WorldCat Identities

Leprêtre, Jean-Claude

Overview
Works: 28 works in 31 publications in 2 languages and 48 library holdings
Roles: Thesis advisor, Other, Opponent, Author
Publication Timeline
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Most widely held works by Jean-Claude Leprêtre
Influence de traitements de surface sur les propriétés de résistance à la corrosion d'alliages de titane à grains ultrafins pour des applications biomédicales by Diego Godoy( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

Titanium and its alloys are used as biomaterials because their excellent combination of high corrosion resistance, low modulus of elasticity and biocompatibility. However, titanium and its alloys cannot meet all the clinical requirements because they present some disadvantages, the most important being the inferior wear resistance. In this sense, this thesis aims to evaluate different strategies to improve mechanical properties and bioactivity of titanium alloys, (alpha' + beta) and (beta), for biomedical applications through severe plastic deformation and different techniques of surface modification.The titanium alloys, Ti13Nb13Zr (alpha' + beta) and Ti35Nb7Zr5Ta (beta), were deformed by the high-pressure torsion (HPT) method. Afterward, surface modification treatments, such as the anodization and chemical treatments, were carried out both in samples non-deformed and deformed by HPT. Finally, corrosion and bioactivity tests were performed in simulated body fluid (SBF). The tests were performed on samples with treated surfaces compared with non-treated surfaces in the deformed and undeformed conditions.The samples's microstructures were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Hardness tests were also performed after the HPT process. On the other hand, surface modification treatments, and the formation of apatite in bioactivity assays were evaluated by scanning electron microscopy (SEM), with chemical analyzes carried out by dispersive energy spectroscopy (EDS) and phase identification by X ray diffraction (XRD).In general, the corrosion resistance of the titanium alloys improved with the anodization treatment. Apatite deposits were observed on Ti13Nb13Zr alloy samples, in the conditions non-deformed and deformed by HPT. The Ti35Nb7Zr5Ta appears to have a lower apatite-formation ability compared to Ti13Nb13Zr
Séparateurs macroporeux innovants à base de poly(fluorure de vinylidène) pour supercondensateurs by Duygu Karabelli( )

1 edition published in 2011 in French and held by 2 WorldCat member libraries worldwide

La technologie supercondensateur a fait l'objet d'un grand intérêt ces dernières années. Cependant, tandis qu'une grande attention a été donnée aux électrodes, aux électrolytes et aux électrolytes de polymère gélifiée, peu d'études ont été centrées sur l'amélioration des séparateurs macroporeux. Dans le cadre du projet SEPBATT/DURAMAT, les séparateurs macroporeux à base de poly(fluorure de vinylidène) (PVdF) ont été préparés par inversion de phase, pour les supercondensateurs. Nos membranes présentent également une bonne stabilité thermique, en revanche leurs propriétés mécaniques sont significativement plus faibles que celles des membranes commerciales. De plus le séparateur PVdF de porosité 80% rempli par l'électrolyte à base d'AN atteint, à 25°C, 18mS/cm, tandis que dans les mêmes conditions mais avec le séparateur commercial en cellulose, la conductivité n'atteint que 10 mS/cm. Ce travail a été complété par l'étude de techniques de renforcement (addition de composites, réticulation par l'irradiation) appliquées aux membranes précédemment préparées, pour augmenter leur tenue mécanique. Ces membranes ont montré un renforcement des propriétés mécaniques sans nuire aux propriétés de conduction ionique (15 mS/cm)
Electrolytes polymères aromatiques nanostructurés pour PEMFC : Relation structure/morphologie/propriété by Huu-Dat Nguyen( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Aromatic ionomers are considered as a promising alternative to Nafion for PEMFCs due to their good oxidative stability, excellent thermomechanical properties, and low cost, etc. Most sulfonated aromatic ionomers reported over the past decades, however, show lower performance than that of Nafion. With similar ion-exchange capacity (IEC), on one hand, aromatic ionomers are much less conductive than Nafion, notably at low relative humidity. Aromatic ionomers with sufficient IEC to give equivalent conduction to that of Nafion, on the other hand, exhibit excessively swelling behavior in water. The shortcomings of sulfonated aromatic ionomers derive from (i) the random distribution of acidic groups on rigid polymer backbone leading to poor hydrophilic-hydrophobic separation, (ii) the proximity of proton-conducting moieties to the polymer main chain resulting in low nanostructure of ionic clusters, and (iii) the low acidity of aryl sulfonic acid. With the aim of overcoming these drawbacks, my PhD work focuses on developing new aromatic ionomers with improved morphology and properties via molecular architecture design, in combination with optimized membrane processing condition. Based on this objective, two series of aromatic ionomers based on partially-fluorinated multi-block copoly(arylene ether sulfone)s bearing pendant perfluorosulfonic acid (InX/Y series) or perfluorosulfonimide (SiX/Y series) side chains have been developed and characterized. Moreover, PEMs based on Nafion/InX/Y blend have also been focused. Much attention has been paid to optimizing the membrane processing condition and elucidating the structure-morphology-property relation in these materials
Synthèse et étude électrochimique de sels de pyridinium 3,5- disubstitués modèles du NAD+ : réactivité et comportement de leurs analogues réduits by Jean-Claude Leprêtre( Book )

