Tailoring electrochemical properties of Si-C anodes by sodium monofluorophosphate treatment

Silicon (Si) is a highly promising anode material for next-generation lithium-ion batteries, yet its practical electro-performance is severely hindered by massive volume changes and unstable solid electrolyte interphase (SEI) film. Herein, we introduce a simple and cost-effective strategy to address these challenges by modifying a Si-Carbon (Si-C) composite with sodium monofluorophosphate (SMFP, a low-cost and environmentally friendly additive with high ionic conductivity). During sintering at 650°C (above the melting point of SMFP, 625°C), the melted SMFP diffuses into the Si-C particles and coats on the surface, thus could not only suppress the side reactions between Si and electrolyte but also behave as an artificial SEI film to diminish the consumption of electrolyte and Li-ions for improving initial Coulombic efficiency (ICE). The optimized SMFP-modified anode (Si-C@0.5SMFP) demonstrates significantly enhanced electrochemical performance, delivering an ICE of 84.08% and retaining a capacity of 450.7 mAh g −1 after 500 cycles at 2 A g −1 , substantially outperforming the pristine Si-C. Mechanistic investigations reveal that the superficial SMFP could protect the Si-C anode from continuous electrolyte decomposition and boost Li-ion diffusion kinetics. This work presents a scalable and economical approach to stabilize Si-based anodes, offering a promising pathway for developing the lithium-ion batteries with high-energy-density.