A 2.4-V asymmetric supercapacitor based on cation-intercalated manganese oxide nanosheets in a low-cost “water-in-salt” electrolyte
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The main challenge for aqueous asymmetric supercapacitors (ASCs) is the relatively low voltage, which significantly diminishes the energy density of the device. Here, cation-intercalated manganese oxide nanosheets Na0.55Mn2O4·1.5H2O (NaMnO) are synthesized via a facile molten salts method. We find that the electrode potential window for NaMnO nanosheets can be extended to 1.2 V using a low-cost and safe superconcentrated sodium perchlorate (NaClO4) “water-in-salt” (WIS) electrolyte. To construct the asymmetric supercapacitor, the as-prepared NaMnO nanosheets and activated carbon (AC) with a potential window of − 1.2–0 V are used as the positive and negative electrode, respectively. A high-voltage 2.4-V NaMnO//AC aqueous ASC in the concentrated NaClO4 WIS electrolyte is successfully assembled, which exhibited excellent rate performance (the highest power density of 24.0 kW kg−1) as well as good cycling stability (94.9% capacitance retention over 20,000 cycles at 5 A g−1). This low-cost WIS electrolyte provides new opportunities for developing high-voltage aqueous ASCs with high energy and high power densities.
KeywordsCation-intercalated manganese oxide Asymmetric supercapacitor Aqueous electrolyte High voltage
This work was financially supported by the National Natural Science Foundation of China (51576164) and Natural Science Foundation of Gansu Province (18JR3RA159).
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