Three-dimensional slit coating simulation method and system, electronic equipment and computer readable storage medium

Abstract

The invention discloses a three-dimensional slit coating simulation method and system, electronic equipment and a computer readable storage medium. The three-dimensional slit coating simulation method comprises the following steps: establishing a three-dimensional geometric model of a coating machine die head; performing grid division on the three-dimensional geometric model; establishing a slurry flow two-phase flow model in the three-dimensional flow field; setting solving parameters, slurry attributes and boundary conditions of a slurry flow model, wherein the boundary conditions comprise a speed inlet and a pressure outlet of slurry and a foil moving wall surface; carrying out initialization solution on the slurry flow model based on the boundary condition, and ending when calculation reaches a convergence condition; and running simulation, analyzing the change of flow velocity distribution and pressure distribution of the slurry in the three-dimensional geometric model, and observing the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model. According to the invention, the flow behavior of the slurry in the coating process can be accurately predicted, especially the problems of edge thickness change and coating uniformity at a slit outlet are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of slit coating simulation, and particularly to a three-dimensional slit coating simulation method and system, an electronic device, and a computer-readable storage medium. Background Art

[0002] The slit coating technology is widely used in the manufacture of lithium battery electrodes. Its core goal is to evenly and quickly coat the slurry on the foil to ensure the consistency and uniformity of the electrode thickness. The slit coating extrudes the slurry from a slit-shaped coating head at a certain flow rate and spreads it onto the foil. However, the traditional coating process relies on experimental and empirical adjustments and is difficult to precisely control the coating thickness and quality. In actual production, the slit coating process also faces the problem of an increased coating thickness in the edge area, that is, the edge thickening phenomenon. The edge thickening phenomenon not only causes a decrease in coating uniformity but also affects the physical properties of the electrode, resulting in instability of the overall battery performance.

[0003] In the research on slit coating for the manufacture of lithium battery electrodes, current research and engineering practices mainly focus on two-dimensional simulation and experimental debugging methods. However, two-dimensional simulation has its limitations. It is difficult to fully simulate the edge thickening phenomenon and lateral coating non-uniformity that occur during the coating process, and it is difficult to truly reflect the three-dimensional fluid flow characteristics of the slurry during the slit coating process, especially the complex flow phenomena in the edge area, thus failing to meet the requirements for high-precision and uniform coating.

[0004] For example, in the simulation of the lithium battery electrode coating process, two-dimensional computational fluid dynamics (CFD) simulation is commonly used to simulate the flow behavior of the slurry. By establishing a two-dimensional cross-sectional model of the coating head, the flow rate of the slurry and the change in coating thickness are studied. This two-dimensional simulation method has significant deficiencies in describing the lateral three-dimensional flow characteristics of the slurry. Although two-dimensional simulation can capture the basic process of the slurry being extruded from the die head and spreading on the foil surface to form a coating, it cannot truly reproduce the flow characteristics in the edge area. In practical applications, the flow state in the coating edge area is affected by multiple three-dimensional effects such as shear force, lateral flow, and interfacial tension. These complex edge effects cannot be reflected in two-dimensional simulation, resulting in a difference between the simulation results and the actual situation. It is difficult to accurately predict the edge thickening phenomenon and the coating non-uniformity in the width direction of the coating head. In addition, there is a bottleneck in the ability of two-dimensional simulation to simulate the edge thickening phenomenon. This two-dimensional simulation method only focuses on the flow rate distribution of the coating head in the two-dimensional plane and ignores the flow and thickness changes of the slurry in the coating width direction. Therefore, two-dimensional simulation cannot effectively analyze the non-uniformity of the flow rate and the lateral thickness change at the coating edge and is difficult to provide optimization suggestions or design improvements for the edge thickening phenomenon. This limitation makes two-dimensional simulation limited in meeting the requirements of high-precision coating and unable to provide effective process optimization support for enterprises.

[0005] In the practice of experimental debugging methods, a large number of trial-and-error processes are usually required, which are time-consuming and costly, and it is difficult to achieve comprehensive optimization of the process in a short time. Specifically, in the actual production process, many enterprises rely on experimental debugging to optimize the slot coating process, and improve the coating uniformity by adjusting the slurry flow rate, geometric parameters of the coating equipment and process conditions. However, experimental debugging usually requires a large number of trial-and-error processes, which are not only costly and inefficient, but also require a full set of experimental verification for each parameter adjustment, resulting in an overly long process optimization cycle and difficulty in quickly responding to changes in production requirements. In addition, the accuracy of experimental debugging is limited, and it is difficult to provide detailed mechanism analysis. Although experimental debugging can observe the coating results by adjusting parameters, it is difficult to deeply reveal the detailed flow behavior of the slurry during the coating process, especially the formation mechanism of the edge thickness phenomenon cannot be intuitively analyzed. Therefore, enterprises usually rely on experience to adjust the process, lacking necessary theoretical support, which makes the optimization of coating quality uncertain.

