Solid-state battery isostatic pressing process optimization method and system based on finite element simulation

Abstract

The invention discloses a solid-state battery isostatic pressing process optimization method and system based on finite element simulation, and the method comprises the following steps: constructing a geometric model of a solid-state battery, and carrying out the mesh generation of the geometric model of the solid-state battery through finite element analysis software, so as to obtain a discretization model; determining material attributes of each component in the solid-state battery, and setting a physical field in finite element analysis software according to the material attributes; according to the physical field, boundary conditions and isostatic pressing loads are applied to the discretization model, simulation operation is conducted on the discretization model, and stress and strain distribution of the solid-state battery in the isostatic pressing process is obtained; and optimizing the isostatic pressing process of the solid-state battery according to the stress and strain distribution. According to the method, the stress-strain behavior of the solid-state battery under isostatic pressing is accurately simulated, the aluminum-plastic film damage mechanism under large pressure is disclosed, proper technological parameters and an optimization method are explored, and theoretical guidance and technological support are provided for manufacturing of the solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and more specifically, to a solid-state battery isostatic pressing process optimization method and system based on finite element simulation. Background Art

[0002] With the continuous growth of energy demand and the increasing emphasis on environmental protection, solid-state batteries, as a battery technology with high energy density, long cycle life and excellent safety performance, have attracted widespread attention. Compared with traditional liquid batteries, solid-state batteries use solid electrolytes, which can effectively avoid electrolyte leakage and combustion, and improve the safety performance of the battery. However, the commercialization process of solid-state batteries still faces many challenges, one of which is the battery manufacturing process. In the manufacturing process of solid-state batteries (such as solid-state soft-pack batteries), isostatic pressing is a commonly used method. It can apply pressure to the solid-state battery evenly in all directions, which helps to improve the interface contact performance and conductivity of the solid-state battery. However, under the action of high pressure, the aluminum-plastic film packaging material of the solid-state battery is prone to damage, resulting in a decrease in solid-state battery performance or even failure. Therefore, how to optimize the isostatic pressing process parameters to prevent the aluminum-plastic film from being damaged has become a key issue in the manufacture of solid-state batteries.

[0003] Traditional experimental methods, which adjust process parameters through trial and error, are not only time-consuming and labor-intensive, but also difficult to precisely control experimental conditions, making it impossible to fully understand the stress and strain distribution within the battery during isostatic pressing. To address this issue, finite element simulation technology, as an effective computational tool, has been widely used in engineering and materials science. By discretizing complex physical problems into a number of simple subproblems, finite element simulation technology can simulate the behavior of materials under mechanical, thermal, and electrical forces on a computer, thereby predicting the stress and strain distribution, temperature field, and electric field of the structure. In the study of solid-state battery isostatic pressing, finite element simulation technology can be used to simulate the stress and strain state of the battery under isostatic pressing, providing a theoretical basis for optimizing process parameters. However, existing finite element simulation technology still has certain limitations when simulating solid-state battery isostatic pressing. On the one hand, the lack of constitutive models and parameters specific to solid-state battery materials leads to low accuracy of simulation results. On the other hand, the mechanism of aluminum-plastic film failure under high pressure is insufficiently studied, and effective preventive measures are lacking. Therefore, this is a technical problem that urgently needs to be addressed in this field. Summary of the Invention

[0004] In view of this, the present invention provides a solid-state battery isostatic pressing process optimization method based on finite element simulation to solve the problem in the prior art of lack of constitutive models and parameters for specific materials of solid-state batteries, resulting in low accuracy of simulation results.

[0005] In a first aspect, the present invention provides a method for optimizing an isostatic pressing process of a solid-state battery based on finite element simulation, comprising the following steps:

[0006] Constructing a geometric model of a solid-state battery, and meshing the geometric model of the solid-state battery using finite element analysis software to obtain a discretized model;

[0007] Determining the material properties of each component in the solid-state battery, and setting the physical field in the finite element analysis software according to the material properties;

[0008] Applying boundary conditions and isostatic pressure loads to the discretized model according to the physical field, and running a simulation on the discretized model to obtain stress and strain distribution of the solid-state battery during the isostatic pressing process;

[0009] Based on the stress and strain distribution, the isostatic pressing process of the solid-state battery is optimized.

[0010] In a second aspect, the present invention provides a solid-state battery isostatic pressing process optimization system based on finite element simulation, comprising:

[0011] A partitioning module is used to construct a geometric model of the solid-state battery and perform mesh partitioning on the geometric model of the solid-state battery using finite element analysis software to obtain a discretized model;

[0012] a material property determination module, coupled to the partitioning module, configured to receive the discretization module, determine the material properties of each component in the solid-state battery, and set a physical field in the finite element analysis software according to the material properties;

[0013] a simulation running module, coupled to the material property determination module, configured to receive a physical field, apply boundary conditions and an isostatic pressure load to the discretized model according to the physical field, and perform a simulation run on the discretized model to obtain stress and strain distribution of the solid-state battery during the isostatic pressing process;

[0014] The isostatic pressing process optimization module is used to receive the stress and strain distribution of the solid-state battery during the isostatic pressing process, and optimize the isostatic pressing process of the solid-state battery according to the stress and strain distribution of the solid-state battery during the isostatic pressing process.

[0015] Compared with the prior art, the solid-state battery isostatic pressing process optimization method and system based on finite element simulation provided by the present invention achieve at least the following beneficial effects:

[0016] The solid-state battery isostatic pressing process optimization method and system provided by the present invention based on finite element simulation, by accurately simulating the stress-strain behavior of solid-state batteries (such as solid-state soft-pack batteries) under isostatic pressing, reveals the mechanism of aluminum-plastic film damage under high pressure, and explores suitable process parameters and optimization methods, providing theoretical guidance and process support for the manufacture of solid-state batteries. Specifically, structural mechanics simulation and analysis are performed using finite element analysis software, and the isostatic pressing process of solid-state batteries is studied. In response to the problem of damage to the outer aluminum-plastic film of solid-state soft-pack batteries under high pressure, the critical isostatic pressing process parameters are calculated, the overall stress and strain of the battery cell are predicted, and the filling material is designed to act as a stress buffer for the battery cell, verifying the method for process improvement, solving common problems in the current isostatic pressing process, providing data support for the production process of solid-state soft-pack batteries, and also proposing feasible reference suggestions for enterprises to improve the process.

