Li ion conducting garnet electrolytes are attracting considerable interest for potential use in all solid state batteries. Nevertheless, their synthesis can be challenging due to the high temperatures required leading to significant Li loss, and consequently the need to add excess Li to counteract this. In this work, we report a low temperature biopolymer sol-gel route to synthesise these garnet materials using Agar (to ensure homogeneous mixing and nucleation through this biotemplating matrix), with the formation of the garnet phase starting at temperatures as low as 600 °C, with single phase samples of tetragonal Li₇La₃Zr₂O₁₂, and cubic Li_6.4Al_0.2La₃Zr₂O₁₂ prepared at 700 °C (~ 400 °C lower than the conventional solid state routes). Significantly, this route also allowed the synthesis of these garnets without the need for Li excess for the first time, due to the low temperature limiting Li loss. Moreover, if Li excess was used in the synthesis of cubic Li_6.4Al_0.2La₃Zr₂O₁₂, Al incorporation was not observed at this temperature, and rather tetragonal Li₇La₃Zr₂O₁₂ was obtained. Contrary to previous assumptions, this indicates that the Li is more stable in the structure than Al at low temperature. Thus, Al incorporation only occurs if there is a deficiency of Li in the starting material, or if the sample is heated to elevated temperatures to induce Li volatility, so as to drive the incorporation of Al to charge balance the resultant Li loss.

锂离子导电石榴石电解质对于所有固态电池的潜在用途引起了极大的兴趣。然而，由于所需的高温导致大量的Li损失，因此它们的合成可能具有挑战性，因此需要添加过量的Li来抵消这一问题。在这项工作中，我们报告了一种低温生物聚合物溶胶-凝胶路线，可使用琼脂合成这些石榴石材料（以确保通过该生物模板基质均匀混合和成核），并在低至600°C的温度下开始形成石榴石相。 ，具有四方Li ₇ La ₃ Zr ₂ O ₁₂和立方Li _6.4 Al _0.2 La ₃ Zr单相样品在700°C（比常规固态路线低约400°C）下制备₂ O ₁₂。值得注意的是，由于低温限制了Li的损失，该路线还允许首次无需过量Li的合成这些石榴石。此外，如果过量的Li用于合成立方Li _6.4 Al _0.2 La ₃ Zr ₂ O ₁₂，则在该温度下未观察到Al的掺入，而是四方的Li ₇ La ₃ Zr ₂ O _12。获得了。与先前的假设相反，这表明在低温下，锂的结构比铝更稳定。因此，仅在起始原料中缺乏Li或将样品加热至升高的温度以引起Li挥发以驱动Al的掺入以平衡产生的Li损失时，才发生Al掺入。