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

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_0.9Mg_0.1Ni_0.35Mn_0.35Ti_0.20O₂). 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.