Preparation of a binder-free electrode with 3D on 2D hierarchical structure through ZIF-67 growth on Co(OH)2 for achieving a high-performance supercapacitor

In order to create a binder-free electrode with 3D on 2D hierarchical structure, Co(OH)2 nanosheet arrays were firstly electrodeposited on nickel foam (NF), and ZIF-67 polyhedral structural material was then grown in situ on the nanosheets to obtain the ZCo@NF electrode. The maximum areal specific capacitance of A-ZCo@NF electrode was 5603 mF cm−2 at 5 mA cm−2, and the capacitance retention rate was 89.18% after 10000 cycles. The 3D on 2D hierarchical structure can simultaneously increase the electrochemically active area and modulate the electronic structure through heterostructural interface coupling to illustrate such excellent capacitive performance. Furthermore, the electrode without binders decreased the resistance of contact, thereby promoting the transportation of electrons/ions. Therefore, the asymmetric supercapacitor, which was assembled of A-ZCo@NF and activated carbon (AC), delivered the areal specific capacitance of 1169.6 mF cm−2 at 1 mA cm−2, the areal energy density of 365.5 μWh·cm−2 at the power density facilitateof 753 μW cm−2. After 10000 cycles, the capacitance retention rate remained 80.86%, which showed good cycling stability. The high-performance illustrated that as-prepared sample was a promising positive electrode material for asymmetric supercapacitor.