Rapid synthesis of π-extended dipyridyl pyrazines toward robust organic cathodes for aqueous Zn-ion batteries

Organic materials have emerged as promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to their structural flexibility, inherent safety, and environmental compatibility. Yet, their practical adoption is impeded by challenges such as inadequate cycling stability and complex synthesis. This work presents a facile, two-minute room-temperature stirring method to synthesize key dipyridyl pyrazine derivatives, which include dipyrido[3,2-f:2′,3′-h]quinoxaline (DPQ), dipyrido[3,2-a:2′,3′-c]phenazine (DPPZ), and benzo[ i ]dipyrido[3,2-a:2′,3′-c]phenazine (DPPN). The corresponding molecular design strategy targeted increased active site density, extended π-conjugation, enhanced electron delocalization, and improved charge transfer kinetics. Accordingly, the DPPZ-based electrode delivered remarkable electrochemical performance, achieving reversible capacities of 120.5 mAh g −1 at 0.05 A g −1 and 83.4 mAh g −1 at 5 A g −1 , along with 76.6% capacity retention over 6000 cycles. Moreover, it further exhibited outstanding low-temperature performance, retaining 62.0 mAh g −1 at 1 A g −1 and 95.4% of its capacity after 7000 cycles at −20 °C, indicating its potential for use in low-temperature environments. The energy storage mechanism, based on the reversible co-insertion of Zn 2+ and H + at C N sites, was investigated by employing ex situ characterizations coupled with density functional theory (DFT) calculations. These findings underscore a rapid molecular engineering approach that paves the way for advanced organic electrodes in AZIBs.