Effect of precursor morphology on the electrochemical performance of porous Si anodes prepared by magnesiothermic reduction

The magnesiothermic reduction of SiO₂ to Si is a promising route for preparing high-energy-density Si-based anode materials for lithium-ion batteries. However, the effect of the initial morphological properties of SiO₂ on the electrochemical performance of Si remains unclear. Herein, porous Si (PSi) particles were prepared from four different SiO₂ precursors, namely, spherical SiO₂ particles with diameters of 0.3 and 20 μm (denoted SiO₂-0.3 and SiO₂-20, respectively), fumed SiO₂ powder (denoted SiO₂-F), and well-ordered mesoporous SiO₂ particles (denoted SiO₂-K). Highly crystalline PSi particles were obtained after magnesiothermic reduction and subsequent HCl and HF etching. PSi prepared from SiO₂-0.3 maintained its precursor morphology to some extent, whereas highly irregular Si particles were produced from SiO₂-20, SiO₂-F, and SiO₂-K. Among the PSi particles, those prepared from SiO₂-0.3 delivered the highest reversible capacity (1427 mAh g^–1 at 0.1 A g^–1) after 50 discharge–charge cycles. Because of the unique hierarchically porous morphology of PSi prepared from SiO₂-0.3, the expansion of its electrode thickness was suppressed below 140 %. Moreover, owing to its nanosized Si domains and good electrode wetting, PSi prepared from SiO₂-0.3 demonstrated improved electrochemical properties compared with those prepared from SiO₂-F and SiO₂-K.