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• A generalized shear band toughness is proposed to characterize energy dissipation. • Both thermal softening and microstructure-related softening are involved. • Generalized shear band toughness is estimated using temperature fields. • Dual-stage and energy-based criterion is crucial to predict shear band propagation. The adiabatic shear band (ASB) criterion is crucial for assessing the shear failure resistance of metals and alloys under dynamic loading. While the critical shear strain obtained from macroscopic stress–strain curves has been widely employed to predict ASB nucleation , it cannot describe the subsequent ASB evolution process, which occurs at extreme spatial (∼µm) and temporal (∼µs) scales. In this work, we introduce a generalized shear band toughness to characterize the post-localization energy dissipation within the band, which can be estimated from temperature fields captured by high-speed, high-resolution infrared thermal detectors. The generalized shear band toughness model accounts for contributions from both thermal softening and microstructure-related softening mechanisms in ASB evolution. We systematically characterize the shear band toughness across a range of materials, from conventional alloys to advanced high-entropy alloys. Finally, the shear band toughness is incorporated into a dual-stage, energy-based shear banding criterion, which proves crucial for accurately predicting the entire shear banding process, particularly in scenarios involving dynamic shear band propagation in large structures. [ABSTRACT FROM AUTHOR]

With the variation of thickness and composition, the color of the nanosilicon film electrode in lithium ion batteries would be changed during lithium ion intercalation and deintercalation. Based on such phenomenon, here we present a method for evaluating the two-dimensional lithium ion concentration in the nanosilicon film. In the demonstration of a silicon film with thickness ∼115 nm, the correlation between tristimulus values and lithium ion concentration is established. In a piece of a large silicon film, the inhomogeneous lithium ion concentration could be obtained, highlighting a fast and noncontact method for in situ observation and analyses of the kinetic process of ion intercalation and deintercalation in nanosilicon films. [ABSTRACT FROM AUTHOR]

Silicon film with pre-crack was used to study the coupling effect of stress and electrochemical field around the crack tip. The in-situ experiments were established to monitor the crack to realize the stress concentration around the crack and simultaneously prevent the crack initiation. The ex-situ Auger electron spectroscopy experiments shown the remarkably Li redistributed phenomenon around the crack tip. Furthermore, the fully coupled finite element method was used to reveal the fundamental mechanisms of the Li gathering effect and the stress relaxation phenomenon around the crack tip. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Mechanical failure is an important reason for electrode degradation, especially for the anodes with large volume change during the electrochemical cycles. Plenty of studies prove that nanostructure materials under the critical size would significantly improve the stability of the electrodes. The commercial electrodes are inevitable defective during preparation, and the defect induced fractures will reduce the critical size. However, the mechanisms of this phenomenon are still unclear and lack of the support of precise experiments. In the present study, silicon islands under critical size are prepared and different types of defects with various curvatures are designed in the island electrodes. The in-situ experiments are employed to observe crack appearance, and the defects with higher curvatures are found to fail earlier than the others. Furthermore, the finite element analysis is used to quantitatively calculate the stress evolution around each defect. The results also show that the safe (no fracture) area of the electrodes is reduced by the defects with high curvature, and the critical failure state of charge could be obtained by the experiments and simulation data. Highlights • Silicon islands with defects were prepared to study the defect induce failure. • In-situ optical system was used to observe crack appearance. • Stress evolution around the defect was calculated by finite element simulations. [ABSTRACT FROM AUTHOR]

An in situ optical system was used to observe the failure processes of two-dimensional silicon film anodes, suggesting a new debonding mode based on crack crushing. The stress evolution upon lithiation was quantitatively analyzed via fully coupled finite element simulations, confirming the crack crushing induced failure mechanisms in 2D silicon anodes. [ABSTRACT FROM AUTHOR]

Elucidating the mechanical forces between two solid surfaces immersed in a communal liquid environment is crucial for understanding and controlling adhesion, friction, and electrochemistry in many technologies. Although traditional models can adequately describe long-range mechanical forces, they require substantial modifications in the nanometric region where electronic effects become important. A hybrid quantum–classical model is employed herein to investigate the separation-dependent disjoining pressure between two metal surfaces immersed in an electrolyte solution under potential control. We find that the pressure between surfaces transits from a long-range electrostatic interaction, attractive or repulsive depending on the charging conditions of surfaces, to a strong short-range van der Waals attraction and then an even strong Pauli repulsion due to the redistribution of electrons. The underlying mechanism of the transition, especially the attractive–repulsive one in the short-range region, is elucidated. This work contributes to the understanding of electrotunable friction and lubrication in a liquid environment. [ABSTRACT FROM AUTHOR]

Mechanical degradation generated by crack nucleation and pulverization can lead to the capacity fade in lithium-ion batteries, which has been attributed to diffusion-induced stress inside battery electrodes in recent years. However, not much attention has been directly taken to the models of diffusion-induced stress for anisotropic electrodes. In this work, we develop an analytical model of diffusion-induced stress for spherically isotropic elastic electrodes under potentiostatic and galvanostatic operation. It is shown that the stresses depend strongly on the lithiation expansion coefficient ratio and the elastic modulus ratio of tangential direction to radial direction. The stresses have the different evolution under potentiostatic and galvanostatic control, but have a common feature that they are all affected by the initial condition. From the standpoint of mechanics, our results indicate that extracting more lithium before lithiation (or inserting lower lithium before delithiation) is a good strategy to minimize stress and thus enhance capacity retention for spherically isotropic electrodes. [ABSTRACT FROM AUTHOR]

Abstract: A moving polarization saturation (PS) model is proposed to study the plane problem of a Yoffe-type crack moving with constant velocity in ferroelectric materials considering electric saturation. Based on the extended Stroh formalism, the model is solved using complex function method. The closed-form expressions for the electroelastic fields are obtained in a concise way. Results are shown to converge to known solutions for static PS model and the moving linear piezoelectric model. Numerical results for PZT-5H material are given graphically. It can be deducted that the dynamic intensity factors are dependent of the electric field and the velocity. It predicts that crack propagation may be promoted by a positive applied electrical field and inhibited by the negative one. For high crack velocity, 0.28 times minimum body wave speed, the hoop stress is maximal for an angle . [Copyright &y& Elsevier]