[0006] In summary, the existing two-dimensional simulation and experimental debugging methods have significant limitations in the coating process and are difficult to effectively solve the problems of edge thickness phenomenon and coating non-uniformity. Therefore, there is an urgent need for a new simulation method to more accurately simulate the complex flow characteristics during the coating process, providing strong theoretical basis and technical support for the optimization of the lithium battery electrode slot coating process. Summary of the Invention

[0007] The purpose of the present invention is to overcome many technical bottlenecks in the existing slot coating process, especially in optimizing coating uniformity and suppressing the edge thickness phenomenon, so as to further improve the coating quality and production efficiency of lithium battery electrodes. A three-dimensional slot coating simulation method and system, an electronic device, and a computer-readable storage medium are proposed. Specifically, a three-dimensional slot coating simulation method based on three-dimensional computational fluid dynamics (CFD) can accurately simulate the three-dimensional flow behavior of the slurry during the coating process, analyze the lateral uniformity of the wet film thickness and the edge thickness, especially conduct in-depth research on the causes and control mechanisms of the edge thickness phenomenon, thereby providing theoretical support and effective solutions for the optimization and prediction of the lithium battery slot coating process, overcoming the defects of the existing technology which are mostly two-dimensional simulations or empirical adjustments and cannot achieve precise control of the whole process and details of the coating process.

[0008] The first object of the present invention is to provide a three-dimensional slot coating simulation method, including the steps of:

[0009] S1. Establish a three-dimensional geometric model of the coating die head, which is established based on the structure of the coating die head and consists of the internal flow domain and the external flow domain of the die head;

[0010] S2. Perform mesh division on the three-dimensional geometric model, using different meshes for different regions to enable the target region to capture the flow characteristics of the slurry;

[0011] S3. Establish a two-phase flow model for the slurry flow in the three-dimensional flow field, including the VOF multiphase flow model for simulating the dynamic change of the interface, the slurry flow model for simulating the slurry flow in the basin, and the surface tension model;

[0012] S4. Set the solution parameters, slurry properties, and boundary conditions of the slurry flow model. The boundary conditions include the velocity inlet and pressure outlet of the slurry, as well as the moving wall surface of the foil;

[0013] S5. Initialize and solve the slurry flow model based on the boundary conditions;

[0014] S6. Determine whether the convergence condition is reached. If yes, go to step S7; otherwise, return to step S2;

[0015] S7. Run the simulation, analyze the changes in the velocity distribution and pressure distribution of the slurry in the three-dimensional geometric model, and observe the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model.

[0016] Among them, the internal basin of the die head is composed of a geometric cavity that is enclosed inside the die head and serves as a slurry delivery channel. The external basin of the die head includes a region that extends a certain distance upward, downward, forward, and backward starting from the upper lip and the lower lip, with the contact area of the foil back roller as the boundary condition of the fluid, and a region formed after extending a preset length outward and upward in the left and right directions of the coating gap.

[0017] Among them, different meshes are used for division in different regions, including:

[0018] Unstructured meshes are used in the homogenizing cavity and buffer tank regions of the model, high-precision hexahedral boundary layer meshes are used in the slit coating outlet and foil moving regions of the model, and refined meshes are used at the foil surface and the coating head edge.

[0019] Among them, the initialization and solution of the slurry flow model include allocating an initial velocity field, an initial pressure field, and a volume fraction, and based on a preset solution method, initially solving the initial flow field, ending when the calculation reaches the convergence condition, and making the gas-liquid interface distribution smooth and stable, meeting the target initial state.

[0020] Among them, the initial solution of the initial flow field includes first obtaining the initial pressure field and velocity field distribution based on the SIMPLE algorithm, and then further iteratively correcting them using the COUPLED algorithm based on the obtained initial pressure field and velocity field distribution to obtain the final flow field solution.

[0021] Among them, obtaining the initial pressure field and velocity field based on the SIMPLE algorithm includes:

[0022] Based on the initial conditions, the SIMPLE algorithm is used to calculate the initial pressure field distribution in the flow field, and the velocity field distribution is calculated in combination with the momentum equation. The initial pressure field is corrected and iteratively calculated through the pressure corrector to make the calculation results converge gradually, so that the velocity field meets the requirements of the continuity equation, and the initial pressure field and velocity field distribution are obtained.

[0023] Among them, the use of the COUPLED algorithm for further iterative correction includes, based on the initial pressure field and velocity field distribution, using the COUPLED algorithm to couple and solve the pressure and velocity equations simultaneously, and solving the continuity equation and momentum equation simultaneously, so that the result meets the convergence standard to obtain the final flow field solution.

[0024] The slurry flow model is established based on the control equations, which include the continuity equation and the momentum conservation equation, including:

[0025]

[0026] Where v is the fluid velocity, ρ is the fluid density, p is the pressure, g is the gravitational acceleration, τ ij For stress.

[0027] The slurry properties include rheological parameters of the slurry, and the rheological parameters include density and viscosity; the slurry flow model adopts a laminar flow model.

[0028] The setting of the solution parameters includes the magnitude and direction of the gravitational acceleration, the selection of the solver and the setting of the solution method, the time step and the number of iterations, and the maximum number of iterations per iteration; the solver selects a transient three-dimensional solver based on pressure.

[0029] A second object of the present invention is to provide a three-dimensional slot coating simulation system, comprising:

[0030] A three-dimensional geometric model building module is used to build a three-dimensional geometric model of the coating machine die head, wherein the three-dimensional geometric model is built based on the coating machine die head structure and is composed of an internal flow domain of the die head and an external flow domain of the die head;

[0031] A mesh partitioning module is used to perform mesh partitioning on the three-dimensional geometric model, using different meshes for partitioning different regions, so that the target region can capture the flow characteristics of the slurry;

[0032] Phase flow model building module, used to build a two-phase flow model of slurry flow in a three-dimensional flow field, including a VOF multiphase flow model that simulates the dynamic changes of the interface, a slurry flow model that simulates the slurry flow in the flow field, and a surface force tension model;

[0033] A solution parameter setting module is used to set solution parameters, slurry properties, and boundary conditions of the slurry flow model. The boundary conditions include the velocity inlet and pressure outlet of the slurry, as well as the moving wall surface of the foil.

