The cubic phase of lithium lanthanum zirconium oxide (LLZO) is a solid electrolyte based on the garnet crystal structure which has shown promise in enabling batteries with significantly higher energy density compared to lithium-ion. Owing to its stability against lithium, LLZO is compatible with metallic lithium electrodes that, when paired with state-of-the-art cathodes, can achieve >1000 Wh/l. The preferred cubic LLZO phase is stabilized at room temperature by doping LLZO, which results in the formation of lithium vacancies (V_Li′) that can achieve ionic conductivities in the 1 mS/cm range. While much attention has been paid to optimizing V_Li′, discrepancies in lanthanum to zirconium (La:Zr) ratios provide an indication of the existence of vacancies at one or both of these sites. As La is the largest cation present, La vacancies should show the most dramatic effects on lattice parameter, which should affect lithium-ion transport within the LLZO sublattice. In turn, changes in lithium-ion site occupancy and solvation should affect activation energy and conductivity. However, the effects of the sub stoichiometric use of La on the crystal structure of LLZO have yet to be characterized.

In this work, La content is varied in the LLZO structure Li_6.5La_2+xZr_1.5Ta_0.5O₁₂ from x = 0 to x = 1.2. X-ray diffraction, SEM imaging, Raman Spectroscopy, electrochemical impedance measurements, and DC cycling were performed in order to correlate the effect of La deficiency on crystal structure and electrochemical properties of LLZO. Vacancy and decomposition mechanism are proposed. A linear increase in lattice parameter is observed over the range of La content measured. An increase in conductivity and CCD are also observed ranging from 0.649 mS/cm and 0.5 mA/cm² at x = 0.2 to 0.789mS/cm and 0.80 mA/cm² at x = 1.0.

锂镧锆锆（LLZO）的立方相是基于石榴石晶体结构的固体电解质，与锂离子相比，锂离子锆电池已显示出使电池具有更高能量密度的前景。由于其对锂的稳定性，LLZO与金属锂电极兼容，当与最先进的阴极配对时，LLZO可以达到> 1000 Wh / l。通过掺杂LLZO，优选的立方LLZO相在室温下稳定，这导致形成锂空位（V _Li '），该空位可以实现1 mS / cm范围内的离子电导率。尽管已经非常关注优化V _Li''，镧与锆之比（La：Zr）的差异提供了这些位点之一或全部存在空位的迹象。由于La是目前存在的最大阳离子，因此La空位应该对晶格参数显示出最显着的影响，这会影响LLZO亚晶格内的锂离子迁移。反过来，锂离子位点占有率和溶剂化的变化会影响活化能和电导率。但是，La的亚化学计量的使用对LLZO晶体结构的影响尚待鉴定。

在这项工作中，La含量在LLZO结构Li _6.5 La _{2 + x} Zr _1.5 Ta _0.5 O _12中从x = 0到x = 1.2变化。进行了X射线衍射，SEM成像，拉曼光谱，电化学阻抗测量和DC循环，以关联La缺乏对LLZO的晶体结构和电化学性质的影响。提出了空位和分解机制。在所测量的La含量范围内观察到晶格参数线性增加。在导电率和CCD的增加还观察到范围从0.649毫秒/厘米和0.5毫安/厘米²在x = 0.2〜0.789mS /厘米0.80毫安/厘米²在x = 1.0。