Self-assembled hierarchical peony-like ZnCo2O4 for high-performance asymmetric supercapacitors

A novel self-assembled 3D hierarchical peony-like ZnCo2O4 electrode material is designed and constructed by a facile effective and additive-free method. The growth mechanism is demonstrated to be the gradual evolving of two-dimensional nanosheets to three-dimensional hierarchical microstructures. Electrochemical tests reveal that the obtained ZnCo2O4 delivers a high specific capacitance of 440 F g (1) at a current density of 1 A g (1), and has excellent cycling stability even after 3000 cycles. The asymmetric device is also assembled with ZnCo2O4//AC, which exhibits a maximum capacitance of 83.7 F g (1) at the current density of 0.5 A g (1). Particularly, two charged asymmetric device connected in series can light one LED for more than 30 min, which indicates its excellent capability as an energy storage device. In view of the novel design and the outstanding performances, it can be deduced that these self-assembled hierarchical ZnCo2O4 electrode material hold potentially promising application for efficient energy harvesting system. (C) 2017 Published by Elsevier Ltd.