Carbon Nanotube Composite Paper Supercapacitors

Supercapacitors are energy storage devices between battery and the traditional capacitor. These devices attract on scientists with high power and long cycle life. Carbon nanotube(CNTs) has the high specific surface area and outstanding conductive properties.It was considered to be a ideal materials for supercapacitors. In this paper, whisker carbon nanotube(WCNTs)was produced by chemical vapor deposition(CVD). Its morphology and structure were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), x-ray diffraction(XRD)and raman spectroscopy, thermogravimetric analysis. Carbon nanotube papers were fabricated with paper fiber as matrix materials and WCNTs as function materials.The CNTs papers were prepared by vacuum filtration method.The performance of supercapacitors were tested by cycle voltammetry, galvanostatic charging /discharging. The effect of graphitization for WCNTs and WCNTs composite were investigated. The CNTs papers were used as electrodes of supercapacitors. The electrochemical performance were tested. Carbonized WCNTs composite papers also were used as electrodes for the supercapacirors. Traditional CNTs and WCNTs were used to prepare CNTs /WCNTs composite paper. AC/WCNTs composite paper also were fabricated. These composite papers were used as electrode for supercapacitors respectively. The electrodes performance were tested. The composite papers exhibited good flexibility and conductivity. The supercapacitor performance was further improved after carbonization of the papers. WCNTs composite paper showed excellent performance with maximum specific capacitance reaching 106 F / g. The results are as follows:1. The crystallinity of WCNTs was greatly increased after graphitization. The WCNTs composite paper electrical conductivity increased from 14.1 S/m to 325.1 S/m after graphitization. When the scan rate was 1mV/s, graphitized WCNTs composite paper has a specific capacitance of 90F/g. When the current density was 800mA/g, specific energy and specific power were 22.3Wh/kg and 2.1Kw/kg.2. The performance of supercapacitor were enhanced with carbonized WCNTs composite paper as electrodes. When the scan rate was 1mV/s, the specific capacitance reached as high as 105F/g. When the discharge current of 12 mA, specific energy and specific power were 22Wh/kg and 1.5kW/kg.3. At a current density of 0.4A/g, WCNTs/CNTs composite paper shown a specific capacitance of 44F/g for first discharge. After 500 cycles, specific capacitance increased to 106 F/g. The specific energy and specific power hold 18.48Wh/kg and 7.39KW/kg at a current density of 3.2A/g.4. AC /WCNTs composite paper as electrodes has a specific capacitance of up to 95F/g at the current density of 0.8A/g.The specific energy and specific power reached 36.76Wh/kg and 5.52Kw/kg respectively.