Juliette SAINT - Academia.edu (original) (raw)
Papers by Juliette SAINT
First of all, I would like to express my sincere gratitude to my advisor, Professor Heike Gabrisc... more First of all, I would like to express my sincere gratitude to my advisor, Professor Heike Gabrisch. Heike’s enthusiasm and insights were constant inspirations during my course of study. I am also very grateful for her friendly, patient guidance and assistance and her support. My gratitude also goes to the members of my committee, Professor Weilie Zhou, Professor John B. Wiley for their helpful comments and constructive suggestions. I would like to give my special thanks to Professor Gerbrand Ceder in Massachusetts
L'invention a pour objet un materiau anodique de type composite silicium-carbone, pour accumu... more L'invention a pour objet un materiau anodique de type composite silicium-carbone, pour accumulateur au lithium, presentant une capacite massique elevee et une bonne stabilite en cyclage. Ce materiau est obtenu par un procede de preparation comprenant les etapes consistant a :a) fournir une poudre de silicium obtenue par la technique de depot chimique en phase vapeur assiste par plasma (PECVD) ou par laser CO2, la taille des particules de silicium etant inferieure a 100 nm ;b) melanger la poudre de silicium a un polymere carbone ; etc) effectuer la pyrolyse du melange.L'invention propose egalement un accumulateur au lithium comprenant au moins une anode dont la matiere active comprend le materiau nanocomposite produit par ce procede.
The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesize... more The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesized from precursors made by glycine-nitrate combustion (GNC) and solid-state synthesis methods (SS) are examined in this paper. The highest specific capacities in lithium cells are obtained for SS-Li x MnO 2 electrodes at low current densities, but GNC-Li x Ti 0.11 Mn 0.89 O 2 electrodes show the best high rate performance. These results can be explained by changes in the voltage characteristics and differences in the particle morphologies induced by the Ti-substitution and synthesis method. Ti-substitution also results in a decrease in the electronic conductivity, but greatly improves the thermal properties and imparts dissolution resistance to the electrode. For these reasons, it is preferable to use Li x Ti 0.11 MnO 0.89 O 2 in lithium battery configurations rather than Li x MnO 2. Suggestions for improving the electrochemical performance of the Ti-substituted variant are given based on the results described herein.
ECS Meeting Abstracts, 2007
ECS Meeting Abstracts, 2008
not Available.
Http Www Theses Fr, 2005
La mise au point d’un materiau d’electrode negative pour accumulateurs au lithium pouvant supplan... more La mise au point d’un materiau d’electrode negative pour accumulateurs au lithium pouvant supplanter le graphite, en vue de nouvelles applications comme le vehicule electrique, genere un nombre croissant d’etudes de par le monde. Parmi les pretendants, les alliages a base de lithium (LixMy) sont les plus prometteurs et de nombreuses voies sont a explorer. Les alliages LixSiy presentent la plus forte capacite electrochimique (4200 mAh/g; plus de dix fois celle du graphite) mais leur tres mauvaise reversibilite empeche leur utilisation. Pour pallier ce probleme, differentes approches ont ete developpees parmi lesquelles l’utilisation de composites Si/C semble la plus efficace et a ete poursuivie dans cette etude. En parallele, d’autres systemes binaires tels que Li-Ga et Li-B, jusqu’alors negliges en depit de potentialites interessantes, ont fait l’objet d’une etude approfondie dans ce travail. La mecanosynthese s’est averee etre une technique parfaitement adaptee pour l’elaboration d’alliages LixGay mais tout a fait inappropriee pour celle des composes LixBy. Pour chacun de ces systemes, tres riches d’un point de vue structural, nous avons mis en evidence des transformations parfaitement reversibles dans un domaine de stœchiometrie restreint, phenomene inhabituel pour des alliages/intermetalliques a base de lithium. Neanmoins, l’exploitation des fortes capacites des composes LixGay et LixBy reste cependant limitee par un effritement de l’electrode qui affecte la reversibilite des processus electrochimiques. Nous avons egalement mis en evidence que les performances electrochimiques des composites Si/C obtenus par pyrolyse de melanges Si nanometrique/polychlorure de vinyl etaient nettement superieures a celles du silicium seul. Il n’en demeure pas moins qu’il reste un travail important d’optimisation a realiser en raison d’une grande sensibilite des composites vis a�� vis du broyage. Toutefois, nous avons demontre, grâce aux spectroscopies Raman et EELS, le role primordial de l’interface Si-C et notamment de la pression exercee par la matrice de carbone sur les particules de silicium qui permet de maintenir une capacite superieure a 1000 mAh/g sur plusieurs dizaines de cycles.
