All fluorine-free lithium battery electrolytes

Fluorine-free lithium battery electrolytes have been prepared from lithium salts with nitrile based anions, LiB(CN)4 or LiDCTA, dissolved in PEGDME or PC. After soaked into electrospun PAN membranes the resulting electrolytes were tested for physical and electrochemical properties and compared with reference PAN electrolytes containing LiPF6 or LiTFSI. The fluorine-free electrolytes were successfully cycled in Li/LiFePO4 cells at room temperature with up to 98% Coulombic efficiency. Small and qualitatively different effects were observed with the addition of Al2O3 particles to the PAN membranes, which could be of importance for long-term performance. However, for fluorine-free electrolytes to be truly competitive, the relatively low anodic stability and elevated temperature performance must first of all be improved by a change of solvent – or addition of co-solvents. Further work in this direction is encouraged by the strong influence of the solvent (PC or PEGDME) on the properties of the LiDCTA electrolytes demonstrated in this work.