Core-shell N-doped active carbon fiber@graphene composites for aqueous symmetric supercapacitors with high-energy and high-power density

• Core-shell graphene wrapped active carbon fibers (ACF@GR) were first prepared.
• The fibers exhibit an extremely high specific capacitance of 552.8 F g−1 in 6 M KOH electrolyte.
• The assembled supercapacitors can deliver both high-energy density and high-power density.

Graphene wrapped nitrogen-doped active carbon fibers (ACF@GR) of a core-shell structure were successfully prepared by a simple dip-coating method using natural silk as template. Compared to pure silk active carbon, the as-prepared ACF@GR composites exhibit high specific surface area in a range of 1628–2035 m2 g−1, as well as superior energy storage capability, an extremely high single-electrode capacitance of 552.8 F g−1 was achieved at a current density of 0.1 A g−1 in 6 M KOH aqueous electrolyte. The assembled aqueous symmetric supercapacitors are capable of deliver both high energy density and high power density, for instance, 17.1 Wh kg−1 at a power density of 50.0 W kg−1, and 12.2 Wh kg−1 at 4.7 kW kg−1 with a retention rate of 71.3% for ACF@GR1-based supercapacitor.

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