Porous Silicon Anodes Derived from Molten Salt Dealloying of CaSi ₂ for Lithium‐Ion Batteries

ABSTRACT A micro‐sized porous crystalline silicon was successfully synthesized through a molten salt decalcification approach by treating CaSi ₂ in both CaCl ₂ and CaCl ₂ ‐KCl melts. Upon treatment in CaCl ₂ at 900°C for 6, 12, and 24 h, the residual calcium content in the silicon products decreased to 6.03%, 4.05%, and 1.30%, respectively. Similarly, in CaCl ₂ ‐KCl melts held at 700°C, 800°C, and 900°C for 24 h, the calcium content dropped to 9.38%, 6.64%, and 1.48%, respectively. Higher temperatures and extended durations facilitated more efficient calcium removal, yielding silicon with increasingly porous and dendritic features. One representative sample, MC‐3 (derived from CaCl ₂ melts at 900°C for 24 h), was coated with a polydopamine‐derived carbon layer via polymerization and subsequent carbonization, forming a uniform shell of 10–30 nm thickness. The resulting MC‐3@C composite, when employed as an anode material for lithium‐ion batteries, delivered a reversible specific capacity of 647.5 mAh g ^{− 1} after 700 cycles at 1 A g ^{− 1} and demonstrated outstanding rate capability. This work presents an efficient molten salt strategy for fabricating microporous crystalline silicon with enhanced electrochemical performance, offering a scalable and cost‐effective alternative to conventional silicon‐based anode materials.