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Terephthalate-Functionalized Conducting Redox Polymers for Energy Storage Applications
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic electrode materials, as sustainable and environmental benign alternatives to inorganic electrode materials, show great promise for achieving cheap, light, versatile and disposable devices for electrical energy storage applications. Conducting redox polymers (CRPs) are a new class of organic electrode materials where the charge storage capacity is provided by the redox chemistry of functional pendent groups and electronic conductivity is provided by the doped conducting polymer backbone, enabling the production of energy storage devices with high charge storage capacity and high power capability. This pendant-conducting polymer backbone combination can solve two of the main problems associated with organic molecule-based electrode materials, i.e. the dissolution of the active material and the sluggish charge transport within the material. In this thesis, diethyl terephthalate and polythiophenes were utilized as the pendant and the backbone, respectively. The choice of pendant-conducting polymer backbone combination was based on potential match between the two moieties, i.e. the redox reaction of terephthalate pendent groups and the n-doping of polythiophene backbone occur in the same potential region. The resulting CRPs exhibited fast charge transport within the polymer films and low activation energies involved charge propagation through these materials. In the design of these CRPs an unconjugated link between the pendant and the backbone was found to be advantageous in terms of the polymerizability of the monomers and for the preservation of individual redox activity of the pendants and the polymer chain in CRPs. The functionalized materials were specifically designed as anode materials for energy storage applications and, although insufficient cycling stability was observed, the work presented in this thesis demonstrates that the combination of redox active functional groups with conducting polymers, forming CRPs, shows promise for the development of organic matter-based electrical energy storage materials.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 60 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1437
Keyword [en]
conducting polymers, terephthalate, polythiophene, PEDOT, conductance
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:uu:diva-304628ISBN: 978-91-554-9715-6OAI: oai:DiVA.org:uu-304628DiVA: diva2:1033276
Public defence
2016-11-24, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2016-11-08 Created: 2016-10-06 Last updated: 2016-11-16
List of papers
1. Conjugated Pyridine-Based Polymers Characterized as Conductivity Carrying Components in Anode Materials
Open this publication in new window or tab >>Conjugated Pyridine-Based Polymers Characterized as Conductivity Carrying Components in Anode Materials
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2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 45, 25956-25963 p.Article in journal (Refereed) Published
Abstract [en]

Herein, polypyridine (P25Py) is for the first time evaluated as an anode material for organic matter based electric energy storage devices. P25Py is synthesized both chemically and electrochemically and the influence of electrolyte and solvent on the doping behavior of the material is investigated in propylene carbonate and acetonitrile with LiClO4 and TBAPF6. A battery consisting of P25Py coupled to a lithium metal disc is assembled and the electrochemical performance and cycling stability of the conjugated polymer is analyzed. In all electrolyte combinations P25Py is conductive and shows reversible redox chemistry between -1.0 and -2.0 V vs ferrocene with capacitive response characteristics. The electrochemical impedance spectroscopy response of the material can be described by a Randles equivalent circuit with a finite length Warburg diffusion element in which the diffusion coefficient of the cations increases with increasing doping level of the polymer. In the battery cell configuration the polymer shows reversible cycling with no capacity fading during the first 100 cycles without conducting additives. P25Py thus provides a promising alternative conducting polymer base for electrical energy storage applications which expands both the potential widow as well as the electrolyte compatibility of the flora of known conducting polymers.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-235773 (URN)10.1021/jp509606c (DOI)000344978000017 ()
Available from: 2014-11-10 Created: 2014-11-10 Last updated: 2016-11-30
2. Matching Diethyl Terephthalate with n-Doped Conducting Polymers
Open this publication in new window or tab >>Matching Diethyl Terephthalate with n-Doped Conducting Polymers
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2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 33, 18956-18963 p.Article in journal (Refereed) Published
Abstract [en]

The combination of small, high charge capacity molecules as pendant groups with a conducting polymer backbone having good electronic conductivity upon doping, gives the possibility to design a high capacity conducting redox polymer material for electric energy storage applications. The desired synergetic effect of the two components requires energy matching as well as chemical compatibility of the pendant group and the polymer backbone. Here we investigate the matching of diethyl terephthalate (DeT) with the thiophene-based conducting polymers polythiophene (PT), poly(3,4-ethylenedioxythiophene) (PEDOT), and polyphenylthiophene. We show that a stable and well-defined electrochemical response of DeT is achieved, together with all conducting polymers except for PT in tetrabutylammonium hexafluorophosphate electrolyte, indicating good energy match as well as chemical compatibility between DeT and polymers. By varying the size of ammonium cations in the electrolytes, we further show how this size affects the conductivity and the cycling stability of the polymers and also that the n-doping performance of all conducting polymers can be improved by the use of smaller alkyl ammonium cations. On the basis of these results, we suggest that PEDOT and PT are suitable candidates for a polymer backbone in conducting redox polymers with DeT pendant groups.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-262423 (URN)10.1021/acs.jpcc.5b05067 (DOI)000360026200015 ()
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilCarl Tryggers foundation Swedish Energy Agency
Available from: 2015-09-17 Created: 2015-09-15 Last updated: 2016-11-30Bibliographically approved
3. Synthesis and Redox Properties of Thiophene Terephthalate Building Blocks for Low-Potential Conducting Redox Polymers
Open this publication in new window or tab >>Synthesis and Redox Properties of Thiophene Terephthalate Building Blocks for Low-Potential Conducting Redox Polymers
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2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 49, 27247-27254 p.Article in journal (Refereed) Published
Abstract [en]

Terephthalate-substituted thiophene derivatives are promising redox-active components for anode materials in lithium-ion batteries. In this study, we present the synthesis of substituted 2-(thiophen-3-yl)terephthalate derivatives (TTDs) as suitable monomers for thiophene-based conducting redox polymers, along with their characterization by electrochemical and spectroscopic techniques. Density functional theory (DFT) calculations, utilizing the universal solvation model based on solute electron density (SMD), were used to predict both the first and the second reduction potentials of these TTDs. The computational results showed good agreement with the experimental data in nonaqueous acetonitrile solvent, with mean absolute errors of 30 and 40 mV for the first and second reduction steps, respectively. Time-dependent (TD) DFT calculations on TTDs indicated terephthalate local transitions at both 200 and 240 nm and charge-transfer transitions above 300 nm by examination of the involved molecular orbitals.

