Exploring battery material failure mechanisms through synchrotron X-ray characterization techniques

Rechargeable battery cycling performance and related safety have been persistent concerns.It is crucial to decipher the capacity fading induced by electrode material failure via a range of techniques.Among these,synchrotron-based X-ray techniques with high flux and brightness play a key role in understanding degradation mechanisms.In this comprehensive review,we summarize recent advancements in degra-dation modes and mechanisms that were revealed by synchrotron X-ray methodologies.Subsequently,an overview of X-ray absorption spectroscopy and X-ray scattering techniques is introduced for charac-terizing failure phenomena at local coordination atomic environment and long-range order crystal struc-ture scale,respectively.At last,we envision the future of exploring material failure mechanism.

Development of High-Pressure Multigrain X-Ray Diffraction for Exploring the Earth’s Interior

The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching;thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 lm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications.

Fast synchrotron X-ray tomography study of the packing structures of rods with different aspect ratios

We present a fast synchrotron X-ray tomography study of the packing structures of rods with different aspect ratios. Utilizing the high flux of the X-rays generated from the third-generation synchrotron source, we can complete a high- resolution tomography scan within a short period of time, after which the three-dimensional （3D） packing structure can be obtained for the subsequent structural analysis. The image phase-retrieval procedure has been implemented to enhance the image contrast. We systematically investigated the effects of particle shape and aspect ratio on the structural properties including packing density and contact number. It turns out that large aspect ratio rod packings will have wider distributions of free volume fraction and larger mean contact numbers.

Understanding fluorine-free electrolytes via small-angle X-ray scattering

Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here,we compare the solvation phenomenon of sodium tetraphenylborate(NaBPh_(4)) salt dissolved in organic solvents of propylene carbonate(PC), 1,2-dimethoxyethane(DME), acetonitrile(ACN) and tetrahydrofuran(THF). Small-angle X-ray scattering(SAXS) reveals a unique two-peak structural feature in this saltconcentrated PC electrolyte, while solutions using other solvents only have one scattering peak.Molecular dynamics(MD) simulations further reveal that there are anion-based clusters in addition to the short-range charge ordering in the concentrated NaBPh4/PC electrolyte. Raman spectroscopy confirms the existence of considerable contact ion pairs(CIPs). This work emphasizes the importance of global and local structural analysis, which will provide valuable clues for understanding the structureperformance relationship of electrolytes.

Temperature-dependent constitutive modeling of a magnesium alloy ZEK100 sheet using crystal plasticity models combined with in situ high-energy X-ray diffraction experiment

A multiscale crystal plasticity model accounting for temperature-dependent mechanical behaviors without introducing a larger number of unknown parameters was developed.The model was implemented in elastic-plastic self-consistent(EPSC)and crystal plasticity finite element(CPFE)frameworks for grain-scale simulations.A computationally efficient EPSC model was first employed to estimate the critical resolved shear stress and hardening parameters of the slip and twin systems available in a hexagonal close-packed magnesium alloy,ZEK100.The constitutive parameters were thereafter refined using the CPFE.The crystal plasticity frameworks incorporated with the temperature-dependent constitutive model were used to predict stress–strain curves in macroscale and lattice strains in microscale at different testing temperatures up to 200℃.In particular,the predictions by the crystal plasticity models were compared with the measured lattice strain data at the elevated temperatures by in situ high-energy X-ray diffraction,for the first time.The comparison in the multiscale improved the fidelity of the developed temperature-dependent constitutive model and validated the assumption with regard to the temperature dependency of available slip and twin systems in the magnesium alloy.Finally,this work provides a time-efficient and precise modeling scheme for magnesium alloys at elevated temperatures.

Bulk preparation of free-standing single-iron-atom catalysts directly as the air electrodes for high-performance zinc-air batteries

The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.