Solid State Ionics, 2005
Li 2 Ga 7 , LiGa, and Li 2 Ga alloys were synthesized by ball-milling, from Li powders and Ga ing... more Li 2 Ga 7 , LiGa, and Li 2 Ga alloys were synthesized by ball-milling, from Li powders and Ga ingots, and characterized for their structural and electrochemical performances. Special attention was devoted to the Li-driven 3D(LiGa) ! 2D(Li 2 Ga) transformation that occurs at 0.02 V vs. Li + /Li on discharge. By in situ X-ray measurements we demonstrated that such a transition, accompanied by a 60% volume change, is initially nicely reversible, but rapidly becomes detrimental to the cell capacity retention upon cycling. Bypassing the (LiGa) ! (Li 2 Ga) transition was shown to considerably increase our cell performances, with capacity retention curves levelling at 300 mA h/g for at least 20 cycles.
Journal of Power Sources, 2007
Computational and experimental work directed at exploring the electrochemical properties of tetra... more Computational and experimental work directed at exploring the electrochemical properties of tetrahedrally coordinated Mn in the +5 oxidation state is presented. Specific capacities of nearly 700 mAh/g are predicted for the redox processes of Li x MnO 4 complexes based on two two-phase reactions. One is topotactic extraction of Li from Li 3 MnO 4 to form LiMnO 4 and the second is topotactic insertion of Li into Li 3 MnO 4 to form Li 5 MnO 4. In experiments, it is found that the redox behavior of Li 3 MnO 4 is complicated by disproportionation of Mn 5+ in solution to form Mn 4+ and Mn 7+ and by other irreversible processes; although an initial capacity of about 275 mAh/g in lithium cells was achieved. Strategies based on structural considerations to improve the electrochemical properties of MnO 4 ncomplexes are given.
![Research paper thumbnail of Compatibility of Li[sub x]Ti[sub y]Mn[sub 1−y]O[sub 2] (y=0, 0.11) Electrode Materials with Pyrrolidinium-Based Ionic Liquid Electrolyte Systems](https://attachments.academia-assets.com/92960716/thumbnails/1.jpg)
](Journal of The Electrochemical Society, 2008
The possibility of using electrolyte systems based on room-temperature ionic liquids ͑RTILs͒ in l... more The possibility of using electrolyte systems based on room-temperature ionic liquids ͑RTILs͒ in lithium-battery configurations is discussed. The nonflammability and wide potential windows of RTIL-based systems are attractive potential advantages, which may ultimately lead to the development of safer, higher energy density devices than those that are currently available. An evaluation of the compatibility of these electrolyte systems with candidate electrodes is critical for further progress. A comparison of the electrochemical behavior of Li/RTIL/Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 cells with those containing conventional carbonate solutions is presented and discussed in terms of the physical properties of two RTIL systems and their interactions with the cathodes. Strategies to improve performance and minimize cathode dissolution are presented.
![Research paper thumbnail of FTIR and Raman Study of the Li[sub x]Ti[sub y]Mn[sub 1−y]O[sub 2] (y=0, 0.11) Cathodes in Methylpropyl Pyrrolidinium Bis(fluoro-sulfonyl)imide, LiTFSI Electrolyte](https://attachments.academia-assets.com/92960529/thumbnails/1.jpg)
](Journal of The Electrochemical Society, 2009
This work demonstrates the protective effect of partial titanium substitution in Li x Ti 0.11 Mn ... more This work demonstrates the protective effect of partial titanium substitution in Li x Ti 0.11 Mn 0.89 O 2 against surface decomposition in room temperature ionic liquid (RTILs) cells. Raman microscopy and reflectance FTIR spectroscopy were used to analyze electrodes recovered from cycled Li/Li x Ti y Mn 1-y O 2 (y = 0, 0.11) cells containing the 0.5 mol/kg LiTFSI in P 13 FSI RTIL electrolyte. Raman and FTIR spectra of cycled Li x MnO 2 cathodes showed many distinct bands that can be attributed to both the electrolyte and electrode decomposition products. The thickness of the amorphous porous layer on the Li x MnO 2 cathode increased during cycling. The surface degradation of Li x MnO 2 and precipitation of electrolyte decomposition products contributed to the film growth. Improved cycling behavior was observed in cells containing Li x Ti 0.11 Mn 0.89 O 2 , yet Raman spectroscopy also showed possible surface degradation. The FTIR spectra of cycled Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 cathodes displayed bands characteristic for LiSO 3 CF 3 and Li 2 NSO 2 CF 3 , which originate from the reaction of the TFSI anion with traces of water present in the cell.
