Interface Degradation Research Articles

Assessment of interfacial properties in a two-layered plate using quasi-static component generation during primary Lamb wave propagation.

This study delves into the feasibility of leveraging quasi-static component (QSC) generation during primary Lamb wave propagation to discern subtle alterations in the interfacial properties of a two-layered plate. Unlike the second-harmonic generation of Lamb waves, QSC generation doesn't necessitate precise phase-velocity matching but rather requires an approximate matching of group velocities to ensure the emergence of cumulative growth effects. This unique characteristic empowers the QSC-based nonlinear ultrasonic method to effectively surmount the limitations associated with inherent dispersion and multimode traits of Lamb wave propagation. Modeling the QSC generation reveals that the integrated amplitude of the QSC pulse, derived from the propagation of the primary Lamb wave tone burst, progressively amplifies with increasing propagation distance. Finite element simulations illustrate an overall decline in the efficiency of QSC generation amidst interfacial degradation. Experimental outcomes obtained via a nonlinear ultrasonic measurement-based setup vividly showcase the cumulative growth effect of QSC generation, evident with the propagation distance under approximate group velocity matching. To substantiate the influence of interfacial properties on QSC generation efficiency, varying thermal fatigue durations under cyclic temperature conditions are employed to simulate subtle changes in the two-layered plate's interfacial properties. The relative nonlinear acoustic parameter exhibits a distinctly sensitive and monotonically decreasing behavior with escalating thermal fatigue durations, corroborating the impact of alterations in interfacial properties on QSC generation efficiency. The alignment between experimental findings and numerical analysis predictions suggests that the effect of QSC generation in primary Lamb wave propagation provides a promising means for sensitively assessing the early-stage degradation of interfacial properties in layered plates.

Lithiated polymer coating for interface stabilization in Li6PS5Cl-based solid-state batteries with high-nickel NCM

During cell cycling with NCM cathode and Li6PS5Cl catholyte, interfacial degradation leads to reduced active mass and particle cracking. We mitigate this by coating NCM with polyvinylpyrrolidone and sulfonated poly(phenylene sulfone).

Decoupling the Effects of Interface Chemical Degradation and Mechanical Cracking in Solid-State Batteries with Silicon Electrode.

Silicon is a promising negative electrode material for solid-state batteries (SSBs) due to its high specific capacity and ability to prevent lithium dendrite formation. However, SSBs with silicon electrodes currently suffer from poor cycling stability, despite chemical engineering efforts. This study investigates the cycling failure mechanism of composite Si/Li6PS5Cl electrodes by decoupling the effects of interface chemical degradation and mechanical cracking. Chlorine-rich Li5.5PS4.5Cl1.5 suppresses interface chemical degradation when paired with silicon, while small-grained Li6PS5Cl shows 4.3-fold increase of interface resistance due to large Si/Li6PS5Cl contact area for interface degradation. Despite this, small-grained Li6PS5Cl improves the microstructure homogeneity of the electrode composites, effectively alleviating the stress accumulation caused by the expansion/shrinkage of silicon particles. This minimizes bulk cracks in Li6PS5Cl during the lithiation processes and interface delamination during the delithiation processes. Mechanical cracking shows a dominant role in increasing interface resistance than interface chemical degradation. Therefore, electrodes with small-grained Li6PS5Cl show better cycling stability than those with Li5.5PS4.5Cl1.5. This work not only provides an approach to decouple the complex effects for cycling failure analysis but also provides a guideline for better use of silicon in negative electrodes of SSBs.

Interface Issues of Layered Transition Metal Oxide Cathodes for Sodium-Ion Batteries: Current Status, Recent Advances, Strategies, and Prospects.

