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. This work presents a rapid room-temperature synthesis of dipyridyl pyrazine derivatives for aqueous Zn-ion batteries. The DPPZ cathode achieves high capacity, exceptional long-term cycling (76.6% retention after 6000 cycles), and superior low-temperature performance. Mechanistic studies reveal a reversible Zn 2+ /H + co-insertion storage mechanism at C N active sites. • DPPZ is synthesized via an ultrafast room-temperature process within 2 min, featuring facile scalable synthesis. • Extended π-conjugation and optimized active sites enhance electron delocalization and zinc ion storage performance. • The electrode shows excellent rate and cycling stability, retaining 76.6% after 6000 cycles at 5 A g -1 . • Outstanding low-temperature performance is achieved, with 95.4% capacity retention after 7000 cycles at -20 ℃. • Reversible Zn 2+ /H + co-insertion at C=N sites is verified by ex situ characterizations and DFT calculations.