A high-performance aqueous rechargeable zinc battery based on organic cathode integrating quinone and pyrazine

In spite of the recent rapid progress of organic cathode materials for aqueous rechargeable zinc batteries (ARZBs), there are still many challenges such as unaffordable synthesis, unsatisfactory electrochemical performance, and unclear mechanisms in this field. Herein, we report 5,7,12,14-tetraaza-6,13-pentacenequinone (TAPQ) as an easily-synthesized organic cathode material with a novel quinone/pyrazine hybrid structure. Benefitting from the multiple electroactive C=O and C=N bonds, TAPQ possessed a theoretical capacity of 515 mAh g(-1) (based on a six-electron reaction) and a practically reversible capacity of 443 mAh g(-1) within 0.1-1.6 V vs. Zn2+/Zn, both of which set new records for organic cathodes in ARZBs. The H+/Zn2+ co-insertion mechanism involving H+ as the predominant participant was confirmed by detailed investigations including various ex-situ characterizations, electrochemical tests, and DFT calculations. Based on the clear mechanism understanding, a modified voltage range of 0.5-1.6 V was adopted to simultaneously achieve high energy density (270 mAh g(-1) x0.84 V = 227 Wh kg(-1)) and excellent cycling stability (capacity retention of 92% after 250 cycles under 50 mA g(-1), with an average Coulombic efficiency of 99.96%). Furthermore, the evolution mechanism of TAPQ electrode structure during cycling was also carefully studied to reveal the origin of capacity decline. The novel molecular structure, easy synthesis, superior electrochemical performance, and deeper mechanism understanding provide researchers important insights into the further development of organic cathode materials for ARZBs toward practical applications.

Automated summary

Despite challenges in the field, the organic cathode material TAPQ, with its easily-synthesized nature and novel structure, demonstrated excellent electrochemical performance and a clear H+/Zn2+ co-insertion mechanism. This provides important insights for further development of organic cathode materials for ARZBs towards practical applications.