Origin of Phase Instability in Battery Cathode Materials From Correlated Electronic Structure Calculations
Eric Isaacs, Columbia University
Li intercalation in certain rechargeable battery cathode materials such as LiFePO4 (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 LiCoO2, 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