The rechargeable Zn-air battery boasts high energy density, safety and environmental friendliness. However, fast charging of Zn-Air batteries confronts a serious problem of bubble precipitation. The bubbles generated by the oxygen precipitation reaction at the anode are attached to the electrode surface, leading to serious hazards such as blocked ion transport in the electrolyte.

Researchers also found that large bubbles require a higher contact angle difference to generate enough unbalanced surface tension on both sides to drive them across the electrode. Accordingly, a phase diagram of bubble behavior related to bubble and contact angle size was developed to guide the electrode design.

A phase design diagram of bubble behavior (Image by TAN’s team)

Through electrochemical mass spectrometry tests, researchers further revealed that under the action of "bubble diode", the gas generated by oxygen precipitation reaction is discharged from the cell system in time, avoiding the adhesion of bubbles and carbon corrosion reaction under high charging oxidation state.

The outcome of electrochemical mass spectrometry tests 

(Image by Tan's team)

The results of Prof. TAN's team point the way for future design on bubble-free electrodes, guiding the development of high-performance Zn-air batteries and other gas-evolved electrochemical systems.

Paper link: https://doi.org/10.1016/j.ensm.2023.02.030

(Written by HUANG Rui, edited by MA Xuange, USTC News Center)