2 editions published in 1992 in French and held by 2 WorldCat member libraries worldwide

L'etude electrochimique de composes 1-alkyl-3,5-dialkylcarbamido-pyridinium montre que ces especes se comportent comme des modeles du nad#+ (nicotinamide adenine dinucleotide forme oxydee). Sur differents materiaux d'electrodes, leur reduction donne deux types de produits: tout d'abord des dimeres 4,4, en general au nombre de trois qui sont des isomeres de conformation dont la structure a ete determinee par rmn. Ensuite les 1,4-dihydropyridines dont la proportion evolue selon la cathode utilisee. Nous avons pu montrer que certaines conditions de travail (variant selon le modele etudie) permettent d'obtenir quantitativement les 1,4-dihydroderives, modeles du nadh. La reactivite de certains modeles du nadh a ete etudiee. La cinetique de la reduction de la quinone diimine par ces modeles a ete determinee par voltammetrie cyclique
Etude physico-chimique de liquides ioniques pour PEMFCs by Maha Hanna( Book )

2 editions published in 2008 in French and held by 2 WorldCat member libraries worldwide

Les liquides ioniques pourront remplacer l'eau dans les électrolytes des PEMFCs opérant à 130°C. Les liquides ioniques résultant de la neutralisation des amines aliphatiques par l'acide trifluoromethanesulfonique montrent que les points de fusion dépendent de plusieurs critères, nature de l'anion, nature des substitutions sur l'amine. D'autre part, la majorité de ces sels sont thermiquement stables jusqu'à 400°C. L'étude par la voltamétrie cyclique a prouvé que les amines et les sels (HNR3+, A) s'oxydent à des potentiels très élevés (> 1,9 V/ESH), compatible avec leur utilisation dans les piles à combustible. D'autre part, les meilleures conductivités sont obtenues par les sels résultant de l'association acide trifluoromethanesulfonique et amines dissymétriques. Les conductivités à 130°C sont entre 5 mS.cm-1 et 45 mS.cm-1. L'incorporation de ces composés dans le Nafion a donné une bonne compatibilité LIP/Nafion. Cependant, l'effet plastifiant du LIP sur le polymère diminue les propriétés mécaniques du Nafion. Les conductivités sont aussi nettement réduites d'un facteur de 5 dans les meilleurs cas
Elaboration et caractérisation des membranes à base de Nafion® / H3 et Nafion® / H1 pour les piles à combustible by Houssemeddine Ben Attia( )

1 edition published in 2013 in French and held by 2 WorldCat member libraries worldwide

This study deals with the elaboration and characterization of composite membranes intendedto be used in PEMFC. These new composites combine a commercial ionomer, Nafion®, withinorganic acidic fillers that are phosphatoantimonic acids. Mono and triacid fillers, H1 and H3, have been used at 5 to 20wt% contents. Besides, their contribution to proton conductionand hydration, both fillers markedly improve, even at low content, the thermomechanicalperformances of the membranes. This reinforcement allows the thickness and, therefore, theohmic drop to be decreased. The MEA tests, performed in a wide range of gas humidificationand temperature, indisputably demonstrate the benefic effect of the fillers; Compositemembranes performing significantly better as soon as the operating temperature reaches orexceed 80°C
Complexes superstructurés de manganèse et de ruthénium à ligands polypyridiniques : synthèse, caractérisations, propriétés rédox et photorédox by Sophie Romain( Book )

2 editions published in 2006 in French and held by 2 WorldCat member libraries worldwide

