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Water-in-polymer electrolyte with a wide electrochemical window and recyclability

Nature Sustainability (2024)Cite this article

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Abstract

Aqueous batteries—with water-based electrolytes—provide safe, reliable and affordable energy storage solutions. However, their energy density and cycling life remain uncompetitive owing to the narrow electrochemical window of the aqueous electrolyte. Adding excessive salt to form saturated electrolytes could address this limitation but at other costs. Here we show a water-in-polymer electrolyte that maximizes the amount of water but works across a voltage range as wide as that for highly concentrated electrolytes. At the heart of this formulation is the introduction of a polyacrylamide network that serves to immobilize and thus tame the otherwise reactive H2O molecules. As a result, our polymerized solid aqueous electrolytes with 4.1 m (18 wt% H2O) and 7.6 m (11 wt% H2O) lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt show extended electrochemical windows of 2.7 V and 3.7 V, comparable to those for the 21 m and 40 m saturated counterparts, respectively. The solid-state Li4Ti5O12//LiMn2O4 cell exhibits stable cycling even under a higher loading of cathode (16 mg cm−2) with a lean electrolyte of 7 g Ah−1. In addition, up to 80% of the LiTFSI salt can be recycled and the polymer matrix can also be regenerated. Our electrolyte design represents a substantial step forwards towards more sustainable aqueous batteries.

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Fig. 1: EW tests of WIPSEs and FWIPSEs.
Fig. 2: Interaction of H2O with Li ion and PAM in WIPSEs.
Fig. 3: Hydrogen bonds and Li+–O interaction in WIPSEs.
Fig. 4: Electrochemical performance of WIPSEs and FWIPSEs in solid-state cells.
Fig. 5: Recycling of LiTFSI and regeneration of FWIPSEs.

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Data availability

Crystallographic data for the structures reported in this study have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2220988 and 2245674. Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. All other relevant data supporting the findings of this study are available in this Article and Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work is financially supported by the National Key Research and Development Program of China (2022YFE0202400, 2022YFA1204500 and 2022YFA1204501 to W.Z.), the National Natural Science Foundation of China (21875016, 22179004 and 22261160570 to W.Z., and 22209009 to S.-M.H.) and the Natural Science Foundation of Beijing (2212014 and L223008 to W.Z.). We acknowledge the valuable suggestions from the late J. B. Goodenough of the University of Texas at Austin.

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  1. These authors contributed equally: Shu-Meng Hao, Jianxun Zhu, Shuang He, Le Ma.

Authors and Affiliations

  1. Beijing Advanced Innovation Center for Soft Matter Science and Engineering, State Key Laboratory of Organic–Inorganic Composites, Beijing University of Chemical Technology, Beijing, China

    Shu-Meng Hao, Jianxun Zhu, Shuang He, Le Ma, Wenzhen Liu, Yaoyao Zhang, Xiaoxin Xie, Xuan Qin, Liqun Zhang & Weidong Zhou

  2. School of Materials Science and Engineering, Zhejiang University, Hangzhou, China

    Xiulin Fan

  3. Key Laboratory for Renewable Energy, Institute of Physics, Chinese Academy of Sciences, Beijing, China

    Hong Li

  4. Institute of Emergent Elastomers, School of Materials Science and Engineering, South China University of Technology, Guangzhou, China

    Liqun Zhang & Weidong Zhou

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Contributions

W.Z. designed this study. S.-M.H., J.Z., S.H. and L.M. performed the experiments and analysed the experimental results. S.H. performed the theoretical calculations. W.Z. and L.Z. wrote the paper. W.L., Y.Z., X.X., X.Q., X.F. and H.L. supported the experiments and data analysis.

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Correspondence to Liqun Zhang or Weidong Zhou.

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Supplementary information

Supplementary Information

Supplementary Note 1, Supplementary Figs. 1–39 and Supplementary Tables 1–3.

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Supplementary Video 1

The solid-state aqueous pouch cell under folding and cutting.

Source data

Source Data Fig. 1

Electrochemical window results.

Source Data Fig. 2

Simulation results of the interaction of H2O with Li+ and PAM.

Source Data Fig. 3

Simulation and experimental study on hydrogen bonds and Li+–O interaction.

Source Data Fig. 4

Electrochemical performance of WIPSEs and FWIPSEs in solid-state aqueous Mo6S8//LiMn2O4 and Li4Ti5O12//LiMn2O4 cells.

Source Data Fig. 5

Recycling of LiTFSI from FWIPSEs and regeneration of FWIPSEs.

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Hao, SM., Zhu, J., He, S. et al. Water-in-polymer electrolyte with a wide electrochemical window and recyclability. Nat Sustain (2024). https://doi.org/10.1038/s41893-024-01327-5

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