Morphology controlled hierarchical NiS/carbon hexahedrons derived from nitrilotriacetic acid-assembly strategy for high-performance hybrid supercapacitors

Abstract

• A nitrilotriacetic acid-assisted strategy for controllable synthesis of NiS/carbon hexahedrons was proposed. • Synchronous realization of the combination of carbon with NiS and morphology controlled in one step. • Formation mechanism and determinants of NiS/carbon composites are revealed. • Enhanced power density (4187.2 W kg −1 ) and energy density (30.8 Wh kg −1 ). Effective adjustment of structure and morphology is considered to be an available strategy to improve the energy storage performance of supercapacitor electrode materials. Herein, a series of hierarchical NiS/carbon hexahedrons consist of self-assembling nanoplates or nanorods were synthesized via nitrilotriacetic acid (NTA)-assisted hydrothermal strategy. This study demonstrates that the micro-morphology of the unit structure constituting the hexahedrons can be controlled by adjusting the concentration of NTA. Benefiting from synergetic effect of high void space, hierarchical assembly mode and integrated composite structure, NiS/carbon hexahedrons promote adequate exposure of abundant active sites and enhance the structural stability, donating superior energy storage performance. As expected, the optimized NiS/carbon electrode (NiS/NTA-2) exhibits superb capacitive performance, including excellent specific capacitance of 1530.4 F g −1 at 1.0 A g −1 and remarkable cycle stability with 85.6% after 5000 cycles. Employing the as-prepared NiS/NTA-2 composites as positive electrode, the hybrid supercapacitor device with spectacular capacity of maximum energy density and power density up to 35.1 Wh kg −1 and 4509.3 W kg −1 and impressive long-term stability of 87.2% retention after 5000 cycles is assembled. Moreover, a light-emitting diode (LED) is successfully illuminated for up to 12 min by two devices connected in series. Based on this strategy, high-performance energy storage devices can be further developed through utilizing the modulation effect of metal complexes to design morphology controlled electrode materials.