Abstract:

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.

Key words: Nb₂O₅, porous carbon, supercapacitors, composites, electrochemistry, synthesis

摘要：

以间苯二酚、甲醛和草酸铌为原料，通过原位聚合和高温煅烧，制备出多孔碳负载的五氧化二铌（Nb₂O₅）材料。X射线粉末衍射和扫描电镜分析表明，负载在多孔碳表面上的五氧化二铌具有三维纳米凸起结构，属于正交晶型。循环伏安测试表明该复合材料的比电容达到290 F·g^-1，并具有良好的大电流放电能力，5 A·g^-1的放电电流下，容量可以达到108 F·g^-1。0.5 A·g^-1的首次放电容量为355 F·g^-1 （1.0~3.0 V vs. Li⁺/Li），100次循环后容量保持率为82%。通过对交流阻抗图谱和等效电路的模拟分析，对其电化学赝电容特性进行了讨论。该复合材料降低了电解液中离子在充放电过程中的迁移路径和扩散阻力，实现Nb₂O₅活性材料的多维度接触，提高了Nb₂O₅的导电性，改善了其超级电容特性。

关键词: 五氧化二铌, 多孔碳, 超级电容器, 复合材料, 电化学, 合成