In order to optimize the electrolyte system of lithium difluoro (oxalato) borate (LiDFOB)-ethyl methyl carbonate (EMC)/ethylene carbonate (EC)/adiponitrile (ADN) to overcome the drawback of low discharge
capacity at room temperature and the easily decomposition of ADN under lower potential, three sulfurcontaining solvents, ethylene sulfite (ES), dimethyl sulfite (DMS) and sulfolane (SL) are introduced. AC impedances, cycling performance, cyclic voltammetry tests as well as compatibilities between electrolytes and positive/negative electrodes are evaluated, respectively. Both of the solution systems of 0.7 M LiDFOB-EMC/ES/ADN (49: 49: 2, vol. % ratio) and 0.7 M LiDFOB-EMC/SL/ADN (65.3: 32.7: 2, vol. % ratio) are recommended as alternative electrolytes for 5 V high-voltage lithium ion batteries, benefitting from the synergistic effect between LiDFOB salt and sulfur-containing solvents. Besides, the effect on the
performance of sulfur-containing solvents on the positive and negative electrodes is studied by theoretical calculation. This paper provides a promising candidate for improving the electrochemical performance of the battery by optimization of electrolyte formula, especially by a combination of lithium salt and solvent mixture.