Low-cost silicon (Si) feedstocks and a facile method to downsize the particle size are two determinants for the application of Si for the lithium-ion battery anode. Among various Si feedstocks, the industrial bulk ferrosilicon (b-Si/FeSi₂) alloy is a promising Si resource, but decreasing the particle size and increasing the utilization of Si remain challenging. Herein, we report a self-driven alloying-electrochemical dealloying approach to converting the b-Si/FeSi₂ to nano-sized Si/FeSi (n-Si/FeSi) in molten salts using Mg to extract one Si atom from one FeSi₂ molecule by breaking down the FeSi–Si chemical bond and simultaneously forming Mg₂Si. Subsequently, the obtained FeSi and Mg₂Si are converted to nano Si and FeSi by electrochemically removing Mg from the Mg₂Si anode to the cathode, making a circular use of Mg and increasing the electroactive Si content. Moreover, the polydopamine-coated n-Si/FeSi (n-Si/FeSi@C) anode exhibits a high capacity of 1449.7 mAh g⁻¹ after 500 cycles at 0.4 A g⁻¹, and an extremely stable reversible capacity of 846.8 mAh g⁻¹ is retained even after 1500 cycles at 2 A g⁻¹. Overall, this work provides an efficient method to convert industrial bulk Si/FeSi₂ to nano-sized Si/FeSi by leveraging the chemical bonds of Fe–Si and Mg–Si.

低成本的硅 (Si) 原料和减小粒径的简便方法是将硅应用于锂离子电池负极的两个决定因素。在各种 Si 原料中，工业大块硅铁 (b-Si/FeSi ₂ ) 合金是一种很有前途的 Si 资源，但减小粒径和提高 Si 的利用率仍然具有挑战性。在此，我们报告了一种自驱动合金化-电化学脱合金方法，使用 Mg 从一个 FeSi _{2 中}提取一个 Si 原子，将 b-Si/FeSi ₂转化为熔盐中的纳米尺寸 Si/FeSi (n-Si/FeSi)分子通过破坏 FeSi-Si 化学键并同时形成 Mg ₂ Si。随后，得到的 FeSi 和 Mg ₂通过电化学从 Mg ₂ Si 阳极到阴极去除 Mg ，循环使用 Mg 并增加电活性 Si 含量，Si 被转化为纳米 Si 和 FeSi 。此外，聚多巴胺涂覆的 n-Si/FeSi (n-Si/FeSi@C) 负极在 0.4 A g ^{-1 下}循环 500 次后表现出 1449.7 mAh g ^-1的高容量和 846.8 mAh的极其稳定的可逆容量即使在 2 A g ^{-1 下}经过 1500 次循环后，g ^-1仍保持不变。总的来说，这项工作提供了一种通过利用 Fe-Si 和 Mg-Si 的化学键将工业块状 Si/FeSi ₂转化为纳米尺寸的 Si/FeSi的有效方法。