High-Performance Aqueous Zinc-Organic Battery with a Photo-Responsive Covalent Organic Framework Cathode.

Abstract

Covalent organic framework (COF) materials, known for their robust porous character, sustainability, and abundance, have great potential as cathodes for aqueous Zn-ion batteries (ZIBs). However, their application is hindered by low reversible capacity and discharge voltage. Herein, a donor-acceptor configuration COF (NT-COF) is utilized as the cathode for ZIBs. The cell exhibits a high discharge voltage plateau of ≈1.4V and a discharge capacity of 214 mAh g-1 at 0.2 A g-1 when utilizing the Mn2+ electrolyte additive in the ZnSO4 electrolyte. A synergistic combination mechanism is proposed, involving the deposition/dissolution reactions of Zn4SO4(OH)6·4H2O and the co-(de)insertion reactions of H+ and SO4 2- in NT-COF. Meanwhile, the NT-COF with a donor-acceptor configuration facilitates efficient generation and separation of electron-hole pairs upon light exposure, thereby enhancing electrochemical reactions within the battery. This leads to a reduction in charging voltage and internal overvoltage, ultimately minimizing electricity consumption. Under ambient weather conditions, the cell exhibits an average discharge capacity of 430 mAh g-1 on sunny days and maintains consistent cycling stability for a duration of 200 cycles (≈19 days) at 0.2 A g-1. This research inspires the advancement of Zn-organic batteries for high-energy-density aqueous electrochemical energy storage systems or photo-electrochemical batteries.