On the Reactivity of Li8-yMnyP4 toward Lithium

International audienceThe Li5.5Mn2.5P4 and Li7MnP4 phases having a tetragonal structure (P4/nmm, a ) b ) 4.176(1) Å andc ) 5.978(1) Å) and a cubic structure (Fm3hm a ) 5.968(3) Å) were synthesized by a two-step process consisting in ball milling Li, Mn, and P powders followed by annealing at 800 °C under argon in a sealed stainless steel tube. The resulting materials were tested on Li cells between 0.01 and 2 V. Bothof them can reversibly react with Li, leading to reversible capacities as high as 1000 mAh/g, but only the Li5.5Mn2.5P4 electrode can nicely maintain its initial capacity upon cycling. The origin of such a difference was found in the partial decomposition of Li7MnP4 in Li3P and Mn nanoparticles at low potential, as deduced by in situ X-ray diffraction measurements. In contrast, no decomposition was shown to occur for the Li5.5Mn2.5P4 electrode that shows the best capacity retention among of ternary LixMyP4 (M ) Ti, V) so far studie

Towards a better understanding of the degradation mechanisms of Li-ion full cells using Si/C composites as anode

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Electrochemical Reactivity and Design of NiP2 Negative Electrodes for Secondary Li-Ion Batteries

International audienceWe report the electrochemical study of cubic and monoclinic NiP2 polymorphs toward Li, as a candidate for anodic applications for Li-ion batteries. We found that the monoclinic form is the most attractive one performance-wise. Monoclinic NiP2 can reversibly uptake 5 lithium per formula unit, leading to reversible capacities of 1000 mAh/g at an average potential of 0.9 V vs Li+/Li°. From complementary X-ray diffraction (XRD) and HRTEM (high-resolution transmission electron microscopy) measurements, it was shown that, during the first discharge, the cubic phase undergoes a pure conversion process (NiP2 + 6 Li+ + 6e- f Ni° + 2Li3P) as opposed to a sequential insertion-conversion process for monoclinic NiP2. Such a different behavior rooted in subtle structural changes was explained through electronic structure calculations. Once the first discharged is achieved, both phases were shown to react with Li through a classical conversion process. More importantly, we report a novel way to design NiP2 electrodeswith enhanced capacity retention and rate capabilities. It consists in growing the monoclinic NiP2 phase,through a vapor-phase transport process, on a commercial Ni-foam commonly used in Ni-based alkaline batteries. These new self-supported electrodes, based on chemically made interfaces, offer new opportunities to fully exploit the capacity gains provided by conversion reaction

Nano silicon carbon hybrid particles and composites for batteries: Fundamentals, properties and applications

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Impact of synthesis conditions in Na-rich Prussian Blue Analogs

International audienceSodium rich iron hexacyanoferrates were prepared by coprecipitation, hydrothermal route, and under reflux, with or without dehydration. They were obtained with different structures described in cubic, orthorhombic or rhombohedral symmetry, with variable compositions in sodium, water and cationic vacancies, and with a variety of morphologies. This series of sodium rich Prussian Blue Analogs allowed to address the relationship between synthesis conditions, composition, structure, morphology and electrochemical properties in Na-ion batteries. A new orthorhombic phase with the Na 1.8 Fe 2 (CN) 6 •0.7H 2 O composition synthesized by an hydrothermal route at 140°C is reported for the first time, whereas a phase of Na 2 Fe 2 (CN) 6 •2H 2 O composition obtained under reflux, previously described with a monoclinic structure, shows in fact a rhombohedral structure

Impact of synthesis conditions in Na-rich Prussian Blue Analogs

Sodium rich iron hexacyanoferrates were prepared by coprecipitation, hydrothermal route, and under reflux, with or without dehydration. They were obtained with different structures described in cubic, orthorhombic or rhombohedral symmetry, with variable compositions in sodium, water and cationic vacancies, and with a variety of morphologies. This series of sodium rich Prussian Blue Analogs allowed to address the relationship between synthesis conditions, composition, structure, morphology and electrochemical properties in Na-ion batteries. A new orthorhombic phase with the Na 1.8 Fe 2 (CN) 6 •0.7H 2 O composition synthesized by an hydrothermal route at 140°C is reported for the first time, whereas a phase of Na 2 Fe 2 (CN) 6 •2H 2 O composition obtained under reflux, previously described with a monoclinic structure, shows in fact a rhombohedral structure.Laboratory of excellency for electrochemical energy storag

Single versus Double Autologous Stem-Cell Transplantation for Multiple Myeloma

BACKGROUND. We conducted a randomized trial of the treatment of multiple myeloma with high-dose chemotherapy followed by either one or two successive autologous stem-cell transplantations. METHODS. At the time of diagnosis, 399 previously untreated patients under the age of 60 years were randomly assigned to receive a single or double transplant. RESULTS. A complete or a very good partial response was achieved by 42 percent of patients in the single-transplant group and 50 percent of patients in the double-transplant group (P=0.10). The probability of surviving event-free for seven years after the diagnosis was 10 percent in the single-transplant group and 20 percent in the double-transplant group (P=0.03). The estimated overall seven-year survival rate was 21 percent in the single-transplant group and 42 percent in the double-transplant group (P=0.01). Among patients who did not have a very good partial response within three months after one transplantation, the probability of surviving seven years was 11 percent in the single-transplant group and 43 percent in the double-transplant group (P<0.001). Four factors were significantly related to survival: base-line serum levels of beta 2-microglobulin (P<0.01) and lactate dehydrogenase (P<0.01), age (P<0.05), and treatment group (P<0.01). CONCLUSIONS. As compared with a single autologous stem-cell transplantation after high-dose chemotherapy, double transplantation improves overall survival among patients with myeloma, especially those who do not have a very good partial response after undergoing one transplantation