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Sandrine Lyonnard

Publications and source records attributed to Sandrine Lyonnard.

14 recordsLinked to original sources

A large scale multi-modal workflow for battery characterization: from concept to implementation

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.

physics.app-ph

4D operando X-ray nano-holo-tomography reveals multiscale chemomechanics in Silicon-Graphite anode

Linking electrode microstructure to electrochemical performance is essential for optimizing Li-ion batteries. However, this requires mechanistic 4D observations at ultimate spatio-temporal scales, which remains elusive. Here we demonstrate the use of operando synchrotron X-ray nano-holo-tomography combined with Digital Volume Correlation to track chemomechanical dynamics at both particle (local) and electrode (averaged) scales. Quantitative scale-bridging image analysis is applied to a high-capacity silicon-graphite anode during its formation cycle. Our findings reveal that local diffusion properties, graphite particle morphology and position in the electrode, distance to silicon clusters, surface contact with electrolyte and mechanical deformations, all have a direct impact on the local electrochemical activity and irreversibility - but these parameters are not equally important. Particularly, we identify fast diffusion channels that play a key role and counterbalance intrinsic depth-dependent reaction heterogeneities due to ionic/electronic diffusion limitations. The various structural factors that determine Gr-Si battery performance beyond ensemble properties are classified using a scale of influence, providing a practical framework for the optimization of materials and electrode manufacturing.

physics.app-ph

Temperature dependent Resonant X-ray Inelastic Scattering at Ni L3-edge for NaNiO2 and LiNiO2

LiNiO2 is a promising cathode material for Li-ion battery but its atomic and electronic structure is under debate. Indeed, two sets of Ni-O distances are identified from local structural probes that are related with either Jahn-Teller distortion or bond disproportionation of NiO6 octahedra. Moreover, LiNiO2 undergoes a monoclinic to rhombohedral transition at 200 K which origin is still unclear. On the other hand, isostructural NaNiO2 shows differences from LiNiO2, as it is a well-known Jahn-Teller distorted system, and it undergoes monoclinic to rhombohedral transition at 500 K associated to the loss of the Jahn-Teller distortion. To understand better these differences, we report here Ni L3-edge Resonant inelastic X-ray scattering experiments on LiNiO2 and NaNiO2 at different temperatures (25 to 520 K) and follow the spectral changes below and above the phase transition temperatures. The observed RIXS spectra and the mapping indicate strong spectral changes for NaNiO2 confirming the disappearance of Jahn-Teller distortion during phase transition while the changes are minor for LiNiO2 suggesting very few modifications in the local structure. Theoretical simulations of RIXS spectra are required for further understanding, however, we believe that the reported dataset can be a crucial resource for developing advanced simulations that are essential to deepening our understanding of the atomic and electronic structure of these nickelates.

cond-mat.mtrl-sci

Dead, Slow and Overworked Graphite: Operando X-ray Microdiffraction Mapping of Aged Electrodes

Aging limits lithium-ion battery lifetime and must be understood to improve durability and performance, requiring a detailed understanding of how aging alters the availability of cyclable lithium and the integrity of active particles. In this work, (de)lithiation mechanisms are examined and spatially-resolved at the microscale in aged graphite electrodes dismounted from a large format graphite/LiFePO4-Li(NiCoAl)O2 cell at 70% remaining capacity. A multi-technique workflow is employed, combining electrochemical methods with post-mortem structural and morphological analyses, and introducing synchrotron microX-ray 2D diffraction imaging as a technique to probe aged graphite, applied at C-rates from C/5 to C. In-plane and through-plane heterogeneities in graphite dynamics are evidenced, showing the presence of inactive regions localized in two dimensions. In these areas, particles are either disconnected (irreversibly lost) or kinetically limited (reactivated at a slow C-rate), with dead or slow particles exhibiting a wide range of compositions, from x = 0 to x = 1 in LixC6. These inactivated graphite particles are found to be heterogeneously distributed throughout the depth of the aged negative electrode. In particular, the most inactivated region localizes at the negative electrode-separator interface, correlating to overworking graphite near the separator.

