Redox-active poly(imide-quinone) covalent organic framework anodes for high-efficient and durable aqueous proton batteries

Hydrogen ions (protons), as the lightest and smallest non-metallic charge carriers, have aroused great interest in the field of aqueous batteries. Unfortunately, most anode materials used for these proton batteries still suffer from low specific capacity and/or unsatisfactory cycle durability due to structural deterioration resulted from corrosion of strong acid electrolytes. Here, we report for the first time a robust poly(imide-quinone) (PIQ) covalent organic framework (COF) with dual redox-active naphthalene diimide-paraquinone motifs in its periodic skeletons for proton storage, which can afford a high reversible capacity of ∼ 255.6 mAh/g at a current density of 1 A/g with outstanding cycling stability. The aqueous proton battery (APB) fabricated with this PIQ-COF anode and a copper hexacyanoferrate (CuHCF) cathode demonstrates an unprecedentedly remarkable combination of reversible capacity (about 138 mAh/g at 0.5 A/g), rate capability (76.5 % capacity retention at 20 A/g), and long-term cyclability (99.999 % per cycle for 10,000 cycles at 3 A/g). The ex situ FTIR characterization reveals that the C = O groups in naphthalene imides and paraquinones contribute abundant and accessible redox-active sites for proton storage.