Methods for operando coherent X-ray diffraction of battery materials at the Advanced Photon Source

Coherent Strain-Inhibiting Phase Construction of Lithium-Rich Manganese-Based Oxide Toward High Mechanochemical Stability

A layered lithium-rich manganese-based oxide cathode, containing R3̅m (LiTMO2, TM = Mn, Ni, Co) and C2/m (Li2MnO3) nanodomains, utilizes both transition metals and oxygen redox to yield substantial energy density. However, the inherent heterogeneous nature and distinct nanodomain redox chemistries of layered lithium-rich oxides will inevitably cause pernicious lattice strain and structural displacement, which can hardly be eliminated by conventional doping or coating strategies and result in accelerated performance decay. Herein, we incorporate a strain-inhibiting perovskite phase coherently grown within the layered structure to effectively restrain the displacement and lattice strain during uneven Li-ion extraction. The enhanced mechanochemical stability of the designed cathode benefits the persistent structure and reversible oxygen redox, thereby achieving high initial Coulombic efficiency and stable cycling and voltage profiles. Our approach of lattice engineering alleviates the strain and displacement caused by inhomogeneous reactivity between heterogeneous nanodomains and promotes the development of advanced cathode materials with long durability.

Reinvestigating atomic ordering inK0.5Na0.5NbO3and its impact on ferroelectric properties

In the present work, we reinvestigate the atomic ordering of a Pb-free morphotropic phase boundary (MPB) compositionviz.,K0.5Na0.5NbO3(KNN50) and its vicinity at various length scales using high-resolution x-ray diffraction and pair distribution function data. We have observed a monoclinic phase (Space Group: Pm) at long/short ranges differing from a very recent report by Sahaet al2024J. Phys.: Condens. Matter36425703. Moreover, the ferroelectric (polarization) dominance of short-range ordering (SRO) over long-range ordering (LRO) has been observed and quantified for the very first time using the amplitude of the ferroelectric frozen phonon mode (Γ4-) (corresponding to the high symmetry cubic phase), thereby structure is linked with ferroelectric (or polarization) property for a widely studied MPB systemviz.,KxNa(1-x)NbO3(KNNxforx= 0.40, 0.50, and 0.60). Two uniquely identified monoclinic phases has been observed for SRO (MSRO) and LRO (MLRO) for all the compositions. The amplitude of ferroelectric frozen phonon mode (Γ4-) corresponding toMSROis significantly higher (≈150%-180%) thanMLRO. A peak is observed in the amplitude ofΓ4-and intensity of prominent Raman peaks (ν1andν5) forx= 0.50, which is held responsible for high physical propertiesviz.,dielectric permittivity, piezoelectric coefficient, remnant polarization, electromechanical coupling coefficient, and many more widely reported in literature for KNN50.

In situ three-dimensional observation of plasticity onset in a Pt nanoparticle

Defects in nanocrystals can dramatically alter their physical and chemical behavior. It is thus crucial to understand the defect behavior at the nanoscale to enhance material properties. Here, we report three-dimensional defect characterization at the onset of plasticity in a 550 nm Pt nanoparticle. By combining in situ nano-indentation with Bragg Coherent X-ray Diffraction Imaging (BCDI), we directly observe the strain field inside the Pt particle during indentation, revealing the nucleation and propagation of prismatic dislocation loops. Subsequent post mortem imaging of the complete dislocation network, coupled with multi-reflection BCDI, enabled us to determine the Burgers vectors of the defects revealing sessile dislocations. Finally, by measuring the elastic field inside the crystal during indentation, we estimate that the shear stress required to generate defects is 6.4 GPa, representing the upper theoretical limit of elasticity and setting an unprecedented standard for Pt nanoparticles. Our findings provide fundamental insights into defect dynamics in nanoscale systems, offering invaluable knowledge for advanced materials design and engineering.

Asynchronous domain dynamics and equilibration in layered oxide battery cathode

To improve lithium-ion battery technology, it is essential to probe and comprehend the microscopic dynamic processes that occur in a real-world composite electrode under operating conditions. The primary and secondary particles are the structural building blocks of battery cathode electrodes. Their dynamic inconsistency has profound but not well-understood impacts. In this research, we combine operando coherent multi-crystal diffraction and optical microscopy to examine the chemical dynamics in local domains of layered oxide cathode. Our results not only pinpoint the asynchronicity of the lithium (de)intercalation at the sub-particle level, but also reveal sophisticated diffusion kinetics and reaction patterns, involving various localized processes, e.g., chemical onset, reaction front propagation, domains equilibration, particle deformation and motion. These observations shed new lights onto the activation and degradation mechanisms of state-of-the-art battery cathode materials.

