Localization of micron-scale lithium polysulfide-rich phases causes anode heterogeneity in lean-electrolyte lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries offer exceptionally high gravimetric energy density, yet their cycling stability remains limited by uneven Li anode reaction. Here, we reveal that the emergence of a micron-scale morphological heterogeneity in the Li anode originates from the localized formation of a micron-scale lithium polysulfide (LiPS)-rich phase in the electrolyte. Notably, the chemical composition of the LiPS-rich phase contains minimal amounts of anions such as FSI− or NO3−, which are typically responsible for forming stable solid-electrolyte interphase (SEI); this deficiency obstructs the formation of Li2O-containing SEI layer, resulting in the localized dendritic Li morphology. We further demonstrate that fragmenting the LiPS-rich phase reduces its locality, suppresses anode heterogeneity, and significantly improves cycling stability.