Liquid lithium battery simulation method and device considering stress effect, and storage medium

Abstract

The invention relates to a liquid lithium battery simulation method and device considering stress action and a storage medium in the technical field of lithium battery simulation, and the method comprises the following steps: constructing a mechanical model for describing the relationship between the deformation of electrode particles and environmental stress in an electrochemical reaction process, including the acting force of an electrolyte on the electrode particles; constructing an electrochemical model for describing the diffusion process of lithium ions in the electrode particles; coupling the electrochemical model with the mechanical model to obtain an electrochemical-mechanical coupling model; and simulating the performance parameters of the battery based on the electrochemical-force coupling model. The liquid electrolyte binding effect is introduced to reflect the stress change of the electrode material in the circulation process, and the electrochemical reaction and mechanical behaviors are coupled to simulate the concentration change of lithium ions at all positions in the electrode particles in the charging and discharging process, so that the model can accurately predict the performance and the service life of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery simulation, and in particular to a liquid lithium battery simulation method, device and storage medium taking stress into consideration. Background Art

[0002] With the widespread application of lithium-ion batteries in consumer electronics, transportation, and energy storage, improving the energy density, cycle life, and safety of batteries has become a research focus. The performance of lithium-ion batteries is not only affected by electrochemical reactions, but also closely related to the mechanical stress in the battery structure. During the charging and discharging process, lithium ions are embedded and de-embedded between the positive and negative electrodes, causing changes in the volume of the electrode materials, which in turn induces stress and affects the cycle life and safety of the battery.

[0003] Liquid electrolyte is a key component of lithium-ion batteries and is usually regarded as a medium used only for ion transport. In practical applications, the interaction between the electrolyte and the electrode material has a significant impact on the electrochemical performance and mechanical behavior of the battery. However, most of the current models consider the stress effect caused by the volume change of the electrode particles themselves due to ion insertion and extraction during the charge and discharge process of the electrode material. However, there are many other factors that affect the mechanical behavior of electrode particles during ion transport, which affect battery performance at the macro level and physical changes in the battery cell at the micro level. Therefore, it is necessary to develop an electrochemical-mechanical coupling model that includes the binding effect of liquid electrolytes to more accurately describe the performance evolution of lithium-ion batteries and improve the prediction accuracy of lithium-ion battery performance and life. Summary of the invention

[0004] In order to solve the above technical problems, the present invention discloses a liquid lithium battery simulation method, device, and storage medium that take stress into consideration. The liquid electrolyte binding effect is introduced to reflect the stress changes of electrode materials during the cycle process. By coupling electrochemical reactions and mechanical behaviors, the charge and discharge process is simulated, and the influence of the electrolyte on the mechanical behavior of electrode particles and the influence of their internal diffusion stress are comprehensively considered. The concentration changes of lithium ions at various locations inside the electrode particles enable the model to accurately predict the performance and life of the battery.

[0005] In a first aspect, the present application provides a liquid lithium battery simulation method considering stress, comprising the following steps:

[0006] Constructing a mechanical model, wherein the mechanical model is used to describe the relationship between the deformation of the electrode particles and the environmental stress during the electrochemical reaction, wherein the environmental stress includes the force exerted by the electrolyte on the electrode particles;

[0007] Constructing an electrochemical model, wherein the electrochemical model is used to describe the diffusion process of lithium ions in electrode particles;

[0008] coupling the electrochemical model with the mechanical model to obtain an electrochemical-mechanical coupling model;

[0009] Based on the electrochemical-mechanical coupling model, the performance parameters of the battery are simulated.

[0010] The electrochemical-mechanical coupling model is expressed as:

[0011]

[0012] Among them, c s is the solid phase lithium ion concentration; D s is the solid phase lithium ion diffusion coefficient, t is time, R is the universal gas constant, T is temperature, r is the radius dimension of the electrode particle, Ω AM is the partial molar volume of lithium ions on the surface of electrode particles, σ h is the comprehensive stress of electrode particles in the normal and circumferential directions;

[0013] The boundary conditions of the electrochemical-mechanical coupling model are:

[0014]

[0015] Where r = 0 represents the center of the particle; r = R AM represents the particle surface; i Far is the interfacial Faraday current density; F is the Faraday constant; τ is the interfacial effective coefficient, representing the relative contact area between the electrolyte and the active material particles, τ is 1; j Far is the Faraday flux of lithium ions, which is negative during lithium insertion and positive during lithium removal; θ represents the stress induction coefficient, which is used to measure the effect of stress on diffusion and is expressed as:

[0016]

[0017] In the above formula, E is Young's modulus, Ω AM is the partial molar volume of lithium ions on the surface of electrode particles, R is the universal gas constant, T is the battery temperature, and v is the Poisson's ratio.

