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CN-122025802-A - High-temperature electrolyte for sodium ion secondary battery, preparation method and application

CN122025802ACN 122025802 ACN122025802 ACN 122025802ACN-122025802-A

Abstract

A high-temperature electrolyte for sodium ion secondary battery and its application are disclosed. The high-temperature electrolyte comprises a solvent and sodium salt, wherein the solvent comprises a high-boiling point solvent and a weak solvated fluorinated 2-alkoxyl ethoxysilane solvent or a derivative thereof, and the concentration of the sodium salt is 0.2-4 mol/L. The electrolyte effectively inhibits side reactions of electrode interfaces at high temperature by introducing fluorinated siloxane solvent with weak solvation characteristic and high stability, and widens the working temperature range of the electrolyte. Experimental results show that the Na 3 V 2 (PO 4 ) 2 O 2 F battery using the electrolyte can still maintain the average coulombic efficiency of more than 98.59% and excellent cycle stability at 90 ℃. The electrolyte provided by the invention has the advantages of simple preparation method and easily obtained raw materials, remarkably improves the high-temperature performance of the sodium ion battery, and has wide application prospect.

Inventors

  • GU ZHENYI
  • WU XINGLONG
  • WANG JIE
  • ZHAO YULONG

Assignees

  • 东北师范大学

Dates

Publication Date
20260512
Application Date
20260411

Claims (10)

  1. 1. The high-temperature electrolyte for the sodium ion secondary battery is characterized by comprising a solvent and sodium salt, wherein the solvent comprises a high-boiling point solvent and a weak solvated fluorinated 2-alkoxyethoxysilane solvent or a derivative thereof, and the concentration of the sodium salt is 0.2-4 mol/L.
  2. 2. The high temperature electrolyte of claim 1 wherein the fluorinated 2-alkoxyethoxysilane solvent has a structure according to formula (I): R f O–CH 2 CH 2 –O–SiR 3 (I) wherein R f is fluoroalkyl, comprises 2-fluoroethyl, 2-difluoroethyl, 2-trifluoroethyl, 2, 3-pentafluoropropyl, 2, 3-tetrafluoropropyl 2,3, 4-heptafluorobutyl, 2,3, 4-hexafluorobutyl, 2,3, 4-hexafluorobutyl, perfluoro-tert-butyl; siR 3 is silyl, including trimethylsilyl, triethylsilyl, triisopropylsilyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl.
  3. 3. The high temperature electrolyte of claim 2 wherein the fluorinated 2-alkoxyethoxy silane solvent is trimethyl (2- (2, 2-trifluoroethoxy) ethoxy) silane.
  4. 4. The high temperature electrolyte of claim 1 wherein the high boiling point solvent is selected from one or more of propylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethoxydimethyl ether, dimethyl carbonate, diethyl carbonate, 1, 3-dioxolane, tetrahydrofuran.
  5. 5. The high temperature electrolyte according to claim 1, wherein the volume ratio of the high boiling point solvent to the fluorinated 2-alkoxyethoxysilane solvent is (1-10): 1.
  6. 6. The high temperature electrolyte of claim 1 wherein the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium bis (trifluoromethylsulfonyl) imide, sodium bis (fluorosulfonyl) imide, sodium bis (oxalato) borate, sodium difluoro (oxalato) borate, sodium perchlorate, sodium tetrafluoroborate, sodium nitrate.
  7. 7. A method for preparing a high-temperature electrolyte according to any one of claims 1 to 6, wherein a high-boiling point solvent and a fluorinated 2-alkoxyethoxysilane solvent or a derivative thereof are mixed under anhydrous and anaerobic conditions, and then sodium salt is added for dissolution, so that the high-temperature electrolyte is obtained, the volume ratio of the high-boiling point solvent to the fluorinated 2-alkoxyethoxysilane solvent or the derivative thereof is (1-10): 1, and the concentration of the sodium salt is 0.2-4 mol/L.
  8. 8. A process for preparing a fluorinated 2-alkoxyethoxysilane solvent comprising the steps of: (a) Reacting fluorine substituted alcohol with ethylene carbonate as a reactant in a high boiling point ether solvent to obtain a fluorinated 2-alkoxy ethanol intermediate: R f O−CH 2 CH 2 −OH (II) (b) Reacting the intermediate with a silyl ether group protecting reagent to obtain fluorinated 2-alkoxyl ethoxysilane.
  9. 9. A sodium ion secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and the high-temperature electrolyte according to any one of claims 1 to 6.
  10. 10. The sodium ion secondary battery according to claim 9, wherein the positive electrode active material in the positive electrode sheet is sodium vanadium oxyfluoride Na 3 V 2 (PO 4 ) 2 O 2 F.

