Li-metal based All-Solid-State Batteries (ASSBs) offer a safer and higher-energy alternative to conventional lithium-ion batteries, but their performances are hindered by interfacial instability between the solid-state electrolyte (SSE) and lithium metal electrode. To stabilize the interface, a nanometer-thick Al2O3 film made by Atomic Layer Deposition (ALD) technique is evaluated as a surface protective layer at the SSE/Li metal interface. We unveil the interfacial stability between beta-Li3PS4 (LPS) SSE and deposited lithium metal using in situ hard X-ray photoemission spectroscopy (HAXPES) approach. Our results on LPS/Al2O3/Li metal system reveal that 4 nm-thick Al2O3 coating enhances interfacial stability by mitigating undesirable side reactions. Although some LPS reduction to Li2S still occurs, it is significantly less pronounced as compared to the pristine LPS/Li metal interface. Additionally, metallic lithium deposition is detected on the surface, with no observable reduction of phosphorus element. These findings underscore the capability of ultrathin oxide coatings made by ALD to significantly stabilize Li/SSE interface thus contributing to the development of more reliable and safety Li-metal based ASSBs.

The development of material acceleration platforms in battery research requires integrating complementary techniques and correlating heterogeneous experimental datasets. Here, this challenge is tackled in a large-scale multimodal program involving fifteen laboratories and facilities across Europe. Coordinated multi-site experiments are performed on state-of-the-art graphite / LiNiO2 Li-ion full cells to address two archetypal scientific questions: is the electrolyte composition impacting electrode properties, and how do electrode materials evolve when cells are cycled to their end-of-life? A fully standardized and centralized workflow is demonstrated, from sample production and delivery, to metadata and data handling, generating seventy-five concatenated datasets shared among all partners. Their integrated analysis shows that scientific conclusions depend critically on both the observable chosen to describe electrode properties, and the measurement technique employed. Individual experiments provide detailed information into specific aspects, such as crystal structures, redox activity, surface processes, morphology, etc., but can also function as binary diagnostic tool. Two-dimensional observable-technique patterns are introduced, in which each pixel encodes a yes, no or uncertain answer to a given scientific question. These patterns serve as multi-property metaviews, e.g. visual genotypes, enabling to classify material behavior and technique suitability according to predefined user demand and criteria, highlighting the interdependencies between measurement choices, extracted parameters and scientific interpretation. This multimodal workflow establishes a proof-of-concept for correlative analysis and underscores challenges toward fully integrated, automated and holistic approaches in energy material science.

This study focuses on a precursor of the synthesis of Laponite, named pre-Laponite. Pre-Laponite shares similar molecular formula and structure with Laponite, but it exhibits reduced long-range order. N2 adsorption isotherms reveal that both materials possess comparable BET (N2) specific surface areas and microporedominated textures consistent with slit-shaped pores. Notably, the study demonstrates a 1.4-fold improvement in hydrogen uptake for pre-Laponite compared to Laponite at-196 degrees C and 1 bar, pointing to new opportunities for designing clay-based materials for hydrogen storage application.

Natural circular dichroism (NCD) provides fundamental insight into molecular chirality and stereochemical environments. Extending this concept into the hard-x-ray regime enables element-specific and site-selective chiral sensitivity inaccessible to optical wavelengths. Here, we demonstrate that 1s2p resonant inelastic x-ray scattering (RIXS) can be used to probe NCD in the enantiomeric model compound [Co(en)3](NO3)2. Using high-resolution detection of Co K alpha emission under circularly polarized excitation at the cobalt 1s pre-edge, we observe pronounced dichroic behavior directly linked to the Co-centered chirality. The RIXS-NCD signal reaches approximate to 23% of the pre-edge maximum-more than twice the amplitude of the previously reported x-ray NCD signal for the same compound-and exhibits the expected angular dependence for the crystal's P6322 symmetry. Two-dimensional RIXS-NCD maps further reveal strong helicity-dependent features across both excitation and emission energies, providing a richer description of the chiral electronic structure. These results establish RIXS-NCD as a photon-in-photon-out methodology for investigating natural optical activity with elemental and orbital specificity, paving the way for future applications to complex chiral and bioinspired materials.

