Interfacial reactions between graphite electrodes and propylene carbonate-based solutions: Electrolyte-concentration dependence of electrochemical lithium intercalation reaction |
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Authors: | Soon-Ki Jeong Minoru Inaba Yasutoshi Iriyama Takeshi Abe Zempachi Ogumi |
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Affiliation: | 1. Department of Chemical Engineering, Soonchunhyang University, Asan, Chungnam 336-745, Republic of Korea;2. Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan;3. Department of Energy & Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan |
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Abstract: | This study examines the electrochemical reactions occurring at graphite negative electrodes of lithium-ion batteries in a propylene carbonate (PC) electrolyte that contains different concentrations of lithium salts such as, LiClO4, LiPF6 or LiN(SO2C2F5)2. The electrode reactions are significantly affected by the electrolyte concentration. In concentrated solutions, lithium ions are reversibly intercalated within the graphite to form stage 1 lithium–graphite intercalation compounds (Li–GICs), regardless of the lithium salt used. On the other hand, electrolyte decomposition and exfoliation of the graphene layers occur continuously in the low-concentration range. In situ analysis with atomic force microscopy reveals that a thin film (thickness of ∼8 nm) forms on the graphite surface in a concentrated solution, e.g., 3.27 mol kg−1 LiN(SO2C2F5)2/PC, after the first potential cycle between 2.9 and 0 V versus Li+/Li. There is no evidence of the co-intercalation of solvent molecules in the concentrated solution. |
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Keywords: | Graphite negative electrode Propylene carbonate Lithium intercalation Atomic force microscopy Surface film |
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