Defect chemistry in layered transition-metal oxides from screened hybrid density functional calculations

Abstract

We report a comprehensive first-principles study of the thermodynamics and transport of intrinsic point defects in layered oxide cathode materials LiMO${}_2$ (M=Co, Ni), using density-functional theory and the Heyd-Scuseria-Ernzerhof screened hybrid functional. We find that LiCoO${}_2$ has a complex defect chemistry; different electronic and ionic defects can exist under different synthesis conditions, and LiCoO${}_2$ samples free of cobalt antisite defects can be made under Li-excess (Co-deficient) environments. A defect model for lithium over-stoichiometric LiCoO${}_2$ is also proposed, which involves negatively charged lithium antisites and positively charged small (hole) polarons. In LiNiO${}_2$, a certain amount of Ni${}^{3+}$ ions undergo charge disproportionation and the concentration of nickel ions in the lithium layers is high. Tuning the synthesis conditions may reduce the nickel antisites but would not remove the charge disproportionation. In addition, we find that LiMO${}_2$ cannot be doped $n$- or $p$-type; the electronic conduction occurs via hopping of small polarons and the ionic conduction occurs via migration of lithium vacancies, either through a monovacancy or divacancy mechanism, depending on the vacancy concentration.

13 pages, 6 figures

References in corpus (3)

• Magnetism and structure of LixCoO2 and comparison to NaxCoO2
• Mechanisms for the decomposition and dehydrogenation of Li amide/imide
• LiH as a Li${}^{+}$ and H${}^{-}$ ion provider

Cited by in corpus (7)

• Understanding the electronic and ionic conduction and lithium over-stoichiometry in LiMn${}_2$O${}_4$ spinel
• Defect physics, delithiation mechanism, and electronic and ionic conduction in layered lithium manganese oxide cathode materials
• Successes and failures of Hubbard-corrected density functional theory: The case of Mg doped LiCoO${}_2$
• Polaron formation, native defects, and electronic conduction in metal tungstates
• Doping Li-rich cathode material Li${}_2$MnO${}_3$: Interplay between lattice site preference, electronic structure, and delithiation mechanism
• First-principles theory of doping in layered oxide electrode materials
• The role of native defects in the transport of charge and mass and the decomposition of Li${}_4$BN${}_3$H${}_{10}$