The optimization of the electrolyte for low temperature LiFePO4-graphite battery.

• Electrolyte is optimized for low-temperature LiFePO 4 -graphite battery. • Multi-component solvent system improves the ionic conductivity at low temperature. • Film-forming additives promote the formation of solid electrolyte interface film. • The optimized battery exhibits excellent performance at low temperatures. The design of electrolyte is crucial to improve the low temperature electrochemical performance of the LiFePO 4 -graphite battery. In this paper, by optimizing the solvent composition and introducing film-forming additives in the electrolyte, the low temperature performance of the battery is significantly improved. In detail, the EP (ethyl propionate) solvent with low melting point and low viscosity is added to the original EC (ethylene carbonate)-EMC (ethyl methyl carbonate)-DMC (dimethyl carbonate) solvent systems, which improved the ionic conductivity of the electrolyte, especially at low temperature (−40 °C). On the other hand, the introduction of FEC (fluoroethylene carbonate)/DTD (ethylene sulfate) film-forming agents promotes the formation of SEI (solid electrolyte interface) film, and the SEI is thin and uniform. As a result, the LiFePO 4 -graphite battery exhibits high capacity and long cycle life under low temperature conditions. [ABSTRACT FROM AUTHOR]