Precipitating Zinc‐Polyethylenimine Complex for Long‐Lasting Aqueous Zn‐I Batteries

Aqueous rechargeable Zn‐I battery offers significant advantages for reliable and cost‐effective energy storage applications. However, current aqueous Zn‐I batteries still face challenges related to limited cycling performance. Herein, we introduce an innovative in‐situ precipitated zinc‐polyethylenimine (PEI–Zn2+) complex design. This approach leverages the complexing effect between Zn2+ cations from the aqueous electrolyte and the amino groups of PEI in the cathode, enhancing the performance of aqueous Zn‐I batteries. The resulting insoluble PEI–Zn2+ complex immobilizes iodide species, facilitating efficient battery operation. This novel design enabled an aqueous Zn‐I battery to achieve over 5000 cycles with 83.3% capacity retention. Additionally, the battery demonstrated promising preliminary performance under practical conditions, including fluctuating charging, various states of charge, and integration with photovoltaic solar panels. This work provides new insights into the design of aqueous zinc batteries.