The Performance Research Of Ionic Liquid Electrolyte For Sodium Ion Batteries

With electric vehicle and smart grid around the corner, the study of energy efficient, environment friendly and rich resources is the essential condition for human beings into the sustainable development society. At present, lithium ion battery is a good prospect of battery system. However, with the growing dependence of the transportation, digital and other industries on lithium ion battery, the shortage of lithium resources will restrict its further development. Sodium and lithium have similar properties, and sodium is rich in resources and low in price. Sodium ion battery has good safety performance, low price, high specific energy and so on, it is likely to become the new generation of energy storage battery system. However, similar to lithium ion battery, organic solvent electrolyte is flammable and volatile, which may cause the battery has some security risks. Therefore, we need develop and study safe and non-toxic, good stability of the electrolyte. Ionic liquids have the advantages of non flammable, volatile and wide electrochemical window, for sodium ion battery electrolyte solvent, it is possible to solve the security problem of the battery and improve the low oxidation and stability. In this paper, ionic liquid electrolyte of sodium ion battery is discussed, the application prospect and development trend of this new type of ionic liquid solvent are also discussed.1. The ionic liquid EMIBF4 and BMIPF6, compared with other ionic liquids, have the advantages of low viscosity and high conductivity. NaBF4 was dissolved in EMIBF4, ionic liquid electrolyte of different sodium concentration was prepared. The experimental results show that the conductivity of EMIBF4 at room temperature can reach 11.1 mS.cm-1, the conductivity of 0.5 mol/L NaBF4/EMIBF4 was 8.7 mS?cm-1, at 60℃, it can reach 27.8 mS?cm-1.2. Tetramethylene sulfone(TMS) has good thermal stability and electrochemical stability. In this paper, TMS was added to 1-butyl-3-methylimidazolium hexafluorophosphate phosphate(BMIPF6) to improve the solubility of sodium salt NaPF6 in ionic liquid BMIPF6, and in order to improve the conductivity and electrochemical properties of electrolyte. The results show that the electrolyte can maintain good security and thermal stability after the addition of TMS. Among them, the amount of TMS was 5%, the electrolyte used in Na/Na3V2(PO4)3/C battery, the first discharge capacity can reach 109.1 mAh?g-1, its rate performance and cycle performance was improved.3. In this paper, the N-methyl-N-butyl piperidine double(three trifluoromethyl sulfonyl) imide(PP14TFSI) as additive added to 0.5mol.L-1NaPF6/ PP14TFSI+EC/DEC electrolyte, the conductivity, flammability and thermal stability of mixed electrolyte and the electrochemical properties of mixed electrolyte of sodium ion cathode material Na3V2(PO4)3/C. Compared with the traditional organic solvent electrolyte, at room temperature, the conductivity of 20%PP14TFSI electrolyte was 7.83 mS?cm-1, was significantly higher than that of organic solvent electrolyte.