Cu-modified Zn anodes enabled by genuine passivation protection of Zn5(OH)8Cl2·H2O nanosheets for aqueous Zn-ion batteries.

The practical application of aqueous Zn-ion batteries (AZIBs) is hindered by Zn dendrites, hydrogen evolution reaction (HER), and corrosion/passivation of Zn anodes. Herein, a Zn-philic Cu layer is first fabricated on Zn anodes, which not only physically covers scratches and fills defects on Zn anodes but also utilizes the high zincophilicity of Cu to guide uniform Zn deposition. A densely packed Zn5(OH)8Cl2·H2O nanosheets (nZCH) layer is formed on Cu layer, which not only selectively adsorbs H2O and repels SO42- to inhibit corrosion/passivation but also prevents electron leakage during Zn deposition in inner Cu layer due to the insulating nature to electrons, thereby suppressing HER. As a result, nZCH-Cu@Zn||nZCH-Cu@Zn symmetric batteries achieve ultra-stable cycling for over 4800 h at 1 mA cm-2 and 3600 h at 5 mA cm-2. It should be emphasized that both Cu layer and nZCH layer constructed in this paper are obtained through a simple and low-cost one-step in-situ configuration strategy. The three-dimensional structure of nZCH facilitates electrolyte diffusion, ensuring uniform distribution of Zn2+ concentration and electric field. Moreover, nZCH is a genuine passivation layer with a dense structure. Its presence inhibits the formation of loose pseudo-passivation Zn4SO4(OH)6·xH2O layer, solving the long-standing passivation problem on Zn anodes.