Interfiber Isolation Synthesis Strategy via Nanosheet Wrapping toward 3D Carbon Nanofiber Networks for High-Performance Supercapacitors

Efficient assembly of robust and chemically resistant carbon nanofibers (CNFs) into three-dimensional (3D) solids suits the increasing demands for flexible and dynamic adaptive conductive structures for functional fabrics and wearable devices quite well. Here, a general and scalable "inter-fiber isolation" strategy is proposed, which could construct CNFs from natural nanofibrils through subtly exploiting the nanosheet wrapping of two-dimensional (2D) nanomaterials (i.e., MXene). The nanosheet wrapping efficiently solves the issue that natural nanofibrils tend to weld together into big carbon chunks during carbonization. The nanofibrous features are well preserved, and the obtained CNFs have adjustable diameters from several hundreds of nanometers to as low as ∼15 nm depending on the MXene ratio. Thanks to the shortened diffusion pathway of the nanoscaled fiber diameter and the interconnecting electrical-conducting network, the free-standing macroscopic 3D CNF solids demonstrate a superior electrical conductivity of ∼34.65 S m^-1, as well as greatly enhanced rate capability and excellent cycling stability up to 340,000 cycles at a current density of 10 A g^-1 as supercapacitor electrodes. The nanosheet wrapping is also extendable to other 2D nanomaterials such as graphene oxide, offering a practical and easy-to-implement strategy of fabricating carbon nanostructures for robust structures and efficient energy storage.