This work deals with the synthesis and physico-chemical study of polynuclear ruthenium manganese complexes, which have been designed to mimic electron transfers in natural photosynthetic system. With bis-bipyridine type ligands, we synthesized binuclear di-J.l-oxo manganese complexes, covalently linked to four ruthenium 'tris~bipyridine type suounits. By examining :electrochemical and photochemical properties, we checked that photoinduced oxidations were thermodynamical1y favoured. Tt was confirmed by irradiation in the presence of a diazonium salt, that act as an irreversible electron acceptor. These irradiation led to different oxidized forms of the complexes in good yield Using a bipyridine-terpyridine type ligand, a new.numganese (Il) complex covalently linked to two ruthenium tris-bipyridine moieties was synthesized. Its redox properties were identified and photoinduced electron transfer have also been investigated. To better understand redox properties of this trinuclear complex, we studied electrochemical properties of sorne mononuclear manganese (II) complexes, [MnIl(L)2]2+, in wich L is a terpyridinic ligand, (L = terpy = 2,2':6',2"-terpyridine, terpy-tolyl = 4'-tolyl-2,2':6,2"-terpyridine et tBu3terpy = 4,4',4"-tri-tert-butyl-2,2':6',2"-terpyridine). We investigated these redox properties by examining the influence of presence of watef in electrolytic medium. We succeeded in identification of oxidized forms, and we showed that in anhydrous medium, mononuclear manganese (III) are produced, while in the presence of water, high valent species, like tetranuclear complexes involving oxo bridgescanbe synthesized
Nanostructures de silicium par croissance chimique catalysée : une plate-forme pour des applications micro-supercondensateurs by Dorian Gaboriau( )

1 edition published in 2016 in French and held by 2 WorldCat member libraries worldwide

Supercapacitors are electrochemical energy storage devices which have been recently developed, and possess intermediate performances between dielectric capacitors and batteries. These components exhibit interesting power and energy densities, combined with an exceptional cycle life and an easy miniaturization. Supercapacitors are thus envisioned as energy storage solutions for electronic micro-devices, such as autonomous micro-sensors or implantable medical devices.In recent studies, CVD nanostructured silicon proved to be an excellent electrode material candidate for micro-supercapacitor applications. Bottom-up synthesis allows an exceptional control of the morphology and electrical properties of the obtained silicon nano-wires and nano-trees. Moreover, the nanostructured electrodes possess superior electrochemical and temperature stability. These arguments lead to consider silicon as an excellent platform for micro-supercapacitors applications.This PhD thesis details various ways to improve and use silicon nano-wires and nano-trees. The nanostructures have been subjected to a systematic optimization study, yielding a significant increase of the electrochemical performances of the electrodes, compared to previously published studies. In addition, surface functionalization using thin ALD alumina layers permitted a considerable increase of the supercapacitor voltage window and an improved electrochemical stability. Finally, “on-chip” nanostructure growth, and temperature stability studies of the device were conducted, opening a broad field of improvements and potential uses for these silicon nanostructures
Nitroxydes chiraux à squelette imidazolidin-4-one comme catalyseurs d'oxydation énantiosélective d'alcools par O2 by Marta Carbo Lopez( )

1 edition published in 2014 in French and held by 2 WorldCat member libraries worldwide

Calculs ab-initio et simulations atomistiques des propriétés thermodynamiques et cinétiques de complexes de métaux de transition utilisés comme batteries by Asif Iqbal Bhatti( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

