Silicon Nanosheet Synthesis via Silicon Tetrachloride Reduction with Facilely Produced Aluminum Templates for Lithium‐Ion Batteries

Metal reduction of silicon gases is a widely explored route for synthesizing low‐dimensional nanosilicon materials; however, achieving specific nanostructures often requires templates that are challenging to produce or expensive. This study proposes a cost‐effective and scalable approach by ball‐milling aluminum into thin flakes (<50 nm), which serve both as reductants and physical templates for the direct gas‐phase synthesis of silicon nanosheets. The study demonstrates that performing the synthesis in the gas phase enables highly controlled surface reactions, crucial for forming well‐defined silicon nanosheets. The reduction of industrial by‐product silicon tetrachloride occurs via a solid–gas reaction at a relatively low temperature of 225 °C in a closed autoclave system. The resulting silicon nanosheets demonstrate uniform morphology (≈20 nm thick) and a high surface‐to‐thickness ratio favorable for lithium‐ion battery anode applications. Electrochemical tests achieve a high initial capacity of 4038 mAh g⁻¹ and a Coulombic efficiency of 83.3%. The nanosheets retain a reversible capacity of 2058 mAh g⁻¹ after 250 cycles at 2.1 A g⁻¹ and excellent rate capability, recovering 87% capacity at 21 A g⁻¹.