Voltage fade prevents effective use of the excess capacity and represents the most crucial technical challenge faced by Li-and Mn-rich cathode materials (LMR) in modern batteries.Although oxygen release has been arguably considered as an initiator for the failure mechanism, its prerequisite driving force has yet to be fully understood. Herein, relying on the in-situ nanoscale sensitive coherent X-ray diffraction imaging (BCDI) technique, we are able to track the dynamic structure evolution of the LMR cathode. The results, surprisingly, reveal that continuous nanostrain accumulation arose from lattice displacement in nano-domain structures during cell operation is the original driving force for detrimental structure degradations together with oxygen loss that triggers the well-known rapid voltage decay in LMR. By further leveraging primary to multi-particle structure and electrode-level as well as atomic scale observations, we demonstrate that the heterogeneous nature of the LMR cathode inevitably causes pernicious phase displacement which cannot be eliminated by the previous trials. With these fundamental discoveries, we propose the structural design strategy to mitigate the lattice displacement and inhomogeneous electrochemical/structural evolutions, thereby achieving stable voltage and capacity profiles. These findings highlight the significance of lattice displacement in voltage decay mechanism and will inspire a wave of efforts to unlock the potential of the broad-scale commercialization of LMR cathode material.

Mechanical integrity issues such as particle cracking are considered one of the leading causes of structural deterioration and limited long-term cycle stability for Ni-rich cathode materials of Li-ion batteries. Indeed, the detrimental effects generated from the crack formation are not yet entirely addressed. Here, applying physicochemical and electrochemical ex situ and in situ characterizations, the effect of Co and Mn on the mechanical properties of the Ni-rich material are thoroughly investigated. As a result, we successfully mitigate the particle cracking issue in Ni-rich cathodes via rational concentration gradient design without sacrificing the electrode capacity. Our result reveals that the Co-enriched surface design in Ni-rich particles benefits from its low stiffness, which can effectively suppress the formation of particle cracking. Meanwhile, the Mn-enriched core limits internal expansion and improve structural integrity. The concentration gradient design also promotes morphological stability and cycling performances in Li metal coin cell configuration.

The ID01 beamline has been built to combine Bragg diffraction with imaging techniques to produce a strain and mosaicity microscope for materials in their native or operando state. A scanning probe with nano-focused beams, objective-lens-based full-field microscopy and coherent diffraction imaging provide a suite of tools which deliver micrometre to few nanometre spatial resolution combined with 10−5 strain and 10−3 tilt sensitivity. A detailed description of the beamline from source to sample is provided and serves as a reference for the user community. The anticipated impact of the impending upgrade to the ESRF – Extremely Brilliant Source is also discussed.

Extensive efforts have been made to improve the Li‐ionic conductivity of solid electrolytes (SE) for developing promising all‐solid‐state Li‐based batteries (ASSB). Recent studies suggest that minimizing the existing interface problems is even more important than maximizing the conductivity of SE. Interfaces are essential in ASSB, and their properties significantly influence the battery performance. Interface problems, arising from both physical and (electro)chemical material properties, can significantly inhibit the transport of electrons and Li‐ions in ASSB. Consequently, interface problems may result in interlayer formation, high impedances, immobilization of moveable Li‐ions, loss of active host sites available to accommodate Li‐ions, and Li‐dendrite formation, all causing significant storage capacity losses and ultimately battery failures. The characteristic differences of interfaces between liquid‐ and solid‐type Li‐based batteries are presented here. Interface types, interlayer origin, physical and chemical structures, properties, time evolution, complex interrelations between various factors, and promising interfacial tailoring approaches are reviewed. Furthermore, recent advances in the interface‐sensitive or depth‐resolved analytical tools that can provide mechanistic insights into the interlayer formation and strategies to tailor the interlayer formation, composition, and properties are discussed.

