Refined DFT plus U method for computation of layered oxide cathode materials

Transition metal oxides are widely used as cathode materials in rechargeable Li-ion batteries. Here we test the performance of the parameter-free DFT+U method for predicting the structural parameters and electronic configuration of three materials: LiCoO2, LiNiO2 and mixed transition metal Li1.2Ni0.19Co0.19Mn0.42O2 compounds. The obtained lattice parameters and band gaps are consistent with the more computationally demanding hybrid functionals and SCAN methods. We emphasize the importance of using a realistic representation of the d orbitals to obtain the correct occupancy of these states, which are highly overestimated when the widely used atomic orbitals are applied as projectors. The applied here Wannier-type projectors result in correct occupancies, allowing for a decisive assignment of the oxidation states of cations and an improved description of the electronic structure. The applied scheme enhances predictive capabilities of the DFT+U method for computation of electrochemically active compounds.