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Conducting Redox Polymers for Electrical Energy Storage: Backbone - Substituent Interactions in Quinone Polypyrrole Model Systems
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. (Nanotechnology and Functional Materials)ORCID iD: 0000-0003-2883-2696
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic electrical energy storage (EES) is a growing field of research that is expected to play an important role in the future, as the need for sustainable EES increases. Conducting redox polymers (CRPs), i.e. conducting polymers with incorporated redox active moieties e.g. as pendant groups (PGs), are proposed as a promising class of compounds for this purpose. Redox cycling of the PGs can be utilized for high charge storage capacity, while the conducting polymer backbone provides fast charge transport through the material. Some of the major challenges with small-molecule systems for EES could be solved by using CRPs, e.g. capacity fading due to dissolution of the active compound, and high resistance due to slow charge transport between molecules. The latter issue is often solved by adding large amounts of conducting additives to the active material, drastically lowering the specific capacity. In this project, CRPs are shown to be able to function in battery cells without any additives, making both high capacity and high power possible. Although several CRPs have been reported in the literature, very few detailed studies have been conducted on the electrochemical processes of the two systems (i.e. the conducting polymer backbone and the redox active PGs). An important factor to consider in CRP design is the possibility for interaction between the two redox systems, which could be either beneficial or detrimental to the function as EES material. In this thesis, CRP model systems composed of hydroquinone functionalized polypyrrole have been studied, and they exhibit separate redox reactions for the PGs and the backbone, overlapping in potential. Significant interaction between them was observed, as oxidation of the PGs has severe impact on the backbone: When the oxidized and hydrophobic p-benzoquinone PGs are formed, they pack and force the polymer backbone to twist, localizing the bipolarons, and decreasing the conductivity. This is accompanied by a contraction of the polymer film and expulsion of electrolyte. Overall, the interaction in these polymers is destructive for their EES function, and it could be eliminated by introduction of a long linker unit between the PGs and the backbone.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 72 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1177
Keyword [en]
Organic energy storage, Hydroquinone polymers, Functionalized polypyrrole, Spectroelectrochemistry, Electrochemical quartz crystal microbalance, In situ conductivity
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:uu:diva-230647ISBN: 978-91-554-9033-1 (print)OAI: oai:DiVA.org:uu-230647DiVA: diva2:745543
Public defence
2014-10-30, Polhemssalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:30 (English)
Opponent
Supervisors
Available from: 2014-10-03 Created: 2014-08-27 Last updated: 2015-01-23Bibliographically approved
List of papers
1. Computational Electrochemistry Study of 16 Isoindole-4,7-diones as Candidates for Organic Cathode Materials
Open this publication in new window or tab >>Computational Electrochemistry Study of 16 Isoindole-4,7-diones as Candidates for Organic Cathode Materials
2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 5, 3793-3801 p.Article in journal (Refereed) Published
Abstract [en]

Prediction of the redox behavior of electroactive molecules enables screening of a variety of compounds and can serve as a guideline in the search for organic molecules for use as cathode materials in, for example, Li ion batteries. In this study, we present a computational strategy, based on density functional theory, to calculate redox potentials and acid dissociation constants for a series of 16 isoindole-4,7-dione (IID) derivatives. The calculations take all possible electron and proton transfers into account, and the results were found to correlate very well with electrochemical and spectroscopic measurements. The possibility of polymerizing the IID derivatives was also assessed computationally, as polymerization serves as a straightforward route to immobilize the active material. Three of the considered IIDs (5,6-dicyano-2-methyl-isoindole-4,7-dione, 5,6-dihydroxy-2-methyl-isoindole-4,7-dione, and 2-methyl-5-(trifluoromethyl)-isoindole-4,7-dione) are predicted to be particularly interesting for making polymers for organic cathodes because these are calculated to have high redox potentials and high specific capacities and to be readily polymerizable. The presented strategy is general and can be applied in the prediction of the electrochemical behavior of quinones as well as other systems involving proton and electron transfers.

