Template synthesis of hollow carbon spheres anchored on carbon nanotubes for high rate performance supercapacitors

A carbon material consisting of hollow carbon spheres anchored on the surface of carbon nanotubes (CNT–HCS) has been synthesized by an easy chemical vapor deposition process using a CNT–MnO2 hybrid as template. An electrode made of this material exhibits a maximum specific capacitance of 201.5 F g−1 at 0.5 A g−1 and excellent rate performance (69% retention ratio at 20 A g−1). It has impressive cycling stability with 90% initial capacitance retained after 5000 cycles at 5 A g−1 in 6 mol L−1 KOH. Symmetric supercapacitors based on CNT–HCS achieve a maximum energy density of 11.3 W h kg−1 and power density of 11.8 kW kg−1 operated within a wide potential range of 0–1.6 V in 1.0 mol L−1 Na2SO4 solution.