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EP-4742315-A1 - POSITIVE ELECTRODE SHEET, BATTERY CELL, BATTERY, AND ELECTRIC DEVICE

EP4742315A1EP 4742315 A1EP4742315 A1EP 4742315A1EP-4742315-A1

Abstract

A positive electrode sheet, a battery cell, a battery, and an electric device relate to the technical field of batteries. The positive electrode sheet includes a positive electrode current collector, and a first positive electrode active material layer and a second positive electrode active material layer which are sequentially arranged on the surface of the current collector. The lattice volume shrinkage of a first positive electrode active material is greater than that of a second positive electrode active material, and the mass percentage of a binder in the first positive electrode active material layer is 0.8 wt% to 1.5 wt%. By limiting the upper limit of the amount of the binder in the first positive electrode active material layer, the first positive electrode active material layer would not be allowed to include more other components such as a positive electrode active material, and the overall energy density and specific capacity of the battery cell or the battery are met. Additionally, the lower limit of the amount of the binder in the first positive electrode active material layer can also be limited, thereby improving the binding performance between the first positive electrode active material layer and the positive electrode current collector and between the first positive electrode active material layer and the second positive electrode active material layer, and preventing a coating from falling off.

Inventors

  • WU, KAI
  • PEI, Renjie
  • SHANG, Yibo
  • PAN, JIANFU
  • QIN, YIMING
  • XU, Xiaofu
  • HE, Jianfu
  • YE, Yonghuang

Assignees

  • Contemporary Amperex Technology Co., Limited

Dates

Publication Date
20260513
Application Date
20231024

Claims (15)

  1. A positive electrode sheet, comprising a positive electrode current collector, and a first positive electrode active material layer and a second positive electrode active material layer which are sequentially arranged on the surface of the current collector, wherein the first positive electrode active material layer comprises a first positive electrode active material and a binder, and the second positive electrode active material layer comprises a second positive electrode active material; and the lattice volume shrinkage of the first positive electrode active material is greater than that of the second positive electrode active material, and the mass percentage of the binder in the first positive electrode active material layer is 0.8 wt% to 1.5 wt%.
  2. The positive electrode sheet according to claim 1, wherein the first positive electrode active material layer comprises 95.5 wt% to 97 wt% of the first positive electrode active material and 2.5 wt% to 3 wt% of a conductive agent.
  3. The positive electrode sheet according to claim 1 or 2, wherein the positive electrode sheet meets the following condition: 0.3 < w 1 ∗ P 2 w 2 ∗ P 1 < 16.5 , wherein w1 = mass of the first positive electrode active material / (mass of the first positive electrode active material + mass of the second positive electrode active material), w2 = mass of the second positive electrode active material / (mass of the first positive electrode active material + mass of the second positive electrode active material), P1 is the particle compaction density of the first positive electrode active material at 3T, and P2 is the particle compaction density of the second positive electrode active material at 3T.
  4. The positive electrode sheet according to claim 3, wherein 0.5 ≤ w1 ≤ 0.95, and 0.05 ≤ w2 ≤ 0.5.
  5. The positive electrode sheet according to claim 3, wherein 3 g/cc ≤ P1 ≤ 4 g/cc, and 2 g/cc ≤ P2 ≤ 2.5 g/cc.
  6. The positive electrode sheet according to claim 3, wherein Dv50 of the first positive electrode active material is greater than Dv50 of the second positive electrode active material.
  7. The positive electrode sheet according to any one of claims 1 to 6, wherein the first positive electrode active material contains Mn element and Ni element, and the positive electrode sheet meets the following condition: 0.02 < w Mn ∗ H 1 w Ni ∗ H 2 < 18 , wherein w(Mn) is the mass percentage of the Mn element in the first positive electrode active material, w(Ni) is the mass percentage of the Ni element in the first positive electrode active material, H1 is the thickness of the first positive electrode active material layer, and H2 is the thickness of the second positive electrode active material layer.
  8. The positive electrode sheet according to any one of claims 1 to 7, wherein the first positive electrode active material contains Ni element and Co element, 2 wt% ≤ w(Co) ≤ 15 wt%, and 20 wt% ≤ w(Ni) ≤ 55 wt%, wherein w(Co) is the mass percentage of the Co element in the first positive electrode active material, and w(Ni) is the mass percentage of the Ni element in the first positive electrode active material.
  9. The positive electrode sheet according to claim 8, wherein the positive electrode sheet meets the following condition: 0.02 < w Co w Ni < 0.45 .
  10. The positive electrode sheet according to any one of claims 1 to 9, wherein the first positive electrode active material has a chemical formula of Li a Ni b Co c M 1d M 2e O f R g , wherein 0.75 ≤ a ≤ 1.2, 0.2 < b < 0.8, 0 < c < 0.4, 0 < d < 1, 0 ≤ e ≤ 0.2, 1 ≤ f ≤ 2.5, 0 ≤ g ≤ 1, and f + g ≤ 3; and M 1 is selected from Mn and/or Al, M 2 is selected from any one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and R is selected from any one or more of N, F, S, and Cl.
  11. The positive electrode sheet according to claim 10, wherein the first positive electrode active material is in a single-crystalline form.
  12. The positive electrode sheet according to any one of claims 1 to 11, wherein the second positive electrode active material has a chemical formula of Li 1+x Mn 1-y A y P 1-z E z O 4 , wherein -0.1 ≤ x ≤ 0.1, 0.001 ≤ y ≤ 0.5, and 0.001 ≤ z ≤ 0.1; and A is selected from any one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and E is selected from any one or more of B, Si, N, S, F, Cl, and Br.
  13. A battery cell, comprising the positive electrode sheet according to any one of claims 1 to 12.
  14. A battery, comprising the battery cell according to claim 13.
  15. An electric device, comprising the battery cell according to claim 13 or the battery according to claim 14, wherein the battery cell or the battery is used to provide electric energy.

