N-doped graphene leaves on carbon nanotubes and NiMn2O4-graphene hybrid nanocomposites with ionogel film for flexible symmetric and asymmetric supercapacitors

The efficient fusion of the various components into hybrid nanostructures in a hierarchical three-dimensional fashion is found to be one of the significant strategies to obtain potential electrode materials for super-capacitors. In addressing this, two diverse kinds of 3D graphene-based hybrid nanomaterials are synthesized using facile and scalable approaches, and then their microstructural properties are studied. The developed 3D nitrogen doped-graphene leaves on bamboo shaped carbon nanotubes (N-glbNT-850) exhibit a high specific capacitance of 528 F/g at a 2 A/g current density. 3D blooming flower structured NiMn2O4-graphene electrode exhibit a high specific capacity and rate capability of 1632 C/g, and 88.1%, respectively. Further, a new ionogel electrolyte film is developed by incorporating a high concentration (96 wt%) of ionic liquid into a 4 wt% polymer host. A flexible symmetric supercapacitor fabricated by using this solid-state ionogel electrolyte film and a flexible asymmetric supercapacitor fashioned of N-glbNT//NiMn2O4-graphene could exhibit a wide working voltage range (3.4 V and 1.6 V, respectively), excellent energy density (96.3 and 156.8 Wh/kg, respectively), outstanding power density (3.39 and 2.34 kW/kg, respectively), and good rate performance with high cycle stability and remarkable flexibility. Thus, the development of inexpensive and efficient electrode materials based on graphene and effective solid-state ionogel electrolytes and the application of these technologies for efficient energy storage devices have all been made possible by the new and effective strategic process, which can be beneficial for commercial applications of energy storage, conversion, and environmental systems.