Mechanistic Insights into Dendrite Growth in Aqueous Zinc-Ion Batteries with Trace Propylene Carbonate Electrolyte Additive

Dendrite formation at elevated current densities presents a major challenge for aqueous zinc-ion batteries (AZIBs), necessitating a deep mechanistic understanding. We investigate dendrite growth in Zn symmetric cells under stringent conditions (20 mA cm–2 and 20 mAh cm–2) in a 2 M ZnSO4 electrolyte. Our analysis reveals zinc carbonate and Zn4SO4(OH)6·5H2O in the solid electrolyte interphase (SEI), due to dissolved CO2, initiating dendritic growth and leading to rapid short-circuit within 40 h. In contrast, trace propylene carbonate (PC) stabilizes CO2, promoting a homogeneous, carbonate-free SEI layer and extending cycle life over 420 h. Moreover, cross-sectional electron backscatter diffraction (EBSD) analysis of the failed electrode demonstrates that the Zn dendrites grow with no epitaxial relationship to the substrate. The Zn//MnO2 full cell with PC-modified electrolyte maintains a capacity of 203 mAh g–1 after 1000 cycles at 2 C, elucidating Zn dendrite formation mechanisms and guiding electrolyte and anode optimization for AZIBs.