Regulating the reduction reaction pathways via manipulating the solvation shell and donor number of the solvent in Li-CO₂ chemistry.
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Date
2023
Authors
Zhang, W.
Zhang, F.
Liu, S.
Pang, W.K.
Lin, Z.
Guo, Z.
Chai, L.
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Proceedings of the National Academy of Sciences of the United States of America, 2023; 120(14):1-7
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Wenchao Zhang, Fangli Zhang, Sailin Liu, Wei Kong Pang, Zhang Lin, Zaiping Guo, and Liyuan Chai
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Abstract
Transforming CO2 into valuable chemicals is an inevitable trend in our current society. Among the viable end-uses of CO2, fixing CO2 as carbon or carbonates via Li-CO2 chemistry could be an efficient approach, and promising achievements have been obtained in catalyst design in the past. Even so, the critical role of anions/solvents in the formation of a robust solid electrolyte interphase (SEI) layer on cathodes and the solvation structure have never been investigated. Herein, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in two common solvents with various donor numbers (DN) have been introduced as ideal examples. The results indicate that the cells in dimethyl sulfoxide (DMSO)-based electrolytes with high DN possess a low proportion of solvent-separated ion pairs and contact ion pairs in electrolyte configuration, which are responsible for fast ion diffusion, high ionic conductivity, and small polarization. The 3 M DMSO cell delivered the lowest polarization of 1.3 V compared to all the tetraethylene glycol dimethyl ether (TEGDME)-based cells (about 1.7 V). In addition, the coordination of the O in the TFSI- anion to the central solvated Li+ ion was located at around 2 Å in the concentrated DMSO-based electrolytes, indicating that TFSI- anions could access the primary solvation sheath to form an LiF-rich SEI layer. This deeper understanding of the electrolyte solvent property for SEI formation and buried interface side reactions provides beneficial clues for future Li-CO₂ battery development and electrolyte design.
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© 2023 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).