Hierarchical three-dimensional nanoflower-like CuCo2O4@CuCo2S4@Co(OH)2 core-shell composites as supercapacitor electrode materials with ultrahigh specific capacitances

Abstract

Here, we prepare three-dimensional nanoflower-shaped CuCo2O4@CuCo2S4@Co(OH)2 core–shell materials on nickel foam (NF). CuCo2O4 (CuC) nanowire arrays and CuCo2S4 (CuS) nanosheets are grown directly on NF as the core through routine hydrothermal and high-temperature calcination methods and Co(OH)2 (CH) small nanosheets deposited on CuC@CuS nanoflowers via the potentiostatic deposition for 15 mins. Due to its distinctive structure and the synergistic effect between multiple components of CuCo2O4@CuCo2S4@Co(OH)2, the electrode has a fantastic specific capacitance (Cs, 4075F/g) under the current density of 1 A/g and satisfying cyclic stability (88.4 % capacitance retention and 84.6 % coulomb efficiency after 10,000 cycles). Additionally, an asymmetric supercapacitor (ASC) device equipped with CuC@CuS@CH-15/NF as a positive and active carbon (AC) electrode as a negative electrode can work steadily at 0–1.6 V. The ASC device can offer an excellent energy density (E, Wh kg−1) of 232.02 Wh kg−1 at a high-power density of 2879.8 W kg−1 (P, W kg−1) and an unexpected cycle stability (84.2 % of the original Cs and 81.7 % of coulombic efficiency after 10,000 repeated GCD tests), which far surpasses other ASCs of the same type. These results guide to enhancement of the electrochemical properties of cobalt-based oxides/sulfides@Co(OH)2 as the positive electrode for supercapacitors.