A Multiphysics Coupled Modeling and Simulation Method for the Puncture Process of a Pouch Lithium Battery

Abstract

This invention belongs to the field of lithium-ion battery modeling technology and discloses a multi-physics coupling modeling and simulation method for the puncture process of a pouch lithium battery. The method includes the following steps: establishing an electrochemical reaction model of the lithium-ion battery based on P2D theory; simulating the electrochemical phenomena of the lithium-ion battery discharge process by constructing a 1D battery model; simulating the current distribution in the positive and negative electrode current collectors by constructing a 2D current collector electron transport model; and simulating the heat generation and heat transfer process by constructing a 3D puncture thermal model. These models are then coupled together to form a comprehensive model. This invention employs the aforementioned multi-physics coupling modeling and simulation method for the puncture process of a pouch lithium battery to simulate the SOC, voltage, current, and temperature after puncture. The electrochemical-thermal coupled full 3D modeling method provides simulation support for estimating the internal state of the pouch lithium-ion battery and studying the impact of external abuse on the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery modeling technology, and in particular to a multi-physics coupling modeling and simulation method for the puncture process of a pouch lithium battery. Background Technology

[0002] Electricity security is crucial to national security. my country has clearly made a strategic deployment to accelerate the construction of a three-dimensional and efficient energy system to ensure the safe, efficient, and sustainable energy security of unmanned platforms, portable equipment, and other fields. Currently, there are many types of energy storage power sources used in unmanned platforms and portable equipment. Lithium batteries are widely used due to their excellent high energy density. However, under various complex application conditions, lithium-ion batteries pose a risk of thermal runaway, leading to fires and explosions. This significantly limits the large-scale application of lithium-ion batteries and is a major problem hindering China's energy security capabilities and the development of next-generation unmanned intelligent swarm technologies.

[0003] In recent years, theoretical simulation has played an increasingly important role in battery technology development, addressing safety issues related to lithium-ion batteries. Compared to experimental research, theoretical simulation offers advantages such as lower cost and shorter design verification cycles. Electrochemical-thermal coupled models are the most widely used models in recent years, comprehensively considering lithium concentration, current / potential distribution, energy conservation, and electrochemical reaction processes within the battery. They can simultaneously obtain information on electrochemical processes and temperature distribution within the battery, exhibiting better predictability. While electrochemical-thermal coupled numerical calculation models are helpful in analyzing the failure mechanisms and thermal runaway mechanisms of lithium-ion batteries, they do not incorporate mechanical forces into the coupled numerical calculation model and cannot be used to study the kinetic response, failure mechanisms, and thermal runaway mechanisms of lithium-ion batteries under impact. Therefore, it is necessary to consider developing a multi-field coupled numerical calculation model involving mechanical, electrochemical, and thermal forces. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-physics coupling modeling and simulation method for the puncture process of pouch lithium batteries. This method is used to investigate the self-discharge, temperature distribution cloud map, and current density concentration of pouch lithium-ion batteries under internal short circuit conditions after puncture, and to conduct simulation studies on the SOC, voltage, current, and temperature after puncture. This invention adopts an electrochemical-thermal coupled full 3D modeling method to provide simulation support for estimating the internal state of pouch lithium-ion batteries and studying the impact of external abuse on the batteries.

[0005] To achieve the above objectives, this invention provides a multiphysics coupling modeling and simulation method for the puncture process of a pouch lithium battery, comprising the following steps:

[0006] Step S1: Establish an electrochemical reaction model for lithium-ion batteries based on P2D theory, and simulate the electrochemical phenomena of lithium-ion battery discharge process by constructing a 1D battery model.

[0007] Step S2: Simulate the current distribution in the positive and negative current collectors by constructing a 2D current collector electron transport model;

[0008] Step S3: Simulate the heat generation and heat transfer process by constructing a 3D thermal model of puncture, and couple these models together to form a comprehensive model.

