Electrochemical performance of electrolytes based upon lithium bis(oxalate)borate and sulfolane/alkyl sulfite mixtures for high temperature lithium-ion batteries

Lithium bis(oxalate)borate (LiBOB) has many unique properties, such as thermal stability and the formation of a stable passivation layer on the surface of carbonaceous anode. In this work, the electrochemical behaviors of sulfolane (SL) with LiBOB were studied by employment of dimethyl sulfite (DMS) and diethyl sulfite (DES) as mixed solvents, respectively. When used in Li/MCMB (mesophase carbon microbeads) cells at 60°C, only LiBOB-SL/DMS electrolyte exhibits not only excellent film-forming characteristics, but also good thermal stability of the interface film on the surface of MCMB. Besides, when used in LiFePO4/Li cells at 60°C, only LiBOB-SL/DMS electrolyte simultaneously exerts several advantages, such as good thermal stability of the interface film on the surface of LiFePO4, stable cycling performance, high mean voltage, and excellent discharge rate performance. It suggests that LiBOB-SL/DMS electrolyte is an excellent candidate electrolyte for high-temperature lithium ion batteries.