Electrochemical Performance and Structures of Chromium and Molybdenum-Doped ϵ-Li_xVOPO₄Predicted as Promising Cathodes for Next Generation Lithium-Ion Batteries

We report here the predicted structural and electrochemical characteristics of ϵ-LixVOPO4 doped with 25% Cr or Mo using density functional theory (DFT) calculations. We predict the charging potentials as a function of lithiation and the DFT energetics for various phases of LixVOPO4 from x = 0 to 2.5. We further highlight the electron localization function (ELF) and magnetic spin distributions over the lithiation cycle. For Cr-LixVOPO4, we find an intermediate phase at x = 1.5, and for Mo-LixVOPO4, we find two intermediate phases at x = 0.5 and 1.5. We predict a 50% increase in lithium capacity for both doped and undoped systems with reasonable voltaic behavior and additionally find that the spins on undoped and Cr-doped LixVOPO4 stay ferromagnetic throughout the entire lithiation cycle. Overall, we predict an increase in the electrochemical and structural capabilities with Cr and Mo dopants, suggesting Cr and Mo-doped ϵ-LiVOPO4 as potentially promising cathodes for next generation lithium-ion batteries.