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Investigating the effect of heterogeneities across the electrode|multiphase polymer electrolyte interfaces in high-potential lithium batteries

Nature Nanotechnology volume 20, pages 787–797 (2025)Cite this article

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Abstract

Polymer electrolytes hold great promise for safe and high-energy batteries comprising solid or semi-solid electrolytes. Multiphase polymer electrolytes, consisting of mobile and rigid phases, exhibit fast ion conduction and desired mechanical properties. However, fundamental challenges exist in understanding and regulating interactions at the electrode|electrolyte interface, especially when using high-potential layered oxide active materials at the positive electrode. Here we demonstrate that depletion of the mobile conductive phase at the interface contributes to battery performance degradation. Molecular ionic composite electrolytes, composed of a rigid-rod ionic polymer with nanometric mobile cations and anions, serve as a multiphase platform to investigate the evolution of ion conductive domains at the interface. Chemical and structural characterizations enable the visualization of concentration heterogeneity and spatially resolve the interfacial chemical states over a statistically significant field of view for buried interfaces. We report that concentration and chemical heterogeneities prevail at electrode|electrolyte interfaces, leading to phase separation in polymer electrolytes. Understanding the hidden roles of interfacial chemomechanics in polymer electrolytes enables us to design an interphase tailoring strategy based on electrolyte additives to mitigate the interfacial heterogeneity and improve battery performance.

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Fig. 1: Graphic representation of interfaces and interphases in an Li metal pouch cell with an MIC electrolyte.
Fig. 2: Electrochemical characterizations in symmetric and asymmetric cell configurations.
Fig. 3: Map and visualization of sulfur-containing ion distribution in basic MIC PEs via ex situ XRF measurements.
Fig. 4: Spatially resolved chemical analyses in basic MIC PE.
Fig. 5: The evolution of surface morphology and diffusion properties of electrochemically cycled MIC electrolyte.
Fig. 6: Evaluating the impact of additives on concentration and chemical heterogeneities in MIC electrolytes via XRF and XAS measurements.

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The data supporting the findings of this study are available in the published article and its Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was primarily supported by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under award number DE-EE0008860 (F.L. and L.A.M.). Part of the work was also supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy through the Advanced Battery Materials Research (BMR) Program (Battery500 Consortium) under contract number 683639 (F.L. and L.A.M.). F.L. and L.A.M. also acknowledge the seedling support from the Virginia Tech College of Science Strategic Initiative in Energy (03400). This work used shared facilities at the Virginia Tech Nanoscale Characterization and Fabrication Laboratory (NCFL) and Surface Analysis Laboratory, supported by the National Science Foundation (NSF) under grant number CHE-1531834. This research used 8-BM of the National Synchrotron Light Source II (NSLS-II), which is a US Department of Energy Office of Science User Facility at Brookhaven National Laboratory under contract number DE-SC0012704. This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract number DE-AC02-06CH11357. NMC811 was produced at the US Department of Energy’s (DOE) CAMP (Cell Analysis, Modeling, and Prototyping) Facility, Argonne National Laboratory. The CAMP Facility is fully supported by the DOE Vehicle Technologies Program (VTP) within the core funding of the Applied Battery Research (ABR) for Transportation Program. We thank M. Hedge and T. J. Dingemans (University of North Carolina-Chapel Hill) and D. Yu (Virginia Tech) for discussions. We also thank M. Ashraf-Khorasani for chromatography analysis and discussions.

Author information

Author notes

  1. Seong-Min Bak

    Present address: Department of Materials Science and Engineering, Yonsei University, Seoul, South Korea

  2. These authors contributed equally: Jungki Min, Seong-Min Bak.

Authors and Affiliations

  1. Department of Chemistry, Virginia Tech, Blacksburg, VA, USA

    Jungki Min, Yuxin Zhang, Mingyu Yuan, Nicholas F. Pietra, Dawei Xia, Lei Tao, Louis A. Madsen & Feng Lin

  2. National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA

    Seong-Min Bak & Yonghua Du

  3. Macromolecules Innovation Institute, Virginia Tech, Blacksburg, VA, USA

    Nicholas F. Pietra, Louis A. Madsen & Feng Lin

  4. Department of Materials Science and Engineering, Boise State University, Boise, ID, USA

    Joshua A. Russell & Hui Xiong

  5. Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA

    Zhifei Deng

  6. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA

    Ling Li

  7. Department of Materials Science and Engineering, Virginia Tech, Blacksburg, VA, USA

    Feng Lin

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Contributions

F.L. conceived and led the project. F.L. and J.M. designed the experiments. J.M. performed the materials synthesis, electrochemical measurements and characterizations. J.M., S.-M.B. and Y.D. performed the synchrotron X-ray characterization. Y.Z. and M.Y. assisted with the membrane processing. D.X. and L.T. helped with data analysis. J.A.R. and H.X. conducted ex situ atomic force microscopy. N.F.P. and L.A.M. conducted the pulsed-field-gradient NMR diffusiometry and participated in scientific discussions. Z.D. and L.L. conducted synchrotron X-ray micro-computed tomography. J.M. and F.L. analysed all the data and wrote the paper with the assistance of L.A.M. and S.-M.B. All authors approved the paper for publication.

Corresponding author

Correspondence to Feng Lin.

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Competing interests

Part of the results in this paper is included in a patent application (application no. 63/734,312) filed by some co-authors (J.M., L.A.M. and F.L.).

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Nature Nanotechnology thanks Xin Guo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Graphic representation of synchrotron X-ray measurements to investigate interfacial degradation in polymer electrolyte-based cells.

Schematic showing synchrotron X-ray measurements of a solid-state battery cross-section, which combines X-ray fluorescence (XRF) microscopy and X-ray absorption spectroscopy (XAS) measurements to visualize ionic concentration and probe chemical states across buried interfaces of solid-state battery components. Sulfur species from IL (TFSI−) and PBDT polymer (-SO3−) are present in the MIC electrolyte. Tracking the sulfur species of polymer electrolytes with XRF mapping reveals local ionic concentration heterogeneities, and spatially resolved XAS analysis informs the evolution of new sulfur species from interfacial side reactions by probing the changes in the oxidation states of sulfur elements therein. From the right panel of the XRF map, the green area represents the regions containing sulfur species, the black areas indicate regions without sulfur species, and the red area represents the sample holder (see also Spatially resolved XRF/XAS measurement and Sample preparation for synchrotron measurements from Methods). The point scanning XAS on the cross-sectional sample probes sulfur chemical states across electrode|electrolyte interfaces with a spatial resolution of a few micrometers (Right part, point 1).

Supplementary information

Supplementary Information

Supplementary Figs. 1–33 and Notes 1–10.

Source data

Source Data Figs. 2–6

Statistical source data of Figs. 2–6.

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Min, J., Bak, SM., Zhang, Y. et al. Investigating the effect of heterogeneities across the electrode|multiphase polymer electrolyte interfaces in high-potential lithium batteries. Nat. Nanotechnol. 20, 787–797 (2025). https://doi.org/10.1038/s41565-025-01885-5

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