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Heterogeneous doping via nanoscale coating impacts the mechanics of Li intrusion in brittle solid electrolytes

Nature Materials (2026)Cite this article

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Abstract

Lithium dendrite intrusion in solid-state batteries limits fast charging and causes short-circuiting, yet the underlying regulating mechanisms are not well-understood. Here we discover that heterogeneous Ag+ doping dramatically affects lithium intrusion into Li6.6La3Zr1.6Ta0.4O12 (LLZO), a brittle solid electrolyte. Nanoscale Ag+ doping is achieved by thermally annealing a 3-nm-thick metallic coating on LLZO, inducing Ag–Li ion exchange and Ag diffusion into grains and grain boundaries. Density functional theory calculations and experimental characterization show negligible impact on the electronic properties and surface wettability from Ag+ incorporation. Mechanically, nanoindentation experiments show a fivefold increase in the mechanical force required to fracture the surface Ag+-doped LLZO, indicating substantial doping-induced surface toughening. Operando microprobe scanning electron microscopy experiments show that the Ag+-doped LLZO surface exhibits improved lithium plating at >250 mA cm−2 and an electroplating diameter that is expanded by over fourfold, even under an extreme indentation stress of 3 GPa. This demonstrates enhanced defect tolerance in LLZO, rather than electronic or adhesion effects. Our study reveals a chemo-mechanical mechanism via surface heterogeneous doping, complementing present bulk design rules to minimize mechanical failures in solid-state batteries.

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Fig. 1: Surface coating on cleaved LLZO with chemical characterization.
Fig. 2: Comparison of the electronic PDOS occupation between uncoated pristine LLZO and Ag+-LLZO.
Fig. 3: Operando Li electroplating and local defects engineering via microprobe experiments inside the SEM chamber.
Fig. 4: Improved Li electroplating stability via Ag+ doping.
Fig. 5: Mechanical characterization of Ag+-LLZO surfaces via in situ nanoindentation (3-nm-thick metallic Ag, post-annealing at 300 °C).

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Data generated or analysed during this study are included in the Supplementary Information. Further data are available from the corresponding authors upon request. Source data are provided with this paper.

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Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency, Vehicle Technologies Office of the US Department of Energy under the Advanced Battery Materials Research Program. Additional support was provided by Samsung Advanced Institute of Technology. T.C., S.S.L. and X.W.G. acknowledge financial support from the StorageX Initiative at Stanford University and the grant DE-SC0021075 funded by the US Department of Energy, Office of Science. X.X. acknowledge additional financial support from the Ira A. Fulton Schools of Engineering at Arizona State University and the grant DE-SC0026366 funded by the US Department of Energy, Office of Science. Y.C. (0000-0002-6103-6352) acknowledges cryo-EM support from the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under contract DE-AC02-76SF00515. H.D.J. and Y.Q. acknowledge financial support from the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy through the Battery 500 Consortium. We thank W. D. Nix for his contributions, including discussions and the examination of nanoindentation data and mechanical analyses; Y. Ju for discussion on the Li-plating dynamics on solid electrolytes; R. Chin, J. Jamtgaard, P. Wallace, C. Jilly-Rehak and M. Mills for assistance with the Helios SEM/FIB and nanoSIMS instruments; and L. Miara, S. Chakravarthy, S. J. Harris, A. Lee, Y. Liu and J. A. Greer for discussions. We extend special thanks to C. Zhao for his contribution to the art design of the schematics used in this work. Finally, we thank J.-H. Lee for discussions and comments on the manuscript. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award ECCS-2026822.

Author information

Author notes

  1. These authors contributed equally: Xin Xu, Teng Cui, Geoff McConohy, Harsh D. Jagad, Samuel S. Lee.

Authors and Affiliations

  1. Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA

    Xin Xu, Geoff McConohy, Celeste Melamed, Yufei Yang, Edward Barks, Emma Kaeli, Leah Narun, Yi Cui, Zewen Zhang, Rong Xu, Melody M. Wang, Levi Hoogendoorn, Ajai Romana, Alexis Geslin, Robert Sinclair, Yi Cui & William C. Chueh

  2. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA

    Xin Xu, Geoff McConohy, Samuel S. Lee, Sunny Wang, Edward Barks, Hye Ryoung Lee, Yi Cui & William C. Chueh

  3. The Polytechnic School, Ira A. Fulton Schools of Engineering, Arizona State University, Mesa, AZ, USA

    Xin Xu

  4. Department of Mechanical Engineering, Stanford University, Stanford, CA, USA

    Teng Cui, Samuel S. Lee & X. Wendy Gu

  5. School of Engineering, Brown University, Providence, RI, USA

    Harsh D. Jagad & Yue Qi

  6. Department of Chemistry, Stanford University, Stanford, CA, USA

    Sunny Wang

  7. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, USA

    Hye Ryoung Lee

  8. Department of Energy Science and Engineering, Stanford University, Stanford, CA, USA

    Alexis Geslin, Yi Cui & William C. Chueh

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  1. Xin Xu
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Contributions

X.X. performed all of the experiments and analysed the results, with contributions from T.C., G.M. and S.S.L. Support in the XPS analysis was provided by S.W. and Y.Y. Contributions to the TEM characterization and analysis were made by Y.C. (0000-0001-8219-1856), Z.Z., H.R.L., R.S. and Y.C. (0000-0002-6103-6352). S.S.L., M.M.W. and R.X. contributed to the nanoindentation measurements. E.B. contributed to preparation of the LLZO samples. E.K., L.N., A.R. and A.G. contributed to electrical measurements and data analysis. C.M. and L.H. contributed to the surface coatings. H.D.J. and Y.Q. performed the DFT calculations on the Ag–Li ion-exchange process. X.W.G. supervised the nanoindentation measurements and their analysis. X.X. and W.C.C. designed the research plan and supervised the work. X.X. wrote the manuscript with input from all authors.

Corresponding authors

Correspondence to Xin Xu, Yue Qi, X. Wendy Gu or William C. Chueh.

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Supplementary information

Source data

Source Data Fig. 1

Depth-profiling XPS data for Ag, Zr and La plotted in Fig. 1c; depth profiling nanoSIMS data for Ag0 | LLZO and Ag+-LLZO plotted in Fig. 1d.

Source Data Fig. 2

DFT density of states data for Ag, Li, La, Oneighbour, Onon-neighbour and Zr plotted in Fig. 2b–g.

Source Data Fig. 4

Operando SEM electrochemical data of the lateral diameter of Li electroplating and the local current density at failure in various LLZO samples plotted in Fig. 4b.

Source Data Fig. 5

Loading–depth data of uncoated LLZO and the calculated Hertzian contact stress curve plotted in Fig. 5c; loading–depth data of Ag+-LLZO plotted in Fig. 5d; histogram data of the loading force at the initial crack for uncoated and Ag+-LLZO plotted in Fig. 5e.

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Xu, X., Cui, T., McConohy, G. et al. Heterogeneous doping via nanoscale coating impacts the mechanics of Li intrusion in brittle solid electrolytes. Nat. Mater. (2026). https://doi.org/10.1038/s41563-025-02465-7

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