Aerosol-based synthesis of silsesquioxane-graphene oxide and graphene-manganese oxide nanocomposites for high-performance asymmetric supercapacitors

A facile aerosol-based synthetic approach is demonstrated for the fabrication of silsesquioxane-graphene oxide (rGO-SQ) and reduced graphene oxide-manganese oxide (MnOx-rGO) nanocomposites, as the materials for negative and positive electrodes in an asymmetric supercapacitor (ASC), respectively. Microwave-assisted hydrothermal treatment is employed to form reduced graphene oxide (AS-rGO). Fourier-transformed infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and x-ray photoelectron spectrometry are used to provide complementary material characterizations for the synthesized nanocomposites. The results show that the composition and the morphology of the synthesized materials are tunable by the adjustment of precursor concentration and annealing temperature. From the shapes of cyclic voltammetric and galvanostatic charge-discharge curves, the conductivity and the subsequent capacitive performance of MnOx are enhanced effectively by the hybridization with rGO. The highest double-layer capacitance of AS-rGO is 118 F g−1, and the highest specific capacitance of MnOx-rGO reaches 183 F g−1 under a scan rate of 5 mV s−1. The ASC assembled with AS-rGO and MnOx-rGO possessed high charge-discharge reversibility at a cell voltage of 2.0 V. A high operation stability of ASC can be achieved, as evidenced by the high retention (98% of the retention) in the 10,000-cycle charge-discharge test at a current density of 2 A g−1. The maximum specific energy and specific power of the ASC respectively reach 16.6 Wh kg−1 and 1.052 kW kg−1 at a current density of 1 A g−1. This study demonstrates a prototype approach for the fabrication of nanocomposite electrode materials by design with the ability of scalable mass production.