Core-shell structured Ni6MnO8@carbon nanotube hybrid as high-performance pseudocapacitive electrode material

Binary metal oxides have been proved to possess better pseudocapacitive performance than single metal oxide analogies. Substitution of toxic and high-cost ions (Co and Mo) in binary metal oxides with low-cost and environmentally-friendly ions (Ni and Mn) is of great economic and environmental importance. In this paper, murdochite-type binary metal oxides (i.e., Ni6MnO8) and binary metal oxides@carbon nanotubes (i.e., Ni6MnO8@CNTs) core-shell structure were synthesized via a facile hydrothermal approach followed by a calcination process. Electrochemical measurement results indicated that the synthesized Ni6MnO8@CNT core-shell structure showed a high specific capacitance of 1213 Fg(-1) at 1 Ag-1 with two times capacitance value of Ni6MnO8 at same current density. Even at the high current density of 20 Ag-1, the Ni6MnO8@CNT core-shell structure can still deliver a high capacitance value of 711 Fg(-1), which value is also much higher than that of Ni6MnO8 at the current density of 1 Ag-1. With the prepared Ni6MnO8@CNT hybrid as positive electrode and activated-polyanilinederived-carbon as negative electrode, an asymmetric supercapacitor cell (ASC) was successfully assembled. The assembled ASC device exhibited excellent pseudocapacitive performance with a high specific capacitance of 154 Fg(-1) at 1 Ag-1 and a high energy density of 58.2 Wh kg(-1) at a power density of 831.4 W kg(-1). Even at a high power density of 16.6 kW kg(-1), the ASC device can still deliver a high energy density of 23.1 Wh kg(-1), suggesting the promising applications of Ni6MnO8@CNT hybrid in supercapacitors. (C) 2019 Elsevier Ltd. All rights reserved.