Mixtures of ionic liquid and organic carbonate as electrolyte with improved safety and performance for rechargeable lithium batteries

摘要

In this paper we report the results of physical-chemical and electrochemical investigations performed on ternary mixtures of the room temperature ionic liquid (IL) N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR_(14)TFSI), propylene carbonate (PC), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as electrolyte for lithium-ion batteries. The thermal stability, ionic conductivity, viscosity and electrochemical stability windows of all considered mixtures were investigated and compared with those of electrolytes based on the pure PYR_(14)TFSI and PC. The mixtures were also used as electrolyte in combination with LiFePO_4-based electrodes. The specific capacity and cycling stability of these systems were investigated at different C-rates, both at room temperature and 60°C.