Origine de la perte de capacité de nanograins d'oxyde de vanadium pour batterie au lithium (influence du greffage moléculaire)

Les batteries au lithium présentent une perte de capacité en cyclage lorsque le matériau actif d électrode positive est Li1,1V3O8 nanométrique. Les caractérisations électrochimiques et physiques ont démontré que la dégradation des propriétés en cyclage s explique par la formation d une couche passivante en surface du matériau d électrode positive. Cette couche se forme d abord du coté électrolyte puis se propage au travers de l électrode jusqu au collecteur de courant. Elle résulte de la dégradation de l électrolyte qui pourrait résulter de l attaque nucléophiles des atomes d oxygène de surface de Li1,1V3O8. Pour étudier l influence de l état de surface sur la perte de capacité la surface spécifique du matériau a été multipliée par six par synthèse par méthode sol-gel en milieu isopropanol. Par la suite, la modification de l état de surface par réduction électrochimique des sels de diazonium a été étudiée. Les modifications ont permis d améliorer la rétention de capacité en limitant la dégradation de l électrolyteNanometric Li1,1V3O8 based lithium batteries suffer from a strong loss of capacity on cycling. The electrochemical and physical characterizations show that the degradation of the properties on cycling stems from the formation of a passivating layer on the surface of active material grains. The latter would come from the degradation of the electrolyte caused by its attack by nucleophilic oxygen atoms of Li1,1V3O8 surface. To study the effects of surface state on the capacity loss, Li1,1V3O8 specific surface area was increased by six fold using synthesis by sol-gel method in isopropanol medium. Thereafter, electrochemical grafting by reduction of diazonium salts was performed. This surface state modification stabilized the capacity loss by limiting the electrolyte decompositionNANTES-BU Sciences (441092104) / SudocSudocFranceF

Progress in all-organic rechargeable batteries using cationic and anionic configurations: Toward low-cost and greener storage solutions?

International audienceCurrent Opinion in Electrochemistry xxx (2018) xxx-xxx Progress in all-organic rechargeable batteries using cationic and anionic configurations: Toward low-cost and greener storage solutions

Synthèse, étude et optimisation de matériaux d'électrode positive pour batteries au lithium Li1+[alpha]V3O8, Li4VO(PO4)2 (des précurseurs au matériau actif)

Une partie de ce travail porte sur l'étude de la nature du gel précurseur de Li1,1V3O8 d'une part, et des processus de formation du matériau anhydre d'autre part. Les composantes solide et liquide du gel présentent la même stœchiométrie 1,1Li/3V. Après séchage à 90ʿC, des oxydes de vanadium lithiés hydratés sont obtenus mais avec des teneurs en eau différentes. Ces composantes conduisent à Li1,1V3O8 pur après traitement thermique à 580ʿC, mais avec une granulométrie et une capacité en cyclage spécifiques. Ces résultats permettent d'établir la nature du xérogel précurseur de Li1,1V3O8 et les mécanismes de formation de Li1,1V3O8 anhydre. D'autre part de nouvelles méthodes de synthèse permettant d'obtenir le précurseur gélifié plus vite et/ou un Li1,1V3O8 avec de meilleures performances électrochimiques ont été explorées. Enfin une étude portant sur la synthèse, la morphologie, la structure et le comportement électrochimique singulier d'un nouveau phosphate de vanadyle a été effectuée.Li1.1V3O8 can be obtained upon firing a gel precursor at a temperature as low as 300ʿC. It is shown that both the liquid and solid components of the gel have the 1,1Li/3V stoichiometry but that they crystallize into different compounds at room temperature. These compounds later lead to lithium vanadium oxide hydrates with different water contents and/or grain sizes on heating. Upon firing at 580ʿC for 10 hours, both samples that come from the liquid and the solid parts of the gel give pure Li1.1V3O8 but with different grain sizes and electrochemical behavior. Other new synthesis routes have been explored leading faster to the gel precursor and/or to anhydrous Li1.1V3O8 with better electrochemical performance. Finally a new vanadyl phosphate which present a singular electrochemical behavior was investigated in terms of synthesis, morphology, structure and Li insertion/deinsertion behavior.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Spontaneous arylation of activated carbon from aminobenzene organic acids as source of diazonium ions in mild conditions

International audienceActivated carbon products modified with benzoic, benzenesulfonic and benzylphosphonic acid groups were prepared by spontaneous reduction of aryldiazonium ions in situ generated in water from the corresponding aminobenzene organic acids without addition of an external acid. Electrochemistry and NMR studies show that the advancement of the diazotization reaction depends both on the acidity and the electronic effect of the organic acid substituent, giving a mixture of diazonium, amine and triazene functionalities. Carbon products prepared by reaction of activated carbon Norit with 4-aminobenzenecarboxylic acid, 4-aminobenzenesulfonic acid and (4-aminobenzyl)phosphonic acid were analyzed by chemical elemental analysis and X-ray photoelectron spectroscopy experiments. Results show that this strategy is well suited for the chemical functionalization, giving a maximized grafting yield due to a chemical cooperation of amine and diazonium functionalities

