scholarly journals In situ small angle X-ray scattering reveals solution phase discharge of Li-O2 batteries with weakly solvating electrolytes

2020 ◽  
Author(s):  
Christian Prehal ◽  
Aleksej Samojlov ◽  
Manfred Nachtnebel ◽  
Manfred Kriechbaum ◽  
Heinz Amenitsch ◽  
...  
Keyword(s):  
Structural Information ◽  
Surface Film ◽  
Phase Evolution ◽  
Scattering Data ◽  
Carbon Surface ◽  
X Ray ◽  
Surface Areas ◽  
X Ray Scattering ◽  
Ray Scattering

Electrodepositing insulating and insoluble Li2O2 is the key process during discharge of aprotic Li-O2 batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved LiO2 governs whether Li2O2 grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, governing factors for Li2O2 packing density and capacity need better understanding, requiring in situ metrologies with structural sensitivity from the atomic to sub-micron scale. Here, we establish in situ small and wide angle X-ray scattering as a suitable method to record the Li2O2 phase evolution with atomic to sub-micrometer resolution during cycling a custom-built in situ Li-O2 cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multi-phase systems. Surprisingly, we find that features are absent that would point at a Li2O2 surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li2O2 platelets eventually forming large toroidal particles. Higher discharge overpotentials (high currents) lead to smaller Li2O2 particles, but there is no transition to an electronically passivating, conformal Li2O2 coating. This implies that mass transport of reactive species rather than electronic transport through a Li2O2 film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in poorly solvating electrolytes. The currently accepted Li-O2 reaction mechanism ought to be reconsidered.<br>

scholarly journals In situ small-angle X-ray scattering reveals solution phase discharge of Li–O2 batteries with weakly solvating electrolytes

2021 ◽  
Vol 118 (14) ◽  
pp. e2021893118
Author(s):  
Christian Prehal ◽  
Aleksej Samojlov ◽  
Manfred Nachtnebel ◽  
Ludek Lovicar ◽  
Manfred Kriechbaum ◽  
...  
Keyword(s):  
Structural Information ◽  
Surface Film ◽  
Phase Evolution ◽  
Scattering Data ◽  
Carbon Surface ◽  
X Ray ◽  
Surface Areas ◽  
X Ray Scattering ◽  
Ray Scattering

Electrodepositing insulating lithium peroxide (Li2O2) is the key process during discharge of aprotic Li–O2 batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved lithium superoxide governs whether Li2O2 grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, better understanding governing factors for Li2O2 packing density and capacity requires structural sensitive in situ metrologies. Here, we establish in situ small- and wide-angle X-ray scattering (SAXS/WAXS) as a suitable method to record the Li2O2 phase evolution with atomic to submicrometer resolution during cycling a custom-built in situ Li–O2 cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multiphase systems. Surprisingly, we find that features are absent that would point at a Li2O2 surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li2O2 platelets potentially forming large toroidal particles. Li2O2 solution growth is further justified by rotating ring-disk electrode measurements and electron microscopy. Higher discharge overpotentials lead to smaller Li2O2 particles, but there is no transition to an electronically passivating, conformal Li2O2 coating. Hence, mass transport of reactive species rather than electronic transport through a Li2O2 film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in weakly solvating electrolytes. The currently accepted Li–O2 reaction mechanism ought to be reconsidered.

scholarly journals In situ small angle X-ray scattering reveals solution phase discharge of Li-O2 batteries with weakly solvating electrolytes

2020 ◽  
Author(s):  
Christian Prehal ◽  
Aleksej Samojlov ◽  
Manfred Nachtnebel ◽  
Manfred Kriechbaum ◽  
Heinz Amenitsch ◽  
...  
Keyword(s):  
Structural Information ◽  
Surface Film ◽  
Phase Evolution ◽  
Scattering Data ◽  
Carbon Surface ◽  
X Ray ◽  
Surface Areas ◽  
X Ray Scattering ◽  
Ray Scattering

Electrodepositing insulating and insoluble Li2O2 is the key process during discharge of aprotic Li-O2 batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved LiO2 governs whether Li2O2 grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, governing factors for Li2O2 packing density and capacity need better understanding, requiring in situ metrologies with structural sensitivity from the atomic to sub-micron scale. Here, we establish in situ small and wide angle X-ray scattering as a suitable method to record the Li2O2 phase evolution with atomic to sub-micrometer resolution during cycling a custom-built in situ Li-O2 cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multi-phase systems. Surprisingly, we find that features are absent that would point at a Li2O2 surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li2O2 platelets eventually forming large toroidal particles. Higher discharge overpotentials (high currents) lead to smaller Li2O2 particles, but there is no transition to an electronically passivating, conformal Li2O2 coating. This implies that mass transport of reactive species rather than electronic transport through a Li2O2 film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in poorly solvating electrolytes. The currently accepted Li-O2 reaction mechanism ought to be reconsidered.<br>

scholarly journals Mechanism of Li2S formation and dissolution in Lithium-Sulphur batteries