cond-mat.mtrl-sci

Operando imaging of crystal structure and orientation in all components of all-solid-state-batteries

A comprehensive understanding of interactions between cathode, electrolyte, anode, and packaging during battery operation is crucial for advancing performances but remains overlooked due to the lack of characterisation technics capable of measuring these components simultaneously. We perform a holistic investigation of a compact all-solid-state-battery using operando synchrotron X-ray micro-diffraction imaging. We image in real time and simultaneously the lattice parameter and crystal orientation of the dense LiCoO2 cathode, the Ti current collector and the electrodeposited Li metal anode. We reveal that reaction mechanism of LiCoO2 depends on the crystal orientation, and that, in dense electrodes as opposed to porous ones, the delithiation is limited by the formation of a Li-rich insulating interface. Li metal crystal orientation is found to be influenced initially by the Ti texture and to change within minutes during plating and stripping. These results demonstrate the power of X-ray imaging to link reaction mechanism and grain orientation during non-equilibrium processes.

cond-mat.mtrl-sci

Understanding the irreversible lithium loss in silicon anodes using multi-edge X-ray scattering analysis

During the first charge-discharge cycle, silicon-based batteries show an important capacity loss because of the formation of the solid electrolyte interphase (SEI) and morphological changes due to expansion-contraction sequence upon alloying. To understand this first-cycle irreversibility, quantitative methods are needed to characterize the chemical environment of silicon and lithium in the bulk of the cycled electrodes. Here we report a methodology based on multi-edge X-ray Raman Scattering performed on model silicon electrodes prepared in fully lithiated and fully delithiated states after the first cycle. The spectra were recorded at the C, O, F and Li K edges, as well as Si L2,3 edge. They were analysed using linear combinations of both experimental and computed reference spectra. We used prototypical SEI compounds as Li2CO3, LiF and LiPF6, as well as electrode constituents as binder and conductive carbon, cristalline Si, native SiO2,LixSi phases (x being the lithiation index) to identify the main species, isolate their relative contributions, and quantitatively evaluate the proportions of organic and inorganic products. We find that 30% of the carbonates formed in the SEI during the lithiation are dissolved on delithiation, and that part of the Li15Si4 alloys remain present after delithiation. By combining electrochemical analysis and XRS results, we identify that 17% of the lithium lost in the first cycle is trapped in disconnected silicon particles, while 30% form a fluorine-rich stable SEI and 53% a carbonate-rich partially-dissolvable SEI. These results pave the way to systematic, reference data-informed, and modelling assisted studies of SEI characteristics in the bulk of electrodes prepared under controlled state-of-charge and state-of-health conditions.

cond-mat.mtrl-sci

Mapping reaction mechanism during overcharge of a LiNiO2/Graphite-silicon lithium-ion battery: a correlative operando approach by simultaneous gas analysis and synchrotron scattering techniques

Li-ion battery degradation processes are multi-scale, heterogeneous, dynamic and involve multiple cell components through cross talk mechanisms. Correlated operando characterization capable of measuring several key parameters are needed to accelerate understanding on these complex degradation processes. In particular, degradation mechanisms during overcharge of LiNiO2/Graphite-Silicon is well known at the material level featuring O2 gas release and concomitant surface reconstruction of LiNiO2. However, there are still debates regarding the role of high voltage O1 phase formation on gas production and no information on the effect of produced gases on the cell components (anode or sensors), or effect of overcharge on electrode level behavior. In this work, we simultaneously measured the gas produced using operando mass spectrometry while spatially resolving nanostructure and lattice changes using operando micro SAXS/WAXS mapping during the formation and over charge of a LiNiO2/Gr-Si pouch cell. This new correlated operando characterization experiment allowed to (1) confirm the absence of O1 phase even with substantial gas produced at end of charge, (2) unveil the effect of gases on reference and negative electrodes, (3) show that overcharge increases in-plane reaction heterogeneities by creating local degraded spots lagging behind the ensemble electrochemistry. These findings will be important to optimize ageing of devices based on similar chemistries, in particular Ni-rich NMC, while showing the strength of correlated characterization leading to more efficient and robust information on complex mechanisms.

