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CN-121986395-A - Lithium secondary battery, method for manufacturing the same, and power consumption device

CN121986395ACN 121986395 ACN121986395 ACN 121986395ACN-121986395-A

Abstract

A lithium secondary battery, a preparation method thereof and an electric device thereof, wherein the lithium secondary battery comprises an electrolyte, the electrolyte comprises a first solvent, a first additive and a second additive, the first solvent comprises a carboxylic ester compound, the reduction potential of the carboxylic ester compound relative to Li + /Li is less than or equal to 1.4V, the reduction potential of the first additive relative to Li + /Li is greater than or equal to 1.4V, and the reduction potential of the second additive relative to Li + /Li is greater than or equal to 1.0V and less than 1.4V. The lithium secondary battery improves the stability and compactness of the SEI film through improving the electrolyte, thereby reducing the gas production degree in the circulation process and the storage process of the lithium secondary battery and comprehensively improving the performance of the lithium secondary battery.

Inventors

  • Niu Congsu
  • LI XIAOWEI
  • PEI ZHENXING
  • YANG LIMEI

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260505
Application Date
20240809
Priority Date
20231208

Claims (20)

  1. A lithium secondary battery, wherein the lithium secondary battery comprises an electrolyte comprising a first solvent, a first additive, and a second additive, the first solvent comprising a carboxylate compound; Wherein the reduction potential of the carboxylic ester compound relative to Li + /Li is less than or equal to 1.4V; The reduction potential of the first additive relative to Li + /Li is greater than or equal to 1.4V; The second additive has a reduction potential of 1.0V or more and less than 1.4V relative to Li + /Li.
  2. The lithium secondary battery according to claim 1, wherein the carboxylic acid ester compound comprises a compound having a structure represented by formula I, Wherein R 1 、R 2 each independently comprises at least one of a C1-C5 alkyl group, a C1-C5 haloalkyl group.
  3. The lithium secondary battery according to claim 1 or2, wherein the carboxylic acid ester compound comprises at least one of ethyl acetate, methyl acetate, propyl acetate, and ethyl formate.
  4. The lithium secondary battery according to any one of claims 1 to 3, wherein the first additive comprises at least one of a tetrafluoroborate compound, an oxaloborate compound, a borate compound, vinyl sulfite, 1, 3-propenesulfonide, and methylene methane disulfonate.
  5. The lithium secondary battery according to any one of claims 1 to 4, wherein the first additive comprises at least one of lithium difluorooxalato borate, lithium bisoxalato borate, tris (trimethylsilane) borate, 1, 3-propenesulfonide.
  6. The lithium secondary battery according to any one of claims 1 to 5, wherein the second additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, organic sulfates, sulfonates, difluorophosphates.
  7. The lithium secondary battery according to any one of claims 1 to 6, wherein the second additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.
  8. The lithium secondary battery according to any one of claims 1 to 7, wherein the electrolyte further comprises a third additive having a reduction potential of less than 1.0V relative to Li + /Li.
  9. The lithium secondary battery according to claim 8, wherein the third additive comprises at least one of an organic phosphide, an organic fluoro compound, a phosphate compound, a borate compound, and a sulfonate compound.
  10. The lithium secondary battery according to claim 8 or 9, wherein the third additive comprises at least one of tris (2, 2-trifluoroethyl) phosphite, tris (trimethylsilane) phosphate.
  11. The lithium secondary battery according to any one of claims 1 to 10, wherein the lithium secondary battery satisfies 0.003≤W1/W4≤0.125, and/or 0.025≤W2/W4≤0.5; Wherein W4 is the mass content of the first solvent in the electrolyte, W1 is the mass content of the first additive in the electrolyte, and W2 is the mass content of the second additive in the electrolyte, in%.
  12. The lithium secondary battery according to any one of claims 1 to 11, wherein the lithium secondary battery satisfies 0.3 g/Ah≤D4+D2)/A≤2.3 g/Ah; Wherein D4 is the mass of the first solvent, D2 is the mass of the second additive, A is the rated capacity of the lithium secondary battery, and A is the rated capacity of the lithium secondary battery.
  13. The lithium secondary battery according to any one of claims 1 to 12, wherein the lithium secondary battery satisfies 0.5 g/Ah≤D4+D2)/A≤2 g/Ah; Wherein D4 is the mass of the first solvent, D2 is the mass of the second additive, A is the rated capacity of the lithium secondary battery, and A is the rated capacity of the lithium secondary battery.
  14. The lithium secondary battery according to any one of claims 8 to 13, wherein the lithium secondary battery satisfies 0.016≤W1/(W1+W2+W3). Ltoreq.0.455, and/or 0.333≤W2/(W1+W2+W3). Ltoreq.0.833; wherein W1 is the mass content of the first additive in the electrolyte, W2 is the mass content of the second additive in the electrolyte, and W3 is the mass content of the third additive in the electrolyte.
  15. The lithium secondary battery according to any one of claims 8 to 14, wherein the lithium secondary battery satisfies 10% to 70% of W4, 0.1% to 5% of W1, 1% to 10% of W2, and/or 0.1% to 5% of W3; Wherein W4 is the mass content of the first solvent in the electrolyte, W1 is the mass content of the first additive in the electrolyte, W2 is the mass content of the second additive in the electrolyte, and W3 is the mass content of the third additive in the electrolyte.
  16. The lithium secondary battery according to any one of claims 8 to 15, wherein the lithium secondary battery satisfies 20% to 50% of W4, 0.5% to 2% of W1, 4% to 8% of W2, and/or 0.5% to 2% of W3; Wherein W4 is the mass content of the first solvent in the electrolyte, W1 is the mass content of the first additive in the electrolyte, W2 is the mass content of the second additive in the electrolyte, and W3 is the mass content of the third additive in the electrolyte.
  17. The lithium secondary battery according to any one of claims 1 to 16, wherein the electrolyte further comprises a second solvent including at least one of a cyclic carbonate compound, a chain carbonate compound; The cyclic carbonate compound comprises at least one of ethylene carbonate, propylene carbonate and butylene carbonate; The chain carbonate compound comprises at least one of dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate.
  18. The lithium secondary battery according to claim 17, wherein the mass content of the second solvent is not less than 30% based on the total mass of the electrolyte.
  19. The lithium secondary battery according to claim 17 or 18, wherein the mass content of the second solvent is 30% -85% based on the total mass of the electrolyte.
  20. The lithium secondary battery according to claim 1 to 19, wherein the lithium secondary battery satisfies 14.2 mS/cm≤S≤16.8 mS/cm; Wherein S is the ionic conductivity of the electrolyte at 25 ℃ and the unit is mS/cm.

