Molecular-level biomass composition and crosslinking regulation towards hard carbon with high initial Coulombic efficiency for sodium-ion battery

• • HC-BO-MA achieves an ICE of 93.9% and a reversible capacity of 324 mAh g−1 at 20 mA g−1, exceeding typical HC anodes (ICE <90%) and approaching graphite's ICE (>93%) while retaining sodium-ion compatibility; this reduces cathode sodium inventory by ~15–20% in full cells, directly boosting energy density and cycle life. • • Modulating lignin:cellulose:hemicellulose ratios in bamboo promotes sp2 hybridization and enlarges graphite-like microcrystalline domains, which enhance sodium storage kinetics and reversible capacity; this compositional control is critical for scaling biomass precursors with consistent electrochemical performance. • • Maleic anhydride (MA)-assisted thermal crosslinking creates closed pores during carbonization, which mitigate irreversible sodium trapping at defect sites and SEI overgrowth; closed pores are essential for minimizing first-cycle capacity loss, a key industrial bottleneck for SIB adoption. • • The dual regulation strategy decouples the traditional trade-off between capacity and ICE, enabling simultaneous optimization; this provides a scalable, low-cost route using abundant bamboo biomass, potentially reducing anode material cost below $10 kg−1 and accelerating SIB deployment in grid storage.