Calendering Process Research Articles

Toward Higher Energy Density All‐Solid‐State Batteries by Production of Freestanding Thin Solid Sulfidic Electrolyte Membranes in a Roll‐to‐Roll Process

AbstractAll‐solid‐state batteries (SSB) show great promise for the advancement of high‐energy batteries. To maximize the energy density, a key research interest lies in the development of ultrathin and highly conductive solid electrolyte (SE) layers. In this work, thin and flexible sulfide solid electrolyte membranes are fabricated and laminated onto a non‐woven fabric using a scalable and solvent‐free, continuous roll‐to‐roll process (DRYtraec). These membranes show significantly improved tensile strength compared to unsupported sheets, which facilitates cell assembly and allows a continuous component production using a single‐step calendering process. By tuning the thickness, densified membranes with thicknesses ranging from 40 to 160 µm are obtained after a compression step. The resulting SE membranes retain a high ionic conductivity (1.6 mS cm−1) at room temperature. An excellent rate capability is demonstrated in a SSB pouch cell with a Li2O–ZrO2‐coated LiNi0.9C0.05Mn0.05O2 cathode, a 55 µm thin SE membrane, and a columnar silicon anode fabricated by a scalable physical vapor deposition process. At stack level, a promising energy density of 673 Wh L−1 (and specific energy of 247 Wh kg−1) is achieved, showcasing the potential for high energy densities by reducing the SE membrane thickness while retaining good mechanical properties.

Insights into cathode densification of calendering process by the combination of in-situ CT and DEM

Insights into cathode densification of calendering process by the combination of in-situ CT and DEM

Gas check prevention during calendering of poly(vinyl chloride) films using poly(caprolactone)‐based additives

AbstractGas checks on poly(vinyl chloride) (PVC) calendered films are a common but not well understood surface quality defect that causes delays and resource wastage during the manufacturing of plastic sheets and films. Three modified poly(caprolactone) (PCL)‐based additives of differing molecular weights were used as a secondary plasticizer in PVC with the goal of preventing the formation of gas checks without modifying the calendering process conditions. To better understand gas check prevention processes, the effects of the PCL‐based additives on the thermal, mechanical, rheological, and chemical properties of PVC blends were assessed. A high molecular weight (2000 g/mol) PCL‐based additive was unable to prevent gas checks in PVC blends, unlike the lower molecular weight (540 g/mol and 900 g/mol) additives. Chemical and physicochemical properties affect the prevention or reduction of gas checks showing that the acid values and molecular weights of the PCL‐based additives are related to the number of gas checks. In contrast, physical properties, including rheological ones like complex viscosity or the storage and loss moduli that were previously hypothesized to be important factors in preventing gas check formation, were not significantly impacted by the addition of the secondary plasticizer. Furthermore, the acid value was observed to be related to the reduction in gas checks, likely due to the interaction of the dispersed functional acid groups with the entrapped air. Consequently, the effectiveness of the additive in eliminating gas checks declines as the acid value decreases.Highlights Low concentrations of PCL‐based additives prevent gas checks on PVC films. They do not significantly affect the physical/mechanical properties of films. Higher molecular weight additives are beneficial, but only below 2000 g/mol. The effectiveness of PCL‐based additives increases with acid value.

Digital Twin-Driven Analysis of Microstructure Evolution in Li-Ion Battery Electrodes during Calendering

