Title Page
국문요약
ABSTRACTS
Contents
Chapter 1. Introduction 19
1.1. General background 19
1.2. Comparison of electrochemical capacitors and batteries 23
1.3. Principle of energy storage 29
1.3.1. Electrical double layer capacitance 31
1.3.2. Pseudocapacitance 35
1.4. Classification of electrode materials 37
1.4.1. Carbon 38
1.4.2. Metal oxides 41
1.4.3. Conductive polymers 43
1.5. Electrochemical capacitor performance 46
1.5.1. Porous electrode 48
1.5.2. Maximum achievable energy density and power density 54
References 58
Chapter 2. Carbon-based electrode materials 62
2.1. Introduction 62
2.2. Characteristics of electrode materials 64
2.3. Carbon structure and form 65
2.4. Engineered carbons 68
2.5. Carbon-based electrode materials 71
2.5.1. Activated carbons 71
2.5.2. Carbon aerogels and xerogels 74
2.5.3. Carbon nanotubes 76
2.5.4. Graphene 82
2.6. Factors for enhancing specific capacitance of carbon materials 88
2.6.1. Activation 88
2.6.2. Electrical properties 90
2.6.3. Surface functionality 94
References 97
Chapter 3. Objective of this work 103
Chapter 4. Synthesis of Hybrid Carbon/Nanocarbon Composites and their High Electrochemical performance 105
4.1. Introduction 105
4.2. Materials and Methods 113
4.2.1. Materials 113
4.2.2. Preparation of the samples 114
4.3. Results and Discussion 123
4.3.1. N-doped carbon/nanocarbons 123
4.3.2. Nanocarbon-embedded microporous carbons 157
4.4. Conclusions 188
References 191
Table 1.1. Comparison of electrochemical capacitor and battery characteristics 24
Table 1.2. Comparison of capacitor, electrochemical capacitor and battery 26
Table 1.3. Comparison of EDLC and pseudocapacitance 30
Table 2.1. Precursors and controlling production factors for various carbons 69
Table 2.2. Comparison of specific capacities, surface area, pore volume and average pore size of activated carbons 72
Table 2.3. The properties of graphene and other carbon allotropes 84
Table 4.1. The element components of MWNTs and C-MWNTs 132
Table 4.2. The element components of graphene, graphen/PANI, and C-graphene 136
Table 4.3. Textural properties of MWNTs, MWNTs/PANI, and C-MWNTs 141
Table 4.4. Textural properties of graphene, graphene/PANI, and C-graphene 144
Table 4.5. The element components of MWNTs and P-MWNTs 165
Table 4.6. The element components and yields of graphene, MCs, and G-MCs 167
Table 4.7. Textural properties of MWNTs, P-MCs, and P-MWNTs 171
Table 4.8. Textural properties of graphene, MCs, and G-MCs 174
Fig. 1.1. Ragone plot for energy storage and conversion devices. 22
Fig. 1.2. Discharge characteristics of battery, electrostatic capacitor and ECs. 28
Fig. 1.3. Principle of a single-cell double-layer capacitor and illustration of the potential drop at the electrode/electrolyte interface. 32
Fig. 1.4. Illustration of pseudocapacitance in a conductive polymer. 36
Fig. 1.5. Classification of the supercapacitor materials. 37
Fig. 1.6. Cyclic voltammograms of activated glassy carbon electrodes. 39
Fig. 1.7. Illustration of specific capacitance of porous carbon, RuO₂, and conductive polymers. 45
Fig. 1.8. Schematic representation of the Nyquist impedance plot of an ideal capacitor (vertical thin line) and an electrochemical capacitor with porous electrodes (thick line). 47
Fig. 1.9. Equivalent circuit representation of the distributed resistance and capacitance within a pore. Five-element transmission line. 49
Fig. 1.10. Calculated impedance plots for porous electrodes with different thickness. 52
Fig. 1.11. Capacitance versus frequency plot for the electrodes of Fig. 1.10. 52
Fig. 1.12. Calculated maximum achievable power density and maximum achievable energy density for two capacitors with aqueous (1 V) and organic electrolyte (2.3 V). 55
Fig. 1.13. Effect of nominal cell voltage on the maximum achievable power and energy density of Fig. 1.12 for the capacitor with organic electrolyte. 57
Fig. 2.1. Various carbon forms; (a) diamond, (b) graphite, (c) lonsdaleite, (d~f) fullerene, (g) amorphous carbon, (h) carbon nanotube. 66
Fig. 2.2. Schematic representation of the carbon nanotube formation by rolling up a 2D graphene sheet of lattice vectors a1 and a2 [38]. 77
Fig. 2.3. Schematic illustration of the spaces in a carbon nanotube bundle for the storage of electrolyte ions. 79
