Engineering Molecular Rivets to Tune Pore Structure for Significantly Enhanced Sodium Storage

ABSTRACT The large‐scale application of hard carbon (HC) has been hindered due to its low specific capacity, poor cycling stability, and the lack of a simple preparation process. This study utilized 5‐hydroxymethylfurfural (HMF) generated from hydrolysis as a crosslinking bridge to construct a crosslinking precursor via intermolecular reaction, thereby synthesizing hard carbon (HC) rich in closed pores and enhancing its reversible capacity. Moreover, the intermolecular cross‐linking strategy results in the HC rich in C═O functional groups, which facilitates the binding of PF 6 − anions and promotes the formation of a stable inorganic‐rich solid electrolyte interphase (SEI), significantly enhancing Na + transport kinetics. The optimized HC increases the closed pore volume to 0.0447 cm 3 g −1 . And delivers a high reversible specific capacity of 329.19 mAh g −1 , with a plateau capacity of 233.8 mAh g −1 . Even under a high current rate of 5C, the material maintains a reversible capacity of 187.33 mAh g −1 . Moreover, it exhibits excellent cycling stability, retaining a specific capacity of 243.85 mAh g −1 after 1000 cycles at 1C. This work provides a new strategy for designing HC with high capacity and long cycling life.