The inverse perovskite BaLiF3: single-crystal neutron diffraction and analyses of potential ion pathways

Doped barium lithium trifluoride has attracted attention as component for scintillators, luminescent materials and electrodes. With lithium and fluoride, it contains two possibly mobile species, which may account for its ionic conductivity. In this study, neutron diffraction on oxide-containing BaLiF3 single-crystals is performed at up to 636.2°C. Unfortunately, ion-migration pathways could not be mapped by modelling anharmonic ion displacement or by inspecting the scattering-length density that was reconstructed via maximum-entropy methods. However, analyses of the topology and bond-valence site energies derived from the high-temperature structure reveal that the anions can migrate roughly along the edges of the LiF6 coordination octahedra with an estimated migration barrier of ∼0.64 eV (if a vacancy permits), whereas the lithium ions are confined to their crystallographic positions. This finding is not only valid for the title compound but for ion migration in all perovskites with Goldschmidt tolerance factors near unity

The Aluminum-Ion Battery: A Sustainable and Seminal Concept?

The expansion of renewable energy and the growing number of electric vehicles and mobile devices are demanding improved and low-cost electrochemical energy storage. In order to meet the future needs for energy storage, novel material systems with high energy densities, readily available raw materials, and safety are required. Currently, lithium and lead mainly dominate the battery market, but apart from cobalt and phosphorous, lithium may show substantial supply challenges prospectively, as well. Therefore, the search for new chemistries will become increasingly important in the future, to diversify battery technologies. But which materials seem promising? Using a selection algorithm for the evaluation of suitable materials, the concept of a rechargeable, high-valent all-solid-state aluminum-ion battery appears promising, in which metallic aluminum is used as the negative electrode. On the one hand, this offers the advantage of a volumetric capacity four times higher (theoretically) compared to lithium analog. On the other hand, aluminum is the most abundant metal in the earth's crust. There is a mature industry and recycling infrastructure, making aluminum very cost efficient. This would make the aluminum-ion battery an important contribution to the energy transition process, which has already started globally. So far, it has not been possible to exploit this technological potential, as suitable positive electrodes and electrolyte materials are still lacking. The discovery of inorganic materials with high aluminum-ion mobility—usable as solid electrolytes or intercalation electrodes—is an innovative and required leap forward in the field of rechargeable high-valent ion batteries. In this review article, the constraints for a sustainable and seminal battery chemistry are described, and we present an assessment of the chemical elements in terms of negative electrodes, comprehensively motivate utilizing aluminum, categorize the aluminum battery field, critically review the existing positive electrodes and solid electrolytes, present a promising path for the accelerated development of novel materials and address problems of scientific communication in this field

Fundamental principles of battery design

With an increasing diversity of electrical energy sources, in particular with respect to the pool of renewable energies, and a growing complexity of electrical energy usage, the need for storage solutions to counterbalance the discrepancy of demand and offer is inevitable. In principle, a battery seems to be a simple device since it just requires three basic components – two electrodes and an electrolyte – in contact with each other. However, only the control of the interplay of these components as well as their dynamics, in particular the chemical reactions, can yield a high-performance system. Moreover, specific aspects such as production costs, weight, material composition and morphology, material criticality, and production conditions, among many others, need to be fulfilled at the same time. They present some of the countless challenges, which make battery design a long-lasting, effortful task. This chapter gives an introduction to the fundamental concepts of batteries. The principles are exemplified for the basic Daniell cell followed by a review of Nernst equation, electrified interface reactions, and ionic transport. The focus is addressed to crystalline materials. A comprehensive discussion of crystal chemical and crystal physical peculiarities reflects favourable and unfavourable local structural aspects from a crystallographic view as well as considerations with respect to electronic structure and bonding. A brief classification of battery types concludes the chapter

Harmonic Principles of Elemental Crystals—From Atomic Interaction to Fundamental Symmetry

