Origin of Phase Instability in Battery Cathode Materials From Correlated Electronic Structure Calculations

Eric Isaacs, Columbia University

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Li intercalation in certain rechargeable battery cathode materials such as LiFePO<sub>4</sub> (LFP) occurs via a two-phase (phase separated) process, which can significantly hinder charge/discharge rate. The phase separation in LFP is not predicted by density functional theory (DFT), but it is captured by DFT plus Hubbard U (DFT+U) calculations, suggesting the significant role of electronic correlations. [F. Zhou et al., Phys. Rev. B 69, 201101 (2004).] In order to understand and improve phase stability of correlated battery cathode materials, here we investigate phase-separating LFP and phase-stable LiCoO<sub>2</sub>, using DFT plus dynamical mean-field theory (DFT+DMFT) using the Hartree-Fock solution to the DMFT impurity problem. We present the relationship between different formation energy contributions and on-site Coulomb repulsion energy. Furthermore, we illustrate how electronic band filling, magnetism, hybridization between p and d orbitals, and charge and orbital ordering impact the phase stability of such systems.

Abstract Author(s): Eric B. Isaacs, Chris A. Marianetti