Conversion-type batteries with electrode materials partially dissolved in a liquid electrolyte exhibit high specific capacity and excellent redox kinetics, but currently poor stability due to the shuttle effect. Using a solid-electrolyte separator to block the mass exchange between the cathode and the anode can eliminate the shuttle effect. A stable interface between the solid-electrolyte separator and the liquid electrolyte is essential for the battery performance. Here, we demonstrate that a stable interface with low interfacial resistance and limited side reactions can be formed between the sulfide solid-electrolyte β-Li3PS4 and the widely used ether-based liquid electrolytes, under both reduction and oxidation conditions, due to the rapid formation of an effective protective layer of ether-solvated Li3PS4 at the sulfide/liquid electrolyte interface. This discovery has inspired the design of a β-Li3PS4-coated solid-electrolyte Li7P3S11 separator with a simultaneously high ion-conduction ability and good interfacial stability with the liquid electrolyte, so that hybrid lithium-sulfur (Li-S) batteries with this composite separator conserve a high discharge capacity of 1047 mA h g-1 and a high second discharge plateau of 2.06 V after 150 cycles.
Keywords: hybrid electrolytes; interfacial stability; liquid-phase synthesis; lithium thiophosphates; lithium−sulfur batteries.