Anode-less Solid-State Li–S Batteries Enabled by Fe-Stabilized Polysulfides

Anode-less solid-state lithium–sulfur batteries (SSLSBs) with lithium sulfide (Li2S) as the cathode promise a high energy density and ease of manufacturing. However, Li2S is plagued by poor conductivity, sluggish activation kinetics, and a poor cycle life. Here, we report an FeCl3-activated Li2S (FLS) cathode with solid-state polysulfide intermediates generated through a redox reaction between FeCl3 and Li2S. This strategy is shown to boost the electrical conductivity of Li2S by 7 orders of magnitude and lower the activation barrier. During cycling, Fe plays a significant role in stabilizing the highly active polysulfide species, contributing to the exceptional electrochemical performance. The FLS cathode achieves 80% capacity retention over 500 cycles with >99% Li2S utilization. Furthermore, a Li-metal-free (anode-less) full cell retained over 80% of its initial capacity after 240 cycles. This work underscores the promise of leveraging Fe-stabilized polysulfides in enabling high-energy, long-lasting, solid-state Li–S batteries.