Binder Content Research Articles

Regolith-Rich PEEK Composite Bricks: Steps Towards Space-Ready Lunar Construction Materials

This study introduces a novel composite construction material composed of lunar regolith combined with PEEK in dry powder form. The work demonstrates significant advantages over alternative methods, primarily by reducing production power consumption and simplifying the manufacturing process. Building on previous research that explored binder optimization through process simplification and targeting predefined shapes, this work delves deeper into a comparative analysis of high-performance thermoplastics. Among the various options, PEEK demonstrates the most favorable properties. The study investigates key processing parameters and evaluates the effects of vacuum processing and temperature testing on mechanical properties. The research also evaluates the effects of vacuum processing and temperature testing to assess the material’s performance under lunar conditions. Comparative analysis is performed with standard performance of various reinforced and unreinforced concretes and with standard requirements for construction bricks as per ASTM standards. This shows that the composite, with an organic binder content as low as 5 wt%, has great potential. Notably, the improvements achieved through vacuum curing ensure compliance with lunar environmental conditions and alignment with most Earth-based engineering standards. Samples compacted at 7.50 MPa with 10 wt% binder, and tested at room temperature, achieve a compression strength of 16.3 MPa, exceeding that of industrial floor bricks and matching that of building bricks used on Earth. Bending strength (7.4 MPa) aligns with steel fiber-reinforced and high-strength concretes. Vacuum curing further enhances these properties, with an observed increase of +66% in bending strength and +33% in compression strength.

Early quality control of stabilised dredged material by correlating heat production with strength

This study explores the use of isothermal calorimetry to assess heat release during the initial phases of dredged sediment (DS) stabilisation with the primary goal of predicting the 28-day unconfined compressive strength (UCS) and enhancing the stabilisation process’ quality control. The study was performed on DS samples collected from Göta river, Gothenburg, Sweden. The water content of the raw DS was set to 138%, 185%, and 291%, and mixing was performed with water-to-binder ratios 4, 5, 6, 7, and 8 using a binder consisting of 40% Portland limestone cement and 60% slag. The heat release measurements were conducted during the first 7 days of hydration, non-destructive free–free resonance tests were performed at 7, 14, and 28 days of hydration, and the 28-day UCS was done to assess the compressive strength of stabilised DS. For each water content, a statistical analysis was performed to determine the strength of the relationship, specifically using linear regression, to assess how well early calorimetric data could predict the UCS, and a correlation was found between the 28-day compressive strength and heat release of stabilised DS after 48 h of hydration. By measuring water content and heat release in the early stages of stabilisation, it is thus possible to assess the binder content and predict the ultimate compressive strength of a treated DS.

Enhancing physical and mechanical properties of single-layer particleboards bonded with canola protein adhesives: impact of production parameters

AbstractThis study investigates the effects of various production parameters on the physical and mechanical properties of one-layer particleboards bonded with canola protein-based adhesives. Two protein-based adhesive formulations, CPI-B-0 with sodium bisulfate and CPI-N-60 with sodium nitrite crosslinkers, were examined under different conditions: binder content, press temperature, and press time factor. Results indicate that the CPI-N-60 outperformed the CPI-B-0 in terms of internal bonding strength (IB), modulus of rupture (MOR), and modulus of elasticity (MOE) due to the stronger covalent bonds formed with primary amines present in the protein adhesive. Increasing binder content led to significant improvements in mechanical properties, with the internal bonding and the MOR increasing by 21% and 9% when using 9% binder content over 7% respectively. The press temperature, as well as the press time were found to yield the highest influence on mechanical properties, with higher values resulting in better performance. Increasing the press temperature from 170 °C to 190 °C led to 33% increment in the internal bonding and 20% in the MOR, while 67% and 28% increment was obtained with 210 °C press temperature, respectively. Increasing the press time also led to an increase in the mechanical properties of the particleboards, by almost the same proportions as the effect of press temperature. The interaction effects between production parameters highlighted the importance of optimized conditions for achieving the desired properties. Indeed, under certain press conditions, the CPI-N-60 outperformed the conventional UF K345, achieving an IB value of 0.8 N/mm2 over 0.65 N/mm2. Overall, this study contributes to a better understanding of canola protein-based bio adhesive, with implications for the optimization of the production parameters for better boards’ properties.

