Evaluating organic mixed-conductor materials for sustainable electrochemical energy storage

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Realising the full potential of renewable electricity resources will require new, sustainable and high-performance materials for electrochemical energy storage in batteries and supercapacitors. Organic electron- and ion-transporting materials are interesting candidates for both electrodes and electrolytes because of their abundance, low cost, low toxicity, mechanical properties and the potential ease of both manufacture and recycling [1]. Conjugated polymers are particularly attractive for use as electrodes in battery or supercapacitor devices. They charge and discharge rapidly, are stable over many cycles and work with non-toxic salt-water electrolytes [2], although their specific capacity is still limited [3]. Their properties can be tuned via chemical design, once their operational mechanisms are properly understood. Polymer-based electrode materials would thus enable a completely new electrochemical storage technology of low environmental impact. In this project we aim to improve the electrochemical storage properties of conjugated polymer-based electrodes by developing a deeper understanding of the interactions between ions, electrons and molecules and of the charging process at a microscopic level and using these ideas to develop new material designs. We will study the ion transport and charging characteristics, specific capacity, redox stability and microstructure of polymer electrodes based on different materials using electrochemical and spectroscopic methods; and seek to relate the observations to chemical structure and energetics. These results will help to identify suitable electrode materials and test them within simple battery devices. The student will have the opportunity to use computational methods (possibly including device models, electronic structure and molecular dynamics) to interpret experimental measurements.The key questions are:- What ultimately limits the capacity of a conjugated polymer electrode?- How does chemical structure and influence operational stability?- What are the chemical design rules for higher performing materials and device architectures? The ultimate goal of this research is to contribute to global climate stabilisation efforts, by exploring the options for storage and use of renewable energy.