Fig. 2.4. Comparison on conducting paths for electron and electrolyte ion in an aligned carbon nanotubes and granular activated carbons. 79
Fig. 2.5. TEM image of individual graphene sheet. 83
Fig. 2.6. (a) SEM and (b) TEM images of chemically modified graphene. (c) Low and high (inset) magnification SEM images of a chemically modified graphene electrode surface. (d) Schematic of test cell assembly. 86
Fig. 2.7. Resistivity (ρ) vs. temperature plots for various forms of carbons: (1) single crystal graphite; (2) highly oriented pyrolytic graphite; (3) graphite whisker; (4) pyrolytic graphite; (5) petroleum coke carbon; (6) lampblack carbon; (7) glassy carbon; (8) carbon film-electron beam evaporated. 92
Fig. 4.1. Scheme for the preparation of N-doped C-MWNTs. 114
Fig. 4.2. Scheme for the preparation of N-doped C-graphene. 115
Fig. 4.3. Scheme for the preparation of P-MCs and P-MWNTs. 117
Fig. 4.4. Thermal degradation behaviors of PVDF and GO/PVDF film. 119
Fig. 4.5. SEM images of (a) MWNTs, (b) MWNTs/PANI, and (c, d) CMWNTs. 124
Fig. 4.6. TEM images of (a) MWNTs, (b) MWNTs/PANI, and (c) C-MWNTs. 125
Fig. 4.7. SEM images of (a) graphene, (b) graphene/PANI, and (c, d) Cgraphene. 127
Fig. 4.8. TEM images of (a) graphene, (b) graphene/PANI, and (c) C-graphene. 128
Fig. 4.9. (a) XRD patterns and (b) Raman spectra of MWNTs, MWNTs/PANI, and C-MWNTs. 131
Fig. 4.10. XPS wide-scan of MWNTs and C-MWNTs. 133
Fig. 4.11. Raman spectra of graphene, graphene/PANI, and C-graphene. 135
Fig. 4.12. XPS wide-scan of graphene, graphene/PANI, and C-graphene. 137
Fig. 4.13. N₂ adsorption/desorption isotherm of MWNTs, MWNTs/PANI, and C-MWNTs at 77K. 139
Fig. 4.14. (a) N₂ adsorption/desorption isotherm, pore distribution of (b) mesopores and (c) micropores of graphene, graphene/PANI, and C-graphene at 77K. 143
Fig. 4.15. Cyclic voltammetry of (a) MWNTs and C-MWNTs at 10 mV/s and (b) C-MWNTs with different scan rates (5 to 100 mV/s). 146
Fig. 4.16. Charge-discharge behaviors of (a) MWNTs and C-MWNTs at 0.2 A/g and (b) C-MWNTs with different current densities (0.1 to 1 A/g). 149
Fig. 4.17. Specific capacitances of MWNTs and C-MWNTs with different scan rates (0.1 to 1 A/g). 150
Fig. 4.18. Cyclic voltammetry of (a) graphene and C-graphene at 10 mV/s and (b) C-graphene with various scan rates (10 to 100 mV/s). 152
Fig. 4.19. Charge-discharge behaviors of (a) graphene and C-graphene at 0.2 A/g and (b) C-graphene with various current densities (0.1 to 1 A/g). 154
Fig. 4.20. Specific capacitances of graphene and C-graphene with various scan rates (0.1 to 1 A/g). 156
Fig. 4.21. SEM images of (a, b) P-MCs and (c, d) P-MWNTs. 158
Fig. 4.22. The SEM images of (a) GO/PVDF films, (b) MCs, (c) G-MCs, and (d) cross-section of G-MCs, and TEM images of (e) G-MCs and (f) magnified G-MCs. 161
Fig. 4.23. The scheme for the preparation of MCs and G-MCs. 163
Fig. 4.24. XRD patterns of MWNTs, P-MCs and P-MWNTs. 164
Fig. 4.25. XPS wide-scan of MWNTs and P-MWNTs. 166
Fig. 4.26. XPS wide-scan of graphene, MCs, and G-MCs. 168
Fig. 4.27. (a) N₂ adsorption/desorption isotherm, (b) mesopore distribution, and (c) micropore distribution of MWNTs, P-MCs and P-MWNTs. 170
Fig. 4.28. (a) N₂ adsorption/desorption isotherm, (b) mesopore distribution, and (c) micropore distribution of graphene, MCs, and G-MCs. 173
Fig. 4.29. Cyclic voltammetry of (a) MWNTs, P-MCs and P-MWNTs prepared with different MWNT contents at 5 mV/s, (b) P-MWNTs-10 with different scan rates (5 to 100 mV/s). 177
Fig. 4.30. Charge-discharge behaviors of (a) MWNTs, P-MCs and P-MWNTs at 0.5 A/g current density and (b) specific capacitance of MWNTs, P-MCs and P-MWNTs with different current densities (0.5 to 3.0 A/g). 179
Fig. 4.31. The ratio of mesopore volume/micropore volume of each sample. 181
Fig. 4.32. Cyclic voltammetry of (a) graphene, MCs, and G-MCs at 5 mV/s, (b) G-MCs with different scan rates (5 to 100 mV/s). 183
Fig. 4.33. Charge-discharge curves of (a) graphene, MCs, and G-MCs at 1.0 A/g current density and (b) graphene, (c) MCs, and (d) G-MCs with different current densities (0.5 to 3 A/g). 185
Fig. 4.34. (a) Specific capacitance of graphene, MCs, and G-MCs with different current densities (0.5 to 3.0 A/g) and (b) the scheme of combined EDLC feature of G-MCs. 187