Microstructure‐Interface Modulation Boosts Sodium Storage Capacity and Stability of Hard Carbon

ABSTRACT The development of hard carbon (HC) anode is severely hindered by limited Na ⁺ storage capacity and poor cycling stability, which are closely related to its microstructure and interface. In this work, a synergistic microstructure‐interface modulation strategy is demonstrated to regulate the Na ⁺ storage active sites and structural stability of resin‐based HC. The introduced C═O enables reversible Na ⁺ adsorption, while carboxyl and neighboring phenolic hydroxyl functional groups anchor the template metal ions (Zn ²⁺ ), thereby constructing a hierarchical pore structure with abundant sites for reversible Na ⁺ storage. Additionally, expanded interlayer spacing promotes the kinetics of reversible Na ⁺ intercalation/deintercalation. Based on this strategy, the optimized HC material (ZGB‐HC) exhibits an extra‐high capacity of 406 mAh g ⁻¹ at 50 mA g ⁻¹ and maintains exceptional cycling stability of over 1000 cycles for 1 A g ⁻¹ . More surprisingly, the assembled Na ₃ V ₂ (PO ₄ ) ₃ ||ZGB‐HC full cell delivers a superior rate capability of 96.4 mAh g ⁻¹ at 4 C and maintains excellent cycling stability for over 250 cycles at 2C. This work develops an innovative strategy for designing HC anodes with advanced microstructure‐interface and new insights into their structural evolution during cycling.