Mechanochemically Prepared Highly Conductive Na2.88Sb0.88W0.12S4-NaI Composite Electrolytes for All-Solid-State Sodium Battery (Supporting Information)

Solid electrolytes with high ionic conductivity, high formability, and high electrochemical properties are required to improve the performance of all-solid-state sodium batteries. In this study, we focus on a combination of Na2.88Sb0.88W0.12S4 and NaI for preparing composite electrolytes Na2.88Sb0.88W0.12S4·xNaI, and investigate their crystal structures, microstructures, and electrochemical properties. NaI is uniformly dispersed in the composites without forming a solid solution with Na2.88Sb0.88W0.12S4. Na2.88Sb0.88W0.12S4·0.5NaI shows a high ionic conductivity of 3.6 × 10−2 S cm−1 after sintering at 275 °C for only 1.5 h. The charge-discharge characteristics of all-solid-state cells using the Na2.88Sb0.88W0.12S4·xNaI composite are also improved.