Investigation of a novel ternary electrolyte based on dimethyl sulfite and lithium difluoromono(oxalato)borate for lithium ion batteries

Lithium difluoromono(oxalato)borate (LiODFB) has been used as a novel lithium salt for battery in recent studies. In this study, a series of novel electrolytes has been prepared by adding 30 vol% dimethyl sulfite (DMS) or dimethyl carbonate (DMC) as co-solvent into an ethylene carbonate (EC)/ethyl methyl carbonate (EMC) + LiX mixture, in which the LiX could be LiClO ₄, LiODFB, LiBOB, LiTFSI, or LiCF₃SO₃. These ternary electrolytes have been investigated for use in lithium ion batteries. FT-IR spectroscopy analysis shows that characteristic functional groups (-CO₃, -SO₃) undergo red-shift or blue-shift with the addition of different lithium salts. The LiODFB-EC/EMC/DMS electrolyte exhibits high ionic conductivity, which is mainly because of the low melting point of DMS, and LiODFB possessing high solubility. The Li/MCMB cells containing this novel electrolyte exhibit high capacities, good cycling performance, and excellent rate performance. These performances are probably because both LiODFB and DMS can assist in the formation of SEI films by reductive decomposition. Additionally, the discharge capacity of Li/LiCoO₂ half cell containing LiODFB-EC/EMC/DMS electrolyte is 130.9 mAh g^-1 after 50 cycles, and it is very comparable with the standard-commercial electrolyte. The results show that this study produces a promising electrolyte candidate for lithium ion batteries.