[0034] A solution module is used to initialize and solve the slurry flow model based on the boundary conditions and determine whether the convergence condition is reached.

[0035] A simulation execution module is used to run the simulation after the convergence condition is reached, analyze the changes in the velocity distribution and pressure distribution of the slurry in the three-dimensional geometric model, and observe the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model.

[0036] The third object of the present invention is to provide an electronic device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the three-dimensional slit coating simulation method are implemented.

[0037] The fourth object of the present invention is to provide a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the three-dimensional slit coating simulation method are implemented.

[0038] The method of the present invention is a coating simulation technology based on three-dimensional CFD (Computational Fluid Dynamics) simulation, which can accurately predict the flow behavior of the slurry during the coating process, especially the edge thickness change and coating uniformity problem at the slit outlet.

[0039] The method of the present invention can deeply analyze the complex flow phenomenon of the slurry in the width direction of the coating head, accurately predict the coating thickness distribution, and has significant advantages especially in terms of the thickness change in the edge area.

[0040] The method of the present invention can not only present the velocity and pressure distribution of the slurry in the coating head, but also capture the influence of shear force and interface effect on the flow behavior, making the analysis of the edge thickness non-uniformity phenomenon more accurate, so as to provide a reliable theoretical basis and technical support for optimizing coating uniformity and thickness control. Description of the Drawings

[0041] Figure 1 It is a schematic diagram of the implementation process of the three-dimensional slit coating simulation method according to an embodiment of the present invention.

[0042] Figure 2 It is a schematic diagram of the three-dimensional geometric model of the coating machine die head established according to an embodiment of the present invention.

[0043] Figure 3 It is the first schematic diagram of the model of the external flow field of the die head according to an embodiment of the present invention.

[0044] Figure 4It is the second schematic diagram of the model of the outer flow domain of the die head in the embodiment of the present invention.

[0045] Figure 5 It is the third schematic diagram of the model of the outer flow domain of the die head in the embodiment of the present invention.

[0046] Figure 6 It is the schematic diagram of the three-dimensional geometric model grid of the coating machine die head established in the embodiment of the present invention.

[0047] Figure 7 It is the cloud chart of the slurry velocity obtained by running the simulation through the Fluent simulation software in the embodiment of the present invention.

[0048] Figure 8 It is the cloud chart of the slurry pressure distribution obtained by running the simulation through the Fluent simulation software in the embodiment of the present invention.

[0049] Figure 9 It is the simulation result of the edge thickness phenomenon showing the change of the coating thickness at the edge obtained by simulation in the embodiment of the present invention.

[0050] Figure 10 It is the comparison chart of the simulation results of the embodiment of the present invention with the results of a similar method (in the figure, Sim represents the data of the simulation, ex1 and ex2 represent two experiments carried out according to the preset working conditions, and ex1-1, ex2-1 and ex1-2, ex2-2 represent collecting data twice for the same experiment).

[0051] Figure 11 It is the schematic diagram of the principle of the three-dimensional slit coating simulation system in the embodiment of the present invention. Detailed implementation manners

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0053] See Figure 1 As shown, a three-dimensional slit coating simulation method in the embodiment of the present invention includes the steps:

[0054] S1. Establish a three-dimensional geometric model of the coating machine die head. The three-dimensional geometric model is established based on the structure of the coating machine die head and consists of an inner flow domain and an outer flow domain of the die head;

[0055] S2. Perform mesh division on the three-dimensional geometric model, and use different meshes for division in different regions so that the target region can capture the flow characteristics of the slurry;

[0056] S3. Establish a two-phase flow model for the slurry flow in the three-dimensional flow field, including the VOF multiphase flow model for simulating the dynamic changes of the interface, the slurry flow model for simulating the slurry flow in the basin area, and the surface tension model;

[0057] S4. Set the solution parameters, slurry properties, and boundary conditions of the slurry flow model. The boundary conditions include the velocity inlet and pressure outlet of the slurry, as well as the moving wall surface of the foil;

[0058] S5. Initialize and solve the slurry flow model based on the boundary conditions;

[0059] S6. Determine whether the convergence condition is reached. If so, enter step S7; otherwise, return to step S2;

[0060] S7. Run the simulation, analyze the changes in the velocity distribution and pressure distribution of the slurry within the three-dimensional geometric model, and observe the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model.

[0061] When the calculation reaches the convergence condition, start the calculation process by running the simulation. Through the simulation, output key data such as the velocity distribution, pressure distribution, and coating thickness of the slurry at the coating die head and coating window, providing a reliable numerical basis for analyzing the stability of the flow field and the uniformity of the coating thickness.

[0062] The three-dimensional slot coating simulation method of the embodiments of the present invention introduces three-dimensional simulation technology and uses three-dimensional computational fluid dynamics simulation to construct an accurate model of the coating area, including the flow fields inside and outside the die head, truly restoring the slurry flow state. Based on the simulation analysis, optimize the structure of the coating head and process parameters to ensure the uniform distribution of the slurry in the coating area, improve the thickness consistency of the coating layer, especially the thickness and coating uniformity in the edge area; through real-time analysis of the changes in the velocity, pressure, and thickness of the slurry by simulation, especially the prediction of the thickness at the coating edge, achieve precise prediction and control of the wet coating thickness and edge thickness, overcoming many defects of the traditional slot coating technology.

