Synergistic Influence of electrolyte additives on the cycling performance of lithium-ion batteries under extreme fast charging condition

Development of lithium-ion batteries under fast charging (XFC) condition (6-C rate) with a charging time of 15 min is expected to accelerate their adoption in electric vehicles in order to eradicate greenhouse gas emission and to minimize the crisis due to oil economy. When lithium-ion batteries are charged at high C-rates various polarizations such as ohmic, concentration and electrochemical etc., take place in addition to other challenges, which adversely affect their performances. In the present work, triethyl phosphate (TEP) and lithium di-fluoro oxalaborate (LiDFOB) were added in the conventional non-aqueous electrolyte comprising 1M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) with 1:1 vol ratio. The lithium-ion cells composed of LiFePO4/Li with a combination of 3 % (TEP 1.5 wt% and LiDFOB 1.5 wt%) additives-incorporated in the electrolyte exhibited a discharge capacity of 110 mAh g−1 at 6 C- rate with 95 % of capacity retention even after 450 cycles. The additives, TEP, and LiDFOB not only enhanced the electrochemical properties but also reduced the self-extinguishing time significantly due to the generation of free-radicals. The fast-charging ability and better cycling performance even at 6C –rate is ascribed to the formation of a stable, robust and conductive solid electrolyte interfaces (SEI). For the first time, we have incorporated a combination of LiDFOB and TEP as electrolyte additives to improve the Li+ transport number and to suppress dendrites formation, thereby facilitating the fast-charging applications.