NiCo2S4 hollow microsphere decorated by acetylene black for high-performance asymmetric supercapacitor

•Acetylene black decorated NiCo2S4 hollow microsphere is prepared via soft template method.•The composite shows high specific capacitance and ultrahigh rate capability.•Unique hollow structure and high conductivity give the excellent electrochemical performance.•The asymmetric supercapacitor exhibits high energy or power density.

High-rate acetylene black (AB) decorated NiCo2S4 hollow microsphere is prepared via a gas bubble soft template and hydrothermal methodology. Benefiting from the combined advantages of the AB with high conductivity and the nanopetals assembled NiCo2S4 with unique hollow micro-/nano- structures, abundant porosity and high conductivity, the as-obtained composites are found to exhibit high specific capacitances (768 F g−1 at 2 A g−1) and remarkable rate capabilities (92.2, 80.1 and 70.3% of capacity retention rate at 20, 50 and 100 A g−1). The fabrication mechanism of the AB-NiCo2S4 composite is also proposed. Furthermore, an asymmetric supercapacitor is fabricated by using the AB-NiCo2S4 composite as a positive electrode and activated carbon as a negative electrode. Owing to the excellent electrochemical properties of the AB-NiCo2S4 electrode, the asymmetric device delivers high energy density (24.7 Wh kg−1) at a power density of 428 W kg−1 or high power density (17.12 kW kg−1) at a reasonable energy density of 7.1 Wh kg−1, and exceptional cycling stability (105.6% of the initial capacity retention at 5 A g−1 over 5000 cycles). These results above demonstrate the significance and great potential of mesoporous NiCo2S4 hollow microsphere-based composites in the development of high-performance energy-storage systems.