Electronic Structure and Properties of Lithium-Rich Complex Oxides

Lithium-rich complex transition-metal oxides Li2MoO3, Li2RuO3, Li3RuO4, Li3NbO4, Li5FeO4, and Li5MnO4 and their derivatives are of interest for high-capacity battery electrodes. Here, we report a first-principles density-functional theory study of the atomic and electronic structure of these materials using the Heyd–Scuseria–Ernzerhof (HSE) screened hybrid functional which treats all orbitals in the materials on equal footing. Dimerization of the transition-metal ions is found to occur in layered Li2MoO3, in both fully lithiated and partially delithiated compounds. The Ru–Ru dimerization does not occur in fully lithiated Li2RuO3, in contrast to what is commonly believed; Ru–Ru dimers are, however, found to occur in the presence of neutral lithium vacancies caused by lithium loss during synthesis and/or lithium removal during use. We also analyze the electronic structure of the complex oxides and discuss the delithiation mechanism in these battery electrode materials.