Sodium-ion batteries (SIBs) hold significant promise in energy storage devices due to their low cost and abundant resources. Layered transition metal oxide cathodes (NaxTMO2, TM = Ni, Mn, Fe, etc.), owing to their high theoretical capacities and straightforward synthesis procedures, are emerging as the most promising cathode materials for SIBs. However, the practical application of the NaxTMO2 cathode is hindered by an unstable interface, causing rapid capacity decay. This work reviewed the critical factors affecting the interfacial stability and degradation mechanisms of NaxTMO2, including air sensitivity and the migration and dissolution of TM ions, which are compounded by the loss of lattice oxygen. Furthermore, the mainstream interface modification approaches for improving electrochemical performance are summarized, including element doping, surface engineering, electrolyte optimization, and so on. Finally, the future developmental directions of these layered NaxTMO2 cathodes are concluded. This review is meant to shed light on the design of superior cathodes for high-performance SIBs.

Adaptive Phase-Locked E-Skin for Sports Physiology and Medicine.

The pursuit of creating materials that replicate the flexibility, stability, and advanced perceptual capabilities of human skin, attributes honed through natural evolution, represents a long-term objective in pioneering fields such as electronic skin (e-skin) research. However, conventional e-skin often struggles with stability and functionality in harsh sports environments, resulting in the degradation of the intimate interface over time. Inspired by the innate biphasic structure of human subcutaneous tissue, an adaptive phase-locked e-skin (APLE) is presented, designed to seamlessly conform to dynamic sports environments, offering robust applications in sports physiology and medical contexts without malfunctioning. The APLE allows one to laminate onto the skin with consistent homeostasis, providing a foundation for advancing data-driven sports physiology and creating personalized sports plans. Additionally, APLE offers immediate on-site medical treatment for common sports injuries, including hemostasis and sutureless wound closure. Ultimately, the reported multifunctional e-skin can provide significant value in managing sport-related burdens through digital and people-centered physiology monitoring, along with real-time sport healthcare.

Commercially Applicable One-Step Method to Construct Homogeneous Anode/Electrolyte Interface and Cathode/Electrolyte Interface Layers in All-Solid-State Lithium-Sulfur Batteries.

Using a solid electrolyte is considered to be the most effective strategy to solve the shuttle effect in lithium-sulfur batteries. However, the practical application of solid-state lithium-sulfur batteries (SLSBs) is still far from being realized. This is because SLSBs, like all other solid-state battery systems, also face the dilemma of interface degradation (including both the anode and cathode interfaces), in addition to terrible kinetics due to the nonliquid solid-state electrolytes infiltrating the nonconductive sulfur particles inside the cathode. It is necessary to consider the factors associated with the cathode, anode, electrolyte, and all the interfaces in an integrated manner to solve the problems existing in SLSBs. Similar to the anode/electrolyte interface formation in a liquid electrolyte, this work simultaneously synthesized the in situ anode/electrolyte and cathode/electrolyte interfaces by one-step electrochemically inducing the polymerization of thiophene monomers in the poly(ethylene oxide) electrolyte. By screening and adjustment of the thiophene polymerization process, a dual ion-electron conductive layer on both sides of the electrolyte as well as the inner surface of the sulfur cathode was synthesized. As a result of these improvements, an ionic conductivity of 1.1 × 10-4 S cm-1 was achieved by the composited electrolyte at 40 °C while maintaining a specific capacity of 1166.6 mAh g-1 after 50 cycles by the SLSBs assembled. This study regulated the dual ion-electron conductive interface on both sides of the electrolyte in a one-step manner and emphasized the important role of the homogeneity inner cathode surface and cathode/electrolyte interface in SLSBs. It might be extended to production applications because of its competitiveness in both technology and economy.

Mitigating Crosstalk by Slurry Additive Toward 5V Cobalt-Free LiNi0.5Mn1.5O4 Cathode.

