Compositional and Structural Aspects of Li-rich Anti-perovskites as Li-ion Battery Cathodes

Alkali-metal ion battery cathode is the part which mostly defines its specific characteristics, thus, studies in this field are always important, to make the batteries fulfill the needs of the rapidly accelerating progress and growing market. Current dissertation represents a comprehensive physicochemical study of novel inorganic compounds with general formula of Li2MChO (M – Mn, Fe, Co; Ch– S, Se) and Pm-3m anti-perovskite structure. One of their key properties is the electrochemical activity, and rather high specific capacity, explained by a high amount of lithium which can be reversibly extracted per formula unit. Although the practical application of these materials as Li-ion battery cathodes is limited due to relatively low operation voltage and high requirements to synthetic conditions, outstanding chemical flexibility of the crystal structure turns the cubic anti-perovskites into excelsior model for studying the synergetic effects of various transition metal cations on the structural stability against lithium removal, as well as on the mechanism of charge compensation. The named investigations are mostly based on operando methods, using synchrotron radiation facilities, and the electrochemical activity of anti-perovskites provides an opportunity to conduct such experiments: while lithium is removed or inserted into the crystal lattice, the electrochemical cell is irradiated, allowing to observe the changes constantly. Such studies may bring use for the battery research in general and give certain hints for creation of new battery materials, in particular, high-entropy ones (if two transition metal cations, or two chalcogenide anions are combined in Li2MChO formula, the compound formally becomes a high-entropy one). Besides, an attempt to extend the research topic was done, introducing the double anti-Ruddlesden-Popper phases (double anti-perovskites). Their structure is layered, which is favorable for the reversible electrochemical alkali-metal, which is in this specific case sodium, extraction, however, as their cationic and anionic sublattices are formed by the same transition metal cations and by the same anions, as in cubic anti-perovskites, they suffer from the same issue of low operation voltage. Nevertheless, from this type of structure it is also possible to expect chemical flexibility, which makes them model compounds as well, but for investigations on layered cathode materials, which are rather common nowadays: one of the most typical examples of those is NMC, which is commercialized, but still has much of unrealized potential. In the end, this dissertation is considered by its author as primarily fundamental research, which is supposed to expand the knowledge in the field of physical chemistry of novel battery compounds, and to give certain keys for their development

Alive publication

An alive publication is a scientific work published on the Internet that is constantly being developed and improved by its author. In this case, serious errors and typos are no longer fatal, nor do they haunt the author for the rest of his or her life. The reader of an alive publication knows that the author is constantly monitoring changes occurring in the science branch under consideration. The dynamics of an alive publication and rejection of the leading role of printing open the door for many of the indispensable qualities that were absent from a printed version. These features allow us to discuss a new genre or a new paradigm of scientific publication.Comment: 26 pages, 4 figure

Structural Behaviour and Charge-Compensation Mechanism in Li2Fe1−xCoxSeO Solid Solutions during Reversible Delithiation

The constantly growing demand for renewable electrical energy keeps the continuation of battery-related research imperative. In spite of significant progress made in the development of Na- and K-ion systems, Li-ion batteries (LIBs) still prevail in the fields of portative devices and electric or hybrid vehicles. Since the amount of lithium on our planet is significantly limited, studies dedicated to the search for and development of novel materials, which would make LIBs more efficient in terms of their specific characteristics and life lengths, are necessary. Investigations of less industry-related systems are also important, as they provide general knowledge which helps in understanding directions and strategies for the improvement of applied materials. The current paper represents a comprehensive study of cubic Li2Fe1−xCoxSeO compounds with an anti-perovskite structure. These solid solutions demonstrate both cationic and anionic electrochemical activity in lithium cells while being applied as cathodes. Cobalt cations remain inactive; however, their amount in the structure defines if the Se0/Se2− or Fe3+/Fe2+ redox couple dominates the charge compensation mechanism upon (de)lithiation. Apart from that, cobalt affects the structural stability of the materials during cycling. These effects were evaluated by means of operando XRD and XAS techniques. The outcomes can be useful for both fundamental and practice-relevant research

Hidden nonlinear supersymmetries in pure parabosonic systems

The existence of intimate relation between generalized statistics and supersymmetry is established by observation of hidden supersymmetric structure in pure parabosonic systems. This structure is characterized generally by a nonlinear superalgebra. The nonlinear supersymmetry of parabosonic systems may be realized, in turn, by modifying appropriately the usual supersymmetric quantum mechanics. The relation of nonlinear parabosonic supersymmetry to the Calogero-like models with exchange interaction and to the spin chain models with inverse-square interaction is pointed out.Comment: 20 pages, one reference corrected, to appear in Int. J. Mod. Phys.

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How to find neutral leptons of the nuMSM?

An extension of the Standard Model by three singlet fermions with masses smaller than the electroweak scale allows to explain simultaneously neutrino oscillations, dark matter and baryon asymmetry of the Universe. We discuss the properties of neutral leptons in this model and the ways they can be searched for in particle physics experiments. We establish, in particular, a lower and an upper bound on the strength of interaction of neutral leptons coming from cosmological considerations and from the data on neutrino oscillations. We analyse the production of neutral leptons in the decays of different mesons and in pp collisions. We study in detail decays of neutral leptons and establish a lower bound on their mass coming from existing experimental data and Big Bang Nucleosynthesis. We argue that the search for a specific missing energy signal in kaon decays would allow to strengthen considerably the bounds on neutral fermion couplings and to find or definitely exclude them below the kaon threshold. To enter into cosmologically interesting parameter range for masses above kaon mass the dedicated searches similar to CERN PS191 experiment would be needed with the use of intensive proton beams. We argue that the use of CNGS, NuMI, T2K or NuTeV beams could allow to search for singlet leptons below charm in a large portion of the parameter space of the νMSM. The search of singlet fermions in the mass interval 2-5 GeV would require a considerable increase of the intensity of proton accelerators or the detailed analysis of kinematics of more than 1010 B-meson decays. © SISSA 2007

Anchorage strength and ductility in shear tests

Article shows shear tests results for anchorage using bent foundation bolts 16, 24 and 36 mm in diameter and torque-controlled undercut anchors 12, 16 and 20 mm in diameter. Load-displacement diagrams were acquired for shear loads in static and dynamic cyclic tests in uncracked and cracked concrete. Cyclic loading pattern simulated seismic loads on anchors. Shear loading tests allowed to estimate influence of cracks and cyclic loading on strength and ductility of anchorage

Flux Growth and Characterization of Bulk InVO4 Crystals

The flux growth of InVO4 bulk single crystals has been explored for the first time. The reported eutectic composition at a ratio of V2O5:InVO4 = 1:1 could not be used as a self-flux since no sign of melting was observed up to 1100 °C. Crystals of InVO4 of typical size 0.5 × 1 × 7 mm3 were obtained using copper pyrovanadate (Cu2V2O7) as a flux, using Pt crucibles. X-ray powder diffraction confirmed the orthorhombic Cmcm structure. Rests of the flux material were observed on the sample surface, with occasional traces of Pt indicating some level of reaction with the crucible. X-ray absorption spectroscopy showed that oxidation states of indium and vanadium ions are +3 and +5, respectively. The size and high quality of the obtained InVO4 crystals makes them excellent candidates for further study of their physical properties