Anglicismos y vida docente

Pertenece a la sección diaria del CVC (Centro Virtual Cervantes).Una de las vías de entrada de anglicismos en nuestra lengua es el mundo universitario y escolar.Peer reviewe

The Solid Solutions Gd2Cu2In1-xMgx - Drastic Increase of the Curie Temperature upon In/Mg Substitution

The Mo2B2Fe-type intermetallic compounds Gd2Cu2In and Gd2Cu2Mg form a complete set of solid solutions Gd2Cu2In1-xMgx. The a lattice parameter, the Weiss constant and the Curie temperature increase with increasing magnesium content in an almost Vegard-like manner, while the c parameter remains almost constant. All members of the solid solutions show ferromagnetism with T(C)s between 114 and 80 K

Rare Earth-rich Cadmium Compounds RE 4 TCd (T = Ni, Pd, Ir, Pt)

New intermetallic compounds RE 4 T Cd (RE = Y, La-Nd, Sm, Gd-Tm, Lu; T = Ni, Pd, Ir, Pt) were synthesized by melting of the elements in sealed tantalum tubes in a highfrequency furnace. They crystallize with the Gd 4 RhIn-type structure, space group F43m, Z = 16. The four gadolinium compounds were characterized by single crystal X-ray diffractometer data: a = 1361.

Comparative Performance Evaluation of Flame Retardant Additives for Lithium Ion Batteries - I. Safety, Chemical and Electrochemical Stabilities

Within this 1st part of a comparative study, flame retardant electrolyte additives (FRs), as candidates for lithium ion battery electrolytes, from four different phosphorous‐containing molecule classes, are investigated. The five FRs (tris(2,2,2‐trifluoroethyl)phosphate (TFP), tris(2,2,2‐trifluoroethyl)phosphite (TTFPi), bis(2,2,2 trifluoroethyl)methylphosphonate (TFMP), (ethoxy)pentafluorocyclotriphosphazene (PFPN) and (phenoxy)pentafluoro‐cyclotriphosphazene (FPPN)) are investigated in a comparative manner to conclude structure‐property relationships according to their self‐extinguishing time (SET), onset temperature of the thermal runaway, chemical and electrochemical stability. SET experiments using standard electrolyte (1 M LiPF6 in ethylene carbonate : dimethyl carbonate 1 : 1 wt%) confirm high reproducibility of the used SET device. The results reveal a strong dependency of the ignition time on the SET. Therefore it is suggested, to investigate the SET for various ignition times. All FR additives remain chemically stable for weeks after added to the standard electrolyte during storage (approved by nuclear magnetic resonance). Cyclophosphazenes show superior results concerning their first time of inflammation and thermal electrolyte stability (approved by adiabatic reaction calorimetry). All additives show partial electrolyte decomposition only during the first charge in voltammetric experiments

Determination of the mechanical integrity of polyvinylidene difluoride in LiNi1/3Co1/3Mn1/3O2 electrodes for lithium ion batteries by use of the micro-indentation technique

Understanding the mechanical aging of lithium ion batteries influencing the binder stability is of particular interest for enhanced battery life. In this study we present an indentation method to investigate the changes in the elasticity of PVdF in NCM electrodes with high reproducibility. To determine changes in elasticity by calculating the indentation work (ηit), a 50 μm flat punch indenter was used. In addition, a drying procedure for DMC washed samples was evaluated to reduce the effect of the washing procedure on the elasticity due to swelling of the binder. NCM electrodes soaked with electrolyte and electrodes after formation were investigated, showing a significant decrease in elasticity due to the contact with the LiPF6 containing organic carbonate solvent based electrolyte and due to the electrochemical formation procedure. Further electrochemical aging reduced the elasticity to nearly ≈50% compared to the pristine electrode. Method development and the obtained results are discussed in detail. The developed method provides a low standard deviation and high reproducibility. Hence, it is a valid methodology for the quantification of related aging mechanisms taking place in lithium ion batteries

Comparative Performance Evaluation of Flame Retardant Additives for Lithium Ion Batteries - II. Full Cell Cycling and Postmortem Analyses