Understanding the chemical structure of the solid electrolyte interphase that forms and evolves during lithium-ion battery cycling is critical for advancing battery technology. This complex task often requires the use of postmortem protocols to extract the electrodes in controlled states of charge and prepare them for further characterization and analysis. Over decades of research and optimization, the scientific community has established and shared post-mortem workflow protocols tailored to specific techniques. However, numerous sources of artifacts can disturb this workflow, introducing experimental uncertainties at various stages, from electrode manufacturing to data interpretation. Here we present the results of a round-robin inter-laboratory study using post-mortem X-ray photoemission spectroscopy to characterize the solid electrolyte interphase formed on graphite electrode after cycling in two different electrolytes. Several leading European research teams, expert in battery manufacturing and characterization by X-ray photoemission spectroscopy, participated in a meticulously designed post-mortem workflow. The goal was to identify the sources of consistency and disparity in the results and their impact on the scientific conclusions. Moreover, human-induced bias and errors were quantified throughout key steps, from cell assembly to photoemission core level peak fitting and interpretation. Based on our findings, we offer key recommendations for identifying and minimizing sources of artifacts in the analysis of the solid electrolyte interphase chemical composition. Effectively addressing these challenges is essential for improving both the performance and longevity of batteries.

Interlayer coupling in 2D heterostructures can result in a reduction of the rotation symmetry and the generation of quantum phenomena. Although these effects have been demonstrated in transition metal dichalcogenides (TMDs) with mismatched interfaces, the role of band hybridization remains unclear. In addition, the creation of flat bands at the valence band maximum (VBM) of TMDs is still an open challenge. In this work, we investigate the electronic structure of monolayer MoS2-black phosphorus heterojunctions with a combined experimental and theoretical approach. The disruption of the rotational symmetry of the MoS2 bands, the creation of anisotropic minigaps and the appearance of flat bands at the Γ valley, accompanied by the switch of VBM from K to Γ, are clearly observed with micro-ARPES. Unfolded band structures obtained from first principles simulations precisely describe these multiple effects – all independent of the twist angle – and demonstrates that they arise from strong band hybridization between Mo d_z^2 and P p_x orbitals. The underlying physics revealed by our results paves the way for innovative electronics and optoelectronics based on TMDs superlattices, adding further flexibility to the approaches adopted in twisted hexagonal superlattices. Stacking layers from different van der Waals materials can enable rotational symmetry breaking and engineering of the electronic band structure. Here, the authors report the observation of the creation of anisotropic minigaps and the appearance of flat bands at the valence band maximum in monolayer MoS2-black phosphorus heterojunctions.

Understanding the interaction between metal ions and their aqueous environment is fundamental in many areas of chemistry, biology, and environmental science. In this study, we investigate the electronic structure of hydrated calcium ions, focusing on how water molecules influence the behavior of the metal ion. We employed advanced X-ray techniques, including X-ray absorption, photoelectron, and Auger spectroscopies, combined with high-level quantum chemical calculations. Our analysis reveals that, alongside normal Auger decay, distinct ultrafast charge transfer processes occur between the calcium ion and surrounding water molecules, underscoring the complex nature of metal-solvent interactions. Two primary mechanisms were identified. The first one involves electron transfer from water to the calcium ion. The second mechanism depends on the photon energy and is tentatively attributed to the decay of photoelectron satellites, the capture of free solvated electrons or electrons from a Cl^- ion in the second solvation shell. Additionally, we observed significant shifts in electron energies due to post-collision interactions and interpreted the Ca 1s-1 photoelectron satellites mainly as originating from inelastic photoelectron scattering (IPES). These findings provide deeper insights into the electronic properties of hydrated metal ions, with potential implications for fields such as catalysis and biochemistry, where metal ions play a crucial role.

We investigate the spin state stability of Mn in alpha-Mn2O3 through the structural, insulator-to-metal transition under high pressure by x-ray emission spectroscopy (XES) and x-ray diffraction (XRD) up to 41 GPa. The XES spectra show a broadening of the main line and a weak shift of the satellite feature as pressure increases but no signature of spin transition while XRD confirms the full conversion to the Cmcm phase at high pressure. Using multiplet calculations, we suggest that the XES spectral changes under pressure is driven by the increased Coulomb interaction in the compressed lattice. The absence of spin transition through the phase transition could be caused by Jahn-Teller distortions on the Mn sites, which stabilize the spin state, possibly leading to hopping conductivity owing to polaronic effects.

We present the design and performance of a new multi-crystal x-ray emission spectrometer installed at the GALAXIES beamline at Synchrotron SOLEIL. The new instrument, which we name “MULTIXS,” can host up to five analyzer crystals and supersedes our previous XES spectrometer design, providing a compact, simple design with all the analyzer crystals contained in the horizontal sample plane. This feature provides a direct view of the sample area and avoids the potential masking of the sample for constrained sample environments. This new design allows for the use of both 0.5 m and 1 m radius spherical analyzer crystals. In addition, the ability to continuously scan the spectrometer energy provides relatively fast scanning with high quality emission data and minimum dead-time overhead.

