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Structural Modifications of Some Nitrogen-containing Redox Couples for Improvement of Non-aqueous Flow Battery Performances
비수계 흐름 전지의 전기화학 성능 향상을 위한 질소를 포함하는 산화환원쌍의 구조 개선

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dc.contributor.advisor오승모-
dc.contributor.author김현승-
dc.date.accessioned2017-07-13T08:45:44Z-
dc.date.available2017-07-13T08:45:44Z-
dc.date.issued2017-02-
dc.identifier.other000000140656-
dc.identifier.urihttps://hdl.handle.net/10371/119818-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2017. 2. 오승모.-
dc.description.abstractAs redox couples for non-aqueous flow batteries, the electrochemical and physicochemical properties of several nitrogen-containing molecules are examined. Nitrogen atom have lone pair electrons, which is applicable as ligand and redox center-
dc.description.abstractthereby applying as redox couple design. Moreover, the negative charged nitrogen atom is nucleophile, resulting readily functional group substitution by SN2 reaction. Thus, nitrogen atom can be applied as ligand molecule, redox center and the attachment center of aliphatic group for structural modification of redox couples. While non-aqueous flow battery is highlighted by its energy density from wide electrochemical stability window of organic electrolyte, the solubility drawback is remained problem for practical application of non-aqueous system. Since the nitrogen can be applied with diverse manner for molecule design, the limitation of solubility can be resolved by rational design of nitrogen-containing redox couples.
At first, an azamacrocyclic ligand-based complex cation, nickel(II)-1,4,8,11-tetraazacyclotetradecane (cyclam) is examined as a single redox couple for non-aqueous flow batteries. Single redox couple has advantageous feature for practical application because permanent loss of active material from cross-contamination at dual electrolyte-comprised cell is completely prevented. The energy density of this complex cation is tailored by easily dissociative counter anions and using highly dielectric solvents. The nickel(II)-chelated complex cation demonstrates high solubility (0.8 M) and working voltage (2.55 V) with bis(trifluoromethane)sulfonimide anion, resulting the energy density of 27.3 W h L-1.
Secondly, nitrogen atom is used as two redox centers in p-phenyldiamines (PD) as positive redox couple. Two amine groups (-NH2) in PD offers two redox reactions with single organic molecule. Thus, the demonstrated volumetric capacity from PD is twice higher than conventional one electron-involved redox couples at same concentration
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dc.description.abstractthereby alloying cost advantages. Nevertheless, the solubility and chemical/electrochemical stability drawbacks are remained for flow battery applications in PD redox couple. Methyl substitution affects the solubility and chemical reversibility of redox couple because the methyl groups eliminates hydrogen bonding and shields foreign attack from electrolyte components. Fully-methyl substituted N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) delivers high energy density with 938.0 W h L-1, which is from 5.0 M of solubility and 3.2 and 3.8 V (vs. Li/Li+) of working voltages. Furthermore, TMPD has facile diffusion rate, which is desirable for good rate capability.
Finally, butyl-substituted, N-butylphthalimide (BPI) is proposed as negative redox couple for non-aqueous flow batteries. The ten-fold increase of solubility (5.0 M) and decrease of melting point is from the less-packed asymmetric structure by attaching butyl groups on nitrogen atom. The strong correlation between maximum solubility and melting point implies this result. The electron-donating effect and solvation change of butyl groups shift the working voltage (0.1 V), resulting higher energy density. Consequently, BPI/TMPD comprised flow cell demonstrates promising electrochemical performance as all-organic flow batteries and the theoretical energy density of this cell is 120.6 W h L-1.
