Thermophysical Flame Retardancy Composite Electrolyte for Room-Temperature-Operating High-Energy Density Solid-State Sodium Metal Batteries

This work presents a flexible PVDF–NaClO4–NaNO3–Mg(OH)2-based solid-state electrolyte for sodium metal batteries that operates at room temperature, prepared via a solution casting method. The electrolyte features a poly(vinylidene fluoride) (PVDF) host polymer matrix combined with an inorganic filler Mg(OH)2, a flame-retardant agent, and dual sodium salts to enhance ion transport. The composite polymer electrolyte (CPE) exhibited a high ionic conductivity of 0.58 × 10–3 S cm–1 and a low activation energy of 0.15 eV. For a practical demonstration, a constructed PWC||PNM-3||Na cell achieved a discharge capacity of 148.0 mAh g–1 at 0.1C and a high energy density of 503.99 Wh kg–1.