Model Studies on the Formation of the Solid Electrolyte Interphase: Reaction of Li with Ultrathin Adsorbed Ionic-Liquid Films and Co3 O4 (111) Thin Films.

In this work we aim towards the molecular understanding of the solid electrolyte interphase (SEI) formation at the electrode electrolyte interface (EEI). Herein, we investigated the interaction between the battery-relevant ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI), Li and a Co3 O4 (111) thin film model anode grown on Ir(100) as a model study of the SEI formation in Li-ion batteries (LIBs). We employed mostly X-ray photoelectron spectroscopy (XPS) in combination with dispersion-corrected density functional theory calculations (DFT-D3). If the surface is pre-covered by BMP-TFSI species (model electrolyte), post-deposition of Li (Li+ ion shuttle) reveals thermodynamically favorable TFSI decomposition products such as LiCN, Li2 NSO2 CF3 , LiF, Li2 S, Li2 O2 , Li2 O, but also kinetic products like Li2 NCH3 C4 H9 or LiNCH3 C4 H9 of BMP. Simultaneously, Li adsorption and/or lithiation of Co3 O4 (111) to Lin Co3 O4 takes place due to insertion via step edges or defects; a partial transformation to CoO cannot be excluded. Formation of Co0 could not be observed in the experiment indicating that surface reaction products and inserted/adsorbed Li at the step edges may inhibit or slow down further Li diffusion into the bulk. This study provides detailed insights of the SEI formation at the EEI, which might be crucial for the improvement of future batteries.

Surface chemistry and electrochemistry of an ionic liquid and lithium on Li4Ti5O12(111)-A model study of the anode|electrolyte interface.

Aiming at a detailed molecular understanding of the initial stage of the solid|electrolyte interphase (SEI) formation in Li-ion batteries, we have investigated the interaction of the battery-relevant ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) (solvent/electrolyte) and Li (Li+ ion shuttle) on well-defined Li-poor Li4Ti5O12(111) and Li-rich Li4.3Ti5O12(111) surfaces/electrodes in a combined surface science and electrochemical model study. X-ray photoelectron spectroscopy (XPS) measurements reveal that postdeposition of Li0 under ultrahigh vacuum (UHV) conditions on a Li-poor Li4Ti5O12(111) surface precovered with a molecularly adsorbed [BMP][TFSI] adlayer leads to little IL decomposition at 80 and 300 K. We assume that most of the Li diffuses through the IL adlayer and rapidly inserts into the Li4Ti5O12(111) bulk. More pronounced IL decomposition was obtained upon IL deposition on a Li-rich Li4.3Ti5O12 phase at 80 K and subsequent heating to 300 K. Cyclic voltammograms (CVs) recorded on the Li4Ti5O12(111) electrodes in Li-TFSI/[BMP][TFSI] indicate an almost reversible Li (de-)insertion, with a slight decay of the amount of (de-)inserted Li with increasing cycle number. XPS measurements performed on the electrode after potential cycling show low intensity signals of IL decomposition products, in addition to dominant signals from residual IL electrolyte, which are related to reaction of the adsorbed IL with Li inserted into/extracted from Li4Ti5O12 during the CV. The results indicate a close similarity between IL decomposition products formed under UHV and under electrochemical conditions, underlining the validity of this experimental approach and the potential of such kind of model studies for obtaining detailed understanding of the SEI formation.

Adsorption of Ultrathin Ethylene Carbonate Films on Pristine and Lithiated Graphite and Their Interaction with Li.

