Core-shell nanostructured ZnO@CoS arrays as advanced electrode materials for high-performance supercapacitors

Cost-effective zinc oxide (ZnO) nanomaterials with high theoretical specific capacity have been regarded as one of the most prospective candidates for high-performance supercapacitor; however, its extensive application is limited by poor active sites and low conductivity, which increase the internal resistance of the electrode and reduce the capacity of the supercapacitor. Herein, we carried out a simple two-step method to synthesize a core-shell structure of ZnO core nanosheets enclosed in a shell of CoS (ZnO@CoS). This well-designed structure improves the electrical conductivity of the electrode, and the large specific surface area provides sufficient active sites. The as-prepared ZnO@CoS electrode exhibits a high specific capacity of 898.9 C g(-1) at a current density of 3 mA cm(-2), which is 1.47 and 1.70 times higher than those of ZnO and ZnO precursor. Moreover, the assembled asymmetric supercapacitor (ASC) with active carbon (AC) as the negative electrode and ZnO@CoS as the positive electrode displays an energy density of 45.2 Wh kg(-1) at a power density of 1039.1 W kg(-1) as well as achieves excellent specific capacity of 2438 mC cm(-2) . The ASC also shows superior cycleability with 107% capacity retention after 11,000 cycles. (C) 2020 Elsevier Ltd. All rights reserved.