Increasing the energy density of electrochemical double layer capacitors (EDLCs) can broaden their applications in energy storage but remains a formidable challenge. Herein, micropore-rich yolk-shell structured N-doped carbon spheres (YSNCSs) were constructed by a one-pot surfactant-free self-assembly method in aqueous solution. The resultant YSNCSs after activation possessed an ultrahigh surface area of 2536 m2 g-1 , among which 80 % was contributed from micropores. When applied in EDLCs, the activated YSNCSs demonstrated an unprecedentedly high capacitance (270 F g-1 at 1 A g-1 ) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4 ]) ionic liquid, affording an ultrahigh energy density (133 Wh kg-1 at 943 W kg-1 ). The present contribution provides insight into engineering porous carbons for capacitive energy storage.
Keywords: Capacitors; carbon spheres; energy density; micropores; yolk-shell structure.
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