Insights into the LiMn2O4 Cathode Stability in Aqueous Electrolyte

LiMn2O4 (LMO), cathodes present large stability when cycled in aqueous electrolytes, contrasting its behavior in conventional organic electrolytes in Lithium-ion batteries (LIBs). To elucidate the mechanisms underlying this distinctive behavior, we employ unconventional characterization techniques, including Variable Energy Positron Annihilation Lifetime Spectroscopy (VEPALS), Tip-Enhanced Raman Spectroscopy (TERS) and macro-Raman Spectroscopy (with mm-size laser spot). These still rather unexplored techniques in the battery field provide complementary information across different length scales, revealing previously hidden features. VEPALS offers atomic-scale insights, uncovering cationic defects and sub-nanometer pores that tend to collapse with cycling. TERS, operating at the nanometric range at the surface, captured the presence of Mn3O4 and its dissolution with cycling, elucidating dynamic changes during operation. Additionally, TERS highlights SO42- accumulation at grain boundaries. Macro-Raman Spectroscopy focuses on the micrometer scale, depicting small changes in the cathode's long-range order, suggesting a slow but progressive loss of crystalline quality under operation. Integrating these techniques provides a comprehensive assessment of LMO cathode stability in aqueous electrolytes, offering multifaceted insights into phase and defect evolution that can help to rationalize the origin of such stability when compared to conventional organic electrolytes. Our findings advance the understanding of LMO behavior in aqueous environments and provide guidelines for its development for next-generation LIBs

Spontaneous formation of spiral-like patterns with distinct periodic physical properties by confined electrodeposition of Co-In disks

Spatio-temporal patterns are ubiquitous in different areas of materials science and biological systems. However, typically the motifs in these types of systems present a random distribution with many possible different structures. Herein, we demonstrate that controlled spatio-temporal patterns, with reproducible spiral-like shapes, can be obtained by electrodeposition of Co-In alloys inside a confined circular geometry (i.e., in disks commensurate with the typical size of the spatio-temporal features). These patterns are mainly of compositional nature, i.e., with virtually no topographic features. Interestingly, the local changes in composition lead to a periodic modulation of the physical (electric, magnetic and mechanical) properties. Namely, the Co-rich areas show higher saturation magnetization and electrical conductivity and are mechanically harder than the In-rich ones. Thus, this work reveals that confined electrodeposition of this binary system constitutes an effective procedure to attain template-free magnetic, electric and mechanical surface patterning with specific and reproducible shapes

Spontaneous formation of spiral-like patterns with distinct periodic physical properties by confined electrodeposition of Co-In disks

Golvano-Escobal, Irati et al.Spatio-temporal patterns are ubiquitous in different areas of materials science and biological systems. However, typically the motifs in these types of systems present a random distribution with many possible different structures. Herein, we demonstrate that controlled spatio-temporal patterns, with reproducible spiral-like shapes, can be obtained by electrodeposition of Co-In alloys inside a confined circular geometry (i.e., in disks that are commensurate with the typical size of the spatio-temporal features). These patterns are mainly of compositional nature, i.e., with virtually no topographic features. Interestingly, the local changes in composition lead to a periodic modulation of the physical (electric, magnetic and mechanical) properties. Namely, the Co-rich areas show higher saturation magnetization and electrical conductivity and are mechanically harder than the In-rich ones. Thus, this work reveals that confined electrodeposition of this binary system constitutes an effective procedure to attain template-free magnetic, electric and mechanical surface patterning with specific and reproducible shapes.This work has been partially funded by the 2014-SGR-1015, 2014-SGR-1216 and 2014-SGR-753 projects from the Generalitat de Catalunya, the MAT2014-57960-C3-1-R, MAT2014-51778-C2-1-R and FIS2013-48668-C2-1-P from the Spanish Ministerio de Economía y Competitividad (MINECO) and the ‘Fondo Europeo de Desarrollo Regional’ (FEDER). Dr. Eva Pellicer and Dr. Neus Domingo are also grateful to MINECO for the “Ramon y Cajal” contracts (RYC-2012-10839 and RYC-2010-06365 respectively). ICN2 and ICMAB acknowledge support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295 and Grant SEV-2015-0496, respectively). The PEEM experiments were performed at CIRCE beamline at ALBA Synchrotron with the collaboration of ALBA staff.Peer reviewe

