Philip Scharfer

• Karlsruhe Institute of Technology

The drying of electrode coatings represents a critical stage in the battery production process, where even slight deviations in drying conditions can lead to defects, resulting in high rejection rates, increased costs, and material waste. To address these challenges, the integration of in-line measurement technologies offers a promising solution. F...

Innovations in scalable fabrication processes are pivotal for transferring record power conversion efficiencies (PCEs) of spin‐coated perovskite/silicon‐based tandem solar cells (TSCs) from the laboratory scale to full‐size photovoltaics. In this regard, the homogeneous large‐area drying of precursor ink wet films poses one of the major hurdles. Ga...

The present work addresses the simulation of pore emptying during the drying of battery electrodes. For this purpose, a model based on the multiphase-field method (MPF) is used, since it is an established approach for modeling and simulating multiphysical problems. A model based on phase fields is introduced that takes into account fluid flow, capi...

To achieve the goal of sustainable and competitive production of battery electrodes, the integration of recycling approaches into the product life cycle is becoming increasingly important. In addition to the fixed recycling quotas for end-of-life batteries, which are legally stipulated for the future, production scrap also plays a decisive role. Pr...

The drying process of battery electrodes is a crucial and expensive step in the battery manufacturing process as it significantly impacts the performance of the final cell. One major challenge is minimising high scrap rates, which has a marked impact on material efficiency and production costs. One approach is to utilise additional in-line sensors...

Multi-layer coating is a promising method for optimizing the properties of battery electrodes. This study examines the simultaneous coating of anodes with a primer layer without the necessity of a second coating and drying step, as it is the case for sequential coating processes. The primer layer is used to concentrate the binder in proximity to th...

Primers are used to promote adhesion and reduce electrical interface resistance. Normally, the process of applying primer and electrode coating happens in two separate, sequential steps. Herein, primer and electrode are applied simultaneously, wet‐in‐wet. For fast drying of electrode coatings, a binder‐redistribution by binder migration happens. A...

At the research level, novel active materials for batteries are synthesised on a small scale, fabricated into electrodes and electrochemically characterised using each group’s established process due to the lack of standards. Recently, eminent researchers have criticised the implementation of e.g. low active material contents/electrode loadings, th...

Two main goals for the industrial, slurry‐based electrode processing are a high process speed and the maximum possible material efficiency. This makes an increased drying rate and active material share favorable, but both are limited by adverse effects on the electrode quality. The adverse effects of fast drying are associated with the migration of...

The drying of solvent‐processed electrodes is a critical process step in the manufacturing of lithium‐ion batteries. The technology used to introduce the energy required for drying into the material, combined with the specified process parameters, significantly influences the resulting electrode properties. A major challenge is to counteract binder...

In the production of catalyst‐coated membranes (CCMs) for proton‐exchange membrane fuel cells and electrolyzers, the ink formulation and its processing are key factors in determining the resulting catalyst layer. Catalyst inks often contain a multicomponent solvent mixture. Selective drying, which can occur with solvent mixtures, changes the compos...

In the battery industry, very thin primer layers are used to improve electrode adhesion on substrates or act as blocker layers to prevent corrosion in case of aqueous cathodes. For these material configurations, high-speed coating is mandatory to ensure the economic viability of the process. One way to realize high-speed coating is a set-up includi...

Nanoparticles have many advantages as active materials, such as a short diffusion length, low charge transfer resistance, or a reduced probability of cracking. However, their low packing density makes them unsuitable for commercial battery applications. Hierarchically structured microparticles are synthesized from nanoscale primary particles by tar...

In this study, carbon nanotubes (CNT) were used as an additive in coating inks for catalyst layers for PEM electrolyzers and fuel cells. Catalyst layers with and without CNT were prepared by direct membrane coating and analyzed for cracking behavior. The influence of CNT on crack prevention is discussed by varying the film thickness. Layers with CN...