Towards extreme fast charging of 4.6 V LiCoO_(2) via mitigating high-voltage kinetic hindrance

High-voltage LiCoO_(2)(LCO) is an attractive cathode for ultra-high energy density lithium-ion batteries(LIBs) in the 3 C markets.However,the sluggish lithium-ion diffusion at high voltage significantly hampers its rate capability.Herein,combining experiments with density functional theory(DFT) calculations,we demonstrate that the kinetic limitations can be mitigated by a facial Mg^(2+)+Gd^(3+)co-doping method.The as-prepared LCO shows significantly enhanced Li-ion diffusion mobility at high voltage,making more homogenous Li-ion de/intercalation at a high-rate charge/discharge process.The homogeneity enables the structural stability of LCO at a high-rate current density,inhibiting stress accumulation and irreversible phase transition.When used in combination with a Li metal anode,the doped LCO shows an extreme fast charging(XFC) capability,with a superior high capacity of 193.1 mAh g^(-1)even at the current density of 20 C and high-rate capacity retention of 91.3% after 100 cycles at 5 C.This work provides a new insight to prepare XFC high-voltage LCO cathode materials.

Adult dental epithelial stem cell-derived organoids deposit hydroxylapatite biomineral

Ameloblasts are specialized cells derived from the dental epithelium that produce enamel,a hierarchically structured tissue comprised of highly elongated hydroxylapatite(OHAp)crystallites.The unique function of the epithelial cells synthesizing crystallites and assembling them in a mechanically robust structure is not fully elucidated yet,partly due to limitations with in vitro experimental models.Herein,we demonstrate the ability to generate mineralizing dental epithelial organoids(DEOs)from adult dental epithelial stem cells(aDESCs)isolated from mouse incisor tissues.DEOs expressed ameloblast markers,could be maintained for more than five months(11 passages)in vitro in media containing modulators of Wnt,Egf,Bmp,Fgf and Notch signaling pathways,and were amenable to cryostorage.When transplanted underneath murine kidney capsules,organoids produced OHAp crystallites similar in composition,size,and shape to mineralized dental tissues,including some enamel-like elongated crystals.DEOs are thus a powerful in vitro model to study mineralization process by dental epithelium,which can pave the way to understanding amelogenesis and developing regenerative therapy of enamel.

磁控功能合金功能行为的原位表征——高能X射线与中子衍射技术

报道了课题组在国际上率先开展利用同步辐射高能X射线衍射和中子衍射技术,成功地实现了多场(温度场,磁场,应力场)耦合作用下,铁磁性记忆合金微结构、晶粒取向、磁结构、母相与变体取向及其与功能行为耦合的原位研究。利用原位飞行时间中子衍射技术,跟踪了铁磁性形状记忆合金Ni-Mn-Ga在单轴压力下马氏体变体的转变行为,这是目前其它方法(如EBSD)仍无法实现的。测试了M_s点为393K的Ni_(47)Mn_(25)Ga_(22)Co_4合金在不同的单轴压力(0,-60MPa,-110MPa,-140MPa,-7MPa)下从523～298K之间的中子衍射花样,并利用GSAS软件获得了不同单轴压力下马氏体相的反极图(IPFs)。利用高能球磨及后续热处理的方法制备出了Ni_(51)Mn_(27)Ga_(22)纳米颗粒。铁磁性Ni_2MnGa纳米颗粒功能行为受晶粒尺寸,原子有序度及固有磁结构交互作用的影响,经历了各种不同的结构转变序,这与它们相应的块体材料是完全不同的。通过高能球磨法制备出尺寸分布均匀约10 nm左右的Ni_(51)Mn_(27)Ga_(22)颗粒,其室温晶体结构由原始的体心四方结构转变为一种无序面心立方结构。高能球磨后的纳米颗粒经过623K,4h退火后,又完全转变为Heusler母相结构。利用高能X射线研究了该纳米颗粒在退火过程中结构的原位转变,证明转变动力学由一种具有非晶结构的中间相控制。高能球磨及后续热处理之后的纳米粒子,在约274K下转变为调制马氏体(14M)结构,并且该结构可以稳定到4K。

MOF-Transformed In_(2)O_(3-x)@C Nanocorn Electrocatalyst for Efficient CO_(2)Reduction to HCOOH

