We present the use of fluorinated carbon black (FCB) with different degrees of surface functionalization as an efficient class of materials for sulfur cathodes in lithium-sulfur batteries (LSBs), suitable for the entrapment of polysulfides. The direct fluorination treatment at different temperatures endowed the carbonaceous surface with C-F functionalities, which mitigated polysulfides migration, enhanced sulfur utilization and inhibited the shuttle effect. FCBs were characterized by X-ray photoelectron spectroscopy (XPS), small-angle neutron scattering (SANS), and UV-vis spectroscopy. Moreover, the "diffusion-limited aggregation" (DLA) was model used for the first time for the analysis of the performance of LSBs cathodes incorporating FCBs via operando X-ray imaging. This method provided insights on the growth of the sulfur crystals and on the dynamics of polysulfides within the cathode materials, highlighting the effectiveness of FCB in promoting homogeneous sulfur deposition and enhancing polysulfide retention. Charge-discharge tests at 0.2C and 3C on cells with FCB-containing electrodes demonstrated a remarkable improvement in capacity retention: a threshold of 80 % was reached after 128 cycles, i.e. 7.5 times more than a reference cell containing pure carbon black (CB) that lasted only for 17 cycles. In addition, cells with FCB-containing cathodes exhibited a coulombic efficiency of 98 % for 200 cycles, exceeding the performance of electrodes prepared with pristine carbon black as sulfur-host matrix.

Predicting the macroscopic properties of thin fiber-based porous materials from their microscopic morphology remains challenging because of the structural heterogeneity of these materials. In this study, computational fluid dynamics simulations were performed to compute volume air flow based on tomographic image data of uncompressed and compressed paper sheets. To reduce computational demands, a pore network model was employed, allowing volume air flow to be approximated with less computational effort. To improve prediction accuracy, geometric descriptors of the pore space, such as porosity, surface area, median pore radius, and geodesic tortuosity, were combined with predictions of the pore network model. This integrated approach significantly improves the predictive power of the pore network model and indicates which aspects of the pore space morphology are not accurately represented within the pore network model. In particular, we illustrate that a high correlation among descriptors does not necessarily imply redundancy in a combined prediction.

Batteries with liquid alkali-metal negative electrodes offer a route to compact, high-performance energy storage. Innovation in alkali-metal management, i.e., controlled storage, release and transport of liquid alkali metal, can enable simpler and cheaper cell designs. Porous carbons have emerged as potential host materials for liquid alkali metals. Here, X-ray computed tomography is used to study the wetting interactions between porous carbon hosts and liquid sodium-potassium alloy (NaK) as a function of carbon host morphology and surface functionalization. While as-received carbon samples show no affinity toward NaK, heat-treated carbon is spontaneously infiltrated with NaK filling almost the entire pore volume. It is explored how forced wetting partially fills pores of NaK-repellant hosts, showing large differences in pore filling based on the average pore size of the host material. In electrochemical discharge experiments, it is shown that both as-received and heat-treated carbon felt enable high areal capacities beyond 40 mAh cm-2. However, the heat-treated carbon shows ten times lower overpotential. Finally, it is demonstrated how heat-treated carbon felt can enable capillary transport of NaK. In summary, this study elucidates important aspects of the interactions between liquid alkali metals and porous carbon hosts, generating insights into possible applications in liquid alkali-metal batteries.

Sn-based electrodes are promising candidates for next-generation lithium-ion batteries. However, it suffers from deleterious micro-structural deformation as it undergoes drastic volume changes upon lithium insertion and extraction. Progress in designing these materials is limited to complex structures. There is a significant need to develop an alloy-based anode that can be industrially manufactured and offers high reversible capacity. This necessitates a profound understanding of the interplay between structural changes and electrochemical performance. Here, operando X-ray imaging is used to correlate the morphological evolution to electrochemical performance in foil and foam systems. The 3D Sn-foam-like structure electrode is fabricated in-house as a practical approach to accommodate the volume expansion and alleviate the mechanical stress experienced upon alloying/dealloying. Results show that generating pores in Sn electrodes can help manage the volume expansion and mitigate the severe mechanical stress in thick electrodes during alloying/dealloying processes. The foam electrode demonstrates superior electrochemical performance compared to non-porous Sn foil with an equivalent absolute capacity. This work advances the understanding of the real-time morphological evolution of Sn bulky electrodes.

