Regularities of ionic solvation and association of lithium difluoro(oxalate)borate in dimethyl carbonate and sulfolane solvent systems

Lithium difluoro(oxalate)borate (LiODFB) is acknowledged as a new type of electrolyte lithium salt with great potential for high-voltage lithium-ion batteries. Utilizing Raman spectroscopy, a conductivity tester, and a viscometer, this study concentrates on the solution structures and properties of LiODFB-solvent systems. The results demonstrated that in the sulfolane (SL) solvent, the main coordination form is among the Li + cation. The ODFB − anion and SL molecules form an ionic solvation as a contact ion pair (CIP). The content of free Li + cations is very considerable, which is beneficial to improve the solubility and conductivity of LiODFB in the SL solvent. In the dimethyl carbonate (DMC) solvent, the main coordination form is ionic association as an aggregate (AGG). In addition, the solvent can display the comprehensive superiority of the SL solvent and LiODFB salt when a high concentration is dissolved in the SL-DMC as a mixed solvent.