Oxygen hole formation controls stability in LiNiO2 cathodes

Annalena R. Genreith-Schriever, Hrishit Banerjee, Ashok S. Menon, Euan N. Bassey, Louis F.j. Piper, Clare P. Grey*, Andrew J. Morris*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Ni-rich lithium-ion cathode materials achieve both high voltages and capacities but are prone to structural instabilities and oxygen loss. The origin of the instability lies in the pronounced oxidation of O during delithiation: for LiNiO2, NiO2, and the rock salt NiO, density functional theory and dynamical mean-field theory calculations based on maximally localized Wannier functions yield a Ni charge state of ca. +2, with O varying between −2 (NiO), −1.5 (LiNiO2), and −1 (NiO2). Calculated X-ray spectroscopy Ni K and O K-edge spectra agree well with experimental spectra. Using ab initio molecular dynamics simulations, we observe loss of oxygen from the (012) surface of delithiated LiNiO2, two surface O⋅− radicals combining to form a peroxide ion, and the peroxide ion being oxidized to form O2, leaving behind two O vacancies and two O2− ions. Preferential release of 1O2 is dictated via the singlet ground state of the peroxide ion and spin conservation.
Original languageEnglish
Pages (from-to)1623-1640
JournalJoule
Volume7
Issue number7
DOIs
Publication statusPublished - 19 Jul 2023

Keywords

  • LiNiO2
  • oxygen loss
  • O redox
  • singlet oxygen
  • DFT
  • DMFT
  • AIMD simulations
  • XAS
  • water oxidation

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