Aqueous asymmetric supercapacitors (ASCs) with a wide voltage window can effectively improve energy storage capacity of energy storage devices. Zeolitic imidazolate framework-67 (ZIF-67) was used as a precursor to prepare nanoporous carbon (NC), and K0.5 Mn2 O4 nanosheets were subsequently grown on the NC surface through a facile in situ redox process (denoted as NCMO). The electrode potential window of NCMO was extended to 1.2 V in a three-electrode system and the value of the potential window was higher than that of most reported manganese oxides. To assemble the asymmetric supercapacitor with a high voltage range, the as-prepared NCMO and NC (with a potential window of -1.2-0 V) were used as the positive and negative electrode, respectively. A 2.4 V NCMO//NC aqueous ASC was constructed and displayed a large energy density of 60 Wh kg-1 at a power density of 1200 W kg-1 and excellent rate performance (41 Wh kg-1 even at a specific power density of 12.3 kW kg-1 ) as well as good cycling stability (92.6 % capacitance retention over 10 000 cycles at 10 A g-1 ). This work provides new opportunities for the development of high voltage ASCs with a high energy density for further practical application.
Keywords: ZIF-67; aqueous; asymmetric; nanoporous carbon; supercapacitors.
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