# Zwitterionic Electrolyte Additives Empowered Robust Zn–I2 Batteries Enduring a Low Temperature of −40 °C

## TL;DR

A new zwitterionic additive improves zinc-iodine batteries by preventing material loss and enabling stable performance even at very low temperatures.

## Contribution

A bifunctional zwitterionic additive is introduced to simultaneously suppress polyiodide shuttling and stabilize the zinc anode.

## Key findings

- ZiPy regulates interfacial pH and alters Zn2+ solvation structure.
- Zn–I2 batteries with ZiPy achieved 45,000 cycles at 8 A g−1 with 90.1% capacity retention at −40 °C.
- ZiPy promotes (002)-oriented Zn deposition for enhanced cycling stability.

## Abstract

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.

A zwitterionic pyrrole (ZiPy) additive is designed to simultaneously suppress polyiodide shuttling and stabilize the zinc anode in Zn–I2 batteries. ZiPy regulates interfacial pH, optimizes Zn2+ solvation, and promotes (002)‐oriented Zn deposition, enabling outstanding cycling stability over 45 000 cycles and excellent low‐temperature endurance, offering new insights for advanced Zn–I2 energy storage systems.