Preparation of niobium pentoxide loaded on porous carbon and its application in supercapacitors

Niobium pentoxide (Nb2O5) loaded on porous carbon was synthesized from resorcinol, formaldehyde and niobium oxalate hydrate based on in-situ polymerization and high-temperature calcination. X-ray diffraction (XRD) and scanning electron microscope (SEM) examinations showed that the orthorhombic type Nb2O5 was synthesized and loaded on porous carbon with protrusion on its surface. Cyclic voltammetry (CV) tests indicated that the specific capacitance of the composites was 290 F·g-1 (1.0~3.0 V vs. Li+/Li) with a good large-current discharge capability evidenced by the capacitance of 108 F·g-1 at a large-current of 5 A·g-1. The initial capacitance was 355 F·g-1 at 0.5 A·g-1 with 82% capacitance being maintained after 100 cycles. The pseudocapacitance characteristics of the complex was studied by analyzing the electrochemical impedance spectroscopy (EIS) and simulation of equivalent circuit. The improved conductivity and pseudocapacitance of Nb2O5 were due to several factors including the shortened distance in the composites and the reduced diffusion resistance of the Li+ in the electrolyte during the charge-discharge process and the enhanced contact with the electrolyte because of the protrusion morphology.