Composites de carbón activado-MnO2 como electrodos para baterías de Li/S

Premio extraordinario de Trabajo Fin de Máster curso 2016-2017. Máster Interuniversitario en QuímicaEl presente trabajo se ha centrado en el estudio de materiales basados en carbón activado y dióxido de manganeso en la fase γ-MnO2 como aditivos de electrodos para baterías Li/S. El MnO2 se preparó en forma de microesferas mediante un tratamiento hidrotermal y el carbón activado se obtuvo de huesos de oliva (CAHO) utilizando como agente de activación con vapor de H2O. Los materiales se caracterizaron mediante diferentes técnicas como: difracción de rayos X, microscopía electrónica de barrido, análisis de dispersión de energía de rayos X, análisis termogravimétrico y medidas de adsorción/desorción de N2. Las propiedades electroquímicas de las celdas se midieron en régimen gslvsnostático. Se estudiaron tres composites con un contenido de S similar (en torno a un 60%): C/S, C/MnO2/S_Mol y C/MnO2/S_BH. Los dos primeros se prepararon por molienda de los componentes y el último mediante tratamiento hidrotermal de la mezcla C/S junto con los precursores del dióxido de manganeso. Los composites formados por el carbón activado y MnO2 dieron mejores rendimientos como electrodo de la batería: mayores capacidades específicas y una buena respuesta electroquímica a altas densidades de corriente durante el ciclado de las baterías. El método de preparación del composite apenas tiene influnecia en el rendimiento de la batería por lo que la mejora observada se debe a la presencia del MnO2 en el composite. La interacción del MnO2 con los polisulfuros formados en la reacción del Li con el S supone una capacidad adicional del composite para atraparlos, atenuando su solubilidad en el electrolito, una de las causas que afectan al rendimiento de las baterias Li/S.This work has been centred in the study of materials based on activated carbon and manganese dioxide (γ-MnO2) as electrode additives for Li/S batteries. MnO2 was prepared as microspheres by hydrothermal treatment and the activated carbon from olive stones (OSAC) using H2O vapour as activating agent. The materials were characterized by different techniques as: X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis and N2 adsorption/desorption measurements. The electrochemical properties of the cells were examined under galvanostatic regime. Three composites with a similar S content (around 60 %) were studied: C/S, C/MnO2/S_Mol and C/MnO2/S_BH. The first two were prepared by grinding and the last one by hydrothermal treatment of the C/S mixture together with manganese dioxide precursors. The composites formed by activated carbon and MnO2 yielded better performances as the battery electrodes: higher specific capacities and a good electrochemical response cycling at high currents. The preparation procedure of the composite hardly affects to the battery performance; therefore, the improved performance of the cell is due the MnO2 presence in the composite. The interaction of MnO2 with polysulfides coming from the Li/S reaction provides an additional ability to the composite for trapping these chemicals, palliating their solubility in the electrolyte, one of the causes which affect to the performance of Li/S batteries

Biomass Porous Carbons Derived from Banana Peel Waste as Sustainable Anodes for Lithium-Ion Batteries

Disordered carbons derived from banana peel waste (BPW) were successfully obtained by employing a simple one-step activation/carbonization method. Different instrumental techniques were used to characterize the structural, morphological, and textural properties of the materials, including X-ray diffraction, thermogravimetric analysis, porosimetry and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The chemical activation with different porogens (zinc chloride, potassium hydroxide and phosphoric acid) could be used to develop functional carbonaceous structures with high specific surface areas and significant quantities of pores. The BPW@H3PO4 carbon exhibited a high specific surface area (815 m2 g−1), chemical stability and good conductivity for use as an anode in lithium-ion batteries. After 200 cycles, this carbon delivered a reversible capacity of 272 mAh g−1 at 0.2 C, showing a notable retention capacity and good cycling performance even at high current densities, demonstrating its effectiveness and sustainability as an anode material for high-energy applications in Li-ion batteries

Simple and Eco-Friendly Fabrication of Electrode Materials and Their Performance in High-Voltage Lithium-Ion Batteries

