Fabrication of hierarchical carbon layer encapsulated polyaniline core-shell structure nanotubes and application in supercapacitors

A novel polyaniline (PANI) nanotube structure was prepared according to a facile in-situ polymerization process using MnO2 nanotubes as the reactive template. The obtained PANI nanotubes possess an excellent specific capacitance of 455.7 F/g at 0.5 A/g, exhibit good rate capability of 63.2% even up to 30 A/g, however PANI nanotubes reveal low cycle stability due to the swelling and shrinking during intercalating/deintercalating process. Thus, carbon layer was introduced via a facile hydrothermal method to fabricate core-shell structure of carbon layer encapsulated PANI (PANI-C) nanotubes, which is supposed to alleviate the swelling and shrinking of PANI and improve the cycle stability. The PANI-C nanotubes prepared with 2 h hydrothermal reaction exhibit well-controlled core-shell structure, possess an excellent specific capacitance of 410.5 F/g at 1 A/g and reveal optimal cycle stability as well, (63% of its original value up to 2000 cycles), which shows significant improvement with the pristine PANI nanotubes (maintaining 39% of its original value). Furthermore, symmetric supercapacitors (SCs) were assembled based on PANI-C 2 h, the symmetric SCs exhibit high energy density of 42.32 Wh/kg and power density of 16.44 kW/kg, which also deliver good cycle stability. Additionally, the tandem SCs can light up a red LED. Above all, the carbon layer encapsulated core-shell structure materials offer a feasible strategy to fabricate high cycle stability material for promising applications in high performance supercapacitors.