How Beam Damage Can Skew Synchrotron Operando Studies of Batteries.

With the advent of high-brilliance synchrotron sources, the issue of beam damage on the samples deserves proper attention. It is especially true for operando studies in batteries, since the intense photon fluxes are commonly used to probe ever finer effects. Here we report on the causes and consequences of synchrotron X-ray beam damage in batteries, based on the case study of operando X-ray diffraction. We show that beam damage is caused by the mingled actions of dose and dose rate. The aftereffects can lie in a broad range, from mild modifications of the crystalline structure to artificial phase transitions, and can thus impede or bias the understanding of the mechanisms at play. We estimate the doses at which the different effects appear in two materials, suggesting that it could be expanded to other materials with the same technology. We also provide recommendations for the design of operando synchrotron experiments.

Lithium-Rich Rock Salt Type Sulfides-Selenides (Li2TiSexS3-x): High Energy Cathode Materials for Lithium-Ion Batteries.

Lithium-rich disordered rocksalt Li2TiS3 offers large discharge capacities (>350 mAh·g−1) and can be considered a promising cathode material for high-energy lithium-ion battery applications. However, the quick fading of the specific capacity results in a poor cycle life of the system, especially when liquid electrolyte-based batteries are used. Our efforts to solve the cycling stability problem resulted in the discovery of new high-energy selenium-substituted materials (Li2TiSexS3−x), which were prepared using a wet mechanochemistry process. X-ray diffraction analysis confirmed that all compositions were obtained in cation-disordered rocksalt phase and that the lattice parameters were expanded by selenium substitution. Substituted materials delivered large reversible capacities, with smaller average potentials, and their cycling stability was superior compared to Li2TiS3 upon cycling at a rate of C/10 between 3.0−1.6 V vs. Li+/Li.

Stabilization of Li-Rich Disordered Rocksalt Oxyfluoride Cathodes by Particle Surface Modification.

Promising theoretical capacities and high voltages are offered by Li-rich disordered rocksalt oxyfluoride materials as cathodes in lithium-ion batteries. However, as has been discovered for many other Li-rich materials, the oxyfluorides suffer from extensive surface degradation, leading to severe capacity fading. In the case of Li2VO2F, we have previously determined this to be a result of detrimental reactions between an unstable surface layer and the organic electrolyte. Herein, we present the protection of Li2VO2F particles with AlF3 surface modification, resulting in a much-enhanced capacity retention over 50 cycles. While the specific capacity for the untreated material drops below 100 mA h g-1 after only 50 cycles, the treated materials retain almost 200 mA h g-1. Photoelectron spectroscopy depth profiling confirms the stabilization of the active material surface by the surface modification and reveals its suppression of electrolyte decomposition.

Environmental Screening of Electrode Materials for a Rechargeable Aluminum Battery with an AlCl3/EMIMCl Electrolyte.

Recently, rechargeable aluminum batteries have received much attention due to their low cost, easy operation, and high safety. As the research into rechargeable aluminum batteries with a room-temperature ionic liquid electrolyte is relatively new, research efforts have focused on finding suitable electrode materials. An understanding of the environmental aspects of electrode materials is essential to make informed and conscious decisions in aluminum battery development. The purpose of this study was to evaluate and compare the relative environmental performance of electrode material candidates for rechargeable aluminum batteries with an AlCl3/EMIMCl (1-ethyl-3-methylimidazolium chloride) room-temperature ionic liquid electrolyte. To this end, we used a lifecycle environmental screening framework to evaluate 12 candidate electrode materials. We found that all of the studied materials are associated with one or more drawbacks and therefore do not represent a "silver bullet" for the aluminum battery. Even so, some materials appeared more promising than others did. We also found that aluminum battery technology is likely to face some of the same environmental challenges as Li-ion technology but also offers an opportunity to avoid others. The insights provided here can aid aluminum battery development in an environmentally sustainable direction.