Organic electrode-active materials (OAMs) enable a variety of charge and storage mechanisms and are advantageous compared with lithium-ion batteries in terms of costs and safety. Cross-linked poly(3-vinyl-N-methylphenothiazine) (X-PVMPT) is a p-type OAM showing high performance and enabling fast and reversible energy storage in different battery configurations. Beyond its molecular or polymer structure, the performance of an OAM depends strongly on the structure of the composite electrode. The porous nanostructure of an electrode composed of X-PVMPT, a conductive carbon additive, and binder is statistically investigated based on highly resolved 3D image data. Univariate probability distributions of relevant morphological descriptors and bivariate distributions of pairs of such descriptors are parametrically modeled. In this way, local heterogeneities and spatial gradients are quantified. While the observed short transportation paths through the solid phase are beneficial in terms of electrical conductivity, the pathways through the pore phase influencing the effective ionic diffusivity are comparatively long.

This study presents an innovative operando analysis of lithium-sulfur (Li/S) multilayer pouch cells, employing a combination of lab-source and synchrotron x-ray imaging to investigate sulfur crystallite dissolution and lithium dendrite formation. By integrating advanced X-ray imaging, impedance spectroscopy, and simultaneous monitoring of temperature and pressure, the research uncovers critical insights into the behavior of active and inactive cell components. The analysis reveals significant degradation increments, primarily driven by side product accumulation and the deterioration of lithium microstructures, which contribute to performance loss over cycling. Additionally, temperature distribution analysis shows a strong correlation between joule heating, polarization resistance, and the observed endothermic processes during crystallization. These findings provide a comprehensive understanding of the mechanistic processes within industrially relevant pouch cells, highlighting opportunities for optimizing Li/S cell designs and advancing high-energy-density battery systems for commercial applications.

A stochastic 3D modeling approach for the nanoporous binder-conductive additive phase in hierarchically structured cathodes of lithium-ion batteries is presented. The binder-conductive additive phase of these electrodes consists of carbon black, polyvinylidene difluoride binder and graphite particles. For its stochastic 3D modeling, a three-step procedure based on methods from stochastic geometry is used. First, the graphite particles are described by a Boolean model with ellipsoidal grains. Second, the mixture of carbon black and binder is modeled by an excursion set of a Gaussian random field in the complement of the graphite particles. Third, large pore regions within the mixture of carbon black and binder are described by a Boolean model with spherical grains. The model parameters are calibrated to 3D image data of cathodes in lithium-ion batteries acquired by focused ion beam scanning electron microscopy. Subsequently, model validation is performed by comparing model realizations with measured image data in terms of various morphological descriptors that are not used for model fitting. Finally, we use the stochastic 3D model for predictive simulations, where we generate virtual, yet realistic, image data of nanoporous binder-conductive additives with varying amounts of graphite particles. Based on these virtual nanostructures, we can investigate structure-property relationships. In particular, we quantitatively study the influence of graphite particles on effective transport properties in the nanoporous binder-conductive additive phase, which have a crucial impact on electrochemical processes in the cathode and thus on the performance of battery cells.

X-ray imaging of hidden carbon-based inks on organic substrates remains an unsolved problem for the recovery of text from written artifacts. Collections that cannot be read without severe textual fragmentation or physical destruction include the Herculaneum papyri and mummy cartonnage, as well as isolated book scroll discoveries. Here, we propose the use of xenon sorption in regions of increased carbon concentration to differentiate ink from substrate in the X-ray imaging of these objects. A mock-up sample was placed in an aluminum vessel and exposed to xenon atmospheres at pressures up to 10 bar. Using the BESSY II synchrotron light source, we acquired a series of images to demonstrate the visibility of xenon uptake in ink particles as well as its subsequent desorption from the sample.

The conductive additive and binder domain (CBD) is an essential component of lithium-ion battery electrodes. It enhances the electrical connectivity and mechanical stability within the solid electrode matrix. The CBD aggregate exhibits inner porosity that significantly impacts ion transport within the electrode. Thus, the spatial distribution of CBD and its morphology play a critical role for ion transport pathways within the electrode. In order to quantify the extent of this influence, we employ high-resolution focused ion beam/scanning electron microscopy (FIB-SEM) imaging and isolate regions with just solid CBD and pore. This enables us to quantitatively correlate the CBD morphology with physical transport parameters and present a function that describes the relationship between CBD porosity and its ionic conductivity. Through our work, we provide insights into the CBD microstructure for use in future continuum-scale models.