The perpendicular magnetic anisotropy (PMA) of metal/ferromagnet (FM)/oxide trilayers is known to depend on the degree of oxidation of the FM/oxide interface. Among the different methods to tune the PMA, magnetoionics is emerging as a promising technique with potential applications in low-power spintronic devices. In this work, the PMA of Pt/Co/AlOx/HfO2 capacitorlike devices was gradually tuned by electric field gating. Hard-x-ray photoelectron spectroscopy (HAXPES) measurements at a synchrotron radiation source, guaranteeing tunable photon energies, a collimated beam, and a large photon flux, have allowed us to probe the composition of the cobalt ultrathin film buried below the dielectric layer of the capacitors, and its evolution upon the application of the gate voltage. The Co 2p HAXPES spectra of the gated devices were compared to those obtained for Pt/Co/AlOx reference samples, for which the PMA was controlled by tuning the Co oxidation with oxygen plasma. For similar magnetic anisotropy states, the two types of samples exhibit equivalent Co 2p HAXPES spectra, with the same weight of metallic Co and CoO signatures. These results constitute direct experimental proof that, in our integrated devices, the gate voltage modifies the PMA through the modification of the oxidation state of the buried cobalt layer driven by oxygen-ion migration.

The performances of lithium-ion batteries depend on the capability of the electrode materials to exchange lithium ions and electrons faster and reversibly. LiNiO2 is a promising electrode candidate for achieving high voltage and capacity. However, its industrialization is hindered by surface and bulk instabilities. These instabilities are due to redox processes involving charge transfer between the cations and anions. Therefore, a fundamental understanding based on further experimental evidence is required to resolve the charge transfer between the cation and anion from the surface to the bulk in LiNiO2. Herein, we resolve the roles of nickel and oxygen in the charge compensation process in LixNiO2 electrodes from the extreme surface down to 30 nm by energy dependent core-level HAXPES supported by an ab initio simulation. We emphasize the central role of oxygen in the bulk charge compensation mechanism from LiNiO2 to NiO2 due to the negative charge transfer and bond/charge disproportionation characters of LiNiO2.

The metal-hydride-based "topochemical reduction" process has produced several thermodynamically unstable phases across various transition metal oxide series with unusual crystal structures and nontrivial ground states. Here, by such an oxygen (de-)-intercalation method we synthesis a samarium nickelate with ordered nickel valences associated with tri-component coordination configurations. This structure, with a formula of Sm9Ni9O22 as revealed by four-dimensional scanning transmission electron microscopy (4D-STEM), emerges from the intricate planes of {303}(pc) ordered apical oxygen vacancies. X-ray spectroscopy measurements and ab initio calculations show the coexistence of square planar, pyramidal, and octahedral Ni sites with mono-, bi-, and tri-valences. It leads to an intense orbital polarization, charge-ordering, and a ground state with a strong electron localization marked by the disappearance of ligand-hole configuration at low temperature. This nickelate compound provides another example of previously inaccessible materials enabled by topotactic transformations and presents an interesting platform where mixed Ni valence can give rise to exotic phenomena.

After decades of research, superconductivity is finally found in nickel-based analogs of superconducting cuprates, with infinite-layer (IL) structure. These results are so far restricted to thin films in the case of IL-nickelates. Therefore, the nature of the interface with the substrate, and how it couples with the thin film properties is still an open question. Here, using scanning transmission electron microscopy (STEM)- electron energy loss spectroscopy (EELS), a novel p-type interface defined by SrO termination with the SrTiO3 substrate is observed in superconducting (SC) IL-praseodymium nickelate samples. Its interfacial charge and polarity are compared with the previously reported n-type interface characterized by TiO2 termination. In combination with ab-initio calculations, it is found that the influence of the interface on the electronic structure is local and does not extend beyond 2-3 unit cells into the thin film. This decouples the direct influence of the interface in driving the superconductivity, and indicates that the IL-nickelate thin films do not have a universal interface model. Insights into the spatial hole-distribution in SC samples, provided by monochromated EELS and total reflection-hard X-ray photoemission spectroscopy, suggest that this particular distribution might be directly influencing superconductivity. The role of interface in controlling superconductivity in infinite-layer (IL) nickelates thin films is a topic of strong debate. Here, it is shown that both p- and n-type interfaces can be formed in superconducting IL-nickelates, and their influence on the electronic structure is local, not beyond 2-3 unit cells. This indicates that the interface has no direct influence on superconductivity in IL-nickelates. image

