Novel, Clean, and Controlled Method for Surface Oxidation of Photovoltaic Silicon Cutting Waste for High-Performance Si–C Anode Materials

The trend of large-scale wafer thinning has led to increased surface activity, oxidation, and uneven oxidation interfaces in photovoltaic silicon cutting waste (SCW) produced by diamond wire cutting, posing significant challenges for its use as a silicon–carbon anode material. To address these issues, we propose a green recycling method that utilizes alkaline solutions to recover silicates from etched SCWs, avoiding the highly corrosive HF acid. By combining inexpensive chitosan (CTS) as a soft template, we achieve controllable reshaping of silicates into amorphous oxide layers (1 to 16 nm) on submicron SCW surfaces. This process involves a one-step method in a vacuum autoclave, which simultaneously eliminates the chitosan template and forms both the oxide layer and the phenolic resin. Unlike self-crystallizing oxide layers, the amorphous layers ensure uniform expansion and contraction, facilitate Li+ transfer, and introduce structural defects, enhancing lithium storage performance. The resulting Si@SiOx@C composite with a 5 nm thick oxide interface significantly improves the cycling performance, coulombic efficiency, and rate capability of the silicon–carbon material, achieving a reversible capacity of over 1000 mAh g–1 after 200 cycles at 1 A g–1. This work demonstrates the value-added utilization of submicron SCWs in the commercial production of high-performance silicon-based lithium-ion battery anodes.