Tuning the solvation structure of zinc ions via urea enables long-cycling alkaline zinc‑manganese flow batteries

This work proposes a novel strategy utilizing urea as a bifunctional anolyte additive for zinc‑manganese (Zn Mn) flow batteries to regulate dead zinc formation and mitigate dendrite growth. Urea reduces the rate of zinc deposition, facilitating a uniform three-dimensional deposition and offering effective protection against alkaline corrosion of zinc via surface adsorption. The results demonstrate that incorporating 0.1 M urea into the anolyte solution of alkaline Zn Mn flow batteries extends the cycling time to 70 h under a current density of 60 mA cm −2 , with an average coulombic efficiency (CE) of 97.1 % and an energy efficiency (EE) of 82.6 %. The results provide a promising and valuable approach to addressing the issue of zinc dendrites while also introducing an economical, sustainable, and highly reliable electrolyte alternative for Zn Mn flow batteries. • The significant role of urea as an anolyte additive to flow batteries is studied. • Urea suppresses zinc dendrites and eliminates dead zinc in alkaline Zn Mn flow batteries. • The self-corrosion and hydrogen evolution of zinc electrodes are diminished by urea. • Urea altered the solvation of Zn 2+ and facilitated homogeneous 3D deposition of Zn. • The cycling stability of Zn Mn flow batteries is enhanced by urea.