Alexey Koposov

• Park, Heesoo; Mohn, Chris Erik; Wragg, David Stephen & Koposov, Alexey Y. (2026). From Disorder to Staging: Mechanism of Li-ion Diffusion in Graphite Revealed by Large-Scale Molecular Dynamics. Journal of Physical Chemistry C. ISSN 1932-7447. doi: 10.1021/acs.jpcc.6c05855. Full text in Research Archive Show summary

  Abstract Capturing the cross-layer kinetics of intercalants remains a fundamental bottleneck in understanding the structural evolution of layered host materials. This challenge is particularly critical in Li-ion batteries, where designing high-rate graphite anodes is hindered by a lack of mechanistic understanding of intercalation, because theoretical models traditionally address structural order only as out-of-plane staging or in-plane migration. Here, we expanded molecular dynamics simulation dimensions to over 8 nm with 12 graphite layers to fully account for dynamic intra- and interlayer correlations. We observed the collective atomistic evolution at various stages of lithiation, revealing unusual diffusive behavior; for example, upper-layer Li islands regulate the diffusivity of the two underlying layers at stage 3. Furthermore, Li-ion transport becomes highly in-plane anisotropic under the steep concentration gradients characteristic of high-rate operation. By explicitly connecting three-dimensional staging with two-dimensional diffusion, these insights provide the realistic mechanistic baseline necessary for predictive macroscale modeling.

• Jr, Andrew Pastusic; Skurtveit, Amalie & Koposov, Alexey Y. (2026). Comparative Study of Bi2S3 and Sb2S3 as Conversion/Alloying Anodes for Na-Ion Batteries. ACS Applied Energy Materials. doi: 10.1021/acsaem.6c02364. Full text in Research Archive Show summary

  Bi- and Sb-based materials have gained a significant interest as anode materials for Na-ion batteries. Bi2S3 and Sb2S3 are isostructural and isovalent chalcogenides that should undergo similar conversion/alloying reaction with the Na-ion when placed in a battery. However, the effect of cation (Bi vs Sb), particle morphology, and electrolyte environment on (de)sodiation mechanisms and cycling stability remains poorly understood. Herein, a systematic study of several morphologies of Bi2S3 and Sb2S3 in two electrolyte systems for Na-ion batteries is presented. Bi2S3 exhibited distinct electrochemical plateaus associated with crystalline-crystalline phase transitions, clearly resolved by operando and ex situ X-ray diffraction, following a conventional Bi-based conversion/alloying pathway via Na3Bi and Na2S during sodiation and a back-conversion reaction culminating in NaBiS2 at the end of desodiation. In contrast, Sb2S3 rapidly lost long-range order and cycled predominantly in the amorphous regime. Ex situ total X-ray scattering and X-ray absorption spectroscopy revealed that the (de)sodiation involved the formation and rearrangements of amorphous Na–Sb–S networks approximated by NaSbS0.5, Na2S4, and ternary Na5–xSbS. In both systems, ether-based electrolytes improved the cyclability relative to carbonate-based electrolytes regardless of particle morphology and size, revealing that electrolyte choice plays a decisive role in controlling the performance of conversion/alloying anodes.

• Dai, Tian; Ahmed, Razan M. N.; North, Eira Tiberg; Valldor, Björn Martin & Koposov, Alexey Y. (2026). Exploring Antiperovskite Cathodes for Na‐Ion Batteries. ChemSusChem. ISSN 1864-5631. 19(10). doi: 10.1002/cssc.70723. Full text in Research Archive Show summary

  Recently discovered cathode materials with antiperovskite (AP) structure have shown a promising performance in Li‐ion batteries. However, their applicability in other battery chemistries have not been well explored. In this work, an AP‐based cathode material, Li 2 FeSeO, was systematically studied for application in Na‐ion batteries (NIBs). Delithiated Li 0.8 FeSeO was used as a precursor for preparing an Na‐ion analog. The electrochemical characterization of Na‐based AP cathode revealed a reversible galvanostatic cycling behavior with an initial capacity of 129 mA g −1 and a capacity retention of 57% after 200 cycles when cycled at a current density of 10 mA g −1 . Up to 0.75 Na + can be reversibly inserted into the AP framework. Synchrotron operando and ex situ X‐ray studies revealed a working mechanism based on a dual redox behavior including both Fe and Se, with Se being the main redox actor. The (de)sodiation capacity below expected value is possibly attributed to the formation of a core–shell structure formed due to kinetic limitation of Na + diffusion into bulk structure, thus preventing a full utilization of the available redox activity. These findings establish AP cathodes as viable candidates for NIBs and provide mechanistic insights that can guide their future structural optimization.

• 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. Full text in Research Archive Show summary

  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.

View all works in NVA

• Toktamyssova, Alina; Wragg, David Stephen; Kathribail, Anish Raj & Koposov, Alexey (2026). Battery-Grade Hard Carbon for Na-ion Batteries. Full text in Research Archive Show summary

  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.

• Mishra, Mochan; Berdiell, Izar Capel; Bazioti, Kalliopi & Koposov, Alexey (2026). Revealing electrolyte-dependent behavior of Sn-based CA anodes for Na-ion batteries. Full text in Research Archive
• Wragg, David Stephen; Kathribail, Anish Raj; Berdiell, Izar Capel; Koposov, Alexey & Toktamyssova, Alina (2026). In situ and Operando studies of Hard Carbon. Full text in Research Archive
• Skurtveit, Amalie; Berdiell, Izar Capel; Khairnar, Abhishek; Amrheim, Simon; Peters, Simone & Gottlinger, Mara [Show all 9 contributors for this article] (2026). Inorganic Coatings of Sulfide-Based Solid Electrolytes Through Atomic Layer Deposition. Full text in Research Archive Show summary

  Solid-state batteries (SSBs) are regarded as a promising next-generation energy storage technology, offering a safer, more sustainable, and potentially cost-effective alternative compared to conventional Li-ion batteries (LIBs). The key component for high-performing SSBs is the solid-state electrolyte (SSE) with targeted properties (such as electrochemical stability window, performance, and safety). However, introduction of SSE also brings new challenges related to ionic conductivity, processability, recyclability, and the interface between the active material and the SSE that needs to be carefully controlled. These challenges are addressed with the FUNCY-SSB (FUNctional Coatings of sulfide electrolYtes for lithium Solid-State Batteries) project.

• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Show all 13 contributors for this article] (2026). Hidden Na5SbSe Unlocks Sb2Se3 Anodes for Na-Ion Batteries. Full text in Research Archive Show summary

  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 [Show all 13 contributors for this article] (2026). Material's Discovery via Synchrotron Operando XRD and XAS: the Case of Sb2Se3 Anodes for Na-Ion Batteries. Full text in Research Archive Show summary

  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.

View all works in NVA