Hierarchically Porous Metal–Organic Gel Hosting Catholyte for Limiting Iodine Diffusion and Self-Discharge Control in Sustainable Aqueous Zinc–I2 Batteries

Rechargeable aqueous zinc–iodine batteries (AZIBs) represent excellent zinc–iodine redox chemistry and emerged as a promising aspirant due to their high safety, low cost, ease of fabrication, and high energy density. Nevertheless, the high-dissolution-induced iodide diffusion toward the zinc anode brings the self-discharge, which governs the capacity fading and poor cycling life of the battery. Herein, a multipurpose sponge-like porous matrix of a metal–organic gel to host a substantial amount of an iodine-based catholyte and uniform distribution of iodine with controlled iodide diffusion is introduced. Limiting the iodine diffusion due to increased viscosity provides superior electrochemical performance of this promising cathode for solid-state AZIBs. As a result, AZIBs delivering high performance and long-term stability are fabricated with a capacity of 184.9 mA h g–1 with a superior capacity retention of 95.8% even after 1500 cycles at 1 C rate. The unique concept of self-discharge protection is successfully evaluated. Prototype flexible band-aid-type AZIBs were fabricated, which delivered 166.4 mA h g–1 capacity in the bending state, and applied to real-scale wearable applications.