Space charge behaviors of electric double layer capacitors with nanocomposite electrode

Space charge distributions of electric double layer capacitors (EDLCs) based on polarizable nanoporous electrodes, containing acetylene black and ketjen black as electrode materials, were investigated by a pulsed electro acoustic (PEA) method. The charge distributions of positive/negative ions were spatially uneven and charge accumulation region concentrated on the central part of the electrode. The polarizable electrodes with ketjen black had higher space charge density. The use of the PEA method allowed us to perform the direct observations of spatio-temporal charge distributions in EDLCs. From the results of cyclic voltammetry, it is clear that EDLCs based on the ketjen black have better capacitive behavior. The specific capacitance of about 55.8 F/g of EDLCs using the polarizable electrodes with ketjen black was obtained. It can be found that ketjen black plays an essential role in the improvement of the charge density and the electrostatic capacity in EDLCs.