Production of Graphitic Carbons from Plant-Based SiC/C Nanocomposites for Li-ion Batteries

Barley husks are a byproduct of grain processing produced in large volumes globally. They contain a large amount of nanostructured silica (nSiO2) which can be converted via magnesiothermic reduction into carbon-rich nanostructured silicon carbide composite (nSiC/C). The nSiC/C can be further utilized as a precursor for the production of graphitic carbons (GCs) under atmospheric pressure at 2400 °C, typically utilized as active material in Li-ion battery (LIB) anodes. However, the current synthesis of graphite utilizes fossil-based precursors and requires temperatures up to 3000 °C. Therefore, we propose the sustainable and renewable plant-based GCs as an alternative anode material for LIBs. The synthesized GCs demonstrated a fully crystalline 3D carbon structure with stacking faults between graphene layers. Particle morphology, carbon structure, and elemental composition of the GCs were not influenced by the amount of free carbon in the precursors but the yield (11–41 wt%) of the GCs increased with increasing content of free carbon (1–26 wt%) in the SiC/C composite. The GC material had a specific capacity of 294 mAh g−1 as an active anode material in LIBs, demonstrated significantly better capacity retention at high current rates (1 and 2 C) compared with commercial graphite, and withheld 80% of the specific capacity over 175 cycles at 1 C. Synthesis of GCs from barley husks may provide an advantageous route of valorization of this underutilized sidestream.