Green biomass: the impact of high-adhesion and well-dispersed binders on the sodium storage performance and interfacial interaction of hard carbon anodes

Abstract

Hard carbon (HC) exhibits promising potential as an anode material for sodium-ion batteries; however, it is confronted with challenges such as low initial coulombic efficiency (ICE) and poor rate performance. Developing biomass-based binders is a significant strategy to promote electrochemical performance and improve the stability of the solid electrolyte interface (SEI). In this work, green biomass of carboxymethyl cellulose (CMC) and sodium lignosulfonate (LS) with excellent adhesion and dispersibility is demonstrated as an efficient binder for hard carbon anodes. The semi-rigid skeleton of LS effectively wraps the hard carbon particles, surface modifies HC, and fills defects. The polar functional groups of the binder facilitate the adsorption of Na⁺ and reduce irreversible Na⁺ insertion. Furthermore, the functional groups induce the formation of a unique SEI layer. The SEI layer consists of an organic outer layer and an inorganic inner layer, promoting ion transport and mechanical integrity. Therefore, the HC anode with the CMC/LS binder demonstrates a high reversible capacity of 348 mA h g⁻¹ at 0.05 A g⁻¹, a high ICE of 87%, and an outstanding rate performance with 243 mA h g⁻¹ at 5 A g⁻¹.