Study on the cycling performance of Li4Ti5O12/LiCoO2 cells assembled with ionic liquid electrolytes containing an additive

Abstract

The cycling behavior of Li4Ti5O12/LiCoO2 cells in the ionic liquid electrolytes based on 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP-TESI) with different additives, such as vinylene carbonate (VC), 1,3-propane sultone (PS) and their mixture is investigated. The cell assembled with BMP-TESI containing 10 wt% VC/PS (1:1 by weight) exhibits reversible cycling behavior with good capacity retention. FTIR studies reveal that the electrochemically stable solid electrolyte interphase forms on Li4Ti5O12 electrode in the presence of a mixture of VC and PS during cycling. The additives hardly affect the composition, thickness and stability of the surface film formed on the LiCoO2 cathode.