A three dimensional kinetic Monte Carlo model for simulating the carbon/sulfur mesostructural evolutions of discharging lithium sulfur batteries

Abstract

The carbon/sulfur composite cathodes of lithium sulfur batteries undergo mesostructural evolutions during discharge due to the dissolution/precipitation reactions of solid sulfur and Li2S. Furthermore, the cathode design and discharge parameters also impact the mesostructural evolutions of carbon/sulfur composites. In order to compare and study these mesostructural evolutions, we have developed a novel three dimensional kinetic Monte Carlo (kMC) model based on an algorithm called Variable Step Size Method (VSSM). Our model describes mechanisms such as dissolution of solid sulfur, reactions and diffusions of different polysulfides and electrodeposition of Li2S. The initial carbon/sulfur mesostructure used in our model is created based on its desired structural and geometric properties using an in silico method. In this paper, we present the theoretical development of our kMC model and demonstrate its capabilities using discharge simulations of a model carbon/sulfur mesostructure under two different rates (C-rates) namely C/2 and 2C. Furthermore, we also present the impact of initial loading on the 2C discharge simulation.