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DC 欄位 | 值 | 語言 |
---|---|---|
dc.contributor.advisor | 吳乃立(Nae-Lih Wu) | |
dc.contributor.author | Yen-Po Lin | en |
dc.contributor.author | 林彥伯 | zh_TW |
dc.date.accessioned | 2021-06-15T06:56:50Z | - |
dc.date.available | 2016-02-20 | |
dc.date.copyright | 2011-02-20 | |
dc.date.issued | 2011 | |
dc.date.submitted | 2011-02-08 | |
dc.identifier.uri | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48438 | - |
dc.description.abstract | 本論文首先利用由MnFe2O4偽電容材料做為陽極和LiMn2O4電池材料做為陰極,以及9M硝酸鋰(LiNO3)水溶液做為電解液所組成一新型水系非對稱超高電容器,其合成與鑑定將在本論文中討論。奈米結晶的MnFe2O4負極材料具有約99 F/g的比電容量,而LiMn2O4正極在10~100 C-rate提供了將近128~100 mAh/g的比電量。整個非對稱型超高電容具有約1.3 V的最大電位操作範圍,該範圍是被MnFe2O4的還原電位所限制。隨著增加負極對正極的重量比(A/C),而非對稱型電容的功率密度和能量密度也跟著增加,且在A/C~4.0時達到飽和,此時基於兩個電極重量的能量密度和功率密度分別為10和5.5 Wh/kg在0.3和1.8 kW/kg下。此非對稱型超高電容表現出良好的循環壽命,其在經過5,000次的充放電後,只有損失5%以內的電容量,以及相較於MnFe2O4對稱型電容及其它非對稱電容有較低的自放電速度。
另外,經由化學共沉法將MnO2沉積在碳黑(CB)和多壁奈米碳管(CNT)形成兩種MnO2@C的複合體,它們的物理性質和在1M NaCl(aq)電解液中的電化學性質將在此被討論。從XRD的數據分析顯示此兩種氧化物的分別為spinel-type MnO2@CNT(S-MnO2@CNT)和birnessite-type MnO2@CB(B-MnO2@CB)。SEM和TEM的觀察顯示MnO2以不同型態分散在CB和CNT上,MnO2均勻地分散在CNT上呈奈米薄片狀,而MnO2在CB上的型態為奈米粒狀。B-MnO2@CB和S-MnO2@CNT 的BET比表面積分別為138和156 m2/g。S-MnO2@CNT在2 mV/s和200 mV/s下表現出309 F/g-MnO2和247 F/g-MnO2,比B-MnO2@CB(在2 mV/s和200 mV/s下表現出229 F/g-MnO2和132 F/g-MnO2)有較好的效能,主要因為高的比表面積提供了較多與電解液接觸面積、較均勻的氧化物分佈,以及高導電的多壁奈米碳管基材也增加了電極的效能。S-MnO2@CNT所組成的對稱電容也展現了相當不錯的循環壽命,其在經過50 mV/s和100 mV/s下各循環5000次,經過循環10,000次後,依然保有96%電容量,而B-MnO2@CB的對稱電容在50 mV/s下循環充放10,000次後,只剩下76.7%的電容量。在自放電的測試中,S-MnO2@CNT電極的自放電速度較B-MnO2@CB和amorphous MnO2@CB複合電極來得慢許多,顯示出其應用在超高電容的潛能。 此外,使用MnO2@CB and MnO2@CNT做為Mn的前驅物,經由一步驟的水熱方式可以成功地合成LiMn2O4@CB和LiMn2O4@CNT複合材料。從XRD的鑑定顯示出此兩種複合體含有spinel LiMn2O4和類石墨碳的結構,其LiMn2O4晶粒大小也分別由Debye-Sherrer方程式計算得到。熱重分析的結果顯示碳含量在LiMn2O4@CB和LiMn2O4@CNT複合材料分別為37.6 wt%和19.2 wt%。LiMn2O4@CB在含有鋰的水系和有機系電解液中表現出128 mAh/g的可逆電容量。此外,LiMn2O4@CB在25 oC和55 oC下進行循環壽命的測試,在5 C-rate下經過了660次充放電後,其電量仍有97%。LiMn2O4@CNT複合材料在0.5 C-rate下的9M LiNO3(aq)電解液中展現出約130 mAh/g的可逆電量,且在500 C的充放電速度下表現出111 mAh/g的高功率輸出。 | zh_TW |
dc.description.abstract | A new type of aqueous asymmetric supercapacitor that contains MnFe2O4 pseudocapacitive anode and LiMn2O4 battery cathode with 9M LiNO3(aq) as electrolyte has been synthesized and characterized. The anode and cathode electrodes were characterized separately in 1M and 9M LiNO3(aq). Both electrodes showed superior performance in high concentration electrolyte and high temperature. The nanocrystalline MnFe2O4 anode material have a specific capacitance of ca. 99 F/g and the LiMn2O4 cathode a specific capacity of ca. 128~100 mAh/g under 10~100 C-rate. The cell has a maximum operating voltage window of ca. 1.3 V, limited by irreversible reaction of MnFe2O4 toward reducing potential. The specific power and specific energy of the full cell were found to increase with increasing anode-to-cathode mass ratio (A/C) and saturate at A/C~4.0, which gives specific cell energies, based on total mass of two electrodes, of 10 and 5.5 Wh/kg at 0.3 and 1.8 kW/kg, respectively. The 4-1 cell shows good cycling stability that only within 5% capacitance loss after 5000 cycles, and exhibits significantly slower self-discharge rate than the MnFe2O4 symmetric cell and other asymmetric capacitors.