Oxygen redox at high-voltage has emerged as a transformative paradigm for high-energy battery cathodes by offering extra capacity beyond conventional transition-metal redox. However, it suffers from voltage hysteresis, voltage fade, and capacity drop upon cycling. Here, we show that, by eliminating the domain boundaries in the often-considered single-crystalline battery particles, layered oxide cathodes demonstrate exceptional capacity and voltage stability during high-voltage operation. Our combined experimental and theory studies for the first time reveal that the elimination of domain boundaries could enhance the reversible lattice oxygen redox while inhibiting the irreversible oxygen release, leading to significantly suppressed structural degradation and improved mechanical integrity during battery cycling and abuse heating. The robust oxygen redox enabled through domain boundary control provides practical opportunities towards high-energy, long-cycling, and safe batteries. MainHigh-energy batteries rely on high-capacity and high-voltage operation of the cathodes.Fundamentally, the capacity of a transition metal oxide-based cathode is determined by the amount of active Li, while the voltage is defined by the redox reactions affected by structural configurations 1 . This has led to two associated trends in recent cathode development: Li-excess compounds due to the large amount of Li (capacity) and oxygen redox (OR) at high-voltage 2-6 .However, intensive studies have shown that OR activities can trigger detrimental structural effects such as oxygen release, surface reactions, and phase transition, leading to severe voltage hysteresis, voltage fade, and poor capacity stability 3,5 . Despite extensive mechanistic understanding 3,5 and material optimization such as structural control [7][8][9] , chemical composition manipulation 10 , and cationic/anionic doping [11][12][13] , the fundamental origin of the OR instability remains under active debate, and the practical control of high-voltage operation involving OR remains a formidable challenge. The key relies on a strategy that enhances the reversible OR in the lattice, while suppressing or even eliminating other detrimental oxygen activities.Theoretical studies suggest that the surface could favour the migration of oxygen ions and promote the formation of oxygen vacancies due to the open atomic structure [14][15][16] . Therefore, surface-initiated irreversible oxygen loss and the associated structural transformation have long been considered as the root cause of the capacity decay and voltage fade of Li-excess layered cathodes when activating the OR process [16][17][18] . However, surface coatings to mitigate the oxygen loss have proven insufficient to achieve a fully reversible OR 5,18,19 .Grain boundaries (GBs), the surface that separates individual grains from each other, play a vital role in materials' properties. In layered oxide cathodes, the GBs have been predominantly referred to the boundaries between primary particles of polycrystalline cathodes, while ...

We present density-functional theory calculations of the dehydrogenation of CH x (x = 1-4) on surfaces, where the Au atoms are substituted on the Ni surface with the ratio of Au atoms to the total stepped Ni atoms being 1 : 4, 1 : 2 and 3 : 4, respectively. To evaluate the role of Au at the step-edge on the process of methane dehydrogenation, CH x adsorption and dissociation on a pure Ni(211) surface is also conducted. Our results show that Au addition weakens the adsorbatesubstrate interaction. With the increase of the Au concentration, the binding energies of CH x gradually decrease and correlate well with the number of Au atoms on each model. On the Ni(211) surface, methane experiences a successive dehydrogenation process at the step-edge site in which carbon is eventually formed. As Au is introduced, the relative formation rate of carbon is greatly hampered even with a small amount of Au addition, while an appropriate amount of Au modification on the Ni catalyst has little effect on the activity of the CH x dissociation. Finally, we also demonstrate that the active center for CH x dissociation is dynamic with the variation of the Au concentration.

This article proposes two integration methods to determine the structure factors along a surface diffraction rod measured with a two‐dimensional detector. The first method applies the classic way of calculating integrated intensities in angular space. This is adapted to work efficiently with two‐dimensional data. The second method is based on integration in reciprocal space. An intensity map is created by converting the detected intensity pixel by pixel to the reciprocal space. The integration is then performed directly on this map. A theoretical framework, as well as a comparison between the two integration methods, is provided.

Hybrid perovskites have attracted much attention as promising photovoltaic materials in the past few years. However, the fundamental understanding of their crystallization behavior lags far behind the pace of empirical solar cell efficiency improvement. Methylammonium iodide (MAPbI 3 ) is a widely studied reference compound whose solar cell performance can be improved by chloride addition (e.g., in the form of PbCl 2 ) during the thin-film preparation. Because of the large difference in the ionic radii of both halides, no mixed perovskites MAPbI 3−x Cl x are formed and generally only minute amounts of chlorine can be detected in the final MAPbI 3 thin films. Here, we demonstrate by means of a variety of complementary X-ray diffraction (XRD) techniques that, unexpectedly, the formation mechanism proceeds via an initial MAPbCl 3 layer, which subsequently transforms to MAPbI 3 in an anion exchange reaction during the thermal annealing step, completing the thin-film preparation. The perovskite lattice is highly strained along the process, much more than what is expected from the sole effect of the difference between the thermal expansion coefficients of the perovskite and the substrate. At room temperature, the existence of a double [hh0]/[00l] texture is explained by the ferroelastic character of the cubic/tetragonal transition of MAPbI 3 , which induces the formation of twins. The relative population of these domains is correlated to their strain level. Although strain is known to weaken the stability of the MAPbI 3 phase, our results unambiguously show that it also favors the reproducibility of the thin-film microstructure. When used as active layers in solar cells, the dependence of the cell efficiency and stability on the annealing time is in striking accordance with the formation kinetics of MAPbI 3 , as revealed by the XRD measurements. Therefore, the understanding of the crystallization behavior achieved with the present approach, applicable also to other types of metal halide perovskites, allows for the rational optimization of the device performance and long-term stability.