Facilitating prelithiation of silicon carbon anode by localized high-concentration electrolyte for high-rate and long-cycle lithium storage

The commercialization of silicon-based anodes is affected by their low initial Coulombic efficiency (ICE) and capacity decay, which are attributed to the formation of an unstable solid electrolyte interface (SEI) layer. Herein, a feasible and cost-effective prelithiation method under a localized high-concentration electrolyte system (LHCE) for the silicon–silica/graphite (Si–SiO₂/C@G) anode is designed for stabilizing the SEI layer and enhancing the ICE. The thin SiO₂/C layers with –NH₂ groups covered on nano-Si surfaces are demonstrated to be beneficial to the prelithiation process by density functional theory calculations and electrochemical performance. The SEI formed under LHCE is proven to be rich in ionic conductivity, inorganic substances, and flexible organic products. Thus, faster Li⁺ transportation across the SEI further enhances the prelithiation effect and the rate performance of Si–SiO₂/C@G anodes. LHCE also leads to uniform decomposition and high stability of the SEI with abundant organic components. As a result, the prepared anode shows a high reversible specific capacity of 937.5 mAh g⁻¹ after 400 cycles at a current density of 1 C. NCM 811‖Li-SSG-LHCE full cell achieves a high-capacity retention of 126.15 mAh g⁻¹ at 1 C over 750 cycles with 84.82% ICE, indicating the great value of this strategy for Si-based anodes in large-scale applications.