CuFe2S3 as electrode material for Li-ion batteries

Electrochemical performances of the isocubanite CuFe2S3 tested as electrode material for Li-ion batteries have been investigated. A first discharge capacity of 860 mA h g(-1) shows a conversion process leading to Li2S, copper and iron nanoparticles. Interestingly, a reversible capacity of 560 mA h g(-1) at 1.5 V is demonstrated with good cyclability up to 30 cycles

The electrochemical storage mechanism in oxy-hydroxyfluorinated anatase for sodium-ion batteries

International audienceReplacing lithium ions with sodium ions as the charge carriers in rechargeable batteries can induce noticeable differences in the electrochemical storage mechanisms of electrode materials. Many material parameters, such as particle size, morphology, and the presence of defects, are known to further affect the storage mechanism. Here, we report an investigation of how the introduction of titanium vacancies into anatase TiO2 affects the sodium storage mechanism. From pair distribution function analysis, we observe that sodium ions are inserted into titanium vacancies at the early stage of the discharge process. This is supported by density functional theory calculations, which predict that sodium insertion is more favourable at vacancies than at interstitial sites. Our calculations also show that the intercalation voltage is sensitive to the anion coordination environment of the vacancy. Sodiation to higher concentrations induces a phase transition toward a disordered rhombohedral structure, similar to that observed in defect-free TiO2. Finally, we find that the X-ray diffraction pattern of the rhombohedral phase drastically changes depending on the composition and degree of disorder, providing further comprehension on the sodium storage mechanism of anatase

A Reversible Phase Transition for Sodium Insertion in Anatase TiO₂

International audienceAnatase TiO2 is a potential negative electrode for sodium-ion batteries. The sodium storage mechanism is, however, still under debate, yet its comprehension is required to optimize the electrochemical properties. To clarify the sodium storage mechanism occurring in anatase, we have used both electrochemical and chemical routes from which we obtained similar trends. During the first discharge, an irreversible plateau region is observed which corresponds to the insertion of Na + within the interstitial sites of anatase and is accompanied by a drastic loss of the long-range order as revealed by x-ray diffraction, high resolution of high angle annular dark field scanning transmission electron microscope (HAADF-STEM) and pair distribution function (PDF) analysis. Further structural analysis of the total scattering data indicates that the sodiated phase displays a layered-like rhombohedral R-3m structure built from the stacking of Ti and Na slabs. Because of the initial 3D network of anatase, the reduced phase shows strong disorder due to cationic inter-mixing between the Ti and Na slabs and the refined chemical formula is (Na0.43Ti0.57)3a(0.22Na0.39Ti0.39)3bO2 where refers to vacancy. The presence of high valence Ti ions in the Na layers induces a contraction of the c-parameter as compared to the ordered phase. Upon de-sodiation, the structure further amorphized and the local structure probed by PDF is shown to be similar to the anatase TiO2 suggesting that the 3D network is recovered. The reversible sodium insertion/de-insertion is thus attributed to the rhombohedral active phase formed during the first discharge, and an oxidized phase featuring the local structure of anatase. Due to the amorphous nature of the two phases, the potential-composition curves are characterized by a sloping curve. Finally, a comparison between the intercalation of lithium and sodium into anatase TiO2 performed by DFT calculations confirmed that for the sodiated phase, the rhombohedral structure is more stable than the tetragonal phase observed during the lithiation of nanoparticles. In many areas of modern life, lithium-ion batteries are ubiquitous as energy-storage solutions. The growing demand for higher energy density and lower cost of electro-chemical energy storage devices, however, has motivated a search for auxiliary technologies based on alternative chemistries. 1,2 One possible candidate is the sodium-ion battery, which is attractive because of the high earth– abundance of sodium, and lower cost versus lithium-ion batteries, due to compatibility with aluminum as the an-odic current collector. 3-5 Development of sodium-ion batteries has been largely stimulated by knowledge of lithium-ion analogues. The intercalation of Na + or Li + ions into a host lattice can, however, give qualitatively different voltage profiles, corresponding to different intercalation mechanisms. For example, lithium insertion in Li4Ti5O12 is accompanied by a spinel to rock-salt phase transition. 6,7 The equivalent sodium insertion, however, proceeds via a complex three-phase–separation mechanism (spinel to two rock-salt phases of Li7Ti5O12 and Na6LiTi5O12). 8 Such differences in intercalation behaviour can often be attributed to different properties of Li versus Na, such as ionic radius and polarizability. 9, 10 In general, however, the performance of electrodes in sodium-ion batteries cannot be understood by simply extrapolating from their behaviour versus lithium, when it is necessary to carefully reexamine the sodium-intercalation behaviour

Aldo Keto Reductase 1B7 and Prostaglandin F2α Are Regulators of Adrenal Endocrine Functions

