Organic pH Buffer for Dendrite-Free and Shuttle-Free Zn-I₂ Batteries

Area of Science:

• Electrochemistry
• Materials Science

Background:

• Aqueous zinc-iodine (Zn-I2) batteries offer potential for grid-scale energy storage.
• Key challenges include zinc dendrite formation, hydrogen evolution reaction (HER), anode corrosion, and cathode polyiodine shuttling.

Purpose of the Study:

• To investigate N-containing heterocyclic compounds as organic pH buffers to mitigate issues in aqueous Zn-I2 batteries.
• To enhance the stability and performance of Zn-I2 batteries through electrolyte engineering.

Main Methods:

• Addition of pyridine and imidazole as organic pH buffers to the electrolyte.
• Electrochemical characterization, including cyclic voltammetry and galvanostatic cycling.
• Analysis of zinc anode morphology and stability.

Main Results:

• Pyridine/imidazole regulated electrolyte pH, suppressing HER and anode corrosion.
• Organic buffers promoted non-dendritic zinc plating/stripping, achieving 99.6% Coulombic efficiency and 3200h stability.
• Pyridine effectively inhibited polyiodine shuttling and improved I-/I2 conversion kinetics.
• The full Zn-I2 battery demonstrated over 25,000 cycles and 105.5 mAh/g capacity at 10 A/g.

Conclusions:

• Organic pH buffer engineering is a practical strategy for developing dendrite-free and shuttle-free aqueous Zn-I2 batteries.
• N-containing heterocyclic compounds offer a viable solution for improving the longevity and efficiency of zinc-based energy storage systems.