Polysulfide reduction and Li2S phase formation in the presence of lithium metal and solid electrolyte interphase layer

Lithium sulfur battery is an attractive next generation technology that can meet many demands of modern society. Unfortunately, the lithium sulfur battery faces unique issues related to the polysulfide shuttle effect, that is due to reduction products dissolving in the electrolyte and their subsequent reduction on the lithium metal electrode. This adds further problems to the already challenging needs of understanding and engineering a solid electrolyte interphase (SEI) layer with desired properties. One of the most important SEI properties is its passivation of lithium metal which is critically important to the overall battery performance. Passivation is difficult to measure experimentally without the influence of many factors. This study reports an investigation of the reduction of the intermediate Li2S8 over lithium already passivated with Li2O, Li2CO3, LiOH, LiF and Li2S along with exploration of Li2S8 reduction over pristine lithium nanoclusters using first principles computational models. Significant formation of Li2S phase nucleation is found to stabilize the reduction products of the Li2S8. The formation of Li2S is explored in-depth with lithium nanocluster-based models determining a 2 V potential increase for the reduction of polysulfides due to the formation of Li2S. This investigation demonstrates passivation effects of important SEI components including Li2S. [Display omitted] •Passivation layer effectiveness depends on electrolyte interfacial components.•Favorability of Li2S formation demonstrated over a variety of passivation layers.•Li2S phase nucleation stabilizes the reduction products of Li2S8.