Powder aerosol deposition (PAD) to produce thin ion-conductive NaSICON films in the µm range for high-performance all solid-state sodium batteries

与液体电解液电池相比，紧凑型固态电池可以实现更高的能量密度，而且更安全。与锂电池相比，钠电池使用的原材料也更环保、更丰富。通过在室温下生产薄而致密的固体电解质层，高性能、低成本和低能量的粉末气溶胶沉积(PAD)具有显著简化平面电池结构的潜力。这种致密但只有几微米薄的薄膜应该具有足够的离子导电性，使全固态钠电池能够在室温下运行。因此，本研究项目的目的是证明PAD是否适合生产用于高性能固态钠电池的微米薄而致密的离子导电膜，并通过对所得电解液膜的比较表征来开发合适的工艺参数。具体地说，将使用三种已知的NaSICON组合物来展示通过PAD可以制备多致密的钠离子传导NaSICON膜，与块状陶瓷相比，在室温下可以获得什么样的离子导电性，以及离子导电率如何受层的形态影响。在第二步中，要弄清楚远低于烧结温度的适度退火在多大程度上可以减少晶格变形，从而提高离子电导率。此外，还可以降低界面电阻。为此，用阻抗谱分析了电导限制过程，并将其与电极相关层的形貌和电解质膜的晶格变形进行了关联。由此可以得出三种NaSICON组分的焊盘和热后处理的离子导电性促进工艺参数。钠离子通过制造的固体电解质层的传输，从而证明了致密和稳定的PAD-NaSICON膜的证明，通过建立和热处理的半电池的恒流循环。在此基础上，用最有前景的NaSICON材料和正极活性材料焊盘制作了一个简单的全电池。这将为平板垫片-NaSICON电池用于未来工作温度较低的固态钠电池提供原理证明，并首次估计可能的电流密度。积极的项目结果可能成为进一步研究固态电池中创新的PAD功能层潜力的起点，由于PAD的工业可扩展性，最终也可能引起业界的兴趣。

With compact solid-state batteries higher energy densities can be achieved compared to cells with liquid electrolytes and they are also safer. Compared to lithium batteries, sodium cells also use more environmentally friendly and abundant raw materials. By producing thin but dense solid electrolyte layers at room temperature, high-performance, low-cost, and low-energy powder aerosol deposition, or PAD, has the potential to significantly simplify the construction of planar cells. The dense but only a few µm-thin membranes should have sufficient ionic conductivities to allow an all solid-state sodium battery to operate at room temperature. The objective of this research project is therefore to demonstrate whether PAD is suitable for producing µm-thin yet dense sufficiently ionic conductive NaSICON membranes for high-performance solid-state sodium batteries and to develop suitable process parameters by comparative characterization of the resulting electrolyte membranes. Specifically, three known NaSICON compositions are to be used to show how dense, sodium ion-conducting NaSICON membranes can be prepared via PAD, what ionic conductivities at room temperature compared to bulk ceramics can be achieved, and how the ionic conductivities are affected by the layer morphology. In a second step, it is to be clarified to what extent moderate annealing far below the sintering temperature can reduce the lattice deformations and thus increase the ionic conductivity. In addition, interfacial resistances could be reduced as a result. For this purpose, the conductivity-limiting processes are analyzed by impedance spectroscopy and correlated with the PAD-related layer morphology and the lattice deformations of the electrolyte membrane. From this, the ion conductivity promoting process parameters of PAD and thermal post-treatment can be derived for the three NaSICON compositions. The transport of sodium ions through the manufactured solid electrolyte layers and thus the proof of dense and stable PAD-NaSICON membranes is demonstrated by galvanostatic cycling of built-up and thermally post-treated half-cells. Based on this, a simple full cell is finally built by PAD of cathode active material and the most promising NaSICON material. This will provide a proof of principle of the functionality of planar PAD-NaSICON cells for future solid sodium batteries with low operating temperatures with a first estimation of possible current densities. Positive project results could be the starting point for further research work on the potential of innovative PAD functional layers in solid-state batteries, which could ultimately also generate industrial interest thanks to the industrial scalability of PAD.