Construction of NiCo2S4@NiMoO4 Core-Shell Nanosheet Arrays with Superior Electrochemical Performance for Asymmetric Supercapacitors

In this work, we develop hierarchical NiCo2S4@NiMoO4 nanosheet arrays directly anchored on nickel foam by a hydrothermal method. The self-supported core-shell architecture take advantage of high electroactive surface area, rapid channels for ion diffusion and electron transport, and the synergistic contributions from both the NiCo2S4 core and NiMoO4 shell. Remarkably, the NiCo2S4@NiMoO4 electrode showed high specific capacitance of 1487.6 F g(-1) at a current density of 1 A g(-1) and superior cycling stability (89.7 % capacitance retention after 8000 charge-discharge cycles). An asymmetric supercapacitor (ASC) with an optimized cell voltage of 1.6 V was assembled by using activated carbon (AC) as the negative electrode and NiCo2S4@NiMoO4 electrode as the positive electrode, achieving an extraordinary energy density of 53.2 Wh kg(-1) at a power density of 560 W kg(-1), and remained 34.8 Wh kg(-1) at a maximum power density of 11.2 kW kg(-1). The outstanding electrochemical behavior indicate that the NiCo2S4@NiMoO4 nanosheet arrays hold great promise for high-performance energy storage devices.