Binder-free MgCo2O4@Ni3S2 core-shell-like composites as advanced battery materials for asymmetric supercapacitors

Herein, a new strategy for the fabrication of emerging MgCo2O4 @Ni3S2 heterostructure array for asymmetric supercapacitors through hydrothermal and subsequent calcination technique is reported. The MgCo2O4 micron flakes are full covered by ultrathin Ni3S2 nanosheets and the comparison of morphology for MgCo2O4 and MgCo2O4 @Ni3S2 electrode has been investigated by scanning electron microscope and transmission electron microscope. The porous structure of MgCo2O4 combined with Ni3S2 causes the composite electrode to have a short ion diffusion path, fast ion/electron transfer with maximized use of active material, resulting in high specific capacitance. When the prepared MgCo2O4 @Ni3S2 core-shell-like structure compound is employed as binder-free electrode for supercapacitors, it shows a prominent specific capacitance (1123.9 F g−1) under 1 A g−1 current density. In addition, high capacitance retention (90.7% after 2000 cycles) can be obtained. Most notably, the asymmetry supercapacitor was fabricated by using the carbon activated as negative electrode and MgCo2O4 @Ni3S2 as positive electrode. This resulting MgCo2O4 @Ni3S2/NF // AC device exhibits a great energy density of 28.37 Wh kg−1 under the condition of 159.6 W kg−1 and 82.9% capacity retention after 8000 cycles.