Modulating Closed Pore Structure to Enhance Rate Capability of Corncob‐Derived Hard Carbon Anode for Fast‐Charging Sodium Ion Battery

ABSTRACT Precise modulation of the closed pore structure within hard carbon anodes plays a crucial role in enhancing the sluggish Na + diffusion kinetics, which is capable of improving rate performance and achieving fast‐charging sodium‐ion batteries (SIBs). Herein, a simple yet effective strategy is proposed to accurately tailor the microstructure of corncob and the closed pore structure in the derived hard carbon through regulating precursor components. Specifically, removing silica suppresses excessive graphitization, while dissolving amorphous components and cleaving crystalline cellulose chains modulate pore wall parameters. Thinner and more disordered pore walls of optimized hard carbon shorten the Na + transport pathway and facilitate Na + transfer, thereby enhancing Na + diffusion kinetics. The optimal hard carbon material demonstrates outstanding rate capability (223.1 mAh g −1 at 20 C) with superior reversible capacity (364.6 mAh g −1 at 0.1 C) and exceptional initial Coulombic efficiency (92.84%). In/ex situ analyses provide evidence for the “adsorption‐filling” mechanism. Additionally, the full battery achieves a high power density of 261.6 Wh kg −1 . This work establishes links between closed pore structure and rate performance, providing guidelines for developing hard carbon materials for fast‐charging SIBs.