Atomic‐Level Regulation of SiC4 Units Enable High Li+ Dynamics and Long‐Life Micro‐Size SiCx Anodes

Abstract Large‐scale applications of high‐capacity silicon‐based anodes remain a challenge for high‐energy lithium‐ion batteries (LIBs) owing to huge volume variation. Although designing nano‐sized Silicon (Si) anodes plays a milestone advance in the commercial development, it's still hindered by issues related to cost and side reactions. A simple co‐pyrolysis of SiH4 and C2H4 is introduced via chemical‐vapor‐deposition (CVD) method to prepare SiCx micro‐sized particles with atomic‐level homogeneous distributions of silicon and carbon. One basic unit of SiC4 tetrahedra in SiCx plays a key role in particles’ microstructure optimization and electrochemical performance improvement: 1) The SiC4‐enriched surface layer is found to hinder Li+ insertion. 2) Proper heat‐treatment temperature is adopted to eliminate the layer and control the transition from SiC4 to SiC nanocrystalline, which is significant for decreasing polarization, enhancing Li+ diffusion kinetics, and cycling stability. Consequently, the optimized architecture exhibits a high capacity of 1455 mA h g−1 with an outstanding capacity retention of 95.8% after 100 cycles. Pouch‐type full‐cell demonstrates that the composite possesses excellent cycling stability with capacity retentions of 82.5% after 500 cycles at 25 °C and 84.0% after 400 cycles at 45 °C. This work provides a scalable yet practical solution to micro‐sized Si‐based anodes.