Coupled Engineering of Short-/Long-Range Disorder in Oxyhalides Unlocks Benchmark Sodium Superionic Conductor

Oxyhalide-based sodium solid electrolytes (SSEs) distinguished by exceptionally high-voltage electrochemical stability and mechanical compliance, have commanded substantial research interest, but their practical implementation remains constrained by sub-optimal ionic conductivity (IC). Here, we demonstrate a concerted manipulation of short- and long-range structural disorder that substantially enhances Na⁺ transport in oxychlorides. Combined experimental characterization and machine learning molecular dynamics simulations unveil that, the sub-second quenching disrupts short-range ordering by fragmenting the original Nb─Cl coordination and inducing more Nb─O bonding, which triggers the distortion and connectivity breakage of NbO₂Cl₄ polyhedra. Such a unique structure endows the material with a record-high ionic conductivity of 1.51 mS cm^-1 for NaNbOCl₄, and 7.2 mS cm^-1 for NaTaOCl₄, surpassing the state-of-the-art oxyhalide-based SSEs. The as-achieved all-solid-state sodium batteries using low-cost NaNbOCl₄ as the electrolyte manifest remarkable capacity retention (82.61%) at 4 V (versus Na⁺/Na) after 250 cycles at a 0.5C, highlighting exceptional cycling stability and rate performance. This work establishes a coupled short- and long-range disorder engineering strategy that unlocks unprecedented ionic conductivity in solid electrolytes, advancing next-generation sustainable energy storage solutions.