Preparation of Slurry for Tape Casting of AlN Ceramic Substrates

AlN ceramics are employed in a multitude of applications including large-scale integrated circuit (LIC) packaging substrates, electrostatic chucks, and transparent ceramics due to their excellent thermal conductivity, insulation and dielectric properties, robust corrosion resistance, and thermal expansion coefficient nearly identical to that of silicon. Tape casting is the optimal methodology for the fabrication of large-area, thin, and flat ceramics and components. However, the well-dispersed slurry with high solid loading is required to obtained the ceramic substrates with excellent properties by tape casting. Therefore, in this study, the effects of dispersant content, first ball milling time, binder content, and R value (plasticizer/binder) on the rheological properties of aluminum nitride slurry and casted sheet qualities were investigated. The results indicated that the optimal dispersant formulation was 1.1 wt%, the binder formulation was 2 wt%, the R value was 1.5, and the solid content was 60 wt%. The utilization of the aforementioned organic system enabled the preparation of AlN sheet exhibiting favorable morphology, high solid content, and flexibility.

SHEAR STRENGTH PARAMETERS AND DEFORMABILITY PROPERTIES OF SILICATE-BASED RESIN ADDED SAND-TYPE SOIL SPECIMENS

In this study, the shear strength, uniaxial compressive strength (UCS) values and deformability properties of silicate-based polymer resin added silty sand type soil specimens were examined through a series of experimental studies. Although the UCS and shear strength values increased, minor decreases in the internal friction angle values were measured as the resin ratio increased. It was determined that the main reason of improvement in the strength values due to the increase in resin content is the increase in cohesion values. It was found that the UCS values calculated according to the cohesion and internal friction angle parameters of the Mohr&Coulomb failure criterion (UCSc) were 2.6-3.0 times lower than the values obtained from the direct UCS experiment. According to this finding, it was concluded that the Mohr&Coulomb failure criterion is not properly usable to represent the mechanical behaviors of resin added sands. As another outcome, the ratio between UCS/UCSc slightly decreased with an increase in the resin amount. In other words, it has been determined that the Mohr&Coulomb failure criterion gives a bit more inaccurate results for the specimens with low binder contents. With the increase in the resin content ratio, significant increases were obtained in both elastic modulus and ductility properties of the samples. It has been evaluated that the silicate-based polymer resin binder is advantageous to provide significant increases in the toughness and energy absorption capacity of soils.

Influence of the Bailey Gradation Method on the Mechanical Behavior of Asphalt Mixture Containing Steel Slag as an Alternative Aggregate

This study evaluates the feasibility of reusing steel slag aggregates in asphalt concrete, analyzing the impact of different gradation methods (Bailey method and conventional Brazilian method) on the mechanical properties of the mix. Using the Marshall methodology and Petroleum Asphalt Concrete (PAC) 30/45, parameters such as Marshall stability, indirect tensile strength, resilient modulus, fatigue life through diametral compression, and permanent deformation (Flow Number) were investigated. Additionally, a simulation for a hypothetical section in the city of Rio de Janeiro, Brazil, was performed using the mechanistic-empirical pavement design software, Medina. The results showed that the mixture produced by the Bailey method outperformed the others in all analyses. This method led to a more compact mix, providing significant advantages, including up to a 35% reduction in final pavement thickness and a 110.6% increase in Flow Number (FN), enabling the mix to withstand extremely heavy traffic, as reported in the literature. Regarding fatigue life, the Bailey mixture achieved a fatigue class of 4, compared to the conventional mixture class 1. These findings indicate that using the Bailey gradation method for producing asphalt mixtures with steel slag can optimize binder content and improve resistance to permanent deformation and fatigue, making it a viable and sustainable alternative for asphalt pavements.