Shear lag model for fiber-reinforced plastics (FRP) composite simply supported II-beams under bending loads was put forward using the energy method. Two pultruded FRP composite simply supported II-beams under three cases of loads were studied with finite element analysis (FEA) and experimental methods to validate the present model. Finally, parametric studies on the shear lag coefficients were presented. It was concluded that the present model of this article agrees closely with the FEA results and the experimental results. [ABSTRACT FROM PUBLISHER]

Extending the polarization saturation (PS) model and Yoffe crack model for ferroelectric materials, a moving PS model is proposed to study the problems of crack propagation considering the electrical nonlinearity. The model is solved using continuous distribution dislocation method. And the explicit expressions of the size of the electric saturation zone, intensity factors and the local energy release rate for the moving PS model are derived. It can be deducted from this model that the intensity factors and the size of the electric saturation zone are independent of the velocity of the crack. The local energy release rate for the moving PS model has the form of that for a stationary crack multiplied by the local energy release rate universal function f( v). And it increases monotonically with increasing v. When the velocity of the crack v → 0, the moving PS model will reduce to the static PS model. When the size of the electric saturation zone r → 0, the moving PS model is in agreement with the moving linear piezoelectric model. [ABSTRACT FROM AUTHOR]

Abstract: The transient response of a semi-infinite mode-III interfacial crack propagating between piezoelectric (PE) and piezomagnetic (PM) half spaces is investigated in this paper. The integral transform method together with the Wiener–Hopf and Cagniard–de Hoop techniques is used to solve the mixed boundary value problem under consideration. The existence of generalized Maerfeld–Tournois interfacial wave is discussed and the solutions of the coupled fields are derived for four different cases of bulk shear wave velocity. The dynamic intensity factors of stress, electric displacement and magnetic induction as well as energy release rate (ERR) are obtained in explicit forms. The numerical results of the universal functions and dimensionless ERR for several different material combinations are presented and discussed in details. It is found that the Bleustein–Gulyaev (generalized Maerfeld–Tournois) waves dominate the dynamic characteristics of the interfacial crack propagation in PE–PM bi-material. [Copyright &y& Elsevier]

Promoting interfacial kinetics of high‐nickel LiNi0.8Mn0.1Co0.1O2 (NMC811) is a critical strategy for enhancing rate capability of lithium‐ion batteries (LIBs). At the solid‐liquid interface of positive electrode, charge transfer across the cathode‐electrolyte interphase (CEI) is responsible for the interfacial redox reaction, which is dominated by desolvation process of Li+ and NMC811 CEI evolution. Since these two processes are significantly impacted by the solvation effect of electrolytes, herein single‐particle Raman spectroscopy and single‐particle probes are established to quantitatively study the influences of solvation effect on CEI evolution and desolvation process of Li+, respectively. Owing to oxidation of the unstable free cyclic carbonate ester from dissociation of solvation structure, the CEI is found to grow thicker during discharge process. Due to the decreased concentration of cyclic carbonate in the solvation structure, the desolvation process of Li+ in the ethyl methyl carbonate‐ethylene carbonate electrolyte can be reduced by 11.8% compared to that in the dimethyl carbonate‐ethylene carbonate electrolyte. With the presence of ethyl methyl carbonate‐ethylene carbonate electrolyte, thinner CEI and easier desolvation process of Li+ can be simultaneously achieved on the NMC811 surface. Accordingly, its corresponding LIBs deliver the highest specific capacity ≈138.8 mAh g−1 at 5C among the LIBs with the other commonly used electrolytes. [ABSTRACT FROM AUTHOR]

Cyclic electric loading induced heat in ferroelectric materials may affect their applications. In this letter, an in-situ non-contact and full-field experimental method was proposed to monitor temperature with a 50 Hz infrared thermal camera. Test results in one bipolar electric loading cycle showed that the heat generation occurs as soon as polarization reversal finishes and is on the order of 500 × 103 J/m3. Due to the competition between the rate-dependent domain switching and the heat convention, it is interesting to note that under some specific electric loadings, heat generation first slightly increases and then decreases with the frequency, and even approaches zero at 200 Hz. [ABSTRACT FROM AUTHOR]

• A chemo-mechanical model is established to study the size effect of nanosphere electrodes. • Surface stress-dependent diffusivity reduces with decreasing the size of electrodes ascribed to the strong effects of surface stress. • Surface stress has a significant impact on higher lithiation of nanoelectrodes on the near-surface region. The experimental evidence suggests that the lithium ions tend to aggregate on the near-surface of nanoscale electrode particles in lithium-ion batteries. However, the underlying mechanism has not been well understood. In this work, based on the established chemo-mechanical coupled model featuring surface stress, stress-dependent chemical potential, and stress-mediated diffusivity, the size-dependence of diffusion kinetics in nanosphere electrodes is investigated. The results show that additional compressive stresses caused by the surface stress retard the attainable lithiation due to the reduced surface stress-dependent diffusivity, and the high lithiation region has a growing tendency to move on the near-surface region with decreasing the dimensions of nanospheres. The work indicates that the effects of surface stress on lithium-ion diffusion kinetics may result in the capacitor-like behavior of battery materials consisting of electrode nanoparticles. Image, graphical abstract [ABSTRACT FROM AUTHOR]

