In situ Construction of Multifunctional Surface Coatings on Zinc Metal for Advanced Aqueous Zinc–Iodine Batteries

Aqueous zinc–iodine batteries (Zn–I2) demonstrate great promise in large scale energy storage systems. However, their practical application faces significant challenges including dendrite formation, corrosion caused by polyiodine ions, and other side reactions at the zinc anode side. Herein, a facile and efficient pretreatment method for zinc anodes through the substitution reaction of Zn and SnF2 to create a dense and durable multifunctional surface layer (MSL). The MSL comprise tin (Sn) and ZnF2 phases on the zinc metal, in which Sn possesses good zinc affinity and a high hydrogen evolution overpotential, while ZnF2 provides pathways for radial ion transport. Importantly, both have a low binding energy with polyiodine ions, preventing the failure of the interface layer. Therefore, this interface layer can effectively mitigate zinc metal electrode dendrite formation, corrosion from polyiodine ions, and other side reactions induced by water, simultaneously. As a result, the Zn–I2 batteries performance is greatly improved and exhibited a stable cycling to 20 000 times with 80% capacity retention at a current density of 2 A g−1. Even the I2 loading is increased to 8 mg cm−2, it can still cycle stably for 5000 cycles with a capacity retention of 94%. The Sn–ZnF2 hybrid interface layer can protect the zinc anode from the corrosion of polyiodide ions and can inhibit the dendrites as well as side reactions caused by water. Benefiting from this, the zinc–iodine full batteries can greatly extend cycle life.