In addition, the physical and electrochemical properties of two kinds of MnO2@C composite materials in 1M NaCl aqueous solution were determined and discussed. MnO2 was deposited onto muti-walled carbon nanotubes (CNT) and carbon black (CB) by chemical co-deposition to form composite materials. From X-ray powder diffraction characterizations, composites are spinel-type MnO2@CNT (abbreviated as S-MnO2@CNT) and birnessite-type MnO2@CB (denoted as B-MnO2@CB). SEM and TEM observations reveal that S-MnO2 was well-dispersed onto MWCNT with nano-flake structure, and the morphology of the B-MnO2 of the other composite was nano-particulate, and the BET surface area of B-MnO2@CB and S-MnO2@CNT are 138 and 156 m2/g. The S-MnO2@CNT-based electrode delivered 309 F/g-MnO2 and 247 F/g-MnO2 at 2 mV/s and 200 mV/s, respectively, which showed superior performance than that of B-MnO2@CB (229 F/g-MnO2 and 132 F/g-MnO2 at 2 mV/s and 200 mV/s), and therefore, the excellent performance is attribute to a larger contact area with the electrolyte, more homogeneous dispersion of oxide and the highly conductive substrate (CNT) also helped to enhance the performance of the electrode. A long-term stability test of the S-MnO2@CNT-based symmetric cell was carried out at 50 mV/s and 100 mV/s, and each sweep rate involved 5000 cycles. After 10000 cycles, the capacitance of the S-MnO2@CNT-based symmetric cell remained above 96%, but the B-MnO2@CB-based symmetric cell only retained 76.7% capacitance after 10000 cycles at 50 mV/s. Self-discharge tests show that S-MnO2@CNT could store charge longer than the B-MnO2@CB composite electrode or the amorphous MnO2@CB composite electrode, indicating that S-MnO2@CNT has superior performance for the application of supercapacitors. Besides, LiMn2O4@CB and LiMn2O4@CNT composite materials were synthesized successfully through a one-step hydrothermal process that employed B-MnO2@CB and S-MnO2@CNT as Mn precursors. The XRD characterizations show the features of spinel LiMn2O4 structure and graphitic structure of carbons, and the crystallite size of LiMn2O4 were calculated by using Debye-Sherrer equation individually. The carbon content among LiMn2O4@CB and LiMn2O4@CNT composite were analyzed using TGA, which are 37.6 wt% and 19.2 wt%, respectively. The electrochemical performance of LiMn2O4@CB composite was characterized in aqueous and organic electrolyte contain with Li ion, and the LiMn2O4@CB electrode exhibited 128 mAh/g reversible capacity in both electrolytes. Moreover, LiMn2O4@CB showed long-term stability while charging/discharging in a half cell at 25 oC and 55 oC, which remained 97% capacity after 660 cycles. The LiMn2O4@CNT electrode showed a reversible capacity of 130 mAh/g at 0.5 C-rate and presented an extremely high power density in 9M LiNO3 aqueous electrolyte, which delivered 111 mAh/g at 500 C charging/discharging rate. | en |
dc.description.provenance | Made available in DSpace on 2021-06-15T06:56:50Z (GMT). No. of bitstreams: 1 ntu-100-D94524004-1.pdf: 6088140 bytes, checksum: 0580dda646a23ea059d66748d025d358 (MD5) Previous issue date: 2011 | en |
dc.description.tableofcontents | 摘要 I
