Academic literature on the topic 'Li O Sn'

Lithium-ion batteries (LIBs) are receiving significant attention from both academia and industry as one of the most promising energy storage and conservation devices due to their high energy density and excellent safety. Graphite, the most widely used anode material, with limitations on energy density, can no longer satisfy the requirements proposed by new applications. Therefore, further improvement on the electrochemical performance of anodes has been long pursued, along with the development of new anode materials. Among potential candidates, Si and Sn based anodes are believed to be the most promising. However, the dramatic volume expansion upon Li-intercalation and contraction upon Li de-intercalation cause mechanical instability, and thus cracking of the electrodes. To overcome this issue, many strategies have been explored. Among them the most efficient strategies include introduction of a nanostructure, coupled with a buffering matrix and coating with a protective film. However, although cycling life has been significantly increased using these three strategies, the capacity retention still needs improvement, especially over extensive charge-discharge cycles. In addition, more efforts are still needed to develop new fabrication methods with low costs and high efficiency. To further improve mechanical stability of electrodes, understanding of the failure mechanisms, particularly, the failure mechanisms of Si and Sn nanomaterials is essential. Therefore, some of the key factors including materials fabrication and microstructural changes during cycling are studied in this work. Hollow Si nanospheres have proved to be have a superior electrochemical performance when applied as anode materials. However, most of fabrication methods either involve use of processing methods with low throughput, or expensive temporary templates, which severely prohibits large-scale use of hollow Si spheres. This work designed a new template-free chemical synthesis method with high throughput and simple procedures to fabricate Si hollow spheres with a nanoporous surface. The characterization results showed good crystallinity and a uniform hollow sphere structure. The substructure of pores on the surface provides pathways for electrolyte diffusion and can alleviate the damage by the volume expansion during lithiation. The success of this synthesis method provides valuable inspiration for developing industrial manufacturing method of hollow Si spheres.3D graphene is the most promising matrix that can provide the necessary mechanical support to Sn and Si nanoparticles during lithiation. 2D graphene, however, results in Sn/graphene nanocomposites with a continuous capacity fade during cycling. It is anticipated that this is due to microstructural changes of Sn, however, no studies have been performed to examine the morphology of such cycled anodes. Hence, a new Sn/2D graphene nanocomposite was fabricated via a simple chemical synthesis, in which Sn nanoparticles (20-200 nm) were attached onto the graphene surface. The content of Sn was 10 wt.% and 20 wt.%. These nanopowders were cycled against pure Li-metal and, as in previous studies, a significant capacity decrease occurred during the first several cycles. Transmission and scanning electron microscopy revealed that during long term cycling electrochemical coarsening took place, which resulted in an increased Sn particle size of over 200 nm, which could form clusters that were 1 m. Such clusters result in a poor electrochemical performance since it is difficult for complete lithiation of the Sn to occur. It is hence concluded that the inability of Sn/2D graphene anodes to retain high capacities is due to coarsening that occurs during cycling. In addition to using forms of carbon to buffer the Sn expansion, it has been proposed to alloy Sn with S, which has a low redox potential vs Li⁰/Li⁺. Therefore, another new anode proposed here is that of SnS attached to graphite. The as prepared powders had a flower-like structure of the SnS alloy. Electrochemical cycling and subsequent microstructural analysis showed that after electrochemical cycling this pattern was destroyed and replaced by Sn and SnS nanoparticles. Based on the electron microscopy and XRD analysis, it was concluded that selective leaching of S occurs during lithiation of SnS particles, which results into nano SnS and Sn particles to be distributed throughout the electrolyte or SEI layer, without being able to take part in the electrochemical reactions. This mechanism has not been noted before for SnS anodes and indicates that it may not be possible to retain the initial morphology of SnS alloy during cycling, or the ability of SnS to be active throughout long term cycling. To conclude it should be stated that the goal and novelty of this thesis was (i) the fabrication of new Si, Sn/graphene and SnS/C nanostructures that can be used as anodes in Li-ion batteries and (ii) the documentation of the mechanisms that disrupt the initial structural stability of Sn/2D graphene and SnS/C anodes and result in severe capacity loss during long term cycling (over 100 cycles). These systems are of high interest to the electrochemistry community and battery developers.

