Vanadium metal-organic framework derived 2D hierarchical VO2 nanosheets grown on carbon cloth for advanced flexible energy storage devices

Abstract

The design and creation of binder-free hierarchical porous structure on flexible substrate based on metal oxides derived from metal-organic frameworks (MOFs) has become as a desirable approach for developing advanced wearable and portable power sources. Herein, a novel flexible electrode was elaborately designed based on vanadium dioxide (VO2) nanosheets anchored on carbon cloth (CC) through the formation of vanadium MOF nanosheets on CC and then transformation to mesoporous VO2. The resulting binder free VO2@CC derived from V-MOF composite was directly used as a flexible electrode in energy storage application. For better understanding the role of V-MOF precursor, another novel electrode was fabricated by a simple hydrothermal growth of vanadium precursor on CC and then transformation to mesoporous VO2. The results confirmed that the type of precursor plays an important role in preparing the final VO2 nanostructures and the V-MOF precursor leads to the preparing highly mesopores VO2 with large surface area, which significantly enhanced the energy storage capability. Benefiting from the intriguing structural properties, high specific capacitance (470 F g−1 at 1 A g−1) and wide potential window (about 2 V), the VO2@CC derived from V-MOF was directly used as both positive/negative electrodes for fabrication of flexible all-solid-state symmetric supercapacitors, which provide high energy density (63.45 Wh kg−1 at 0.9 kW kg−1) and high power density (9.0 kW kg−1 at 50.4 Wh kg−1) with superior flexibility and outstanding cycling stability (about 95.% capacitance retention over 5000 cycles at 1.0 A g−1), which comparable to or higher than most of the previous reported devices based on VO2 nanostructures, indicating a great capability of our designed electrode in creating and developing next-generation high-performance supercapacitors for the future.