Heart failure in COVID-19 patients: prevalence, incidence and prognostic implications

Aims: Data on the impact of COVID-19 in chronic heart failure (CHF) patients and its potential to trigger acute heart failure (AHF) are lacking. The aim of this work was to study characteristics, cardiovascular outcomes and mortality in patients with confirmed COVID-19 infection and a prior diagnosis of heart failure (HF). Further aims included the identification of predictors and prognostic implications for AHF decompensation during hospital admission and the determination of a potential correlation between the withdrawal of HF guideline-directed medical therapy (GDMT) and worse outcomes during hospitalization. Methods and results: Data for a total of 3080 consecutive patients with confirmed COVID-19 infection and follow-up of at least 30 days were analysed. Patients with a previous history of CHF (n = 152, 4.9%) were more prone to the development of AHF (11.2% vs. 2.1%; P < 0.001) and had higher levels of N-terminal pro brain natriuretic peptide. In addition, patients with previous CHF had higher mortality rates (48.7% vs. 19.0%; P < 0.001). In contrast, 77 patients (2.5%) were diagnosed with AHF, which in the vast majority of cases (77.9%) developed in patients without a history of HF. Arrhythmias during hospital admission and CHF were the main predictors of AHF. Patients developing AHF had significantly higher mortality (46.8% vs. 19.7%; P < 0.001). Finally, the withdrawal of beta-blockers, mineralocorticoid receptor antagonists and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers was associated with a significant increase in in-hospital mortality. Conclusions: Patients with COVID-19 have a significant incidence of AHF, which is associated with very high mortality rates. Moreover, patients with a history of CHF are prone to developing acute decompensation after a COVID-19 diagnosis. The withdrawal of GDMT was associated with higher mortalit

Joint Observation of the Galactic Center with MAGIC and CTA-LST-1

MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes (IACTs), designed to detect very-high-energy gamma rays, and is operating in stereoscopic mode since 2009 at the Observatorio del Roque de Los Muchachos in La Palma, Spain. In 2018, the prototype IACT of the Large-Sized Telescope (LST-1) for the Cherenkov Telescope Array, a next-generation ground-based gamma-ray observatory, was inaugurated at the same site, at a distance of approximately 100 meters from the MAGIC telescopes. Using joint observations between MAGIC and LST-1, we developed a dedicated analysis pipeline and established the threefold telescope system via software, achieving the highest sensitivity in the northern hemisphere. Based on this enhanced performance, MAGIC and LST-1 have been jointly and regularly observing the Galactic Center, a region of paramount importance and complexity for IACTs. In particular, the gamma-ray emission from the dynamical center of the Milky Way is under debate. Although previous measurements suggested that a supermassive black hole Sagittarius A* plays a primary role, its radiation mechanism remains unclear, mainly due to limited angular resolution and sensitivity. The enhanced sensitivity in our novel approach is thus expected to provide new insights into the question. We here present the current status of the data analysis for the Galactic Center joint MAGIC and LST-1 observations

Volume resistive switching in metallic perovskite oxides driven by the metal-Insulator transition

