Surface selective electrocatalysis-derived ultra-dense and mechanically robust fluorinated solid electrolyte interface for high-capacity and long-cycling silicon electrode

Abstract

The commercial application of silicon anode is significantly impeded by its poor cycling life due to the fragility and continued growth of the solid electrolyte interface (SEI). It is currently considered feasible to employ fluorine-rich electrolyte additives to derive LiF-rich SEI, while the decomposition of these electrolyte additives would simultaneously lead to the interweavement of loose and porous organic components with LiF-rich SEI, thereby destructing the compactness and mechanical integrity of the SEI. Herein, we propose the surface selective electrocatalysis strategy to construct ultra-dense and robust fluoride-SEI on the Si surface, and the surface 1T-MoS₂ with rich sulfur vacancies can not only selectively adsorb fluorine-containing lithium salts and solvents, but also electrocatalyze the defluorination reactions of P-F and C-F bonds into fluorides. The optimized Si@MS electrode displays outstanding capacity retention of 95.5 %, and average coulombic efficiency above 99.8 % within 1000 cycles at 1 A g⁻¹. This study provides significant guidance to design advanced anode materials for rechargeable batteries with long cycle life.