[0017] Of course, any product implementing the present invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0018] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0020] Figure 1 1 is a flow chart of a solid-state battery isostatic pressing process optimization method based on finite element simulation provided by the present invention;

[0021] Figure 2 Schematic diagram of the geometric model of the solid-state battery provided by the present invention;

[0022] Figure 3 It is a unit grid divided by the geometric model of the solid-state battery provided by the present invention;

[0023] Figure 4 is the load-displacement curve of the tensile test provided by the present invention;

[0024] Figure 5 Schematic diagram of the stress and strain distribution of the solid-state battery provided by the present invention during the isostatic pressing process;

[0025] Figure 6 It is a flow chart of the discretization model provided by the present invention;

[0026] Figure 7a This is a schematic diagram of the stress and strain of a battery cell under 300 MPa isostatic pressure provided by the present invention;

[0027] Figure 7b The present invention provides a Figure 7a Middle partial enlarged view;

[0028] Figure 7c This is a schematic diagram of a structure in which the aluminum-plastic film at the top corner of a battery cell is damaged after 300 MPa isostatic pressing provided by the present invention;

[0029] Figure 8a This is a schematic diagram of the displacement of a battery cell under 300 MPa isostatic pressure provided by the present invention;

[0030] Figure 8b This is another schematic diagram of the displacement of a battery cell under 300 MPa isostatic pressure provided by the present invention;

[0031] Figure 8c This is another schematic diagram of the displacement of a battery cell under 300 MPa isostatic pressure provided by the present invention;

[0032] Figure 9a It is a schematic diagram of geometry and mesh division of an optimization solution provided by the present invention;

[0033] Figure 9b It is a schematic diagram of geometry and mesh division of another optimization solution provided by the present invention;

[0034] Figure 10a This is the stress and strain of the entire battery cell when nylon is used as the buffer material in an optimization solution provided by the present invention;

[0035] Figure 10b This is the stress and strain of the entire battery cell when nylon is used as the buffer material in another optimization solution provided by the present invention;

[0036] Figure 10c This is the stress and strain of the entire battery cell when nylon is used as the buffer material in another optimization solution provided by the present invention;

[0037] Figure 11a This is the stress and strain of the entire battery cell when acrylic is used as the buffer material in an optimization solution provided by the present invention;

[0038] Figure 11b This is the stress and strain of the entire battery cell when acrylic is used as the buffer material in another optimization solution provided by the present invention;

[0039] Figure 11c This is the stress and strain of the entire battery cell when acrylic is used as the buffer material in another optimization solution provided by the present invention;

[0040] Figure 12 This is the stress and strain of the entire battery cell when wood is used as the buffer material in an optimization solution provided by the present invention;

[0041] Figure 13 It is a structural schematic diagram of the solid-state battery isostatic pressing process optimization system based on finite element simulation provided by the present invention. DETAILED DESCRIPTION

[0042] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0043] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0044] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0045] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0046] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0047] Reference Figure 1-Figure 3 As shown, Figure 1 1 is a flow chart of a solid-state battery isostatic pressing process optimization method based on finite element simulation provided by the present invention; Figure 2 Schematic diagram of the geometric model of the solid-state battery provided by the present invention; Figure 3 is a unit grid divided by the geometric model of the solid-state battery provided by the present invention; this embodiment provides a solid-state battery isostatic pressing process optimization method based on finite element simulation, comprising the following steps:

[0048] Step 101: construct a geometric model of the solid-state battery, and use finite element analysis software to mesh the geometric model of the solid-state battery to obtain a discretized model;

[0049] Specifically, a geometric model of a solid-state battery is constructed using 3D modeling software (such as SolidWorks, AutoCAD, etc.). Figure 2As shown in Figure 2, the geometric model of the solid-state battery can include all key components of the solid-state battery, such as the laminated core and aluminum-plastic film. This geometric model is the foundation of finite element analysis, and its accuracy directly affects the accuracy of the simulation results. The geometric model of the solid-state battery must accurately reflect the actual structure of the solid-state battery to facilitate subsequent meshing and simulation analysis.

[0050] Finite element analysis software (such as COMSOL Multiphysics, ANSYS, etc.) is used to mesh the geometric model of the solid-state battery to obtain a discretized model, such as Figure 3 As shown in Figure 2. Meshing is the process of breaking down complex geometric structures into small units for numerical calculations. Discretization is the core of finite element analysis. Through meshing, the continuous geometric model of a solid-state battery can be converted into a collection of discrete units, enabling complex mechanical problems to be solved numerically. The quality of the mesh (such as unit shape and size) directly affects the accuracy and computational efficiency of the simulation.

[0051] SolidWorks is a 3D mechanical design software, mainly used for 3D part modeling, sheet metal weldment design, assembly, engineering drawings and rendering, etc. AutoCAD is a 2D drawing software, mainly used for 2D geometric graphics and drawing, and has basic 3D design functions. The above-mentioned COMSOL Multiphysics is a multi-physics simulation software for engineers and scientists. The "COMSOL" in its name stands for "Complex Physical Phenomena Simulation", which means simulation of complex physical phenomena. ANSYS is a large-scale general-purpose finite element analysis (FEA) software, and the "ANSYS" in its name stands for "Analysis and System Simulation", which means analysis and system simulation.

[0052] Step 102: Determine the material properties of each component in the solid-state battery, and set the physical field in the finite element analysis software according to the material properties;

[0053] Specifically, the material properties of each component in the solid-state battery are determined, including the physical parameters of the core stack and aluminum-plastic film (such as density, elastic modulus, Poisson's ratio, initial porosity, reference stress, reference strain, and initial yield stress, etc.). Based on the physical parameters of the core stack and aluminum-plastic film, the corresponding physical field is set in the finite element analysis software. The physical field can be selected from solid mechanics. Material properties are an indispensable part of finite element analysis. They determine the mechanical behavior of each unit when subjected to force. Accurate material parameters can ensure the reliability of the simulation results. The setting of the physical field defines the mechanical relationship between units based on the material properties.

[0054] Step 103: applying boundary conditions and isostatic pressure loads to the discretized model according to the physical field, and performing simulation on the discretized model to obtain the stress and strain distribution of the solid-state battery during the isostatic pressing process;

[0055] Specifically, boundary conditions are added to the discretized model and isostatic loads are applied. The boundary conditions define the constraint state of the discretized model in the simulation, while the isostatic load simulates the uniform pressure that the battery is subjected to in the actual process. Boundary conditions and isostatic loads are key inputs for simulation analysis. The boundary conditions determine the degrees of freedom of movement of the discretized model, while the isostatic load defines the external forces acting on the discretized model. Through the discretized model, it is possible to accurately define which units are subject to fixed constraints and which units are subject to pressure loads, thereby simulating the actual isostatic pressing process. Correct boundary conditions and discretized model settings can ensure that the simulation results are consistent with the actual process. The simulation is run in the finite element analysis software to obtain the stress and strain distribution of the solid-state battery during the isostatic pressing process. Subsequent simulation results provide detailed mechanical behavior of the solid-state battery during the isostatic pressing process, including stress concentration areas, strain distribution, etc. This information is an important basis for optimizing the process.

