Synergy of Weakly‐Solvated Electrolyte and Optimized Interphase Enables Graphite Anode Charge at Low Temperature

Abstract

Graphite anode suffers from great capacity loss and even fails to charge (i.e. Li+‐intercalation) under low temperature, mainly arising from the large overpotential including sluggish de‐solvation process and insufficient ions movement in the solid electrolyte interphase (SEI). Herein, an electrolyte is developed by utilizing weakly solvated molecule ethyl trifluoroacetate and film‐forming fluoroethylene carbonate to achieve smooth de‐solvation and high ionic conductivity at low temperature. Evolution of SEI formed at different temperatures is further investigated to propose an effective room‐temperature SEI formation strategy for low‐temperature operations. The synergetic effect of tamed electrolyte and optimized SEI enables graphite with a reversible charge/discharge capacity of 183 mAh g−1 at −30 °C and fast‐charging up to 6C‐rate at room temperature. Moreover, graphite||LiFePO 4 full cell maintains a capacity retention of 78 % at −30 °C, and 37 % even at a super‐low temperature of −60 °C. This work offers a progressive insight towards fast‐charging and low‐temperature batteries.