Fast and Scalable Complete Chemical Prelithiation Strategy for Si/C Anodes Enabling High-Performance Li_xSi–S Full Cells

Owing to the high theoretical specific capacity of Si, Si-based anodes have been attracting increasing attention for achieving high-energy-density Li-based secondary batteries. However, Si-based anodes usually suffer from large volume expansion upon lithiation and delithiation, accompanied by the continual formation and destruction of the solid electrolyte interface (SEI) and thus the low Coulombic efficiency, greatly hindering their commercial application. The fabrication of Si/C composites can mitigate the undesirable volume expansion to some degree, while the initial Coulombic efficiency is still below 70%. Prelithiation of Si/C anodes has been regarded as an effective means to compensate for the massive loss of Li + in the first discharge process. Here, a fast and scalable complete prelithiation method was developed based on the chemical reaction between lithium 4,4′-dimethylbiphenyl/2-methyltetrahydrofuran and Si/C. The complete prelithiation extent can be easily controlled by tuning the reaction time. An SEI layer was formed during chemical prelithiation, and the lithiated Li x Si/C electrode exhibited reduced interfacial impedance. When matched with a S@polyacrylonitrile cathode, the assembled Li x Si–S full cell with a low negative-to-positive ratio of 1.8 delivered a specific energy of 578.7 Wh kg –1 . Moreover, the full cell can run steadily for over 400 cycles with a high capacity retention of 78.2%. This first attempt to achieve complete chemical prelithation provides a promising solution for the practical application of Si/C anodes in next-generation high-energy-density Li-based secondary batteries.