[0056] Step 104: Optimize the isostatic pressing process of the solid-state battery according to the stress and strain distribution of the solid-state battery during the isostatic pressing process.

[0057] Specifically, the stress and strain distribution of the above-mentioned solid-state battery during isostatic pressing is a simulation result, and the simulation result is obtained based on a discretization model. By analyzing the simulation result, stress concentration areas can be identified, and isostatic pressing process is optimized accordingly. Specifically, according to the simulation result, the isostatic pressing process of the solid-state battery is optimized. Optimization content includes adjusting isostatic pressing parameters, designing stress buffer structures (such as filling materials) to reduce the stress level in stress concentration areas, improving the structural safety and production reliability of the battery. In the present embodiment, isostatic pressing can be 300MPa. When the physical field selects solid mechanics, it is necessary to perform the calculation of solid mechanics, analyze and study the 300MPa isostatic pressing process, draw a stress body distribution diagram, and insert maximum and minimum values ​​in the figure, draw global displacement, x component (width direction) displacement, z component (length direction) displacement, analyze the stress distribution of the battery core under different working conditions, displacement conditions. Optimizing process is the ultimate goal of the whole method. The simulation result obtained by simulation analysis can improve process in a targeted manner, solve problems that may occur in actual production, such as damage to aluminum-plastic film, etc.

[0058] Compared with the prior art, the solid-state battery isostatic pressing process optimization method based on finite element simulation provided in this embodiment achieves at least the following beneficial effects:

[0059] The solid-state battery isostatic pressing process optimization method based on finite element simulation provided in this embodiment, by accurately simulating the stress-strain behavior of solid-state batteries (such as solid-state soft-pack batteries) under isostatic pressing, reveals the mechanism of aluminum-plastic film damage under high pressure, and explores suitable process parameters and optimization methods, providing theoretical guidance and process support for the manufacture of solid-state batteries. Specifically, structural mechanics simulation and analysis are performed through finite element analysis software, and the isostatic pressing process of solid-state batteries is studied. In response to the problem of damage to the outer aluminum-plastic film of solid-state soft-pack batteries under high pressure, the critical isostatic pressing process parameters are calculated, the overall stress and strain of the battery cell are predicted, and the filling material is designed to serve as a stress buffer for the battery cell, verifying the method of process improvement, solving common problems in the current isostatic pressing process, providing data support for the production process of solid-state soft-pack batteries, and also providing feasible reference suggestions for enterprises to improve the process.

[0060] In an optional embodiment, the material properties of the components of the solid-state battery include the physical parameters of the core stack and the aluminum-plastic film, and the physical parameters of the core stack and the aluminum-plastic film include density, elastic modulus, Poisson's ratio, initial porosity, reference stress and reference strain and initial yield stress, as shown in Table 1. Table 1 shows the physical parameters of the core stack and the aluminum-plastic film.

[0061] Table 1 Physical properties of core and aluminum-plastic film

[0062] property Stacked Core Aluminum-plastic film <![CDATA[Density kg / m 3 > 1421 1425 Elastic modulus Pa 9.5e9 1.6e9 Poisson's ratio 0.20 0.36 Initial porosity 0.05 - <![CDATA[Reference stress N / m 2 > 3e8 101325 Reference strain 0.05 0 Initial yield stress Pa 2e8 28e6

[0063] Specifically, the above density is the mass of material per unit volume.

[0064] In mechanical analysis, density is mainly used to calculate the inertial force of the material (such as in dynamic analysis). In static analysis, although density has little effect on the results, it is an indispensable parameter when considering gravity or other body forces. As shown in Table 1 above, the density of the core stack in this embodiment can be 1421 kg / m 3 , the density of aluminum plastic film can be 1425kg / m 3 The density of the core stack and the density of the aluminum-plastic film can be adjusted according to actual conditions. In this embodiment, the density of the core stack is only 1421kg / m 3 The density of aluminum plastic film is 1425kg / m 3 Give an example.

[0065] The elastic modulus is the material's ability to resist deformation in the elastic phase and represents the ratio of stress to strain. It is also known as Young's modulus. It is an important parameter for describing material rigidity. In simulations, it determines the degree of deformation of a material under load. A higher elastic modulus means a more rigid material with less deformation. The elastic modulus of aluminum-plastic film can be 1.6e9 Pa, while that of laminated cores can be 9.5e9 Pa. The Poisson's ratio is the ratio of transverse strain to longitudinal strain under load. This describes the material's transverse deformation characteristics under load. Together with the elastic modulus, it is used to calculate the shear modulus and bulk modulus of the material, thereby comprehensively describing the material's mechanical behavior. The Poisson's ratio of aluminum-plastic film can be 0.36, while that of laminated cores can be 0.20. The initial porosity ratio is the ratio of the pore volume to the total volume of the material. This initial porosity ratio is crucial in describing the mechanical behavior of porous materials. It influences parameters such as density, elastic modulus, and initial yield stress. The initial porosity of the core stack can be 0.05. The above-mentioned reference stress is the stress value of the material at a specific strain level and is used to describe the nonlinear behavior of the material. In elastic-plastic analysis, the reference stress is used to define the yield criterion of the material. It is the critical stress value at which the material begins to undergo plastic deformation. The reference stress of the aluminum-plastic film can be 101325N / m 2 , and the reference stress of the core can be 3e8 N / m 2 .

[0066] The reference strain is the material's strain value at a specific stress level and is used to describe the material's nonlinear behavior. The reference strain is used to define the material's yield criterion and, together with the reference stress, describes the material's behavior during the plastic deformation stage. The reference strain for aluminum-plastic film can be 0, and the reference strain for laminated cores can be 0.05. The initial yield stress is the stress at which the material begins to undergo plastic deformation. The initial yield stress is the critical point at which the material transitions from elastic to plastic deformation. In simulations, it is used to define the material's yield criterion, thereby accurately simulating the material's behavior under high stress. The initial yield stress for aluminum-plastic film can be 28e6 Pa, and for laminated cores can be 2e8 Pa.

[0067] The above scheme, using density, elastic modulus, Poisson's ratio, initial void ratio, reference stress, reference strain, and initial yield stress, not only accurately describes the mechanical behavior of the material—for example, ensuring that the discretized model truly reflects the material's mechanical response under actual operating conditions—but also improves the reliability of simulation results. It also optimizes isostatic pressing process parameters and enhances the structural safety and reliability of solid-state batteries. In other words, the physical properties of the laminated core and aluminum-plastic film are key to successful finite element simulations and directly impact the accuracy and reliability of the simulation results.

