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CN-116315104-B - Electrolyte, secondary battery and electric equipment

CN116315104BCN 116315104 BCN116315104 BCN 116315104BCN-116315104-B

Abstract

The invention relates to the technical field of batteries, in particular to electrolyte, a secondary battery and electric equipment. An electrolyte comprising a compound of formula I: X 1 and X 2 are each independently selected from alkylene, alkenylene or alkynylene having 1 to 20 carbon atoms, R 1 and R 2 are each independently selected from alkyl or haloalkyl, cy is attached to formula I Enclosing to form five-membered or six-membered ring group. The compound shown in the formula I adopted in the electrolyte has lower LUMO, can be reduced by a solvent preferentially, has strong electron donating ability of amine in the compound shown in the formula I, is favorable for combining with Li + , ensures that the solvent competes to participate in forming a solvation structure, inhibits solvolysis, forms a better SEI film on the surface of a graphite negative electrode, and improves the cycle performance of a battery.

Inventors

  • LV GUOXIAN
  • XU CAN
  • QIAO FEIYAN
  • CHU CHUNBO

Assignees

  • 欣旺达电动汽车电池有限公司

Dates

Publication Date
20260508
Application Date
20230426

Claims (7)

  1. 1. An electrolyte comprising a compound of formula I: ; X 1 and X 2 are each independently selected from an alkylene group, an alkenylene group or an alkynylene group having 1 to 20 carbon atoms; R 1 and R 2 are each independently selected from alkyl or haloalkyl; Cy is attached to formula I Enclosing to form five-membered or six-membered ring base; The compound shown in the formula I comprises at least one of the structural formulas I 1 、Ⅰ 2 and I 3 : 、 、 。
  2. 2. The electrolyte according to claim 1, wherein the compound represented by formula I is used in an amount of 0.1% to 5% by mass of the total mass of the electrolyte.
  3. 3. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte of any one of claims 1 to 2.
  4. 4. The secondary battery according to claim 3, wherein the negative electrode sheet includes a negative electrode active material including at least one of natural graphite, artificial graphite, soft carbon, hard carbon, nano carbon, and silicon carbon composite; The positive electrode sheet includes a positive electrode active material, the chemical formula of the positive electrode active material comprises at least one of LiFePO 4 and Li a Ni x Co y Mn （1-x-y） O 2 , wherein a is more than or equal to 0.9 and less than or equal to 1.1,0< x <1,0< y <1, and x+y <1.
  5. 5. The secondary battery according to claim 3, wherein the charge cutoff voltage of the secondary battery is 4.2 to 4.5V.
  6. 6. The secondary battery according to claim 3, wherein the active material layer of the positive electrode sheet has a thickness of 20 to 90 μm.
  7. 7. An electrical device comprising the secondary battery according to any one of claims 3 to 6.

Description

Electrolyte, secondary battery and electric equipment Technical Field The invention relates to the technical field of batteries, in particular to electrolyte, a secondary battery and electric equipment. Background With the rapid development of electric vehicles, the energy density, cycle life and safety requirements of lithium ion batteries are continuously improved. However, in the traditional electrolyte system, the ternary positive electrode material can undergo severe structural change and interface side reaction at high pressure and high temperature, which brings great challenges to practical application, in particular to the cycle life and safety of the high-nickel ternary material. In addition, the SEI film formed on the graphite cathode for the first time plays an important role on the battery performance, and the formed SEI film has too high impedance to exacerbate the polarization of the battery, so that lithium is easily separated out from the surface of the cathode, and the reversible capacity of the battery is greatly reduced. Development of adapted electrolyte additives is one of the most cost effective ways to improve the electrochemical performance of lithium ion batteries. In view of this, the present invention has been made. Disclosure of Invention An object of the present invention is to provide an electrolyte in which a compound represented by formula I is reduced with priority to a solvent to form a better SEI film, and is advantageous to combine with Li +, compete with the solvent to participate in forming a solvated structure, and inhibit solvolysis. Another object of the present invention is to provide a secondary battery comprising the above electrolyte. Still another object of the present invention is to provide an electric device including the above secondary battery. An electrolyte comprising a compound of formula I: ; X 1 and X 2 are each independently selected from an alkylene group, an alkenylene group or an alkynylene group having 1 to 20 carbon atoms; R 1 and R 2 are each independently selected from alkyl or haloalkyl; Cy is attached to formula I Enclosing to form five-membered or six-membered ring group. Further, the five-or six-membered cyclic group includes any one of a 2,4, 5-imidazoline trione group, a substituted or unsubstituted 2-imidazolidinone group, and a substituted or unsubstituted 1,3, 5-triazine-2, 4, 6-trione group. Further, at least one of R 1 and R 2 is substituted with halogen. Further, the compound shown in the formula I comprises at least one of the structural formulas I 1、Ⅰ2 and I 3: 、、。 Further, the halogenated alkyl group comprises a fluorinated alkyl group, and the number of fluorine atoms in the fluorinated alkyl group is more than or equal to 1. Further, the dosage of the compound shown in the formula I is 0.1% -5% of the total mass of the electrolyte. The invention also provides a secondary battery, which comprises a positive plate, a negative plate, a diaphragm and the electrolyte. Further, the negative electrode sheet includes a negative electrode active material including at least one of natural graphite, artificial graphite, soft carbon, hard carbon, nano carbon, and silicon carbon composite; The positive electrode sheet includes a positive electrode active material, the chemical formula of the positive electrode active material comprises at least one of LiFePO 4 and Li aNixCoyMn（1-x-y）O2, wherein a is more than or equal to 0.9 and less than or equal to 1.1,0< x <1,0< y <1, and x+y <1. Further, the charging cut-off voltage of the secondary battery is 4.2-4.5V. Further, the thickness of the active material layer of the positive plate is 20-90 μm. The invention also provides electric equipment, which comprises the secondary battery. Compared with the prior art, the invention has the beneficial effects that: (1) The compound shown in the formula I adopted in the electrolyte has lower LUMO, can be reduced by a solvent preferentially, has strong electron donating ability for amine in the structure of the compound shown in the formula I, is favorable for combining with Li +, and can inhibit solvolysis by competing with the solvent to form a solvated structure; (2) The C-F bond in the molecule of the compound shown in the formula I adopted in the electrolyte is beneficial to forming LiF, forming an SEI film on the cathode, improving the performance of the SEI film on the surface of a graphite cathode, and the fluorine-rich chain is beneficial to reducing molecular interaction and preventing the viscosity of the electrolyte from increasing; (3) The secondary battery adopting the electrolyte provided by the invention has better cycle performance. Detailed Description The technical solution of the present invention will be clearly and completely described in conjunction with the specific embodiments, but it will be understood by those skilled in the art that the examples described below are some, but not all, examples of the present invention, and are i