Densification behavior of ultrafine WC‐based composites with AlxCoCrCuFeNi high‐entropy alloy binders

AbstractUltrafine WC‐based cemented carbides with 10 wt.%AlxCoCrCuFeNi high‐entropy alloy (HEA) binders were fabricated by spark plasma sintering, and the effects of HEA binders on the densification behavior of the WC‐HEA cemented carbides were studied. The densification of the WC‐HEA cemented carbide, as well as traditional WC‐Co, can be divided into the slow densification stage, rapid densification stage, and final densification stage. The densification behavior of the WC‐HEA cemented carbides largely depends on the performance of the HEA binder during the SPS process. The sluggish diffusion effect of HEA weakens the diffusion of W atom on the powder particle surface and inhibits the growth of WC grain. Consequently, the disappearance of pores in the sintered compact is hindered, which leads to a low relative density of the WC‐HEA cemented carbide. With the increase of Al content, the inhibitory effect of the AlxCoCrCuFeNi binder on the growth of WC grain is suppressed, and an Al‐containing phase with a low melting point is more likely to form. Therefore, the relative density of the WC‐10 wt.%AlxCoCrCuFeNi cemented carbide raises linearly with increasing Al content of the HEA binder.

Formulation of Morinda Citrifolia L. Dried Extract in Tablet form by Direct Compression and Evaluation Using Design of Experiments

Introduction: The work aims to prepare tablets of Morinda citrifolia hygroscopic dry powder extract by direct compression method and applying DoE 32 factorial design. Methods: All the statistical calculations and interpretation of the results were carried out using the Design Experiment 10 software version. Nine different formulation trials were conducted. Varying concentrations of binder (Ethyl cellulose) and disintegrating agents (Microcrystalline cellulose) are considered as two independent variables. Magnesium stearate, polyethene glycol-4000, sucrose and starch are used as bulking agents. The effect of the two variables on the hardness, time of disintegration and in vitro drug release were evaluated. Results: All the materials were compatible and found stable during the study. Among the nine different formulations, F9 formulation with binder and disintegrating in a 20:40 ratio showed 90.31% drug release. From the overlay plot, the F10 checkpoint batch was formulated and evaluated. F10 formulation was the most suitable formulation with a hardness of 5.2Kg/cm2, a disintegrating time of 31.6 min with 86.98% drug release. Conclusion: DoE 32 factorial design can be used to formulate tablets of Morinda citrifolia hygroscopic dry powder extract. The F10 formulation is considered as the optimized preparation. According to the Design of experiments, it is concluded that as the concentration of binder and disintegrating agent increases then the hardness, disintegration and percent drug release of the formulation also increases.

Evaluating the Strength and Durability Properties of Geopolymer-Stabilized Soft Soil for Deep Mixing Applications

Soft soil poses serious challenges and is unsuitable for engineering projects because of its insufficient bearing capacity, low shear strength, and high compressibility. Deep soil mixing (DSM) is one of the most popular methods of enhancing soft soil qualities, such as increased bearing capacity and reduced settling, which are critical for building any structure. The environmental effects of creating binders such as cement and lime make it crucial to identify alternative materials for geotechnical applications. This study employed fly ash (class C) --based geopolymer to investigate its effectiveness as an environmentally friendly substitute for cement for DSM applications. The experimental program included unconfined compressive strength, flexure strength, and durability tests. The parameters in the study are binder content (10, 15, and 20%) and activator/binder ratio (0.4, 0.6). Results revealed that UCS and flexural strength, GP-treated soil were in the range of 0.9–5.3 and 0.8–1.5 MPa, respectively (depending on the ratio of fly ash and activator). These strengths were even higher than those of cement-stabilized soil. The geopolymer-treated specimens exhibited excellent endurance over the wetting-drying cycle, with a modest weight loss of less than 4.5%. A binder dosage of more than 10% and an AC ratio of 0.6 were recommended to meet DSM application guidelines. The current study concludes that employing a fly ash-geopolymer binder to stabilize soft soil is an effective alternative to cement in DSM applications.