LiNi0.8Co0.1‐Mn0.1O2 (NMC811) is widely used in high energy density lithium‐ion batteries, while dynamic variation of liquid‐solid interface induced by oxygen release/evolution results in unexpected performance decay. Surface coating is an effective strategy in promoting the stability of NMC811 materials, and both coating composition and nanostructure arrangement would substantially impact the dynamic variation of liquid‐solid interfaces. To understand such dynamic variation, here evolution and stability of two selected NMC811 materials coated with oxides (the same oxide composition but different nanostructure arrangements) are compared, i.e., concentration uniform core‐shell NMC811 (CUCS811) and concentration gradient core‐shell NMC811 (CGCS811). The gas evolution from the home‐setup operando gas monitors (at 45 and 65 °C) implies that CUCS811 presents more operation and thermal stability because of less amount of CO2 and CH4 along with prolonged interval time in gas production. Composition variation of interfaces indicates that CUCS811 presents more stable interfacial evolution behaviors since more F‐ and P‐rich species for stabilizing the solid‐electrolyte interfaces are detected. The stability analysis suggests that uniform arrangement of Al2O3 and boride in the coating is prone to prevent the interface from degradation upon dynamic interface variation, which is useful in promoting the performance stability of NMC811 positive electrode materials. [ABSTRACT FROM AUTHOR]

As a typical failure behavior, the dynamic fracture is critical for material safety assessment and design, whose rapid evolution in the crack tip over a short time causes tremendous challenges in characterizing the evolution of the local temperature field. Although researchers have pointed out that temperature significantly affects fracture toughness, the temperature rise and the role of thermal softening in the crack tip region during the dynamic crack initiation need to be clarified. This work aims to evaluate the temperature rise effect at crack initiation in TC4 (Ti-6Al-4V) alloy under impact loading. We developed a thermal-mechanical coupled in-situ measurement system to obtain synchronized COD (crack-tip opening displacement) and temperature field evolution for the dynamic mode I fracture with high temporal and spatial resolution. The evolution of synchronous COD and temperature field during crack initiation under dynamic loading was investigated. The corresponding simulation was conducted to analyze the thermal softening effect at dynamic crack initiation. In TC4 alloy, the maximum temperature detected at crack initiation is about 130 °C, and the thermal effect on the material property is minor. The results of this work fulfill data support for investigating the coupled thermal-mechanical fracture behavior of metal. [ABSTRACT FROM AUTHOR]

The relationship between interface structure (e. g., the facet of the solid phase and the configuration of solvation) and the reactivity of the corresponding electrode is a critical issue in electrochemistry. Compared to macroscopic electrode measurements, electrochemical methods established on the single‐particle scale have advantages in establishing the structure‐property relationship. In recent years, great achievements have been made in electrochemical energy storage and electrocatalysis that allow the evolution and kinetics of electrodes to be understood by employing single‐particle measurements. This concept aims to provide an overview of the update of single‐particle measurements in related electrochemical processes. Furthermore, the challenges and prospects for the development and application of single‐particle measurements are also discussed. [ABSTRACT FROM AUTHOR]

Diffusion-induced stress can result in failure of layered electrodes in lithium-ion batteries during the process of fast lithiation and delithiation. Recent studies have demonstrated that the electro-chemo-mechanical properties of compositions-gradient nanoparticles are superior to those of homogeneous ones. In light of this aspect, we develop a theoretical model to probe the effects of composition-gradient on the stress evolution in layered electrodes. Our analysis concludes that, compared with the corresponding homogeneous structure, symmetrical negative-exponent gradient active plates or positive-exponent gradient bilayer electrodes can significantly reduce the maximum compressive stress and the stress drop at the electrode–collector interface, while the energy release rate of interface delamination is slightly weakened by it. These results, again, show that the composition-gradient could improve the mechanical performance of electrodes in lithium-ion batteries, and are instrumental to the design of electrode structures. [ABSTRACT FROM AUTHOR]

The calendering process, which is a common compaction technique, serves as the final step in the manufacturing of lithium-ion battery electrodes. Calendering plays an irreplaceable role in enhancing the volumetric energy density and electrochemical performance due to the densification of pore structure. To investigate the densification of active particles, this study designs and develops a micro-CT loading device, which can capture the in-situ evolution during the electrode compression. By combining the in-situ CT with discrete element method (DEM) scheme, we analyze the internal load transfer paths, particle contacts, and pore structure evolution during the densification. The results indicate that the particle compaction process can be divided into two stages, exhibiting a state transition from a non-uniform compaction stage to a uniform compaction stage, and the large particles show a higher breakage risk after over-compaction. This study successfully in-situ tracks the densification during electrode compression and it would promote a deeper understanding of the evolution of electrode microstructure and particle fracture, and optimize the structures and performance of electrodes. In situ CT technology and DEM have been used to understand the calendering process of the cathode for Li-ion battery, which shows a transition from a non-uniform compaction stage to a uniform compaction stage. [Display omitted] • Developed an in-situ micro-mechanical stage to characterize the cathode calendering process using CT. • Using DEM based on X-ray tomography to analyze the mechanical transfer path of active particles during calendering. • Revealed the transition from non-uniform compression to uniform compression in electrode densification. • Analyzed the potential fragmentation of active particles caused by the over compaction. [ABSTRACT FROM AUTHOR]

Characterizing microscale single particles directly is requested for dissecting the performance‐limiting factors at the electrode scale. In this work, we build a single‐particle electrochemical setup and develop a physics‐based model for extracting the solid‐phase diffusion coefficient (Ds) and exchange current density (i0) from electrochemical impedance measurements. We find that the carbon coating on the LiNi1/3Mn1/3Co1/3O2 surface enhances i0. In addition, Ds and i0 decay irreversibly by ≈25 % and ≈10 %, respectively, when the cutoff charge voltage increases from 4.3 V to 4.4 V. Moreover, we correlate intrinsic parameters of single particles with the performance of porous electrodes. Porous electrodes assembled with active particles with higher i0 values deliver a greater capacity and faster capacity fade. The methods developed in this combined experimental and theoretical work can be useful in correlating the single‐particle scale and porous‐electrode scale for other similar systems. [ABSTRACT FROM AUTHOR]

