Battery module cushion material selection method, compression amount determination method, and application

Abstract

This disclosure belongs to the field of battery technology and discloses a method for selecting buffer materials for battery modules, a method for determining compression amount, and their application. The selection method includes: constructing a battery module expansion force simulation model; constructing the battery cells in the battery module using solid cell unit meshes; constructing the insulating film covering the surface of the battery cells using insulating film shell unit meshes; and constructing the buffer material using one-dimensional elastic elements; determining the battery module stress corresponding to various types of buffer materials based on the compression parameters of different types of buffer materials and the battery module expansion force simulation model; assigning a thermal expansion coefficient β to the solid cell unit meshes, allowing the battery module expansion force simulation model to transmit force between the solid cell unit meshes and the insulating film shell unit meshes through contact; and finally determining the target type of buffer material. The target type of buffer material selected by this method can provide sufficient expansion space for the battery cells and provide sufficient preload to suppress cell expansion.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a method for selecting buffer materials for battery modules, a method for determining compression amount, and their application. Background Technology

[0002] During the charge and discharge cycle, lithium-ion batteries will undergo a certain degree of expansion and deformation. This expansion and deformation is mainly the result of the combined effect of lithium insertion and extraction phase transitions in the positive and negative electrode materials. At the end of the battery's life, excessive expansion and deformation may cause problems such as cracking of the battery module end plate and out-of-tolerance module dimensions.

[0003] Battery modules often use buffer materials between the cells. These materials serve two purposes: first, to provide a buffer space for cell expansion; and second, to provide a pre-tightening force through the initial compression of the buffer material to suppress cell expansion. Currently, most methods rely on human experience to select the appropriate type of buffer material for battery module manufacturing. This selection method may not yield suitable buffer materials, potentially leading to problems such as cracking of the battery module endplate due to excessive cell expansion force, thus affecting the battery module's performance. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a method for selecting buffer materials for battery modules, a method for determining compression amount, and its application.

[0005] A first aspect of the present invention provides a method for selecting a buffer material for a battery module, comprising:

[0006] A simulation model of the expansion force of a battery module is constructed. The battery cells in the battery module are constructed using solid cell unit meshes, the insulating film covering the surface of the battery cells is constructed using insulating film shell unit meshes, and the buffer material set outside the insulating film is constructed using one-dimensional elastic elements.

[0007] Based on the compression parameters of various types of buffer materials and the battery module expansion force simulation model, the battery module stress corresponding to various types of buffer materials is determined; wherein, the compression parameters include the initial compression amount and the stress-strain curve; by assigning the cell solid unit mesh a thermal expansion coefficient β, the battery module expansion force simulation model enables the cell solid unit mesh and the insulating film shell unit mesh to transfer force through contact relationship;

[0008] Based on the battery module stress corresponding to the various types of buffer materials, the target type of buffer material is determined.

[0009] Preferably, the expansion force simulation model of the battery module is constructed using the finite element method; wherein, the battery module includes a battery, a buffer material and end plates, the battery includes at least one cell, the surface of the cell is covered with an insulating film, and the end plates are disposed on both sides of the battery away from the buffer material.

[0010] Preferably, the stress-strain curve of the buffer material is converted into the variable stiffness curve of the one-dimensional elastic element.

[0011] Preferably, the one-dimensional elastic unit is a spring unit.

[0012] Preferably, the insulating film adopts an insulating film shell unit grid, and the one-dimensional elastic unit is arranged between adjacent insulating film shell unit grids;

[0013] The area of ​​the side of the insulating film shell unit grid facing the one-dimensional elastic unit is S, and the number of nodes is N1; the number of one-dimensional elastic units is N2, and N2 = N1.

[0014] Preferably, the variable stiffness curve of the one-dimensional elastic element is:

[0015] F=-σ×S÷N2

[0016] x=-1×T×ε

[0017] Where F is the elastic force of the one-dimensional elastic element, x is the compression of the one-dimensional elastic element; σ is the compressive stress of the buffer material, ε is the strain of the buffer material, and T is the free state thickness of the buffer material.

[0018] Preferably, the actual thickness t of the insulating film is used as the thickness of the insulating film shell unit grid.

[0019] Preferably, the distance between the insulating film shell unit grid and the buffer material is half the actual thickness t of the insulating film, and the distance between the insulating film shell unit grid and the battery cell is half the actual thickness t of the insulating film.

[0020] Preferably, the battery cell adopts a battery cell solid unit grid, and the battery cell solid unit grid and the insulating film shell unit grid are connected by frictional contact, so that the battery module expansion force simulation model presents the real battery cell expansion effect of large deformation in the middle of the large surface of the battery cell and small deformation around the perimeter.

[0021] Preferably, the modeling parameters of the battery cell solid unit mesh are obtained, including density ρ, elastic modulus E, Poisson's ratio υ, and coefficient of thermal expansion β; wherein, the Poisson's ratio is a preset Poisson's ratio; and the density ρ = m / v is determined based on the actual volume v and actual mass m of the battery cell.

[0022] Preferably, the elastic modulus E is obtained by means of simulation and experimental benchmarking, including:

[0023] A charge-discharge test is performed on a battery cell in a clamped state to obtain the expansion force at the end of the battery cell's lifespan; wherein, the end of the battery cell's lifespan is defined as the number of charge-discharge tests performed on the battery cell.

[0024] By inputting different elastic moduli into the battery module expansion force simulation model, the end plate support reaction force corresponding to different elastic moduli is obtained. The elastic moduli corresponding to the difference between the end plate support reaction force and the expansion force at the end of the battery cell charging period within a preset threshold is taken as the optimal elastic moduli E of the battery cell solid unit mesh.

[0025] Preferably, the method for obtaining the coefficient of thermal expansion β includes:

[0026] Charge and discharge tests are performed on the battery cell in a free state to obtain the expansion amount δ at the end of the battery cell's life.

[0027] Based on the expansion amount δ at the end of the cell's lifespan, the coefficient of thermal expansion β is determined as follows:

[0028] β=δ÷(ΔT×μ)

[0029] Where ΔT is the preset temperature rise and μ is the original thickness of the battery cell.

[0030] Preferably, the end plate adopts an end plate shell unit grid, and the distance between the side of the end plate shell unit grid facing the cell and the adjacent insulating film is equal to half of the sum of the actual thickness of the end plate and the actual thickness of the insulating film;

[0031] Alternatively, the end plate may be a solid end plate unit, wherein the distance between the side of the solid end plate unit facing the cell and the adjacent insulating film is equal to half the actual thickness of the insulating film.

