Sulfolane as a co-solvent for carbonate-electrolytes in lithium-ion batteries using a LiMn2O4 cathode

Abstract

In this study, we aimed to evaluate the effect of sulfolane (SL) as a co-solvent in conventional carbonate-based electrolytes and its compatibility with a LiMn2O4 (LMO) cathode. The amount of SL was varied from 10 to 50 vol.% in an EC-DMC mixture (1:1 vol. ratio) within a 1.0-M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The thermal properties of the electrolytes were studied using thermogravimetric analysis (TGA). Solvent flammability was measured via self-extinguishing time (SET) and ignition time indexes while viscosity was gauged by the Ostwald method. Ionic conductivity was evaluated by electrochemical impedance spectroscopy (EIS). Electrochemical techniques such as cyclic voltammetry (CV) and galvanostatic cycling with potential limitation (GCPL) were carried out to evaluate battery performance with the selected electrolytes. The results indicated that an increasing proportion of SL leads to an enhancement of the thermal and oxidation stability of the electrolytes. At 20-vol.% SL and below, the as-synthesized electrolytes exhibited a high ionic conductivity of 7.45 mS.cm-1 (25oC) and enabled LMO to deliver a specific capacity of 103 mAh.g-1 with a capacity retention of 92% after 20 cycles at C/10 rate. Due to such favourable properties, SL can be used as a co-solvent in EC-DMC systems to enhance the safety of lithium-ion batteries under high voltage conditions.