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, 4075 F g-1) under the current density of 1 A g-1 and satisfying cyclic stability (88.4% capacitance retention and 84.6% coulomb efficiency after 10000 cycles). Additionally, an asymmetric supercapacitor (ASC) device equipped with CuC@CuS@CH-15/NF as a positive and an 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 10000 repeated GCD tests), which far surpasses other ASCs of the same type. These results provide guidance to enhance the electrochemical properties of cobalt-based oxides/sulfides@Co(OH)2 as the positive electrode for supercapacitors.

Keywords: core-shell structure, Supercapacitor, Three-dimensional structure, Nanoflower, CuCo2O4@CuCo2S4@Co(OH)2, Ultrahigh specific capacitances