Carbon nanocapsule (CNC)@MnO2 core-shell particles are prepared with a reaction of KMnO4 with CNC at 90 degrees C. Birnessite-type MnO2 nanoflakes are grown on CNC seeds, resulting in CNC@MnO2 particles with a petal-like structure. The electrochemical characteristics of the prepared materials show that the highest specific capacitance (163 Fg(-1)) was obtained with a scan rate of 2 mVs(-1) in 1 M Na2SO4. In addition, the synthesized material has superior cycling stability. The capacitance retains 97.8% of its initial value after 5000 cycles with a scan rate of 100 mVs(-1). (C) 2014 The Electrochemical Society. All rights reserved.