David Stephen Wragg

• Wind, Julia; Ostrander, John; Gilljam, Johan Martin; Lian, Torleif; Wragg, David Stephen & Foss, Carl Erik Lie [Vis alle 9 forfattere av denne artikkelen] (2026). Detailed Characterization and Parameterization of a Large State-of-the-Art Commercial Li-Ion Pouch Cell: Part I. Cell Characterization. Journal of the Electrochemical Society. ISSN 0013-4651. 173(6). doi: 10.1149/1945-7111/ae508f. Fulltekst i vitenarkiv
• Skurtveit, Amalie; North, Eira Tiberg; Berdiell, Izar Capel; Beek, Wouter Van; Wragg, David S. & Koposov, Alexey (2026). Operando X‐Ray Diffraction and Total Scattering Characterization of Battery Materials: Not Just a Pretty Picture. Advanced Energy Materials. ISSN 1614-6832. doi: 10.1002/aenm.202506777. Fulltekst i vitenarkiv Vis sammendrag

  The development of rechargeable batteries can be accelerated by the fundamental understanding of their chemistries. Multiple characterization techniques have been deployed to study the chemical processes in batteries, but structural studies at the atomic level using X‐ray diffraction (XRD) and total X‐ray scattering (TXS) show enduring popularity. These methods are relatively easy to apply in operando mode, where structural data is collected alongside electrochemical data under operating conditions. With a growing interest in this powerful methodology, it is important to review the general principles of operando XRD/TXS characterization and develop a set of guidelines for the collection, analysis, and presentation of data that are acceptable to the community and can lead to reliable, representative, and reproducible results that are easy to judge and compare. This Review aims to survey and discuss important steps in operando XRD and TXS. From cell and electrode design to data treatment, we survey the major experimental aspects of operando studies, pointing out potential pitfalls and identifying best‐practice. In addition, we review some unconventional experiments conducted in operando mode to illustrate how such methods can be used beyond studies of the early‐stage cycling mechanisms of battery active materials.

• Brennhagen, Anders; Saha, Dipankar; Berdiell, Izar Capel; Jr, Andrew Pastusic; Koposova, Marta & Wragg, David S. [Vis alle 10 forfattere av denne artikkelen] (2025). Mechanical deformations in battery current collectors observed by operando X-ray diffraction on Si/graphite anodes. Chemical Communications. ISSN 1359-7345. 61(98), s. 19485–19488. doi: 10.1039/d5cc04995d. Fulltekst i vitenarkiv Vis sammendrag

  Current collectors in Li-ion batteries are often considered passive components with minimal influence on performance. However, materials with large expansion during lithiation may influence the current collector. Herein, we demonstrate mechanical deformations of the Cu current collector in Si/graphite electrodes using operando X-ray diffraction.

• Berdiell, Izar Capel; Cordero-Lanzac, Tomás; Junge, Nicolai Haaber; Nogueira, Liebert Parreiras; Vaughan, Gavin & Michiel, Marco Di [Vis alle 10 forfattere av denne artikkelen] (2025). X-ray absorption and diffraction computed tomography characterization of deactivation and coking in spray-dried ZSM-5/alumina catalysts. Catalysis Science & Technology. ISSN 2044-4753. doi: 10.1039/d5cy01023c. Fulltekst i vitenarkiv Vis sammendrag

  One of the main drawbacks of acid-based heterogeneous catalytic processes involving hydrocarbons is coke formation. Still, research on shaped catalysts remains limited. The main objective of this study was to gain insight into the catalyst deactivation in the methanol-to-hydrocarbon (MTH) reaction. Diffraction and absorption computed tomography experiments were performed on spray dried, hollow semi-spherically shaped ZSM-5/alumina catalysts of approximately 250 microns in size. The catalysts were employed in the MTH reaction at two different pressures, resulting in varying degrees of coking. Absorption tomography (0.027 μm3 per voxel) revealed the structural features and sponginess of the shaped catalysts. These are not perfect spheres; they rather have openings as they burst during the spray drying process. Further, high resolution powder X-ray diffraction computed tomography slices (0.125 μm3 per voxel) were analyzed by parametric Rietveld refinement. The analysis showed that the catalyst and binder overall are rather homogeneously spatially distributed within each sphere, but bubbles and agglomerates of a single phase are frequent. In addition, it is demonstrated that there were no coking gradients across the sphere wall at both partial and full deactivation. This indicates that the binder and the catalyst shape and size were suitable for the reaction conditions. Indeed, the catalyst lifetime was almost doubled relative to the pure, powdered zeolite catalyst. A series of catalysts with varying degrees of deactivation have been fully characterized ex situ, suggesting significant spillover of coke from the zeolite to the alumina matrix. These findings demonstrate the need for greater efforts to understand the formulation of shaped catalyst objects, where the matrix should not only hold the components together but also support and enhance the overall catalytic process.

• Sitorus, Fernando; Stromberg, Elin; Rouquette, Lea; Vorland, Kim Andre Nesse; Khalifeh, Mahmoud & Wragg, David Stephen [Vis alle 8 forfattere av denne artikkelen] (2025). Sustainable leaching of critical metals from lithium ion battery black mass using a citric acid and choline chloride deep eutectic solvent. Discover Sustainability. 6(1), s. 1–16. doi: 10.1007/s43621-025-02214-5. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The recycling of lithium-ion batteries (LIBs) is of critical importance due to the increasing demand for electric vehicles and portable electronic devices. It also helps address supply risks of critical raw materials and reduces the environmental impact of mining. Traditional recycling methods are often inefficient and environmentally damaging. This study investigates the use of deep eutectic solvents (DES), made from citric acid and choline chloride, for leaching valuable metals from black mass derived from spent LIBs. The research focuses on optimizing the leaching parameters, such as temperature, DES ratio, and solid-to-liquid ratio, to maximize the extraction efficiency of lithium, cobalt, nickel, and manganese. A key aspect of the study was the examination of the rheological properties of the DES system, as these properties significantly impact the leaching process. The viscosity and pH of the DES were measured, providing insights into their behavior under various conditions. Understanding the viscosity and flow characteristics of these DES systems is crucial for developing scalable and effective recycling methods. The DES mixture with a 2:1 ratio of citric acid to choline chloride, mixed with 50% water, showed the best performance. At 90 °C for 24 h, this DES mixture achieved leaching efficiencies of 77.5% for lithium, 79.9% for cobalt, 80% for manganese, 66.2% for nickel, 82.5% for copper, and 93.8% for aluminum. These findings suggest the potential of citric acid-choline chloride DES as a sustainable and environmentally friendly reagent for recycling LIBs.

• North, Erlend Tiberg; Skautvedt, Casper; Thiagarajan, Abilash Kanish; Michiel, Marco Di; Checchia, Stefano & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2025). X-ray Beam Damage Effects in a Lithium-Ion Battery Probed by Spatially Resolved X-ray Diffraction. ACS Energy Letters. 10(10), s. 4930–4932. doi: 10.1021/acsenergylett.5c02442. Fulltekst i vitenarkiv Vis sammendrag

  The use of synchrotron radiation has become common for probing the structural changes in rechargeable batteries, particularly for operando analysis. Herein, we report the exposure of the electrode to high photon flux during an operando study shutting down electrochemical transformations in the irradiated area of an electrode and causing a gradient of lithiation around the operando beam position. We rationalize such beam damage through radiation induced ionization and, consequently, electrolyte decomposition.

• Skurtveit, Amalie; Maddar, Faduma M.; Hasa, Ivana; Cavallo, Carmen; Wragg, David Stephen & Koposov, Alexey (2025). Origin of High-Rate Performance of Sb2Se3/Sb Composite Anodes for Na-Ion Batteries. ACS Applied Energy Materials. 8(19), s. 14058–16064. doi: 10.1021/acsaem.5c02418. Fulltekst i vitenarkiv Vis sammendrag

  Improving the energy density of Na-ion batteries (NIBs) requires advances in anode materials. This study investigates Sb2Se3/Sb composite anodes, which offer better capacity and stability than the individual constituents. Operando X-ray diffraction (XRD) revealed that (de)sodiation is driven by synergies between the operating mechanisms of Sb2Se3 and Sb, enabling a reversible capacity of 360 mAh g–1 (at 1000 mA g–1). This performance is also aided by amorphization of the sodiated phases, which promotes rapid Na-diffusion. The work emphasizes the need for continuous material and structural optimizations to fully harness their benefits for enabling efficient and fast-charging NIBs.

• Skurtveit, Amalie; North, Erlend Tiberg; Park, Heesoo; Chernyshov, Dmitry; Wragg, David Stephen & Koposov, Alexey (2025). Stepwise Structural Relaxation in Battery Active Materials. ACS Materials Letters. 7(1), s. 343–349. doi: 10.1021/acsmaterialslett.4c02058. Fulltekst i vitenarkiv Vis sammendrag

  Whenever the cycling of Li-ion batteries is stopped, the electrode materials undergo a relaxation process, but the structural changes that occur during relaxation are not well-understood. We have used operando synchrotron X-ray diffraction with a time resolution of 1.24 s to observe the structural changes that occur when the lithiation of graphite and LiFePO4 electrodes are interrupted. Assessing the kinetics of the relaxation processes coupled with molecular dynamics simulations allows us to identify three relaxation stages in graphite. The atomistic origin for the relaxation process within the partially lithiated graphite structure is driven by the reorganization of Li ions into Li clusters. Relaxation in LiFePO4 electrodes is considerably slower than for graphite, but the observed structural changes is also attributed to reorganization of Li ions. These insights highlight the nature of the structural changes that occur during relaxation and the importance of using operando structural studies to avoid misleading conclusions about the reaction mechanisms in battery materials.

• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Vis alle 13 forfattere av denne artikkelen] (2025). Unique Na5−xSbSe Phase Enables High-Rate Performance of Sb2Se3 Anodes in Na-Ion Batteries. Advanced Energy Materials. ISSN 1614-6832. 15(31), s. 1–16. doi: 10.1002/aenm.202501433. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries (NIBs) need new anode materials to improve energy density. Metal chalcogenides, such as Sb2Se3, represent a promising alternative to commonly used hard carbon materials, demonstrating high-rate performance up to 5 A g−1 with minimal capacity losses. However, Sb2Se3 is believed to operate under the conversion/alloying mechanism, typically linked with large structural transformations and volumetric changes—quite contrary to its performance. Herein, by combining multiple operando techniques and atomistic simulations, a new fully sodiated phase, Na5−xSbSe, is unambiguously revealed as the origin of the high-rate performance of Sb2Se3. Na5−xSbSe is stable within 0.01–0.80 V versus Na/Na+ and crystallizes in I4/mmm. The remarkable structural flexibility of Na5SbSe to changes in Na-content allows the anode to be (de)sodiated with minimal volumetric changes (≈3.4%). This unique “breathing effect” is intimately linked to high inherent vacancy concentration, disordered, and structurally flexible anion sublattice, providing a stable framework for fast Na diffusion, contributing to the fast-charging properties of Sb2Se3. The study showcases the power of operando methods for discovering new phases that are hidden in the mechanistic paths of well-studied reactions and underlines the intertwined nature of various characterization methods assisted by atomistic insights for a comprehensive understanding of complex (de)sodiation mechanisms.

• Berdiell, Izar Capel; Lundegaard, Lars F.; Beato, Pablo; Michiel, Marco Di; Wragg, David Stephen & Svelle, Stian (2025). Spatiotemporal investigation of the regeneration of a shaped zeolite catalyst extrudate using operando powder X-ray diffraction computed tomography. Journal of Catalysis. ISSN 0021-9517. 450. doi: 10.1016/j.jcat.2025.116300. Fulltekst i vitenarkiv Vis sammendrag

  We have used operando powder X-ray diffraction computed tomography (PXRD-CT) analysed by parametric Rietveld refinements to monitor the regeneration of a deactivated ZSM-5 zeolite based extrudate employed as a catalyst in the methanol-to-hydrocarbon reaction. This investigation thus advances beyond previous studies of pure, powdered zeolites. We follow the coke oxidation by monitoring three XRD based descriptors. Lattice relaxation, monitored as the difference in length of the a- and b-lattice parameters (a-b), occurs first at the core of the extrudate and progresses towards the outer surface. This demonstrates a radial distribution of different coke species, wherein the heaviest, more oxidation resistant coke is matured near the external surface of the extrudate. In contrast, the total non-framework species mass (NFSM) decreased more uniformly throughout the extrudate, suggesting that chemical transformations of the coke species can occur prior to full oxidation. This notion is supported by in situ temperature programmed oxidation, which demonstrates that the regeneration of the ZSM-5/binder composite occurs in two distinct steps. We also observe that irreversible (hydro)thermal damage occurs in the severely coked regions of the extrudate during regeneration. Additionally, we demonstrate that the three different XRD based descriptors carry slightly different and complementary information. The (a-b) descriptor describes lattice distortion induced by rigid coke species. The total non-framework species mass (NFSM) and the unit cell volume (UCV), in contrast, capture all guest species, including volatile compounds and water. However, as a drawback, the UCV is strongly influenced also by thermal effects, whereas the (NFSM) is virtually unaffected by temperature.