Description

Lithium secondary battery, method for manufacturing the same, and power consumption device Cross reference The present application claims priority from chinese patent application No. 202311680333.9 entitled "lithium secondary battery, its manufacturing method and electric device", filed on month 08 of 2023, which is incorporated herein by reference in its entirety. Technical Field The application relates to the technical field of lithium batteries, in particular to a lithium secondary battery, a preparation method thereof and an electric device. Background In recent years, along with the wider application range of lithium ion batteries, the lithium ion batteries are widely applied to energy storage power supply systems such as hydraulic power, firepower, wind power, solar power stations and the like, and a plurality of fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like. As lithium ion batteries have been greatly developed, higher demands are also being made on energy density, cycle performance, safety performance, and the like. Improving the power performance, cycle and storage life of the battery is always a pursuit goal of the industry, but the overall performance of the battery core is poor due to side reactions of the electrolyte at the interface of the anode and the cathode. Disclosure of Invention The present application has been made in view of the above problems, and an object thereof is to provide a lithium secondary battery and a method for manufacturing the same, which aim to improve stability and compactness of an SEI (Solid Electrolyte Interphase, solid electrolyte interface) film, reduce the gas generation degree during cycling and storage of the lithium secondary battery, improve the storage performance and cycle performance of the lithium secondary battery, and comprehensively improve the performance of the lithium secondary battery by improving an electrolyte. In order to achieve the above object, a first aspect of the present application provides a lithium secondary battery comprising an electrolyte comprising a first solvent, a first additive and a second additive, the first solvent comprising a carboxylic ester compound, wherein the carboxylic ester compound has a reduction potential of 1.4V or less with respect to Li +/Li, the first additive has a reduction potential of 1.4V or more with respect to Li +/Li, and the second additive has a reduction potential of 1.0V or more with respect to Li +/Li and less than 1.4V. The carboxylate solvent has low viscosity, so that the ionic conductivity of the electrolyte can be improved, and the quick charge performance of the battery can be improved. The reduction potential of the first additive relative to Li +/Li is controlled to be higher than that of the carboxylate solvent relative to Li +/Li, so that the first additive is favorable for forming an SEI film in preference to the carboxylate solvent, and side reactions and gas production of the carboxylate solvent are reduced. Meanwhile, the SEI film is formed by introducing the second additive and competing with the carboxylate solvent, and the SEI film formed by the second additive is beneficial to improving the compactness and stability of the whole SEI film, further reducing the risk of side reaction induced by the carboxylate solvent passing through the SEI film, and improving the storage performance and the cycle performance of the battery. In any embodiment, the electrolyte further comprises a third additive having a reduction potential of less than 1.0V relative to Li +/Li. The third additive introduced into the electrolyte can participate in solvation and form solvation structure, and inhibit oxidative decomposition and gas production of the battery at high temperature and normal temperature. In addition, part of the third additive can also participate in film formation after the first additive and the second additive form films, so that the compactness and the stability of the SEI film are further enhanced. In any embodiment, the carboxylic acid ester compound comprises a compound with a structure shown in a formula I Wherein R 1、R2 each independently comprises at least one of a C1-C5 alkyl group, a C1-C5 haloalkyl group. In any embodiment, the carboxylate compound comprises at least one of ethyl acetate, methyl acetate, propyl acetate, and ethyl formate. In any embodiment, the carboxylate compound comprises at least one of ethyl acetate, methyl acetate, propyl acetate. When the carboxylic ester compound is used as a solvent, the viscosity of the electrolyte can be reduced, the conductivity of the electrolyte can be improved, and the quick charge performance of the battery can be further improved. In any embodiment, the first additive comprises at least one of tetrafluoroborate compounds, oxalato borate compounds, borate ester compounds, vinyl sulfite, 1, 3-propenesulfonide, and methylene methane disulfo