Surface engineering of conductive material-based composites for energy applications
Type of DegreePhD Dissertation
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With the increasing concern on renewable sources (wind, wave and solar), energy storage and power management have become increasingly important topics. Supercapacitors (SCs) with features of ultrahigh power output, excellent cycle life, fast charge/discharge rates and environment-friendly nature have been considered as one kind of promising energy storage devices for meeting the ever-increasing power requirements of energy storage systems. Obviously, the specific capacitances, the energy and power densities and the cycling stability are important parameters for evaluating SCs. Many attempts have been tried to enhance their performance by exploring various kinds of electrode materials. Conducting polymers (CPs) and transition metal (TM)-based materials are two kinds of vital electrode materials for SCs. CPs, also known as synthetic metals, are basically organic polymers with both metallic and semi‐metallic features. Polypyrrole (PPy) and polyaniline (PANI) are commonly used CPs electrode materials for SCs, even for flexible SCs, due to their pseudo‐capacitive characteristic, easy processible, flexible, and high specific capacitance values. However, the low cycling stability of CPs caused by structure degeneration during the reversable charge/discharge processes becomes a major bottleneck and hinders their further development. TM-based materials, especially the multicomponent metal materials, are another type of excellent electrode material for SCs due to their richer redox-active reactions sites. However, this type of material usually faces conductivity problems. Therefore, trying to solve above mentioned issues is essential for the further development of SCs. My Ph.D. research aimed to find easy and feasible strategies to design and improve the electrochemical performance of electrode materials. In the whole work, I demonstrated dopants have a great effect on the electrochemical performance of CPs (mainly focus on PPy and PANI)-based electrodes and selecting a suitable dopant can be used as an effective way for enhancing the electrochemical behavior of CPs-based electrode materials. In addition, a high-rate and ultra-stable transition metal phosphide (TMP) electrode (Mn-CoP/Ni nanosheets) was successfully prepared by a facile electrodeposition method. Moreover, a simple and ultra-fast microwave method was successfully used to synthesis the high-performance transition metal sulfide (TMS)-based electrode material (nickel-cobalt sulfide/graphene hybrid material). The outcomes of my Ph.D. research will provide a much easier route in achieving high performance CPs-based and TM-based electrode materials as promising candidates for energy storage application and broaden their practical applications.