Dendrite-free Zn deposition enabled by a TFSI-Nafion modified carbon felt electrode for zinc bromine flowless batteries

Abstract

Aqueous zinc-bromine flowless batteries (ZBFLBs) are emerging as promising next-generation energy storage systems owing to their low-cost active materials, simplified cell configuration, intrinsic safety, and high energy densities. However, zinc dendrite formation on the anode remains a critical challenge that limits cycling stability and operational lifetime in aqueous zinc-based batteries. During repeated cycling, nonuniform Zn2+ nucleation and growth induce surface short circuits and dead zinc formation, collectively leading to capacity fading and cell failure. Herein, a TFSI-Nafion composite coating strategy is proposed to enhance Zn2+ transport kinetics and promote uniform zinc plating/stripping. The modified electrode enables homogeneous zinc deposition, thereby extending the ZBFLB lifespan. At a depth of charge of 96.5 mAh, the electrode maintains an average coulombic efficiency of 96.52% with uniform zinc deposition morphology. Furthermore, a practical ZBFLB demonstrates stable operation at a high depth of charge of 386 mAh for 800 h with a coulombic efficiency of 78.08%. This work provides an effective electrode design strategy to promote uniform Zn deposition and extend the cycle life of ZBFLBs.