Site institutionnel du Laboratoire Ampère - CNRS UMR5005

Layal ABDALLAH will defend her PhD on May. 13th, 2026 at 9 AM.
Place : Amphitheatre 203 in the W1 building of École Centrale de Lyon in Ecully

Jury :
Rapporteuses :
 Sophie Tingry, DR2 CNRS, Institut Européen des Membranes, ENSCM, Université de Montpellier
 Elsa Weiss-Hortala, MCF, HDR, IMT Mines Albi, UMR CNRS 5302, Université de Toulouse

Examinatrices :
 Hafsa Korri-Youssoufi, Directrice de recherche, ICMMO, UMR-CNRS-8182, Université Paris-Saclay, CNRS (Présidente du jury)
 Valerie Stambouli-Sene, Chargée de Recherche CNRS, Laboratoire des Matériaux et du Génie Physique, INP, UGA

Encadrement :
 Christian Vollaire, Pr, Laboratoire Ampère, Centrale Lyon (Directeur de thèse)
 Naoufel Haddour, MCF, Laboratoire Ampère, Centrale Lyon (co-encadrant)
 Chantal Gondran, Pr, Département de Chimie Moléculaire de Grenoble, UGA (co-encadrante)

Abstract : Global energy production remains heavily reliant on non-renewable resources such as coal, natural gas, and oil. These resources are limited, and their exploitation results in significant environmental impacts. To address these challenges, renewable energy resources, including solar and wind power, are increasingly being explored. However, the intermittent nature of these alternatives necessitates the implementation of sustainable energy storage solutions capable not only of balancing energy production and demand but also of managing the rapid power fluctuations associated with their operation. In this context, electrochemical double-layer capacitors (EDLC) occupy a distinct position among electrochemical energy storage technologies.
Although they are not suitable for long-term energy storage due to their limited energy density, EDLCs are distinguished by high power density, extremely fast response times, and excellent cycling stability, ensuring rapid and highly reversible charge/discharge processes. These properties make them particularly effective for handling rapid load variations and enhancing the stability of energy systems, thereby complementing storage technologies with higher energy capacity.
The performance of EDLCs strongly depends on the nature of their electrodes, which typically consist of an active material, a conductive additive, and a binder, often based on fluorinated polymers. However, conventional electrode materials used for this purpose, such as graphene and carbon nanotubes, are predominantly derived from fossil resources and require costly and energy-intensive manufacturing processes. Consequently, the development of more environmentally friendly and sustainable alternatives, that can maintain electrode performance, is of critical importance.
In this framework, the present study is devoted to developing and optimizing bio-based conductive electrodes for EDLC. In particular, this research investigates the use of biochar as an alternative to conventional electrode active materials. Produced by the pyrolysis of biomass, biochar is a carbonaceous material with several remarkable properties, including renewable origin, relatively low production cost, high carbon content, and a high specific surface area with engineered porous structure. Moreover, its properties can be tuned through synthesis conditions and modification methods, making it a particularly promising candidate for the fabrication of electrodes for EDLC.
The work of this thesis is structured around three main axes. The first axis investigates the influence of biomass pyrolysis temperature on the structural, physicochemical, and electrical properties of the biochars from cedar wood, as well as their electrochemical performance as electrode materials. Biochars obtained at pyrolysis temperatures between 800 and 1100 °C were characterized using structural (SEM, BET), physico-chemical (FTIR, Raman, contact angle), electrical (4-probe method), and lectrochemical (CV, EIS, GCD) techniques. Furthermore, a bio-based chitosan binder was examined as an alternative to conventional fluorinated binders, with the aim of reducing the environmental impact of electrodes. The second axis aims to explore biochars derived from different biomasses, such as coffee grounds, cedar wood, bamboo, and wheat straw, and chemical treatment methods (nitric acid, iron nitrate), to highlight the impact of the feedstock type and the applied treatments on the properties of the produced biochars and their electrochemical performance. Finally, the third axis focuses on the valorization of cotton-based textile waste for the fabrication of structured, self-supporting electrodes without the need for fluorinated binders. This approach enhances electrode sustainability while valorizing textile waste and enables the production of fibrous-morphology electrodes, thereby simplifying their implementation.

Keywords: Biomass, biochar, pyrolysis temperature, biochar structural and physico-chemical properties, prepyrolytic modification, electrode material, biobased binder, self-assembled electrodes, EDLC.