A method for constructing a multi-scale and multi-dimensional electrochemical-force-thermal coupling model of a lithium ion battery

Abstract

The application discloses a kind of construction methods of lithium ion battery multiscale multidimensional electrochemistry-force-thermal coupling model, it is related to lithium ion battery coupling model development field, specific steps are as follows: (1) according to the electrochemistry, force and thermal model solution problem determines model scale;(2) based on the model scale determined, select appropriate model dimension to simplify model;(3) select monomer battery, obtain its electrochemistry parameter, thermal physical property parameter and stress related parameter;(4) determine the electrochemistry-force-thermal model coupling mechanism of multiscale multidimension, construct multiscale multidimensional electrochemistry-force-thermal model;(5) based on the electrochemistry-force-thermal model established, can compare lithium ion battery charging and discharging process diffusion stress and thermal stress difference and similarity.The application can systematically clarify the interrelation of battery internal electrochemistry process, stress generation and temperature change, can provide theoretical guidance for battery charging and discharging process thermal design, structure design and optimization.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery modeling, specifically involving a method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model of lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are highly favored as a novel and efficient energy storage medium. The charging and discharging of lithium-ion batteries is a complex process involving multiple physical fields, including electrochemistry, force, and heat. However, traditional experimental methods can only monitor the battery's apparent characteristics, such as voltage, temperature, and capacity, and struggle to obtain information on the battery's internal electrochemical, mechanical, and thermal characteristics from the microscopic to the macroscopic levels. This includes aspects such as lithium-ion concentration, current and potential distribution, temperature distribution across internal layers, and even the stress and strain of internal particles. Therefore, it is crucial to establish a multi-scale, multi-dimensional model coupling electrochemistry, force, and heat to elucidate the multi-field coupling characteristics and mechanisms within the battery from the microscopic to the macroscopic level.

[0003] Currently, the most widely used models are two-field coupled models that address electrochemistry, mechanics, and heat. However, three-field coupled models have received less attention due to their complex coupling mechanisms and cross-scale and dimensional limitations. Therefore, this paper proposes a method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal model for lithium-ion batteries. First, the criteria for selecting the model's scale and dimensions are given. Then, the coupling mechanism and calculation process of the electrochemical-mechanical-thermal model are elucidated. Finally, based on the constructed electrochemical-mechanical-thermal model, a comparison between diffusion stress and thermal stress is achieved. This invention can systematically clarify the interrelationships between internal electrochemical processes, stress generation, and temperature changes in batteries, providing theoretical guidance for thermal design, structural design, and optimization during battery charging and discharging. Summary of the Invention

[0004] This invention provides a method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for lithium-ion batteries. By selecting different model dimensions and scales, the coupling mechanism of the electrochemical-mechanical-thermal model is determined. Based on the constructed multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for lithium-ion batteries, the comparison between diffusion stress and thermal stress during charging and discharging is realized.

[0005] The technical solution adopted in this invention is: a method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal model for lithium-ion batteries, comprising the following steps:

[0006] Step 1: Determine the model scale of the three models based on the problems to be solved by the electrochemical model, the force model, and the thermal model;

[0007] Step 2: Based on the determined model scale, determine the model dimensions to simplify the model;

[0008] Step 3: Select individual battery cells, obtain their electrochemical parameters, thermophysical parameters, and stress-related parameters, and construct an electrochemical-mechanical-thermal coupling model;

[0009] Step 4: Based on the coupling relationship between electrochemical-mechanical-thermal properties, determine the coupling mechanism of the multi-scale, multi-dimensional electrochemical-mechanical-thermal model, and realize the construction of the multi-scale, multi-dimensional electrochemical-mechanical-thermal model;

[0010] Step 5: Based on the constructed electrochemical-mechanical-thermal model, calculate the diffusion stress and thermal stress, and compare the similarities and differences between the diffusion stress and thermal stress during the charging and discharging process of lithium-ion batteries.

