Facile synthesis of graphene-like carbon-coated Ni3S2 nanoparticles self-assembled on 3D dendritic nanostructure as high-performance anode materials of sodium-ion batteries

Although sodium-ion battery is promising to be an alternative to current lithium-ion batteries, it is still facing many challenges and depends on the innovation of the high-performance electrode materials. At present, limited candidates can meet the expectations of high-rate capability, high specific capacity, and long cycle stability simultaneously. Herein, Ni3S2 nanoparticles uniformly embedded in graphene-like carbon layer (Ni3S2/C) self-assembled on three-dimensional (3D) dendritic nanostructure were successfully synthesized with thiourea as sulfur source and ionic liquid as carbon precursor through a simple one-step solid phase calcine strategy. When used as anode material for SIBs, Ni3S2/C nanocomposites afford a high specific capacity of 434.4 mAh g−1 at 0.1 A g−1, excellent rate capability of 277.6 mAh g−1 at current density of 3.0 A g−1, and great cycling stability with a capacity well-maintained to 172.6 mAh g−1 after 200 cycles at 0.1 A g−1. Exceptional cycling capabilities and rate performances could be ascribed to the synergistic effect between graphene-like carbon-coated Ni3S2 nanoparticles and 3D dendritic nanostructure. The unique 3D dendritic nanostructure consists of interconnected porous carbon network, which increases contact between electrode and electrolyte and accelerates the electron transport and ionic diffusion during the discharge-charge process. Furthermore, the graphite-like carbon layer effectively alleviates volume changes and guaranteed structural integrity of Ni3S2 nanoparticles during Na ion insertion and extraction from active material. The kinetic analysis shows that the total charge comes from the contribution of both surface capacitive effect and diffusion-controlled intercalation.