Synthesis and high electrochemical performance of polyaniline/MnO ₂-coated multi-walled carbon nanotube-based hybrid electrodes

Multi-layered electrodes which consist of polyaniline (PANI)/manganese dioxide (MnO ₂)-multi-walled carbon nanotubes (MWNTs) are prepared as the electrode materials for supercapacitors. MnO ₂-MWNTs are made by the in situ direct coating method to deposit MnO ₂ onto MWNTs; the core/shell structure of multi-layered fibrous electrodes can also be obtained by PANI coating onto the MnO ₂-MWNTs. The effect of PANI coating on the electrochemical performance and cyclic stability of MnO ₂-MWNTs is investigated. From the cyclic voltammograms, the PANI/MnO ₂-MWNTs show remarkably enhanced specific capacitance and cycle stability compared to MnO ₂-MWNTs, where the highest specific capacitance (350 F/g) is obtained at a current density of 0.2 A/g for the PANI/MnO ₂-MWNTs as compared to 92 F/g for pristine MWNTs and 306 F/g for MnO ₂-MWNTs. This indicates that the improved electrochemical performance of PANI/MnO ₂-MWNTs is due to the enhanced electrical properties by nano-scale-coated MnO ₂ onto MWNTs and the PANI coating that leads to the increased cycle stability by delaying the dissolution of MnO ₂ during charge/discharge tests.