Experimental investigation and optimization of one-part alkali-activated self-compacting concrete mixes

Emphasizing the growing importance of sustainability, alkali-activated materials (AAMs) have emerged as a revolutionary alternative for cement in the construction sector. This study delves into the fresh, mechanical, and microstructural properties of One-Part Alkali-activated Self-compacting Concrete (OPASC) mixes. While mixtures of Ground Granulated Blast Furnace Slag (GGBFS) and Fly Ash (FA) were utilized as the precursors, powdered sodium metasilicate was employed to function as the activator. To streamline experimental design and reduce the economic demands of extensive testing, the Taguchi-Grey Relational Analysis (GRA) was utilized to identify optimal multi-response parameter levels. This method considered binder content (B) within a range of 700–800kg/m³, water-to-binder (W/B) ratios between 0.38 and 0.42, and Na2O percentages from 5% to 7% as key input variables. Results indicated that the designed mixes recorded workability values satisfying the EFNARC guidelines, compressive strengths greater than 60MPa, split-tensile strengths in the range of 3.5-4.6MPa, and flexural strengths varying between 5.5-7.2MPa. The mix parameters for the optimal mix, with the highest mean grey relational grade, were identified from the Taguchi-GRPA approach as B = 750kg/m3, W/B = 0.4, and N = 6%. Microstructural analysis revealed the formation of C/N-A-S-H type gels, which are instrumental in developing a compact matrix enhancing the mechanical properties. A good agreement between actual experimental results obtained for a different set of verification mixes with those predicted by regression-equations confirmed the potency of the Taguchi-GRA approach in optimizing the OPASC mix parameters.

Strength and Durability Characteristics of Sustainable Pavement Base Course Stabilized with Cement Bypass Dust and Spent Fluid Catalytic Cracking Catalyst

This study explores the potential of a composite binder comprising cement bypass dust (CBD) and spent fluid catalytic cracking (FCC) catalyst for sustainable pavement base stabilization. Various CBD/FCC ratios (30:70, 50:50, 70:30) and binder contents (4%, 6%, 8%, 10%) were evaluated through laboratory testing. The 50:50 CBD/FCC mixture demonstrated optimal performance, achieving an unconfined compressive strength (UCS) of 15.6 MPa at 28 days with 10% binder content. The mix exhibited improved stiffness (E50 modulus up to 13,922 MPa) and resistance to degradation under wetting–drying cycles, attributable to synergistic cementitious and pozzolanic reactions. Microstructural analysis revealed a denser matrix, validating the enhanced performance. These findings suggest CBD and FCC, as promising materials for sustainable pavement construction, align with circular economy principles.

Evaluating the effect of reclaimed asphalt pavement on rubberized hot mix asphalt in pilot projects

The study goal is to evaluate the use of up to 10 % reclaimed asphalt pavement (RAP) by aggregate replacement in rubberized hot mix asphalt-gap graded RHMA-G mixes to identify any significant potential problems for durability. Five pilot projects were built, each including a control RHMA-G (without RAP) and an RHMA-G with 10 % RAP. The mixes were sampled during production and evaluated using volumetric assessment, and performance related tests including stiffness, four-point bending fatigue resistance, fracture resistance measured with the IDEAL cracking test, and rutting resistance. Mix testing results indicate that the addition of 10 % RAP had minor effects on the mechanical properties. With a few exceptions related to the total binder content of the mixes, the effect of the RAP addition was negligible compared to normal production variability. Modeling with CalME, Caltrans mechanistic-empirical asphalt pavement design software and four-point bending testing results, indicated that RAP addition effects on pavement cracking performance were either negligible or comparable to mix-to-mix RHMA-G variability. Regarding constructability, RAP addition did not create any problems. The life cycle assessment completed in the study indicates that the addition of 10 % RAP to the RHMA-G can reduce the greenhouse gasses emissions associated with the RHMA-G production (cradle-to-gate) by up to 5 %.

