Novel mixtures of ether-functionalized ionic liquids and non-flammable methylperfluorobutylether as safe electrolytes for lithium metal batteries

Two mixtures of ether-functionalized quaternary ammonium ILs and non-flammable methylperfluorobutylether were used as new safe electrolytes for lithium metal batteries, and compared with the corresponding pure IL electrolytes. The mixed electrolytes had lower viscosity and higher conductivity than the pure IL electrolytes. The test results of flammability and flash point indicated that the addition of methylperfluorobutylether didn't reduce the safety of the pure IL electrolytes. The mixed electrolytes exhibited slightly narrower electrochemical windows due to the decrease of the cathodic stability. The effects of lithium redox on the Ni electrode and cycle performance of the symmetric lithium cell were investigated, and the addition of MFE could optimize the passivation layer on the Ni electrode and the SEI film on the lithium metal. The Li/LiFePO4 cells using the mixed electrolytes had good cycle performance at 0.1 C, and showed better rate performance than the cells using the pure IL electrolytes.