Size-controlled synthesis of carbon microspheres from resorcinol/formaldehyde for high electrochemical performance

Nanostructured phenolic resin-based carbon aerogels with abundant network structure are regarded as ideal energy storage materials for supercapacitors. However, the initial bulk form and low capacitance of previously reported porous carbon aerogels are problematic for practical application. Herein, phenolic resin-based porous carbon spheres were synthesized by a facile hydrothermal synthetic approach. The porous carbon spheres were investigated by various characterizations, such as SEM, BET, XPS, ect. Interestingly, it is found that the number of ammonium groups, length of the alkyl chain and hydrothermal temperature play a vital role in determining the porous structure, size and uniformity of carbon spherical. Besides, NH4+ is necessary to obtain the carbon sphere and there is no obvious effect on the crystal structure of porous carbon spheres by varying these parameters. The CN-80 sample exhibites the highest specific capacitance of 233.8 F g−1 at the current density of 1.0 A g−1. This result shows that the higher specific surface area, porosity and defect are probably the crucial factors to improve the electrochemical capacitance. CN-80 displays excellent capacitance retention ratio of 98% after 10000 charge/discharge cycles at 7 A g−1, indicating its good cycle stability.