A physicochemical model-based digital twin of Li–S batteries to elucidate the effects of cathode microstructure and evaluate different microstructures

Abstract

We are presenting a physicochemical model-based digital twin of Li–S batteries which involves continuum, volume-averaged ion transport equations including species migration, dissolution and precipitation, and electrochemical reactions, where the cathode microstructure is taken into account in terms of pore size distribution, hierarchy and tortuosity. The digital twin is applied in simulations of galvanostatic charge-discharge of a Li–S cell, exploring three types of cathode microstructure, activated carbon, graphene and hollow particles, two different amounts of sulphur and two different cathode coating thicknesses. Very good agreement is observed between predictions and experimental data in all case-studies. The best cathode is 70 wt% sulphur in host with porous hollow particles which trap the polysulphides from migrating to the anode. The simulations reveal that other reasons for low sulphur utilization, preventing the Li–S cell from reaching its theoretical capacity, are undissolved sulphur in micropores and sulphur leaching to macropores, especially in the cathode region near the separator, and reprecipitating.