Los óxidos de perovskita fuertemente correlacionados son una clase de materials con fascinantes propiedades físicas intrínsecas debido a la interacción de efectos de carga, spin, órbita y cristalinos. Efectos exóticos, como superconductividad, ferromagnetismo, ferroelectricidad o transiciones metal-aislante se producen gracias a la competición de los diferentes grados de libertad del sistema. El uso de estos efectos en una nueva generación de dispositivos es una fuente de inspiración continua para la comunidad científica. Los dispositivos de Memoria Resistiva de Acceso aleatorio (RRAM) son uno de los candidatos más prometedores para ganar la carrera hacia la memoria universal del futuro, debido a sus excelentes propiedades en términos de escalabilidad, fatiga frente a ciclado, retención y velocidad de operación. Están basadas en el efecto de Conmutación Resistiva (RS), dónde dos (o más) estados de resistencia, reversibles y no volátiles son inducidos mediante la aplicación de un campo eléctrico intenso. Este fenómeno ha sido observado en una gran variedad de óxidos, donde es ampliamente aceptado que el movimiento de oxígeno juega un papel fundamental para explicar su origen. Sin embargo, el mecanismo físico preciso que gobierna el efecto depende del material, y en algunos de ellos, dicho mecanismo aún no es comprendido en su totalidad. Esta falta de compresión es hoy en vía es uno de los cuellos de botella que está retrasando el uso generalizado de esta tecnología. En esta tesis, presentamos un novedoso mecanismo de RS basado en la Transición Metal-Aislante (MIT) perovskitas metálicas con correlación electrónica fuerte. Hemos estudiado el comportamiento RS de tres diferentes familias de perovskitas metálicas: La1-xSrxMnO3, YBa2Cu3O7-d y RENiO3 y demostramos que estos tres sistemas con conducción mixta eletrónica-iónica pueden experimentar una MIT, como consecuencia de la aplicación del campo eléctrico intenso, y que puede transformar su volumen bulk. Esta conmutación resistiva de carácter volúmico tiene una naturaleza diferente the los usuales tipos filamentar e interfacial, y abre nuevas oportunidades para el diseño de nuevos dispositivos robustos. Hemos caracterizado conciencudamente el efecto de RS a la nanoescala mediante Microscopía de Fuerzas Atómicas en modo Conducción (C-AFM). Espectroscopía de Fuerza Túnel (STS) y medidas de transporte dependientes de la temperatura han sido realizadas en los diferentes estados resistivos para obtener detalles de su estructura electrónica. Hemos reproducido con éxito el comportamiento memristivo nanoscópico en una escala micrómetrica mediante el uso de sondas de W-Au en una estación de puntas. Usando esta aproximación, hemos llevado a cabo medidas en diferentes atmósferas, las cuales sugieren el intercambio de oxígeno con la atmósfera. Además, presentamos una prueba de concepto de una configuración de tres terminales, donde la conmutación resistiva es inducida en la puerta del dispositivo. En el caso particular del superconductor YBa2Cu3O7-d, hemos estudiado la influencia en las propiedades superconductoras de zonas de alta resistencia embebidas en la matriz del material. Esta aproximación sienta las bases hacia el diseño de dispositivos con zonas de anclaje de vórtices reconfigurables. La interpretación de los resultados se hará en términos de una transición volúmica de tipo Mott, que estimamos ser de validez general para perovskitas metálicas de óxidos complejos.Strongly correlated perovskite oxides are a class of materials with fascinating intrinsic physical functionalities due to the interplay of charge, spin, orbital ordering and lattice effects. The exotic phenomena arising from these competing degrees of freedom include superconductivity, ferromagnetism, ferroelectricity and metal-insulator transitions, among others. The use of these exotic phenomena in a new generation of devices with new and enhanced functionalities is continuing inspiring the research community. In this sense, Resistive-Random Access Memories (RRAM) are one of the most promising candidates to win the race towards the universal memory of the future, which could overcome the limitations of actual technologies (Flash and Dynamic-RAM), due to their excellent properties in terms of scalability, endurance, retention and switching speeds. They are based on the Resistive Switching effect (RS), where the application of an electric field produces a reversible, non-volatile change in the resistance between two or more resistive states. This phenomenon has been observed in a large variety of oxide materials, where the motion of oxygen is widely accepted to play a key role in their outstanding properties. However, the exact mechanism governing this effect is material-dependent and for some of them it is still far to be understood. This lack of understanding is actually one of the main bottlenecks preventing the widespread use of this technology. In this thesis, we present a novel Resistive Switching mechanism based on the Metal-Insulator Transition (MIT) in metallic perovskite oxides with strong electron electron interaction. We analyse the RS behaviour of three different families of metallic perovskites: La1-xSrxMnO3, YBa2Cu3O7-δ and RENiO3 and demonstrate that the MIT of these mixed electronic-ionic conductors can be tuned upon the application of an electric field, being able to transform the entire bulk volume. This volume RS is different in nature from interfacial or filamentary type and opens new possibilities of robust device design. Thorough nanoscale electrical characterization of the RS effect in these systems has been performed by means of Conductive-Atomic Force Microscopy (C-AFM). Scanning Tunnelling Spectroscopy (STS) and temperature-dependent transport measurements were performed in the different resistive states to get insight into their electronic features. The nanoscale memristive behaviour of these systems is successfully reproduced at a micrometric scale with W-Au tips in probe station experiments. Using this approach, atmosphere dependent measurements were undertaken, where oxygen exchange with the ambience is strongly evidenced. In addition, we present a proof-of-principle result from a 3-Terminal configuration where the RS effect is applied at the gate of the device. In the particular case of superconducting YBa2Cu3O7-δ films, we have studied the influence of high resistance areas, which are embedded in the material, on the superconducting transport properties enabling vortex pinning modification and paving the way towards novel reconfigurable vortex pinning sites. We interpret the RS results of these strongly correlated systems in terms of a Mott volume transition, that we believe to be of general validity for metallic perovskite complex oxides. We have verified that strongly correlated metallic perovskite oxides are a unique class of materials very promising for RS applications due to its intrinsic MIT properties that boosts a robust volumetric resistive switching effect. This thesis settles down the framework to understand the RS effect in these strongly correlated pervoskites, which could eventually lead to a new generation of devices exploiting the intrinsic MIT of these systems