[0011] Step one's model scale includes particle scale, electrode scale, and cell scale. The particle scale refers to the particles that make up the positive and negative electrode active materials, at the "μm" level; the electrode scale refers to the various components of the battery, such as the current collector, positive and negative electrode active layers, and separator, at the "mm" level in the thickness direction; the cell scale refers to the individual battery cell, at the "cm or m" level. The problems addressed by the electrochemical model, force model, and thermal model, and their corresponding scales, are shown in Table 1. The electrochemical model describes the electrode processes and electrochemical reaction mechanisms within a lithium-ion battery, and its modeling scale is generally at the particle and electrode scales. The force model studies diffusion stress and thermal stress. The former is the stress caused by the concentration gradient created by the continuous insertion and extraction of lithium between the positive and negative electrodes, and its modeling scale is at the particle or electrode scale. The latter is the thermal stress caused by temperature differences, and its modeling scale is at the electrode or cell scale. The thermal model obtains the battery temperature through the heat generated by the cell, and its modeling scale is generally at the electrode or cell scale. (See the attached instruction manual.) Figure 1 The correspondences between the three models and different scales shown reveal the cross-scale coupling modes of electrochemistry, force, and heat: the coupling of electrochemistry and force fields can be completed simultaneously at both the particle and cell scales; the coupling of electrochemistry and thermal fields can only be completed at the electrode scale; and the coupling of force and heat can be completed simultaneously at both the electrode and cell scales. To achieve multi-scale coupling, this method selects the particle scale for diffusion stress in the force model, incorporates both particle and electrode scales in the electrochemical model, selects the cell scale for diffusion stress in the force model, and selects the cell scale for the thermal model, thus achieving coupling from the particle to the electrode and then to the cell scale.

[0012] Table 1. Problems solved by electrochemical models, mechanical models, and thermal models, and their corresponding scales.

[0013]

[0014] In step two, the model dimensions generally include zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D). Unlike model scale, which is related to the problem described by the model, different dimensional models can be built for any model. However, the higher the model dimension, the higher the model complexity. Therefore, in the establishment of multi-field coupling models, a fully three-dimensional model is generally not built; some sub-models are dimensionality-reduced to simplify calculations. In this method, the electrochemical model is one-dimensional, but because an additional dimension of electrode particles is added to the one-dimensional model, it can also be called a pseudo-two-dimensional model (P2D), although this additional dimension is not reflected in the model geometry. The diffusion stress in the force model is an additional dimension; the diffusion stress in the force model is three-dimensional; the thermal model is also three-dimensional; thus, multi-scale and multi-dimensional coupling of the electrochemical-force-thermal model is achieved.

[0015] The basic theory of the electrochemical-mechanical-thermal coupling model in step four includes the following five parts: (1) The lithium diffusion process is described by Fick's law, and the changes in lithium ion concentration in the solid phase and liquid phase are obtained. The governing equations and boundary conditions are shown in equations (1) to (9) in Table 2; (2) The electromigration process is described by Ohm's law, and the current density and potential distribution are obtained. The governing equations and boundary conditions are shown in equations (10) to (8) in Table 2; (3) The charge transfer reaction is described by the Butler-Volmer kinetic equation, and the chemical reaction rate is obtained. The governing equations and boundary conditions are shown in equations (19) to (21) in Table 2; (4) The diffusion stress is calculated by the stress-strain relationship and the relationship between the electrode particle volume change rate and the lithium concentration. The governing equations and boundary conditions are shown in equations (22) to (33) in Table 2; (5) The temperature distribution is calculated by the energy conservation equation. The governing equations and boundary conditions are shown in equation (34) in Table 2. ~(36); (6) Thermal stress is obtained through the stress-strain relationship and its relationship with temperature difference. Its governing equations and boundary conditions are shown in equations (37) to (38) in Table 2. The above (1) to (3) parts belong to the electrochemical model, (4) and (6) belong to the force model, and (5) belongs to the thermal model.

