Supercapacitor Electrode Materials Comprising Uniformly Dispersed Chromium Nitride/ Carbon Fiber Composite

Nowadays, researchers and industrial designers are looking for an eco-friendly alternative energy source to fulfill the increasing need for energy and reduce environmental pollution. Electricity based on energy storage devices can be a way of solving the crisis. Among different energy storage devices, the faster charging and discharging speeds or higher power densities, working in a wider range of temperatures, and longer cycle life of supercapacitor make them attractive for several applications. The commercially available supercapacitors are mostly electric double-layer capacitors (EDLCs) and to a lesser degree of pseudocapacitors. Recently, researchers have been focusing on hybrid supercapacitors (HSCs) due to their ability to combine the properties of both EDLCs and pseudocapacitors to expand the applications. Engineered carbon nanofibers can be coupled with conductive metal nitrides to form composites and used as electrode materials for supercapacitor applications. In this work, a new hybrid nanocomposite of carbon fibers and chromium nitride (CFs/CrN) was fabricated as electrode materials, where polyacrylonitrile (PAN) was utilized as the carbonizing materials and polymethyl methacrylic acid (PMAA) as the sacrificial agents. Here, pore-forming agents, PMAA, assisted in improving the supercapacitor's performance by increasing the electrode materials' surface area. Also, growing CrN nanoparticles in the fiber contributed by the pseudocapacitance from proton adsorption. Furthermore, the chelation ability of the PMAA might be beneficial for the homogeneous distribution of CrN all over the CFs. Furthermore, the use of aqueous electrolytes and comparatively low-cost transition metal materials lowered the fabrication costs, and the utilization of the electrospinning technique makes CFs/metal nitrides composite electrodes freestanding and readily produced. Chapter 1 describes a detailed introduction to supercapacitors, including a brief description of the storage principle of EDLCs, pseudo capacitors, and hybrid supercapacitors and their advantages and disadvantages. It also describes the basics of the electrospinning process, thermal treatments, and aqueous electrolytes, all of which were applied to fabricate the supercapacitors using CFs and metal nitrides composite-based electrodes. Chapter 2 represents the fabrication of CFs and chromium nitrides composites using polymer blends containing PAN and PMAA and Cr precursor as a source of chromium. This chapter also describes the characterization of synthesized PAM-PMAA-CrN electrode materials and their electrochemical performance and analysis. The highest capacitance was obtained from PANPMAA-CrN based electrode 159 F/g at 5 mV/s. Also, the highest energy densities of 13.26 Wh/Kg at 1.2 V were obtained from the PAN-PMAA-CrN and CNFs based asymmetric device. Furthermore, the PAN-PMAA-CrN electrode showed higher stability with 80.4% capacitance retention after 10000 cycles.