Lithium-Ionen-Batterien besitzen ein ausgezeichnetes Potential für die Energiespeicherung. Das derzeit dominierende Anodenmaterial in Lithium-Ionen-Batterien mit einer Energiespeicherkapazität von 339 mAh/g ist Graphit. Als Alternative hierfür bieten sich Lithiumsilicide und Lithiumstannide an. Diese Materialien zeichnen sich durch eine viel größere Speicherkapazität und geringere Selbstentladungspotentiale aus. Für die kommerzielle Anwendung dieser beiden Systeme in Lithium-Ionen-Batterien werden grundlegende und verlässliche thermodynamische Daten benötigt. Derzeit ist die Existenz von sieben Lithiumsiliciden sicher nachgewiesen. Dazu zählen die sechs stabilen Phasen Li17Si4, Li16.42Si4, Li13Si4, Li7Si3, Li12Si7, die Hochdruckphase LiSi und die metastabile Phase Li15Si4. Für die ersten fünf genannten Phasen wurden in der ersten Förderperiode des Schwerpunktprogrammes 1473 Wärmekapazitäten und Standardentropien bestimmt. Bei den Lithiumstanniden sind derzeit sieben Phasen gesichert belegt. Allerdings existiert für keine Phase der Lithiumstannide ein verlässlicher thermodynamischer Basisdatensatz. Aus diesem Grund wurden für die beiden zuletzt genannten Lithiumsilicide (Li15Si4 und LiSi), sowie für die Lithiumstannide Li17Sn4, Li7Sn2, Li13Sn5 und Li7Sn3 die fehlenden thermodynamischen Daten experimentell bestimmt. Die hergestellten Phasen wurden zunächst mittels Röntgenbeugung, thermischer und chemischer Analyse charakterisiert. Ein Schwerpunkt dieser Arbeit lag auf der experimentellen Bestimmung der Wärmekapazitäten in einem Temperaturbereich von 2 K bis zur jeweiligen Zersetzungstemperatur der untersuchten Verbindungen. Hierfür wurden zwei unterschiedliche Kalorimeter verwendet: ein Physical Property Measurement System (Quantum Design) von 2 K bis 300 K und eine DSC 111 (Setaram), beginnend ab 300 K. Die experimentellen Daten konnten mit Messunsicherheiten von 1 % bis 2 % über 20 K und bis zu 20 % unterhalb von 20 K angegeben werden. Die Messungen bei niedrigen Temperaturen erlauben zudem die Berechnung der Standardentropien, sowie die Bestimmung von elektronischen Beiträgen und Gitterschwingungsbeiträgen zur Wärmekapazität. Weiterhin ist Fokus dieser Arbeit die Bestimmung der Standardbildungsenthalpien der Lithiumsilicide und Lithiumstannide auf Basis von Wasserstoffsorptionsmessungen mittels einer Sieverts-Apparatur. Hierfür wurden erstmals Messungen an den Lithiumsiliciden ausgehend von Li17Si4, LiH:Si (Li:Si = 17:4), Li16.42Si4 und LiSi durchgeführt. Für die Lithiumstannide dienten als Ausgangsmaterial Li17Sn4, LiH:Sn (Li:Sn =17:4), sowie Li7Sn2 und LiH:Sn (Li:Sn = 7:2). Die Anwendung des van´t-Hoff-Plots resultierte in Messunsicherheiten von mindestens 10 %. Aus diesem Grund wurde eine alternative Auswertemethode gewählt, bei der die ermittelten Wärmekapazitäten und Standardentropien mit den Gleichgewichtsdrücken aus den Wasserstoffsorptionsmessungen miteinander verknüpft werden. Auf diese Weise konnten Standardbildungsenthalpien für die untersuchten Phasen mit Fehlern kleiner 1 % ermittelt werden. Aus den Ergebnissen dieser Arbeit resultierte ein vollständiger, gesicherter thermodynamischer Datensatz für das System Li-Si. Das berechnete Li-Si-Phasendiagramm ist im sehr guten Einklang mit experimentellen literaturbekannten Daten. Für die Lithiumstannide erfolgte eine Validierung der ermittelten thermodynamischen Werte. Die in dieser Arbeit erzielten Ergebnisse liefern einen wesentlichen Beitrag zur Verbesserung der Datenbasis für thermodynamische Berechnungen und für das Verständnis von Phasensequenzen und Gleichgewichten beim Einsatz von Lithiumsiliciden bzw. Lithiumstanniden als Anodenmaterialien in Lithium-Ionen-Batterien.

