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Issue 15, 2014
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Defect chemistry in layered transition-metal oxides from screened hybrid density functional calculations

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Abstract

We report a comprehensive first-principles study of the thermodynamics and transport of intrinsic point defects in layered oxide cathode materials LiMO2 (M = Co, Ni), using density-functional theory and the Heyd–Scuseria–Ernzerhof screened hybrid functional. We find that LiCoO2 has a complex defect chemistry; different electronic and ionic defects can exist under different synthesis conditions, and LiCoO2 samples free of cobalt antisite defects can be made under Li-excess (Co-deficient) environments. A defect model for lithium over-stoichiometric LiCoO2 is also proposed, which involves negatively charged lithium antisites and positively charged small (hole) polarons. In LiNiO2, a certain amount of Ni3+ 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 LiMO2 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.

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

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Publication details

The article was received on 08 Feb 2014, accepted on 27 Feb 2014 and first published on 27 Feb 2014


Article type: Paper
DOI: 10.1039/C4TA00673A
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J. Mater. Chem. A, 2014,2, 5224-5235

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

    K. Hoang and M. D. Johannes, J. Mater. Chem. A, 2014, 2, 5224
    DOI: 10.1039/C4TA00673A

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