The electrochemical behaviour of sodium metal electrodes is explored in symmetrical Na cells with 1 M NaPF₆ EC:DMC (1:1) electrolyte. Like Li metal, Na metal shows a characteristic voltage behaviour during galvanostatic cycling, which correlates with changes of the electrode surface area and the morphology. The deposition and dissolution behaviour of both alkali metals is largely similar: during dissolution pits form, the metal deposition takes place inhomogeneously, resulting in dendrites. In contrast to Li metal, the electrode surface of Na metal undergoes pronounced morphological and chemical modifications within the first cycles. Since the alkali metals react with relevant organic solvents or with electrolyte anions, a passivating surface film, the solid electrolyte interphase (SEI), is formed. This means the evolution of the Na electrode morphology is governed by two competing processes: (i) metal deposition and dissolution, and (ii) electrode morphology modification during SEI growth. Therefore, Na metal electrodes need at least four formation cycles until their behaviour is stable. Using light microscopy, we observed during Na electrodeposition, that deposits detach from the electrode, indicative for a lack of SEI passivation. We applied the distribution of relaxation times analysis to evaluate the impedance spectra and identified the different contributions to polarization losses.

在具有1 M NaPF _6的对称Na电池中探索钠金属电极的电化学行为EC：DMC（1：1）电解质。类似于锂金属，钠金属在恒电流循环过程中表现出特征性的电压行为，这与电极表面积和形态的变化相关。两种碱金属的沉积和溶解行为在很大程度上相似：在形成溶蚀坑的过程中，金属沉积不均匀地发生，从而导致了枝晶。与锂金属相比，钠金属的电极表面在最初的循环中经历了明显的形态和化学修饰。由于碱金属与相关的有机溶剂或电解质阴离子发生反应，因此形成了钝化的表面膜，即固体电解质中间相（SEI）。这意味着Na电极形态的演变受两个相互竞争的过程控制：（i）金属沉积和溶解，（ii）SEI生长过程中的电极形态改变。因此，Na金属电极需要至少四个形成周期，直到其行为稳定为止。使用光学显微镜，我们在钠电沉积过程中观察到，沉积物从电极上脱落，表明缺乏SEI钝化。我们应用了弛豫时间的分布分析来评估阻抗谱，并确定了对极化损耗的不同贡献。