Sodium‐ion batteries are becoming an increasingly important complement to lithium‐ion batteries. However, while extensive knowledge on the preparation of Li‐ion batteries with excellent cycling behavior exists, studies on applicable long‐lasting sodium‐ion batteries are still limited. Therefore, this study focuses on the cycling stability of batter...

Sodium‐ion batteries are an emerging technology that is still at an early stage of development. The electrode processing for anode and cathode is expected to be similar to lithium‐ion batteries (drop‐in technology), yet a detailed comparison is not published. There are ongoing questions about the influence of the active materials on processing para...

Sodium-ion batteries are becoming an increasingly important complement to lithium-ion batteries. However, while extensive knowledge on the preparation of Li-ion batteries with excellent cycling behavior exists, studies on applicable long-lasting sodium-ion batteries are still limited. Therefore, this study focuses on the cycling stability of batter...

Porous, nanostructured particles ensure the wetting of electrolyte up to the particle core and shortened diffusion paths, which is relevant not only for lithium‐ion batteries but also for postlithium systems like sodium‐ion batteries. The porous structure leads to a high C‐rate capability. However, compared to conventional compact NCM, porous NCM s...

Sodium‐ion batteries are considered to be one of the most promising postlithium batteries on the verge of commercialization. The electrode processing is expected to be similar to lithium‐ion batteries. However, the producibility and material processing challenges of potential electrode materials for anodes and cathodes are poorly understood. For in...

Fuel cells used for transport applications hold polymer membranes as a key element. Their efficiency can be significantly increased if structured ion channels are implemented at the molecular level into the proton‐conducting membrane. New functional molecules with selective affinity for ionomers are needed to obtain such a membrane design. This stu...

The selection of an appropriate cathode active material is important for operation performance and production of high‐performance lithium‐ion batteries. Promising candidates are nickel‐rich layered oxides like LiNixCoyMnzO2 (NCM, x+y+z=1) with nickel contents of ‘x’ ≥ 0.8, characterized by high electrode potential and specific capacity. However, th...

A precise understanding of the mass transport kinetics of water inside the porous structure of battery electrodes is crucial to understanding and optimizing their post-drying process. This process and the moisture management during the production of Li-ion battery electrodes adjust and remove residual water from electrodes and are cost intensive. F...

Previous investigations on porous NCM particles with shortened diffusion paths and an enlarged interface between active material and electrolyte showed improved rate capability and cycle stability compared to compact particles. Due to the additional intragranular porosity of the active material, the pore structure of the overall electrode, and, as...

Lithium‐ion batteries are used in a wide range of applications, with the electromobility sector being the main contributor to the increasing demand predicted for the next decade. Although batteries play an important role in decarbonizing the transportation sector, their production includes energy‐intensive processes that hinder a more sustainable p...

Produktionslinien für Batterieelektroden bestehen aus hoch produktiven aber starren Prozessen. So können Änderungen nur langsam umgesetzt werden, und eine Reaktion auf neue Bedingungen ist kaum möglich. Im Projekt ReFlexBat (Regelbare Beschichtungseinheit für die flexible Beschichtung von Batterieelektroden) wird deshalb eine autonome Beschichtungs...

Understanding and reducing edge elevations at the lateral edges are crucial aspects to reduce reject rates during electrode production for lithium‐ion batteries (LIB). Herein, different process conditions to reduce edge elevations at the lateral edges of water‐based, shear‐thinning coatings in the production of LIB electrodes are presented. The red...

The drying of electrodes represents a critical process step in the production of lithium‐ion batteries. In this process step, unfavorably adjusted drying conditions can result in deteriorated electrode properties. Furthermore, the process speed is restricted by limited heat and mass transfer in purely convective drying. To counteract those effects,...

Lithium‐ion batteries are state‐of‐the‐art and still their performance is subject to constant improvement. These enhancements are based, among other things, on optimization in the electrode production process chain. High optimization potential exists for the drying process of electrodes, as aiming for high drying speeds can greatly reduce both, inv...

