Premature deposition of lithium polysulfide in lithium–sulfur batteries

Lithium–sulfur (Li−S) batteries have attracted extensive attention due to ultrahigh theoretical energy density of 2600 Wh kg−1. Liquid–solid deposition from dissolved lithium polysulfides (LiPSs) to solid lithium sulfide (Li2S) largely determines the actual battery performances. Herein, a premature liquid–solid deposition process of LiPSs is revealed at higher thermodynamic potential than Li2S deposition in Li–S batteries. The premature solid deposit exhibits higher chemical state and hemispherical morphology in comparison with Li2S, and the premature deposition process is slower in kinetics and higher in deposition dimension. Accordingly, a supersaturation deposition mechanism is proposed to rationalize the above findings based on thermodynamic simulation. This work demonstrates a unique premature liquid–solid deposition process of Li–S batteries.