Designing of manganese-based oxides and oxyhydroxides as positive electrode materials and activated carbon from Phyllanthus emblica as negative electrode material for battery type supercapacitor

Effective energy storage and prompt energy discharge using better catalysts is the cornerstone for clean energy-based applications. Manganese based materials is an abundant, environmentally friendly and low-cost catalyst for supercapacitor applications. In this work, three manganese based systems (β-MnO2, γ-MnOOH and Mn3O4) were synthesised by hydrotermal method. The ability of manganese to interchage it oxidation state through electron transfer reactions made manganese based systems become one of the prominent cathode material for supercapaciter applications. The supercapacitor studies were carried out using Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) analysis. In this work Mn3O4 showed better charge transfer resistence and specific capacity (597 C/g) compared to β-MnO2 and γ-MnOOH. The high surface area (1189.14 m2/g) activated carbon prepared in-house from Phyllanthus emblica was used as negative electrode and Mn3O4 as positive electrode in device fabrication. The cycling stability study of the fabricated device reveals 92% capacity retention after 5000 cycles at 100 mV/s. The Power density value of 800 W/kg and the energy density of 4 W/kg was achieved at a current density 1 A/g.