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Electrochemical Capacitors (ECs), also known as supercapacitors, have now reached the technical maturity for complementing- and sometimes replacing- batteries in a broad range of applications. Conventional electrolytes based on... more
Electrochemical Capacitors (ECs), also known as supercapacitors, have now reached the technical maturity for complementing- and sometimes replacing- batteries in a broad range of applications. Conventional electrolytes based on acetonitrile or propylene carbonate solvents have been mainly used in combination with ammonium cations and fluoride anions. Designing solid electrolytes for ECs would be of great interest in the aim of solving packaging issues, corrosion, self-discharge or leaks. Moreover these solid electrolytes could be used for flexible supercapacitors applications. Ionogels are quasi-solid electrolyte obtained from the trapping of an IL into a silica scaffold using a sol-gel process. The first part of our work has been devoted to a better understanding of the non-hydrolytic sol-gel mechanisms occurring during the formation of ionogels, using electrochemical impedance spectroscopy. Change of the conductivity of the sol-gel mixture (a Formic acid and Tetraethyl orthosilicate mixture) shows two different time domains. The mixture conductivity is first decreasing drastically during the first 25 minutes of the sol-gel process, assuming to originate from the in-situ generation of water through esterification reaction. In the second time range (t>25 min), the conductivity tends to level off, associated with a series of chemical reactions. More details about this study will be added during the presentation. In a second part of the talk, we will show the electrochemical performance of an supercapacitors cell assembled with activated carbon as active materials and an ionogel electrolyte containing an ionic liquid mixture (1:1 by weight or molar ratio) of N-methyl-N-propylpiperidinium bis(fluorosulfonyl)imide (PIP13FSI) and N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI). Cyclic voltammetries and electrochemical impedance spectroscopy plots in a large temperature range (-40°C to +60°C) will be presented and discussed. The ionogel exhibits a high ionic conductivity over a wide temperature range (from 0.2 mS.cm−1 at −40 °C up to 10 mS.cm−1 at 60 °C). The ionogel-based supercapacitor using two activated carbon electrodes can be operated over 3 V cell voltage window. Moreover this all solid-supercapacitor shows a capacitance up to 90 F.g−1 at room temperature. These encouraging results show the interest of developing such devices, including non-toxic and safer electrolytes, packaging issues and flexible devices development.
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Research Interests: Engineering, Materials Engineering, Condensed Matter Physics, Materials Science, Chemistry, and 15 moreElectrochemistry, Energy, Li, Lithium Ion Battery, Iron, Composite Material, CHEMICAL SCIENCES, In Situ Polymerization, Monomer, Direct methanol fuel cell, Charge transfer, Electrode, Catechol, Meeting Abstracts, and Ion exchange capacity
Processed data from molecular dynamics simulations + corresponding figures<br>
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Un objet de la presente invention concerne un procede et un dispositif bon marche et efficaces pour eliminer les ions d'un milieu electrolytique, par exemple, un dessalement de l'eau. L'invention concerne une cellule adaptee... more
Un objet de la presente invention concerne un procede et un dispositif bon marche et efficaces pour eliminer les ions d'un milieu electrolytique, par exemple, un dessalement de l'eau. L'invention concerne une cellule adaptee pour eliminer les ions d'un milieu electrolytique liquide, comprenant un logement (10) avec : • deux entrees (11) et deux sorties (12), • une membrane poreuse unique (13) conductrice ionique, mais isolante electrique, se trouvant entre les deux entrees et les deux sorties pour constituer deux compartiments, comprenant chacun une des entrees et une des sorties, • deux electrodes, chacune en contact electronique avec un compartiment.
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Flexible power for flexible electronics A challenge for flexible electronics is to couple devices with power sources that are also flexible. Ideally, they could also be processed in a way that is compatible with current microfabrication... more
Flexible power for flexible electronics A challenge for flexible electronics is to couple devices with power sources that are also flexible. Ideally, they could also be processed in a way that is compatible with current microfabrication technologies. Huang et al. deposited a relatively thick layer of TiC on top of an oxide-coated Si film. After chlorination, most, but importantly not all, of the TiC was converted into a porous carbon film that could be turned into an electrochemical capacitor. The carbon films were highly flexible, and the residual TiC acted as a stress buffer with the underlying Si film. The films could be separated from the Si to form free-floating films, with the TiC providing a support layer. Science , this issue p. 691
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Carbon nano-powders (CNP) have been prepared by the electrochemical reduction of molten Li-Na-K carbonates at the eutectic composition (43.5-31.5-25 mol %) at 450 °C. After removing traces of carbonates by washing using aqueous... more
Carbon nano-powders (CNP) have been prepared by the electrochemical reduction of molten Li-Na-K carbonates at the eutectic composition (43.5-31.5-25 mol %) at 450 °C. After removing traces of carbonates by washing using aqueous based-solutions and filtration, the powders are composed of amorphous and graphitized domains, as revealed by XRD, with a low crystallinity. XPS investigations have pointed out the presence of different types of CO bonds with a surface oxygen content of about 6%. Finally Raman spectroscopy measurements have evidenced the presence of graphene, confirming observations by TEM and AFM measurements. The carbon powders prepared in our experimental conditions exhibit high specific surface area (≈1100 m2 g−1) and are characterized by the presence of ultra- and super-microporosity, meso- and macroporosity. The carbon powders were tested in electrochemical capacitors as negative electrode in presence of aqueous or inorganic electrolyte. Capacitance of about 150 F g−1 in aqueous 0.1 M K2SO4 and about 45 F g−1 in 1M NEt4BF4 in acetonitrile have been observed after 10,000 cycles.
