Channel engineering strategy of precisely modified MOF/nanofiber composite separator for advanced aqueous zinc ion batteries

As the combination of metal-organic framework (MOF) materials with adjustable channels and flexible polymeric matrix, MOF/nanofiber composite separators enable the controllable ion transport behavior, which offers promising candidates for developing novel battery separators. In this study, series MOF functionalized electrospun polyacrylonitrile nanofiber separators were successfully developed via a precisely surface grafting strategy and then served as the separators for highly efficient aqueous zinc (Zn)-ion batteries (ZIBs). Moreover, channel engineering was developed by placing amino (MOF-N) and sulfonic acid groups (MOF-NS) on the channel surface of UIO-66, which then effectively promoted the ion transport progress. In particular, the resultant MOF-NS shows an excellent ionic conductivity (22.81 mS cm- 1), improved Zn2+ transference number (0.78), and outstanding cyclic durability. These enhanced properties can be contributed by the effectively promoted dissociation of zinc salts and desolvation processes of hydrated Zn ions through strong ion-dipole interactions, as confirmed by the theoretical simulations. Our work demonstrates the great importance of channel engineering in modifying porous MOFs materials and the strong power of the precisely modified MOF/nanofiber separators in regulating ion transmission behavior and thus offers a promising separator candidate for high performance aqueous ZIBs.