Thermoelectric stack sample cooling modification of a commercial atomicforce microscopy

Enabling temperature dependent experiments in Atomic Force Microscopy is of great interest to study materials and surface properties at the nanoscale. By studying Curie temperature of multiferroic materials, temperature dependent phase transitions on crystalline structures or resistive switching phenomena are only a few examples of applications. We present an equipment capable of cooling samples using a thermoelectric cooling stage down to −61.4°C in a 15 × 15 mm2 sample plate. The equipment uses a four-unit thermoelectric stack to achieve maximum temperature range, with low electrical and mechanical noise. The equipment is installed into a Keysight 5500LS Atomic Force Microscopy maintaining its compatibility with all Electrical and Mechanical modes of operation. We study the contribution of the liquid cooling pump vibration into the cantilever static deflection noise and the temperature dependence of the cantilever deflection. A La0.7Sr0.3MnO3-y thin film sample is used to demonstrate the performance of the equipment and its usability by analyzing the resistive switching phenomena associated with this oxide perovskite.This research was supported by Consolider NANOSELECT (CSD 2007-00041). ICMAB acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496). The authors thank ICMAB Scientific and Technical Services.Peer reviewe

Safe extended-range cycling of Li4Ti5O12-based anodes for ultra-high capacity thin-film batteries

