Triquinoxalinediol as organic cathode material for rechargeable aqueous zinc-ion batteries

Aqueous zinc-ion batteries are one of the most promising candidates for large-scale energy storage applications. Herein, we report a rationally designed triquinoxalinediol (TQD) organic cathode material for aqueous zinc-ion batteries. Integration of hydroquinone units with hexaazatriphenylene (HAT) core enabled a high theoretical capacity of 669 mA h g(-1) (based on a twelve-electron exchange reaction) and a practical reversible capacity of 503 mA h g(-1) at 100 mA g(-1). Both values are among the highest available in the literature. The charge storage mechanism was systematically studied using ex situ FT-IR and various electrochemical measurements revealing a co-insertion mechanism involving protons and zinc cations. The TQD suffers from significant capacity fading, which was attributed to the dissolution of active material in the electrolyte. That was supported by using in situ UV-vis spectroscopy. This work adds a promising material in a rapidly expanding mosaic of pyrazine/quinone organic cathode materials.