Synthesis of hierarchical Ni3S2@NiMoO4 core-shell nanosheet arrays on Ni foam for high-performance asymmetric supercapacitors

Hierarchical Ni3S2@NiMoO4 core-shell nanosheet arrays were directly fabricated on Ni foam through a simple two-step hydrothermal reaction followed by an annealing treatment. The shell, ultra-thin NiMoO4 nanosheets grew on the surface of the core, interconnected Ni3S2 nanosheet arrays. The growth density of the NiMoO4 nanosheets was adjusted by controlling the hydrothermal reaction time. When the hydrothermal time was 1 h, the as-prepared Ni3S2@NiMoO4 with a core-shell structure could achieve a high specific capacity up to 1121.4 C g(-1) at a current density of 5 mA cm(-2). In addition, the Ni3S2@NiMoO4 demonstrated 91.6% capacity retention of its initial value for 5000 cycles at a current density of 30 mA cm(-2). Additionally, an asymmetric supercapacitor (ASC) device was assembled based on the optimized Ni3S2@NiMoO4 electrode as the positive electrode and activated carbon (AC) as the negative electrode. The ASC exhibited a maximum energy density of 28.4 W h kg(-1) at a power density of 90.8 W kg(-1), and showed a remarkable cycling performance with 93.1% retention of the initial capacitance after 10,000 cycles at a current density of 30 mA cm(-2).