Aiming at a better understanding of the solid-electrolyte interphase formation in Li-ion batteries, we have investigated the interaction of ultrathin films of ethylene carbonate (EC), which is a key solvent of battery electrolytes, with pristine and lithiated highly oriented pyrolytic graphite (HOPG) and with postdeposited Li. Employing X-ray and ultraviolet photoelectron spectroscopy as well as Fourier transform infrared spectroscopy under ultrahigh-vacuum conditions, in combination with density functional theory (DFT)-based calculations, we find that EC adsorbs molecularly intact on pristine HOPG in the entire temperature range between 80 K and desorption at 200 K. Features in the ultraviolet photoelectron spectra could be related to the molecular orbitals of EC obtained from DFT calculations, and a similar adsorption/desorption behavior is obtained also on lithiated HOPG. In contrast, stepwise postdeposition of ∼0.5 and one monolayer of Li0 on a preadsorbed EC adlayer leads not only to stabilization of Li+/Liδ+ at the surface, possibly as adsorbed Li+(EC) n species, but also to EC decomposition, forming products such as Li2CO3, ROCO2Li (CH2OCO2Li)2, and Li2O. Consequences on the electronic surface properties and on the stabilization of the resulting adlayer are discussed. Upon annealing up to room temperature, some residual Li-containing decomposition products remain on the surface, which is considered as the initial stage of the solid|electrolyte interphase formation at the electrode|electrolyte interface.

Temperature-dependent insertion and adsorption of lithium on spinel Li4Ti5O12(111) thin films - an angle-resolved XPS study.

Aiming at a detailed understanding of the Li adsorption and insertion behavior on/into lithium titanate (Li4Ti5O12, LTO), which is a promising anode material in Li-ion batteries, we have investigated the interaction of vapor deposited Li with LTO in the temperature range between 80 K and room temperature by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The experiments were performed under ultrahigh vacuum (UHV) conditions, and the presence of additional Li species was detected by the formation of Ti3+ in the Ti 2p core level signal due to charge transfer from adsorbed/inserted Li to Ti. Even at 80 K most of the deposited Li diffuses into the bulk of LTO, reflecting the facile insertion and diffusion of Li into and in LTO. Deposition of up to 3 monolayers equivalent (MLE) of Li at 80 K results in an increase in Li concentration in the surface region (topmost 6 nm), up to a stoichiometry of Li4+xTi5O12 with x > 0.3, and slightly lower values in the near-surface region (topmost 1 nm). For higher Li doses, the amount of Li in the near-surface region, including adsorbed Li, increases more than the concentration in the underlying surface region. This is attributed to the blocking of diffusion channels by inserted Li at a stoichiometry of Li4.3Ti5O12 and above. Upon increasing the temperature, Li+ starts to diffuse into the LTO bulk at temperatures between 120 K and 175 K, depending on the concentration in the surface region. It has completely disappeared at 260 K. The consequences of these results for the understanding of physical Li insertion will be discussed.

Structure formation and surface chemistry of ionic liquids on model electrode surfaces-Model studies for the electrode | electrolyte interface in Li-ion batteries.

Ionic liquids (ILs) are considered as attractive electrolyte solvents in modern battery concepts such as Li-ion batteries. Here we present a comprehensive review of the results of previous model studies on the interaction of the battery relevant IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) with a series of structurally and chemically well-defined model electrode surfaces, which are increasingly complex and relevant for battery applications [Ag(111), Au(111), Cu(111), pristine and lithiated highly oriented pyrolytic graphite (HOPG), and rutile TiO2(110)]. Combining surface science techniques such as high resolution scanning tunneling microscopy and X-ray photoelectron spectroscopy for characterizing surface structure and chemical composition in deposited (sub-)monolayer adlayers with dispersion corrected density functional theory based calculations, this work aims at a molecular scale understanding of the fundamental processes at the electrode | electrolyte interface, which are crucial for the development of the so-called solid electrolyte interphase (SEI) layer in batteries. Performed under idealized conditions, in an ultrahigh vacuum environment, these model studies provide detailed insights on the structure formation in the adlayer, the substrate-adsorbate and adsorbate-adsorbate interactions responsible for this, and the tendency for chemically induced decomposition of the IL. To mimic the situation in an electrolyte, we also investigated the interaction of adsorbed IL (sub-)monolayers with coadsorbed lithium. Even at 80 K, postdeposited Li is found to react with the IL, leading to decomposition products such as LiF, Li3N, Li2S, LixSOy, and Li2O. In the absence of a [BMP]+[TFSI]- adlayer, it tends to adsorb, dissolve, or intercalate into the substrate (metals, HOPG) or to react with the substrate (TiO2) above a critical temperature, forming LiOx and Ti3+ species in the latter case. Finally, the formation of stable decomposition products was found to sensitively change the equilibrium between surface Li and Li+ intercalated in the bulk, leading to a deintercalation from lithiated HOPG in the presence of an adsorbed IL adlayer at >230 K. Overall, these results provide detailed insights into the surface chemistry at the solid | electrolyte interface and the initial stages of SEI formation at electrode surfaces in the absence of an applied potential, which is essential for the further improvement of future Li-ion batteries.