Within this 2nd part of a comparative study five flame retardant additives (FRs) as candidates for lithium ion battery (LIB) electrolytes are evaluated in terms of their electrochemical performance in order to investigate performance differences and their long‐term stability. FRs from four different phosphorus‐containing molecule classes, (namely tris(2,2,2‐trifluoroethyl)phosphate (TFP), tris(2,2,2‐trifluoroethyl)phosphite (TTFPi), bis(2,2,2‐trifluoroethyl)methylphosphonate (TFMP), (ethoxy)pentafluorocyclotriphosphazene (PFPN), (phenoxy)pentafluorocyclotriphosphazene (FPPN)) are investigated using MCMB graphite anode/NMC111 cathode full cells and cycled up to 501 times. A major part of the investigations focuses on the effect of different FRs on the first cycle performance, the raising additional resistance, the rate capability and the self‐discharge behavior of the cells. It is shown that the addition of fluorinated cyclophosphazenes (PFPN and FPPN) provides the best electrochemical performance among the evaluated additives. Postmortem investigations by gas chromatography‐mass spectrometry and scanning electron microscopy further validate the decomposition of TFP and TTFPi during prolonged cycling, thus explaining the detrimental impact on electrochemical performance. Hence, these additives are not suitable for application in LIB in terms of safety enhancement. In contrast, TFMP, PFPN and FPPN improve the electrolyte stability. The formation of typical decomposition products (e. g. dimethyl‐2,5‐dioxahexanedicarboxylate) that indicate severe electrolyte degradation, is avoided by using these additives

Safety Performance of 5 Ah Lithium Ion Battery Cells Containing the Flame Retardant Electrolyte Additive (Phenoxy) Pentafluorocyclotriphosphazene

Investigations on the effect of flame retardant additives (FRs) on the abuse tolerance of large scale lithium ion battery (LIB) cells (5 Ah) are of high relevance in battery science and industry but rarely performed as they are cost and time consuming. In addition, even though FRs are frequently investigated, their positive effect on the safety properties of larger full LIB cells under abusive condition has not been proven yet. The promising FR (phenoxy) pentafluorocyclotriphosphazene (FPPN) is known to exhibit excellent flame retardant‐ and electrochemical properties at the same time. Therefore, FPPN is investigated towards abuse tolerance in 5 Ah LIB cells in this study. Calorimetric investigations show that a mass percentage of 5 wt % FPPN mixed to a standard electrolyte, significantly reduces the self‐heating rate of 5 Ah cells in the temperature range from 80 °C to 110 °C. While nail penetration and external short circuit experiments provide no significant difference between standard and FPPN‐containing cells, an increased overcharge tolerance and a favorable thermal stability at ≈120 °C in overcharge and oven experiments could be shown

Influence of temperature on the aging behavior of 18650-type lithium ion cells: A comprehensive approach combining electrochemical characterization and post-mortem analysis

The understanding of the aging behavior of lithium ion batteries in automotive and energy storage applications is essential for the acceptance of the technology. Therefore, aging experiments were conducted on commercial 18650-type state-of-the-art cells to determine the influence of the temperature during electrochemical cycling on the aging behavior of the different cell components. The cells, based on Li(Ni0.5Co0.2Mn0.3)O2 (NCM532)/graphite, were aged at 20 °C and 45 °C to different states of health. The electrochemical performance of the investigated cells shows remarkable differences depending on the cycling temperature. At contrast to the expected behavior, the cells cycled at 45 °C show a better electrochemical performance over lifetime than the cells cycled at 20 °C. Comprehensive post-mortem analyses revealed the main aging mechanisms, showing a complex interaction between electrodes and electrolyte. The main aging mechanisms of the cells cycled at 45 °C differ strongly at contrast to cells cycled at 20 °C. A strong correlation between the formed SEI, the electrolyte composition and the electrochemical performance over lifetime was observed

Comparison of Different Synthesis Methods for LiNi −0.5-{0.5} Mn 1.5_{1.5} O 4_{4} -Influence on Battery Cycling Performance, Degradation, and Aging

The high-voltage spinel LiNi0.5Mn1.5O4 is one of the most promising candidates for use in high-energy-density lithium-ion batteries. To investigate the influence of the synthesis method and the resulting particle morphology on the electrochemical performance, performance degradation, and aging, different synthesis routes for LiNi0.5Mn1.5O4 were evaluated in this study. Inhomogeneous transition metal cation intermixing and exposure to high temperatures during synthesis led to the formation of a small amount of impurities, which had a severe impact on the electrochemical performance. Furthermore, the particle morphology influences the electrolyte decomposition and the formation of the cathode electrolyte interphase (CEI) on the surface of particles. Moreover, transition metal dissolution was investigated by analyzing the Ni and Mn content in the electrolyte after constant current charge–discharge cycling. The results suggest that an unstable delithiated structure at high potentials leads to the dissolution of Mn and Ni into the electrolyte, whereas the particle morphology had only a minor influence on the extent of transition metal dissolution