Fluoroethylene carbonate electrolyte and its use in lithium ion batteries with graphite anodes

The electrolyte decomposition during the first lithiation of graphite is reduced to 85 mA h/g in an electrolyte containing equal volumes of fluoroethylene carbonate (Fluoro-EC) and of a co-solvent propylene carbonate (PC). The volume fraction of Fluoro-EC can be further reduced to 0.05 in a tri-solvent system with a co-solvent containing equal volumes of ethylene carbonate (EC) and PC. A lithium ion cell containing Fluoro-EC PC and EC shows a long cycle life. The capacity decreases by 37% from the initial value in over 200 cycles. Cell current efficiency is 100%, thus solving the poor cell current efficiency when chloroethylene carbonate (Chloro-EC) is used in place of Fluoro-EC.