Origin of structural degradation in Li-rich layered oxide cathode

Li- and Mn-rich (LMR) cathode materials that utilize both cation and anion redox can yield substantial increases in battery energy density^1-3. However, although voltage decay issues cause continuous energy loss and impede commercialization, the prerequisite driving force for this phenomenon remains a mystery^3-6 Here, with in situ nanoscale sensitive coherent X-ray diffraction imaging techniques, we reveal that nanostrain and lattice displacement accumulate continuously during operation of the cell. Evidence shows that this effect is the driving force for both structure degradation and oxygen loss, which trigger the well-known rapid voltage decay in LMR cathodes. By carrying out micro- to macro-length characterizations that span atomic structure, the primary particle, multiparticle and electrode levels, we demonstrate that the heterogeneous nature of LMR cathodes inevitably causes pernicious phase displacement/strain, which cannot be eliminated by conventional doping or coating methods. We therefore propose mesostructural design as a strategy to mitigate lattice displacement and inhomogeneous electrochemical/structural evolutions, thereby achieving stable voltage and capacity profiles. These findings highlight the significance of lattice strain/displacement in causing voltage decay and will inspire a wave of efforts to unlock the potential of the broad-scale commercialization of LMR cathode materials.

Performance Evaluation of Deep Neural Network Model for Coherent X-ray Imaging

We present a supervised deep neural network model for phase retrieval of coherent X-ray imaging and evaluate the performance. A supervised deep-learning-based approach requires a large amount of pre-training datasets. In most proposed models, the various experimental uncertainties are not considered when the input dataset, corresponding to the diffraction image in reciprocal space, is generated. We explore the performance of the deep neural network model, which is trained with an ideal quality of dataset, when it faces real-like corrupted diffraction images. We focus on three aspects of data qualities such as a detection dynamic range, a degree of coherence and noise level. The investigation shows that the deep neural network model is robust to a limited dynamic range and partially coherent X-ray illumination in comparison to the traditional phase retrieval, although it is more sensitive to the noise than the iteration-based method. This study suggests a baseline capability of the supervised deep neural network model for coherent X-ray imaging in preparation for the deployment to the laboratory where diffraction images are acquired.

Multiscale Understanding of Surface Structural Effects on High-Temperature Operational Resiliency of Layered Oxide Cathodes

The worldwide energy demand in electric vehicles and the increasing global temperature have called for development of high-energy and long-life lithium-ion batteries (LIBs) with improved high-temperature operational resiliency. However, current attention has been mostly focused on cycling aging at elevated temperature, leaving considerable gaps of knowledge in the failure mechanism, and practical control of abusive calendar aging and thermal runaway that are highly related to the eventual operational lifetime and safety performance of LIBs. Herein, using a combination of various in situ synchrotron X-ray and electron microscopy techniques, a multiscale understanding of surface structure effects involved in regulating the high-temperature operational tolerance of polycrystalline Ni-rich layered cathodes is reported. The results collectively show that an ultraconformal poly(3,4-ethylenedioxythiophene) coating can effectively prevent a LiNi_0.8 Co_0.1 Mn_0.1 O₂ cathode from undergoing undesired phase transformation and transition metal dissolution on the surface, atomic displacement, and dislocations within primary particles, intergranular cracking along the grain boundaries within secondary particles, and intensive bulk oxygen release during high state-of-charge and high-temperature aging. The present work highlights the essential role of surface structure controls in overcoming the multiscale degradation pathways of high-energy battery materials at extreme temperature.

