Atomic-level characterization of liquid/solid interface

The detailed understanding of various underlying processes at liquid/solid interfaces requires the development of interface-sensitive and high-resolution experimental techniques with atomic precision.In this perspective,we review the recent advances in studying the liquid/solid interfaces at atomic level by electrochemical scanning tunneling microscope(EC-STM),non-contact atomic force microscopy(NC-AFM),and surface-sensitive vibrational spectroscopies.Different from the ultrahigh vacuum and cryogenic experiments,these techniques are all operated in situ under ambient condition,making the measurements close to the native state of the liquid/solid interface.In the end,we present some perspectives on emerging techniques,which can defeat the limitation of existing imaging and spectroscopic methods in the characterization of liquid/solid interfaces.

Thermal rectification induced by Wenzel–Cassie wetting state transition on nano-structured solid–liquid interfaces

Thermal rectification refers to the phenomenon by which the magnitude of the heat flux in one direction is much larger than that in the opposite direction.In this study,we propose to implement the thermal rectification phenomenon in an asymmetric solid–liquid–solid sandwiched system with a nano-structured interface.By using the non-equilibrium molecular dynamics simulations,the thermal transport through the solid–liquid–solid system is examined,and the thermal rectification phenomenon can be observed.It is revealed that the thermal rectification effect can be attributed to the significant difference in the interfacial thermal resistance between Cassie and Wenzel states when reversing the temperature bias.In addition,effects of the liquid density,solid–liquid bonding strength and nanostructure size on the thermal rectification are examined.The findings may provide a new way for designs of certain thermal devices.

Recent Progress in Metallurgical Bonding Mechanisms at the Liquid/Solid Interface of Dissimilar Metals Investigated via in situ X-ray Imaging Technologies

The liquid/solid(L/S)interface of dissimilar metals is critical to the microstructure,mechanical strength,and structural integrity of interconnects in many important applications such as electronics,automotive,aeronautics,and astronautics,and therefore has drawn increasing research interests.To design preferential microstructure and optimize mechanical properties of the interconnects,it is crucial to understand the formation and growth mechanisms of diversified structures at the L/S interface during interconnecting.In situ synchrotron radiation or tube-generated X-ray radiography and tomography technologies make it possible to observe the evolution of the L/S interface directly and therefore have greatly propelled the research in this field.Here,we review the recent progress in understanding the L/S interface behaviors using advanced in situ X-ray imaging techniques with a particular focus on the following two issues:(1)interface behaviors in the solder joints for microelectronic packaging including the intermetallic compounds(IMCs)during refl ow,Sn dendrites,and IMCs during solidification and refl ow porosities and(2)growth characteristics and morphological transition of IMCs in the interconnect of dissimilar metals at high temperature.Furthermore,the main achievements and future research perspectives in terms of metallurgical bonding mechanisms under complex conditions with improved X-ray sources and detectors are remarked and discussed.

Integrated interface configuration by in-situ interface chemistry enabling uniform lithium deposition in all-solid-state lithium metal batteries

All-solid-state lithium metal batteries(ASSLMBs)are considered as one of the ultimate goals for the development of energy storage systems due to their high energy density and high safety.However,the mismatching of interface transport kinetics as well as interfacial instability induces the growth of lithium dendrite and thus,leads to severe degradation of battery electrochemical performances.Herein,an integrated interface configuration(IIC)consisting of in-situ generated Li I interphase and Li-Ag alloy anode is proposed through in-situ interface chemistry.The IIC is capable of not only regulating charge transport kinetics but also synchronously stabilizing the lithium/electrolyte interface,thereby achieving uniform lithium platting.Therefore,Li||Li symmetric cells with IIC achieve a critical current density of up to 1.6 mA cm^(-2)and achieve stable cycling over 1600 hours at a high current density of 0.5 mA cm^(-2).Moreover,a high discharge capacity of 140.1 mA h g-1at 0.1 C is also obtained for the Li(Ni_(0.6)Co_(0.2)Mn_(0.2))O_(2)(NCM622)full battery with a capacity retention of 65.6%after 300 cycles.This work provides an effective method to synergistically regulate the interface transport kinetics and inhibit lithium dendrite growth for high-performance ASSLMBs.

