Advancements for aqueous Zn-based flow batteries: challenges and perspectives

Aqueous Zn-based flow batteries (FBs) have emerged as a promising technology for large-scale, long-duration energy storage owing to their inherent safety, low-cost Zn resources, and high-capacity Zn-anode chemistry. These advantages make Zn-based FBs particularly attractive for grid-scale integration of renewable energy. However, their practical deployment and commercialization are still hindered by coupled degradation processes, especially Zn-anode reversibility loss and active-species crossover/shuttle under realistic operating conditions. This review provides a focused overview of failure mechanisms and recent mitigation strategies in aqueous Zn-based FBs. The key challenges associated with non-uniform Zn deposition/stripping, parasitic reactions, and crossover/shuttle are discussed, together with recent advances in electrolyte regulation, electrode-architecture design, chemistry-side crossover control, and membrane/separator engineering. The coupling and trade-offs among interfacial stability, transport selectivity, ionic conductivity, and full-cell performance are also highlighted. Future research directions are finally suggested to focus on practical-condition benchmarking, forced-flow validation of strategies developed in static cells, reliable charge-state and health-state diagnostics and control, and the development of truly flowable Zn-containing energy reservoirs for achieving practical Zn-based FBs.