Electronic Properties & Intercalation Voltages of Li-Ion Battery Cathode Materials - Iurii Timrov

Abstract: The design of novel cathode materials for Li-ion batteries would greatly benefit from accurate first-principles predictions of structural, electronic, and magnetic properties as well as intercalation voltages in compounds containing transition-metal elements. For such systems, density-functional theory (DFT) with standard (semi-)local exchange-correlation functionals is of limited use as it often fails due to strong self-interaction errors that are especially relevant in the partially filled d shells. In this talk I will present a detailed comparative study of the phospho-olivine cathode materials LixMnPO4, LixFePO4, and mixed-TM LixMn0.5$Fe0.5$PO4 (x=0, 0.25, 0.5, 0.75, 1) using four electronic-structure methods: DFT, DFT+U, DFT+U+V, and HSE06 [1]. We show that DFT+U+V [2], with onsite U and intersite V Hubbard parameters determined from first-principles and self-consistently with respect to the structural parameters by means of density-functional perturbation theory (linear response) [3-5], provides the most accurate description of the electronic structure of these challenging compounds. In particular, we demonstrate that DFT+U+V displays very clearly "digital'' changes in oxidation states of the transition-metal ions in all compounds, including the mixed-valence phases occurring at intermediate Li concentrations, leading to voltages in remarkable agreement with experiments. We show that the inclusion of intersite Hubbard interactions is essential for the accurate prediction of thermodynamic quantities, balancing the drive for localization induced by the onsite U with intersite V orbital hybridizations. At variance with other methods, DFT+U+V describes accurately such localization-hybridization interplay, and thus opens the door for the study of other complex cathode materials, e.g. spinel LixMn2O4 and LixMn1.5Ni0.5O4 [6].

[1] I. Timrov, F. Aquilante, M. Cococcioni, N. Marzari, PRX Energy, accepted (2022), arXiv:2203.15732.
[2] V. L. Campo Jr, M. Cococcioni, J. Phys.: COndens. Matter 22, 055602 (2010).
[3] I. Timrov, N. Marzari, M. Cococcioni, Phys. Rev. B 98, 085127 (2018).
[4] I. Timrov, N. Marzari, M. Cococcioni, Phys. Rev. B 103, 045141 (2021).
[5] I. Timrov, N. Marzari, M. Cococcioni, Comput. Phys. Commun. 279, 108455 (2022).
[6] I. Timrov, M. Kotiuga, N. Marzari, in preparation.

[HARIHARANDHANASEKARAN-mv]

Iurii Timrov, good DFT framework for beginner, Thanks a lot.

[nrb]

Looking forward to your publication and the computational details of the DFT calculations of the spinel materials.