Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
CORRECTED PROOF
Capacity Deterioration Analysis of Li-ion Battery Cathode Li[Ni1/3Co1/3Mn1/3]O2 Material by Soft X-ray Absorption Spectroscopy
Tetsuo NAGAMIToyokazu NOMOTOHarue SUGIYAMAShoji TACHIKIRen SAKAMOTOToshiaki OHTA
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JOURNALS OPEN ACCESS Advance online publication

Article ID: 21-00031

CORRECTED PROOF: May 18, 2021
UNCORRECTED PROOF: April 17, 2021
ACCEPTED MANUSCRIPT: April 03, 2021
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Abstract

We report detailed studies of capacity deterioration mechanism of Li[Ni1/3Co1/3Mn1/3]O2 (NCM) cathode after several numbers of cycling with the voltage range of 3.0–4.1 V/cell at 85 °C and after storage at charged states (3.7, 4.0 and 4.1 V/cell) at 70 °C for 150 days by soft X-ray absorption spectroscopy (XAS) and X-ray powder diffraction (XRD). Morphological changes were also observed by scanning electron microscopy (SEM).

Ni, Co, and Mn L-edge XAS analysis revealed that Ni, a part of Co and no Mn were active for charge/discharge in the above-described voltage range. Only Ni L-edge XAS exhibited significant spectral changes by capacity deterioration. Ni mean valence at discharged state increased with the capacity deterioration rate of each sample either after storage test or after cycling test, which corresponds to the increase of the lattice constant ratio c/a, obtained by the XRD analysis. Chemically decomposed species on the NCM particle surfaces increased with capacity deterioration. Many cracks were observed in the SEM image of the sample after extended cycling. Crack generation, formation of the cubic spinel phase on the surface and deposition of decomposed species on the particles hamper the Li ion insertion to the cathode material at discharge, which is responsible for capacity deterioration. The crack generation is enhanced in case of the cycling test, while the deposition of decomposed species and the formation of the cubic spinel phase on the surface are more enhanced in case of the storage test.

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© The Author(s) 2021. Published by ECSJ.

This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium provided the original work is properly cited. [DOI: 10.5796/electrochemistry.21-00031].
http://creativecommons.org/licenses/by/4.0/
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