[0018] Furthermore, the step of constructing the mechanical model includes:

[0019] Construct the static stress balance equation of electrode particles;

[0020] Construct the diffusion induction equation within the electrode particles;

[0021] According to the surface pressure of the electrolyte on the electrode particles, the hydrostatic stress equation of the electrode particles is constructed;

[0022] Construct stress / strain relationship equations;

[0023] The boundary conditions of the porous electrode include the surface stress of the electrode particles. Specifically, the surface stress of the electrode particles is the pressure of the electrolyte on the surface of the electrode particles.

[0024] The mechanical model of electrode particles is obtained by coupling the above equations.

[0025] Furthermore, the static stress balance equation of the electrode particles is expressed as:

[0026]

[0027] The diffusion induction equation within the electrode particles is expressed as:

[0028]

[0029] In the above formulas, εr is the normal strain, εt is the hoop strain, σ r is the normal stress, σ t is the hoop stress, E is Young's modulus, v is Poisson's ratio, ΔC S is the change in lithium ion concentration on the particle surface, Ω is the partial molar volume of the material;

[0030] The hydrostatic stress equation of the electrode particles is expressed as:

[0031]

[0032] Among them, σ h It represents the combined stress in the normal and hoop directions of the electrode particles;

[0033] The stress / strain relationship equation is expressed in spherical coordinates as:

[0034]

[0035] Among them, u is the displacement variable;

[0036] The boundary conditions of the porous electrode are:

[0037] σ AM-r (r=R AM )=p

[0038] u(r=0)=0

[0039] Among them, σ AM-r (r=R AM ) represents the normal stress on the surface of the electrode particles, and p represents the pressure of the electrolyte on the surface of the electrode particles.

[0040] Furthermore, the pressure p of the electrolyte on the surface of the electrode particles includes the pressure P1 generated by the gravity of the electrolyte itself on the electrode particles, which is expressed as:

[0041] P1=ρgh

[0042] Where ρ is the density of the liquid electrolyte, g is the acceleration due to gravity, and h is the depth of the electrode particles from the electrode surface.

[0043] Further, h is the deepest point at which the electrolyte penetrates the thickness of the electrode.

[0044] Furthermore, the pressure p of the electrolyte on the surface of the electrode particles also includes the pressure ΔP generated by the compression of the electrolyte liquid due to the volume change of the electrode particles, which is expressed as:

[0045]

[0046] The equation is converted to:

[0047] KΔV / V=-ΔP

[0048] Where K is the bulk elastic modulus of the electrolyte, and ΔV / V is the volume change rate of the electrolyte.

[0049] Furthermore, the static stress balance equation of the electrode particles is constructed including:

[0050] Assuming the electrode particles wrapped by electrolyte to be regular spheres, the stress equilibrium relationship of the electrode particles in spherical coordinates is analyzed according to the principles of elastic-plastic mechanics:

[0051]

[0052] Among them, f r Expressed as the micro-element weight of the electrode particles; ignoring the influence of the micro-element weight of the electrode particles on the elastic-plastic mechanical equilibrium, based on the symmetry of the spherical structure, the static stress equilibrium equation of the electrode particles is obtained as follows:

[0053]

[0054] Furthermore, the electrochemical model includes an equation describing the diffusion process of lithium ions based on the electrode particle size, and the expression is as follows:

[0055]

[0056] Among them, c s is the solid phase lithium ion concentration, t is the time, D s is the solid phase diffusion coefficient of lithium ions, r is the radius dimension of the electrode particles;

[0057] The initial condition corresponding to the constant current operation is expressed as:

[0058] c s (r,0)=c s,0 ,0≤r≤R

[0059] Among them, c s (r,0) is the lithium ion concentration at each location in the electrode particles at the beginning of charge and discharge.

[0060] Furthermore, based on the electrochemical-mechanical coupling model, the performance parameters of the battery are simulated, solved by the finite difference method, and numerically simulated by the host computer software to simulate the battery behavior at different charge and discharge rates.

[0061] In a second aspect, the present application provides a liquid lithium battery simulation device that takes stress into account, the device comprising: a memory configured to store a computer program; and a processor configured to call the computer program to execute the liquid lithium battery simulation method that takes stress into account according to the first aspect of the present application.