Cette thèse a pour sujet l'élaboration et la caractérisation d'anodes nano-architecturées pour des applications en microbatteries Li-ion 3D. Ces électrodes sont basées sur un collecteur de courant nano-structuré, constitué d'un tapis de nano-piliers de cuivre (Ø200nm, L=2µm) alignés verticalement. L'objectif de ce travail a été de montrer les avantages d'une électrode tridimensionnelle en revêtant ce substrat avec différents matériaux actifs en utilisant différentes techniques. De l'étain métallique Sn a pu être déposé par voie électrochimique et forme une couche conforme sur la nanostructure de cuivre. L'électrode obtenue cycle à une capacité de 0,02 mAh. Cm-2 durant plus de 500 cycles, ainsi que 75% de rétention de capacité entre 0,05 et 6C. L'alliage Cu6Sn5 formé à l'interface cuivre/étain a été identifié comme responsable de cette bonne tenue en cyclage. Suite à ce résultat, on a tenté de réaliser un dépôt conforme de matériau actif par électrophorèse (EPD). Dans un premier temps, la faisabilité de ce dépôt a été prouvée en utilisant des nanoparticules de silice SiO2. Ces expériences ont permis de mettre en lumière l'importance de la qualité de la dispersion lors d'un dépôt électrophorétique sur un substrat nanométrique de géométrie complexe. Le dépôt EPD de nanoparticules d'oxyde d'étain SnO2 a ensuite été réalisé. Les tests électrochimiques de l'anode obtenue ont montrés un comportement identique à celui de l'anode de Sn. Ceci confirme l'intérêt de la technique d'EPD pour l'élaboration d'électrodes nanostructurées<br>The aim of this thesis is to elaborate and characterise nano-architectured anodes for Li-ion 3D microbatteries. These electrodes are based on a nanostructured current collector, consisting in vertically-aligned arrays of copper nanopillars (Ø200nm, L=2µm). The goal of this work is to highlight the merits of a 3D electrode prepared by coating this substrate using different techniques and active materials. Tin metal has been deposited by ELD and formed a conformal layer onto the Cu current collectors. The obtained electrode showed a capacity of 0,02 mAh. Cm-2 during more than 500 cycles and a retention capacity of 75 % between 0,05 and 6C. Cu6Sn5 alloy, formed at the Cu/Sn interface was identified as responsible of this good cycling behaviour. Then, we attempted to realise a conformal coating using the electrophoretic deposition technique. In a first step, the feasibility of this deposition was proved using silica nanoparticules. These experiments enlighted the importance of the quality of the dispersion during EPD onto a nanostructured substrate. After this, an EPD depositin of SnO2 nanoparticle has been realised. Electrochemical charactyerisations of the obtained SnO2 anodes show similar behavior as Sn anodes. This confirms the interest of EPD techniques for elaboration nanostructured electrodes

Les composés organostanniques α–aminés chiraux constituent des précurseurs d'anions α-aminés optiquement actifs très utiles en synthèse organique. L'étude méthodologique de la réaction de transmétallation étain-lithium a permis d'en montrer les possibilités et les limites. Des analyses par RMN 1H, 119Sn et 6Li à basse température ont été réalisées afin d'obtenir des informations sur les conformations des composés organostanniques et des organolithiens correspondants en solution. Par la suite, cette réaction de transmétallation a été appliquée à la synthèse d'esters boroniques α–aminés chiraux et de nombreuses difficultés ont été rencontrées pour leur déprotection. Ceci nous a amené à considérer d'autres cas de déprotections très délicates sur des motifs N-sulfonylés et dans ce cas, nous avons pu, par une approche raisonnée du problème, réaliser la déprotection électrochimique de sulfonamides chiraux α-stannylés en évitant à la fois la β-fragmentation et l'épimérisation<br>Enantioenriched α-aminoorganostannanes have emerged as useful reagents for organic synthesis. A methodoligical study about tin-lithium exchange is described, showing possibilities and limits of this reaction. 1H,119Sn and 6Li NMR spectra were recorded at low temperature in order to obtain information on the structure of these compounds. In a second part, this transmetalation reaction was applied to the synthesis of α-aminoboronic esters but numerous difficulties were encountered for their deprotection. Therefore, we consider other cases of very delicate deprotection of N-sulfonylated moeity and, we were able to achieve the electrochemical deprotection of chiral α-stannylated sulfonamides by avoiding both β-fragmentation and epimerization

