1- (P-toluenesulfonyl)imidazole (PTSI) as the novel bifunctional electrolyte for LiCoO2-based cells with improved performance at high voltage

Abstract Higher charging cutoff voltages of LiCoO2/graphite pouch-cells with high energy density can meet the advanced requirement of new generation lithium-ion batteries. However, the poor cycling performance derives from severe the electrolyte's decomposition on interface of the cathode/electrolyte at high charging cutoff voltage limits its wider commercial application. To resolve these detrimental effects of battery at high operating voltage, a novel bifunctional electrolyte additive (PTSI) is added into electrolyte for the LiCoO2/graphite pouch-cells. Upon operating at higher charging cut-off voltage (4.4 V) after 200 cycles, the LiCoO2/graphite pouch-cells with 1.0 wt.% PTSI in the electrolyte reveals preferable cycle performance over those in baseline electrolyte. The capacity retention of the pouch-cells with 1.0 wt. % PTSI in the electrolyte is 95.33% after 200 cycles, which is only 61.74% for those in baseline electrolyte. The results of electrochemical and spectroscopic techniques indicate that PTSI decomposes before the electrolyte solvents are consumed, and then took part in the interface layer formation on the interfaces of the electrodes, improving the cells performance. This work develops the novel bifunctional electrolyte additive that meets the requirement of a LiCoO2-based pouch-cells at high voltage.