Characterization of lithiation reactions on sulfur surfaces in Li-S batteries

• Applicants: Dr. Pouya Partovi-Azar; Professor Dr. Daniel Sebastiani
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces ; Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446879138

Sulfur has a very high theoretical lithium capacity of 1675 mAh/g. Therefore, sulfur is among the most promising materials for the storage and conversion of renewable energies. However, the available lithium-sulfur batteries suffer from low sulfur utilization and a poor cycle life which limit their applicability. From a chemical point of view, these problems are mainly related to the dissolution of Li-polysulfides (which form during lithiation of the sulfur cathodes) into the electrolyte. This leads to an irreversible capacity fade. In this project, we aim at modeling (quantum mechanical calculations and molecular dynamics simulations) lithiation reactions of alpha-sulfur crystal which is the most stable polymorph of sulfur under standard conditions. Here, several surfaces will be considered, which represent the most common modifications of the crystalline alpha-sulfur. The focus of the project is to analyze the structural changes brought about by lithiation reactions at different sulfur surfaces. This will provide insights into how the cathode morphology can be optimized in order to improve the cycle life of the battery, particularly through suppressing the formation of Li-polysulfide intermediates.In order to validate the theoretically predicted structures, quantum-chemical calculations and molecular dynamics simulations will be combined with the calculation of spectroscopic parameters.

• DFG Programme: Research Grants