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CN-116315086-B - Electrolyte and lithium ion battery

CN116315086BCN 116315086 BCN116315086 BCN 116315086BCN-116315086-B

Abstract

The application relates to the technical field of lithium ion batteries, in particular to electrolyte and a lithium ion battery. The electrolyte comprises an organic solvent, lithium salt, silane compounds, a bicyclo compound and lithium difluoro oxalato borate. The electrolyte effectively improves the performance and the safety performance of the battery cell through the synergistic effect between the additives, and simultaneously has the long-cycle and low-expansion performance. According to the application, ethyl propionate and more easily dissociated lithium bistrifluoromethylsulfonyl imide are also added into the electrolyte, so that the solvent viscosity is reduced, the wettability and the ionic conductivity of the electrolyte are greatly improved, and the low-temperature disadvantage caused by the thicker SEI film with larger impedance generated by the combination of the silane compound and the allied compound is improved, thereby improving the low-temperature performance of the battery cell. According to the application, through the synergistic effect of the electrolyte and the negative electrode material, the lithium ion battery prepared by the negative electrode silicon-doped material can effectively improve the safety performance of the battery core and simultaneously give consideration to the long-cycle and low-temperature performance of the battery core.

Inventors

  • Mu Yingdi
  • WANG HAI
  • LI SULI

Assignees

  • 珠海冠宇电池股份有限公司

Dates

Publication Date
20260508
Application Date
20230104

Claims (14)

  1. 1. An electrolyte, characterized in that the electrolyte comprises an organic solvent, a lithium salt, a first additive, a second additive and a third additive; The first additive comprises a silane compound; The second additive comprises a bi-cyclic compound; The third additive comprises lithium difluorooxalato borate; the silane compound comprises tetravinyl silane; The bi-cyclic compound comprises at least one compound shown in the formula T1-formula T8; ; the addition amount of the first additive accounts for 0.2 wt% -1 wt% of the total mass of the electrolyte; the addition amount of the second additive accounts for 1-5 wt% of the total mass of the electrolyte; The addition amount of the third additive accounts for 0.1-1 wt% of the total mass of the electrolyte; the addition amounts of the first additive and the second additive satisfy the following conditions: 0.07≤C A /C B ≤0.8; Wherein C A represents the addition amount of the first additive, and C B represents the addition amount of the second additive.
  2. 2. The electrolyte of claim 1, wherein the organic solvent comprises a first organic solvent or comprises a first organic solvent and a second organic solvent; the first organic solvent comprises ethyl propionate; The second organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, propyl propionate, and propyl acetate.
  3. 3. The electrolyte according to claim 2, wherein the addition amount of the first organic solvent is 5wt% to 70wt% of the total mass of the electrolyte.
  4. 4. The electrolyte of claim 1, wherein the lithium salt comprises lithium hexafluorophosphate and/or lithium bis (trifluoromethylsulfonyl) imide.
  5. 5. The electrolyte according to claim 4, wherein the addition amount of the lithium hexafluorophosphate is 13-20 wt% of the total mass of the electrolyte, and/or, The addition amount of the lithium bis (trifluoromethyl) sulfonyl imide is 0.5-10 wt% of the total mass of the electrolyte.
  6. 6. The electrolyte according to any one of claims 1 to 5, wherein the electrolyte further comprises a fourth additive and/or a fifth additive; The fourth additive comprises at least one of tris (trimethylsilyl) phosphite, tris (trimethylsilyl) borate, lithium difluorosulfonimide, 1, 3-propane sultone, 1, 3-propene sultone, ethylene sulfite, ethylene sulfate, ethylene carbonate, fluoroethylene carbonate, lithium dioxaborate, lithium difluorooxalato phosphate, and vinyl ethylene carbonate; the fifth additive comprises fluorine-containing substituted boron ether compounds.
  7. 7. The electrolyte according to claim 6, wherein the fourth additive accounts for 0-10 wt% of the total mass of the electrolyte.
  8. 8. The electrolyte according to claim 6, wherein the fluorine-containing substituted boron ether compound comprises at least one of compounds represented by formulas T9 to T11; 。
  9. 9. The electrolyte according to claim 6, wherein the fluorine-containing substituted boron ether compound accounts for 0.1 wt% -1wt% of the total mass of the electrolyte.
  10. 10. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and the electrolyte of any one of claims 1 to 9; the negative electrode active material of the negative electrode sheet contains a silicon-based material.
  11. 11. The lithium ion battery of claim 10, wherein the silicon-based material is selected from at least one of silicon, silicon carbon, siOx, siO 2 , wherein 0< x <2.
  12. 12. The lithium ion battery according to claim 10 or 11, wherein the negative electrode active material of the negative electrode sheet further comprises a carbon material.
  13. 13. The lithium ion battery of claim 12, wherein the carbon material comprises at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon.
  14. 14. The lithium ion battery of claim 12, wherein the mass ratio of the silicon-based material to the carbon material is (1-40): (60-99).

