In Situ-Formed Artificial Solid Electrolyte Interphase for Boosting the Cycle Stability of Si-Based Anodes for Li-Ion Batteries

Si is being actively developed as one of the most promising high-capacity anodes for next-generation lithium-ion batteries (LIBs). However, low cycling coulombic efficiency (CE) due to the repetitive growth of the solid electrolyte interphase (SEI) film is still an issue for its application in full batteries. Here, we propose a strategy to in situ form an artificial solid electrolyte interphase (ASEI) on the ferrosilicon/carbon (FeSi/C) anode surface by a purposely designed nucleophilic reaction of polysulfides with vinylene carbonate (VC) and fluoroethylene carbonate (FEC) molecules. The as-formed ASEI layer is mechanically dense and ionically conducting and therefore can effectively prevent the electrolyte infiltration and decomposition while allowing Li⁺ transport across, thus stabilizing the interface of the FeSi/C anode. As a result, the ASEI-modified FeSi/C anode exhibits a large reversible capacity of 1409.4 mA h g^-1, an excellent cycling stability over 650 cycles, and a greatly elevated cycling CE of 99.8%, possibly serving as a high-capacity anode of LIBs.