[0032] Preferably, determining the target type of buffer material based on the battery module stress corresponding to the various types of buffer materials includes:

[0033] Select the type of buffer material with the lowest stress, or stress less than a preset stress threshold, or stress within the stress threshold range from the various types of buffer materials corresponding to the battery module stress, and use it as the target type of buffer material.

[0034] In a second aspect, the present invention provides a battery module comprising a target type buffer material determined by the selection method for battery module buffer materials described in any embodiment of the present application.

[0035] A third aspect of the present invention provides a method for determining the initial compression amount of a one-dimensional elastic element in a battery module expansion force simulation model, wherein the battery module expansion force simulation model is constructed based on the battery module buffer material selection method described in any embodiment of the present application; the method for determining the initial compression amount of the one-dimensional elastic element includes:

[0036] Different preset reference original lengths L are set for the one-dimensional elastic elements corresponding to known types of cushioning materials. Based on the different preset reference original lengths L of the one-dimensional elastic elements and the initial actual length L' in the mesh model of the one-dimensional elastic elements, the initial compression amount a of the known type of cushioning material under different preset reference original lengths L is determined, as follows:

[0037] L = T + t

[0038] L'=T'+t

[0039] a = T - T' = L - L'

[0040] Where L is the preset reference original length of the one-dimensional elastic element; T is the free state thickness of the buffer material; L' is the initial actual length in the mesh model of the one-dimensional elastic element; T' is the initial compressed state thickness of the buffer material; t is the actual thickness of the insulating film; and a is the initial compression amount of the buffer material.

[0041] Based on the initial compression amount a of the known type of buffer material under different preset reference original lengths L and the battery module expansion force simulation model, the battery module stress corresponding to different initial compression amounts is obtained.

[0042] Based on the battery module stress corresponding to the different initial compression amounts, the initial compression amount of the one-dimensional elastic unit corresponding to the known type of buffer material is determined.

[0043] Preferably, determining the initial compression of the one-dimensional elastic unit corresponding to the known type of buffer material based on the battery module stress corresponding to the different initial compression amounts includes:

[0044] The initial compression amount corresponding to the minimum stress, the stress less than the preset stress threshold, or the stress within the stress threshold range corresponding to the different initial compression amounts of the battery module is selected as the initial compression amount of the one-dimensional elastic unit corresponding to the known type of buffer material.

[0045] In a fourth aspect, the present invention provides a battery module expansion force simulation model, the battery module expansion force simulation model including a one-dimensional elastic element, the initial compression amount of the one-dimensional elastic element being obtained by the method for determining the initial compression amount of the one-dimensional elastic element of the battery module expansion force simulation model described in any embodiment of the present application.

[0046] According to the battery module buffer material selection method, compression determination method, and application provided by the present invention, in constructing a battery module expansion force simulation model, the battery cell and insulating film are modeled separately and the two are connected in contact to transmit force. A one-dimensional elastic element is used to construct the buffer material. The constructed battery module expansion force simulation model can realistically simulate the battery cell expansion process, preventing simulation distortion of expansion and compression transmission. The model has high accuracy. The target type of buffer material determined using this battery module expansion force simulation model can provide sufficient expansion space for the battery cell and provide sufficient preload to suppress the expansion of the battery cell. Battery modules made with this target type of buffer material will not experience problems such as cracking of the battery module end plate due to excessive battery cell expansion force, thus ensuring the performance and service life of the battery module. Attached Figure Description

[0047] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0048] Figure 1 An exemplary flowchart of a method for selecting battery module buffer materials provided in this application embodiment;

[0049] Figure 2 An exemplary structural diagram of the battery module expansion force simulation model provided in the embodiments of this application;

[0050] Figure 3 A partial enlarged view of the battery module expansion force simulation model provided in the embodiments of this application;

[0051] Figure 4 A partial enlarged view of the battery module expansion force simulation model provided in the embodiments of this application;

[0052] Figure 5 This is a partial structural diagram of the insulating film shell unit grid provided in an embodiment of this application;

[0053] Figure 6 A location diagram of the insulating film shell unit grid provided in the embodiments of this application;

[0054] Figure 7 Stress-strain curves of buffer materials A and B provided in the embodiments of this application;

[0055] Figure 8 The simulation stress result diagram of the buffer material A provided in the embodiments of this application;

[0056] Figure 9 The simulation stress result diagram of the buffer material B provided in the embodiments of this application;

[0057] Figure 10 A flowchart illustrating the method for determining the initial compression of a one-dimensional elastic element in a battery module expansion force simulation model provided in this application embodiment.

[0058] above Figure 3 In the middle: 300 Battery module expansion force simulation model; 310 Cell solid element mesh; 320 Insulating film shell element mesh; 330 One-dimensional elastic element; 340 End plate solid element. Detailed Implementation

[0059] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0060] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0061] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” as used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0062] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open and encompassing, that is, "including, but not limited to".

[0063] In the description of this specification, the terms "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0064] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0065] Currently, most methods rely on human experience to select the appropriate type of buffer material for battery module manufacturing. However, the buffer material obtained by this selection method may not be suitable, which may lead to problems such as cracking of the battery module end plate due to excessive cell expansion force, thus affecting the performance of the battery module.

[0066] Existing methods also employ the construction of battery module expansion force simulation models to predict the stress on different types of buffer materials. However, in existing methods for constructing battery module expansion force simulation models, the battery cell is often replaced by an equivalent solid, i.e., the battery cell and the aluminum-plastic film are modeled as a whole, and the expansion of the battery cell is simulated using the coefficient of thermal expansion and temperature difference. However, this battery cell equivalence method causes the large surface area of ​​the battery cell to expand outward as a whole, rather than presenting the bulging effect of a real battery cell, where the deformation is large in the middle and small around the edges, resulting in a certain deviation from reality.

[0067] Existing simulation techniques often neglect buffer materials or use isotropic homogeneous materials to construct the battery module expansion force simulation model. This conventional modeling method has certain drawbacks. First, it is impossible to specify the pre-compression amount of the buffer material. Second, because the buffer material is generally very thin, the mesh becomes flat. When using a conventional elastoplastic model to simulate the nonlinear compressive deformation mechanical behavior of the buffer material, sometimes the mesh collapses and the deformation is too large, leading to difficulty in convergence and causing the calculation to stop. Therefore, it lacks universality.

