Sol-gel routed NiMn₂O₄ nanofabric electrode materials for supercapacitors

NiMn₂O₄ (NMO) nanomaterials were prepared via a facile sol-gel process and small pieces of tissue paper were used as a template to obtain one-dimensional (1D) nanofabric shape. Connectivity of the nanoparticles in fabric shape was observed by field-emission scanning electron microscope and transmission electron microscope images. X-ray diffraction pattern was analyzed to confirm the pure phase and crystallinity of the end product. Energy dispersive X-ray spectroscopy was done to check the homogeneous distribution of the Ni, Mn and O elements. The 1D nanofabric NMO was further employed as an electrode material for supercapacitors (SCs). The cyclic voltammetry, galvanostatic charging/discharging and electrochemical impedance spectroscopy techniques were used to determine the supercapacitive properties of electrode materials. The high specific capacitance of 303 F g⁻¹ was obtained at the current density of 0.5 A g⁻¹. Almost stable specific capacitance was obtained till 5000 cycles. The high specific capacitance and stability of the electrode material may be attributed to the fabric shape and connectivity of the particles where voids/gaps in between particles provide more accommodation for the ions. Asymmetric SC (ASC) device was also fabricated and its electrochemical performance was checked. Two yellow color light-emitting diodes and a motor fan were powered from series-connected two ASCs.