Ce travail théorique vise à étudier, via les méthodes Premiers Principes, les propriétés des complexes de métaux de transitions, left[Mleft(dmbpyright)_{3}right]^{n+}nCi^{-} pour un usage en batterie. Pour cette étude ab-initio, les composés mono et bi-nucléaires ont été retenus. La pertinance de notre modélisation a été validée sur les composés mononucléaires. Nous nous sommes interessé au complexes de Fe, Ru et Cu pour lesquels une validation expérimentale était possible. Notre étude a principalement consisté à faire varier les degrés de liberté que nous possédons pour optimiser le voltage et la cinétique de chargement des batteries. Pour cela, nous avons fait varier le TM = Fe, Ru, et Cu, la nature des contre-ions Ci^{-}=PF_{6}^{-}, TFSI^{-} et ClO_{4}^{-} en interaction avec le polymère lors du processus de charge, ainsi que la longeur de la chaîne alkyl qui sépare les deux monomers dans le cas des composés binucléaires. Le composé à base de Fe avec une chaîne -left(CH_{2}right)_{n=6}- a été retenu comme le meilleur candidat pour une application batterie. Le composé à base Ru montre un comportement proche de celui du Fe, quant-au complexe de Cu, il présente des changements de géométrie locale sous chargement trop importants, le rendant peu apte à conduire à une cinétique efficace. Cette étude nous a permis de déterminer que l'approximation PBE était le meilleur choix possible pour modéliser nos complexes dans les conditions de fonctionnement en batterie (dans le champ créé par les contre-ions) et que l'approximation PBE0, généralement utilisée dans la littérature, ne pouvait rendre compte de la physico-chimie de nos composés dans de telles conditions.De surcroît, nous avons dévelopé pour le complexe de Fe, un potentiel atomistique de type “Champ de forces” de manière à pouvoir aborder les aspects dynamiques impliquant de plus grandes tailles de boîte de simulation. Ici, nous modélisons une structure 3D, totalement réticulée à partir de nos monomères à base de Fe. Nous nous sommes servi de la base de donnés DFT que nous avions généré (énergies, géométries, état de spin et fréquences vibrationnelles calculées) pour ajuster les paramètres entrant dans l'écriture du modèle. La construction de la géométrie initiale du polymère 3D a nécessité l'écriture d'un code de calcul visant à produire un arrangement complétement réticulé et à assigner les charges effectives issues des calculs DFT. Ce modèle nous a permis de déterminer les coefficients de diffusion des contre-ions pour les états totalement chargé et non-chargé. Un calcul plus ambitieux vise à déterminer les chemins de diffusion des contre-ions lors d'un processus de chargement en considérant un seul centre de degré d'oxydation 3+ au centre du polymère 3D, pour lequel les centres actifs possèdent un degré d'oxidation 2+. Les contre-ions assurent la neutralité globale.Keyword: Polymer, Electrochemistry, Li-ion Battery, DFT, Force Field development, 3D structure, Atomistic modeling
Matériaux nanocomposites polypyrrole-oxyde métallique pour l'oxydation de l'eau en oxygène par voie électrocatalytique et photocatalytique by Daniela Valentina Morales Montecinos( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

This thesis is focused on the development of efficient anodes and photonanodes for electrocatalytic and photocatalytic water oxidation based on nanocomposite materials in which nickel or cobalt oxide nanoparticles have been inserted in a positively charged poly(pyrrole-alkylammonium) film.The nanocomposite anodes exhibit small nanoparticles of nickel or cobalt oxides and high nanostructuration induced by the polypyrrole matrix leading to very high catalytic performance in comparison with bare anodes on which nickel and cobalt oxides have been deposited without polypyrrole. These nanocomposite electrodes outperform the nickel-based anodes of the literature (undoped by iron) and those using precious metal oxides, such as RuO2 and IrO2.This strategy has been successfully extended to the design of hybrid photoanodes by introducing a perylene diimine chromophore in these nickel or cobalt oxide nanocomposite materials. These photoanodes display very high photocurrent density with nickel oxide and cobalt oxide under visible light illumination along with a relatively good stability over time. These photocurrent density values largely exceed those reached by similar hydrid photoanodes of literature combining an organic dye and a metal oxide as catalyst, demonstrating the great potentialities of our approach to implement (photo)electrochemical cells devoted to water splitting into H2 and O2
Nouvelles générations d'électrolyte pour batterie lithium polymère by Amadou Thiam( )

1 edition published in 2015 in French and held by 2 WorldCat member libraries worldwide

The aim of this thesis was to develop new polymer electrolytes for application of lithium metal polymer batteries. The first part concerns the development of semi-interpenetrating networks based on POE and a polycondensat. These types of electrolytes made it possible to improve the mechanical properties and conductivity at high and low temperatures. The addition of NCC as a reinforcement on the semi-interpenetrating network has led to interesting physicochemical properties and high cycle life for batteries.The partial hydrogenation of the polycondensat allowing the modulation of the reticulation ratio has allow to elaborate as an electrolyte (in the presence of LiTFSI) exhibiting 1S.cm-1 conductivities at 90 ° C for a ratio O/Li=20 and O/Li=30 with a mechanical strength of 0.5MPa to 100 ° C. In the second part a range of lithium with organic anion was synthesized and characterized. These lithium salts show good electrochemical and thermal stability, whereas ionics conductivities are sometimes higher than LiTFSI in polymer medium. The last part concerns the synthesis and physicochemical characterization of new perfluorinated ionomers. These new cationic ionomers with a unipolar conduction are obtained from aromatic monomers carriers ionic functional having a high ability to dissociation and cation transport numbers close to 1 at 70 ° C
Synthèse et étude physico-chimique de nouveaux matériaux organiques d'électrode positive à base de phénothiazine pour les applications dans les accumulateurs au lithium by Thibault Godet-Bar( )