Abstract III Table of Contents VI List of Tables X List of Figures XI Chapter 1 Introduction 1 1.1 Background 1 1.2 Motivations and Objectives 3 Chapter 2 Theory and Literature Review 5 2.1 Introduction to Electrochemical Capacitors 5 2.1.1 Classifications of Electrochemical Capacitors 7 2.1.2 Models and Structures of Electric Double-Layers 14 2.1.3 Characteristics of Superapacitors and Batteries 18 2.1.4 Self-discharge Mechanism of Supercapacitors 19 2.2 Development of Electrochemical Capacitors 21 2.2.1 Electrode Materials 21 2.2.2 Electrolytes 23 2.2.3 Development of Asymmetric Supercapacitors 25 2.3 Introduction to Manganese Ferrite, MnFe2O4 28 2.3.1 Structure and Characteristics 28 2.3.2 Synthesis and Development on Supercapacitors 32 2.4 Introduction to Manganese Oxide, MnO2 34 2.4.1 Structure and Characteristics 34 2.4.2 Synthesis and Development on Supercapacitors 40 2.5 Introduction to Spinel Lithium Manganese Oxide, LiMn2O4 45 2.5.1 Structure and Characteristics 45 2.5.2 Synthesis and Development on Supercapacitors 48 Chapter 3 Experimental 51 3.1 Synthesis of Electrode Materials 51 3.1.1 MnFe2O4@Carbon black Composite Materials 53 3.1.2 Birnesite-type MnO2@Carbon Black Composite Materials 53 3.1.3 Spinel-type MnO2@Carbon Nanotube Composite Materials 54 3.1.4 Amorphous MnO2@Carbon Black Composite Materials 54 3.1.5 LiMn2O4@Carbon Black Composite Materials 55 3.1.6 LiMn2O4@Carbon Nanotube Composite Material 55 3.2 Analysis and Characterization 61 3.2.1 Phase Identification 61 3.2.2 Microstructure Characterizations 62 3.2.3 Surface Area and Pore Structure Analysis 63 3.3 Electrochemical Characterizations 64 3.3.1 Preparation of Electrodes 64 3.3.2 Cyclic Voltammetry 65 3.3.3 Chronopotentiometry 66 Chapter 4 Characterization of MnFe2O4@CB and LiMn2O4 electrodes 69 4.1 Introduction 69 4.2 Physical Properties of MnFe2O4@CB Composite Materials 71 4.3 Basic Electrochemical Characterization of MnFe2O4@CB in LiNO3 Aqueous Electrolyte 77 4.4 Advanced Electrochemical Characterization of MnFe2O4@CB in LiNO3 Aqueous Electrolyte 82 4.5 Investigation on the Electrochemical Behaviors of LiMn2O4 in LiNO3 Aqueous Electrolyte 88 4.6 Summary 94 Chapter 5 Investigation on MnFe2O4/LiMn2O4 Asymmetric Capacitors 95 5.1 Introduction 95 5.2 Basic Characterization of MnFe2O4/LiMn2O4 Asymmetric Capacitors 98 5.3 Optimization of MnFe2O4@CB/LiMn2O4 Asymmetric Capacitors 104 5.4 Conclusions 117 Chapter 6 Characterization of Various Oxide@C Composite Materials 118 6.1 Introduction 118 6.2 Characterization of MnO2@CB Composite Materials 122 6.2.1 Physical analysis of MnO2@Carbon Black Composite Materials 122 6.2.2 Electrochemical Characterization of MnO2@Carbon Black Composite Materials 127 6.3 Investigation on MnO2@CNT Composite Materials 133 6.3.1 Physical Analysis of MnO2@CNT Composite Materials 133 6.3.2 Electrochemical Characterization of MnO2@Carbon Nanotube Composite Materials 139 6.4 Characterization of LiMn2O4@CB Composite Materials 150 6.4.1 Physical Analysis of LiMn2O4@CB Composite Materials 150 6.4.2 Electrochemical Analysis of LiMn2O4@CB Composite Materials in Aqueous Electrolyte 155 6.4.3 Electrochemical Analysis of LiMn2O4@CB Composite Materials in Organic Electrolyte 158 6.5 Characterization of LiMn2O4@CNT Composite Materials 164 6.5.1 Physical Analysis of LiMn2O4@CNT Composite Materials 164 6.5.2 Electrochemical investigation on LiMn2O4@CNT Composite Materials 169 6.6 Summary 174 References 176 Curriculum Vitae of Author and Publication List 198 List of Tables Table 2-1. Energy-storage characteristics of electrochemical capacitors and batteries 11 Table 2-2. Metal ion distribution and saturated magnetization at 0 K for simple ferrites with spinel structure. 