Description

Electrolyte and lithium ion battery Technical Field The application relates to the technical field of lithium ion batteries, in particular to electrolyte and a lithium ion battery. Background In recent years, lithium ion batteries have been widely used in the fields of smart phones, tablet personal computers, smart wear, electric tools, electric automobiles, and the like. With the increasing wide application of lithium ion batteries, the use environment and the requirements of consumers on the lithium ion batteries are continuously improved, so that the lithium ion batteries are required to have high safety while the long service life and the high and low temperature performance are considered. Currently, the lithium ion battery has potential safety hazards in the use process, for example, when the battery is in extreme use conditions such as continuous high temperature, serious safety accidents such as fire and explosion easily occur. The main reasons for the problems include unstable structure of the active material at high temperature and high voltage, and severe reaction of the electrolyte and the lithiated graphite releases a large amount of heat, which causes the continuous rise of the temperature of the battery cell, thereby causing thermal runaway of the battery cell. In order to overcome the above technical problems, development of a lithium ion battery having high safety and high voltage is urgently required. Currently, flame retardants (such as trimethyl phosphate) are mainly added into electrolyte to improve the safety performance of batteries, however, the use of the flame retardant additives often leads to the degradation of the battery performance and severely shortens the service life of the battery cells. Therefore, how to develop a lithium ion battery with high safety and high voltage without affecting the electrochemical performance of the battery is a technical problem to be solved at present. Disclosure of Invention In view of this, the present invention provides an electrolyte and a lithium ion battery. The high-voltage lithium ion battery not only has excellent electrochemical performance and long service life, but also has high safety. In order to achieve the above object, the present invention provides the following technical solutions: the invention provides an electrolyte, which comprises an organic solvent, lithium salt, a first additive, a second additive and a third additive; the first additive comprises a silane compound; the second additive comprises a bicyclo compound; The third additive comprises lithium difluorooxalato borate. Preferably, the first additive silane compound comprises tetravinyl silane; preferably, the second additive bicyclo compound comprises at least one of compounds shown in formulas T1-T8; Preferably, the addition amount of the first additive accounts for 0.2wt% to 1wt% of the total mass of the electrolyte, and is exemplified by 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any two values in the range of the values and any point value in the range of the values. Preferably, the addition amount of the second additive accounts for 1wt% to 5wt% of the total mass of the electrolyte, and is exemplified by 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or any one point value in a range value and range value of any two values of the foregoing. Preferably, the addition amount of the third additive accounts for 0.1wt% to 1wt% of the total mass of the electrolyte, and is exemplified by 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any two values in the range and any point value in the range. In the specific embodiment provided by the invention, the addition amount of the third additive accounts for 0.13-1 wt% of the total mass of the electrolyte. Preferably, the addition amounts of the first additive and the second additive satisfy the following conditions: 0.07≤CA/CB≤0.8 Wherein C A represents the addition amount of the first additive, and C B represents the addition amount of the second additive. More preferably, the addition amounts of the first additive and the second additive satisfy the following conditions: 0.08≤CA/CB≤0.77 preferably, the organic solvent includes a first organic solvent, or includes a first organic solvent and a second organic solvent; the first organic solvent comprises ethyl propionate; The second organic solvent includes at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate, diethyl carbonate, methylethyl carbonate, propyl Propionate (PP), and propyl acetate; In a specific embodiment provided herein, the second organic solvent includes Ethylene Carbonate (EC), propylene Carbonate (PC), and Propyl Propionate (PP). The three solvents may be mixed in any mass ratio, illustratively 1:1:1. Preferably, the addition amount of the first organic solvent accounts for 5-70 wt% of the total mass of the electrolyte. Exemplary are 5wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60w