The nitrogen-containing redox couple design is accomplished by directional approaching based on ideal solubility equation. Designed redox couples have higher energy density than conventional aqueous electrolyte ones
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dc.description.abstractfor instance, all-vanadium redox flow batteries, 25.0 W h L-1. Thus, the high energy density non-aqueous flow batteries are designed by comprising nitrogen-containing molecules.-
dc.description.tableofcontentsAbstract i
List of Figures iv
List of Tables x
1. Introduction 1
2. Background 5
2.1. Electrochemistry and electrochemical methods 5
2.2. Thermodynamics of melting and its effect on solubility 10
2.3. Redox-flow batteries 12
2.3.1. Aqueous flow batteries 13
2.3.2 Non-aqueous flow batteries 16
2.3.2.1 Metal-ligand complex based system 18
2.3.2.2 Organic molecule based system 19
2.3.2.3 Semi-solid suspension based system 21
2.3.2.4 Polymer-dissolved electrolyte based system 21
3. Experimental 23
3.1. Synthesis of Ni(II)-chelated complex cations 23
3.1.1 Synthesis of Ni(II)(azamacrocyclic ligands)X2 (X = Cl-, ClO4-) 23
3.1.2 Synthesis of Ni(II)(cyclam)X2 (X = Tf-, TFSI-) 23
3.2. Electrochemical characterization 24
3.2.1 Cyclic voltammetry 24
3.2.2 Cell preparation and galvanostatic cell cycling 24
3.2.2.1 Non-flowing H-cell test 24
3.2.2.2 Non-flowing coin-cell test 25
3.2.2.3 Flow battery test 25
3.2.3 Electrochemical quartz crystal microbalance (EQCM) test 25
3.2.4 Galvanostatic intermittent titration technique (GITT) 26
3.3. Spectroscopic characterization 26
3.3.1 Surface analysis of inert electrode 26
3.3.2 Assignment of metal-ligand complex 27
3.3.3 Post-mortem electrolyte analysis 27
3.3.4 Maximum solubility measurement 27
3.4. Quantitative analysis on thermal properties of solids 28
3.5. Estimation of redox couple stability by theoretical calculation 28
4. Results and discussion 29
4.1. Uncompensated resistance and inert electrode surface 29
4.2. Verification of thermodynamic parameters for solubility enhancement of redox couples 34
4.3. A tetradentate azamacrocylic Ni(II) complex cation as a single redox couple for non-aqueous flow batteries 36
4.3.1 The effects of cavity size and counter anion on the electrochemistry and solubility of complex cation 37
4.3.2 The electrochemistry of Ni(II)(cyclam)[ClO4]2 and its application for non-aqueous flow battery electrolyte 50
4.3.3 Further modification of counter anions for enhancement of solubility of complex cation 61
4.4. Introduction of functional groups on redox couples for desirable dual functionalities as non-aqueous flow battery electrolytes 66
4.4.1 Functional group effects on organic redox couples: solubility, chemical stability and redox potential 67
4.4.1.1 Methylation effects on solubility and stability of p-phenylenediamine-based positive redox couples 68
4.4.1.2 Introduction effects of aliphatic chain on solubility and redox potential of phthalimide-based negative redox couples 77
4.4.2 The effects and plausible mechanism of acetyl group introduction on ferrocene for non-aqueous Li-flow battery 85
5. Conclusion 102
References 105
요약 (국문초록) 111
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dc.formatapplication/pdf-
dc.format.extent2809787 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectRedox-flow batteries-
dc.subjectRedox couples-
dc.subjectNon-aqueous electrolytes-
dc.subjectSolubility-
dc.subjectEnergy density-
dc.subjectElectrochemical performances-
dc.subject.ddc660-
dc.titleStructural Modifications of Some Nitrogen-containing Redox Couples for Improvement of Non-aqueous Flow Battery Performances-
dc.title.alternative비수계 흐름 전지의 전기화학 성능 향상을 위한 질소를 포함하는 산화환원쌍의 구조 개선-
dc.typeThesis-
dc.contributor.AlternativeAuthorHyun-seung Kim-
dc.description.degreeDoctor-
dc.citation.pagesxiii, 113-
dc.contributor.affiliation공과대학 화학생물공학부-
dc.date.awarded2017-02-
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Theses (Ph.D. / Sc.D._화학생물공학부)
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