Investigation of Ion–Solvent Interactions in Nonaqueous Electrolytes Using in Situ Liquid SIMS
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- Beijing National Laboratory for Molecular Sciences, National Centre for Mass Spectrometry in Beijing, CAS Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China; University of Chinese Academy of Sciences, Beijing 100049, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China; CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, P.O. Box 2735, Beijing 100190, P. R. China
- School of Physics, State Key Laboratory of Crystal Materials and Key Laboratory of Particle Physics and Particle Irradiation (MOE), Shandong University, Jinan, 250100, P. R. China
- Electrochemistry Branch, Power and Energy Division, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783, United States
Ion-solvent interactions in non-aqueous electrolytes are of fundamental interest and practical importance, yet debates regarding ion preferential solvation and coordination numbers persist. In this work, in situ liquid SIMS was used to examine ion-solvent interactions in three representative electrolytes, i.e., lithium hexafluorophosphate (LiPF6) at 1.0 M in ethylene carbonate (EC)-dimethyl carbonate (DMC), and lithium bis(fluorosulfonyl)imide (LiFSI) at both low (1.0 M) and high (4.0 M) concentrations in 1,2-dimethoxyethane (DME). In the positive ion mode, solid molecular evidence strongly supports the preferential solvation of Li+ by EC. Besides, from the negative spectra, we also found that PF6- forms association with EC, which has been neglected by previous studies due to the relatively weak interaction. While in both LiFSI in DME electrolytes, no evidence shows that FSI- is associated with DME. Furthermore, strong salt ion cluster signals were observed in the 1.0 M LiPF6 in EC-DMC electrolyte, suggesting that a significant amount of Li+ ions stay in vicinity of anions. In sharp comparison, weak ion cluster signals were detected in dilute LiFSI in DME electrolyte, suggesting most ions are well separated, in agreement with our molecular dynamics (MD) simulation results. These findings indicate that with virtues of little bias on detecting positive and negative ions and the capability of directly analyzing concentrated electrolytes, in situ liquid SIMS is a powerful tool that can provide key evidence for improved understanding on the ion-solvent interactions in non-aqueous electrolytes. Therefore, we anticipate wide applications of in situ liquid SIMS on investigations of various ion-solvent interactions in the near future.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1436847
- Report Number(s):
- PNNL-SA-131962; 49188; KP1704020
- Journal Information:
- Analytical Chemistry, Vol. 90, Issue 5; ISSN 0003-2700
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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