[0062] In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program is executed to implement the liquid lithium battery simulation method considering stress effects according to the first aspect of the present application.

[0063] The present invention can not only simulate the performance parameters of specific batteries, such as the voltage curve of lithium-ion batteries, the voltage-current change curve, the lithium ion concentration distribution inside the positive and negative electrode particles of different particle sizes, but also intuitively simulate the stress distribution of electrode particles and the deformation of electrode materials. Through simulation, a large amount of manpower and material resources can be saved, the experimental cycle can be shortened, the efficiency can be improved, and the trial and error of designers can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0065] The same parts are denoted by the same reference numerals. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, and the words "bottom" and "top", "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0066] Figure 1 The schematic diagram of the static stress balance equation of electrode particles is constructed according to the embodiment of the present invention; wherein: Figure 1 (a) in the equation is the spherical coordinate. Figure 1 (b) is the static stress equilibrium equation of the electrode particles in spherical coordinates;

[0067] Figure 2 A comparison diagram of the solid phase lithium ion concentration versus radius curves for simulating a 1c rate discharge condition using two different models in an embodiment of the present invention;

[0068] Figure 3 This is a comparison diagram of curves of changes in electrode particle stress over time in simulations performed with and without considering electrolyte stress according to an embodiment of the present invention. DETAILED DESCRIPTION

[0069] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific implementation methods are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0071] In the description of the specific implementation methods of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0072] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention may be combined with other embodiments.

[0073] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0074] Throughout the present invention, numerical values ​​represent approximate measures or limits of ranges to cover minor deviations from given values ​​as well as embodiments with about the values ​​mentioned and embodiments with the exact values ​​mentioned. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., amounts or conditions) in this specification (including the appended claims) should be understood to be modified by the term "about" in all cases, regardless of whether "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows some minor imprecision (close to the exact value of the value to some extent; approximately or reasonably close to the value; almost). If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about" as used in the present invention at least indicates the variation that can be produced by the ordinary methods of measuring and using such parameters. For example, "about" may include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0075] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further divided ranges, including endpoints and sub-ranges given for such ranges.

[0076] The embodiments of the present invention will be described in more detail below by way of examples. It should be noted that the embodiments of the present invention are not limited to these examples.

[0077] The present application provides a liquid lithium battery method and storage medium that considers stress effects. Based on Fick's second law of diffusion, the present application couples the diffusion-induced stress inside the battery cell and the surface stress of the electrolyte on the electrode particles with the equation of Fick's second law of diffusion to construct an electrochemical-force coupling model. In the calculation process of the above model, the internal stress and the surface stress of the electrolyte on the electrode particles can be calculated according to mathematical formulas. By simulating the above model using appropriate numerical calculation methods, more accurate calculation results can be obtained than the traditional pseudo-two-dimensional model. In the electrochemical-force coupling model constructed by the present application, the influence of liquid electrolyte constraints on battery performance and mechanical stress is taken into account. The physical process, electrochemical reaction and mechanical stress form a multi-field coupling, which makes up for the defect that the traditional Fick's second law of diffusion cannot consider mechanical effects, improves the simulation accuracy, and can more accurately judge the working state of the lithium-ion battery.

[0078] The technical solution of the present application will be described in detail below.

[0079] The main method steps for implementing the present invention include:

[0080] S1, constructing a mechanical model to describe the relationship between the deformation of electrode particles and environmental stress, wherein the environmental stress includes the force of the electrolyte on the electrode particles; the specific steps are as follows:

[0081] S1.1, construct the static stress balance equation of electrode particles:

[0082] like Figure 1 As shown, the electrode particles wrapped by the electrolyte are assumed to be regular spheres. According to the principles of elastic-plastic mechanics, the stress equilibrium relationship of the electrode particles in spherical coordinates is analyzed:

[0083]

[0084] Among them, f r It is expressed as the microelement weight of the electrode particle. Since its weight is too light, its influence on the elastic-plastic mechanical balance is ignored. In addition, considering the symmetry of the spherical structure, the static stress balance equation of the electrode particle is obtained.

[0085]

[0086] S1.2, construct the diffusion induction equation within the electrode particles, expressed as:

[0087]

[0088] Among them, εr is the normal strain, εt is the hoop strain, σ r is the normal stress, σ t is the hoop stress, E is Young's modulus, v is Poisson's ratio, ΔC S is the change in lithium ion concentration on the particle surface, and Ω is the partial molar volume of the material.

