Jury :

• Rabah BOUKHERROUB, DR1, Université de Lille, CoDirecteur de thèse
• Abderrahim RAMDANE, Research Director, Centre for Nanosciences and Nanotechnologies (C2N), Rapporteur
• Djoudi BOUHAFS, Research Director, Centre de Recherche en Technologie des Semi-conducteurs pour l'Energitique (CRTSE), Rapporteur
• Sorin MELINTE, University Professor, Université Catholique de Louvain, Examiner
• Fatima SETIFI, University Professor, Chemistry, Molecular Engineering and Nanostructures Laboratory. Department of Chemistry, Faculty of Science, Ferhat Abbas University, Sétif 1, Examiner
• Toufik HADJERSI, Research Director, Centre de Recherche en Technologie des Semi-conducteurs pour l'Energitique (CRTSE), Thesis supervisor

Summary:

The aim of this thesis is to develop micro-supercapacitor (µSC) electrodes based on chromium nitride deposited on a silicon substrate used as a current collector. Their electrochemical performance can be improved by increasing their specific surface area and/or porosity to improve the accessibility of the electrolyte to the active material.
The first part of the first chapter is devoted to the state of the art in supercapacitors and micro-supercapacitors, as well as the different energy storage systems, the different types and applications of supercapacitors and their storage mechanisms. In the second part, we describe the typical architecture of a supercapacitor as well as the electrode materials and electrolytes used to manufacture supercapacitors.
The second chapter concerns the manufacture of electrodes based on a thin film of chromium nitride (CrN) deposited by bipolar magnetron sputtering under oblique incidence. The use of this new technique makes it possible to control the surface morphology of the electrodes, which directly affects their storage capacity. We will then describe the fabrication of a CrN-based microdevice with an interdigitated configuration and good electrochemical performance.
The third chapter is devoted to the development of composite electrodes based on silicon nanowires (NFSi), synthesised by the VLS mechanism, and coated with a layer of CrN. The coating of NFSi with CrN offers several advantages, such as an increase in the faradic capacitance and an improvement in the electrical conductivity of the CrN and NFSi composite, as well as energy storage properties.
The fourth chapter concerns the development of carbon nanowall (CNW) composite electrodes decorated with CrN layers. We describe the advantages of using a template with a large specific surface area on the electrochemical performance of composite electrodes. The large specific surface area of NMCs and their good electrical conductivity make it possible to improve not only the surface capacitance of CrN-based electrodes but also their lifetime. Next, we describe the fabrication of a microdevice with a stacked configuration based on CNW-CrN electrodes with excellent electrochemical stability.
Finally, the conclusion summarises the results obtained during the course of this thesis and the prospects for the future.

Abstract:

The aim of this thesis work is the elaboration of micro-supercapacitor electrodes based on chromium nitride (CrN) deposited on a silicon current collector. Their electrochemical performance can be improved by increasing their specific surface area and/or porosity for better accessibility of the electrolyte to the active material.
The first part of the first chapter is devoted to the state of the art on supercapacitors and micro-supercapacitors as well as the different energy storage systems, various types and applications of supercapacitors and their storage mechanisms. In the second part, we describe the architecture of a supercapacitor as well as materials and electrolytes used for the fabrication of supercapacitors.
The second chapter concerns the fabrication of electrodes based on a thin film of chromium nitride (CrN) deposited by bipolar magnetron sputtering at a glancing angle (PVD-GLAD). The use of this new technique allows controlling the morphology of the surface of the electrodes, which directly affects their storage capacity. Subsequently, we will describe the fabrication of a micro-device with an inter-digital configuration based on chromium nitride with good electrochemical performance.
The third chapter is dedicated to the development of composite electrodes based on silicon nanowires (SiNWs), synthesized via a VLS mechanism, and coated with a thin layer of highly pseudo-capacitive CrN material. Post-coating SiNWs with CrN offers many benefits, such as enhanced faradaic capacitance and electrical conductivity of the composite, and improved energy storage performance.
The fourth chapter focuses on the development of composite electrodes made of carbon nanowalls (CNW) decorated with CrN. We will describe the benefits of using a template with a large specific surface area on the electrochemical performance of the composite electrodes. The large surface area of CNW and their good electrical conductivity allow improving not only the areal capacitance of CrN based electrodes, but also their cycle life. Subsequently, we will discuss the fabrication of a micro-device with a staked configuration based on CNW-CrN electrodes with robust electrochemical stability over 30,000 cycles.
Finally, the conclusion summarises the results obtained during this thesis as well as the prospects envisaged.