Lithium bis(fluorosulfonyl)imide/poly(ethylene oxide) polymer electrolyte

New solid polymer electrolytes (SPEs) comprising of lithium bis(fluorosulfonyl)imide (LiFSI) and high molecular weight poly(ethylene oxide) (PEO, M-v =5 x 10(6) g mol(-1)) have been prepared and characterized, and are comparatively studied with the representative SPEs, Li[N(SO2CF3)(2)](LiTFSI)/PEO, at a molar ratio of EO/Li+ = 20. Their physicochemical properties have been investigated in terms of phase transition behavior, ionic conductivity, lithium-ion transference number (t(Li)(+)), electrochemical stability, and with particular attention to the interfacial behavior between lithium electrode and SPEs. It has been demonstrated that the ionic conductivities of LiFSI/PEO electrolyte are higher than those of LiTFSI/PEO one above 60 degrees C, and exceeds 10(-3) S cm(-1) at 80 degrees C. The interface resistances of Li symmetric cell (Li metal I polymer electrolytes vertical bar Li metal) using LiFSI/PEO electrolyte are much lower than those using LiTFSI/PEO. The Li/LiFePO4 cell using LiFSI/PEO electrolyte exhibits good cycling performance at 80 degrees C. These outstanding properties of the LiFSI/PEO electrolyte make it attractive as SPEs for Li battery. (C) 2014 Elsevier Ltd. All rights reserved.