NiMoO4@Ni3S2 core–shell composites grown in situ on nickel foam for applications in supercapacitors

A binder-free Ni3S2 nanosheets wrapped NiMoO4 nanorods hybrid electrode (NiMoO4@Ni3S2) was prepared on conductive Ni-foam via a simple two-step hydrothermal process. The microstructure and chemical composition of as-prepared NiMoO4@Ni3S2 core–shell hybrid electrode was confirmed by means of SEM, TEM, XRD, and XPS. The SEM analysis results demonstrated that the NiMoO4@Ni3S2 composites consisted of NiMoO4 nanorods in the core, which were surrounded by a myriad of Ni3S2 nanosheets in the shell. Electrochemical characterization revealed that the integrated structure of the NiMoO4@Ni3S2 electrode exhibited a high areal capacitance (2.3 F cm−2 at areal current density of 1 mA cm−2), which was 1.8 times than the NiMoO4 nanorods, excellent rate performance and outstanding cycling performance (84.4% retention at 30 mA cm−2 after 6000 cycles). An asymmetric capacitor assembled with NiMoO4@Ni3S2 core–shell composites and AC as the positive and negative electrodes, respectively, delivered a maximum area energy density of 158.4 mWh cm−2 at an area power density of 2.199 W cm−2, and exceptional capacitance retention of 93.1% after 20k cycles. With such outstanding electrochemical performance, this NiMoO4@Ni3S2 electrode material will have a potential application value in the field of portable and flexible energy storage equipment.