Hierarchical Cu(OH)2@MnO2 core-shell nanorods array in situ generated on three-dimensional copper foam for high-performance supercapacitors.

Manganese dioxide (MnO2) with high theoretical capacity (1380 F g-1), high natural abundance and low cost has been considered as one of the most competitive active materials for preparing the electrode of supercapacitors. However, the poor electrical conductivity limits its broad applications. To solve this problem, we design a hierarchical Cu(OH)2@MnO2 core-shell nanorods array on copper foam (CF), in which the one-dimensional (1D) Cu(OH)2 nanorod core provides the scaffold for the growth of MnO2 nanosheets and a short ion and electronic diffusion pathway and the two-dimensional (2D) MnO2 nanosheets shell provides enormous active sites due to their large surface area. The obtained Cu(OH)2@MnO2/CF nanorods array displays an excellent areal capacitance of 708.62 mF cm-2 at the current density of 2 mA cm-2 (283.45 F g-1 at 0.8 A g-1). Additionally, the assembled Cu(OH)2@MnO2/CF//activated carbon (AC) asymmetric supercapacitor shows an outstanding energy density of 18.36 Wh kg-1 at a power density of 750 W kg-1. Two such capacitors connected in series can light up a red LED bulb for over fifteen minutes.