cond-mat.mtrl-sci

A fundamental correlative spectroscopic study on LixNiO2 and NaNiO2

The intimate correlation between the local atomic arrangement and electronic states in Li-ion battery cathode materials plays a crucial role in determining their electrochemical properties, including capacity, cycling stability, and rate capability. Despite almost 30 years of research efforts on high performance cathodes based on Ni rich layered oxides, there is still no consensus on LiNiO2 local atomic and electronic structure. Ni sites could be either Jahn-Teller distorted or bond disproportionated and the role of Ni and oxygen in the charge compensation mechanism remains unclear. In this study, we compare the local and electronic structure of LiNiO2 and NaNiO2, a long-range Jahn-Teller system, using a novel approach which aims at correlating the results from bulk spectroscopy techniques, particularly under operando conditions, obtained on standard samples to ensure sample interoperability and enhance the reliability and robustness of our results. Despite being a site-selective and local technique, XAS is unable to discriminate between the proposed scenarios, as confirmed also by theoretical calculations. On the contrary, Raman spectroscopy show local structural differences between monoclinic distorted NaNiO2 and rhombohedral LiNiO2. Additionally, HAXPES confirms the presence of multiple formal oxidation states for Ni, and RIXS data provides evidence of 3d8 states, confirming the negative charge transfer character of Ni and some degree of bond disproportionation in LiNiO2. Regarding the charge compensation mechanism, XRS and RIXS support the participation of oxygen holes in the redox activity, while Raman spectroscopy does not detect molecular oxygen. By combing several high-fidelity spectroscopy datasets, this study shows the value of correlative characterization workflows to provide insights into complex structural-electrochemical relationships.

cond-mat.mtrl-sci

Data Management Plans: the Importance of Data Management in the BIG-MAP Project

Open access to research data is increasingly important for accelerating research. Grant authorities therefore request detailed plans for how data is managed in the projects they finance. We have recently developed such a plan for the EU-H2020 BIG-MAP project - a cross-disciplinary project targeting disruptive battery-material discoveries. Essential for reaching the goal is extensive sharing of research data across scales, disciplines and stakeholders, not limited to BIG-MAP and the European BATTERY 2030+ initiative but within the entire battery community. The key challenges faced in developing the data management plan for such a large and complex project were to generate an overview of the enormous amount of data that will be produced, to build an understanding of the data flow within the project and to agree on a roadmap for making all data FAIR. This paper describes the process we followed and how we structured the plan.

cond-mat.mtrl-sci

Holistic Multi-scale Imaging of Oxygen Reduction Reaction Catalyst Degradation in Operational Fuel Cells

Wide proliferation of low temperature hydrogen fuel cell systems, a key part of the hydrogen economy, is hindered by degradation of the platinum cathode catalyst. Here, we provide a device level assessment of the molecular scale catalyst degradation phenomena, using advanced operando X-ray scattering tomography tailored for device-scale imaging. Each cell component, including the catalyst, carbon support, polymer electrolyte, and liquid water can be simultaneously mapped, allowing for deep correlative analysis. Chemical and thermal gradients formed inside the operating fuel cell produce highly heterogeneous degradation of the catalyst nanostructure, which can be linked to the macroscale design of the flow field and water distribution in the cell materials. Striking differences in catalyst degradation are observed between operating fuel cell devices and the liquid cell routinely used for catalyst stability studies, highlighting the rarely studied but crucial impact of the complex operating environment on the catalyst degradation phenomena. This degradation knowledge gap highlights the necessity of multimodal in situ characterization of real devices when assessing the performance and durability of electrocatalysts.

physics.app-ph

Contribution of X-ray experiments and modeling to the understanding of the heterogeneous lithiation of graphite electrodes

