Co3O4/CNTs复合电极材料的水热法合成及电化学性能

Hydrothermal Synthesis of the Co3O4/CNTs Composite Electrode and Its Electrochemical Performance

为了考察CNTs使Co3O4/CNTs导电性和Co3O4分散性的提高对增大复合电极材料比电容的影响,以Co(NO3)2·6H2O和CNTs为原料,通过水热法成功制备了Co3O4和Co3O4/CNTs复合电极材料,并采用TEM和XRD表征了复合材料的粒径大小、微观形貌和物相结构等物性,测试了Co3O4和Co3O4/CNTs的循环伏安(CV)、恒电流充放电(GCD)和电化学阻抗(EIS)等电化学性能。结果表明:由于CNTs的分散作用,复合材料中Co3O4的粒径从87 nm减小到13 nm,且具有尖晶石结构的Co3O4纳米粒子主要负载在CNTs的外表面;Co3O4/CNTs复合材料的比电容和电容保持率均远高于Co3O4,且其导电性能提高对比电容增加的贡献远高于Co3O4粒径减小的贡献;经过2000次充放电循环后,Co3O4/CNTs复合材料的比电容保持在180 F/g左右,表现出良好的倍率性能和循环稳定性。

To investigate the effects of enhancing the conductivity of Co3O4/CNTs and the dispersion of Co3O4 by CNTs on increasing the specific capacitance of composite electrode material,Co3O4(87 nm),Co3O4(14 nm)and Co3O4(13 nm)/CNTs composite were prepared by the hydrothermal method using Co(NO3)2·6 H2O and CNTs as the raw materials.The microstructure,particle size,morphology and phase structure were characterized by transmission electron microscopy(TEM)and X-ray diffraction(XRD).The results show that the size of Co3O4 nanoparticles in Co3O4(13 nm)/CNTs composite is decreased from 87 nm to 13 nm due to the dispersion of CNTs.Co3O4 nanoparticles with spinel structure are mainly supported on the outer surface of CNTs.Electrochemical performances of pure Co3O4 and Co3O4/CNTs composite were investigated by cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy.It is found that the specific capacitance of Co3O4(13 nm)/CNTs is 174.1 F/g at a current density of 0.5 A/g,and the capacitance retention rate of the composite maintains 89.3%when the current density is increased to 10 A/g.Both the specific capacitance and the capacitance retention rate of Co3O4(13 nm)/CNTs are much higher than those of pure Co3O4.Moreover,the conductivity of the composite shows much more importance on the specific capacitance than the particle size.After 2000 cycles of charge and discharge,the specific capacitance of Co3O4(13 nm)/CNTs composite remains at about 180 F/g,exhibiting excellent rate capacity and cycling stability.