Comptes Rendus Chimie, 2005
A staggering development over the last few years within the field of electrode materials, whateve... more A staggering development over the last few years within the field of electrode materials, whatever battery technology considered, has been the use of mechanochemistry to optimize materials’ electroactivity. This low temperature physical synthesis technique, which does not require solvent, is critical not only to control powder morphology, crystallinity and state of division, but also to enable the stabilization of metastable
Chemistry of Materials, 2008
The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesize... more The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesized from precursors made by glycine-nitrate combustion (GNC) and solid-state synthesis methods (SS) are examined in this paper. The highest specific capacities in lithium cells are obtained for SS-Li x MnO 2 electrodes at low current densities, but GNC-Li x Ti 0.11 Mn 0.89 O 2 electrodes show the best high rate performance. These results can be explained by changes in the voltage characteristics and differences in the particle morphologies induced by the Ti-substitution and synthesis method. Ti-substitution also results in a decrease in the electronic conductivity, but greatly improves the thermal properties and imparts dissolution resistance to the electrode. For these reasons, it is preferable to use Li x Ti 0.11 MnO 0.89 O 2 in lithium battery configurations rather than Li x MnO 2. Suggestions for improving the electrochemical performance of the Ti-substituted variant are given based on the results described herein.
Chemistry of Materials, 2004
Stable (c) and metastable (h) forms of Mg 2 Sn were prepared as crystallized phases by ball-milli... more Stable (c) and metastable (h) forms of Mg 2 Sn were prepared as crystallized phases by ball-milling of elemental powders. Through in situ X-ray diffraction measurements, we deduced the reactivity mechanisms of c-Mg 2 Sn toward lithium. It entails first a monophasic insertion of about one lithium per formula unit into the fcc Sn framework without extrusion of either Mg or Sn, then a biphasic process leading to the formation of cubic Li 2 MgSn concomitant with a progressive expulsion of Mg, and finally the formation of Li-Mg solidsolution alloys. Upon charging, the poor reversibility of the alloying reaction of Li with Mg leads to a deficit in free Mg, resulting in the formation of a Mg 2 Sn + Sn mixture, and accounting for the poor cyclability of Mg 2 Sn/Li cells over the 0.0-1.5 V voltage window. Limiting the cycling to the monophasic process was shown to improve the cycling behavior. Finally, we found that the electrochemical reaction of h-Mg 2 Sn with Li leads to the same Li 2 MgSn intermediate and the same subsequent sequence of transformations, resulting in similarly poor capacity retention upon cycling.
Advanced Functional Materials, 2007
First of all, I would like to express my sincere gratitude to my advisor, Professor Heike Gabrisc... more First of all, I would like to express my sincere gratitude to my advisor, Professor Heike Gabrisch. Heike’s enthusiasm and insights were constant inspirations during my course of study. I am also very grateful for her friendly, patient guidance and assistance and her support. My gratitude also goes to the members of my committee, Professor Weilie Zhou, Professor John B. Wiley for their helpful comments and constructive suggestions. I would like to give my special thanks to Professor Gerbrand Ceder in Massachusetts
L'invention a pour objet un materiau anodique de type composite silicium-carbone, pour accumu... more L'invention a pour objet un materiau anodique de type composite silicium-carbone, pour accumulateur au lithium, presentant une capacite massique elevee et une bonne stabilite en cyclage. Ce materiau est obtenu par un procede de preparation comprenant les etapes consistant a :a) fournir une poudre de silicium obtenue par la technique de depot chimique en phase vapeur assiste par plasma (PECVD) ou par laser CO2, la taille des particules de silicium etant inferieure a 100 nm ;b) melanger la poudre de silicium a un polymere carbone ; etc) effectuer la pyrolyse du melange.L'invention propose egalement un accumulateur au lithium comprenant au moins une anode dont la matiere active comprend le materiau nanocomposite produit par ce procede.
The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesize... more The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesized from precursors made by glycine-nitrate combustion (GNC) and solid-state synthesis methods (SS) are examined in this paper. The highest specific capacities in lithium cells are obtained for SS-Li x MnO 2 electrodes at low current densities, but GNC-Li x Ti 0.11 Mn 0.89 O 2 electrodes show the best high rate performance. These results can be explained by changes in the voltage characteristics and differences in the particle morphologies induced by the Ti-substitution and synthesis method. Ti-substitution also results in a decrease in the electronic conductivity, but greatly improves the thermal properties and imparts dissolution resistance to the electrode. For these reasons, it is preferable to use Li x Ti 0.11 MnO 0.89 O 2 in lithium battery configurations rather than Li x MnO 2. Suggestions for improving the electrochemical performance of the Ti-substituted variant are given based on the results described herein.