Moisture management and postdrying are crucial for Li‐ion battery lifetime and performance as well as overall energy efficiency of electrode production. An optimization of these processes by a fundamental comprehension of sorption and mass transport mechanisms in the electrode holds potential to increase sustainability of this technology. The compo...

Slot die coating is a state-of-the-art process to manufacture lithium-ion battery electrodes with high accuracy and reproducibility, covering a wide range of process conditions and material systems. Common approaches to predict process windows are one-dimensional calculations with a limited expressiveness. A more detailed analysis can be performed...

Porous, nanostructured Li(NixCoyMn)O2 (NCM) achieves an improvement in the fast‐charging capability and the durability of lithium‐ion batteries. This improvement is attributed to an extended electrolyte—active material interface, where the electrochemical reactions take place and thus shorter diffusion paths inside the active material particles are...

In this manuscript, a method to reduce superelevations of lateral edges in cross-web direction during slot die coating of shear-thinning slurries for Li-ion battery electrodes (LIB) was developed. Therefore, the impact of the inner slot die geometry on the edge elevations was investigated. These elevations of the coating could be almost eliminated...

As moisture presents a critical contamination in lithium-ion batteries (LIBs), electrodes and separators need to be post-dried before cell assembly. The moisture adsorption, desorption and re-adsorption of electrodes during processing is strongly dependent on their material system, manufacturing route and microstructure. The microstructure, in turn...

To scale up production of perovskite photovoltaics, state‐of‐the‐art laboratory recipes and processes must be transferred to large‐area coating and drying systems. The development of in situ monitoring methods that provide real‐time feedback for process control is pivotal to overcome this challenge. Herein, correlative in situ multichannel imaging...

A new empiric correlation for the critical solutal Marangoni number as function of the Péclet and Schmidt numbers is proposed. It is based on previously published experimental flow field data in drying poly(vinyl acetate)-methanol films with an initial thickness in the range of 20–100 μm and an initial solvent load of 1 to 2 gMeOH/gPVAc, as well as...

During the coating and drying of thin polymer‐particle composites, the particle geometry has a big impact on the prediction of concentration profiles in the dry film. In this work, a plate‐like geometry is used to evaluate the mass transport of the particles with the aspect ratio as a variable. The experimental determination of the viscosity and se...

The extended process chain starting from slurry mixing up to the operative lithium‐ion battery requires a deep understanding of each individual process step and knowledge of the interaction of the different process steps with each other. In particular, the intertwining of slurry mixing and drying determines the microstructure of the electrode, whic...

In order to assess the driving forces of Marangoni instabilities in drying polymer solution films, surface tension data over a wide concentration are necessary. While experimental data and mixing rule equations for the surface tension of liquid-liquid mixtures are readily available, data for polymer solutions are scarce. The aim of this work is to...

In order to reduce the residual moisture in lithium‐ion batteries, electrodes and separators need to be post‐dried prior to cell assembly. On an industrial scale, this is often conducted batch‐wise in vacuum ovens for larger electrode and separator coils. Especially for electrodes, the corresponding post‐drying parameters have to be carefully chose...

The drying behavior of two different polymers [polyvinyl pyrrolidone (PVP) and polyisobutylene (PIB)] with different glass transition temperatures are investigated and compared as a function of film thickness from micrometer (∼3 μm) to nanometer scale (∼10 nm). The focus of this study is to distinguish between solvent diffusion, polymer relaxation,...

Convective Marangoni instabilities in drying polymer films may induce surface deformations, which persist in the dry film, deteriorating product performance. While theoretic stability analyses are abundantly available, experimental data are scarce. We report transient three-dimensional flow field measurements in thin poly(vinyl acetate)-methanol fi...

In this work, a detailed study of the drying of battery electrodes of different thicknesses is presented. A mathematical model to calculate the solvent loading and film temperature over the drying time is experimentally validated. The model is based on a first study presenting a simulation model to predict the drying course when linear drying kinet...