LiNi0.5Mn1.5O4 (LNMO), with its spinel symmetry, emerges as a promising cathode material for high-voltage lithium-ion batteries (LIBs). Nonetheless, the vulnerability of LNMO to interfacial degradation, particularly electrolyte breakdown during high-voltage operation, compromises its long-term cycling performance. To overcome this longstanding challenge, a slurry additive-polyester-urethane-acrylate (PEUA)-to form a multi-functional ultra-thin electrode coating, enhancing the lifespan and energy density of LIBs is introduced. Comprehensive characterizations and theoretical analyses reveal that the PEUA slurry additive effectively maintains electrode integrity, facilitates electrons and lithium ions transport, and inhibits hazardous side reactions, thus preventing the by-products from triggering cathode-electrolyte-anode interface crosstalk. Consequently, the 5V LNMO || Li cell with PEUA slurry additive maintains a high-capacity retention of 97.8%, with improved cycling stability at high-temperature and full-cell configurations. This crosstalk-mitigation strategy offers a promising avenue for extending the lifespan and electrochemical performance of high-voltage cobalt-free cathodes, advancing the practical use of high-energy density LIB technology.

Visualising the Effect of Areal Current Density on the Performance and Degradation of Lithium Sulfur Batteries Using Operando Optical Microscopy

The degradation of lithium sulfur (Li-S) batteries poses significant challenges to their commercial viability and occurs largely due to the complex electrochemical reactions and structural transformations that take place during charge-discharge cycles. This study employs optical microscopy techniques to investigate and quantify the degradation mechanisms in Li-S batteries. By capturing high-resolution, time-lapsed images of both electrodes and the electrolyte-filled interelectrode space, key morphological changes can be identified and analysed, such as the formation and growth of lithium dendrites, sulfur dissolution, and electrode-electrolyte interface degradation. Quantitative image analysis is conducted to measure the extent of these changes, providing insights into their impact on battery performance. Our findings reveal critical correlations between specific morphological features and electrochemical inefficiencies, contributing to a deeper understanding of the degradation pathways in Li-S batteries. This optical microscopy approach offers a non-destructive, cost-effective, real-time method to monitor battery health, potentially guiding the development of more durable and efficient Li-S batteries.

New insights of the imprint at the catalyst-layer/ microporous-layer interface in PEMFC after heavy duty operation of commercial vehicles

Structural degradation and property decay of membrane electrode assemblies (MEAs) are primary causes for the stack performance and lifetime degradation. This study particularly investigates the structural damage and properties evolution of the catalyst-layer/microporous-layer (CL/MPL) interface in the MEA by conducting real-vehicle heavy-duty operational durability test and interfacial structure characterization. This research presents the first report and revelation of the causes and effects of CL/MPL interface imprints, and provides targeted advice for relieving MEA interfacial degradation. Results indicate that excessive assembly stress and stress variation during operation of stack causing the detachment of MPL materials at the region below the bipolar plate ridges is the essential cause of the imprints. The average surface contact angles of the aged CLs generally increase and the imprinted region exhibit stronger hydrophobicity than non-imprinted region due to the attachment of MPL materials. While the opposite is observed in MPL. Carbon corrosion induce structural degradation of the CL/MPL interface, leading to significant loss of carbon support and hydrophobic agent. The surface of aged CL become rougher and the pore size become more larger compared to the fresh CL. The formation of the interface imprint makes the contact between CL and MPL at the imprint region tighter, which reduces the interface resistance and inhibits the increase in ohmic polarization.

Interface Degradation of LaCl3-Based Solid Electrolytes Coupled with Ultrahigh-Nickel Cathodes.

Despite competitive compatibility with high-nickel cathodes, chloride solid electrolytes (SEs) still experience inevitable side reactions at the cathode/SE interface, causing capacity decay in all-solid-state lithium batteries (ASSLBs) during cycling. Herein, a three-electrode ASSLB testing device is developed to comprehensively reveal the interface failure mechanisms of the ultrahigh-nickel LiNi0.92Co0.05Mn0.03O2 (NCM92) cathode paired with LaCl3-based chloride SE Li0.447La0.475Zr0.059Ta0.179Cl3 (LLZTC). Distribution of relaxation time (DRT) analysis clearly shows the ASSLB degradation accompanied by a significant NCM92/LLZTC interface impedance increase, which becomes more pronounced at the higher cutoff charging voltage of 4.8 V vs Li+/Li. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and focused ion beam scanning electron microscopy (FIB-SEM) analysis also confirm the deterioration arising from active lattice oxygen and loss of physical contact at the NCM92/LLZTC interface. These findings reveal both electrochemical degradation and physical contact failure at the cathode/SE interface as key causes of the ASSLBs' capacity decay.