Polarized neutron imaging has many applications through characterization of magnetic fields generated from currents or magnetic moments. If local magnetic field directions change slowly relative to its precession frequency, the angle between neutron polarization vector and the local field vector remains constant. Conversely, if the fields change rapidly relative to the precession frequency, this angle may vary. The transition between these scenarios follows the adiabatic condition. In this study, we analyze the effects of the adiabatic condition on a polarized neutron image. Two case studies are used for illustrating possible scenarios. The first case shows how an external field, due to the adiabatic condition, influences the symmetry of a polarized neutron image of a current carrying solenoid. The second case study shows how the adiabatic coupling of the beam polarization could lead to the loss of contrast in a polarized neutron image while studying field penetration in type II superconductors. Both case studies serve to highlight the importance of taking this phenomenon into account while interpreting polarized neutron imaging data given the rising importance of the technique as a characterization method in magnetism and superconductivity research.

In this study, we report the first case of non -destructive characterization of the dependence of the flux trapping mechanism on the grain properties of a bulk type II superconductor using a combination of polarized neutron tomography and diffraction contrast tomography. The high temperature superconductor, YBa 2 Cu 3 O 7_ delta , has been used in this study due to its viable commercial growth processes typically resulting in the production of polycrystalline specimens. The diffraction tomography revealed the pseudo-single crystal nature of the sample i.e. a polycrystalline sample with 47 composite grains having a maximum grain misorientation angle of 1.86 degrees . Polarized neutron tomography was used for characterization of the flux trapped in the material after field cooling to 90.5 K in a field of 0.5 mT and switching off the field. A combination of the results from these two nondestructive characterization techniques indicate a correlation between the anisotropy of the trapped flux with the orientation of the grains in the material in addition to a preference for the flux trapping in the grain boundaries.

Local variations in the 3D microstructure can control the macroscopic behavior of heterogeneous porous materials. For example, the permittivity through porous sheets or membranes is governed by local high-volume pathways or bottlenecks. Due to local variations, unfeasibly large amounts of microstructure data may be needed to reliably predict such material properties directly from image data. Here it is demonstrated that a vine copula approach provides parametric models for local microstructure descriptors that compactly capture the 3D microstructure including its local variations and efficiently probe it with respect to selected, measurable properties. In contrast to common methods of complexity reduction, the proposed approach creates parametric models for the multivariate probability distribution of high-dimensional descriptor vectors that inherently contain the complex, nonlinear dependencies between these descriptors. Therein, material properties are offered in physically motivated distributions of microstructure descriptors rather than as normally distributed data. Applied to porous fiber networks (paper) before and after unidirectional compression, it is shown that the copula-based models reveal material-characteristic relationships between two or more microstructure descriptors. In this way, the presented modeling approach can provide deeper insight into the microscopic origin of effective macroscopic properties of heterogeneous porous materials. This data-driven approach uses R-vine copulas to quantify and interpret relationships between five preselected local microstructure descriptors in porous materials. The R-vine copula models the 5D multivariate distribution of the local descriptors. Once built from data, the model provides material-specific relationships between all combinations of the five descriptors. image

Engineering devices from High Temperature Superconductors (HTS) for practical applications such as in transport and medical imaging requires an understanding of their critical current density (JC) distribution and how the material properties affect this. JC describes the maximum gradient of flux that can be found in a superconductor sustained by vortex pinning which is the preferential positioning of vortex in defective regions of weaker superconductivity. Local correlation of imperfections with high pinning has required destructive methods such as slicing then scanning with local magnetic probes. We describe the first case of non-destructive spatial correlation of flux pinning and consequently JC with bulk imperfections at different temperatures in top-seeded melt grown (TSMG) YBa2Cu3O7−δ chosen for its high pinning in addition to a rich structure of pores, twins and grain boundaries. This is facilitated by a combination of polarized neutron tomography to image trapped magnetic fields in a range around the material critical temperature and conventional neutron tomography to characterize potential pinning objects. The results indicate that there is indeed preferential trapping in the porous regions independent of the resolvable pore size. Polarized optical microscopy data suggests that the observed phenomenon is attributable to twin boundaries and crack defects located at the pore interface.

