Garnet-type Li₇La₃Zr₂O₁₂ (LLZ) is regarded as a promising oxide-based solid electrolyte (SE) for solid-state lithium batteries (SSLBs) or other advanced Li-battery concepts like Li–air or Li–S batteries. A thin free-standing LLZ sheet can be fabricated by tape-casting and used e.g. as separators in SSLBs, since tape casting is an industrially established process and enables large-scale production of such SEs. However, organic solvents and additives employed in conventional slurry recipes for tape-casting give rise to health and safety concerns and also cause a high cost for solvent recovery. Hence, development of a green, water-based processing route can reduce both manufacturing costs and environmental footprint. In this work, we developed a tape-casting process for LLZ SEs using water as solvent, the water-soluble biopolymer methylcellulose as binder and other eco-friendly polymers as plasticizers. Although a Li⁺/H⁺ exchange takes place during our procedure, we demonstrate that the Li⁺/H⁺ exchange reaction is reversible in our procedure and results in the formation of stoichiometric cubic LLZ at the end. The obtained free-standing LLZ sheets with thickness of 150 μm and relative density of approx. 90% offer an ionic conductivity of 0.15 mS cm⁻¹ at room temperature. We thereby prove that it is feasible to use water as dispersion medium and eco-friendly polymer additives for the fabrication of thin garnet-based SE layers.

中文翻译：

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用于固态锂电池的石榴石基固体电解质隔板的水基制造

石榴石型Li ₇ La ₃ Zr ₂ O ₁₂（LLZ）被认为是用于固态锂电池（SSLB）或其他高级锂电池概念（如Li–air或Li– S电池。薄的独立式LLZ薄板可以通过流延成型制造，例如由于流延是工业上已建立的工艺，并且可以大规模生产此类SE，因此它可以用作SSLB中的分离器。然而，用于流延的常规浆料配方中使用的有机溶剂和添加剂引起健康和安全问题，并且还导致溶剂回收的高成本。因此，开发绿色的水基加工路线可以降低制造成本和环境足迹。在这项工作中，我们开发了使用水作为溶剂，水溶性生物聚合物甲基纤维素作为粘合剂以及其他环保聚合物作为增塑剂的LLZ SE的流延铸造工艺。尽管在我们的程序中进行了Li ⁺ / H ⁺交换，但我们证明了Li ⁺ / H ⁺交换反应在我们的程序中是可逆的，最终导致化学计量立方LLZ的形成。所获得的独立式LLZ片材的厚度为150μm，相对密度大约为1。90％的离子电导率在室温下为0.15 mS cm ^-1。因此，我们证明了使用水作为分散介质和生态友好的聚合物添加剂来制造薄石榴石型SE层是可行的。