Modelling disorder in Mg-ion battery cathode materials

University of Northumbria in Newcastle (UK), Centre for Doctoral Training in Renewable Energy Northeast Universities

A problem with developing new materials for battery cathodes is that while the fully charged material may fill the requirements for an ideal cathode (e.g. thermodynamic stability, ion conduction), the actual performance during use may be lower than expected. For example, in the high voltage spinel cathode LiNi0.5Mn1.5O4 (LNMO) the disordering of Ni/Mn results in the formation of Mn2+ ions that dissolve into the electrolyte. Knowledge of atomic disorder in these materials, and how this relates to charge transport and chemical stability, is crucial for optimising their performance during operation.

We will combine quantum chemistry, statistical techniques and high-performance computing to predict the materials performance of chalcogenide spinel battery cathode materials. The chalcogenide spinels show good Mg-ion mobility, with a diffusion activation energy <650 meV; initial studies have identified candidate cathode materials (MgB2S4 with B = Cr, Ti, Mn). Mixed S/Se spinels provide the possibility of tuning optical and electronic properties via anion stoichiometry and disorder, a currently unexplored research area.

In year one we will use density functional theory to predict the compounds that will optimise cathode performance. In years two/three we will develop a cluster expansion model to consider i) the impact of anion disorder on performance (charge/discharge rates, cell voltage and chemical stability) and ii) whether disorder can be utilised for further optimisation. In the final year, to enable comparison with experiment, we will predict the vibrational spectra of the disordered materials. We will use best practice in research software engineering to ensure that the methods and codes developed can be used by the wider research community (see, for example, our package: dx.doi.org/10.21105/joss.00797). This project builds on our expertise modelling defects and vibrations in complex energy materials and complements a growing programme of electrochemical research at Northumbria.

This project is supervised by Dr Lucy Whalley (https://lucydot.github.io). For informal queries, please contact [email protected].

The application closing date is 24 January 2021 and interviews will take place in mid-February 2021. Please note that interviews, should they be arranged, will be online rather than in person due to COVID-19. The project start date is 1st October 2021.