• Yartys, Volodymyr; Denys, Roman Volodymyrovich; Akselrud, Lev G.; Ponniah, Vajeeston; Dankelman, Robert & Plomp, Jeroen [Vis alle 11 forfattere av denne artikkelen] (2024). Structure and bonding in TiNiSi type LaMgSnH intermetallic hydride. Journal of Alloys and Compounds. ISSN 0925-8388. 976. doi: 10.1016/j.jallcom.2023.173198. Fulltekst i vitenarkiv
• Chernyshov, Dmitry; Marshall, Kenneth P.; North, Erlend Tiberg; Fuller, Chloe A. & Wragg, David Stephen (2024). Instrumental broadening and the radial pair distribution function with 2D detectors. Acta Crystallographica Section A: Foundations and Advances. 80(5), s. 358–366. doi: 10.1107/S2053273324006569. Fulltekst i vitenarkiv Vis sammendrag

  The atomic pair distribution function (PDF) is a real-space representation of the structure of a material. Experimental PDFs are obtained using a Fourier transform from total scattering data which may or may not have Bragg diffraction peaks. The determination of Bragg peak resolution in scattering data from the fundamental physical parameters of the diffractometer used is well established, but after the Fourier transform from reciprocal to direct space, these contributions are harder to identify. Starting from an existing definition of the resolution function of large-area detectors for X-ray diffraction, this approach is expanded into direct space. The effect of instrumental parameters on PDF peak resolution is developed mathematically, then studied with modelling and comparison with experimental PDFs of LaB6 from measurements made in different-sized capillaries.

• Brennhagen, Anders; Skautvedt, Casper; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2024). Unraveling the (De)sodiation Mechanisms of BiFeO<inf>3</inf> at a High Rate with Operando XRD. ACS Applied Materials & Interfaces. ISSN 1944-8244. 16(10), s. 12428–12436. doi: 10.1021/acsami.3c17296. Fulltekst i vitenarkiv Vis sammendrag

  Development of new anode materials for Na-ion batteries strongly depends on a detailed understanding of their cycling mechanism. Due to instrumental limitations, the majority of mechanistic studies focus on operando materials’ characterization at low cycling rates. In this work, we evaluate and compare the (de)sodiation mechanisms of BiFeO3 in Na-ion batteries at different current densities using operando X-ray diffraction (XRD) and ex situ X-ray absorption spectroscopy (XAS). BiFeO3 is a conversion-alloying anode material with a high initial sodiation capacity of ∼600 mAh g–1, when cycled at 0.1 A g–1. It does not change its performance or cycling mechanism, except for minor losses in capacity, when the current density is increased to 1 A g–1. In addition, operando XRD characterization carried out over multiple cycles shows that the Bi ⇋ NaBi (de)alloying reaction and the oxidation of Bi at the interface with the Na–Fe–O matrix are detrimental for cycling stability. The isolated NaBi ⇋ Na3Bi reaction is less damaging to the cycling stability of the material.

• Paredes, Patricio; Rauwel, Erwan Yann; Wragg, David Stephen; Rapenne, Laetitia; Gélard, Isabelle & Rauwel, Protima (2024). A comparative study of Cu-based nanoparticles and their spin-coated films: photocatalytic degradation mechanisms and efficiencies towards malachite green and neutral red azo dyes. Environmental Science and Pollution Research. ISSN 0944-1344. 32, s. 314–334. doi: 10.1007/s11356-024-35785-3. Fulltekst i vitenarkiv Vis sammendrag

  In this work, a comparison of the photocatalytic activity of free-standing Cu-based nanoparticle mixtures and spin-coated nanoparticle films under visible-light radiation is conducted. Herein, Cu2O, Cu2O-Cu, Cu2O-Cu3N-Cu, and Cu3N-Cu nanoparticle mixtures were successfully synthesized by a non-aqueous sol–gel route and then deposited on a glass substrate by spin-coating. The surface chemistry of the nanoparticles studied by X-ray photoelectron spectroscopy (XPS) allowed elucidating the nanoparticle synthesis mechanism. The UV–Vis absorption spectroscopy illustrates that photocatalytic activity is attributed to the high specific surface of the nanoparticles and their wider absorption range region from 500 to 1100 nm. Unlike the free-standing photocatalysts, the photocatalytic effect of spin-coated nanoparticle films enabled their facile reclamation, which solves a key issue for practical applications of the photocatalysts. The photocatalytic performances on neutral red and malachite green organic dyes were influenced by the type of visible light sources, i.e., solar simulator and natural sunlight. The results indicate that photodegradation efficiency is the highest for Cu2O nanoparticles, reaching values of 82% for neutral red and 94% for malachite green. We also demonstrate that the degradation of cationic neutral red undergoes a photoconversion to its neutral form during the degradation process, which in turn, lowers its degradation efficiency. On the other hand, higher degradation efficiency was observed on malachite green owing to its unique cationic form, soluble in aqueous solutions.

• Yartys, Volodymyr; Akselrud, Lev; Denys, Roman V.; Ponniah, Vajeeston; Ouladdiaf, Bachir & Dankelman, Robert [Vis alle 14 forfattere av denne artikkelen] (2024). Crystal, Magnetic Structures, and Bonding Interactions in the TiNiSi-Type Hydride CeMgSnH: Experimental and Computational Studies. Chemistry of Materials. ISSN 0897-4756. 36(12), s. 6257–6268. doi: 10.1021/acs.chemmater.4c01104. Fulltekst i vitenarkiv
• Park, Heesoo; Wragg, David Stephen & Koposov, Alexey (2024). Replica exchange molecular dynamics for Li-intercalation in graphite: a new solution for an old problem. Chemical Science. ISSN 2041-6520. doi: 10.1039/d3sc06107h. Fulltekst i vitenarkiv Vis sammendrag

  Li intercalation and graphite stacking have been extensively studied because of the importance of graphite in commercial Li-ion batteries. Despite this attention, there are still questions about the atomistic structures of the intermediate states that exist during lithiation, especially when phase dynamics cause a disordered Li distribution. The Li migration event (diffusion coefficient of 10−5 nm2 ns−1) makes it difficult to explore the various Li-intercalation configurations in conventional molecular dynamics (MD) simulations with an affordable simulation timescale. To overcome these limitations, we conducted a comprehensive study using replica-exchange molecular dynamics (REMD) in combination with the ReaxFF force field. This approach allowed us to study the behavior of Li-intercalated graphite from any starting arrangement of Li at any value of x in LixC6. Our focus was on analyzing the energetic favorability differences between the relaxed structures. We rationalized the trends in formation energy on the basis of observed structural features, identifying three main structural features that cooperatively control Li rearrangement in graphite: Li distribution, graphite stacking mode and gallery height (graphene layer spacing). We also observed a tendency for clustering of Li, which could lead to dynamic local structures that approximate the staging models used to explain intercalation into graphite.

• Brennhagen, Anders; Skurtveit, Amalie; Wragg, David Stephen; Cavallo, Carmen; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2024). (De)sodiation Mechanism of Bi2MoO6 in Na-Ion Batteries Probed by Quasi-Simultaneous Operando PDF and XAS. Chemistry of Materials. ISSN 0897-4756. 36(15), s. 7514–7524. doi: 10.1021/acs.chemmater.4c01503. Fulltekst i vitenarkiv Vis sammendrag

  Operando characterization can reveal degradation processes in battery materials and are essential for the development of battery chemistries. This study reports the first use of quasi-simultaneous operando pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) of a battery cell, providing a detailed, atomic-level understanding of the cycling mechanism of Bi2MoO6 as an anode material for Na-ion batteries. This material cycles via a combined conversion-alloying reaction, where electrochemically active, nanocrystalline NaxBi particles embedded in an amorphous Na–Mo–O matrix are formed during the first sodiation. The combination of operando PDF and XAS revealed that Bi obtains a positive oxidation state at the end of desodiation, due to formation of Bi–O bonds at the interface between the Bi particles and the Na–Mo–O matrix. In addition, XAS confirmed that Mo has an average oxidation state of +6 throughout the (de)sodiation process and, thus, does not contribute to the capacity. However, the local environment of Mo6+ changes from tetrahedral coordination in the desodiated state to distorted octahedral in the sodiated state. These structural changes are linked to the poor cycling stability of Bi2MoO6, as flexibility of this matrix allows movement and coalescence of the NaxBi particles, which is detrimental to the electrochemical stability.

• Schweigart, Philipp; Hua, Weicheng; Sánchez, Pedro Alonso; Lian, Camilla; Nylund, Inger-Emma & Wragg, David Stephen [Vis alle 10 forfattere av denne artikkelen] (2024). Deciphering the Impact of Current, Composition, and Potential on the Lithiation Behavior of Si-Rich Silicon-Graphite Anodes. Small. ISSN 1613-6810. doi: 10.1002/smll.202406615. Fulltekst i vitenarkiv Vis sammendrag

  Adding silicon (Si) to graphite (Gr) anodes is an effective approach for boosting the energy density of lithium-ion batteries, but it also triggers mechanical instability due to Si volume changes upon (de)lithiation reactions. In this work, component-specific (de)lithiation dynamics on Si-rich (30 and 70 wt.% Si) SiGr anodes at various charge/discharge C-rates are unveiled and compared to a graphite-only electrode (100Gr) via operando synchrotron X-ray diffraction coupled with differential capacity plots analysis. Results show preferential lithiation of amorphous Si above ≈200 mV and competing lithiation of Gr, amorphous Si, and crystalline Si below ≈200 mV. Discharge proceeds via sequential delithiation of Gr and amorphous lithium silicide. Si shifts the interconversion potentials of graphite intercalation compounds, lowering the Gr state of charge compared to 100Gr. In the 30% Si electrode, crystalline Si amorphization at potentials <110 mV is found to be kinetically hindered at C-rates higher than C/5, which can be key for enhancing the cycling stability of SiGr anodes. The 70% Si electrode exhibits restricted lithium diffusion in Gr, full Si amorphization, and Li15Si4 formation. These findings related to the potential- and current-dependent dynamic changes on SiGr blends are crucial for designing stable high energy density SiGr anodes.

• Gerz, Isabelle; Aunan, Erlend; Finelli, Valeria; Rasheed, Mouhammad Abu; Deplano, Gabriele & Pupo, Rafael Cortez Sgroi [Vis alle 15 forfattere av denne artikkelen] (2024). Enabling a bioinspired N,N,N-copper coordination motif through spatial control in UiO-67: synthesis and reactivity. Dalton Transactions. ISSN 1477-9226. 53, s. 8141–8153. doi: 10.1039/d3dt03096b. Fulltekst i vitenarkiv Vis sammendrag

  Metal–organic frameworks (MOFs) featuring zirconium-based clusters are widely used for the development of functionalized materials due to their exceptional stability. In this study, we report the synthesis of a novel N,N,N-ligand compatible with a biphenyl dicarboxylic acid-based MOF. However, the resulting copper(I) complex exhibited unexpected coordination behaviour, lacking the intended trifold coordination motif. Herein, we demonstrate the successful immobilization of a bioinspired ligand within the MOF, which preserved its crystalline and porous nature while generating a well-defined copper site. Comprehensive spectroscopic analyses, including X-ray absorption, UV/Vis, and infrared spectroscopy, were conducted to investigate the copper site and its thermal behaviour. The immobilized ligand exhibited the desired tridentate coordination to copper, providing access to a coordination motif otherwise unattainable. Notably, water molecules were also found to coordinate to copper. Upon heating, the copper centre within the MOF exhibited reversible dehydration, suggesting facile creation of open coordination sites. Furthermore, the copper site displayed reduction at elevated temperatures and subsequent susceptibility to oxidation by molecular oxygen. Lastly, both the molecular complexes and the MOF were evaluated as catalysts for the oxidation of cyclohexane using hydrogen peroxide. This work highlights the successful immobilization of a bioinspired ligand in a zirconium-based MOF, shedding light on the structural features, thermal behaviour, and catalytic potential of the resulting copper sites.

