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XPS-Surface Analysis of SEI Layers on Li-Ion Cathodes: Part II. SEI-Composition and Formation inside Composite Electrodes

Schulz, Natalia and Hausbrand, René and Wittich, Carolin and Dimesso, Lucangelo and Jaegermann, Wolfram (2018):
XPS-Surface Analysis of SEI Layers on Li-Ion Cathodes: Part II. SEI-Composition and Formation inside Composite Electrodes.
In: Journal of The Electrochemical Society, Electrochemical Society Publishing, pp. A833-A846, 165, (5), ISSN 0013-4651,
DOI: 10.1149/2.0881803jes,
[Online-Edition: https://doi.org/10.1149/2.0881803jes],
[Article]

Abstract

In this contribution, we investigate the solid electrolyte interface (SEI) layers’ composition depending on the spatial location within LiCoO2 composite cathode of a commercial Li-Ion battery. The surface chemistry is analyzed by X-ray photoelectron spectroscopy (XPS), and possible SEI morphology and the differences in the SEI composition are discussed in detail. Finally, related SEI formation reactions and the controlling processes are characterized as a function of the depth in the composite cathode. The SEI is assumed to be a multi-component, layered system. The inorganic inner SEI layer consists of LiF and degraded LiCoO2, confirmed as Co(II,III)xOy(OH)z. The much thicker outer SEI layer is mainly composed of a poly-organic network with a significantly smaller portion of, presumably, randomly distributed macroscopic LixPOyFz/LixPOy-1Fz+1 and LixPOy domains. A higher content of Co(II,III)xOy(OH)z, and especially of the poly-organic deposit, was found on the outer cathode surface compared to the analysis position near the current collector, resulting in a 4 nm thicker SEI and indicating a stronger decomposition of LiCoO2 and solvents. These differences in SEI composition and thickness are attributed to a significantly higher cathode polarization at the outer electrode surface during cell operation leading to a higher rate of electrochemically induced decomposition reactions.

Item Type: Article
Erschienen: 2018
Creators: Schulz, Natalia and Hausbrand, René and Wittich, Carolin and Dimesso, Lucangelo and Jaegermann, Wolfram
Title: XPS-Surface Analysis of SEI Layers on Li-Ion Cathodes: Part II. SEI-Composition and Formation inside Composite Electrodes
Language: English
Abstract:

In this contribution, we investigate the solid electrolyte interface (SEI) layers’ composition depending on the spatial location within LiCoO2 composite cathode of a commercial Li-Ion battery. The surface chemistry is analyzed by X-ray photoelectron spectroscopy (XPS), and possible SEI morphology and the differences in the SEI composition are discussed in detail. Finally, related SEI formation reactions and the controlling processes are characterized as a function of the depth in the composite cathode. The SEI is assumed to be a multi-component, layered system. The inorganic inner SEI layer consists of LiF and degraded LiCoO2, confirmed as Co(II,III)xOy(OH)z. The much thicker outer SEI layer is mainly composed of a poly-organic network with a significantly smaller portion of, presumably, randomly distributed macroscopic LixPOyFz/LixPOy-1Fz+1 and LixPOy domains. A higher content of Co(II,III)xOy(OH)z, and especially of the poly-organic deposit, was found on the outer cathode surface compared to the analysis position near the current collector, resulting in a 4 nm thicker SEI and indicating a stronger decomposition of LiCoO2 and solvents. These differences in SEI composition and thickness are attributed to a significantly higher cathode polarization at the outer electrode surface during cell operation leading to a higher rate of electrochemically induced decomposition reactions.

Journal or Publication Title: Journal of The Electrochemical Society
Volume: 165
Number: 5
Publisher: Electrochemical Society Publishing
Uncontrolled Keywords: Commercial Li-ion battery, SEI-composition/thickness and formation inside composite electrodes, XPS-surface analysis of the cathodic SEI
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Surface Science
Profile Areas
Profile Areas > Thermo-Fluids & Interfaces
Date Deposited: 06 Jun 2018 10:00
DOI: 10.1149/2.0881803jes
Official URL: https://doi.org/10.1149/2.0881803jes
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