[0063] Moreover, due to the adoption of simulation technology, parameters such as coating uniformity control, slurry flow rate adjustment, and die head geometric structure optimization are realized through simulation to achieve the best coating effect and efficient production process, achieving the optimization of process parameters and equipment parameters based on the simulation results. Replace a large number of experimental debugging processes with a simulation model, reduce material and equipment losses, and achieve cost savings and production efficiency improvement.

[0064] Such as Figure 2As shown, in the embodiments of the present invention, the three-dimensional geometric model is used to simulate the flow characteristics of the coating area, and is composed of the internal flow domain and the external flow domain of the coating die head. It is established based on the actual structure of the coating equipment, that is, the design parameters and dimensions of the actual coating equipment are constructed, aiming to achieve a high degree of consistency between the simulation and the actual process conditions, accurately restoring the actual structure of the coating equipment, and being able to truly simulate the flow process of the slurry in the slot coating head.

[0065] Among them, the internal flow domain of the die head is composed of a geometric cavity that is closed inside the die head and serves as a slurry conveying channel, so as to accurately simulate the flow process of the slurry from feeding to the extrusion slot and ensure the stability of the flow field. As Figure 3 and Figure 4 、 Figure 5 shown, among them, the external flow domain of the die head includes a certain distance extended up and down, front and back starting from the upper lip and the lower lip, such as extending 0.7 mm and 5 mm, as Figure 3 shown, the area formed by taking the contact area of the foil back roll as the boundary condition of the fluid, and the area formed after extending a preset length (such as extending a preset 2.25 mm and 0.8 mm) outward and upward in the left and right directions of the coating gap, as Figure 4 、 Figure 5 shown. Specifically, the width and length of the coating gap are appropriately extended to the left, right and upward according to the geometric parameters of the actual equipment, with the principle of covering the flow characteristics during coating. Through the above-designed external flow domain boundary, the details of the diffusion and flow of the slurry at the outlet can be captured more comprehensively.

[0066] In some embodiments, the relevant geometric parameter values of the model are shown in the following table:

[0067] Parameter Parameter value Spacer thickness 0.6mm Coating speed 0.25m / s Coating gap 134μm Preset wet film thickness of coating 132μm Coating width 386mm Slurry density <![CDATA[1450kg / m 3 > Solid content 61％

[0068] In the embodiments of the present invention, CFD simulation tools such as Fluent can be used to perform mesh division on the three-dimensional geometric model. Specifically, high-precision mesh division is performed on the three-dimensional geometric model of the combined internal and external flow fields using Ansys Meshing, and a high-precision mesh division strategy is adopted, especially using a fine boundary layer mesh at the slot outlet. According to the flow characteristics of the coating area, a combination of structured meshes and unstructured meshes is preferably used to improve the simulation accuracy.

[0069] Specifically, different meshes are used for division in different regions, as Figure 6 shown, including:

[0070] Unstructured mesh division is used in the material homogenization cavity and buffer tank regions of the three-dimensional geometric model to ensure the overall uniformity of the model and reduce numerical discretization errors;

[0071] In the slit coating outlet of the three-dimensional geometric model and the foil moving area (i.e., the gasket area and the narrow area between the die head and the foil), namely the coating gap, due to its special geometric shape and key flow characteristics, a high-precision hexahedral boundary layer mesh division is adopted to ensure that the flow behavior in this area can be analyzed more carefully, so as to capture the shear effect and velocity distribution of the slurry at the outlet and the foil surface. The hexahedral boundary layer mesh enables more accurate reflection of fluid characteristics such as velocity gradient and pressure change at the slit outlet;

[0072] At the edge of the foil surface and the coating head, a refined mesh division is adopted. The edge refined mesh is used for division, that is, further refined mesh division is adopted, especially in the foil edge area. The edge fluid behavior is highly unstable due to the influence of shear force and surface tension. The refined mesh helps to capture the subtle flow state in the edge area and ensure the accurate simulation of the edge effect and thickness non-uniformity.

[0073] Considering that the slit coating process has extremely high requirements for precision, the entire flow field mesh division adopts a local encryption strategy. For the gap area between the die head and the foil surface and the edge coating area, a smaller mesh size is used for refinement. This encryption treatment ensures that the flow characteristics such as edge flow, shear force, and thickness change can be accurately captured in the key area.

[0074] In this way, through the above optimized mesh division strategy, the subtle changes of the slurry in the three-dimensional flow field can be accurately captured, making the simulation results highly credible and providing effective technical support for process optimization.

[0075] In addition, since the mesh size and quantity will directly affect the calculation accuracy and efficiency during the mesh setting process, a mesh independence verification is carried out for the calculation results of different mesh quantities. Through multiple groups of tests with different mesh quantities, it is ensured that the final calculation results can maintain consistency under different mesh division conditions, and the accuracy and reliability of the results are avoided from being affected by mesh factors.

