Functionalized ionic liquids based on quaternary ammonium cations with three or four ether groups as new electrolytes for lithium battery

► Some new functionalized ILs with three or four ether groups are reported. ► They have good electrochemical stability. ► Li/LiFePO 4 cells using five IL electrolytes have good capacity and cycle property. New functionalized ILs based on quaternary ammonium cations with three or four ether groups and TFSI − anion were synthesized and characterized. Physical and electrochemical properties, including melting point, thermal stability, viscosity, conductivity and electrochemical stability were investigated for these ILs. Five ILs with lower viscosity in these ILs were applied in lithium battery as new electrolytes. Behavior of lithium redox and charge–discharge characteristics of lithium battery were investigated for these IL electrolytes with 0.6 mol kg −1 LiTFSI. Lithium plating and striping on Ni electrode could be observed in these IL electrolytes. Li/LiFePO 4 cells using these IL electrolytes without additives had good capacity and cycle property at the current rate of 0.1 C, and the N(2o1) 3(2o2)TFSI and N2(2o1) 3TFSI electrolytes owned better rate property.