Effect of polyphenylene sulfide content on the properties of injection molding bonded NdFeB magnets

AbstractThe effect of polyphenylene sulfide binder content on the properties of injection molding polyphenylene sulfide/NdFeB magnets were investigated. The maximum filling amount of NdFeB magnetic powder was 87.6 wt.‐%, and the mixing process and subsequent injection molding of the polyphenylene sulfide/NdFeB were in good condition. The melt mass‐flow rate of the polyphenylene sulfide/NdFeB granular materials reached 121.7 g/10 min, the compressive strength of the polyphenylene sulfide/NdFeB magnet was 92.18 MPa, and its maximum magnetic energy product reached 5.59 MGOe. The structure and morphology characteristics of polyphenylene sulfide/NdFeB magnets were investigated using scanning electron microscopy and atomic force microscopy. The corrosion behavior of polyphenylene sulfide/NdFeB magnets was also studied using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results indicated that the injection molding process facilitated the uniform coating of polyphenylene sulfide particles on NdFeB powder, which directly enhanced the corrosion resistance of polyphenylene sulfide/NdFeB magnets. With an increase in polyphenylene sulfide content, the surface of polyphenylene sulfide/NdFeB magnets became more uniform. The corrosion current density of 13 wt.‐% polyphenylene sulfide/NdFeB magnet was approximately one order of magnitude lower than that of 9 wt.‐% polyphenylene sulfide/NdFeB magnet, indicating an improved corrosion resistance of polyphenylene sulfide/NdFeB magnet.

Evaluation of Concrete Compressive Strength Prediction Using the Maturity Method Incorporating Various Curing Temperatures and Binder Compositions.

This study aims to systematically analyze the effects of different curing temperatures, unit binder content, and the mixture ratios of ground granulated blast-furnace slag and fly ash based on ordinary Portland cement in binders on the development of concrete compressive strength. Particularly, the study evaluates strength characteristics by calculating the maturity equivalent to 28 days of curing at 20 °C. A model based on the relationship between maturity and strength was applied to predict the compressive strength, and the experimental data were analyzed to derive strength coefficients for each variable. The results showed that at a low temperature of 5 °C, the actual strength was lower than the predicted strength, leading to higher error rates. In contrast, at temperatures of 20 °C and 40 °C, the coefficient of determination (R2 > 0.90) for the predictive equation was high, and the error rates were reduced to within 10%. The study demonstrates that by combining the maturity method with the strength-maturity relationship, the concrete compressive strength can be effectively predicted under specific curing and binder design conditions.

Additive Manufacturing of Tungsten Carbide (WC)-Based Cemented Carbides and Niobium Carbide (NbC)-Based Cermets with High Binder Content via Laser Powder Bed Fusion

The additive manufacturing technique performed via laser powder bed fusion has matured as a technology for manufacturing cemented carbide parts. The parts are built by additive consolidation of thin layers of a WC and Co mixture using a laser, depending on the power and scanning speed, making it possible to create small, complex parts with different geometries. NbC-based cermets, as the main phase, can replace WC-based cemented carbides for some applications. Issues related to the high costs and dependence on imports have made WC and Co powders emerge as critical raw materials. Furthermore, avoiding manufacturing workers’ health problems and occupational diseases is a positive advantage of replacing WC with NbC and alternative binder phases. This work used WC and NbC as the main carbides and three binders: 100% Ni, 100% Co, and 50Ni/50Co wt.%. For the flowability and spreadability of the powders of WC- and NbC-based alloy mixtures in the powder bed with high cohesiveness, it was necessary to build a vibrating container with a pneumatic turbine ranging from 460 to 520 Hz. Concurrently, compaction was promoted by a compacting system. The thin deposition layers of the mixtures were applied uniformly and were well distributed in the powder bed to minimize the defects and cracks during the direct sintering of the samples. The parameters of the L-PBF process varied, with laser scanning speeds from 25 to 125 mm.s─1 and laser power from 50 to 125 W. Microstructural aspects and the properties obtained are presented and discussed, seeking to establish the relationships between the L-PBF process variables and compare them with the liquid phase sintering technique.

