Hard carbons derived from green phenolic resins for Na-ion batteries

Hard carbons have become recently one of the most promising classes of anode materials for sodium ion batteries (NIBs) owing to their high specific capacity and good cycling stability. Among the precursors used to prepare hard carbon, phenolic resins are of great interest due to their high carbon yield, however, their toxicity must be overcome. In this paper, we propose a green, simple and scalable procedure to obtain phenolic resins which by pyrolysis at high temperature (>1000 °C) result in eco-friendly hard carbons with low surface area, disordered structure and high carbon yield. The influence of several synthesis parameters (type of solvent, thermopolymerization/annealing temperature and gas flow) was studied to determine the impact on both phenolic resin and hard carbon characteristics. The synthesis time (12 h-3 days) was found to depend on the used solvent whereas the carbon yield (25–35%) on the cross-linking degree which could be controlled by adjusting both thermopolymerization temperature and atmosphere. The structure of the hard carbons mainly changed with the carbonization temperature (1100–1700 °C) while the texture of the material was sensitive to most of the studied parameters. Stable reversible capacity up to 270 mAhg−1 and 100% coulombic efficiency (CE) after few cycles are obtained, demonstrating the potential for Na-ion applications

Hard carbons derived from green phenolic resins for Na-ion batteries

Hard carbons have become recently one of the most promising classes of anode materials for sodium ion batteries (NIBs) owing to their high specific capacity and good cycling stability. Among the precursors used to prepare hard carbon, phenolic resins are of great interest due to their high carbon yield, however, their toxicity must be overcome. In this paper, we propose a green, simple and scalable procedure to obtain phenolic resins which by pyrolysis at high temperature (>1000 °C) result in eco-friendly hard carbons with low surface area, disordered structure and high carbon yield. The influence of several synthesis parameters (type of solvent, thermopolymerization/annealing temperature and gas flow) was studied to determine the impact on both phenolic resin and hard carbon characteristics. The synthesis time (12 h-3 days) was found to depend on the used solvent whereas the carbon yield (25–35%) on the cross-linking degree which could be controlled by adjusting both thermopolymerization temperature and atmosphere. The structure of the hard carbons mainly changed with the carbonization temperature (1100–1700 °C) while the texture of the material was sensitive to most of the studied parameters. Stable reversible capacity up to 270 mAhg−1 and 100% coulombic efficiency (CE) after few cycles are obtained, demonstrating the potential for Na-ion applications

Self-supported binder-free hard carbon electrodes for sodium-ion batteries: insights into their sodium storage mechanisms

Hard carbons are one of the most promising negative electrode materials for sodium-ion batteries (NIBs). In contrast to most of the published works employing powder-like electrodes containing binders, additives and solvents, we report herein an innovative way to prepare binder-free electrodes by simple impregnation of cellulose and cotton filter papers with a phenolic resin solution. The latter enables improvement of the poor mechanical properties and thermal stability observed for pristine hard carbon self-standing electrodes (SSEs) along with the carbon yield. A high reversible specific capacity and long-term stability were observed for cellulose compared to those of cotton-based SSEs in NIBs, i.e., 240 mAh·g-1 vs. 140 mAh·g-1, respectively, for C/10 rate and high mass loading (~5.2 mg·cm-2). This could be ascribed to the larger amount of defects on cellulose than cotton as quantified by temperature programmed desorption coupled with mass-spectrometry (TPD-MS), the structure and porosity being similar for both materials. Furthermore, the addition of a conductive sputter coating on the cellulose SSE surface improved the reversible specific capacity (to ~300 mAh·g-1) and initial coulombic efficiency (ICE) (to 85%). Operando X-ray diffraction (XRD) was performed to provide additional insights on the Na storage mechanisms. Although no shift was noticed for the graphite (002) diffraction peak, clear evidence of sodium intercalation was observed in the plateau region appearance of a new diffraction peak (~28.0° 2θ) likely associated with a sodium intercalation compound. Consequently, the sloping region could be related to the Na+ adsorption on hard carbon defects and pores

Profound Depletion of HIV-1 Transcription in Patients Initiating Antiretroviral Therapy during Acute Infection

Early intervention resulted in profound depletion of PBMC expressing HIV-1 RNA. This is contrary to chronically infected patients who predominantly showed continuous UsRNA expression on cART. Thus, antiretroviral treatment initiated during the acute phase of infection prevented establishment or expansion of long-lived transcriptionally active viral cellular reservoirs in peripheral blood

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Development of eco-friendly hard carbons for Na-ion batteries

