Energy‐Preferring Mechanism Competition in Molecularly Programmed Hard Carbon for High‐Plateau‐Capacity Sodium‐Ion Batteries

ABSTRACT Anodes composed of hard carbon for sodium‐ion batteries face several key limitations: inadequate capacity within the plateau region, suboptimal initial coulombic efficiency (ICE), and a storage mechanism that remains debated—particularly whether sodium storage proceeds through a traditional three‐stage “adsorption‐intercalation‐filling” sequence or a more direct two‐stage “adsorption followed by combined intercalation/filling” process. Herein, we design a molecularly programmed hard carbon that helps to resolve the sodium storage mechanism through precise microstructure manipulation. The material achieves an ultra‐high plateau capacity of 402.1 mAh g − 1 and an ICE of 80.0% at 0.1 A g − 1 , along with exceptional rate capability and cycling stability (83.8% capacity retention after 2000 cycles at 5 A g − 1 ). By integrating comprehensive in situ/ex situ analyses with molecular dynamics (MD) simulation, an energy‐preferring competition mechanism is proposed within the plateau region: Na + storage mechanism is governed by the competition between the intercalation energy (E i ) and the pore‐filling energy (E f ): when E f <<E i , the pore‐filling mechanism dominates; when E f ≈E i , a hybrid “adsorption–intercalation–filling” storage behavior occurs. This work helps resolve the discrepancy in sodium storage mechanisms and establishes a novel design paradigm for high‐performance carbon‐based anodes.