Analytical Observation of Cathodic Zinc Deposition in High-Capacity Zinc Oxide Electrodes for Rechargeable Zinc-based Batteries: Influence of the Current Rate in the First Charging (Supporting Information)

The effects of the current rate used during the first charging (pre-charging: so-called “formation”) on the cathodic deposition of metallic zinc (Zn) were analyzed for the high capacity (thick) zinc oxide (ZnO) electrode in rechargeable Zn-based batteries. Pre-charging at a lower current rate (1.875 mA cm−2) enabled greater electrode performances for the subsequent charge-discharge cycles. The Zn deposition profiles were investigated by conventional postmortem X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy using a scanning electron microscope, as well as in situ synchrotron XRD and ex situ synchrotron X-ray computed tomography. The results revealed significant differences in the deposition profiles of the metallic Zn depending on the current rates used during pre-charging. The higher rate (18.75 mA cm−2) resulted in an inhomogeneous deposition of Zn, whereas the lower rate yielded finer Zn particles dispersed homogeneously throughout the thick ZnO electrode. These morphological and spatial variations in the Zn deposition during pre-charging affected the subsequent cycling behavior of the thick ZnO electrode.针对可充电锌基电池中的高容量（厚型）氧化锌（ZnO）电极，本研究分析了首次充电（预充电：即所谓的“化成”）阶段所采用的电流密度对金属锌（Zn）阴极沉积的影响。采用较低电流密度（1.875 mA·cm⁻²）进行预充电，可使后续充放电循环获得更优异的电极性能。本研究通过常规事后X射线衍射（X-ray Diffraction, XRD）、配合扫描电子显微镜的能量色散X射线能谱，以及原位同步辐射X射线衍射和非原位同步辐射X射线计算机断层扫描，对锌沉积形貌进行了表征。结果表明，预充电阶段采用的电流密度会显著影响金属锌的沉积形貌：较高电流密度（18.75 mA·cm⁻²）会导致锌沉积不均匀，而较低电流密度则可得到均匀分散在厚型氧化锌电极中的细小锌颗粒。预充电阶段锌沉积的形貌与空间分布差异，会对厚型氧化锌电极的后续循环性能产生影响。