Interface coordination regulation of zinc ions for advanced zinc-iodine batteries

Aqueous rechargeable zinc-iodine batteries, as an alternative to lithium-ion batteries (LIBs), deliver the advantages of high theoretical specific capacity, high safety, environmental friendliness, and abundant reserves, making them suitable for large-scale energy storage applications. Nevertheless, unstable Zn anodes would cause a series of symptoms, such as the growth of Zn dendrites and side reactions, which endanger the stability and lifespan of the batteries. Herein, an organic-metal (PAA-Zn) functional film is introduced onto the surface of Zn foil via the coordination of polyacrylic acid and divalent ions to address the above challenges of Zn anodes. The PAA-Zn functional films adjust the uniform distribution of the interfacial electric field, which is advantageous for uniform Zn plating/stripping. Additionally, the abundant oxygen-containing functional groups not only significantly enhance the interfacial hydrophilicity, but also reduce the number of free water molecules reaching the Zn foil surface through the isolation and desolvation effect of functional groups, thus inhibiting corrosion and hydrogen evolution side reactions. As a result, PAA-Zn electrodes exhibited a stable cycling for over 1000 h in symmetrical cells. Most importantly, the Zn-I2 batteries demonstrated a high specific capacity with a retention rate of 89.9 % during 3500 cycles when assembled with PAA-Zn anodes.