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Hydrotropic solubilization of zinc acetates for sustainable aqueous battery electrolytes

Nature Sustainability volume 6, pages 1474–1484 (2023)Cite this article

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Abstract

Among the more sustainable battery chemistries, the aqueous zinc system is receiving renewed interest. To accelerate the practical applications of this promising technology, an effective strategy is to deploy high salt concentration electrolytes that could address the critical technical barriers, notably hydrogen evolution reaction and dendrite growth at the anode side. However, the state-of-the-art recipes are either zinc-ion deficient or halogen salt dependent, both of which unfortunately create extra challenges. Here we show a highly concentrated aqueous electrolyte formula utilizing zinc acetate, an otherwise poorly water-soluble but cheap and eco-friendly salt. The unprecedented solubility (up to 23 m) is a result of the introduction of hydrotropic agents that transform the acetate anion ligands to a hydrophilic coordination structure. All three hydrotropic agents including potassium acetate, urea and acetamide are effective in constructing highly concentrated zinc acetate electrolytes with which the assembled Zn//pyrene-4,5,9,10-tetraone full cell retains 70% of its initial capacity after 4,000 cycles. This work provides a unique opportunity to design high-performance electrolytes for applications in the wide battery space.

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Fig. 1: Solvation-sheath structure of Zn2+.
Fig. 2: Advantages of Zn-rich highly concentrated electrolytes.
Fig. 3: H2O structure and inhibited hydrogen evolution reaction.
Fig. 4: High Zn2+/Zn reversibility and uniform Zn metal deposits.
Fig. 5: Zn symmetric cells and Zn//PTO full cells.

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Data availability

The datasets generated and/or analysed during the current study are available from the corresponding authors on reasonable request.

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Acknowledgements

The work described in this paper was fully supported by two grants from the Research Grant Council of the Hong Kong Special Administrative Region, China (No. CUHK14308321, Y.-C.L. and C1002-21GF, Y.-C.L. and J.F.). We thank Z. J. Liang and J. Xie for the OEMS tests, J. F. Lei and W. W. Wang for the SEM tests, and L. W. Jiang for insightful discussion of the mechanism.

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  1. Electrochemical Energy and Interfaces Laboratory, Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Hong Kong SAR, China

    Dejian Dong, Yue Sun & Yi-Chun Lu

  2. Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR, China

    Tairan Wang & Jun Fan

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Contributions

D.D. and Y.-C.L. conceived the project; D.D. carried out electrochemical tests and characterizations; T.W. and J.F. conducted MD simulations. Y.S. carried out cathode synthesis. D.D. and Y.-C.L. wrote the paper; all authors participated in manuscript preparation.

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Correspondence to Yi-Chun Lu.

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Dong, D., Wang, T., Sun, Y. et al. Hydrotropic solubilization of zinc acetates for sustainable aqueous battery electrolytes. Nat Sustain 6, 1474–1484 (2023). https://doi.org/10.1038/s41893-023-01172-y

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