Electronegativity-programmed N-B dipolar carbon nanofiber interlayers for spatially confined iodine redox in aqueous zinc-iodine batteries

Aqueous zinc-iodine (Zn-I₂) batteries are promising candidates for safe and low-cost energy storage; however, their operation is severely limited by the uncontrolled migration of soluble polyiodide intermediates. Beyond the conventional shuttle effect, this challenge arises from the spatial delocalization of iodine redox chemistry, where I^-/I₃^-/I₅^- species propagate from the cathode and trigger electrochemical crosstalk with the Zn anode. Here, inspired by electronegativity-driven activation of heteroatom-doped carbon catalysts, we propose an electronegativity-programmed strategy for iodine-redox-field engineering using self-standing nitrogen–boron co-doped carbon nanofiber (NB-CNF) interlayers. The lower electronegativity of B and higher electronegativity of N relative to C induce charge-asymmetric N/B environments with dipolar character that serve as polar anchoring centers for iodine species, while the superwettable, conductive nanofiber network further integrates the immobilized intermediates into a spatially confined interfacial redox field. This design transforms bulk-diffusion-dominated iodine chemistry into a spatially regulated surface-confined and spatially regulated reaction process. The resulting redox-field confinement suppresses iodine-induced Zn degradation, enabling a smooth Zn surface with reduced roughness and stable Zn symmetric-cell cycling over 1,200 h. Consequently, Zn-I₂ full cells deliver excellent rate capability, with the capacity at 50 C reaching 1.8 times that of pristine carbon nanofiber controls, 87% capacity retention after 48 h resting, and stable cycling over 10,000 cycles at 10 C. This work extends Zn-I₂ battery design from molecular confinement to electronegativity-programmed spatial engineering of electrochemical redox fields.