Prismatic Na-Ion Coordination in the Sulfide-Chloride Solid Electrolyte Enables Fast Na-Ion Transport

Abstract

Designing halide solid electrolytes with high ionic conductivity and robust electrochemical stability is crucial for advanced all-solid-state sodium-ion batteries. Currently, most sodium-based halide conductors suffer from the limited ionic conductivity. In this work, we report a new fast-ion-conductive sulfide-chloride solid electrolyte Na1.0Zr0.5Al0.5Cl3.5S0.5 (NZACS), where highly conductive prismatic Na-ion coordination units were developed by Al3+/S2–-triggered glass–ceramic evolution of the P21/n phase. The resulting material exhibits a high ionic conductivity of 3.2 × 10–4 S cm–1 at room temperature and 1.0 × 10–3 S cm–1 at 60 °C, and a low activation energy of 0.35 eV. Moreover, the excellent formability and high electrochemical oxidative stability of the NZACS solid electrolyte ensure a tight junction between the electrolyte-electrode interface, thus delivering superior cycling stability and rate capability, 93% capacity retention after 150 cycles at 0.1C and 80% capacity retention after 800 cycles at 1C. This study establishes a new paradigm of precise local-structure engineering for the development of high-performance solid electrolytes.