Facile Synthesis of 2D SiOx -3D Si Hybrid Anode Materials by Ca Modification Effect for Enhanced Lithium Storage Performance

Abstract

Al-Si dealloying method is widely used to prepare Si anode for alleviating the issues caused by a drastic volume change of Si-based anode. However, this method suffers from the problems of low Si powder yield (<20 wt.% Si) and complicated cooling equipment due to the hindrance of large-size primary Si particles. Here, a new modification strategy to convert primary Si to 2D SiO_x nanosheets by introducing a Ca modifier into Al-Si alloy melt is presented. The thermodynamics calculation shows that the primary Si is preferentially converted to CaAl₂ Si₂ intermetallic compound in Al-Si-Ca alloy system. After the dealloying process, the CaAl₂ Si₂ is further converted to 2D SiO_x nanosheets, and eutectic Si is converted to 3D Si, thus obtaining the 2D SiO_x -3D Si hybrid Si-based materials (HSiBM). Benefiting from the modification effect, the HSiBM anode shows a significantly improved electrochemical performance, which delivers a capacity retention of over 90% after 100 cycles and keeps 98.94% capacity after the rate test. This work exhibits an innovative approach to produce stable Si-based anode through Al-Si dealloying method with a high Si yield and without complicated rapid cooling techniques, which has a certain significance for the scalable production of Si-based anodes.

Keywords: 2D SiOx; Ca modifier; CaAl2Si2; Si anode; dealloy.