Place, publisher, year, edition, pages
American Chemical Society, 2012
National Category
Other Chemistry Topics Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-168889 (URN)10.1021/jp211851f (DOI)000299985300073 ()
Available from: 2012-02-17 Created: 2012-02-17 Last updated: 2017-12-07Bibliographically approved
2. Investigation of the Redox Chemistry of Isoindole-4,7-diones
Open this publication in new window or tab >>Investigation of the Redox Chemistry of Isoindole-4,7-diones
2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 2, 894-901 p.Article in journal (Refereed) Published
Abstract [en]

Quinone derivatives have been proposed as active components in lithium ion battery (LIB) electrode materials. In this work the electrochemistry of a series of substituted isoindole-4,7-diones (IIDs) was investigated. Three new IID derivatives were synthesized and characterized by various electrochemical and spectroscopic techniques. Polymerization was attempted to achieve a conducting polymer with redox active quinone side groups, which would be advantageous in a LIB application. A combination of in situ spectroelectrochemical measurements and density functional theory (DFT) calculations was used to investigate the proton coupled redox reactions of the IIDs. Results from a previous computational study of the IIDs were compared with experimental data here, and the agreement was very good. The energy of the spectroscopic transitions in the UV and in the visible region showed different correlation with redox potential and quinone substituent in the series of IIDs. This behavior was rationalized by examination of the involved molecular orbitals. The results indicated that the properties of the quinone unit, such as the redox potential, could be selectively varied by substitution.

National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-192605 (URN)10.1021/jp311009z (DOI)000313932800017 ()
Available from: 2013-01-23 Created: 2013-01-23 Last updated: 2017-12-06Bibliographically approved
3. Polymer–Pendant Interactions in Poly(pyrrol-3-ylhydroquinone): A Solution for the Use of Conducting Polymers at Stable Conditions
Open this publication in new window or tab >>Polymer–Pendant Interactions in Poly(pyrrol-3-ylhydroquinone): A Solution for the Use of Conducting Polymers at Stable Conditions
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2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 45, 23558-23567 p.Article in journal (Refereed) Published
Abstract [en]

While various organic molecules have been suggested as environmentally friendly alternatives to inorganic electrode materials for lithium ion batteries, most of them suffer from slow kinetics as well as capacity fading due to dissolution. Herein we present the synthesis of poly(pyrrol-3-ylhydroquinone) (PPyQ), a polypyrrole (PPy) derivative with pending hydroquinone groups, for investigation of the use of a conducting polymer to immobilize redox active quinone units. This strategy eliminates dissolution of the active material while also increasing the conductivity. The quinone pending groups in PPyQ cycle reversibly in the potential region where the polymer backbone is conducting and chemically stable. In situ spectroelectrochemistry on PPyQ films reveals UV/vis transitions inherent to PPy, as well as quinone centered transitions, allowing detailed investigation of the interplay between the polymer doping process and the quinone redox conversion. Intriguingly, it is found that the charging of the PPy backbone halts during the redox reaction of the quinone pending groups. This opens up for the possibility of using PPy at low and constant doping levels while utilizing the charge storage capacity of the quinone pending groups when creating electric energy storage materials based on sustainable and renewable components.

National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-210983 (URN)10.1021/jp408567h (DOI)000327110500015 ()
Available from: 2013-11-18 Created: 2013-11-18 Last updated: 2017-12-06Bibliographically approved
4. Probing Polymer-Pendant Interactions in the Conducting Redox Polymer Poly(pyrrol-3-ylhydroquinone)
Open this publication in new window or tab >>Probing Polymer-Pendant Interactions in the Conducting Redox Polymer Poly(pyrrol-3-ylhydroquinone)
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2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 41, 23499-23508 p.Article in journal (Refereed) Published
Abstract [en]

