Effects of Reduction Temperature on the Structure and Lithium Storage Performance of Elemental Silicon Prepared by Aluminothermic Reduction of Micrometer‐Sized SiO ₂

Abstract Silicon (Si) is regarded as a highly promising anode material for lithium‐ion batteries due to its ultrahigh theoretical specific capacity, high abundance, and environmental friendliness. Currently, silicon is primarily synthesized via the reduction of silicon dioxide (SiO 2 ), with carbothermal reduction and magnesiothermic reduction being the most widely adopted methods. However, these approaches suffer from high reaction temperatures, excessive energy consumption, and insufficient product purity. In contrast, aluminothermic reduction attracts significant attention owing to its advantages of lower reaction temperatures, operational simplicity, and cost‐effectiveness. Herein, commercial micrometer‐sized SiO 2 is utilized as the precursor to systematically investigate the effects of reduction temperatures (220, 240, 260, and 280 °C) on the yield, grain size, crystallinity, and specific surface area of silicon synthesized via aluminothermic reduction process. Experimental results demonstrate that complete reduction of SiO 2 is achieved at 260 °C. As the temperature increases, the particle size and specific surface area of the silicon decrease gradually, while the crystallinity improves significantly. The yield shows a trend of increasing first and then decreasing. When used as an anode for lithium‐ion batteries, the Si(260) sample displays optimal cycling stability and rate performance, attributed to its balanced specific surface area, moderate grain size, and enhanced crystallinity. The Si(260) electrode delivered an initial discharge capacity of 2667 mAh g −1 and an initial coulombic efficiency of 86%. It retained a reversible capacity of 182 mAh g −1 at 0.2 A g −1 after 200 cycles. Notably, when the current density is increased to 2 A g −1 and subsequently restored to 0.1 A g −1 , the capacity recovered to 938 mAh g −1 . This work elucidates the temperature‐dependent structure–property relationship in low‐temperature aluminothermic reduction, providing critical insights for the cost‐effective and controllable synthesis of high‐performance silicon‐based anodes.