van der Waals Interactions in Layered Lithium Cobalt Oxides
journal contributionposted on 20.08.2015, 00:00 by Muratahan Aykol, Soo Kim, C. Wolverton
The role of van der Waals (vdW) interactions in density functional theory (DFT) + U calculations of the layered lithium-ion battery cathode LixCoO2 (x = 0–1) is investigated using (i) dispersion corrections in the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation functional, (ii) vdW density functionals, and (iii) the Bayesian error estimation functional with vdW correlation. We find that combining vdW corrections or functionals with DFT+U can yield lithiation voltages, relative stabilities, and structural properties that are in much better agreement with experiments for the phases O1-CoO2, O3-CoO2, layered-Li0.5CoO2, spinel-Li0.5CoO2, and LiCoO2 than using DFT+U or vdW-inclusive methods alone or using the hybrid Heyd–Scuseria–Ernzerhof functional. Contributions of vdW interactions to the lithiation voltages are estimated to have a similar magnitude with that of applying a typical U in the range 2–4 eV for cobalt, each accounting for 5–10% of calculated voltages relative to PBE. Relative stabilities of O1 and O3-CoO2 as well as layered- and spinel-Li0.5CoO2 are correctly predicted with vdW-inclusive methods combined with the +U correction.