In the continuation of this project we will expand our studies to polymeric systems addressing charge trapping in quinone based conducting redox polymers (CRPs), i.e. conducting polymers with redox active pendant groups. We will also expand the studies to inclyde tereptalate-based CRPs for use as negative electrodes.
The purpose of the first aspect of this research proposal is to use first-principles calculations to (i) achieve fundamental understanding on how charge trapping by binding of the counter ion in the vicinity of the redox active group influences the reduction potential
For the second part of the proposal we will explore how the tereptalate redox chemistry is affected by the polarity of the suroundings, the ordering and paching of redox centers and the counterion involved in the redox conversion. The computational results will be compared with experimental results, including data from in-situ UV-vis-IR absorption and in-situ conductance measurements during electrochemical redox conversion. The results are expected to provide the community with a level of understanding of the how structure and experimental conditions affects the redox chemistry of quinone and terephtalate sybstituted CRPs.
The study is motivated by the need to develop environmentally benign electrical energy storage systems and one alternative is to replace inorganic materials with organic ones. The development of organic matter based electrical energy storage systems are however currently hampered by the poor conductivities of organic matter as well as by the solubility of most small organic molecules in common battery electrolytes. As experimental capacities of organic matter based electrode materials have been found that are comparable to, and even succeeds, conventional cathode material capacities, resolution of these issues may provide the society with technologically competent alternatives based on renewable and readily accessible resources. The adopted strategy in our research group to overcome conductivity- and dissolution-problem is to attach high capacity redox active pendant groups on a CP backbone forming a CRP. In order to enable rational design of these systems an improved understanding of chare transfer mechanisms as well as of potential tuning in these systems are require.
By employing first-principles theory based on density functional theory (DFT), we will investigate how the nature of an ion trap (T) affects the redox potential of the quinone in CRPs. The redox potentials in solution will be calculated by combining DFT and self-consistent reaction field methods where the free energies (including all internal energy and entropic contribution) are calculated using the Born–Haber thermodynamic cycle. The explicit solvent effect will be assessed by carrying out ab-initio molecular dynamics (MD) simulations. A sequential MD/DFT scheme will be used to determine the electronic structure at a given temperature. In this approach, snapshots of the MD simulations are selected to carry out high-accurate single point DFT calculations, and subsequently, the obtained electronic structures are averaged. We will explore the Born-Oppenheimer molecular dynamics as implemented in the Vienna Ab-initio Simulation Package (VASP).