The phase equilibrium as well as the diffusion kinetics of toluene-poly (methyl methacrylate) have been investigated over a concentration range from 0 – 75 v% toluene with independent measurements in order to describe drying and sorption processes under different conditions. The phase equilibrium of a micrometer thick layer, measured using a magnet...

During the coating and drying of thin polymer-particle composites, the particle geometry has a big impact on the prediction of concentration profiles in the dry film. In this work, a plate-like geometry is used to evaluate the mass transport of the particles with the aspect ratio as a variable. The experimental determination of the viscosity and se...

Herein, an experimental setup comprised of a stationary convection dryer (Comb Nozzle Dryer) supplemented by a measurement for gravimetric drying curves is introduced. The drying process of anodes for lithium‐ion batteries is experimentally investigated and compared to modeling results, showing very good agreement for the investigated films. Heat t...

Since the loading of electrodes for Li-ion batteries with an excessive amount of moisture affects the performance of the cells, the moisture is partly removed in a post-drying process step. The drying time is thereby controlled by the amount of moisture that has to be removed as well as the mass transport kinetics of water. This mass transport kine...

A reduction of the inactive components can increase the energy density and reduce production cost of Li‐ion batteries. But an effective reduction of the binder amount also negatively affects the adhesion of the electrode. Herein, slot‐die coating of a primer layer for Li‐ion anodes is investigated. It is shown that the use of a primer layer with on...

Multilayer coatings and drying of polymer films are widely used to produce different applications like organic electronics or barrier foils. If the product quality requires separated layers, partial or immiscible systems can be used to avoid interdiffusion between the layers. For the prediction of a possible phase separation of a ternary polymer–po...

In previews works, the influence of the drying conditions on the particle distribution in filled polymer films was investigated using spherical silica particles and polystyrene pellets. The results showed that changing drying conditions can influence the particle distribution in the dry film, and were summarized in drying regime maps to predict the...

A hysteresis in the sorption equilibrium influences the production process of many multi-component material systems. Electrodes for Li-ion batteries consist of several materials, some of which exhibit a hysteresis in their sorption equilibrium with water. The moisture content ad- and absorbed in the electrodes of the Li-ion battery turned out to be...

This contribution presents a method to examine the drying process of thin films of polymer gravimetrically, ranging from a few micrometers to below 20nm using a quartz crystal microbalance (QCM). Polyvinyl acetate (PVAc) and toluene (tol) serve as the model system to validate the method by drying experiments, simulations and the determination of th...

The use of thicker electrodes can contribute to a reduction in cell costs. However, the properties of the electrode must be kept in view to be able to meet the performance requirements. Herein, the possibility of simultaneous multilayer slot die coating is investigated to improve the electrode properties of medium‐ and high‐capacity anodes. The sta...

When fabricating battery electrodes, their properties are strongly determined by the adjusted drying parameters. This does not only affect their microstructure in terms of adhesion, but also influences cell performance. The reason is found to be the binder transported to the surface during drying. Herein, it is shown that when thicker electrodes ar...

In the light of continuous improvement and optimization, recent experiments that the authors conducted give new insights into the applied evaluation method of Riegel et al 1: Thorough investigations of the previous results regarding the usage of the Lowry Assay showed discrepancies in the determination of the released amount of protein in the analy...

A key challenge for the commercialization of perovskite photovoltaics is the transfer of high‐quality spin coated perovskite thin‐films toward applying industry‐scale thin‐film deposition techniques, such as slot‐die coating, spray coating, screen printing, or inkjet printing. Due to the complexity of the formation of polycrystalline perovskite thi...

For the first time, multilayer OLEDs with four solution-processed layers are fabricated step-by-step using slot die coating. A suitable choice of coating parameters and fluid formulation enables the application of different material classes as large-area homogeneous layers with thicknesses in the nanometer range. The AFM measurements of the slot di...

