Hoppe Antonia, Dirksen Cornelius, Skadell Karl, Stelter Michael, Schulz Matthias, Carstens Simon, Enke Dirk, Koppka Sharon
Institute of Chemical Technology, Universität Leipzig, 04109 Leipzig, Germany.
Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Michael-Faraday-Str. 1, 07629 Hermsdorf, Germany.
Materials (Basel). 2021 Feb 10;14(4):854. doi: 10.3390/ma14040854.
A new preparation concept of a partially porous solid-state bilayer electrolyte (BE) for high-temperature sodium-ion batteries has been developed. The porous layer provides mechanical strength and is infiltrated with liquid and highly conductive NaAlCl salt, while the dense layer prevents short circuits. Both layers consist, at least partially, of Na-β-alumina. The BEs are synthesized by a three-step procedure, including a sol-gel synthesis, the preparation of porous, calcined bulk material, and spin coating to deposit a dense layer. A detailed study is carried out to investigate the effect of polyethylene oxide (PEO) concentration on pore size and crystallization of the bulk material. The microstructure and crystallographic composition are verified for all steps via mercury intrusion, X-ray diffraction, and scanning electron microscopy. The porous bulk material exhibits an unprecedented open porosity for a NaAlO bilayer-system of ≤57% with a pore size of ≈200-300 nm and pore volume of ≤0.3 cm3∙g. It contains high shares of crystalline α-AlO and Na-β-alumina. The BEs are characterized by impedance spectroscopy, which proved an increase of ionic conductivity with increasing porosity and increasing Na-β-alumina phase content in the bulk material. Ion conductivity of up to 0.10 S∙cm at 300 °C is achieved.
一种用于高温钠离子电池的部分多孔固态双层电解质（BE）的新制备概念已被开发出来。多孔层提供机械强度，并被液体且高导电的NaAlCl盐渗透，而致密层防止短路。两层至少部分由Na-β-氧化铝组成。BE通过三步法合成，包括溶胶-凝胶合成、多孔煅烧块状材料的制备以及旋涂以沉积致密层。开展了一项详细研究以考察聚环氧乙烷（PEO）浓度对块状材料孔径和结晶的影响。通过压汞法、X射线衍射和扫描电子显微镜对所有步骤的微观结构和晶体组成进行了验证。对于NaAlO双层系统，多孔块状材料展现出前所未有的开孔率≤57%，孔径约为200 - 300 nm，孔体积≤0.3 cm3∙g。它含有高比例的结晶α-AlO和Na-β-氧化铝。通过阻抗谱对BE进行了表征，结果表明随着孔隙率增加以及块状材料中Na-β-氧化铝相含量增加，离子电导率升高。在300℃时实现了高达0.10 S∙cm的离子电导率。
