Asymmetric supercapacitors have potential applications in renewable-energy technology owing to their remarkable electrochemical properties. A high-voltage asymmetric supercapacitor was developed based on a core–shell-structured MnO2@carbon sphere composite (MnO2@CS) as the cathode, nitrogendopedactivated carbon as the anode and a neutral aqueous Na2SO4 solution as the electrolyte. MnO2@CS was successfully fabricated by hydrothermally growing MnO2 on the surface of carbon spheres. A nitrogencontaining benzoxazine resin was adopted as a precursor to produce in situ nitrogen-doped activated carbon.Such an aqueous electrolyte-based asymmetric supercapacitor can be cycled reversibly in the high-voltage region of 0–1.9 V and exhibits a superior energy density of 8 Wh kg-1 at an ultrahigh power density of 9627 W kg-1 owing to the matching of MnO2@CS and porous nitrogen-doped activated carbon. Moreover,the asymmetric supercapacitor presents acceptable cycling performance, with 74.4% retention after 1000 cycles at 1 A g-1, and a charge–discharge efficiency of the electrode of almost 100%.
Volume 132, 2020
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