Understanding the effect of cation disorder on the voltage profile of lithium transition-metal oxides

Aziz Abdellahi, Alexander Urban, Stephen Dacek, Gerbrand Ceder*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)

Abstract

Cation disorder is a phenomenon that is becoming increasingly important for the design of high-energy lithium transition metal oxide cathodes (LiMO2) for Li-ion batteries. Disordered Li-excess rocksalts have recently been shown to achieve high reversible capacity, while in operando cation disorder has been observed in a large class of ordered compounds. The voltage slope (dVdxLi) is a critical quantity for the design of cation-disordered rocksalts, as it controls the Li capacity accessible at voltages below the stability limit of the electrolyte (∼4.5-4.7 V). In this study, we develop a lattice model based on first principles to understand and quantify the voltage slope of cation-disordered LiMO2. We show that cation disorder increases the voltage slope of Li transition metal oxides by creating a statistical distribution of transition metal environments around Li sites, as well as by allowing Li occupation of high-voltage tetrahedral sites. We further demonstrate that the voltage slope increase upon disorder is generally smaller for high-voltage transition metals than for low-voltage transition metals due to a more effective screening of Li-M interactions by oxygen electrons. Short-range order in practical disordered compounds is found to further mitigate the voltage slope increase upon disorder. Finally, our analysis shows that the additional high-voltage tetrahedral capacity induced by disorder is smaller in Li-excess compounds than in stoichiometric LiMO2 compounds.

Original languageEnglish
Pages (from-to)5373-5383
Number of pages11
JournalChemistry of Materials
Volume28
Issue number15
Early online date13 Jul 2016
DOIs
Publication statusPublished - 9 Aug 2016

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