[0009] Preferably, the electrochemical reaction model of the lithium-ion battery is a two-dimensional model P2D, which simplifies the battery geometry into a one-dimensional line segment. The basic internal single-layer structure includes three regions: negative electrode, separator, and positive electrode. Among them, the electrode structure parameters include: negative electrode thickness, separator thickness, positive electrode thickness, lateral dimension between the positive and negative electrodes, radial dimension of the electrode active particles in spherical coordinates, porosity of the electrode, volume fraction of each component, and electrode reaction surface area.

[0010] Preferably, the computational domain of the 1D battery model includes the negative electrode coating, the separator, and the positive electrode coating; the left side of the negative electrode is set to ground, i.e., the potential is 0; the positive electrode side is set to a current density interface, and the current value is calculated in real time based on the battery voltage and the short-circuit resistance during the calculation process; when the voltage is 0, the current becomes 0.

[0011] Preferably, when the lithium-ion battery is connected to a load and discharged, the voltage between the positive and negative electrodes exceeds the equilibrium voltage, and electrochemical reactions occur at both the negative and positive electrodes, causing lithium ions (Li) to... + It is extracted from the negative electrode active particles, passes through the electrolyte to the positive electrode, and is embedded in the positive electrode active particles;

[0012] The reaction rate per unit area at the electrode / electrolyte interface was calculated using the Butler-Volmer equation for electrochemical reactions, as shown below:

[0013]

[0014] Where, j Li The current density for the electrochemical reaction is expressed in A / cm². 2 i0 is the electrode reaction exchange current density at equilibrium, in A / cm². 2 ;α a α c , respectively, are the conversion coefficients of the anodic and cathode electrode reactions; R is the universal gas constant, 8.314 J / (mol·K). 3 T is the thermodynamic temperature; η is the overpotential, in volts (V); F is the Faraday constant, 96487 C / mol; φ s Let V be the average potential of the solid phase and φ be the φ value. e The average potential of the liquid phase is V; E eq This represents the equilibrium potential.

[0015] Preferably, lithium-ion Li+ The lithium ions (Li) are extracted from the surface of the active particles, thus resulting in lithium ions appearing inside the active particles. + The concentration gradient;

[0016] In lithium ion Li + Driven by the concentration gradient, lithium ions Li + Diffusion within active particles is a solid-phase diffusion process, which follows Fick's second law, as shown below:

[0017]

[0018] Where cs is the average volume concentration of lithium during solid-phase diffusion, in mol / cm³. 3 Ds is the diffusion coefficient of lithium during solid-state diffusion, in cm⁻¹ 2 / S; r is the radius of the active material particles, cm; x is the lateral dimension between the positive and negative electrodes of the battery.

[0019] Preferably, when lithium ions Li + After being extracted from the negative electrode active particles, lithium ions (Li) in the electrolyte surrounding the negative electrode sheet... + As the concentration increases, when lithium ions (Li) + After being embedded into the positive electrode active particles, lithium ions (Li) in the electrolyte surrounding the positive electrode sheet... + Concentration decreased;

[0020] Driven by a concentration gradient, lithium ions (Li) + Lithium ions diffuse from the negative electrode to the positive electrode, while simultaneously diffusing from the negative electrode to the positive electrode. + The movement is influenced by electromigration and convection, which is the liquid-phase diffusion process, as shown below:

[0021]

[0022] Where, ε e c is the volume fraction during the liquid-phase diffusion process. e The average volume concentration of lithium during liquid-phase diffusion is given in mol / cm³. 3 ; Let be the diffusion coefficient of lithium during liquid-phase diffusion, in cm. 2 / S; is the lithium-ion transference number, 1.

[0023] Preferably, electron transfer and lithium ion Li-2 are present on the current collector and the electrode. + The generation and absorption of [something] cause changes in the potential of the current collector and the electrode, which is the solid-state potential process, as shown below:

[0024]

[0025] Where, σeff ν represents the solid-phase conductivity of the electrode active material, in S / cm.

