Synthesis of core-shell structured Ni3S2@MnMoO4 nanosheet arrays on Ni foam for asymmetric supercapacitors with superior performance

Abstract

The present study successfully synthesized core-shell structured Ni3S2@MnMoO4 nanosheet arrays on Ni foam via a simple two-step hydrothermal method followed by the annealing process. MnMoO4 nanosheets as the shell were grown on the surface of the Ni3S2 nanosheet as the core, and the growth density of the MnMoO4 nanosheets was controlled by changing the hydrothermal time. The optimized Ni3S2@MnMoO4 electrode was able to deliver a specific capacity of 979.3 C g−1 at a current density of 2 mA cm−2 in a 2 M KOH solution and also exhibited an ultrahigh cycling stability of 88.3% capacity retention after 7000 charge-discharge cycles under a current density of 10 mA cm−2. In addition, an asymmetric supercapacitor (ASC) device was fabricated using the optimized electrode as the positive electrode and activated carbon (AC) as the negative electrode, and its electrochemical performance was determined. The device achieved a maximal energy density of 31.4 W h kg−1 at a power density of 399.9 W kg−1 as well as an excellent cycling stability with 91.3% retention of its initial value at a high current density of 20 mA cm−2.