Cationic Potential‐Driven Surface Reconstruction Enables Stable High‐Voltage Cylindrical Sodium‐Ion Batteries

ABSTRACT Reconciling the trade‐off between high specific capacity and high‐voltage structural stability is the “holy grail” for advanced sodium‐ion batteries. While constructing O3/P2 multiphase heterostructures offers a theoretical solution, preventing stochastic phase distribution while maintaining atomic‐level precision during scalable synthesis remains a formidable hurdle. Herein, a scalable cationic‐potential‐driven surface reconstruction strategy is developed to engineer the interface of O3‐type layered cathodes (O3‐Na 0.9 Mg 0.1 Ni 0.35 Mn 0.35 Ti 0.20 O 2 ). Leveraging a significant ionic potential gradient, the incorporation of a high‐ionic‐potential modifier induces a self‐limiting, nanometric, and Na‐deficient P2 shell that homogeneously encapsulates the O3 core via a coherent epitaxial interface. This robust architecture effectively suppresses lattice oxygen release and transition metal migration while preserving expanded interlayer spacing for rapid Na + kinetics. Consequently, the resulting O3‐core@P2‐shell material delivers excellent cycling stability, retaining 76.3% of its capacity after 400 cycles at 2 C (2.0–4.4 V), vastly outperforming the pristine counterpart (47.8%). Notably, the industrial feasibility (550 g/batch) of this strategy is validated in 1.5 Ah 18650 high‐voltage cylindrical batteries, which maintain 82% capacity after 400 cycles. This work establishes an effective paradigm for harmonizing atomic‐level precision with mass production, unlocking a tangible pathway for high‐energy‐density and long‐life sodium‐ion storage.