Regensburg 2022 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 2: Computational Materials Modelling: Energy Materials

MM 2.1: Talk

Monday, September 5, 2022, 10:15–10:30, H44

Importance of electronic correlations in exploring the exotic phase diagram of Li ion battery cathodes — •Hrishit Banerjee^1,2, Clare P. Grey¹, and Andrew J. Morris² — ¹Department of Chemistry, University of Cambridge, UK — ²School of Metallurgy and Materials, University of Birmingham, UK.

We explore electronic and magnetic states of layered Li_xMnO₂, a well known cathode material for Li ion batteries, as a function of states of charge x, using ab-initio dynamical mean-field theory. Projecting onto low-energy subspace of Mn 3d states, and solving a multi-impurity problem, we find that an antiferromagnetic insulating state appears in LiMnO₂, with a moderate Néel temperature in agreement with experimental studies. As the system is delithiated we find various exotic states emerge such as ferrimagnetic correlated metals, charge ordered ferromagnetic correlated metals with large quasiparticle weight, ferromagnetic metals with small quasiparticle weight, as a function of various states of delithiation of LiMnO₂ and finally an antiferromagnetic insulator for the fully delithiated state, which is albeit unstable. At moderate states of charge, x=0.67-0.33, a mix of +3/+4 formal oxidation states of Mn is observed, while its overall nominal oxidation state changes from +3 in LiMnO₂ to +4 in MnO₂. In all these cases the high-spin state emerges as the most likely state. The quasiparticle peaks in the correlated metallic states could be attributed to polaronic states. We explore the temperature vs. state of charge phase diagram and conclude that the state of charge is a key ingredient for the emergence of the exotic correlated phase transitions in this material.