All-Round stannic iodide as electrolyte additive Enables high-capacity and Long-Life aqueous zinc ion batteries

The practical large-scale application of high-safety and low-cost aqueous zinc ion batteries (AZIBs) is hindered by inferior reversibility of commercial zinc anodes and unsatisfactory specific capacity of the commonly used cathode materials. In this work, we demonstrate that these challenges are simultaneously tackled by the introduction of multifunctional stannic iodide into ZnSO4 electrolyte. Density functional theory calculations and electrochemical analysis reveal that the in situ produced bilayer interphase consisting of a zincophilic Sn protective layer and I- rich adsorption layer notably enhances long-term reversibility of zinc metal anode since it decreases Zn nucleation energy barrier, facilitates Zn2+ diffusion, guides homogeneous Zn deposition and constrains water-related side reactions. For the cathode side, additional I-/I2 redox with adsorption-desorption improves specific capacity. As a result, zinc symmetric cell using stannic iodide operates stably for 3100 h at 1 mA cm- 2/1 mAh cm- 2 and has a cycle life beyond 1660 h at 5 mA cm- 2/5 mAh cm- 2. The assembled Zn// MnO2-PAC battery exhibit high specific capacity and an impressive cyclability with high-capacity retention of 98 % after 800 cycles at 1 A g-1. Our results provide an effective approach to construct advanced AZIBs with high energy density and long-life for future large-scale application.