[0026] Preferably, lithium ions (Li) are present in the electrolyte. + The diffusion, migration, convection, generation, and absorption of electrolytes cause changes in the electrolyte potential, which is the liquid phase potential process, as shown below:

[0027]

[0028] in, The conductivity of the electrolyte is expressed in S / cm. Lithium-ion diffusion conductivity, S / cm;

[0029] Based on the above electrochemical P2D model principle, the electrochemical process equations of lithium-ion batteries are numerically solved.

[0030] Preferably, in step S2, the electron transport process in the current collector is simulated by constructing a 2D current collector electron transport model. Based on the previous analysis, the positive and negative current collectors of the punctured part and the positive and negative current collectors of the unpunctured part are simulated respectively. The resistance and heat generation are analyzed by simulating the current formed by electron transport. The current and potential of the current collector are calculated based on Ohm's law. Based on the potential results, the physical quantities of resistance, conductivity, electric field, current density and power loss are further calculated.

[0031] Preferably, in step S3, the 3D thermal model divides the battery into two parts: a punctured part and a non-punctured part;

[0032] First, the heat generated in the 1D battery model is loaded into the entire 3D thermal model structure of the battery. The heat generated in the punctured and non-punctured 2D current collector electron transport models is loaded into the punctured and non-punctured parts of the 3D thermal model, respectively.

[0033] Then, the ohmic heat is calculated based on the steel needle current and resistance calculated from the 1D battery model and the 2D current collector electron transport model, and then applied to the steel needle region of the 3D thermal model.

[0034] Finally, the heat transfer in the 3D thermal model structure of the battery is calculated to obtain the battery temperature distribution.

[0035] Therefore, this invention employs the aforementioned multi-physics coupling modeling and simulation method for the puncture process of a pouch lithium battery to investigate the self-discharge, temperature distribution cloud map, and current density concentration of a pouch lithium-ion battery under internal short circuit conditions after puncture, and to conduct simulation studies on the SOC, voltage, current, and temperature after puncture. This invention also uses an electrochemical-thermal coupled full 3D modeling method to provide simulation support for estimating the internal state of a pouch lithium-ion battery and studying the impact of external abuse on the battery.

[0036] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0037] Figure 1 This is a flowchart of a multi-physics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to the present invention;

[0038] Figure 2 This is the 1D battery model of the present invention;

[0039] Figure 3 This is the 2D current collector electron transport model of the present invention; wherein, (a) is the positive current collector; (b) is the negative current collector; and (c) is the unpunctured current collector;

[0040] Figure 4 This is the 3D thermal model of the present invention;

[0041] Figure 5 This is the voltage evolution curve during the discharge process in an embodiment of the present invention;

[0042] Figure 6 This describes the evolution of the SOC (State of Charge) of the positive and negative electrodes of the battery during the needle penetration process in this embodiment of the invention.

[0043] Figure 7 This is the evolution of the voltage of the battery tabs when punctured in the embodiments of the present invention;

[0044] Figure 8 This refers to the heat generated by the battery and the steel needle in the embodiments of the present invention;

[0045] Figure 9 This refers to the heat generation of the current collector tab in the embodiment of the present invention (the y-coordinate is very small);

[0046] Figure 10 This describes the evolution of the highest temperatures of the tabs, battery, and needles in the embodiments of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] like Figure 1 As shown, this invention provides a multi-physics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery. Based on COMSOL Multiphysics software, it employs a COMSOL lithium-ion battery model, a heat transfer module, and a current conservation module to simulate and analyze the electrochemical and thermal aspects of the puncture process, simulating battery puncture under different conditions. This invention establishes a triple numerical model, including the following steps:

[0049] Step S1: Establish an electrochemical reaction model for lithium-ion batteries based on P2D theory, and simulate the electrochemical phenomena of lithium-ion battery discharge process by constructing a 1D battery model.

