Sustainable Closed-Pore Engineering of Bamboo-Derived Hard Carbon for High-Capacity Sodium-Ion Battery Anodes

Hard carbon (HC) from lignocellulosic biomass is a promising candidate for sodium-ion batteries (SIBs) anodes, but its sodium-storage performance is severely limited by the imprecise regulation of pore architecture. Herein, a green and scalable strategy was developed to tailor the closed-pore structure of bamboo-derived HC by mild p-toluenesulfonic acid (p-TSA) pretreatment. This environmentally benign organic acid selectively hydrolyzes hemicellulose and dissolves lignin while preserving the crystalline cellulose skeleton for optimized Na⁺ storage. Systematic characterization and electrochemical tests revealed that the moderately treated PTSC-5% formed an optimized closed-pore structure and expanded carbon interlayer spacing, delivering an initial discharge capacity of 399.63 mAh g^–1 (244.8 mAh g^–1 from plateau capacity) at 0.1C, an initial Coulombic efficiency (ICE) of 83.08%, and ∼84% capacity retention after 100 cycles. This work provides a cost-effective, sustainable, and industrially scalable route for the pore regulation of biomass-derived HC, clarifies the structure-performance relationship of closed-pore engineered HC for sodium storage, and advances the practical application of high-performance SIBs in sustainable large-scale energy storage systems.