Hyper‐Crosslinking to Customize Ultrathin‐Wall Closed Pores in Pitch‐Derived Carbon for Sodium‐Ion Batteries

Abstract Pitch is a highly preferable and cost‐effective precursor of carbon materials. Nevertheless, its direct pyrolysis typically yields highly graphitized soft carbon, posing challenges to the modulation of closed‐pore architecture, due to intense intermolecular π–π interactions. This results in a negligible plateau capacity and sluggish diffusion kinetics in sodium‐ion batteries (SIBs). In this study, an innovative hyper‐crosslinking strategy is proposed to reconstruct pitch molecularly and precisely tailor the closed‐pore structure of the derived carbon. The crosslinker intertwined the pitch units, transforming the linear molecules into 3D porous polymers. Structurally, these 3D cavities tactfully reserved space for forming closed‐pore cores, with the single‐layer pitch network skeleton transforming into ultrathin pore walls upon carbonization. This strategy enabled the disruption of intense π–π interactions and, therefore, inhibited structural ordering, facilitating a structure transition from graphitic soft carbon to highly‐disordered carbon with abundant closed pores featuring appropriate pore sizes (2 nm) and ultrathin pore walls (1–2 layers). The optimal sample delivered a high capacity of 370 mAh g ⁻¹ at 30 mA g ⁻¹ , as well as a rate capability that surpassed those of most previously reported pitch‐derived carbons. Hyper‐crosslinking has advanced the development of low‐cost and high‐performance carbon materials for large‐scale energy storage.