[0068] To solve at least some of the above technical problems, refer to Figure 1 In a first aspect, this application provides a method S100 for selecting a battery module buffer material, comprising:

[0069] S110: Construct a simulation model of the expansion force of a battery module; wherein, the battery cells in the battery module are constructed using a solid cell unit mesh, the insulating film covering the surface of the battery cells is constructed using an insulating film shell unit mesh, and the buffer material set outside the insulating film is constructed using one-dimensional elastic elements;

[0070] S120: Based on the compression parameters of various types of buffer materials and the battery module expansion force simulation model 300, determine the battery module stress corresponding to various types of buffer materials; wherein, the compression parameters include the initial compression amount and the stress-strain curve; by assigning the cell solid unit mesh a thermal expansion coefficient β, the battery module expansion force simulation model enables the cell solid unit mesh and the insulating film shell unit mesh to transmit force through contact relationship;

[0071] S130: Determine the target type of buffer material based on the battery module stress corresponding to the various types of buffer materials.

[0072] In this embodiment, the battery cell and the aluminum-plastic film are modeled separately. The battery cell adopts a hexahedral-shaped battery cell solid unit mesh 310, and the aluminum-plastic film adopts an insulating film shell unit mesh 320. The battery cell solid unit mesh 310 and the insulating film shell unit mesh 320 transmit force through contact. By only assigning the battery cell thermal expansion coefficient β and the force transmission, the battery cell expansion effect close to the actual situation can be achieved. The constructed battery module expansion force simulation model 300 is closer to the actual effect and has a better simulation effect.

[0073] The buffer material in the battery module expansion force simulation model 300 is constructed using a one-dimensional elastic element 330. This method can consider both the pre-compression effect of the buffer material and simulate the nonlinear compressive deformation mechanical behavior of the buffer material during the cell expansion process. There is no problem with computational convergence, making it universally applicable.

[0074] By inputting the initial compression and stress-strain curves corresponding to various types of buffer materials into the battery module expansion force simulation model 300, the stress conditions of each component of the battery module can be simulated. By analyzing the stress conditions of each component of the battery module (such as cells, end plates, etc.), it is beneficial to select a suitable type of buffer material as the target type of buffer material from various types of buffer materials.

[0075] By constructing a battery module expansion force simulation model 300, the stress and strain of battery modules containing different types of buffer materials can be simulated. This allows for the prediction of whether the selected type of buffer material is suitable, ensuring the product yield of the battery module. Furthermore, based on the battery module stress corresponding to various types of buffer materials predicted by the battery module expansion force simulation model 300, a suitable buffer material can be selected as the target type buffer material. This target type buffer material can provide sufficient expansion space for the battery cell and provide sufficient pre-tightening force to suppress the expansion of the battery cell. Battery modules made with this target type buffer material will not experience problems such as cracking of the battery module end plate due to excessive battery cell expansion force, thus ensuring the performance and service life of the battery module.

[0076] In some embodiments, in S110, a simulation model 300 of the battery module expansion force is constructed using the finite element method; wherein, the battery module includes a battery, a buffer material and end plates, the battery includes at least one cell, the surface of the cell is covered with an insulating film, and the end plates are disposed on both sides of the battery away from the buffer material.

[0077] Specifically, the battery module includes a battery, cushioning material, and end plates. The battery includes multiple cells arranged in an array, each cell's surface is covered with an insulating film, which is an aluminum-plastic film. Cushioning material is placed between any two adjacent insulating films, and end plates are placed on the sides of the battery away from the cushioning material. The cushioning material can be various types of foam material.

[0078] The fundamental principle of the finite element method is to discretize the continuous solution domain into a set of elements, and use an approximation function assumed within each element to represent the unknown field function to be solved on the solution domain piecewise. The approximation function is typically represented by numerical interpolation functions of the unknown field function and its derivatives at each node of the element. This transforms a continuous problem with infinite degrees of freedom into a discrete problem with finite degrees of freedom.

[0079] In this embodiment, the finite element method is used to establish a mesh simulation model of the battery module assembly, namely the battery module expansion force simulation model 300, which can realistically simulate the deformation of the battery module caused by cell expansion and the strength of the battery module end plate after being subjected to extrusion force, and the model simulation accuracy is high.

[0080] In some implementations, such as Figures 2 to 4 As shown, in S110, the stress-strain curve of the buffer material is converted into the variable stiffness curve of the one-dimensional elastic element 330.

[0081] In this embodiment, during the construction of the battery module expansion force simulation model 300, the buffer material is simulated using a one-dimensional elastic element 330, preferably a spring element. The variable stiffness curve of the one-dimensional elastic element 330 is derived from the compressive stress-strain curve of the buffer material. The one-dimensional elastic element 330 can be preset with a variable stiffness curve and a preset reference original length L. The difference between the preset reference original length L and the initial actual length L' in the mesh model yields the initial compression amount a of the buffer material.

[0082] In this example, a one-dimensional elastic element 330 is used instead of the buffer material. This can take into account the pre-compression effect of the buffer material and simulate the nonlinear compressive deformation mechanical behavior of the buffer material during the cell expansion process. It can avoid the problem of computational convergence and make it universal.

[0083] In some implementations, in S110, such as Figures 2 to 5 As shown, the insulating film adopts an insulating film shell unit grid 320, and the one-dimensional elastic unit 330 is arranged between adjacent insulating film shell unit grids 320;

[0084] The area of ​​the insulating film shell unit grid 320 facing the one-dimensional elastic unit 330 is S, and the number of nodes is N1; the number of one-dimensional elastic units 330 is N2, and N2 = N1.

[0085] Specifically, in the construction of the battery module expansion force simulation model 300, the insulating film adopts an insulating film shell unit mesh 320, each of which is a quadrilateral, such as a square. Multiple one-dimensional elastic elements 330 are set between any two adjacent insulating film shell unit meshes 320, that is, one-dimensional elastic elements 330 are established on the nodes corresponding to two adjacent insulating film shell unit meshes 320; wherein, the number of nodes N1 on the side of the insulating film shell unit mesh 320 facing the one-dimensional elastic element 330 (this side can be the large surface of the insulating film shell unit 320) is equal to the number of one-dimensional elastic elements 330 on the corresponding side N2, and the area of ​​the large surface of the insulating film shell unit 320 is S.

