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|Title:||Colloidal Fabrication Techniques for the Development of Supercapacitor Electrodes and Devices|
|Advisor:||Puri, Ishwar K|
|Abstract:||In this thesis, an advanced colloidal fabrication technique, called particle extraction through liquid-liquid interface (PELLI), has been developed to fabricate components of positive and negative electrodes of electrochemical capacitors (ECs). This new colloidal strategy is applied to create stable suspensions for the electrophoretic deposition (EPD) of thin films and advanced inks for screen printing applications. Bottom-up and top-down PELLI strategies were developed to extract MnO2 particles synthesized in an aqueous phase to the organic phases of 1-butanol and dichloromethane, respectively. During both extraction processes, hexadecylamine with amine functional group was used as the extractor for transferring the MnO2 particles. Compared to the top-down PELLI technique, the bottom-up PELLI synthesized particles of relatively small sizes, which is beneficial for fabricating MnO2-multiwalled carbon nanotube (MWCNT) binary composite EC electrodes with enhanced electrochemical performance. Hence, the subsequent work was carried out using the bottom-up strategy for PELLI. Head-tail extractors with a single functional group, such as carboxylic acid and phosphonate, and head-tail-head (HTH) multifunctional extractors with functional groups of both carboxylic acid and phosphonate were used as the vehicles for transferring MnO2 from the synthesis media to the device processing media to achieve a good suspension of MnO2-MWCNT to fabricate positive EC electrodes. Advanced FeOOH-MWCNT negative electrodes were also prepared by PELLI strategies using HT and HTH extractors. The experimental results showed that both positive and negative electrodes prepared by HTH extractors exhibit the highest electrochemical performance. Moreover, stable suspensions of MnO2 particles synthesized by PELLI with multifunctional HTH extractors were prepared to fabricate advanced thin films by EPD and also MnO2-carbon black printing inks for screen printing of thin EC electrodes. Subsequently, to fabricate efficient polypyrrole (PPy) based composite negative electrodes, for the first time, non-agglomerated FeOOH particles were prepared with PELLI using tetradecylamine as extractor. Introduction of PPy enhances the electrochemical performance of the binary composite of PPy coated MWCNT in a potential range of -0.8 - +0.1V. Advanced asymmetric ECs devices with MnO2-MWCNT positive electrodes and PPy-FeOOH-MWCNT negative electrodes were fabricated. These devices with comparable capacitance for both the positive and negative electrodes and high active mass loading were found to have high electrochemical performance in a wide working voltage window of 1.6V in aqueous electrolyte.|
|Appears in Collections:||Open Access Dissertations and Theses|
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