Shining Light on New Additives for Lithium Sulfur Batteries through Polysulfide Shuttle Tracking Operando Optical Fluorescence Microscopy

Lithium Sulfur (Li-S) batteries are uniquely poised to provide exciting new opportunities in the field of energy storage, possessing an impressive theoretical gravimetric specific capacity an order of magnitude greater than current lithium-ion batteries (1672 mA h g-1), and energy density over 5 times higher (2567 Wh kg-1), while also using far safer and more sustainable materials.However, their wilder proliferation and commercialisation suffers heavily from the polysulfide shuttle effect, where the lithium polysulfide intermediates generated at the cathode during the conversion mechanism of Li-S operation dissolve into the battery electrolyte and diffuse towards the lithium metal anode. This leads to parasitic reactions between the polysulfides and the anode, causing rapid cell degradation from active material loss, degradation of the anode solid electrolyte interface (SEI), and subsequent rapid dendrite formation. The shuttle effect is a primary mechanism of cell failure, and as such, most research into Li-S focuses on its mitigation. Current methods of characterizing the shuttle effect provide limited detail or are overly time consuming, so more robust characterization methods are required to further understand the distribution, dynamics, and degree of polysulfide transport.Here, the newly established Optical Fluorescence Microscopy (OFM) technique, for visualising the spatial distribution of polysulfides within the Li-S electrolyte and through sufficiently large cathode pores during operando cycling, is utilised for facile assessment of the efficacy of a variety of additives to Li-S batteries in reducing the polysulfide shuttle effect. Using a polysulfide sensitive fluorescent dye, established to be inert to both the components of a Li-S battery and the additives, the intermediate polysulfides formed throughout cycling can be made to fluoresce, and thus directly visualised. The correlation between fluorescence intensity and polysulfide concentration is also linear when below the linear concentration range of the dye, allowing for polysulfide concentration to be spatially quantified through use of a calibration curve. This enables direct observation of the kinetics of sulfur dissolution and the subsequent diffusion towards the anode and dendrite formation, and thus measurement of the efficacy of steps taken to prevent this.The effects of various additives are elucidated using this method – including the standard LiNO3 additive in sacrificially protecting the lithium anode through SEI formation, as well as novel fibroin-based additives trapping polysulfides within the cathode. Further, the total lack of solubilised intermediate polysulfides within the electrolyte potentially granted by a quasi-solid-state Li-S morphology is assessed through OFM. As is the impact of catalytic additives on the kinetics of the Li-S conversion mechanism, through reduction in the time polysulfides spend in the solubilised state. With OFM, one can directly and conveniently assess the real-time spatial distribution, dynamics, and degree of polysulfide transport in a cycling Li-S cell far faster and significantly easier then would be possible with other methods, and with a very robust dataset. OFM is thus an ideal platform for the development of polysulfide shuttle mitigation strategies, allowing rapid iteration of mitigation methods such as new additives or cathode morphologies. It has the potential for a widespread impact in the field of Li-S batteries, in both industry and academia, through collaboration with and usage by other researchers developing shuttle mitigation techniques. Figure 1

Interfacial Phase Separation Governs the Chemomechanics of Polymer Electrolytes in High-Voltage, Solid-State Lithium Batteries

