Stabilizing electrode/electrolyte interface in Li-S batteries using liquid/solid Li2S-P2S5 hybrid electrolyte

Abstract

Lithium-sulfur (Li-S) batteries using hybrid electrolytes, which are composed of solid-electrolyte separator and liquid-electrolyte wetting agent, can effectively eliminate the polysulfide shuttling issue. The cycling performance of these hybrid batteries is mainly limited by the interfacial stability between the solid and liquid electrolytes. This work detailly discusses the influence of the composition on the stability of a highly ionic conductive sulfide solid electrolyte, lithium thiophosphate xLi2S·(100–x)P2S5 (70 ≤ x ≤ 75, SSEs), in hybrid Li-S batteries. It reveals that the solid electrolyte with low Li2S content favors the formation of a SEI layer containing Li3PS4 and therefore improves the interfacial stability with Li anode, while the one with high Li2S content behaves more stable with the cathode. Using 75Li2S·25P2S5 as the separator, a hybrid battery runs more than 400 cycles with a low capacity fading rate of 0.14%/cycle. This is benefited from the elimination of polysulfide shutting and especially the excellent compatibility of the sulfide solid electrolyte with both anode and cathode.