High-voltage and dendrite-free zinc-iodine flow battery.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Zinc-iodine (Zn-I2) flow batteries offer safety and sustainability advantages.
• Challenges include zinc dendrite growth and zinc ion crossover, limiting high current density cycling.
• Current Zn-I2 flow batteries have a standard voltage of 1.29 V.

Purpose of the Study:

• To develop a novel negolyte for Zn-I2 flow batteries that suppresses dendrite formation and ion crossover.
• To enhance the cycle stability and power density of Zn-I2 flow batteries.
• To achieve higher cell voltages for improved energy storage performance.

Main Methods:

• Introduction of a chelated zinc pyrophosphate (Zn(PPi)2^6-) negolyte.
• Electrochemical characterization of Zn plating/stripping behavior.
• Cycling tests at high current densities to evaluate stability and power performance.

Main Results:

• The Zn(PPi)2^6- negolyte facilitated dendrite-free zinc plating and prevented Zn2+ crossover.
• The Zn2+/Zn plating/stripping potential shifted to -1.08 V (vs. SHE), increasing cell voltage to 1.61 V.
• The high voltage battery demonstrated stability over 250 cycles at 200 mA cm-2 and a power density of 606.5 mW cm-2.

Conclusions:

• Chelated Zn(PPi)2^6- negolyte effectively addresses key limitations in Zn-I2 flow batteries.
• The proposed system offers a promising pathway for high-performance, stable, and safe energy storage.
• This advancement could accelerate the adoption of Zn-I2 flow batteries in practical applications.