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Journal Article High-rate cycling performance and surface analysis of LiNi1-Co/2Mn/2O2 (x=2/3, 0.4, 0.2) cathode materials
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Authors
Jimin Oh, Jumi Kim, Yong Min Lee, Dong Ok Shin, Ju Young Kim, Young-Gi Lee, Kwang Man Kim
Issue Date
2019-01
Citation
Materials Chemistry and Physics, v.222, pp.1-10
ISSN
0254-0584
Publisher
Elsevier
Language
English
Type
Journal Article
DOI
https://dx.doi.org/10.1016/j.matchemphys.2018.09.076
Abstract
The electrochemical performance of layered LiNi1-xCox/2Mnx/2O2 cathode materials (x = 2/3, 0.4, 0.2; so-called NCM333, NCM622, NCM811) in 1.0 M LiPF6-dissolved conventional carbonate-based electrolyte during formation at a 0.1 C-rate and consequent cycling at a 1.0 C-rate is measured and considered together with the results of morphology observation, impedance spectroscopy, and surface analysis. X-ray photoelectron spectroscopy (XPS) is carried out on the surface of the cathode materials before and after formation and cycling to investigate the effects of solid electrolyte interphase (SEI) formation on the electrochemical performance. As the Ni content increases, the initial specific capacity increases but the capacity retention ratio decreases. High-rate cycling overrides the SEI formation on the NCM surfaces, but NCM622 suffers great changes in the SEI components with a thick layer resulting in large interfacial resistance. It is also proved that NCM811 shows significant dissolution and accumulation of Ni species on the surface, contributing structural degradation and leading to fast capacity fading.