A high-performance COF-based aqueous zinc-bromine battery

Aqueous zinc-bromine batteries can fulfil the energy storage requirement for sustainable techno-scientific advancement owing to its intrinsic safety and cost-effectiveness. Nevertheless, the uncontrollable zinc dendrite growth and spontaneous shuttle effect of bromine species have prohibited their practical implementation. Herein, we develop an aqueous zinc-bromine battery integrated with the exfoliated covalent organic framework (exCOF)-bromine cathode and COF-coated zinc metal anode. As verified by experimental and theoretical investigations, exCOF with abundant functional groups exhibits strong adsorption toward Br species, therefore immobilizes Br species and facilitates bidirectional conversion of polybromide. Meanwhile, the COF artificial layer on the surface of zinc metal anode can effectively regulate zinc flux and enable the uniform Zn deposition without dendrite growth. Consequently, owing to the synergistic effect of both COF-Zn anode and Br2-exCOF cathode, the as-assembled COF-Zn||Br2-exCOF full cell can deliver a remarkable capacity of ∼183 mAh g−1 (∼0.61 mAh cm−2) after 1000 cycles with capacity retention of ∼83 % at 2 A g−1 and high Coulombic efficiency of ∼99 %. Ultimately, this work can inspire insight into developing high-performance aqueous zinc-bromine battery systems.