Oxygen hole formation controls stability in LiNiO2 cathodes

•Dominant O-redox contributions to Ni–O redox in LiNiO2 and oxygen holes•Excellent agreement between predicted experimental X-ray absorption spectra•Reaction pathway of evolution via peroxide intermediate•Spin conservation ground-state singlet causes release High Ni content layered transition metal oxides enable lithium-ion batteries with high operating voltages but are prone degradation. Electrolyte oxidation results as the material is delithiated, along surface reconstructions cathodes. Mitigating these phenomena requires a comprehensive understanding relevant processes. We here propose that major source instabilities arises from oxide anion on delithiation: “Ni” processes occur whereby essentially all charge removed O ions directly bound Ni. Our simulations show O⋅− radicals formed during combine form ions, disproportionate molecular anions. The intermediate governs spin conservation. This bulk/surface reaction mechanisms provides insights into how maximize performance lifetime future Ni-rich cathode materials achieve both capacities structural loss. origin instability lies pronounced for LiNiO2, NiO2, rock salt NiO, density functional theory dynamical mean-field calculations based maximally localized Wannier functions yield state ca. +2, varying −2 (NiO), −1.5 (LiNiO2), −1 (NiO2). Calculated spectroscopy K K-edge spectra agree well spectra. Using ab initio dynamics simulations, we observe loss (012) delithiated two combining ion, ion being oxidized O2, leaving behind vacancies O2− ions. Preferential 1O2 dictated ground exhibit excellent high-voltage materials, enabling energy densities, widely used current electric vehicle batteries.1Xiao P. Shi T. Huang W. Ceder G. Understanding densified phases Ni-Rich compounds.ACS Energy Lett. 2019; 4: 811-818https://doi.org/10.1021/acsenergylett.9b00122Crossref Scopus (44) Google Scholar,2Li Erickson E.M. Manthiram A. 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By contrast, 1A other hand, significantly even further NiO. electronic (DOS) 1B) ferromagnetic 0 Of particular interest just below Fermi energy, electrons material. can estimated DOS spherical harmonics, local orbitals. indicate (red) only small extent (blue) contributions. (yellow isosurface 1C) confirms weaker eg (the highlighted 1B). Due near separating charges, also analyzed more advanced Wannierization Kohn-Sham case LNO, nominal eg∗ highest occupied (orbitals shown yellow green 1C), bands strongly hybridized. band structure S2 supplemental information) very close requiring included correlated subspace Wannierization. If explicitly d-p centers 1C; identifies orientation lobes, allowing plotted relative global coordinate system). while NiO contains separated, making sufficient information additional S3). calculated occupancies middle set) larger values than (by 0.5–0.8 e 0.3–0.9 O) confirm trends seen states; again, nearly identical whereas vary substantially, then whether artifact, themselves static treatment correlation, lowers potentially causing unphysical energy. performed address this, account correlations obtain integrating basis. spectral 1D case, resembling temperatures above Curie temperature, becomes paramagnetic, 1E, half (red line). band-gap paramagnetic good findings temperatures.39Reynaud Ghorayeb A.M. Ksari Menguy Stepanov Delmas On