A Chemically Polished Zinc Metal Electrode with a Ridge-like Structure for Cycle-Stable Aqueous Batteries

Abstract

Aqueous rechargeable zinc (Zn) metal batteries show great application prospects in grid-scale energy storage devices due to their good safety, low cost, and considerable energy density. However, the electrical and topographical inhomogeneity caused by the native passivation layer of metallic Zn foil leads to inhomogeneous electrochemical plating and stripping of metallic Zn, and the limited accessible area to the electrolyte of the regular foil electrode causes the poor rate capability, which together hinder the practical application of the Zn metal electrode in rechargeable aqueous batteries. In this work, we show that the native passivation layer on the Zn foil electrode can be removed by a simple chemical polishing strategy, associated with the formation of a three-dimensional ridge-like structure of metallic Zn (r-Zn) on the surface of the Zn foil electrode due to the selective etching of weak crystallographic planes and grain boundary of metallic Zn. The clean and uniform surface of the metallic Zn electrode enables homogeneous plating and stripping of metallic Zn, and the ridge-like structure of r-Zn increases the accessible surface area to the electrolyte and reduces the local current density, which elevates the electrochemical performance of the Zn metal anode with regard to the cycling stability and rate capability. It is demonstrated that a r-Zn anode cycles stably for over 200 h at 1 mA cm −2 and 0.5 mA h cm −2 with a low overpotential of 20 mV, which far outperforms 39 h of cycling with an overpotential of 72 mV for its pristine metallic Zn counterpart.

Synergistic Manipulation of Zn2+ Ion Flux and Desolvation Effect Enabled by Anodic Growth of a 3D ZnF2 Matrix for Long‐Lifespan and Dendrite‐Free Zn Metal Anodes

“…As shown in Figure 1e,f, there are many scratches observed on the surface of the Zn foil, which may be formed during its manufacturing process. [ 28 ] These scratches increase the surface roughness and enhance the tip electric field density, aggravating the formation of Zn dendrites during cycling. SEM images of the Zn@ZnF 2 electrode (Figure 1g,h) display that the surface of the Zn substrate is tightly covered with a continuous and dense ZnF 2 matrix with interconnected 3D morphology, which can increase the contact area of electrode/electrolyte and afford abundant porous tunnels for ion transport.…”

Strategies for the Stabilization of Zn Metal Anodes for Zn‐Ion Batteries

“…For instance, a 3D porous Zn electrode was prepared by removing the ZnO species from Zn substrate, which is generated by partially oxidizing Zn foil in air. [ 88 ] Similar to the aforementioned 3D Cu host, the skeleton and pores of this porous Zn respectively offer pathways for electron and ion transportation, and its larger contact area with electrolyte also provides more sites for Zn deposition compared with the bare Zn foil. Accordingly, the polarization of Zn deposition on this porous Zn foil is decreased, and the dendrite formation of Zn is suppressed.…”

Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

“…Compared with planar electrodes, 3D Ni-Zn has a larger specific surface area, which redistributes the local electric field and induces the preferential and uniform Zn deposition into the 3D microchannels, thus successfully suppressing dendrites and significantly improving the electrochemical performance of the battery. Besides, Zn itself is also designed as the main body of the 3D structure [99][100][101].…”

“…Compared with planar electrodes, 3D Ni-Zn has a larger specific surface area, which redistributes the local electric field and induces the preferential and uniform Zn deposition into the 3D microchannels, thus successfully suppressing dendrites and significantly improving the electrochemical performance of the battery. Besides, Zn itself is also designed as the main body of the 3D structure [ 99 – 101 ]. For example, a 3D porous Zn anode with dual channels, consisting of a continuous cavity and a conductive framework, allows ions and electrons to migrate quickly at the anode interface [ 99 ].…”