[0068] In an optional embodiment, combined with Figure 1 and Figure 4 As shown, Figure 4 is the load-displacement curve of the tensile test provided by the present invention; Figure 4 The three different colored lines represent three repeated tests. Step 102: determining the material properties of each component in the solid-state battery. Setting the physical field in the finite element analysis software based on the material properties includes:

[0069] In the physical field, select the Solid Mechanics interface. The aluminum-plastic film is an isotropic elastic-plastic material. The stress-strain of the elastic-plastic material in the elastic process satisfies the following relationship:

[0070]

[0071] Where E is the elastic modulus, v is Poisson's ratio, G is the shear modulus, ε11, ε22, and ε33 are the normal strains along the three coordinate axes (usually the x, y, and z axes), γ12, γ13, and γ23 are the shear strains in the xy plane, xz plane, and yz plane, respectively; σ11, σ22, and σ33 represent the normal stresses in the directions of the three coordinate axes, and σ12, σ13, and σ23 represent the shear stresses in different main directions of the three coordinate axes, respectively.

[0072] Specifically, in finite element analysis, setting up the physical field is a key step in defining the material behavior model, which determines how the material responds to the applied isostatic load in the simulation. For the aluminum-plastic film used in solid-state batteries, it is defined as an isotropic elastic-plastic material, meaning that its mechanical properties are the same in all directions, and the material behavior includes both elastic and plastic stages.

[0073] In the elastic phase, the material follows Hooke's law, which states that stress is proportional to strain. For isotropic materials, this relationship can be described by a generalized Hooke's law, as shown in the matrix equation above. Here, E represents the elastic modulus, a measure of the material's stiffness against elastic deformation; v represents the Poisson's ratio, which describes the material's expansion or contraction in a perpendicular direction when compressed in one direction; and G represents the shear modulus, a measure of the material's resistance to shear deformation.

[0074] When the stress exceeds the yield strength of the material, the material enters the plastic stage, during which the material undergoes permanent deformation. Plastic behavior is usually described by plasticity theory, such as the yield criterion and hardening model. Plastic deformation in the plastic stage is nonlinear. The stress-strain of the plastic process is described by the hardening function, which is derived from the load-displacement curve of the tensile test, such as Figure 4 What is shown here is an interpolation function, not a specific mathematical formula. The interpolation data comes from experimental tests.

[0075] By adopting the above solution, by setting up a solid mechanics interface in the finite element analysis software and defining the aluminum-plastic film as an isotropic elastic-plastic material, the behavior of the material under stress, including elastic and plastic deformation, can be more accurately simulated. Through simulation, the stress and strain distribution of the material under different loading conditions, as well as the possible plastic deformation area, can be predicted, which is crucial for evaluating the performance of the material and the reliability of the structure. It can be understood that setting up the physical field in finite element analysis, especially for elastic-plastic materials, is a key step in ensuring the accuracy of simulation results. By defining the elastic and plastic behavior of the material, the response of the material under stress can be more realistically simulated, thus providing a scientific basis for design optimization, process improvement and safety assessment.

[0076] In some optional embodiments, the linear elastic properties are determined according to the elastic modulus and Poisson's ratio, and the constitutive matrix of the material is filled with the isotropic linear elastic properties. The constitutive matrix of the material is expressed as:

[0077]

[0078] The calculation formulas for C11, C12, and C44 are as follows:

[0079]

[0080] C 44 =G,

[0081] Where C is a function of material properties, C11 and C12 are stiffness matrix elements, and C44 is an element in the stiffness matrix related to shear stress and shear strain.

[0082] Specifically, the function of the material properties mentioned above is a key tool for describing the relationship between material stress and strain. For isotropic linear elastic materials, the function of the material properties provides a mathematical expression for calculating the response of the material when subjected to stress. The function C of the material properties is a fourth-order tensor used to describe the elastic properties of the material in three-dimensional space. In matrix form, it is usually represented as a 6x6 matrix because both stress and strain in three-dimensional space can be represented by six independent components (three normal stresses and three shear stresses / strains).

[0083] C11, C12, and C44 are key elements in the constitutive matrix. They are related to the material's elastic modulus E and Poisson's ratio ν. C11 and C12 describe the material's elastic response under normal stress, while C44 describes the response under shear stress. Functions of material properties include the elastic constant tensor.

[0084] C11 is an element in the stiffness matrix. In isotropic elastic materials, it is related to the elastic modulus E and Poisson's ratio ν. It reflects the stiffness characteristics of the material under a specific stress-strain relationship, corresponding to the coupling of normal stress and normal strain directions, and reflects the material's ability to resist deformation along a specific direction.

[0085] C12 is also a stiffness matrix element, representing the coupling stiffness between normal stress and normal strain in different directions, reflecting the influence of normal stress in one direction on normal strain in another direction.

[0086] C44 is an element in the stiffness matrix related to shear stress and shear strain. For isotropic elastic materials, C44 is equal to the shear modulus G, which characterizes the material's stiffness properties against shear deformation.

[0087] The calculation formulas for the above elements (C11, C12 and C44) are as follows:

[0088] Here, G is the shear modulus, which is related to the elastic modulus E and Poisson's ratio ν.

[0089] The elastic properties of a material can be viewed as functions of E, v, and G, such as C = C(E, v, G). By using functions of material properties, the stress-strain relationship of isotropic linear elastic materials under load can be accurately simulated in finite element analysis. By understanding the elastic properties of a material, engineers can optimize the design to ensure that the structure performs as expected under load, while avoiding over- or under-design. Functions of material properties allow different material properties or design parameters to be tested in simulation, thereby comparing the performance of different solutions and selecting the optimal design.

[0090] Alternatively, the shear modulus is expressed as: G = E / [2(1 + v)].

[0091] The above-mentioned shear modulus G is a physical quantity that measures the material's ability to resist shear deformation. It is also an important indicator of the material's mechanical properties, which helps to fully understand the material's behavior under different loading conditions. In materials science and engineering, it is an important elastic constant used to describe the elastic response of a material under shear stress. The above formula shows that the shear modulus G is proportional to the elastic modulus E and inversely proportional to 1+ν. This means that for a given Poisson's ratio, the larger the elastic modulus of a material, the larger its shear modulus, indicating that the material is more difficult to shear deform.

[0092] Using this approach, the shear modulus provides a way to quantify how easily a material deforms under shear forces. In engineering design, the shear modulus can be used to select appropriate materials to ensure that the structure possesses sufficient stiffness and strength under the expected shear stresses. By considering the shear modulus, it is possible to more accurately predict the behavior of materials in real-world applications, thereby improving the reliability and safety of structural designs.