[0016] Table 2. Governing equations and boundary conditions for the electrochemical-mechanical-thermal coupling model.

[0017]

[0018]

[0019]

[0020] The model coupling mechanism is determined based on the model governing equations; see the appendix in the instruction manual. Figure 2 .

[0021] (1) First, the electrochemical-force model coupling mechanism is introduced: the electrochemical model is the P2D electrochemical model. The extra dimension in P2D, namely the dimension of the active material particles, is used to couple the diffusion stress. The lithium concentration obtained in real time in P2D can be used to calculate the diffusion stress of the active particles caused by the lithium concentration difference. It is a one-way coupling, and the coupling is carried out through formula (23) in Table 2.

[0022] (2) Then, the electrochemical-thermal model coupling mechanism is introduced: it is a two-way coupling. Some parameters in the electrochemical model, such as conductivity, diffusion coefficient, and reaction rate constant, are functions of temperature. According to the control equations related to electromigration, charge transfer, and lithium diffusion, the dependent variables of the electrochemical model, namely the solid-liquid phase potential and the solid-liquid phase lithium concentration, can be calculated. Then, the heat generated in each part of the battery can be calculated. The thermal model is a 3D average model, that is, the battery is regarded as an anisotropic thermally conductive material. Therefore, the heat generated in the electrochemical model will be brought into the 3D average thermal model through the "average" method. That is, the heat source in the thermal model is the average heat source calculated in the electrochemical model. Based on the energy conservation equation, the change of heat can be reflected as the change of temperature in the thermal model. The change of temperature, in turn, affects the temperature-related parameters in the electrochemical model, forming a closed-loop feedback. This coupling method is realized through formula (36) in Table 2.

[0023] (3) Finally, the thermo-mechanical model coupling mechanism is introduced: The thermal model is used to calculate the battery temperature. Due to the uneven heat generation and dissipation, a temperature gradient will be generated, which will be reflected in the generation of thermal stress in the mechanical model, thus exhibiting thermal expansion behavior. Through the coupling of formula (38) in Table 2, it is a unidirectional coupling. The above is the three-field coupling mechanism. Through the three-field coupling, the electrochemical characteristics of the battery, such as potential and lithium concentration, the diffusion stress distribution at the particle scale, and the temperature, heat generation and thermal stress distribution at the cell scale can be obtained simultaneously in one model, and the intrinsic characteristics and correlations of the battery at different scales can be obtained more comprehensively. The symbols and terms appearing in the text are shown in Table 3.

[0024] Symbols and terms appearing in Table 3

[0025]

[0026]

[0027]

[0028] The advantages of this invention compared to existing technologies are as follows: 1. It constructs a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model, clarifying the interrelationships of the internal electrochemical-mechanical-thermal characteristics of the battery; 2. The multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model constructed by this method can be used to solve all related electrochemical-mechanical-thermal problems during charging and discharging; 3. It can dynamically monitor changes in lithium concentration, diffusion stress, temperature, and thermal stress, and can achieve a comparison between diffusion stress and thermal stress, which is of great significance for stress comparison research of lithium-ion batteries; 4. This method provides novel research ideas for lithium-ion battery model development and researchers, and can simultaneously provide theoretical guidance for thermal design, structural design, and optimization during battery charging and discharging; 5. It overcomes the difficulty of experimentally observing internal electrochemical-mechanical-thermal characteristics, and uses the results of the multi-field coupling model of lithium batteries to provide numerical methods for characterizing electrochemical, mechanical, and thermal performance. At the same time, the data can provide numerical range and theoretical guidance for lithium battery safety management system models. Attached Figure Description

[0029] Figure 1 This illustrates the relationship between the electrochemical model, force model, and thermal model in this invention and different scales.

