슈퍼커패시터을 위한 MXene 기반전극 = MXene-based Heterostructure Electrodes for Supercapacitor

다국어 초록 (Multilingual Abstract)

With the increasing demand for high-performance energy storage devices, the preparation of high specific capacitance electrode materials and their application in supercapacitors is an important research direction. MXene, as an emerging two-dimensional material, is widely used in energy storage devices such as batteries and capacitors due to its unique physicochemical properties, including a large specific surface area, abundant surface functional groups, excellent hydrophilicity, and high conductivity. However, like many two-dimensional materials, MXene tend to suffer from stacking and aggregation, which hinders ion transport performance, reduces their intrinsic specific capacitance, and ultimately deteriorates their electrochemical performance.
In this thesis, two-dimensional layered titanium carbide and titanium carbide-graphene heterojunction materials were synthesized through structural design. The effect of the microstructure and chemical composition of the electrode materials on their electrochemical performance were systematically investigated., the electrochemical behavior of the supercapacitor was analyzed, and the underlying electrochemical energy storage mechanism was elucidated. This work provides a theoretical basis and practical guidance for the design and development of MXene-based electrode materials and supercapacitor devices with high energy density and long-term stability. The main contents are summarized as follows:
(1) In this study, MXene was synthesized using Ti3AlC2 as a precursor via two different routes: direct etching with hydrofluoric acid and in-situ etching with lithium fluoride and hydrochloric acid. The structure and morphology of the resulting samples were systematically characterized using XRD, SEM, and TEM. The results showed that although both etching approaches effectively removed the intermediate Al layer to produce titanium carbide, the resulting MXene materials exhibited pronounced differences in interlayer spacing, sheet morphology, and dispersibility. (Corresponding to Chapter 2 of the thesis)
(2) In this study, MXene prepared via lithium fluoride and hydrochloric acid etching was mixed with graphene dispersed using water-soluble quantum dots, followed by ultrasonic treatment. Through the synergistic interaction between the two-dimensional components, a MXene/graphene heterostructure was successfully constructed. The heterostructure was subsequently combined with polythiophene to fabricate a conductive MXene/Graphene/PEDOT:PSS electrode, which was then assembled into a high-capacitance supercapacitor. The GCD test using a two-electrode configuration showed that the specific capacitance reached a maximum of 47.6 F/cm³ at an MXene concentration of 0.033 mg/ml. These results confirm that high-capacitance performance arises from the synergistic effect associated with the carbon-based graphite structure the two-dimensional material. (Corresponding to Chapter 3 of the thesis)
Through MXene synthesis and surface functional group design, and the design of electrodes for the two-dimensional heterostructure composite material, This research, is of great significance for the development of high-performance energy storage devices.

목차 (Table of Contents)

• Introduction 1
• 1.1 The importance of energy storage devices 1
• 1.2 History of the Development of Supercapacitors 3
• 1.3 Energy storage mechanism and classification of supercapacitors 4
• 1.4 Introduction to MXene and 2D materials 8
• 1.5. MXene synthesis method 13
• 1.6. Applications of MXene 18
• 1.7 Research Content and Innovations of This Thesis 20
• Synthesis and Performance Characterization of MXene by Different Methods 22
• 2.1 Introduction 22
• 2.2 Experiment 23
• 2.2.1 hydrofluoric acid method (HF etching) 23
• 2.2.2 Situ HF-Forming Etching with HCl/LiF (Fluoride-based acid etching) 23
• 2.3 Result and discussion 25
• 2.4 Conclusion 43
• Graphitic Carbon-Assisted Synergistic Enhancement of MXene/PEDOT: PSS Composite Electrodes for High-Performance Energy Storage 44
• 3.1 Introduction 44
• 3.2 Experimental section 48
• 3.2.1 Materials 48
• 3.2.2 Electrode solution preparation 48
• 3.2.3. PVA/H3PO4 Electrolyte solution 52
• 3.2.4. Supercapacitor Assembly 52
• 3.3 Characterization 54
• 3.4 Result and discussion 56
• 3.4 Conclusion 97
• Summary and outlook 99
• 4.1 summary 99
• 4.2 outlook 100
• Reference 103
• 국문 초록 121
• Acknowledgments 123