In industrial lithium‐ion battery manufacturing, patterned structured electrodes are required due to subsequent processes. In particular, novel and advanced cell stack formation processes cause challenging design requirements for electrode geometry. This work examines the influence of coating speeds up to 50 m min–1 and wet‐film thicknesses up to 4...

Excessive moisture adsorbed in electrodes and separators of a Li‐ion battery hampers its performance and is, therefore, removed to a certain amount in a post‐drying process. An insufficient understanding of the process results thereby in high process costs. Cost reductions can only be achieved efficiently with an improved process understanding by m...

Surface-tension induced flows may have a significant impact on the surface topography of thin films or small printed structures derived from polymer solution processing. Despite a century of research on Marangoni convection, the community lacks quantitative experimental flow field data, especially from within drying solutions. We utilize multifocal...

In this study, multilayer organic light-emitting diodes (OLEDs) consisting of three solution-processed layers are fabricated using slot die coating, gravure printing, and inkjet printing, techniques that are commonly used in the industry. Different technique combinations are investigated to successively deposit a hole injection layer (poly(3,4-ethy...

Work on interdiffusion has been mainly carried out in binary systems in the past, and this work has focused on polymer–solvent (S) systems and polymer blends. To understand and predict the interdiffusion of two solids in the presence of one S, we present a new mathematical model based on the Onsager approach. Within our model, interdiffusion kineti...

Slot die coating is applied to deposit thin and homogenous films in roll-to-roll and sheet-to-sheet applications. The critical step in operation is to choose suitable process parameters within the process window. In this work, we investigate an upper limit for stripe coatings. This maximum film thickness is characterized by stripe merging which nee...

To understand the effects of inhomogeneous drying on the quality of polymer coatings, an experimental setup to resolve the occurring flow field throughout the drying film has been developed. Deconvolution microscopy is used to analyze the flow field in 3D and time. Since the dimension of the spatial component in the direction of the line-of-sight i...

Control of the blend nanomorphology in bulk heterojunctions (BHJs) is still a challenge that demands more fundamental knowledge of the mechanism of phase separation and crystallization during solvent drying. In this review we show that in situ studies using combined laser reflectometry and grazing-incidence wide-angle X-ray scattering provide a fun...

Particles are frequently incorporated into a polymer coating to tailor material properties. For coatings prepared from a dispersion of particles in a polymer solution, it is essential to understand how drying conditions and dispersion composition influence the component distribution during drying. In a companion paper, a model was developed to pred...

In the current work, graphite electrodes comprising PVDF binder and carbon black are subjected to characterization. An energy selective backscatter detector is used to localize carbon black and fluorine of PVDF. Therefore, it is necessary to distinguish between graphite, amorphous carbon and fluorine rich regions. Typically, an angular selective ba...

Organic electronics have been thoroughly investigated due to their broad application potential, ranging from light-emitting diodes to photovoltaics. The processing of organic electronics is trending from vacuum toward wet chemical deposition, which allows fast low-cost mass production of devices with scalable dimension. One of the current challenge...

In this study, we investigate the impact of process parameters on homogeneity and electrical conductivity of slot-die-coated PEDOT:PSS–PVA composite films that are doped with DMSO. Due to a strong correlation between conductivity and morphology of PEDOT:PSS films and the latter’s dependency on the processing step itself, we apply slot die coating f...

The knowledge of mass transport parameters in polymer/protein blend films is of substantial interest for the preparation of glucose biosensor test strips where drying and rehydration need to be controlled. In this study, the diffusion of water in bovine serum albumin (BSA) and polyvinylpyrrolidone (PVP) films and blends of BSA with PVP and polyviny...

The key challenge in solution-processing efficient OLEDs is to realize the multilayer device architecture. We demonstrate that slot die coating is applicable to deposit small-molecule (SM) layers on top of each other without dissolving the underlying layer. A stack for a blue SMOLED is chosen comprising slot die-coated PEDOT:PSS, an SM emissive lay...