[0050] The electrochemical reaction model of lithium-ion batteries is a two-dimensional (P2D) model, which simplifies the battery geometry to a one-dimensional line segment. The basic internal single-layer structure mainly includes three regions: the negative electrode, the separator, and the positive electrode. Specific electrode structure parameters include: negative electrode thickness, separator thickness, positive electrode thickness, lateral dimension between the positive and negative electrodes, radial dimension of the electrode active particles in spherical coordinates, electrode porosity, volume fraction of each component, and electrode reaction surface area, etc.

[0051] 1D battery model such as Figure 2 As shown, the computational domain includes the negative electrode coating, the separator, and the positive electrode coating. The left side of the negative electrode is electrically grounded, meaning its potential is 0. The positive electrode side is equipped with a current density interface; this current value is calculated in real-time based on the battery voltage and the short-circuit resistance during the calculation process. When the voltage is 0, the current becomes 0.

[0052] When a lithium-ion battery is connected to a load for discharge, the open-circuit equilibrium is disrupted. The voltage between the positive and negative electrodes exceeds the equilibrium voltage, and electrochemical reactions occur at both electrodes. This causes lithium ions to be released from the active particles of the negative electrode, pass through the electrolyte, reach the active particles of the positive electrode, and embed themselves. The reaction rate per unit area at the electrode / electrolyte interface is calculated using the Butler-Volmer equation, as shown below:

[0053]

[0054] Where, j Li The current density for the electrochemical reaction is expressed in A / cm². 2 i0 is the electrode reaction exchange current density at equilibrium, in A / cm². 2 ;α a α c , respectively, are the conversion coefficients of the anodic and cathode electrode reactions; R is the universal gas constant, 8.314 J / (mol·K). 3 T is the thermodynamic temperature; η is the overpotential, in volts (V); F is the Faraday constant, 96487 C / mol; φ s Let V be the average potential of the solid phase and φ be the φ value. e The average potential of the liquid phase is V; E eq This represents the equilibrium potential.

[0055] Lithium ion Li + It is extracted from the surface of the active particles, therefore a lithium ion (Li) will appear inside the active particles. + The concentration gradient. Driven by this concentration gradient, lithium ions (Li) +Diffusion within active particles, a process known as solid-phase diffusion, follows Fick's second law, as shown below:

[0056]

[0057] Where cs is the average volume concentration of lithium during solid-phase diffusion, in mol / cm³. 3 Ds is the diffusion coefficient of lithium during solid-state diffusion, in cm⁻¹ 2 / S; r is the radius of the active material particles, cm; x is the lateral dimension between the positive and negative electrodes of the battery.

[0058] When lithium ions Li + After being extracted from the negative electrode active particles, lithium ions (Li) in the electrolyte surrounding the negative electrode sheet... + As the concentration increases, when lithium ions (Li) + After being embedded into the positive electrode active particles, lithium ions (Li) in the electrolyte surrounding the positive electrode sheet... + As the concentration decreases, a concentration gradient exists within the electrolyte inside the battery. Driven by this concentration gradient, lithium ions (Li)... + Lithium ions diffuse from the negative electrode to the positive electrode, while simultaneously diffusing from the negative electrode to the positive electrode. + They move under the influence of factors such as electromigration and convection; this process is called liquid-phase diffusion, as shown below:

[0059]

[0060] Where, ε e c is the volume fraction during the liquid-phase diffusion process. e The average volume concentration of lithium during liquid-phase diffusion is given in mol / cm³. 3 ; Let be the diffusion coefficient of lithium during liquid-phase diffusion, in cm. 2 / S; is the lithium-ion transference number, 1.

[0061] Electron transfer and lithium ion Li-2O2 processes occur on the current collector and electrode. + The generation and absorption of [something] cause a change in the potential of the current collector and the electrode. This process is called the solid-state potential process, as shown below:

[0062]

[0063] Where, σ eff ν represents the solid-phase conductivity of the electrode active material, in S / cm.