[0086] In some embodiments, in S110, the variable stiffness curve of the one-dimensional elastic element 330 is:

[0087] F=-σ×S÷N2

[0088] x=-1×T×ε

[0089] Where F is the elastic force of the one-dimensional elastic element 330, x is the compression of the one-dimensional elastic element 330; σ is the compressive stress of the buffer material, ε is the strain of the buffer material, and T is the free state thickness of the buffer material.

[0090] Specifically, the above formula can be used to convert the compressive stress σ-strain ε curve of the buffer material into the corresponding variable stiffness curve of the one-dimensional elastic element 330, i.e., the elastic force F-compression x curve, which facilitates the construction of the battery module expansion force simulation model 300. Since the variable stiffness curve of the one-dimensional elastic element 330 is a two-dimensional curve, the convergence problem of the battery module expansion force simulation model 300 can be avoided.

[0091] In some embodiments, in S110, the actual thickness t of the insulating film is used as the thickness of the insulating film shell unit grid 320.

[0092] Specifically, the actual thickness t is simulated by assigning a thickness value to the insulating film shell unit grid 320. For example, by measuring the actual thickness t of the insulating film and using the measured t as the thickness value of the insulating film shell unit grid 320, the battery module expansion force simulation model 300 can be constructed more realistically, thereby improving the accuracy of the battery module expansion force simulation model 300.

[0093] In some implementations, in S110, such as Figure 6 As shown, the distance between the insulating film shell unit grid 320 and the buffer material is half the actual thickness t of the insulating film, and the distance between the insulating film shell unit grid 320 and the battery cell is half the actual thickness t of the insulating film.

[0094] Specifically, the distances between the insulating film shell unit grid 320 and the buffer material (which is an actual material and is not simulated using a one-dimensional elastic unit 330) and the battery cell are both half the actual thickness t of the insulating film. The sum of these two distances is exactly the thickness of the insulating film shell unit grid 320.

[0095] In some implementations, in S110, such as Figures 2 to 3 As shown, the battery cell adopts a battery cell solid unit grid 310, and the battery cell solid unit grid 310 and the insulating film shell unit grid 320 are connected by frictional contact, so that the battery module expansion force simulation model presents the real battery cell expansion effect of large deformation in the middle of the large surface of the battery cell and small deformation around the perimeter.

[0096] In this embodiment, the battery cell adopts a solid cell unit mesh 310 with a hexahedral shape. The solid cell unit mesh 310 and the insulating film shell unit mesh 320 transmit force through frictional contact. That is, the battery cell and the insulating film are modeled separately, and the two transmit force through contact. By only assigning the thermal expansion coefficient to the battery cell, the battery module expansion force simulation model presents the real battery cell expansion effect of large deformation in the middle of the large surface of the battery cell and small deformation around the perimeter. It can achieve a battery cell expansion effect close to the actual situation. The constructed battery module expansion force simulation model 300 is closer to the actual effect and has a better simulation effect.

[0097] In some embodiments, in S110, the modeling parameters of the cell solid unit mesh 310 are obtained, including density ρ, elastic modulus E, Poisson's ratio υ, and coefficient of thermal expansion β; wherein, the Poisson's ratio is a preset Poisson's ratio; and the density ρ = m / v is determined according to the actual volume v and actual mass m of the cell.

[0098] Specifically, the modeling parameters of the cell solid unit mesh 310 are obtained for the construction of the battery module expansion force simulation model 300. The density of the cell solid unit mesh 310 is derived from the actual volume v and actual mass m of the cell. The Poisson's ratio υ is preset empirically, such as υ = 0.3, 0.4, 0.5, 0.6, etc. The elastic modulus E is determined by comparing simulation with experiments, and the coefficient of thermal expansion β is determined experimentally.

[0099] In some implementations, in S110, the elastic modulus E is obtained by comparing simulation with experimental methods, including:

[0100] A charge-discharge test is performed on a battery cell in a clamped state to obtain the expansion force at the end of the battery cell's lifespan; wherein, the end of the battery cell's lifespan is defined as the number of charge-discharge tests performed on the battery cell.

[0101] By inputting different elastic moduli into the battery module expansion force simulation model 300 through simulation, the end plate support reaction force corresponding to different elastic moduli is obtained. The elastic moduli corresponding to the difference between the end plate support reaction force and the expansion force at the end of the battery cell charging period within a preset threshold is taken as the optimal elastic moduli E of the battery cell solid unit mesh 310.

[0102] Specifically, the elastic modulus E of the cell solid unit grid 310 is obtained by simulation and experimental benchmarking. During the test, a single cell is tested by a fixed plate expansion force tester to measure the expansion force of the cell at the end of its life under the fixed clamping of the fixed plate. The expansion force at the end of the cell's life refers to the expansion force value measured after the cell has been charged and discharged 800 to 1500 times, such as 1000 or 1200 times.

[0103] Then, through simulation, different elastic moduli E are input into the battery module expansion force simulation model 300 to obtain different end plate support reactions of the battery module. Based on the measured expansion force at the end of the cell's lifespan and the different end plate support reactions, the optimal elastic modulus E of the cell solid unit mesh 310 is determined. That is, the different end plate support reactions are subtracted from the measured expansion force at the end of the cell's lifespan, and the elastic modulus corresponding to the difference not exceeding a preset threshold is selected as the optimal elastic modulus E of the cell solid unit mesh 310.

[0104] In this process, the difference between different endplate support reactions and the measured expansion force at the end of the cell's lifespan is calculated. If all the differences are greater than a preset threshold, the elastic modulus E value input to the model is readjusted, and the endplate support reaction is predicted again using the battery module expansion force simulation model 300 until the obtained endplate support reaction is not greater than the preset threshold. The elastic modulus corresponding to the endplate support reaction not being greater than the preset threshold is then selected as the optimal elastic modulus E for the cell solid unit mesh 310. If at least two of the obtained differences are less than the preset threshold, the elastic modulus corresponding to the smallest difference is selected as the optimal elastic modulus E for the cell solid unit mesh 310.

[0105] It should be noted that those skilled in the art can set preset thresholds according to actual needs, with preset thresholds ≥ 0, such as preset thresholds of 0, 0.1, 0.2, 0.3, etc.

