Flexible and High Performance Supercapacitors Based on NiCo(2)O(4)for Wide Temperature Range Applications

Binder free nanostructured NiCo(2)O(4) were grown using a facile hydrothermal technique. X-ray diffraction patterns confirmed the phase purity of NiCo(2)O(4). The surface morphology and microstructure of the NiCo(2)O(4) analyzed by scanning electron microscopy (SEM) showed flower-like morphology composed of needle-like structures. The potential application of binder free NiCo(2)O(4) as an electrode for supercapacitor devices was investigated using electrochemical methods. The cyclic voltammograms of NiCo(2)O(4) electrode using alkaline aqueous electrolytes showed the presence of redox peaks suggesting pseudocapacitance behavior. Quasi-solid state supercapacitor device fabricated by sandwiching two NiCo(2)O(4) electrodes and separating them by ion transporting layer. The performance of the device was tested using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The device showed excellent flexibility and cyclic stability. The temperature dependent charge storage capacity was measured for their variable temperature applications. Specific capacitance of the device was enhanced by ~150% on raising the temperature from 20 to 60 °C. Hence, the results suggest that NiCo(2)O(4) grown under these conditions could be a suitable material for high performance supercapacitor devices that can be operated at variable temperatures.