Reaction Mechanism of Li2MnO3 Electrodes in an All-Solid-State Thin-Film Battery Analyzed by Operando Hard X-ray Photoelectron Spectroscopy

Kazuhiro Hikima; Keisuke Shimizu; Hisao Kiuchi; Yoyo Hinuma; Kota Suzuki; Masaaki Hirayama; Eiichiro Matsubara; Ryoji Kanno

doi:10.1021/jacs.1c09087

Reaction Mechanism of Li₂MnO₃ Electrodes in an All-Solid-State Thin-Film Battery Analyzed by Operando Hard X-ray Photoelectron Spectroscopy

J Am Chem Soc. 2022 Jan 12;144(1):236-247. doi: 10.1021/jacs.1c09087. Epub 2021 Dec 27.

Authors

Kazuhiro Hikima^{1

2}, Keisuke Shimizu³, Hisao Kiuchi⁴, Yoyo Hinuma^{3

5}, Kota Suzuki^{1

3}, Masaaki Hirayama^{1

3}, Eiichiro Matsubara⁶, Ryoji Kanno^{1

3}

Affiliations

¹ Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
² Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580, Japan.
³ Research Center for All-Solid-State Battery, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
⁴ Office of Society-Academia Collaboration for Innovation, Kyoto University, Kyoto 611-0011, Japan.
⁵ Research Institute of Electrochemical Energy, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31, Midorigaoka, Ikeda, Osaka 563-8577, Japan.
⁶ Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan.

PMID: 34957828
DOI: 10.1021/jacs.1c09087

Abstract

Li₂MnO₃ is a promising cathode candidate for Li-ion batteries because of its high discharge capacity; however, its reaction mechanism during cycling has not been sufficiently explicated. Observations of Mn and O binding energy shifts in operando hard X-ray photoelectron spectroscopy measurements enabled us to determine the charge-compensation mechanism of Li₂MnO₃. The O 1s peak splits at an early stage during the first charge, and the concentration of lower-valence O changes reversibly with cycling, indicating the formation of a low-valence O species that intrinsically participates in the redox reaction. The O 1s peak-splitting behavior, which indicates the number of valences of O in Li₂MnO₃, is supported by the computational results for an O3 to O1 structural transition. This is in agreement with the results of our previous study, wherein we confirmed this O3 to O1 transition based on in situ surface X-ray diffraction analysis, X-ray photoelectron spectroscopy, and first-principles formation energy calculations.