(531e) Optimization and Surface Characterization of Porous Zinc Anodes for Zinc Metal Batteries

The current energy storage market is dominated by lithium-ion batteries (LIBs); however, LIBs are reaching their theoretical energy density. Researchers are looking into alternative solutions in different battery chemistries ranging from metal-sulfur batteries to metal-air batteries. One type of metal air battery that has peak interest in recent years is zinc air batteries (ZABs). Zinc-based batteries are considered as a replacement for LIBs due to their inherent safety, abundance, low cost, and its 2-electron transfer. However, zinc, like all other planar metals, has uneven plating cycles that cause dendrites to form leading to the battery shorting. Therefore, it is critical to improve plating and stripping of zinc ions during the charge and discharge process to enhance the cycle life of the battery.

In this work, we have successfully synthesized porous zinc electrodes (PZE) via a gel-binder method that can stably charge and discharge for over 800 hours at 1mA/cm² before showing signs of failure. We compared PZEs synthesized from small(60nm), intermediate(10µm), and large(150µm) zinc particles to determine which surface features are best suited to mitigate dendritic growth and to improve electrolyte stability. From Scanning electron microscopy (SEM) images seen in Figure 1, large PZE exhibits the best platting patterns of the three PZE examined. The zinc deposits on the large PZE shows a stable and flat morphology and does not form the hexagonal close-packed (HCP) crystal structure that is seen on planar zinc anodes. The deposits seem to melt onto the surface, promoting even plating. The intermediate PZE has an increased affinity to deposit onto the glass microfiber separator leading to a decrease of active material and causing instability during galvanostatic cycling. SEM images of both planar zinc and small PZE show HCP that are normal to the surface, which resulted in very poor electrochemical performance. As the particle size increases, the deposits transition from HCP crystals to flat metal deposits, increasing cyclic stability. Linear sweep voltammetry (LSV) was also performed to test the stability of the electrolyte. The large porous structure of the electrode improved the stability of the electrolyte by increasing the voltage by 300mVs before the electrolyte decomposed compared to planar zinc.