Abstract
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. © 2013 Elsevier B.V. All rights reserved.