30 Table 2-3. Classification of manganese oxides and corresponding crystallographic data [127]. 36 Table 3-1. The chemical reagents used in this study. 51 Table 4-1. BET specific surface area and pore volume of CB, MnFe2O4, as-synthesized MnFe2O4@CB and calcined MnFe2O4@CB. 73 Table 5-1. Properties of individual electrodes of MnFe2O4(anode)/LiMn2O4(cathode) cells. 116 Table 6-1. The microstructure and the electrochemical performance of B-MnO2@CB and S-MnO2@CNT composites. 149 Table 6-2. Characteristics of commercial LiMn2O4, LiMn2O4@CB and LiMn2O4@CNT. 173 List of Figures Figure 2-1. Ragone plot of energy storage devices including ceramic capacitors, electrochemical capacitors and batteries. 12 Figure 2-2. A schematic illustration of an electrochemical capacitor. 12 Figure 2-3. The construction of the double layer along with the corresponding potential profile across the double layer region, where IHP and OHP are the inner and outer Helmholz plane, respectively. 13 Figure 2-4. Schemes of the electric double layer. (a) the Helmholtz model, (b) the Gouy-Chapman model, and (c) the Stern model. 17 Figure 2-5. Ragone plot of various asymmetric capacitors; based on the total mass of electrode materials of cathode and anode. 27 Figure 2-6. The structure of ferrite materials. (a) ball-and-stick model, and (b) polyhedral model with alternating octahedral and tetrahedral-octahedral layers. 31 Figure 2-7. Polyhedral representations of the crystal structures of (a) pyrolusite, (b) ramsdellite, (c) hollandite, (d) romanechite, and (e) todorokite, looking approximately parallel to the Mn octahedral chains [140]. 37 Figure 2-8. Polyhedral representation of (a) lithiophorite showing alternately layers of MnO6 and (Al,Li)(OH)6, (b) chalcophanite with Zn occupying vacancies in the MnO6 layers, and (c) Na-rich birnessite-like showing disordered H2OyNa sites between MnO6 sheets [140]. 38 Figure 2-9. Illustration of proton locations in (a) ramsdellite and (b) pyrolusite [149]. 38 Figure 2-10. Crystallographic structure of spinel MnO2[167]. 39 Figure 2-11. Crystal structure of layered LiMnO2. 47 Figure 2-12. The structure of LiMn2O4 and λ-MnO2. 47 Figure 3-1. The flowchart for synthesis of MnFe2O4@CB composite via co-precipitation process. 56 Figure 3-2. Procedure for synthesis of B-MnO2@CB composite 57 Figure 3-3. Procedure for synthesis of S-MnO2@CNT composite 58 Figure 3-4. The flowchart for synthesis of LiMn2O4@CB composite via hydrothermal process 59 Figure 3-5. Procedure for preparation of LiMn2O4@CNT composite via hydrothermal process 60 Figure 3-6. The configurations of the electrochemical instrument: (a) a three-electrode cell and (b) a two-electrode cell.. 67 Figure 3-7. The configuration of a coin-type half cell. 68 Figure 4-1. (a) The BJH pore volume (V) distribution and (b) the surface area (A) of as-synthesized (─○─) and calcined (─●─) MnFe2O4@CB. 74 Figure 4-2. X-ray powder diffraction patterns of MnFe2O4@CB (---) as-synthesized and (—) calcined powders at 350 oC. 75 Figure 4-3. SEM image of CB (XC72). 75 Figure 4-4. SEM micrograph of MnFe2O4@CB composite. 76 Figure 4-5. Cyclic voltammograms of CB and Ti in 1M LiNO3(aq). 79 Figure 4-6. Voltammogram of MnFe2O4@CB composite in 1M LiNO3(aq). 79 Figure 4-7. Cyclic voltammograms of the MnFe2O4@CB-based symmetric cell at various scan rates in 1M LiNO3(aq). 