• Lundegaard, Lars Fahl; Berdiell, Izar Capel; König, Nico; Junge, Nicolai Haaber; Beato, Pablo & Chernyshov, Dmitry [Vis alle 8 forfattere av denne artikkelen] (2023). Tracking deactivation of zeolite beta with and without a detailed structure model: XRD analysis and in situ studies. Microporous and Mesoporous Materials. ISSN 1387-1811. 366. doi: 10.1016/j.micromeso.2023.112911. Fulltekst i vitenarkiv
• Berdiell, Izar Capel; Braghin, Giorgio Bruno; Cordero-Lanzac, Tomas; Beato, Pablo; Lundegaard, Lars F. & Wragg, David Stephen [Vis alle 8 forfattere av denne artikkelen] (2023). Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst During MTH with XRD. Topics in catalysis. ISSN 1022-5528. 66, s. 1418–1426. doi: 10.1007/s11244-023-01780-0. Fulltekst i vitenarkiv Vis sammendrag

  Abstract We used the methanol-to-hydrocarbon (MTH) reaction as a shape-selective model reaction to investigate coke formation in zeolite H-Ferrierite. Despite being a 2D topology in terms of channel propagation, the FER framework displays a lattice expansion in all three dimensions of space upon deactivation. Therefore, the volume of the unit cell is an excellent X-Ray diffraction (XRD) descriptor for the catalyst deactivation. A model with dummy atoms added, also proved to be an accurate approach to measure the amount of internal coke and/or water inside the pore network correlated with thermogravimetric analysis results. While the catalyst deactivation of the H-Ferrerite during the MTH was fast, a comparably long induction period was observed. We were able to track such fast deactivation with the aforementioned descriptors by means of an operando XRD study by a standard laboratory diffractometer.

• Wragg, David Stephen; Skautvedt, Casper; Brennhagen, Anders; Geiss, Carina; Checchia, Stefano & Koposov, Alexey (2023). Tracking Lithiation of Si-Based Anodes in Real Time by Total Scattering Computed Tomography. Journal of Physical Chemistry C. ISSN 1932-7447. 127(48), s. 23149–23155. doi: 10.1021/acs.jpcc.3c06414. Fulltekst i vitenarkiv Vis sammendrag

  The existing set of characterization tools does not permit a full description of the three-dimensional (3D) structure and operating mechanisms of amorphous, low-scattering alloying active materials in metal-ion batteries. In this article, we describe and demonstrate a new methodology for analysis of this class of materials based on total scattering computed tomography. Using silicon (Si)-based anodes as a testing platform, we can not only visualize the chemical changes taking place in the electrodes during lithiation but also create a 3D mapping of the electrode components including amorphous active and inactive materials. The mapping was used to select a region of interest in the electrode from which the best possible operando pair distribution function (PDF) of the active material could be obtained. Finally, we deployed differential analysis to highlight the small but systematic changes in the PDF during lithiation, revealing subtle structural transformations at the atomic scale.

• Kumar, Rohit; Rauwel, Protima; Kriipsalu, Mait; Wragg, David Stephen & Rauwel, Erwan (2023). Nanocobalt based (Co@Co(OH)2) sand nanocomposite applied to manganese extraction from contaminated water. Journal of Environmental Chemical Engineering. 11(3). doi: 10.1016/j.jece.2023.109818. Fulltekst i vitenarkiv Vis sammendrag

  This study presents the adsorption capability of a filter composed of sand coated with cobalt nanomaterials (CoNM) for the extraction of manganese ions from aqueous media. The study was performed in both batch and dynamic modes in order to evaluate the adsorption capabilities of free-standing CoNM and CoNM-coated sand. The Langmuir and Freundlich isotherm models were applied to the adsorption of manganese ions in batch-mode. The Langmuir model estimated a maximum adsorption capacity of 17.86 mg/g corresponding to a single layer adsorption. Nevertheless, the Freundlich model also characterized the adsorption with a high coefficient of determination, suggesting a multilayered adsorption mechanism of Mn on CoNM. Dynamic mode studies were conducted with different influent Mn concentrations, pH and in the presence of foreign or competing ions (Fe3+, As3+, As5+ and Cu2+). The experimental data was fitted with linearized Thomas and Yoon-Nelson models in order to determine adsorption capacities. The multilayered adsorption mechanism was confirmed owing to a high adsorption capacity of 3360 mg/g of active nanomaterials at pH = 6.

• Monasterial, Abigale P.; Weddle, Peter J.; Atkinson, Kristen; Wragg, David Stephen; Colclasure, Andrew M. & Usseglio-Viretta, Francois L. E. [Vis alle 11 forfattere av denne artikkelen] (2023). Dynamic In-Plane Heterogeneous and Inverted Response of Graphite to Fast Charging and Discharging Conditions in Lithium-Ion Pouch Cells. Small Science. 3(7). doi: 10.1002/smsc.202200067. Fulltekst i vitenarkiv
• Paredes, Patricio; Rauwel, Erwan Yann; Wragg, David Stephen; Rapenne, Laetitia; Estephan, Elias & Volobujeva, Olga [Vis alle 7 forfattere av denne artikkelen] (2023). Sunlight-Driven Photocatalytic Degradation of Methylene Blue with Facile One-Step Synthesized Cu-Cu<inf>2</inf>O-Cu<inf>3</inf>N Nanoparticle Mixtures. Nanomaterials. 13(8). doi: 10.3390/nano13081311. Fulltekst i vitenarkiv Vis sammendrag

  Sunlight-driven photocatalytic degradation is an effective and eco-friendly technology for the removal of organic pollutants from contaminated water. Herein, we describe the one-step synthesis of Cu-Cu2O-Cu3N nanoparticle mixtures using a novel non-aqueous, sol-gel route and their application in the solar-driven photocatalytic degradation of methylene blue. The crystalline structure and morphology were investigated with XRD, SEM and TEM. The optical properties of the as-prepared photocatalysts were investigated with Raman, FTIR, UV-Vis and photoluminescence spectroscopies. The influence of the phase proportions of Cu, Cu2O and Cu3N in the nanoparticle mixtures on the photocatalytic activity was also investigated. Overall, the sample containing the highest quantity of Cu3N exhibits the highest photocatalytic degradation efficiency (95%). This enhancement is attributed to factors such as absorption range broadening, increased specific surface of the photocatalysts and the downward band bending in the p-type semiconductors, i.e., Cu3N and Cu2O. Two different catalytic dosages were studied, i.e., 5 mg and 10 mg. The higher catalytic dosage exhibited lower photocatalytic degradation efficiency owing to the increase in the turbidity of the solution.

• Strandbakke, Ragnar; Wragg, David Stephen; Sørby, Magnus Helgerud; Guzik, Matylda; Gunnæs, Anette Eleonora & Szpunar, Iga [Vis alle 12 forfattere av denne artikkelen] (2022). Structural properties of mixed conductor Ba1−xGd1−yLax+yCo2O6−δ. Dalton Transactions. ISSN 1477-9226. 51(48), s. 18667–18677. doi: 10.1039/d2dt02277j. Fulltekst i vitenarkiv Vis sammendrag

  Ba1−xGd1−yLax+yCo2O6−δ (BGLC) compositions with large compositional ranges of Ba, Gd, and La have been characterised with respect to phase compositions, structure, and thermal and chemical expansion. The results show a system with large compositional flexibility, enabling tuning of functional properties and thermal and chemical expansion. We show anisotropic chemical expansion and detailed refinements of emerging phases as La is substituted for Ba and Gd. The dominating phase is the double perovskite structure Pmmm, which is A-site ordered along the c-axes and with O vacancy ordering along the b-axis in the Ln-layer. Phases emerging when substituting La for Ba are orthorhombic Ba-deficient Pbnm and cubic LaCoO3-based R[3 with combining macron]c. When La is almost completely substituted for Gd, the material can be stabilised in Pmmm, or cubic Pm[3 with combining macron]m, depending on thermal and atmospheric history. We list thermal expansion coefficients for x = 0–0.3, y = 0.2.

• Hylland, Knut Tormodssønn; Schmidtke, Inga; Wragg, David Stephen; Nova, Ainara & Tilset, Mats (2022). Synthesis of substituted (N,C) and (N,C,C) Au(iii) complexes: the influence of sterics and electronics on cyclometalation reactions. Dalton Transactions. ISSN 1477-9226. 51(13), s. 5082–5097. doi: 10.1039/d2dt00371f. Fulltekst i vitenarkiv Vis sammendrag

  Cyclometalated Au(III) complexes are of interest due to their catalytic, medicinal, and photophysical properties. Herein, we describe the synthesis of derivatives of the type (N,C)Au(OAcF)2 (OAcF = trifluoroacetate) and (N,C,C)AuOAcF by a cyclometalation route, where (N,C) and (N,C,C) are chelating 2-arylpyridine ligands. The scope of the synthesis is explored by substituting the 2-arylpyridine core with electron donor or acceptor substituents at one or both rings. Notably, a variety of functionalized Au(III) complexes can be obtained in one step from the corresponding ligand and Au(OAc)3, eliminating the need for organomercury intermediates, which is commonly reported for similar syntheses. The influence of substituents in the ligand backbone on the resulting complexes was assessed using DFT calculations, 15N NMR spectroscopy and single-crystal X-ray diffraction analysis. A correlation between the electronic properties of the (N,C) ligands and their ability to undergo cyclometalation was found from experimental studies combined with natural charge analysis, suggesting the cyclometalation at Au(III) to take place via an electrophilic aromatic substitution-type mechanism. The formation of Au(III) pincer complexes from tridentate (N,C,C) ligands was investigated by synthesis and DFT calculations, in order to assess the feasibility of C(sp3)–H bond activation as a synthetic pathway to (N,C,C) cyclometalated Au(III) complexes. It was found that C(sp3)–H bond activation is feasible for ligands containing different alkyl groups (isopropyl and ethyl), although the C–H activation is less energetically favored compared to a ligand containing tert-butyl groups.

• Sottmann, Jonas; Ruud, Amund; Fjellvåg, Øystein; Vaughan, Gavin B. M.; Michel, Marco Di & Fjellvåg, Helmer [Vis alle 9 forfattere av denne artikkelen] (2022). 5D total scattering computed tomography reveals the full reaction mechanism of a bismuth vanadate lithium ion battery anode. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 24(44), s. 27075–27085. doi: 10.1039/d2cp03892g. Fulltekst i vitenarkiv Vis sammendrag

  We have used operando 5D synchrotron total scattering computed tomography (TSCT) to understand the cycling and possible long term deactivation mechanisms of the lithium-ion battery anode bismuth vanadate. This anode material functions via a combined conversion/alloying mechanism in which nanocrystals of lithium–bismuth alloy are protected by an amorphous matrix of lithium vanadate. This composite is formed in situ during the first lithiation of the anode. The operando TSCT data were analyzed and mapped using both pair distribution function and Rietveld methods. We can follow the lithium–bismuth alloying reaction at all stages, gaining real structural insight including variations in nanoparticle sizes, lattice parameters and bond lengths, even when the material is completely amorphous. We also observe for the first time structural changes related to the cycling of lithium ions in the lithium vanadate matrix, which displays no interactions beyond the first shell of V–O bonds. The first 3D operando mapping of the distribution of different materials in an amorphous anode reveals a decline in coverage caused by either agglomeration or partial dissolution of the active material, hinting at the mechanism of long term deactivation. The observations from the operando experiment are backed up by post mortem transmission electron microscope (TEM) studies and theoretical calculations to provide a complete picture of an exceptionally complex cycling mechanism across a range of length scales.

• Fjellvåg, Asbjørn Slagtern; Jørgensen, Peter Stanley; Waller, David; Wragg, David Stephen; Michiel, Marco Di & Sjåstad, Anja Olafsen (2022). Mechanism of grain reconstruction of Pd and Pd/Ni wires during Pt–catchment. Materialia. 21. doi: 10.1016/j.mtla.2022.101359. Fulltekst i vitenarkiv Vis sammendrag

  We have investigated industrial Pd and Pd/Ni (91.3/8.7 at.%) wires and gauzes used for Pt-catchment during the ammonia oxidation process, focusing on the origin of the grain reconstruction phenomena. In situ X-ray absorption tomography experiments reveal severe reconstruction of polycrystalline Pd and Pd/Ni wires over the course of 10 days, caused solely by the presence of gaseous PtO2 and dry air. A high partial pressure of PtO2 results in higher Pt-catchment rates, which in turn causes more severe reconstruction of the Pd-based wire. Additionally, the Pt-catchment efficiency is reduced when the Pt-content on the wire surface increases. Scanning electron microscopy accompanied by energy dispersive X-ray analysis reveal that Pt diffuses rapidly into the wire core via grain boundaries already after 1 day of Pt catchment. However, quasi monocrystalline (pre-annealed) Pd and Pd/Ni samples show significantly less Pt-catchment and only a little reconstruction compared to the polycrystalline samples. With support from experiments and simulations, we conclude that bulk diffusion is one of the main limitations for Pt-catchment on both poly- and quasi monocrystalline Pd and Pd/Ni wires. The diffusion limitation causes a high surface concentration of Pt, which in turn limits further Pt-catchment due to a gas-surface equilibrium. The polycrystalline wire can overcome the diffusion limitation by utilizing a rapid grain boundary diffusion, transporting both Pt to the wire core and Pd to the wire surface. However, this transport process is also the cause of grain reconstruction.

