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<p>The lithium-stuffed garnet-type oxide Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> (LLZO) is a promising candidate electrolyte material in all-solid-state Li-ion batteries. In order to further increase the ionic conductivity, we report a combined experimental and computational investigation of high-valence Nb<sup>5+</sup> doping of the Zr<sup>4+</sup>-site in LLZO. In this paper, the nominal compositions of Li<sub>7−<i>x</i></sub>La<sub>3</sub>Zr<sub>2−<i>x</i></sub>Nb<sub><i>x</i></sub>O<sub>12</sub> (<i>x</i> = 0, 0.25, 0.375, 0.5, and 0.75) electrolyte sheets were prepared by solid-state reaction. The effect of Nb<sup>5+</sup> doping was investigated through the theoretical calculation and experimental characterization measurement. The super-valent doping strategy causes a reduction in the octahedral site (tetragonal 16f and 32g sites) occupancy, which can weaken the blocking influence of tetragonal 16f sites, promote the lithium redistribution, lower the temperature of tetragonal-cubic phase transition, and eventually enhance the ionic conductivity. The garnet-type Li<sub>6.5</sub>La<sub>3</sub>Zr<sub>1.5</sub>Nb<sub>0.5</sub>O<sub>12</sub> ceramic sample calcined at 950&#xa0;°C for 12&#xa0;h and 1160&#xa0;°C for 24&#xa0;h shows the maximum ionic conductivity of 1.05 × 10<sup>−3</sup>&#xa0;S&#xa0;cm<sup>−1</sup> at room temperature and the minimum the activation energy of 0.297&#xa0;eV, which can be correlated to the highest relative density of 95.7%, and good crystallinity of the grains. Further, the Li symmetric battery and Li-sulfur half batteries using garnet-type Li<sub>6.5</sub>La<sub>3</sub>Zr<sub>1.5</sub>Nb<sub>0.5</sub>O<sub>12</sub> electrolyte exhibit good electrochemical performances. This work provides a simple and effective strategy on high-performance solid-state electrolytes.</p>

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Phase transition and lithium conduction of Nb-doped Li7La3Zr2O12 garnet-type electrolytes

  • 期刊论文

  • 发表日期：

    2025年6月12日

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  • Yali Luo,
  • Jiaxin Dong,
  • Yan Yan,
  • Junjie Liu,
  • Liang Wang,
  • Zi’ang Chen,
  • He Zhang

摘要

The lithium-stuffed garnet-type oxide Li7La3Zr2O12 (LLZO) is a promising candidate electrolyte material in all-solid-state Li-ion batteries. In order to further increase the ionic conductivity, we report a combined experimental and computational investigation of high-valence Nb5+ doping of the Zr4+-site in LLZO. In this paper, the nominal compositions of Li7−xLa3Zr2−xNbxO12 (x = 0, 0.25, 0.375, 0.5, and 0.75) electrolyte sheets were prepared by solid-state reaction. The effect of Nb5+ doping was investigated through the theoretical calculation and experimental characterization measurement. The super-valent doping strategy causes a reduction in the octahedral site (tetragonal 16f and 32g sites) occupancy, which can weaken the blocking influence of tetragonal 16f sites, promote the lithium redistribution, lower the temperature of tetragonal-cubic phase transition, and eventually enhance the ionic conductivity. The garnet-type Li6.5La3Zr1.5Nb0.5O12 ceramic sample calcined at 950 °C for 12 h and 1160 °C for 24 h shows the maximum ionic conductivity of 1.05 × 10−3 S cm−1 at room temperature and the minimum the activation energy of 0.297 eV, which can be correlated to the highest relative density of 95.7%, and good crystallinity of the grains. Further, the Li symmetric battery and Li-sulfur half batteries using garnet-type Li6.5La3Zr1.5Nb0.5O12 electrolyte exhibit good electrochemical performances. This work provides a simple and effective strategy on high-performance solid-state electrolytes.