Characterizing microscale single particles directly is requested for dissecting the performance‐limiting factors at the electrode scale. In this work, we build a single‐particle electrochemical setup and develop a physics‐based model for extracting the solid‐phase diffusion coefficient (Ds) and exchange current density (i0) from electrochemical impedance measurements. We find that the carbon coating on the LiNi1/3Mn1/3Co1/3O2 surface enhances i0. In addition, Ds and i0 decay irreversibly by ≈25 % and ≈10 %, respectively, when the cutoff charge voltage increases from 4.3 V to 4.4 V. Moreover, we correlate intrinsic parameters of single particles with the performance of porous electrodes. Porous electrodes assembled with active particles with higher i0 values deliver a greater capacity and faster capacity fade. The methods developed in this combined experimental and theoretical work can be useful in correlating the single‐particle scale and porous‐electrode scale for other similar systems. [ABSTRACT FROM AUTHOR]

This article describes a study of an analytic interfacial stresses solution of FRP bond tendon anchorage, under different boundary conditions. The analytic solution was obtained with the cohesive zone model (CZM): the concept of the minimum relative interface displacement sm is introduced and used as the fundamental variable to express all other parameters. The presented analytic solution agrees well with the result of experiment and that of finite element analysis (FEA). Furthermore, the interface shear stress distributions under two kinds of boundary conditions are discussed. It is indicated that the boundary conditions affected distribution of interfacial stress greatly. Under different boundary conditions, at the same load level, the peak interface shear stress corresponding to the first boundary condition is smaller than it is corresponding to the second boundary condition. The FRP tendon anchor under the first boundary condition can alleviate the peak bond stress, resulting in better uniformity in bond stress distribution. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, analytical solutions based on a cohesive zone model (CZM) are developed for the bond fiber-reinforce dpolymer (FRP) tendon anchorage under axial load. With bilinear cohesive laws, the analytical solutions of tensile capacity of anchorages are derived. The concept of the minimum relative interface displacement sm is introduced and used as the fundamental variable to express all other parameters, such as external tensile load. Experimental and analytical results show that the thickness of the anchoring material is main factor affecting tensile capacity. The characteristic bond strength depends mainly on the properties of the bonding agent-anchoring material, the geometry and surface conditions of the tendon, and the radial stiffness of the confining medium. A comparison of the calculated and experimental results showed good agreement. Formulas based on fracture energy of the tension load capacity derived in the present work can be directly used in the design of FRP tendon anchorage. [Copyright &y& Elsevier]

Double network elastomer is a class of molecular composites consisting of a brittle filler network and a ductile matrix network. Upon deformation, progressive scission of the filler network dissipates strain energy while the matrix network resists the micro defect propagation, thus enhancing both stiffness and toughness of the composites. Over the past few years, several types of constitutive models have been developed to capture the nonlinear stress-strain relation of double network elastomers, most of which were formulated by taking consideration of network interaction, chain scission and damage evolution. In parallel, despite the abundant macroscopic experiments and microscopic characterizations on the multiscale failure mechanism of double network elastomers, a theoretical prediction for the ultimate strength of the composites is yet to be built up. In this paper, we develop a multiscale model which describes the deformation and tensile failure of double network elastomer composites at the same time. The progressive damage at molecular level is captured by the stretch-induced scission of randomly distributed polymer chains; the propagation of chain-scission-induced defects at microscale is modeled with analogy to cavitation; finally, the macroscopic necking failure is predicted by tracking the stress softening phenomenon. Our model is validated through the comparison between theoretical calculations and experiments, as well as the predictions and analysis of empirical design principles for double network elastomer composites. • A multiscale model for the deformation and tensile failure of double network elastomer composites. • Prediction for the pre-stretch-dependent failure behaviors in double network elastomers. • Investigation on the competition and transition of different failure mechanisms. [ABSTRACT FROM AUTHOR]

The safety of lithium-ion batteries is an essential concern where instant and accurate temperature sensing is critical. It is generally desired to put sensors inside batteries for instant sensing. However, the transmission of internal measurement outside batteries without interfering their normal state is a non-trivial task due to the harsh electrochemical environment, the particular packaging structures and the intrinsic electromagnetic shielding problems of batteries. In this work, a novel in-situ temperature sensing framework is proposed by incorporating temperature sensors with a novel signal transmission solution. The signal transmission solution uses a self-designed integrated-circuit which modulates the internal measurements outside battery via its positive pole without package breaking. Extensive experimental results validate the noninterference properties of the proposed framework. Our proposed in-situ temperature measurement by the self-designed signal modulation solution has a promising potential for in-situ battery health monitoring and thus promoting the development of smart batteries. [ABSTRACT FROM AUTHOR]

Summary: Considering that the anode and cathode in batteries have different heat generation behaviors and that there is almost no technique for measuring the heat generation of the anode and cathode under nondestructive conditions, we proposed a novel in‐situ nondestructive temperature measurement technique for acquiring the heat generated by the anode and cathode. To this end, a Swagelok Li‐ion battery cell is designed to visualize the temperature of the anode and cathode by using an infrared camera. Compared with the anode's heat generation, the cathode generates more heat at a 0.5 C current. The reversible heat generation of the electrode has an exothermic effect, which could be transformed into an endothermic effect within 0% to 100% depth of discharge (DoD). The irreversible heat generation always has an exothermic effect and decreases during the delithiation process. Therefore, it can be concluded that it is likely that variations in the heat generated by the anode and cathode can be measured by using the proposed nondestructive method. Finally, it is meaningful that the effects of the anode/cathode chemistry and other factors such as C‐rate and temperature on the local heat generation will be investigated in future works. [ABSTRACT FROM AUTHOR]

