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[en] Nickel-polymer composite electrode materials have been synthesized using various strategies, all comprising the electrochemical reduction of nickel(II) cations or complexes, incorporated by either ion-exchange or complexation into various poly(pyrrole-carboxylate) thin films coated by oxidative electropolymerization onto carbon electrodes. The electrocatalytic activity and the stability of the different composites have been then evaluated in the course of the electrocatalytic hydrogenation of ketones and enones in aqueous electrolytes. The best results were obtained using nickel-polymer composites synthesized by electroreduction of nickel(II) ions complexed into polycarboxylate films, which are characterized by a high catalytic activity and a good operational stability. (author)
[en] Human activity generates an environmental impact increasingly important including in the field of transport and portable electronics. It is therefore essential to develop of new technologies capable of producing and storing electrical energy. In this context, organic material based battery can constitute an interesting alternative compared to inorganic ones. Less costly and toxic and allowing to involve other alkali cation (rather than Li"+), since few years such materials are evoked in literature. However, their performance yet do not compete with that of involving inorganic cathodic material (i.e. Lithium iron phosphate). In this context, multi electron process can be the way to reach high performance organic compounds. This can be done using phenothiazine which, through an adapted chemical modification, can undergo a two electron oxidation in the potential window stability of classical electrolyte. This work is dedicated to the impact of N-methyl-phenothiazine chemical modification on its electrochemical behavior. The stability of oxidized forms of modified phenothiazine is investigated helping to select the best monomer to be involved as cathodic polymer material in battery.
[en] ABSTRACT: Electrolyte compositions based on LiTFSI dissolved in fluorinated linear and cyclic carbonates were characterized regarding their transport and thermal properties, viscosity, solvation ability, electrochemical stability towards oxidation, as well as their ability to inhibit the aluminum current collector corrosion. As a result of the thorough investigation, different binary mixtures were prepared, which offer beneficial properties in terms of aluminum current collector protection and provide optimized transport properties. The use of LiTFSI as electrolyte salt rather than the state-of-the-art lithium salt, LiPF_6, enables substantial improvements with respect to safety, while maintaining high performance liquid electrolyte
[en] Highlights: ► Liquid electrolyte composition for lithium/sulfur secondary batteries. ► Carbonate-based electrolytes prove not to be compatible with the sulfur electrode. ► Poor electrochemical performances related to low polysulfide solubility. ► Increase in the discharge capacity using ether solvents with high solvating ability such as PEGDME. ► Evidence of DIOX polymerization during cycling. -- Abstract: The lithium/sulfur (Li/S) battery is a promising electrochemical system that has a high theoretical capacity of 1675 mAh g−1. However, the system suffers from several drawbacks: poor active material conductivity, active material dissolution, and use of the highly reactive lithium metal electrode. In this study, we investigated the electrolyte effects on electrochemical performances of the Li/S cell, by acting on the solvent composition. As conventional carbonate-based electrolytes turned out to be unusable in Li/S cells, alternative ether solvents had to be considered. Different kinds of solvent structures were investigated by changing the ether/alkyl moieties ratio to vary the lithium polysulfide solubility. This allowed to point out the importance of the solvent solvation ability on the discharge capacity. As the end of discharge is linked to the positive electrode passivation, an electrolyte having high solvation ability reduces the polysulfide precipitation and delays the positive electrode passivation
[en] After contributions on the national strategy for energetic research, on the relationship between climate change, CO2 emissions and energy systems, and on actions by the CNRS Energy Cell, a first session addressed the issue of energy efficiency in buildings, transports and industry: a necessary multi-scale approach to energy efficiency in industry; decision aid tool for the synthesis and remoulding of networks of flexible heat exchangers; infrared cell for the reactional follow-up of metallic nano-particles; elaboration and study of phase-change materials for innovating constructions for thermal comfort; the Academy's opinion on energy technologies. The second session gathers contributions on hydrogen and fuel cells: relationship between hydrogen, fuel cell and sustainable development; new exchanger reactors for hydrogen production by reforming; materials for hydrogen reversible storage at room temperature; scientific challenges and technological deadlocks for hydrogen-energy systems. The third session addressed energy storage and distribution: the smart building integrated into smart grids; redox flow batteries in the case of vanadium; BALIPA or lithium-ion battery with photo-aided charge. Several projects are presented under the form of posters.