Polyhydroxy Molecular Regulator Enabled Interfacial Microenvironment Programming for Alkaline Zinc-Iron Flow Batteries.

Alkaline zinc-iron flow batteries (ZIFBs) are attractive for large-scale energy storage because of their low cost, intrinsic safety, and scalable architecture, yet their practical deployment remains hindered by hydrogen evolution and uncontrolled Zn deposition in three-dimensional porous electrodes. Here, we report that isomalt acts as a polyhydroxy molecular regulator that reconfigures the interfacial microenvironment of porous carbon felt, thereby endowing the porous electrode with a more deposition-directing function for reversible Zn plating/stripping. In the bulk electrolyte, isomalt reconstructs the local hydrogen-bond network, lowers water activity, and suppresses hydrogen evolution. At the carbon/electrolyte interface, its preferential lateral adsorption establishes a hydroxyl-rich interphase that homogenizes zincate transport and directs Zn growth toward a preferred (002) orientation, thus promoting compact and reversible deposition. This interfacial microenvironment programming markedly reduces the charge-transfer resistance and activation barrier of the Zn anode, enabling stable cycling for over 500 cycles at 20 mA cm-2. In full-cell tests, the optimized ZIFB delivers a high energy efficiency of 87.5%, substantially outperforming the pristine electrolyte. Beyond identifying a low-cost green additive, this work establishes polyhydroxy molecules as interfacial programming units for three-dimensional porous electrodes, offering a new design concept for directional metal deposition in aqueous flow-battery systems.