Anionic Co-insertion Charge Storage in Dinitrobenzene Cathodes for High-Performance Aqueous Zinc-Organic Batteries.

Highly active and stable cathodes are critical for aqueous Zn-organic batteries with high capacity, fast redox kinetics, and long life. We herein report para-, meta-, and ortho-dinitrobenzene (p-, m-, and o-DB) containing two successive two-electron processes, as cathode materials to boost the battery performance. Theoretical and experimental studies reveal that nitro constitutional isomerism is key to zincophilic activity and redox kinetics. p-DB hosted in carbon nanoflower harvests a high capacity of 402 mAh g -1 and a superior stability up to 25 000 cycles at 5 A g -1 , giving a Zn-organic battery with a high energy density of 230 Wh kg -1 . An anionic co-insertion charge storage mechanism is proposed, entailing a two-step (de)coordination of Zn(CF 3 SO 3 ) + with nitro oxygen. Besides, dinitrobenzene can be electrochemically optimized by side group regulation via implanting electron-withdrawing motifs. This work opens a new window to design multielectron nitroaromatics for Zn-organic batteries.