In Situ Observation of Sodiation and Magnesiation of ZnO Nanowire Compared to Lithiation Process

The over-growing demand of high capacity storage for application in electrical vehicles and green power backup energy has triggered the new battery concept search beyond Li-ion. Na-ion and Mg multivalent rechargeable batteries are recent concepts. The natural abadency of Na and Mg on earth makes these batteries more eco-friendly and affordable.  Another considerable issues in batteries are performance and cyclability of batteries. The anode materials usually experience large volume changes through the ion insertion and extraction. This volume change and lithium embrittlement usually causes cracks and loss of contact in the anode material, which ultimately causes the failure of battery. Here, we investigated and compared the structural and mechanical changes of ZnO nanowires during sodiation and magnesiation to lithiation process by using in situ transmission electron microscopy. The cracks were created upon the first lithiation process of single crystalline ZnO nanowire. The lithiated ZnO nanowire shows multiple glassy domains, which has low strength and ductility. This results in poor cyclability of battery. On the other hand, ZnO nanowires do not show any cracks and degradation after sodiation and magnesiation. The direct comparison between Na and Mg-ion batteries to most consumed Li-ion battery would pave the new search for high capacity battery.