Abstract
Electrochemical supercapacitors (ECs) have emerged as one of the answers to the challenges posed in the areas of compact electronics, high-power military devices, and smart transport systems. Porous transition metal-based nanomaterials are now employed to design supercapacitors because of their large surface areas, high pore volumes, consistent pore structures, stable electronic configuration, multi-metallic ion synergy, and stability. Primarily, this research describes some materials science aspects of manganese oxide, tin oxide, and graphene-based nanomaterials for these energy storage applications, as well as the methods involved in the fabrication of these conductive nanomaterials. Nano-structurization, chemical modification, and incorporation to a large extent were the major methods involved in the development of superior manganese oxide, tin oxide, and graphene-based electrodes for EC applications. In this work, nano-hybrid anode consisting of SnO2, and MnO2 anchored on few-layered reduced graphene oxide (rGO) with high capacity, long cycle life, and good rate capability were synthesized. Samples were characterized using FTIR, XRD, TEM, and RAMAN spectroscopy. Electrochemical properties were investigated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS).
The first composite of MnO2+SnO2, which was prepared through physical mixing, delivered a higher energy density of 56.5 Wh/Kg, a power density of 22321.4 W/kg (based on a mass of 5 mg active material only), and then a specific capacitance of 1256.9 F/g at 5mV/s. The retention capacity of the MnO2+SnO2 based electrodes, was 73.0 % after 5000 cycles. The MnO2+SnO2+rGO achieved an energy density of 49.1Wh/Kg, a power density of 16447.4 W/kg (based on a mass of 5 mg active material only), and a specific capacitance of 1572.5
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F/g at 5 mV/s. A retention capacity of 76.7% was achieved after 5000 cycles at 5mV/s, indicating the relative stability of the physically prepared composite. Composites prepared through hydrothermal mixing, samples MnO2-SnO2, had an energy density of 7.3Wh/Kg, a power density 25000 W/kg (based on a mass of 5 mg active material only), and a specific capacitance of 161.1 F/g at 5mV/s. The retention capacity of MnO2-SnO2 based electrodes was 93% after 5000 cycles. The MnO2-SnO2-rGO samples prepared using hydrothermal methods, had an energy density of 8.6 Wh/Kg, a power density of 19565.2W/kg, and a specific capacitance of 192.2 F/g at 5 mV/s. A retention capacity of 96.1% was achieved after 5000 cycles at 5mV/s.
Investigations on single metal oxide materials found that the SnO2 samples had an energy density of 40.3 W/Kg, power a density 1500W/kg, and specific capacitance of 126.1 F/g at 5mV/s. The retention capacity of The SnO2 based electrodes was 71.6 % after 5000 cycles. The MnO2 samples, had an energy density of 9.1 W/Kg, a power density 900 W/kg, and specific capacitance of 288.9F/g at 5mV/s. The retention capacity of the MnO2 based electrodes was 71.6 % after 5000 cycles.