Hydrothermally prepared sugar-derived carbon spheres for all-solid-state symmetric electrochemical capacitors

Abstract

Carbon spheres were prepared by template-free hydrothermal process and further modified via heat treatment and activation to form oxygen doped graphitic carbon spheres with higher surface area. FTIR, XRD, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), BET surface area analysis, cyclic voltammetry (CV), galvanic charge-discharge (GCD) experiments and electrochemical impedance spectroscopy (EIS) techniques were used for analyzing structural and chemical composition, morphological features and electrochemical properties of the prepared materials. The electrochemical properties of materials were thoroughly investigated by using three electrode systems. In two electrode studies, all-solid-state symmetric supercapacitor devices were constructed where hydrothermally prepared carbon spheres showed areal capacitance, energy density and power density values 20.5 mF cm−2, 2.9 μWh cm−2 and 50.0 μW cm−2 respectively at current density 0.1 mA cm−2. Under identical condition, these parameters for activated carbon sphere were 70.5 mF cm−2, 9.8 μWh cm−2 and 50.0 μW cm−2 respectively. Moreover, hydrothermally prepared carbon sphere exhibits remarkable cyclic stability by retaining 102% of its initial areal capacitance even after completion of 5000 cycles. Thus hydrothermally prepared carbon spheres without activation may be a promising low cost material for supercapacitors of low energy density with excellent cyclic stability.