[0076] It should be noted that in the embodiment of the present invention, during the simulation calculation, it is assumed that the inside of the extrusion slit die head is an incompressible two-phase flow of air and slurry. Therefore, the VOF multiphase flow model is adopted to process the gas-liquid two-phase interface. Especially at the junction of the coating from the slit die head outlet and air, that is, at the slit outlet, the dynamic change of the interface is simulated; the slurry flow model is used to simulate the flow of the slurry in the basin area. And since the fluid interface where the slurry contacts the rigid boundary will produce an adhesion effect, especially at the edge of the wet coating, this will affect the flow state of the boundary wet coating. In order to more realistically simulate the slurry flow state, a surface tension model is introduced. At the same time, in order to simplify the calculation, it is further assumed that the system is isothermal during the slurry flow process, that is, heat transfer is not considered.

[0077] Among them, the slurry flow model is established based on the governing equations, and the governing equations include the continuity equation and the momentum conservation equation, including:

[0078]

[0079] Among them, v is the slurry fluid velocity, ρ is the slurry fluid density, p is the pressure, g is the acceleration due to gravity, and τ ij is the stress.

[0080] During the simulation process, the governing equations can be further numerically solved in combination with the boundary conditions and initial conditions of the coating process to accurately describe the flow behavior of the slurry, especially the flow characteristics at the edge of the coating die.

[0081] In the embodiments of the present invention, in the setting of the boundary conditions, the boundary condition of the velocity inlet is used to make the coating enter the die at a stable flow rate, and the flow rate value is adjusted according to the actual production requirements to meet the expected coating thickness. Specifically, the feeding speed of the slurry is set according to the actual production demand to ensure that the slurry enters the die stably and is evenly distributed in the coating area. The inlet velocity set in this example is 0.0585 m / s.

[0082] The boundary condition of the pressure outlet is used to ensure that the slurry flows out smoothly and deposits on the surface of the foil from the slit outlet. Regarding the movement of the foil surface, for the moving wall surface, its speed is set according to the running speed of the production line, and its speed is set to match the coating speed to achieve the uniformity of the coating layer, so that the flow rate of the foil and the slit die is coordinated to achieve a uniform coating effect.

[0083] In the present invention, the slurry properties include the rheological parameters of the slurry, and the rheological parameters include density and viscosity to ensure that the fluid behavior during the coating process conforms to the true material characteristics.

[0084] It should be noted that in the present invention, since the slurry is a non-Newtonian fluid, its flow state is determined to be laminar flow by the Reynolds number, and the slurry flow model adopts a laminar model.

[0085] It should be noted that in the present invention, the setting of the solution parameters includes the magnitude and direction of the acceleration due to gravity, the selection of the solver and the setting of the solution method, the time step and the number of iterations, and the maximum number of iterations for each step of iteration; the solver is selected as a pressure-based transient three-dimensional solver.

[0086] Among them, the magnitude and direction of the acceleration due to gravity are used to simulate the influence of gravity in the actual operating environment, and the solver is selected as a pressure-based transient three-dimensional solver to better capture the transient flow behavior. The time step, the number of iterations, and the maximum number of iterations for each step of iteration ensure the calculation efficiency and accuracy.

[0087] In the present invention, the initialization of the slurry flow model is to initialize the flow domain model based on the boundary conditions, including allocating the initial velocity field, the initial pressure field and the volume fraction, and performing the initial solution to the initial flow field based on the preset solution method. The calculation is terminated when the convergence condition is reached, so that the gas-liquid interface distribution is smooth and stable, meeting the target initial state, and providing a reliable initial state for subsequent steady-state simulation.

[0088] The initial solution of the initial flow field includes first obtaining the initial pressure field and velocity field distribution based on the SIMPLE algorithm in Fluent, and then further iteratively correcting the initial pressure field and velocity field distribution using the COUPLED algorithm to obtain the final flow field solution.

[0089] The initial pressure field and velocity field are obtained based on the SIMPLE algorithm, including:

[0090] Based on the initial conditions, the SIMPLE algorithm is used to calculate the initial pressure field distribution in the flow field, and the velocity field distribution is calculated in combination with the momentum equation. The initial pressure field is corrected and iteratively calculated through the pressure corrector to make the calculation results converge gradually, so that the velocity field meets the requirements of the continuity equation, and the initial pressure field and velocity field distribution are obtained.

[0091] In the calculation, after the initial pressure and velocity fields reach a certain accuracy, the solver is switched to the COUPLED algorithm in Fluent to further improve the accuracy and efficiency of the calculation. In the present invention, the COUPLED algorithm is further iteratively corrected, including using the COUPLED algorithm to solve the pressure and velocity equations in a coupled manner based on the initial pressure field and velocity field distribution, and solving the continuity equation and momentum equation in a coupled manner, so that the result reaches the convergence standard and the final flow field solution is obtained. The COUPLED algorithm is further iteratively corrected to reduce the separation correction steps of the pressure field, so that the mutual coupling between the physical quantities is closer, and the overall stability and accuracy of the flow field are significantly improved.

[0092] The embodiment of the present invention adopts a separation algorithm during the initial solution, firstly calculates the initial pressure field in the flow field, and calculates the initial velocity field based on the momentum equation. Then, the pressure field is corrected and iteratively calculated until the velocity field meets the requirements of the continuity equation, and then a coupling algorithm is introduced based on the initial solution, and the continuity equation and momentum equation are solved simultaneously by using the coupled solution of the pressure and velocity fields. Through more precise correction iterations, it is ensured that the results meet strict convergence standards, thereby obtaining an accurate flow field solution, which significantly improves the overall stability and accuracy of the flow field.

