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Issue 1, 2020
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Entropymetry for non-destructive structural analysis of LiCoO2 cathodes

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Upon the emergence of electric vehicles, accurate and non-destructive monitoring of battery electrode materials during operation is highly desirable. Structural degradation of widely adopted intercalation-based materials constitutes the origin of their capacity fading and safety deterioration. Here, we introduce entropymetry to monitor the structural changes of LiCoO2 (LCO) and its nickel (Ni)-doped derivatives at different states of charge (SOC). While simple lithium (Li) extraction on charging gives a monotonic decline of entropy change (ΔS) based on progressive vacancy occupation over Li sites, the presence of a monoclinic intermediate phase inverses the slope of the ΔS profile to reflect its limited atomic configurations with high ordering. Furthermore, Ni-doping lessens the ordering of the monoclinic phase, decreasing the height amplitude of ΔS profile in the monoclinic regime. The increased disorder by Ni-doping enhances the stability of the lattice framework, extending the cycle life with high voltage cut-off (4.6 V vs. Li/Li+). The present study highlights entropymetry as a unique, non-destructive tool in monitoring the structural ordering and relevant degradation of electrode materials in lithium-ion batteries.

Graphical abstract: Entropymetry for non-destructive structural analysis of LiCoO2 cathodes

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Article information

13 Sep 2019
04 Dec 2019
First published
04 Dec 2019

Energy Environ. Sci., 2020,13, 286-296
Article type

Entropymetry for non-destructive structural analysis of LiCoO2 cathodes

H. J. Kim, Y. Park, Y. Kwon, J. Shin, Y. Kim, H. Ahn, R. Yazami and J. W. Choi, Energy Environ. Sci., 2020, 13, 286
DOI: 10.1039/C9EE02964H

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