[0093] In an alternative embodiment, see Figure 5 As shown, Figure 5 1 is a flow chart of the stress and strain distribution of the solid-state battery during the isostatic pressing process provided by the present invention; step 103, applying boundary conditions and isostatic pressure loads to the discretized model according to the physical field, and running a simulation on the discretized model to obtain the stress and strain distribution of the solid-state battery during the isostatic pressing process includes:

[0094] Step 1031: applying boundary conditions and isostatic loads to specific nodes or surfaces of the discretized model;

[0095] Specifically, boundary conditions (such as fixed constraints, symmetry constraints, etc.) and isostatic loads (such as uniform pressure) are applied to specific nodes or surfaces of the discretized model. The boundary conditions define the constraint state of the discretized model in the simulation, and the isostatic load simulates the uniform pressure that the battery is subjected to in the actual process. For example, the surfaces where the three symmetry axes x, y, and z are located are selected as symmetric boundaries to simulate the zero constraint situation during the isostatic pressing process. Symmetric boundary conditions can reduce the amount of calculation, and they can use symmetry to simplify the model. Apply external loads, such as pressure, to specific nodes or surfaces of the discretized model. In the above example, all external surfaces except the three symmetry surfaces are added as boundary loads. The load is pressure, and the pressure magnitude is 3e8 Pa. The pressure value can be entered according to the actual situation.

[0096] Step 1032: Obtain a deformation gradient of each unit in the discretized model based on the applied boundary conditions and isostatic loads, decompose the deformation gradient of each unit in the discretized model into an elastic part and an elastic-plastic part, and obtain elastic strain based on the elastic part;

[0097] Specifically, based on the applied boundary conditions and isostatic loads, the deformation gradient of each unit in the discretized model is calculated to describe the deformation of the material from the reference configuration to the current configuration. Its purpose is to describe the deformation of the material after being subjected to force. The deformation gradient is the derivative of the displacement field, which describes the degree and direction of deformation of the material after being subjected to force; by integrating the deformation gradient, the displacement of each node in the discretized model is obtained. The displacement field is the integral result of the deformation gradient, which reflects the displacement distribution of the discretized model after being subjected to force.

[0098] The deformation gradient of each element in the discretized model is decomposed into an elastic component and an elastoplastic component. The elastic component is the deformation that can be recovered, while the elastoplastic component includes plastic deformation and possible damage. Based on the deformation gradient of the elastic component, the elastic strain is calculated. Elastic strain is reversible; when the external force is removed, the material returns to its original state.

[0099] Step 1033: Obtain elastic stress according to the constitutive relation of the material and the elastic strain, such as calculating the elastic stress according to the constitutive relation of the material (such as linear elasticity, elastic-plastic part, etc.) and the elastic strain.

[0100] Step 1034: Obtain an equilibrium equation based on the applied boundary conditions, isostatic load, elastic stress, and elastic strain.

[0101] Based on the applied boundary conditions, isostatic loads, elastic stresses, and elastic strains, the equilibrium equations are solved to ensure the equilibrium state of the discretized model after being subjected to the forces.

[0102] In the above scheme, the imposed boundary conditions and isostatic loads define the physical constraints and stress conditions of the discretized model. The deformation gradient describes the degree and direction of deformation of the material after being subjected to stress. The deformation gradient is decomposed, such as decomposing the total strain into the elastic part and the elastoplastic part to obtain the elastic strain; the elastic stress is the stress distribution of the material under elastic deformation. Solving the equilibrium equation ensures the equilibrium state of the discretized model after being subjected to stress. The above steps can not only obtain the deformation and stress distribution of the material after being subjected to stress, but also provide a basis for structural analysis and optimization design. For example, through accurate stress and strain analysis, weaknesses in the solid-state battery structure can be identified, measures can be taken to avoid failure, and the safety of the product can be improved.

[0103] Alternatively, the deformation gradient is expressed as:

[0104] Where F is the deformation gradient tensor, I is the unit tensor, It is the displacement gradient tensor, which describes the deformation of a material point from the reference configuration to the current configuration. The deformation gradient is the basis for understanding material deformation and is used to calculate strain and stress.

[0105] The deformation gradient of each element in the discretized model is decomposed into the elastic part and the elastic-plastic part and expressed as:

[0106] S=S inel +S el ,

[0107] Where S is the total stress, S inel is the elastic stress, S el is the second Piola-Kirchhoff stress tensor, that is, the total stress S is decomposed into the elastic stress S inel and the second Piola-Kirchhoff stress S el ,This decomposition helps to analyze the mechanical behavior of materials in different deformation stages (elastic and plastic).

[0108] The Second Piola-Kirchhoff Stress Tensor (SPT) is a tensor used in continuum mechanics to describe the internal stress state of a material. It is defined at the material's reference configuration (i.e., its original, undeformed configuration) and is dependent on the material's deformation.

[0109] The elastic strain is expressed as:

[0110] ∈ el is the elastic strain energy density, F el is the elastic deformation gradient, I is the trace of the unit tensor, and T is an operator representing the transpose of the matrix. The elastic strain energy density is used to calculate the energy stored in the material during elastic deformation, which is very important for understanding the elastic response and energy release process of the material.

[0111] Among them, ∈ represents the total strain tensor, which is a symmetric tensor used to describe the strain state of the material. is the displacement gradient tensor, which represents the spatial rate of change of the displacement field, Represents the transpose of the displacement gradient tensor.

[0112] The above formula symmetrizes the displacement gradient tensor to ensure that the total strain tensor is symmetric. In continuum mechanics, the strain tensor is usually symmetric because the asymmetric part is usually related to the rotation of the material rather than the actual deformation.

[0113] Elastic stress is expressed as:

[0114] S inel =S o +S ext +S q , where S o is the initial stress, S ext is the external stress, S q is the internal stress; initial stress, external stress and internal stress are helpful to analyze and calculate the response of materials under different stress states.

[0115]

[0116] Where, J i is the volume ratio, C is a function of material properties, and F inel It is the inverse of the elastic deformation gradient, and ":" represents the double dot product. This representation is used to calculate the stress state of the material during the elastic deformation stage, which helps to understand the elastic behavior of the material.

[0117] The equilibrium equation is expressed as:

[0118] Where, Represents the divergence of stress, F V Represents body force.

[0119] The equilibrium equation is an equilibrium equation in continuum mechanics, which represents the balance between the divergence of stress and the volume ratio inside a solid in the absence of external forces. The equilibrium equation ensures the physical correctness of the discretized model and is the basis for finite element analysis and structural design.

