Construction method of winding type lithium battery full-three-dimensional electric-thermal coupling simulation model

Abstract

The invention discloses a winding type lithium battery full-three-dimensional electric-thermal coupling simulation model construction method. The method comprises the following steps: firstly, disassembling the lithium battery, and measuring geometric parameters of each component; then, constructing a full-three-dimensional electric-thermal coupling simulation model of the lithium battery; and finally, a P2D model is constructed, parameters of the P2D model are adjusted and optimized, the adjusted and optimized parameters of the P2D model are transmitted to the lithium battery full-three-dimensional electric-thermal coupling simulation model, secondary adjustment and optimization are performed on key sensitive parameters in the lithium battery full-three-dimensional electric-thermal coupling simulation model based on a parameter adjustment strategy of first medium-high temperature and second low temperature, and the lithium battery full-three-dimensional electric-thermal coupling simulation model is obtained. Simulation values of the terminal voltage and the temperature are obtained through the simulation model, the simulation values of the terminal voltage and the temperature are compared with experimental values, and if the error is smaller than or equal to a set threshold value, an optimal lithium battery full-three-dimensional electro-thermal coupling simulation model is obtained; otherwise, correcting the key sensitive parameters until the error is smaller than or equal to a set threshold value. According to the method, cross-dimension parameter mapping is realized, secondary tuning is carried out on key sensitive parameters, and the modeling and optimization efficiency is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of design, optimization and application of lithium-ion battery simulation models, and particularly relates to a method for constructing a full three-dimensional electro-thermal coupling simulation model of a wound lithium battery. Background Art

[0002] With the wide application of lithium-ion batteries in fields such as electric vehicles and energy storage systems, their performance, lifespan and safety have become core challenges in the research and industrialization process. In actual applications, lithium-ion batteries not only need to meet the requirements of high energy density and long cycle life, but also need to maintain stable thermal management and electrochemical performance under complex working conditions. However, due to the strong coupling characteristics of the electrochemical reactions and thermal effects inside the battery, its dynamic response behavior is affected by various factors, including temperature distribution, current rate, charge-discharge rate, and aging of internal battery materials. These factors may lead to performance degradation, thermal runaway and even safety hazards during actual use of the battery. Therefore, it is necessary to construct a simulation model to simulate and analyze the thermal behavior of the battery.

[0003] Currently, the simulation modeling research on lithium-ion batteries mainly focuses on aspects such as electrochemical models, thermal models and electro-thermal coupling models. However, the existing models still have the following deficiencies in terms of accuracy and applicability: First, the model accuracy is insufficient. Traditional P2D models mostly adopt simplified assumptions and are difficult to accurately describe the complex physical and chemical processes inside the battery. Especially under high-rate charge-discharge or extreme temperature conditions, there are large deviations between the simulation results and the actual working conditions. Second, the coupling effect is limited. Existing electro-thermal coupling models are mostly based on one-dimensional or two-dimensional simplifications, which can effectively analyze the global performance of the battery to a certain extent, but there are still obvious limitations in the analysis of local battery states and details. Especially, it is difficult to accurately capture the complex physical processes and local phenomena inside the wound lithium battery, and it is impossible to comprehensively reflect the full three-dimensional temperature distribution and electrochemical behavior inside the battery, resulting in the simulation results being difficult to guide actual design optimization. Even if the model dimension is extended to improve the information dimension of the lithium battery, the high-dimensional characteristics of the model lead to a long tuning process and a significant decrease in computational efficiency. Finally, parameter tuning is difficult. The battery model involves a large number of parameters, and there is a strong correlation between the parameters. During the tuning process, it is urgent to formulate a clear and systematic parameter tuning strategy. Existing tuning methods mostly rely on experience or local optimization, lacking systematicness and globality, and it is difficult to achieve efficient calibration of model parameters. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the technical problem to be solved by the present invention is to provide a method for constructing a full three-dimensional electro-thermal coupling simulation model of a wound lithium battery.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] A method for constructing a full three-dimensional electro-thermal coupling simulation model of a wound lithium battery, characterized by comprising the following steps:

[0007] Step 1: Disassemble the wound lithium battery to obtain the components of the lithium battery, and measure the geometric parameters of each component;

[0008] Step 2: Construct a full three-dimensional electro-thermal coupling simulation model of the lithium battery, including a geometric model, an electrochemical model, and a thermal model;

