LiF/LiBO ₂ -Rich Silicon-Based Anode Enabling Stable Operation of Sulfide All-Solid-State Lithium-Ion Batteries without Extra External Pressure

A critical challenge facing silicon-based anodes in all-solid-state lithium-ion batteries (ASSLBs) is the need for high stack pressure to maintain good interfacial contact (often up to tens of megapascals). However, bulky pressurization systems degrade the energy density and increase the cost of ASSLBs. Herein, a modified silicon anode is proposed to achieve stable operation of sulfide ASSLBs without extra external pressure. LiBO₂ and LiF phases are <i>in situ</i> constructed on the surface of nano silicon by a simple solid phase reaction. Chemical analysis, theoretical calculations, and simulations all demonstrate that the uniformly distributed LiBO₂ improves lithium storage kinetics, while LiF acts as a mechanical buffer phase. Its high Young's modulus not only restrains the large volume expansion of silicon but also preserves the structural integrity of the electrode-electrolyte interface by dispersing lithiation stress. This ingenious interface architecture eliminates bulky external pressurization and enables high energy density ASSLBs.