Polymer electrolytes hold great promise for safe and high-energy solid-state batteries. Multiphase polymer electrolytes, consisting of mobile and rigid phases, exhibit fast ion conduction and desired mechanical properties. However, fundamental challenges exist in understanding and regulating intricate chemomechanical interactions at the electrode-electrolyte interface, especially when using a high-voltage layered cathode. Here, we report that depletion of the mobile conductive phase at the interface contributes to battery performance degradation. Molecular ionic composite electrolytes, composed of a rigid-rod ionic polymer with small mobile cations and anions, serve as a multiphase platform to investigate the evolution of conductive domains at the interface. Synchrotron chemical and structural analyses enable the direct visualization of concentration polarization and spatially resolve the interfacial chemical states over a statistically significant field of view for buried interfaces. We discover that concentration and chemical heterogeneities prevail at electrode-electrolyte interfaces, leading to interfacial chemomechanical degradation. We further demonstrate an interphase tailoring strategy based on electrolyte additives to mitigate such interfacial heterogeneity and improve battery stability. While polymer electrolytes have been considered "deformable" for conformal interfaces, our work shows the hidden roles of interfacial chemomechanics in polymer electrolytes and provides an effective mitigation approach. Figure 1

Solid State Gradients: One Step Aqueous Spray Deposition of Novel Graduated Cathode/Solid Electrolyte Interfaces for Improved Solid State Batteries.

Lithium ion batteries are a necessity of daily life, being used more than ever in increasing size and power for applications like handheld devices, large scale energy storage and transport. They also offer huge potential in our shift towards renewable energy, therefore the production and use of these batteries is set to increase dramatically.Solid state batteries (SSB’s) replace the liquid electrolyte with a solid. This offers more stability against lithium dendrite formation which is the main cause of battery short-circuiting and failure. Because of this, solid state electrolytes (SSE’s) may be the answer to the challenge of pure lithium anodes, which are the highest theoretical capacity anode, but are hampered by rapid dendrite formation. SSE’s can have higher gravimetric and volumetric capacity due to the reduced electrolyte content and also make for safer batteries, particularly under stress, as the flammable liquid electrolyte has been removed.This work demonstrates a new manufacturing method for SSB’s, that allows for the formation of a novel design of the electrode/electrolyte interface. Ultrasonic spray coating is the process of spraying a material layer by layer to form thin films. By graduating between two or more different materials a gradient can be manufactured.Current SSB’s are formed by separately manufacturing a cathode film and a solid electrolyte film, then assembling these on top of each other to make the battery. This can cause interface issues between the cathode and the SSE, particularly, areas of poor contact, poor solid electrolyte interface (SEI) formation and degradation of the cathode. All of these issues lead to higher resistance, lower capacity and higher degradation.This work shows that a spray deposited graduated combined cathode/SSE removes the interfacial issues seen in the literature to create a battery that has 10x lower resistance, longer cycle life, lower capacity loss and performs substantially better under high rate conditions. All of which are necessary to help solid state batteries become more real world applicable.This new manufacturing technique is the only known way to produce this structure in a cheap, industrially relevant way, and is easily expandable to a larger scale. On top of this, unlike standard manufacturing methods, the methodology is almost entirely water based, which removes costs of solvent recapture and increases safety.This layer by layer gradient deposition technique is also applicable to other areas of materials research and has been used on silicon anodes and lithium sulfur batteries, as well as membranes for direct air capture and fuel cells. Figure 1

(Invited) Dynamics and Heterogeneity of Particle Network in Composite Electrodes

We use a data-driven approach to assess the heterogeneous electrochemistry and mechanics in composite cathodes. We visualize the morphological defects at multi-scales ranging from the macroscopic composite, particle ensembles, to individual single particles. Particle fracture and interfacial debonding are identified in a large set of tomographic data. The mechanical damage of active particles is highly heterogeneous. The difference originates from the polarization of the electrolyte potential, various local conducting environments, and thus the non-uniform distribution of the activation energy for the charge transfer reaction. We model the kinetics of intergranular fracture and interfacial degradation to assess the heterogeneous mechanical damage in composite electrodes using microstructure-informed mechanics modeling. We quantify the influence of the mechanical damage on the metrics of battery performance. More interestingly, the interfacial failure reconstructs the conductive network and redistribute the electrochemical activities that render a dynamic nature of electrochemistry and mechanics evolving over time in the composite electrodes.

