A Lignin‐Targeted Pre‐Oxidation Strategy for Mitigating Closed Pore Collapse Toward High‐Stability Wood‐Based Hard Carbon Anodes for Na‐Ion Batteries

ABSTRACT Wood‐based biomass is the most promising precursor of hard carbon anode for sodium‐ion batteries, due to its structural diversity. To realize precise control of the microstructure for hard carbons, we engineer a generally applicable lignin‐targeted pre‐oxidation strategy utilizing differential thermal responsiveness between lignin and cellulose in biomass. We employed NEXAFS, PDF, and SAXS analysis, which reveals that targeted pre‐oxidation mitigates closed‐pore collapse during carbonization, enabling precise structural engineering that significantly enhances platform capacity. This method delivers a reversible capacity of 392.0 mAh g ⁻¹ with an initial columbic efficiency of 92.2% at 0.1 C, and a capacity retention exceeded 81.2% can be achieved after 2700 cycles at 5.0C. Moreover, full cells with Na ₄ Fe ₃ (PO ₄ ) ₂ P ₂ O ₇ were assembled, coin cell retains ∼85% capacity after 11 000 cycles, and 14Ah pouch cells can exhibit ∼100% retention after 1500 cycles. This strategy validated across diverse biomass, providing mechanistic insights for designing commercial sodium‐ion battery anodes.