2021 ◽  
Author(s):  
Christian Prehal ◽  
Sara Drvarič Talian ◽  
Alen Vizintin ◽  
Heinz Amenitsch ◽  
Robert Dominko ◽  
...  
Keyword(s):  
High Performance ◽  
Surface Film ◽  
Rate Capability ◽  
Stochastic Modelling ◽  
Phase Evolution ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Chemical Phase

Abstract Insufficient understanding of the mechanism that reversibly converts sulphur into lithium sulphide (Li2S) via soluble polysulphides (PS) hampers the realization of high performance lithium-sulphur cells. Typically Li2S formation is explained by direct electroreduction of a PS to Li2S; however, this is not consistent with the size of the insulating Li2S deposits. Here, we use in situ small and wide angle X-ray scattering (SAXS/WAXS) to track the growth and dissolution of crystalline and amorphous deposits from atomic to sub-micron scales during charge and discharge. Stochastic modelling based on the SAXS data allows quantification of the chemical phase evolution during discharge and charge. We show that Li2S deposits predominantly via disproportionation of transient, solid Li2S2 to form primary Li2S crystallites and solid Li2S4 particles. We further demonstrate that this process happens in reverse during charge. These findings show that the discharge capacity and rate capability in Li-S battery cathodes are therefore limited by mass transport through the increasingly tortuous network of Li2S / Li2S4 / carbon pores rather than electron transport through a passivating surface film.

scholarly journals Machine learning deciphers structural features of RNA duplexes measured with solution X-ray scattering

IUCrJ ◽  
2020 ◽  
Vol 7 (5) ◽  
pp. 870-880
Author(s):  
Yen-Lin Chen ◽  
Lois Pollack
Keyword(s):  
Machine Learning ◽  
Structural Information ◽  
Structural Parameters ◽  
Supervised Machine Learning ◽  
Scattering Data ◽  
Length Scales ◽  
X Ray ◽  
X Ray Scattering ◽  
Extreme Gradient Boosting ◽  
Ray Scattering

Macromolecular structures can be determined from solution X-ray scattering. Small-angle X-ray scattering (SAXS) provides global structural information on length scales of 10s to 100s of Ångstroms, and many algorithms are available to convert SAXS data into low-resolution structural envelopes. Extension of measurements to wider scattering angles (WAXS or wide-angle X-ray scattering) can sharpen the resolution to below 10 Å, filling in structural details that can be critical for biological function. These WAXS profiles are especially challenging to interpret because of the significant contribution of solvent in addition to solute on these smaller length scales. Based on training with molecular dynamics generated models, the application of extreme gradient boosting (XGBoost) is discussed, which is a supervised machine learning (ML) approach to interpret features in solution scattering profiles. These ML methods are applied to predict key structural parameters of double-stranded ribonucleic acid (dsRNA) duplexes. Duplex conformations vary with salt and sequence and directly impact the foldability of functional RNA molecules. The strong structural periodicities in these duplexes yield scattering profiles with rich sets of features at intermediate-to-wide scattering angles. In the ML models, these profiles are treated as 1D images or features. These ML models identify specific scattering angles, or regions of scattering angles, which correspond with and successfully predict distinct structural parameters. Thus, this work demonstrates that ML strategies can integrate theoretical molecular models with experimental solution scattering data, providing a new framework for extracting highly relevant structural information from solution experiments on biological macromolecules.

scholarly journals A new method for in situ structural investigations of nano-sized amorphous and crystalline materials using mixed-flow reactors

2019 ◽  
Vol 75 (5) ◽  
pp. 758-765 ◽  
Author(s):  
Alexandria Hoeher ◽  
Sebastian Mergelsberg ◽  
Olaf J. Borkiewicz ◽  
Patricia M. Dove ◽  
F. Marc Michel
Keyword(s):  
Flow Reactor ◽  
Calcium Phosphates ◽  
Scattering Data ◽  
Mixed Flow ◽  
Structural Investigations ◽  
X Ray ◽  
X Ray Scattering ◽  
Pdf Analysis ◽  
Ray Scattering

Structural investigations of amorphous and nanocrystalline phases forming in solution are historically challenging. Few methods are capable of in situ atomic structural analysis and rigorous control of the system. A mixed-flow reactor (MFR) is used for total X-ray scattering experiments to examine the short- and long-range structure of phases in situ with pair distribution function (PDF) analysis. The adaptable experimental setup enables data collection for a range of different system chemistries, initial supersaturations and residence times. The age of the sample during analysis is controlled by adjusting the flow rate. Faster rates allow for younger samples to be examined, but if flow is too fast not enough data are acquired to average out excess signal noise. Slower flow rates form older samples, but at very slow speeds particles settle and block flow, clogging the system. Proper background collection and subtraction is critical for data optimization. Overall, this MFR method is an ideal scheme for analyzing the in situ structures of phases that form during crystal growth in solution. As a proof of concept, high-resolution total X-ray scattering data of amorphous and crystalline calcium phosphates and amorphous calcium carbonate were collected for PDF analysis.

