Phase Stability and Electrochemical Performance of La-Site-Doped Li6La3Zr0.5Nb0.5Ta0.5Hf0.5O12 High-Entropy Garnets

Li, Chang [Mechanical Engineering, School of Science, Engineering and Technology, Pennsylvania State University]; Raj giri, Nava [The Pennsylvania State University]; Jin, Zhihao [Pennsylvania State University]; Chen, Yan [ORNL] (ORCID:0000000160951754); Fu, Zhezhen [Mechanical Engineering, School of Science, Engineering and Technology, Pennsylvania State University]

doi:10.1021/acs.inorgchem.5c05633

DOE OSTI · 3682447

Phase Stability and Electrochemical Performance of La-Site-Doped Li6La3Zr0.5Nb0.5Ta0.5Hf0.5O12 High-Entropy Garnets

Li, Chang [Mechanical Engineering, School of Science, Engineering and Technology, Pennsylvania State University]·Raj giri, Nava [The Pennsylvania State University]·Jin, Zhihao [Pennsylvania State University]·Chen, Yan [ORNL] (ORCID:0000000160951754)·Fu, Zhezhen [Mechanical Engineering, School of Science, Engineering and Technology, Pennsylvania State University]

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Abstract

We investigate La-site substitution in the high-entropy garnet Li6La3Zr0.5Nb0.5Ta0.5Hf0.5O12 (LLZNTH) using Ba2+, Sr2+, and Sm3+ to elucidate how dopant governs phase stability, Li-site distribution, and electrochemical behavior. X-ray diffraction shows that Sr2+ is incorporated homogeneously into the garnet lattice, whereas the larger Ba2+ and smaller Sm3+ ions partially exceed the structural tolerance, generating secondary phases. Nevertheless, the Sm-doped composition (x = 0.05) exhibits the highest room-temperature ionic conductivity (2.7 × 10–4 S cm–1). Neutron powder diffraction reveals that Sm substitution drives a redistribution of Li+ from the tetrahedral 24 d sites into the higher-mobility 96 h positions, enhancing the connectivity of the three-dimensional Li-ion migration network. A Sm-doping series (x = 0.01–0.05) further shows that only sufficiently high Sm levels induce this redistribution, whereas lower concentrations retain Li arrangements similar to the undoped garnet. Critical current density measurements demonstrate that La-site dopants also influence interfacial stability against Li metal, underscoring a trade-off between bulk transport enhancement and mechanical robustness. Collectively, these findings reveal that in high-entropy garnets improved ionic conductivity can originate not only from phase-pure structures but also from targeted modification of the Li sublattice, even when accompanied by secondary phases, offering a compositional design principle for garnet electrolytes.

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Li, Chang [Mechanical Engineering, School of Science, Engineering and Technology, Pennsylvania State University], Raj giri, Nava [The Pennsylvania State University], Jin, Zhihao [Pennsylvania State University], Chen, Yan [ORNL] (ORCID:0000000160951754), Fu, Zhezhen [Mechanical Engineering, School of Science, Engineering and Technology, Pennsylvania State University]. 2026-02-01. Phase Stability and Electrochemical Performance of La-Site-Doped Li6La3Zr0.5Nb0.5Ta0.5Hf0.5O12 High-Entropy Garnets. https://doi.org/10.1021/acs.inorgchem.5c05633

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