For electrochemical CO_(2) reduction to HCOOH,an ongoing challenge is to design energy efficient electrocatalysts that can deliver a high HCOOH current density(JHCOOH)at a low overpotential.Indium oxide is good HCOOH production catalyst but with low con-ductivity.In this work,we report a unique corn design of In_(2)O_(3-x)@C nanocatalyst,wherein In_(2)O_(3-x)nanocube as the fine grains dispersed uniformly on the carbon nanorod cob,resulting in the enhanced conductivity.Excellent performance is achieved with 84%Faradaic efficiency(FE)and 11 mA cm^(−2)JHCOOH at a low potential of−0.4 V versus RHE.At the current density of 100 mA cm^(−2),the applied potential remained stable for more than 120 h with the FE above 90%.Density functional theory calculations reveal that the abundant oxygen vacancy in In_(2)O_(3-x) has exposed more In^(3+) sites with activated electroactivity,which facilitates the formation of HCOO*intermediate.Operando X-ray absorp-tion spectroscopy also confirms In^(3+) as the active site and the key intermediate of HCOO*during the process of CO_(2) reduction to HCOOH.

Insights into Ti doping for stabilizing the Na_(2/3)Fe_(1/3)Mn_(2/3)O_(2)cathode in sodium ion battery

Iron-and manganese-based layered metal oxides,as cathodes for sodium ion batteries,have received widespread attention because of the low cost and high specific capacity.However,the Jahn-teller effect of Mn^(3+)ions and the resulted unstable structure usually lead to continuously capacity decay.Herein,Titanium(Ti)has been successfully doped into Na_(2/3)Fe_(2/3)Mn_(2/3)O_(2)to suppress the Jahn-Teller distortion and improve both cycling and rate performance of sodium ion batteries.In situ high-energy synchrotron X-ray diffraction study shows that Ti-doped compound(Na_(2/3)Fe_(1/3)Mn_(0.57)Ti_(0.1)O_(2))can maintain the single P2 phase without any phase transition during the whole charging/discharging process.Various electrochemical characterizations are also applied to explore the better kinetics of sodium ions transfer in the Na_(2/3)Fe_(1/3)Mn_(0.5)7 Ti_(0.1)O_(2).This work provides a comprehensive insight into the Ti-doping effects on the performance from both structural and electro kinetic perspectives.

Highly active and stable Co nanoparticles embedded in nitrogen-doped mesoporous carbon nanofibers for aqueous-phase levulinic acid hydrogenation

Developing a highly active and durable non-noble metal catalyst for aqueous-phase levulinic acid(LA)hydrogenation to g-valerolactone(GVL)is an appealing yet challenging task.Herein,we report well-dispersed Co nanoparticles(NPs)embedded in nitrogen-doped mesoporous carbon nanofibers as an efficient catalyst for aqueous-phase LA hydrogenation to GVL.The Co zeolitic imidazolate framework(ZIF-67)nanocrystals were anchored on the sodium dodecyl sulfate modified wipe fiber(WF-S),yielding one-dimensional(1-D)structured composite(ZIF-67/WF-S).Subsequently,Co NPs were uniformly embedded in nitrogen-doped mesoporous carbon nanofibers(Co^(R)NC/SMCNF)through a pyrolysis-reduction strategy using ZIF-67/WF-S as the precursor.Benefiting from introducing modified wipe fiber WF-S to enhance the dispersion of Co NPs,and Co^(0) with Co-N_xdual active sites,the resulting Co^(R)NC/SMCNF catalyst shows brilliant catalytic activity(206 h^(-1) turnover frequency).Additionally,the strong metal-support interactions greatly inhibited the Co NPs from aggregation and leaching from the mesoporous carbon nanofibers,and thus increasing the reusability of the Co^(R)NC/SMCNF catalyst(reusable nine times without notable activity loss).