[0120] The above equations form the basis for finite element analysis (FEA) to simulate and analyze material deformation, stress, and strain. These analyses predict the behavior of materials under varying loads and deformations, enabling design optimization and improved structural safety and performance. The application of these equations and concepts helps engineers and scientists more accurately predict material response when designing and analyzing structures, leading to optimized designs and improved structural performance and safety.

[0121] Alternatively, the elastic deformation gradient is expressed as:

[0122] Where F is the total deformation gradient, F inel is the plastic deformation gradient.

[0123] The total deformation gradient F described above describes the complete deformation process of the material from the reference configuration to the current configuration. inel Describes the permanent (irrecoverable) deformation of a material. Plastic deformation is often associated with the yielding and hardening behavior of a material. inel is the elastic deformation gradient, which describes the recoverable portion of the material’s deformation. When the external force is removed, the material can return to a near-original state through the elastic deformation gradient. The above formula indicates that the elastic deformation gradient is the product of the total deformation gradient and the inverse of the plastic deformation gradient.

[0124] The calculation and application of elastic deformation gradient is an important aspect in continuum mechanics and finite element analysis. It helps to more accurately simulate and understand the deformation and recovery behavior of materials after being subjected to stress, thereby optimizing design and improving product performance.

[0125] In an alternative embodiment, see Figure 6 As shown, Figure 6 1 is a flow chart of the discretization model provided by the present invention; Step 101, constructing a geometric model of a solid-state battery, meshing the geometric model of the solid-state battery using finite element analysis software, and obtaining a discretization model including:

[0126] Step 1011: seal the stacked core into a solid-state battery formed by an aluminum-plastic film, and model the solid-state battery according to the principle of symmetry to obtain a geometric model of the solid-state battery;

[0127] Specifically, the simulation object is a solid-state battery consisting of a rectangular stacked core sealed in an outer layer of aluminum-plastic film. The solid-state battery can be a solid-state soft-pack battery. Since the solid-state soft-pack battery has symmetry, in order to simplify the calculation, according to the principle of symmetry, a 1 / 8 modeling (hereinafter referred to as the 1 / 8 model) is performed on the solid-state battery while ensuring the accuracy of the simulation results. For example, a corner of the solid-state soft-pack battery is selected to establish a geometric model of the 1 / 8 part including the stacked core and the aluminum-plastic film.

[0128] In this embodiment, the dimensions of the core stack portion may be 0.049m x 0.157m x 0.004m, and the thickness of the outer aluminum-plastic film may be 0.00015m. The core stack and the aluminum-plastic film model are combined to form a joint body. Of course, depending on actual conditions, the dimensions of the core stack portion and the thickness of the outer aluminum-plastic film may also adopt other values, which are not specifically limited in this embodiment.

[0129] Step 1012: Divide the geometric model of the solid-state battery using a free tetrahedral mesh;

[0130] In step 1011, the solid-state battery geometry is meshed using a free tetrahedral mesh. This free tetrahedral mesh is composed of irregular tetrahedral elements and is suitable for complex geometries. Free tetrahedral meshes are simple to generate and are suitable for complex geometries, particularly when the solid-state battery geometry contains many sharp corners or holes.

[0131] Step 1013: Automatically adjust the density and distribution of the grid according to the characteristics of the physical field;

[0132] Specifically, the sequence type is controlled by the physical field, that is, the density and distribution of the grid are automatically adjusted according to the characteristics of the physical field; physical field control refers to automatically adjusting the grid size according to the characteristics of the physical field (such as stress distribution, strain distribution, etc.). Physical field control can improve the accuracy and efficiency of simulation results because it ensures that the grid units are fine enough in critical areas and coarse enough in non-critical areas. The above-mentioned physical field control is also an option of finite element analysis software. Manual control or physical field control can be selected. This embodiment adopts physical field control, and the physical field used in the embodiment is solid mechanics.

[0133] Step 1014: The mesh size is predefined as refined, and the mesh is automatically generated using the physical model.

[0134] Specifically, the mesh size is predefined as refined to improve the accuracy of the simulation results. A refined mesh can better capture geometric details and areas of stress concentration. Refinement refers to reducing the size of mesh elements to improve the accuracy of the simulation results. Refinement is an option in finite element analysis software, and you can choose between refined, regular, or coarse. In this example, refinement is selected.

[0135] The physics used in this example is solid mechanics, which is suitable for simulating the stress, strain, and deformation of solid materials. Automatic mesh generation using the physical model is convenient and suitable for simple geometries.

[0136] Using this approach, we can generate high-quality meshes for geometric models, laying a solid foundation for subsequent finite element analysis. Simultaneously, through physical field control and mesh refinement, we can improve the accuracy of simulation results and computational efficiency.

