Protein Cage Inspired Bridge-Island Effect Enables Low-Temperature Targeted Self-Assembly of Hierarchical Hollow Polyanionic Cathodes for Sodium-Ion Batteries.

Achieving targeted morphological control over polyanionic cathodes under mild conditions remains a critical challenge. Drawing inspiration from the self-assembly of protein cages, we propose an ionic weaving strategy for the low-temperature fabrication of hierarchical hollow Na₃V₂O₂(PO₄)₂F (NVOPF) cathodes. By introducing low-cost monosodium glutamate as a template precursor, the derived glutamate species self-assemble into hollow micellar soft templates under the coordination bridging of VO²⁺ ions. Subsequently, PO₄ ^3-, Na⁺, and F^- ions are electrostatically attracted to VO²⁺-anchored microdomains, triggering island-like nucleation. The VO²⁺-mediated bridge-island effect facilitates both the construction of microscale hollow soft templates and the localized nucleation of nanocrystals, thereby enabling micro/nano hierarchical hollow morphology control of NVOPF under mild conditions. Moreover, the self-assembly mechanism underlying hollow soft template formation is systematically elucidated for the first time through a combination of soft matter probing techniques, including fluorescence microscopy and negative staining, supported by density functional theory calculations and all-atom molecular dynamics simulations. The resulting NVOPF-based cathode exhibits ultra-stable high-rate cycling and excellent low-temperature durability. This work establishes a new paradigm that integrates supramolecular self-assembly with metal-ion coordination chemistry for the rational design of fast-charging polyanionic cathode materials.