New Thiourea-Based Ionic Liquid as an Electrolyte Additive to Improve Cell Safety and Enhance Electrochemical Performance in Lithium-Ion Batteries

Our society is critically dependent on lithium-ion batteries (LIBs) as a power source for portable electronic gadgets. One of the major problems with these batteries is the degradation of the materials inside them. In addition to the reduced cell life, building-up of these degraded products inside the cells is very detrimental to the safe operation. Herein, we report the synthesis and characterization of a novel thiourea-based room temperature ionic liquid (IL), 3-heptyl-1-(3-(3-heptyl-3-phenylthioureido)­propyl)-1H-imidazole-3-ium hexafluorophosphate. Its electrochemical and thermal properties including transport phenomena have been studied. It is proposed to be used as a nominal additive to commercially used electrolytes, ethylene carbonate and di-methyl carbonate mixtures. The comparative performance characteristics of the LIBs in the presence and the absence of this IL additive have been demonstrated with a traditional lithium nickel cobalt manganese oxide cathode (NMC111), a graphite anode, and an ethylene carbonate and di-methyl carbonate (1:1, v/v) electrolyte. It is further demonstrated that use of this electrolyte additive in batteries helps to address some of the major concerns of the conventional electrolytes such as safety issues and cycling performance as well as coulombic efficiency with enhanced discharge capacities.