Thiometallate-mediated polysulfide chemistry and lithium stabilization for stable anode-free lithium-sulfur batteries

Achieving long life with energy-dense lithium-sulfur (Li-S) batteries requires improving the reversibility of Li plating and stripping. The formation of soluble polysulfide intermediates, which degrade the Li-metal anode by reducing into insulating Li2S and Li2S2, create a unique problem in the Li-S system. Here, we show that the introduction of ammonium tetrathiomolybdate ((NH4)2MoS4) and ammonium tetrathiotungstate ((NH4)2WS4) as cathode additives stabilize Li deposition by (1) complexing with polysulfides and acting as a polysulfide buffer, thereby mitigating the corrosive shuttle effect and (2) forming a stable and passivating Mo/W-enriched solid-electrolyte interphase (SEI) layer on the Li surface. The resulting stabilization of Li electrodeposition enables a nearly 3-fold improvement in the cycle of anode-free full cells. This work demonstrates that the rich chemistry between thiometallate complexes and polysulfide species can be exploited to solve the formidable challenges with achieving a realistic Li-S battery and, more generally, metal-chalcogen batteries.