Stabilizing Zinc‐Iodine Batteries via Amyloid Fibril‐Based Electrolytes: Ion Transport and pH Regulation Through Hierarchical Networks

Abstract Zinc‐iodine (Zn‐I 2 ) batteries offer promising prospects for efficient energy storage applications, attributed to their intrinsic safety, high energy density and cost‐effectiveness. However, the widespread adoption of Zn‐I 2 in demanding energy applications necessitates overcoming challenges such as the instability of Zn anode surface electrochemistry and polyiodide shuttling effect. As an innovative proof‐of‐concept, the modulation of ion transport behavior is proposed through the delicate modification of the Zn‐I 2 battery electrolyte environment using amyloid fibrils (AFs) derived from milk proteins. The incorporation of AFs effectively regulated the nucleation and growth behavior of Zn ions and stabilized the local pH fluctuations during the reaction process, thereby inhibiting the side reactions such as hydrogen evolution and byproduct formation. Furthermore, the 3D physicochemical double cross‐linked network of AFs mitigated the shuttling effect of polyiodide ions and enhanced the electrocatalytic activity of the I 2 cathode. The modified electrolytes exhibit a remarkable capacity decay rate of 1.17% after exceeding 30 000 cycles at 5 A·g −1 , coupled with superior anti‐self‐discharge performance over 500 h. The work introduces a novel strategy for regulating coordinated cation and ion transport through meticulous electrolyte design and expands the potential engineering applications of protein‐based materials for enhancing the performance of Zn‐I 2 batteries.