[0030] Figure 2 This invention relates to the multi-scale, multi-dimensional electrochemical-mechanical-thermal model coupling mechanism for lithium-ion batteries.

[0031] Figure 3 This is a schematic diagram illustrating the scale and dimension relationship between electrochemistry, mechanics, and heat in a lithium-ion battery, as well as the computational domain, in an embodiment of the present invention.

[0032] Figure 4 The following is an example of the variation of the von Mises stress tangential component with time at the interface between the negative electrode separator and the current collector during a 1.5C charge-discharge cycle in this invention.

[0033] Figure 5 This is a diagram showing the maximum thermal stress, displacement, and distribution during a 1.5C charge-discharge cycle in an embodiment of the present invention. Figure 5a shows the evolution of the maximum thermal stress over time. Figure 5 b represents the evolution of the maximum displacement over time. Figure 5 c is the maximum displacement distribution map, where the deformation scale factor of the displacement distribution map is 1000. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Example

[0036] Taking a commercial ternary lithium nickel cobalt manganese oxide (NCM) / graphite cylindrical 26650 single cell with a rated capacity of 5Ah (EF Battery Technology (Shenzhen) Co., Ltd.) as an example, a multi-scale, multi-dimensional electrochemical-mechanical-thermal model of lithium-ion batteries is constructed to comprehensively and in detail describe the present invention. This method is not limited to this type of cylindrical cell, but is applicable to all commercial and self-made lithium-ion batteries. The method is mainly divided into the following four parts: (1) determination and description of model scale and dimension; (2) description of model coupling mechanism and calculation process; (3) acquisition of electrochemical-mechanical-thermal model parameters; (4) comparison of diffusion stress and thermal stress based on the model.

[0037] 1. First, the selection of model dimensions and scale is described, which consists of three steps, as follows:

[0038] Step 1: Determining the model dimensions. See the attached diagram for a schematic of each model dimension. Figure 3 The electrochemical model used is the classic P2D model, proposed by Newman et al. in 1993 and widely used to solve the electrochemical field problem of lithium-ion batteries. P2D, or "pseudo-two-dimensional," simplifies the model along the electrode thickness direction to a single line segment, typically containing a negative electrode domain, a separator domain, and a positive electrode domain. This one-dimensional line segment constitutes one dimension of P2D—the electrode thickness dimension. It's called "pseudo-two-dimensional" because the positive and negative electrode domains in the one-dimensional line segment are extended, considered to be porous electrodes filled with positive and negative electrode particles, conductive agents, binders, and electrolytes; this is called the "extra dimension." The diffusion stress in the force model describes the stress generated by the insertion and extraction of lithium ions in the positive and negative electrode materials; therefore, it is coupled with the extra dimension in the electrochemical model—electrode particles. The thermal stress component of the force model and the thermal model are both three-dimensional models.

[0039] Step two, model scale selection. The diffusion stress in the force model is selected at the particle scale, while the electrochemical model includes both electrode and particle scales. The diffusion stress component of the force model and the thermal model are both at the cell scale, achieving coupling from the particle to the electrode and then to the cell scale. Schematic diagrams for each scale are attached to the instruction manual. Figure 3 It should be noted that the particle scale in the electrochemical model is an additional dimension of the active material in the one-dimensional model. Based on the porous electrode theory, it is believed that the line segments representing the positive and negative electrodes in the one-dimensional model are composed of numerous spherical particles, and this additional dimension is not reflected in the model geometry.

