Effects of fluoroethylene carbonate on low temperature performance of mesocarbon microbeads anode

Effects of fluoroethylene carbonate (FEC) on low temperature performance of mesocarbon microbeads (MCMB) anode are investigated in 1 mol L-1 LiPF6-ethylene carbonate (EC)/propylene carbonate (PC)/ethyl methyl carbonate (EMC) (1:3:8 vol.%). The addition of FEC is found to improve deintercalation capacity, rate performance and cycling performance at low temperature to some extent. The surface morphology and chemical composition of the solid electrolyte interphase (SE!) formed on the surface of the MCMB electrode are studied through scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The results show that a stabler and more conductive SEI film is formed by introducing the FEC to the electrolyte. Combined with the electrochemical impedance spectrum (EIS) analysis, the presence of FEC is found to decrease the LiF content in SEI layer, which enhances the ion conductivity of SEI film and accelerates the migration of lithium ion through SE! film. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.