In Situ Grown Hierarchical Electrospun Nanofiber Skeletons with Embedded Vanadium Nitride Nanograins for Ultra‐Fast and Super‐Long Cycle Life Aqueous Zn‐Ion Batteries

The issues of inadequate cycle stability and energy density for aqueous zinc-ion batteries (ZIBs) can be partly addressed by controlling cathode dissolution and structural deterioration and improving electronic conductivity and reaction kinetics. Herein, vanadium nitride embedded nitrogen-doped carbon nanofiber (VN/N-CNFs) composites with 3D self-supported skeletons and hierarchical structures are developed by an electrospinning technique and thermal treatments. The introduction of vanadium-based metal organic frameworks (V-MOFs) contributes to in situ hierarchical growth of whisker-like secondary structures and homogeneous distribution of 0D active VN nanograins into both trunk nanofibers and branched nano-whiskers. The protective and conductive carbon matrix derived from functional V-MOFs and electrospun nanofibers not only prevents the self-aggregation of highly-active 0D nanograins, but also provides encapsulating shells to suppress the vanadium dissolution by controlling the direct contact with aqueous electrolytes. Furthermore, the flexible and free-standing 3D electrospun VN/N-CNFs skeletons contribute high structural integrity for the aqueous ZIBs, exhibiting an ultra-long cycle lifespan with reversible capacity of 482 mAh g(-1) after cycling at 50 A g(-1) for 30,000 cycles and a super-high rate capability with discharge capacity of 297 mAh g(-1) at high rate of 100 A g(-1). This research sheds light upon a pathway toward designing superior ZIBs.