Development of Model Vitrimers Based on Disulfide Bonds for Solid State Polymer Electrolytes

Details

Supervisors

Fustin, Charles-André

Faculty

Faculté des sciences

Degree label

Master [120] en sciences chimiques, à finalité approfondie

Abstract

The transition to a low-carbon energy future is being taken more and more seriously these days, and the key to this is the use of renewable energy sources. But this solution is driving up the demand for storage devices, which also need to be high-performance and safe. At present, lithium-metal batteries remain the best option, although those using liquid electrolytes have safety issues. Research is now being carried out on batteries using a solid polymer electrolyte, which offer safety, good performance and correct conductivity. To add to these characteristics the durability of these batteries, the idea of having an electrolyte that is damaged as little as possible over time should not be overlooked. Better than that, there are materials that have the self-healing ability. These materials, known as vitrimers, are polymer networks containing dynamic covalent bonds, meaning bonds that allow reversible exchange. These materials provide a structure with a certain degree of rigidity while remaining malleable. The subject of this Master thesis is taken from a project that is based on this type of material, since it aims to use vitrimers as electrolytes and to implement them to obtain the future generation of solid-state lithium-metal batteries. The objective of this Master thesis is to synthesise a vitrimer-type polymer network based on disulfide bonds that can be used as a solid-state polymer electrolyte. To achieve this network, the polymer considered is a tetra-functional star-shaped poly(ethylene glycol) (PEG). This topology is used to synthesise the most perfect network possible. PEG was chosen for its qualities in terms of ionic conductivity and mechanical and thermal stabilities. The dynamic covalent bond selected is the disulfide bond, which offers high reactivity but also good reversibility and easy experimental control of bond exchange. This work is divided into three different parts. The integration of the disulfide bonds between the PEG stars, which leads to the formation of the network, requires a first step of functionalization of the polymer chain-ends. To achieve this, numerous parameters were varied during this reaction in order to optimise it and obtain the best degree of functionalization, while minimising secondary reactions. Various types of reaction were considered and the one that gave the best results provided functionalized PEG stars which, by reaction with a diamine containing the disulfide bond, made it possible to obtain gels. The mechanical properties of these gels were finally defined by different rheological measurements.