Efecto del peso molecular en la fabricación de cátodos compuestos para baterías de estado sólido

El impacto del procesado en el rendimiento del electrodo en el área de las baterías de estado sólido (SSB) es uno de los menos desarrollados, a pesar de ser un aspecto clave de cara a un escalado para producción industrial. Para demostrar que el conocimiento de los parámetros de producción es esencial para superar las limitaciones de las SSB (como, por ejemplo, los tiempos de carga y descarga), se ha fabricado una serie de baterías SSB con ánodo de litio y un electrolito de polímero PEO, con dos pesos moleculares diferentes (700 kg mol-1 y 400 kg mol-1) para la fabricación del cátodo. El descenso en el peso molecular permite la adición de una mayor cantidad de contenido sólido (ca. 50 wt%), que resulta en cátodos compuestos con superficies más regulares, bajas porosidades y buena adhesión al colector cuando se laminan sobre aluminio con sustrato de carbono. En cuanto al rendimiento electroquímico de los cátodos, se ha analizado en celdas de petaca completas, obteniendo resultados de carga y descarga cercanos a los valores teóricos (170 mAh g-1), incluso a C/5. Tras varios ciclados, los compuestos de PEO 700 kg mol-1, son capaces de alcanzar más de 100 ciclos a C/10 y C/5. Desgraciadamente, el rendimiento de las celdas con PEO 400 kg mol-1 C/5 se pierde tras 5 ciclos, pudiendo relacionarse con el menor peso molecular del propio PEO, que aporta peores propiedades mecánicas.The significant impact of the processing on the electrode performance is one of the least developed aspects in the field of solid-state batteries (SSB) despite being a key issue for the transference of lab scale developments to production scale. To demonstrate that the knowledge of production parameters is essential and can help to overcome current SSBs limitations such as the improvement of the charge and discharge times, a set of SSBs with a lithium metal anode and a polymer electrolyte have been fabricated employing PEO, with two different molecular weights (700 kg mol-1 and 400 kg mol-1) for the catholyte preparation. The decrease in the molecular weight of the polymer allows for slurries with higher solid contents (ca. 50 wt%) that result in composite cathodes with very smooth surfaces, low porosities and decent adhesion to the current collector when laminated onto carbon coated aluminium foils. The electrochemical performance of each cathode is studied in full cell configuration obtaining discharge and charge capacities close to the theoretical ones (170 mAh g-1) even at C/5. After several cycles, composite cathodes mixed with PEO 700 kg mol-1 are able to reach more than 100 cycles at C/10 and C/5. Unfortunately, the performance of cells with PEO 400 kg mol-1 is lost after 5 cycles at C/5 which could be related with the worst mechanical properties related with the use of PEO with lower molecular weight.Egoera solidoko baterien (SSB) eremuan, prozesatzeak elektrodoaren errendimenduan duen eragina gutxien garatuenetako bat da, industria-produkziorako eskalatze bati begira funtsezko propietatea den arren. Produkzio-parametroen ezagutza SSBn mugak gainditzeko funtsezkoa dela frogatzeko (adibidez, karga/deskarga denboretan), bateria batzuk fabrikatu dira litio-anodoarekin eta PEO polimero elektrolito batekin, katodoa fabrikatzeko bi pisu molekular desberdinekin (700 kg mol-1 eta 400 kg mol-1). Pisu molekularraren jaitsierak eduki solido gehiago gehitzea ahalbidetzen du (ca. 50 wt%), azalera erregularragoarekin, porotasun baxuagoarekin eta kolektorearekiko atxikimendu ona dituzten katodo konposatuetan ateratzen dena aluminioaren gainean karbono-substratuarekin ijezten direnean. Katodoen errendimendu elektrokimikoari dagokionez, petaka-gelaxka osoetan aztertu da, eta balio teorikoetatik (170 mAh g-1) hurbil dauden karga- eta deskarga-emaitzak lortu dira, baita C/5 ekoak ere. Hainbat ziklo ondoren, PEO 700 kg mol-1 konposatuak a C/10 eta C/5 100 ziklotik gora lortzeko gai dira. Zoritxarrez, PEO 400 kg mol-1 C/5 duten gelaxken errendimendua 5 zikloren ondoren galtzen da, eta PEO beraren pisu molekular txikiagoarekin lotu daiteke, propietate mekaniko okerragoak ematen baitit

The brigand's frontier: bandits, lineages and towns between Álava, Guipúzcoa and Navarra in the Late Middle Ages

[ES] El objetivo de este trabajo es el estudio del espacio fronterizo entre Álava, Guipúzcoa y Navarra en los siglos finales de la Edad Media. En particular a través del análisis del bandidaje, de las sucesivas reorganizaciones del espacio fronterizo, la presión de los linajes sobre el campesinado y los enfrentamientos internobiliarios.[EN] The aim of this article is to analyze the border between Álava, Guipúzcoa and Navarra during the last centuries of the Middle Ages through the analysis of banditry, the process of consolidation of the frontier area, the pressure exerted by the nobility on the local peasantry and the study of the conflicts that divided the different noble lineages of this region.Este trabajo es fruto del proyecto de investigación "De la lucha de bandos a la hidalguía universal: transformaciones sociales, políticas e ideológicas en el País Vasco (ss. XIV y XV)", financiado por el MEC, Ref. HUM2004-0144

