Predeposited lead nucleation sites enable a highly reversible zinc electrode for stable zinc-bromine flow batteries

Aqueous zinc-bromine flow batteries are promising for grid storage due to their inherent safety, cost-effectiveness, and high energy density. However, they have a low energy/power density and inferior cycle stability due to irreversible reactions of uncontrolled zinc dendrite growth and hydrogen evolution reaction. Here, we develop a highly reversible carbon felt electrode with uniformly distributed Pb nanoparticles, which can be realized via an effective in situ predeposition strategy. Owing to abundant Pb nanoparticles as zincophilic nucleation sites, the Pb nanoparticles effectively induce uniform Zn deposition with a dendrite-free morphology. Moreover, the Pb-modified electrode accommodates higher hydrogen evolution reaction overpotential to inhibit the H₂ evolution. Consequently, the modified electrode-based zinc-bromine flow batteries demonstrate a cumulative plating capacity (23 Ah cm^-2) over 2300 h with an average Coulombic efficiency of over 97.4%. This work contributes insights into the design of highly reversible Zn electrode in Zn-based flow batteries.