Exploiting the synergistic effects of multiple components with a uniform design method for developing low-temperature electrolytes

Abstract

The low temperature performance is an apparent shortcoming of current lithium batteries, which renders them incompetent for various low temperature application scenarios. Developing low-temperature electrolytes is a facile but effective approach to elevate the performance of lithium batteries at low temperatures. The design of low-temperature electrolytes usually involves the usage of co-solvents, novel lithium salts and additives, but how to maximize the synergistic effects of these multiple components remains a great challenge. Herein, we develop a multicomponent electrolyte system consisting of dual-lithium salts (LiBF4 and LiFSI) and three solvents (PC, DME, and iBA), and find out the optimized electrolyte formula which can fully utilize the synergistic benefits of these multiple components, through an ingenious "uniform design" method. Lithium/graphite fluoride (Li/CFx) cells employing the optimized electrolyte display great enhancements in their low temperature performance, delivering more than 52% of the room temperature capacity and an energy density of 679.4 Wh/kg (based on cathode active material) at −60 °C. Moreover, electrochemical tests and theoretical calculations reveal that reducing the desolvation energy of lithium-ion is critical to improving the low temperature performance of electrolytes. This work provides valuable theoretical and design of experiments (DOE) guidance for rational design of low-temperature electrolytes.