Aqueous zinc-based batteries are expected to be realized as low-cost and high energy density batteries; however, dendrite formation during the charging process of zinc-air batteries remains a major problem. Dendrite growth from the zinc anode is known to cause short-circuiting in zinc-based batteries because of their fast growth toward the cathode and it seems to be the main cause of cycle degradation for these batteries. Therefore, to realize long-life rechargeable zinc-based batteries, characterization of electrochemical zinc deposition is required. In situ transmission electron microscopy (TEM) observation was utilized to visualize the initial state of electrodeposition of a zinc anode with high spatial resolution. A platinum counter electrode was covered with metallic zinc by vacuum deposition, so that observation of the electrodeposition process of pure zinc was successfully achieved while preventing elution of the counter electrode. Analysis using in situ TEM observations of the zinc deposition and dissolution indicated that dissolution after dendrite growth proceeds from the parts near the root to the tips of the dendrites. It is concluded that this phenomenon is evidence that there are concentration gradients between the electrode surface and the surrounding environment during the initial process of dendrite formation.

锌基水性电池有望实现为低成本，高能量密度的电池。然而，锌-空气电池充电过程中枝晶的形成仍然是一个主要问题。从锌阳极的枝晶生长已知会导致锌基电池短路，因为它们向阴极快速生长，这似乎是这些电池循环劣化的主要原因。因此，为了实现长寿命的可再充电锌基电池，需要表征电化学锌沉积。原位透射电子显微镜（TEM）观察用于可视化具有高空间分辨率的锌阳极电沉积的初始状态。铂对电极通过真空沉积被金属锌覆盖，从而在防止对电极洗脱的同时，成功实现了对纯锌电沉积过程的观察。使用原位TEM观察到的锌沉积和溶解的分析表明，树枝状晶体生长后的溶解从根部附近的部分一直延伸到树枝状晶体的尖端。结论是，这种现象证明了在枝晶形成的初始过程中电极表面和周围环境之间存在浓度梯度。