Manganese oxides, as a type of two-dimensional (2D) material with high specific area and low cost, are considered promising energy storage materials. Here, we report novel AgMn2O4/Na0.55Mn2O4 nanosheets created by a popular liquid precipitation method with different AgNO3 contents, and their corresponding physical and electrochemical characterizations are performed. The results show that the ultra-thin Na0.55Mn2O4 nanosheets were combined with the AgMn2O4 nanoparticles and an enhancement in their specific capacity was observed compared to the pristine sheets. This electrode material displays a peak specific capacitance of 335.94 F g−1 at 1 A g−1. Using an asymmetric supercapacitor (ASC) assembled using a positive electrode made of AgMn2O4/Na0.55Mn2O4 nanosheets and a reduced graphene oxide (rGO) negative electrode, a high energy density of 65.5 Wh kg−1 was achieved for a power density of 775 W kg−1. The ASC showed good cycling stability with a capacitance value maintained at 90.2% after 10000 charge/discharge cycles. The excellent electrochemical performance of the device was ascribed to the heterostructures and the open space formed by the interconnected manganese oxide nanosheets, which resulted in a rapid and reversible faraday reaction in the interface and further enhanced its electrochemical kinetics.

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