Fused Functional Organic Material with the Alternating Conjugation of Quinone-Pyrazine as Cathode for Aqueous Zinc Ion Batteries

Organic cathode materials for aqueous rechargeable zinc batteries (ARZBs) are rapidly gaining prominence, while the exploration of compounds with affordable synthesis, satisfactory electrochemical performance, and understandable mechanisms still remains challenging. In this study, 6,8,15,17-tetraaza-heptacene-5,7,9,14,16,18-hexaone (TAHQ) as an easily synthesized organic cathode material with novel quinone/pyrazine alternately conjugated molecule structure is presented. This organic electrode exhibits good capacity with highly reversible redox reactions, and the influence of multi-active structures on the Zn2+/H+ loading behavior is systematically investigated by ex situ spectroscopy, electrochemical tests, and computation. Both experimental and theoretical studies effectively address the Zn2+/H+ intercalation/deintercalation kinetics. Benefitting from the fused active functionalities, the assembled Zn//TAHQ battery displays a maximum discharge specific capacity of 254.3 mAh g-1 at 0.5 A g-1, and it maintains remarkable cycle performance with 71% capacity retention after 1000 cycles under 5 A g-1. Organic cathode material TAHQ with alternating conjugated molecular structure of quinone/pyrazine was synthesized.The redox mechanism was investigated by characterization and DFT calculation.It was proved that the quinone active unit mainly encapsulated Zn2+2, the pyrazine ring encapsulated H+, and stabilized zinc ions to form a five-membered ring through the interaction of lone pair electrons with Zn2+.image