Papers by daniel lemordant
Journal of Chemical & Engineering Data, Jul 23, 2019
Battery Energy
Silicon (Si)‐based anodes have long been viewed as the next promising solution to improve the per... more Silicon (Si)‐based anodes have long been viewed as the next promising solution to improve the performance of modern lithium‐ion batteries. However, the poor cycling stability of Si‐based anodes impedes their application and calls for solutions for further improvements. In the present work, the incorporation of phosphate groups on the surface of an amorphous Si‐carbon composite (a‐Si/C) has been achieved by a hydrothermal reaction using phosphoric acid and sodium dihydrogen phosphate at pH = 2. Different levels of the surface P‐doping have been realized using reaction times (2, 4, and 8 h) at two different phosphate concentrations. The presence of phosphate groups on the particle's surface has been confirmed by energy‐dispersive X‐ray, infrared, and Raman spectroscopy. The cycling stability of the P‐treated a‐Si/C composites has been significantly improved when using lithium bis(trifluoromethanesulfonyl)imide as a salt in ether‐based solvents mixture compared to a conventional el...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
ECS Meeting Abstracts, 2014
One of the most important components in electrochemical storage devices (batteries and supercapac... more One of the most important components in electrochemical storage devices (batteries and supercapacitors) is undoubtedly the electrolyte. The basic function of any electrolyte in these systems is the transport of ions between the positive and negative electrodes. In addition, electrochemical reactions occurring at each electrode/electrolyte interface are the origin of the current generated by storage devices. In other words, performances (capacity, power, efficiency and energy) of electrochemical storage devices are strongly related to the electrolyte properties, as well as, to the affinity for the electrolyte to selected electrode materials. Indeed, the formulation of electrolyte presenting good properties, such as high ionic conductivity and low viscosity, is then required to enhance the charge transfer reaction at electrode/electrolyte interface (e.g. charge accumulation in the case of Electrochemical Double Layer Capacitor, EDLC). For practical and safety considerations, the formu...
2018 6th International Renewable and Sustainable Energy Conference (IRSEC), 2018
The Journal of Physical Chemistry C, 2013
ABSTRACT Previous work demonstrated that TiSnSb is a promising negative electrode material with h... more ABSTRACT Previous work demonstrated that TiSnSb is a promising negative electrode material with high electrochemical performance due to the benefit of conversion type reaction vs Li. At low potentials, the volumetric change upon cycling entails electrolyte degradation which remains the main factor limiting the cycling life of TiSnSb based electrodes. To further improve the understanding of the formation of a solid electrolyte interphase (SEI) in the presence of alkyl carbonate based electrolytes and of its evolution upon cycling, powerful surface characterization techniques are combined for studying the electrode/electrolyte interface of TiSnSb composite electrodes. Electrochemical impedance spectroscopy is used for monitoring in situ the resistivity of the SEI, while XPS and solid state NMR spectroscopy can provide useful information on the SEI chemical composition and its evolution during cycling.
The Journal of Physical Chemistry B, 2006
X-ray photoelectron valence spectra of lithium salts LiBF4, LiPF6, LiTFSI, and LiBETI have been r... more X-ray photoelectron valence spectra of lithium salts LiBF4, LiPF6, LiTFSI, and LiBETI have been recorded and analyzed by means of density functional theory (DFT) calculations, with good agreement between experimental and calculated spectra. The results of this study are used to characterize electrode/electrolyte interfaces of graphite negative electrodes in Li-ion batteries using organic carbonate electrolytes containing LiTFSI or LiBETI salts. By a combined X-ray photoelectron spectroscopy (XPS) core peaks/valence analysis, we identify the main constituents of the interface. Differences in the surface layers' composition can be evidenced, depending on whether LiTFSI or LiBETI is used as the lithium salt.
Surface and Interface Analysis, 2005
ABSTRACT The formation of a passivation film (solid electrolyte interphase, SEI) at the surface o... more ABSTRACT The formation of a passivation film (solid electrolyte interphase, SEI) at the surface of the negative electrode of full LiCoO2/graphite lithium-ion cells using LiPF6 (1M) in carbonate solvents as electrolyte was investigated by means of x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The analyses were carried out at different potentials of the first and the fifth cycles, showing the potential-dependent character of the surface-film species formation. These species were mainly identified as Li2CO3 up to 3.8 V and LiF up to 4.2 V. This study shows the formation of the SEI during charging and its partial dissolution during discharge. Copyright © 2005 John Wiley & Sons, Ltd.
