Hierarchical ZnO@MnO2@PPy ternary core-shell nanorod arrays: an efficient integration of active materials for energy storage

In this paper, ZnO@MnO2@PPy ternary core-shell nanorod arrays (NRAs) were fabricated through the layer-by-layer process. In this process, the incorporation of polypyrrole, a highly conductive material, on the surface of a binary ZnO@MnO2 core-shell structured composite is adopted to optimize the charge transfer process to further improve the electrochemical performance. Because of enhanced electron transfer capability, charge transfer resistances of the ZnO@MnO2@PPy ternary core-shell nanorod arrays are reduced and the electrochemical performances are improved. The electrochemistry tests show that these self-supported electrodes are able to deliver ultrahigh specific capacitance (1281 F g(-1) at a current density of 2.5 A g (1)), together with a considerable areal capacitance (1.793 F cm (2) at a current density of 3.5 mA cm(-2)). Furthermore, a capacitance retention of 90% after 5000 charge-discharge cycles at 5 A g(-1) is obtained, indicating the excellent cycling stability of the ZnO@MnO2@PPy ternary core-shell electrode. The superior electrochemical capacity demonstrates the potential of ZnO@MnO2@PPy ternary core-shell NRAs to further improve the performance in supercapacitor electrodes.