Dual‐Electrode Stabilization of Aqueous Zinc‐Iodide Batteries Enabled by an Amino‐Functional Imidazolium Bromide Additive

ABSTRACT Aqueous zinc‐iodide (Zn‐I 2 ) batteries with low cost and high safety have been considered a promising candidate for large‐scale energy storage. However, they suffer issues of instability Zn metal anode and polyiodides shuttle effect at the cathode. In this work, 3‐(3‐aminopropyl)‐1‐methyl‐1H‐imidazol‐3‐ium bromide (APMImBr) ionic liquid was introduced as a novel electrolyte additive for simultaneously stabilizing both the anode and cathode. On the anode, AMIPm + adsorbs on the Zn surface, ensuring uniform Zn deposition, while the tuned solvation structure promotes a robust solid‐electrolyte‐interphase formation. As a result, symmetric cells exhibit significantly prolonged cycle life, operating stably for up to 2000 h at 1 mA cm −2 . Even under extreme current densities of 50 mA cm −2 and 100 mA cm −2 , the cells maintain stable cycling for 300 h and 120 h, respectively. On the cathode, the strong interaction of AMIPm + with polyiodides confines polyiodides to the cathode and suppresses its shuttle effect. Additionally, Br − activates the I − /I 0 /I + four‐electron conversion, enhancing the capacity. Consequently, the aqueous Zn‐I 2 full cells achieve a high capacity of 200 mAh g −1 at 5 A g −1 and show a high cycling stability over 14,000 cycles. Furthermore, the pouch cell also demonstrates high cycling stability under various mechanical abuse.