[0106] For example, when the preset threshold is 0, that is, when the simulated end plate support reaction force is equal to the tested expansion force, the input elastic modulus E is the optimal value of the elastic modulus E obtained by benchmarking.

[0107] In some embodiments, in S110, the method for obtaining the coefficient of thermal expansion β includes:

[0108] Charge and discharge tests are performed on the battery cell in a free state to obtain the expansion amount δ at the end of the battery cell's life.

[0109] Based on the expansion amount δ at the end of the cell's lifespan, the coefficient of thermal expansion β is determined as follows:

[0110] β=δ÷(ΔT×μ)

[0111] Where ΔT is the preset temperature rise and μ is the original thickness of the battery cell.

[0112] Specifically, by conducting charge-discharge cycle tests on a single battery cell in a free state (i.e., without a fixed plate clamping), the expansion amount δ at the end of the cell's lifespan is measured. Then, based on the original thickness μ of the battery cell and a preset temperature rise ΔT, the thermal expansion coefficient β of the battery cell solid unit grid 310 can be obtained. It should be noted that the thermal expansion coefficient β is set to the calculated value in the cell thickness direction, and set to 0 in the direction of cell length and width.

[0113] In some implementations, in S110, such as Figure 2 and Figure 3 As shown, the end plate adopts an end plate shell unit grid, and the distance between the side of the end plate shell unit grid facing the cell and the adjacent insulating film is equal to half of the sum of the actual thickness of the end plate and the actual thickness of the insulating film;

[0114] Alternatively, the end plate may be an end plate solid unit 340, wherein the distance between the side of the end plate solid unit 340 facing the cell and the adjacent insulating film is equal to half the actual thickness of the insulating film.

[0115] Specifically, the end plate can adopt an end plate shell unit grid or an end plate solid unit 340. When the end plate adopts an end plate shell unit grid, the distance between the side of the end plate shell unit grid facing the cell (i.e., the large surface of the end plate) and the adjacent insulating film is equal to half of the sum of the actual thickness of the end plate and the actual thickness of the insulating film. When the end plate adopts an end plate solid unit 340, the distance between the large surface of the end plate and the adjacent insulating film is equal to half of the actual thickness of the insulating film.

[0116] In this embodiment, finite element simulation is used to simulate the battery (including the cell and aluminum-plastic film), buffer material, and end plate within the battery module, thus constructing a battery module expansion force simulation model 300. By modeling the cell and aluminum-plastic film separately, the expansion of the cell can be simulated more realistically. Furthermore, a one-dimensional elastic element 330 is used to simulate the buffer material, which can consider both the initial compression amount and the nonlinear compression deformation characteristics of the buffer material, and can also preset the initial compression amount of the buffer material, thus possessing universality. The constructed battery module expansion force simulation model 300 has high simulation accuracy and strong applicability.

[0117] In some embodiments, in S120, determining the target type of buffer material based on the battery module stress corresponding to the various types of buffer materials includes:

[0118] Select the type of buffer material with the lowest stress, or stress less than a preset stress threshold, or stress within the stress threshold range from the various types of buffer materials corresponding to the battery module stress, and use it as the target type of buffer material.

[0119] Specifically, the battery module stress corresponding to various types of buffer materials is predicted by the battery module expansion force simulation model 300. Based on the predicted battery module stress corresponding to various types of buffer materials, those skilled in the art can determine the required target type of buffer material according to actual needs.

[0120] For example, one could select the buffer material with the lowest stress from among various types of buffer materials corresponding to the battery module stress as the target type of buffer material.

[0121] For example, from various types of buffer materials corresponding to battery module stresses, a buffer material with stresses below a preset stress threshold can be selected as the target type buffer material. In the simulation model, stresses below the preset stress threshold can be characterized by no out-of-range areas, meaning there are no black areas on the endplate corresponding to the battery module. If black areas appear on the endplate corresponding to the battery module, it indicates an out-of-range stress. If there are multiple buffer materials with stresses below the preset stress threshold, those skilled in the art can select a specific buffer material as the target type buffer material, taking into account factors such as cost.

[0122] For example, from the various types of buffer materials corresponding to the battery module stress, the stress within the stress threshold range [F] can be selected. min ,F max The corresponding type of buffer material is used as the target type buffer material.

[0123] It should be noted that the embodiments of this application do not impose any particular restrictions on the specific type of battery cell. Those skilled in the art can make the settings according to actual needs, such as using a lithium-ion battery cell.

[0124] For example, the following specific example illustrates the method for selecting battery module buffer materials provided in this application embodiment:

[0125] Example 1

[0126] S110: A simulation model of battery module expansion force was constructed using the finite element method.

[0127] The battery comprises a cell and an aluminum-plastic film covering the cell surface. The cell uses a hexahedral cell solid unit grid 310, while the aluminum-plastic film uses a quadrilateral insulating film shell unit grid 320. The insulating film shell unit grid 320 covers the surface of the cell solid unit grid 310, and their relationship is simulated through frictional contact. A thickness value t is assigned to the insulating film shell unit grid 320 to simulate the actual thickness of the aluminum-plastic film. The distance between the insulating film shell unit grid 320 and the buffer material and the cell is half the actual thickness of the aluminum-plastic film. The area of ​​the large surface of the insulating film shell unit grid 320 is S, and the number of nodes is N1.

[0128] The cushioning material uses one-dimensional elastic elements 330, that is, one-dimensional elastic elements 330 are set between two adjacent insulating shell unit grids 320. One-dimensional elastic elements 330 are established on the nodes on the large surface of the insulating shell unit grid 320. The number of one-dimensional elastic elements 330 N2 is equal to the number of nodes N1 on the side of the insulating shell unit grid 320 facing the one-dimensional elastic element 330, that is, N2 = N1.

[0129] When the end plate uses an end plate shell element mesh, the distance between the side of the end plate shell element mesh facing the cell (i.e., the large surface of the end plate) and the adjacent insulating film is equal to half the sum of the actual thickness of the end plate and the actual thickness of the insulating film; or the end plate uses an end plate solid element 340, and the distance between the large surface of the end plate and the adjacent insulating film is equal to half the actual thickness of the insulating film. The end plate and the insulating film shell element mesh 320 are simulated through frictional contact.

[0130] S111: Obtain the modeling parameters of the battery module expansion force simulation model 300.

