Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte: Linking Lattice and Ionic Dynamics with Thermal Transport

Yitian Wang; Yaokun Su; Jesús Carrete; Huanyu Zhang; Nan Wu; Yutao Li; Hongze Li; Jiaming He; Youming Xu; Shucheng Guo; Qingan Cai; Douglas L. Abernathy; Travis Williams; Kostiantyn V. Kravchyk; Maksym V. Kovalenko; Georg K.H. Madsen; Chen Li; Xi Chen

doi:10.1103/6wj2-kzhh

Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte: Linking Lattice and Ionic Dynamics with Thermal Transport

Yitian Wang
, Yaokun Su
, Jesús Carrete
, Huanyu Zhang
, Nan Wu
, Yutao Li
, Hongze Li
, Jiaming He
, Youming Xu
, Shucheng Guo
, Qingan Cai
, Douglas L. Abernathy
, Travis Williams
, Kostiantyn V. Kravchyk
, Maksym V. Kovalenko
, Georg K.H. Madsen
, Chen Li
, Xi Chen

Direct Geometry

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

Understanding thermal transport in solid electrolytes is essential for improving the performance, reliability, and safety of all-solid-state batteries. Garnet-type lithium-ion conductors are promising candidates for solid electrolytes, yet their thermal-transport mechanisms remain poorly understood. Here, we connect the lattice and ion dynamics of single-crystal garnet-type Li6.5La3Zr1.5Ta0.5O12 to its intrinsically low thermal conductivity. Our study reveals that the single crystals grown by the floating-zone method exhibit remarkably low glasslike thermal conductivity. Using first-principles calculations and inelastic-neutron-scattering measurements, we identify both the acoustic and numerous optical phonon modes, which stem from the complex crystal structure of the material. Notably, a low-energy optical branch exhibits an avoided crossing with acoustic phonons near 7 meV. These optical modes can enhance the scattering of heat-carrying acoustic phonons and reduce thermal conductivity. Furthermore, the calculated Grüneisen parameters are large, especially for the vibrational modes around 6 meV, indicating strong anharmonicity, with a noticeable contribution from lithium-ion vibrations. A two-channel thermal-transport model is employed to describe the weak temperature dependence of the thermal conductivity, which can be attributed to the substantial contribution of diffuson transport facilitated by the abundance of optical phonons and intrinsic anharmonicity. These results offer valuable insights into the thermal transport in a broad class of ionic conductors of interest for energy conversion and storage applications.

Original language	English
Article number	033004
Journal	PRX Energy
Volume	4
Issue number	3
DOIs	https://doi.org/10.1103/6wj2-kzhh
State	Published - Jul 2025

Funding

This work was supported by the National Science Foundation under Grants No. 2144328 and No. 1750786. X.C. and Y.W. acknowledge support from the Opportunity to Advance Sustainability Innovation and Social Inclusion (OASIS) internal funding award from the University of California, Riverside. Y.S., Q.C., and C.L. are supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0023874. This study was also supported by the Ministry of Science and Innovation (MCIN) with funding from the European Union NextGenerationEU (PRTR-C17.I1), promoted by the Government of Aragon. J.C. acknowledges funding from Ministry of Science, Innovation, and Universities (MICIU)-State Research Agency (AEI) (DOI:10.13039/501100011033) through Grant No. CEX2023-001286-S. This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a Department of Energy Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to TAX on Proposal No. IPTS-28205.1 and to ARCS on Proposal No. IPTS-30640.1. Research conducted at ORNL's HFIR and SNS was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. This work was supported by the National Science Foundation under Grants No. 2144328 and No. 1750786. X.C. and Y.W. acknowledge support from the Opportunity to Advance Sustainability Innovation and Social Inclusion (OASIS) internal funding award from the University of California, Riverside. Y.S., Q.C., and C.L. are supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0023874. This study was also supported by the Ministry of Science and Innovation (MCIN) with funding from the European Union NextGenerationEU (PRTR-C17.I1), promoted by the Government of Aragon. J.C. acknowledges funding from Ministry of Science, Innovation, and Universities (MICIU)–State Research Agency (AEI) (DOI:10.13039/501100011033) through Grant No. CEX2023-001286-S. This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a Department of Energy Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to TAX on Proposal No. IPTS-28205.1 and to ARCS on Proposal No. IPTS-30640.1. Research conducted at ORNL’s HFIR and SNS was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

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Wang, Y., Su, Y., Carrete, J., Zhang, H., Wu, N., Li, Y., Li, H., He, J., Xu, Y., Guo, S., Cai, Q., Abernathy, D. L., Williams, T., Kravchyk, K. V., Kovalenko, M. V., Madsen, G. K. H., Li, C., & Chen, X. (2025). Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte: Linking Lattice and Ionic Dynamics with Thermal Transport. PRX Energy, 4(3), Article 033004. https://doi.org/10.1103/6wj2-kzhh

