image: (a−i) SEM images of electrodissolution at current densities of (a−c) 0.1 mA cm−2, (d−f) 1 mA cm−2, and (g−i) 5 mA cm−2, respectively. (j−l) Proportion of dissolved area to total electrode area for current densities of (j) 0.1 mA cm−2, (k) 1 mA cm−2, and (l) 5 mA cm−2, respectively. (m−o) LSCM images and section profiles for a capacity of 0.5 mAh cm−2 at current densities of (m) 0.1 mA cm−2, (n) 1 mA cm−2, and (o) 5 mA cm−2, respectively. (p) Depth analysis of different current densities with a capacity of 0.5 mAh cm−2. (q) Schematic illustration of the electrodissolution mechanism at different current densities.
Credit: ©Science China Press
Aqueous Zinc-based Batteries (AZBs) have emerged as promising candidates for grid-scale energy storage systems due to their inherent safety, environmental friendliness, low cost, and high energy density. However, the irreversible plating and stripping behaviors of zinc electrode during long-term cycling lead to uncontrolled dendrite growth, significantly hindering the practical application of this technology.
Unlike the cathode materials of commercial lithium-ion batteries, which are lithium-containing compounds (e.g., LiFePO4, LiMn2O4), the cathode materials of AZBs are typically zinc-free (e.g., manganese-based oxides, vanadium-based oxides, air electrodes). As a result, the first operational step of AZBs is the discharge process, wherein the zinc electrode undergoes an electrodissolution reaction rather than electrodeposition. Once electrodissolution occurs, the surface state of the zinc electrode changes, inevitably influencing subsequent steps. Therefore, a comprehensive understanding of electrodissolution behavior deserves equal attention to the deposition process, as it is critical for constructing robust zinc electrode and practical AZBs.
The researchers conducted detailed electrodissolution experiments using finely polished zinc foil. The results revealed that as the current density increased, the electrodissolution behavior exhibited a transformation from "point-line-surface" and a dimensional crossover from 0D to 1D to 2D.
Furthermore, combining EBSD characterization of polycrystals, corrosion potential testing of single crystals, and DFT calculations, the study revealed differences in the electrodissolution behavior among various zinc crystal planes. The results showed that the (002) plane is the most resistant to dissolution, while the (110) plane is the most susceptible to degradation.
Building on the understanding of electrodissolution behavior and mechanisms, the study further investigated the impact of electrodissolution on the spatial and capacity irreversibility of zinc electrodes. Importantly, the formation mechanism of "dead zinc" was elucidated by considering both the structural heterogeneity of dendrites and the external micro-environment. Based on these findings, the researchers constructed zinc electrodes with preferred orientations through epitaxial growth, effectively mitigating dissolution inhomogeneity and enhancing electrode reversibility.
Starting from the practical operational steps of aqueous zinc-based batteries, this study delved deeply into the electrodissolution behavior and mechanisms of zinc electrodes, providing a novel approach to enhancing zinc electrode reversibility. Moreover, the findings can be extended to the study of other metal-based electrodes.
Journal
Science Bulletin