Reformulation of Electrolyte for Enhanced Fast-Charge Capability of Li-Ion Battery

Solvent crucially determines ionic conductivity and operating temperature range of liquid electrolytes, which consequently affects the cycling performance of Li-ion batteries. Aimed to enhance fast-charge capability, in this work the effects of 1,2-dimethoxyethane (DME) and ethyl acetate (EA) on the rate capability and cycle life of Li-ion batteries are studied by selecting a graphite-LiNi0.80Co0.15Al0.05O2 chemistry and replacing 10 wt% of ethyl methyl carbonate (EMC) with either DME or EA in a 1.0 m LiPF6 3:7 (wt.) ethylene carbonate (EC)/EMC electrolyte. It is shown that both of DME and EA increase ionic conductivity of the resultant electrolytes whereas their adverse impacts on the electrochemical stability and the formation of solid electrolyte interphase with the graphite anode are negligible. As such, the rate capabilities for both of the discharging and charging processes are enhanced in the order of DME > EA > the baseline electrolyte. Analyses on the Li-ion cell's impedance reveal that enhancements in the rate capability of Li-ion batteries are attributed to a significantly reduced charge-transfer resistance, or in other words, a significantly increased cell reaction kinetics.