• Kalantzopoulos, Georgios; Gama, Daniel Rojo; Pappas, Dimitrios; Dovgaliuk, Iurii; Olsbye, Unni & Beato, Pablo [Vis alle 9 forfattere av denne artikkelen] (2022). Real-time regeneration of a working zeolite monitored via operando X-ray diffraction and crystallographic imaging: how coke flees the MFI framework. Dalton Transactions. ISSN 1477-9226. 51(44), s. 16845–16851. doi: 10.1039/d2dt02845j. Fulltekst i vitenarkiv Vis sammendrag

  We have monitored the regeneration of H-ZSM-5 via operando time-resolved powder X-Ray diffraction (PXRD) coupled with mass spectroscopy (MS). Parametric Rietveld refinements and calculation of the extra-framework electronic density by differential Fourier maps analysis provide details on the mode of coke removal combined with the corresponding sub-unit cell changes of the zeolite structure. It is clear that the coke removal is a complex process that occurs in at least two steps; a thermal decomposition followed by oxidation. In a coked zeolite, the straight 10-ring channel circumference is warped to an oval shape due to structural distortion induced by rigid aromatic coke species. The data presented explain why the difference in length between the a-vector and the b-vector of the MFI unit cell is a robust descriptor for bulky coke, as opposed to the unit cell volume, which is affected also by adsorbed species and thermal effects. Our approach holds the promise to quantify and identify coke removal (and formation) in structurally distinct locations within the zeolite framework.

• Nagpal, Keshav; Rapenne, Laetitia; Wragg, David Stephen; Rauwel, Erwan Yann & Rauwel, Protima (2022). The role of CNT in surface defect passivation and UV emission intensification of ZnO nanoparticles. Nanomaterials and Nanotechnology (NMNT). 12. doi: 10.1177/18479804221079419. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2022). Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries. Nanotechnology. ISSN 0957-4484. 33(18). doi: 10.1088/1361-6528/ac4eb5. Fulltekst i vitenarkiv Vis sammendrag

  Based on the same rocking-chair principle as rechargeable Li-ion batteries, Na-ion batteries are promising solutions for energy storage benefiting from low-cost materials comprised of abundant elements. However, despite the mechanistic similarities, Na-ion batteries require a different set of active materials than Li-ion batteries. Bismuth molybdate (Bi2MoO6) is a promising NIB anode material operating through a combined conversion/alloying mechanism. We report an operando x-ray diffraction (XRD) investigation of Bi2MoO6-based anodes over 34 (de)sodiation cycles revealing both basic operating mechanisms and potential pathways for capacity degradation. Irreversible conversion of Bi2MoO6 to Bi nanoparticles occurs through the first sodiation, allowing Bi to reversibly alloy with Na forming the cubic Na3Bi phase. Preliminary electrochemical evaluation in half-cells versus Na metal demonstrated specific capacities for Bi2MoO6 to be close to 300 mAh g−1 during the initial 10 cycles, followed by a rapid capacity decay. Operando XRD characterisation revealed that the increased irreversibility of the sodiation reactions and the formation of hexagonal Na3Bi are the main causes of the capacity loss. This is initiated by an increase in crystallite sizes of the Bi particles accompanied by structural changes in the electronically insulating Na–Mo–O matrix leading to poor conductivity in the electrode. The poor electronic conductivity of the matrix deactivates the NaxBi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David; Sottmann, Jonas; Koposov, Alexey & Fjellvåg, Helmer (2021). Understanding the (De)Sodiation Mechanisms in Na‐Based Batteries through Operando X‐Ray Methods. Batteries & Supercaps. 4(7), s. 1039–1063. doi: 10.1002/batt.202000294. Fulltekst i vitenarkiv Vis sammendrag

  Progress in the field of Na‐based batteries strongly relies on the development of new advanced materials. However, one of the main challenges of implementing new electrode materials is the understanding of their mechanisms (sodiation/desodiation) during electrochemical cycling. Operando studies provide extremely valuable insights into structural and chemical changes within different battery components during battery operation. The present review offers a critical summary of the operando X‐ray based characterization techniques used to examine the structural and chemical transformations of the active materials in Na‐ion, Na‐air and Na‐sulfur batteries during (de)sodiation. These methods provide structural and electronic information through diffraction, scattering, absorption and imaging or through a combination of these X‐ray‐based techniques. Challenges associated with cell design and data processing are also addressed herein. In addition, the present review provides a perspective on the future opportunities for these powerful techniques.

• Bernal, Fabian Leonardo Martinez; Lundvall, Fredrik; Kumar, Susmit; Hansen, Per-Anders S.; Wragg, David S. & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2021). Jahn-Teller active fluoroperovskites ACrF3 (A=Na+, K+): Magnetic and thermo-optical properties. PHYSICAL REVIEW MATERIALS. 5(6). doi: 10.1103/PhysRevMaterials.5.064420. Fulltekst i vitenarkiv Vis sammendrag

  Chromium (II) fluoroperovskites A CrF 3 ( A = Na + , K + ) are strongly correlated Jahn-Teller active materials at low temperatures. In this paper, we examine the role that the A -site ion plays in this family of fluoroperovskites using both experimental methods (x-ray diffraction, optical absorption spectroscopy, and magnetic fields) and density functional theory simulations. Temperature-dependent optical absorption experiments show that the spin-allowed transitions E 2 and E 3 only merge completely for A = Na at 2 K. Field-dependent optical absorption measurements at 2 K show that the oscillating strength of the spin-allowed transitions in NaCrF 3 increases with increasing applied field. Direct magneto-optical correlations suppress the spin-flip transitions for KCrF 3 below its Néel temperature. In NaCrF 3 the spin-flip transitions vanish abruptly below 9 K revealing magneto-optical correlations possibly linked to crystal structure changes. This suggests that as the long range ordering is reduced, local Jahn-Teller effects in the individual CrF 4 − 6 octahedra take control of the observed behavior. Our results show clear deviation from the pattern found for the isoelectronic A x MnF 3 + x system. The size of the A -site cation is shown to be central in dictating the physical properties and phase transitions in A CrF 3 , opening up the possibility of varying the composition to create novel states of matter with tunable properties.

• Wragg, David Stephen; Kalantzopoulos, Georgios; Pappas, Dimitrios; Herrero, Irene Pinilla; Rojo-Gama, Daniel & Redekop, Evgeniy [Vis alle 10 forfattere av denne artikkelen] (2021). Mapping the coke formation within a zeolite catalyst extrudate in space and time by operando computed X-ray diffraction tomography. Journal of Catalysis. ISSN 0021-9517. 104, s. 1–6. doi: 10.1016/j.jcat.2021.07.001. Fulltekst i vitenarkiv Vis sammendrag

  We have used operando X-ray diffraction computed tomography (XRD-CT) analysed by rigorous crystallographic methods to reveal the behaviour of a zeolite/alumina based catalyst extrudate in the methanol-to-hydrocarbon reaction under working conditions (Treaction = 440 °C; ambient total pressure; WHSV = 12 gMeOH gextrudate−1 h−1). By doing so, we demonstrate that it is possible to precisely monitor how the cylindrical extrudate is deactivated during the process by gradual filling with coke from the outer surface towards the core. The operando data thus collected are simulated by a model taking both the reaction kinetics and the diffusion within the extrudate into account, and this analysis provides the tools required for future optimization of the degree of utilization of the catalyst. Both the operando experiment and post mortem XRD-CT of fully deactivated extrudates from a test reactor show clearly that the core of the catalyst body, around 1/3 of its volume, remains completely untouched by the reaction, even when the reactor output indicates zero activity.

• Gerz, Isabelle; Jannuzzi, Sergio Augusto Venturinelli; Hylland, Knut Tormodssønn; Negri, Chiara; Wragg, David Stephen & Øien-Ødegaard, Sigurd [Vis alle 10 forfattere av denne artikkelen] (2021). Structural Elucidation, Aggregation, and Dynamic Behaviour of N,N,N,N-Copper(I) Schiff Base Complexes in Solid and in Solution: A Combined NMR, X-ray Spectroscopic and Crystallographic Investigation. European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. doi: 10.1002/ejic.202100722. Fulltekst i vitenarkiv Vis sammendrag

  A series of Cu(I) complexes of bidentate or tetradentate Schiff base ligands bearing either 1-H-imidazole or pyridine moieties were synthesized. The complexes were studied by a combination of NMR and X-ray spectroscopic techniques. The differences between the imidazole- and pyridine-based ligands were examined by 1H, 13C and 15N NMR spectroscopy. The magnitude of the 15Nimine coordination shifts was found to be strongly affected by the nature of the heterocycle in the complexes. These trends showed good correlation with the obtained Cu−Nimine bond lengths from single-crystal X-ray diffraction measurements. Variable-temperature NMR experiments, in combination with diffusion ordered spectroscopy (DOSY) revealed that one of the complexes underwent a temperature-dependent interconversion between a monomer, a dimer and a higher aggregate. The complexes bearing tetradentate imidazole ligands were further studied using Cu K-edge XAS and VtC XES, where DFT-assisted assignment of spectral features suggested that these complexes may form polynuclear oligomers in solid state. Additionally, the Cu(II) analogue of one of the complexes was incorporated into a metal-organic framework (MOF) as a way to obtain discrete, mononuclear complexes in the solid state.

• Hylland, Knut Tormodssønn; Gerz, Isabelle; Wragg, David Stephen; Øien-Ødegaard, Sigurd & Tilset, Mats (2021). The Reactivity of Multidentate Schiff Base Ligands Derived from Bi- and Terphenyl Polyamines towards M(II) (M=Ni, Cu, Zn, Cd) and M(III) (M=Co, Y, Lu). European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. s. 1869–1889. doi: 10.1002/ejic.202100170. Fulltekst i vitenarkiv Vis sammendrag

  Multidentate Schiff base ligands derived from a selection of biphenyl- and terphenyl polyamines were synthesized, and their reactivity towards divalent (Ni, Cu, Zn, Cd) and trivalent (Co, Y, Lu) metals was studied by single-crystal X-ray diffraction analysis, NMR spectroscopy, and UV/Vis spectroscopy for the Cu(II) complexes. Large variations in the resulting complexes were observed based on the relative position of the amine substituents in the parent triamines, as well as the electronic properties of the Schiff base ligand itself. Most notably, Schiff base ligands derived from a m-terphenyl-2,2’,2’’-triamine were found to coordinate in a tetradentate, pentadentate or hexadentate fashion, depending on the size and the valency of the corresponding metal center.

• Berntsen, Linn Neerbye; Solvi, Thomas Nordbø; Sørnes, Kristian; Wragg, David Stephen & Sandtorv, Alexander Harald (2021). Cu-catalyzed C(sp2)-N-bond coupling of boronic acids and cyclic imides. Chemical Communications. ISSN 1359-7345. 57(89), s. 11851–11854. doi: 10.1039/d1cc04356k. Fulltekst i vitenarkiv
• Bernal, Fabian Leonardo Martinez; Sottmann, Jonas; Wragg, David; Fjellvåg, Helmer; Fjellvåg, Øystein & Drathen, Christina [Vis alle 8 forfattere av denne artikkelen] (2020). Structural and magnetic characterization of the elusive Jahn-Teller active NaCrF3. PHYSICAL REVIEW MATERIALS. 4(5). doi: 10.1103/PhysRevMaterials.4.054412. Fulltekst i vitenarkiv Vis sammendrag

  We report on the structural and magnetic properties of the elusive Jahn-Teller active compound NaCrF3, for first time synthesized in large quantities allowing detailed characterization. The crystal structure of NaCrF3 is initially described from a DFT model, which helped serve as the basis for indexing and structure determination confirmed by high-resolution synchrotron x-ray diffraction experiments. NaCrF3 adopts the triclinic space group P¯1 (isostructural with NaCuF3). Magnetometry studies at low temperature show that NaCrF3 is a weak antiferromagnet, Weiss temperature θ=−4 K. The Néel temperature is TN=21.3 K and the paramagnetic moment μ=4.47μB is in accordance with the theoretical S=2. Field-dependent measurements between 2 and 12 K unveil the onset of metamagnetic behavior. Our experiments revealed a weakly canted A-type magnetic structure observed by neutron powder diffraction, with a magnetic propagation vector (1/2,1/2,0) and a magnetic moment of 3.51μB at 1.5 K. Our results shed further light on the Jahn-Teller effects and strong correlations as a function of A-ion size in the family ACrF3.

• Finegan, Donal; Quinn, Alexander; Wragg, David; Andrew, Colclasure; Xueken, Lu & Tan, Chun [Vis alle 17 forfattere av denne artikkelen] (2020). Spatial dynamics of lithiation and lithium plating during high-rate operation of graphite electrodes. Energy & Environmental Science. ISSN 1754-5692. 13, s. 2570–2584. doi: 10.1039/d0ee01191f. Fulltekst i vitenarkiv Vis sammendrag

  The principal inhibitor of fast charging lithium ion cells is the graphite negative electrode, where favorable conditions for lithium plating occur at high charge rates, causing accelerated degradation and safety concerns. The local response of graphite, both at the electrode and particle level, when exposed to fast charging conditions of around 6C is not well understood. Consequently, the conditions that lead to the onset of lithium plating, as well as the local dynamics of lithium plating and stripping, have also remained elusive. Here, we use high-speed (100 Hz) pencil-beam X-ray diffraction to repeatedly raster along the depth of a 101 μm thick graphite electrode in 3 μm steps during fast (up to 6C) charge and discharge conditions. Consecutive depth profiles from separator to current collector were each captured in 0.5 seconds, giving an unprecedented spatial and temporal description of the state of the electrode and graphite's staging dynamics during high rate conditions. The electrode is preferentially activated near the separator, and the non-uniformity increases with rate and is influenced by free-energy barriers between graphite's lithiation stages. The onset of lithium plating and stripping was quantified, occurring only within the first 15 μm from the separator. The presence of lithium plating changed the behavior of the underlying graphite, such as causing co-existence of LiC6 and graphite in the fully discharged state. Finally, the staging behavior of graphite at different rates was quantified, revealing a high dependency on rate and drastic hysteresis between lithiation and delithiation.

