Three birds with one stone: In-situ etching-constructing nanocubes protective layer toward highly reversible aqueous zinc-iodine batteries

The severe side reactions caused by H 2 O molecules and polyiodides, along with rampant dendrite growth have critically impeded the progress of aqueous zinc-iodide batteries (ZIBs). Herein, we propose a strategy for in-situ constructing a zinc oxalate protective layer with an ordered nanocube structure (ZCO NC) on the surface of Zn metal anode (ZMA). This approach aims to remove the superficial passivation layer of ZMA and simultaneously suppress the formation of dendrites and the occurrence of parasitic reactions via a facile and cost-effective oxalic acid etching process. Initially, the removal of passivation layer homogenizes the ion distribution near the electrode, alleviating concentration polarization. Secondly, the ZCO NC protective layer serves as a robust physical barrier to resist the attack of H 2 O molecules, while simultaneously trapping free and active H 2 O molecules to accelerate Zn 2+ migration at the electrode/electrolyte interface through its high H 2 O affinity, in turn restraining H 2 O-triggered side reactions and dendrite growth. Moreover, the ZCO NC protective layer can immobilize I 3 − on the surface of the Zn anode, thus preventing the polyiodide-related corrosion. Benefiting from these synergistic effects, the symmetric cell with Zn@ZCO NC exhibit an extended lifespan of 1800 h at 1 mA cm −2 , while ZIBs demonstrate exceptional cycling stability with a discharge specific capacity of 121 mAh g −1 after 6000 cycles at 1 A g −1 .