Effect of Cement Substitution with Mineral Fillers on NOx Air-Purification Efficiency and Photocatalytic Reaction Selectivity of Nano-TiO2-Modified Cementitious Composites.

This research investigated the properties of photocatalytic cementitious composites, including their air-purification efficiency. A method of characterizing the removal of airborne pollutants (nitrogen oxides), simulating the actual NOx concentration and irradiation conditions in Warsaw, Poland, in the autumn/winter season was established. The study analyzed the impact of changes in the composition of cement mortars-partial substitution of the binder with mineral fillers-on the properties of the external photoactive surface of the composite. The designed experimental plan included both quantitative and qualitative variables (type and amount of fillers used). It was found that the photocatalytic performance of the composite was correlated with its pore total content and pore size distribution-the higher the content of mineral fillers, the lower the porosity and the less effective its photocatalytic properties. The selectivity of the photocatalytic NOx reactions also deteriorated as the content of the mineral fillers increased. The study confirmed the validity of increasing the binder content in cementitious composites to enhance their photocatalytic performance.

Investigating the Impact of Various Binder Contents and Compression on Graphite Electrode Thickness Change Measurements

Volume change of active materials during the insertion of Li+-ions into the electrode’s host structure in lithium-ion batteries (LiBs) has become an increasingly researched topic. Reversible and irreversible thickness changes occur during operation because of active material volume change upon lithiation/delithiation and SEI growth. In LiBs, particularly the volume change of the negative active material can cause mechanical disintegration of the composite coating [1], causing loss of active material. LiBs are usually operated in a compressed state maintained by geometrical boundary conditions to ensure uniform contact between electrode layers. Therefore, the thickness changes can cause increased stack pressure and, subsequently, microstructural changes [2] and thus affect the performance and lifetime of the battery [3]. To better understand the aforementioned phenomena, accurate thickness measurements are required.Measuring the thickness change of a cell stack does not provide accurate information about the individual thickness change of the two electrodes. Therefore, single-electrode electrochemical dilatometry (ECD) can help to better understand the impact of the individual electrodes on cell stack thickness change. Due to the common use of a commercially available setup (EL-Cell, ECD-3-nano, Germany) in literature, most ECD experiments were conducted at a pressure of ~ 16 kPa onto a Ø10 mm working electrode (WE). Only in some publications higher pressures > 0.1 MPa were applied during single electrode measurements [4]. The applied pressure in lab-scale coin cell setups and state-of-the-art LiBs is usually significantly higher (0.1 – 0.5 MPa) than that of single-electrode ECD investigations. Therefore, the question arises whether the pressure has an impact on the measured thickness change.Thus, this work integrates a wave spring washer into a commercially available single-electrode ECD Setup (ECD-3-nano, El-Cell GmbH, Germany) to apply additional pressure onto the WE, without requiring geometrical modifications of the setup. The integration of the wave spring washer increases the applied pressure from 16 kPa to > 100 kPa. Graphite electrodes with different binder types and contents are investigated since distinct measurement artifacts were observed for electrodes with certain binder compositions in preliminary experiments. Electrodes without additional pressure show a first-cycle lithiation thickness increase of up to 30% (see Figure 1), which is much higher than the active material volume change of graphite obtained from XRD data [5] would suggest. For all examined electrodes at lower pressure the first and tenth cycle lithiation thickness change is more than 50 % higher compared to the setup at high pressure. The mechanism causing the discrepancy between measurements at the two pressure levels is identified as the curvature of the electrode edges at low pressures present in commercially available ECDs. Therefore, the setup at increased pressure enables a meaningful investigation of the influence of the binder content on irreversible and reversible thickness change for the electrodes under investigation using more realistic mechanical boundary conditions. Measurements show that irreversible thickness change decreases with increasing binder content. Possibly the higher binder content helps to prevent restructuring of the particles during cycling due to higher mechanical strength of the electrode. Delithiation thickness change is similar among electrodes with normal to high binder contents. Only electrodes with a very low binder content have a significantly lower reversible thickness change.Overall, this study shows that the influence of pressure onto the WE should be considered for future ECD-experiments and setups. This work presents an easy to implement solution to apply additional pressure onto the WE for a common commercially available ECD-setup.