From Liquid to Solid‑State Lithium Metal Batteries:Fundamental Issues and Recent Developments

The widespread adoption of lithium-ion batteries has been driven by the proliferation of portable electronic devices and electric vehicles,which have increasingly stringent energy density requirements.Lithium metal batteries(LMBs),with their ultralow reduction potential and high theoretical capacity,are widely regarded as the most promising technical pathway for achieving high energy density batteries.In this review,we provide a comprehensive overview of fundamental issues related to high reactivity and migrated interfaces in LMBs.Furthermore,we propose improved strategies involving interface engineering,3D current collector design,electrolyte optimization,separator modification,application of alloyed anodes,and external field regulation to address these challenges.The utilization of solid-state electrolytes can significantly enhance the safety of LMBs and represents the only viable approach for advancing them.This review also encompasses the variation in fundamental issues and design strategies for the transition from liquid to solid electrolytes.Particularly noteworthy is that the introduction of SSEs will exacerbate differences in electrochemical and mechanical properties at the interface,leading to increased interface inhomogeneity—a critical factor contributing to failure in all-solidstate lithium metal batteries.Based on recent research works,this perspective highlights the current status of research on developing high-performance LMBs.

Multistate transition and coupled solideliquid modeling of motion process of long-runout landslide

The recognition,repetition and prediction of the post-failure motion process of long-runout landslides are key scientific problems in the prevention and mitigation of geological disasters.In this study,a new numerical method involving LPF3D based on a multialgorithm and multiconstitutive model was proposed to simulate long-runout landslides with high precision and efficiency.The following results were obtained:(a)The motion process of landslides showed a steric effect with mobility,including gradual disintegration and spreading.The sliding mass can be divided into three states(dense,dilute and ultradilute)in the motion process,which can be solved by three dynamic regimes(friction,collision,and inertial);(b)Coupling simulation between the solid grain and liquid phases was achieved,focusing on drag force influences;(c)Different algorithms and constitutive models were employed in phase-state simulations.The volume fraction is an important indicator to distinguish different state types and solid‒liquid ratios.The flume experimental results were favorably validated against long-runout landslide case data;and(d)In this method,matched dynamic numerical modeling was developed to better capture the realistic motion process of long-runout landslides,and the advantages of continuum media and discrete media were combined to improve the computational accuracy and efficiency.This new method can reflect the realistic physical and mechanical processes in long-runout landslide motion and provide a suitable method for risk assessment and pre-failure prediction.

In situ formed LiF-Li_(3)N interface layer enables ultra-stable sulfide electrolyte-based all-solid-state lithium batteries

Sulfide solid electrolytes are promising for high energy density and safety in all-solid-state batteries due to their high ionic conductivity and good mechanical properties.However,the application of sulfide solid electrolytes in all-solid-state batteries with lithium anode is restricted by the side reactions at lithium/electrolytes interfaces and the growth of lithium dendrite caused by nonuniform lithium deposition.Herein,a homogeneous LiF-Li_(3)N composite protective layer is in situ formed via a manipulated reaction of pentafluorobenzamide with Li metal.The LiF-Li_(3)N layer with both high interfacial energy and interfacial adhesion energy can synergistically suppress side reactions and inhibit the growth of lithium dendrite,achieving uniform deposition of lithium.The critical current densities of Li_(10)GeP_(2)S_(12)and Li_(6)PS_(5)Cl are increased to 3.25 and 1.25 mA cm^(-2)with Li@LiF-Li_(3)N layer,which are almost triple and twice as those of Li-symmetric cells in the absence of protection layer,respectively.Moreover,the Li@LiF-Li_(3)N/Li10GeP2S12/Li@LiF-Li_(3)N cell can stably cycle for 9000 h at 0.1 mA cm^(-2)under 0.1 mA h cm^(-2),and Li@LiF-Li_(3)N/Li_(6)PS_(5)Cl/Li@LiF-Li_(3)N cell achieves stable Li plating/stripping for 8000 h at 0.1 mA cm^(-2)under10 m A h cm^(-2).The improved dynamic stability of lithium plating/stripping in Li@LiF-Li_(3)N/Li_(10)GeP_(2)S_(12)or Li_(6)PS_(5)Cl interfaces is proved by three-electrode cells.As a result,LiCoO_(2)/electrolytes/Li@LiF-Li_(3)N batteries with Li_(10)GeP_(2)S_(12)and Li_(6)PS_(5)Cl exhibit remarkable cycling stability of 500 cycles with capacity retentions of 93.5%and 89.2%at 1 C,respectively.

