MnO₂/Porous Carbon Nanotube/MnO₂ Nanocomposites for High-Performance Supercapacitor

Abstract

In\nthis paper, a superior supercapacitor nanocomposite based on\nporous carbon nanotubes (PCNTs), MnO₂/PCNT/MnO₂, was synthesized, which displayed superior specific capacitance\n(<i>C</i> = 341.5 F g^–1, 2 mV s^–1), excellent rate capability (<i>C</i> = 214.3 F g^–1, 63% capacity retention, 100 mV s^–1), and high cyclic stability (98% efficiency after 6000 charge/discharge\ncycles). The outstanding improvement of its electrochemical performances\nresulted from the massive nanopores on the walls of PCNTs, which made\nmore MnO₂ nanoparticles filled both in the nanocavity and\non the surface of PCNTs as electroactive sites. At the same time,\nPCNTs improve the electrical conductivity with the pore structure\nbeing beneficial to ion exchange, they shorten the ion transport distance,\nand adjust to the volume expansion and contraction among charge/discharge.\nIn addition, the Mn­(IV)/Mn­(III) redox electric pair in the nanocavity\nenhances the capacity storage. Therefore, the MnO₂/PCNT/MnO₂ nanocomposite shows higher specific capacitance and excellent\ncyclic stability.