As electric vehicles (EVs) have replaced internal combustion engine vehicles (ICEVs), there's a requirement to increase the energy density of lithium-ion batteries (LIBs) to match the mileage capabilities of ICEVs. Achieving this accompanies optimization in the calendering process, which plays a crucial role in designing high-energy-density LIBs under the same materials. A well-designed calendering process not only boosts energy density but also improves the electronic conductivity and mechanical durability of electrodes. However, excessive calendering can result in detrimental effects such as the formation of tortuous ion percolation pathways and mechanical breakdown like crack formation in active materials. This underscores the importance of understanding how calendering impacts the microstructure of composite electrodes, which varies depending on the pressure levels applied. Therefore, a thorough analysis of the effect of the calendering process on composite electrodes is essential. Nonetheless, it is challenging to analyze microstructural changes and correlate them with electrochemical characteristics solely through experimental means.Addressing this challenge, herein, digital twin 3D structures of composite electrodes were obtained from FIB-SEM tomographic images before and after the calendering process. Subsequently, simulations of the calendering process are conducted to analyze the microstructure evolution depending on the calendering ratio or electrode density. As a result, virtual structures derived from the calendering simulation are created with varying densities. Key parameters related to electrochemical performance are calculated, enabling a systematic analysis of the structural, electrochemical, and mechanical characteristics during the calendering process.

Direct Contact Prelithiation of Silicon-Dominant Anodes Using Ultra-Thin Lithium Foils

With the steady growth of the electric vehicle market, the development of high-energy-density lithium-ion batteries is increasingly coming into focus. Silicon has a nearly ten times higher specific capacity for lithium storage than conventionally used graphite, making silicon a promising anode material for high-performance lithium-ion battery applications[1]. However, silicon shows a high volume expansion upon lithiation, leading to a rapid capacity fade due to the loss of active lithium associated with continuous solid electrolyte interphase formation[2]. Direct contact prelithiation is a method to compensate for the loss of active lithium by incorporating additional lithium metal during battery cell production. The use of lithium foil is a facile approach but depends on the availability of ultra-thin lithium foils[3].In this study, silicon-dominant anodes with a silicon content of ca. 70 % were prelithiated by lithium foils with a thickness of 5 and 10 µm using a calendering process. A glove box integrated calender under an argon atmosphere was used to transfer the ultra-thin lithium foils from a carrier foil on the entire anode surface. This facilitates a homogenous prelithiation of the anode and equal compression force over the entire anode surface. A process study was conducted to find suitable process parameters for the full-surface lithium foil application on the anodes. The formed anode-lithium-composite was investigated with and without the presence of an electrolyte. Pouch cells with nickel-rich cathodes were built to show the performance improvement through the presented prelithiation technique in the full cell setup.An increase of 16 % in full cell capacity shows the potential of direct contact prelithiation to boost the energy density of already high-energy lithium-ion battery material systems. The incorporated lithium metal compensates for the loss of active lithium and thereby enhances the cycle life of the battery cells, making the proposed prelithiation method an enabler for the use of silicon-dominant anodes for high-performance applications.

Calendering of non-isothermal viscoelastic sheets of finite thickness: A theoretical study

Abstract In this article, the sheeting of pseudoplastic material under non-isothermal conditions has been studied. It is an excellent forecasting instrument for sheeting, where the thickness of the sheet is relatively thin in relation to the roll size, according to theoretical study based on the lubrication theory. At the calendering process, the detachment point is determined by taking the material parameter’s impact into account. The governing equations are derived for the constitutive equation of the Carreau fluid with momentum and energy equations. Suitable non-dimensional parameters are used to develop the non-linear partial differential expressions into ordinary differential systems. The maximum pressure, roll separating force, normal stress effect, and power delivered to the fluid by rolls are among the engineering-relevant quantities that are determined. Moreover, a graphic analysis is conducted to examine the impact of different material parameters on the temperature profile, pressure gradient, velocity profile, and pressure distribution. The results specific mechanism is explained in depth.