80 Figure 4-8. Galvanostatic tests of the MnFe2O4 symmetric cell at various current densities, (a) from 0.1 to 0.5 A/g, (b) from 1 to 5 A/g in 1M LiNO3(aq). 81 Figure 4-9. Cyclic voltammograms of the MnFe2O4@CB based symmetric cell; the tests were carried out at 25oC in 9M LiNO3(aq). 84 Figure 4-10. Galvanostatic tests of the MnFe2O4 symmetric cell; tests were carried out in 9M LiNO3(aq) and at various current densities: (a) from 0.1 to 0.5 A/g, and (b) from 1 to 5 A/g 85 Figure 4-11. The comparison of galvanostatic tests of the MnFe2O4 symmetric cell in different electrolyte concentrations: 1M and 9M LiNO3(aq). 86 Figure 4-12. OCP of MnFe2O4@CB electrode with respected to pH value of electrolyte. 86 Figure 4-13. Cyclability characterization of MnFe2O4@CB-based symmetric cell at 1 A/g for 5000 cycles 87 Figure 4-14. Microscopic surface morphology of MnFe2O4@CB electrode after 5000 cycles 87 Figure 4-15. SEM micrograph of LiMn2O4 powder 90 Figure 4-16. Cyclic voltammograms of LiMn2O4 electrode in 1M LiNO3(aq) at 0.2 mV/s cycled for three cycles 90 Figure 4-17. Cyclic voltammogram of the conductive additives (KS6/Super P = 5/1) based electrode at 4 mV/s and in 9M LiNO3 aqueous electrolyte 91 Figure 4-18. Galvanostatic curves of LiMn2O4 electrode at 0.5 C-rate for three cycles in 1M LiNO3 aqueous electrolyte 91 Figure 4-19. Potential curves of LiMn2O4 electrode at various C-rates at 25 oC in 1M LiNO3 aqueous electrolyte 92 Figure 4-20. Discharge curves at various C-rates from 0.5 to 100 C-rate and in 9M LiNO3 aqueous electrolyte 92 Figure 4-21. The comparisons of rate performance of LiMn2O4 electrode in 1M and 9M LiNO3 aqueous electrolyte 93 Figure 5-1. Cyclic voltammograms of MnFe2O4@CB electrode (4 mV/s) and LiMn2O4 electrode (0.2 mV/s)scanned individually in 9M LiNO3 aqueous electrolyte. 100 Figure 5-2. Galvanostatic curves of MnFe2O4/LiMn2O4 (1-1) asymmetric capacitor 100 Figure 5-3. Charged/discharged potential curves of a MnFe2O4@CB/LiMn2O4 asymmetric capacitor at 0.1 A/g-anode; the highest operation voltage is 1 V 101 Figure 5-4. Potential curves of a MnFe2O4@CB/LiMn2O4 (1-1) asymmetric capacitor at 0.1 A/g-anode; the highest operation voltage is 1.1 V. 101 Figure 5-5. Potential curves of anode and cathode of a MnFe2O4@CB/LiMn2O4 (1-1) asymmetric capacitor; the highest operation voltage is 1.2 V. 102 Figure 5-6. Potential curves of anode and cathode of a MnFe2O4@CB/LiMn2O4 (1-1) asymmetric capacitor; the highest operation voltage is 1.3 V. 102 Figure 5-7. Galvanostatic curves of MnFe2O4@CB/LiMn2O4 (1-1) asymmetric capacitor; charge/discharge current density ranges from 1 to 5 A/g-anode 103 Figure 5-8. Charged/discharged potential curves of 2-1 cell at (a) 0.1 A/g and (b) 1 A/g; solid line (—) represents the potential curve of cathode, dashed line (---) represents the potential curve of anode. 109 Figure 5-9. Constant current charged/discharged analyses of 2-1 cell: current density ranges from 1 to 3 A/g-anode. 110 Figure 5-10. Charged/discharged potential curves of 3-1 cell; solid line (—) represents the potential curve of cathode, dashed line (---) represents the potential curve of anode. 110 Figure 5-11. Constant current charged/discharged analyses of 3-1 cell: current density ranges from 1 to 3 A/g-anode. 111 Figure 5-12. Charged/discharged potential curves of 4-1 cell; solid line (—) represents the potential curve of cathode, dashed line (---) represents the potential curve of anode. 