[0040] Step 3: Representation of the Electrode Computational Domain. Based on the determination of the model scale and dimensions in Steps 1 and 2, the computational domain is also confirmed accordingly. The 3D model contains two computational domains—the battery casing and the electrode domain. In this 3D model, the internal electrode domain ignores the complex winding structure inside the battery and treats it as a whole. In addition, to facilitate the setting of stress constraint boundary conditions in the force model, an additional cylinder with a diameter of 0.1 mm is added at the center of the 3D electrode domain to describe the constraint center of the force model. This additional cylinder is considered as the equivalent internal center of the cell. In the thermal model, it is regarded as the same computational domain as the cell. In the 3D force model, its material properties and initial conditions are exactly the same as those of the electrode domain, except that a specified displacement boundary condition is applied to its surface boundary, and the displacement of the internal center of the cell is considered to be zero. The 1D computational domain is a simplified line segment in the thickness direction at the electrode scale. The three line segments represent the negative electrode, the separator, and the positive electrode, respectively; the four points represent the negative electrode current collector, the negative electrode / separator interface, the positive electrode / separator interface, and the positive electrode current collector, respectively.

[0041] 2. The model coupling mechanism and calculation process are then described in two steps, as detailed in the appendix of the instruction manual. Figure 2 As described below:

[0042] Step 1, Model Coupling Mechanism. Electrochemical-Mechanical Coupling Mechanism: In the extra dimension of the electrochemical P2D model, namely the dimension of the active material particles, the diffusion stress and electrochemical process are coupled. The lithium concentration obtained in real time in P2D can be used to calculate the diffusion stress of the active particles caused by the lithium concentration difference, which is a one-way coupling. (2) Electrochemical-Thermal Coupling Mechanism: It is a two-way coupling. The electrochemical model contains temperature-related parameters Φ. According to the control equations related to electromigration, charge transfer and lithium diffusion, the dependent variables of the electrochemical model, namely the solid-liquid phase potential and the solid-liquid phase lithium concentration, can be calculated. Then, the heat generated in each part of the battery can be calculated. This heat generated will be brought into the 3D average thermal model in an "average" manner. That is, the heat source in the thermal model is the average heat source calculated in the electrochemical model. Based on the energy conservation equation, the change of heat can be reflected as the change of temperature in the thermal model, and the change of temperature in turn affects the temperature-related parameters in the electrochemical model, forming a closed-loop feedback. (3) Thermo-Mechanical Coupling Mechanism: The temperature is obtained in the thermal model, and the resulting temperature gradient is reflected in the generation of thermal stress in the force model, thus manifesting as thermal expansion behavior. The governing equations and boundary conditions described above can be found in Table 2.

[0043] Step 2, Numerical Calculation Process. Based on the above coupling mechanism, the numerical calculation process based on COMSOL Multiphysics is as follows: Due to the different dimensions, the simulation calculation includes two components. Component 1 is a one-dimensional electrochemical module and an additional-dimensional stress-strain calculation node. The current boundary conditions are set using the "charge-discharge cycle" node. Component 2 is a three-dimensional heat transfer module and a solid mechanics module. The lithium concentration obtained from Component 1 is applied to its built-in "stress and strain" node to calculate the diffusion stress in the additional dimension. It should be noted that research shows that the diffusion stress of negative electrode particles is generally much greater than that of positive electrode particles. Therefore, in this embodiment, only the diffusion stress of negative electrode graphite particles is calculated. The heat source obtained from Component 1 is coupled to Component 2 through an averaging method. The temperature obtained from Component 2 is coupled to Component 1 in real time, completing the coupling of electrochemistry and heat generation. The temperature obtained from Component 2 is coupled to thermal force within the same component through the "solid mechanics" module and its preset multiphysics node—thermal expansion.

[0044] 3. Electrochemical-mechanical-thermal model parameter acquisition. The electrochemical-mechanical-thermal model parameters of the battery, obtained based on some experimental tests and methods from the references, are listed in Table 4.

[0045] Table 4 Parameters of the Electrochemical-Mechanical-Thermal Coupling Model

[0046]

[0047] Note: The " / " parameter is not considered or does not exist.

[0048] This parameter was measured experimentally.

[0049] The parameter b has no references and was derived through adjustments based on experimental data.

