Thèse Fibres Composites Cnt - Oxydes Métalliques Conçues pour des Applications de Supercondensateurs H/F

Doctorat_Gouv

Établissement : Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes
École doctorale : Sciences Mécaniques et Energétiques, Matériaux et Géosciences
Laboratoire de recherche : LMPS - Laboratoire de Mécanique Paris-Saclay
Direction de la thèse : Jinbo BAI ORCID 0000000265810157
Début de la thèse : 2026-10-01
Date limite de candidature : 2026-04-30T23:59:59

Ce travail vise à développer des fibres composites flexibles de nanotubes de carbone (CNT) et d'oxyde métallique pour des applications de supercondensateurs avancées. Des fibres de CNT multi-parois (MWCNT) seront fabriquées par filage humide. Des nanostructures de cobaltite seront électrodéposées in situ sur les fibres, formant ainsi une structure coeur-coquille. Cette structure intégrera des mécanismes de stockage à double couche électrique et pseudocapacitifs, améliorant les performances électrochimiques. Des supercondensateurs textiles flexibles, sous forme de fibres tissées, seront assemblés et évalués sous contrainte mécanique. Le projet vise à établir une stratégie évolutive pour le stockage d'énergie portable.

The growing demand for portable electronics, electric mobility, and the integration of intermittent renewable energy necessitates efficient, lightweight, and long-life energy-storage technologies. Conventional batteries deliver high energy density but are constrained by slow charge-discharge kinetics, limited power density, and degradation during repeated cycling. In contrast, electrochemical supercapacitors bridge the gap between dielectric capacitors and batteries by combining rapid charge-discharge capability, high power density, and excellent cycle stability, making them suitable for hybrid energy systems, pulse-power supply units, and wearable electronics. Among advanced electrode materials, carbon nanotubes (CNTs), particularly multi-walled carbon nanotubes (MWCNTs), are attractive due to their high electrical conductivity, large accessible surface area, mechanical robustness, and chemical stability. Their one-dimensional conductive framework forms continuous electron-transport pathways and interconnected porous channels, promoting rapid diffusion of ions in the electrolyte. However, charge storage in pristine CNTs mainly arises from electrochemical double-layer capacitance, which restricts the attainable energy density.
To overcome this limitation, coupling CNT fibers with pseudocapacitive transition-metal oxides such as MnO or spinel cobaltites (e.g., NiCoO-type systems) introduces reversible faradaic redox reactions, thereby increasing specific capacitance and energy density while retaining rate capability. Wet-spinning and related fiber-forming strategies enable the fabrication of macroscopic, binder-free CNT fibers with aligned conductive pathways and superior mechanical flexibility. Subsequent hybrid coating or in-situ growth of metal-oxide nanostructures produces hierarchical core-shell architectures that integrate electrical double-layer and pseudocapacitive storage mechanisms and improve electrode/electrolyte interfacial area. These flexible fiber-shaped electrodes are particularly promising for textile-integrated and wearable energy storage, where bending tolerance, lightweight construction, and structural integrity are essential. Consequently, engineering CNT/cobaltite nanohybrid fibers via wet-spinning offers a viable route toward next-generation flexible supercapacitors with enhanced electrochemical performance and durability.

To fabricate mechanically robust and electrically conductive wet-spun multi-walled carbon nanotube (MWCNT) fibers with controlled alignment and hierarchical porosity suitable for binder-free electrode applications.
To integrate MgCo2O4/NiCoO nanoarchitectures onto MWCNT fibers via in-situ electrodeposition, forming a nanohybrid/composite electrode with strong interfacial coupling.
To achieve enhanced pseudocapacitive performance with a target specific capacitance.
To assemble flexible fiber-shaped and woven textile supercapacitor devices and evaluate their electrochemical performance, including energy density and power density.
To investigate long-term electrochemical and mechanical durability, targeting stable operation over an extended charge-discharge cycle under repeated bending deformation.

The study will be conducted in multiple phases, with the methodology corresponding to each phase outlined below.
Phase 1: MWCNT Fiber Optimization and Preparation
MWCNT fibers will be fabricated using a wet-spinning process. MWCNTs are dispersed in chlorosulfonic acid (true solvent) to form a liquid-crystalline dope, extruded into a coagulation bath where the nanotubes reassemble into continuous fibers. The fibers are washed, dried under tension, and thermally annealed (in inert atmosphere) to improve alignment, electrical conductivity, and mechanical strength. The fibers will then be characterized by Raman spectroscopy, scanning electron microscopy (SEM), BET analysis, tensile testing, etc., to evaluate the defect level, morphological features, surface area/porosity, and mechanical strength, respectively.
Phase 2: CNT/Cobaltite Hybrid Electrode Formation
Cobaltite nanostructures will be deposited onto the CNT fibers via in-situ electrodeposition while varying the CNT-to-cobaltite ratio to optimize electrochemical performance. The electrodes will be studied using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) to determine capacitance, reversibility, and ion-transport kinetics.
Phase 3: Textile Supercapacitor Fabrication
Hybrid fibers will be twisted into yarns and assembled into a woven textile device using a gel electrolyte as both separator and ionic conductor. The flexible two-electrode supercapacitor will be evaluated electrochemically and under bending conditions for capacitance retention, rate capability, and cycling stability.