Three-dimensional and nanoscale resolved hierarchical structure of electroplated zinc complex in aqueous zinc battery

ABSTRACT Aqueous zinc batteries offer safety and cost-effectiveness for grid-scale energy storage although the electrochemical and chemical corrosion of zinc in water results in complex Zn species and 3D morphology, ultimately degrading battery performance. Thus far, the atomic and nanoscale 3D structure of the electroplated Zn complex remains unclear. Here, by employing advanced transmission electron microscopy, particularly cryogenic electron tomography, we resolve the preserved 3D architecture of electroplated zinc. A hierarchical solid–electrolyte interphase (SEI) comprising two critical structures that could impact battery performance is delineated—an epitaxial ZnO nanolayer on a Zn nanoplate as the inner SEI and petal-like zinc hydroxide sulfate (ZHS) flakes emerging from the edges of a Zn–ZnO crystal as the extended SEI. We discovered three epitaxial conditions of ZnO on electrochemically plated Zn nanocrystals: (0001)ZnO ∥ (0001)Zn, (10$\overline{1}$0)ZnO ∥ (10$\overline{1}$0)Zn and (0001)ZnO ∥ (10$\overline{1}$0)Zn. This complex Zn–ZnO–ZHS structure implies a correlation between the zinc-crystal edges and the heterogeneous chemical environment, which can be correlated with the zinc-texture- dependent battery performance.