Programmable Steric‐Enhanced Dual‐Crosslinking Preoxidation Unlocks Closed‐Pore Dominated Sodium Storage in Pitch‐Derived Carbon Anodes
Guangyue Zhang, Like Liu, Jie Yang, Xu Tian, Jianyu Li, Canshang Liu, Hengjin Ren, Kunfang Wang, Haiyong He, Xin Su, Weiwei Zhou
Abstract
Abstract Pitch is an ideal hard carbon precursor for sodium‐ion batteries (SIBs) owing to its abundant availability, low cost, and high carbon yield, yet its pronounced graphitization tendency during carbonization limits sodium storage capacity. To address this, a Steric‐Enhanced Dual‐Crosslinking (SEDC) preoxidation strategy is developed by integrating multifunctional organophosphorus molecules (e.g., phytic acid) during air preoxidation. The SEDC mechanism synergistically combines two concurrent pathways: (i) steric hindrance induced by multifunctional organophosphorus groups, which utilize their voluminous molecular structures to suppress π–π stacking, and (ii) dual‐crosslinking via inherent oxygen‐functionality bonding (from air preoxidation) and phosphate‐group condensation reactions among organophosphorus molecules. This synergy expands interlayer spacing to 0.390 nm, generates pseudo‐graphitic domains with abundant closed nanopores, and maximizes pore‐filling‐dominated Na + storage. The optimized anode delivers outstanding performance: a reversible capacity of 378.4 mAh g −1 with 68.5% plateau‐capacity contribution and 90% initial Coulombic efficiency, surpassing most state‐of‐the‐art pitch‐derived carbons. Critically, systematic extension to other organophosphorus systems with graded P‐functionality (3–6) validates universality—higher functionality strengthens crosslinking, amplifies disorder/closed‐pore density, and elevates electrochemical metrics. Thus, this approach establishes a universal platform for molecularly tailored synthesis of high‐performance pitch‐derived hard carbon anodes through programmable crosslinking design.