Organic Molecular Differential Lock Balancing Transport-Reaction Kinetics for Long-Life Alkaline Zinc-Based Flow Batteries

Alkaline zinc-based flow batteries (AZFBs) have attracted huge attention due to their advantages of high safety, high voltage, and low cost. Nevertheless, the zinc dendrites and side reactions attributed to the contradiction between slow zinc ion transport and rapid electrochemical reaction significantly restrict their development as promising long-duration energy storage devices. Herein, a strategy for constructing organic molecular differential locks using L-serine (Ser) additives is reported to balance transport-reaction kinetics and mitigate side reactions. In the bulk electrolyte, Ser reshapes the solvation structure of zinc ions, effectively shielding coulombic repulsion to enhance transport rate. Meanwhile, the increased solvation energy and steric hindrance confine the rapid reduction kinetics. At the electrode/electrolyte interface, Ser preferentially adsorbs on the electrode surface, thereby homogenizing interfacial ion flux and promoting stable 3D diffusion. Concurrently, the elevated nucleation overpotential decelerates zinc deposition kinetics. In addition, Ser can anchor onto the metallic zinc surface to establish an interface protective layer depleted of H₂O and OH⁻, suppressing hydrogen evolution reactions and corrosion. Remarkably, the alkaline zinc-iron flow batteries with Ser can operate stably for over 230 h at 50 mA cm⁻² (30 mAh cm⁻²). This work provides a unique strategy for developing high-stability and long-life AZFBs.