Distributions of potential and lithium content inside lithium ion batteries highly affects their performance and durability. An increased heterogeneity of the lithium distribution is expected in thick electrodes with high energy densities or cycling at high currents. To optimize electrodes and cells designs, it is crucial to probe lithium concentration gradients across the depth of the electrode, but also to predict their occurrence and magnitude as a function of materials properties. Here, we follow the lithium distribution across a $80~\mu m$ thick porous graphite electrode using a $1~\mu m$ focused synchrotron X-ray beam. The sequential formation of the individual Li$_x$C$_6$ phases during lithium de-insertion is extracted from X-ray diffraction patterns, allowing the quantification of lithium concentration across the electrode thickness. Analyzing the evolution of heterogeneities as a function of time, we recover the striking features we predicted with a porous electrode model, including the succession of homogeneous and heterogeneous distributions of lithium. However, a clear difference is obtained at high stoichiometry, with a much more homogeneous distribution than initially predicted. Revisiting the interplay between transport and kinetic transfers limitations in the porous electrode model, we suggest that the kinetics of lithium (de)-insertion is highly reduced during the LiC$_6$/LiC$_{12}$ phase transition.

cond-mat.mtrl-sci

Water sub-diffusion in membranes for fuel cells

We investigate the dynamics of water confined in soft ionic nano-assemblies, an issue critical for a general understanding of the multi-scale structure-function interplay in advanced materials. We focus in particular on hydrated perfluoro-sulfonic acid compounds employed as electrolytes in fuel cells. These materials form phase-separated morphologies that show outstanding proton-conducting properties, directly related to the state and dynamics of the absorbed water. We have quantified water motion and ion transport by combining Quasi Elastic Neutron Scattering, Pulsed Field Gradient Nuclear Magnetic Resonance, and Molecular Dynamics computer simulation. Effective water and ion diffusion coefficients have been determined together with their variation upon hydration at the relevant atomic, nanoscopic and macroscopic scales, providing a complete picture of transport. We demonstrate that confinement at the nanoscale and direct interaction with the charged interfaces produce anomalous sub-diffusion, due to a heterogeneous space-dependent dynamics within the ionic nanochannels. This is irrespective of the details of the chemistry of the hydrophobic confining matrix, confirming the statistical significance of our conclusions. Our findings turn out to indicate interesting connections and possibilities of cross-fertilization with other domains, including biophysics. They also establish fruitful correspondences with advanced topics in statistical mechanics, resulting in new possibilities for the analysis of Neutron scattering data.

cond-mat.mtrl-sci

Sub-diffusion and population dynamics of water confined in soft environments

We have studied by Molecular Dynamics computer simulations the dynamics of water confined in ionic surfactants phases, ranging from well ordered lamellar structures to micelles at low and high water loading, respectively. We have analysed in depth the main dynamical features in terms of mean squared displacements and intermediate scattering functions, and found clear evidences of sub-diffusive behaviour. We have identified water molecules lying at the charged interface with the hydrophobic confining matrix as the main responsible for this unusual feature, and provided a comprehensive picture for dynamics based on a very precise analysis of life times at the interface. We conclude by providing, for the first time to our knowledge, a unique framework for rationalising the existence of important dynamical heterogeneities in fluids absorbed in soft confining environments.

cond-mat.soft

Water confined in self-assembled ionic surfactants nano-structures

We present a coarse-grained model for ionic surfactants in explicit aqueous solutions, and study by computer simulation both the impact of water content on the morphology of the system, and the consequent effect of the formed interfaces on the structural features of the adsorbed fluid. On increasing the hydration level at ambient conditions, the model exhibits a series of three distinct phases: lamellar, cylindrical and micellar. We characterize the different structures in terms of diffraction patterns and neutron scattering static structure factors. We demonstrate that the rate of variation of the nano-metric sizes of the self-assembled water domains shows peculiar changes in the different phases. We also analyse in depth the structure of the water/confining matrix interfaces, the implications of their tunable degree of curvature, and the properties of water molecules in the different restricted environments. Finally, we discuss our results compared to experimental data and their impact on a wide range of important scientific and technological domains, where the behavior of water at the interface with soft materials is crucial.

cond-mat.soft