[0009] Construct a winding unit structure according to the length and thickness of each component of the lithium battery. The winding unit structure is stacked in the order of "positive current collector - positive electrode - separator - negative electrode - negative current collector - negative electrode - separator - positive electrode", starting from the positive current collector and winding from the inside out, so that the positive current collector is directly connected to the positive electrode tab; with the negative current collector as the end, and the negative current collector is directly connected to the negative electrode tab; then stretch the winding unit structure according to the width of each component of the lithium battery to obtain a full three-dimensional geometric model of the lithium battery;

[0010] Step 3: Adjust the parameters of the full three-dimensional electro-thermal coupling simulation model of the lithium battery to obtain the best full three-dimensional electro-thermal coupling simulation model of the lithium battery under different working conditions;

[0011] Construct a P2D model, and optimize the parameters of the P2D model based on the experimental data of the terminal voltage and temperature rise of the lithium battery; transfer the optimized parameters of the P2D model to the full three-dimensional electro-thermal coupling simulation model of the lithium battery, and based on the parameter adjustment strategy of "first medium and high temperature, then low temperature", perform secondary optimization on the key sensitive parameters in the full three-dimensional electro-thermal coupling simulation model of the lithium battery. Obtain the simulation values of the terminal voltage and temperature through the simulation model, and compare the simulation values of the terminal voltage and temperature with the experimental values. If the error is less than or equal to the set threshold, the best full three-dimensional electro-thermal coupling simulation model of the lithium battery is obtained; otherwise, correct the key sensitive parameters until the error is less than or equal to the set threshold; the key sensitive parameters include the solid-phase diffusion coefficient of lithium ions, the liquid-phase diffusion coefficient of lithium ions, the reaction rate constant, the electrolyte conductivity, the liquid-phase volume fraction, the particle radius of the electrode material, and the convective heat transfer coefficient.

[0012] Further, the electrochemical model includes:

[0013] The concentration distribution equation of lithium ions in spherical particles is described by Fick's law in spherical coordinates, then there is:

[0014]

[0015] The boundary conditions are:

[0016]

[0017] In the formula, cs (x, r, t) represents the lithium-ion concentration at radius r of a spherical particle at coordinate x at time t. is the lithium-ion solid-phase diffusion coefficient, R s is the radius of the electrode material particle, and j(x, t) is the reaction current density.

[0018] The concentration distribution equation of lithium ions in the liquid phase is:

[0019]

[0020] In the formula, c e (x, t) represents the lithium-ion concentration at coordinate x in the liquid phase at time t, ε e is the liquid-phase volume fraction, a s is the specific surface area of the solid-phase particles, t + represents the lithium-ion transference number. is the lithium-ion liquid-phase diffusion coefficient.

[0021] Based on Ohm's law, the solid-phase potential distribution equation in the electrode region is as follows:

[0022]

[0023] In the formula, σ eff is the effective solid-phase conductivity of the electrode, φ s (x, t) represents the solid-phase potential at coordinate x in the electrode region, and F is the Faraday constant.

[0024] Based on Ohm's law, the liquid-phase potential distribution equation in the electrode region is:

[0025]

[0026] In the formula, κ eff is the electrolyte conductivity, φ e (x, t) represents the liquid-phase potential at coordinate x in the electrode region, R represents the ideal gas constant, and T represents the battery temperature.

[0027] The charge transfer process at the solid-liquid interface is described by the Bulter-Volmer equation, so there is:

[0028]

[0029] η = φ s (x, t) - φ e (x, t) - U ocv (9)

[0030] In the formula, i0(x, t) is the exchange current density at coordinate x, α a 、α cThey are all transfer coefficients, η represents the reaction overpotential, and k eff is the reaction rate constant, is the lithium-ion concentration on the surface of the electrode solid-phase particles at coordinate x, is the maximum lithium-ion concentration in the electrode solid-phase particles, is the reference concentration of lithium ions in the liquid phase, and U ocv is the open-circuit potential of the electrode material;

[0031] The input quantity of the full three-dimensional electro-thermal coupling simulation model of the lithium battery is the external current, and its relationship with the charge and discharge current density is as follows:

[0032]

[0033] In the formula, I(t) is the external current of the lithium battery at time t, S is the effective area of the electrode, and i(t) is the charge and discharge current density of the lithium battery;

[0034] The output of the lithium battery, that is, the terminal voltage, is the potential difference between the solid phases at the boundaries of the positive and negative electrodes, which is expressed as:

[0035]

[0036] In the formula, is the solid-phase potential at the end of the positive electrode close to the positive current collector, is the solid-phase potential at the end of the negative electrode close to the negative current collector;

