Hollow Ni-Intercalated ZIF-67 Integrated with PVDF-Derived Carbon Sheets for High-Performance Supercapacitor Electrodes

Zeolite imidazole framework (ZIF)-67 is a type of metal organic framework material that demonstrates a potential candidate to become a high energy density supercapacitor. However, due to its inferior electrical conductivity and low mesoporosity, this material cannot reach a high specific capacitance, limiting its utilization for a supercapacitor electrode. In this work, the incorporation of hollow nickel-intercalated ZIF-67 with poly(vinylidene fluoride)-derived carbon sheets is proposed to address these issues. The resulting hollow nickel-intercalated ZIF-67/carbon sheet (ZNC) electrode improves the specific capacitance and rate capability of pristine ZIF-67 and hollow nickel-intercalated ZIF-67. The electrochemical properties of the obtained ZNC are mainly governed by the composite’s surface area, along with the residual fluorine content and surface chemistry in carbon sheets. The highest specific capacity of 537.4 C g–1 at 1 A g–1 is obtained from ZNC containing carbon produced at 700 °C (ZNC 700) with an average capacity retention of 76.7% at 10 A g–1. Moreover, two-electrode measurement of an asymmetric ZNC 700//activated carbon cell achieves an energy density of 35.6 Wh kg–1 at a power density of 405.3 W kg–1 and a stability of 87.2% over 10,000 charge–discharge cycles at 5 A g–1. This finding demonstrates the potential of ZNC composites to achieve high performance electrodes for supercapacitor devices.