Imidazolium Cation‐Stabilized Interfacial Chemistry for Durable Aqueous Cadmium‐Iodine Batteries

Abstract

ABSTRACT Aqueous metal batteries are attractive candidates for large‐scale energy storage owing to their intrinsic safety and low cost. However, their practical application is constrained by dendrite growth, corrosion, and hydrogen evolution reaction (HER), as well as dissolution‐induced parasitic reactions of the cathode materials. Here, we report a durable cadmium‐iodine (Cd//I 2 ) battery enabled by a dual‐interfacial chemistry regulation strategy. The Cd 2+ /Cd redox couple offers moderate potential to suppress HER and strong resistance to acidic and polyiodide corrosion, rendering Cd metal a highly stable anode. Moreover, the incorporation of 1‐butyl‐3‐methylimidazolium cation (BMIM + ) induces preferential adsorption on the Cd anode, forming a functional interphase that lowers local charge density, suppresses dendrite growth, and promotes uniform Cd deposition. At the cathode, strong electrostatic interactions and steric hindrance between BMIM + and polyiodide anions effectively mitigate the shuttle effect. Benefiting from these synergistic effects, the Cd//I 2 battery delivers a high reversible specific capacity of 152.5 mAh g −1 at 10 A g −1 and achieves ultralong cycling stability over 50,000 cycles, with an ultralow per‐cycle capacity decay of 0.00032%. Even under a high I 2 loading of 17.78 mg cm −2 , the battery maintains 400 cycles with high specific capacity of 173.1 mAh g −1 , underscoring its potential for practical application.