The huge consumption of rechargeable Li-ion batteries (LIBs) make it necessary to recover and reuse the different components of spent batteries, thus favoring sustainable development. Graphite is a critical material in the manufacture of the current LIBs so recycling it should be prioritized in the management of spent batteries. In this work, graphite is manually recovered from spent batteries used in smartphones. The impurities from the different components of the batteries are drastically reduced by simple leaching with HCl. This treatment significantly improves the delivered specific capacity, with average values of 300 and 390 mAh g−1 without and with leaching, respectively. To test recycled graphite as an anode material in real cells, it is paired with LiNi0.5Mn1.5O4, the most promising cathode material for high-voltage batteries. LiCl, produced directly by chlorination of spodumene, is used as the Li source to obtain the spinel sample. The real cell gives satisfactory values for both initial specific capacity (100 mAh g−1) and capacity retention after 100 cycles. These results are comparable to and in some cases even better than those for cells that use commercial graphite and conventional Li sources as primary raw materials. Moreover, the cell shows good performance during the rate capability test; the delivered capacity values decrease smoothly from 73 to 62 mAh g−1 while the rate increases from 0.1 to 1 C

Biomass-derived carbon/γ-MnO2 nanorods/S composites prepared by facile procedures with improved performance for Li/S batteries

The promising prospects of the Li/S battery, due to its theoretical energy density of about 2500 Wh kg─1, are severely limited by two main weaknesses: the poor conductivity of S and the solubility of the polysulphides in the electrolyte. A combination of carbon and transition metal oxides is the best option for mitigating both of these shortcomings simultaneously. In this work, we use hydrothermally-tailored γ-MnO2 nanorods combined with an activated biomass-derived carbon, which is an inexpensive material and easy to prepare. This strategy was also followed for a AC/MnO2/S composite, a preparation of which was made by grinding; this is the simplest method for practical applications. More complex procedures for the formation of in situ hydrothermal MnO2 nanorods gave similar results to those obtained from grinding. Compared with the AC/S composite, the presence of MnO2 markedly increased the delivered capacity and improved the cycling stability at both low (0.1 C) and high (1 C) currents. This behaviour results from a combination of two main effects: firstly, the MnO2 nanorods increase the electrical conductivity of the electrode, and secondly, the small particle size of the oxide can enhance the chemisorption properties and facilitate a redox reaction with polysulphides, more efficiently blocking their dissolution in the electrolyte

Versatile protein-templated TiO2 nanocomposite for energy storage and catalytic applications

A protein-templated titania nanocomposite (PT-TiO2) was successfully synthesized by a water-free mechanochemical approach. A biomass valorization strategy was developed by employing egg white from expired eggs to control the morphology and textural features of the prepared titania. A remarkable enhancement of the surface area was achieved, in comparison with the synthesis of the material in absence of the biomass-derived template. Several techniques, such as scanning electron microscopy-mapping and CNHS analysis, supported the presence of carbon, nitrogen and sulfur residues in the obtained composite. Catalytic performance of PT-TiO2 was explored in the oxidation of diphenyl sulfide, displaying promising results in terms of conversion, selectivity and stability. The effect of the oxidant agent was additionally investigated by using hydrogen peroxide, urea hydrogen peroxide, oxygen and t-butyl-hydroperoxide. On the other hand, PT-TiO2 nanocomposite was successfully proved as anodic material for lithium-ion batteries delivering a reversible capacity of 107 mAh g–1 at 0.1C with an excellent Coulombic efficiency of 100% from the second cycle. In addition, the as-synthesized material showed significant capacity retention values of 76% among the 2nd cycle and 100th cycle. PT-TiO2 resulted to be a versatile material with potential catalytic and energy storage applications

Effect of aliskiren on post-discharge outcomes among diabetic and non-diabetic patients hospitalized for heart failure: insights from the ASTRONAUT trial

