On the Durability of Protective Titania Coatings on High-Voltage Spinel Cathodes.

TiO2 -coating of LiNi0.5-x Mn1.5+x O4 (LNMO) by atomic layer deposition (ALD) has been studied as a strategy to stabilize the cathode/electrolyte interface and mitigate transition metal (TM) ion dissolution. The TiO2 coatings were found to be uniform, with thicknesses estimated to 0.2, 0.3, and 0.6 nm for the LNMO powders exposed to 5, 10, and 20 ALD cycles, respectively. While electrochemical characterization in half-cells revealed little to no improvement in the capacity retention neither at 20 nor at 50 °C, improved capacity retention and coulombic efficiencies were demonstrated for the TiO2 -coated LNMO in LNMO||graphite full-cells at 20 °C. This improvement in cycling stability could partly be attributed to thinner cathode electrolyte interphase on the TiO2 -coated samples. Additionally, energy-dispersive X-ray spectroscopy revealed a thinner solid electrolyte interphase on the graphite electrode cycled against TiO2 -coated LNMO, indicating retardation of TM dissolution by the TiO2 -coating.

A molecular dynamics study of a fully zwitterionic copolymer/ionic liquid-based electrolyte: Li+ transport mechanisms and ionic interactions.

The development of polymer electrolytes (PEs) is crucial for advancing safe, high-energy density batteries, such as lithium-metal and other beyond lithium-ion chemistries. However, reaching the optimum balance between mechanical stiffness and ionic conductivity is not a straightforward task. Zwitterionic (ZI) gel electrolytes comprising lithium salt and ionic liquid (IL) solutions within a fully ZI polymer network can, in this context, provide useful properties. Although such materials have shown compatibility with lithium metal in batteries, several fundamental structure-dynamic relationships regarding ionic transport and the Li+ coordination environment remain unclear. To better resolve such issues, molecular dynamics simulations were carried out for two IL-based electrolyte systems, N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) with 1 M LiTFSI salt and a ZI gel electrolyte containing the IL and a ZI copolymer: poly(2-methacryloyloxyethyl phosphorylcholine-co-sulfobetaine vinylimidazole), poly(MPC-co-SBVI). The addition of ZI polymer decreases the [TFSI]- -[Li]+ interactions and increases the IL ion diffusivities, and consequently, the overall ZI gel ionic conductivity. The structural analyses showed a large preference for lithium-ion interactions with the polymer phosphonate groups, while the [TFSI]- anions interact directly with the sulfonate group and the [BMP]+ cations only display secondary interactions with the polymer. In contrast to previous experimental data on the same system, the simulated transference numbers showed smaller [Li]+ contributions to the overall ionic conductivities, mainly due to negatively charged lithium aggregates and the strong lithium-ion interactions in the systems.

Living under psychosocial pressure: Perception of mothers of children with autism spectrum disorders.

PROBLEM: Mothers of children with autism spectrum disorders (ASD) experience higher levels of stress compared to mothers of typically developing children. This study identified mothers' perceptions of the stress caused by lifelong caregiving to a child with ASD. METHODS: The current study was conducted in Iran using qualitative methods. In-depth, semi-structured interviews were conducted with twenty-seven mothers. Content analysis was used to analyze and categorize the data. FINDINGS: The main categories included (1) psychological concerns and suffering and (2) sociocultural challenges. The first category consisted of two subcategories, including disruption in mother-child relationships and fears and worries. Also, the second category included subcategories of cultural constraints and lack of social support. CONCLUSIONS: In this study, the mothers of autistic children experienced psychosocial pain. Identifying the stressors for these mothers could lead to appropriate planning to provide psychological, social, and cultural support for them in Iranian society.

Interfacial Structures in Ionic Liquid-Based Ternary Electrolytes for Lithium-Metal Batteries: A Molecular Dynamics Study.

Lithium-metal batteries are promising candidates to fulfill the future performance requirements for energy storage applications. However, the tendency to form metallic dendrites and the undesirable side reactions between the electrolyte and the Li electrode lead to poor performance and safety issues in these batteries. Therefore, understanding the interfacial properties and the Li-metal surface/electrolyte interactions is crucial to resolve the remaining obstacles and make these devices feasible. Here, we report a computational study on the interface effects in ternary polymer electrolytes composed by poly(ethylene oxide) (PEO), lithium salts, and different ionic liquids (ILs) confined between two Li-metal slabs. Atomistic simulations are used to characterize the local environment of the Li+ ions and the transport properties in the bulk and at the interface regions. Aggregation of ions at the metal surface is seen in all investigated systems; the structure and composition are directly correlated to the IL components. The strong interactions between the electrolyte species and the Li-metal atoms result in the structuring of the electrolyte at the interface region, in which comparatively small and flat ions result in a well-defined region with extensive Li+ populations and high self-diffusion coefficients. In contrast, large ions such as [P222mom]+ increase the PEO density in the bulk due to large steric effects at the interface. Therefore, the choice of specific ILs in ternary polymer electrolytes can tune the structure-dynamic properties at the Li-metal surface/electrolyte interface, controlling the SEI formation at the electrode surface, and thereby improve battery performance.

