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    FT-Raman spectroscopy study of solvent-in-salt electrolytes
    Liumin Suo(索鎏敏), Zheng Fang(方铮), Yong-Sheng Hu(胡勇胜), Liquan Chen(陈立泉)
    Chin. Phys. B, 2016, 25 (1): 016101.   DOI: 10.1088/1674-1056/25/1/016101
    Abstract801)   HTML    PDF (2474KB)(849)      
    Cation-anion interaction with different ratios of salt to solvent is investigated by FT-Raman spectroscopy. The fitting result of the C-N-C bending vibration manifests that the cation-anion coordination structure changes tremendously with the variation of salt concentration. It is well known that lithium-ion transport in ultrahigh salt concentration electrolyte is dramatically different from that in dilute electrolyte, due to high viscosity and strong cation-anion interaction. In ultrahigh salt concentrated “solvent-in-salt” electrolyte (SIS-7#), we found, on one hand, that the cation and anion in the solution mainly formed cation-anion pairs with a high Li+ coordination number ( ≥ 1), including intimate ion pairs (20.1%) and aggregated ion pairs (79.9%), which not only cause low total ionic conductivity but also cause a high lithium transference number (0.73). A possible lithium transport mechanism is proposed: in solvent-in-salt electrolytes, lithium ions' direct movement presumably depends on Li-ion exchange between aggregated ion pairs and solvent molecules, which repeats a dissolving and re-complexing process between different oxygen groups of solvent molecules.
ISSN 1674-1056   CN 11-5639/O4

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