Bragg Coherent Diffraction Imaging for In Situ Studies in Electrocatalysis

Electrocatalysis is at the heart of a broad range of physicochemical applications that play an important role in the present and future of a sustainable economy. Among the myriad of different electrocatalysts used in this field, nanomaterials are of ubiquitous importance. An increased surface area/volume ratio compared to bulk makes nanoscale catalysts the preferred choice to perform electrocatalytic reactions. Bragg coherent diffraction imaging (BCDI) was introduced in 2006 and since has been applied to obtain 3D images of crystalline nanomaterials. BCDI provides information about the displacement field, which is directly related to strain. Lattice strain in the catalysts impacts their electronic configuration and, consequently, their binding energy with reaction intermediates. Even though there have been significant improvements since its birth, the fact that the experiments can only be performed at synchrotron facilities and its relatively low resolution to date (∼10 nm spatial resolution) have prevented the popularization of this technique. Herein, we will briefly describe the fundamentals of the technique, including the electrocatalysis relevant information that we can extract from it. Subsequently, we review some of the computational experiments that complement the BCDI data for enhanced information extraction and improved understanding of the underlying nanoscale electrocatalytic processes. We next highlight success stories of BCDI applied to different electrochemical systems and in heterogeneous catalysis to show how the technique can contribute to future studies in electrocatalysis. Finally, we outline current challenges in spatiotemporal resolution limits of BCDI and provide our perspectives on recent developments in synchrotron facilities as well as the role of machine learning and artificial intelligence in addressing them.

Using In-Situ Laboratory and Synchrotron-Based X-ray Diffraction for Lithium-Ion Batteries Characterization: A Review on Recent Developments

Renewable technologies, and in particular the electric vehicle revolution, have generated tremendous pressure for the improvement of lithium ion battery performance. To meet the increasingly high market demand, challenges include improving the energy density, extending cycle life and enhancing safety. In order to address these issues, a deep understanding of both the physical and chemical changes of battery materials under working conditions is crucial for linking degradation processes to their origins in material properties and their electrochemical signatures. In situ and operando synchrotron-based X-ray techniques provide powerful tools for battery materials research, allowing a deep understanding of structural evolution, redox processes and transport properties during cycling. In this review, in situ synchrotron-based X-ray diffraction methods are discussed in detail with an emphasis on recent advancements in improving the spatial and temporal resolution. The experimental approaches reviewed here include cell designs and materials, as well as beamline experimental setup details. Finally, future challenges and opportunities for battery technologies are discussed.

Nanoscale Mapping of Heterogeneous Strain and Defects in Individual Magnetic Nanocrystals

We map the three-dimensional strain heterogeneity within a single core-shell Ni nanoparticle using Bragg coherent diffractive imaging. We report the direct observation of both uniform displacements and strain within the crystalline core Ni region. We identify non-uniform displacements and dislocation morphologies across the core–shell interface, and within the outer shell at the nanoscale. By tracking individual dislocation lines in the outer shell region, and comparing the relative orientation between the Burgers vector and dislocation lines, we identify full and partial dislocations. The full dislocations are consistent with elasticity theory in the vicinity of a dislocation while the partial dislocations deviate from this theory. We utilize atomistic computations and Landau–Lifshitz–Gilbert simulation and density functional theory to confirm the equilibrium shape of the particle and the nature of the (111) displacement field obtained from Bragg coherent diffraction imaging (BCDI) experiments. This displacement field distribution within the core-region of the Ni nanoparticle provides a uniform distribution of magnetization in the core region. We observe that the absence of dislocations within the core-regions correlates with a uniform distribution of magnetization projections. Our findings suggest that the imaging of defects using BCDI could be of significant importance for giant magnetoresistance devices, like hard disk-drive read heads, where the presence of dislocations can affect magnetic domain wall pinning and coercivity.

Coherent Bragg imaging of 60 nm Au nanoparticles under electrochemical control at the NanoMAX beamline

Nanoparticles are essential electrocatalysts in chemical production, water treatment and energy conversion, but engineering efficient and specific catalysts requires understanding complex structure-reactivity relations. Recent experiments have shown that Bragg coherent diffraction imaging might be a powerful tool in this regard. The technique provides three-dimensional lattice strain fields from which surface reactivity maps can be inferred. However, all experiments published so far have investigated particles an order of magnitude larger than those used in practical applications. Studying smaller particles quickly becomes demanding as the diffracted intensity falls. Here, in situ nanodiffraction data from 60 nm Au nanoparticles under electrochemical control collected at the hard X-ray nanoprobe beamline of MAX IV, NanoMAX, are presented. Two-dimensional image reconstructions of these particles are produced, and it is estimated that NanoMAX, which is now open for general users, has the requisites for three-dimensional imaging of particles of a size relevant for catalytic applications. This represents the first demonstration of coherent X-ray diffraction experiments performed at a diffraction-limited storage ring, and illustrates the importance of these new sources for experiments where coherence properties become crucial.