CN-116742122-B - Electrolyte, secondary battery and electric equipment

Abstract

The embodiment of the invention provides an electrolyte, a secondary battery and electric equipment, wherein the electrolyte provided by the embodiment of the invention comprises sodium salt, an organic solvent and an additive, and the additive at least comprises a B-O bond, a C=C bond and a C=O bond, wherein B in the B-O bond is in an electron-deficient state, so that the additive is acidic and can complex acid radical ions of the sodium salt, thereby improving the dissociation degree of the sodium salt and the migration number of the sodium ions, reducing the interface impedance of a bulk phase and an electrode, and the C=C bond and the C=O bond in the additive can effectively reduce the deposition of transition metals such as negative electrode Mn and the like, reduce the impedance, form a highly stable electrode-electrolyte interface structure, stabilize a positive electrode interface film and a negative electrode interface film, and improve the high-temperature storage and cycle performance of a battery, and solve the problems of unstable electrode/electrolyte interface of the traditional sodium ion battery, which is easy to cause deformation and performance attenuation of the battery.

Inventors

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

Assignees

• 欣旺达动力科技股份有限公司

Dates

Publication Date

20260508

Application Date

20230526

Claims (9)

1. 1. An electrolyte is characterized by comprising sodium salt, an organic solvent and an additive, wherein the additive at least comprises a B-O bond, a C=C bond and a C=O bond at the same time; In the electrolyte, the content of the additive is 0.1-5.0 wt%, the content of the sodium salt is 8-15 wt%, and the content of the organic solvent is 80-90 wt%; The structural formula of the additive is at least one of the formula (A) and the formula (B): Wherein R 1 is independently selected from one of methylene, C1-C10 linear alkyl subunit, naphthene subunit, benzene subunit, alkoxy subunit, naphthene oxy subunit and phenoxy subunit, R 21 is independently selected from one of methyl, C1-C10 linear alkyl, cycloalkyl and phenyl, R 2 is independently selected from one of methylene, C1-C10 linear alkyl subunit, naphthene subunit, benzene subunit, alkoxy subunit, naphthene oxy subunit and phenoxy subunit, and R 3 、R 4 、R 5 、R 6 is independently selected from one of C1-C10 alkyl, phenyl, C1-C10 haloalkyl, halophenyl and trimethylsilyl.
2. 2. The electrolyte of claim 1, wherein R 3 、R 4 、R 5 、R 6 is each independently selected from one of -CH 3 、-C 2 H 5 、-CH 2 CF 3 、-CHC 2 F 6 、-C(CH 3 ) 3 .
3. 3. The electrolyte according to claim 1, wherein the structural formula of the additive is at least one of formulas (A1) to (A4) and formulas (B1) to (B4):
4. 4. The electrolyte of claim 1 wherein R 3 、R 4 、R 5 、R 6 is selected from trimethylsilyl groups.
5. 5. The electrolyte according to claim 4, wherein the structural formula of the additive is at least one of formulas (A5) to (A8) and formulas (B5) to (B8):
6. 6. The electrolyte according to claim 1, wherein the sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bisoxalato borate, sodium difluorooxalato borate, sodium difluorobisoxalato phosphate, sodium bis (fluorosulfonyl) imide, and sodium bis (trifluoromethylsulfonyl) imide.
7. 7. The electrolyte of claim 1, wherein the organic solvent is at least two of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, dimethyl carbonate, methylethyl carbonate, diethyl carbonate, methylpropyl carbonate, diphenyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, gamma-butyrolactone, acetonitrile, sulfolane.
8. 8. A secondary battery comprising a positive electrode sheet, a negative electrode sheet and the electrolyte according to any one of claims 1 to 7, wherein the positive electrode sheet comprises a positive electrode active material comprising a sodium-containing compound.
9. 9. An electric device comprising the secondary battery according to claim 8 as a power supply source of the electric device.