Powder Compaction Characteristics and Modeling of Calendering Process for Powder-based Solvent-free Manufacturing of Electrodes for Lithium-ion Batteries

Abstract Powder-based solvent-free manufacturing of electrodes for Li-ion batteries represents an emerging and promising technology in electrode fabrication. This method involves a two-roll powder calendering process, where electrode powder materials are compressed onto a current collector to form electrodes with desired properties. The calendering or compaction of dry powders onto a current collector is a crucial step in solvent-free electrode manufacturing, significantly impacting the microstructures, mechanical properties, and electrochemical performance of the produced electrodes. In this paper, we investigate the compaction characteristics of electrode powders to gain insights into their behavior. A powder-on-current collector calendering model is developed based on Johanson's rolling theory of granular solids. This model enables us to infer the underlying calendering parameters essential for the solvent-free manufacturing of Li-ion batteries. To validate the model, we compare it with experimental calendering results, utilizing measured powder properties and roll design parameters as inputs. This approach offers a comprehensive understanding of the effects of roll geometries, particularly roll diameter, and various equipment design parameters on final electrode properties. Such insights have not been thoroughly explored in the emerging field of solvent-free battery electrode manufacturing, thereby contributing to advancements in this area.

Analysis of wrinkles and corrugations in the electrode calendering process

ABSTRACT Calendering is a crucial process in manufacturing of lithium-ion batteries electrodes. Wrinkles and corrugations are the main manufacturing defects in the calendering process. This study aims at studying the formation mechanism of wrinkles and corrugations. Corrugations and wrinkles of the electrodes were revealed to be more dependent on the difference between the front and back tensions. The tortuosity of corrugations was reduced by 34.2% when the tension difference decreased from 20 to 5 N. The increase in the tension difference led to a linear increase of the shear displacement δ, causing severe wrinkles in the uncoated area of the electrodes. The analytical prediction model for wrinkles during calendering was established based on the shearing of a rectangular membrane. The optimal web tension conditions, at a tension difference of 17 N, was achieved to obtain the optimal calendered electrodes.

Architecting Sturdy Si/Graphite Composite with Lubricative Graphene Nanoplatelets for High-Density Electrodes.

Densification of the electrode by calendering is essential for achieving high-energy density in lithium-ion batteries. However, Si anode, which is regarded as the most promising high-energy substituent of graphite, is vulnerable to the crack during calendering process due to its intrinsic brittleness. Herein, a distinct strategy to prevent the crack and pulverization of Si nanolayer-embedded Graphite (Si/G) composite with graphene nanoplatelets (GNP) is proposed. The thickly coated GNP layer on Si/G by simple mechanofusion process imparts exceptional mechanical strength and lubricative characteristic to the Si/G composite, preventing the crack and pulverization of Si nanolayer against strong external force during calendering process. Accordingly, GNP coated Si/G (GNP-Si/G) composite demonstrates excellent electrochemical performances including superior cycling stability (15.6% higher capacity retention than P-Si/G after 300 cycles in the full-cell) and rate capability under the industrial testing condition including high electrode density (>1.6gcm-3) and high areal capacity (>3.5mAhcm-2). The material design provides a critical insight for practical approach to resolve the fragile properties of Si/G composite during calendering process.

Negative Effect of the Calendering Process on the Interphase Formation and Electrochemical Behavior of Reduced Graphene Oxide Electrodes.

Many studies on electrode material development for rechargeable batteries have focused on improving the intrinsic physicochemical and electrochemical properties of active materials, but the electrochemical performances of batteries are exhibited by the overall electrode unit consisting of active materials, conductive additives, and a binder. Additionally, the electrodes have undergone an essential calendering process to enhance the physical contact between those components. Therefore, the electrochemical behavior and performance of a cell should be analyzed at the electrode level, as the inherent properties of active materials might be changed in electrode preparation, including the calendaring process and real-operating environments. In this study, we aimed to understand the electrochemical properties of the reduced graphene oxide (RGO)-containing electrodes rather than the RGO-active materials by studying the changes in the RGO electrode before and after the calendering process. Specifically, the study investigates the effect of the calendering process on the electrochemically active interphase formation and electrochemical properties of the RGO electrode. We found that the calendering process deteriorates the electrochemical properties of RGO electrodes by impeding enough electrolyte wetting, limiting the formation of thin and stable solid-electrolyte interphase, and leaving unreacted RGO sheets. Additional experiments with carbon-coated silicon/RGO composite electrodes demonstrate that after the calendering process, the sequential participation of Si/C particles in the electrochemical reaction resulted in much more severe capacity degradation over repeated cycling processes. The studies suggest that fine-controlling the number of RGO sheets and maintaining enough distance between those sheets even after the calendering process are required for the utilization of RGO in rechargeable batteries.

