Hierarchical core-shell structured CoNi2S4/Ni3S2@Ni(OH)2 nanosheet arrays as electrode for electrochemical energy storage

Herein, hierarchical core-shell structured CoNi2S4/Ni3S2@Ni(OH)(2) nanosheet arrays are synthesized through a facile method. The electrochemical results show that combining CoNi2S4/Ni3S2 nanosheet arrays (as core) with Ni(OH)(2) nanosheets (as shell) is an effective way to improve electrochemical capacitive properties due to the synergetic effect between CoNi2S4/Ni3S2 and Ni(OH)(2). The as-prepared CoNi2S4/Ni3S2@Ni(OH)(2) exhibits a high capacity of about 772.2 mu Ah cm(-2) at a current density of 1 mA cm(-2) , with an excellent capacity at very high current densities e.g. 500 mu Ah cm(-2) at 30 mA cm(-2) and an outstanding durability (ca. 98% of the capacity retention after 4000 cycles). Moreover, the electrochemical capacitive property of CoNi2S4/Ni3S2@Ni(OH)(2) is also evaluated in an asymmetric two-electrode cell assembled by using CoNi2S4/Ni3S2@Ni(OH)(2) as the cathode and the active carbon (AC) as the anode. The asymmetric cell shows a high energy density of about 0.432 mWh cm(-2) when the power density was 1.646 mW cm(-2), making it a promising electrode material for practical energy storage applications. (C) 2019 Elsevier B.V. All rights reserved.