ECS Meeting Abstracts, 2007
ECS Meeting Abstracts, 2008
not Available.
Http Www Theses Fr, 2005
La mise au point d’un materiau d’electrode negative pour accumulateurs au lithium pouvant supplan... more La mise au point d’un materiau d’electrode negative pour accumulateurs au lithium pouvant supplanter le graphite, en vue de nouvelles applications comme le vehicule electrique, genere un nombre croissant d’etudes de par le monde. Parmi les pretendants, les alliages a base de lithium (LixMy) sont les plus prometteurs et de nombreuses voies sont a explorer. Les alliages LixSiy presentent la plus forte capacite electrochimique (4200 mAh/g; plus de dix fois celle du graphite) mais leur tres mauvaise reversibilite empeche leur utilisation. Pour pallier ce probleme, differentes approches ont ete developpees parmi lesquelles l’utilisation de composites Si/C semble la plus efficace et a ete poursuivie dans cette etude. En parallele, d’autres systemes binaires tels que Li-Ga et Li-B, jusqu’alors negliges en depit de potentialites interessantes, ont fait l’objet d’une etude approfondie dans ce travail. La mecanosynthese s’est averee etre une technique parfaitement adaptee pour l’elaboration d’alliages LixGay mais tout a fait inappropriee pour celle des composes LixBy. Pour chacun de ces systemes, tres riches d’un point de vue structural, nous avons mis en evidence des transformations parfaitement reversibles dans un domaine de stœchiometrie restreint, phenomene inhabituel pour des alliages/intermetalliques a base de lithium. Neanmoins, l’exploitation des fortes capacites des composes LixGay et LixBy reste cependant limitee par un effritement de l’electrode qui affecte la reversibilite des processus electrochimiques. Nous avons egalement mis en evidence que les performances electrochimiques des composites Si/C obtenus par pyrolyse de melanges Si nanometrique/polychlorure de vinyl etaient nettement superieures a celles du silicium seul. Il n’en demeure pas moins qu’il reste un travail important d’optimisation a realiser en raison d’une grande sensibilite des composites vis a�� vis du broyage. Toutefois, nous avons demontre, grâce aux spectroscopies Raman et EELS, le role primordial de l’interface Si-C et notamment de la pression exercee par la matrice de carbone sur les particules de silicium qui permet de maintenir une capacite superieure a 1000 mAh/g sur plusieurs dizaines de cycles.
Solid State Ionics, 2005
Li 2 Ga 7 , LiGa, and Li 2 Ga alloys were synthesized by ball-milling, from Li powders and Ga ing... more Li 2 Ga 7 , LiGa, and Li 2 Ga alloys were synthesized by ball-milling, from Li powders and Ga ingots, and characterized for their structural and electrochemical performances. Special attention was devoted to the Li-driven 3D(LiGa) ! 2D(Li 2 Ga) transformation that occurs at 0.02 V vs. Li + /Li on discharge. By in situ X-ray measurements we demonstrated that such a transition, accompanied by a 60% volume change, is initially nicely reversible, but rapidly becomes detrimental to the cell capacity retention upon cycling. Bypassing the (LiGa) ! (Li 2 Ga) transition was shown to considerably increase our cell performances, with capacity retention curves levelling at 300 mA h/g for at least 20 cycles.
Journal of Power Sources, 2007
Computational and experimental work directed at exploring the electrochemical properties of tetra... more Computational and experimental work directed at exploring the electrochemical properties of tetrahedrally coordinated Mn in the +5 oxidation state is presented. Specific capacities of nearly 700 mAh/g are predicted for the redox processes of Li x MnO 4 complexes based on two two-phase reactions. One is topotactic extraction of Li from Li 3 MnO 4 to form LiMnO 4 and the second is topotactic insertion of Li into Li 3 MnO 4 to form Li 5 MnO 4. In experiments, it is found that the redox behavior of Li 3 MnO 4 is complicated by disproportionation of Mn 5+ in solution to form Mn 4+ and Mn 7+ and by other irreversible processes; although an initial capacity of about 275 mAh/g in lithium cells was achieved. Strategies based on structural considerations to improve the electrochemical properties of MnO 4 ncomplexes are given.
