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

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 Zn²⁺ and H⁺ in the ZnSO₄ 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.