Mechanochemically Prepared Highly Conductive Na_2.88Sb_0.88W_0.12S₄-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 Na_2.88Sb_0.88W_0.12S₄ and NaI for preparing composite electrolytes Na_2.88Sb_0.88W_0.12S₄·xNaI, and investigate their crystal structures, microstructures, and electrochemical properties. NaI is uniformly dispersed in the composites without forming a solid solution with Na_2.88Sb_0.88W_0.12S₄. Na_2.88Sb_0.88W_0.12S₄·0.5NaI 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 Na_2.88Sb_0.88W_0.12S₄·xNaI composite are also improved.