Prostaglandin F2α (PGF2α), represses ovarian steroidogenesis and initiates parturition in mammals but its impact on adrenal gland is unknown. Prostaglandins biosynthesis depends on the sequential action of upstream cyclooxygenases (COX) and terminal synthases but no PGF2α synthases (PGFS) were functionally identified in mammalian cells. In vitro, the most efficient mammalian PGFS belong to aldo-keto reductase 1B (AKR1B) family. The adrenal gland is a major site of AKR1B expression in both human (AKR1B1) and mouse (AKR1B3, AKR1B7). Thus, we examined the PGF2α biosynthetic pathway and its functional impact on both cortical and medullary zones. Both compartments produced PGF2α but expressed different biosynthetic isozymes. In chromaffin cells, PGF2α secretion appeared constitutive and correlated to continuous expression of COX1 and AKR1B3. In steroidogenic cells, PGF2α secretion was stimulated by adrenocorticotropic hormone (ACTH) and correlated to ACTH-responsiveness of both COX2 and AKR1B7/B1. The pivotal role of AKR1B7 in ACTH-induced PGF2α release and functional coupling with COX2 was demonstrated using over- and down-expression in cell lines. PGF2α receptor was only detected in chromaffin cells, making medulla the primary target of PGF2α action. By comparing PGF2α-responsiveness of isolated cells and whole adrenal cultures, we demonstrated that PGF2α repressed glucocorticoid secretion by an indirect mechanism involving a decrease in catecholamine release which in turn decreased adrenal steroidogenesis. PGF2α may be regarded as a negative autocrine/paracrine regulator within a novel intra-adrenal feedback loop. The coordinated cell-specific regulation of COX2 and AKR1B7 ensures the generation of this stress-induced corticostatic signal

Introduction: Debates on Experience and Empiricism in Nineteenth Century France

The lasting effects of the debate over canon-formation during the 1980s affected the whole field of Humanities, which became increasingly engaged in interrogating the origin and function of the Western canon (Gorak 1991; Searle 1990). In philosophy, a great deal of criticism was, as a result, directed at the traditional narrative of seventeenth-and eighteenth-century philosophies—a critique informed by postcolonialism (Park 2013) as well as feminist historiography (Shapiro 2016). D. F. Norton (1981), L. Loeb (1981) and many others1 attempted to demonstrate the weaknesses of the tripartite division between rationalism, empiricism and critical philosophy.2 As time went on, symptoms of dissatisfaction with what has been called the “standard narrative” ( Vanzo 2013) and the “epistemological par-adigm” (Haakonssen 2004, 2006) only increased. Indeed, at present, a consensus has been reached that the narrative of the antagonism between “Continental rationalism” and “British empiricism”, and the consequent Aufhebung provided by “German critical philosophy,” has been unable to make sense of the complexity, variety and dynamics of early modern.Fil: Antoine-Mahut, Delphine. Ecole Normale Supérieure; FranciaFil: Manzo, Silvia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Humanidades y Ciencias Sociales. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales; Argentin

Swedenborgite-Type Cobaltites and Ferrites: Tetrahedral Frameworks with Exceptional Magnetic Properties

International audienceSwedenborgite‐type cobaltites and ferrites and derivatives, represent a very important class of oxides, LnBaM4O7 and CaBaM4O7 (M = Co, Fe). They are one of the rare families of mixed valent transition metal oxides, where the transition element exhibits exclusively the tetrahedral coordination. Their complex crystal chemistry, involving closely related structures with various symmetries (orthorhombic, hexagonal cubic) and possibility of oxygen “hyperstoichiometry”, leading to LnBaM4O7+δ oxides is described herein, as well as their ability to exhibit structural transitions vs. temperature. It is also shown that the triangular geometry of these new strongly electron correlated systems, plays an important role in their physics, particularly in the competition that appears between the 1D magnetic ordering and the 2D magnetic frustration. The generation of new magnetodielectric properties for CaBaCo4O7 is also emphasized

The “114” Cobaltites and Ferrites : New Routes to Ferrimagnetism and Magnetic Frustration

International audienceAn overview of the magnetic properties of the “114” cobaltites and ferrites in connection with their crystal structure, built up of triangular and kagomé layers of CoO4 tetrahedra is presented. These oxides can be classified into three different structural types according to their room temperature structure: the trigonal P31c phases LnBaCo4O7 and CaBaFe4O7, the orthorhombic Pbn21 CaBaCo4O7 phase and the cubic LnBaFe4O7 oxides. The magnetic properties show complex transitions for LnBaCo4O7 oxides, whereas spin glas behavior is observed for LnBaFe4O7 and ferrimagnetic like properties are observed for CaBaFe4O7 and CaBaCo4O7. The topotactic oxidation of those oxides is also discussed

CuFe2S3 as electrode material for Li-ion batteries

International audienceElectrochemical performances of the isocubanite CuFe2S3 tested as electrode material for Li-ion batteries have been investigated. A first discharge capacity of 860 mA h g(-1) shows a conversion process leading to Li2S, copper and iron nanoparticles. Interestingly, a reversible capacity of 560 mA h g(-1) at 1.5 V is demonstrated with good cyclability up to 30 cycles