The formation of crystals and symmetry on the atomic scale has persistently attracted scientists through the ages. The structure itself and its subtle dependence on boundary conditions is a reflection of three principles: atomic attraction, repulsion, and the limitations in 3D space. This involves a competition between simplicity and high symmetry on the one hand and necessary structural complexity on the other. This work presents a simple atomistic crystal growth model derived for equivalent atoms and a pair potential. It highlights fundamental concepts, most prominently provided by a maximum number of equilibrium distances in the atom’s local vicinity, to obtain high symmetric structural motifs, among them the Platonic Solids. In this respect, the harmonically balanced interaction during the atomistic nucleation process may be regarded as origin of symmetry. The minimization of total energy is generalized for 3D periodic structures constituting these motifs. In dependence on the pair potential’s short- and long-range characteristics the, by symmetry, rigid lattices relax isotropically within the potential well. The first few coordination shells with lattice-specific fixed distances do not necessarily determine which equilibrium symmetry prevails. A phase diagram calculated on the basis of these few assumptions summarizes stable regions of close-packed fcc and hcp, next to bcc symmetry for predominantly soft short-range and hard long-range interaction. This lattice symmetry, which is evident for alkali metals as well as transition metals of the vanadium and chromium group, cannot be obtained from classical Morse or Lennard-Jones type potentials, but needs the range flexibility within the pair potential

Vorrichtung und Verfahren zur Energiewandlung von thermischer Energie in elektrische Energie

Die Erfindung betrifft eine Vorrichtung (20, 21, 46, 47, 48) und ein Verfahren zur Umwandlung von thermischer Energie in elektrische Energie, wobei die Vorrichtung (20) zumindest eine Anordnung (19, 39, 41, 42) umfasst, die zumindest enthält - ein erstes elektrisch leitfähiges Kontaktelement (31), - ein zweites elektrisch leitfähiges Kontaktelement (32), - ein zwischen den beiden elektrischen Kontaktelementen (31, 32) befindliches Material (4), - einen ersten thermischen Energieträger (1) mit hoher Temperatur Th, - einen zweiten thermischen Energieträger (2) mit vorgegebener niedriger Temperatur Tt, wobei der erste thermische Energieträger (1) zumindest in Verbindung mit dem ersten elektrisch leitfähigen Kontaktelement (31) und der zweite thermische Energieträger (2) zumindest in Verbindung mit dem zweiten elektrisch leitfähigen Kontaktelement (32) stehen.; Dabei ist als Material (4) ein Material mit ionischem oder zumindest kovalentem Bindungscharakter eingesetzt ist, wobei das Material (4) innerhalb seines Volumens (22) mindestens eine Art von Defektspezies (12, 13) aufweist, wobei durch einen eingestellten Temperaturgradienten [Delta]T, ggf. um eine Temperatur (11) mit Tc eines existierenden Defektlöslichkeits-Phasensprungs (3), zwischen einer hohen Temperatur Th im ersten thermischen Energieträger (1) und einer vorgegebenen niedrigen Temperatur Tt im zweiten thermischen Energieträger (2) eine Umlagerung der Defektspezies im Volumen (6, 7) vorhanden ist, wobei ein erster Teil (6) des Volumens (22) des Materials (4) eine hohe Temperatur Th, ggf. oberhalb der Temperatur (11) Tc des Defektlöslichkeits-Phasensprungs (3), und ein zweiter Teil (7) des Volumens (22) des Materials (4) eine niedrige Temperatur Tt, ggf.; unterhalb der Temperatur (11) Tc des Defektlöslichkeits-Phasensprunges (3), aufweisen, so dass mittels des Temperaturgradienten [Delta]T eine Umlagerung der vorhandenen Defektspezies (12, 13) und ggf. ein Dipolmoment erreicht wird, wobei nach Beendigung der Umlagerung infolge des Aufhebens des eingestellten Temperaturgradienten [Delta]T eine Rückdiffusion der Defektspezies (12, 13), bedingt durch den aufgebauten Konzentrationsgradienten und ggf. ein aufgebautes elektrisches Feld, und somit eine elektromotorische Kraft zur Abnahme von gespeicherter elektrischer Energie aus dem Material (4) vorhanden ist