MnCo2S4 nanoparticles anchored to N- and S-codoped 3D graphene as a prominent electrode for asymmetric supercapacitors

Binary composites MnCo2S4 nanoparticles are potential and attractive materials for supercapacitors. Here, we synthesis the MnCo2S4 nanoparticles anchored on both N and S co-doped 3D graphene composites via a facile two-step controlled sulfurization route. Thiourea contents shows strong effect on the nanostructures and electrochemical properties of the 3D composites. When adjusting the molar ratio of thiourea to Mn2+ as 48:1, the optimal composite electrode achieves a largest specific capacitance of 1324.3 F g−1 at 1 A g−1, with high conductivity, excellent rate performance and outstanding cyclic stability due to its unique structural advantages. Moreover, we fabricate an asymmetric supercapacitor with an operating voltage of 1.5 V using the composite and N, S co-doped graphene nanosheets as both electrodes and it delivers a high energy density of 62.9 Wh kg−1 at a power density of 0.74 kW kg−1, and 28.0 Wh kg−1 at a power density of 1.80 kW kg−1, which are higher than those of reported similar devices. These results prove that the design and optimization of MnCo2S4 and graphene composites is a method to achieve high performance supercapacitors.