Sandwich-structured PEO-based composite solid-state electrolytes for lithium–sulfur batteries†

Solid-state lithium–sulfur batteries (SSLSBs) employing poly(ethylene oxide) (PEO)-based electrolytes have garnered significant attention as a promising energy storage system due to their high specific energy, straightforward manufacturability and cost-effectiveness. However, the inherent low ionic conductivity of PEO-based electrolytes at room temperature and sluggish conversion kinetics of dissolved lithium polysulfides (LiPS) result in significant active material depletion through irreversible LiPS accumulation, ultimately hindering their practical application. Therefore, composite solid-state electrolytes by incorporating inorganic fillers into the PEO matrix have been proposed to address these challenges. In this work, PEO–TiO₂ composite solid-state electrolytes with a sandwich-structure containing inorganic oxide fillers have been prepared for lithium–sulfur batteries by a simple and efficient solution casting method. The incorporation of TiO₂ inhibits the shuttle effect of Li₂S_x species, reduces the glass transition temperature of PEO and increases the amount of amorphous portion, thus improving the ionic conductivity and mechanical strength. The ionic conductivity of the CSE-5 electrolyte is 5.04 × 10⁻⁴ S cm⁻¹ at 60 °C, and the Li//CSE-5//Li cell could be stably cycled for 2400 h at a current density of 0.1 mA cm⁻². The initial discharge specific capacity of the Li//CSE-5//S@C solid-state cell is 1054 mA h g⁻¹ at 0.1C, and it still can remain at 703 mA h g⁻¹ after 100 cycles.