Fluorine-doping and biomass nanocellulose synergy enable ultra-stable ZnMn2O4 cathodes for aqueous zinc-ion batteries

In this work, we introduce a dual approach, combining defect engineering with fiber reinforcement, for the first time, to simultaneously improve the structural stability and transport kinetics of ZnMn 2 O 4 (ZMO) in aqueous zinc-ion batteries (AZIBs). Incorporating fluorine into the ZMO lattice successfully introduces a high concentration of oxygen vacancies, enhancing Zn 2+ diffusion and electron conductivity while optimizing the electronic structure. At the same time, straw cellulose nanofibers (SCNFs), derived from agricultural corn stalk waste, were co-assembled with carbon nanotubes (CNT) to prepare a straw cellulose nanofibers@carbon nanotubes (SCNFs@CNT) flexible conductive film that serves dually as a robust loading platform and a continuous conductive network for the microspheres. The fabricated ZMO/CNT-F cathode achieved a high specific capacity of 534.7 mAh·g −1 (0.53mAh·cm −2 ) at 0.5 A·g −1 and retained 224.5 mAh·g −1 (0.22mAh·cm −2 ) after 4000 cycles under a high current density of 3 A·g −1 , highlighting its outstanding long-term cycling stability. First-principles calculations showed that fluorine doping leads to bandgap narrowing, charge density localization, and bond length elongation, all contributing to reducing the diffusion energy barrier. This study presents valuable perspectives on defect and interface engineering for AZIB cathodes and introduces an eco-friendly method for repurposing agricultural waste.