Effects of vinyl ethylene carbonate on the performance of Li-ion battery

Vinyl ethylene carbonate(VEC) as a film-forming additive for Li-ion battery was investigated by quantum chemical calculation,cyclic voltammetry,electrochemical impedance spectroscopy and discharge-charge tests.The result of quantum chemical calculation showed that the VEC had lower lowest unoccupied molecular orbital(LUMO) energy value.The electrochemical reduction potential of VEC was about 1.2 V(vs.Li/Li+),much higher than that of solvents of electrolyte,this reaction produced solid electrolyte interface(SEI) film on the anode.Because of the stable SEI film,VEC was capable of improving the cycle performance,preventing the gas generation of battery.The impedance of SEI formed in VEC-electrolyte was higher than that of blank sample,which was not suitable for intercalation-deintercalation reactions and led to lower initial charge-discharge capacity and efficiency.