Zwitterionic Electrolyte Additives Empowered Robust Zn–I ₂ Batteries Enduring a Low Temperature of −40 °C

The shuttling of polyiodides in zinc-iodine (Zn-I₂) batteries causes severe active-material loss and zinc-anode corrosion, leading to poor cycling stability. In this work, zwitterionic pyrrole (ZiPy) is designed as a bifunctional additive to adsorb polyiodides and simultaneously stabilize the Zn anode. Experimental and theoretical results demonstrate that the incorporation of ZiPy regulates the interfacial pH, alters the solvation structure of Zn²⁺ ions, and promotes the preferential growth of zinc along the (002) crystal plane. Furthermore, the Zn-I₂ battery incorporating ZiPy demonstrated superior cycling performance (completing 45 000 cycles at a high current density of 8 A g^-1) and low-temperature endurance, achieving a capacity retention of nearly 90.1% after 45 000 cycles at -40 °C. This work sheds light on the development of future high-performance Zn-I₂ batteries through zwitterionic electrolyte engineering.