| Summary: | Silicon-based anodes can increase the energy density of Li-ion batteries (LIBs) owing to their large weights and volumetric capacities. However, repeated charging and discharging can rapidly deteriorate the electrochemical properties because of a large volume change in the electrode. In this study, a commercial Fe-Si powder was coated with Al<sub>2</sub>O<sub>3</sub> layers of different thicknesses via atomic layer deposition (ALD) to prevent the volume expansion of Si and suppress the formation of crack-induced solid electrolyte interfaces. The Al<sub>2</sub>O<sub>3</sub> content was controlled by adjusting the trimethyl aluminum exposure time, and higher Al<sub>2</sub>O<sub>3</sub> contents significantly improved the electrochemical properties. In 300 cycles, the capacity retention rate of a pouch full-cell containing the fabricated anodes increased from 69.8% to 72.3% and 79.1% depending on the Al<sub>2</sub>O<sub>3</sub> content. The powder characterization and coin and pouch cell cycle evaluation results confirmed the formation of an Al<sub>2</sub>O<sub>3</sub> layer on the powder surface. Furthermore, the expansion rate observed during the charging/discharging of the pouch cell indicated that the deposited layer suppressed the powder expansion and improved the cell stability. Thus, the performance of an LIB containing Si-alloy anodes can be improved by coating an ALD-synthesized protective Al<sub>2</sub>O<sub>3</sub> layer.
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