Carbon Materials And Metal Oxide Composite In The Application Of Supercapacitors

Supercapacitors have been recognized as unique energy storage devices which have higher energy density than conventional capacitors, and higher power density and longer cycle life than batteries, filling the gap between conventional dielectric capacitors and batteries. They can release huge discharge current instantly. Based on the above, the promising application of supercapacitors in the field such as mobile telecommunication, information technology, consumer electronics, electric vehicle, aviation&aerospace, and military force, have been attracting more and more attention throughout the world. Studies on supercapacitors are mainly focused on the study of high performance electrode material. Nano-ZnO, MWCNTs and MWCNTs/ZnO composite, CNFs and CNFs/MnO2composite have been used as electrode materials for supercapacitors. The microstructure and morphology of the samples were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD). Capacitance performance was characterized by cycle voltammetry (CV), galvanostatic charge/discharge. The main research contents and innovations are as follows:1. For the first time, nano-ZnO has been used as electrode material for supercapacitor. Petals form ZnO and silk ball shape ZnO nanoparticles have been synthesized by chemical coprecipitation method and by using Zn(NO3)2-6H2O as the raw material and PEG as the structure oriented agent and changing the amount of precipitation agent KOH. The effects of the morphology on the capacitance performances were also discussed. The results indicate that the petals form ZnO electrode and silk ball shape ZnO electrode all have good capacitance performance and good power characteristics at the potential window of0.00～1.00V(vs.SCE) in2mol/L KNO3. Compared with silk ball shape ZnO electrode, petals form ZnO electrode has higher specific capacitance. This may be because that petals form ZnO electrode has higher specific surface area and higher electrochemical activity. When the current is0.5μA, the specific capacitance of petals form ZnO electrode is84.90F/g. Its energy density is42.45Wh/Kg. Its power density is4.25KW/Kg. After200cycles, the specific capacitance of two kind of morphology of ZnO electrodes increased by9.38%.8.70%. This shows that they have good cycle stability and capacitance stability.2. High surface area, high conductivity MWCNTs and MWCNTs/ZnO composite have been used as electrode material for supercapacitor. On the basis of the study of capacitance performance of MWCNTs, MWCNTs/ZnO composite has been synthesized by ultrasound chemical method and its capacitance performance is discussed. The results indicate that MWCNTs electrode and MWCNTs/ZnO composite electrode all have good capacitance performance and good power characteristics at the potential window of0.00～1.00V(vs.SCE) in2mol/L KNO3. When the current is10μA, the specific capacitance of MWCNTs electrode and MWCNTs/ZnO composite electrode respectively is188.25F/g and333.10F/g. After200cycles, the specific capacitance of MWCNTs electrode and MWCNTs/ZnO composite electrode respectively decreased by19.83%.16.43%. This shows that MWCNTs electrode and MWCNTs/ZnO composite electrode have good cycle stability and capacitance stability.3. CNFs and CNFs/MnO2composite have been synthesized by electrospinning and for the first time used as electrode material for supercapacitor. The results indicate that CNFs and CNFs/MnO2composite all have good capacitance performance and good power characteristics at the potential window of0.00～1.00V(vs.SCE) in2mol/L KNO3. When the current is5μA, the specific capacitance of CNFs and CNFs/MnO2composite electrode respectively is59.00F/g、146.03F/g. After200cycles, the specific capacitance of CNFs and CNFs/MnO2composite electrode decreased by8.96%.12.54%. This shows that CNFs and CNFs/MnO2composite electrode have good cycle stability and capacitance stability.