High-voltage asymmetric supercapacitor based on MnO2 nanotubes//active carbon-multiwalled carbon nanotubes

Abstract

Active carbon (AC) composited with multiwall carbon nanotubes (CNTs) is synthesized through a high-temperature process for application as a negative electrode material of capacitors. Highly porous interconnected CNTs are uniformly coated onto the surface of AC sheet with a large area that reversibly absorbed hydrogen, resulting in a supercapacitor with larger working voltage and higher pseudocapacitance. A MnO2 nanotubes//AC–CNTs asymmetric electrochemical capacitor is assembled within a wide voltage region of 0–2.4 V in 2.0 M Li2SO4 aqueous electrolyte. Moreover, high energy density and power density, as well as superior cycling stability with >92 % capacitance retention over 6000 cycles, are observed. The reversible hydrogen absorption of the negative electrode may have practical applications in supercapacitors with high energy density and power density. The AC–CNTs composite was synthesized through a high-temperature process for application as a negative electrode which electrically sorbed hydrogen that not only enlarge the potential window, but also improve the pseudocapacitance, which having excellent energy density and power density.