[0089] S1.3, based on the surface pressure of the electrolyte on the electrode particles, the hydrostatic stress equation of the electrode particles is constructed and expressed as:

[0090]

[0091] Among them, σ h It represents the comprehensive stress (i.e. average pressure) in all directions at a certain position of the electrode particle, and the directions are normal and circumferential.

[0092] S1.4, construct the stress / strain relationship equation, expressed in spherical coordinates as:

[0093]

[0094] Among them, u is the displacement variable.

[0095] S1.5, the boundary conditions of the porous electrode, including the surface stress of the electrode particles. Specifically, the surface stress of the electrode particles is the pressure of the electrolyte on the surface of the electrode particles. The boundary conditions of the porous electrode are expressed as:

[0096] σ AM-r (r=R AM )=p

[0097] u(r=0)=0

[0098] Among them, σ AM-r (r=R AM ) represents the normal stress on the surface of the electrode particles, and p represents the pressure of the electrolyte on the surface of the electrode particles.

[0099] In some embodiments, p includes the pressure P exerted by the gravity of the electrolyte on the electrode particles, expressed as:

[0100] P=ρgh

[0101] Where ρ is the density of the liquid electrolyte, g is the acceleration due to gravity, and h is the depth of the electrode particles from the electrode surface.

[0102] In some more specific embodiments, h is the deepest point where the electrolyte penetrates the thickness of the electrode. Specifically, h=80 μm.

[0103] In some preferred embodiments, the pressure p of the electrolyte on the surface of the electrode particles also includes the pressure ΔP generated by the compression of the electrolyte liquid due to the volume change of the electrode particles, which is expressed as:

[0104]

[0105] Where K is the bulk elastic modulus of the electrolyte, and ΔV / V is the volume change rate of the electrolyte.

[0106] The force exerted by the gravity of the electrolyte on the surface of the electrode particles is 10-9 orders of magnitude smaller than the stress caused by the volume change of the electrode particles due to the mismatch between the center and the surface of the particles. Therefore, in order to further improve the simulation effect of the simulation model, the pressure ΔP caused by the compression of the electrolyte liquid caused by the volume change of the electrode particles should also be considered when establishing the simulation model.

[0107] In some embodiments, the bulk elastic modulus of the electrolyte can be obtained by observing the volume change of the electrolyte when it is subjected to pressure using a Michelson interferometer.

[0108] In other embodiments, the bulk elastic modulus of the electrolyte may also be simulated by the bulk elastic modulus of water. The present invention does not impose any limitation on the specific method used to simulate the bulk elastic modulus of the electrolyte.

[0109] In some preferred embodiments, the interaction between the electrolyte and the electrode particles can limit the expansion of LCO (electrode particles) to within 8%, so we can calculate the volume change of the electrolyte and the volume change rate of the electrolyte.

[0110] S1.6, coupling the above equations can derive the mechanical model of the electrode particles.

[0111] S2, construct an electrochemical model to describe the diffusion process of lithium ions in electrode particles (the change of concentration over time);

[0112] In some embodiments, the diffusion process of lithium ions in electrode particles is described based on Fick's second law, and the expression is as follows:

[0113]

[0114] Among them, c s is the solid phase lithium ion concentration, t is the time, D s is the solid phase diffusion coefficient of lithium ions, and r is the radius dimension of the electrode particles.

[0115] The initial condition corresponding to the constant current operation is expressed as:

[0116] c s (r,0)=c s,0 ,0≤r≤R

[0117] Among them, c s (r,0) is the lithium ion concentration at each location in the electrode particles at the beginning of charge and discharge.

[0118] S3, coupling the electrochemical model with the mechanical model to obtain the electrochemical-mechanical coupling model, which is expressed as:

[0119]

[0120] The boundary conditions of the electrochemical-mechanical coupling model are:

[0121]

[0122] The Faraday process on the surface of the electrode particles is:

[0123]

[0124] Where r = 0 represents the center of the particle; r = R AM Represents the particle surface. Far is the interfacial Faraday current density, F is the Faraday constant, and τ is the interfacial effective coefficient, which represents the relative contact area between the electrolyte and the active material particles. Far is the Faraday flux of lithium ions, which is negative during lithium insertion and positive during lithium deintercalation.

[0125] Furthermore, τ is 1.

