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On the origin of reversible and irreversible reactions in LiNixCo(1-x)/2Mn(1-x)/2O2

DOI: 10.1149/1945-7111/ac3c21 DOI Help

Authors: Karin Kleiner (University of Münster) , Claire A. Murray (Diamond Light Source) , Cristina Grosu (Research Centre Jülich) , Bixian Ying (University of Münster) , Martin Winter (University of Münster) , Peter Nagel (Karlsruher Institut fur Technologie) , Stefan Schuppler (Karlsruher Institut fur Technologie) , Michael Merz (Karlsruher Institut fur Technologie)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The Electrochemical Society

State: Published (Approved)
Published: November 2021
Diamond Proposal Number(s): 19772 , 22706

Open Access Open Access

Abstract: Bond formation and breakage is crucial upon energy storage in lithium transition metal oxides (LiMeO2, Me = Ni, Co, Mn), i.e., the conventional cathode materials in Li ion batteries. Near-edge x-ray absorption finestructure spectroscopy (NEXAFS) of the Me L and O K edge performed upon the first discharge of LiNixCo(1-x)/2Mn(1-x)/2O2 (x = 0.33: NCM111, x = 0.6: NCM622, x = 0.8: NCM811) in combination with charge transfer multiplet calculations provide unambiguous experimental evidence that redox reactions in NCMs proceed via a reversible oxidation of Ni associated with the formation of covalent bonds to O neighbors, and not, as widely assumed, via pure cationic or more recently discussed, pure anionic redox processes. Correlating these electronic changes with crystallographic data using operando synchrotron X-ray powder diffraction shows that the amount of ionic Ni limits the reversible capacity - at states of charge where all ionic Ni is oxidized (above 155 mAh/g), the lattice parameters collapse, and irreversible reactions are observed. Yet the covalence of the Ni-O bonds also triggers the electronic structure and thus the operation potential of the cathodes.

Diamond Keywords: Batteries; Lithium-ion; Electric Vehicles

Subject Areas: Materials, Chemistry, Energy

Instruments: I11-High Resolution Powder Diffraction

Added On: 29/11/2021 09:35


Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Diffraction X-ray Powder Diffraction