• Arstad, Bjørnar; Blom, Richard; Håkonsen, Silje Fosse; Pierchala, Joanna; Cobden, Paul & Lundvall, Fredrik [Vis alle 10 forfattere av denne artikkelen] (2020). Synthesis and Evaluation of K-Promoted Co3-xMgxAl-Oxides as Solid CO2 Sorbents in the Sorption-Enhanced Water−Gas Shift (SEWGS) Reaction. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 59(40), s. 17837–17844. doi: 10.1021/acs.iecr.0c02322. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogen is essential in a variety of large-scale chemical processes. As a carbon-free energy carrier, hydrogen has a potential for wide use within power production and transportation. However, most of the recent production methods involve the release of CO2 as a by-product. Hence, decarbonization of hydrogen production is one step to reduce CO2 emission into the Earth’s atmosphere. Several process schemes have been suggested for low-carbon emission production of hydrogen. In this work, we show how to improve solid sorbents for the sorption-enhanced water–gas shift (SEWGS) process, which is a process that exploits a solid sorbent in the water–gas shift reactor to capture CO2 in situ and drive the process toward an improved hydrogen yield. We report herein a series of CoxMg3-xAl materials based on hydrotalcites, promoted with various loadings of K. The materials have been characterized by BET, XRD, and NMR and tested for their CO2 adsorption performance in three adsorption–desorption cycles in a lab-scale fixed-bed reactor (20–22 bar, CO2 + steam as reactant gas, and isothermal conditions at 375 and 400 °C). The most promising material was subjected to a long-term test (120 adsorption–desorption cycles at similar conditions). This test indicates that a K-promoted Co1.5Mg1.5Al (22 wt % of added K2CO2 to the oxide) material has a higher cyclic capacity for CO2 than standard reference cases. We have estimated that the volumetric capacity (in mol/L unit) of this sorbent will be 23–26% higher than a standard reference material at 400 °C and 30–39% higher at 375 °C. This would, in fixed-bed columns, lead to significant reduction in the needed column volumes in the final process and reduce costs.

• Bernal, Fabian Leonardo Martinez; Gonano, Bruno Raymond Gino; Lundvall, Fredrik; Wragg, David; Fjellvåg, Helmer & Veillon, Fabien [Vis alle 8 forfattere av denne artikkelen] (2020). Canted antiferromagnetism in high-purity NaFeF3 prepared by a novel wet-chemical synthesis method. PHYSICAL REVIEW MATERIALS. 4(11). doi: 10.1103/PhysRevMaterials.4.114412. Fulltekst i vitenarkiv Vis sammendrag

  We report a synthesis method, and structural and magnetic characterization, for the fluoroperovskite NaFeF3. We have developed a wet-chemical method that allows preparation of large volumes of air-sensitive fluoroperovskites with high purity. NaFeF3 has a Néel temperature (TN) of 90 K and a Weiss constant (θ) of −124 K, corresponding to dominant antiferromagnetic interactions. Below TN, a slight difference is observed between zero-field and field-cooled samples, indicating spin canting and weak ferromagnetism. AC magnetometry supports that weak ferromagnetism is inherent to NaFeF3 and not due to an impurity. From powder neutron diffraction data, we describe the magnetic structure precisely as a weakly canted G-type (magnetic space group Pn′ma′). A ferromagnetic component is allowed in Pn′ma′, however, this component is too small to be confirmed on the basis of powder neutron diffraction data and may be absent in zero magnetic fields.

• Agote-Arán, Miren; Kroner, Anna B.; Wragg, David; Slawinski, Wojciech Andrzej; Briceno, Martha & Islam, Husn U. [Vis alle 12 forfattere av denne artikkelen] (2020). Understanding the Deactivation Phenomena of Small-Pore Mo/H-SSZ-13 during Methane Dehydroaromatisation. Molecules. ISSN 1431-5157. 25(21), s. 1–15. doi: 10.3390/molecules25215048. Fulltekst i vitenarkiv Vis sammendrag

  Small pore zeolites have shown great potential in a number of catalytic reactions. While Mo-containing medium pore zeolites have been widely studied for methane dehydroaromatisation (MDA), the use of small pore supports has drawn limited attention due to the fast deactivation of the catalyst. This work investigates the structure of the small pore Mo/H-SSZ-13 during catalyst preparation and reaction by operando X-ray absorption spectroscopy (XAS), in situ synchrotron powder diffraction (SPD), and electron microscopy; then, the results are compared with the medium pore Mo/H-ZSM-5. While SPD suggests that during catalyst preparation, part of the MoOx anchors inside the pores, Mo dispersion and subsequent ion exchange was less effective in the small pore catalyst, resulting in the formation of mesopores and Al2(MOO4)3 particles. Unlike Mo/H-ZSM-5, part of the Mo species in Mo/H-SSZ-13 undergoes full reduction to Mo0 during MDA, whereas characterisation of the spent catalyst indicates that differences also exist in the nature of the formed carbon deposits. Hence, the different Mo speciation and the low performance on small pore zeolites can be attributed to mesopores formation during calcination and the ineffective ion exchange into well dispersed Mo-oxo sites. The results open the scope for the optimisation of synthetic routes to explore the potential of small pore topologies.

• Berntsen, Linn Neerbye; Nova, Ainara; Wragg, David & Sandtorv, Alexander Harald (2020). Cu-catalyzed N-3-Arylation of Hydantoins Using Diaryliodonium Salts. Organic Letters. ISSN 1523-7060. 22(7), s. 2687–2691. doi: 10.1021/acs.orglett.0c00642. Fulltekst i vitenarkiv Vis sammendrag

  A general Cu-catalyzed, regioselective method for the N-3-arylation of hydantoins is described. The protocol utilizes aryl(trimethoxyphenyl)iodonium tosylate as the arylating agent in the presence of triethylamine and a catalytic amount of a simple Cu-salt. The method is compatible with structurally diverse hydantoins and operates well with neutral aryl groups or aryl groups bearing weakly donating/withdrawing elements. It is also applicable for the rapid diversification of pharmaceutically relevant hydantoins.

• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Thorshaug, Knut; Lind, Anna Maria; Vajeeston, Ponniah & Dovgaliuk, Iurii [Vis alle 9 forfattere av denne artikkelen] (2020). Factors Determining Microporous Material Stability in Water: The Curious Case of SAPO-37. Chemistry of Materials. ISSN 0897-4756. 32(4), s. 1495–1505. doi: 10.1021/acs.chemmater.9b04510. Fulltekst i vitenarkiv Vis sammendrag

  Silicoaluminophosphates (SAPOs) are a special class of zeolites that, due to their acidic and shape-selective properties, play a major role in ion exchange and separation processes and in crude oil cracking. SAPO-37 has the faujasite (FAU) topology same as zeolites X and Y, which are involved in more than 40% of the total crude oil conversion worldwide. A critical parameter that promotes detrimental structural transformations in SAPOs during real-life applications is the presence of humidity. In this study, we employ a multidisciplinary approach combining in situ synchrotron radiation powder X-ray diffraction (SR-PXRD), water adsorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory (DFT) calculations to describe the mechanism and reveal the reasons why SAPO-37 collapses upon contact with humidity below 345 K. SR-PXRD revealed that the sodalite (SOD) cages (subunits of the FAU structure) have the strongest affinity to water during hydration below 345 K. Furthermore, below 345 K, the faujasite framework takes up an order of magnitude more water molecules than at temperatures above 345 K. DRIFTS confirmed the presence of Si−OH and P−OH surface structural defects that act as hydration centers, accelerating the loss of a long-range order. Finally, DFT calculations showed that the enthalpy of water adsorption in the sodalite cage and the faujasite supercage is −212 and −13 kJ/mol, respectively. The results presented in this work are highly topical for understanding the effect of water on the frameworks of the SAPO microporous catalysts family. The notorious instability of SAPO-37 is the result of the accumulative contribution of topological, physical, and chemical effects, leading to an array of rapidly evolving cascading effects. Our work shows how advancements in SR-PXRD methodology and hardware give new insight into highly dynamic features previously difficult to observe. In addition, this work introduces the conceptual insight that nonhomogeneous sorption of molecular species will induce dynamic features with dramatic consequences at both molecular and atomic levels. This is a highly impactful factor opening research paths for further work within catalysis, porous material design and chemistry, and sorption reactions and processes.

• Levchenko, Vladimir; Øien-Ødegaard, Sigurd; Wragg, David & Tilset, Mats (2020). Crystal structure of (N^C) cyclo-metalated Au III diazide at 100 K. Acta Crystallographica Section E: Crystallographic Communications. 76, s. 1725–1727. doi: 10.1107/S2056989020012955. Fulltekst i vitenarkiv
• Li, Xinyu; Bianchini, Federico; Wind, Julia; Pettersen, Christine; Vajeeston, Ponniah & Wragg, David [Vis alle 7 forfattere av denne artikkelen] (2020). Insights into Crystal Structure and Diffusion of Biphasic Na2Zn2TeO6. ACS Applied Materials & Interfaces. ISSN 1944-8244. 12(25), s. 28188–28198. doi: 10.1021/acsami.0c05863. Fulltekst i vitenarkiv Vis sammendrag

  The layered oxide Na2Zn2TeO6 is a fast Na+ ion conductor and a suitable candidate for application as a solid-state electrolyte. We present a detailed study on how synthesis temperature and Na-content affect the crystal structure and thus the Na+ ion conductivity of Na2Zn2TeO6. Furthermore, we report for the first time an O′3-type phase for Na2Zn2TeO6. At a synthesis temperature of 900 °C, we obtain a pure P2-type phase, providing peak performance in Na+ ion conductivity. Synthesis temperatures lower than 900 °C produce a series of mixed P2 and O′3-type phases. The O′3 structure can only be obtained as a pure phase by substituting Li on the Zn-sites to increase the Na-content. Thorough analysis of synchrotron data combined with computational modeling indicates that Li enters the Zn sites and, consequently, the amount of Na in the structure increases to balance the charge according to the formula Na2+xZn2–xLixTeO6 (x = 0.2–0.5). Impedance spectroscopy and computational modeling confirm that reducing the amount of the O′3-type phase enhances the Na+ ion mobility.

Sjå alle arbeida i NVA

• Wragg, David Stephen; Wachs, Israel E.; Bañares, Miguel A. & Svelle, Stian (2023). Springer Handbook of Advanced Catalyst Characterization. Springer. ISBN 9783031071256. 1117 s. Fulltekst i vitenarkiv

Sjå alle arbeida i NVA

• Toktamyssova, Alina; Wragg, David Stephen; Kathribail, Anish Raj & Koposov, Alexey (2026). Battery-Grade Hard Carbon for Na-ion Batteries. Fulltekst i vitenarkiv Vis sammendrag

  Compared to its well spread Li-ion batteries (LIBs) predecessor, Na-ion batteries (NIBs) technology offers a potentially more environmentally friendly alternative with some performance advantages. Cost-effectiveness, safety, balance of power and energy density make NIBs as a preferable option for use in large-scale energy storage systems. Currently, the research in the field of NIBs is mainly focused on active materials with the aim of improving performance characteristics. Among many materials used for NIBs anodes, hard carbon (HC) materials are the most popular choice for commercial batteries or prototypes. However, the choice of precursors severely affects the electrochemical performance of these materials, making direct preparation of HC with programmed properties almost impossible. In this study, a comprehensive evaluation of potential precursors for HC anodes that are accessible in Norway will be beneficial to the greater scientific community. The application of a wide variety of characterization techniques for the different HC materials will help reinforce the basic understanding by deepening the comprehension of the basic relationships between the precursor, processing into HC, and final cell characterizations. It will be possible to fully correlate structural features with electrochemistry through operando characterization. The selection of the precursors for the project was driven by their scalability and local availability: they come from domestic sources, including industrial carbon provided by the industry partners and forestry waste. The main outcome of the proposed research is the development of low-cost battery-grade HCs with low environmental impact, stable and predictable electrochemical performance.

