An organic cathode integrating carbonyl and imino groups for high-performance aqueous zinc-ion battery with air self-charging ability

Air-self-charging aqueous zinc-ion batteries (AZIBs) are a promising system applied in some special occasions, where no external power source can be provided to recharge the battery. Here, a new π-conjugated aromatic compound 2,7,12-tri(4H-1,2,4-triazol-4-yl)-1H-pyrrolo [3,4-b]pyrrolo[3′,4′:5,6]pyrazino[2,3f]pyrrolo[3′,4′:5,6]pyrazi-no[2,3−h]quinoxaline-1,3,6,8,11,13(2H,7H,12H)-hexaone (THQH) is reported. Because THQH contains multiple redox-active groups (CN and CO) and its insolubility in 2 M ZnSO4, as the cathode material of flexible/coin-type AZIBs, it owns outstanding discharge specific capacity, higher-rate performance and longer cycle life. Various ex-situexperiments and theoretical calculation revealed H+and Zn2+participated in the THQH cathode reaction. Notably, as the discharged flexible Zn//THQH battery is exposed to air, it can be self-recharged viathe redox reaction between oxygen in air and the discharged THQH cathode, along with H+ions removal. The flexible Zn//THQH battery can deliver a discharge capacity of up to 566 mA h g−1at 0.5 A g−1, a higher-rate capability and an excellent self-charging cycle stability (31 cycles) after exposed to air for 28 h, displaying an excellent reusability. This work paves a way for the development of high-performance flexible air self-charging AZIBs.