High-performance asymmetric supercapacitor consisting of Ni-Co-Cu oxy-hydroxide nanosheets and activated carbon

Ternary Ni-Co-Cu oxy-hydroxide nanosheets with excellent pseudocapacitive characteristics are prepared by cathodic deposition. From the x-ray photoelectron spectroscopic and Fourier transform-infrared spectroscopic analyses, the as-deposited material consists of ternary hydroxides and some copper oxide (denoted as (Ni-Co-Cu)(OH)2-CuO). The charge capacity and capacitance retention of (Ni-Co)(OH)2 are significantly improved by introducing Cu(OH)2/CuO. An asymmetric supercapacitor consisting of a positive (Ni-Co-Cu)(OH)2-CuO electrode and a negative activated carbon (AC) electrode shows ideal capacitive performances with a cell voltage of 1.8 V. This asymmetric supercapacitor exhibits 94.5% cell-capacitance retention and 99.4% coulombic efficiency at 5 A g− 1 in a 4000-cycle test, meanwhile about 86% cell-capacitance retention is obtained in another 47000-cycle test at 25 A g− 1, revealing its excellent stability.