Dual-Phase SiC + C Coated Microsize Si@SiO_x Powder as Anode Material for Li-Ion Batteries

Severe volume expansion and poor ionic transport greatly impede the further application of micro-Si anodes despite their high energy density and low processing cost. To address these challenges, we propose a Si/C composite anode (denoted as WM-30C). In this design, wet milling introduces an oxide layer as the core, while high-temperature heat treatment with bitumen regulates the silicon valence state and introduces a strong Si–C bond, forming the shell. In this design, during the wet milling process of micro-Si, a layer of oxide is introduced in situ on the surface to form Si@SiO2 as the core. The high-temperature heat treatment is then employed to adjust the valence state of silicon, and in conjunction with bitumen, strong Si–C bonds are introduced, ultimately forming the shell layer. As a result, the WM-30C composites exhibit an impressive initial Coulombic efficiency of 83.4% and high rate performance. Furthermore, they maintain a steady cycling rate of 614 mA h/g (0.2C) for 325 cycles and nearly negligible capacity degradation at a constant capacity of 600 mA h/g. These results highlight the significant improvement in electrochemical properties achieved by incorporating a multiphase structure (SiOx + SiC + C) through a cost-effective wet chemical reaction of silicon and a bitumen heat treatment process in micro-Si-based composites.