Transition between growth of dense and porous films: theory of dual-layer SEI

The formation of passivating films is a common aging phenomenon, for example in weathering of rocks, silicon, and metals. In many cases, a dual-layer structure with a dense inner and a porous outer layer emerges. However, the origin of this dual-layer growth is so far not fully understood. In this work, a continuum model is developed, which describes the morphology evolution of the solid-electrolyte interphase (SEI) in lithium-ion batteries. Transport through the SEI and a growth reaction governed by the SEI surface energies are modelled. In agreement with experiments, this theory predicts that SEI grows initially as a dense film and subsequently as a porous layer. This dynamic phase transition is driven by the slowing down of electron transport as the film thickens. Thereby, the model offers a universal explanation for the emergence of dual-layer structures in passivating films

relationships and interdependencies

Behavioral and personality characteristics are factors that may jointly regulate body weight. This study explored the relationship between body mass index (BMI) and self-reported behavioral and personality measures. These measures included eating behavior (based on the Three-Factor Eating Questionnaire; Stunkard and Messick, 1985), sensitivity to reward and punishment (based on the Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) scales) (Carver and White, 1994) and self-reported impulsivity (based on the Barratt Impulsiveness Scale-11; Patton et al., 1995). We found an inverted U-shaped relationship between restrained eating and BMI. This relationship was moderated by the level of disinhibited eating. Independent of eating behavior, BIS and BAS responsiveness were associated with BMI in a gender-specific manner with negative relationships for men and positive relationships for women. Together, eating behavior and BIS/BAS responsiveness accounted for a substantial proportion of BMI variance (men: ∼25%, women: ∼32%). A direct relationship between self-reported impulsivity and BMI was not observed. In summary, our results demonstrate a system of linear and non-linear relationships between the investigated factors and BMI. Moreover, body weight status was not only associated with eating behavior (cognitive restraint and disinhibition), but also with personality factors not inherently related to an eating context (BIS/BAS). Importantly, these relationships differ between men and women

Modeling dynamic personality theories in a continuous‐time framework: An illustration

Objective Personality psychology has traditionally focused on stable between-person differences. Yet, recent theoretical developments and empirical insights have led to a new conceptualization of personality as a dynamic system (e.g., Cybernetic Big Five Theory). Such dynamic systems comprise several components that need to be conceptually distinguished and mapped to a statistical model for estimation. Method In the current work, we illustrate how common components from these new dynamic personality theories may be implemented in a continuous time-modeling framework. Results As an empirical example, we reanalyze experience sampling data with N = 180 persons (with on average T = 40 [SD = 8] measurement occasions) to investigate four different effects between momentary happiness, momentary extraverted behavior, and the perception of a situation as social: (1) between-person effects, (2) contemporaneous effects, (3) autoregressive effects, and (4) cross-lagged effects. Conclusion We highlight that these four effects must not necessarily point in the same direction, which is in line with assumptions from dynamic personality theories.Peer Reviewe

Modelling of Lithium Droplet Formation During Lithium Dissolutio

Lithium metal anode batteries have regained a lot of research attention as they are promising candidates for next-generation energy storage systems. However, the poor Coulombic efficiency limits the battery’s cyclability. The main causes for low efficiencies are the irreversible loss of active lithium due to the formation of a solid electrolyte interface (SEI) and the formation of unreactive, dead metallic lithium which is disconnected from the current collector. Experiments show that during the dissolution of lithium whiskers, which grow as irregular structures during plating, the tip cannot be dissolved. We developed a generalized phase-field model of the dissolution process to gain insights into the underlying mechanisms of “dead” lithium formation and capacity fade. Our model describes the dissolution of a single lithium whisker in a liquid electrolyte based on lithium surface tension and the interaction between lithium and the interphase, utilizing the framework of non-equilibrium thermodynamics. We study under which circumstances instabilities occur and dead lithium forms. Our model predicts the nucleation of an instability for low stripping current densities, induced by interactions with the SEI. This leads to an incomplete dissolution and the formation of an electrically disconnected metallic lithium droplet, in agreement with optical microscope observations of lithium dissolution

A volume-based description of transport in incompressible liquid electrolytes and its application to ionic liquids

Transference numbers play an important role in understanding the dynamics of electrolytes and assessing their performance in batteries. Unfortunately, these transport parameters are difficult to measure in highly concentrated liquid electrolytes such as ionic liquids. Also, the interpretation of their sign and magnitude has provoked an ongoing debate in the literature further complicated by the use of different languages. In this work, we highlight the role of the reference frame for the interpretation of transport parameters using our novel thermodynamically consistent theory for highly correlated electrolytes. We argue that local volume conservation is a key principle in incompressible liquid electrolytes and use the volume-based drift velocity as a reference. We apply our general framework to electrophoretic NMR experiments. For ionic liquid based electrolytes, we find that the results of the eNMR measurements can be best described using this volume-based description. This highlights the limitations of the widely used center-of-mass reference frame which for example forms the basis for molecular dynamics simulations – a standard tool for the theoretical calculation of transport parameters. It shows that the assumption of local momentum conservation is incorrect in those systems on the macroscopic scale

In vivo imaging enables high resolution preclinical trials on patients' leukemia cells growing in mice.

