Asymmetric supercapacitors based on porous MnMoS4 nanosheets-anchored carbon nanofiber and N, S-doped carbon nanofiber electrodes

Abstract

Electrode materials with high electrochemical activity and a favorable morphology are highly desired for improving the energy density of supercapacitors. A ternary metal sulfide with higher electrochemical activity and capacity than mono-metal sulfides offers immense promise as an energy storage material. In the present investigation, an advanced flexible hybrid electrode material composed of porous manganese molybdenum sulfide (MnMoS4) nanosheets supported on flexible carbon nanofiber (CNF) mat has been prepared via three sequential steps: (i) electrospinning, (ii) stabilization/carbonization, and (iii) hydrothermal reaction. Advantages from the rich electrochemical redox properties of MnMoS4 and the 3D interconnected network architecture of porous CNF mat, a large specific capacitance of 2187.5 F/g (at 1 A/g), and a good capacity retention ability (>87%) were achieved for the MnMoS4 @CNF hybrid electrode. In addition, asymmetric supercapacitor (ASC) devices were assembled by utilizing two different binder-free electrodes, i.e., MnMoS4 @CNF mat as the positive electrode and N, S doped CNF mat as the negative electrode, and evaluated their capacitive performances in two different electrolytes, i.e., KOH and Na2SO4. As-assembled ASC with 1 M Na2SO4 electrolyte delivered a high energy density of 72.5 Wh kg−1 and a power density of 2.7 kW kg−1 together with a capacity retention of 93.5% after 5000 cycles. The overall outcome of this investigation indicates that the binder-free nanostructured MnMoS4 @CNF hybrid mat has great potential for the development of next-generation supercapacitor devices.