Hybrid density functional investigations of Li2MSiO4 (M = Mn, Fe and Co) cathode materials

Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional investigations have been performed to study the structural properties, electronic structures and Li intercalation voltages of Li2MSiO4 (M = Mn, Fe and Co) compounds. For comparison, GGA and GGA+U calculations are also carried out. GGA is shown to yield good predictions for the structural properties, but seriously underestimates the band gaps and intercalation voltages for Li2MSiO4. By introducing appropriate U parameters, GGA+U can predict very accurate intercalation voltages and improve the description of the band gaps over GGA. HSE06 can also reach relatively accurate intercalation voltages of Li2MSiO4, though not as accurate as GGA+U, and generally yield larger band gaps than both the GGA and GGA+U methods, by introducing the Hartree–Fock exchange to treat the self-interaction errors. Moreover, HSE06 is shown to predict more accurate lattice parameters than GGA+U for all Li2MSiO4 compounds. In general, hybrid functional may provide good alternatives to GGA+U in predicting the battery-related properties.