Premature deposition of lithium polysulfide in lithium-sulfur batteries

Abstract

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.