In recent years, electrical double layer capacitor (EDLCs) has become one of the most popular energy storage devices. This can be attributed to its high capacity, long life cycle and fast charge/discharge rates. However, it has some drawbacks – mainly it stores less amount of energy than batteries. Hence, there is a need to optimize the EDLC to increase its capacity and decrease its equivalent series resistance (ESR), resulting in a supercapacitor that is able to charge quickly and will hold a large amount of energy for a long time.
This thesis presents a design, build and setup process of a supercapacitor pilot plant in the University of Nottingham Malaysia Campus for manufacturing and optimization of EDLCs. Two packages were considered, cylindrical and coin type packages. In addition, the design of a manufacturing process flow, with details on steps for fabrication, which will meet specific standards (BS EN 62391-1:2006, BS EN 62391-2-1: 2006, BS EN 62391-2-1: 2006 and DOD-C-29501/3 NOT 1) for quality and throughput for both the packaging types is discussed. Following this, significant factors of the fabrication process were identified and optimized by adopting the Taguchi design of experiment (DOE) methodology.
Results of the optimization process show that the most significant factors that affect the EDLC capacitance are PVDF % (polyvinylidene diflouride) and mixing time; the optimum values are determined to be 5% and 3 hours respectively. In the case of ESR optimization, the most significant factors are PVDF % and carbon black %. The optimum values are 5% for both. Using these optimized values, a final prototype EDLC was fabricated. The capacitance value obtained for the cell was 54.70mF.
The final EDLC prototypes were tested according to the international standards (ISO) and compared with the supercapacitors available in the market. Results indicated that the electrochemical performance of the prototypes has a good resemblance to the performance of the supercapacitors available in the market. A selected prototype samples were sent for benchmark testing to companies in mobile applications in Korea and the Netherlands to confirm that the prototypes meet the required standards.
Finally the research work sets the basis for integrating genetic algorithms with the Taguchi technique for future research in improving the optimization process for robust EDLC fabrication
