Improved compatibility of graphite anode for lithium ion battery using sulfuric esters

Ethylene sulfate (DTD), propylene sulfite (1,2-PS) and trimethylene sulfate (1,3-PCS) were investigated as electrolyte additives in lithium ion battery. Density functional theory (DFT) calculation shows that DTD, 1,2-PS and 1,3-PCS possess relatively low lowest unoccupied molecule orbital (LUMO) energies, which is easier to be reduced on the graphite anode. The CV curves, cycling performance and AC impedance of Li/graphite half cells reveal that DTD and 1,3-PCS were preferentially reduced to form stable SEI films. The initial efficiency, cycling performance and high temperature storage properties were greatly improved in the electrochemical tests by adding 1% DTD to LiCoO2/graphite battery. The SEM images show that the graphite electrode surface with SEI film formed by adding 1% DTD became smoother and more homogeneous. IR analysis results show that the SEI film included both inorganic components (Li2SO3 and Li2CO3) and organic components (ROCO2Li and ROSO2Li).