Byproduct reverse engineering to construct unusually enhanced protection layers for dendrite-free Zn anode

Rechargeable aqueous Zn-ion batteries have received numerous attention due to low cost, non-flammability, and high energy density. However, the limited lifespan of Zn metal anodes resulting from uncontrollable growth of Zn dendrites impedes their practical application. Here, we use zinc hydroxide sulfate hydrate (ZHS), well known as a byproduct produced in aqueous Zn-ion batteries, to instead reverse engineer the material as an artificial protection layer for the first time. Unlike the uneven microflake-structured ZHS formed by corrosion reaction reported in previous studies that induce unstable Zn dendrite growth, the produced porous ZHS protection layer can evenly guide Zn-ion flux to the surface of Zn metal by charateristics including hydrophilicity, high Zn-ion conductivity, low electronic conductivity, and diffusion channels of ZHS, leading to endow remarkable plating/stripping reversibility without Zn dendrite growth and suppressed side reactions. Accordingly, the porous ZHS protection layer coated Zn electrode exhibits a low overpotential (15.5 mV) and a long cycle lifespan of 1000 h at 1 mA cm-2 for 1 mAh cm-2 in symmetric cell conditions and outstanding capacity retention of 82.7 % after 2000 cycles at 5.0 A g-1 in full cell conditions. We believe that this work provides deep and new insights into the design of artificial protection layers using byproduct materials.