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Polymerization and Interface Engineering of Polymer Gels for the Development of All-Solid-State Supercapacitors

  • 김종식 (아주대학교 일반대학원)

초록/요약

Energy storage device has become an essential part of the modern society. However, one of the key components of the device, liquid electrolyte, poses a potential hazard. Therefore, it comes as no surprise that research on polymer electrolyte is gaining much interest and attention. Polymer-based electrolyte, while maintaining the advantages of the predecessor also provides stronger interfaces stability, mechanical properties, and charge/discharge stability. Making use of such advantages of the polymer electrolyte, all-solid-state supercapacitor with the component has better mechanical properties and reduced interfacial resistance. Theses physical progresses ultimately bring advanced electrochemical properties. Also, by using polymer electrolyte, packaging is omitted thereby once again fueling the interest at hand. In this study, polymer electrolyte was applied to all-solid-state supercapacitor to promote interfacial stability between the electrode and the electrolyte. The study focused on reducing the interface resistance and upgrading the mechanical properties of the proposed supercapacitor. In chapter 1, an introduction to gel electrolyte based on hydrogel and polymer was detailed. The chapter presented schematic explanations to how such properties of the electrolytes could be applied to all-solid-state supercapacitor. In chapter 2, all-solid-state supercapacitor with hydrogel electrolyte having reversible phase transition characteristic was detailed. The sol-gel reversibility was used to assemble the all-solid-state supercapacitor, thereby all the interfaces between the current collector, electrode and electrolyte was fused. This effort was achieved first by letting the solution state electrolyte to sip through the 3D structure current collector and changing the state from solution to gel. Then, during polymerization the interface between electrodes and current collector was fused. The hydrogel electrode prepared as mentioned was covered with the solution state electrolyte then polymerized to fuse the interface between the electrode and the electrolyte. Through the method explained, an integrated all-solid-state supercapacitor was prepared. By integrating the interfaces of all the components, the supercapacitor’s interfacial resistance was decrease, and the electrochemical property improved by 35%. Also, the mechanical properties were enhanced 10 times, and the interface stability made the supercapacitor more resilient to mechanical deformation from repeated use. In chapter 3, all-solid-state supercapacitor with ionogel which has a better stability towards the outside environment was detailed. The electrode was coated the current collector by using functional aqueous polymer binder in slurry. On the prepared electrode, prepolymer electrolyte was applied, then by polymerization the interface between the electrode and the electrolyte was fused. The polymer binder and the ionogel electrolyte was designed so that the two could fuse through covalent bonds. With the method mentioned an all-solid-state supercapacitor with covalent bonding between the electrode and the electrolyte was prepared. The supercapacitor with functionalized binder showed 1.3 times improvement in mechanical strength and 2.47 times improvement in electrochemical function compared to its counterpart. Also, the supercapacitor with ionogel showed electrochemical stability for 15 days even without any packaging process. In chapter 4, advanced all-solid-state supercapacitors that can be visually verified for charge and discharge states was prepared. Electrochromic electrodes had a short diffusion distance for lithium ions due to their porous structure. This porous structure was regularly aligned and had a structural color. The structural color not only indicated the charge/discharge state of the supercapacitor, but also added an aesthetic element. The reflection intensity changed instantaneously with changes in voltage, providing a visual indication of the real-time charge/discharge state. This thesis described the research on all-solid-state supercapacitors that combined soft matter and the interfacial engineering. By controlling the interfaces formed on the supercapacitors, which had improved interfacial stability and mechanical strength enhancement, and confirmed that the electrochemical performance was stable for a long period of time in ambient atmosphere without any packaging process. The combination of interfacial engineering and soft matters could provide new form-factors for supercapacitors. As a result, polymer gel electrolytes were expected to play a key role in future all-solid-state energy storage devices. *Key-words: all-solid-state supercapacitor, interface engineering, polymer electrolyte

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목차

Chapter 1. Introduction 1
1.1. Polymer gel electrolytes in energy storage devices 1
1.1.1. Hydrogel electrolytes 2
1.1.2. Ionogel electrolytes 4
1.2. All-solid-state supercapacitors 6
1.3. Objective of the thesis 7
1.4. References 10
Chapter 2. Aqueous All-Solid-State Supercapacitor Having Seamless Interfaces by Reversible Phase Transition of Hydrogels 15
2.1. Introduction 15
2.2. Experimental 18
2.2.1. Materials 18
2.2.2. Preparation of fully integrated all-solid-state supercapacitor 18
2.2.3. Lap-shear test of fully integrated all-solid-state supercapacitor 19
2.2.4. Capacitive performance measurement of fully integrated all-solid-state supercapacitor 19
2.2.5. Characterization 20
2.3. Results and discussion 21
2.3.1. The rapid phase transition behaviors of agarose gels 21
2.3.2. Seamless integration between the electrode and current collector 24
2.3.3. Seamless integration between the electrode and electrolyte 30
2.3.4. The mechanically robust seamless all-solid-state supercapacitor 33
2.3.5. Electrochemical performance of seamless all-solid-state supercapacitor 37
2.3.6. Stable electrochemical performances upon mechanical deformation 43
2.3.7. Seamless all-solid-state supercapacitor in series 46
2.4. Conclusion 50
2.5. References 51
Chapter 3. Air Stable All-Solid-State Supercapacitors Designed for Covalent Bonds of Polymeric Binders and Ionogel Electrolytes 55
3.1. Introduction 55
3.2. Experimental 59
3.2.1. Materials 59
3.2.2. Synthesis of the polymeric binder dispersions 59
3.2.3. Preparation of the electrode slurry 60
3.2.4. Preparation of the ionogel prepolymer 60
3.2.5. Fabrication of the all-solid-state supercapacitor 62
3.2.6. Lap-shear test of all-solid-state supercapacitor 62
3.2.7. Electrochemical potential window of the ionogel electrolyte 62
3.2.8. Capacitive performance measurement of all-solid-state supercapacitor 62
3.2.9. Characterization 63
3.3. Results and discussion 65
3.3.1. Characterization of the cross-linked polymeric binders 65
3.3.2. Improvement in mechanical strength via covalent bonds 70
3.3.3. Electrochemical performance of all-solid-state supercapacitor 73
3.4. Conclusion 83
3.5. References 84
Chapter 4. Advanced All-Solid-State Supercapacitor with Structural Color-Based Electrochromic Electrodes 87
4.1. Introduction 87
4.2. Experimental 89
4.2.1. Materials 89
4.2.2. Synthesis of the polystyrene nanoparticles 89
4.2.3. Preparation of the electrochromic electrode with inverse opal structure 90
4.2.4. Electrochromic characterization of WO3 electrode 91
4.2.5. Preparation of advanced all-solid-state supercapacitor 91
4.2.6. Characterization 93
4.3. Results and discussion 94
4.3.1. Characterization of PS templates 94
4.3.2. Characterization of WO3 inverse opal electrochromic electrode 94
4.3.3. Electrochromic characterization of WO3 inverse opal electrode 98
4.3.4. Characterization of WO3/SiO2 inverse opal electrochromic electrode 104
4.3.5. Electrochromic characterization of all-solid-state supercapacitor 109
4.4. Conclusion 112
4.5. References 113
Summary in Korean 114

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