Space charge distributions of an electric double layer capacitor with carbon nanotubes electrode

Space charge distributions of an electric double layer capacitors (EDLCs) based on polarizable nanoporous electrodes, containing carbon nanotubes (CNTs) as electrode material, were investigated by a pulsed electro acoustic (PEA) method. The EDLCs samples were prepared using CNTs and carbon black (i.e. acetylene and ketjen black) as electrode materials with different types pore structures. The charge distributions of positive/negative ions were spatially uneven and charge accumulation region concentrated on central part of electrode. The polarizable electrodes with ketjen black and CNTs-5 wt.% had higher space charge density. From the results of discharge characteristics, it is clear that EDLCs based on the ketjen black/CNTs-3 wt.% have better capacitive behavior. The specific capacitance of about 14 F/g of EDLCs using the polarizable electrodes with ketjen black and CNTs-3 wt.% were obtained. It can be found that CNTs plays an essential role in the improvement of the charge density and the electrostatic capacity in EDLCs. The use of PEA method allowed us to perform the direct observations of spatio-temporal charge distributions in EDLCs based on CNTs.