Galvanic Corrosion of Lithium Metal Anodes in Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries are promising next-generation rechargeable batteries due to their ultrahigh theoretical energy density. However, their cycling lifespan is hindered by the poor stability of Li metal anodes. The main challenge lies in the severe Li polysulfide (LiPS) corrosion on Li metal anodes. Herein, galvanic corrosion induced by LiPSs is identified as the main cause of nonuniform Li deposition and dissolution in working Li-S batteries. Concretely, LiPSs continuously corrode the Li metal anode and thereby increase its electrode potential to different extents according to the corrosion kinetics. The electrical connection of the Li metals with different corrosion kinetics causes galvanic corrosion and consequent selective Li deposition in severely corroded locations. Consequently, spatially heterogeneous LiPS corrosion eventually induces localized Li utilization, uneven Li distribution, and accelerated cell failure. To alleviate the galvanic corrosion, a Li fluoride-rich solid electrolyte interphase is preconstructed to passivate Li metal, suppress LiPS corrosion, and extend the cycling lifespan of Li-S batteries by 57% under harsh working conditions. This work identifies the chemical nature of nonuniform Li deposition following the galvanic corrosion mechanism and highlights the importance of passivating Li metal anodes to realize long-cycling Li-S batteries.