Mullite Mineral‐Derived Robust Solid Electrolyte Enables Polyiodide Shuttle‐Free Zinc‐Iodine Batteries

Zinc dendrite, active iodine dissolution, and polyiodide shuttle caused by the strong interaction between liquid electrolyte and solid electrode are the chief culprits for the capacity attenuation of aqueous zinc‐iodine batteries (ZIBs). Herein, mullite is adopted as raw material to prepare Zn‐based solid‐state electrolyte (Zn‐ML) for ZIBs through zinc ion exchange strategy. Owing to the merits of low electronic conductivity, low zinc diffusion energy barrier, and strong polyiodide adsorption capability, Zn‐ML electrolyte can effectively isolate the redox reactions of zinc anode and AC@I2 cathode, guide the reversible zinc deposition behavior, and inhibit the active iodine dissolution as well as polyiodide shuttle during cycling process. As expected, wide operating voltage window of 2.7 V (vs Zn2+/Zn), high Zn2+ transference number of 0.51, and low activation energy barrier of 29.7 kJ mol−1 can be achieved for the solid‐state Zn//Zn cells. Meanwhile, high reversible capacity of 127.4 and 107.6 mAh g−1 can be maintained at 0.5 and 1 A g−1 after 3 000 and 2 100 cycles for the solid‐state Zn//AC@I2 batteries, corresponding to high‐capacity retention ratio of 85.2% and 80.7%, respectively. This study will inspire the development of mineral‐derived solid electrolyte, and facilitate its application in Zn‐based secondary batteries. Mullite is transformed as high‐performance solid‐state electrolyte (Zn‐ML) to address the issues of zinc dendrites, iodine dissolution, and polyiodide shuttle for Zn//AC@I2 batteries. For the Zn anode, Zn‐ML electrolyte eliminates the side reactions and guides the uniform zinc deposition behavior. For the AC@I2 cathode, Zn‐ML electrolyte minimizes the active iodine dissolution and inhibits the polyiodide shuttle, endowing long‐term cyclic stability.