Electrodeposition of ultrathin NiBDC lamellar arrays as a novel binder-free electrode for flexible all-solid-state supercapacitors†

Abstract

The Ni-based metal–organic framework (Ni-MOF) shows significant potential for energy storage due to its high specific capacity and active sites for electrochemical reactions. This study investigates the microstructural control of NiBDC on indium tin oxide/polyethylene terephthalate (ITO/PET) by varying the electrodeposition time (NiBDC/ITO/PET). The resulting microstructure exhibits a well-ordered and uniform porous array, with NiBDC nanosheets growing into ultra-thin layers of 50 nm thickness. As an electrode material for flexible, binder-free all-solid-state supercapacitors, the NiBDC/ITO/PET electrode demonstrates optimal electrochemical performance at an electrodeposition time of 30 minutes. In a three-electrode configuration, the NiBDC/ITO/PET electrode material achieves an areal capacitance of 72.2 mF cm⁻² at a discharge current density of 50 μA cm⁻². Even after 2000 cycles, it retains over 90% of its initial capacity at a current density of 500 μA cm⁻². The resultant symmetric supercapacitor device exhibits remarkable mechanical flexibility and robust cycling stability, maintaining over 87.8% of its initial specific capacitance after 5000 cycles. Moreover, three such devices connected in series can power a light-emitting diode (LED), demonstrating practical energy storage applications.