An integrated simulation and experimental study of calendering process in water-based manufacturing of lithium-ion battery graphite electrode

Lithium-ion batteries produced from water-based manufacturing processes are favored for their environmental and economic advantages, while currently sacrificing some technical performance. This paper reports an integrated study on the calendering process of water-based manufacturing of lithium-ion battery graphite electrode, aiming to improve electrochemical performance of the manufactured lithium-ion batteries. The interactive mechanism between the calendering process and the porous microstructure of the produced graphite electrode was systematically investigated. It reveals that the graphite electrode with 40 % of porosity produced under 79,509 N/m calendering force achieves an optimal 333 mAh/g of specific capacity and 91.2 % of capacity retention after 100 cycles.

2D Discrete Element Simulation of Electrode Structural Evolutions in Li‐Ion Battery During Drying and Calendering

Drying and calendering are critical steps in the manufacture of electrodes for lithium‐ion battery that affect their mechanical and electrochemical properties. A 2D representative volume element (RVE) model, including active material and carbon binder domain particles of different shapes and sizes, is developed. The evolution of the RVE structure is simulated using the discrete element method, providing insight into changes in velocity, coordination number, porosity, pore size distribution, tortuosity, and stress. Based on this analysis, a three‐step drying scheme is proposed in accordance with the experimental drying results. In addition, the calendering process significantly improves the mechanical integrity and electronic conductivity of the electrode. Through simulations and experimental observations of changes in surface morphology and porosity, an optimal compression ratio of about 20% is determined for the electrode.

The Influence of Calendering Process on the Graphite Anode

Calendering, or pressing, is the final property-defining process for battery electrode manufacturing to maximize the volumetric capacity of the cell through the compaction of an electrode between two large calender rollers12. On one hand, it can reduce the porosity of battery materials thus increase the conductivity of the materials. On the other hand, it can control the thickness of the electrodes, making sure it is uniform and proper thickness to guarantee the minimal variation in the cell thickness, reaching even stack pressure for module assembly and impacting the thermal management [3]. The calendering process significantly influence the performance of lithium-ion battery (LIB).Graphite anode coating on Cu foil was chosen as our baseline coating for this calendering process investigation. The slurry was mixed in a planetary and dispersive mixer and then coated using reverse comma coating method by a scale-up coater with drying zones of 70 °C. Then the coating was calendered by a calendering machine at various conditions.Calendering, though seemingly a simply process, is influenced by several different parameters significantly. In this study, we systematically investigated the calendering process by carrying-out a Design-of-experiment (DOE). The following calendering parameters were investigated: the parameters of calendering machine gap size, calendering pressure, and the speed of the coating web. The calendered graphite coating was then measured for the morphology by scanning electron microscopy (SEM), the pore size change by BET surface area measurement, and Direct current internal resistance (DCIR) by building half cells and cycling and Electrochemical Impedance Spectroscopy (EIS) at 50% State-of-Charge (SOC).The result showed that pressure is the most critical parameter for calendering and the internal resistance and ionic conductivity changes in response to the calendering parameters. The half-cell with calendering at the pressure of 37 MPa, gap size targeted for 30% porosity, the BET surface area around 0.75 m2/g showed highest cell capacity and lowest internal resistance.