The effective properties of lithium-ion battery (LIB) cathode are determined by both the volume fractions of constituents and the morphological features of microstructure. However, it is difficult to establish an accurate quantitative relationship between the macroscopic effective properties and microstructural features. Deep learning techniques, due to their exceptional nonlinear fitting capabilities, have been widely applied in various complex fields. Our study presents a generation scheme of numerous three-dimensional (3D) digital microstructures of cathode, using a deep convolutional neural network (CNN)-based stochastic reconstruction algorithm combining with the scanning electron microscope (SEM) images. The reconstructed samples are substituted with the corresponding finite element (FE) models, and the effective mechanical and electrochemical properties are assessed through the FE-based homogenization theory. Finally, the generated cathode samples and their effective properties are used to train the 3D CNN for performance prediction. This study demonstrates that the deep learning approaches can accurately and rapidly reconstruct the microstructure of cathode and predict their effective properties. Furthermore, the established framework can be extended to other heterogeneous materials. • Cathode microstructure feature extraction based on transfer learning is proposed. • A CNN-based stochastic reconstruction method for microstructures is developed. • CNN and homogenization theory are used for properties prediction of microstructures. [ABSTRACT FROM AUTHOR]

Stable electrochemical performance and mechanical integrity for large-volume-change alloy anodes with high capacity remain a formidable challenge in battery industries. The roles of diverse binders, crucial for the stability of electrode microstructure in alloy electrodes, are not yet fully comprehended. For a good understanding of interactions between binders and active materials, in this work, by turning real silicon-based electrodes with irregular geometries into constrained silicon micropillars with regular ones, chemomechanical functions of binders for silicon electrodes are conducted by experimental observations and numerical simulations. The observations suggest that the addition of binder can enhance the fracture behaviors of silicon micropillars and hinder the debonding of the lithiated silicon for all solid, isometric-hollow and anisometric-hollow geometric designs. Accordingly, the constrained electrodes have more superior electrochemical performance than free-standing ones, which is ascribed to the improvement of mechanical integrity. The results emphasize the vital roles of suitable binders in structural stability and provide an instructive design for real composite alloy electrodes in Li-ion batteries. Image 1 • Chemomechanical interactions between binders and Si anodes are investigated. • Fracture and interface debonding could be alleviated with the addition of binders. • Geometric design combined with suitable binders is a must for alloy electrodes. [ABSTRACT FROM AUTHOR]

The non-uniform growth of lithium dendrites is the main factor causing internal short-circuits and thermal runaway in lithium-ion batteries. Due to the internal environment of the battery being a complex multi-field coupling, the mechanisms of triggering lithium deposition are still unclear. Here, a cross-sectional in-situ optical microscope device was fabricated to observe lithium dendrite evolution. The amount of irreversible and reversible lithium was quantified by the image binarization method and titration gas chromatography, which is used to analyze the relationship between separator deformation, current density, and lithium deposition. The greater the separator deformation and current density, the more irreversible lithium increases. The pore defect mapping algorithm was developed to reconstruct a high-precision three-dimensional finite element model of the separator, which was used to quantify the relationship between displacement loading and the microstructure evolution. A three-dimensional lithium deposition model was established on the actual microstructural parameters of the separator, predicting the concentration and electrochemical field of lithium deposition processes. A phase diagram of lithium precipitated failure in lithium-ion batteries with mechano-electrochemical coupling was developed with silicon-graphite electrode. This work will provide a new direction for understanding the mechanism of lithium deposition and guidance for commercial battery design. • The lithium dendrites evolution was observed by in-situ microscope. • A 3D finite element model of the separator was developed to predict porosity. • A multi-field coupled phase diagram was established for lithium deposition failure. [ABSTRACT FROM AUTHOR]

• Incremental variational formulation is developed for chemomechanical problem of heterogeneous composites. • Computation Homogenization-based FE2 solving algorithm is realized for heterogeneous composite. • Chemomechanical properties of composites are solved by two-scale consistent tangential solving algorithm. • The 'moment of mass concentration' is discussed for heterogeneous composites under mass diffusion. The chemomechanical properties of heterogeneous composites under mass diffusion are of significance in modern advanced technology and engineering applications. A homogenization-based two-scale chemomechanical model is developed for heterogeneous composites undergoing chemical mass diffusion. A two-scale incremental variational formulation is established for heterogeneous composites consisting of multiconstituents featuring local dissimilar diffusion-deformation properties. The minimization problems for coupled chemomechanical behaviors are solved for both macrostructure and microstructure contexts, where the macroscopic material properties are extracted from the results of local boundary value problem on the nested representative volume elements (RVEs). Through a staggered finite element method (FEM) implementation procedure, the proposed homogenization-based two-scale solution algorithm is implemented in the FEM package ABAQUS (V6.14). The developed variational model and tangential algorithm is checked by solving chemomechanical properties of particles enforced composite, where several numerical examples are conducted applying two-scale solution algorithm and validated by full-scale simulations. Parametric studies are carried out on the size effects of RVEs, with respect to the 'inertia effect' associated with 'moment of mass concentration', and the coupling mechanisms are discussed for mechanical and chemical solutions. To the end, the inelastic dissipations are solved on subscale BVPs and their effects on the mechanical deformation and chemical mass diffusion are checked. The contributions of this work are mainly two-folds. One is the theoretical advance for self-consistent homogenization modeling of the coupled multi-physics of heterogeneous composites, and a rigorous FE2 solution procedure. The other is providing numerical reference for evaluation of approximation algorithm as well as advanced data-driven method, which is needed for high-efficient material design. [ABSTRACT FROM AUTHOR]

