Kingshuk Roy1
Purdue University1
The study delves into the hurdles faced by aqueous zinc metal batteries (AZMBs), including challenges like the unwanted hydrogen evolution reaction (HER), corrosion of the zinc substrate, and dendrite growth, all of which hinder the overall effectiveness of these batteries. To thoroughly understand HER, the study introduces the use of in-situ electrochemical mass spectrometry (ECMS) for precise real-time monitoring of HER during zinc electrodeposition. It is highlighted that even a minute fraction (0.3%) of the total charge attributed to HER has a detrimental impact on the long-term cycling performance of AZMBs. The study establishes a significant platform by introducing a method to accurately determine the faradaic efficiency in zinc electrodeposition. This advancement becomes a valuable tool in evaluating additives and modifications aimed at enhancing the stability of AZMBs and suppressing the HER. Moreover, the text introduces a thoughtful approach to improving AZMBs by employing tetraalkylsulfonamide (TAS) additives. This additive is designed to tackle challenges like dendrite formation, HER, and ZnO passivation on the anode, which have historically impeded the development of AZMBs. Through various techniques such as nuclear magnetic resonance spectroscopy, mass spectrometry, and density functional theory studies, we demonstrate that TAS molecules displace water from Zn2+ solvation. This alters the solvation matrix, disrupting the hydrogen bond network in free water. The study reports promising outcomes with TAS additives, including suppressed dendritic growth and HER, along with a remarkable ~25-fold cycle life improvement—from approximately 100 hours to over 2500 hours—at a current density of 1 mA/cm2. Techniques such as X-ray diffraction and X-ray photoelectron spectroscopy reveal impressive suppression of insulating side products and the formation of ion-conductive solid electrolyte interphase components. Post-cycling analysis further illustrates uniform, planar zinc growth in the presence of TAS, in contrast to the inhomogeneous, void-containing clusters observed in its absence. In conclusion, the findings from this study suggest that TAS additives offer a comprehensive framework for realizing robust zinc metal batteries, presenting a promising alternative to lithium-ion batteries.