[0050] 4. Based on the model, a comparison between diffused stress and thermal stress is achieved, which consists of the following three steps:

[0051] Step 1: Calculation of diffusion stress. We use von Mises stress to characterize the magnitude of diffusion stress, as shown in equation (32). Since the particles are spherical, the radial component of the diffusion stress on their surface is zero. Therefore, the surface von Mises stress actually reflects the characteristics of the tangential component of the surface diffusion stress. Figure 4The relationship between the tangential component of von Mises stress at the interface between the negative electrode separator and the current collector during a 1.5C charge-discharge cycle is presented. 1) The von Mises stress at the separator end changes faster and is greater than that at the current collector end. This is attributed to the "proximity principle" mechanism of lithium insertion / extraction, which causes preferential lithium insertion / extraction at the separator end, resulting in a larger concentration gradient and stress. 2) During charging, lithium insertion first occurs on the surface of the negative electrode particles, causing the outer side to expand, while the volume of the un-lithi-intercalated internal region does not change. Therefore, the von Mises stress on the particle surface is compressive stress and has a negative value. Conversely, during discharging, lithium de-lithiation first occurs on the surface of the negative electrode particles, causing the outer side to contract. The volume of the un-lithi-de-lithiated internal region is larger than that of the outer side. Therefore, the von Mises stress on the particle surface is tensile stress and has a positive value. 3) The maximum von Mises stress values ​​on the particle surface are basically consistent during the charge-discharge process and are around 30 MPa.

[0052] Step 2, calculation of thermal stress. Based on the temperature distribution calculated by the energy conservation equation, the stress-strain relationship is coupled to obtain the result of thermal stress, as shown in equation (37). Figure 5 Figures a and b show the relationship between maximum thermal stress and displacement over time during a 1.5C charge-discharge cycle, excluding the internal equivalent cell portion (i.e., the constraint boundary portion) in the post-processing domain. The maximum thermal stress and displacement during the 1.5C cycle occur at the end of discharge, with a maximum thermal stress of 131.7 kPa and a maximum displacement of 10.3 μm, which is 0.079% of the battery radius (13 mm). Furthermore, according to... Figure 5 As shown in the displacement distribution diagram, the battery tends to expand towards the top and bottom sides due to thermal stress, indicating that the parts of the cylindrical cell most prone to yielding due to thermal stress are on both sides of the positive and negative electrode tabs.

[0053] Step 3: Comparative analysis of diffusion stress and thermal stress. Finally, by comparing diffusion stress and thermal stress, it can be seen that at a 1.5C rate, the maximum thermal stress is 131.7 kPa, while the maximum diffusion stress is 30 MPa. The thermal stress value is several orders of magnitude smaller than the diffusion stress. Therefore, during normal charge-discharge cycles, diffusion stress requires greater attention than thermal stress.

