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Non-Arrhenius Lithium Diffusion With Temperature-Independent Haven Ratio in Garnet-Type Li6.5La3Zr1.5Ta0.5O12 Single Crystals

Kaori Sugii1, Gen Hasegawa1, Kunimitsu Kataoka2, Kenjiro Hashi3, Junji Akimoto1, Kazunori Takada1, and Naoaki Kuwata1,4,*

  • *Contact author: KUWATA.Naoaki@nims.go.jp
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PRX Energy 5, 043003 – Published 21 October, 2026

DOI: https://doi.org/10.1103/zld4-bjxp

Abstract

Lithium-ion dynamics of garnet-type Li6.5La3Zr1.5Ta0.5O12 single crystals were investigated using pulsed field gradient (PFG) NMR and impedance spectroscopy over a wide temperature range up to 700 K. The diffusion coefficient measured by PFG-NMR exhibits non-Arrhenius behavior at elevated temperatures (>400  K). The conductivity diffusion coefficient is consistently higher than the PFG-NMR diffusion coefficient across the entire temperature range, with a Haven ratio of 0.3–0.4, indicating that the motion of mobile Li+ ions is correlated. Remarkably, the Haven ratio exhibits little temperature dependence despite the non-Arrhenius behavior, representing the first experimental observation in garnet-type electrolytes and consistent with the molecular dynamics simulations. This indicates that ion-ion correlations remain essentially unchanged over a wide temperature range. Combined with the local Li+ ion dynamics obtained from spin-lattice relaxation analysis, these results suggest that long-range diffusion is suppressed at low temperatures due to short-range ordering of Li+ ions.

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Popular Summary

Garnet-type oxides are promising materials for next-generation solid-state batteries because they enable fast lithium-ion transport. However, the mechanism behind lithium-ion movement, especially its unusual temperature dependence, has remained unclear. As temperature increases, ion transport deviates from simple expectations, suggesting more complex underlying processes. In this study, the authors used pulsed-field gradient nuclear magnetic resonance technique to directly measure the lithium-ion diffusion coefficient over a wide temperature range. The results show that correlations between lithium-ion motions remain nearly unchanged over the measured temperature range. This finding suggests that ion-ion interactions are unlikely to be the primary cause of the anomalous behavior of conductivity. Instead, it points to temperature-driven changes in the material’s internal structure as the key factor controlling ion transport. These insights provide a new microscopic understanding of lithium-ion conduction and offer important guidance for designing high-performance solid-state battery materials.

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Outline

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PRX Energy 5, 043003– Published 21 October, 2026
  • Received 24 April 2026
  • Revised 5 August 2026
  • Accepted 4 September 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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