Electrochemical Oscillatory Screening Anion to Form LiF-Rich SEI for Enhanced Stability of Silicon Anode.

Abstract

The solid electrolyte interphase (SEI) formed by the conventional constant-current process is often uneven and fragile, leading to low initial Coulombic efficiency, which induces rapid capacity degradation of silicon (Si) anodes. To obtain stable and uniform SEI, a pulse voltage method is proposed to construct a lithium fluoride(LiF) rich bilayer SEI on the Si anode surface, which selectively involves more anions in the SEI formation reaction by applying pulse voltage perturbations without altering the composition of the electrolyte. In-depth research has found that the pulse voltage protocol establishes an oscillation screening mechanism for anions, facilitating the arrival and decomposition of more anions on the surface of the Si anode to form a LiF-rich bilayer SEI. Such SEI exhibits high mechanical stability and rapid lithium-ion transport kinetics, achieving the initial Coulombic efficiency (ICE) of the Si anode improved to 90.8% and an enhanced capacity retention rate.