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Scalable fabrication of micro-sized bulk porous Si from Fe–Si alloy as a high performance anode for lithium-ion batteries

Silicon has been perceived as one of the most promising anodes in the next generation lithium-ion batteries (LIBs) due to its superior theoretical capacity. However, bulk silicon experiences an enormous volume expansion during the lithiation/delithiation process, resulting in rapid capacity fading. And, its high-cost and low coulombic efficiency also present significant challenges for applications. Here, we presented a facile and large-scale approach for preparing micro-sized porous silicon by acid etching the abundant and inexpensive metallurgical Fe–Si alloy as a high-performance anode in LIBs. Profiting from the unique micro-sized structure, it exhibited a fantastic first-cycle coulombic efficiency of 88.1% and an excellent reversible capacity of 1250 mA h g−1 at 500 mA g−1 after 100 cycles. Furthermore, the micro-sized porous silicon without carbon coating could deliver a reversible capacity of 558 mA h g−1 at a high current density of 5 A g−1 due to the unique porous structure. This work provides a promising route for a large-scale production of high-performance micro-sized Si as anode materials in LIBs.