Elucidating the Electrochemical Impact of the Calendering Process on Three-Dimensional Designed Electrodes for Lithium-Ion Batteries

Significant advancements in battery technology are imperative to meet the ambitious demands for electromobility and stand-alone energy storage devices. This stems from the need to achieve operations with high energy and power density, coupled with stringent safety standards and extended lifespans, while reducing production and material costs. The preferred energy storage technology for the coming decade is anticipated to remain lithium-ion battery (LIB) technology. The focus on researching high-energy active materials to optimize this technology is paramount. In addition to optimizing materials, significant performance enhancements can be achieved by using electrodes with high mass loading and a multiscale tailored electrode design that can be scaled up to production level.The technological challenges of achieving a breakthrough in gaining simultaneously high energy and power density characteristics while maintaining high process and operational reliability with significant cost savings are the subject of current research and development in the field of LIB technology. To tackle this, the study explores the laser-assisted generation of three-dimensional (3D) electrode architectures and assesses its impact on battery performance and future integration into battery production. The advanced electrode design involves micro and sub-micron structures that can be tailored in various ways, leading to notable improvements in battery lifespan, battery safety, and fast charging and high-power operation capabilities compared to batteries with conventional two-dimensional (2D) electrodes. High-power ultrafast laser ablation emerges as a precise method for introducing such structures.Coordinating the production of 3D electrodes with laser assistance necessitates synchronization with established manufacturing steps in the battery production process. Notably, the calendering of electrodes holds significance due to its substantial influence on the microstructural properties of the electrode material, encompassing porosity, material density, and layer adhesion. The study investigates the impact of laser-induced structuring, encompassing micro-/nano-porosities and microtopography, on electrodes with varying mass loadings ranging from 2mAh/cm² to 6mAh/cm². Electrochemical characteristics such as high-rate capability, fast charging, and cycle lifetime are evaluated accordingly, employing cells with graphite anodes and lithium-nickel-manganese-cobalt oxide cathodes.

Numerical study of slip and Magnetohydrodynamics (MHD) in calendering process using non-Newtonian fluid

Numerical study of slip and Magnetohydrodynamics (MHD) in calendering process using non-Newtonian fluid

Non-Asbestos Fiber Gasket Materials & Their Applications in Automobile Powertrain Sealing

Review Non-Asbestos Fiber Gasket Materials & Their Applications in Automobile Powertrain Sealing Weiting Hu 1,2, * , Hong Li 1,2, and Jinfeng Zhuang 1,2 1 China National Pulp and Paper Research Institute, Beijing 100102, China 2 SinoLight Fiber Composite Materials Co., Ltd., Beijing 100102, China * Correspondence: sinogasket@hotmail.com Received: 19 March 2024; Revised: 27 May 2024; Accepted: 19 June 2024; Published: 25 June 2024 Abstract: Non-asbestos fiber gasket material is a ternary composite mainly composed of fibers, rubber, and fillers. Due to the carcinogenic risks associated with asbestos fibers, research and development of non-asbestos materials have become increasingly active. The manufacturing technologies of non-asbestos gasket materials primarily include calendering and papermaking processes. These materials, especially the gasket made by the papermaking method, are mainly applied for sealing in engines, transmissions, and water pumps, playing a crucial role in improving emission standards, safety, and the sustainability of automobiles. The sealing mechanism and relevant properties of asbestos-free fiber gasket materials are also introduced in this article. In the future, there should be a focus on developing high-performance non-asbestos gasket materials to provide more efficient and highly cost-effective sealing solutions for the automotive industry.

Discrete modeling of the calendering process for positive electrodes of Li-ion batteries

The electronic properties of Li-ion batteries crucially depend on the microstructure of their electrodes. One step of the manufacturing process, called ‘calendering’, consists in compressing the electrodes between two counterrotating cylinders to increase their density. Through a new simulation model, we investigate the effect of calendering on microstructural and electronic properties of the electrodes. Our model takes into account the real geometry of the rotating cylinder and a new contact law involving the elastic behavior of the active material and the cohesive-plastic behavior of the binder layer. Our results align well with experimental data for porosity, final thickness, and elongation. We show that the bonding structure induced by calendering involves mostly vertical tensile contacts and horizontal compressive contacts. This unexpected observation highlights the importance of shear deformation induced by rolling and thickness reduction. Using the FFT method, we also investigate the ionic and electronic conductivities of the numerically calendered electrodes.

