The compatibility strategy of COFs cathode and optimized electrolyte have been developed for a durable and long-lasting recharged aqueous zinc-ion batteries. The abundant redox-active functional groups of the COF cathode, together with the optimized electrolyte using triflate anions, have resulted in the development of a COF cathode with fast-charging capability, high Coulombic efficiency, flat charge-discharge plateaus, and exceptional long-term cyclability.

Abstract

Rechargeable aqueous zinc-ion batteries (RAZIBs) are attractive due to their affordability, safety, and eco-friendliness. However, their potential is limited by the lack of high-capacity cathodes and compatible electrolytes needed for reliable performance. Herein, we have presented a compatibility strategy for the development of a durable and long-lasting RAZIBs. The covalent organic frameworks (COFs) based on anthraquinone (DAAQ-COF) is created and utilized as the cathode, with zinc metal serving as the anode. The electrolyte is made up of an aqueous solution containing zinc salts at various concentrations. The COF cathode has been designed to be endowed with a rich array of redox-active groups, enhancing its electrochemical properties. Meanwhile, the electrolyte is formulated using triflate anions, which have exhibited superiority over sulfate anions. This strategy lead to the development of an optimized COF cathode with fast charging capability, high Coulombic efficiency (nearly 100 %) and long-term cyclability (retention rate of nearly 100 % at 1 A g⁻¹ after 10000 cycles). Moreover, through experimental analysis, a co-insertion mechanism involving Zn²⁺ and H⁺ in this cathode is discovered for the first time. These findings represent a promising path for the advancement of organic cathode materials in high-performance and sustainable RAZIBs.