Multiscale characterization of a lithium/sulfur battery by coupling operando X-ray tomography and spatially-resolved diffraction.

Due to its high theoretical specific capacity, the lithium/sulfur battery is one of the most promising candidates for replacing current lithium-ion batteries. In this work, we investigate both chemical and morphological changes in the electrodes during cycling, by coupling operando spatially resolved X-ray diffraction and absorption tomography to characterize Li/S cells under real working conditions. By combining these tools, the state of the active material in the entire cell was correlated with its electrochemical behavior, leading to a deeper understanding of the performance limiting degradation phenomena in Li/S batteries. Highly heterogeneous behavior of lithium stripping/plating was observed in the anode, while the evolution of sulfur distribution in the cathode depth was followed during cycling.

Synthesis and Characterization of the LiMnBO3-LiCoBO3 Solid Solution and Its Use as a Lithium-Ion Cathode Material.

A complete solid solution of m-Li(Mn1-xCox)BO3 has been successfully synthesized for the first time with the idea of improving the average potential versus m-LiMnBO3. These compounds have been obtained by a multiple-step process. Interestingly, transmission electron microscopy results indicate that the C2/c space group previously reported for m-LiMBO3 (M = Mn, Co) cannot describe m-Li(Mn1-xCox)BO3 compounds. Each material shows electrochemical activity, without in situ carbon coating. Despite a large polarization, we report a capacity of almost 60 mAh/g at the first discharge at C/20 rate with good stability up to five cycles for LiMn0.7Co0.3BO3.

New insight into the working mechanism of lithium-sulfur batteries: in situ and operando X-ray diffraction characterization.

In order to improve the electrochemical performances of lithium-sulfur batteries, it is crucial to understand profoundly their working mechanism and the limitation factors. This communication presents synchrotron-based in situ XRD studies of structural modifications occurring inside the cell upon cycling, since the active material changes constantly its form between solid and liquid phases.

First evidence of manganese-nickel segregation and densification upon cycling in Li-rich layered oxides for lithium batteries.

Lithium-rich manganese-based layered oxides Li[Li(x)Mn(y)TM(1-x-y)]O2 with TM standing for Ni, Co, or Fe are of great interest as cathode materials for lithium ion batteries. Indeed, among all of the materials, they offer the highest rechargeable capacity and energy density. However, when used, they suffer from complex evolutions that need to be understood before their practical use. Here we report on such evolutions studied using advanced transmission electron microscopy. Structural modifications are directly observed at the atomic scale using Cs corrected STEM HAADF imaging technique, and the chemical modifications are probed by the means of STEM EELS experiments. For the first time, segregation between nickel and manganese close the particle surface is pointed out. Finally, observed evolutions are correlated within a proposed mechanism that leads to the densification of the material. Our results allow understanding the link between the decrease of electrochemical performance and these evolutions occurring into the material upon cycling.

Transanal endoscopic microsurgery: long-term experience, indication expansion, and technical improvements.

BACKGROUND: This study aimed to review the authors' 16-year experience with transanal endoscopic microsurgery (TEM). Mortality, morbidity, recurrence rate, and functional outcome were assessed. New indications and technical improvements are presented. METHODS: From November 1991 to August 2008, 123 patients (72 men and 51 women; median age, 68 years; range, 21-91 years) underwent TEM for excision of 105 adenomas with low- or high-grade dysplasia, 9 invasive adenocarcinomas (5 curative and 4 palliative resections), 2 neuroendocrine tumors, and 2 extramucosal lesions. Five additional patients had excisional biopsies, allowing staging after previous endoscopic resection. Most of the resections were full-thickness rectal resections using electrocautery or, more recently, the Harmonic scalpel. The latest mucosectomies were performed using the endoscopic submucosal dissection (ESD) technique. In addition, nontumoral indications included pelvic abscess (7 patients) and rectal strictures, which were either anastomotic or chemical. Pelvic abscesses were drained transrectally, whereas rectal stenoses were treated by strictureplasty. Foreign object retrieval and collagen plug placement for anal fistulas were performed using TEM in three patients. RESULTS: No mortality occurred. One intraoperative rectal perforation required conversion to laparotomy. The postoperative complications included one pneumoperitoneum, which was treated medically, and one rectal perforation requiring Hartmann's procedure. In the polyp subgroup, six patients (6/91, 7%) experienced local recurrence. Pelvic abscesses were successfully treated, and stenosis did not recur after strictureplasty. Anorectal manometry showed functional alterations without significant clinical impact. CONCLUSIONS: The findings showed TEM to be a safe and effective procedure for local excision of rectal lesions with a low recurrence rate and minimal consequences in terms of anorectal function. In addition, TEM proved to be feasible and effective for pelvic abscess drainage and rectal stenosis treatment. New technologies such as the Harmonic scalpel and ESD increase the precision already offered by this approach.