Exploring the Interaction between EC and Ta-Doped LLZO

Solid-state electrolytes are a primary strategy for unlocking the use of lithium metal anodes and enabling batteries with higher energy density.1 Garnet-type Li7La3Zr2O12 (LLZO) is a leading candidate among ceramic-type materials due to its high ionic conductivity and kinetic stability against lithium metal.2 However, LLZO is air sensitive, spontaneously reacting with CO2 in ambient air to form lithium carbonate layers.3–6 Additionally, we have recently collected evidence, as described below, that suggests that LLZO may even be reactive towards ethylene carbonate (EC), a key liquid electrolyte solvent typically used in battery systems. This reactivity has broad implications for hybrid liquid-solid electrolytes, which have been suggested to alleviate prevalent contact issues between ceramic electrolytes and active materials in battery cathodes.7–9 Previous work has shown that a solution of 1.2M LiBF4 in EC/DEC (diethyl carbonate) can remove surface Li2CO3 from LLZO pellets through an acid-base reaction involving the displacement of labile F- in the BF4 anion.4 Our initial studies expanded this carbonate removal strategy to ceramic powders primarily used in polymer composites. By monitoring the CO2 evolution from particles immersed in a 1.8M LiBF4 in EC solution, we discovered a unique 2-peak structure (see Figure 1) when washing LLZO powders with the procedure described above. Additionally, we evolved 2x more CO2 than would be expected given the amount of Li2CO3 present in our sample. Intriguingly, this behavior seems unique to solutions with EC as the solvent, suggesting some reaction occurring between EC and LLZO. Given the ubiquity of EC as a liquid electrolyte, and potential use in hybrid solid-state/liquid electrolytes, it is critical to inform the solid-state battery community of this previously unknown reaction.(1) Janek, J.; Zeier, W. G. A Solid Future for Battery Development. Nat. Energy 2016, 1 (9). https://doi.org/10.1038/nenergy.2016.141.(2) Connell, J. G.; Fuchs, T.; Hartmann, H.; Krauskopf, T.; Zhu, Y.; Sann, J.; Garcia-Mendez, R.; Sakamoto, J.; Tepavcevic, S.; Janek, J. Kinetic versus Thermodynamic Stability of LLZO in Contact with Lithium Metal. Chem. Mater. 2020, 32 (23), 10207–10215. https://doi.org/10.1021/acs.chemmater.0c03869.(3) Sharafi, A.; Yu, S.; Naguib, M.; Lee, M.; Ma, C.; Meyer, H. M.; Nanda, J.; Chi, M.; Siegel, D. J.; Sakamoto, J. Impact of Air Exposure and Surface Chemistry on Li-Li7La3Zr2O12 Interfacial Resistance. J. Mater. Chem. A 2017, 5 (26), 13475–13487. https://doi.org/10.1039/c7ta03162a.(4) Besli, M. M.; Usubelli, C.; Metzger, M.; Pande, V.; Harry, K.; Nordlund, D.; Sainio, S.; Christensen, J.; Doeff, M. M.; Kuppan, S. Effect of Liquid Electrolyte Soaking on the Interfacial Resistance of Li7La3Zr2O12 for All-Solid-State Lithium Batteries. ACS Appl. Mater. Interfaces 2020, 12 (18), 20605–20612. https://doi.org/10.1021/acsami.0c06194.(5) Hoinkis, N.; Schuhmacher, J.; Leukel, S.; Loho, C.; Roters, A.; Richter, F. H.; Janek, J. Particle Size-Dependent Degradation Kinetics of Garnet-Type Li6.5La3Zr1.5Ta0.5O12 Solid Electrolyte Powders in Ambient Air. J. Phys. Chem. C 2023. https://doi.org/10.1021/acs.jpcc.3c01027.(6) Delluva, A. A.; Kulberg-Savercool, J.; Holewinski, A. Decomposition of Trace Li2CO3 During Charging Leads to Cathode Interface Degradation with the Solid Electrolyte LLZO. Adv. Funct. Mater. 2021, 31 (34). https://doi.org/10.1002/adfm.202103716.(7) Busche, M. R.; Drossel, T.; Leichtweiss, T.; Weber, D. A.; Falk, M.; Schneider, M.; Reich, M.-L.; Sommer, H.; Adelhelm, P.; Janek, J. Dynamic Formation of a Solid-Liquid Electrolyte Interphase and Its Consequences for Hybrid-Battery Concepts. Nat. Chem. 2016, 8 (5), 426–434. https://doi.org/10.1038/nchem.2470.(8) Fu, K. (Kelvin); Gong, Y.; Liu, B.; Zhu, Y.; Xu, S.; Yao, Y.; Luo, W.; Wang, C.; Lacey, S. D.; Dai, J.; Chen, Y.; Mo, Y.; Wachsman, E.; Hu, L. Toward Garnet Electrolyte–Based Li Metal Batteries: An Ultrathin, Highly Effective, Artificial Solid-State Electrolyte/Metallic Li Interface. Sci. Adv. 2017, 3 (4), e1601659. https://doi.org/10.1126/sciadv.1601659.(9) Shi, K.; Chen, L.; Wan, Z.; Biao, J.; Zhong, G.; Li, X.; Yang, L.; Ma, J.; Lv, W.; Ren, F.; wang, H.; Yang, Y.; Kang, F.; He, Y. B. Lithium-Ion Spontaneous Exchange and Synergistic Transport in Ceramic-Liquid Hybrid Electrolytes for Highly Efficient Lithium-Ion Transfer. Sci. Bull. 2022, 67 (9), 946–954. https://doi.org/10.1016/j.scib.2022.01.026. Figure 1

