Influence of carbon substrate on the electrochemical performance of carbon/manganese oxide hybrids in aqueous and organic electrolytesElectronic supplementary information (ESI) available: Transmission electron micrographs of the carbon materials are shown. See DOI: 10.1039/c6ra24181f

Manganese oxide presents very promising electrochemical properties as an electrode material in supercapacitors, but there remain important open questions to guide further development of the complex manganese oxide/carbon/electrolyte system. Our work addresses specifically the influence of carbon ordering and the difference between outer and inner porosity of carbon particles for the application in aqueous 1 M Na 2 SO 4 and 1 M LiClO 4 in acetonitrile. Birnessite-type manganese oxide was hydrothermally hybridized on two kinds of carbon onions with only outer surface area and different electrical conductivity, and conventional activated carbon with a high inner porosity. Carbon onions with a high degree of carbon ordering, high conductivity, and high outer surface area were identified as the most promising material, yielding 179 F g −1 . Pore blocking in activated carbon yields unfavorable electrochemical performances. The highest specific energy of 16.4 W h kg −1 was measured for a symmetric full-cell arrangement of manganese oxide coated high temperature carbon onions in the organic electrolyte. High stability during 10 000 cycles was achieved for asymmetric full-cells, which proved as a facile way to enhance the electrochemical performance stability. The carbon substrate has an important influence on the electrochemical performance of manganese oxide/carbon supercapacitors. Stable performance further requires asymmetric cell design in organic and aqueous electrolytes.