Crystallography of low Z material at ultrahigh pressure:Case study on solid hydrogen

Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensedmatter.However,the onlyway to determine crystal structures of materials above 100 GPa,namely,X-ray diffraction(XRD),especially for lowZ materials,remains nontrivial in the ultrahigh-pressure region,even with the availability of brilliant synchrotron X-ray sources.In thiswork,we performa systematic study,choosing hydrogen(the lowest X-ray scatterer)as the subject,to understand how to better perform XRD measurements of low Z materials at multimegabar pressures.The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254GPa at room temperature[C.Ji et al.,Nature 573,558–562(2019)].Wepresent our discoveries and experienceswith regard to several aspects of thiswork,namely,diamond anvil selection,sample configuration for ultrahigh-pressure XRDstudies,XRDdiagnostics for low Z materials,and related issues in data interpretation and pressure calibration.Webelieve that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures,eventually testing structural models of metallic hydrogen.

Controlled high-density interface engineering of Fe_(3)O_(4)-FeS nanoarray for efficient hydrogen evolution

The rational design of double active sites system is vital for constructing high-efficiency iron sulfides electrocatalysts towards hydrogen evolution reaction(HER) in alkaline media. However, it remains a challenge to controllably create the high-density interface of double sites for optimal synergistic effect.Herein, we reported a simple chemical oxidation-induced surface reconfiguration strategy to obtain the interface-rich Fe_(3)O_(4)-FeS nanoarray supported on iron foam(Fe_(3)O_(4)-FeS/IF) using FeS nanosheets as precursors. The abundant Fe_(3)O_(4)-FeS interfaces could improve the dispersion of active sites and facilitate the electron transfer, leading to enhanced hydrogen evolution efficiency. And meanwhile, by altering the oxidation temperature, the content of S and O could be effectively controlled, further achieving the ratio optimization of Fe_(3)O_(4)to FeS. Synchrotron-based X-ray absorption near-edge structure, X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy consistently confirm the changes of electronic structure and d-band center of Fe_(3)O_(4)-FeS after chemical oxidation. Consequently, Fe_(3)O_(4)-FeS/IF exhibits excellent alkaline HER activity with a low overpotential of 120.8 mV to reach 20 mA cm^(-2),and remains stable ranging from 10, 20 to 50 mA cm^(-2) for each 20 h, respectively. Therefore, the facile and controllable chemical oxidation may be an effective strategy for designing high-density interfaces of transition metal-based sulfides towards alkaline HER.

An advanced low-cost cathode composed of graphene-coated Na_(2.4)Fe_(1.8)(SO_(4))_(3) nanograins in a 3D graphene network for ultra-stable sodium storage

Iron-based electrodes have attracted great attention for sodium storage because of the distinct cost effectiveness.However,exploring suitable iron-based electrodes with high power density and long duration remains a big challenge.Herein,a spray-drying strategy is adopted to construct graphene-coated Na_(2.4)Fe_(1.8)(SO_(4))_(3) nanograins in a 3D graphene microsphere network.The unique structural and compositional advantages endow these electrodes to exhibit outstanding electrochemical properties with remarkable rate performance and long cycle life.Mechanism analyses further explain the outstanding electrochemical properties from the structural aspect.

Grain size and structure distortion characterization of α-MgAgSb thermoelectric material by powder diffraction

Nanostructuring, structure distortion, and/or disorder are the main manipulation techniques to reduce the lattice thermal conductivity and improve the figure of merit of thermoelectric materials. A single-phase α-MgAgSb sample, MgAg0.97Sb0.99, with high thermoelectric performance in near room temperature region was synthesized through a high-energy ball milling with a hot-pressing method. Here, we report the average grain size of 24–28 nm and the accurate structure distortion, which are characterized by high-resolution neutron diffraction and synchrotron x-ray diffraction with Rietveld refinement data analysis. Both the small grain size and the structure distortion have a contribution to the low lattice thermal conductivity in MgAg0.97Sb0.99.