Reliable Simulation Analysis of Interface and SiON Degradation Effects on Water Vapor Barrier in Laminated Thin‐Film Encapsulation

The water vapor barrier performance of laminated thin‐film encapsulations (TFEs) is crucial for ensuring the stability of flexible organic light‐emitting diode (OLED) devices. In this study, the effects of interfaces and SiON degradation on the water vapor barrier performance of TFEs consisting of SiNx and SiON by finite‐element simulation are investigated. In the results, it is illustrated that the interface can significantly hinder water vapor transmission, and the interfacial phase of SiON/SiNx is found to be more effective in impeding water vapor transmission compared to that of SiNx/SiON. The barrier property of TFEs can be weakened by SiON degradation due to oxidation under high temperature and humidity. Among the analyzed four structures, 450 nm SiNx/50 nm SiON/450 nm SiNx/50 nm SiON exhibits the best barrier performance due to strongest interface effects and minimal SiON degradation. These simulation results correlate well with experimental reliability tests, validating the simulation model's reliability. In this study, valuable insights into optimizing TFEs designs for enhanced barrier performances in flexible OLED devices are provided.

Intrusion kinetics and interfacial degradation mechanism of PU-steel system in chloride ion environment: A multiscale study

This study utilised density functional theory (DFT) to predict the movement pathways and rates of chloride ions within polyurethane (PU), as well as their molecular dynamics and charge distribution during the erosion process. Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical tests revealed chemical and electrochemical changes at the PU/steel interface after immersion in sodium chloride solution. Shear strength and nanoindentation tests were used to examine the impact of microscale erosion on macroscale mechanical properties. The results showed that chloride-ion penetration into PU requires overcoming a substantial energy barrier driven by the concentration gradient between the saline solution and PU. After immersion in sodium chloride solution, the −NCO functional groups in PU were disrupted, reducing chemical stability and molecular elasticity. This process accelerates the hydrolysis of ester bonds, leading to a decline in interfacial mechanical properties. Electrochemical results showed that the resistance of the PU coating decreased over time, indicating a transition in the electrochemical reactions that eventually led to interfacial corrosion. After prolonged immersion, both the interfacial shear strength and modulus significantly decreased, whereas the shear ductility initially increased but later decreased.

