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

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