Sea urchin-like Ni-Co sulfides with different Ni to Co ratios for superior electrochemical performance

Nickel cobalt (Ni-Co) sulfides with different stoichiometric Ni to Co ratios have been successfully synthesized based on a facile anion-exchange reaction of Ni (x) Co3-x (CO3)(1.5)(OH)(3) precursors with S2-. All of the Ni-Co sulfides share similar sea urchin-like structures with numerous nanotubes extend outward from the center. The electrochemical performance of Ni-Co sulfides can be tuned owing to the synergistic effect between Ni and Co ions. The bimetallic Ni-Co sulfides show much higher specific capacity than monometallic Co sulfide. Especially, the Ni0.25Co0.75 sulfide shows superior electrochemical performance, which delivers the highest specific capacity of 676 C g(-1) at 1 A g(-1) combined with excellent cycling stability. Sea urchin-like Ni-Co sulfides with different stoichiometric Ni to Co ratios have been synthesized for charge storage, and the sulfides with Ni to Co ratio of 1:3 show superior electrochemical performance.