[0093] Specifically, after initialization calculations, simulation runs are carried out. During the simulation runs, it can be through Fluent simulation software to run the simulation, analyze the flow velocity distribution of the slurry in the coating head, such as Figure 7 the slurry velocity contour diagram shown, and the change of pressure distribution, such as Figure 8 the slurry pressure distribution contour diagram shown, observe the three-dimensional flow characteristics of the slurry in the coating head, especially pay attention to the edge effect and coating non-uniformity that may occur during the coating process, such as Figure 9 the simulation results of the edge thickness phenomenon of the change of the coating thickness at the edge shown.

[0094] Among them, in the analysis of the simulation results, the wet film thickness of the coating area can also be obtained by extracting the slurry volume fraction at the outlet boundary. This wet film thickness not only reflects the uniformity of the slurry coating, but can also be further used to evaluate the distribution characteristics of the coating thickness in the transverse direction, so as to judge the uniformity of the coating and the thickness characteristics of the edge area. Through the visualization processing and numerical analysis of the simulation data, the thickness change trend of the slurry at the outlet of the coating head can be clearly displayed, providing key reference data for optimizing the coating uniformity.

[0095] Among them, the wet coating thickness and the thickness of the edge area are predicted in real time through CFD simulation, such as Figure 10 shown, the error between the simulation results and the experiment is controlled within 1.25%, which proves that the method of the present invention realizes the accurate simulation and effective control of the edge thickness, and solves the problem that the traditional two-dimensional simulation cannot predict the edge thickness phenomenon.

[0096] The slit coating optimization method based on three-dimensional computational fluid dynamics (CFD) simulation of the present invention overcomes multiple defects of the traditional slit coating technology by introducing three-dimensional simulation technology, and realizes the accurate prediction and control of the wet coating thickness and the edge thickness. It has significant technical advantages and beneficial effects in the following aspects:

[0097] 1. Accurately predict the wet coating thickness

[0098] Defects of the prior art: In the traditional slit coating process, the determination of the coating thickness depends on a large number of trial coating experiments, and accurate coating thickness information cannot be obtained in the early stage. This method not only wastes materials, but also increases the load of the experimental equipment and is difficult to quickly respond to production requirements.

[0099] The present invention realizes the real-time prediction of the wet coating thickness by establishing a highly accurate three-dimensional CFD simulation model to simulate the entire process of the flow behavior of the slurry, especially in the slit outlet area. The simulation test results show that the error between the simulation data and the actual experimental results is controlled within 1.25%, significantly reducing the material loss and the load of the experimental equipment, and at the same time improving the response speed of the process parameter adjustment. This method significantly improves the production efficiency and reduces the production cost.

[0100] 2. Edge Thickness Prediction

[0101] Defects of the prior art: The two-dimensional simulation technology is difficult to effectively predict and control the thickness increase phenomenon (edge thickening phenomenon) in the coating edge area. During the slot coating process, due to the low slurry flow rate in the edge area, accumulation is likely to occur, resulting in an increase in the coating thickness, affecting the consistency of the electrode thickness, and thus affecting the overall performance of the lithium battery.

[0102] Through the establishment of a complete three-dimensional CFD simulation model, this patent can accurately simulate the three-dimensional flow behavior of the slurry during the coating process, especially in the edge area at the slot exit, and effectively simulate the edge thickness.

[0103] 3. Coating Uniformity and Process Optimization

[0104] Based on the three-dimensional CFD simulation, this invention can comprehensively optimize the coating uniformity, edge thickness control, process parameters, and equipment parameters:

[0105] Process parameter optimization: The simulation technology allows for precise adjustment of process parameters such as slurry flow rate and die gap in a virtual environment to achieve the best coating effect, significantly shortening the process optimization cycle.

[0106] Equipment parameter optimization: Based on the simulation analysis, reasonable adjustments are made to equipment parameters such as the geometric structure of the die and the configuration of the back roller to ensure a uniform distribution of the slurry flow rate at the die exit and improve the thickness consistency of the coating layer.

[0107] The current two-dimensional simulation model only considers the flow rate distribution of the coating head in the two-dimensional plane, ignoring the flow and thickness change of the slurry in the width direction, and it is difficult to truly reflect the edge thickening phenomenon and the fluid flow in the width direction. This invention innovatively adopts a simulation method based on three-dimensional computational fluid dynamics (CFD), which can accurately capture the flow behavior of the slurry in the three-dimensional space during the slot coating process, especially with high precision in terms of the flow rate, shear force distribution, and slurry spreading process in the edge area of the coating head. In particular, in the method of this invention, the flow state at the edge of the coating head can be detailedly simulated to accurately reproduce the edge effect and capture the change in the flow state of the fluid at the edge; in addition, through the three-dimensional spreading process of the slurry at the coating head exit, including the flow of the slurry in the width direction, pressure distribution, and coating thickness, the fluid state at each position during the coating process can be presented in all aspects, especially the complex three-dimensional flow characteristics in the edge area; thus, through the three-dimensional simulation method of this invention, it is possible to deeply understand and effectively control the uneven coating thickness phenomenon, ensuring the stability of the electrode thickness and coating quality.

