Waste-wood-derived sustainable N and S co-doped hard carbon for enhanced sodium-ion storage

Abstract

Constructing sustainable, cost-effective and high-performance biomass-derived hard carbon has emerged as a legitimate approach to address the critical bottlenecks of anodes in sodium-ion batteries. Herein, the N and S co-doped hard carbon (NS-HC) derived from waste wood was synthesized by removing lignin and hemicellulose, combined with heteroatom doping and calcination. The results demonstrated that NS-HC exhibited superior sodium-storage capability, and after 100 cycles at 0.05 A g⁻¹, NS-HC exhibited a reversible capacity of 370.4 mA h g⁻¹. Increasing the current density from 0.05 to 2 A g⁻¹, the electrode still yielded a capacity of 65%. Moreover, after 2500 cycles at 2 A g⁻¹, the NS-HC electrode demonstrated a high capacity of 207.9 mA h g⁻¹. The enhanced electrochemical performance was due to the elimination of lignin and hemicellulose, facilitating the development of graphite-like domains and creating a rich micropore structure. Meanwhile, N and S co-doping contributed to enhanced electrical conductivity and the formation of defects, which enabled a considerable increase in both active sites and effective channels, thereby facilitating the diffusion and storage of sodium ions. Theoretical calculations revealed that N/S co-doping modulated the local charge distribution of carbon, optimizing the electronic structure to promote more stable Na⁺ adsorption and active-site formation. Furthermore, full-cell tests assembled with the NS-HC anode and a Na₃V₂(PO₄)₃ (NVP) cathode demonstrated its promising potential for practical applications. This work achieves the value-added reuse of waste wood and provides a promising pathway for the development of sustainable, low-price, and high-performance wood-derived hard carbon anodes.