Impact of diffusion layer structure of air electrodes on their performance in neutral zinc/iron - air batteries

Neutral metal-air batteries are of promising practical significance due to their excellent safety, environmental friendliness and strong resistance to carbon dioxide. Among them, the electrochemical performance and stability of air cathode will become a crucial factor restricting the development of neutral metal-air batteries. Herein, gas diffusion layer of an air electrode was constructed by applying different carbon materials including acetylene black (AB), carbon nanotubes (CNT), graphite (GP), ball milled graphite (m-GP) and their mixture with different mass ratios. Corresponding air electrodes were fabricated based on the MnO2/C as the catalyst. For the air electrode AB2@CNT8, its gas diffusion layer was obtained by using the mixture of AB and CNT with a mass ratio of 2:8, and it reveals good oxygen reduction reaction (ORR) performance and high discharge stability when applied to neutral zinc/iron - air batteries. In the neutral chloride electrolyte system, the discharge life of the AB2@CNTCNT8 zinc-air battery reaches 381.39 h and its specific discharge capacity is 765 mA h gZn−1. For the neutral AB2@CNTCNT8 iron-air battery, its specific discharge capacity reaches 863 mA h gFe−1, and it can last a long working time of over 1384 h. In addition, the performance of the air electrode AB2@CNTCNT8 that undergone a long-term operation can be quickly restored by simple hot water treatment. Results indicate that the air electrode AB2@CNTCNT8 has good performance, high stability and durability in the neutral chloride system, and is expected to be a potential candidate for the air cathode of neutral zinc/iron - air batteries. •Optimized gas diffusion layer structure extremely improves the stability of air electrode.•Air electrode with gas diffusion layer of AB-CNT mixture exhibits superior ORR performance.•AB2@CNT8 air electrode exhibits ultra long-term reusable stability when applied to Zn-air battery.