Real-Time Identification and Understanding of Zinc Compounds in Rechargeable Zinc-Alkaline Electrodes

Abstract

Rechargeable zinc-alkaline electrodes are attractive forms of electrochemical energy storage for commercial applications because of the high theoretical energy density of zinc metal and the low cost, safety, and environmentally friendliness of aqueous zinc systems. The rechargeable zinc electrode has been historically limited in depth-of-discharge and cycle life, which has prevented it from being widely used on a commercial scale. This limitation is partly due to irreversible reactions occurring during discharge, which lead to passivation of the zinc electrode. Despite extensive study, the properties of these oxide species and the conditions leading to their formation are not fully understood. In this work, we identify different compounds that form on zinc electrodes using in operando optical microscopy, in operando X-ray diffraction, and scanning electron microscopy, as well as chemically identify these species and the conditions at which they form using in operando confocal Raman spectroscopy. Identification of zinc species that detrimentally affect zinc reachargeability and understanding their formation will promote the design of better electrodes and electrolytes, leading to improved cycle life and depth-of-discharge in rechargeable zinc-alkaline batteries. Figure 1