Engineering homotype heterojunctions in hard carbon to induce stable solid electrolyte interfaces for sodium-ion batteries

Developing effective strategies to improve the initial Coulombic efficiency(ICE)and cycling stability of hard carbon(HC)anodes for sodium-ion batteries is the key to promoting the commercial application of HC.In this paper,homotype heterojunctions are designed on HC to induce the generation of stable solid electrolyte interfaces,which can effectively increase the ICE of HC from 64.7%to 81.1%.The results show that using a simple surface engineering strategy to construct a homotypic amorphous Al_(2)O_(3) layer on the HC could shield the active sites,and further inhibit electrolyte decomposition and side effects occurrence.Particularly,due to the suppression of continuous decomposition of NaPF 6 in ester-based electrolytes,the accumulation of NaF could be reduced,leading to the formation of thinner and denser solid electrolyte interface films and a decrease in the interface resistance.The HC anode can not only improve the ICE but elevate its sodium storage performance based on this homotype heterojunction composed of HC and Al_(2)O_(3).The optimized HC anode exhibits an outstanding reversible capacity of 321.5mAhg^(−1) at 50mAg^(−1).The cycling stability is also improved effectively,and the capacity retention rate is 86.9%after 2000 cycles at 1Ag^(−1) while that of the untreated HC is only 52.6%.More importantly,the improved sodium storage behaviors are explained by electrochemical kinetic analysis.

A critical review on composite solid electrolytes for lithium batteries:Design strategies and interface engineering

The rapid development of new energy vehicles and 5G communication technologies has led to higher demands for the safety,energy density,and cycle performance of lithium-ion batteries as power sources.However,the currently used liquid carbonate compounds in commercial lithium-ion battery electrolytes pose potential safety hazards such as leakage,swelling,corrosion,and flammability.Solid electrolytes can be used to mitigate these risks and create a safer lithium battery.Furthermore,high-energy density can be achieved by using solid electrolytes along with high-voltage cathode and metal lithium anode.Two types of solid electrolytes are generally used:inorganic solid electrolytes and polymer solid electrolytes.Inorganic solid electrolytes have high ionic conductivity,electrochemical stability window,and mechanical strength,but suffer from large solid/solid contact resistance between the electrode and electrolyte.Polymer solid electrolytes have good flexibility,processability,and contact interface properties,but low room temperature ionic conductivity,necessitating operation at elevated temperatures.Composite solid electrolytes(CSEs) are a promising alternative because they offer light weight and flexibility,like polymers,as well as the strength and stability of inorganic electrolytes.This paper presents a comprehensive review of recent advances in CSEs to help researchers optimize CSE composition and interactions for practical applications.It covers the development history of solid-state electrolytes,CSE properties with respect to nanofillers,morphology,and polymer types,and also discusses the lithium-ion transport mechanism of the composite electrolyte,and the methods of engineering interfaces with the positive and negative electrodes.Overall,the paper aims to provide an outlook on the potential applications of CSEs in solid-state lithium batteries,and to inspire further research aimed at the development of more systematic optimization strategies for CSEs.

An APXPS endstation for gas–solid and liquid–solid interface studies at SSRF

In the past few decades, various surface analysis techniques find wide applications in studies of interfacial phenomena ranging from fundamental surface science,catalysis, environmental science and energy materials.With the help of bright synchrotron sources, many of these techniques have been further advanced into novel in-situ/operando tools at synchrotron user facilities, providing molecular level understanding of chemical/electrochemical processes in-situ at gas–solid and liquid–solid interfaces.Designing a proper endstation for a dedicated beamline is one of the challenges in utilizing these techniques efficiently for a variety of user's requests. Many factors,including pressure differential, geometry and energy of the photon source, sample and analyzer, need to be optimized for the system of interest. In this paper, we discuss the design and performance of a new endstation at beamline02 B at the Shanghai Synchrotron Radiation Facility for ambient pressure X-ray photoelectron spectroscopy studies.This system, equipped with the newly developed hightransmission HiPP-3 analyzer, is demonstrated to be capable of efficiently collecting photoelectrons up to 1500 eV from ultrahigh vacuum to ambient pressure of 20 mbar.The spectromicroscopy mode of HiPP-3 analyzer also enables detection of photoelectron spatial distribution with resolution of 2.8 ± 0.3 lm in one dimension. In addition,the designing strategies of systems that allow investigations in phenomena at gas–solid interface and liquid–solid interface will be highlighted through our discussion.

