Relevance of the Electrode and Cell Design for the Performance of Li-S Batteries - Continuum Modeling as a Tool for Battery Development

Abstract

Lithium-Sulfur (Li-S) batteries are one of the most promising technologies for next generation energy storage. Known drawbacks of Li-S batteries are reduced coulombic efficiency and rapid self-discharge due to the polysulfide shuttle [1]. Several mitigation strategies to reduce the polysulfide shuttle effect have been developed for Li-S batteries, resulting in significant improvements in sulfur composite materials. The electrode and cell design aspect has received less attention in the literature, but is equally important to enable the development of commercial Li-S batteries. Virtual Material Design is a generic term summarizing versatile and efficient tools for material development and has been used extensively for the design of electrode architectures of Li-ion batteries [2]. Corresponding tools with a similar level of complexity and predictive power have yet to be developed for Li-S batteries [3-5]. In this contribution, we will provide an overview of our recent developments in the field of continuum models for Li-S and Li-SPAN batteries. Special emphasis will be placed on the effect of material morphology and electrode microstructure on the operation and performance of Li-S batteries. A major challenge is the development and coupling of models on the relevant time and length scales. Using the Lattice Boltzmann Method (LBM), our simulations are able to provide insight into the pore scale processes of carbon electrode materials. The LBM model has been specifically developed to simulate the relevant physico-chemical phenomena, including polysulfide diffusion, as well as solid phase dissolution and heterogeneous precipitation. The simulations are used to investigate the effect of pore clogging and surface passivation. The detailed submodels are intended to inform cell-level simulations allowing optimization of cell performance. Therefore, our simulation tools couple the relevant scales for material and cell design and provide guidelines for the development of Li-S batteries.