[0054] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for lithium-ion batteries, characterized in that, Includes the following steps: Step 1: Determine the model scale of the three models based on the problems that the electrochemical model, mechanical model, and thermal model are intended to solve. Step 2: Based on the determined model scale, determine the model dimensions to simplify the model; Step 3: Select individual battery cells, obtain their electrochemical parameters, thermophysical parameters, and stress-related parameters, and construct an electrochemical-mechanical-thermal coupling model; among them, establish an electrochemical model based on Fick's law, Ohm's law, and the Butler-Volmer kinetic equation to obtain changes in lithium concentration, potential, and current; establish a battery thermal model based on the energy conservation equation to obtain the battery temperature; A battery force model is established based on the stress-strain relationship to obtain the battery diffusion stress and thermal stress. Step 4: Based on the coupling relationship between electrochemical-mechanical-thermal properties, determine the coupling mechanism of the multi-scale, multi-dimensional electrochemical-mechanical-thermal model, and realize the construction of the multi-scale, multi-dimensional electrochemical-mechanical-thermal model; Step 5: Based on the established electrochemical-mechanical-thermal model, calculate the diffusion stress and thermal stress, and compare the similarities and differences between the diffusion stress and thermal stress during the charging and discharging process of lithium-ion batteries. In step one, the electrochemical model aims to address the problems of lithium-ion battery electrode processes and / or electrochemical reaction mechanisms; the force model aims to address the problems of diffusion stress and / or thermal stress; and the thermal model aims to address the problems of cell heat generation and / or temperature. The model scale of electrochemical models includes particle scale and / or electrode scale; When the force model is intended to solve the problem of diffused stress, the model scale of the force model includes the particle scale and / or the electrode scale. When the problem to be solved by the force model is thermal stress, the model scale of the force model includes the electrode scale and / or the cell scale; The thermal model's scale includes electrode scale and / or cell scale; The particle size refers to the particles that make up the positive and negative electrode active materials, which are at the μm level; the electrode size refers to the various components of the battery, such as the current collector, positive and negative electrode active layers, and separator, which are at the mm level in the thickness direction; and the cell size refers to the single cell that people see, which is at the cm or m level. In step two, the model dimensions include one, two, three, or four of the following: zero-dimensional, one-dimensional, two-dimensional, and three-dimensional. The electrochemical-mechanical-thermal model is a multi-scale model that covers the particle scale, electrode scale, and cell scale of lithium-ion batteries. Specifically, the electrochemical model is established at the electrode scale, the diffusion stress in the mechanical model is calculated at the particle scale, and the thermal stress in the thermal and mechanical models is calculated at the cell scale. The electrochemical-mechanical-thermal model is a multi-dimensional model, encompassing both one-dimensional and three-dimensional models; the electrochemical model is a one-dimensional model, the diffusion stress in the force model is a one-dimensional model, the thermal stress in the force model is a three-dimensional model, and the thermal model is a three-dimensional model.

2. The method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for lithium-ion batteries according to claim 1, characterized in that, Step four achieves the coupling of the electrochemical-mechanical-thermal model, where the coupling between the models adopts a combination of unidirectional and bidirectional coupling.

3. The method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for lithium-ion batteries according to claim 1, characterized in that, The electrochemical-mechanical coupling mechanism in step four lies in the additional dimension in the one-dimensional electrochemical model, namely the dimension of the active material particles. The lithium concentration obtained in real time can be used to calculate the diffusion stress of the active particles caused by the lithium concentration difference, thereby realizing the coupling of diffusion stress and electrochemical process, which is a one-way coupling.

4. The method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for lithium-ion batteries according to claim 1, characterized in that, The electrochemical-thermal coupling mechanism in step four is as follows: based on the principles of electromigration, charge transfer, and lithium diffusion, the dependent variables of the electrochemical model, namely the solid-liquid phase potential and the solid-liquid phase lithium concentration, can be calculated, and then the heat generated in each part of the battery can be calculated; this heat generated will be brought into the three-dimensional average thermal model in an "averaging" manner; based on the energy conservation equation, the change in heat can be reflected as the change in temperature in the thermal model, and the change in temperature, in turn, affects the temperature-related parameters in the electrochemical model, forming a closed-loop feedback, which is a two-way coupling.

5. The method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for a lithium-ion battery according to claim 1, characterized in that, The thermo-mechanical coupling mechanism in step four is that the temperature obtained in the thermal model leads to the generation of thermal stress in the force model, which in turn manifests as thermal expansion behavior.

6. The method for constructing a multi-scale, multi-dimensional electrochemical-mechanical-thermal coupling model for a lithium-ion battery according to claim 1, characterized in that, Based on this model, the diffusion stress and thermal stress during the charging and discharging process of lithium-ion batteries can be compared. The diffusion stress was calculated by coupling the lithium concentration obtained from the electrochemical model with the stress-strain relationship in the force model. Thermal stress is calculated by coupling the temperature obtained in the thermal model with the stress-strain relationship in the force model; based on this model, it can be used to solve all related electrochemical-mechanical-thermal problems in the charging and discharging process.

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