111 Figure 5-13. Constant current charged/discharged analyses of 4-1 cell: current density ranges from 1 to 3 A/g-anode. 112 Figure 5-14. Potential vs. specific capacity (based on the total mass of cathode and anode) diagram of 1-1, 2-1, 3-1 and 4-1 asymmetric capacitors. 112 Figure 5-15. Energy and power performance of MnFe2O4@CB/LiMn2O4 full-cells having different anode-to-cathode mass ratios: (a) specific cell capacitance and specific cell capacity, based on total electrode active-layer mass, versus current density/C-rate of cathode; (b) Ragone plot showing specific cell energy versus specific cell power. 113 Figure 5-16. Ragone plot of various asymmetric capacitors. 114 Figure 5-17. Cycle life tests of 1-1, 2-1, 3-1 and 4-1 asymmetric capacitors. 114 Figure 5-18. Self-discharge voltage curves of MnFe2O4@CB/LiMn2O4, MnO2/LiMn2O4 and activated carbon (AC) fiber/LiMn2O4 asymmetric cells and symmetric MnFe2O4@CB cell. 115 Figure 6-1. X-ray powder diffraction patterns of carbon black (CB) and birnessite-type MnO2@CB. 124 Figure 6-2. SEM micrograph of B-MnO2@CB composite. 124 Figure 6-3. TEM image of B-MnO2@CB composite 125 Figure 6-4. (a) The BJH pore volume (V) distribution and (b) the surface area (A) of birnessite-type MnO2@CB as a function of pore diameter (D) 126 Figure 6-5. Cyclic voltammograms of B-MnO2@CB electrode at 2 mV/s in 1M NaCl aqueous solution. 129 Figure 6-6. Voltammograms of birnessite-type MnO2@CB based symmetric capacitor under various sweep rates, from 4 to 200 mV/s in 1M NaCl aqueous electrolyte. 129 Figure 6-7. Galvanostatic charged/discharged curves of B-MnO2@C based symmetric capacitor at several current densities (based on the mass of composite), (a) from 0.1 to 0.5 A/g-com; (b) from 1 to 5 A/g-com. 130 Figure 6-8. Self-discharge tests of B-MnO2@CB electrode, the electrode was charged/discharged to 0 V, 0.1 V, 0.8 V and 0.9 V vs. Ag/AgCl in 1M NaCl(aq). 131 Figure 6-9. Self-discharge tests of B-MnO2@CB electrode; the electrode was charged to 0.9V, and held for 1 h and 12 h in 1M NaCl(aq). 131 Figure 6-10. Cycle life tests of B-MnO2@CB at 50 mV/s in 1M NaCl aqueous electrolyte: (a) voltammograms; (b) capacitance retention vs. cycle number. 132 Figure 6-11. XRD patterns of CNT and as-synthesized S-MnO2@CNT. 135 Figure 6-12. TEM micrographs of: (a) and (b) are pristine MWCNT (CNT); (c) and (d) are S-MnO2@CNT composite material. 136 Figure 6-13. SEM images of: (a) and (b) are pristine MWCNT (CNT); (c) and (d) are S-MnO2@CNT composite material. 137 Figure 6-14. (a) The BJH pore volume (V) distribution and (b) the surface area (A) of S-MnO2@CNT as a function of pore diameter (D). 138 Figure 6-15. Cyclic voltammograms of (a) MWCNT and (b) S-MnO2@CNT electrode in 1M NaCl aqueous electrolyte at 2 mV/s. 143 Figure 6-16. Cyclic voltammograms of S-MnO2@CNT-based symmetric cell in 1M NaCl aqueous electrolyte, the sweep rate ranges from 4 to 500 mV/s. 144 Figure 6-17. Electrochemical performance of MnO2 comparison between S-MnO2@CNT and B-MnO2@CB. 144 Figure 6-18. Galvanostatic charged/discharged curves of S-MnO2@CNT-based symmetric capacitor at several current densities (based on the mass of composite), (a) from 0.1 to 0.5 A/g-com; (b) from 1 to 10 A/g-com. 145 Figure 6-19. Self-discharge tests of (a) S-MnO2@CNT; (b) a-MnO2@CB in 1M NaCl aqueous electrolyte at 0 V, 0.1 V, 0.8 V and 0.9 V(vs. Ag/AgCl); open circuit potential