Revealing the Critical Role of Amide Bonds in Pore Structure and Interfacial Stability of Hard Carbon Anodes for Sodium‐Ion Batteries

ABSTRACT

Hard carbon (HC) is considered the most promising anode material for sodium‐ion batteries (SIBs). However, precisely engineering closed pores for high plateau capacity while securing long‐term cycling stability remains a formidable challenge. Herein, a molecular engineering strategy based on amide‐bond crosslinking is proposed to achieve the synergistic optimization of the closed‐pore structure and interfacial chemistry in HC. Graphite fragmentation is suppressed by the atomic‐level amide anchors through the regulation of π – π stacking, whereby local curvature is induced to drive planar carbon layers into ultrathin‐walled closed pores. Simultaneously, the highly active pyridinic nitrogen sites introduced by the crosslinked network alter the electrolyte reduction pathway, lowering the decomposition energy barrier of PF ₆ ⁻ and promoting the formation of a robust, NaF‐rich solid electrolyte interphase. Consequently, the optimized HC anode delivers highly reversible sodium storage performance, achieving a remarkably low‐voltage plateau capacity of 250 mAh g ⁻¹ . Even at a high current density of 1 A g ⁻¹ , the electrode maintains a capacity retention of 95.14% after 1000 cycles. When coupled with a Na ₃ V ₂ (PO ₄ ) ₃ /C cathode, the assembled full cell demonstrates extended cycling durability. This work links precursor molecular topology to the structural and interfacial chemistry of hard carbon, paving a new design pathway for SIBs.