Engineering a Novel AgMn(2)O(4)@Na(0.55)Mn(2)O(4) Nanosheet toward High-Performance Electrochemical Capacitors

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 AgMn(2)O(4)/Na(0.55)Mn(2)O(4) nanosheets created by a popular liquid precipitation method with different AgNO(3) contents, and their corresponding physical and electrochemical characterizations are performed. The results show that the ultra-thin Na(0.55)Mn(2)O(4) nanosheets were combined with the AgMn(2)O(4) 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 AgMn(2)O(4)/Na(0.55)Mn(2)O(4) 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 10,000 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.