[0108] Traditional two-dimensional simulation technology cannot effectively predict the edge thickness phenomenon in the coating edge area. Due to the relatively low flow velocity at the edge, the slurry is prone to accumulation, resulting in an increase in the coating thickness and affecting the consistency of the electrode sheet. The precise analysis method for the edge thickness phenomenon based on three-dimensional simulation of the present invention can effectively capture the fluid behavior in the edge area and achieve precise prediction and analysis of the edge thickness phenomenon. In particular, by adopting refined grid division in the edge area, the capture accuracy of the change in the edge fluid state is improved, and the formation mechanism of the edge thickness phenomenon is carefully analyzed; based on the initial pressure and velocity distribution obtained by the SIMPLE algorithm, the COUPLED algorithm is further iteratively corrected, significantly improving the overall stability and accuracy of the flow field. In addition, during the simulation process, the changes in the flow velocity and flow direction of the edge slurry can be focused on to reveal the dynamic formation process of the edge thickness phenomenon, thereby providing theoretical support for process improvement. Through the high-precision three-dimensional simulation of the present invention, the edge accumulation trend can be effectively predicted, helping enterprises to prevent the edge thickness phenomenon in advance during the process design and achieve product thickness consistency and quality improvement.

[0109] Under the existing technical conditions, process optimization often relies on a large number of experimental debuggings. By repeatedly trial and error to adjust parameters, not only is the cost high, but the experimental cycle is long and the efficiency is low. The repeated adjustments during the experiment are time-consuming and it is difficult to comprehensively grasp the fluid behavior, which limits the response speed to complex process optimization. The present invention adopts three-dimensional simulation technology, enabling enterprises to directly adjust and optimize process parameters in a virtual environment, thereby reducing the dependence on physical experiments, achieving an improvement in optimization efficiency and a reduction in the dependence on experimental debugging. In particular, in the simulation environment, the coating head structure and slurry flow velocity can be quickly preset, and the change in the coating thickness can be monitored in real time without relying on physical experiment verification, greatly reducing the experimental cost; achieving a significant improvement in optimization efficiency, reducing the downtime of experimental equipment and the economic losses caused by frequent debugging, and realizing a more efficient process optimization process.

[0110] In summary, the method of the present invention has significantly improved the process prediction accuracy, uniformity control, and process optimization of the slot coating process through the introduction of three-dimensional CFD simulation technology. The method of the present invention realizes the intelligent control of the coating process and the effective saving of costs, has significant application value and broad market prospects, can predict the edge thickness problem in the existing coating process, and based on three-dimensional simulation, can optimize the geometric design of the coating head and process parameters, improving the coating quality and production efficiency.

[0111] In short, by adopting the three-dimensional computational fluid dynamics (CFD) simulation technology of the present invention, the three-dimensional flow characteristics of the slurry in the slot coating process can be accurately simulated. Through CFD simulation, the complex flow phenomenon of the slurry in the width direction of the coating head can be deeply analyzed, and the coating thickness distribution can be accurately predicted, especially having significant advantages in terms of the thickness change in the edge area.

[0112] The method of the present invention can not only present the flow velocity and pressure distribution of the slurry in the coating head, but also capture the influence of shear force and interface effect on the flow behavior, making the analysis of the edge thickness non-uniformity phenomenon more accurate, thereby providing a reliable theoretical basis and technical support for optimizing coating uniformity and thickness control.

[0113] By introducing the three-dimensional CFD simulation technology, the method of the present invention has significantly improved the process prediction accuracy, uniformity control and process optimization of the slot coating process, realized the intelligent control of the coating process and the effective saving of costs, and has significant application value and broad market prospects.

[0114] See Figure 11 As shown, the second object of the embodiment of the present invention is to provide a three-dimensional slot coating simulation system, including: a three-dimensional geometric model establishment module for establishing a three-dimensional geometric model of the coating machine die head, the three-dimensional geometric model being established based on the structure of the coating machine die head and consisting of the internal flow domain and the external flow domain of the die head; a network division module for dividing the three-dimensional geometric model into grids, using different grids for different regions so that the target region can capture the flow characteristics of the slurry; a two-phase flow model establishment module for establishing a two-phase flow model of the slurry flow in the three-dimensional flow field, including a VOF multiphase flow model for simulating the dynamic change of the interface, a slurry flow model for simulating the slurry flow in the flow domain and a surface tension model; a solution parameter setting module for setting solution parameters, slurry properties and boundary conditions of the slurry flow model, the boundary conditions including the velocity inlet and pressure outlet of the slurry and the moving wall surface of the foil; a solution module for initializing and solving the slurry flow model based on the boundary conditions and judging whether the convergence condition is reached; a simulation execution module for running the simulation after reaching the convergence condition, analyzing the change of the flow velocity distribution and pressure distribution of the slurry in the three-dimensional geometric model, and observing the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model.

[0115] The three-dimensional slot coating simulation system of the embodiment of the present invention is used to execute each step of the three-dimensional slot coating simulation method of the embodiment of the present invention. Each step of the three-dimensional slot coating simulation method can be realized through its respective modules, and each of the modules is composed of a preset software program and executes corresponding functions.

[0116] The third object of the embodiment of the present invention is to provide an electronic device, including a memory and a processor, where the memory stores a computer program, and when the processor executes the computer program, each step of the three-dimensional slot coating simulation method of the embodiment of the present invention is realized.

[0117] The fourth object of the embodiments of the present invention is to provide a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, each step of the three-dimensional slit coating simulation method of the embodiments of the present invention is implemented.

[0118] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms.

