A localized high concentration carboxylic ester-based electrolyte for high-voltage and low temperature lithium batteries

In this work, a methyl propionate (MP)/fluoroethylene carbonate (FEC)-based localized high concentration electrolyte with lithium difluoro(oxalato)borate (LiDFOB) as the additive is reported. The tuned solvation structure and the addition of LiDFOB enable fast desolvation process of Li+ and good formation of cathode/electrolyte interphase. This optimized electrolyte shows good compatibility with both lithium cobaltate (LCO) cathode and lithium metal anode, enabling 4.5 V Li/LCO cell to cycle 300 cycles at 1C (180 mAh g−1) rate with 87.7 % capacity retention. Even at 10C high-rate cycling, around 75.0 % of initial capacity is also achieved. In addition, it possesses decent conductivity and viscosity at low temperature, demonstrating the great low-temperature performance. It enables the high-loading Li/LCO cell to deliver 136.9 mAh g−1capacity at −70 °C, showing the great discharge performance and application potential at such low temperature. In addition, the cell with this electrolyte could even be cycled at −40 °C with 77.8 % capacity retention after 100 cycles. This work implements the high-voltage, high-rate and low-temperature functions of battery by choosing appropriate electrolyte component and tuning its formulation. This work provides an effective method for designing a multifunctional lithium battery electrolyte.