Regression Trees Identify Relevant Interactions: Can This Improve the Predictive Performance of Risk Adjustment?

Risk equalization formulas have been refined since their introduction about two decades ago. Because of the complexity and the abundance of possible interactions between the variables used, hardly any interactions are considered. A regression tree is used to systematically search for interactions, a methodologically new approach in risk equalization. Analyses are based on a data set of nearly 2.9 million individuals from a major German social health insurer. A two-step approach is applied: In the first step a regression tree is built on the basis of the learning data set. Terminal nodes characterized by more than one morbidity-group-split represent interaction effects of different morbidity groups. In the second step the 'traditional' weighted least squares regression equation is expanded by adding interaction terms for all interactions detected by the tree, and regression coefficients are recalculated. The resulting risk adjustment formula shows an improvement in the adjusted R2 from 25.43% to 25.81% on the evaluation data set. Predictive ratios are calculated for subgroups affected by the interactions. The R2 improvement detected is only marginal. According to the sample level performance measures used, not involving a considerable number of morbidity interactions forms no relevant loss in accuracy. Copyright © 2015 John Wiley & Sons, Ltd.

Interaction of the ionic liquid [BMP][TFSA] with rutile TiO2(110) and coadsorbed lithium.

Aiming at a fundamental understanding of the processes at the electrode|ionic liquid interface in Li ion batteries, we investigated the interaction of the ionic liquid n-butyl-n-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSA] and of Li with a reduced rutile TiO2(110) (1 × 1) surface as well as the interaction between [BMP][TFSA] and Li on the TiO2(110) surface under ultrahigh vacuum (UHV) conditions by X-ray photoelectron spectroscopy and scanning tunnelling microscopy. Between 80 K and 340 K [BMP][TFSA] adsorbs molecularly on the surface and at higher temperatures decomposition is observed, resulting in products such as Sad, Fad and TiNx. The decomposition pattern is compared to proposals based on theory. Small amounts of Li intercalate even at 80 K into TiO2(110), forming Li(+) and Ti(3+) species. The stoichiometry in the near surface region corresponds to Li7Ti5O12. For higher coverages in the range of several monolayers part of the Li remains on the surface, forming a Li2O cover layer. At 300 K, Ti(3+) species become sufficiently mobile to diffuse into the bulk. Li post-deposition on a [BMP][TFSA] covered TiO2(110) surface at 80 K results in two competing reactions, Li intercalation and reaction with the IL, resulting in the decomposition of the IL. Upon warming up, the Ti(3+) formed at low T is consumed by reaction with the IL adlayer and intermediate decomposition products. Post-deposition of [BMP][TFSA] (300 K) on a surface pre-covered with a Li2O/Li7Ti5O12 layer results in the partial reaction of [BMP][TFSA] with the Li(+) and Ti(3+) species, which gets completed at higher temperatures.

Interaction of ionic liquids with noble metal surfaces: structure formation and stability of [OMIM][TFSA] and [EMIM][TFSA] on Au(111) and Ag(111).

