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.