Enhancing Charging Efficiency with Lithium Silicate in Silicon Composite Anode Materials Through Lithiothermic Reduction Reaction Synthesis

AbstractThis study synthesizes silicon (Si) powders with lithium silicates including lithium orthosilicate (Li4SiO4), lithium metasilicate (Li2SiO3), and lithium disilicate (Li2Si2O5), creating a composite structure of crystalline Si within a LixSiyOz matrix through the lithiothermic reduction reaction (LTRR) process. The reduction of Li‐ion consumption of the anode is investigated by 1) initial solid electrolyte interphase (SEI) layer formation, 2) SEI layer formation in response to Si expansion‐induced damage, 3) trapping of Li ions at Si defects, and 4) side reactions during initial charge and discharge cycles. Si/LixSiyOz electrode exhibits a specific capacity of 1522.2 mAh g−1 and an initial coulombic efficiency of 83.5%. The effect of the calendering process is observed, and a pressurization condition of 5000 kgf cm−2 or less is set, and the ICE is improved to 93.4%–96%. Si/LixSiyOz electrodes outperform pure crystalline Si electrodes in specific capacity (7.3%), ICE (42%), and retention characteristics (17%). The integration of the LixSiyOz matrix into Si anodes enhances Li‐ion transport and partially suppresses Si expansion. Additionally, the Si/LixSiyOz electrode exhibits superior rate capability in the 0.2–1.6 A g−1 range.

Influence of variable viscosity on existing sheet thickness in the calendering of non-isothermal viscoelastic materials

Abstract The calendering process is pivotal in enhancing various materials’ surface properties and characteristics, making them indispensable for achieving desired product quality and performance. Also, this process holds significant relevance in various industrial applications, such as polymer processing, food production, and the manufacturing of composite materials. So, the aim of this study is to theoretically examine the calendering process applied to third-grade materials. It specifically explores how temperature variations impact material behavior during passage through two counter-rotating heated rolls. Particular consideration is given to the influence of temperature-dependent viscosity via Reynold’s model. The complexities of mass, momentum, and energy balance equations are reduced through the application of the Lubrication approximation theory. Solutions to these equations for variables such as velocity, flow rate, and temperature fields are accomplished by combining perturbation and numerical techniques. In relation to the calendering process, the thickness of the exiting sheet is specifically explored. Furthermore, this study quantifies substantial engineering parameters such as roll-separating force, pressure distribution, and power transferal from the rolls to the fluid. The governing equations belong to three key dimensionless parameters, namely, the Brinkman number, which is a product of Eckert number and Prandtl number, the temperature-dependent consistency index μ \mu , and a parameter η \eta correlating to non-Newtonian behavior. The outcomes of this study are presented both graphically and in tabular form. It has been observed that a rise in the third-grade parameter decreases detachment point and sheet thickness due to increased material rigidity. Furthermore, established results in the literature regarding the calendering of Newtonian fluids are validated.

Optimization of electrode manufacturing processes from the perspective of mechanical properties

Abstract As the fundamental part of battery production, the electrode manufacturing processes have a key impact on the mechanical and electrochemical properties of batteries. A comprehensive study is designed in this paper to reveal the manufacturing effect from the perspective of mechanical properties. Initially, the electrodes samples are prepared after different manufacturing process, i.e., slurry mixing, coating, drying, calendering, slitting, punching, cutting, assembling, electrolyte filling and formation. The effects of these processes on the mechanical response and morphology of electrodes are investigated. The calendering process significantly enhances the strength of both anode and cathode while providing a more uniform distribution of particles on the electrode. Besides, according to literature studies, the slurry mixing process has a critical impact on electrode deformation and failure. Hence, the effects of compaction density ρc and binder content Bc are further discussed to improve the slurry mixing and calendering processes. The active layer will debond from the current collector during cathode failure process as ρc and Bc decreases. This study provides valuable suggestions for optimizing the mechanical response of electrodes under key electrode processes.