Sodium storage behavior of hard carbon derived from waste sorghum distiller's grains

Abstract

Hard carbons featuring low cost and high capacity are considered some of the most promising anode materials for sodium ion batteries (SIBs). Biomass-derived precursors offer inherent advantages such as abundant porosity and wide availability; however, their intrinsic impurities often deteriorate electrochemical performance by hindering ion diffusion and triggering irreversible side reactions. In this study, a straightforward HCl-related pretreatment strategy was employed to remove impurities and modulate the microstructure of hard carbon from sorghum distiller's grains (SDG), an agricultural byproduct. The HCl-treated SDG-derived hard carbon exhibits exceptional electrochemical performance, achieving a high reversible capacity of 320.3 mA h g⁻¹ at 30 mA g⁻¹, a significant improvement of 143.2 mA h g⁻¹ compared to untreated counterparts. Notably, it retains 94.9% capacity after 300 cycles at 1 A g⁻¹, highlighting exceptional cycling stability. This low-cost biomass-derived hard carbon anode holds promising commercial potential for SIBs.