Synergistic Dual‐Engineering of Hard Carbons via Graphene Oxide Nanosheets: Enabling Ultrahigh ICE Sodium‐Ion Batteries through Edge Passivation and Catalytic SEI Design

Abstract The commercialization of sodium‐ion batteries (SIBs) faces a critical challenge in balancing the high reversible capacity and initial Coulombic efficiency (ICE) of hard carbon anodes, hindered by reactive edge‐induced electrolyte degradation. This study introduces an innovative dual‐functional modification strategy leveraging graphene oxide (GO) nanosheets to simultaneously passivate edge‐active sites and catalytically tailor interfacial chemistry. By constructing an atomic‐scale hydrogen‐bonding network, oxygen‐rich functional groups (─OH/─COOH) on GO chemically anchor to carbon edges, suppressing parasitic reactions while inducing closed‐pore architectures for efficient Na⁺ storage. Simultaneously, strategically retained carbonyl (C═O) moieties act as Lewis‐acid catalytic centers, directing preferential NaPF₆ decomposition into an inorganic‐dominated NaF‐rich solid electrolyte interphase (SEI) via molecular‐level interactions. The optimized anode delivers a record‐high ICE of 90.9% with 441.3 mAh g⁻¹ reversible capacity at 0.1 A g⁻¹ (4.6 mg cm⁻ 2 ), coupled with exceptional rate capability (161.1 mAh g⁻¹ at 2.0 A g⁻¹) and ultralong cyclability (83.1% retention after 1 000 cycles). Full cells paired with Na₃V₂(PO₄)₃ cathodes achieve 286.4 Wh kg⁻¹ energy density while maintaining operation under extreme mechanical deformation and −20 °C conditions. This work resolves the intrinsic capacity‐ICE trade‐off through spatially resolved edge regulation and interfacial catalysis, establishing a universal framework for designing high‐performance, flexible energy storage systems.