Solvation Structure and Dynamics of Mg(TFSI)_(2) Aqueous Electrolyte

Using ab initio molecular dynamics(AIMD)simulations,classical molecular dynamics(CMD)simulations,small-angle X-ray scattering(SAXS),and pulsed-field gradient nuclear magnetic resonance(PFG-NMR),the solvation structure and ion dynamics of magnesium bis(trifluoromethanesulfonyl)imide(Mg(TFSI)_(2))aqueous electrolyte at 1,2,and 3 m concentrations are investigated.From AIMD and CMD simulations,the first solvation shell of an Mg;ion is found to be composed of six water molecules in an octahedral configuration and the solvation shell is rather rigid.The TFSI^(-)ions prefer to stay in the second solvation shell and beyond.Meanwhile,the comparable diffusion coefficients of positive and negative ions in Mg(TFSI)_(2)aqueous electrolytes have been observed,which is mainly due to the formation of the stable[Mg(H_(2)O_(6))_(2)]^(+)complex,and,as a result,the increased effective Mg ion size.Finally,the calculated correlated transference numbers are lower than the uncorrelated ones even at the low concentration of 2 and 3 m,suggesting the enhanced correlations between ions in the multivalent electrolytes.This work provides a molecular-level understanding of how the solvation structure and multivalency of the ion affect the dynamics and transport properties of the multivalent electrolyte,providing insight for rational designs of electrolytes for improved ion transport properties.

Concurrent multi-peak Bragg coherent x-ray diffraction imaging of 3D nanocrystal lattice displacement via global optimization

In this paper we demonstrated a method to reconstruct vector-valued lattice distortion fields within nanoscale crystals by optimization of a forward model of multi-reflection Bragg coherent diffraction imaging(MR-BCDI)data.The method flexibly accounts for geometric factors that arise when making BCDI measurements,is amenable to efficient inversion with modern optimization toolkits,and allows for globally constraining a single image reconstruction to multiple Bragg peak measurements.This is enabled by a forward model that emulates the multiple Bragg peaks of a MR-BCDI experiment from a single estimate of the 3D crystal sample.We present this forward model,we implement it within the stochastic gradient descent optimization framework,and we demonstrate it with simulated and experimental data of nanocrystals with inhomogeneous internal lattice displacement.We find that utilizing a global optimization approach to MR-BCDI affords a reliable path to convergence of data which is otherwise challenging to reconstruct.

Goss Texture Evolution of Grain Oriented Silicon Steel by High-Energy X-ray Diffraction

High energy synchrotron diffraction offers great potential to study the recrystallization kinetics of metallic materials. To study the formation of Goss texture （{ [10}（001）） of grain oriented （GO） silicon steel during secondary recrystallization process, an in situ experiment using hi gh energy X-ray diffraction was designed. The results showed that the secondary recrystallization began when the heating temperature was 1,494 K, and the grains grew rapidly above this temperature. With an increase in annealing temperature, the large grains with 7 orientation [〈111〉//normal direction] formed and gradually occupied the dominant position. As the annealing temperature increased even further, the grains with Goss orientation to a very large size by devouring the 7 orientation grains that formed in the early annealing stage. A single crystal with a Goss orientation was observed in the GO silicon steel when the annealing temperature was 1,540 K.

In-Situ Annealing Study of Transformation of α and γ Texture of Interstitial-Free Steel Sheet by High-Energy X-Ray Diffraction

High-energy synchrotron diffraction offers great potential for experimental study of recrystallization kinetics. An experimental design to study the recrystallization mechanism of interstitial-free （IF） steel was implemented. The whole annealing process of cold-rolled IF steel with 80% reduction was observed in situ using high-energy X-ray diffraction （HEXRD）. The results show how the main texture component of IF steel change, i.e. the α [∥rolling direction （RD）] fiber texture decreases and the γ [∥normal direction （ND）] fiber texture increases. The important part of the α fiber texture is that both the {100} and {112} texture decrease at the beginning of recrystallization. The γ fiber texture increases at the early stage of recrystallization which stems from the increase of {111}. Nevertheless, the {111} does not change after recrystallization. The dynamic evolution of the main texture components {100}, {112}, {111} and {111} is given by in-situ HEXRD.