Design and characterization of supercapacitors obtained by combining sandwich and interdigitated structures

Abstract

The world today faces enormous issues linked to energy, savings, and energy management in order to enhance and extend the standard of life for a growing population and to do so while utilizing sustainable technology. Many technologies and applications need energy storage systems that can store and release large amounts of energy. Researchers are interested in supercapacitors (SCs) because of their unique characteristics, such as quick charging and discharging, better power density, flexibility, and environmental friendliness. The supercapacitor can bridge the gap between batteries and regular capacitors in terms of energy storage and power bursts, despite its lower energy density than projected. Because they store energy via a physical mechanism rather than a chemical method, SCs are extremely safe to use and have an extremely extended life cycle. The biggest challenge for SCs is to increase their specific energy density while maintaining their high specific power density, in other words, to improve the electrochemical performance of SCs. To date, a significant amount of research has been focused on improving the performance of SCs. The key factors influencing the performance of SCs are design and manufacturing processes together with materials. The configuration of SCs typically includes sandwich structures and interdigitated structures. All of the structures have their own advantages and disadvantages. There are lots of parameters that influence the performance of each configuration. The sandwich structure has a lower power density than the interdigitated structure because of its long ion path. On the other hand, interdigitated structures have low energy density due to their small surface area compared to sandwich structures. This thesis focuses on developing novel designs and structures to improve the performance of SCs in this area. The materials used here are conductive polymers like PEDOT: PSS, and PANI because of their high conductivity and excellent electrical performance. All of the designs and structures were characterized by cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), and Electrochemical impedance spectroscopy (EIS), and the results were discussed in detail. The studies can be divided into two experimental parts. In the first part, the pattern of the interdigitated structure was modified with the laser etching method, and different patterns were etched at different distances. In this study, PEDOT: PSS and Graphite were used as electrode materials. Next, different patterns were analyzed in solution electrolyte (6 M KOH), and the CV curve and GCD curve of the desired patterns were analyzed in detail. In the second part, to overcome the limitations of each structure that was mentioned above and use the advantages of each of them, a new structure named a Combination (COM) structure was designed and manufactured. The new structure consists of two interdigitated patterned electrodes that are stacked to each other. xxiii First, Polyaniline (PANI) was synthesized and modified to be an electrode material. Next, the new structure was designed and coated with electrode material, and PVA/KOH gel electrolyte was used here as the electrolyte of the cell. After that, the CV, GCD, and EIS curves of the new structure were measured and analyzed in detail. And this study provides a comparison between the new structure's performance with other structures of SCs. The new structure shows enhancement in a manner over other structures. The new structure enhances the amount of current, self-leakage, and capacitance of SCs In summary, the studies presented in this thesis developed and analyzed various patterns on in plane SCs by using the laser etching method. It demonstrates the manufacturing setup and effects of the pattern on the performance of SCs. After that, new structures named "combined structures" (COM) were designed and manufactured. It is named "combined" because it combines the advantages and disadvantages of other conventional structures and uses both the charge transfer mechanisms of sandwich and interdigitated type SCs. The new structure enhances the performance of SCs and reduces the internal resistance or self-leakage compared to other structures.