[0131] 1) Obtain the modeling parameters of the cell solid element mesh 310, including density ρ, elastic modulus E, Poisson's ratio υ, and coefficient of thermal expansion β; where Poisson's ratio υ is 0.4; determine the density ρ = m / v based on the actual volume v and actual mass m of the cell.

[0132] The elastic modulus E was obtained by comparing simulation and experiment. During the experiment, the two ends of a single cell were clamped by a fixing plate, and the expansion force of the cell at the end of its life was measured under the clamping state. Different elastic moduli E were input into the constructed battery module expansion force simulation model 300 to obtain different end plate support reaction forces. When the simulation showed that the end plate support reaction force was equal to the measured expansion force at the end of the cell's life, the elastic modulus input into the battery module expansion force simulation model 300 at this time was the optimal elastic modulus of the cell solid unit mesh 310.

[0133] The coefficient of thermal expansion β is obtained by measuring the expansion amount δ at the end of the cell's lifespan through charge-discharge cycle tests on a single cell in a free state (i.e., without a fixed plate clamping). Based on the cell's original thickness μ and a preset temperature rise ΔT, the coefficient of thermal expansion β of the cell's solid unit grid 310 can be obtained.

[0134] β=δ÷(ΔT×μ)

[0135] The coefficient of thermal expansion β is set to the calculated value above in the direction of cell thickness, and set to 0 in the direction of cell length and width.

[0136] 2) Obtain the modeling parameters of the one-dimensional elastic element 330.

[0137] The modeling parameters of the one-dimensional elastic element 330 include the variable stiffness curve of the one-dimensional elastic element 330, namely the force F-compression curve.

[0138] The stress-strain curve of the buffer material is converted into the variable stiffness curve of a one-dimensional elastic element 330 as follows:

[0139] F=-σ×S÷N2

[0140] x=-1×T×ε

[0141] Where F is the elastic force of the one-dimensional elastic element, x is the compression of the one-dimensional elastic element; σ is the compressive stress of the buffer material, ε is the strain of the buffer material, and T is the free state thickness of the buffer material.

[0142] The initial compression amount 'a' of the buffer material is characterized by the difference between the preset reference original length L of the one-dimensional elastic element 330 and the initial actual length L' in the mesh model of the one-dimensional elastic element. Different initial compression amounts 'a' of the buffer material correspond to different preset reference original lengths L of the one-dimensional elastic element 330, as detailed below:

[0143] L = T + t

[0144] L'=T'+t

[0145] a = T - T' = L - L'

[0146] Where L is the preset reference original length of the one-dimensional elastic element; T is the free state thickness of the buffer material; L' is the initial actual length in the mesh model of the one-dimensional elastic element; T' is the initial compressed state thickness of the buffer material; t is the actual thickness of the insulating film; and a is the initial compression amount of the buffer material.

[0147] The modeling parameters obtained in step S111, such as elastic modulus E, coefficient of thermal expansion β, preset reference original length L of one-dimensional elastic element 330, and variable stiffness curve force F-compression curve, can be input into the battery module expansion force simulation model 300 constructed in step S110 to simulate the stress and strain of the battery module end plate.

[0148] S120: Selection of cushioning materials

[0149] For known types of cushioning materials A and B, the stress-strain curves of cushioning materials A and B can be obtained, such as... Figure 7 As shown, the initial compression of buffer material A is a1, and the initial compression of buffer material B is a2.

[0150] The stress-strain curve of buffer material A is converted into the variable stiffness curve of the corresponding one-dimensional elastic element 330A, and the initial compression of buffer material A, a1, is converted into the preset reference original length L1 of the one-dimensional elastic element 330A. The variable stiffness curve of the one-dimensional elastic element 330A and the preset reference original length L1 are then input into the constructed battery module expansion force simulation model 300 to obtain the stress and strain of the battery module end plate. Figure 8 As shown, the black area represents the area where the stress exceeds the standard, indicating that under the condition that the initial compression and stress-strain of the buffer material A are fixed, the end plate was damaged under the expansion of the battery cell, which poses a safety risk.

[0151] The stress-strain curve of the buffer material B is converted into the variable stiffness curve of the corresponding one-dimensional elastic element 330B, and the initial compression of the buffer material B, a2, is converted into the preset reference original length L2 of the one-dimensional elastic element 330B. The variable stiffness curve of the one-dimensional elastic element 330B and the preset reference original length L2 are then input into the constructed battery module expansion force simulation model 300 to obtain the stress and strain of the battery module end plate. Figure 9 As shown, under the conditions of fixed initial compression and stress-strain, the end plate of buffer material B has no stress exceeding the standard area, and the strength of the end plate under the action of cell expansion force meets the requirements, that is, buffer material B is suitable.

[0152] In a second aspect, the present invention provides a battery module comprising a target type buffer material determined by the selection method for battery module buffer materials described in any embodiment of the present application.

[0153] Specifically, the battery module includes a battery, a buffer material, and end plates. The battery includes at least one cell, and the surface of each cell is covered with an insulating film. A buffer material is disposed between two adjacent insulating films, and end plates are disposed on the sides of the battery away from the buffer material. The buffer material is a target type buffer material determined by the battery module buffer material selection method described in any embodiment of this application.

[0154] In this embodiment, the battery module includes a target type of buffer material. The target type of buffer material is appropriately selected, which can provide sufficient expansion space for the battery cell and provide sufficient preload to suppress the expansion of the battery cell. The resulting battery module will not have problems such as cracking of the battery module end plate due to excessive expansion force of the battery cell, thus ensuring the performance and service life of the battery module.

[0155] The third aspect of the invention, as Figure 10 As shown, a method 200 for determining the initial compression of a one-dimensional elastic element 330 in a battery module expansion force simulation model 300 is provided. The battery module expansion force simulation model 300 is constructed based on the battery module buffer material selection method described in any embodiment of this application. The method for determining the initial compression of the one-dimensional elastic element 330 includes:

[0156] S210: Set different preset reference original lengths for the one-dimensional elastic element 330 corresponding to the known type of buffer material. Different initial compression amounts of the buffer material correspond to different preset reference original lengths. The initial compression amount of the buffer material is characterized by the difference between the preset reference original length of the one-dimensional elastic element 330 and the initial actual length in the mesh model of the one-dimensional elastic element. The specific formula is as described above.