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 Currently, sodium ion batteries are widely focused due to the advantages of higher theoretical capacity, more sodium resources, excellent high-low temperature performance, high safety and the like. The electrochemical performance and safety of sodium ion batteries are affected by the electrolyte, which not only determines the electrochemical window and energy density of the battery, but also controls the properties of the electrode/electrolyte interface. However, the electrode/electrolyte interface of the existing sodium ion battery is unstable, which easily causes deformation and performance degradation of the battery. Disclosure of Invention The invention aims to solve the technical problems of unstable electrode/electrolyte interface of the existing sodium ion battery, easy battery deformation and performance attenuation. In order to solve the problems, the invention is realized by the following technical scheme: The invention provides an electrolyte, which comprises sodium salt, an organic solvent and an additive, wherein the additive at least comprises a B-O bond, a C=C bond and a C=O bond. Further, in the electrolyte, the structural formula of the additive is at least one of the formula (a) and the formula (B): Wherein R 1 is independently selected from one of methylene, C1-C10 linear alkyl subunit, naphthene subunit, benzene subunit, alkoxy subunit, naphthene oxy subunit and phenoxy subunit, R 21 is independently selected from one of methyl, C1-C10 linear alkyl, cycloalkyl and phenyl, R 2 is independently selected from one of methylene, C1-C10 linear alkyl subunit, naphthene subunit, benzene subunit, alkoxy subunit, naphthene oxy subunit and phenoxy subunit; R 3、R4、R5、R6 is independently selected from one of C1-C10 alkyl, phenyl, halogenated alkyl and C1-C10 halogenated phenyl. Further, in the electrolyte, R 3、R4、R5、R6 is independently selected from one of -CH3、-C2H5、-CH2CF3、-CHC2F6、-C(CH3)3. Further, in the electrolyte, the structural formula of the additive is at least one of formulas (A1) - (A4) and formulas (B1) - (B4): further, in the electrolyte, R 3、R4、R5、R6 is selected from trimethylsilyl groups. Further, in the electrolyte, the structural formula of the additive is at least one of formulas (A5) - (A8) and formulas (B5) - (B8): Further, in the electrolyte, the content of the additive is 0.1-5.0 wt%, the content of the sodium salt is 8-15 wt%, and the content of the organic solvent is 80-90 wt%. Further, in the electrolyte, the sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bisoxalato borate, sodium difluorooxalato borate, sodium difluorobisoxalato phosphate, sodium bis (fluorosulfonyl) imide and sodium bis (trifluoromethylsulfonyl) imide. Further, in the electrolyte, the organic solvent is at least two of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, gamma-butyrolactone, acetonitrile and sulfolane. The invention also provides a secondary battery, which comprises a positive electrode plate, a negative electrode plate and the electrolyte, wherein the positive electrode plate comprises a positive electrode active material, and the positive electrode active material comprises a sodium-containing compound. The invention also provides electric equipment, which comprises the secondary battery, wherein the secondary battery is used as a power supply of the electric equipment. Compared with the prior art, the embodiment of the invention has the following advantages: In the embodiment of the invention, the provided electrolyte comprises sodium salt, an organic solvent and an additive, wherein the additive at least comprises a B-O bond, a C=C bond and a C=O bond, wherein B in the B-O bond is in an electron-deficient state, so that the additive is acidic and can complex acid radical ions of the sodium salt, thereby improving the dissociation degree of the sodium salt and the migration number of the sodium ions, reducing the interface impedance of a bulk phase and an electrode, and the C=C bond and the C=O bond in the additive can effectively reduce the deposition of Mn of a negative electrode and reduce the impedance, can form a highly stable electrode-electrolyte interface structure, can stabilize an anode-cathode interface film, and improve the high-temperature storage and cycle performance of a battery, and solve the problems of unstable electrode/electrolyte interface of the traditional sodium ion battery, easy deformation and performance attenuation of the battery. It is to be under