• Wragg, David Stephen (2026). Sodium Ion Batteries: Materials development and why it is important. doi: https:/www.ntnu.edu/fmebattery/news-webinar-recording-na-ion. Fulltekst i vitenarkiv
• Wragg, David Stephen; Kathribail, Anish Raj; Berdiell, Izar Capel; Koposov, Alexey & Toktamyssova, Alina (2026). In situ and Operando studies of Hard Carbon. Fulltekst i vitenarkiv
• Wragg, David Stephen (2026). Natrium ion og faststoff batterier i energilagring. Fulltekst i vitenarkiv
• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Vis alle 13 forfattere av denne artikkelen] (2026). Hidden Na5SbSe Unlocks Sb2Se3 Anodes for Na-Ion Batteries. Fulltekst i vitenarkiv Vis sammendrag

  Antimony selenide (Sb2Se3) is a promising alternative to commonly used NIB anodes, storing 12 Na+ per formula unit, to achieve a capacity of 670 mAh g-1. The (de)sodiation mechanism is very complex: the material progresses through multiple phases when interacting with Na+, including intercalation, con-version, and alloying reactions. These multiple chemical transformations may kinetically limit the material at high rates, however, Sb2Se3 can deliver almost 150 mAh g-1 at 5000 mA g-1. Understanding this unusual behavior is important not only to rationalize the electrochemical performance, but also for the design of other materials capable of working at high (dis)charge rates. Meanwhile, subtle phase transitions or transformations of active battery materials can be traced in operando X-ray diffraction (XRD), which enables the extraction of real-time information about potentially hidden mechanistic pathways, including the discovery of new materials. In this study, Na5SbSe was discovered as the main sodiated product of Sb2Se3 anodes. Na5SbSe is predominantly composed of Na-ions and has a highly flexible composition (breathing effect) that unlocks the exceptional high rate performance of Sb2Se3 anodes

• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Vis alle 13 forfattere av denne artikkelen] (2026). Material's Discovery via Synchrotron Operando XRD and XAS: the Case of Sb2Se3 Anodes for Na-Ion Batteries. Fulltekst i vitenarkiv Vis sammendrag

  Antimony selenide (Sb2Se3) is a promising alternative to commonly used NIB anodes, storing 12 Na+ per formula unit, to achieve a capacity of 670 mAh g-1. The (de)sodiation mechanism is very complex: the material progresses through multiple phases when interacting with Na+, including intercalation, con-version, and alloying reactions. These multiple chemical transformations may kinetically limit the material at high rates, however, Sb2Se3 can deliver almost 150 mAh g-1 at 5000 mA g-1. Understanding this unusual behavior is important not only to rationalize the electrochemical performance, but also for the design of other materials capable of working at high (dis)charge rates. Meanwhile, subtle phase transitions or transformations of active battery materials can be traced in operando X-ray diffraction (XRD), which enables the extraction of real-time information about potentially hidden mechanistic pathways, including the discovery of new materials. In this study, operando XRD and X-ray absorption spectroscopy (XAS) were employed to unravel the mysteries of the (de)sodiation mechanism of Sb2Se3 anodes. Complete elucidation of the reaction pathway was further enabled by solid-state NMR, ex situ work, and ab initio simulations.

• Wind, Julia; Ostrander, John; Hassani, Alireza; Lian, Torleif; Wragg, David Stephen & Vie, Preben Joakim Svela (2025). DETAILED CHARACTERIZATION AND PARAMETERIZATION OF A LARGE STATE-OF-THE-ART COMMERCIAL LI-ION POUCH CELL. Fulltekst i vitenarkiv
• Ostrander, John; Wragg, David Stephen & Vie, Preben Joakim Svela (2025). On the Development of Post-Mortem Analyses and Techniques in a Dynamic and Emerging Battery Industry. Fulltekst i vitenarkiv Vis sammendrag

  The rapid pace of battery production presents new challenges when batteries reach the end of their primary service life or become unserviceable. Post-mortem analysis of batteries and battery materials is a developing field of study that needs to advance for efficient and reliable assessments of used batteries from the cell to pack level. Presently there is a push towards ontology based approaches which would facilitate upscaling and automation1 that might eventually adapt to the many different battery types and formats which are in production2. Extensive information can be obtained characterizing cells during operation, providing data to diagnose and determine a battery’s state of health. However, confirmation by physical sampling and direct characterization through various electrochemical, x-ray, and microscopy methods is still necessary to complete the story of the effects of battery aging, abuse, and which ageing mechanisms that have contributed to the battery’s end of life. Here we examine methodology for cell disassembly and some post-mortem analyses used in cell characterization including electrochemical testing, imaging, and x-ray analysis (EDX, XRD, XRCT, etc.). We also discuss results from selected commercial cells. An overview of disassembly techniques highlights considerations for preserving sample integrity and will be compared to procedures described in recent literature for large format pouch cells, high capacity prismatic cells, and 21700 cylindrical cells. Some of the applications of interest are the use in electric vehicles (EVs), as components in larger stationary energy storage units, and for use in the maritime industry in Norway. 1. Yu, J., et al., J. of Manufacturing Systems., 2022. 62: p. 347-366. 2. Baazouzi, S., et al., Batteries, 2023. 9(6): p. 309.

• Wind, Julia; Ostrander, John; Wragg, David Stephen; Hassani, Alireza; Lian, Torleif & Gilljam, Martin [Vis alle 7 forfattere av denne artikkelen] (2025). Detailed Characterization and Parameterization of a Large State-of-the-Art Commercial Li-Ion Pouch Cell. Fulltekst i vitenarkiv Vis sammendrag

  Lithium-ion batteries (LIBs) serve a critical role in modern technology, powering portable electronics, electric vehicles, and energy storage systems essential for renewable energy integration. The LIB market is rapidly expanding, offering diverse battery cells with specific advantages and trade-offs due to variations in cell chemistry and design. However, manufacturers often provide limited information on cell characteristics, particularly regarding cell chemistries, electrode designs, and cell architecture. This knowledge is crucial for understanding the complex relationships between cell chemistry, design, and performance, and for advancing LIB technology. Here we present the thorough characterization and parameterization of a large-scale 64 Ah Lithium-ion pouch cell with NMC/graphite chemistry, optimized for high-power applications and frequently used e.g. in maritime applications and large-scale energy storage systems. This work contributes to the understanding of properties and design of state-of-the-art cells, and support the modelling on several levels, in addition to setting the benchmark for further work on ageing, degradation and safety on this cell. Extensive characterization on the cell level: The battery cells were characterized on the full cell level. This included charge/discharge capacities, advanced pulsing protocols, internal resistances, entropy measurements and estimations of the cell’s open-circuit voltage profile. The rate capability and corresponding temperature evolution across the cells surface was studied. The characterization of a total of 140 cells further allowed for a statistical analysis of initial capacities and internal resistances. Cell teardown: Details on cell architecture and electrode design were extracted as part of a cell teardown. Cells were carefully opened and disassembled, the individual cell components were counted, weighed and prepared for subsequent characterization. Materials characterization: Detailed analysis of the extracted cell parts with respect to their composition, including not only electrodes, but also separator, electrolyte, tabs and pouch materials. The extracted electrodes were reassembled into coin cells and characterized electrochemically. This included advanced cycling protocols such as GITT, and electrochemical impedance spectroscopy at various temperatures. The electrodes’ microstructure was assessed by SEM imaging and porosimetry measurements. Model parameterization: The collected data was compiled into a full P2D parameter set. The obtained parameters were compared to and supplemented by established literature values. Selected parameters were optimized, and the obtained parameter set was validated against experimental full cell data for a range of different conditions. A full parameter set ready for use within the Python Battery Mathematical Modelling framework PyBaMM was established [1]. References Sulzer, V., et al., Python Battery Mathematical Modelling (PyBaMM). Journal of Open Research Software, 2021.

• Sitorus, Fernando; Stromberg, Elin; Rouquette, Lea; Vorland, Kim Andre Nesse; Khalifeh, Mahmoud & Wragg, David Stephen [Vis alle 8 forfattere av denne artikkelen] (2025). Correction: Sustainable leaching of critical metals from lithium ion battery black mass using a citric acid and choline chloride deep eutectic solvent. Discover Sustainability. 6(1). doi: 10.1007/s43621-025-02407-y. Fulltekst i vitenarkiv Vis sammendrag

  The recycling of lithium-ion batteries (LIBs) is of critical importance due to the increasing demand for electric vehicles and portable electronic devices. It also helps address supply risks of critical raw materials and reduces the environmental impact of mining. Traditional recycling methods are often inefficient and environmentally damaging. This study investigates the use of deep eutectic solvents (DES), made from citric acid and choline chloride, for leaching valuable metals from black mass derived from spent LIBs. The research focuses on optimizing the leaching parameters, such as temperature, DES ratio, and solid-to-liquid ratio, to maximize the extraction efficiency of lithium, cobalt, nickel, and manganese. A key aspect of the study was the examination of the rheological properties of the DES system, as these properties significantly impact the leaching process. The viscosity and pH of the DES were measured, providing insights into their behavior under various conditions. Understanding the viscosity and flow characteristics of these DES systems is crucial for developing scalable and effective recycling methods. The DES mixture with a 2:1 ratio of citric acid to choline chloride, mixed with 50% water, showed the best performance. At 90 °C for 24 h, this DES mixture achieved leaching efficiencies of 77.5% for lithium, 79.9% for cobalt, 80% for manganese, 66.2% for nickel, 82.5% for copper, and 93.8% for aluminum. These findings suggest the potential of citric acid-choline chloride DES as a sustainable and environmentally friendly reagent for recycling LIBs.

• Wragg, David Stephen (2025). Time resolved X-ray diffraction and total scattering computed tomography for understanding batteries and catalysts. Fulltekst i vitenarkiv
• Wragg, David Stephen (2025). Synchrotron radiation for understanding and developing batteries. Fulltekst i vitenarkiv
• Paredes, Patricio; Rauwel, Erwan; Wragg, David Stephen; Rapenne, Laetitia; Gélard, Isabelle & Rauwel, Protima (2025). Correction to: A comparative study of Cu-based nanoparticles and their spin-coated films: photocatalytic degradation mechanisms and efficiencies towards malachite green and neutral red azo dyes (Environmental Science and Pollution Research, (2024), 32, 1, (314-334), 10.1007/s11356-024-35785-3). Environmental Science and Pollution Research. ISSN 0944-1344. doi: 10.1007/s11356-025-35973-9. Fulltekst i vitenarkiv
• Schweigart, Philipp; Hua, Weicheng; Sánchez, Pedro Alonso; Lian, Camilla; Nylund, Inger-Emma & Dyadkin, Vadim [Vis alle 11 forfattere av denne artikkelen] (2024). Deciphering the Impact of Current, Composition, and Potential on the Lithiation Behavior of Graphite in Silicon-Graphite Anodes. Fulltekst i vitenarkiv
• Vie, Preben Joakim Svela; Wragg, David Stephen; Lian, Torleif; Gandrud, Knut Bjarne & Koposov, Alexey (2024). Post-Mortem Analysis of commercial Li-ion Pouch Cells For Use in Second Life Applications. Fulltekst i vitenarkiv
• Wragg, David Stephen; Koposov, Alexey; Ulvestad, Asbjørn; Skare, Marte Orderud; Skautvedt, Casper & Geiss, Carina [Vis alle 7 forfattere av denne artikkelen] (2024). Where’s my silicon battery? Amorphous battery materials and how to study them. Fulltekst i vitenarkiv
• Wragg, David Stephen (2024). Operando Studies of Batteries at SNBL. Fulltekst i vitenarkiv
• Brennhagen, Anders; Skurtveit, Amalie; Skautvedt, Casper; Cavallo, Carmen; Wragg, David Stephen & Vajeeston, Ponniah [Vis alle 9 forfattere av denne artikkelen] (2024). Revealing the (de)sodiation mechanisms of Bi-metallates through operando X-ray characterisation. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries is entering the battery market as an alternative to Li-ion batteries. To improve their overall performance it is crucial to develop new types of anode materials with high capacity and long cycle life. Materials combing conversion and alloying mechanisms (CAMs) are promising anodes with their high capacity, but obtaining good cycling stability is still challenging. A comprehensive understanding of the cycling and degradation mechanism of these materials is crucial to improve their performance. Bi-metallates, with a general formula of Bi−TM−O (TM = transition metal) is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction forming nanoparticles of Bi-metal embedded in a Na-TM-O matrix during the first sodiation, followed by a reversible two-step alloying reaction forming Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction (XRD), pair distribution function (PDF) analysis and X-ray absorption spectroscopy (XAS) to investigate the desodiation mechanisms of Bi2MoO6 and BiFeO3. Through this work, we discovered that Bi2MoO6 forms the cubic version of Na3Bi (c-Na3Bi) while BiFeO3 forms hexagonal Na3Bi (h-Na3Bi) in addition to c-Na3Bi during the first sodiation. In the desodiated state, the Bi-particles are partially oxidised, while still maintaining the Bi-metal structure, indicating that it is only the Bi atoms at the interface between the Bi nanoparticles and the Na−TM−O matrix that is oxidised. During cycling the NaxBi particles grow larger thus increasing the distance between them and increasing the impedance in the material. This is considered to be the main driver for the capacity degradation that was observed during the first 20 cycles. The operando XAS data also revealed that Mo6+ in Bi2MoO6 does not change oxidation state during cycling, but changes coordination between tetrahedral and distorted octahedral coordination during cycling. The cycling and degradation mechanisms of Bi2MoO6 is summarised in Figure 1.

