Quasi-parallel arrays with a 2D-on-2D structure for electrochemical supercapacitors†
Construction of two-dimensional nanostructured arrays is important to improve the specific capacitance and rate performance of supercapacitors. In this work, we demonstrate a novel type of pseudocapacitive NiMn oxide@MnO2 quasi-parallel array assembled via 2D-on-2D structures. The quasi-parallel arrays markedly reduce the “dead area” caused by the bending stack of traditional 2D assembled structures, which obviously increases the number of active sites of the MnO2 electrode. The small aspect ratio of the quasi-parallel arrays ensures mechanical adhesion and electrical connection between the active material and the current collector. Therefore, the NiMn oxide@MnO2 arrays exhibit outstanding pseudocapacitive performance, including high specific capacitance (801 F g−1 at 1 A g−1, capacity: 151.3 mAh g−1), long-term cycling stability, and outstanding rate capability (79% capacitance retention rate at 40 A g−1). The constructed asymmetric supercapacitor based on a NiMn oxide@MnO2 cathode and an activated graphene anode exhibits extraordinary cyclic stability (96% capacitance retention after 10 000 cycles). This new type of quasi-parallel array could become a versatile electrode platform, which would open up a wide range of applications in supercapacitors, batteries and electrocatalysis.