Journal of Surface Analysis
Online ISSN : 1347-8400
Print ISSN : 1341-1756
ISSN-L : 1341-1756
Paper
Investigation of charge compensation mechanism of LiNiCoMnO2 Positive Electrode during Initial Charge Process by Operando Soft X-ray XAFS Measurement
Koji Nakanishi Koji KitadaYoshiyuki MoritaHajime TanidaYusuke TamenoriKazuki TsurutaToyonari YajiYuki OrikasaKentaro YamamotoYoshiharu UchimotoZempachi OgumiToshiaki Ohta
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2018 Volume 25 Issue 2 Pages 90-102

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Abstract
The charge compensation mechanism of a LiNiCoMnO2 (NCM333) positive electrode, used in a commercial lithium ion battery, was investigated by operando soft X-ray absorption fine structure (SX-XAFS) spectroscopy. The SX-XAFS spectral analyses recorded with the partial fluorescence yield revealed followings. The pristine NCM333 consisted of Ni2+, Co3+, Mn4+ and O2-. During charge, Ni2+ was oxidized to Ni4+, and Mn4+ did not change at all. O2- was oxidized by creating O 2p holes during charge, which caused an appearance of a new pre-edge peak in the O K-edge XAFS spectra. Co L3-edge peak shifted to higher energy, indicating that Co3+ is oxidized during charge. Hence nickel ions play the central role of the charge compensation in the NCM333 positive electrode, and Mn ions are not contribute to the charge compensation. O ions and Co ions are not as large as Ni ions, but they are also contribute to the charge compensation.
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© 2018 by The Surface Analysis Society of Japan
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