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Reference : UMR5253-LORSTI-001
Workplace : MONTPELLIER
Date of publication : Monday, February 04, 2019
Scientific Responsible name : Lorenzo Stievano, Laure Monconduit, Patrik Johansson
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 April 2019
Proportion of work : Full time
Remuneration : 1 768,55 € gross monthly
Description of the thesis topic
The World depends strongly on energy storage and while Li-ion batteries (LIBs) today are the ultimate rechargeable energy storage systems for portable needs, they depend on limited and highly localized lithium resources and are too expensive for very large-scale applications (TWh). We should now look beyond and research alternative performant and low-cost options.
Potassium-ion batteries (KIBs) have recently appeared as a promising low-cost candidate, together with a very low standard potential in conventional alkyl carbonate solvents and a smaller solvation ionic radius than both lithium and sodium, inducing higher ionic conductivity. As for LIBs, but in contrast to Na-ion batteries (NIBs), graphite can be used as anode in KIBs. Indeed, K+ ions can be electrochemically inserted up to the formation of KC8 (273 mAh/g) and furthermore also other forms of carbon such as carbon fibres (CFs) have shown interesting performance for KIBs. Some of our own preliminary results for graphite vs. K show excellent performance, which can be even improved as shown by our first tests of electrospun CFs, but so far we lack a rationale to connect the nature of the carbon host to performance and explain the likely complex insertion mechanisms. The objectives of this project are to:
1. Shed light on the electrochemical reaction mechanisms of different carbon hosts, in order to understand the insertion mechanism of potassium;
2. Considerably improve capacity retention and cycling performance via optimisation of the electrolyte formulation and studies of the nature of the SEI formed.
Indeed, SEI formation on graphite is highly dependent on the electrochemical stability of the surface as well as on the electrolyte composition. This is even more critical for potassium batteries, given the high reactivity of potassium metal and also the K+ insertion phases towards the electrolyte.
The highly exploratory character of this project will give the candidate the opportunity to first study the electrochemical mechanism of different carbon based materials as possible electrodes, and subsequently pursue to study those with the highest potential in terms of capacity and performance in realistic battery systems.
The PhD will run mainly at ICGM, at the University of Montpellier in the group Battery led by Dr. L. Monconduit & L. Stievano and also partially in Sweden, at the Chalmers University of Göteborg (Group of Prof. P. Johansson).
The two groups are complementary: while both teams have a good expertise on battery materials,the team in Montpellier has also developed many experimental approaches for the study of the mechanism of bulk electrode materials as well as electrolyte/electrode interfaces, whereas the team in Göteborg has a strong background in the study of electrolytes as well of mechanisms by operando Raman spectroscopy.
La thèse se déroulera principalement à l'ICGM, à l'Université de Montpellier, dans le groupe des Batteries dirigé par le Dr L. Monconduit et Pr. L. Stievano et, en partie, en Suède, à la Chalmers Univeristy de Göteborg (groupe de Prof. P. Johansson).
Les deux groupes sont complémentaires: si les deux équipes ont une bonne expertise des matériaux de batterie, l'équipe de Montpellier a également développé de nombreuses approches spectroscopie pour le suivi de l'étude du mécanisme des matériaux d'électrodes ainsi que des interfaces électrolyte / électrode lors du cyclage de la batterie et l'équipe de Göteborg possède une solide expérience dans les études des électrolytes ainsi que des mécanismes électrochimiques utilisant la spectroscopie Raman.
Constraints and risks
The thesis is financed by the European network ALISTORE-ERI. The PhD student will be officially enrolled at the Univeristy of Montpellier, but its work time will be shared between the two laboratories (ICGM and Chalmers) following the plan and needs of the project.
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