On the influence of nucleation and growth of S8 and Li2S in lithium-sulfur batteries

Abstract

Lithium-sulfur (Li–S) batteries have the potential to outperform state-of-the-art lithium-ion batteries. One of the bottle necks is the limited power density which most conversion based systems have in common. One of the reasons is the formation of solid, insulating charge and discharge products which passivate active surfaces during operation of the cell. In depth knowledge of the formation and dissolution is needed in order to develop counter-measures overcoming the current limitations. In this article we present a continuum model of Li–S batteries including a detailed description of the formation and dissolution of solid particles based on the classical theory of nucleation and growth. By evolving a particle size distribution of the Li2S and S8 phase we are able to provide a qualitative description of the resulting particle morphology as well as their effect on active surface areas and transport processes. Results of the simulations are in agreement with experimental data published in the literature. We perform intensive parameter studies which provide guidelines for the development of surface modifications enabling a spatial control of solid discharge product precipitation resulting in improved battery performance.