[0137] Application Examples

[0138] Figure 7a This is a schematic diagram of the stress and strain of a battery cell under 300MPa isostatic pressure provided by the present invention; body: vonMises stress, Gauss point calculation (Pa): represents Figure 7a The figure shows the von Mises stress distribution inside the material. von Mises stress is a stress indicator used to assess whether a material will yield under complex stress conditions. Gaussian point calculation refers to the process of calculating stress at Gaussian points inside a unit in finite element analysis to approximate the stress distribution of the entire unit. The unit is Pascal Pa. The maximum value of the von Mises stress inside the material is 6.39925E7 Pa, and the minimum value is 224838Pa. These values ​​represent the distribution range of the von Mises stress inside the material during the simulation. Figure 7b The present invention provides a Figure 7a Middle partial enlarged view; Figure 7c This is a schematic diagram of the structure of a battery cell with damaged aluminum-plastic film at the top corner after 300 MPa isostatic pressing provided by the present invention; Figure 8a This is a schematic diagram of the displacement of a battery cell under 300MPa isostatic pressure provided by the present invention. Figure 8a The displacement of the battery cell at each point is in millimeters. Figure 8a The maximum value of the displacement is 5.55781 mm, and the minimum value is 0.00000 mm; Figure 8b This is another schematic diagram of the displacement of the battery cell under 300MPa isostatic pressure provided by the present invention. Figure 8b The displacement component of the battery cell in the X direction, the displacement distribution range of the battery cell in the X direction is from -2.44012mm to 0.00000mm; Figure 8c This is another schematic diagram of the displacement of the battery cell under 300 MPa isostatic pressure provided by the present invention. Figure 8c The displacement component of the battery cell in the Z direction, the displacement distribution range of the battery cell in the Z direction is from -5.00760mm to 0.00000mm; Figure 9a It is a schematic diagram of geometry and mesh division of an optimization solution provided by the present invention; Figure 9bIt is a schematic diagram of geometry and mesh division of another optimization solution provided by the present invention; Figure 10a This is the stress and strain of the entire battery cell when nylon is used as the buffer material in an optimization solution provided by the present invention. Figure 10a The maximum value of the von Mises stress inside the material is 5.18727E7Pa, and its minimum value is 151609Pa, which means that in the simulation, the distribution range of the von Mises stress inside the material is from 151609Pa to 51872700Pa; Figure 10b This is the stress and strain of the entire battery cell when nylon is used as the buffer material in another optimization solution provided by the present invention. Figure 10b The value displayed is the displacement component of the cell in the Z direction. The maximum value of the displacement component of the cell in the Z direction is 0.0000mm, and the minimum value is -4.47130mm. These values ​​indicate that in the simulation or experiment, the displacement distribution of the cell in the Z direction ranges from -4.47130mm to 0mm. Figure 10c This is the stress and strain of the entire battery cell when nylon is used as the buffer material in another optimization solution provided by the present invention. Figure 10c Represents the displacement component of the cell in the X direction. The maximum value of the displacement component of the cell in the X direction is 0.00000mm, and the minimum value is -1.86164mm. These values ​​indicate that in the simulation or experiment, the displacement distribution range of the cell in the X direction is from -1.86164mm to 0mm; Figure 11a This is the stress and strain of the entire cell when acrylic is used as the buffer material in an optimization solution provided by the present invention. Figure 11a The maximum value of the von Mises stress inside the material is 5.40403E7 Pa, and the minimum value is 126894 Pa. These values ​​indicate that in the simulation, the distribution range of the von Mises stress inside the material is from 126894 Pa to 5.40403E7 Pa; Figure 11b This is another optimization solution provided by the present invention when acrylic is used as the buffer material to measure the stress and strain of the entire battery cell. Figure 11b The maximum value of the displacement component of the cell in the Z direction is 0.0000mm, and the minimum value is -4.41932mm. These values ​​indicate that in the simulation or experiment, the displacement distribution of the cell in the Z direction ranges from -4.41932mm to 0mm; Figure 11c This is the stress and strain of the entire cell when acrylic is used as the buffer material in another optimization solution provided by the present invention. Figure 11c The maximum value of the displacement component of the cell in the X direction is 0.0000mm, and the minimum value is -1.80154mm. This means that under simulation or experimental conditions, the displacement distribution range of the cell in the Z direction is from -1.80154mm to 0mm; Figure 12This is the stress and strain of the entire battery cell when wood is used as a buffer material in an optimization solution provided by the present invention. Figure 12 The maximum value of the von Mises stress inside the material is 7.80460E8 Pa, and the minimum value is 564413 Pa. These values ​​indicate that in the simulation, the distribution range of the von Mises stress inside the material is from 564413 Pa to 7.80460E8 Pa;

[0139] Figure 7a is the overall stress distribution diagram of the 1 / 8 model, Figure 7a As shown in the figure, the maximum stress of the battery cell is concentrated at the top corner of the battery cell, and the minimum stress of the battery cell is located at the top corner of the aluminum-plastic film. The maximum stress of the battery cell is 66.9MPa, and the tensile strength of the aluminum-plastic film is 55MPa. The maximum stress of the battery cell is greater than the tensile strength of the aluminum-plastic film. The main surface stress and side stress of the battery cell are about 30-40MPa, and the stress range of the aluminum-plastic film is 10MPa-20MPa, which is completely consistent with the experimental situation (the aluminum-plastic film is damaged at the top corner of the battery cell after 300MPa isostatic pressing) ( Figure 7c ); Figure 7b for Figure 7a The local enlarged view shows the stress concentration location more clearly.

[0140] Figure 8a is the absolute displacement of all points in the cell. It can be seen that all points in the volume shrink toward the inside of the cell, and the displacement at the top corner of the cell is the largest. Figure 8b Displayed as the x-direction displacement component, the narrow side strain displacement of the cell is -2.44mm, that is, the width direction shrinks inward by 4.9mm, and the shrinkage is basically consistent with the actual measurement; Figure 8c It shows the displacement component in the z direction, and the strain displacement of the long side of the battery cell is -5.0mm, that is, a contraction of 10mm in the length direction, which is basically consistent with the measured value. The model can reflect the changing trend and optimization direction of the stress and strain of the battery cell during isostatic pressing to a certain extent, and provide data support and feasibility suggestions for process improvement.

[0141] Propose and verify improvement plans;

[0142] Simulate filling buffer around the battery cell with a height difference from the aluminum-plastic film to reduce stress and strain. Specifically, in the geometric model of the solid-state battery drawn in step 101, construct the filler geometry (rose red area), such as Figure 9a ; and re-divide the unit grid, such as Figure 9b The following three possible cushioning materials were selected from the built-in material library of the software for testing: nylon, acrylic, and wood. Their physical properties are shown in Table 2, Table 3, and Table 4.

[0143] Table 2 Physical properties of nylon

[0144]

[0145] Table 3 Physical parameters of acrylic;

[0146]

[0147] Table 4 Physical properties of wood

[0148]

[0149] Specifically, when nylon is added as a cushioning material, Figure 10a The stress distribution under a load of 300MPa shows that the maximum stress is still located at the top corner, but it is 15.1MPa lower than that without filler and lower than the tensile strength of 55MPa, so the damage of the aluminum-plastic film can be avoided. At this time, the overall deformation of the battery cell is as follows: Figure 10b and 10c As shown: length direction -8.94mm, width direction -3.72mm, surface shrinkage rate 5.12%, 1.15% lower than the original. When acrylic is added as a buffer material, Figure 11a The stress distribution under the static pressure load of 300MPa shows that it can also reduce the top angle stress to 54.0MPa, <55MPa, and can also effectively avoid the damage of the aluminum-plastic film; at this time, the overall deformation of the battery cell is as follows Figure 11b and Figure 11c As shown: length direction -8.84mm, width direction -3.60mm, area shrinkage rate 5.04%, 1.23% lower than the original. When wood is added as a buffer material, Figure 12 Due to the stress distribution under a load of 300MPa, the overall stress of the battery cell is greatly increased, with the highest point at the top corner reaching 780MPa.

[0150] Therefore, in order to effectively alleviate the problem of aluminum-plastic film breakage at the top corners of the battery cell under 300MPa isostatic pressure, nylon or acrylic can be used as a buffer material, and shape-fitting buffers can be filled around the battery cell to reduce the overall stress and control the maximum value within the tensile strength of the aluminum-plastic film. It has been verified in this solution that the battery cell shrinkage rate is the smallest when acrylic is used.

