Investigation of Lithium Tetrafluorooxalatophosphate [LiPF4(C2O4)] as a Lithium-Ion Battery Electrolyte for Elevated Temperature Performance

The thermal stability of lithium tetrafluorooxalatophosphate [LiPF4(C2O4)] electrolyte was investigated. Although the thermal stabilities of the solid LiPF4(C2O4) and LiPF6 were comparable, the thermal stability of the liquid LiPF4(C2O4)/carbonate electrolyte was better than LiPF6/carbonate electrolytes. Lithium-ion cells containing LiPF4(C2O4) electrolyte had better capacity retention than LiPF6 electrolyte containing cells upon cycling after storage at 65 S C for 2 weeks. Ex situ analysis of the electrodes before and after storage at 65 degrees C and cycling suggested that differences in the structures of the anode and cathode surface films contributed to the superior performance of cells containing LiPF4(C2O4) electrolyte. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3258290] All rights reserved.