Remarkable supercapacitor electrodes with a high specific supercapacitance and a super long cycle life
were achieved by using hierarchical porous hollow carbon microcapsules (HPHCMs) as active materials.
HPHCMs were prepared by a facile chemical route based on pyrolysis of a soft sacrificial template
involving a non-crosslinked core of poly(styrene-r-methylacrylic acid) and a crosslinked shell of
poly(styrene-r-divinylbenzene-r-methylacrylic acid), which were synthesized by using traditional radical
polymerization and emulsion polymerization. The results of scanning electron microscopy, transmission
electron microscopy and Brunauer–Emmett–Teller characterizations revealed that HPHCM possessed
the desired pore structure with apparent macro-/meso- and micropores, which not only provided
a continuous electron-transfer pathway to ensure good electrical contact, but also facilitated ion
transport by shortening diffusion pathways. As electrode materials for supercapacitor, a high specific
capacitance of 278.0 F g1 was obtained at the current density of 5 mA cm2. Importantly, after 5000
potential cycles in 2 M KOH electrolyte at the discharge current density of 20 mA cm2, the capacitance
actually increased from 125 to 160 F g1 and then remained 151 F g1, corresponding to a capacitance
retention of 120%, likely due to electrochemical self-activation