Interest of molecular functionalization for electrochemical storage

International audienceDespite great interests in electrochemical energy storage systems for numerous applications, considerable challenges remain to be overcome. Among the various approaches to improving the stability, safety, performance, and cost of these systems, molecular functionalization has recently been proved an attractive method that allows the tuning of material surface reactivity while retaining the properties of the bulk material. For this purpose, the reduction of aryldiazonium salt, which is a versatile method, is considered suitable; it forms robust covalent bonds with the material surface, however, with the formation of multilayer structures and sp3 defects (for carbon substrate) that can be detrimental to the electronic conductivity. Alternatively, non-covalent molecular functionalization based on π–π interactions using aromatic ring units has been proposed. In this review, the various advances in molecular functionalization concerning the current limitations in lithium-ion batteries and electrochemical capacitors are discussed. According to the targeted applications and required properties, both covalent and non-covalent functionalization methods have proved to be very efficient and versatile. Fundamental aspects to achieve a better understanding of the functionalization reactions as well as molecular layer properties and their effects on the electrochemical performance are also discussed. Finally, perspectives are proposed for future implementation of molecular functionalization in the field of electrochemical storage

Formation of Li1+nV3O8/beta-Li1/3V2O5/C nanocomposites by carboreduction and resulting improvements of the capacity retention

International audienceThe formation of the xerogel precursor of Li1CaV3O8 within a suspension of carbon black allows the synthesis of Li1CaCxV3O8/b-Li1/3V2O5/C nanocomposites upon heating under argon at 350 8C for a few minutes. The intimate contact of the active material with carbon particles ensures a limitation of the particle growth, a reduction–insertion of the pristine Li1CaV3O8 compound along with the formation of b-Li1/3V2O5 and an efficient electronic transport to the active materials. The electrochemical performance of these nanocomposites is significantly better than those of standard Li1CaV3O8

Greffage de molécules électroactives sur carbones activés pour le stockage électrochimique de l'énergie

L augmentation rapide de la consommation d électricité dans les pays émergents oblige à produire cette énergie à partir de ressources polluantes et l absence de dispositifs de stockage performants oblige à mettre en place des réseaux de distributions complexes. Parmi les principaux systèmes de stockage existants, les batteries se caractérisent par une densité d énergie élevée et une faible puissance, tandis que les supercondensateurs ont une densité de puissance élevée, mais une faible densité d énergie. Afin d améliorer les performances des dispositifs, des efforts récents ont été fait pour concevoir de nouveaux systèmes hybrides combinant les avantages des batteries et des supercondensateurs. Une stratégie prometteuse consiste à introduire des molécules organiques électroactives à la surface des carbones activés couramment utilisés comme matériaux d électrodes, pour ajouter une contribution faradique au stockage de la charge électrique. L objectif de ce travail de thèse concerne précisément l étude de l impact du greffage de molécules sur les performances des matériaux composites obtenus. Des molécules électroactives en milieux aqueux et organiques ont été sélectionnées et différentes procédures de modification ont été testées afin de maximiser le taux de greffage Des carbones activés microporeux et mésoporeux ont été modifiés afin d évaluer l effet de la porosité du carbone sur le stockage électrochimique de l énergie. Enfin, des poudres de carbones modifiées utilisées comme matériaux d électrodes positive et négative ont été combinées et les performances du dispositif hybride ainsi obtenu ont été évaluées en termes de densité d énergie et de puissance.The rapid increase in electricity consumption in emerging countries obliges to produce this energy from polluting resources and the absence of efficient storage devices obliges to set up complex distribution networks. At present, electric storage devices range from electrochemical capacitors, which can supply high power to batteries, which suffer from low power but can supply high electrical energy density. In retrospect, a promising approach would consist in combining both the advantages of capacitors and batteries to achieve versatile energy storage systems. A promising strategy consists to introduce redox active molecules onto the surface of activated carbon commonly used as electrode materials, for adding a faradaic contribution to the charge storage. The object of this work is to study the impact of the grafting on the performances of the composite materials obtained. Electroactive molecules in aqueous and organic media were selected and different grafting procedures were experimented for maximizing the grafting yield. Here, we propose a promising architecture for the design of organic batteries constructed from generic elements which consist in fast redox-active small molecules combined to a porous carbon network. The energy density and the power of the resulting hybrid system were evaluated.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Chapter 6. Perspectives in Lithium Batteries

International audienceLi-ion batteries still fall short of fulfilling the ever-increasing storage needs while keeping their environmental footprint as low as possible. In this chapter, without being exhaustive we tackle what next promising Li-based battery technologies could be; through the implementation of alternative (electro)chemistries including the use of more abundant components and/or less polluting processing solutions. Li-chalcogen (O2 and S) batteries are presented herein as quite promising systems especially for the market of electrically powered vehicles thanks to particularly high (expected) energy density values. Li-aqueous batteries, beyond the obvious environmental benefit in using water-based electrolytes, offer also some attractive perspectives to promote low-cost electrical storage solutions, potentially interesting for stationary applications. Finally, electroactive organic compounds could play an important role in the forthcoming battery technologies, since they exhibit several assets such as the possibility of being prepared from renewable resources and eco-friendly processes coupled with a simplified recycling management

Toward fully organic rechargeable charge storage devices based on grafting of redox molecules

Date du colloque : 06/2013</p

Modification chimique spontanée de carbones activés par réduction de sels de diazonium générés in situ par auto-diazotation. Préparation et études de matériaux pseudo-capacitifs appliqués au stockage de l’énergie

Date du colloque : 07/2011</p