Critical metals are of growing economic importance for the low carbon sector but are susceptible to resource restrictions and have no viable substitutes in their applications. In this study, 134 samples of the Cornubian Batholith, SW England, with associated early Permian mafic and ultramafic rocks were sampled and analysed by ICP-MS and XRF for their major, trace and critical metal (Li, Be, Ga, Ge, Nb, Ta, In, Sb, W and Bi) abundance. The mineral chemistry of feldspars, micas, tourmaline, topaz and cordierite was determined for 8 samples by EPMA and LA-ICP-MS. The Cornubian Batholith is a peraluminous, composite pluton intruded into Devonian and Carboniferous metasedimentary and volcanic rocks. Geochemical fractionation trends recorded by whole rock geochemistry and mineral chemistry permit trace element modelling of two distinct fractional crystallisation series, biotite-muscovite (>282 Ma) and biotite-tourmaline (<282 Ma). The biotite-muscovite granites formed through muscovite and minor biotite dehydration melting of a metagreywacke source at moderate temperatures and pressures. Fractionation of an assemblage dominated by feldspars and biotite, enriched muscovite granites in Li (average 340 ppm), Be (13 ppm), Nb (16 ppm), Ta (3.7 ppm), In (77 ppb), Sn (17 ppm), W (12 ppm) and Bi (2.6 ppm) and are spatially associated with greisen style Sn-W mineralisation. Muscovite is the major host of In, Sn and W, and as muscovite is late-stage / subsolidus this implies these metals are highly incompatible in magmatic minerals and likely to partition into fluids exsolving from evolved muscovite granites. The biotite-tourmaline granites formed through higher-T melting than the first suite due to underplating of the region by mantle-derived melts during tectonic extension. Fractionation of feldspars, biotite and cordierite enriched Li (average 525 ppm), Ga (28 ppm), In (122 ppb), Sn (14 ppm), Nb (30 ppm), Ta (5.5 ppm), W (7.1 ppm) and Bi (2.7 ppm) in the tourmaline granites with retention of Be in the biotite granite due to partitioning of Be into cordierite. Distribution of Nb and Ta is controlled by accessory phases such as columbite within the evolved tourmaline granites, promoting disseminated Nb and Ta mineralisation. Lithium, In, Sn and W are hosted in biotite group micas which may prove favourable for breakdown on ingress of hydrothermal fluids and partitioning of the critical metals into mineralising fluids emanating from evolved tourmaline granites. Topaz granites are analogues of Rare Metal Granite described in France and Germany. They contain albite, polylithionite and topaz as major minerals and show differing trends on major and trace element plots relative to the other two granite series. These granites are enriched in Li (average 1363 ppm), Ga (38 ppm), Sn (21 ppm), W (24 ppm), Nb (52 ppm) and Ta (15 ppm) and formed through partial melting of a biotite-rich residue left after melting that formed early biotite granites.

A jazida do granito Madeira, associada à fácies albita granito, é um depósito de classe mundial com minério disseminado de Sn, Nb, Ta e F (Y, ETR, Li, U, Th) e, em sua parte central, contém um depósito de criolita maciça com 10 Mt (teor de 38% de Na3AlF6). O objetivo do trabalho foi compreender que contexto geológico permitiu a formação desta associação rocha-minério única no mundo. Para tanto, foram efetuados estudos isotópicos (Sm-Nd, Rb-Sr e Pb-Pb) e estudos tectônicos, enfocando o granito Madeira, seus correlatos e as rochas regionais. Durante uma primeira fase extensional, formaram-se as rochas vulcânicas do Grupo Iricoumé (1.890 a 1881 Ma), constituindo um complexo de caldeiras, e os corpos graníticos associados da Suíte Intrusiva Mapuera, ambos gerados a partir de fontes mantélicas. Concomitantemente aos estágios finais do vulcanismo iniciou-se a sedimentação na bacia Urupi (possivelmente um rift), acompanhada por um segundo pico de vulcanismo há 1.825 Ma. Fluidos mantélicos migraram para a zona afetada pela extensão regional, ascenderam acompanhando as isotermas e iniciaram a fenitização da crosta. Na continuidade deste processo, durante uma segunda fase extensional, rochas até refratárias tornaram-se fusíveis e originaram 5 magmas diferentes, todos com assinatura de fonte crustal e mantélica, que se posicionaram, entre 1.839 e 1.824 Ma, em estruturas geradas na fase anterior, formando os 3 corpos graníticos da Suíte Madeira. Numa terceira fase tectônica, desta feita transtensiva, fluidos mantélicos, possivelmente de natureza carbonatítica, fenitizaram rochas de nível crustal mais alto, enriquecidas em Sn, e nelas introduziram F, Nb, Y, ETR, U e Th em concentrações anômalas. Da fusão destas rochas resultou o magma do albita granito que se alojou, há 1.822 Ma, dentro do granito Madeira, mas com uma orientação N-S discordante da orientação geral NE-SW do granito Madeira e da estrutura que o aloja.