Lithium titanium oxide thin films are increasingly popular anode materials in microbatteries and hybrid supercapacitors, due to their improved safety, cost, and cycle lifetime. So far, research efforts have mainly focused on the pure spinel phase Li4Ti5O12 (LTO) and only a small fraction is dedicated to a broader spectrum of titanium-based metal oxide thin films. In this work, pulsed laser deposition is used in a multilayer approach by alternating LTO and Li2O ablations to create a heterogeneous landscape in the titania-based micro-anodes. This rich microstructure enables the safe extension of the accessible electrochemical window down to 0.2 V. This leads to extraordinary high specific capacities of 250–300 mAh/g at 1 C, maintaining a stable discharge capacity of 180 mAh/g at 16 C. Operando spectroscopic ellipsometry and Raman spectroscopy are used to track optical and structural changes as a function of the discharge voltage down to 0.01 V. A kinetically limited degradation mechanism based on the effective trapping of Li-ions at the octahedral 16c positions is proposed when cycling in the range of 0.2–0.01 V. In essence, our work contributes to titania-based nanoshapes as anodes of increased specific capacity due to a higher Li-site occupation, while maintaining their good stability and safety.This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 824072 (HARVESTORE), the European Regional Development Fund under the FEDER Catalonia Operative Programme 2014–2020 (FEM-IoT, 001-P-00166), and the “Generalitat de Catalunya” (2017 SGR 1421, NANOEN). FIB, STEM, and STEM-EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, Spain. R. A. gratefully acknowledges the support from the Spanish MICINN through project grant PID2019-104739 GB-100/AEI/10.13039/501100011033, from the Government of Aragon (project DGA E13-20R) and European Union H2020 program “ESTEEM3" (823717). J. C. G.- R., acknowledges the financial support provided by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 801342 (Tecniospring INDUSTRY), as well as by the Agency for Business Competitiveness of the Government of Catalonia. Spectroscopic Ellipsometry measurements and models have been developed in collaboration with HORIBA France SAS. Suitable Pt-covered Si substrates have been provided by the Institute of Microelectronics of Barcelona IMB-CNM. GI-XRD measurements have been collected at the Scientific and Technological Center (CCiT) at the University of Barcelona.Peer reviewe

High performance LATP thin film electrolytes for all-solid-state microbattery applications

This article is part of the themed collection: Recent Open Access Articles.The NASICON superionic solid electrolyte Li1+xAlxTi2−x(PO4)3 (LATP) with 0.3 ≤ x ≤ 0.5 remains one of the most promising solid electrolytes thanks to its good ionic conductivity and outstanding stability in ambient air. Despite the intensive research for bulk systems, there are only very few studies of LATP in a thin film form (thickness < 1 μm) and its implementation in all-solid-state batteries and microbatteries. The following study fills this gap by exploring the properties of high performance LATP thin films fabricated by large-area Pulsed Laser Deposition (PLD). The as-deposited thin films exhibit an ionic conductivity of around 0.5 μS cm−1 at room temperature (comparable to the state-of-the-art of LiPON) which increases to a remarkably high value of 0.1 mS cm−1 after an additional annealing at 800 °C. A possible cause for this significant enhancement in ionic conductivity by two orders of magnitude is the formation of a glassy, intergranular phase. The performance of both as-deposited and annealed LATP films makes them suitable as solid electrolytes, which opens the path to a new family of stable and high performance all-solid-state thin film batteries.This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 824072 (HARVESTORE), from the European Regional Development Fund under the FEDER Catalonia Operative Programme 2014-2020 (FEM-IoT, 001-P-00166) and the “Generalitat de Catalunya” (2017 SGR 1421, NANOEN). FIB, HRSTEM, EDS and EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, Spain. R. A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MINECO) and the MICINN through project grants MAT2016-79776-P (AEI/FEDER, UE) and PID2019-104739GB-I00 as well as from the European Union H2020 program “ESTEEM3” (823717). J. C. G.-R., acknowledges the financial support provided by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 801342 (Tecniospring INDUSTRY), as well as by the Agency for Business Competitiveness of the Government of Catalonia. NMR measurements were supported and carried out at the Centre for Cooperative Research on Alternative Energies (CIC energiGUNE) as a member of the Basque Research and Technology Alliance (BRTA). Suitable Si3N4 substrates and microelectrodes have been provided by the Institute of Microelectronics of Barcelona IMB-CNM. Pt-covered Si substrates have been fabricated by the Interuniversity Microelectronics Centre (imec) in Leuven, Belgium. GI-XRD measurements have been collected at the Scientific and Technological Center (CCiT) at the University of Barcelona.Peer reviewe