Conducting polymers with redox active pendant groups show properties typical of both conducting polymers (i.e., capacitive charging and intrinsic conductivity) and redox polymers (i.e., electrochemical surface response at the formal potential of the pendant groups). The two components can also exert significant interaction on each other during their separate electrochemical reactions. In poly(pyrrol-3-ylhydroquinone), a polypyrrole derivative functionalized with hydroquinone units, the redox conversion of the pendant groups has a large impact on the polymer backbone. This interaction is manifested by a loss of bipolaron states during the hydroquinone oxidation, leading to a decreasing p-doping level with increasing potential, something which, to the best of our knowledge, has never been observed for a conducting polymer. Another effect is a contraction of the polymer film, and subsequent mass loss due to solvent expulsion upon hydroquinone oxidation, which counteracts the normal swelling of polypyrrole with increased potential. The conducting redox polymer under investigation has been synthesized via two routes, leading to different fractions of subunits bearing redox active hydroquinone groups. While the redox potentials are unaffected by the synthesis route, the backbone/pendant group interaction varies notably depending on the degree of quinone functionalization. This type of polymers could find use in, e.g., organic energy storage materials, since the polymer backbone both increases the electronic conductivity and prevents dissolution of the active material, as well as in actuator application, due to polymer contraction over the relatively narrow potential region where the pendant group redox chemistry occurs.

National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-230486 (URN)10.1021/jp506821z (DOI)000343333600007 ()
Available from: 2014-09-10 Created: 2014-08-26 Last updated: 2017-12-05Bibliographically approved
5. Quinone Pendant Group Kinetics in Poly(pyrrol-3-ylhydroquinone)
Open this publication in new window or tab >>Quinone Pendant Group Kinetics in Poly(pyrrol-3-ylhydroquinone)
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2014 (English)In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 735, 95-98 p.Article in journal (Refereed) Published
Abstract [en]

Herein, we investigate the kinetics of the redox processes occurring in acidic aqueous electrolyte in electropolymerized poly(pyrrol-3-ylhydroquinone), which has been proposed for electrical energy storage applications. The redox conversion of the pendant groups is found to be limited by the quinone redox kinetics in thin films, rather than by the conduction through the polypyrrole backbone. Rate constants for the elementary steps involved in this 2e, 2H+ process are reported. As the films are made thicker, a gradual transition to a diffusion limited reaction is observed. The origin of the diffusion process, as well as the elementary reaction steps limiting the pendant group redox conversion is analyzed using DFT computations. The fact that the electron transport through the thin film conducting polymer backbone is not limiting the quinone reaction kinetics should allow for design of battery electrodes with high rate capabilities based on the studied material.

National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-230487 (URN)10.1016/j.jelechem.2014.10.013 (DOI)000346214800015 ()
Available from: 2014-09-10 Created: 2014-08-26 Last updated: 2017-12-05Bibliographically approved
6. Impact of Linker in Polypyrrole/Quinone Conducting Redox Polymers
Open this publication in new window or tab >>Impact of Linker in Polypyrrole/Quinone Conducting Redox Polymers
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2015 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 15, 11309-11316 p.Article in journal (Refereed) Published
Abstract [en]

Organic conducting redox polymers are being investigated as the active component for secondary battery applications, as they have the potential to solve two of the main problems with small molecule-based organic electrodes for electrical energy storage, viz dissolution of the active compound in the electrolyte, and slow charge transport through the material. Herein we report the synthesis of a series of conducting redox polymers based on polypyrrole with hydroquinone pendant groups that are attached to the backbone via different linkers, and we investigate the impact of the linker on the interaction between the backbone and the pendant groups. For the directly linked polymer, oxidation of the pendant groups leads to a decrease of bipolaron absorbance, as well as a decrease in mass of the polymer film, both of which are reversible. The origin of these effects is discussed in light of the influence of the linker unit, electrolyte polarity, and electrolyte salt. For the longest linkers in the series, no interaction was observed, which was deemed the most beneficial situation for energy storage applications, as the energy storage capacity of the pendant groups can be utilized without disturbing the conductivity of the polymer backbone.

National Category
Physical Chemistry Engineering and Technology Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-230488 (URN)10.1039/c4ra15708g (DOI)000348986900057 ()
Available from: 2014-09-10 Created: 2014-08-26 Last updated: 2017-12-05

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