Restricted Ion Transport by Plasticizing Side Chains in Polycarbonate-Based Solid Electrolytes.

Increasing the ionic conductivity has for decades been an overriding goal in the development of solid polymer electrolytes. According to fundamental theories on ion transport mechanisms in polymers, the ionic conductivity is strongly correlated to free volume and segmental mobility of the polymer for the conventional transport processes. Therefore, incorporating plasticizing side chains onto the main chain of the polymer host often appears as a clear-cut strategy to improve the ionic conductivity of the system through lowering of the glass transition temperature (T g). This intended correlation between T g and ionic conductivity is, however, not consistently observed in practice. The aim of this study is therefore to elucidate this interplay between segmental mobility and polymer structure in polymer electrolyte systems comprising plasticizing side chains. To this end, we utilize the synthetic versatility of the ion-conductive poly(trimethylene carbonate) (PTMC) platform. Two types of host polymers with side chains added to a PTMC backbone are employed, and the resulting electrolytes are investigated together with the side chain-free analogue both by experiment and with molecular dynamics (MD) simulations. The results show that while added side chains do indeed lead to a lower T g, the total ionic conductivity is highest in the host matrix without side chains. It was seen in the MD simulations that while side chains promote ionic mobility associated with the polymer chain, the more efficient interchain hopping transport mechanism occurs with a higher probability in the system without side chains. This is connected to a significantly higher solvation site diversity for the Li+ ions in the side-chain-free system, providing better conduction paths. These results strongly indicate that the side chains in fact restrict the mobility of the Li+ ions in the polymer hosts.

Electrolyte decomposition on Li-metal surfaces from first-principles theory.

An important feature in Li batteries is the formation of a solid electrolyte interphase (SEI) on the surface of the anode. This film can have a profound effect on the stability and the performance of the device. In this work, we have employed density functional theory combined with implicit solvation models to study the inner layer of SEI formation from the reduction of common organic carbonate electrolyte solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate) on a Li metal anode surface. Their stability and electronic structure on the Li surface have been investigated. It is found that the CO producing route is energetically more favorable for ethylene and propylene carbonate decomposition. For the two linear solvents, dimethyl and diethyl carbonates, no significant differences are observed between the two considered reduction pathways. Bader charge analyses indicate that 2 e- reductions take place in the decomposition of all studied solvents. The density of states calculations demonstrate correlations between the degrees of hybridization between the oxygen of adsorbed solvents and the upper Li atoms on the surface with the trend of the solvent adsorption energies.

Sphingosine kinase 2 deficiency increases proliferation and migration of renal mouse mesangial cells and fibroblasts.

Both of the sphingosine kinase (SK) subtypes SK-1 and SK-2 catalyze the production of the bioactive lipid molecule sphingosine 1-phosphate (S1P). However, the subtype-specific cellular functions are largely unknown. In this study, we investigated the cellular function of SK-2 in primary mouse renal mesangial cells (mMC) and embryonic fibroblasts (MEF) from wild-type C57BL/6 or SK-2 knockout (SK2ko) mice. We found that SK2ko cells displayed a significantly higher proliferative and migratory activity when compared to wild-type cells, with concomitant increased cellular activities of the classical extracellular signal regulated kinase (ERK) and PI3K/Akt cascades, and of the small G protein RhoA. Furthermore, we detected an upregulation of SK-1 protein and S1P3 receptor mRNA expression in SK-2ko cells. The MEK inhibitor U0126 and the S1P1/3 receptor antagonist VPC23019 blocked the increased migration of SK-2ko cells. Additionally, S1P3ko mesangial cells showed a reduced proliferative behavior and reduced migration rate upon S1P stimulation, suggesting a crucial involvement of the S1P3 receptor. In summary, our data demonstrate that SK-2 exerts suppressive effects on cell growth and migration in renal mesangial cells and fibroblasts, and that therapeutic targeting of SKs for treating proliferative diseases requires subtype-selective inhibitors.

