Synthesis of ZIF-8 and ZIF-L on carbon fiber fabric for supercapacitor structural electrodes

Abstract

One potential solution to the problem of energy storage in certain transportation vehicles is the development of multifunctional materials. Specifically, structural supercapacitors offer a combination of mechanical strength and energy storage capabilities, which could replace vehicle components and reduce overall vehicle weight. However, structural electrodes made from carbon fiber face a significant limitation due to their low specific surface area. This study examines the direct synthesis of metal-organic frameworks on the surface of carbon fibers. Structures such as ZIF-8 and ZIF-L can be easily synthesized from the same metal-organic precursors and exhibit high surface areas, making them ideal for this application. Both ZIF structures form a continuous coating on the carbon fiber, increasing the specific surface area of the electrodes. For the ZIF-8 structure, the coating achieves a thickness of 1 μm and a specific surface area of 30.24 m2/g. In contrast, the sheet-like geometry of the ZIF-L results in greater thicknesses, though with a lower specific surface area of only 0.7 m2/g. The potential use of these electrodes in supercapacitor devices has been demonstrated through the assembly of structural supercapacitors with a polymeric solid electrolyte. The supercapacitor with ZIF-8 electrodes has achieved a specific capacitance of 7.78 mF/g. Despite the limitations associated with internal resistance, all structural electrodes have shown stability over charge and discharge cycles.