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CN-121983666-A - Lithium ion battery electrolyte and lithium ion battery

CN121983666ACN 121983666 ACN121983666 ACN 121983666ACN-121983666-A

Abstract

The invention relates to a lithium ion battery electrolyte and a lithium ion battery. The lithium ion battery electrolyte comprises lithium salt, a solvent and an additive, wherein the solvent comprises a carbonate solvent and a carboxylate solvent, the carboxylate solvent comprises a compound A with a structure of a formula I, the additive comprises a film forming additive, the film forming additive comprises an anhydride additive, and the anhydride additive comprises an anhydride compound B with a structure of a formula II. The invention solves the problem of poor cycle performance of the existing lithium cobalt oxide lithium ion battery under 5V high voltage by designing the composition of the lithium ion battery electrolyte, and improves the high-temperature cycle performance and the high-temperature storage performance under 5V high voltage.

Inventors

  • WANG JIAXU
  • YANG HUAN
  • YU JINPING

Assignees

  • 湖州昆仑亿恩科电池材料有限公司

Dates

Publication Date
20260505
Application Date
20260226

Claims (10)

  1. 1. The lithium ion battery electrolyte is characterized by comprising lithium salt, a solvent and an additive, wherein the solvent comprises a carbonate solvent and a carboxylate solvent, the carboxylate solvent comprises a compound A with a structure of a formula I, the additive comprises a film forming additive, the film forming additive comprises an anhydride additive, and the anhydride additive comprises an anhydride compound B with a structure of a formula II; , wherein R1 and R2 are each independently selected from any one of hydrogen, halogen, substituted or unsubstituted C1-C5 alkyl, or substituted or unsubstituted C1-C2 trifluoro; The substituted substituents are each independently selected from any one of deuterium, halogen, cyano or C1-C5 alkyl.
  2. 2. The lithium ion battery electrolyte according to claim 1, wherein the mass percentage of the compound a in the lithium ion battery electrolyte is 10% -60%, and more preferably 30% -50%.
  3. 3. The lithium ion battery electrolyte according to claim 1 or 2, wherein R1 and R2 are each independently selected from any one of -CF 3 、-CH 2 CF 3 、-CH 3 、-CH 2 CH 3 、-C(CH 3 ) 3 、-CH 2 C(CH 3 ) 3 、-CH(CH 3 ) 2 or-CH 2 CH 2 CH 3 ; Preferably, R2 is selected from-C (CH 3 ) 3 ; Preferably, the compound a comprises any one or a combination of at least two of the following compounds: ; Preferably, the compound a comprises the following compounds: 。
  4. 4. The lithium ion battery electrolyte of any of claims 1-3, wherein the film-forming additive further comprises an ester additive; Preferably, the ester additive comprises any one or a combination of at least two of vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, methylene methane disulfonate, ethylene sulfate, 1, 3-propane sultone, tris (trimethylsilane) borate or tris (trimethylsilane) phosphate; preferably, the additive further comprises a lithium salt additive; Preferably, the lithium salt additive comprises any one or a combination of at least two of lithium difluorosulfonate, lithium difluorooxalato borate, lithium tetrafluoroborate, bisoxalato borate, lithium difluorophosphate or lithium difluorobisoxalato phosphate; preferably, the mass percentage of the ester additive in the electrolyte of the lithium ion battery is 0.1% -5%; Preferably, the mass percentage of the anhydride additive in the lithium ion battery electrolyte is 0.1% -5%; preferably, the mass percentage of the lithium salt additive in the lithium ion battery electrolyte is 0.2% -6.0%.
  5. 5. The lithium ion battery electrolyte of any of claims 1-4, wherein the lithium salt comprises LiPF 6 ; preferably, the mass percentage of the lithium salt in the lithium ion battery electrolyte is 2% -22%.
  6. 6. The lithium ion battery electrolyte of any of claims 1-5, wherein the carbonate-based solvent comprises a cyclic carbonate; Preferably, the carbonate-based solvent comprises any one or a combination of at least two of ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, ethylmethyl carbonate, dimethyl carbonate or methylpropyl carbonate; Preferably, the carboxylic acid ester solvent comprises any one or a combination of at least two of ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate, methyl acetate, propyl acetate, methyl propionate, compound a or gamma-butyrolactone; preferably, the mass percentage of the solvent in the lithium ion battery electrolyte is 75% -94%.
  7. 7. A lithium ion battery, characterized in that the lithium ion battery comprises an electric core and an electrolyte, the electric core comprises a positive electrode, a negative electrode and a diaphragm, the diaphragm is arranged between the positive electrode and the negative electrode, and the electrolyte is the lithium ion battery electrolyte according to any one of claims 1-6.
  8. 8. The lithium ion battery of claim 7, wherein the positive electrode comprises a positive electrode active material, a conductive agent, and a binder; Preferably, the positive electrode active material includes LiCoO 2 .
  9. 9. The lithium ion battery according to claim 7 or 8, wherein the anode includes an anode active material; Preferably, the negative active material includes any one or a combination of at least two of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, graphene, graphite alkyne, metallic lithium, nanocarbon, carbon nanotubes, elemental silicon, a silicon oxygen compound, a silicon/copper oxide compound, an AG compound, a silicon alloy, elemental tin, a tin oxygen compound, a tin carbon compound, a tin alloy, or lithium titanate.
  10. 10. The lithium ion battery of any of claims 7-9, wherein the separator material comprises any one or a combination of at least two of polyethylene, polypropylene, or a composite ceramic membrane.

