Electronic structure and properties of lithium-rich complex oxides

TL;DR

This study uses first-principles density-functional theory with the HSE hybrid functional to analyze the atomic and electronic structures of lithium-rich complex oxides, revealing transition-metal dimerization behaviors and insights into their delithiation mechanisms.

Contribution

It provides detailed atomic and electronic structure analysis of lithium-rich complex oxides using advanced hybrid functional calculations, highlighting transition-metal dimerization phenomena.

Findings

Dimerization of transition-metal ions occurs in Li$_2$MoO$_3$.

Ru--Ru dimerization is absent in fully lithiated Li$_2$RuO$_3$ but occurs with lithium vacancies.

Insights into the delithiation mechanism of these materials.

Abstract

Lithium-rich complex transition-metal oxides Li$_2$MoO$_3$, Li$_2$RuO$_3$, Li$_3$RuO$_4$, Li$_3$NbO$_4$, Li$_5$FeO$_4$, Li$_5$MnO$_4$ 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 Li$_2$MoO$_3$, in both fully lithiated and partially delithiated compounds. The Ru--Ru dimerization does not occur in fully lithiated Li$_2$RuO$_3$, in contrast to what is commonly believed; Ru--Ru dimers are, however, found to occur in the presence of 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.