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EP-4738459-A1 - LITHIUM SECONDARY BATTERY AND ELECTRIC DEVICE

EP4738459A1EP 4738459 A1EP4738459 A1EP 4738459A1EP-4738459-A1

Abstract

A lithium secondary battery and an electric device. The lithium secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a first active layer coated on at least one side of a positive electrode current collector and containing a positive electrode active material and a polycrystalline lithium supplementing agent and a second active layer coated on the side of the first active layer away from the current collector and containing a positive electrode active material, and the lithium supplementing agent comprises at least one of LixNi1-yMyO2, LixRO2, and LiNi α Co β Mn γ O2, wherein M comprises one or more of Cu, Al, and Mn; R comprises one of Ni and Mn; 1 < x < 2, 0 < y ≤ 0.01, α + β + γ =1 and α ≥ 0.5. The lithium supplementing agent rapidly releases sufficient active lithium during initial charge, thereby improving the energy density of a secondary battery, and persistently releases active lithium during a cycle, thereby slowing down the attenuation of a battery cell.

Inventors

  • XIANG, Chengcheng
  • Chen, XueFang
  • YAO, BIN
  • LIU, JIANG
  • LIU, XIAOMEI

Assignees

  • Contemporary Amperex Technology Co., Limited

Dates

Publication Date
20260506
Application Date
20240513

Claims (13)

