Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 13: Materials for Storage and Conversion of Energy (joint session MM/KFM)

KFM 13.2: Vortrag

Dienstag, 6. September 2022, 10:30–10:45, H46

Oxygen Hole Formation Controls Stability in LiNiO₂ Cathodes: DFT Studies of Oxygen Loss and Singlet Oxygen Formation in Li-Ion Batteries — •Annalena Genreith-Schriever^1,3, Hrishit Banerjee^1,2,3, Clare P. Grey^1,3, and Andrew J. Morris^2,3 — ¹Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom — ²School of Metallurgy and Materials, University of Birmingham, Birmingham, United Kingdom — ³The Faraday Institution, Harwell Science and Innovation Campus, Didcot, United Kingdom

Ni-rich cathode materials achieve both high voltages and capacities in Li-ion batteries but are prone to structural instabilities and oxygen loss via the formation of singlet oxygen. Using ab initio molecular dynamics simulations, we observe spontaneous O₂ loss from the (012) surface of delithiated LiNiO₂, singlet oxygen forming in the process. We find that the origin of the instability lies in the pronounced oxidation of O during delithiation, i.e., O plays a central role in Ni-O redox in LiNiO₂, as analysed with density-functional theory and dynamical mean-field theory calculations based on maximally localised Wannier functions. The O₂ loss route observed here consists of 2 surface O^.− radicals combining to form a peroxide ion, which is oxidised to O₂, leaving behind 2 O vacancies and 2 O²⁻ ions: effectively 4 O^.− radicals disproportionate to O₂ and 2 O²⁻ ions. Singlet oxygen formation is caused by the singlet ground state of the peroxide ion, with spin conservation dictating the preferential release of ¹O₂.