Morphologic simulations of lithium-sulfur cathodes using the lattice Boltzmann method

Abstract

Lithium-sulfur (Li-S) batteries show promising characteristics and are a potentially viable post lithium-ion battery technology [1]. To make the technology competitive, improvements to the cell performance and cell design are still needed. Assisting in that, conventional continuum modelling is used, typically limited in one-dimension, to describe, among other characteristics, the charge and discharge behaviour [2]. Their predictions are, however, limited since the driving physical phenomena are dominated by the microstructure. Morphological changes in the microstructure, from surface reactions, dissolution and precipitation, are difficult to capture via modelling, due to their complex interactions. Thus, observed physical phenomena are abstractly modelled [1,3,4] or a single volume element is used as a representative electrode structure [5]. Overall, understanding of the complete complex interaction remains elusive. They are, however, important to model, such that future developments can mitigate their impact on cell performance and cyclability. On the mesoscopic level, computational simulations can more readily provide insight. Many conventional methods are outperformed by computationally efficient, yet detailed, lattice Boltzmann methods (LBM). An LBM model was developed to simulate the relevant physicochemical phenomena, including polysulfide diffusion, electrochemical effects, as well as dissolution and precipitation. In the present work, three-dimensional porous cathodes, fully resolved in sub-micron resolution, were simulated and studied. The simulations successfully capture precipitates growth, and were applied to investigate the resulting pore clogging and surface passivation, with their cell performance impacts. The morphological impact in porous cathodes due to physicochemical phenomena are studied at the pore scale with the novel LBM approach. It is shown to reproduce the complex interactions in Li-S batteries. The current study gives further insight into the pore-scale behaviour and will help with design and optimisation of Li-S battery systems. [1] Richter, R. et al. (2021) ACS Appl. Energy Mater., 4(3), pp. 2365-2376. [2] Kumaresan, K. et al. (2008) J. Electrochem. Soc., 155(8), p. A576. [3] Danner, T. and Latz, A. (2019) Electrochim. Acta, 322, p. 134719. [4] Ren, Y.X. et al. (2016) J. of Power Sources, 336, pp. 115-125. [5] Mistry, A. and Mukherjee, P.P. (2017) J. Phys. Chem. C, 121(47), pp. 26256-26264.