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Thickness estimation of interface films formed on Li1−xCoO2 electrodes by hard X-ray photoelectron spectroscopy |
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| Authors: | Yu Takanashi Yuki OrikasaMasato Mogi Masatsugu OishiHaruno Murayama Kenji SatoHisao Yamashige Daiko TakamatsuTakahiro Fujimoto Hajime TanidaHajime Arai Toshiaki OhtaEiichiro Matsubara Yoshiharu UchimotoZempachi Ogumi |
| Affiliation: | a Center for Advanced Science and Innovation, Uji Campus Gokashou, 611-0011, Japan b SR Center, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577, Japan c Department of Materials Science & Engineering, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan d Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan |
| Abstract: | Solid electrolyte interface (SEI) films formed on Li1−xCoO2 electrodes were observed with hard X-ray photoelectron spectroscopy (HX-PES). This paper particularly focuses on film thickness estimation using HX-PES with theoretical calculation. The validity of the calculation was proven by experiments using model SEI films. The native film formed on a LiCoO2 composite electrode was estimated to be LiF with its thickness of 5 nm. Formation of Co (II) species on top of LiCoO2 was also indicated. Storage of the electrode at 60 °C brought about considerable film growth (30-40 nm) with carbonate compounds formation. SEI film changes during charging of the LiCoO2 electrode were also examined. The main component in the film was deduced to be LiF or a kind of fluorite, with its thickness decreased during charging. The SEI formation mechanisms are also elucidated. |
| Keywords: | Lithium ion batteries SEI HX-PES |
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