Coordination Geometry Reconstruction Mitigates α‑Dihedral Angle Restriction of Polyanionic‐Type Cathodes for Ultrafast Sodium Storage

ABSTRACT Sodium‐ion batteries have attracted extensive attention for large‑scale energy storage owing to the abundance and low cost of sodium resources. However, the near‑coplanar structure geometry of polyanionic‐type cathodes causes in‑plane stress and electrostatic barriers, which lead to blocked Na + transport kinetics and hinder their practical application. Herein, an α‑plane, defined by the transition metal and its coordinating dangling anions, is identified as the critical structural bottleneck for Na + diffusion. By screening and tuning the dangling anions, a coordination geometry reconstruction is achieved that twists the α‑plane into α1‐ and α2‐planes. This twisting behavior breaks α‑plane restriction and relieves the in‑plane stress, thereby lowering the Na + migration barrier. Concurrently, the geometry reconstruction enlarges the Na2‑centered polyhedral volume and increases the Na2 site occupancy from 0.56 to 0.62. Thus, the modified cathode delivers a high reversible capacity of 130 mAh g −1 and outstanding rate capability, with 80% retention at 30 C and 83 mAh g −1 at 50 C. It also exhibits excellent wide‐temperature operability (−40°C to 55°C) and stable full‑cell performance. The universality of this strategy is validated on several polyanionic cathodes. This work reveals the α‑plane as a tunable structural parameter, offering a geometry‑electronic synergy paradigm for high‑power polyanionic‐type cathodes.