A Novel Continuum Model and Simulation Study Of Magnesium-Sulfur Battery With Sulfurized Polyacrylonitrile (SPAN) Cathodes

Abstract

Magnesium-Sulfur (Mg-S) batteries are considered as promising contender for the next generation batteries due to its set of advantages: high gravimetric energy density (3.837 mAh/cm3), its abundancy, absence of scarce elements such as nickel or cobalt, and its reduced tendency to dendrite formation [1]. Unfortunately, sulfur-based batteries suffer from low coulombic efficiency and fast self-discharge due to the polysulfide shuttle. Several mitigation strategies to reduce the polysulfide shuttle effect have been developed and transferred to Mg-S batteries [2]. One of the promising approaches is to covalently bind the sulfur to a polymer backbone. Long cycle life and high specific capacities have been demonstrated for Sulfurated Poly(acrylonitrile) (SPAN) cathodes for Mg-SPAN batteries [3,4].

We present a novel continuum model for Mg-SPAN battery, which includes both red/ox reactions of sulfur covalently bound to the polymeric backbone of SPAN, species transport, and electrochemical reactions of the polysulfides in solution. The model parameters are extracted from structural and electrochemical characterization, such that the measured discharge curves are reproduced. In our study, we discovered that for a case of denser electrode, the capacity faded quite significantly as the tortuosity value increases and hinders the diffusion process. This shows that the morphology study of electrode essential for upscaling an SPAN cathode based battery. In collaboration with our experimental partners, we aim on providing more insights into the degradation mechanisms and limiting factors for battery performance, which are able to guide new developments for Mg-SPAN batteries.