  1. A positive electrode plate, wherein the positive electrode plate comprises a first active layer applied on at least one side of a positive electrode current collector and containing a positive electrode active material and a polycrystalline lithium supplementing agent, and a second active layer applied on a side of the first active layer away from the current collector and containing a positive electrode active material; wherein the lithium supplementing agent comprises at least one of Li x Ni 1-y M y O 2 , Li x RO 2 , and LiNi α Co β Mn γ O 2 , wherein M comprises one or more of Cu, Al, and Mn, and R comprises one of Ni and Mn; and 1 < x < 2 , 0 < y < 0.01 , α + β + γ = 1 , and α ≥ 0.5 .
  2. The positive electrode plate according to claim 1, wherein the lithium supplementing agent comprises one or more of Li x NiO 2 , Li x MnO 2 , Li x Ni 1-y M y O 2 , and LiNi α Co β Mn γ O 2 , wherein M comprises one or more of Cu, Al, and Mn, and R comprises one of Ni and Mn; and 1.1 < x < 1.8 , 0 < y < 0.01 , α + β + γ = 1 , α ≥ 0.5 , 0 < β < 1 , and 0 < γ < 1 .
  3. The positive electrode plate according to claim 1 or 2, wherein a volume-based median particle size D v 50 of the lithium supplementing agent is 2.5-12.5 µm, optionally 3.5-11.5 µm.
  4. The positive electrode plate according to any one of claims 1 to 3, wherein a mass percentage p/q of the lithium supplementing agent in the first active layer is not less than 0.5% and not more than 12%, optionally not less than 2% and not more than 10%; wherein p is a ratio of a mass of the lithium supplementing agent in the first active layer to a total mass of the first active layer and the second active layer of the positive electrode plate; and q is a ratio of a mass of the first active layer to the total mass of the first active layer and the second active layer of the positive electrode plate.
  5. The positive electrode plate according to any one of claims 1 to 4, wherein p is not more than 5% and not less than 0.2%, optionally 0.8%-4%.
  6. The positive electrode plate according to any one of claims 1 to 5, wherein q is 10%-70%, optionally 20%-60%.
  7. The positive electrode plate according to any one of claims 1 to 6, wherein the positive electrode active materials in the first active layer and the second active layer each comprise one or more of lithium-containing phosphate with an olivine structure, lithium transition metal oxide, and respective modified compounds thereof, optionally one or more of lithium iron phosphate and modified compounds thereof.
  8. The positive electrode plate according to any one of claims 1 to 7, wherein the positive electrode active material in the first active layer and/or the second active layer comprises Li z Fe 1-k Me k PO 4 and coating modified compounds thereof, wherein Me comprises one or more of Sc, V, Cr, Mn, Ti, Al, Co, Ni, Cu, and Zn, 0.8 ≤ z ≤ 1.3, and 0 ≤ k ≤ 0.7.
  9. The positive electrode plate according to any one of claims 1 to 8, wherein a cycling voltage window of a secondary battery prepared from the positive electrode plate is 2.0-3.8 V or 2.0-4.1 V.
  10. A lithium secondary battery, comprising the positive electrode plate according to any one of claims 1 to 9.
  11. An application of the lithium secondary battery according to claim 10, wherein a cycling voltage window of the lithium secondary battery is 2.0-4.1 V.
  12. The application according to claim 11, wherein the cycling voltage window of the lithium secondary battery is 2.0-3.8 V, or an upper limit voltage of a cycling voltage is 3.6-3.8 V, optionally 3.65-3.8 V.
  13. An electric apparatus, comprising the lithium secondary battery according to claim 10.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Chinese Patent Application No. 202311075173.5, filed on August 24, 2023 and entitled "LITHIUM SECONDARY BATTERY AND ELECTRIC APPARATUS", which is incorporated herein by reference in its entirety. TECHNICAL FIELD This application relates to the field of lithium battery technology, and in particular, to a lithium secondary battery and an electric apparatus. BACKGROUND Due to advantages such as high discharge voltage, high energy density, and long cycle life, lithium-ion batteries have been widely used in various portable electronic devices such as laptop computers, mobile phones, and cameras, and are also increasingly favored in high-tech fields such as aerospace satellites, electric vehicles, and military applications. These applications all require lithium-ion batteries with better capacity and cycle life. Active lithium in a lithium-ion battery comes from a positive electrode material. During the first charge-discharge cycle of the lithium-ion battery, active lithium is consumed on a negative electrode surface to form a solid electrolyte film being an SEI film, resulting in initial capacity loss (Initial Capacity Loss, ICL), thus leading to capacity fade and reduced cycling efficiency of the lithium-ion battery. Therefore, developing simple and efficient lithium supplementation technology is of great significance. SUMMARY This application is made in view of the above issues and intended to provide a positive electrode plate, where the positive electrode plate includes a first active layer applied on at least one side of a positive electrode current collector and containing a positive electrode active material and a polycrystalline lithium supplementing agent, and a second active layer applied on a side of the first active layer away from the current collector and containing a positive electrode active material; where the lithium supplementing agent includes at least one of LixNi1-yMyO2, LixRO2, and LiNiαCoβMnγO2, where M includes one or more of Cu, Al, and Mn, and R includes one of Ni and Mn; and 1<x<2,0<y<0.01,α+β+γ=1,andα≥0.5. During cycling of a secondary battery, the polycrystalline lithium supplementing agent in the first active layer exhibits faster decay during the first charge due to significant concentration polarization, rapidly releasing sufficient active lithium to compensate for active lithium consumed on a negative electrode surface during the first charge-discharge cycle, thereby improving a first-cycle specific capacity of the secondary battery and increasing the energy density of the secondary battery. Lithium deintercalated from the lithium supplementing agent cannot be reintercalated into the lithium supplementing agent, and the positive electrode active material in the second active layer accepts active lithium deintercalated from the lithium supplementing agent. Therefore, the lithium supplementing agent persistently releases all lithium inside during cycling, significantly improving the cycling performance of the secondary battery, thereby mitigating cell degradation. In any embodiment, the lithium supplementing agent includes one or more of LixNiO2, LixMnO2, LixNi1-yMyO2, and LiNiaCoβMnγO2, where M includes one or more of Cu, Al, and Mn; and R includes one of Ni and Mn. Optionally, 1.1 < x < 1.8, 0 < y ≤ 0.01, α + β + γ = 1, α ≥ 0.5, 0 < β < 1, and 0 < γ < 1. In any embodiment, a volume-based median particle size Dv50 of the lithium supplementing agent is 2.5-12.5 µm, optionally 3.5-11.5 µm. Dv50 of the lithium supplementing agent within the range helps control the lithium deintercalation amount and residual amount of the lithium supplementing agent during the first charge-discharge cycle, allowing the positive electrode plate to achieve a balance between an initial specific capacity and a later-stage slow-release lithium amount. Additionally, Dv50 of the lithium supplementing agent within the range helps reduce the gas generation performance of the secondary battery, improving the storage performance of the secondary battery. In any embodiment, a mass percentage p/q of the lithium supplementing agent in the first active layer is not less than 0.5% and not more than 12%, optionally not less than 2% and not more than 10%, where p is a ratio of a mass of the lithium supplementing agent in the first active layer to a total mass of the first active layer and the second active layer of the positive electrode plate; and q is a ratio of a mass of the first active layer to the total mass of the first active layer and the second active layer of the positive electrode plate. The mass percentage p/q of the lithium supplementing agent in the first active layer within an appropriate range helps improve a capacity retention rate or first-cycle specific capacity of the secondary battery. In any embodiment, based on the total mass of the first active layer and the second active layer of the positive electrode plate, the mass