Aiming at a comprehensive understanding of the interaction of ionic liquids (ILs) with metal surfaces we have investigated the adsorption of two closely related ILs, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSA] and 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide [OMIM][TFSA], with two noble metal surfaces, Au(111) and Ag(111), under ultrahigh vacuum (UHV) conditions using scanning tunneling microscopy (STM). At room temperature, the ILs form a 2D liquid on either of the two surfaces, while at lower temperatures they condense into two-dimensional (2D) islands which exhibit ordered structures or a short-range ordered 2D glass structure. Comparison of the adlayer structures formed in the different adsorption systems and also with those determined recently for n-butyl-n-methylpyrrolidinium [TFSA](-) adlayers on Ag(111) and Au(111) (B. Uhl et al., Beilstein J. Nanotechnol., 2013, 4, 903) gains detailed insight into the adsorption geometry of the IL ions on the surface. The close similarity of the adlayer structures indicates that (i) the structure formation is dominated by the tendency to optimize the anion adsorption geometry, and that (ii) also in the present systems the cation adsorbs with the alkyl chain pointing up from the surface.

On the energetics of conformational switching of molecules at and close to room temperature.

We observe and induce conformational switching of individual molecules via scanning tunneling microscopy (STM) at and close to room temperature. 2H-5,10,15,20-Tetrakis-(3,5-di-tert-butyl)-phenylporphyrin adsorbed on Cu(111) forms a peculiar supramolecular ordered phase in which the molecules arrange in alternating rows, with two distinct appearances in STM which are assigned to concave and convex intramolecular conformations. Around room temperature, frequent bidirectional conformational switching of individual molecules from concave to convex and vice versa is observed. From the temperature dependence, detailed insights into the energy barriers and entropic contributions of the switching processes are deduced. At 200 K, controlled STM tip-induced unidirectional switching is possible, yielding an information storage density of 4.9 × 10(13) bit/inch(2). With this contribution we demonstrate that controlled switching of individual molecules at comparably high temperatures is possible and that entropic effects can be a decisive factor in potential molecular devices at these temperatures.

Temperature-induced structural and chemical changes of ultrathin ethylene carbonate films on Cu(111).

The interaction of the Li-ion battery solvent ethylene carbonate (EC) with Cu(111) was investigated by scanning tunnelling microscopy (STM) and variable temperature X-ray photoelectron spectroscopy (XPS) under ultrahigh vacuum (UHV) conditions. Between 80 and 420 K, the decomposition of EC occurs along with distinct structural and chemical changes of the adlayer.

Preconditions for efficiency and affordability in competitive healthcare markets: Are they fulfilled in Belgium, Germany, Israel, the Netherlands and Switzerland? Ten years later.

From the mid-1990s several countries have introduced elements of the model of regulated competition in healthcare. In 2012 we assessed the extent to which in five countries ten important preconditions for achieving efficiency and affordability in competitive healthcare markets were fulfilled. In this paper we assess to what extent the fulfilment of these preconditions has changed ten years later. In 2022, as in 2012, in none of the five countries all preconditions are completely fulfilled. In the period 2012-2022 on balance there have been some improvements in the fulfillment of the preconditions, although to a different extent in the five countries. The only preconditions that were improved in most countries were 'consumer information and transparency' and 'cross-subsidies without incentives for risk selection'. On balance the Netherlands and Switzerland made most progress in the number of better fulfilled preconditions. For Belgium these preconditions no longer seem relevant because the idea of regulated competition has been completely abandoned. In Germany, Israel and Switzerland, the preconditions 'effective competition policy' and 'contestability of the markets' are not sufficiently fulfilled in 2022, just as in 2012. In Germany and Switzerland this also holds for the precondition 'freedom to contract and integrate'. Overall, the progress towards realizing the preconditions has been limited.

Coverage dependent disorder-order transition of 2H-tetraphenylporphyrin on Cu(111).

