C2H2O4 etching of AlSi alloy Powder:an efficient and mild preparation approach for high performance micro Si anode

Metal-assisted chemical etching, such as AlSi alloy powder, has been extensively utilized in the preparation of micro-nano structure porous Si anode due to the self-template role of metal in alloy powder, low cost, and low energy consumption. In this work, we systematically investigated that the effects of etchants on the structure morphology and electrochemical performances of porous Si from etching AlSi alloy powder. C₂H₂O₄, HCl, HNO₃, H₂SO₄ and NaOH etchants were studied based on the principles including metallic/metalloid characteristics of Al and chemical coordination effects. The results shows that C₂H₂O₄ can be employed as an efficient and mild alternative etchant for AlSi system instead of widely used HCl. The resulted porous Si–C₂H₂O₄ possessed an average diameter of about 1–2 μm with numerous bicontinuous nanochannel and exhibited a specific capacity of 1063 mAh g⁻¹ after 200 cycles at 0.5 A g⁻¹. Futhermore, XRD, XPS, ICP and SEM characterizations reveal that the residual Al/Al₂O₃ show great effect on the structure morphology and the electrochemical performance of porous Si. Dominating roles of residual trace Al/Al₂O₃ (e.g. Si–C₂H₂O₄) in the porous Si was also discussed to understand the structure and electrochemical performance of Si–C₂H₂O₄. The results potentially provide a green and effective preparation approach for large-scale Si production via etching AlSi alloy powder.