Polymer-Rich Composite Electrolytes for All-Solid-State Li–S Cells

Polymer-rich composite electrolytes with lithium bis(fluorosulfonyl)imide/poly(ethylene oxide) (LiFSI/PEO) containing either Li-ion conducting glass ceramic (LICGC) or inorganic Al2O3 fillers are investigated in all-solid-state Li–S cells. In the presence of the fillers, the ionic conductivity of the composite polymer electrolytes (CPEs) does not increase compared to the plain LiFSI/PEO electrolyte at various tested temperatures. The CPE with Al2O3 fillers improves the stability of the Li/electrolyte interface, while the Li–S cell with a LICGC-based CPE delivers high sulfur utilization of 1111 mAh g–1 and areal capacity of 1.14 mAh cm–2. In particular, the cell performance gets further enhanced when combining these two CPEs (Li | Al2O3–CPE/LICGC–CPE | S), reaching a capacity of 518 mAh g–1 and 0.53 mAh cm–2 with Coulombic efficiency higher than 99% at the end of 50 cycles at 70 °C. This study shows that the CPEs can be promising electrolyte candidates to develop safe and high-performance all-solid-state Li–S batteries.