[0064] Lithium ions (Li) are present in the electrolyte. + The diffusion, migration, convection, generation, and absorption of electrolytes cause changes in the electrolyte potential. This process is called the liquid phase potential process, as shown below:

[0065]

[0066] in, The conductivity of the electrolyte is expressed in S / cm. ν is the lithium-ion diffusion conductivity, S / cm.

[0067] Based on the above electrochemical P2D model theory, the electrochemical process equations of lithium-ion batteries are numerically solved.

[0068] Step S2: Simulate the current distribution in the positive and negative current collectors by constructing a 2D current collector electron transport model.

[0069] The 2D current collector electron transport model mainly simulates the electron transport process in the current collector. Based on the previous analysis, the positive and negative current collectors in the punctured portion and the positive and negative current collectors in the unpunctured portion are simulated separately. The mesh generation and boundary conditions are as follows: Figure 3 As shown, resistance and heat generation are effectively analyzed by simulating the current generated by electron transport. The current and potential of the current collector are calculated based on Ohm's law. Based on the potential results, further calculations are performed on physical quantities such as resistance, conductivity, electric field, current density, and power loss.

[0070] Step S3: Simulate the heat generation and heat transfer process by constructing a 3D thermal model of puncture, and couple these models together to form a comprehensive model.

[0071] like Figure 4 As shown, the 3D thermal model mainly divides the battery into two parts: the punctured part and the non-punctured part.

[0072] First, the heat generated in the 1D battery model is loaded into the entire 3D thermal model structure of the battery. Then, the heat generated in the punctured and unpunctured 2D current collector electron transport models is loaded into the punctured and unpunctured parts of the 3D thermal model, respectively.

[0073] Then, ohmic heat is calculated based on the steel needle current and resistance calculated from the 1D battery model and the 2D current collector electron transport model, and applied to the steel needle region of the 3D thermal model.

[0074] Finally, the heat transfer in the 3D thermal model structure of the battery is calculated to obtain the battery temperature distribution.

[0075] Example

[0076] This embodiment takes the 602040 lithium-ion battery as an example, and its parameters are shown in Table 1.

[0077] Table 1602040 Lithium-ion Battery Parameters

[0078]

[0079]

[0080] 1. The model constructed in this invention is subjected to charge and discharge simulation, and the results are compared and analyzed with experimental data.

[0081] The voltage evolution curves of the battery during discharge at currents of 200mA and 500mA, respectively, are shown below. Figure 5 As shown.

[0082] The accuracy of the model is evaluated using mean absolute error and root mean square error. Mean absolute error is the average of the absolute errors between the results of multiple measurements or calculations and the true value, as shown below:

[0083]

[0084] Where MAE represents the mean absolute error, X i Let X represent the result of the i-th calculation. t,i The value represents the i-th measurement; n represents the number of measurements or calculations.

[0085] The root mean square error is the square root of the average of the sum of the squares of the absolute errors between the results of multiple measurements or calculations and the true value, as shown below:

[0086]

[0087] Where RMSE represents the root mean square error, X i Let X represent the result of the i-th calculation. t,i The value represents the i-th measurement; n represents the number of measurements or calculations.

[0088] The measured mean absolute error was 0.0263V, and the root mean square error was 4.20%.

[0089] 2. The algorithm is applied using the common scenario of a steel needle completely piercing the battery without remaining inside it as an example.

[0090] At this point, the calculation needs to consider the previously mentioned 1D battery model, 2D current collector electron transport model, and puncture 3D thermal model. The residence time of the steel needle inside the battery is calculated based on the needle's velocity. This simplifies the internal short-circuit process that occurs within this time, and it is assumed that the battery will no longer experience a short circuit after the needle exits.

