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

Abstract

Abstract 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 NbO 2 Cl 4 polyhedra. Such a unique structure endows the material with a record‐high ionic conductivity of 1.51 mS cm −1 for NaNbOCl 4 , and 7.2 mS cm −1 for NaTaOCl 4 , surpassing the state‐of‐the‐art oxyhalide‐based SSEs. The as‐achieved all‐solid‐state sodium batteries using low‐cost NaNbOCl 4 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.