Highly Stable Hybrid Lithium–Sulfur Batteries Using Sulfide Electrolyte Separators with Minimized Leachate Levels

Hybrid lithium–sulfur batteries utilizing a sulfide solid electrolyte separator exhibit high specific capacity and excellent redox kinetics. Moreover, the sulfide separator can block material exchange between the cathode and anode, eliminating shuttle effect occurrence and enhancing battery cycling stability. However, the long-term cycling stability of these hybrid batteries is still compromised due to the gradual release of soluble thiophosphate from the sulfide separator. Here, we minimized the release of the leachate from the separator through the implementation of a soaking treatment of the separator in an ether solution of lithium salt prior to battery assembly. Consequently, reducing the release of the leachate inhibits the growth of lithium dendrites on the anode, thereby lowering the risk of battery short-circuits. It also suppresses the formation of a passivation layer on the cathode associated with redox products of the leachate, thus ensuring rapid redox kinetics of the cathode. Benefited from this presoaked sulfide separator, the hybrid lithium–sulfur batteries maintained a high discharge capacity of 810 mA·h·g–1 and a high secondary discharge plateau voltage of 2.04 V after 500 cycles.