LAUSR

Among various energy storage devices, flexible supercapacitors having high mechanical stability with extremely bending and foldable features are highly attractive for a large number of emerging portable light weight consumer devices. Here, we report the fabrication of such a superflexible supercapacitor by using novel octahedron shaped NiCo2O4 nanoparticles as the electrode material for the first time. A new, low-cost hydrothermal method was used to synthesize 50-60 nm size monodispersed perfect octahedron nanoparticles without any structural deformation. An all solid-state symmetric flexible supercapacitor was fabricated by sandwiching the octahedron nanoparticles and [EMIM][BF4] ionic liquid electrolyte between two sheets of newly developed superflexible current collector substrate. The calculated specific capacity and specific capacitance values are found to be 97.9 mAhg1 and 117.3 Fg1, respectively at 0.625 Ag1 current density and at applied potential of 3.0 V. It also offered high energy density value of 33.54 Whkg1 and 10000 measured cycling stability. The supercapacitor is so flexible that, it can be bent or fold upto 180o without any mechanical deformation and the measured capacitance, energy and power density remain almost constant at any angle of twisting. For instance, calculated values of capacitances obtained by bending the cell at an angle of 180°, 150°, 135°, 90°, and 45° are found to be 62, 63.3, 63.73, 64, and 66 Fg1 respectively, in comparison to 67 Fg1 for a non-bending or flat (0o) cell. A faster ion switching between electrode/electrolyte interface, [EMIM][BF4] electrolyte and octahedron shape of the nanoparticle electrode material are found to be responsible for these outstanding charge storage behaviour.