1 edition published in 2013 in French and held by 2 WorldCat member libraries worldwide

The aim of this work is to develop phenothiazine-based redox organic materials for lithium positive electrode. Comparatively to inorganic materials, organic ones can constitute clear break by decreasing the cost, toxicity and security issues while keeping good performances. In that purpose, redox materials involving phenothiazine moieties have been synthesized, characterized, then, their electrochemical properties have been analyzed electrochemically, the most promising ones have been tested in lithium and sodium cells. The redox target chosen, the phenothiazine, has been polymerized and functionalized onto phosphazene backbone. Cell tests showed material dissolution contribution has to be avoided. In this context, insoluble polyphenothiazine and cross-linkable copolymers were able to upgrade significantly the cyclability and the energetic performances of lithium cells. Moreover, sodium cells with a poor lipophilic anion showed lower dissolution contribution. Carbon grafting by phenothiazine has also been investigated. It has been performed by electrochemical and chemical means and has led to promising electrochemical performances
Complexes de ruthénium (II) intégrant l'unité photochromique Diméthyldihydropyrène : Vers de nouvelles photo-réactivités by Margot Jacquet( )

1 edition published in 2017 in French and held by 2 WorldCat member libraries worldwide

The work of this thesis is devoted to the development of original photo-switchable ruthenium(II) complexes incorporating the photochromic Dimethyldihydropyrene (DHP) / Cyclophanediene (CPD), for future optoelectronic molecular devices.In order to realize complex systems capable of reproducing the functions of a logic circuit, an interesting strategy is based on the association of photo-switchable molecules and metal complexes. However, this strategy is confronted with some major obstacles, generally associated with the loss of the switching properties of organic photochromes. In response to previous results confirming this trend, two new families of DHP-based terpyridine ruthenium(II) complexes have been synthesized. Since the presence of pyridinium function significantly improves the isomerization properties of the DHP core, the metal centers were connected either via a pyridinium benzyl linkage (Ru-Lpy+tpy) or via an aryl pyridinium linkage (Ru-LZincke). Although operating at lower energy, Ru-LZincke complex exhibits lessened performance, whereas Ru-Lpy+tpy complexes exhibit a notable preservation of their switching properties. Following the discovery of an original photo-reactivity favored by the presence of metal center, an analogue family based on ruthenium (II) bipyridine complexes (Ru-Lpy+bpy) was studied. Even if the mechanisms are not completely rationalized, Ru-Lpy+bpy complexes have proved to be remarkable candidates for the realization of quantitatively reversible photo-switches in the visible domain
Accumulateurs Li/S : barrières organiques à la réactivité des polysulfures by Valentin Vinci( )

1 edition published in 2018 in French and held by 2 WorldCat member libraries worldwide

The objectives of this thesis work were to explore new strategies to improve the performance of Li / S accumulators, systems exhibit with high theoretical energy densities whose performance is limited by an electrochemical mechanism including soluble and reactive intermediates. These intermediates induce a low coulombic efficiency and a significant loss of capacity during cycling. Several strategies have been evaluated to create a barrier of organic nature, which mitigate the transport or the reactivity of these polysulfides. The solutions explored are versatile and simple to implement. Good results have been obtained in terms of coulombic efficiency and cyclability, in particular through the use of a polymeric material enables to form ionic interactions with the sulfur intermediates. The mechanism of lithium deposition and dendritic growth has also been studied, for a more complete understanding of the system
Effect of standard light illumination on electrolyte's stability of lithium-ion batteries based on ethylene and di-methyl carbonates by Gaspard Bouteau( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

Electrolyte based on fluorinated cyclic quaternary ammonium ionic liquids by My-Loan-Phung Le( )

1 edition published in 2012 in English and held by 2 WorldCat member libraries worldwide

