Augmentation of the energy storage potential by harnessing the defects of charcoal for supercapacitor application

The depletion of fossil fuel reserves coupled with an avalanche in the global energy demand has driven the need for developing facile techniques for energy storage devices to a large extent. Supercapacitors, has emerged as one of the most promising energy storage devices to address the demands of providing high energy density, quick charge discharge cycles and long cyclic stability. Although carbon based materials play an imperative role in the fabrication of electrode material of this device, the inherent defects are known to hinder the performance of the system. Even so, these defects can be engineered in a way to improve its overall functionality. The present work reports the tuning of the inherent defects of wood charcoal by surface functionalisation and doping via thermal annealing in order to incorporate substitutional impurities such as Nitrogen and Sulfur resulting in the improvement of the surface area and porosity of the system. The specific surface area of the system is observed to increase significantly from 4.2 m²/g of the bare material to 411.19 m²/g and 865.36 m²/g with the addition of Nitrogen and Sulfur respectively at a pyrolysis temperature of 900 °C. Furthermore, the incorporation of Nitrogen exhibits a remarkable specific capacitance of 567 F/g and 193.24 F/g, and the addition of Sulfur exhibits 644 F/g and 255.1 F/g in the three-electrode and two-electrode systems respectively at a current density of 1 A/g. They also exhibit an energy density of 26.83 Whkg⁻¹ and 17.36 Whkg⁻¹ respectively with a capacitance retention of 88.5 % and 86.1 % for 5000 cycles.