Xenograft mouse models represent helpful tools for preclinical studies on human tumors. For modeling the complexity of the human disease, primary tumor cells are by far superior to established cell lines. As qualified exemplary model, patients' acute lymphoblastic leukemia cells reliably engraft in mice inducing orthotopic disseminated leukemia closely resembling the disease in men. Unfortunately, disease monitoring of acute lymphoblastic leukemia in mice is hampered by lack of a suitable readout parameter

Local volume conservation in concentrated electrolytes is governing charge transport in electric fields

While ion transport processes in concentrated electrolytes, e.g. based on ionic liquids (IL), are a subject of intense research, the role of conservation laws and reference frames is still a matter of debate. Employ-ing electrophoretic NMR, we show that momentum conservation, a typical prerequisite in molecular dynamics (MD) simulations, is not governing ion transport. Involving density measurements to deter-mine molar volumes of distinct ion species, we propose that conservation of local molar species volumes is the governing constraint for ion transport. The experimentally quantified net volume flux is found as zero, implying a non-zero local momentum flux, as tested in pure ILs and IL-based electrolytes for a broad variety of concentrations and chemical compositions. This constraint is consistent with incom-pressibility, but not with a local application of momentum conservation. The constraint affects the calcu-lation of transference numbers as well as comparisons of MD results to experimental findings

Modelling of Lithium Whisker Dissolution

In the search for next generation batteries, lithium metal anode research experiences a refreshed attention due to its high theoretical energy density. Focus lies on enhancing the durability of lithium metal anode batteries and eliminating safety concerns. The battery capacity fades over cycling due to continuous SEI buildup, consuming lithium and electrolyte, and the formation of inactive lithium, which is electrically disconnected from the anode. As the surface of the anode is highly irregular and tends to form whisker during charging, experiments show that during discharge, the tip of the whisker is not dissolved and a droplet stays behind inside the SEI shell. We developed a generalized phase-field model of the dissolution in order to gain insights in the droplet formation process. Utilizing non-equilibrium thermodynamics, our phase-field model describes the dissolution of a single lithium whisker by taking the surface tension of lithium metal into account, and the interaction between lithium and the SEI. We are able to predict the nucleation of a Reyleigh instability behind the tip, leading to the formation of an electronically isolated lithium metal droplet

Solution structure of the Legionella pneumophila Mip-rapamycin complex

<p>Abstract</p> <p>Background</p> <p><it>Legionella pneumphila </it>is the causative agent of Legionnaires' disease. A major virulence factor of the pathogen is the homodimeric surface protein Mip. It shows peptidyl-prolyl cis/trans isomerase activty and is a receptor of FK506 and rapamycin, which both inhibit its enzymatic function. Insight into the binding process may be used for the design of novel Mip inhibitors as potential drugs against Legionnaires' disease.</p> <p>Results</p> <p>We have solved the solution structure of free Mip^77–213and the Mip^77–213-rapamycin complex by NMR spectroscopy. Mip^77–213showed the typical FKBP-fold and only minor rearrangements upon binding of rapamycin. Apart from the configuration of a flexible hairpin loop, which is partly stabilized upon binding, the solution structure confirms the crystal structure. Comparisons to the structures of free FKBP12 and the FKBP12-rapamycin complex suggested an identical binding mode for both proteins.</p> <p>Conclusion</p> <p>The structural similarity of the Mip-rapamycin and FKBP12-rapamycin complexes suggests that FKBP12 ligands may be promising starting points for the design of novel Mip inhibitors. The search for a novel drug against Legionnaires' disease may therefore benefit from the large variety of known FKBP12 inhibitors.</p

Understanding instabilities in lithium based batteries: dual- layer SEI and isolated lithium formation

Lithium metal batteries with liquid electrolytes have regained attention as candidates for next-generation high-energy-density batteries. However, the low cycle life is an ob-stacle to commercialization. The performance and durability of lithium metal batteries are largely influenced by the operating conditions and often find their underlying cause in the nano- and microscale physical processes at the interfaces of the negative electrode. The continuous growth of solid electrolyte interphase (SEI) consumes lithium and electrolyte. Additionally, stripping is not completely reversible, and parts of lithium remain isolated from the current collector. This so-called isolated lithium remains attached to the an-ode only via an insulating SEI. We develop thermodynamic consistent mesoscale models to explain observed instabili-ties on the negative electrode and investigate its dependence on operating conditions. For the SEI growth under storage conditions, we present a surface growth model combined with a diffusion-based SEI growth mechanism. We observe a universal instability that can explain the emergence of a dual-layer SEI with a compact inner layer and a porous outer layer. For lithium stripping, we present a generalized phase-field model of the dissolution of a single lithium whisker covered by SEI. We find that the instability caused by the interaction between lithium metal and SEI leads to the for-mation of isolated lithium