Ethylenediaminetetraacetic acid enables uniform zinc deposition for long life alkaline zinc-manganese flow battery

Zn-based flow batteries are a suitable choice for scale-up due to the potential benefits of the anode redox material (Zn), and the batteries' high safety, low cost, and high energy density. Notwithstanding advancements in the technical development of these batteries, considerable hurdles persist, especially with the formation of Zn dendrites. This work explores an efficient anolyte additive in improving the performance of a zinc-manganese (Zn-Mn) flow battery. Mn is appealing as a cathode redox material due to its availability, elevated theoretical capacity, and benefits in energy density. The results evidence that the incorporation of the chelating agent ethylenediaminetetraacetic acid (EDTA) as an anolyte additive facilitated the modification of the solvation structure of alkaline zincate, thereby promoting homogeneous deposition of Zn²⁺. This approach effectively addresses the longstanding challenge of Zn dendrite formation in Zn-Mn flow batteries. Our batteries have a lifespan beyond 160 h (over 600 cycles) at a current density of 60 mA cm⁻², with an average coulombic efficiency (CE) of 98.3 % and an average energy efficiency (EE) of 82.4 %. This study endorses the utilization of EDTA as an effective anolyte additive in advancing Zn-Mn flow batteries, characterized by extended cycle life and elevated energy densities, thereby providing credible data to facilitate the broader implementation of this technology.