Adiabatic shear band (ASB) is a significant failure mechanism observed in metals and alloys under impact loading. Though ASB formation has been widely assumed to be a one-dimensional thermo-mechanically-coupled instability problem, it is crucial to recognize that adiabatic shear banding is essentially a two-dimensional propagating event in space. However, it is challenging to perform in-situ characterization of temperature-deformation fields during ASB formation due to the extremely small spatial and temporal scales involved. To obtain the two-dimensional features of ASB evolution, a newly developed plane-array infrared imaging system and microspeckle-based digital image correlation (DIC) technique are synchronized with the Kolsky bar system. By incorporating interrupted tests, "quasi-synchronous" characterization of temperature-deformation-microstructure evolution during ASB formation in hat-shaped specimens of Ti–6Al–4V is achieved. A phase-field model incorporating energy-based shear banding criteria and independently calibrated model parameters is established to simulate the dynamic shear failure process, which is demonstrated to be able to well reproduce experimentally observed temperature and deformation evolution. Based on experimental characterization and simulation results, the two-dimensional features and thermo-mechanical aspects of ASB formation are presented. Energy dissipation of shear banding is estimated based on the measured temperature field, demonstrating good agreement with the calibrated values in the phase-field model. The "propagation" and "percolation" modes along the band are analyzed, which can be predicted by the introduction of a shear band process zone. The influences of thermal and microstructural softening on shear failure are also clarified through a comprehensive analysis of temperature and microstructure evolution. • Temperature and deformation fields during dynamic shear failure are captured. • The energy-based phase-field model well reproduces dynamic shear banding. • Energy dissipation of shear banding is estimated based on the temperature field. • Two-dimensional features of dynamic shear banding are analyzed. [ABSTRACT FROM AUTHOR]

Internal short circuit in lithium-ion batteries is a crucial hazard threatening. It is accurately difficult to monitor the internal signals in time of the lithium-ion batteries during the process of internal short circuit. Herein, a novel method is developed to monitor multiple signal evolution behaviour using a sealed tank and sensors. The internal signals of LFP batteries and NMC batteries exhibit different evolution behaviours, especially in the response sequence of pressure and gas. Battery capacity has an impact on ISC signal response sequence and time for LFP batteries, showing identical sequence and shorter time with the increase of capacity. The voltage and temperature are considered as sensitive signals for both LFP and NMC811 batteries that sensitive signals are defined based on their response speed. This operando technique provides a suitable platform for understanding the side reaction mechanism during thermal runaway in commercial LIBs. • A novel in-situ method was developed for internal short circuit measurement. • ISC behaviour of LFP and NMC811 batteries was investigated. • Battery capacity has an impact on ISC evolution behaviour for LFP batteries. • Established sensitive signals for internal short circuit in LFP and NMC811 batteries. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors are gaining increasing attention owing to their broad practical application prospects in biomedicine, real-time monitoring, and robotics. Although the microstructure design for improving their performance has been extensively investigated, the fabrication of high-sensitivity flexible pressure sensors (more than 1 kPa−1) with a wide working range (more than 1000 kPa) remains challenging. In this paper, we report a preparation strategy for a high-sensitivity flexible pressure sensor (1.412 kPa−1) with a working range of 1275 kPa. Here, we improved the preparation process by mixing anhydrous ethanol with polydimethylsiloxane (PDMS) and synthesized a small-aperture (50 μm) composite with excellent connectivity. Importantly, the sensing mechanism of these porous composites was theoretically studied, and after excluding the surface-microstructure effect, a mechanical-electrical response model considering the effect of the pore size for uniform porous sensing composite was established. Significantly, we propose a gradient hierarchical structure with coplanar electrodes. This strategy can be combined with the existing surface-microstructure strategy to improve the sensitivity of the composites-based sensor. Finally, the potential of the as-fabricated flexible sensor for application as a wearable device for speech recognition was demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]

Ion intercalation and deintercalation (IID) reactions in rechargeable metal-ion batteries are affected by the electrochemical double layer (EDL) at solid-liquid interfaces. Yet, EDL effects on the kinetics of IID reactions are less considered. Here, we develop a hybrid quantum-classical model for IID reactions at graphite-electrolyte interfaces that accounts for the coupling of ion and electron transfer processes, and the influence of the inhomogeneous local EDL environment. The model is employed to understand how the structural deformation of the graphite electrode, the electric potential, and the solvent dipole moment shape the kinetics of IID reactions. [Display omitted] • Hybrid quantum-classical model explains mechano-electrochemical coupling effects. • Electrochemical driving factors are derived from a modified EDL model. • Smaller dipole moment of electrolyte accelerates the reaction kinetics. • Structural changes and electronic interactions affect the reaction kinetics. [ABSTRACT FROM AUTHOR]

Keywords: electrocatalysis; electrochemical energy storage; electrochemistry; electrode process; single-particle measurements EN electrocatalysis electrochemical energy storage electrochemistry electrode process single-particle measurements 1 1 1 02/03/23 20230201 NES 230201 In recent years, single-particle measurements have been applied to electrochemical energy storage as well as electrocatalysis and have led to great achievements in understanding the evolution and kinetics of electrodes. Frontispiece: Single-Particle Measurements: A Powerful Method for Investigating Electrochemical Reactions Electrocatalysis, electrochemical energy storage, electrochemistry, electrode process, single-particle measurements. [Extracted from the article]

Inhomogeneity can accelerate performance degradation and reduce the lifetime of large-format batteries and battery modules. It is necessary to in-situ monitor the internal heterogeneous information and investigate the mechanical inhomogeneity of the batteries and modules. In this study, an in-situ measurement platform based on the integrating sensors and optical methods is developed. The internal stress and strain evolutions at the module-level are characterized and related to the deformation evolution at the cell-level. Both levels are suffering the serious mechanical inhomogeneity, which is quantitatively analyzed by the in-situ experiments and corresponding simulations, significantly affecting the long-term cyclic performance and consistency of the module. A new concept of mechanical consistency is introduced to correlate the mechanical inhomogeneity with module aging. This study can provide a basis for analyzing the aging mechanism and optimizing the structure of battery modules. • An in-situ measurement platform is developed to monitor mechanical parameters. • Multiple structural levels are suffering the serious mechanical inhomogeneity. • Heterogeneous features are mainly derived from the structure of the module. • Module inconsistency correlates with mechanical inhomogeneity in the module. [ABSTRACT FROM AUTHOR]