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-268481 (URN)10.1021/acs.jpcc.5b08518 (DOI)000366339000008 ()
Funder
Swedish Research Council, VR 621-2011-4423Swedish Foundation for Strategic Research Swedish Energy Agency
Available from: 2015-12-05 Created: 2015-12-05 Last updated: 2016-12-01Bibliographically approved
4. Conducting Redox Polymer Based Anode Materials for High Power Electrical Energy Storage
Open this publication in new window or tab >>Conducting Redox Polymer Based Anode Materials for High Power Electrical Energy Storage
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2016 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 204, 270-275 p.Article in journal (Refereed) Published
Abstract [en]

In this report we present the synthesis and characterization of two conducting redox polymers (CRPs) with polythiophene backbone and diethyl terephthalate pendant groups for the use as anode materials in secondary batteries. The materials show excellent rate capability allowing 301,Lm layers to be fully converted within seconds without the use of conductive additives. The high rate capability is traced to the open morphology of the materials that allows for fast ion transport, and to the mediation of electrons through the conducting polymer (CP) backbone. The requirements for the latter are i) that the redox chemistry of the pendant groups and the CP backbone overlaps and ii) that the CP conductivity is not compromised by the presence of the pendant groups. In the CRPs presented herein both these requirements are met and this is thus the first report on successful combination of the redox chemistry of organic redox molecules with the n-doping of conducting polymers.

Keyword
conducting redox polymers, terephthalates, polythiophene, n-doping
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-298055 (URN)10.1016/j.electacta.2016.03.163 (DOI)000376136700031 ()
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilCarl Tryggers foundation Stiftelsen Olle Engkvist ByggmästareSwedish Energy AgencyEU, Horizon 2020, 644631
Available from: 2016-07-05 Created: 2016-06-29 Last updated: 2016-11-30Bibliographically approved
5. Effect of the Linker in Terephthalate-Functionalized Conducting Redox Polymers
Open this publication in new window or tab >>Effect of the Linker in Terephthalate-Functionalized Conducting Redox Polymers
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The combination of high capacity redox active pendent groups and conducting polymers, realized in conducting redox polymers (CRPs), provides materials with high charge storage capacity that are electronically conducting whichmakes CRPs attractive for electrical energy storage applications. In this report, six polythiophene and poly(3,4-ethylenedioxythiophene)(PEDOT)-based CRPs with a diethyl terephthalate unit covalently bound to the polymer chain byvarious linkers have been synthesized and characterized electrochemically. The effects of the choice of polymer backboneand of the nature of the link on the electrochemistry, and in particular the cycling stability of these polymers, are discussed.All CRPs show both the doping of the polymer backbone as well as the redox behavior of the pendent groups and the redoxpotential of the pendent groups in the CRPs is close to that of corresponding monomer, indicating insignificant interactionbetween the pendant and the polymer backbone. While all CRPs show various degrees of charge decay upon electrochemical redox conversion, the PEDOT-based CRPs show significantly improved stability compared to the polythiophene counterparts. Moreover, we show that by the right choice of link the cycling stability of diethyl terephthalate substituted PEDOTbased CRPS can be significantly improved.

Keyword
conducting redox polymers, PEDOT, polythiophene, terephthalate
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-304623 (URN)
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-06
6. Conducting Redox Polymers with non-Activated Charge Transport Properties
Open this publication in new window or tab >>Conducting Redox Polymers with non-Activated Charge Transport Properties
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Intrinsic electronic conductivity is the crucial characteristic that distinguishes conducting polymers from most otherorganic materials. The conduction mechanism is structure dependent and the charge transfer character ranges from metallic to temperature-activated hopping as a function of the level of order. Introduction of covalently bound redox active pendant groups toconducting polymers, forming conducting redox polymers (CRPs), introduces additional functionality to conducting polymers butthe effect of the pendant groups on the polymer structure and on the mechanism of charge transport is largely unknown. In thisreport we show that non-activated charge transport can be achieved in terephthalate-functionalized CRPs and we correlate the lowactivation barriers involved with a relatively high degree of polymer order. The charge transport properties were investigated bytemperature dependent conductance measurements performed in situ during electrochemical redox conversion. The resulting temperature dependence showed a transition from a temperature-activated regime to a residual scattering regime, the latter being associated with an apparent negative activation barrier for charge transport indicating low electron transfer reorganization-energies.Activation barriers derived from spectroscopic measurements suggest much higher activation barriers than the temperature dependent conductance data indicate which is rationalized by electron transport through interconnected crystal domains in a predominantamorphous polymer matrix. The finding that non-activated charge transport can be accomplished in CRP materials suggests thatmetallic conductivities can be achieved also for conducting polymers with redox active pendant groups.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-304625 (URN)
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2016-10-06

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