Toward High-Capacity Li–S Solid-State Batteries: The Role of Partial Ionic Transport in the Catholyte

To address the challenges of tortuous partial ionic transport and chemomechanical failure due to the large volumetric changes of sulfur during all-solid-state battery cycling, we evaluate a hybrid electrolyte composed of the lithium chloride argyrodite Li6PS5Cl (LPSCl) and an ionic liquid-based lithium liquid electrolyte (ILE) in the cathode composite of Li–S half-cells. We confirm the stability of the LPSCl/ILE interface by coupling Raman and impedance spectroscopy measurements. Charge–discharge curves show a capacity improvement for the hybrid cells (1364 ± 151 mAh·g–1), compared to 904 ± 186 mAh·g–1 for pristine cells. Transport measurements quantify an increase in the partial ionic conductivity of proxy cathode layers from 0.2 to 0.4 mS·cm–1 in hybrid cells. Taken together, the use of the ILE increases the partial ionic transport and access to sulfur which results in higher and more stable discharge capacities.