Lithium-Sulfur Batteries

8 Lithium–Sulfur Model Development

Teng Zhang¹, Monica Marinescu² and Gregory J. Offer²

¹ University of Surrey, Department of Mechanical Engineering Sciences, 388 Stag Hill, Guildford, GU2 7XH, UK

² Imperial College, Department of Mechanical Engineering, London, UK

8.1 Introduction

Modeling Li–S cells presents many challenges due to their complex mechanisms including electrochemical reactions, ionic transport, and morphology change. So far, Li–S modeling research is still at the early stages and no single Li–S model has been able to capture all aspects of a Li–S cell's complex behaviors. A useful Li–S model should at least retrieve the key features during charge and discharge qualitatively. In terms of physical mechanisms, a basic Li–S model should consider the following:

• Cathode electrochemistry : the reduction and oxidation of sulfur is a multistep process involving multiple intermediate polysulfide species. Chemical reactions also occur among different polysulfides in the form of disproportionation and association reactions [1,2]. Owing to the complexity of the electrochemical and chemical reactions involved, Li–S models employ simplified, linear reaction mechanisms involving a few representative polysulfide species. The thermodynamics of the cathodic reactions are typically described with the Nernst equation, whereas the charge‐transfer kinetics is modeled using the Butler–Volmer equation.
• Precipitation and dissolution : the formation and dissolution ...