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title = "Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte: Linking Lattice and Ionic Dynamics with Thermal Transport",

abstract = "Understanding thermal transport in solid electrolytes is essential for improving the performance, reliability, and safety of all-solid-state batteries. Garnet-type lithium-ion conductors are promising candidates for solid electrolytes, yet their thermal-transport mechanisms remain poorly understood. Here, we connect the lattice and ion dynamics of single-crystal garnet-type Li6.5La3Zr1.5Ta0.5O12 to its intrinsically low thermal conductivity. Our study reveals that the single crystals grown by the floating-zone method exhibit remarkably low glasslike thermal conductivity. Using first-principles calculations and inelastic-neutron-scattering measurements, we identify both the acoustic and numerous optical phonon modes, which stem from the complex crystal structure of the material. Notably, a low-energy optical branch exhibits an avoided crossing with acoustic phonons near 7 meV. These optical modes can enhance the scattering of heat-carrying acoustic phonons and reduce thermal conductivity. Furthermore, the calculated Gr{\"u}neisen parameters are large, especially for the vibrational modes around 6 meV, indicating strong anharmonicity, with a noticeable contribution from lithium-ion vibrations. A two-channel thermal-transport model is employed to describe the weak temperature dependence of the thermal conductivity, which can be attributed to the substantial contribution of diffuson transport facilitated by the abundance of optical phonons and intrinsic anharmonicity. These results offer valuable insights into the thermal transport in a broad class of ionic conductors of interest for energy conversion and storage applications.",

author = "Yitian Wang and Yaokun Su and Jes{\'u}s Carrete and Huanyu Zhang and Nan Wu and Yutao Li and Hongze Li and Jiaming He and Youming Xu and Shucheng Guo and Qingan Cai and Abernathy, \{Douglas L.\} and Travis Williams and Kravchyk, \{Kostiantyn V.\} and Kovalenko, \{Maksym V.\} and Madsen, \{Georg K.H.\} and Chen Li and Xi Chen",

note = "Publisher Copyright: {\textcopyright} 2025 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the {"}https://creativecommons.org/licenses/by/4.0/{"}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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Wang, Y, Su, Y, Carrete, J, Zhang, H, Wu, N, Li, Y, Li, H, He, J, Xu, Y, Guo, S, Cai, Q, Abernathy, DL, Williams, T, Kravchyk, KV, Kovalenko, MV, Madsen, GKH, Li, C & Chen, X 2025, 'Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte: Linking Lattice and Ionic Dynamics with Thermal Transport', PRX Energy, vol. 4, no. 3, 033004. https://doi.org/10.1103/6wj2-kzhh

TY - JOUR

T1 - Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte

T2 - Linking Lattice and Ionic Dynamics with Thermal Transport

AU - Wang, Yitian

AU - Su, Yaokun

AU - Carrete, Jesús

AU - Zhang, Huanyu

AU - Wu, Nan

AU - Li, Yutao

AU - Li, Hongze

AU - He, Jiaming

AU - Xu, Youming

AU - Guo, Shucheng

AU - Cai, Qingan

AU - Abernathy, Douglas L.

AU - Williams, Travis

AU - Kravchyk, Kostiantyn V.

AU - Kovalenko, Maksym V.

AU - Madsen, Georg K.H.

AU - Li, Chen

AU - Chen, Xi

N1 - Publisher Copyright: © 2025 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"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.

PY - 2025/7

Y1 - 2025/7

N2 - Understanding thermal transport in solid electrolytes is essential for improving the performance, reliability, and safety of all-solid-state batteries. Garnet-type lithium-ion conductors are promising candidates for solid electrolytes, yet their thermal-transport mechanisms remain poorly understood. Here, we connect the lattice and ion dynamics of single-crystal garnet-type Li6.5La3Zr1.5Ta0.5O12 to its intrinsically low thermal conductivity. Our study reveals that the single crystals grown by the floating-zone method exhibit remarkably low glasslike thermal conductivity. Using first-principles calculations and inelastic-neutron-scattering measurements, we identify both the acoustic and numerous optical phonon modes, which stem from the complex crystal structure of the material. Notably, a low-energy optical branch exhibits an avoided crossing with acoustic phonons near 7 meV. These optical modes can enhance the scattering of heat-carrying acoustic phonons and reduce thermal conductivity. Furthermore, the calculated Grüneisen parameters are large, especially for the vibrational modes around 6 meV, indicating strong anharmonicity, with a noticeable contribution from lithium-ion vibrations. A two-channel thermal-transport model is employed to describe the weak temperature dependence of the thermal conductivity, which can be attributed to the substantial contribution of diffuson transport facilitated by the abundance of optical phonons and intrinsic anharmonicity. These results offer valuable insights into the thermal transport in a broad class of ionic conductors of interest for energy conversion and storage applications.

AB - Understanding thermal transport in solid electrolytes is essential for improving the performance, reliability, and safety of all-solid-state batteries. Garnet-type lithium-ion conductors are promising candidates for solid electrolytes, yet their thermal-transport mechanisms remain poorly understood. Here, we connect the lattice and ion dynamics of single-crystal garnet-type Li6.5La3Zr1.5Ta0.5O12 to its intrinsically low thermal conductivity. Our study reveals that the single crystals grown by the floating-zone method exhibit remarkably low glasslike thermal conductivity. Using first-principles calculations and inelastic-neutron-scattering measurements, we identify both the acoustic and numerous optical phonon modes, which stem from the complex crystal structure of the material. Notably, a low-energy optical branch exhibits an avoided crossing with acoustic phonons near 7 meV. These optical modes can enhance the scattering of heat-carrying acoustic phonons and reduce thermal conductivity. Furthermore, the calculated Grüneisen parameters are large, especially for the vibrational modes around 6 meV, indicating strong anharmonicity, with a noticeable contribution from lithium-ion vibrations. A two-channel thermal-transport model is employed to describe the weak temperature dependence of the thermal conductivity, which can be attributed to the substantial contribution of diffuson transport facilitated by the abundance of optical phonons and intrinsic anharmonicity. These results offer valuable insights into the thermal transport in a broad class of ionic conductors of interest for energy conversion and storage applications.

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DO - 10.1103/6wj2-kzhh

M3 - Article

AN - SCOPUS:105022620230

SN - 2768-5608

VL - 4

JO - PRX Energy

JF - PRX Energy

IS - 3

M1 - 033004

ER -

Origin of Intrinsically Low Thermal Conductivity in a Garnet-Type Solid Electrolyte: Linking Lattice and Ionic Dynamics with Thermal Transport

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