Nuclear Magnetic Resonance Studies of the Solvation Structures of a High-Performance Nonaqueous Redox Flow Electrolyte

Journal Article · Tue Feb 09 04:00:00 EST 2016 · Journal of Power Sources

DOI:https://doi.org/10.1016/j.jpowsour.2015.12.005· OSTI ID:1331730

Deng, Xuchu; Hu, Mary Y.; Wei, Xiaoliang; Wang, Wei; Mueller, Karl T.; Chen, Zhong; Hu, Jian Z.

Understanding the solvation structures of electrolytes should prove conducive for the development of nonaqueous redox flow batteries that hold considerable potential for future large scale energy storage systems. The utilization of an emerging ionic-derivatived ferrocene compound, ferrocenylmethyl dimethyl ethyl ammonium bis(trifluoromethanesulfonyl)imide (Fc1N112-TFSI), has recently overcome the issue of solubility in the supporting electrolyte. In this work, 13C, 1H and 17O NMR investigations were carried out using electrolyte solutions consisting of Fc1N112-TFSI as the solute and the mixed alkyl carbonate as the solvent. It was observed that the spectra of 13C experience changes of chemical shifts while those of 17O undergo linewidth broadening, indicating interactions between solute and solvent molecules. Quantum chemistry calculations of both molecular structures and chemical shifts (13C, 1H and 17O) are performed for interpreting experimental results and of understanding the detailed solvation structures and molecular dynamics. The results indicate that Fc1N112-TFSI is dissociated at varying degrees in mixed solvent depending on concentrations. Solvent molecules encircle Fc1N112 and TFSI respectively as solvation shells, rapidly exchanging with both bulk solvent and TFSI. Additionally, the solvent with high dielectric constant is more capable of dissociating Fc1N112-TFSI molecules compared with those with low dielectric constant. At saturated concentration, contact ion pairs are formed and the solvent molecules are interacting with the Fc rings rather than interacting with the ionic pendant arm of Fc1N112-TFSI. These studies will contribute to the development of nonaqueous electrolytes of storage systems.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1331730
• Report Number(s): PNNL-SA-113232; 44591; KC0208010
• Journal Information: Journal of Power Sources, Journal Name: Journal of Power Sources Vol. 308; ISSN 0378-7753
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

13C
17O NMR
Electrolyte
non aqueous redox flow battery
Environmental Molecular Sciences Laboratory
molecular dynamics
solvation structures