Description

CROSS REFERENCE The present application claims priority to Chinese Patent Application No. 202310882443.7, filed on July 18, 2023 and entitled "Positive Electrode Sheet, Battery Cell, Battery, and Electric Device", which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present application relates to the technical field of batteries, and in particular, to a positive electrode sheet, a battery cell, a battery, and an electric device. BACKGROUND The positive electrode active material with high energy density such as a ternary material has the characteristics of low cost, long life, insufficient safety performance and controllability of the production process, and the like, and the positive electrode active material with low energy density such as lithium manganese phosphate has the characteristic of high safety performance, so that the combined use of the positive electrode active material with high energy density and the positive electrode active material with low energy density is beneficial to exerting the advantages of different positive electrode active materials. However, due to the difference in electrochemical performance of the two positive electrode active materials, if the positive electrode active material layer is prepared by directly physically mixing the two positive electrode active materials, the battery cell or the battery will be rapidly degraded in the early stage of cycling. When the two positive electrode active materials are separately coated to form two independent positive electrode active material layers, the binding effect between different positive electrode active material layers needs to be considered. SUMMARY In view of the above problems, provided in the present application are a positive electrode sheet, a battery cell, a battery, and an electric device, which can improve or avoid the detachment of the positive electrode active material and increase the energy density. In a first aspect, provided in the present application is a positive electrode sheet, including a positive electrode current collector, and a first positive electrode active material layer and a second positive electrode active material layer which are sequentially arranged on the surface of the current collector, where the first positive electrode active material layer includes a first positive electrode active material and a binder, and the second positive electrode active material layer includes a second positive electrode active material. The lattice volume shrinkage of the first positive electrode active material is greater than that of the second positive electrode active material, and the mass percentage of a binder in the first positive electrode active material layer is 0.8 wt% to 1.5 wt%. In the technical solutions of the embodiments of the present application, according to the positive electrode sheet in the present application, the first positive electrode active material layer formed by the first positive electrode active material with high lattice volume shrinkage is arranged between the positive electrode current collector and the second positive electrode active material layer, which can reduce the risk of particle detachment caused by the great volume change of the first positive electrode active material during cyclic deintercalation of the battery cell or the battery, effectively reduce the probability of cycling degradation, improve the cycling capability of the battery cell or the battery, and prolong the cycle life. When the mass percentage of the binder in the first positive electrode active material layer is 0.8 wt% to 1.5 wt%, the upper limit of the amount of the binder in the first positive electrode active material layer can be limited, so that the first positive electrode active material layer would not be allowed to include more other components such as a positive electrode active material, and the overall energy density and specific capacity of the battery cell or the battery are met. Additionally, the lower limit of the amount of the binder in the first positive electrode active material layer can also be limited, thereby improving the binding performance between the first positive electrode active material layer and the positive electrode current collector and between the first positive electrode active material layer and the second positive electrode active material layer, and preventing a coating from falling off. In some embodiments, the first positive electrode active material layer includes 95.5 wt% to 97 wt% of the first positive electrode active material and 2.5 wt% to 3 wt% of a conductive agent. When the first positive electrode active material layer includes 95.5 wt% to 97 wt% of the first positive electrode active material and 2.5 wt% to 3 wt% of the conductive agent, the prepared battery or battery cell has high energy density and capacity. In some embodiments, the positive electrode sheet meets the following condition: 0.3<w1∗P2w2∗P1<16.5 , where