A Novel Approach to Electrode Delamination for Mechanism Analysis and Signal Detection: Fault-Simulated Li-Ion Batteries

The demand for increasing energy density of lithium-ion batteries (LIBs) continues to drive research into new compositions and designs. Some prominent strategies are to reduce the content of inactive materials, such as binders and conductive materials, and to increase a thickness of electrodes. However, these approaches can lead to uneven binder distribution and delamination of electrode layers due to the continuous volumetric expansion of the active material reducing the capacity and lifespan of the LIBs. Therefore, binder content and distribution analysis plays a critical role in evaluating battery performance. However, most extensive research has focused on improving the properties and distribution of binders, and systematic analysis and non-destructive detection of defects by binders remain largely unexplored. This research also is crucial for evaluating the remaining life of the battery and determining its suitability for reuse. In this study, we fabricated a fault-simulated electrodes which can be easily delaminated during electrochemical reactions. When the morphology and composition of the electrode were analyzed, there were no significant morphological differences compared to a normal electrode, but it was observed that the binder compositions were different. As a result of the adhesive strength measurement of the defected electrode at different thicknesses, it was demonstrated that the adhesive strength at the electrode layers and interfaces decreased compared to normal electrodes. The electrochemical signals such as capacity fading and resistance characteristics by the electrode delamination were confirmed. Through the post-mortem analysis, the composition change in the cathode-electrolyte interphase (CEI) inside the electrode was compared and analyzed in relation to the change in current density distribution based on simulation. Furthermore, in order to nondestructively detect the electrode delamination defects, a magnetic field imaging and simulation analyses were conducted, and it was confirmed that the detection of defect spots was possible through this method. By systematically analyzing the electrode delamination, the main cause of electrode degradation was elucidated.

Bi-Dimensional PTFE Fibrillation Process Implemented in Solvent-Free Manufacturing of Ultra Thick Electrodes for Lithium-Ion Batteries

A method for manufacturing electrodes via a solvent-free dry process can dramatically increase the energy density of lithium-ion batteries (LIBs) without the use of toxic organic solvents. This innovative approach is a strong candidate for advanced battery technologies due to its environmental benefits and cost savings. However, ultra thick electrode required to achieve high energy density significantly intensifies the migration resistance (Rion) and charge transfer resistance (Rct) by longer diffusion length of lithium ions and electrons.The fundamental solution proposed to solve this problem is to increase the conductive additives content to form the enhanced electronic conductivity networks. However, the higher the content of conductive additives in the electrode composition, the more binder is required. If the binder content is insufficient, the increased contact area and excessive agglomeration due to the high specific surface area of the conductive additives will result in reduced interparticle cohesion and uneven packing density. This hinders the formation of a continuous fiber matrix in the PTFE fibrillation process and consequently weakens the mechanical properties of the electrode.In this study, the proposed bi-dimensional PTFE fibrillation process can be effectively utilized to form a uniform and efficient fiber matrix within electrodes, even at high conductive additives content (≥5 wt%) and low binder content (≤1 wt%). This process enables the electrodes to be stored and transported in roll form and preserves the structural integrity of the electrodes during mass production. Moreover, the high and uniform conductivity of the manufactured electrodes prevents significant increases in resistance, even with increased electrode thickness, thus enhancing the electrochemical performance of high energy density LIBs.