We have built and commissioned a novel standalone multi-crystal x-ray spectrometer (MOSARIX) in the von Hamos configuration based on highly annealed pyrolytic graphite crystals. The spectrometer is optimized for the energy range of 2–5 keV, but this range can be extended up to 20 keV by using higher reflection orders. With its nine crystals and a Pilatus detector, MOSARIX achieves exceptional detection efficiency with good resolving power (better than 4000), opening the door to study small cross section phenomena and perform fast in situ measurements. The spectrometer operates under a He atmosphere, which provides a flexible sample environment for measurements in gas, liquid, and solid phases.

Synchrotron radiation facilities provide highly polarized x-ray beams across a wide energy range. However, the exact type and degree of polarization vary according to the beamline and experimental setup. To accurately determine the angle and degree of linear polarization, a portable x-ray polarimeter has been developed. This setup consists of a silicon drift detector that rotates around a target made of high-density polyethylene. The imprint generated in the angular distribution of scattered photons from the target at a 90-degree angle between the incident x-rays and detector has been exploited to determine the beam polarization. Measurements were conducted at the GALAXIES beamline of the SOLEIL synchrotron. The expected angular distribution of the scattered photons for a given beam polarization was obtained through simulations using the Geant4 simulation toolkit. An excellent agreement between simulations and the collected data has been obtained, validating the setup and enabling a precise determination of the beam polarization.

The dynamic formation of chemical species composing the solid electrolyte interphase (SEI) layer at the surface of a carbonaceous electrode in a carbonate-based liquid electrolyte was observed in real-time using operando near-ambient pressure XPS (NAP-XPS). The potential of the glassy carbon electrode vs. metallic lithium was controlled during the XPS experiment. By following the binding energy shifts as a function of applied potential, we could identify the main SEI species and observe their deposition on the electrode surface during the formation of the SEI. These results demonstrate that NAP-XPS is a powerful tool to investigate the SEI formation and stability in Li- and post-Li-ion batteries, paving the way for future studies on the effect of electrolyte additives and solvent mixtures on battery performance.

The performances of lithium-ion batteries are set by the electrodes materials capacity to exchange lithium ions and electrons faster and reversibly. To this goal Ni-rich layered metal oxides, especially LiNiO2, are attractive electrode candidate to achieve both high voltage and capacities. Despite its attractiveness, several drawbacks for its industrialization are related to different form of surface and bulk instabilities. These instabilities are due to redox process involving the charge transfer between cations and anions. Therefore, a fundamental understanding based on further experimental evidence is required to resolve of charge transfer between the cation and anion from the surface to the bulk in LiNiO2. Herein, we resolve the role of nickel and oxygen in the charge compensation process in LixNiO2 electrodes from the extreme surface down to 30 nm by energy-dependent core-level HAXPES supported by ab initio simulation. We emphasize the central role of oxygen in the bulk charge compensation mechanism from LiNiO2 to NiO2 due to the negative charge transfer and bond/charge-disproportionation characters of LiNiO2. This bulk behavior is in turn responsible for surface deoxygenation and nickel reduction upon delithiation.

We present first hard X-ray photoelectron spectroscopy (HAXPES) results of aqueous salt solutions and dispersions of gold nanoparticles in liquid cells equipped with specially designed microfabricated thin silicon nitride membranes, with thickness in the 15–25 nm range, mounted in a high-vacuum-compatible environment. The experiments have been performed at the HAXPES endstation of the GALAXIES beamline at the SOLEIL synchrotron radiation facility. The low-stress membranes are fabricated from 100 mm silicon wafers using standard lithography techniques. Platinum alignment marks are added to the chips hosting the membranes to facilitate the positioning of the X-ray beam on the membrane by detecting the corresponding photoemission lines. Two types of liquid cells have been used, a static one built on an Omicron-type sample holder with the liquid confined in the cell container, and a circulating liquid cell, in which the liquid can flow in order to mitigate the effects due to beam damage. We demonstrate that the membranes are mechanically robust and able to withstand 1 bar pressure difference between the liquid inside the cell and vacuum, and the intense synchrotron radiation beam during data acquisition. This opens up new opportunities for spectroscopic studies of liquids.