Abstract:

Sodium ion batteries are promising for large scale energy storage due to high abundance and low cost of sodium resources. So far, researchers have proposed several possible cathode and anode materials for sodium ion batteries. Electrolytes, serving as the media for redox reactions on cathode and anode, largely determine the electrode-electrolyte interfaces through the redox window, Na⁺ diffusion and migration, solvation structure of Na ions, and the coupled Na cation-anion-solvent (or solid framework) correlations etc. The electrolyte and interface play important roles in the thermodynamic and kinetics situations in sodium ion batteries, such as the electrode material stability, SEI formation, battery rate performance, thermal stability and cycling performance. In this work, we reviewed recent progresses in non-aqueous liquid and solid electrolytes for sodium ion batteries. The physicochemical properties of electrolytes and their remaining issues such as low ionic conductivity, narrow electrochemical window and poor stability of SEI layers are carefully discussed. The commercialization of sodium ion battery technology still requires development of functional and low-cost sodium ion battery electrolyte and comprehensive understanding the electrode-electrolyte interface properties.

Key words: non-aqueous sodium ion batteries, liquid electrolyte, solid electrolyte, electrochemical performance