Sodium–Sulfur Batteries Enabled by a Protected Inorganic/Organic Hybrid Solid Electrolyte

Sodium–sulfur batteries are promising energy-dense, cost-effective energy storage systems. However, a low-resistance solid electrolyte is necessary to stabilize the sodium anode. While sulfide-based solid electrolytes offer high ionic conductivity, they suffer from chemical reactivity when in contact with sodium metal and are mechanically brittle. This paper implements an in situ cross-linking reaction to embed sodium-ion-conducting sodium thioantimonate in a protective polymer host. The enhanced flexibility enables the formation of a thin but transferable hybrid electrolyte film (30 μm in thickness, 65 ohm cm2 room temperature resistance). Owing to the chemical bonding between sodium thioantimonate and the polymer, the hybrid electrolyte maintains a stable interface with sodium when cycling at a current density of 0.5 mA cm–2. The hybrid solid electrolyte protects the sodium metal from corroding with polysulfide-containing liquid electrolyte and enables the stable operation of a sodium–sulfur battery using a nonencapsulated sulfur cathode for 90 cycles.