Rosewood-Derived Hard Carbon with a Tailored Microstructure as a High-Performance Anode for Sodium-Ion Batteries

Biomass-derived hard carbon has attracted extensive attention as a sustainable anode material for sodium-ion batteries (SIBs), yet simultaneously achieving high initial Coulombic efficiency (ICE) and large low-voltage plateau capacity remains challenging because both are strongly governed by carbon microstructure evolution during pyrolysis. Herein, waste rosewood is regulated through time-controlled alkaline treatment combined with multistage carbonization to balance surface stabilization and internal structural evolution. Moderate hemicellulose removal suppresses disordered surface defects and oxygen-rich unstable sites, leading to a compact carbon surface with reduced irreversible sodium consumption. Meanwhile, multistage carbonization promotes graphitic rearrangement and internal nanopore development for plateau sodium storage. Consequently, AMHC-5 delivers a reversible capacity of 325.2 mAh g−1 with an ICE of 90.0% at 0.1 A g−1 and a plateau capacity of 219.6 mAh g−1. Electrochemical measurements and in situ Raman and impedance analyses reveal sequential sodium storage involving adsorption, intercalation, and pore filling. A full cell paired with Na3V2(PO4)3 retains 85.6% of its capacity after 100 cycles. This work clarifies the relationship between precursor composition, carbon evolution, and sodium-storage behavior, offering a simple route for designing advanced biomass-derived hard carbon anodes for SIBs.