[0151] Example 2

[0152] Reference Figure 13 As shown, Figure 13: This is a structural schematic diagram of a solid-state battery isostatic pressing process optimization system based on finite element simulation provided by the present invention. This embodiment provides a solid-state battery isostatic pressing process optimization system based on finite element simulation, including: a partitioning module 200, used to construct a geometric model of the solid-state battery, and use finite element analysis software to mesh the geometric model of the solid-state battery to obtain a discretized model; a material property determination module 201, coupled to the partitioning module 200, used to receive the discretization module, determine the material properties of each component in the solid-state battery, and set a physical field in the finite element analysis software according to the material properties; a simulation operation module 202, coupled to the material property determination module 201, used to receive the physical field, apply boundary conditions and isostatic pressure loads to the discretized model according to the physical field, and perform simulation operation on the discretized model to obtain the stress and strain distribution of the solid-state battery during the isostatic pressing process; an isostatic pressing process optimization module 203, used to receive the stress and strain distribution of the solid-state battery during the isostatic pressing process, and optimize the isostatic pressing process of the solid-state battery according to the stress and strain distribution of the solid-state battery during the isostatic pressing process.

[0153] The specific details of the solid-state battery isostatic pressing process optimization system based on finite element simulation in Example 2 can be referred to Example 1 and will not be repeated here.

[0154] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A solid-state battery isostatic pressing process optimization method based on finite element simulation, characterized in that: The following steps are involved: Constructing a geometric model of a solid-state battery, and meshing the geometric model of the solid-state battery using finite element analysis software to obtain a discretized model; Determining the material properties of each component in the solid-state battery, and setting the physical field in the finite element analysis software according to the material properties; Applying boundary conditions and isostatic pressure loads to the discretized model according to the physical field, and running a simulation on the discretized model to obtain stress and strain distribution of the solid-state battery during the isostatic pressing process; Based on the stress and strain distribution, the isostatic pressing process of the solid-state battery is optimized.

2. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 1, characterized in that: The material properties of the components of the solid-state battery include the physical parameters of the core stack and the aluminum-plastic film, and the physical parameters of the core stack and the aluminum-plastic film include density, elastic modulus, Poisson's ratio, initial porosity, reference stress and reference strain, and initial yield stress.

3. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 2, characterized in that: Determining the material properties of each component in the solid-state battery and setting the physical field in the finite element analysis software according to the material properties includes: A solid mechanics interface is selected in the physical field. The aluminum-plastic film is an isotropic elastic-plastic material. The stress-strain of the elastic-plastic material in the elastic process satisfies the following relationship: Wherein, E is the elastic modulus, v is the Poisson's ratio, G is the shear modulus, ε11, ε22, and ε33 are the normal strains along the three coordinate axes, γ12, γ13, and γ23 are the shear strains in the xy plane, xz plane, and yz plane, respectively, σ11, σ22, and σ33 represent the normal stresses in the directions of the three coordinate axes, respectively, and σ12, σ13, and σ23 represent the shear stresses in different main directions of the three coordinate axes, respectively.

4. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 3, characterized in that: The linear elastic properties are determined according to the elastic modulus and the Poisson's ratio, and the constitutive matrix of the material is filled with the isotropic linear elastic properties. The constitutive matrix of the material is expressed as: The calculation formulas for C11, C12, and C44 are as follows: C 44 =G, Where C is a function of material properties, C11 and C12 are stiffness matrix elements, and C44 is an element in the stiffness matrix related to shear stress and shear strain.

5. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 4, characterized in that: The shear modulus is expressed as: G=E / [2(1+v)].

6. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 4, characterized in that: According to the physical field, boundary conditions and isostatic pressure loads are applied to the discretized model, and simulation is performed on the discretized model to obtain the stress and strain distribution of the solid-state battery during the isostatic pressing process, including: Applying boundary conditions and isostatic loads on specific nodes or surfaces of the discretized model; Obtaining a deformation gradient of each unit in the discretized model according to the applied boundary conditions and the isostatic load, decomposing the deformation gradient of each unit in the discretized model into an elastic part and an elastic-plastic part, and obtaining an elastic strain according to the elastic part; According to the constitutive relation of the material and the elastic strain, the elastic stress is obtained; An equilibrium equation is obtained based on the applied boundary conditions, the isostatic load, the elastic stress, and the elastic strain.

7. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 6, characterized in that: The deformation gradient is expressed as: Where F is the deformation gradient tensor, I is the unit tensor, and ▽u is the displacement gradient tensor; The deformation gradient of each element in the discretized model is decomposed into the elastic part and the elastic-plastic part and expressed as: S=S inel +S el , Where S is the total stress, S inel is the elastic stress, S el is the second Piola-Kirchhoff stress tensor; The elastic strain is expressed as: Where,∈ el is the elastic strain energy density, F el is the elastic deformation gradient, I is the trace of the unit tensor, and T represents the transpose of the matrix; The elastic stress is expressed as: S inel =S o +S ext +S q , where S o is the initial stress, S ext is the external stress, S q is the internal stress; Where, J i is the volume ratio, ":" represents the double dot product; The equilibrium equation is expressed as: Where, Represents the divergence of stress, F V Represents body force.

8. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 7, characterized in that: The elastic deformation gradient is expressed as: Where F is the total deformation gradient, F inel is the plastic deformation gradient.

9. The solid-state battery isostatic pressing process optimization method based on finite element simulation according to claim 1, characterized in that: Construct a geometric model of a solid-state battery, and use finite element analysis software to mesh the geometric model of the solid-state battery to obtain a discretized model including: A solid-state battery consisting of a stacked core sealed in an aluminum-plastic film is modeled according to a symmetry principle to obtain a geometric model of the solid-state battery; Dividing the geometric model of the solid-state battery using a free tetrahedral mesh; Automatically adjust the density and distribution of the grid according to the characteristics of the physical field; The mesh size is predefined to be refined and the mesh is automatically generated using the physical model.

10. A solid-state battery isostatic pressing process optimization system based on finite element simulation, characterized in that: include: A partitioning module is used to construct a geometric model of the solid-state battery and perform mesh partitioning on the geometric model of the solid-state battery using finite element analysis software to obtain a discretized model; a material property determination module, coupled to the partitioning module, configured to receive the discretization module, determine the material properties of each component in the solid-state battery, and set a physical field in the finite element analysis software according to the material properties; a simulation running module, coupled to the material property determination module, configured to receive a physical field, apply boundary conditions and an isostatic pressure load to the discretized model according to the physical field, and perform a simulation run on the discretized model to obtain stress and strain distribution of the solid-state battery during the isostatic pressing process; The isostatic pressing process optimization module is used to receive the stress and strain distribution of the solid-state battery during the isostatic pressing process, and optimize the isostatic pressing process of the solid-state battery according to the stress and strain distribution of the solid-state battery during the isostatic pressing process.

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