中国物理B ›› 2016, Vol. 25 ›› Issue (1): 16101-016101.doi: 10.1088/1674-1056/25/1/016101

• SPECIAL TOPIC—Fundamental physics research in lithium batteries • 上一篇    下一篇

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)   

  1. Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 收稿日期:2015-05-26 修回日期:2015-08-15 出版日期:2016-01-05 发布日期:2016-01-05
  • 通讯作者: Liumin Suo E-mail:suoliumin@gmail.com
  • 基金资助:
    Project supported by the National Basic Research Program of China (Grant No. 2014CB932300), the National Natural Science Foundation of China (Grant Nos. 51222210, 51472268, and 11234013), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09010300).

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)   

  1. Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • Received:2015-05-26 Revised:2015-08-15 Online:2016-01-05 Published:2016-01-05
  • Contact: Liumin Suo E-mail:suoliumin@gmail.com
  • Supported by:
    Project supported by the National Basic Research Program of China (Grant No. 2014CB932300), the National Natural Science Foundation of China (Grant Nos. 51222210, 51472268, and 11234013), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09010300).

摘要: 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.

关键词: FT-Raman spectroscopy, lithium-ion batteries, electrolyte, solvent-in-salt electrolytes

Abstract: 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.

Key words: FT-Raman spectroscopy, lithium-ion batteries, electrolyte, solvent-in-salt electrolytes

中图分类号:  (Techniques for structure determination)

  • 61.05.-a
61.20.Gy (Theory and models of liquid structure) 61.20.Qg (Structure of associated liquids: electrolytes, molten salts, etc.)