[0126] θ represents the stress induction coefficient, which is used to measure the effect of stress on diffusion and is expressed as:

[0127]

[0128] Where E is Young's modulus, Ω AM is the partial molar volume of lithium ions on the surface of electrode particles, R is the universal gas constant, and T is the battery temperature.

[0129] S4, based on the electrochemical-mechanical coupling model, simulates the performance parameters of the battery.

[0130] In some embodiments, the performance parameters of the battery are simulated based on the electrochemical-mechanical coupling model, solved by the finite difference method (FDM), and numerically simulated by MATLAB R2024a software, which can simulate the battery behavior under different charge and discharge rates.

[0131] The present application embodiment also provides a computer-readable storage medium. A person of ordinary skill in the art can understand that all or part of the steps in the method for implementing the above embodiment can be completed by instructing the processor through a program, and the program can be stored in a computer-readable storage medium, and the storage medium is a non-transitory medium, such as a random access memory, a read-only memory, a flash memory, a hard disk, a solid-state hard disk, a magnetic tape, a floppy disk, an optical disc, and any combination thereof. The above storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a digital video disc (DVD)), or a semiconductor medium (e.g., a solid-state disk (SSD)), etc.

[0132] This embodiment takes a liquid lithium battery with lithium cobalt oxide (LCO) positive electrode material as an example and uses the electrochemical-mechanical coupling model of the present invention to perform simulation.

[0133] The specific parameters of the simulation model are shown in the following table.

[0134]

[0135] Figure 2The figure is a comparison of the solid phase lithium ion concentration versus radius curves simulated under 1C rate discharge conditions using two different models. Specifically, the two lines are respectively the solid phase lithium ion concentration versus radius curves simulated under 1C rate discharge conditions using the electrochemical-mechanical coupling model in this application and the pure electrochemical model.

[0136] according to Figure 2 It can be seen that the simulation effect of the electrochemical-mechanical coupling model in this application is different from that of the traditional pseudo-two-dimensional model. This is because the electrochemical-mechanical coupling model in this application takes into account the stress on the electrode particles during ion transport. Figure 2 The results show that the presence of stress will reduce the gradient of lithium ion concentration in the electrode particles, the lithium ion concentration on the surface will decrease, and the lithium ion concentration in the center of the particles will increase. Therefore, the electrochemical-mechanical coupling model of the present application can better simulate the working state of liquid lithium batteries.

[0137] Figure 3 The stress comparison diagram of the electrode particles simulated by using the electrochemical-mechanical coupling model of the present application with and without considering the electrolyte stress p is shown. Figure 3 (a) is the normal stress comparison diagram; Figure 3 (b) is the comparison diagram of hoop stress; Figure 3 (c) is the comprehensive stress comparison diagram; Figure 3 In (a), (b), and (c), the red x represents the surface stress of the electrode particles when the electrolyte stress p is considered, the green x represents the central stress of the electrode particles when the electrolyte stress p is considered, the red solid line represents the central stress of the electrode particles without considering the electrolyte stress p, and the green solid line represents the surface stress of the electrode particles without considering the electrolyte stress p.

[0138] Specifically, the liquid electrolyte is assumed to be H2O, and the expansion volume change rate of the electrode particles is set to 2%. Figure 3 It can be seen that considering the pressure exerted by the liquid electrolyte on a single particle, the tensile stress on the surface of the electrode particle will increase and the compressive stress in the center will decrease.

[0139] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid lithium battery simulation method considering stress, characterized in that: The steps include: Constructing a mechanical model, wherein the mechanical model is used to describe the relationship between the deformation of the electrode particles and the environmental stress during the electrochemical reaction, wherein the environmental stress includes the force exerted by the electrolyte on the electrode particles; Constructing an electrochemical model, wherein the electrochemical model is used to describe the diffusion process of lithium ions in electrode particles; coupling the electrochemical model with the mechanical model to obtain an electrochemical-mechanical coupling model; Based on the electrochemical-mechanical coupling model, the performance parameters of the battery are simulated.