El discurso político de los protagonistas de las luchas sociales en el País Vasco al final de la Edad Media

Acompaña al nº monográfico dedicado a: Lucha política. Condena y legitimación en la España medieva

Acceso al poder y discurso político en las villas cantábricas al final de la Edad Media

Our proposal revolves around the themes of political discourse and culture in the coastal towns of Cantabria from the late fourteenth to the early sixteenth centuries. Drawing on both municipal and legal documentation, we will examine the means of access to municipal office in the period before the carve-up of power among factions, the political culture of the factions themselves and the alternatives to such culture. Indeed the factions' political discourse centred on their role as protectors of the community, their control of certain posts since time immemorial and their belonging to ancient lineages, which in turn guaranteed the prestige, honour and renown regarded as fundamental to such positions of power. The opposition to such power-sharing came chiefly from the influential brotherhoods of fishermen and from the artisans' guilds in the several Cantabrian towns, but it generally failed to obtain significant municipal posts. The faction system only came to an end when, from 1476 onwards, the political model proposed in 1435 by the merchants of Bilbao came to be widely adopted.La propuesta que presentamos gira en tomo a los discursos y las culturas políticas en las villas cantábricas desde la llegada de los Trastámara hasta los primeros años del siglo XVI. A partir de la documentación municipal y judicial, abordaremos el acceso al gobierno municipal antes del reparto del poder entre los bandos, la cultura política de los banderizos y las propuestas alternativas a la misma. El discurso político de los banderizos, se apoya sobre su papel en la defensa de la comunidad, la inmemorialidad en la ocupación de los oficios y la pertenencia a un antiguo linaje, garantía del prestigio, honor y buena fama imprescindibles para detentar los oficios de la villa. La oposición a ese reparto del poder de las influyentes cofradías de pescadores o de los cabildos artesanos de las villas cantábricas no se concretó en su acceso a los oficios. La cultura política banderiza solo terminó cuando, a partir de 1476, se impuso definitivamente un modelo político que los mercaderes habían propuesto en la villa de Bilbao en 1435

Role of dispersion interactions in Endohedral TM@(ZnS)12 structures

Role of dispersion interactions in Endohedral TM@(ZnS)(12) structures[EN] II−VI semiconducting materials are gaining attention due to their optoelectronic properties. Moreover, the addition of transition metals, TMs, might give them magnetic properties. The location and distance of the TM are crucial in determining such magnetic properties. In this work, we focus on small hollow (ZnS)12 nanoclusters doped with TMs. Because (ZnS)12 is a cage-like spheroid, the cavity inside the structure allows for the design of endohedral compounds resembling those of C60. Previous studies theoretically predicted that the first-row TM(ZnS)12 endohedral compounds were thermodynamically unstable compared to the surface compounds, where the TM atom is located at the surface of the cluster. The transition states connecting both structure families were calculated, and the estimated lifetimes of these compounds were predicted to be markedly small. However, in such works dispersion effects were not taken into account. Here, in order to check for the influence of dispersion on the possible stabilization of the desired TM(ZnS)12 endohedrally doped clusters, several functionals are tested and compare to MP2. It is found that the dispersion effects play a very important role in determining the location of the metals, especially in those TMs with the 4s3d shell half-filled or completely filled. In addition, a complete family of TM doped (ZnS)12 nanoclusters is explored using ab initio molecular dynamics simulations and local minima optimizations that could guide the experimental synthesis of such compounds. From the magnetic point of view, the Cr(7S)@(ZnS)12 compound is the most interesting case, since the endohedral isomer is predicted to be the global minimum. Moreover, molecular dynamics simulations show that when the Cr atom is located at the surface of the cluster, it spontaneously migrates toward the center of the cavity at room temperature.Financial support comes from Eusko Jaurlaritza through project IT1254-19. The authors are thankful for technical and human support provided by SGIker (UPV/EHU, ERDF, EU). E.J.I. acknowledges the support of the Ikerbasque Fellowship. E.R.C. acknowledges funding from the Juan de la Cierva program IJCI-2017-34658

Numerical characterization of local and global non-uniformities in the load distribution in ball screws

Load distribution in ball screws is a representation of the ball contact stress, and it is fundamental to understanding the behavior of these machine elements. This work aims to conduct a multi-variable analysis of the load distribution in ball screws. For this purpose, a numerical tool is developed for the generation and calculation of ball screw finite element (FE) models, which has been validated against the state of the art. This tool is based on the combination of an analytical contact model and the use of high-order FE models for the analysis of the load distribution of ball screws and stands out for its accuracy (less than 1% error against high-order FE models), adaptability, versatility (models are generated with more than 20 design variables and they can be introduced as components in larger models) and efficiency (being the computational time 1.25% of that of a high-order FE models) with respect to other existing models. Many different design variables (number of start threads, pitch, contact angle, ball size, slenderness and load arrangement) are studied in order to obtain a general characterization of the morphology of the load distribution in ball screws. Among them, the most influential variables on the load distribution and therefore on the structural behavior of ball screws are, load arrangement (with ratio r variations of up to 25% on the same ball screw) and slenderness (with ratio variations of up to 13% on ball screws with two turns of difference). The two most characteristic features, the non-uniformity at a local and global level are identified, along with as the possible causes of their appearance and the consequences that they may cause