[0157] S220: Based on the different initial compression amounts and the battery module expansion force simulation model 300, the battery module stress corresponding to the different initial compression amounts is obtained;

[0158] S230: Determine the initial compression amount of the one-dimensional elastic unit 330 corresponding to the known type of buffer material based on the battery module stress corresponding to the different initial compression amounts.

[0159] Specifically, multiple different preset reference original lengths L are set for the one-dimensional elastic unit 330 to characterize different initial compression amounts a of the corresponding buffer material. The multiple different preset reference original lengths L of the one-dimensional elastic unit 330 are input into the pre-built battery module expansion force simulation model 300 to predict the battery module stress corresponding to different initial compression amounts. In this way, the influence of different initial compression amounts on cell expansion can be evaluated, and a suitable initial compression amount a can be selected as the final set initial compression amount of the one-dimensional elastic unit 330.

[0160] In this embodiment of the application, the battery module expansion force simulation model 300 can predict the battery module stress under different initial compression amounts of the one-dimensional elastic unit 330, which is beneficial to determine the optimal initial compression amount of the one-dimensional elastic unit 330, and thus beneficial to select a suitable buffer material with an appropriate initial compression amount when manufacturing the battery module.

[0161] In some embodiments, in S230, determining the initial compression of the one-dimensional elastic unit 330 corresponding to the known type of buffer material based on the battery module stress corresponding to the different initial compression amounts includes:

[0162] The initial compression amount corresponding to the minimum stress, the stress less than the preset stress threshold, or the stress within the stress threshold range corresponding to the different initial compression amounts of the battery module stress is selected as the initial compression amount of the one-dimensional elastic unit 330 corresponding to the known type of buffer material.

[0163] Specifically, the battery module stress corresponding to different initial compression amounts predicted by the battery module expansion force simulation model 300 can be used to determine the optimal initial compression amount of the one-dimensional elastic unit 330 based on the predicted battery module stress corresponding to different initial compression amounts.

[0164] For example, the initial compression amount with the lowest stress can be selected from the battery module stress corresponding to different initial compression amounts as the optimal initial compression amount for the one-dimensional elastic unit 330.

[0165] For example, from the battery module stress corresponding to different initial compression amounts, an initial compression amount less than a preset stress threshold can be selected as the optimal initial compression amount for the one-dimensional elastic unit 330. This compression amount less than the preset stress threshold can be characterized in the simulation model as the absence of any excessive areas, i.e., no black areas appearing on the endplate corresponding to the battery module. If a black area appears on the endplate corresponding to the battery module, it indicates that the stress exceeds the limit. If there are multiple initial compression amounts less than the preset stress threshold, those skilled in the art can select one as the optimal initial compression amount for the one-dimensional elastic unit 330, taking into account factors such as cost.

[0166] For example, from the battery module stress corresponding to different initial compression amounts, the stress is selected to be within the stress threshold range [F]. min ,F max The initial compression amount corresponding to the inner value is taken as the optimal initial compression amount for the one-dimensional elastic unit 330.

[0167] For example, the following specific example illustrates the method for determining the initial compression of the one-dimensional elastic element 330 of the battery module expansion force simulation model 300 provided in this application embodiment, as follows:

[0168] Example 2

[0169] In this embodiment, the finite element method is used to construct the battery module expansion force simulation model 300 and obtain the modeling parameters of the battery module expansion force simulation model 300, which are the same as in Embodiment 1, and will not be repeated here.

[0170] In the battery module expansion force simulation model 300 constructed by inputting the preset reference original length L1 of the one-dimensional elastic element 330 corresponding to the known type of buffer material A, the initial compression amount a1 of the buffer material is characterized by the difference between the preset reference original length of the one-dimensional elastic element 330 and the initial actual length in the mesh model of the one-dimensional elastic element. If there is no area where the stress of the battery module end plate exceeds the standard, then the preset initial compression amount a1 is the optimal initial compression amount of the one-dimensional elastic element 330 corresponding to the buffer material A; if there is an area exceeding the standard, i.e., a black area is displayed, then the preset initial compression amount value needs to be adjusted until there is no area where the stress of the battery module end plate exceeds the standard, and the final adjusted initial compression amount value is taken as the optimal initial compression amount of the one-dimensional elastic element 330 corresponding to the buffer material A.

[0171] The fourth aspect of the invention, as follows Figures 2 to 6 As shown, a battery module expansion force simulation model 300 is provided. The battery module expansion force simulation model 300 includes a one-dimensional elastic element 330. The initial compression amount of the one-dimensional elastic element 330 is obtained by the method for determining the initial compression amount of the one-dimensional elastic element 330 of the battery module expansion force simulation model 300 described in any embodiment of this application.

[0172] Specifically, the battery module expansion force simulation model 300 includes a cell solid unit grid 310, an insulating film shell unit grid 320, a one-dimensional elastic unit 330, and an end plate shell unit grid or an end plate solid unit 340. The initial compression amount of the one-dimensional elastic unit 330 is obtained by the method for determining the initial compression amount of the one-dimensional elastic unit 330 of the battery module expansion force simulation model 300 described in any embodiment of this application. The constructed battery module expansion force simulation model 300 has better stability and better simulation effect.

[0173] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for selecting a buffer material for a battery module, characterized in that, include: A simulation model of the expansion force of a battery module is constructed. The battery cells in the battery module are constructed using solid cell unit meshes, the insulating film covering the surface of the battery cells is constructed using insulating film shell unit meshes, and the buffer material set outside the insulating film is constructed using one-dimensional elastic elements. Based on the compression parameters of various types of buffer materials and the battery module expansion force simulation model, the battery module stress corresponding to various types of buffer materials is determined; wherein, the compression parameters include the initial compression amount and the stress-strain curve; by assigning the cell solid unit mesh a thermal expansion coefficient β, the battery module expansion force simulation model enables the cell solid unit mesh and the insulating film shell unit mesh to transfer force through contact relationship; Based on the battery module stress corresponding to the various types of buffer materials, the target type of buffer material is determined.

2. The method for selecting battery module buffer materials according to claim 1, characterized in that, A simulation model of the expansion force of the battery module is constructed using the finite element method; wherein, the battery module includes a battery, a buffer material and end plates, the battery includes at least one cell, the surface of the cell is covered with an insulating film, and the end plates are disposed on both sides of the battery away from the buffer material.