The demand for lithium-ion batteries is ever increasing while its safety is arousing great public concerns. The feature of a defective cell that may evolve to catastrophic failure is difficult to characterize, given the observation of the cell's internal structure is hard to make. Herein, this paper proposes a new method using thermography to characterize the evolution process from internal short circuit to thermal runaway inside a lithium-ion cell. The spatial and temporal temperature variation around the initiation point of the internal short circuit as well as the voltage and surface temperature are recorded in high frequency. The internal short circuit is triggered by the magnet and wax. The results show that the aluminum-anode-type internal short circuit can lead to thermal runaway by a sequence of the hot spot, gas generation, and combustion. Inadequate internal short circuit heat generation contributes to a temporary hot spot that gradually cools down to ambient temperature. Thermal runaway tends to occur when the hot spot above 150 °C reaches the area of 50 mm2 and the majority of the exothermic side reaction heat in the hot spot area is released within ca. 2s. These results are expected to guide the design of safer lithium-ion batteries. • Internal short circuit evolution is revealed by in-situ internal infra-red imaging. • The time sequence of thermal runaway caused by internal short circuit is analyzed. • Internal short circuits with inadequate heat cool down with limited thermal hazards. • Hot spot areas and side reaction heat distinguish thermal runaway initiation or not. [ABSTRACT FROM AUTHOR]

Characterizing microscale single particles directly is requested for dissecting the performance‐limiting factors at the electrode scale. In this work, we build a single‐particle electrochemical setup and develop a physics‐based model for extracting the solid‐phase diffusion coefficient (Ds) and exchange current density (i0) from electrochemical impedance measurements. We find that the carbon coating on the LiNi1/3Mn1/3Co1/3O2 surface enhances i0. In addition, Ds and i0 decay irreversibly by ≈25 % and ≈10 %, respectively, when the cutoff charge voltage increases from 4.3 V to 4.4 V. Moreover, we correlate intrinsic parameters of single particles with the performance of porous electrodes. Porous electrodes assembled with active particles with higher i0 values deliver a greater capacity and faster capacity fade. The methods developed in this combined experimental and theoretical work can be useful in correlating the single‐particle scale and porous‐electrode scale for other similar systems. [ABSTRACT FROM AUTHOR]

The electro-chemo-mechanical (ECM) coupling effects are nontrivial in alloying electrode materials, whose applications are hindered by the severe volume change during cycling. However, due to the difficulty in the in-situ application of mechanical load onto the active materials, these effects in many emerging lithium-ion battery (LIB) chemistries are largely unknown. Herein, we report a new setup for the in-situ characterizing ECM coupling effects in alloying electrode materials, and the coupling effects in aluminum (Al) foil electrode is studied. The elastic moduli of the Al foil show an increasing then slightly decreasing trend with the lithiation. Meanwhile, electrochemical impedance spectroscopy spectra of the Al foil imply an increasing surface atomistic energetic heterogeneity of the Al foil with the growing tensile force. Furthermore, the stress relaxation phenomena of the Al foil electrode during lithiation are observed. The newly developed setup opens a valuable window into investigating complicated ECM coupling effects in LIBs. [Display omitted] [ABSTRACT FROM AUTHOR]

Natural tissues possess the self-strengthening ability through biological growth, during which additional building blocks are transported into the tissues and attached to the pre-existing microstructures. In contrast, synthetic materials are typically static, meaning neither their dimensions nor their mechanical properties are able to be altered after the materials are manufactured into specific structures. Recently the concept of bio-inspired synthetic material arises, aiming at developing materials with dynamically programmable performances. Based on the idea of multinetwork (MN) elastomer, we propose a solvent-free elastomer composite system that can be strengthened through tunable self-growth cycles. Resembling biological tissues, chemical structures of the composite remain constant after self-growing, while its dimension, modulus, strength and swelling ability can be programmed on demand. The elastomer composite is naturally compatible with Digital Light Processing (DLP) 3D printing, which directly enables the fast manufacturing of high-precision structures. Applications of the self-growing composites in metamaterials with tunable mechanical performance and waterproof structures are exhibited at the same time. [ABSTRACT FROM AUTHOR]

The internal fiber structure of composites determined via X-ray micro-computed tomography (μ-CT) is a key factor affecting their properties. However, the low resolution and blurred fiber-matrix interfaces of the μ-CT images obtained for large composite structures as well as the different grayscale distributions caused by the uneven thicknesses of their complex shapes considerably reduce the accuracy of the reconstructed model. Meanwhile, the relatively long scanning time of μ-CT limits the usability of this technique for in-situ loading tests. Therefore, in this study, an image segmentation method based on U-net convolution neural network is applied to the segmentation of μ-CT image of fabric rubber composite to realize the high-precision reconstruction of its internal fabric structure. This approach effectively minimizes the image noise caused by fast scanning and reduces the scanning time by 80%. The accuracy of the reconstructed model and the high efficiency of the developed method are verified through finite element analysis. Hence, the described μ-CT image processing method enables high-precision reconstruction of fiber-reinforced composites and provides a significant reduction in the μ-CT scanning time. [Display omitted] [ABSTRACT FROM AUTHOR]

Debonding often occurs in flexible batteries due to mechanical and electrochemical coupling during service. Debonding of electrode will seriously affect the capacity and life of the battery, and even cause a short circuit inside the battery, resulting in spontaneous combustion. Here, the adhesion performance between the electrode sheet and the active material are investigated under the electrolyte environment and different states of charge (SOCs). A small stretcher loading device is used to perform stripping experiments on positive electrodes and negative electrodes in a glove box filled with argon to obtain the peel strength. The binders used in the positive and negative electrodes in this paper are polyvinylidene fluoride (PVDF) and Styrene-Butadiene Rubber/Carboxymethyl Cellulose (SBR/CMC). Compared with the electrode sheet without electrolyte, the peel strength of the positive electrode and negative electrode is decreased by 89.7% and 46.3%, respectively. The significant reduction in peel strength is due to the swelling effect of the electrolyte on the binder. The scanning electron microscope observation shows that there is a large number of active material particles at the interface of the positive electrode and the negative electrode after peeling. Additionally, the peel strength of the positive electrode was increases slightly with the increase of SOC and the added value is 14.8%. But the peel strength of negative electrode decreased with the increase of SOC and the added value is 47.6%. These results play an essential role in evaluating the interface peel strength of the electrode sheet in the different environment and designing electrochemical performance for batteries. [ABSTRACT FROM AUTHOR]