Aims The objective of the Aliskiren Trial on Acute Heart Failure Outcomes (ASTRONAUT) was to determine whether aliskiren, a direct renin inhibitor, would improve post-discharge outcomes in patients with hospitalization for heart failure (HHF) with reduced ejection fraction. Pre-specified subgroup analyses suggested potential heterogeneity in post-discharge outcomes with aliskiren in patients with and without baseline diabetes mellitus (DM). Methods and results ASTRONAUT included 953 patients without DM (aliskiren 489; placebo 464) and 662 patients with DM (aliskiren 319; placebo 343) (as reported by study investigators). Study endpoints included the first occurrence of cardiovascular death or HHF within 6 and 12 months, all-cause death within 6 and 12 months, and change from baseline in N-terminal pro-B-type natriuretic peptide (NT-proBNP) at 1, 6, and 12 months. Data regarding risk of hyperkalaemia, renal impairment, and hypotension, and changes in additional serum biomarkers were collected. The effect of aliskiren on cardiovascular death or HHF within 6 months (primary endpoint) did not significantly differ by baseline DM status (P = 0.08 for interaction), but reached statistical significance at 12 months (non-DM: HR: 0.80, 95% CI: 0.64-0.99; DM: HR: 1.16, 95% CI: 0.91-1.47; P = 0.03 for interaction). Risk of 12-month all-cause death with aliskiren significantly differed by the presence of baseline DM (non-DM: HR: 0.69, 95% CI: 0.50-0.94; DM: HR: 1.64, 95% CI: 1.15-2.33; P < 0.01 for interaction). Among non-diabetics, aliskiren significantly reduced NT-proBNP through 6 months and plasma troponin I and aldosterone through 12 months, as compared to placebo. Among diabetic patients, aliskiren reduced plasma troponin I and aldosterone relative to placebo through 1 month only. There was a trend towards differing risk of post-baseline potassium ≥6 mmol/L with aliskiren by underlying DM status (non-DM: HR: 1.17, 95% CI: 0.71-1.93; DM: HR: 2.39, 95% CI: 1.30-4.42; P = 0.07 for interaction). Conclusion This pre-specified subgroup analysis from the ASTRONAUT trial generates the hypothesis that the addition of aliskiren to standard HHF therapy in non-diabetic patients is generally well-tolerated and improves post-discharge outcomes and biomarker profiles. In contrast, diabetic patients receiving aliskiren appear to have worse post-discharge outcomes. Future prospective investigations are needed to confirm potential benefits of renin inhibition in a large cohort of HHF patients without D

Advances in lithium-sulfur battery technology: performance, safety and sustainability