vs. logarithmic time. 146 Figure 6-20. Self-discharge curves of a-MnO2, B-MnO2@CB and S-MnO2@CNT in 1M NaCl(aq); open circuit potential vs. (a) time; (b) logarithmic time. 147 Figure 6-21. Long-term stability test of symmetric cell of S-MnO2/CNT composite using cyclic voltammetry, the operation voltage is between – 0.8V and 0.8 V, and cycled at 50 mV/s for 5000 cycles and then additional 5000 cycles at 100 mV/s. 148 Figure 6-22. XRD patterns of commercial LiMn2O4, LiMn2O4@CB and JCPDS database file (number: 88-1750). 152 Figure 6-23. SEM image of LiMn2O4@CB at (a) low magnification; (b) high magnification. 153 Figure 6-24. TGA-DTA curves of LiMn2O4@CB composite material. 154 Figure 6-25. (a) Potential curves of LiMn2O4@CB at 0.5 C-rate in 9M LiNO3 aqueous solution and (b) dQ/dV vs. potential of 3rd cycle 156 Figure 6-26. Constant current discharged curves of LiMn2O4@CB in 9M LiNO3(aq) at various C-rates. 157 Figure 6-27. Charged/discharged potential curves of LiMn2O4@CB-based half cell at 0.1C-rate for three cycles... 161 Figure 6-28. Discharged potential curves of LiMn2O4@CB-based half cell at room temperature-25 oC under various C-rates. 161 Figure 6-29. Discharged potential curves of LiMn2O4@CB-based half cell at elevated temperature-55 oC under various C-rates. 162 Figure 6-30. Long-term stability testing results of LiMn2O4@CB-based half cell at room temperature-25 oC; (●) represents for capacity retention vs. cycle number, (▽) represents for coulombic efficiency vs. cycle number. 162 Figure 6-31. Cyclic stability testing results of LiMn2O4@CB-based half cell at elevated temperature-55 oC; (●) represents for capacity retention vs. cycle number, (▽) represents for coulombic efficiency vs. cycle number. 163 Figure 6-32. X-ray diffraction patterns of LiMn2O4@CB electrode after electrochemical tests. 163 Figure 6-33. X-ray powder diffraction patterns of LiMn2O4@CNT composite, commercial LiMn2O4 and JCPDS database. 166 Figure 6-34. SEM micrographs of LiMn2O4@CNT at (a) low magnification and (b) high magnification. 167 Figure 6-35. TGA solid line (—) and DTA dashed line (---) characterizations of LiMn2O4@CNT composite material. 168 Figure 6-36. (a) Potential curves of LiMn2O4@CNT at 0.5 C-rate in 9M LiNO3(aq) and (b) dQ/dV vs. potential of 3rd cycle 171 Figure 6-37. Discharged curves of LiMn2O4@CNT at various C-rates, from 1 C-rate to 1000 C-rate. 172 Figure 6-38. Ragone plot of MnFe2O4/LiMn2O4 (4-1), expected AC/LiMn2O4@CNT (2.5-1) and other asymmetric capacitors. 172 | |
dc.language.iso | en | |
dc.title | 非對稱超高電容器之製備與分析 | zh_TW |
dc.title | Synthesis and Characterization of Asymmetric Supercapacitors | en |
dc.type | Thesis | |
dc.date.schoolyear | 99-1 | |
dc.description.degree | 博士 | |
dc.contributor.oralexamcommittee | 何國川(Kuo-Chuan Ho),徐振哲(Cheng-Che Hsu),胡啟章(Chi-Chang Hu),鄧熙聖(Hsisheng Teng) | |
dc.subject.keyword | 非對稱超高電容,錳鐵氧尖晶石材料,鋰錳氧尖晶石材料,二氧化錳,水系電解液, | zh_TW |
dc.subject.keyword | Asymmetric Supercapacitors,MnFe2O4,LiMn2O4,MnO2,Aqueous Electrolyte, | en |
dc.relation.page | 200 | |
dc.rights.note | 有償授權 | |
dc.date.accepted | 2011-02-08 | |
dc.contributor.author-college | 工學院 | zh_TW |
dc.contributor.author-dept | 化學工程學研究所 | zh_TW |
顯示於系所單位: | 化學工程學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
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ntu-100-1.pdf 目前未授權公開取用 | 5.95 MB | Adobe PDF |
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