Two caesium vanadium hydrogenphosphates with tunnelled structures: Cs(2)V(2)O(3)(PO(4))(HPO(4)) and Cs(2)[(VO)(3)(HPO(4))(4)(H(2)O)].H(2)O.

Dicaesium divanadium trioxide phosphate hydrogenphosphate, Cs(2)V(2)O(3)(PO(4))(HPO(4)), (I), and dicaesium tris[oxidovanadate(IV)] hydrogenphosphate dihydrate, Cs(2)[(VO)(3)(HPO(4))(4)(H(2)O)].H(2)O, (II), crystallize in the monoclinic system with all atoms in general positions. The structures of the two compounds are built up from VO(6) octahedra and PO(4) tetrahedra. In (I), infinite chains of corner-sharing VO(6) octahedra are connected to V(2)O(10) dimers by phosphate and hydrogenphosphate groups, while in (II) three vanadium octahedra share vertices leading to V(3)O(15)(H(2)O) trimers separated by hydrogenphosphate groups. Both structures show three-dimensional frameworks with tunnels in which Cs(+) cations are located.

Influence of HIV infection on the response to interferon therapy and the long-term outcome of chronic hepatitis B.

BACKGROUND & AIMS: The outcome of chronic hepatitis B and the efficacy of interferon alfa (IFN-alpha) remain controversial in human immunodeficiency virus (HIV)-positive patients. We analyzed the influence of HIV coinfection on the response to IFN-alpha therapy, long-term virologic status, progression to cirrhosis, and mortality. METHODS: This was a retrospective follow-up cohort study of 141 consecutive hepatitis B e antigen-positive patients (69 HIV positive) followed up for 45 months. RESULTS: The short-term response to IFN-alpha therapy was not significantly different in HIV-positive and HIV-negative patients (28% vs. 51%; P = 0.06) but was poorer in cases of low CD4 cell count (P = 0.038). The hepatitis B virus (HBV) reactivation rate was higher in HIV-positive patients (P = 0.033) and was associated with low CD4 cell count. The risk of cirrhosis was higher in HIV-positive patients with a CD4 cell count <200/mm(3) (relative risk [RR], 4.57; P = 0.007), in IFN-alpha-untreated patients (RR, 2.63; P = 0.041), in patients older than 33 years (RR, 4.59; P = 0.008), and in cases of high necroinflammatory score at baseline (RR, 1.27; P = 0.010). Cirrhosis-related death was more frequent in HIV-positive patients with low CD4 cell count at baseline (P = 0.041), in alcohol consumers (P = 0.001), in IFN-alpha-untreated patients (P = 0.052), and in patients with high histology activity index at baseline (P = 0.005). CONCLUSIONS: HIV coinfection was associated with poorer response to IFN-alpha therapy, more frequent HBV reactivations, and increased incidence of cirrhosis and cirrhosis-related death in cases of low CD4 count. IFN-alpha therapy decreased the incidence of HBV cirrhosis regardless of HIV status or serologic response.