Journal of Power Sources, 2006
3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (... more 3-Methyl-2-oxazolidinone (MeOx) has been mixed to ethylene carbonate (EC) or dimethyl carbonate (DMC) in presence of lithium tetrafluoroborate (LiBF4) or lithium hexafluorophosphate (LiPF6) for use as electrolyte in lithium batteries. The optimized electrolytes in term of conductivity and viscosity are MeOx:EC, x(MeOx)=0.5 and MeOx:DMC, x(MeOx)=0.4 in presence of LiBF4 (1M) or LiPF6 (1M). MeOx:EC electrolytes have a better thermal stability
Journal of Membrane Science, 1992
Abstract To estimate the pore size of ultrafiltration (UF) membranes, a method using micellar fil... more Abstract To estimate the pore size of ultrafiltration (UF) membranes, a method using micellar filtration is proposed. Lithium dodecylsulfate (LiDS) forms micellar aggregates of spherical shape even at high ionic strength. The surfactant rejection rate of micellar solutions show a remarkable dependence upon the ionic strength (LiCl: 0 to 1 mol/l). From the size dependence of the aggregates on the ionic strength (micelle radius plus ionic atmosphere thickness) and the rejection rate of the micellized surfactant, we determine the mean pore diameter of a 40 kDa UF polysulfone membrane. Obtained results are in accordance with the hindered transport theory through capillaries: small LiDS micelles behave like neutral hard spheres in the presence of excess salt. Microscopic examination of the membrane surface shows a quasi-uniform distribution of pores. Pore surface density can be easily determined, but, due to gold aggregates at the pores entrance, the average mean diameter obtained by this method appears to be too large.
Electrochimica Acta, 2013
The Journal of Physical Chemistry, 2021
Journal of The Electrochemical Society, 2017
International audienc
Journal de Chimie Physique, 1983
RESUME Les solubilités de différents sels de l'acide picrique (picrates de potassium, de tétraéth... more RESUME Les solubilités de différents sels de l'acide picrique (picrates de potassium, de tétraéthylammonium, de butylammonium, et de pyridiniums diversement substitués) ont été mesurées dans quelques solvants purs de basse constante diélectrique et dans les mélanges binaires du dioxanne avec le benzène, le cyclohexane et le tétrachlorométhane à la température de 293 K. En l'absence de dimérisation ou de formation d agrégats d ordre supérieur, les enthalpies libres de transfert des picrates du dioxanne aux autres milieux mixtes peuvent être déterminées et corrélées à la variable de solvant F (S) précédemment introduite; de plus, les grandeurs de transfert ainsi obtenues sont en accord avec celles qui peuvent être déduites de l'étude des réactions de transfert du proton entre l'acide picrique et les mêmes bases (pyridines substituées). D'autres applications sont envisagées : il apparaît que l'effet du solvant sur les constantes d'équi libre relatives è la formation de complexes non chargés peut être prévu à partir des valeurs du paramètre f (S).
The Journal of Physical Chemistry C, 2021
The isotopic Li-ion exchange occurring in the solid electrolyte interphase (SEI) of a graphite el... more The isotopic Li-ion exchange occurring in the solid electrolyte interphase (SEI) of a graphite electrode is studied by time of flight secondary ions mass spectrometry analysis (ToF-SIMS) of Li isot...
Journal of Power Sources, 2012
Acetonitrile (ACN) is widely used as solvent for electrolyte in supercapacitors in the presence o... more Acetonitrile (ACN) is widely used as solvent for electrolyte in supercapacitors in the presence of tetraethylammonium tetrafluoroborate (Et 4 N + BF 4 −). The main advantage is its low viscosity leading to high conductivities in the presence of salts, but unfortunately it is too volatile and flammable. In order to reduce both the flammability and the volatility of ACN based electrolytes, aprotic room temperature ionic liquids, RTILs, are added either to ACN or to ␥-butyrolactone (GBL), another typical solvent for the electrochemical devices. The effects of these molten salts on ACN and GBL are investigated with the aim of improving the supercapacitors security. Flammability tests are performed on these electrolytes to study their security. The results show that mixtures GBL based are more flammable than those ACN based, in spite of a higher boiling point for pure GBL because of the presence of solvates. DSC measurements over ambient temperature strengthen these flammability results. To complete this study, physical and electrochemical characteristics (density, viscosity, conductivity, linear and cyclic voltamperometry) are investigated. The results indicate that no degradation of the electrochemical performances appears with RTIL/ACN mixture by comparison with the standard electrolyte (ACN + 1 M Et 4 N + BF 4 −).
Journal de Chimie Physique et de Physico-Chimie Biologique, 1998
Des électrolytes-gels ont été réalisés par photopolymérisation du tétra(éthylène glycol) diacryla... more Des électrolytes-gels ont été réalisés par photopolymérisation du tétra(éthylène glycol) diacrylate (TEG). Le plastifiant est un solvant ternaire : carbonate dîéthylène (EC), carbonate de propylene (PC), 2-méthoxyéthyléther (diglyme DG). La conductivité est assurée par l'addition de trifluorométhane sulfonate de lithium (triflate, TL). L'optimisation de la composition a permis d'obtenir un matériau transparent, stable entre-25 et 100°C et d'une conductivité voisine de 5.10" 4 S.cnr 1 à 20°C. Ces propriétés en font des matériaux compatibles avec les systèmes électrochromes. Mots clés: Électrolytes-gels photopolymérisés, systèmes électrochromes.
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Papers by daniel lemordant