Loutati A, Sohn Y J, Tietz F
Institute of Energy and Climate Research, Materials Synthesis and Processing (IEK-1), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
Helmholtz Institute Münster: Ionics in Energy Storage (IEK-12), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
Chemphyschem. 2021 May 17;22(10):995-1007. doi: 10.1002/cphc.202100032. Epub 2021 May 3.
Two types of solid electrolytes have reached technological relevance in the field of sodium batteries: ß/ß"-aluminas and NaSICON-type materials. Today, significant attention is paid to room-temperature stationary electricity storage technologies and all-solid-state Na batteries used in combination with these solid electrolytes are an emerging research field besides sodium-ion batteries. In comparison, NaSICON materials can be processed at lower sintering temperatures than the ß/ß"-aluminas and have a similarly attractive ionic conductivity. Since Na O-SiO -ZrO -P O ceramics offer wider compositional variability, the series Na Zr Si P O with seven compositions (0≤x≤3) was selected from the quasi-quaternary phase diagram in order to identify the predominant stability region of NaSICON within this series and to explore the full potential of such materials, including the original NaSICON composition of Na Zr Si PO as a reference. Several characterization techniques were used for the purpose of better understanding the relationships between processing and properties of the ceramics. X-ray diffraction analysis revealed that the phase region of NaSICON materials is larger than expected. Moreover, new ceramic NaSICON materials were discovered in the system crystallizing with a monoclinic NaSICON structure (space group C2/c). Impedance spectroscopy was utilized to investigate the ionic conductivity, giving clear evidence for a dependence on crystal symmetry. The monoclinic NaSICON structure showed the highest ionic conductivity with an optimum ionic conductivity of 1.22×10 at 25 °C for the composition Na Zr Si PO . As the degree of P content increases, the total ionic conductivity is initially enhanced until x=1 and then decreases again. Simultaneously, the increasing amount of phosphorus leads a decrease in the sintering temperatures for all samples, which was confirmed by dilatometry measurements. The thermal and microstructural properties of the prepared samples are also evaluated and discussed.
在钠电池领域，有两种类型的固体电解质已具有技术相关性：β/β″-氧化铝和NASICON型材料。如今，室温固定式蓄电技术备受关注，除了钠离子电池外，与这些固体电解质结合使用的全固态钠电池是一个新兴的研究领域。相比之下，NASICON材料的烧结温度比β/β″-氧化铝低，且具有同样吸引人的离子电导率。由于Na₂O-SiO₂-ZrO₂-P₂O₅陶瓷具有更广泛的成分变化性，因此从准四元相图中选择了具有七种成分（0≤x≤3）的NaₓZr₂Si₃₋ₓPₓO₁₂系列，以确定该系列中NASICON的主要稳定区域，并探索此类材料的全部潜力，包括将原始的NASICON成分Na₃Zr₂Si₂PO₁₂作为参考。为了更好地理解陶瓷的加工与性能之间的关系，使用了几种表征技术。X射线衍射分析表明，NASICON材料的相区比预期的要大。此外，在该体系中发现了以单斜NASICON结构（空间群C2/c）结晶的新型陶瓷NASICON材料。利用阻抗谱研究离子电导率，明确证明了其对晶体对称性的依赖性。单斜NASICON结构显示出最高的离子电导率，对于成分Na₃Zr₂Si₂PO₁₂，在25℃时的最佳离子电导率为1.22×10⁻³ S/cm。随着P含量的增加，总离子电导率最初会增强，直到x = 1，然后再次下降。同时，磷含量的增加导致所有样品的烧结温度降低，这通过膨胀计测量得到了证实。还对制备样品的热性能和微观结构性能进行了评估和讨论。