Understanding Electrochemical Reaction Mechanisms of All-Electrochem-Active Mg2Si Electrode in All-Solid-State Batteries.

To better understand the electrochemical reaction mechanism of the Mg2Si electrode in all-solid-state batteries (ASSBs), a rational all-electrochem-active Mg2Si electrode is first designed to minimize the inactive component-related interfacial degradation. This is due to its unique mixed conductivity properties, including a high electronic conductivity of up to 8.9 × 10-2 S cm-1 and an ionic conductivity of 9.7 × 10-5 S cm-1, which allow for fast charges transport. In ASSBs, the Mg2Si electrode exhibits a higher initial Coulombic efficiency of 83.5% at 300 mA g-1 compared with the Si electrode (72.3%). X-ray diffraction and X-ray photoelectron spectroscopy results demonstrate that intermediate products (LixMg2Si, Li-Si alloy, and Li-Mg alloy) can form when the Mg2Si electrode discharges to 0.01 V, and partial Mg2Si still does not react with lithium. This work provides valuable insights into the reaction mechanisms and guides optimization strategies for developing next-generation Si-based ASSBs.

Distinct photooxidation and interface degradation of waterborne epoxy resin coatings on mortar substrate affected by bulk water

Epoxy-based coatings are widely used in engineering but are prone to degrade under aggressive environmental actions, especially in hygrothermal environments. However, the degradation mechanisms of a coating-substrate system under coupled UV irradiation and bulk water remain insufficiently explored. Herein, we designed three parallel accelerated aging tests, including UV irradiation only, UV/flush, and UV/submerged, on a waterborne epoxy resin (WER) coating on cement mortar substrate. The chemical structure, micro-morphology, and hydrophilicity over aging time were comprehensively characterized by the tests of attenuated total reflectance Fourier transformation infrared spectrometer (ATR-FTIR), scanning electron microscopy (SEM), image analysis, water contact angle (WCA). Results show that the UV/flush environments induced more micro-pinholes on the WER outer surface than the neat UV photooxidation. The UV/ submerged environment led to a blistering rate over 24% after 60 d's exposure owing to the significant osmotic pressure built between the inner and outer surfaces of the WER coating. Additionally, the physicochemical and microstructure changes to the outer surface of WER also caused the changes of WCA. The osmotic, hydrolysis, and thermal stresses were evaluated to clarify the water-accelerated photooxidation and interface degradation mechanisms. These findings contribute to a deeper understanding of epoxy coating degradation mechanisms in response to environmental stressors, and offer insights for enhancing coating performance under varying conditions.

Layered/Olivine Composite Structure-Induced Stable Gradient Interfacial Chemistry toward High-Temperature Lithium-Ion Batteries.

The state-of-the-art layered oxide as the cathode material for lithium-ion batteries has attracted wide attention; however, harsh operations of high-energy and high-safety energy-storage technology at high temperature is challenging owing to the aggravated structural instability and parasitic reactions at the cathodes. Herein, the layered/olivine composite structure architecture is designed at the grain surface to govern constant electrochemistry in a harsh environment, and a gradient LiF interlayer is developed onto the cathodes to suppress the interfacial degradation. By a combination of interfacial-sensitive characterizations and theoretical analysis at the cathode/interface, the formation mechanism of this special interphase induced by the composite structure cathode is revealed. The composite structure cathode could deliver an excellent high-temperature cycling stability with 90.8% retention for 300 cycles in the half cell and 95.6% retention for 1000 cycles in the pouch cell and simultaneously enhances ∼51% of the thermal stability, which broadens the approaches for developing high-stable cathodes that work in extreme environments.