A LiF-Pie-Structured Interphase for Silicon Anodes

Abstract Silicon (Si) is a promising anode material for rechargeable batteries due to its high theoretical capacity and abundance, but its practical application is hindered by the continuous growth of porous solid-electrolyte interphase (SEI), leading to capacity fade. Herein, a LiF-Pie structured SEI is proposed, with LiF nanodomains encapsulated in the inner layer of the organic cross-linking silane matrix. A series of advanced techniques such as cryogenic electron microscopy, time-of-flight secondary ion mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry have provided detailed insights into the formation mechanism, nanostructure, and chemical composition of the interface. With such SEI, the capacity retention of LiCoO 2 ||Si is significantly improved from 49.6% to 88.9% after 300 cycles at 100 mA g −1 . These findings provide a desirable interfacial design principle with enhanced (electro) chemical and mechanical stability, which are crucial for sustaining Si anode functionality, thereby significantly advancing the reliability and practical application of Si-based anodes.