Rational design of 2D/1D ZnCo-LDH hierarchical structure with high rate performance as advanced symmetric...

Hierarchical microstructures of electrode materials for supercapacitors have attracted strong attention owing to the enlarged surface area, fast charge transportation and enhanced volume expansion. All these advantages of hierarchical structures are available for facilitating the electrochemical performances and stability of electrode materials for advanced supercapacitors. However, few reports focused on the development of transition metal-based homogeneous 2D/1D hierarchical structures use the same material. Herein, the ZnCo-LDH with 3D hierarchical microstructure was self-assembled with 1D nanoneedles and 2D nanosheets that in situ synthesized on Ni foam through a simple and effective strategy. The optimal sample (ZnCo-LDH-2) exhibited the ultra-high specific capacitance of 3871.2 F  g ^-1 at 1 A g ^-1 and excellent cycle life span (capacitance retention of 87.5% after 6000 cycles at 5 A g^-1). Particularly, the current density was as high as 100 A g^-1, the specific capacitance of ZnCo-LDH-2 still remained 1526 F g^-1. Moreover, the symmetric supercapacitor (SSC) fabricated with ZnCo-LDH-2 showed the maximum energy density of 40.3 Wh kg^-1 and power density of 15.08 kW kg^-1.