Structural and electronic properties of the Pt(n)-PAH complex (n = 1, 2) from density functional calculations.

A detailed density functional study of the Pt atom and the Pt dimer adsorption on a polyaromatic hydrocarbon (PAH) is presented. The preferred adsorption site for a Pt atom is confirmed to be the bridge site. Upon adsorption of a single Pt atom, however, it is found here that the electronic ground state changes from the triplet state (5d(9)6s(1) configuration) to the closed-shell singlet state (5d(10)6s(0) configuration), which consequently will affect the catalytic activity of Pt when single Pt atoms bind to a carbon surface. The preferred adsorption site for the Pt dimer in the upright configuration is the hollow site. In contrast to the adsorption of a single Pt atom, the formation of a Pt-C bond in the adsorption of a Pt dimer is not accompanied by a change in the spin state, so the most stable electronic state is still the triplet state. While the atomic charge on the Pt atoms and dimers (in parallel configuration) in the Ptn-PAH complex is positive, a negative charge is found on the upper Pt atom for the upright configuration, indicating that single layers of Pt atoms will have a different catalytic activity as compared to Pt clusters on a carbon surface. Comparing the Pt-C bond length and the charge transfer on different sites, the magnitude of the charge transfer decreases with bond elongation, indicating that the catalytic activity of the Pt atom and dimer can be changed by modifying its chemical surroundings. The adsorption energy for the Pt dimer on a PAH surface is larger than that for two individual Pt atoms on the surface indicating that aggregation of Pt atoms on the PAH surface is favorable.

Nano structures of group 13-15 mixed heptamer clusters: a computational study.

The structural and thermodynamic characteristics of lowest-energy structures of group 13-15 mixed heptamers in two distinct series [(HM)(k)(HM')(l)(NH)(7)] (M, M' = B, Al, Ga and k + l = 7) and [(HGa)(7)(YH)(m)(Y'H)(n)] (Y,Y' = N, P, As and m + n = 7) have been systematically investigated using the density functional approach. Our main goal is to get knowledge of the preferential bonding patterns of the first three rows of group 13-15 elements for the construction of mixed heptameric clusters. Structural parameters, thermodynamic properties of oligomerization reaction, band gaps, and dipole moments of the 18 lowest-energy structures of the studied heptamers in each series are compared to their corresponding binary parents, that is, [(HM)(7)(NH)(7)] and [(HGa)(7)(YH)(7)]. The stability of different isomer structures is discussed to reveal the competitiveness of group 13 and 15 bonding. Mixed heptamers are predicted to be thermodynamically more stable compared to a mixture of monomers. However, the favorability for the generation of mixed heptamers strongly depends on the nature of inserted metal and nonmetal pairs of group 13-15. Moreover, it is found that among all studied heptamers the smaller band gaps correspond to arsenic containing species which are close to the semiconducting regime, around 4.62-4.98 eV.

Glucocorticoids protect renal mesangial cells from apoptosis by increasing cellular sphingosine-1-phosphate.

Neutral ceramidase (NCDase) and sphingosine kinases (SphKs) are key enzymes regulating cellular sphingosine-1-phosphate (S1P) levels. In this study we found that stress factor-induced apoptosis of rat renal mesangial cells was significantly reduced by dexamethasone treatment. Concomitantly, dexamethasone increased cellular S1P levels, suggesting an activation of sphingolipid-metabolizing enzymes. The cell-protective effect of glucocorticoids was reversed by a SphK inhibitor, was completely absent in SphK1-deficient cells, and was associated with upregulated mRNA and protein expression of NCDase and SphK1. Additionally, in vivo experiments in mice showed that dexamethasone also upregulated SphK1 mRNA and activity, and NCDase protein expression in the kidney. Fragments (2285, 1724, and 1126 bp) of the rat NCDase promoter linked to a luciferase reporter were transfected into rat kidney fibroblasts and mesangial cells. There was enhanced NCDase promoter activity upon glucocorticoids treatment that was abolished by the glucocorticoid receptor antagonist RU-486. Single and double mutations of the two putative glucocorticoid response element sites within the promoter reduced the dexamethasone effect, suggesting that both glucocorticoid response elements are functionally active and required for induction. Our study shows that glucocorticoids exert a protective effect on stress-induced mesangial cell apoptosis in vitro and in vivo by upregulating NCDase and SphK1 expression and activity, resulting in enhanced levels of the protective lipid second messenger S1P.