3. The method for selecting battery module buffer materials according to claim 2, characterized in that, The stress-strain curve of the buffer material is converted into the variable stiffness curve of the one-dimensional elastic element.

4. The method for selecting battery module buffer materials according to claim 3, characterized in that, The one-dimensional elastic unit is a spring unit.

5. The method for selecting battery module buffer materials according to claim 3, characterized in that, The area of ​​the side of the insulating film shell unit grid facing the one-dimensional elastic unit is S, and the number of nodes is N1; the number of one-dimensional elastic units is N2, and N2 = N1.

6. The method for selecting battery module buffer materials according to claim 5, characterized in that, The variable stiffness curve of the one-dimensional elastic element is as follows: F=-σ×S÷N2 x=-1×T×ε Where F is the elastic force of the one-dimensional elastic element, x is the compression of the one-dimensional elastic element; σ is the compressive stress of the buffer material, ε is the strain of the buffer material; and T is the free-state thickness of the buffer material.

7. The method for selecting battery module buffer materials according to claim 6, characterized in that, The actual thickness t of the insulating film is used as the thickness of the insulating film shell unit grid.

8. The method for selecting battery module buffer material according to claim 7, characterized in that, The distance between the insulating film shell unit grid and the buffer material is half the actual thickness t of the insulating film, and the distance between the insulating film shell unit grid and the battery cell is half the actual thickness t of the insulating film.

9. The method for selecting a battery module buffer material according to any one of claims 5-8, characterized in that, The cell solid unit grid and the insulating film shell unit grid are connected by frictional contact, so that the battery module expansion force simulation model presents the real cell expansion effect of large deformation in the middle of the cell surface and small deformation around the perimeter.

10. The method for selecting a battery module buffer material according to claim 9, characterized in that, The modeling parameters of the battery cell solid unit mesh are obtained, including density ρ, elastic modulus E, and Poisson's ratio υ; wherein, the Poisson's ratio adopts a preset Poisson's ratio; the density ρ = m / v is determined according to the actual volume v and actual mass m of the battery cell.

11. The method for selecting battery module buffer materials according to claim 10, characterized in that, The elastic modulus E is obtained by means of simulation and experimental benchmarking, including: A charge-discharge test is performed on a battery cell in a clamped state to obtain the expansion force at the end of the battery cell's lifespan; wherein, the end of the battery cell's lifespan is defined as the number of charge-discharge tests performed on the battery cell. By inputting different elastic moduli into the battery module expansion force simulation model, the end plate support reaction force corresponding to different elastic moduli is obtained. The elastic moduli corresponding to the difference between the end plate support reaction force and the expansion force at the end of the cell's lifespan within a preset threshold is taken as the optimal elastic moduli E of the cell's solid unit mesh.

12. The method for selecting battery module buffer materials according to claim 10, characterized in that, The method for obtaining the coefficient of thermal expansion β includes: Charge and discharge tests are performed on the battery cell in a free state to obtain the expansion amount δ at the end of the battery cell's life. Based on the expansion amount δ at the end of the cell's lifespan, the coefficient of thermal expansion β is determined as follows: β=δ÷(ΔT×μ) Where ΔT is the preset temperature rise and μ is the original thickness of the battery cell.

13. The method for selecting a battery module buffer material according to any one of claims 2-8, characterized in that, The end plate adopts an end plate shell unit grid, and the distance between the side of the end plate shell unit grid facing the cell and the adjacent insulating film is equal to half of the sum of the actual thickness of the end plate and the actual thickness of the insulating film. Alternatively, the end plate may be a solid end plate unit, wherein the distance between the side of the solid end plate unit facing the cell and the adjacent insulating film is equal to half the actual thickness of the insulating film.

14. The method for selecting a battery module buffer material according to any one of claims 1-8, characterized in that, The step of determining the target type of buffer material based on the battery module stress corresponding to the various types of buffer materials includes: Select the type of buffer material with the lowest stress, or stress less than a preset stress threshold, or stress within the stress threshold range from the various types of buffer materials corresponding to the battery module stress, and use it as the target type of buffer material.

15. A battery module, characterized in that, The battery module includes a target type of buffer material determined by the selection method for battery module buffer material according to any one of claims 1-14.

16. A method for determining the initial compression of a one-dimensional elastic element in a battery module expansion force simulation model, characterized in that, The battery module expansion force simulation model is based on the battery module expansion force simulation model constructed in the battery module buffer material selection method according to any one of claims 1-14; the method for determining the initial compression amount of the one-dimensional elastic unit includes: Different preset reference original lengths L are set for the one-dimensional elastic elements corresponding to known types of cushioning materials. Based on the different preset reference original lengths L of the one-dimensional elastic elements and the initial actual length L' in the mesh model of the one-dimensional elastic elements, the initial compression amount a of the known type of cushioning material under different preset reference original lengths L is determined, as follows: L = T + t L'=T'+t a = T - T' = L - L' Where L is the preset reference original length of the one-dimensional elastic element; T is the free state thickness of the buffer material; L' is the initial actual length in the mesh model of the one-dimensional elastic element; T' is the initial compressed state thickness of the buffer material; t is the actual thickness of the insulating film; and a is the initial compression amount of the buffer material. Based on the initial compression amount a of the known type of buffer material under different preset reference original lengths L and the battery module expansion force simulation model, the battery module stress corresponding to different initial compression amounts is obtained. Based on the battery module stress corresponding to the different initial compression amounts, the initial compression amount of the one-dimensional elastic unit corresponding to the known type of buffer material is determined.

17. The method for determining the initial compression of a one-dimensional elastic element in a battery module expansion force simulation model according to claim 16, characterized in that, The step of determining the initial compression of a one-dimensional elastic unit corresponding to a known type of buffer material based on the battery module stress corresponding to the different initial compression amounts includes: The initial compression amount corresponding to the minimum stress, the stress less than the preset stress threshold, or the stress within the stress threshold range corresponding to the different initial compression amounts of the battery module stress is selected as the initial compression amount of the one-dimensional elastic unit corresponding to the known type of buffer material.

18. A simulation model for the expansion force of a battery module, characterized in that, The battery module expansion force simulation model includes a one-dimensional elastic element, and the initial compression amount of the one-dimensional elastic element is obtained by the method for determining the initial compression amount of the one-dimensional elastic element of the battery module expansion force simulation model as described in claim 16 or 17.

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