<br>The deposit of the Madeira granite, associated with albite granite facies is a world-class deposit with disseminated ore of Sn, Nb, Ta and F (Y, REE, Li, U, Th), and its central part contains a deposit of massive cryolite with 10 Mtons (containing 38% of Na3AlF6). The objective was to understand the geological context to the formation of ore-rock association unique in the world. Therefore isotopic studies were performed (Sm-Nd, Rb-Sr and Pb-Pb) and tectonic studies focusing on the Madeira granite, its related and regional rocks. During a first extensional phase volcanic rocks of the Iricoumé Group (1890 to 1881 Ma) was originated forming a caldera complex and granitic bodies associated with Mapuera Intrusive Suite, both generated from mantle sources. At the same time the final stages of volcanism began the sedimentation in Urupi basin (possibly a rift), followed by a second peak of volcanism in 1825 Ma ago. Mantle fluids migrated to the area affected by regional extension rose following the isotherms and started the fenitization crust. Continuing this process in a second extensional phase , rocks become refractory and fuses originating 5 different magmas, all with crustal signature and mantle source, which is positioned between 1839 and 1824 Ma, in structures generated in previous phase, forming 3 granitic bodies of Madeira suite . In a third tectonic phase,, this time transtensive, mantle fluid, possibly of a carbonatitic fenitizated rocks from higher crustal level , enriched in Sn, and introduced F, Nb, Y, REE , U and Th in anomalous concentrations. The fusion of these rocks resulted in the albite granite magma that has positioned, there in 1822 Ma, within the Madeira granite, but with a NS orientation ,discordant of the general NE-SW of Madeira granite and the structure that it was contained.

Le tungstène est défini comme “ressource minérale critique” par la Commission Européenne. La province de Jiangxi, située au sud-est de la Chine, dans le bloc Cathaysia, représente 90 % des réserves en tungstène chinoises. Ce travail est basé sur l’étude des gisements hydrothermaux à W-Sn de Maoping et Piaotang, tous deux situés dans le district de Dayu (sud de la province de Jiangxi). Cette thèse a permis de (i) développer des traceurs pétrographiques et minéralogiques de processus minéralisateurs à travers des études paragénétiques détaillées et la géochimie des micas lithinifères et donc d’apporter un modèle impliquant des fluides multiples se chevauchant dans le temps et associés à plusieurs épisodes distincts de mise en place de minéralisations en métaux rares, (ii) définir par l’étude d’inclusions fluides deux processus fluides comme seul responsables de la précipitation de la minéralisation dans ces gisements « géants » : la différenciation magmatique de granites peralumineux et des processus de mélange, et (iii) de développer des approches de datation associés à ces systèmes montrant que la minéralisation en tungstène se met en place aux alentours de 160 Ma, antérieurement à la plupart des âges obtenus sur les minéraux de gangue datés dans cette zone et défini alors une remise à zéro majeure des systèmes isotopiques par de multiples circulations fluides entre 150 et 155 Ma. De plus, les stades post-minéralisations ont pu être définis pour la première fois et révèlent l’implication de magmatisme peralcalin impliqué dans la précipitation de minéralisations à Nb-Ta-Y-REE aux alentours de 130 Ma. A la lumière de cette observation, cette thèse s’est aussi tournée vers le développement de méthodes de datation in situ sur columbo-tantalite<br>Tungsten is defined as a “critical mineral resource” by the European Commission. The Jiangxi province, located in the southeastern part of China, in the Cathaysia block, represents 90% of the Chinese tungsten resources. This work is based on the study of the Maoping and Piaotang W-Sn hydrothermal deposits located in the Dayu district (southern Jiangxi). This thesis managed to (i) develop mineralogical and petrological tracers of ore-forming processes through detailed paragenetic sequences and geochemistry of Li-micas and shows that multiple overlapping fluids associated to several and distinct rare-metal mineralizing stages, (ii) distinguish by fluid inclusions studies that peraluminous magmatic differentiation and mixing processes are the only prequisite for the formation of these giant deposits, and (iii) develop dating approaches associated to these systems to demonstrate that the W mineralization formed at ca. 160 Ma, prior to most ages obtained on gangue minerals in the area, defining a major resetting of isotopic systems due to multiple fluid circulations around 150-155 Ma. Moreover, post-“silicate-oxide” stages have been defined for the first time and reveal the implication of peralkaline new fluid sources involved in the precipitation of Nb-Ta-Y-REE minerals at ca. 130 Ma. In the light of these results, this thesis gives new developments for in situ direct dating of ore-bearing minerals such as columbo-tantalite