Achievement of Durable and Efficient Br₂ Storage for Flowless Zn//Br₂ Batteries via Cathode Decoration

Flowless zinc–bromine batteries (FL-ZBBs) exhibit high application prospects owing to high energy density and significantly reduced cost compared with flow ones. However, the issues existed in flow ones are more serious in FL-ZBBs, mainly including the formation of Zn dendrites, Br2/Brn– shuttle-induced Zn corrosion, and sluggish reaction kinetics of Br2 ↔ Br– couple on the cathode. The latter two are highly concerned with the cathode. Herein, toward these two issues, N-doped CNT-decorated carbon felt, NC–CF, was developed. NC–CFs exhibit a largely increased surface area and active sites for the Br2 ↔ Br– redox couple, significantly boosting the adsorption and catalytic properties. Meanwhile, graphitic-N defects make NC–CFs possess better conductivity than the raw CFs. At a high charging capacity of 2 mAh·cm–2, FL-ZBBs assembled using Zn plates as anodes and NC–CFs as cathodes can run stably for 1200 cycles accompanied by a high average Coulombic efficiency (CE) of 92.26% at 10 mA·cm–2, much better than the cells assembled using CFs as cathodes. Meanwhile, the average energy efficiency (EE) of the modified cell is as high as 83.11% due to the small polarization and the high CE, exhibiting high practical application potential.