The Ni/Ni3S2 nanocomposite derived from Ni-ZIF with superior energy storage performance as cathodes for asymmetric supercapacitor and rechargeable aqueous zinc ion battery

The design of cathode material with unique structure and excellent electrochemical property is critical for the development of energy storage device. We report herein the synthesis of a nanocomposite with heterostructure of metallic nickel (Ni) and nickel sulfide (Ni3S2) through a facile solid-gas state reaction method, using Ni-ZIF MOFs and sulfur as precursors. The electrochemical energy storage capabilities of the synthesized composite as cathodes for both supercapacitor and zinc ion batteries have been investigated. Owing to the good conductivity of metallic Ni and superior pseudocapacitive behavior of the Ni3S2, the Ni/Ni3S2 nanocomposite exhibit excellent energy storage capability in both supercapacitor and zinc ion batteries. It was revealed that the Ni/Ni3S2 nanocomposite exhibit an excellent specific capacity of 2228 F g−1 at a current density of 4 A g−1. A high capacity of 1496 F g−1 is remained even at a high current density of 12 A g−1, demonstrating good rate capability of the electrode material. When the Ni/Ni3S2 was used as the cathode material for zinc ion battery, the assembled Ni/Ni3S2//Zn aqueous zinc ion battery can provide a high energy density of 379 Wh kg−1 at power density of 0.34 kW kg−1. The battery also exhibits long-term cyclic stability with capacity retention ratio of 84.1% after 1000 cycles and good rate performance. Our work proposed a facile route to produce transition metal sulfide nanocomposite with excellent capacitive properties as cathode material for the supercapacitor and aqueous zinc ion batteries in green energy storage application.