Comparisons of different carbon conductive additives on the electrochemical performance of activated carbon

Three kinds of carbon conductive additives, i.e. multi-walled carbon nanotubes (MWNTs), vapour grown carbon fibres (VGCFs) and acetylene carbon blacks (AB), were investigated to improve the electrochemical performance of activated carbon (AC) used as electrode materials for supercapacitors. Galvanostatic charge/discharge and cyclic voltammetric measurements demonstrate that MWNTs are the most effective additive to improve the electrochemical performance of AC under the same conditions. To get the same results for AC in a symmetric supercapacitor, the desired additive amount was 3.0 wt% MWNTs, ∼5.0 wt% VGCFs and ∼9.0 wt% AB, respectively. X-ray diffraction analysis results demonstrate MWNTs have the sharpest (002) peak and highest graphitic degree. Scanning electron microscopy images show MWNTs have a vimineous fibre shape and VGCFs have a stubbed virgate shape. MWNTs run across AC particles and VGCFs distribute discretionarily among AC particles. High-resolution transmission electron microscopy demonstrates the microstructural difference between MWNTs and VGCFs. Some mechanisms were then developed to explain the different performance of the three kinds of carbon conductive additives