Modeling of Magnesium Intercalation into Chevrel Phase Mo6S8: Report on Improved Cell Design

Abstract

A good understanding of the limiting processes in rechargeable magnesium batteries is key to develop novel high-capacity/high-voltage cathode materials. Thereby, the performance of magnesium-ion batteries can strongly depend on the morphology of the intercalation cathode. Moreover, high mass loadings are essential for commercialization. In this work the influence of different mass loadings are studied in addition to the impact of the particle size distribution of the active material. Therefore, a detailed continuum model is developed, which is able to describe the complex intercalation of magnesium into a Chevrel phase (CP) cathode. The model considers the thermodynamics, kinetics and interplay of the two energetically different intercalation sites of Mo6S8, which results from its unique crystal structure, as well as the impact of the desolvation on the electrochemical reactions and possible ion agglomeration. Ideal combinations of mass loading and electrolyte concentration as well as the desired CP particle size are determined for the state-of-the-art magnesium tetrakis(hexafluoroisopropyloxy)borate Mg[B(hfip)4]2 electrolyte.