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| Home > Publications database > Neutron powder diffraction study of high Li-ion conductive Li7-xAlxLa3Zr2O12 |
| Home > Publications database > Neutron powder diffraction study of high Li-ion conductive Li7-xAlxLa3Zr2O12 |
| Conference Presentation (Other) | FZJ-2016-04487 |
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2016
Abstract: The garnet-type lithium oxides with the general formula Li7La3Zr2O12 (LLZ) are promising candidates for all-solid-state lithium batteries due to their high ionic conductivity and electrochemical stability. The tetragonal LLZ crystallizes in the space group I41/acd at room temperature and exhibits a relatively low total Li-ionic conductivity of ≈ 10-6 Scm-1 [1], whereas the high-temperature cubic phase with the space group Ia-3d gives an elevated total ionic conductivity of ≈ 10-4 Scm-1 [2]. Li-occupancy in the crystal structure plays a significant role in the conduction, since Li-ion jump can take place through the energetically favorable atom positions that are only partially occupied [3, 4]. The presence of vacancies in LLZ lowers the activation energy and enhances Li-ionic conductivity. 20 mol % aluminum-doped LLZ was synthesized by solid state reaction to stabilize the crystal structure, and hence to improve the total ionic conductivity by increasing the number of vacancies. The X-ray powder diffraction analysis shows a mixture of tetragonal and cubic Al-doped LLZ with the weight fraction ratio of almost 1:1. The impedance measurement on this mixture compound revealed a high total ionic conductivity of ≈ 10-4 Scm-1, despite of the presence of the poorly conducting tetragonal phase. To elucidate this phenomenon, neutron powder diffraction was performed on the mixed phase Al-doped LLZ as well as on the pure tetragonal one. Rietveld analysis was carried out to obtain detailed crystal structure information, and a possible mechanism of the Li-ion conduction was discussed according to its crystal structure. [1] Awaka J., Kijima N., Hayakawa H., Akimoto J. J. Solid State Chem. 2009, 182, 2046. [2] Murugan R., Thangadurai V., Weppner W. Angew. Chem. Int. Ed. 2007, 46, 7778.[3] Li Y., Han J., Wang C., Vogel S., Xie H., Xu M., Goodenough J. J. Power Sources 2012, 209, 278.[4] Meier K., Laino T., Curioni A. J. Phys. Chem. C. 2014, 118, 6668Keywords: neutron powder diffraction, crystal structure, Li-ionic conductivity
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