Aqueous zinc metal batteries (AZMBs) are an emerging technology with promising applications in grid-level energy storage. Here, we explore their potential while addressing the fundamental challenges that impede their practical development, including hydrogen evolution reaction (HER), zinc corrosion, and dendrite formation. To do this, we implement in situ techniques to probe the real-time charge- and mass-transfer kinetics of zinc electrodeposition, which is the main mechanism of energy storage in AZMBs. Using correlated microscopy, electrochemical mass spectrometry (ECMS), electrochemical quartz crystal microbalance (EQCM), and other analytical techniques, we measure accurate insights about the correlated nature of zinc electrodeposition and HER. These insights provide critical information about how we can predict, control, and mitigate parasitic side reactions that limit AZMB reversibility and stability, leading to efficient design strategies. 

Recent work by our group has showcased several new insights toward understanding the interplay between HER and zinc deposition. The first of these is that high current densities lead to an interfacial pH gradient while electrodepositing zinc. At high pH values driven by high current densities, strong electric fields drive the uniform formation of a solid electrolyte interphase (SEI) in batteries. This phenomenon promotes more reversible and stable ion transport, leading to higher overall battery performance and offering a viable strategy for artificial SEI formation. 

Dually, we have uncovered the role of the current collector as a main driver of corrosion while batteries are at rest. Once zinc electrodeposits, the thermodynamic potential of the system favors zinc dissolution and chemical corrosion. Electrons generated through the zinc dissolution step can “spillover” into a conductive substrate (i.e., copper or titanium), leading to delocalized HER across the entire substrate. This charge transfer pathway highlights why recent studies across multiple groups have found zinc resting losses are so crippling for AZMBs. 

The recent findings by our group and new discoveries around the corner highlight the importance of building a strong fundamental understanding of existing energy storage and conversion systems. Driven by fundamentals, we can make new and unique measurements, understand interesting truths about interfacial charge- and mass-transfer phenomena, and drive the discussion on mechanistically focused energy advancements.