Poly(3-methylthiophene)/Vertically Aligned Multi-walled Carbon Nanotubes: Electrochemical Synthesis, Characterizations and Electrochemical Storage Properties in Ionic Liquids

Poly(3-methylthiohpene) (P3MT) was electrodeposited on long thick vertically aligned carbon nanotubes mats (VACNT, length=180μm) using a sequenced galvanostatic synthesis in ionic liquid (ILs) media i.e. 1-ethyl-3-methyl-imidazolium-bis(trifluoromethanesulfonyl) imide (EMITFSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYRTFSI). Pulsed galvanostatic conditions (current density, polymerization time, open circuit time) were optimized in order to ensure homogeneous polymer deposit inside the VACNT structure. The highest specific charge storage performances were obtained with current density J=4mA/cm2, time of polymerization per pulse of 45s and open-circuit time of 300s. The resulting nanocomposites were electrochemically characterized by cyclic voltammetry and electrochemical impedance spectroscopy in ionic liquid in order to determine their performances (capacitance, charge/discharge time). The best capacitance (126F/g) was obtained for nanocomposite containing 83w% of P3MT. SEM-EDX experiments as well as TEM experiments bring the evidence that the P3MT is homogeneously covering the VACNTs. Furthermore, SEM pictures demonstrate that for P3MT amount >50% in mass, the nanocomposites possess a thin layer of P3MT at the bottom of the carpet. In addition these nanocomposites reveal that some VACNTs are connected together by P3MT affording self-supported and flexible properties to the nanocomposite. The ratio P3MT/CNT was optimized for electrochemical storage properties (capacitance, time of charge/discharge) and the best capacitance (126F/g) in EMITFSI at 30°C was obtained for nanocomposite containing 83w% of P3MT. The performances obtained with optimized nanocomposites are more than 33% higher than the specific capacitance obtained with a comparative weight ratio entangled (nano-)composites.