Performance boosting of one-pot topochemical synthesized 2D silicon anode via simultaneous SEI optimization and conductive pillar

Two-dimensional silicon nanosheets are promising anodes for next-generation lithium-ion batteries due to their high capacity and moderate volume expansion, but complex synthesis and stacking issues hinder practical application. In this study, a simple and cost-effective one-pot method is reported to synthesize Si/SiO_x/Sn (0 < x < 2) nanocomposites using Zintl compound CaSi₂ as the precursor via topochemical reaction. The samples consist of layered silicon nanosheets with Sn nanoparticles embedded as conductive and ductile pillars. Subsequent acid washing adjusts the Sn content, optimizing the structure to enhance conductivity, prevent stacking of silicon nanosheets, and reduce expansion. Furthermore, the surface hydroxyl (–OH) group density decreases with prolonged acid washing time. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals that the hydroxyl content influences the concentration of organic components and Li₂CO₃ content of solid electrolyte interphase (SEI). Benefiting from this unique structure, the silicon-based nanosheets deliver capacity of 687 mAh·g⁻¹ after 200 cycles, with a capacity retention rate of 90% and a maximum Coulombic efficiency of 99.4%. Additionally, the material demonstrates excellent performance at a high rate (484 mAh·g⁻¹ at 2 A·g⁻¹). This work provides a novel approach for synthesizing stable silicon nanosheet materials, offering new insights for the development of high-performance lithium-ion battery anodes.