Coordination‐Bond‐Mediated Biomass Interfaces Govern Zinc Nucleation and Transport in Flow Batteries

ABSTRACT The energy efficiency of aqueous zinc‐iodine flow batteries (AZIFBs) is constrained by unstable Zn electrodeposition/stripping at the anode, originating from inhomogeneous interfacial mass/charge transport and mismatched energy barriers for zinc nucleation vs. growth. Herein, we report a coordination‐bond‐mediated interfacial engineering strategy that directly regulates Zn ^{2 +} transport and nucleation at the molecular level. A conformal, bio‐derived interphase is constructed on oxygen plasma–activated carbon felt (CF) by immobilizing carboxyl‐functionalized bacterial cellulose (C‐BC) through interfacial hydrogen bonding. The C‐BC coating uniformly enriches the electrode surface with ─COO ⁻ groups, which act as spatially distributed zincophilic anchoring sites. At the electrode–electrolyte interface, deprotonated carboxylates undergo ligand‐exchange reactions with [Zn(H ₂ O) ₆ ] ^{2 +} species to form stable Zn─O coordination bonds. This coordination interaction locally redistributes electron density around Zn ^{2 +} , disrupts its hydration shell, and lowers both the desolvation barrier and the critical nucleation free energy (ΔG*), thereby homogenizing zinc nucleation and suppressing dendritic growth. Thus, AZIFBs employing C‐BC@CF anodes deliver a cumulative capacity of 72 Ah at 40 mA cm ^{− 2} /20 mAh cm ^{− 2} , with an average Coulombic efficiency of 98.7%, voltage efficiency of 70.3%, and energy efficiency of 68.3% over 900 cycles. This work establishes coordination‐bond‐mediated biomass interfaces as a scalable and cost‐effective paradigm for overcoming anode limitations in AZIFBs.