Title:	High potential quinones for battery applications
DNr:	SNIC 2016/1-124
Project Type:	SNIC Medium Compute
Principal Investigator:	Martin Sjödin <Martin.Sjodin@angstrom.uu.se>
Affiliation:	Uppsala universitet
Duration:	2016-04-01 – 2017-04-01
Classification:	10402 10405 20499
Keywords:

Abstract

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. In addition we will investigate the mechanism of electron transport in these systems. 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 and (ii) To develop a new first-principles high-throughput screening system to establish trends in counter ion binding sites. For the second part of the proposal, i.e. to understand charge transport in CRPs, computations will be used to determine the energy levels in CRPs in reduced, neutral and oxidized state. 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 charge transport in CRPs commensurable to the current understanding of conducting polymers (CPs). 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).