Microstructure and Solid/Liquid Interface Evolutions of Directionally Solidified Fe-Al-Ta Eutectic Alloy

A modified Bridgman directional solidification technique was used to prepare Fe-Al-Ta eutectic in situ composites at different growth rates ranging from 6 to 80 gm/s. The directionally solidified Fe- Al-Ta eutectic composites are composed of two phases: Fe(Al,Ta) matrix phase, and Fe2Ta(Al) Laves phase. Solidification microstructure is affected by solidification rate. Microstructure of the Fe-Al-Ta eutectic alloy grown at 6.0 pm/s is broken-lamellar eutectic. Eutectic colonies are formed with the increase of the solidification rate. Microstructures are mainly composed of the lamellar or fibrous eutectic at the center of the colony and coarse lamellar eutectic zone at the boundary. Meanwhile, the inter-lamellar spacing (or the inter-rod spacing) is decreased. The spacing adjustments are also observed in Fe-Al-Ta eutectic alloy. The solid/liquid interface evolves from planar interface to shallow cellular interface, then to deep cellular, and finally to shallow cellular planar with the increase of the solidification rate.

Treatment of discontinuous interface in liquid-solid forming with extended finite element method

Extended finite element method(XFEM) is proposed to simulate the discontinuous interface in the liquid-solid forming process.The discontinuous interface is an important phenomenon happening in the liquid-solid forming processes and it is difficult to be simulated accurately with conventional finite element method(CFEM) because it involves solid phase and liquid phase simultaneously.XFEM is becoming more and more popular with the need of solving the discontinuous problem happening in engineering field.The implementation method of XFEM is proposed on Abaqus code by using UEL(user element) with the flowchart.The key is to modify the element stiffness in the proposed method by using UEL on the platform of Abaqus code.In contrast to XFEM used in the simulation of solidification,the geometrical and physical properties of elements were modified at the same time in our method that is beneficial to getting smooth interface transition and precise analysis results.The analysis is simplified significantly with XFEM.

Mathematical Modelling of Particle Movement Ahead of the Solid-liquid Interface in Continuous Casting

Whether the particle will be trapped by the solid-liquid interface or not is dependent on its moving behavior ahead of the interface, so a mathematical model has been developed to investigate the movement of the particle ahead of the solid-liquid interface. Based on the theory for the boundary layer, the fluid velocity field near the solid-liquid interface was obtained, and the trajectories of particles were calculated by the equations of motion for particles. In this model, the drag force, the added mass force, the buoyance force, the gravitational force, the Saffman force and the Basset history force are considered. The results show that the behavior of the particle ahead of the solid-liquid interface is affected by the physical property of the particle and fluid flow. And in the continuous casting process, if it moves in the stream directed upward or downward near vertical solid-liquid interface or in the horizontal flow under the solid-liquid interface, the particle with the diameter from 5 um to 60um can reach the solid-liquid interface. But if it moves in horizontal flow above the solid-liquid interface, only the particle with the diameter from 5 um to 10 um can reach the solid-liquid interface.

First‐mode of negative streamers:Inception at liquid/solid interfaces

An experimental study of the inception of the first‐mode negative streamer at liquid/solid interfaces is presented in this article.The study is performed with a point‐plane configuration under square high voltage pulses.The electrode configuration is immersed in mineral oil and the liquid/solid interface is assembled in contact with the point electrode or in its vicinity.Four polymers and two impregnated papers have been tested as solids of the liquid/solid interface.Thus,it is possible to compare the influence of different parameter of the solid and the interface on the streamer inception.For example:Permittivity,solid surface roughness,chemical composition,etc.It has been observed that streamer inception voltages at interfaces with solids of higher permittivity to that of the mineral oil are statistically similar.Additionally,streamer inception voltages of streamer initiated free in the oil(no liquid/solid interface)are similar to that of the inception voltage of cases with solids with high permittivity.In contrast,the inception voltage of streamers initiated at permittivity matched interfaces are shown to be highest of the cases.The streamer inception voltage is also studied for different distances be-tween the liquid/solid interface and the point electrode with a permittivity matched interface.The results show a dependency of the inception voltage and the distance be-tween the point electrode and the interface.Finally,an analysis of the observation is performed to show that the Townsend‐Meek criterion cannot predict the obtained results.

