Eco-Friendly High-Performance Symmetric All-COF/Graphene Aqueous Zinc-Ion Batteries

Developing high-performance aqueous symmetric all-organic batteries (SAOBs) by replacing metal-based batteries or batteries with organic electrolytes is highly attractive to achieve a greener rechargeable world. However, such a new energy storage system still exhibits unsatisfactory rate capability and cycling stability due to the limitations in electrode materials screening. Here, a novel covalent organic framework (COF) containing abundant CN and CO for the electrode material is designed, which is combined with graphene and assembled into all-COF/graphene batteries for the first time. Moreover, the co-storage of Zn²⁺ and H⁺ in COF can be achieved in a mild aqueous electrolyte. Impressively, benefiting from the extended porous structure of COF, plentiful active reaction sites, more extensive electron delocalization from CO modification at molecular level, as well as enhanced fast H⁺ storage capacity of graphene and CO in COF, this kind of SAOBs show excellent cycle life and high rate performance (over 15000 cycles with a capacity of 80 mAh g^-1 at a high current density of 5 A g^-1 in pouch cell). This work will open a new window for the design of high-performance aqueous organic batteries, further moving toward a more eco-friendly electrochemical world.