2. The liquid lithium battery simulation method considering stress according to claim 1, characterized in that: The electrochemical-mechanical coupling model is expressed as: Among them, c s is the solid phase lithium ion concentration; D s is the solid phase lithium ion diffusion coefficient, t is time, R is the universal gas constant, T is temperature, r is the radius dimension of the electrode particle, Ω AM is the partial molar volume of lithium ions on the surface of electrode particles, σ h is the comprehensive stress of electrode particles in the normal and circumferential directions; The boundary conditions of the electrochemical-mechanical coupling model are: Where r = 0 represents the center of the particle; r = R AM represents the particle surface; i Far is the interfacial Faraday current density; F is the Faraday constant; τ is the interfacial effective coefficient, representing the relative contact area between the electrolyte and the active material particles, τ is 1; j Far is the Faraday flux of lithium ions, which is negative during lithium insertion and positive during lithium removal; θ represents the stress induction coefficient, which is used to measure the effect of stress on diffusion and is expressed as: In the above formula, E is Young's modulus, Ω AM is the partial molar volume of lithium ions on the surface of electrode particles, R is the universal gas constant, T is the battery temperature, and v is the Poisson's ratio.

3. The liquid lithium battery simulation method considering stress according to claim 2, characterized in that: The step of constructing the mechanical model includes: Construct the static stress balance equation of electrode particles; Construct the diffusion induction equation within the electrode particles; According to the surface pressure of the electrolyte on the electrode particles, the hydrostatic stress equation of the electrode particles is constructed; Construct stress / strain relationship equations; The boundary conditions of the porous electrode include the surface stress of the electrode particles. Specifically, the surface stress of the electrode particles is the pressure of the electrolyte on the surface of the electrode particles. The mechanical model of electrode particles is obtained by coupling the above equations.

4. The liquid lithium battery simulation method considering stress according to claim 3, characterized in that: The static stress balance equation of the electrode particles is expressed as: The diffusion induction equation within the electrode particles is expressed as: In the above formulas, εr is the normal strain, εt is the hoop strain, σ r is the normal stress, σ t is the hoop stress, E is Young's modulus, v is Poisson's ratio, ΔC S is the change in lithium ion concentration on the particle surface, Ω is the partial molar volume of the material; The hydrostatic stress equation of the electrode particles is expressed as: Among them, σ h It represents the combined stress in the normal and hoop directions of the electrode particles; The stress / strain relationship equation is expressed in spherical coordinates as: Among them, u is the displacement variable; The boundary conditions of the porous electrode are: s AM-r (r=R AM )=p u(r＝0)＝0 Among them, σ AM-r (r=R AM ) represents the normal stress on the surface of the electrode particles, and p represents the pressure of the electrolyte on the surface of the electrode particles.

5. The liquid lithium battery simulation method considering stress according to claim 4, characterized in that: The pressure p of the electrolyte on the surface of the electrode particles includes the pressure P1 generated by the gravity of the electrolyte itself on the electrode particles, which is expressed as: P1=ρgh Where ρ is the density of the liquid electrolyte, g is the acceleration due to gravity, and h is the depth of the electrode particles from the electrode surface.

6. The liquid lithium battery simulation method considering stress according to any one of claims 4 or 5, characterized in that: The pressure p of the electrolyte on the surface of the electrode particles includes the pressure ΔP generated by the compression of the electrolyte liquid due to the volume change of the electrode particles, which is expressed as: The equation is converted to: KΔV / V=-ΔP Where K is the bulk elastic modulus of the electrolyte, and ΔV / V is the volume change rate of the electrolyte.

7. The liquid lithium battery simulation method considering stress according to claim 4, characterized in that: The construction of the static stress balance equation of electrode particles includes: According to the principle of elastic-plastic mechanics, the stress equilibrium relationship of electrode particles in spherical coordinates is analyzed: Among them, f r Expressed as the micro-element weight of the electrode particles; ignoring the influence of the micro-element weight of the electrode particles on the elastic-plastic mechanical equilibrium, based on the symmetry of the spherical structure, the static stress equilibrium equation of the electrode particles is obtained as follows:

8. The liquid lithium battery simulation method considering stress according to claim 2, characterized in that: The electrochemical model includes an equation describing the diffusion process of lithium ions based on the electrode particle size, which is expressed as follows: Among them, c s is the solid phase lithium ion concentration, t is the time, D s is the solid phase diffusion coefficient of lithium ions, r is the radius dimension of the electrode particles; The initial condition corresponding to the constant current operation is expressed as: c s (r,0)=c s,0 ,0≤r≤R Among them, c s (r,0) is the lithium ion concentration at each location in the electrode particles at the beginning of charge and discharge.

9. A liquid lithium battery simulation device considering stress, characterized in that: The device comprises: a memory configured to store a computer program; and A processor is configured to call the computer program to execute the lithium battery simulation method considering stress according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer program is executed to implement the liquid lithium battery simulation method considering stress according to any one of claims 1 to 9.

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