Li dendrites penetration through solid electrolytes (SEs) challenges the development of solid‐state Li batteries (SSLBs). To date, significant efforts are devoted to understand the mechanistic dynamics of Li dendrites nucleation, growth, and propagation in SEs, and various strategies that aim to alleviate and even inhibit Li dendrite formation have been proposed. Nevertheless, most of these conventional strategies require either additional material processing steps or new materials/layers that eventually increase battery cost and complexity. In contrast, using external fields, such as mechanical force, temperature physical field, electric field, pulse current, and even magnetic field to regulate Li dendrites penetration through SEs, seems to be one of the most cost‐effective strategies. This review focuses on the current research progress of utilizing external physical fields in regulating Li dendrites growth in SSLBs. For this purpose, the mechanical properties of Li and SEs, as well as the experimental results that visually track Li penetration dynamics, are reviewed. Finally, the review ends with remaining open questions in future studies of Li dendrites growth and penetration in SEs. It is hoped this review can shed some light on understanding the complex Li dendrite issues in SSLBs and potentially guide their rational design for further development.

Electrochemical CO 2 reduction (eCO 2 R) has emerged as a promising technology to support the shift away from fossil fuels in the chemical industry. When coupled with renewable energies it allows for an overall carbon-negative process, while enabling CO 2 as a carbon source for the production of commodity chemicals. Efficient eCO 2 R requires gas diffusion electrodes (GDEs) that provide a large wetted surface area inside the porous system, while also preserving gaseous diffusion pathways for CO 2 mass transport through their hydrophobicity. Under the high cathodic overpotential in eCO 2 R, electrowetting diminishes the hydrophobicity of the GDE and can lead to excessive flooding of the porous system [1]. This severely hinders the CO 2 mass transport and thus gives rise to the competing hydrogen evolution reaction (HER), lowering the Faradaic efficiency of the process. Therefore, understanding the flooding behavior of GDEs is of major interest for further development of the process. Mathematic models can be applied here to describe the flooding state under the influence of electrowetting and elucidate its influence on the gas transport through the GDE. The validation of such models requires direct experimental measurements of the electrolyte saturation during eCO 2 R, which can be accomplished with the use of synchrotron radiation [2]. In this work, experimental results for the direct measurement of the electrolyte saturation during eCO 2 R in sprayed silver GDEs are presented. In a first, these measurements were obtained in operando synchrotron tomography experiments, utilizing a high beam energy to penetrate through the 3 mm diameter GDE in the in-plane direction. The results indicate a higher beam absorption towards the gas side of the GDE, as well as higher absorption at increased current density. Key to the interpretation of these results is the disentanglement of the effects of concentration increase due to migration in the electric field and the actual increase in electrolyte saturation. The experimental results are used to validate a continuum model for a sprayed silver GDE in eCO 2 R which includes the effect of electrowetting on flooding behavior by introducing capillary pressure – saturation and contact angle – potential correlations [3]. A good agreement between model and tomography results is reached, showing an interplay between concentration increase and flooding effects. [1] Bienen, F., Paulisch, M. C., Mager, T., Osiewacz, J., Nazari, M., Osenberg, M., Ellendorff, B., Turek, T., Nieken, U., Manke, I., & Friedrich, K. A., Investigating the electrowetting of silver‐based gas‐diffusion electrodes during oxygen reduction reaction with electrochemical and optical methods. Electrochemical Science Advances (2022) e2100158. [2] Hoffmann, H., Paulisch, M. C., Gebhard, M., Osiewacz, J., Kutter, M., Hilger, A., Arlt, T., Kardjilov, N., Ellendorff, B., Beckmann, F., Markötter, H., Luik, M., Turek, T., Manke, I., & Roth, C., Development of a Modular Operando Cell for X-ray Imaging of Strongly Absorbing Silver-Based Gas Diffusion Electrodes. Journal of The Electrochemical Society 169 (2022) 044508. [3] Osiewacz, J., Löffelholz, M., Turek, T., Modeling the Influence of Electrolyte Distribution in Silver Gas Diffusion Electrodes for CO 2 Electroreduction. ECS Meeting Abstracts 01 (2023) 1727. Figure 1

The uncontrolled Li dissolution/deposition dynamics and rapid Li pulverizations hinder the widespread deployment of Li metal batteries (LMB). Designing a Li composite electrode possessing a mechanically robust and lithiophilic three-dimensional (3D) framework represents a promising strategy to address these challenges. This study involves the preparation of three uniquely tailored Li-B-Mg composites using a combined metallurgical process of melting, casting, and rolling, along with the synergistic application of in situ X-ray computed tomography (CT) and post-mortem failure analysis to explore the most promising composite electrode candidate for LMBs. During the in-depth investigation, the optimal 70Li-B-Mg composite electrode stands out due to its robust skeleton fiber structure, uniform Li dissolution/deposition characteristics and high capacity of free-Li. Its promising prospects for enabling high-performance LMBs are showcased by the superior performance of the built Li||O2, 2 , Li||LiFePO4, 4 , Li||NCM622 and Li||NCM811 battery systems. This work offers a novel approach for exploring universally applicable and robust Li composite electrodes to realize high-performance LMBs using in situ CT analysis.