Hasta hace dos siglos, la humanidad vivía sin el uso de combustibles fósiles para cumplir con las necesidades de su día a día. Su base energética era principalmente la energía humana y animal, y los únicos combustibles como la madera o el carbón, eran utilizados por el para cocinar, calentarse y desempeñar oficios artesanales. No fue hasta la aparición de la Revolución Industrial, cuando el empleo de los combustibles fósiles comenzó a desempeñar un papel dominante en la economía y la sociedad. Primero, con el carbón como la principal fuente de energía para proporcionar movimiento en las primeras locomotoras y barcos de vapor, así como el impulso y la modernización de los procesos de fabricación. A finales del siglo XIX, con el uso extendido de la electricidad en las ciudades y una mayor demanda de energética, ocurrió otra revolución con el descubrimiento de grandes reservas de petróleo y gas natural. Principalmente, la extracción y el refinamiento del crudo de petróleo se convirtió en una industria importante, pues se comenzó a emplear como combustible para el transporte, en forma de gasolina o diésel con la invención de los motores de combustión interna para los primeros vehículos. En consecuencia, a partir del siglo XX hasta la actualidad, con la mejora de la calidad de vida y el constante aumento de la población, el uso y quema de combustibles fósiles se ha incrementado de forma exponencial, tanto en la producción energética, el transporte como en la confección de productos de uso cotidiano. Esto ha ocasionado un constante aumento de la contaminación, siendo el CO2 uno de los principales actores, que ha provocado la aparición de fenómenos como el efecto invernadero y contribuye al calentamiento global, uno de los orígenes de los cambios climáticos del Planeta, que han hecho tomar conciencia a muchos países con su participación y aprobación de la Agenda 2030 establecida por la Asamblea General de la Organización de Naciones Unidas (AG-ONU) que marca una serie de retos para alcanzar unos Objetivos de Desarrollo Sostenible (ODS).Until two centuries ago, mankind lived without the use of fossil fuels to meet its daily needs. Its energy base was mainly human and animal energy, and the only fuels, such as wood or coal, were used for cooking, heating, and craftsmanship. It was not until the advent of the Industrial Revolution that the use of fossil fuels began to play a dominant role in the economy and society. First, with coal as the main source of energy to provide motion in the first locomotives and steamships, as well as driving and modernizing manufacturing processes. At the end of the 19th century, with the widespread use of electricity in cities and an increased demand for energy, another revolution occurred with the discovery of large reserves of oil and natural gas. Primarily, the extraction and refining of crude oil became an important industry, as it began to be used as a transportation fuel, in the form of gasolina or diesel, with the invention of internal combustion engines for the first vehicles. Consequently, from the 20th century to the present day, with the improvement in the quality of life and the constant increase in population, the use and burning of fossil fuels has increased exponentially, both in energy production, transportation and in the manufacture of everyday products. This has caused a constant increase in pollution, CO2 being one of the main actors, which has caused the emergence of phenomena such as the greenhouse effect and contributes to global warming, one of the origins of climate change on the Planet, which have made many countries aware with their participation and approval of the 2030 Agenda established by the General Assembly of the United Nations Organization (UNGA), which sets a series of challenges to achieve Sustainable Development Goals (SDGs)

Synergistic effect between PPy:PSS copolymers and biomass-derived activated carbons: a simple strategy for designing sustainable high-performance Li–S batteries

Embargado hasta 21/02/2023An activated carbon from the seed of an avocado, a fruit highly and increasingly demanded by consumers, has been used as a sulfur host for lithium sulfur (Li–S) batteries. Although the performance of the resulting composite is acceptable at low current densities, the discharge capacity is stabilized at about 780 mA h g−1 after 250 cycles at 0.1C. It is poor at higher currents, about 75 mA h g−1 after 500 cycles at 5C. Carbon impregnation with a dual copolymer, polypyrrole (PPy) and polystyrene sulfonate (PSS), with conductive properties of an electronic and ionic type, respectively, not only improves the performance of the electrode at low current densities, about 1200 mA h g−1 after 250 cycles at 0.1C, but also at high currents, 640 mA h g−1 after 500 cycles at 5C. We believe that the copolymer not only improves the electrode conductivity, reflected in the electrochemical behaviour of the cell through different parameters such as a notable decrease in charge transfer resistance and an increase in the Li+ diffusion coefficient, but also increases the capacity of inhibition of the polysulfide migration because of the presence of heteroatoms (N, O, S) in its structure

Biomass Porous Carbons Derived from Banana Peel Waste as Sustainable Anodes for Lithium-Ion Batteries

Disordered carbons derived from banana peel waste (BPW) were successfully obtained by employing a simple one-step activation/carbonization method. Different instrumental techniques were used to characterize the structural, morphological, and textural properties of the materials, including X-ray diffraction, thermogravimetric analysis, porosimetry and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The chemical activation with different porogens (zinc chloride, potassium hydroxide and phosphoric acid) could be used to develop functional carbonaceous structures with high specific surface areas and significant quantities of pores. The BPW@H3PO4 carbon exhibited a high specific surface area (815 m2 g−1), chemical stability and good conductivity for use as an anode in lithium-ion batteries. After 200 cycles, this carbon delivered a reversible capacity of 272 mAh g−1 at 0.2 C, showing a notable retention capacity and good cycling performance even at high current densities, demonstrating its effectiveness and sustainability as an anode material for high-energy applications in Li-ion batteries