Improving the High-Temperature Resilience of LiMn2O4Based Batteries: LiFNFSI an Effective Salt

Li(FSO2)(C4F9SO2)N (LiFNFSI) has been investigated as a single electrolyte salt to improve the stability of LiMn2O4 at 60 degrees C. The performances of LiFNFSI as an electrolyte salt have been comparatively studied with those of LiPF6 in a mixture of ethylene carbonate: dimethyl methyl carbonate (EC:DMC, v/v, 1: 1), in terms of separator wettability, battery cycling performance, dissolution of Mn2+ ions into the electrolytes, AC impedance and morphology evolution of electrodes. The wetting ability of the LiFNFSI based electrolyte with the battery materials is better, indicated by a smaller electrolyte/separator contact angle and lower AC impedances for LiMn2O4/Li and Li/Li cells. In addition, Mn2+ ions dissolution from LiMn2O4 cathode into the electrolytes at 60 degrees C is significantly suppressed. The LiMn2O4/Li cell with 1M LiFNFSI/EC:DMC (1:1, v/v) could be cycled over 400 times at 60 degrees C, while that with 1M LiPF6/EC: DMC (1: 1, v/v) failed rapidly after 38 cycles. These results suggest that LiFNFSI would be a highly potential contender to replace LiPF6 to extend the cycle life of LiMn2O4 battery at elevated temperatures. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.026208jes] All rights reserved.