Microstructure and fractal characteristics of the solid-liquid interface forming during directional solidification of Inconel 718

The solidification microstructure and fractal characteristics of the solid-liquid interfaces of Inconel 718,under different cooling rates during directional solidification,were investigated by using SEM. Results showed that 5 μm/s was the cellular-dendrite transient rate. The prime dendrite arm spacing (PDAS) was measured by Image Tool and it decreased with the cooling rate increased. The fractal dimension of the interfaces was calculated and it changes from 1.204310 to 1.517265 with the withdrawal rate ranging from 10 to 100 μm/s. The physical significance of the fractal dimension was analyzed by using fractal theory. It was found that the fractal dimension of the dendrites can be used to describe the solidification microstructure and parameters at low cooling rate,but both the fractal dimension and the dendrite arm spacing are needed in order to integrally describe the evaluation of the solidification microstructure completely.

Effect of current density on distribution coefficient of solute at solid-liquid interface

When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between the distribution of solute at solid-liquid interface and current density was established, and the effect of current on the distribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and the radius of curvature at the dendritic tip was discussed. The results show that as the current density increases, the distribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm 2, the latter varies significantly.

Fractal Description of the Solid/Liquid Interface of a Directionally Solidified Superalloy with Different Phosphorus Content

The solid/liquid interface of a directionally solidified Ni-base superalloy with different phosphorus contents was quantitatively described by means of fractat method.When the solidification rate was fixed,the relationship between the fractal dimensionality of the solid/liquid interface and the phos- phorus content of the test alloy was given.Combined the thermodynamics and fractal theory,the ef- fect mechanism of phosphorus content on fractal dimensionality of the solid/liquid interface was discussed.

Apparent Active Adsorption Force at a Solid-Liquid Interface with Active Adsorption

The paper presents a new relationship between the three surface tensions on the solid-liquid-vapor interface, γ_(sl)-γ_(sv)+γ_(lv)cosθ=βin order to understand the wetting on the liquid-solid interface in the case of active adsorption.The authors suggest a new force“apparent active adsorption force”βto take part in the balance at the three interface lines of contact in the solid-liquid-vapor phases,its dimen- sion isβ=Σα_iRT(Γ_i^(sl)-Γ_i^(sv)+Γ_i^(lv)cosθ),and its direction is dependent on the sign of β,whenβis a positive, the direction is agree with surface tension of the sol- id-vapor interface γ and vice versa.

Phase difference and interference between reflected cylindrical wave and head wave at a liquid/solid interface

The reflected field of pulsed cylindrical waves from a liquid-solid interface is studied by the numerical method and the experimental method. The reflected field is calculated and shown in gray pictures. The calculated incident angles θn (n=1, 2, 3, ...) of a series of minimums (or nulls) on the reflected wavefront are presented. The measured angle of the minimum from Schlieren photograph is consistent with that by calculation. The appearance of minimums is explained by the interference between the reflected wave and the head wave, and by the radiated dissipation of the head wave. The leading phase angle of the head wave to the reflected wave is proved to be about 3π/4 by the numerical calculation.

Mechanistically Novel Frontal-Inspired In Situ Photopolymerization:An Efficient Electrode|Electrolyte Interface Engineering Method for High Energy Lithium Metal Polymer Batteries

The solvent-free in situ polymerization technique has the potential to tailor-make conformal interfaces that are essential for developing durable and safe lithium metal polymer batteries(LMPBs).Hence,much attention has been given to the eco-friendly and rapid ultraviolet(UV)-induced in situ photopolymerization process to prepare solid-state polymer electrolytes.In this respect,an innovative method is proposed here to overcome the challenges of UV-induced photopolymerization(UV-curing)in the zones where UV-light cannot penetrate,especially in LMPBs where thick electrodes are used.The proposed frontal-inspired photopolymerization(FIPP)process is a diverged frontal-based technique that uses two classes(dual)of initiators to improve the slow reaction kinetics of allyl-based monomers/oligomers by at least 50%compared with the conventional UV-curing process.The possible reaction mechanism occurring in FIPP is demonstrated using density functional theory calculations and spectroscopic investigations.Indeed,the initiation mechanism identified for the FIPP relies on a photochemical pathway rather than an exothermic propagating front forms during the UV-irradiation step as the case with the classical frontal photopolymerization technique.Besides,the FIPP-based in situ cell fabrication using dual initiators is advantageous over both the sandwich cell assembly and conventional in situ photopolymerization in overcoming the limitations of mass transport and active material utilization in high energy and high power LMPBs that use thick electrodes.Furthermore,the LMPB cells fabricated using the in situ-FIPP process with high mass loading LiFePO_(4)electrodes(5.2 mg cm^(-2))demonstrate higher rate capability,and a 50%increase in specific capacity against a sandwich cell encouraging the use of this innovative process in large-scale solid-state battery production.