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Electrochemical double layer capacitors (EDLCs) are energy storage devices that can complement Li-ion batteries (LiBs) for high power uptake applications[1]. However, EDLCs suffer from limited energy density (about 10Wh/kg compared to 250... more
Electrochemical double layer capacitors (EDLCs) are energy storage devices that can complement Li-ion batteries (LiBs) for high power uptake applications[1]. However, EDLCs suffer from limited energy density (about 10Wh/kg compared to 250 Wh/kg for LiBs). A way to increase the energy density still maintaining high power capability and long cycle life is the next challenge of this technology. An approach to achieve this objective is to increase the voltage window. Nevertheless, using a high voltage window lead to a faster ageing. So, a better understanding of degradation process during the ageing is needed to improve EDLCs storage and their cycle life. In this work, degradation mechanisms at porous carbon electrodes have been investigated in non-aqueous electrolytes, following an ageing protocol previously reported [2]. Electrochemical performances before and after ageing have been compared. Then, post-mortem analyses were performed using various analytical methods. Raman spectroscopy allowed us for better understanding of degradation processes occurring at the carbon/electrolyte interface. Leading to a partial amorphization of the positive porous carbon electrode. The carbon disorder was further correlated with possible degradation mechanisms during ageing to explain the performance decrease. References: [1] P. Simon and Y. Gogotsi, ‘Perspectives for electrochemical capacitors and related devices’, Nature Materials, p. 13, doi: https://doi.org/10.1038/s41563-020-0747-z. [2] Y. Liu, B. Soucaze-Guillous, P.-L. Taberna, and P. Simon, ‘Understanding of carbon-based supercapacitors ageing mechanisms by electrochemical and analytical methods’, Journal of Power Sources, vol. 366., pp. 123-130., 2017, doi: https://doi.org/10.1016/j.jpowsour.2017.08.104. Figure 1
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Physical grafting of 1-nitropyrene (Pyr-NO2) onto carbon onion via in situ reduction of the NO2 group and pyrene polymerization for supercapacitor positive electrode.
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Nanoporous carbon-based supercapacitors store electricity through adsorption of ions from the electrolyte at the surface of the electrodes. Room temperature ionic liquids, which show the largest ion concentrations among organic liquid... more
Nanoporous carbon-based supercapacitors store electricity through adsorption of ions from the electrolyte at the surface of the electrodes. Room temperature ionic liquids, which show the largest ion concentrations among organic liquid electrolytes, should in principle yield larger capacitances. Here, we show by using electrochemical measurements that the capacitance is not significantly affected when switching from a pure ionic liquid to a conventional organic electrolyte using the same ionic species. By performing additional molecular dynamics simulations, we interpret this result as an increasing difficulty of separating ions of opposite charges when they are more concentrated, that is, in the absence of a solvent that screens the Coulombic interactions. The charging mechanism consistently changes with ion concentration, switching from counterion adsorption in the diluted organic electrolyte to ion exchange in the pure ionic liquid. Contrarily to the capacitance, in-pore diffusion...
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Thin films of (TTF)(TCNQ)(TTF= tetrathiafulvalene, TCNQ= tetracyanoquinodimethane) are deposited on Si (001), KBr, and stainless steel conversion coatings (SSCC) using chemical vapor deposition. These films are characterized by IR, XRD,... more
Thin films of (TTF)(TCNQ)(TTF= tetrathiafulvalene, TCNQ= tetracyanoquinodimethane) are deposited on Si (001), KBr, and stainless steel conversion coatings (SSCC) using chemical vapor deposition. These films are characterized by IR, XRD, conductivity measurements, ...
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The spark plasma sintering (SPS) is an emerging process for shaping any type of materials (metals, ceramic, polymers and their composites). The advantage of such a process is to prepare densified ceramic materials in a very short time,... more
The spark plasma sintering (SPS) is an emerging process for shaping any type of materials (metals, ceramic, polymers and their composites). The advantage of such a process is to prepare densified ceramic materials in a very short time, while keeping the materials internal porosity. In the present work, we have used the SPS technique to prepare activated carbon-based electrodes for Electrochemical Double Layer Capacitor applications (EDLC). Self-supported 600 and 300μm-thick electrodes were prepared and characterized using of Electrochemical Impedance Spectroscopy and galvanostatic cycling in a non-aqueous 1.5M NEt4BF4 in acetonitrile electrolyte. Electrochemical performance of these sintered electrodes were found to be in the same range – or even slightly better – than the conventional tape-casted activated carbon electrodes. Although organic liquid electrolyte was used to characterize the electrochemical performance of the sintered electrodes, these results demonstrate that the SPS technique could be worth of interest in the ultimate goal of designing solid-state supercapacitors.