A High‐Capacity and High‐Voltage Aqueous Zn‐Polymer Battery with Self‐Charging Function

Abstract Organic electrodes in aqueous batteries rely on electrochemical redox reactions for charge and discharge. The organic cathode at a discharged state can be spontaneously oxidized when exposed to air, which facilitates the development of air‐charging batteries. However, polymer cathodes in aqueous rechargeable Zn‐ion batteries (ARZIBs) generally show low discharge median voltage below 1 V. Herein, a new polymer cathode is reported that is prepared by electrodepositing poly(4‐hydroxydiphenylamine, HDPA) onto mesoporous activated carbon and shows a relatively high discharge voltage plateau at ≈1.1 V when coupled with a Zn anode. Its self‐charging performances at different conditions are investigated. Also, a high areal capacity of 3.8 mAh cm −2 of the cathode is achieved. The poly(4‐HDPA) contains both amino and carbonyl groups, and the carbonyl group is found to be fully responsible for redox reaction. Further investigation suggests that both Zn 2+ and H + in the ZnSO 4 electrolyte participate in the charge storage process, and the H + plays a dominant role. The air‐charging mechanism of this polymer cathode is elucidated both experimentally and theoretically. To demonstrate the practical applications, prototypes of box‐shaped battery pack are air‐charged to either drive a mini electric fan or light up LEDs.