Preparation of carbon nanotubes/polyaniline buckypaper composite electrode by directional pressure filtration and its electrochemical properties

Carbon nanotubes/polyaniline (CNT/PANI) buckypaper self-supporting flexible electrodes with a diameter of about 120 mm and a thickness of about 10 μm were obtained by directional pressure filtration technology. CNTs distributed uniformly and dispersed in the electrode, and PANI was uniformly embedded in the CNT network. PANI was spherical particles of nanometer to submicron size, with a maximum loading capacity of 2.7 mg·cm⁻². The electrode with PANI loading of 2.2 mg·cm⁻² has a porosity of 70.33%, a density of 0.4 g·cm⁻³ and a total pore area of 67.31 m²·g⁻¹. The electrode can be wound several times around the glass rod with diameter of 4 mm without damage. At the current density of 4 mA·cm⁻², the specific capacitance of the electrode is 1.88 F·cm⁻². In the process of 1200 charging-discharging cycles, the specific capacitance decreases first and then increases, and reaches 2.41 F·cm⁻² at the 900th cycle, and the capacity retention rate is 125.78% at the 1 200th cycle. After 500 times of bending at 180° angle, the retention rate of capacity is 78.43%. The symmetrical sandwich structure supercapacitor assembled by this electrode has a capacitance of 0.48 F·cm⁻² at a current density of 5 mA·cm⁻². Its capacity retention rate after 1000 charge-discharge cycles is 94.3%. Its energy density and power density are 213.75 mW·h·cm⁻³ and 2163.22 mW·cm⁻³, respectively.