Constriction Effect in All-Solid-State Cathodes

The demand for batteries with high gravimetric and volumetric energy density is driving research towards the development of new battery technologies. All-solid-state batteries (ASSBs) offer the potential to address current challenges faced by liquid electrolyte-based batteries, such as the implementation of Li-metal or fully utilized silicon as an anode material.1 To date, however, there are no commercially available ASSBs with an inorganic solid electrolyte on the market, because of new challenges when using solid electrolytes, such as interfacial stability, solid-solid contact problems, or the ability to operate at low pressures.2 Eckhardt et al.3 recently demonstrated that voids at the interface of a solid electrolyte based separator and a Li-metal anode cause an additional resistance called constriction resistance. This effect occurs when current lines are constricted by bottlenecks (voids) at the interface. In the absence of voids at the interface, the current lines are not constricted, and no additional resistance is observed.4 Due to its frequency-dependent nature, this additional resistance can generally only be detected by impedance spectroscopy. During Li stripping, voids may form at the interface, resulting in a higher current density at the remaining contact areas during plating.5 This ultimately leads to the formation of Li dendrites, making the constriction effect the primary driver of a critical failure mechanism of ASSBs.In the present study, we present experimental evidence of a constriction effect in composite cathodes, composed of either single or polycrystalline LiNi0.6Mn0.2Co0.2O2, solid electrolyte (Li6PS5Cl), conductive carbon additive, and a polymeric binder. Voids can be caused by a poor microstructure or by the incorporation of a non-conductive polymer binder, which exhibits properties analogous to those of voids. However, large-scale roll-to-roll production of sulfidic ASSB components requires polymeric binders.6 The constriction effect can be observed through impedance spectroscopy of cathodes in blocking conditions as a semicircle that overlaps with the 45° line of the transmission line model. We investigate fitting with different equivalent circuits that model the constriction effect, and show the dependence of the constriction effect on densification pressure, binder content, and active material loading. Using a µ-reference electrode in ASSB single-layer pouch cells,7 the change of the constriction effect in the cathode is monitored during cycling. Additionally, LiNi0.6Mn0.2Co0.2O2/Li6PS5Cl core-shell particles are explored to examine whether this can reduce the constriction effect in sheet-type cathodes. Overall, the constriction of current lines in the cathode is a solid-state-related geometric effect that increases the overall cell resistance and is not observed in liquid electrolyte-based batteries. Our findings provide an overview of the constriction effect in all-solid-state cathodes and its impact on cell performance. Acknowledgment The authors wish to thank C. Sedlmeier and F. Friedrich from BMW as the project initiator and for the scientific support. This work is part of the BMW project “IPCEI EuBatIn” (16BZF205), which is funded by the German Federal Ministry for Economic Affairs and Climate Action and the Bavarian Ministry of Economic Affairs, Regional Development and Energy. References J. Janek and W. G. Zeier, Nat Energy, 8(3), 230–240 (2023).T. Schmaltz, F. Hartmann, T. Wicke, L. Weymann, C. Neef and J. Janek, Advanced Energy Materials, 13(43), 2301886 (2023).J. K. Eckhardt, P. J. Klar, J. Janek and C. Heiliger, ACS Applied Materials & Interfaces, 14(31), 35545–35554 (2022).J. K. Eckhardt, T. Fuchs, S. Burkhardt, P. J. Klar, J. Janek and C. Heiliger, Adv Materials Inter, 10(8) (2023).P. Barai, T. Fuchs, E. Trevisanello, F. H. Richter, J. Janek and V. Srinivasan, Chem. Mater., 36(5), 2245–2258 (2024).J. Lee, T. Lee, K. Char, K. J. Kim and J. W. Choi, Accounts of chemical research, 54(17), 3390–3402 (2021).C. Sedlmeier, R. Schuster, C. Schramm and H. A. Gasteiger, J. Electrochem. Soc., 170(3), 30536 (2023).