[0037] The thermal model includes:

[0038] Assuming that the heat generation inside the lithium battery is evenly distributed, the calculation formula for the heat generation rate q per unit volume inside the lithium battery is as follows:

[0039]

[0040] In the formula, V cell is the volume of a single battery cell, I is the current, U is the working voltage, is the temperature coefficient of the battery;

[0041] For a wound lithium battery, the numerical model equation is established in polar coordinates as follows:

[0042]

[0043] In the formula, k r 、k θ 、k z are the thermal conductivities of the lithium battery in the r, θ, and z directions respectively, and ρ and c p are the density and specific heat capacity of the lithium battery;

[0044] According to Newton's cooling law, the boundary conditions of the lithium battery thermal model are expressed as follows:

[0045]

[0046] In the formula, λ is the thermal conductivity of the battery housing, n is the radial vector of the battery, h is the convective heat transfer coefficient, T amb is the temperature of the surrounding fluid, and T surf is the temperature of the battery surface.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] 1. The winding unit structure is stacked in the order of "positive current collector - positive electrode - separator - negative electrode - negative current collector - negative electrode - separator - positive electrode", and is wound from the inside out with the positive current collector as the starting end, so that the positive current collector can be directly connected to the positive electrode tab, with the negative current collector as the end, and the negative current collector is directly connected to the negative electrode tab. Furthermore, a high-precision full three-dimensional geometric model is constructed, realizing refined modeling, making up for the limitations of the traditional P2D model in describing spatial distribution, and being able to accurately describe the complex physical processes inside the battery, especially the local temperature gradient and potential distribution characteristics.

[0049] 2. Since the battery thickness is extremely sensitive to the simulation results, and both the P2D model and the full three-dimensional model are based on the same physical process for modeling, and their focuses in battery simulation are the same, covering phenomena such as ion diffusion, electrochemical reaction, electron conduction, and heat conduction inside the electrode. Therefore, the P2D model is used for preliminary parameter adjustment, and the optimized parameters of the P2D model are transferred to the full three-dimensional model to achieve cross-dimensional parameter mapping, realizing the efficient transfer and optimization of parameters, and significantly improving the simulation efficiency.

[0050] 3. Based on the parameter adjustment strategy of "first medium and high temperature, then low temperature", the key sensitive parameters are secondarily optimized to achieve the secondary optimization of the full three-dimensional model, significantly improving the optimization efficiency and accuracy of the model parameters. The full three-dimensional model and the optimization method are applicable to different types of lithium-ion batteries, providing a general solution for battery performance optimization and safety assessment, and having wide applicability.

[0051] Therefore, the present invention has the advantages of high-precision modeling, multi-dimensional collaborative optimization, efficient parameter adjustment, and wide applicability, etc., and can significantly improve the practicality and reliability of the lithium-ion battery simulation model. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is the overall flow schematic diagram of the present invention;

[0053] Figure 2 is the schematic diagram of the winding unit structure of the present invention;

[0054] Figure 3The terminal voltage change curves of the P2D model and the full three-dimensional model of the embodiments of the present invention under the conditions of 25°C and 1C discharge;

[0055] Figure 4 The temperature rise change curves of the P2D model and the full three-dimensional model of the embodiments of the present invention under the conditions of 25°C and 1C discharge;

[0056] Figure 5 The temperature change curves corresponding to adjusting the convective heat transfer coefficient in the embodiments of the present invention;

[0057] Figure 6 The terminal voltage change curves corresponding to adjusting the activation energies of the diffusion coefficients of the positive and negative electrodes and the electrolyte in the embodiments of the present invention;

[0058] Figure 7 The terminal voltage change curves corresponding to adjusting the reaction rate constant in the embodiments of the present invention;

[0059] Figure 8 The terminal voltage change curves corresponding to adjusting the activation energies of the liquid phase volume fraction of the negative electrode and the electrolyte conductivity in the embodiments of the present invention;

[0060] Figure 9 The terminal voltage change curves corresponding to adjusting the particle radii of the positive and negative electrode materials in the embodiments of the present invention;

[0061] Figure 10 The comparison between the terminal voltage simulation and the experimental results during the charge and discharge process at 25°C in the embodiments of the present invention;

[0062] Figure 11 The comparison between the temperature rise simulation and the experimental results during the charging process at 25°C in the embodiments of the present invention;

[0063] Figure 12 The comparison between the temperature rise simulation and the experimental results during the discharging process at 25°C in the embodiments of the present invention;

[0064] Figure 13 The comparison between the terminal voltage simulation and the experimental results during the charge and discharge process at 0°C in the embodiments of the present invention;

[0065] Figure 14 The comparison between the temperature rise simulation and the experimental results during the charging process at 0°C in the embodiments of the present invention;

[0066] Figure 15 The comparison between the temperature rise simulation and the experimental results during the discharging process at 0°C in the embodiments of the present invention. Specific Embodiments

[0067] Specific embodiments are given below in conjunction with the accompanying drawings. The specific embodiments are only used to introduce the technical solutions of the present invention in detail and do not limit the protection scope of this application.

