High‐Entropy Solid‐State Na‐Ion Conductor for Stable Sodium‐Metal Batteries

Abstract

AbstractSolid‐state sodium‐metal batteries (SSBs) hold great promise for their merits in low‐cost, high energy density, and safety. However, developing solid electrolyte (SE) materials for SSBs with high performance is still a great challenge. In this study, high‐entropy Na4.9Sm0.3Y0.2Gd0.2La0.1Al0.1Zr0.1Si4O12 was synthesized at comparatively low sintering temperature of 950 °C with high room‐temperature ionic conductivity of 6.7×10−4 S cm−1 and a low activation energy of 0.22 eV. More importantly, the Na symmetric cells using high‐entropy SE show a high critical current density of 0.6 mA cm−2, outstanding rate performance with fairly flat potential profiles at 0.5 mA cm−2 and steady cycling over 700 h under 0.1 mA cm−2. Solid‐state Na3V2(PO4)3||high‐entropy SE||Na batteries are further assembled manifesting a desirable cycling stability with almost no capacity decay after 600 cycles and high Columbic efficiency over 99.9 %. The findings present opportunities for the design of high‐entropy Na‐ion conductors toward the development of SSBs.