Modeling and measurement of the temperature distribution in cylindrical Li-ion cells are critical challenges that directly affect both the performance and safety. Most available electrochemical-thermal models for cylindrical cells are validated through the surface temperature. In this paper, high fidelity internal morphology two-dimensional electrochemical-thermal models based on geometric parameters extracted from computed tomography images are developed for the 18650 cylindrical Li-ion battery. An optical cell has been made to obtain the inner temperature distribution on the cross-section by using an infrared camera. The modeling results are validated for both the electrochemical performance and thermal behavior during the galvanostatic discharge process. The modeling results agree with the experimental data of the optical cell well. The effects of the inlet ratio, jelly roll structure and positive tab position on the temperature field on the cross-section are analyzed. The results presented in this paper contribute to the modeling and manufacturing of 18650 cylindrical Li-ion batteries. • The high fidelity internal morphology electrochemical-thermal model was developed. • The model accuracy was validated through internal temperature distribution. • Higher inlet ratio leads to lower temperature rise and lower temperature gradient. • The real structure model is more accuracy than the concentric structure model. • The best position of the positive tab was found through the simulation. [ABSTRACT FROM AUTHOR]

The silicon-graphite composite electrode is the main focus of the high energy and high power density 18650 Li-ion battery cells, while the large volume expansion of the composite electrode may induce the steel case of the cell to deform largely, even rupture. The mechanical reliability of the steel case is very important to the safety and durability of the battery cell. In the paper, the hoop strain of the steel case is in-situ monitored during 18650 Li-ion battery cell operation. At the early cycle stage, the hoop strain of the steel case is induced by the thermal expansion. After a long-term cycle (cycled number > 300 times), inhomogeneous strain distribution, even negative strain, is found on the steel case. Based on the CT images and non-concentric numerical model, it is found that the gap between the jelly roll and steel case is the root of the different hoop strain on the steel case during the cycle. It is suggested that the gap (the diameter ratio of the jelly roll to steel case) need be focused in the engineering design for the cylindrical Li-ion battery cell with next-generation silicon composite electrode. Inhomogeneous hoop strain phenomenon on the steel case of the 18650 Li-ion battery cell Image, graphical abstract [ABSTRACT FROM AUTHOR]

Li-ion batteries (LIBs) are the optimal carrier of the renewable energy, while remarkable self-heating can cause performance degradation, even thermal runaway and explosion in the LIBs. Thus, it is important to monitor internal temperature for improving the safety of LIBs. Currently, the inserted temperature sensors induce the electrode damage and capacity degradation of battery, which is not suitable for practical applications. By integrating the multi-point thin film sensor into the LIB electrodes, a novel method is proposed to assemble an integrated battery that remains a stable capacity with high Coulombic efficiency in 100 cycles. The long-term cyclic experimental results show that the inserted thin film sensor has limited impact on the performance of the integrated LIBs. The thin film sensor with electrochemically inert feature demonstrates the internal temperature variation in real-time under different current rates. Consequently, the proposed novel method is used for analyzing failure mechanism and improving safety of Li-ion batteries. Image 1 • A novel method is proposed to assemble the thin film sensor with the battery. • The battery with inserted thin film sensor has a stable electrochemical performance. • The thin film sensor can demonstrate the stable internal temperature measurement. [ABSTRACT FROM AUTHOR]

Temperature is one of the most important parameters in the safety issues of Li-ion batteries. Generally, the temperature distribution inside the cell is not uniform, and the observation and mechanism of the heat generation inside the batteries has not been fully understood. For well addressing this problem, here we have developed a new in-situ measurement setup to visualize the two-dimensional internal temperature field distribution of the internal cross-section in the cylindrical cells. Owing to the non-destructed advantage, this technology allows for well observing the 2D temperature field distribution at various discharge rates, which suggests the maximum temperature difference ~4.73 °C(3C rate) on the internal cross-section. The observation indicates the presence of remarkable temperature gradient inner the cylindrical cells, and such visualized inhomogeneous temperature features are more pronounced for fundamentally understanding heat generation and distribution. The technology opens a novel platform for acquiring solid evidence in studying the mechanism of thermal behaviors and designing safe Li-ion batteries. Image 1 • In-situ cell and in-situ system to visualize the section's temperature directly. • Non-destructed method to obtain the inner plane temperature distribution. • The huge sectional temperature inhomogeneity inside the cell. [ABSTRACT FROM AUTHOR]

Here an in situ system is presented to simultaneously study the evolution of both morphology and stress in the silicon thin film electrode during lithiation and delithiation. Owing to the specific design with two observation windows in the in situ cell, both the curvature and color of the silicon thin-film electrodes upon lithiation and delithiation processes can be measured by multi-optical sensor and optical microscope. By such colorimetric method, the color evolution can be used to represent the thickness of silicon thin film electrode, and the quantitative relationship can be obtained by in situ atomic force microscope and optical microscopy experiments. Combining the real thickness with Stoney equation, the accurate stress of the Li x Si film can be obtained during the electrochemical cycles. • Simultaneous stress measurement and optical observation system for Si electrode. • Correction of theoretical expansion thickness of Si film by colorimetric method. • Stress evolution by multi optical sensor setup and correction expansion thickness. [ABSTRACT FROM AUTHOR]