Flexible Electrospun Carbon Nanofiber @ NiS Core/Sheath Hybrid Membranes as Binder-Free Anodes for Highly Reversible Lithium Storage

The lithium storage performance of metal sulfides is restricted by their intrinsic poor conductivity, large volumetric expansion, and involvement of insulating polymer binders during the electrode preparation process, which can be solved by constructing binder-free hybrid electrodes with nanostructured metal sulfides grown on self-standing conductive templates. In this work, flexible hybrid membranes with nickel sulfide (NiS) nanoparticles uniformly anchored on electrospun carbon nanofibers (CNFs) have been prepared as binder-free anodes for high-performance lithium-ion batteries. The hierarchical CNF@NiS core/sheath hybrid membranes with 3D macroporous architecture can provide open and continuous channels for rapid diffusion of lithium ions to access the electrochemically active NiS nanoparticles. Moreover, the CNF can act as both a conductive core to provide efficient transport of electrons for fast lithiation/delithiation of the NiS sheath, and as a buffering matrix to mitigate the local volumetric expansion/contraction upon long-term cycling. As a consequence, the optimized CNF@NiS hybrid membranes exhibit a high reversible capacity of 1149.4 mA h g(-1) with excellent cycling stability, and high rate capability of 664.3 mA h g(-1) even at a high current density of 3 A g(-1), making them promising flexible and binder-free anode materials for highly reversible lithium storage.