In this study, we investigate the peculiar coverage dependent supramolecular arrangement of 2H-tetraphenylporhpyrin (2HTPP) on Cu(111) with scanning tunneling microscopy at room-temperature. At low coverage, "slow" diffusion of individual 2HTPP molecules along the close-packed atomic rows of the substrate is observed, and no supramolecular ordering occurs. However, at higher coverage, the formation of ordered, checkerboard-like domains is found, with two molecules per unit cell at different distances from the surface. This behavior is attributed to a complex interplay of site specific molecule-substrate interaction, mainly the strong interaction between the iminic N atoms and Cu substrate atoms, with intermolecular T-type and π-π interactions.

Towards the engineering of molecular nanostructures: local anchoring and functionalization of porphyrins on model-templates.

We demonstrate that Cu(111) surfaces pre-covered with a submonolayer of copper oxide or metallic nickel are suitable model-templates for the selective adsorption and/or localized functionalization of functional molecules such as different free base porphyrins and metalloporphyrins. The oxide/Cu(111) model-template is able to steer the adsorption of tetraphenylporphyrins (TPP): 2HTPP selectively adsorbs on the bare Cu areas, and for CoTPP anchoring at the rim of the copper oxide islands is found. On the Ni/Cu(111) model-template TPP molecules are pinned on the Ni areas while they are mobile on the bare Cu surface. Interestingly, adsorption of free base octaethylporphyrin on Ni/Cu(111) leads to a local functionalization, namely the metalation to NiOEP on the Ni areas. Model-template preparation and characterization by scanning tunneling microscopy is performed at room temperature.

Neural-network-backed evolutionary search for SrTiO3(110) surface reconstructions.

The determination of atomic structures in surface reconstructions has typically relied on structural models derived from intuition and domain knowledge. Evolutionary algorithms have emerged as powerful tools for such structure searches. However, when density functional theory is used to evaluate the energy the computational cost of a thorough exploration of the potential energy landscape is prohibitive. Here, we drive the exploration of the rich phase diagram of TiO x overlayer structures on SrTiO3(110) by combining the covariance matrix adaptation evolution strategy (CMA-ES) and a neural-network force field (NNFF) as a surrogate energy model. By training solely on SrTiO3(110) 4×1 overlayer structures and performing CMA-ES runs on 3×1, 4×1 and 5×1 overlayers, we verify the transferability of the NNFF. The speedup due to the surrogate model allows taking advantage of the stochastic nature of the CMA-ES to perform exhaustive sets of explorations and identify both known and new low-energy reconstructions.

Ordering aspects and intramolecular conformation of tetraphenylporphyrins on Ag(111).

A systematic scanning tunnelling microscopy study of the self-assembly, intramolecular conformation and supramolecular ordering of different tetraphenylporphyrins (xTPP) with or without a central metal atom (x = 2H, Fe, Co) on Ag(111) at room temperature is presented. The investigation covers a wide range, i.e. the adsorption behaviour from the low sub-monolayer up to the multilayer regime is described in detail and conclusively discussed in regard to molecule-molecule and molecule-substrate interactions. At monolayer coverage the molecules self-assemble in domains with a square unit cell caused by "T-type" intermolecular interactions, while the orientation of the domains along the symmetry axes is determined by adsorbate-substrate interactions. Interestingly for ordered monolayers domain boundaries always separate domains of different organizational chirality but same orientation of the square unit cell. This demonstrates that in the particular system chirality obviously restricts the long range order of the supramolecular TPP assemblies. In combination with DFT calculations it is also demonstrated that the previously reported intramolecular saddle shape deformation of TPPs upon adsorption is more pronounced for metallo-TPP than for 2HTPP.

Surface Science and Electrochemical Model Studies on the Interaction of Graphite and Li-Containing Ionic Liquids.

