An Air-Rechargeable Zn/Organic Battery with Proton Storage

Air-rechargeable zinc batteries are a promising candidate for self-powered battery systems since air is ubiquitous and cost-free. However, they are still in their infancy and their electrochemical performance is unsatisfactory due to the bottlenecks of materials and device design. Therefore, it is of great significance to develop creative air-rechargeable Zn battery systems. Herein, an air-rechargeable Zn battery with H+-based chemistry was developed in a mild ZnSO4 electrolyte for the first time, where benzo[i]benzo[6,7]quinoxalino[2,3-a]benzo[6,7]quinoxalino[2,3-c]phenazine-5,8,13,16,21,24-hexaone (BQPH) was employed as cathode material. In this Zn/BQPH battery, a Zn2+ coordination with adjacent C═O and C═N groups leads to an inhomogeneous charge distribution in the BQPH molecule, which induces the H+ uptake on the remaining four pairs of the C═O and C═N groups in subsequent discharge processes. Interestingly, the large potential difference between the discharged cathode of the Zn/BQPH battery and oxygen triggers the redox reaction between them spontaneously, in which the discharged cathode can be oxidized by oxygen in air. In this process, the cathode potential will gradually rise along with H+ removal, and the discharged Zn/BQPH battery can be air-recharged without an external power supply. As a result, the air-rechargeable Zn/BQPH batteries exhibit enhanced electrochemical performance by fast H+ uptake/removal. This work will broaden the horizons of air-rechargeable zinc batteries and provide a guidance to develop high-performance and sustainable aqueous self-powered systems.