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.