Novel strategies for constructing highly efficient silicon/carbon anodes: Chemical prelithiation and electrolyte...

Chemical prelithiation is an effective method to compensate for the loss of active lithium due to the formation of solid electrolyte interface, effectively addressing the issue of low initial coulombic efficiency (ICE) in silicon/carbon (Si/C) materials. Herein, the Si/C anode is prelithiated in a 1 M lithium-phenanthrene/2-methyltetrahydrofuran (Li-Phe/2-MTHF) solution in our work, and the prelithiated Si/C anode is followed by post-treatment with commercial electrolytes containing lithium difluorobis(oxalato)phosphate (LiDFBOP). The PSi/C-L_0.5, originated from the reaction between residual Li-Phe/2-MTHF and the commercial electrolyte containing 0.5 wt% LiDFBOP, possesses the artificial SEI film, which not only contains a proper amount of LiF but also is rich in Li₂C₂O₄ and Li₃P. Among them, LiF and Li₂C₂O₄ ensures the stability of the SEI film. Simultaneously, the synergistic effect of Li₃P and LiF improves its Li⁺ transport kinetics. Therefore, the ICE of PSi/C-L_0.5 reaches 92.50 %, and almost no drop in capacity occurs after 100 cycles at 0.5 A/g. Furthermore, the capacity stays steady at about 270 mAh/g through nearly 500 cycles at 1 A/g, achieving an impressive capacity retention rate of 97.8 %, significantly outperforming un-treated Si/C. This study offers new directions for constructing SEI films with stable structures and high Li⁺ kinetics transport.