A novel multifunctional electrolyte system for high performance Li-ion batteries

Abstract

Lithium-ion batteries have advantages such as environmental protection and sustainable use, but the widespread application of lithium-ion battery-powered vehicles is limited by the inability to quickly charge and extreme ambient temperatures, and reasonable design of electrolyte components can effectively solve these problems. Here, a novel fluoroethylene carbonate (FEC)/ethyl acetate (EA) based electrolyte containing lithium difluorophosphate (LiPO2F2, 2 wt%) and lithium bis(fluorosulfonyl)imide salt (LiFSI, 1.0 M) is first reported. The electrolyte containing these components has the characteristics of low freezing point, low viscosity and high ionic conductivity. Especially, due to the preferential decomposition of FEC, LiFSI and LiPO2F2, uniform multiphase inorganic LiF and Li3N species are formed on the electrode surface with enhanced robustness and ion transfer kinetics. So, the graphite||LiNi0.5Co0.2Mn0.3O2&LiMn2O4 (Gr||LMO&NCM523) batteries in the designed electrolyte maintain high capacity and coulombic efficiency (100 %) after 200 times at 1C charge and discharge current density at 25 °C and 45 °C. At −20 °C, the batteries have a coulombic efficiency of 50 % and capacity of 38.0 mA h g−1 after 200 charging and discharging cycles, showing excellent low-temperature fast dynamics. Our work supplies an efficient way to accelerate the engineering application of Li-ion batteries.