Wagner Reinhard, Redhammer Günther J, Rettenwander Daniel, Senyshyn Anatoliy, Schmidt Walter, Wilkening Martin, Amthauer Georg
Department of Chemistry and Physics of Materials, University of Salzburg , Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
Heinz Maier-Leibnitz Zentrum, Technische Universität München , Lichtenbergstrasse 1, 85748 Garching b. München, Germany.
Chem Mater. 2016 Mar 22;28(6):1861-1871. doi: 10.1021/acs.chemmater.6b00038. Epub 2016 Feb 10.
Li-oxide garnets such as LiLaZrO (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group -3, has to be stabilized with supervalent cations. LLZO stabilized with Ga shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li Ga LaZrO with > 0.07 crystallizes in the acentric cubic space group -43. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga. Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group -43 compared to space group -3. Despite all efforts undertaken to reveal structure-property relationships for this class of materials, this study highlights the potential for new discoveries.
锂氧化物石榴石，如LiLaZrO（LLZO），是下一代锂离子电池中固态电解质最有前途的候选材料之一。具有空间群-3的LLZO石榴石结构立方变体必须用高价阳离子来稳定。与用类似阳离子稳定的LLZO相比，用Ga稳定的LLZO表现出优异的性能；然而，这种行为的原因仍然未知。在本研究中，通过单晶X射线衍射对Ga稳定的LLZO进行了全面的结构表征。通过固态反应获得了晶体尺寸为几百微米的粗晶样品。单晶X射线衍射结果表明，Li Ga LaZrO（其中 > 0.07）结晶于非中心立方空间群-43。这是LLZO材料这种立方变体的首次明确记录，可能解释了与Al稳定的LLZO相比，Ga稳定的LLZO具有优异的电化学性能。这种相变似乎是由Ga的位点偏好引起的。Li NMR光谱表明，与空间群-3相比，具有空间群-43的LLZO存在额外的锂离子扩散过程。尽管为揭示这类材料的结构-性能关系付出了种种努力，但本研究突出了新发现的潜力。
