Modification of single walled carbon nanotube thin films for supercapacitor electrodes

Durukan, Mete Batuhan
Electrochemical capacitors, or supercapacitors, attracted a lot of attention in recent years due to their stability under numerous charge-discharge cycles, high charge discharge rates, and high power density when compared to batteries and conventional capacitors. Since their energy density is much lower than batteries, current research on supercapacitors is focused on improving the energy density through the development of novel active materials and innovative design of the electrodes. Carbon nanotubes are promising materials for batteries and supercapacitors with their unique morphology and electrical properties. They have highly accessible surface area, efficient electronic transport without scattering and high stability, all of which makes them suitable candidates as electrode materials for electrochemical capacitors. Furthermore, their composites in conjunction with pseudocapacitive materials are also investigated extensively primarily for the electrochemical performance enhancement. In this work, single walled carbon nanotube (SWNT) thin films are used as supercapacitor electrodes. Main idea of this thesis is to fabricate nanocomposite supercapacitors and micro-supercapacitors using cost effective and simple and scalable routes. In this regard, in the first part, SWNT thin film electrodes are used as current collectors and decorated with cobalt oxide (Co3O4) nanoflakes using electrodeposition and consecutive annealing process. A gravimetric capacitance of 313.9 F.g−1, corresponding to an areal specific capacitance of 70.5−2 is obtained from the fabricated electrodes at a scan rate of 1 mV/s. A capacity retention of up to 80% following 3000 charge/discharge cycles is obtained for the fabricated nanocomposite electrodes, while morphological evolution of the electrodes was monitored through high-resolution transmission electron microscopy during cycling. In the second part, are laser patterned SWNT thin films on glass substrates are used for the fabrication of micro-supercapacitors. Laser patterning is proposed for the formation of interdigitated electrodes. A specific capacitance of 3.50 at a scan rate of 10 mV/s was obtained from the SWNT buckypaper that was laser ablated to form interdigitated finger electrodes. A capacity retention up to 97% was attained at an applied current of 3 mA following 1000 charge/discharge cycles.