Synthesis and application of NiMnO3-rGO nanocomposites as electrode materials for hybrid energy storage devices

Demand for more efficient and ecofriendly energy storage systems arouse research efforts in seeking to develop new energy materials with promising properties. In this regard, mixed transition metal oxides have recently attracted great attention due to their improved electrochemical and electrical properties in comparison with simple oxides. Herein, NiMnO3 and their composites with reduced graphene oxide (NiMnO3-rGO) were synthesized via a facile hydrothermal route, followed by a thermal treatment and their electrochemical properties have been evaluated as electrode materials for hybrid energy storage devices. The prepared samples were characterized by using X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and N2 adsorption measurements. The energy storage behavior of the samples was investigated using different electrochemical techniques including cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. Accordingly, a NiMnO3-rGO nanocomposite showed a high capacity of 91 mAh g−1 at a scan rate of 5 mV s−1, 48% higher than that of the pure NiMnO3 sample (47.7 mAh g−1). Furthermore, this nanocomposite was integrated as a positive electrode with reduced graphene oxide nanosheets as the negative electrode in an aqueous hybrid energy storage device. This system displayed a high specific energy of 23.5 Wh kg−1 and a maximum specific power of 7.64 kW kg−1.