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

• Hierarchical Ni 3 S 2 @NiMoO 4 core-shell nanosheet arrays were synthesized on Ni foam. • The growth density of the NiMoO 4 nanosheets as the shell was adjusted by controlling the hydrothermal reaction time. • The assembled ASC device exhibited a maximum energy density of 28.4 W h kg −1 . Hierarchical Ni 3 S 2 @NiMoO 4 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 NiMoO 4 nanosheets grew on the surface of the core, interconnected Ni 3 S 2 nanosheet arrays. The growth density of the NiMoO 4 nanosheets was adjusted by controlling the hydrothermal reaction time. When the hydrothermal time was 1 h, the as-prepared Ni 3 S 2 @NiMoO 4 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 Ni 3 S 2 @NiMoO 4 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 Ni 3 S 2 @NiMoO 4 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 .