Des anodes en carbone dur, respectueuses de l'environnement, pour les batteries Na-ion, alternatives prometteuses des batteries actuelles du type Li-ion, ont été développées au cours de cette thèse. Des connaissances approfondies sur les propriétés physico-chimiques et électrochimiques des matériaux ainsi que sur leurs mécanismes de stockage des ions Na sont proposées. Trois catégories de précurseurs : la biomasse, les biopolymères et les polymères synthétiques sont sélectionnées pour synthétiser des carbones durs à propriétés bien maitrisées. Le développement des premières résines phénoliques respectueuses de l'environnement, alternative aux résines toxiques, a été mis au point. Ces nouvelles résines ont conduit à des carbones capables de délivrer une capacité de ~ 300 mAh/g. Un autre volet d’un grand intérêt a consisté en la mise au point d'électrodes carbonées sans liant et sans solvant qui ont servi de matériaux modèles pour la compréhension des mécanismes de stockage des ions Na. Cela a permis de démontrer expérimentalement la formation d'espèces d’intercalation sodiées par des techniques in-situ lors du fonctionnement de la batterie. L’impact des impuretés des biomasses sur les propriétés et les performances des carbones a également été étudié en détail. Dans la dernière partie de cette thèse, une transition des tests de l'échelle du laboratoire à grande échelle a été réalisée. Des électrodes compactes de sphères de carbones ont été développées, permettant l’obtention de performances exceptionnelles en batteries complètes. L'origine de ces performances est mise en évidence via de nombreuses corrélations propriétés – performances.This thesis deals with the development of eco-friendly hard carbon anodes for Na-ion batteries, promising alternatives to the state-of-the-art, Li-ion batteries. In-depth knowledge on the physico-chemical and electrochemical properties of the materials, as well as on the storage mechanisms of Na ions in carbon hosts were emphasized. Three categories of precursors: biomass, biopolymers and synthetic polymers were selected to synthesize hard carbon materials with well-controlled properties. The development of the first eco-friendly phenolic resins, an alternative to the toxic resins, was successfully accomplished. The new resins have led to hard carbons capable of delivering a high capacity of ~ 300 mAh/g. Another aspect of great interest consisted in the development of binder/solvent-free carbon electrodes which served as model materials to understand the storage mechanisms of Na ions. By performing in-situ characterization analyses, it was possible to demonstrate, experimentally, the formation of intercalated sodium species, during battery cycling. The impact of biomass impurities on hard carbons properties and electrochemical performance was studied in detail, as well. In the last part of the thesis, the transition from lab-scale tests to large scale tests was accomplished. Compact electrodes made of carbon spheres were developed, allowing exceptional performance in full-cells. The reasons behind the improvement of the delivered capacity are highlighted via numerous correlations properties - performance

Vegetal-extracted polyphenols as a natural hard carbon anode source for Na-ion batteries

International audienceHard carbons are promising anode materials for Na-ion batteries and can be produced using a wide variety of precursors either from synthetic or natural sources. This work focuses on the development of hard carbons using natural polyphenols from different vegetal extracts. Herein, five natural tannin based-polyphenols (catechu, chestnut, myrobalan and two mimosa extracts) were selected to synthesize hard carbons after a single pyrolysis process at 1500°C. The morphology, texture, structure and surface chemistry of these materials were characterized. Precursors lead to a high carbon yield between 35-44 % and the obtained hard carbons possess disordered structure. The presence of a low volume of meso-, micro- and ultramicro-pores was observed by N2 and CO2 physisorption assays while the specific surface areas found were very low (N2-SSA 84%) reaching 100 % after few cycles, and good cycling stability. Catechu and chestnut derived hard carbons exhibit reversible capacities around 280 mAh·g-1, when cycled at C/10 (C=372 mA·g-1); whereas the other hard carbons deliver 304 mAh·g-1. This is due to the presence of impurities, graphitized domains and slightly lower d002 values. The electrochemical behavior of these two materials differs considerably from myrobalan and mimosa derived hard carbons when a C current density is applied. Best performance was achieved for materials exhibiting low amount of impurities, more disordered structure and low specific surface area (i.e. myrobalan derived hard carbon)

REMOVAL OF REMAZOL ROSSO RB DYE FROM AQUEOUS EFFLUENTS BY HOMOGENOUS FENTON OXIDATION PROCESSES

The paper presents some data from our laboratory-setup experiments of homogenous oxidative processes with hydrogen peroxide (i.e. advanced Fenton oxidation processes) applied for Remazol Rosso RB dye-containing aqueous systems, especially textile effluents. Therefore, some different operating parameters (including pH, concentration of dye, H2O2 and ferrous ions, oxidation time, temperature, stirring regime, among its) were tested for determination of the best performance in effluent decoloration and dye removal, meaning the optimal values of each studied parameters for highest decoloration or dye removal

Le carbone dur pour les batteries Na-ion : de la synthèse aux performances et mécanismes de stockage

International audienc