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

A versatile electrolyte additive, stannic iodide, is employed for synchronous enhancement of both anode and cathode towards high-capacity and long- life aqueous zinc ion batteries. 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. And additional I - /I 2 redox with adsorption–desorption at the cathode side improve specific capacity. • Stannic iodide (SnI 4 ) as a multifunctional electrolyte additive is identified. • Simultaneous improvement of both the cathode and anode for AZIBs is achieved. • SnI 4 induced bilayer interphase enhances long-term reversibility of zinc anode. • Additional I - /I 2 redox at the cathode side improve specific capacity. 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 ZnSO 4 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 Zn 2+ diffusion, guides homogeneous Zn deposition and constrains water-related side reactions. For the cathode side, additional I - /I 2 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//MnO 2 -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.