Hard carbon derived from coconut shells, walnut shells, and corn silk biomass waste exhibiting high capacity for Na-ion batteries

Abstract In recent years, hard carbon materials have gained significant interest as anode materials for Na-ion batteries. Biomass waste is considered one of the most interesting, renewable, available, and cost-effective precursor to obtain hard carbon (HC); however, HC properties must be finely tuned to achieve performance comparable to those provided by Li-ion batteries. In this work, three biomass wastes (coconut shells, walnut shells, and corn silk) were evaluated as potential precursors for HC preparation involving a pyrolysis process and subsequent acid washing to remove the inorganic impurities. All obtained materials exhibited low and similar specific surface areas (