Time-Resolved Measurements of Overlayer Ordering in Electrodeposition

1996 ◽  
Vol 451 ◽  
Author(s):  
A. C. Finnefrock ◽  
L. J. Bullert ◽  
K. L. Ringland ◽  
P. D. Tingi ◽  
H. D. Abruña ◽  
...  
Keyword(s):  
Scattering Data ◽  
Electrode Position ◽  
Initial Value ◽  
Time Resolved ◽  
X Ray ◽  
Surface Ordering ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

ABSTRACTWe report in situ time-resolved surface x-ray scattering measurements of the underpoten-tial deposition of Cu2+ on Pt(111) in the presence of Cl− in HClO4 solution. Chronoamperometric (current vs. time) measurements indicate that after a potential step, the electrode-position current decays to 1/e of its initial value in at most 0.12 seconds. In contrast, our simultaneous time-resolved surface x-ray scattering data reveal that the overlayer requires on the order of two seconds to develop long-range periodic order. These results demonstrate that the kinetics of surface ordering can be significantly different from the kinetics of charge-transfer and illustrate the power of time-resolved surface x-ray scattering for in situ studies of electrodeposition.

scholarly journals Three-dimensional Pt-nanoparticle networks studied by anomalous small-angle X-ray scattering and X-ray absorption spectroscopy

2002 ◽  
Vol 35 (4) ◽  
pp. 459-470 ◽  
Author(s):  
T. Vad ◽  
H.-G. Haubold ◽  
N. Waldöfner ◽  
H. Bönnemann
Keyword(s):  
Small Angle ◽  
Structural Information ◽  
Hard Spheres ◽  
Multicomponent System ◽  
Three Dimensional ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
X Ray Absorption ◽  
Ray Scattering

Anomalous small-angle X-ray scattering (ASAXS) experiments with synchrotron radiation were performed to study the three-dimensional nanostructures of metal/organic hybrids formed by crosslinking aluminium-organic-stabilized platinum nanoparticles with various bifunctional organic spacer molecules. The advantage of ASAXS is the possibility of separating the particle scattering from that of the organic components, thus providing unbiased information about particle size distributions and interparticle correlation. In order to obtain the structural information from the scattering data, a model function based on Vrij's analytical solution for a multicomponent system of hard spheres is proposed. The model is applied to three different samples and the results are compared with those obtained from the application of Fourier methods (characteristic function) and X-ray absorption measurements.

Applications of principal component analysis to pair distribution function data

2015 ◽  
Vol 48 (6) ◽  
pp. 1619-1626 ◽  
Author(s):  
Karena W. Chapman ◽  
Saul H. Lapidus ◽  
Peter J. Chupas
Keyword(s):  
Principal Component Analysis ◽  
Distribution Function ◽  
Pair Distribution Function ◽  
Principal Component ◽  
Component Analysis ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Developments in X-ray scattering instruments have led to unprecedented access toin situand parametric X-ray scattering data. Deriving scientific insights and understanding from these large volumes of data has become a rate-limiting step. While formerly a data-limited technique, pair distribution function (PDF) measurement capacity has expanded to the point that the method is rarely limited by access to quantitative data or material characteristics – analysis and interpretation of the data can be a more severe impediment. This paper shows that multivariate analyses offer a broadly applicable and efficient approach to help analyse series of PDF data from high-throughput andin situexperiments. Specifically, principal component analysis is used to separate features from atom–atom pairs that are correlated – changing concentration and/or distance in concert – allowing evaluation of how they vary with material composition, reaction state or environmental variable. Without requiring prior knowledge of the material structure, this can allow the PDF from constituents of a material to be isolated and its structure more readily identified and modelled; it allows one to evaluate reactions or transitions to quantify variations in species concentration and identify intermediate species; and it allows one to identify the length scale and mechanism relevant to structural transformations.

A Revised O2 Reduction Model in Li-O2 Batteries as Revealed by in Situ Small Angle X-Ray Scattering

2019 ◽  
Author(s):  
Christian Prehal ◽  
Aleksej Samojlov ◽  
Manfred Nachtnebel ◽  
Manfred Kriechbaum ◽  
Heinz Amenitsch ◽  
...  
Keyword(s):  
Small Angle ◽  
Wide Angle ◽  
Reduction Mechanism ◽  
Reduction Model ◽  
X Ray ◽  
X Ray Scattering ◽  
O2 Reduction ◽  
Ray Scattering

<b>Here we use in situ small and wide angle X-ray scattering to elucidate unexpected mechanistic insights of the O2 reduction mechanism in Li-O2 batteries.<br></b>

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