[0091] like Figure 6 As shown, the state of charge (SOC) evolution of the positive and negative electrodes of the battery during the needle penetration process, the self-discharge of the battery during the needle penetration short circuit, and the lithium-ion Li + The energy is transferred from the negative electrode to the positive electrode. The SOC at the negative electrode decreases, while the SOC at the positive electrode increases. Under this condition, the steel needle remains inside the battery for a very short time, the short-circuit time between the positive and negative electrodes is very low, and the change in SOC is minimal.

[0092] like Figure 7 As shown, the voltage evolution of the battery tabs after being punctured is as follows: the voltage drops rapidly to below 0.8V after a short circuit, but rises rapidly to the open-circuit voltage after the steel needle penetrates the battery.

[0093] like Figure 8 and Figure 9 The heat generation power shown refers to the heat generated during the electrochemical reaction of the battery. The heat generated by the current collector, tabs, and steel needle refers to the Joule heat generated when current flows through them. Since almost no current flows through the positive and negative electrode tabs, the heat generated by the tabs is very small. Furthermore, the steel needle pierces all electrode layers, creating a short circuit in each layer, resulting in almost no current flow between the layers. The current passing through the steel needle is also smaller than if only half the electrode was pierced. However, the battery short circuit time is very short; after the steel needle penetrates the battery, the positive and negative electrodes are no longer short-circuited.

[0094] The highest temperature evolution process of the battery body, tabs and steel pins, such as Figure 10 As shown, the highest temperature occurs inside the steel needle.

[0095] Therefore, this invention employs the aforementioned multi-physics coupling modeling and simulation method for the puncture process of a pouch lithium battery to investigate the self-discharge, temperature distribution cloud map, and current density concentration of a pouch lithium-ion battery under internal short circuit conditions after puncture, and to conduct simulation studies on the SOC, voltage, current, and temperature after puncture. This invention also uses an electrochemical-thermal coupled full 3D modeling method to provide simulation support for estimating the internal state of a pouch lithium-ion battery and studying the impact of external abuse on the battery.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery, characterized in that, Includes the following steps: Step S1: Establish an electrochemical reaction model for lithium-ion batteries based on P2D theory, and simulate the electrochemical phenomena of lithium-ion battery discharge process by constructing a 1D battery model. Step S2: Simulate the current distribution in the positive and negative current collectors by constructing a 2D current collector electron transport model, simulating the positive and negative current collectors in the punctured part and the positive and negative current collectors in the unpunctured part respectively; analyze the resistance and heat generation by simulating the current formed by electron transport; calculate the current and potential of the current collector based on Ohm's law; based on the potential results, further calculate the physical quantities of resistance, conductivity, electric field, current density and power loss. Step S3: Simulate heat generation and heat transfer processes by constructing a 3D thermal model of puncture, and couple these models together to form a comprehensive model; The 3D thermal model divides the battery into two parts: the punctured part and the non-punctured part; First, the heat generated in the 1D battery model is loaded into the entire 3D thermal model structure of the battery. The heat generated in the punctured and non-punctured 2D current collector electron transport models is loaded into the punctured and non-punctured parts of the 3D thermal model, respectively. Then, the ohmic heat is calculated based on the steel needle current and resistance calculated from the 1D battery model and the 2D current collector electron transport model, and then applied to the steel needle region of the 3D thermal model. Finally, the heat transfer in the 3D thermal model structure of the battery is calculated to obtain the battery temperature distribution.

2. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 1, characterized in that: The electrochemical reaction model of lithium-ion batteries is a two-dimensional model, P2D, which simplifies the battery geometry into a one-dimensional line segment. The basic internal single-layer structure includes three regions: negative electrode, separator, and positive electrode. Among them, the electrode structure parameters include: negative electrode thickness, separator thickness, positive electrode thickness, lateral dimension between the positive and negative electrodes, radial dimension of the electrode active particles in spherical coordinates, porosity of the electrode, volume fraction of each component, and electrode reaction surface area.

3. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 1, characterized in that: The computational domain of the 1D battery model includes the negative electrode coating, the separator, and the positive electrode coating; the left side of the negative electrode is set to ground, i.e., the potential is 0; the positive electrode side is set to a current density interface, and the current value is calculated in real time based on the battery voltage and the short-circuit resistance during the calculation process; when the voltage is 0, the current becomes 0.

4. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 3, characterized in that: When a lithium-ion battery is connected to a load and discharged, the voltage between the positive and negative electrodes exceeds the equilibrium voltage. Electrochemical reactions occur at both the positive and negative electrodes, causing lithium ions (Li) to... + It is extracted from the negative electrode active particles, passes through the electrolyte to the positive electrode, and is embedded in the positive electrode active particles; The reaction rate per unit area at the electrode / electrolyte interface was calculated using the Butler-Volmer equation for electrochemical reactions, as shown below: ； in, The current density for the electrochemical reaction is expressed in A / cm². 2 ; The electrode reaction exchange current density at equilibrium, in A / cm². 2 ; , These are the conversion coefficients of the anode and cathode electrode reactions, respectively. The universal gas constant is 8.314 J / (mol·K). 3 ); Thermodynamic temperature; For overpotential, V; The value is Faraday's constant, 96487 C / mol; Let V be the average potential of the solid phase. The average potential of the liquid phase is V; This represents the equilibrium potential.

5. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 4, characterized in that: Lithium ion Li + The lithium ions (Li) are extracted from the surface of the active particles, thus resulting in lithium ions appearing inside the active particles. + The concentration gradient; In lithium ion Li + Driven by the concentration gradient, lithium ions Li + Diffusion within active particles is a solid-phase diffusion process, which follows Fick's second law, as shown below: ； in, The average volume concentration of lithium during solid-phase diffusion is given in mol / cm³. 3 ; Let be the diffusion coefficient of lithium during solid-state diffusion, in cm. 2 / S; Where is the particle radius of the active material, in cm; This refers to the lateral dimension between the positive and negative electrodes of the battery.

6. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 5, characterized in that: When lithium ions Li + After being extracted from the negative electrode active particles, lithium ions (Li) in the electrolyte surrounding the negative electrode sheet... + As the concentration increases, when lithium ions (Li) + After being embedded into the positive electrode active particles, lithium ions (Li) in the electrolyte surrounding the positive electrode sheet... + Concentration decreased; Driven by a concentration gradient, lithium ions (Li) + Lithium ions diffuse from the negative electrode to the positive electrode, while simultaneously diffusing from the negative electrode to the positive electrode. + The movement is influenced by electromigration and convection, which is the liquid-phase diffusion process, as shown below: ； in, This represents the volume fraction during the liquid-phase diffusion process. The average volume concentration of lithium during liquid-phase diffusion is given in mol / cm³. 3 ; Let be the diffusion coefficient of lithium during liquid-phase diffusion, in cm. 2 / S; This represents the lithium-ion transference number.

7. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 6, characterized in that, Electron transfer and lithium ion Li-2O2 processes occur on the current collector and electrode. + The generation and absorption of [something] cause changes in the potential of the current collector and the electrode, which is the solid-state potential process, as shown below: ； in, ν represents the solid-phase conductivity of the electrode active material, in S / cm.

8. The multiphysics coupling modeling and simulation method for the puncture process of a soft-pack lithium battery according to claim 7, characterized in that, Lithium ions (Li) are present in the electrolyte. + The diffusion, migration, convection, generation, and absorption of electrolytes cause changes in the electrolyte potential, which is the liquid phase potential process, as shown below: ； in, The electrolyte conductivity is expressed in S / cm. Lithium-ion diffusion conductivity, S / cm; Based on the principle of the electrochemical P2D model, the electrochemical process equations of lithium-ion batteries are solved numerically.

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