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Reference : UPR8001-SARPEC-001
Workplace : TOULOUSE
Date of publication : Saturday, February 02, 2019
Scientific Responsible name : David Pech
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 May 2019
Proportion of work : Full time
Remuneration : 1 768,55 € gross monthly
Description of the thesis topic
With the development of embedded electronic systems arises the question of miniaturization of electrical energy storage devices. Today, this function is mainly provided by microbatteries. These components, however, have a low power, a limited life and a restricted temperature range. On-chip "microsupercapacitors" would overcome these limitations, but today they are only at the university research stage with energy densities much lower than those of microbatteries.
The energy and power stored in a supercapacitor are proportional to the square of the potential window, which itself depends on the electrochemical stability of the electrolyte used. The electrolyte thus plays a major role in the properties of supercapacitors (voltage, temperature range, leakage current, lifetime, etc.).
Ionic liquids (ILs) are liquids consisting only of cations and anions. They are generally liquid below 100 ° C and have a very low saturation vapor pressure. Protic ionic liquids (PILs), formed from a mixture of an acid and a Bronsted base, have a labile proton increasing the conductivity of the PILs compared to the highly viscous and poorly conductive aprotic ones. In addition, protic ionic liquids have greater electrochemical and thermal stability than the aqueous medium.
The thesis will consist in synthesizing and studying various anhydrous PILs. It will be necessary to understand in particular how the difference of pKa between the base and the acid as well as the chemical structure of the PIL influences its properties and its reaction (transfer of the proton) with the RuO2. Physicochemical characterizations will be carried out in order to study their electrochemical behavior, potential range, thermal properties and lifetime (reduction of labile protons in H2?) with different electrode materials (RuO2, hydrated RuO2, C) and compared with a conventional aprotic ionic liquid.
A series of PILs will subsequently be integrated into RuO2 micro-supercapacitors made at LAAS. The performance of these components (temperature range, leakage current and voltage) will be tested. Liquid electrolytes, however, constitute a technological barrier to the production of functional microsupercapacitors compatible with microfabrication processes. It will therefore ultimately be necessary to produce, from these PILs, protic ionogels composed of a solid matrix in which the PIL will be confined.
LAAS-CNRS (Laboratory of Analysis and Architecture of Systems located in Toulouse) has been involved for ten years in the microscale realization of supercapacitors based on hydrated ruthenium oxide RuO2, a pseudocapacitive material with extremely high specific capacitance in an aqueous medium. Moreover, studies carried out at UdeM (University of Montreal) have shown in the past that it is possible to use protic ionic liquids as electrolyte of ruthenium oxide-based supercapacitors.
Constraints and risks
Within a framework of an ERC project dealing with the development of 3D Micro-Supercapacitors.
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