Zinc Nucleation and Growth in Secondary Alkaline Batteries

Zinc morphology strongly affects the performance of secondary alkaline batteries. The formation of mossy and dendritic structures is detrimental to anode performance and cycle life. The initial stages of zinc deposition on carbon structures are investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and electron-diffraction. Mossy zinc is formed by the aggregation of zinc clusters in a nucleation-controlled process. Dendritic zinc is formed by the unstable growth of zinc along preferred growth axes. An attempt is made to develop a free-energy based phase-field model of electrodeposition to simulate dendritic growth. Preliminary results using a solidification model are able to qualitatively simulate zinc deposition. Understanding the nucleation and growth processes is key to developing innovations to improve battery performance in alkaline zinc anodes.