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.