A High-Performance All-Solid-State Sodium Battery with a Poly(ethylene oxide)–Na₃Zr₂Si₂PO₁₂ Composite Electrolyte

Rechargeable sodium-based batteries are receiving increasing attention as large-scale energy storage systems, because of the abundant resource and low cost of sodium. The widely used nonaqueous liquid electrolytes in sodium-based batteries pose thermal instability, flammability, and risk of safety issues. The booming research in all-solid-state lithium-based batteries also triggers the interest in pursuing all-solid-state sodium-based batteries toward circumventing the safety issues. This study presents a composite-solid-electrolyte approach, which combines the flexibility of a polymer electrolyte and the high ionic conductivity of a ceramic electrolyte, for the development of all-solid-state sodium batteries. A composite electrolyte comprising a poly(ethylene oxide) matrix, NaClO4 salt, and a ceramic Na+-ion conductor (Na3Zr2Si2PO12) dispersed in it has been fabricated with a facile slurry-casting method. The resulting PEO–NaClO4–Na3Zr2Si2PO12 composite electrolyte shows enhanced Na+-ion conductivity, improved dendrite suppression, reduced interfacial problems, and an elastic feature. With the PEO–NaClO4–Na3Zr2Si2PO12 composite electrolyte, all-solid-state batteries with a sodium–metal anode and a Na2MnFe(CN)6 cathode show stable long-term cycling performance.