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Solid-state rigid-rod polymer composite electrolytes with nanocrystalline lithium ion pathways

Abstract

A critical challenge for next-generation lithium-based batteries lies in development of electrolytes that enable thermal safety along with the use of high-energy-density electrodes. We describe molecular ionic composite electrolytes based on an aligned liquid crystalline polymer combined with ionic liquids and concentrated Li salt. This high strength (200 MPa) and non-flammable solid electrolyte possesses outstanding Li+ conductivity (1 mS cm−1 at 25 °C) and electrochemical stability (5.6 V versus Li|Li+) while suppressing dendrite growth and exhibiting low interfacial resistance (32 Ω cm2) and overpotentials (≤120 mV at 1 mA cm−2) during Li symmetric cell cycling. A heterogeneous salt doping process modifies a locally ordered polymer–ion assembly to incorporate an inter-grain network filled with defective LiFSI and LiBF4 nanocrystals, strongly enhancing Li+ conduction. This modular material fabrication platform shows promise for safe and high-energy-density energy storage and conversion applications, incorporating the fast transport of ceramic-like conductors with the superior flexibility of polymer electrolytes.

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Fig. 1: Fabrication processes to form LiMICs.
Fig. 2: X-ray diffraction patterns of RMIC and LiMIC.
Fig. 3: Chemical identification, diffusion coefficients, activation energies and transport mechanism in RMICs and LiMICs.
Fig. 4: Ionic conductivity, activation energy, Li+ transference number, electrochemical window, Li symmetric cell cycling performance and interfacial charge-transfer resistance in MICs.
Fig. 5: Thermal and mechanical properties of RMICs and LiMICs.
Fig. 6: Voltage–time profiles for Li|Li symmetric cells incorporating LiMICs at ambient temperature.

Data availability

All data generated and analysed in this study are included in this published article and its Supplementary Information file and are also available from the corresponding author on reasonable request. Source data are provided with this paper.

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Acknowledgements

This work was supported primarily by the US National Science Foundation under awards DMR 1507764 and 1810194 and in part by the US Department of Energy under award EE0008860. We also gratefully thank C. Slebodnick at the Virginia Tech Crystallography Lab for assistance with X-ray diffraction analysis.

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Authors

Contributions

Y.W. designed and executed all major experiments and composed and edited article draughts. X.W., R.K., L.J. and M.F. performed and assisted with electrochemistry and impedance experiments and contributed written sections and editing to the article. C.J.Z. performed SSNMR experiments and contributed written sections and editing to the article. W.H.K. analysed the X-ray diffraction data and contributed written sections to the article. T.J.D. modified and supplied the polymer, conceived experiments and contributed written sections and editing to the article. L.A.M. conceived ideas, oversaw experiments, and composed and edited the article.

Corresponding author

Correspondence to Louis A. Madsen.

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The authors declare no competing interests.

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Peer review information: Nature Materials thanks Fannie Alloin 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. 1–11, Notes 1–12 and Tables 1–4.

Source data

Source Data Fig. 2e,f

X-ray diffraction pattern and refinement results.

Source Data Fig. 3d–f,h

Diffusion and activation energy data.

Source Data Fig. 4a–f

Electrochemical data.

Source Data Fig. 5a,b

Thermal and mechanical data.

Source Data Fig. 6c,f

Li symmetric cell and energy-dispersive X-ray data.

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Wang, Y., Zanelotti, C.J., Wang, X. et al. Solid-state rigid-rod polymer composite electrolytes with nanocrystalline lithium ion pathways. Nat. Mater. (2021). https://doi.org/10.1038/s41563-021-00995-4

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