[0119] Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0120] In addition, it should be understood that although this specification is described in accordance with the embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A three-dimensional slit coating simulation method, characterized in that: Includes steps: S1. Establishing a three-dimensional geometric model of a coating machine die, wherein the three-dimensional geometric model is established based on the coating machine die structure and is composed of an internal flow domain of the die and an external flow domain of the die; S2. Meshing the three-dimensional geometric model, using different meshes for different regions, so that the target region can capture the flow characteristics of the slurry; S3. Establish a two-phase flow model of slurry flow in a three-dimensional flow field, including a VOF multiphase flow model for simulating dynamic changes of the interface, a slurry flow model for simulating slurry flow in the flow field, and a surface force tension model; S4. Setting solution parameters, slurry properties and boundary conditions of the slurry flow model, wherein the boundary conditions include a velocity inlet and a pressure outlet of the slurry and a moving wall of the foil; S5. Initialize and solve the slurry flow model based on the boundary conditions; S6. Determine whether the convergence condition is met, if so, proceed to step S7, otherwise return to step S2; S7. Run the simulation, analyze the changes in velocity distribution and pressure distribution of the slurry in the three-dimensional geometric model, and observe the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model.

2. The three-dimensional slit coating simulation method according to claim 1, characterized in that: The internal flow area of ​​the die head is composed of a geometric cavity enclosed inside the die head that serves as a slurry conveying channel. The external flow area of ​​the die head includes an area formed by extending a certain distance up and down and forward and backward from the upper lip and the lower lip as the starting point, with the contact area of ​​the foil back roller as the boundary condition of the fluid, and an area formed by extending outward and upward in the left and right directions of the coating gap by a preset length.

3. The three-dimensional slit coating simulation method according to claim 1, characterized in that: The method of dividing different areas by using different grids includes: Unstructured meshing is used in the material mixing chamber and buffer tank area of ​​the model, high-precision hexahedral boundary layer meshing is used in the slit coating outlet and foil moving area of ​​the model, and refined meshing is used on the foil surface and the edge of the coating head.

4. The three-dimensional slit coating simulation method according to claim 1, characterized in that: The initialization solution of the slurry flow model includes allocating an initial velocity field, an initial pressure field and a volume fraction, performing an initial solution to the initial flow field based on a preset solution method, and terminating when the calculation reaches a convergence condition, so that the gas-liquid interface distribution is smooth and stable, meeting the target initial state.

5. The three-dimensional slit coating simulation method according to claim 4, characterized in that: The initial solution of the initial flow field includes first obtaining the initial pressure field and velocity field distribution based on the SIMPLE algorithm, and then further iteratively correcting the initial pressure field and velocity field distribution using the COUPLED algorithm to obtain the final flow field solution.

6. The three-dimensional slit coating simulation method according to claim 5, characterized in that: The initial pressure field and velocity field are obtained based on the SIMPLE algorithm, including: Based on the initial conditions, the SIMPLE algorithm is used to calculate the initial pressure field distribution in the flow field, and the velocity field distribution is calculated in combination with the momentum equation. The initial pressure field is corrected and iteratively calculated through the pressure corrector to gradually converge the calculation results so that the velocity field meets the requirements of the continuity equation, and the initial pressure field and velocity field distribution are obtained. Preferably, the COUPLED algorithm is further iteratively corrected, including based on the initial pressure field and velocity field distribution, using the COUPLED algorithm to couple and solve the pressure and velocity equations simultaneously, and solving the continuity equation and momentum equation simultaneously so that the result reaches the convergence standard to obtain the final flow field solution.

7. The three-dimensional slit coating simulation method according to claim 1, characterized in that: The slurry flow model is established based on control equations, which include continuity equations and momentum conservation equations, including: Where v is the fluid velocity, ρ is the fluid density, p is the pressure, g is the gravitational acceleration, τ ij is stress, Preferably, the slurry properties include rheological parameters of the slurry, and the rheological parameters include density and viscosity; the slurry flow model adopts a laminar flow model. Preferably, the setting of solution parameters includes the magnitude and direction of gravitational acceleration, selection of a solver and setting of a solution method, a time step and number of iterations, and a maximum number of iterations per iteration; the solver selects a pressure-based transient three-dimensional solver.

8. Three-dimensional slot coating simulation system, characterized in that: include: A three-dimensional geometric model building module is used to build a three-dimensional geometric model of the coating machine die head, wherein the three-dimensional geometric model is built based on the coating machine die head structure and is composed of an internal flow domain of the die head and an external flow domain of the die head; A mesh partitioning module is used to perform mesh partitioning on the three-dimensional geometric model, using different meshes for partitioning different regions, so that the target region can capture the flow characteristics of the slurry; Phase flow model building module, used to build a two-phase flow model of slurry flow in a three-dimensional flow field, including a VOF multiphase flow model that simulates the dynamic changes of the interface, a slurry flow model that simulates the slurry flow in the flow field, and a surface force tension model; A solution parameter setting module, used to set solution parameters, slurry properties and boundary conditions of the slurry flow model, wherein the boundary conditions include the velocity inlet and pressure outlet of the slurry and the moving wall of the foil; A solution module, used for initializing and solving the slurry flow model based on the boundary conditions to determine whether a convergence condition is met; The simulation execution module is used to run the simulation after reaching the convergence condition, analyze the flow velocity distribution and pressure distribution changes of the slurry in the three-dimensional geometric model, and observe the three-dimensional flow characteristics of the slurry in the three-dimensional geometric model.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the three-dimensional slot coating simulation method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the three-dimensional slot coating simulation method according to any one of claims 1 to 7 are implemented.

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