Description

Lithium ion battery electrolyte and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to lithium ion battery electrolyte and a lithium ion battery. Background In order to adapt to the rapidly growing digital product market, society has put higher demands on the capacity and use environment of lithium ion batteries. The lithium cobaltate system battery has higher energy density, which makes the lithium cobaltate system battery very suitable for light and thin type equipment (such as mobile phones, superbooks and tablet computers) with extremely severe space requirements. CN116544418a discloses a lithium cobalt oxide positive electrode material, which adopts a phosphorus-containing lithium compound to coat the lithium cobalt oxide positive electrode, so that the capacity performance, the rate capability and the cycle performance of a battery (4.45-4.55V) where the lithium cobalt oxide positive electrode material is positioned can be improved. CN119009196a discloses a lithium cobaltate battery which has strong stability under high temperature and high humidity environment, less capacity loss and long service life. CN118645591a discloses a lithium cobaltate positive plate, and the addition of the coated carbon black of polydopamine, the silica-polyester compound and the polyester binder in the positive electrode slurry can effectively improve the battery cycle capacity retention rate and improve the energy density and safety of the battery. However, in the current commercial environment, the common lithium cobaltate system cannot meet the market demand. The upper voltage limit of the lithium cobaltate system is raised to 5V, so that the energy density of the lithium cobaltate system lithium ion battery can be further raised, a higher voltage platform is maintained, and the lithium cobaltate system lithium ion battery has a larger specific capacity. However, the corresponding result is a shortened cycle life, serious side reactions of the electrolyte and higher stability and safety risks. Therefore, in order to effectively improve the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery of the 5V high-voltage lithium cobalt oxide system, the performance and the reliability of the lithium ion battery are improved, and the development of the novel lithium ion battery electrolyte has important significance. Disclosure of Invention In order to solve the technical problems, the invention aims to provide lithium ion battery electrolyte and a lithium ion battery. By designing the composition of the lithium ion battery electrolyte, the problem of poor cycle performance of the existing lithium cobalt oxide lithium ion battery under 5V high voltage is solved, and the high-temperature cycle performance and high-temperature storage performance under 5V high voltage are improved. To achieve the purpose, the invention adopts the following technical scheme: in a first aspect, the present invention provides a lithium ion battery electrolyte comprising a lithium salt, a solvent and an additive, the solvent comprising a carbonate solvent and a carboxylate solvent, the carboxylate solvent comprising a compound a having the structure of formula I, the additive comprising a film forming additive comprising an anhydride compound B having the structure of formula II; , Wherein R1 and R2 are each independently selected from any of hydrogen, halogen, substituted or unsubstituted C1-C5 (e.g., C2, C3, or C4) alkyl, or substituted or unsubstituted C1-C2 trifluoro; The substituted substituents are each independently selected from any one of deuterium, halogen, cyano or alkyl of C1-C5 (e.g. may be C2, C3 or C4). Preferably, the halogen substituent includes any one of a fluorine substituent, a chlorine substituent, a bromine substituent, or an iodine substituent. According to the invention, the carboxylic ester solvent with the structure of formula I and the anhydride compound additive with the structure of formula II are added into the electrolyte, so that the cycle performance of a lithium cobaltate 5V high-voltage system is improved, and the high-temperature storage performance is improved. The carboxylic ester solvent with the structure shown in the formula I is a high-voltage solvent, and the solvent utilizes the alkyl to replace all carbonyl alpha positions of carboxylic ester, so that the oxidation resistance of the substance is improved, the oxidation potential of molecules is greatly improved, and the stability of electrolyte under the high voltage of lithium cobaltate 5V is effectively improved. The anhydride compound additive with the structure shown in the formula II can be used as an electrolyte additive to form a stable SEI film, so that the occurrence of side reaction of a solvent is obviously reduced, the gas production phenomenon of a battery is reduced, and the safety of the battery is improved. The su