Biowaste-Derived Si@SiOx/C Anodes for Sustainable Lithium-Ion Batteries

In this study, rice husks and waste coffee grounds (WCGs) are utilized as precursors for synthesizing Si@SiO x /C composite anode materials. The magnesiothermic method is applied to reduce the nano-sized silica derived from rice husks to Si@SiO x . The Si@SiO x product is then mixed with WCGs and carbonized at a high temperature to produce Si@SiO x /WCGC. After optimization, the Si@SiO x /WCGC with a precursor ratio of 1:2 provides a high reversible capacity of 1125 mA h g −1 at 100 mA g −1 . The capacity retention of Si@SiO x /WCGC (1:2) is 80% after 100 cycles at 1 A g −1 , which is considerably higher than that of pristine Si@SiO x (only 1.8%). In addition, the lithium-ion diffusivity of Si@SiO x increased from 2.7 × 10 −12 to 4.5 × 10 −11 cm 2 s −1 after it is combined with the WCGC. Furthermore, a full cell using Si@SiO x /WCGC (1:2) as the anode and LiNi 0.5 Mn 1.5 O 4 as the cathode is assembled, which exhibits a high energy density of 396 W h kg −1 . This demonstrates that biowaste-derived Si@SiO x /WCGC is a promising and environmentally friendly anode material for lithium-ion batteries.