• Skurtveit, Amalie; North, Erlend Tiberg; Park, Heesoo; Chernyshov, Dmitry; Wragg, David Stephen & Koposov, Alexey (2024). Elucidating relaxation mechanisms in Li-ion batteries through operando X-ray diffraction: Spontaneous Li-ion clustering as a structural origin of relaxation in battery electrodes. Fulltekst i vitenarkiv
• Wragg, David Stephen (2024). Understanding The Properties Of Working Batteries With Crystallography. Fulltekst i vitenarkiv
• Wragg, David Stephen (2024). Operando Studies of Batteries at SNBL. Fulltekst i vitenarkiv
• Wragg, David Stephen; Koposov, Alexey; Thiagarajan, Abilash Kanish; Chernyshov, Dmitry; Brennhagen, Anders & Slawinski, Wojciech Andrzej [Vis alle 7 forfattere av denne artikkelen] (2024). Structural Origins of Graphite Staging. Fulltekst i vitenarkiv
• Ostrander, John; Wragg, David Stephen; Vie, Preben Joakim Svela; Wind, Julia & Koposov, Alexey (2024). Identifying key degradation patterns as a function of ageing temperature: A post-mortem study. Fulltekst i vitenarkiv
• North, Erlend Tiberg; Skautvedt, Casper; Thiagarajan, Abilash Kanish; Checchia, Stefano; Koposov, Alexey & Wragg, David Stephen (2024). Spatially Resolved Beam Damage on a Graphite Anode in Operando. Fulltekst i vitenarkiv Vis sammendrag

  Modern synchrotron beam lines can offer higher luminance and energy, providing more opportunities for scientists performing structural analysis of materials. However, this benefit comes with a risk of questionable results as continual exposure can lead to damage to the studied materials. This effect is well established in protein crystallography but has recently gained attention in the field of material science including operando studies of battery materials. We have investigated the electrochemical cycling of a graphite-based anode for Li-ion batteries under continuous exposure to high-energy X-ray radiation, exploring the consequences of the exposure on the structure and cycling capabilities. We analyze damage by correlating the dose of radiation to the inhibition of electrochemistry.

• Ostrander, John; Vie, Preben Joakim Svela; Wragg, David Stephen; Koposov, Alexey; Lian, Torleif & Wind, Julia [Vis alle 8 forfattere av denne artikkelen] (2023). Post-Mortem Analysis of a Commercial Li-Ion Pouch Cell and the Effects of Aging on Overall Battery State of Health (SOH). Fulltekst i vitenarkiv
• Brennhagen, Anders; Skautvedt, Casper; Cavallo, Carmen; Skurtveit, Amalie; Wragg, David Stephen & Koposov, Alexey [Vis alle 9 forfattere av denne artikkelen] (2023). Revealing the Cycling and Degradation Mechanism of Bi-Metallates as Anode Materials fro Na-ion Batteries. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries (NIBs) represent an emerging alternative to modern Li-ion batteries. To improve the overall performance of NIBs it is crucial to develop new types of anode materials with high capacity and long cycle life. Among the anode candidates, materials operating under combined conversion and alloying mechanisms (CAMs) are considered as promising. They are capable of delivering high capacity, however, despite theoretical predictions the cycling stability is still below expectations. Therefore, a comprehensive understanding of the cycling and degradation mechanisms of CAMs is crucial to improve their performance. However, these materials undergo multiple chemical transformations, which often involves formation of amorphous and nanocrystalline phases during cycling. Such chemical complexity substantially impedes their full characterization and understanding. Bismuth metallates, with a general formula of Bi-TM-O (TM = transition metal), is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction, which leads to formation of Bi nanoparticles embedded in a Na-TM-O matrix during the first sodiation. This is followed by a reversible two-step alloying reaction leading to formation of Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction over the course of ∼30 cycles to study the cycling and degradation mechanisms of two CAMs - Bi2MoO6 and BiFeO3. With the help of ex situ X-ray absorption spectroscopy and pair distribution function (PDF) analysis, we have revealed new insights into these materials in addition to confirming the general cycling mechanism. Both materials form the cubic phase of Na3Bi (c-Na3Bi) in the sodiated state with some noticeable differences. While, the hexagonal Na3Bi (h-Na3Bi) phase starts to form after 10 cycles in Bi2MoO6, a combination of c-Na3Bi and h-Na3Bi can be observed after the first cycle in BiFeO3. The formation of c-Na3Bi is kinetically favorable in these systems, while h-Na3Bi is the more thermodynamically stable and, therefore, forms later in the cycling process. Both materials shows three distinct regions of capacity degradation, where the first is initiated by a growth in the crystallite sizes of Bi-particles. This is followed by a disappearance of the Bi-phase as the second step. The last degradation phase is related to the disappearance of the NaBi-phase and locking the system in the sodiated state. The present talk will discuss the mechanisms of these degradation steps in view of the future development of CAMs in greater details.

• Wragg, David Stephen (2023). Cleaning Up Operando Battery X-Ray Diffraction With Total Scattering Computed Tomography. Fulltekst i vitenarkiv
• Svelle, Stian; Lundegaard, Lars Fahl; Beato, Pablo & Wragg, David Stephen (2023). Case Studies: Crystallography as a Tool for Studying Methanol Conversion in Zeolites, Springer Handbook of Advanced Catalyst Characterization. Springer. ISSN 9783031071256. s. 541–563. doi: 10.1007/978-3-031-07125-6_26. Fulltekst i vitenarkiv
• Skurtveit, Amalie; Pastusic, Andrew; Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen & Koposov, Alexey (2023). High-Rate Performance of Antimony Chalcogenides (Sb2X3) Studied by Operando X-ray Diffraction (XRD). Fulltekst i vitenarkiv
• Sottmann, Jonas; Ruud, Amund; Fjellvåg, Øystein Slagtern; Vaughan, Gavin B. M.; Michel, Marco Di & Fjellvåg, Helmer [Vis alle 9 forfattere av denne artikkelen] (2023). Erratum: 5D total scattering computed tomography reveals the full reaction mechanism of a bismuth vanadate lithium ion battery anode (Phys. Chem. Chem. Phys. (2022) 24 (27075-27085) DOI: 10.1039/D2CP03892G). Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. doi: 10.1039/d3cp90076b. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey; Ponniah, Vajeeston & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2023). Tracing the (De)sodiation of Bi2MoO6 Through Good and Bad Times With Operando XRD. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries (NIBs) generally have slightly lower energy densities than Li-ion batteries (LIBs), but the abundancy of Na could make NIBs cheaper and more sustainable. The search for new anode materials is essential for further development of NIBs. Anode materials combining conversion and alloying mechanisms (CAMs) are promising because of their high capacity and high rate capabilities, but their complex cycling mechanisms involving amorphous phases are challenging to study [1]. Bi2MoO6 is an example of a CAM that has high initial capacity, but struggles with cycling stability and undergoes major changes during cycling. Detailed understanding of its cycling and degradation mechanism will hopefully enable us to improve the cycling stability of Bi2MoO6 and CAMs in general. Therefore, we have studied Bi2MoO6 using a combination of operando X-ray diffraction (Fig. 1), pair distribution function, X-ray absorption spectroscopy and transmission electron microscopy [3]. This revealed that during the first sodiation, an irreversible conversion of Bi2MoO6 occurs, creating Bi nanoparticles embedded in an amorphous Na-Mo-O matrix. The Bi particles then reversibly alloy with Na, forming cubic Na3Bi leading to a specific capacity close to 300 mAh g−1 for the 10 first cycles. During these cycles, we observe a growth in the crystallite size of the alloying particles, which is probably the leading cause of the rapid capacity decay after cycle 10 where the sodiation of Bi becomes irreversible leaving several inactive Na3Bi particles.

• Svelle, Stian; Berdiell, Izar Capel; Wragg, David Stephen; Beato, Pablo & Lundegaard, Lars Fahl (2023). In situ and operando X-ray diffraction as a tool to monitor zeolite catalyst deactivation. Fulltekst i vitenarkiv
• Berdiell, Izar Capel; Wragg, David Stephen; Beato, Pablo; Lundegaard, Lars Fahl; Michel, Marco Di & Svelle, Stian (2023). Temperature Programmed Oxidation Probed with X-ray Diffraction Computed Tomography. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey; Ponniah, Vajeeston & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2022). Tracing the (De)sodiation of Bi2MoO6 Through Good and Bad Times With Operando XRD. Fulltekst i vitenarkiv Vis sammendrag

  Anode materials combining conversion and alloying mechanisms (CAMs) are promising for Na-ion batteries, but their complex cycling mechanisms are challenging to study. Understanding the (de)sodiation mechanism is crucial and, in several cases, requires advanced synchrotron characterization. Operando synchrotron studies are generally limited to one or two sodiation cycles, which are not fully comprehensive for CAMs. Therefore, herein, we studied the sodiation and desodiation of Bi2MoO6-based anodes with laboratory-based operando X-ray diffraction exceeding more than 30 cycles to have a complete overview of our CAM’s mechanism. This revealed important aspects of the cycling and degradation mechanisms in the material. During the first sodiation, an irreversible conversion of Bi2MoO6 occurs, creating Bi nanoparticles embedded in an amorphous Na-Mo-O matrix. The Bi particles then reversibly alloy with Na forming cubic Na3Bi leading to a specific capacity close to 300 mAh g−1 for the 10 first cycles. This is followed by a rapid capacity decay where the sodiation of Bi becomes irreversible leaving several inactive Na3Bi particles. To the best of our knowledge, this is due to the observed crystal growth of the Bi particles accompanied by structural changes in the insulating Na-Mo-O leading to poor conductivity in the electrodes. The poor electronic conductivity of the matrix deactivates the NaxBi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

• Skurtveit, Amalie; Cavallo, Carmen; Wragg, David Stephen & Koposov, Alexey (2022). Revealing the (de)sodiation mechanism of antimony chalcogenides Sb2X3 with operando XRD. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2022). Tracing the (de)sodiation of Bi2MoO6 through good and bad times with operando XRD. Fulltekst i vitenarkiv Vis sammendrag

  Anode materials combining conversion and alloying mechanisms (CAMs) are promising for Na-ion batteries, but their complex cycling mechanisms are challenging to study1. Understanding the (de)sodiation mechanism is crucial and, in several cases, requires advanced synchrotron characterization. Operando synchrotron studies are generally limited to one or two sodiation cycles, which are not fully comprehensive for CAMs2. Therefore, herein, we studied the sodiation and desodiation of Bi2MoO6-based anodes with laboratory-based operando X-ray diffraction exceeding more than 30 cycles to have a complete overview of our CAM’s mechanism (Figure 1)3. This revealed important aspects of the cycling and degradation mechanisms in the material. During the first sodiation, an irreversible conversion of Bi2MoO6 occurs, creating Bi nanoparticles embedded in an amorphous Na-Mo-O matrix. The Bi particles then reversibly alloy with Na forming cubic Na3Bi leading to a specific capacity close to 300 mAh g−1 for the 10 first cycles. This is followed by a rapid capacity decay where the sodiation of Bi becomes irreversible leaving several inactive Na3Bi particles. To the best of our knowledge, this is due to the observed crystal growth of the Bi particles accompanied by structural changes in the insulating Na-Mo-O leading to poor conductivity in the electrodes. The poor electronic conductivity of the matrix deactivates the NaxBi particles and prevents the formation of the solid electrolyte interface layer as shown by post-mortem scanning electron microscopy studies.

• Wragg, David Stephen (2022). Big Data in XRD: Processing a huge number of sub optimal datasets with TOPAS. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Koposov, Alexey [Vis alle 7 forfattere av denne artikkelen] (2022). Corrigendum: Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries (Nanotechnology (2022)33 (185402) DOI: 10.1088/1361-6528/ac4eb5). Nanotechnology. ISSN 0957-4484. 33(35). doi: 10.1088/1361-6528/ac72b2. Fulltekst i vitenarkiv
• North, Erlend Tiberg; Chernyshov, Dmitry; Diadkin, Vadim; Koposov, Alexey; Svelle, Stian & Wragg, David Stephen (2022). Multivariate Analysis of Synchrotron X-ray Data for Battery Research. Fulltekst i vitenarkiv Vis sammendrag

  By utilizing multivariate analysis of x-ray operando data from working batteries one can separate and enhance scattering signals from specific components of the battery, identifying the critical responses that are connected to its performance and failure. This can enable faster and easier analysis of operando data, especially from complex materials that are difficult to analyze manually. In this poster I will present the preliminary results that we have obtained so far, focusing mainly on comparing analysis methods on simulated data sets, along with the current plan of the research project in my PhD.

