A stable silicon anode with closed-pore structure constructed via trace ammonia-induced etching for lithium-ion batteries

<p dir="ltr">The primary challenge encountered in the practical application of silicon lies in the instability of the solid electrolyte interface (SEI) triggered by the severe volume changes during cycling, as this causes a continuous consumption of active lithium and rapid capacity decay. Creating a structure with pores and conformal coating has proven to be an effective strategy to enhance cyclability. Here we report a closed-pore silicon nanowire (CP-SiNW) featuring internal voids and external SiOx layer, that was synthesized through an eco-friendly, convenient, and cost-effective trace ammonia-induced etching method. The trace ammonia served as the initiator to determine etching sites, while water acted as the etchant to create voids. The generated orthosilicic acid underwent polymerization on the silicon nanowire surface, forming thickened SiOx layer. This coating effectively inhibits sustained SEI growth by preventing contact between the inner pore surface and electrolyte. Additionally, its higher mechanical strength enabled the expansion of silicon upon lithiation to occupy primarily the internal voids, thus improving structural durability. Consequently, CP-SiNW exhibited a remarkable cycling performance (1162.3 mAh g‒1 capacity retention after 500 cycles at 2.0 A g‒1) and good structural stability (23.6% thickness expansion after 50 cycles). The CP-SiNW@C anode, achieved through carbon coating, manifested an enhanced electrochemical performance. When paired with a LiCoO2 cathode, the full cell demonstrated excellent cycling stability, retaining 95.6% of its capacity after 100 cycles. This work introduces an efficient process for fabrication of durable and high-performance silicon anodes, with the potential to advance their widespread adoption in lithium-ion batteries and beyond.</p>