Abstract:

Ethylene sulfate(DTD) was studied as an additive to 1 mol/L LiPF₆/ethylene carbonate(EC)+dimethyl carbonate(DMC)+methyl ethyl carbonate(EMC)(1∶1∶1 by volume) electrolyte for lithium ion batteries. The effects of DTD on lithium ion battery performance and on the mesocarbon microbead(MCMB) electrode/electrolyte interphase were investigated by galvanostatic charge-discharge measurements, cyclic voltammetry(CV), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and electrochemical impedance spectroscopy(EIS). The results show that DTD with a volume ratio of 0.01% can increase the reversible discharge capacity(from 300 mA·h/g to 350 mA·h/g) and cycleability of MCMB/Li cell. SEM observation and EIS analysis suggest that DTD facilitates the morphology of solid electrolyte interface(SEI) formed on the surface of the MCMB electrode and reduces the total resistance of the cell. CV measurements reveal that DTD can be electrochemically reduced at potentials around 1.4 V(vs Li/Li⁺) during the first reduction engaged in the formation of SEI. At the same time, DTD has no adverse effect on the LiMn₂O₄ electrode.

Key words: lithium ion battery, ethylene sulfate, additive, solid electrolyte interface