Biowaste-derived Si@SiOx/C anodes for sustainable lithium-ion batteries

Abstract

In this study, rice husks and waste coffee grounds (WCGs) are utilized as precursors for synthesizing Si@SiOx/C composite anode materials. The magnesiothermic method is applied to reduce the nano-sized silica derived from rice husks to Si@SiOx. The Si@SiOx product is then mixed with WCGs and carbonized at a high temperature to produce Si@SiOx/WCGC. After optimization, the Si@SiOx/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@SiOx/WCGC (1:2) is 80% after 100 cycles at 1 A g−1, which is considerably higher than that of pristine Si@SiOx (only 1.8%). In addition, the lithium-ion diffusivity of Si@SiOxincreased from 2.7 × 10−12 to 4.5 × 10−11 cm2 s−1 after it is combined with the WCGC. Furthermore, a full cell using Si@SiOx/WCGC (1:2) as the anode and LiNi0.5Mn1.5O4 as the cathode is assembled, which exhibits a high energy density of 396 W h kg−1. This demonstrates that biowaste-derived Si@SiOx/WCGC is a promising and environmentally friendly anode material for lithium-ion batteries.