Trimetallic layered double hydroxides with a hierarchical heterostructure for high-performance supercapcitors

Hierarchical nanostructures have attracted intensive attention due to their ability to boost electrochemical performance. However, it remains challenging to construct such intriguing structures. In the present work, a MnCo-LDH/NiCo-LDH array with hierarchical heterostructures is designed based on 1D nanoneedles, 2D nanosheets, and 3D hollow nanocages on nickel foam. It is synthesized by combined trimetallic co-doping, in-situ co-precipitation, and hydrothermal techniques. Benefiting from the delicately structure, the MnCo-LDH/NiCo-LDH array exhibits a specific capacitance of 1778.2 F g−1 at a current density of 1 A g−1. Furthermore, an asymmetric supercapacitor composed of positive MnCo-LDH/NiCo-LDH electrode and a negative activated carbon electrode offers an energy density of 36.9 Wh kg−1 at a power density of 750.0 W kg−1. The ASC device features outstanding cycling stability (e.g., 91.4 % of initial capacitance even after 8000 charge/discharge cycles at a current density of 7 A g−1). Therefore, the hierarchical nanostructure provides an effective strategy to construct high-performance electrodes. The assembled flexible ASCs are demonstrated to power electronic devices effectively.