[0068] The present invention provides a method for constructing a full three-dimensional electro-thermal coupling simulation model of a wound lithium battery, comprising the following steps:

[0069] First step: Disassemble the wound lithium battery to obtain the components of the lithium battery, including the positive electrode, negative electrode, separator, positive current collector, and negative current collector; use precision measuring tools to measure the geometric parameters of the positive electrode, negative electrode, separator, positive current collector, and negative current collector respectively, including length, width, and thickness;

[0070] Second step: Construct a full three-dimensional electro-thermal coupling simulation model of the lithium battery, including a geometric model, an electrochemical model, and a thermal model;

[0071] The electrochemical mathematical model of the lithium battery includes:

[0072] Based on the P2D theory, the present invention accurately describes the electrochemical reaction process inside the lithium battery. The diffusion equation of lithium ions in spherical particles, i.e., the concentration distribution equation, is described by Fick's law in spherical coordinates, so there is:

[0073]

[0074] The boundary conditions are:

[0075]

[0076] In the formula, c s (x, r, t) represents the concentration of lithium ions at the radius r of the spherical particle at the coordinate x at time t, is the solid-phase diffusion coefficient of lithium ions, R s is the radius of the electrode material particles; j(x, t) is the reaction current density, characterizing the electrochemical reaction rate at the solid-liquid interface;

[0077] The transport of lithium ions in the liquid phase is mainly diffusion and migration, and its concentration distribution equation is:

[0078]

[0079] In the formula, c e (x, t) represents the concentration of lithium ions at the coordinate x in the liquid phase at time t, ε e is the liquid-phase volume fraction, a s is the specific surface area of the solid-phase particles, t + represents the lithium ion transference number, is the liquid-phase diffusion coefficient of lithium ions, calculated by the Bruggeman equation;

[0080]

[0081] In the formula, D e is the electrolyte diffusion coefficient, is the Bruggman coefficient, usually taking a value of 1.5;

[0082] Based on Ohm's law, the solid-phase potential distribution equation in the electrode region is as follows:

[0083]

[0084] where σ eff is the effective solid-phase conductivity of the electrode, and φ s (x, t) represents the solid-phase potential at coordinate x in the electrode region, F is the Faraday constant;

[0085] Based on Ohm's law, the liquid-phase potential distribution equation in the electrode region is:

[0086]

[0087] where κ eff is the electrolyte conductivity, and φ e (x, t) represents the liquid-phase potential at coordinate x in the electrode region, R represents the ideal gas constant, and T represents the battery temperature;

[0088] At the solid-liquid interface, charge transfer occurs on the surface where the active material particles contact the electrolyte. The charge transfer process is described by the Bulter-Volmer equation, so there is:

[0089]

[0090] η = φ s (x, t) - φ e (x, t) - U ocv (9)

[0091] where i0(x, t) is the exchange current density at coordinate x, α a , α c are both transfer coefficients, η represents the reaction overpotential, k eff is the reaction rate constant, is the lithium-ion concentration on the surface of the electrode solid-phase particles at coordinate x, is the maximum lithium-ion concentration in the electrode solid-phase particles, is the reference concentration of lithium ions in the liquid phase, and U ocv is the open-circuit potential of the electrode material;

[0092] The only input quantity of the full three-dimensional electro-thermal coupling simulation model of the lithium battery is the external current, and its relationship with the charge and discharge current density is as follows:

[0093]

[0094] Where, \(I(t)\) is the external current of the lithium battery at time \(t\), \(S\) is the effective area of the electrode, and \(i(t)\) is the charge-discharge current density of the lithium battery;

[0095] The output of the lithium battery, i.e., the terminal voltage, is the boundary solid-phase potential difference between the positive and negative electrodes, which is expressed as:

[0096]

[0097] Where, is the solid-phase potential at the end of the positive electrode close to the positive current collector, is the solid-phase potential at the end of the negative electrode close to the negative current collector;

