode active material is - 1.88 or less, and optionally -1.98 ~ -1.88; and/or wherein the compaction density of the first positive electrode active material at 3 tons (T) is 2.0 g/cm 3 or more, and optionally 2.2 g/cm 3 or more; and/or wherein the sum of the masses 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.
  13. A secondary battery, comprising the positive electrode sheet according to any one of claims 1 to 12.
  14. A battery module, comprising the secondary battery according to claim 13.
  15. An electrical apparatus, comprising at least one selected from the secondary battery according to claim 13 and the battery module according to claim 14.

Description

Technical Field The present application relates to the technical field of secondary batteries, and in particular to a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical apparatus. Background In recent years, with the increasingly wide use of secondary batteries, secondary batteries are widely used in energy storage power systems such as water power, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have also been put forward for their energy density, cycling performance and safety performance. A secondary battery is made by admixing the existing lithium manganese iron phosphate as a main material with ternary materials such as lithium nickel cobalt manganate, lithium nickel cobalt aluminate or lithium cobalt oxide. Although this technology combines the respective advantages of lithium manganese iron phosphate and ternary materials, lithium manganese iron phosphate makes the dynamic performance of the battery poor, and the rate performance of battery cell is lower, which cannot meet the demand for power batteries. Summary of the Invention The present application has been made in view of the above-mentioned problems, and an object thereof is to provide a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical apparatus, so as to solve the problems of low energy density, low battery cell rate performance, poor dynamic performance, poor low temperature performance, short cycle life and low safety of the secondary battery made with the existing positive electrode active materials. In order to achieve the above object, a first aspect of the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector; the positive electrode film layer is of a single-layer structure or a multi-layer structure; when the positive electrode film layer is of a single-layer structure, at least one positive electrode film layer comprises both a first positive electrode active material having a core-shell structure and a second positive electrode active material; and/or, when the positive electrode film layer is of a multi-layer structure, at least one layer of the at least one positive electrode film layer comprises both a first positive electrode active material having a core-shell structure and a second positive electrode active material; the first positive electrode active material comprises an inner core, a first coating layer covering the inner core and a second coating layer covering the first coating layer; wherein the inner core comprises Li1+xMn1-yAyP1-zRzO4, the first coating layer comprises pyrophosphate MP2O7 and phosphate XPO4, and the second coating layer comprises carbon element; wherein A is selected from one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; R is selected from one or more elements of B, Si, N and S; x is selected from any value in the range of -0.100-0.100; y is selected from any value in the range of 0.001-0.500, z is selected from any value in the range of 0.001-0.100; M and X are independently selected from one or more elements of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; and the second positive electrode active material is selected from one or more of LiNiaCobMn(1-a-b)O2, LiNiaCobAl(1-a-b)O2 and LiCoO2; wherein a is independently selected from any value in the range of 0.3-0.9 (optionally 0.33-0.8), and the sum of a and b is independently selected from any value in the range of 0.3-0.9 (optionally 0.66-0.9). Thus, the applicant has unexpectedly found that by doping a specific element in a specific amount at the Mn position and the P position of the compound LiMnPO4 at the same time and coating the compound surface with two layers to obtain the first positive electrode active material, the dissolution of transition metals can be greatly reduced, the oxygen activity on the particle surface can be reduced, the migration of lithium ions can be promoted, the conductivity and desolvation performance of the material can be improved, the rate performance of the battery can be improved, the cycling performance and high temperature performance of the secondary battery can be improved, and the corrosion of the active material by electrolyte solution can be reduced. According to the present application, the first positive electrode active material and the second positive electrode active material are mixed for use, so that the advantages of the two materials are complementary, the energy density of the secondary battery is improved, and the battery simultaneously has excellent rate performance, dynamic performance, c