Mise au point d'electrolytes innovants et performants pour supercondensateurs by Emmanuelle Perricone( )

1 edition published in 2011 in French and held by 2 WorldCat member libraries worldwide

L'objectif de cette thèse est de développer et d'optimiser un électrolyte organique performant et sécuritaire pour supercondensateur. En effet, l'acétonitrile est un solvant couramment employé dans la conception des électrolytes, mais celui-ci étant inflammable, il faut lui trouver une alternative performante. Différentes familles de solvants ont été évaluées. Les solvants stables d'un point de vue électrochimique ont été sélectionnés en vue de leur utilisation dans des électrolytes. Dans le but de trouver un compromis entre mobilité et concentration ionique, des mélanges de solvants ont été réalisés. L'addition de solvants peu visqueux comme des esters ou le méthoxypropionitrile dans l'éthylène carbonate et le sulfolane ont permis d'obtenir des électrolytes performants. L'étude des interactions solvant / solvant et solvant / sel ont été menées par des mesures calorimétriques, viscosimétriques et spectroscopiques. Ces interactions, bien que de très faible amplitude, permettent d'augmenter notablement la température d'évaporation du solvant volatil de l'électrolyte, donc son point éclair
Vers des batteries lithium organiques innovantes mettant en jeu des polymères à base de Nméthylphénothiazines modifiées by Romain Guilmin( )

1 edition published in 2016 in French and held by 2 WorldCat member libraries worldwide

The N-methylphenothiazine (MPT) is a prime target with the aim of developing innovative redox organic materials useful as positive electrode of lithium-ion battery. These organic materials are today a credible alternative to inorganic materials by their lower cost and toxicity.It is in this context that MPT-based redox polymers have been synthesized and characterized. Their electrochemical properties have been investigated in lithium cells to estimate their potential.But why the N-methylphenothiazine ? This redox target has two reversible systems but only the first is exploited. The project was therefore the chemical modification of the MPT molecule to modulate potential values of two systems. These chemical developments thus allow improving notably the MPT derivative theoretical capacities accessible in the electrochemical stability range of lithium-ion technology electrolyte.These derivatives were synthesized and tested in lithium cell. Some of them present interesting performances. But despite the use of insoluble materials at the neutral state, cell tests showed material dissolution in the oxidized state, which decreases significantly the obtained capacities
Développement d'accumulateurs sodium-ion by Virginie Simone( )

1 edition published in 2016 in French and held by 2 WorldCat member libraries worldwide

Because of the development of renewable energy and electric vehicles, the need for a large scale energy storage has increased. This type of storage requires a large amount of raw materials. Therefore low cost and abundant resources are necessary. Consequently the use of sodium batteries is of interest because sodium's low cost, high abundance, and worldwide availability. This PhD thesis deals with the study of a full Na-ion cell containing a hard carbon negative electrode, and a layered oxide positive electrode. A shorter part concerns the electrolyte.Concerning the negative electrode, the first objective was to understand in detail the influence of the pyrolysis temperature of a hard carbon precursor, cellulose, on the final structure of the material and its consequences on the electrochemical performance. Many techniques were used to characterize the hard carbon structure as a function of the pyrolysis temperature. Localized graphitization, pore closure, and an increase in micropore size have been observed with increasing temperature. The best electrochemical performance has been reached with the hard carbon synthesized at 1600°C: a reversible capacity of around 300 mAh.g-1 stable over 200 cycles is obtained at 37.2 mA.g-1 with an initial coulombic efficiency of 84%. To deeper understand sodium insertion mechanisms in hard carbon structures impedance spectroscopy, SAXS and EDX were carried out on hard carbon electrodes cycled at different voltages.The layered oxide Na0.6Ni0.25Mn0.75O2 was investigated as the positive electrode. It was observed that with increasing calcination temperature the number of P3-type stacking faults decreases in favor of a more crystalline P2 phase. Then, the carbonate-based electrolyte has been optimized to guarantee the reproducibility of the electrochemical tests performed in a layered oxide//sodium metal configuration. A first oxidation capacity of around 130 mAh.g-1 is reached. However this value drops quickly after 40 cycles. Operando XRD analysis did partially explain the capacity decrease. Finally, the results of these investigations were used to design an optimized full cell which demonstrated promising performance during initial testing
 
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Alternative Names
Jean-Claude Leprêtre onderzoeker

Languages
French (17)

English (6)