• Berdiell, Izar Capel; Braghin, Giorgio Bruno; Cordero-Lanzac, Tomas; Beato, Pablo; Lundegaard, Lars Fahl & Wragg, David Stephen [Vis alle 8 forfattere av denne artikkelen] (2022). Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst during MTH with XRD. Fulltekst i vitenarkiv
• Berdiell, Izar Capel; König, Nico; Junge, Nicolai Haaber; Kalantzopoulos, Georgios; Beato, Pablo & Svelle, Stian [Vis alle 8 forfattere av denne artikkelen] (2022). Tracking deactivation level of zeolite H-beta catalysts with novel XRD models. Fulltekst i vitenarkiv
• Brennhagen, Anders; Wragg, David; Fjellvåg, Helmer; Vajeeston, Ponniah; Sjåstad, Anja Olafsen & Cavallo, Carmen (2021). Beyond Insertion: Conversion alloying Bi/RGO-based materials as novel anodes for Na-ion batteries. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Sjåstad, Anja Olafsen; Ponniah, Vajeeston & Fjellvåg, Helmer (2021). Operando XRD studies on Bi2MoO6 as anode material for Na-ion batteries. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries (NIBs) could be a good alternative to Li-ion batteries (LIBs) due to the large abundance and availability of sodium resources. The search for good anode materials is one of the big challenges since graphite, which is the most common anode material for LIB, does not work well in NIBs. We are developing Bi2MoO6 as an anode material for NIBs, and will explain the main cycling mechanism. By utilizing a combination of conversion and alloying reactions, the material achieves high capacity while still maintaining a decent cycling stability. The complex cycling mechanism also makes it an interesting and challenging material to characterize during cycling. In this poster, we present high quality operando XRD data of the material during several cycles, acquired in the home lab. The data clearly shows that the reversible alloying reaction of Bi-metal to cubic Na3Bi gives the main capacity contribution, after the initial conversion reaction. This indicates formation of nanocrystalline Bi-particles, as nanocrystalline Bi-metal has shown the same reaction mechanism while microcrystalline Bi instead forms the hexagonal phase of Na3Bi. The molybdenum goes into an amorphous matrix that is only partially electrochemically active. The phases formed with molybdenum during cycling are difficult to characterize, due to their amorphous nature, and remain an unsolved mystery.

• Espuny, Montserrat Capellas; Wragg, David Stephen & Brennhagen, Anders (2021). From Oslo to Grenoble in the search of next generation batteries. [Internet]. esrf.fr. Fulltekst i vitenarkiv
• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Koposov, Alexey; Ponniah, Vajeeston & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2021). Operando XRD study on Bi2MoO6 as anode material for Na-ion batteries. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries (NIBs) could be a good alternative to Li-ion batteries (LIBs) due to the large abundance and availability of sodium resources. The search for good anode materials is one of the big challenges since graphite, which is the most common anode material for LIB, does not work well in NIBs. We are developing Bi2MoO6 as an anode material for NIBs, and will explain the main cycling mechanism. By utilizing a combination of conversion and alloying reactions, the material achieves high capacity while still maintaining a decent cycling stability. The complex cycling mechanism also makes it an interesting and challenging material to characterize during cycling. In this poster, we present high quality operando XRD data of the material during several cycles, acquired in the home lab. The data clearly shows that the reversible alloying reaction of Bi-metal to cubic Na3Bi gives the main capacity contribution, after the initial conversion reaction. This indicates formation of nanocrystalline Bi-particles, as nanocrystalline Bi-metal has shown the same reaction mechanism while microcrystalline Bi instead forms the hexagonal phase of Na3Bi. The molybdenum goes into an amorphous matrix that is only partially electrochemically active. The phases formed with molybdenum during cycling are difficult to characterize, due to their amorphous nature, and remain an unsolved mystery.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David; Vajeeston, Ponniah; Sjåstad, Anja Olafsen & Fjellvåg, Helmer (2021). Bi4V2O11/RGO composite as conversion and alloying anode for Na-ion batteries. Fulltekst i vitenarkiv
• Cavallo, Carmen; Brennhagen, Anders; Wragg, David & Fjellvåg, Helmer (2020). Beyond Insertion: Conversion alloying Bi/RGO-based materials as anode for Na-ion batteries. Fulltekst i vitenarkiv
• Wragg, David; Fjellvåg, Øystein; Fjellvåg, Helmer; Sottmann, Jonas; Vaughan, Gavin B M & Michel, Marco Di [Vis alle 7 forfattere av denne artikkelen] (2020). Operando Total Scattering Computed Tomography: Making the Invisible Visible. Fulltekst i vitenarkiv
• Wragg, David (2020). Beamline Facilities for Chemistry and Materials Science. Fulltekst i vitenarkiv
• Skurtveit, Amalie; Koposov, Alexey; Wragg, David Stephen & Cavallo, Carmen (2025). Operando Characterization of Anode Materials for Li/Na-ion Batteries. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Understanding the working principles and degradation mechanisms of battery active materials at the atomic scale is important for developing high-performing, long-lasting batteries. In the past decade, operando characterization has emerged as a powerful method to understand chemical changes during battery operation, providing dynamic insights into reaction mechanisms under realistic conditions. This approach helps illuminate potential degradation pathways and guides strategies for optimizing battery materials, including the recovery of materials that are approaching their end-of-life. This Thesis investigates the operating mechanisms of negative electrode (i.e., anode) materials for Li-ion batteries (LIBs) and Na-ion batteries (NIBs) using operando X-ray-based methods, including X-ray diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) spectroscopy. The first part focuses on the relaxation mechanisms in graphite anodes for LIBs, employing synchrotron operando XRD with a time resolution of 1.24 s. The relaxation process in a partially lithiated graphite was found to be driven by structural reorganization of Li-ions into Li-clusters and -islands. A complementary operando XRD relaxation study of LiFePO4 (LFP) electrodes was also conducted, and it was found that the relaxation mechanism in LFP was considerably slower compared to that in graphite but could also be attributed to a reorganization of Li-ions. These findings emphasize the importance of operando structural studies for accurately interpreting reaction mechanisms in battery materials. The main part of this Thesis focuses on the (de)sodiation mechanisms of Sb2X3 (X = S, Se, Te) anode materials for NIBs. The electrochemical behavior of these materials is very similar, with their Na-storage mechanisms characterized by a combination of intercalation-conversion/alloying processes that form multiple phases. A detailed mechanistic study of Sb2Se3-based anodes was conducted using operando XRD and XAFS, coupled with post-cycling (ex situ) XRD, XAFS, solid-state nuclear magnetic resonance (ssNMR), and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy. Two aspects of the (de)sodiation mechanism of Sb2Se3-based anodes were of particular interest: firstly, the reversibility of the conversion reaction, and secondly, the evolution of the Na—Se matrix compound during cycling. Upon investigating of the (de)sodiation mechanism of Sb2Se3-based anodes, the mechanism can be determined and explained through a combination of intercalation-conversion/alloying reactions forming NaxSb2Se3 (product after intercalation), Na2Se (inactive matrix after conversion) and Sb (active part after conversion), and NaxSb (product after alloying reaction). A completely new sodiated phase was discovered in operando mode – namely a ternary compound corresponding to Na5-xSbSe (sodium antimonide(3-) selenide) as the final sodiated product. Na5-xSbSe crystallizes in the tetragonal space group I4/mmm and displays an exceptional structural flexibility in accommodating/releasing Na-ions that was attributed to high inherent vacancy concentration and a disordered structurally flexible Sb—Se sublattice. This disorder creates a stable framework for fast Na diffusion that enables the fast-charging properties of Sb2Se3-based anodes. It was found that Sb2Se3-based anodes can be (de)sodiated at 5000 mA g-1 with minimal capacity losses. A complimentary operando XRD measurement of Sb2Te3-based anodes revealed the formation of a Na—Sb—Te compound as the final sodiation product, likely isostructural to Na5-xSbSe. These operando observations suggested that unique (de)sodiation pathways occur for Sb2X3 (X = Se, Te), and challenge the conventional understanding of Sb-based conversion/alloying anodes in NIBs. A composite material, Sb2Se3/Sb, was studied via operando XRD at various cycling rates (100 mA g-1, 335 mA g-1, and 1000 mA g-1). The mechanism for this composite could be described through a combination of the respective (de)sodiation mechanisms Sb and Sb2Se3, forming Na3Sb and Na5-xSbSe at the final products of sodiation. The findings indicate that the high-rate performance of Sb2Se3-based materials is facilitated by amorphization of Na5-xSbSe after the first electrochemical cycle that further benefits rapid Na-diffusion. Despite the promising high-rate behavior observed for Sb2Se3-based anodes in NIBs (up to 5000 mAh g-1), the long-term cycling stability was limited to ~120 (de)sodiation cycles. Post-cycling SEM-EDX analysis of the cross-sections of cycled Sb2Se3/Sb-based electrodes suggested that the main pathway of degradation was caused by electrode architecture failure, such as delamination of the coating from the current collector. Central to this work was also to investigate the promise of Sb2Se3-based materials under more realistic conditions, i.e., full-cell configurations. Sb2Se3-based anodes coupled with Prussian white (PW) cathode materials displayed promising behavior over 100 (de)sodiation cycles. Operando XRD revealed that the (de)sodiation mechanism of Sb2Se3-based anodes remained the same in full-cells as in half-cells, forming Na5-xSbSe. Presodiation strategies through direct-contact and electrochemical methods were explored in order to stabilize the capacity fade of Sb2Se3-based full-cells. The results illustrated that presodiation strategies might become for the successful implementation of high-capacity, and stable, Sb2Se3-based anodes in practical NIB applications.

• Brennhagen, Anders; Cavallo, Carmen; Wragg, David Stephen; Ponniah, Vajeeston; Sjåstad, Anja Olafsen & Fjellvåg, Helmer (2024). Bi metallates as conversion-alloying anodes for Na-ion batteries. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Rechargeable batteries are essential for the green energy transition and Li-ion batteries (LIBs) are currently dominating the marked. Li and other elements used in LIBs are limited resources on the planet, which makes them relatively expensive. Na-ion batteries (NIBs) work similarly to LIBs, but with slightly lower capacities due to the higher mass of Na compared to Li. However, the much higher and widespread abundance of Na could make NIBs cheaper and more sustainable that LIBs, perfect for large scale stationary energy storage. One of the major challenges with NIBs is to find a good anode material. In this work, we have not been able to do that. However, we have shown how a group of anode materials works during charge and discharge to a much greater detail than before, and understood why they do not perform so well. We used these results to improve the performance of the materials, but not enough to be of commercial interest. Nevertheless, the methods, ideas and knowledge developed in this thesis can be used for other materials and lead to a great improvements of NIBs in the future.

• Thiagarajan, Abilash Kanish; Brennhagen, Anders; Wragg, David Stephen & Koposov, Alexey (2023). Structural changes in graphite-based anodes of Li-ion batteries elucidated through operando XRD. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Lithium-ion batteries (LIBs) with graphite-based anodes dominate the battery market around the world and have been studied extensively for the past decades, but the structural changes during cycling are still not fully understood. In this work, we used galvanostatic cycling (GC) to characterize the electrochemical performance of graphite samples in LIB. We also attempted to achieve stable capacities over hundreds of cycles to monitor the effect of long-term cycling on the mechanisms of graphite, with limited success. The fabricated coin cells experienced poor capacity retention across all graphite samples and some abnormal capacity increases that had not been observed previously. We noticed that electrolytes containing FEC made a noticeable change to the electrochemical performance as it resulted in irregular cycling, but also better capacity retention. Operando X-ray diffraction is a powerful technique to understand structural changes. We looked at multiple graphite reflections, mainly 002, 100, 101, 102 and 004, and observed that the expansion of the structure is not only 2 dimensions but all 3 dimensions as the interlayer distance and graphene layers expands during lithiation. We also monitored this expansion of graphene layers with pair distribution function (PDF) as the three C-C distances in hexagonal carbon rings, 1.41 Å, 2.41 Å and 2.85 Å, changed lengths at different points during lithiation and delithiation. We looked at diffraction peaks during lithiation and delithiation to study the mechanisms and observed that they were different. Lithiation showed solid solution like behavior indicating disordered intermediate phases, while delithiation showed two-phase transition indicating ordered structures. In this work we have used Operando X-ray diffraction to show that the structural changes graphite undergoes during cycling, transition from graphite to LiC6, is not specific to each graphite sample and the structural changes depend on the condition of the material. Pristine graphite samples transitioned fully to LiC6 during cycling with C-rate of C/6, but only LiC12 when a higher C-rate of C/2 was used. Graphite electrodes cut from commercial pouch cells that had cycled many hundreds of electrochemical cycles were able to transition to LiC6 during C/20, but only LiC12 during C/6, indicating an “ageing” mechanism.

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