Rechargeable sodium-oxygen batteries (NaOBs) are receiving extensive research interests because of their advantages such as ultrahigh energy density and cost efficiency. However, the severe failure of Na metal anodes has impeded the commercial development of NaOBs. Herein, combining in situ synchrotron X-ray computed tomography (SXCT) and other complementary characterizations, a novel electro-chemo-mechanical failure mechanism of sodium metal anode in NaOBs is elucidated. It is visually showcased that the Na metal anodes involve a three-stage decay evolution of a porous Na reactive interphase layer (NRIL): from the initially dot-shaped voids evolved into the spindle-shaped voids and the eventually-developed ruptured cracks. The initiation of this three-stage evolution begins with chemical-resting and is exacerbated by further electrochemical cycling. From corrosion science and fracture mechanics, theoretical simulations suggest that the evolution of porous NRIL is driven by the concentrated stress at crack tips. The findings illustrate the importance of preventing electro-chemo-mechanical degradation of Na anodes in practically rechargeable NaOBs. A novel electro-chemo-mechanical failure mechanism of Na anode in sodium-oxygen battery is unveiled by in situ synchrotron X-ray computed tomography. This degradation mechanism is characterized by the detected porous Na reactive phase layer (NRIL) involving three stages evolution, i.e., the initial dot-like voids (stage I) evolving to spindle-shaped voids (stage II) and finally to rupture cracks (stage III). image

A novel solid polymer electrolyte based on chemically stable vinylene-linked covalent organic framework was developed, demonstrating enhanced Li + conductivity and improved battery performance.

Rechargeable alkali metal-CO2 batteries, which combine high theoretical energy density and environmentally friendly CO2 fixation ability, have attracted worldwide attention. Unfortunately, their electrochemical performances are usually inferior for practical applications. Aiming to reveal the underlying causes, a combinatorial usage of advanced nondestructive and postmortem characterization tools is used to intensively study the failure mechanisms of Li/Na-CO2 batteries. It is found that a porous interphase layer is formed between the separator and the Li/Na anode during the overvoltage rising and battery performance decaying process. A series of control experiments are designed to identify the underlying mechanisms dictating the observed morphological evolution of Li/Na anodes, and it is found that the CO2 synergist facilitates Li/Na chemical corrosion, the process of which is further promoted by the unwanted galvanic corrosion and the electrochemical cycling conditions. A detailed compositional analysis reveals that the as-formed interphase layers under different conditions are similar in species, with the main differences being their inconsistent quantity. Theoretical calculation results not only suggest an inherent intermolecular affinity between the CO2 and the electrolyte solvent but also provide the most thermodynamically favored CO2 reaction pathways. Based on these results, important implications for the further development of rechargeable alkali metal-CO2 batteries are discussed. The current discoveries not only fundamentally enrich our knowledge of the failure mechanisms of rechargeable alkali metal-CO2 batteries but also provide mechanistic directions for protecting metal anodes to build high-reversible alkali metal-CO2 batteries.

We present a data-driven modeling approach to quantify morphology effects on transport properties in nanostructured materials. Our approach is based on the combination of stochastic modeling of the 3D nanostructure and numerical modeling of effective transport properties, which is used to investigate process-structure–property relationships of hierarchically structured cathode materials for lithium-ion batteries. We focus on nanostructured LiNi1/3Mn1/3Co1/3O2 (NMC) particles, the nanoporous morphology of which has a crucial impact on their effective transport properties (i.e, effective ionic and electric conductivity) and thus on the performance of the cell. First, we develop a parametric stochastic model for the 3D morphology of the nanostructured NMC particles based on excursion sets of so-called χ2-fields. This model, which has only two parameters, is then fitted to FIB-SEM image data of the NMC particles manufactured with different calcination temperatures and different particle sizes. This way it is possible to generate digital twins of the NMC particles. In a second step, measured 3D image data and corresponding digital twins are used as input for the numerical simulation of effective transport properties. Based on the results obtained by these simulations, we can quantify process-structure–property relationships. Overall, we present a methodological framework that allows for an efficient optimization of the fabrication process of nanostructured NMC particles.