Preparation and electrochemical characterization of porous carbon pearls from carboxymethyl cellulose for electrical double-layer capacitors

Porous carbon pearls (PCPs) were successfully prepared from syringe droplets of highly concentrated carboxymethyl cellulose solution via ice-templating followed by carbonization. The PCPs, which look like a solid bead with a pearly luster, were found to have well-developed bi-modal pore structures with a large specific surface area of 1,338.6 m(2)/g and a total pore volume of 0.81 cm(3)/g (a mesopore volume of 0.28 cm(3)/g and a micropore pore volume of 0.53 cm(3)/g). In a three-electrode system, the PCPs-based electrode exhibited high supercapacitive performance, such as a high specific capacitance of 217 F/g at 1 A/g in 6 M aqueous KOH electrolyte, outstanding cycling stability of 100% after 10,000 cycles at 30 A/g, and excellent rate capability of 63.7%. To investigate actual supercapacitive performance, a symmetric capacitor device was assembled using a coin cell. The PCPs-based device showed a specific capacitance of 37 F/g at a current density of 1 A/g and a power density of 5.0 kW/kg at an energy density of 2.88 Wh/kg. Furthermore, the PCPs-based device also exhibited superior cycling stability with capacitance retention of 98.5% after 10,000 cycles at a current density of 10 A/g.