Synergistic Current Collector and Electrolyte Additive Enable 10 000‐Cycle Zinc Iodine Batteries with Low N/P Ratios

ABSTRACT Aqueous zinc//iodine (Zn//I 2 ) batteries with low negative‐to‐positive (N/P) ratios promise high volumetric and gravimetric energy densities by minimizing the thickness of the Zn anode. However, their commercial viability is hindered by hydrogen evolution reactions (HER) and Zn corrosion, which is exacerbated by polyiodide shuttle. Herein a synergistic strategy, using single‐layer graphene‐coated copper foil (G@Cu) as the current collector and introducing poly(quaternary ammonium salt)‐2 (PUB) electrolyte additive, is proposed to stabilize bilateral electrodes, thus extending the lifespan of low N/P Zn//I 2 batteries. The graphene monolayer transfers and redistributes electrons from the underlying Cu foil via its conjugated π‐bonds, increasing the over‐potential of the HER. The G@Cu exhibits a low H 2 evolution rate of 13.14 µmol h – 1 cm −2 , which is 2.5‐fold lower than that of bare Cu. Concurrently, the positively charged quaternary ammonium (N + R 4 ) groups of PUB electrostatically confine polyiodides, mitigating the shuttle effect. Density functional theory (DFT) calculations reveal a high adsorption energy of −0.887 eV between PUB and I 3 − . Consequently, the G@Cu//I 2 battery, utilizing the PUB‐containing aqueous electrolyte at an N/P ratio of 3.0, delivers an ultra‐long cycle life of 10 000 cycles at 2 A g −1 , representing a 172.4‐fold improvement over a conventional Cu//I 2 cell.