Advanced self-charging aqueous battery with rapid charging capability and a high open-circuit voltage

Abstract

Air self-charging aqueous Zn-ion batteries (AZBs) integrating advantages of aqueous batteries and self-charging have attracted significant attention. However, they suffer from the time-consuming cathodic self-charging process and low capacity, limiting their real application. Herein, we report a donor-acceptor typed covalent organic framework incorporating naphthalenediimide and triphenylamine units (NT-COF) as an advanced cathode for self-charging AZBs. NT-COF features a porous structure with abundant redox-active sites and a narrow bandgap, which significantly boosts electron/ion transport properties and O₂ diffusion. Upon exposure to air, the OCV of Zn//NT-COF battery rapidly increases from 0.2 to 1.03 V within 1 min, followed by a gradual rise to 1.25 V within 1 h. The battery also shows a 100% self-charging efficiency even under a current density of 0.5 A g⁻¹, while maintaining a stable average discharge capacity of 109.4 mAh g⁻¹ at 0.2 A g⁻¹ after 1 h of self-charging upon cycling. Despite self-charging and galvanostatic charging modes, Zn//NT-COF batteries exhibit high performance in hybrid configurations. Experimental and stimulation results reveal the NT-COF cathode experiences the co-insertion of Zn²⁺/H⁺ with H⁺ ions playing a dominant role. The rapid kinetics of H⁺ removal during the air-oxidation process are critical in enabling the ultrafast air self-charging capability of Zn//NT-COF batteries. This study advances the development of sustainable and efficient self-powered devices.