Low-temperature and high-performance Si/graphite composite anodes enabled by sulfite additive

Lithium ion batteries (LIBs) with Si/graphite composites anode promise a high energy density larger than 400 Wh kg−1 with low costs, however, they still suffer from rapid performance degradation and potential safety hazard at cold climate. This is mainly associated with the fragile solid electrolyte (SEI) layer and the formation of Li dendrite. Here, we report on designing of electrolyte additives which endows a capacity retention of 66.7% over 200 cycles and an excellent rate performance with Si (10 wt%)/graphite composite anode. Moreover, the initial coulombic efficiency (CE) achieves 87% and rapidly approaches 100% in the 2nd cycle. The high-ductility organic/inorganic solid electrolyte interfaces (SEI) layer, which is composed by ROSO2Li and LiF, contribute to the enhanced performance. The introduction of Diethyl Sulfite (DES) promotes the rapid defluorination of Fluoroethylene carbonate (FEC) and polymerization of sulfide to form the organic layer during the initial discharging. Our results provide a facile but practical method to enhance the low-temperature performance and prove the way of commercial LIBs which could be operated at cold climate.