Description

High-temperature electrolyte for sodium ion secondary battery, preparation method and application Technical Field The invention relates to the technical field of electrochemistry, in particular to a high-temperature electrolyte for a sodium ion secondary battery, and a preparation method and application of the electrolyte. Background With the increasing demands of society for energy storage, development of battery technologies having high energy density, high power density, and excellent environmental suitability is becoming increasingly urgent. Sodium ion batteries are important research objects in the field of large-scale energy storage due to the advantages of abundant resources, low cost and the like. The sodium ion secondary battery using sodium vanadium oxyfluoride (Na 3V2(PO4)2O2 F) as the positive electrode material has wide application prospect in high-end fields such as medical treatment, military, aerospace and the like due to the characteristics of high theoretical energy density (exceeding 494 Wh kg -1), good safety, low self-discharge rate and the like. However, existing sodium ion batteries present significant challenges in high temperature environments (e.g., above 50 ℃). The high temperature can aggravate the decomposition of the electrolyte, narrow the electrochemical window of the electrolyte, accelerate the side reaction at the electrode/electrolyte interface, lead to the rapid reduction of the coulomb efficiency, the increase of the internal resistance and the rapid decay of the capacity of the battery, and finally seriously shorten the service life of the battery. For example, most cells have a coulombic efficiency of less than 95% at 50 ℃ and do not even function properly at higher temperatures. Therefore, the development of the electrolyte which can keep stability in a wide temperature range (especially high temperature) has important significance for expanding the application scene of the sodium ion battery. Disclosure of Invention Aiming at the problem of poor high-temperature performance of a sodium ion battery in the prior art, the invention provides a high-temperature electrolyte for a sodium ion secondary battery. The electrolyte remarkably improves the cycle stability and coulombic efficiency of the battery at high temperature by using a novel fluorinated siloxane solvent. In order to achieve the above object, the present invention provides the following technical solutions: A high-temperature electrolyte for a sodium ion secondary battery comprises a solvent and sodium salt, wherein the solvent comprises a high-boiling point solvent and a weak solvated fluorinated 2-alkoxyethoxysilane solvent or a derivative thereof, and the concentration of the sodium salt is 0.2-4 mol/L. Preferably, the fluorinated 2-alkoxyethoxysilane solvent has a structure as shown in formula (I): RfO–CH2CH2–O–SiR3 (I) Wherein R f is fluoroalkyl and SiR 3 is silane. 2, 3-Tetrafluoropropyl group 2,3, 4-heptafluorobutyl 2, 3-tetrafluoropropyl group, 2,3, 4-heptafluorobutyl group 2,3, 4-hexafluorobutyl, 2,3, 4-hexafluorobutyl, perfluoro-tert-butyl; the silyl SiR 3 includes, but is not limited to, trimethylsilyl, triethylsilyl, triisopropylsilyl, t-butyldimethylsilyl, t-butyldiphenylsilyl. Preferably, the fluorinated 2-alkoxyethoxysilane solvent is trimethyl (2- (2, 2-trifluoroethoxy) ethoxy) silane. The invention also provides a preparation method of the fluorinated 2-alkoxyl ethoxysilane solvent, which comprises the following steps: (1) Reacting fluorine substituted alcohol with ethylene carbonate as a reactant in a high boiling point solvent to synthesize a fluorinated 2-alkoxy ethanol intermediate: RfO−CH2CH2−OH (II) (2) Reacting the intermediate with a silyl ether group protecting reagent to obtain fluorinated 2-alkoxyl ethoxysilane. Preferably, in step (1), the reaction temperature is 100-200 ℃ and the reaction time is 4-24 hours. Preferably, in step (2), the reaction is carried out in the presence of an organic base at a temperature of from-5 to 30 ℃. Preferably, the high boiling point solvent is selected from one or more of propylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dimethyl carbonate, diethyl carbonate, 1, 3-dioxolane and tetrahydrofuran. Preferably, the volume ratio of the high boiling point solvent to the fluorinated 2-alkoxyethoxysilane solvent is (1-10): 1. Preferably, the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium bis (trifluoromethylsulfonyl) imide, sodium bis (fluorosulfonyl) imide, sodium bisoxalato borate, sodium difluorooxalato borate, sodium perchlorate, sodium tetrafluoroborate, sodium nitrate. The invention further provides application of the high-temperature electrolyte in sodium ion secondary batteries. Preferably, the positive electrode active material of the sodium ion secondary battery is sodium vanadyl fluorophosphate (Na 3V2(PO4)2O2 F). The invention also provides