The process of solid-electrolyte interphase (SEI) formation is systematically investigated along with its chemical composition on carbon electrodes in an ionic liquid-based, Li-containing electrolyte in a combined surface science and electrochemical model study using highly oriented pyrolytic graphite (HOPG) and binder-free graphite powder electrodes (Mage) as model systems. The chemical decomposition process is explored by deposition of Li on a pre-deposited multilayer film of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSI]) under ultrahigh vacuum conditions. Electrochemical SEI formation is induced by and monitored during potential cycling in [BMP][TFSI]+0.1 m LiTFSI. The chemical composition of the resulting layers is characterized by X-ray photoelectron spectroscopy (XPS), both at the surface and in deeper layers, closer to the electrode|SEI interface, after partial removal of the film by Ar+ ion sputtering. Clear differences between chemical and electrochemical SEI formation, and also between SEI formation on HOPG and Mage electrodes, are observed and discussed.

Oxygen Reduction and Evolution on Ni-modified Co3 O4 (1 1 1) Cathodes for Zn-Air Batteries: A Combined Surface Science and Electrochemical Model Study.

The performance of structurally and chemically well-defined Ni-free and Ni-modified single-crystalline Co3 O4 (1 1 1) thin-film electrodes in the oxygen reduction and evolution reactions (ORR and OER) was investigated in a combined surface science and electrochemistry approach. Pure and Ni-modified Co3 O4 (1 1 1) film electrodes were prepared and characterized under ultrahigh-vacuum conditions by scanning tunneling microscopy and X-ray photoelectron spectroscopy. Both Ni decoration (by post-deposition of Ni) and Ni doping (by simultaneous vapor deposition of Ni, Co, and O2 ) induced distinct differences in the base cyclic voltammograms in 0.5 m KOH at potentials higher than 0.7 V compared with Co3 O4 (1 1 1) electrodes. Also, all oxide film electrodes showed a higher overpotential for the ORR but a lower one for the OER than polycrystalline Pt. Ni modification significantly improved the ORR current densities by increasing the electrical conductivity, whereas the OER onset of approximately 1.47 VRHE (RHE: reversible hydrogen electrode) at 0.1 mA cm-2 was almost unchanged.

Risk-adjusted capitation payments: how well do principal inpatient diagnosis-based models work in the German situation? Results from a large data set.

Five models of risk adjusters were tested as a (proxy) measure for health status with data from a large German sickness fund. The first two models use standard demographic and socio-demographic variables. One model incorporates a simple binary indicator for hospitalization and the last two are based on the hierarchical coexisting conditions (HCCs: DxCG Risk Adjustment Software Release 6.1) using in-patient diagnoses. Special investigations were done on the subgroups of insurees who left, joined or stayed with the fund over the observation period. Age and gender grouping accounted for 3.2% of the variation in total expenditure for concurrent as well as prospective models. The current German risk adjusters age, sex, and invalidity status account for 5.1 and 4.5% of the variance in the concurrent and prospective models, respectively. Age, gender, invalidity status and in-patient HCC covariates explain about 37% of the variations of the total expenditures in a concurrent model and roughly 12% of the variations of total expenditures in a prospective model. Only modest improvement can be achieved with the long-term-care (LTC) indicator. For high-risk (cost) groups, substantial under-prediction remains; conversely, for the low-risk group, represented by enrolees who did not show any health care expense in the base year, all of the models over-predict expenditure. Special investigations were done on the subgroups of insurees who left, joined or stayed with the fund over the observation period.

Intercalation and Deintercalation of Lithium at the Ionic Liquid-Graphite(0001) Interface.

The intercalation and deintercalation of lithium (Li) into / out of graphite(0001), which is a highly important process in Li-ion batteries, was investigated under ultrahigh vacuum conditions as a function of temperature, employing X-ray and ultraviolet photoelectron spectroscopy. Both the up-shifts of the core-level binding energy and the lowering of the work function ΔΦ reveal that heating of a monolayer of the battery-relevant ionic liquid (IL) 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]+[TFSI]-) adsorbed on lithiated graphite at 80 K to >230 K facilitates an accumulation of partially charged Liδ+ atoms at the IL-graphite(0001) interface. This is accompanied by a partial IL decomposition, which is associated with the initial stages of the chemical formation of the solid-electrolyte interphase.