Stabilized Lithium–Metal Surface in a Polysulfide-Rich Environment of Lithium–Sulfur Batteries

Lithium–metal anode degradation is one of the major challenges of lithium–sulfur (Li–S) batteries, hindering their practical utility as next-generation rechargeable battery chemistry. The polysulfide migration and shuttling associated with Li–S batteries can induce heterogeneities of the lithium–metal surface because it causes passivation by bulk insulating Li₂S particles/electrolyte decomposition products on a lithium–metal surface. This promotes lithium dendrite formation and leads to poor lithium cycling efficiency with complicated lithium surface chemistry. Here, we show copper acetate as a surface stabilizer for lithium metal in a polysulfide-rich environment of Li–S batteries. The lithium surface is protected from parasitic reactions with the organic electrolyte and the migrating polysulfides by an in situ chemical formation of a passivation film consisting of mainly Li₂S/Li₂S₂/CuS/Cu₂S and electrolyte decomposition products. This passivation film also suppresses lithium dendrite formation by controlling the lithium deposition sites, leading to a stabilized lithium surface characterized by a dendrite-free morphology and improved surface chemistry