Engineering Low-Cost Organic Cathode for Aqueous Rechargeable Battery and Demonstrating the Proton Intercalation Mechanism for Pyrazine Energy Storage Unit.

Seeking organic cathode materials with low cost and long cycle life that can be employed for large-scale energy storage remains a significant challenge. This work has synthesized an organic compound, triphenazino[2,3-b](1,4,5,8,9,12-hexaazatriphenylene) (TPHATP), with as high as 87.16% yield. This compound has a highly π-conjugated and rigid molecular structure, which is synthesized by capping hexaketocyclohexane with three molecules of 2,3-diaminophenazine derived from low-cost o-phenylenediamine, and is used as a cathode material for assembling aqueous rechargeable zinc ion batteries. Both experiments and DFT calculations demonstrate that the redox mechanism of TPHATP is predominantly governed by H+ storage. The Zn-intercalation product of nitride-type compound, is too unstable to form in water. Moreover, the TPHATP cathode exhibits a capacity of as high as 318.3 mAh g-1 at 0.1 A g-1, and maintained a stable capacity of 111.9 mAh g-1 at a large current density of 10 A g-1 for 5000 cycles with only a decay of 0.000512% per cycle. This study provides new insights into understanding pyrazine as an active redox group and offers a potential affordable aqueous battery system for grid-scale energy storage.