Engineering zincophilic-hydrophobic anode-anolyte interface via electrolyte additive for sustainable zinc‑manganese flow batteries

Zinc‑manganese flow batteries (ZMFB) have become a strategically important technology in the field of large-scale grid energy storage due to their abundant resources, low cost, and inherent safety. However, challenges such as the growth of Zn dendrites on the Zn anode and the formation of ‘dead Zn' have severely hindered their widespread application. Research shows that the reversibility and stability of Zn metal anodes are closely related to the chemical properties of the anode-electrolyte interface, particularly the inter-Helmholtz plane (IHP). An optimised anolyte additive can enhance anode durability by reducing the free water content of the IHP, mitigating the decomposition of active H₂O molecules, suppressing the hydrogen evolution reaction, reducing dead Zn formation, and inhibiting dendrite growth. N, N, N′, N′-Tetrakis(2-hydroxyethyl)ethylenediamine (TETRA) is innovatively introduced as a multifunctional additive into the anolyte of the ZMFB to regulate the IHP in this work. The results show that adding 5 mM of TETRA to the anolyte effectively reduces the free water content in the IHP, increases the Zn deposition rate, and promotes uniform three-dimensional deposition. Additionally, due to the adsorption of TETRA on the Zn surface, the corrosion resistance of the Zn anode in the alkaline electrolyte is significantly improved. This work has developed an alkaline Zinc‑manganese flow battery (AZMFB) capable of operating at current densities up to 60 mA cm⁻², achieving a cycle life of 130 h with an average coulombic efficiency (CE) of 99.8 %. Furthermore, an innovative and sustainable electrolyte additive strategy has been proposed, effectively addressing issues such as Zn dendrite formation, hydrogen evolution, and anode corrosion within the ZMFB.