Journal of The Electrochemical Society, 2008
The possibility of using electrolyte systems based on room-temperature ionic liquids ͑RTILs͒ in l... more The possibility of using electrolyte systems based on room-temperature ionic liquids ͑RTILs͒ in lithium-battery configurations is discussed. The nonflammability and wide potential windows of RTIL-based systems are attractive potential advantages, which may ultimately lead to the development of safer, higher energy density devices than those that are currently available. An evaluation of the compatibility of these electrolyte systems with candidate electrodes is critical for further progress. A comparison of the electrochemical behavior of Li/RTIL/Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 cells with those containing conventional carbonate solutions is presented and discussed in terms of the physical properties of two RTIL systems and their interactions with the cathodes. Strategies to improve performance and minimize cathode dissolution are presented.
Journal of The Electrochemical Society, 2009
This work demonstrates the protective effect of partial titanium substitution in Li x Ti 0.11 Mn ... more This work demonstrates the protective effect of partial titanium substitution in Li x Ti 0.11 Mn 0.89 O 2 against surface decomposition in room temperature ionic liquid (RTILs) cells. Raman microscopy and reflectance FTIR spectroscopy were used to analyze electrodes recovered from cycled Li/Li x Ti y Mn 1-y O 2 (y = 0, 0.11) cells containing the 0.5 mol/kg LiTFSI in P 13 FSI RTIL electrolyte. Raman and FTIR spectra of cycled Li x MnO 2 cathodes showed many distinct bands that can be attributed to both the electrolyte and electrode decomposition products. The thickness of the amorphous porous layer on the Li x MnO 2 cathode increased during cycling. The surface degradation of Li x MnO 2 and precipitation of electrolyte decomposition products contributed to the film growth. Improved cycling behavior was observed in cells containing Li x Ti 0.11 Mn 0.89 O 2 , yet Raman spectroscopy also showed possible surface degradation. The FTIR spectra of cycled Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 cathodes displayed bands characteristic for LiSO 3 CF 3 and Li 2 NSO 2 CF 3 , which originate from the reaction of the TFSI anion with traces of water present in the cell.
Comptes Rendus Chimie, 2005
A staggering development over the last few years within the field of electrode materials, whateve... more A staggering development over the last few years within the field of electrode materials, whatever battery technology considered, has been the use of mechanochemistry to optimize materials’ electroactivity. This low temperature physical synthesis technique, which does not require solvent, is critical not only to control powder morphology, crystallinity and state of division, but also to enable the stabilization of metastable
Chemistry of Materials, 2008
The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesize... more The physical and electrochemical properties of Li x MnO 2 and Li x Ti 0.11 Mn 0.89 O 2 synthesized from precursors made by glycine-nitrate combustion (GNC) and solid-state synthesis methods (SS) are examined in this paper. The highest specific capacities in lithium cells are obtained for SS-Li x MnO 2 electrodes at low current densities, but GNC-Li x Ti 0.11 Mn 0.89 O 2 electrodes show the best high rate performance. These results can be explained by changes in the voltage characteristics and differences in the particle morphologies induced by the Ti-substitution and synthesis method. Ti-substitution also results in a decrease in the electronic conductivity, but greatly improves the thermal properties and imparts dissolution resistance to the electrode. For these reasons, it is preferable to use Li x Ti 0.11 MnO 0.89 O 2 in lithium battery configurations rather than Li x MnO 2. Suggestions for improving the electrochemical performance of the Ti-substituted variant are given based on the results described herein.
Chemistry of Materials, 2004
Stable (c) and metastable (h) forms of Mg 2 Sn were prepared as crystallized phases by ball-milli... more Stable (c) and metastable (h) forms of Mg 2 Sn were prepared as crystallized phases by ball-milling of elemental powders. Through in situ X-ray diffraction measurements, we deduced the reactivity mechanisms of c-Mg 2 Sn toward lithium. It entails first a monophasic insertion of about one lithium per formula unit into the fcc Sn framework without extrusion of either Mg or Sn, then a biphasic process leading to the formation of cubic Li 2 MgSn concomitant with a progressive expulsion of Mg, and finally the formation of Li-Mg solidsolution alloys. Upon charging, the poor reversibility of the alloying reaction of Li with Mg leads to a deficit in free Mg, resulting in the formation of a Mg 2 Sn + Sn mixture, and accounting for the poor cyclability of Mg 2 Sn/Li cells over the 0.0-1.5 V voltage window. Limiting the cycling to the monophasic process was shown to improve the cycling behavior. Finally, we found that the electrochemical reaction of h-Mg 2 Sn with Li leads to the same Li 2 MgSn intermediate and the same subsequent sequence of transformations, resulting in similarly poor capacity retention upon cycling.
Advanced Functional Materials, 2007