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Aqueous interphase formed by CO2 brings electrolytes back to salt-in-water regime

Nature Chemistry volume 13, pages 1061–1069 (2021)Cite this article

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Abstract

Super-concentrated water-in-salt electrolytes make high-voltage aqueous batteries possible, but at the expense of high cost and several adverse effects, including high viscosity, low conductivity and slow kinetics. Here, we observe a concentration-dependent association between CO2 and TFSI anions in water that reaches maximum strength at 5 mol kg−1 LiTFSI. This TFSI–CO2 complex and its reduction chemistry allow us to decouple the interphasial responsibility of an aqueous electrolyte from its bulk properties, hence making high-voltage aqueous Li-ion batteries practical in dilute salt-in-water electrolytes. The CO2/salt-in-water electrolyte not only inherits the wide electrochemical stability window and non-flammability from water-in-salt electrolytes but also successfully circumvents the numerous disadvantages induced by excessive salt. This work represents a deviation from the water-in-salt pathway that not only benefits the development of practical aqueous batteries, but also highlights how the complex interactions between electrolyte components can be used to manipulate interphasial chemistry.

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Fig. 1: Quantitative analysis of the contribution to the initial discharge capacity in various WIS electrolytes.
Fig. 2: The evaluation of the SEI on the Mo6S8 electrode in WIS electrolyte (21 m LiTFSI) saturated with various gases in the three-electrode device.
Fig. 3: The physicochemical properties of 5 m LiTFSI solution.
Fig. 4: The interaction between CO2 and the TFSI anion before and after treatment with CO2.
Fig. 5: The electrochemical performance of an aqueous full-cell (LiMn2O4/CO2–SIW/Mo6S8).
Fig. 6: The kinetics-determining electrochemical performances of the LiMn2O4/Mo6S8 aqueous full-cell in CO2–SIW and WIS electrolytes.

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Data availability

All the data generated or analysed during this study are included in this article and its Supplementary Information. The details of the molecular dynamics simulation are available in Supplementary Data 1. Source data are provided with this paper.

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Acknowledgements

All authors except K.X. acknowledge the support of the National Natural Science Foundation of China (51872322) and the Center for Clean Energy. J.Z., M.C. and G.F. thank the Hubei Provincial Natural Science Foundation of China (2020CFA093) and the Program for Huazhong University of Science and Technology, Academic Frontier Youth Team. K.X. thanks the Joint Center of Energy Storage Research, an energy hub funded by the US Department of Energy, Basic Energy Sciences, for support.

Author information

Authors and Affiliations

  1. Beijing Advanced Innovation Center for Materials Genome Engineering, 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, China

    Jinming Yue, Yuxin Tong, Lilu Liu, Liwei Jiang, Tianshi Lv, Yong-sheng Hu, Hong Li, Xuejie Huang, Lin Gu, Liumin Suo & Liquan Chen

  2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China

    Jinming Yue, Yuxin Tong, Liwei Jiang, Tianshi Lv & Liumin Suo

  3. State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, China

    Jinkai Zhang, Ming Chen & Guang Feng

  4. Battery Science Branch, Sensor and Electron Devices Directorate, US Army Research Laboratory, Adelphi, MD, USA

    Kang Xu

  5. Yangtze River Delta Physics Research Center Co. Ltd, Liyang, China

    Liumin Suo

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Contributions

L.S. and K.X. conceived the idea. J.Y. and L.S. designed the experiments. J.Y. performed the material preparation, electrochemical measurements and data analysis. L.J. performed the NMR measurements. Y.T. collected the TEM images, and L.L. measured the XPS spectra. T.L. performed the cost analysis of the electrolyte. J.Z., M.C. and G.F. performed the molecular dynamics simulations and analysed the data. J.Y., G.F., K.X. and L.S. wrote the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Kang Xu or Liumin Suo.

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Peer review information Nature Chemistry thanks Jin Han and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–39, Tables 1–3 and experimental details.

Supplementary Data 1

Bulk files for molecular dynamics simulation.

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Source Data Fig. 3

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Yue, J., Zhang, J., Tong, Y. et al. Aqueous interphase formed by CO2 brings electrolytes back to salt-in-water regime. Nat. Chem. 13, 1061–1069 (2021). https://doi.org/10.1038/s41557-021-00787-y

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