[0098] The mathematical model of heat transfer and heat dissipation of the lithium battery is:

[0099] For the heat generation of the lithium battery, the first law of thermodynamics is mostly used to calculate the heat generation; assuming that the internal heat generation of the lithium battery is uniformly distributed, the calculation formula for the heat generation rate \(q\) per unit volume inside the lithium battery is as follows:

[0100]

[0101] Where, the first term is the irreversible Joule heat, the second term is the reversible reaction heat, \(V\) cell is the volume of a single battery cell; \(I\) is the current, which is positive during charging and negative during discharging; \(U\) is the working voltage, is the temperature coefficient of the battery;

[0102] For the wound lithium battery, the numerical model equation is established in polar coordinates as follows:

[0103]

[0104] Where, \(k\) r , \(k\) θ , \(k\) z are the thermal conductivities of the lithium battery in the \(r\), \(\theta\), and \(z\) directions respectively, and \(\rho\) and \(c\) p are the density and specific heat capacity of the lithium battery;

[0105] According to Newton's cooling law, the boundary conditions of the lithium battery thermal model are expressed as follows:

[0106]

[0107] Where, \(\lambda\) is the thermal conductivity of the battery shell, \(n\) is the battery radial vector, \(h\) is the convective heat transfer coefficient, \(T\) amb is the temperature of the surrounding fluid, and \(T\) surf is the battery surface temperature.

[0108] Construct a winding unit structure according to the lengths and thicknesses of the components of the lithium battery. The winding unit structure is laminated in the order of "positive current collector - positive electrode - separator - negative electrode - negative current collector - negative electrode - separator - positive electrode". Starting from the positive current collector as the starting end, it is wound from the inside out so that the positive current collector can be directly connected to the positive tab, thus solving the modeling problem of the positive tab; by setting the rotation angle of the winding helix, after the winding unit structure is wound, with the negative current collector as the end, and the negative current collector is directly connected to the negative tab, solving the modeling problem of the negative tab; stretch the winding unit structure according to the widths of the components of the lithium battery to obtain a full three-dimensional geometric model of the lithium battery.

[0109] In the COMSOL Multiphysics software, construct a full three-dimensional electro-thermal coupling simulation model of the lithium battery based on the electrochemical mathematical model, heat transfer and heat dissipation mathematical model, and full three-dimensional geometric model of the lithium battery.

[0110] Step 3: Adjust the parameters of the full three-dimensional electro-thermal coupling simulation model of the lithium battery to obtain the optimal full three-dimensional electro-thermal coupling simulation model of the lithium battery under different working conditions;

[0111] Since both the P2D model and the full three-dimensional electro-thermal coupling simulation model of the lithium battery are based on the same physical process, the P2D model is used for preliminary optimization, that is, a P2D model is constructed according to the thicknesses of the components of the lithium battery, the electrochemical mathematical model, heat transfer and heat dissipation mathematical model of the lithium battery; based on the experimental data of the terminal voltage and temperature rise of the lithium battery, the parameters of the P2D model are quickly optimized to ensure that the P2D model can accurately reflect the actual working state of the lithium battery; the optimized parameters of the P2D model are transferred to the full three-dimensional electro-thermal coupling simulation model of the lithium battery, and a cross-dimensional mapping relationship between the P2D model and the full three-dimensional electro-thermal coupling simulation model of the lithium battery is established based on the thickness dimension of the lithium battery to achieve efficient parameter transfer between different dimensional models;

[0112] Based on the parameter adjustment strategy of "first medium and high temperature, then low temperature", perform secondary optimization on the key sensitive parameters that significantly affect the performance of the lithium battery in the full three-dimensional electro-thermal coupling simulation model of the lithium battery to obtain the optimal full three-dimensional electro-thermal coupling simulation model of the lithium battery; the key sensitive parameters include the solid-phase diffusion coefficient of lithium ions the liquid-phase diffusion coefficient of lithium ions the reaction rate constant k eff 、the electrolyte conductivity κ eff 、the liquid-phase volume fraction ε e 、the particle radius R of the electrode material s and the convective heat transfer coefficient h, etc.;

[0113] The parameter adjustment strategy of "first medium-high temperature, then low temperature" has the following significant advantages: First, since the electrochemical reaction rate has tended to saturate under medium-high temperature conditions, when using the Arrhenius formula to correct the low-temperature parameters, the influence of the activation energy on the medium-high temperature reaction rate is small, thus ensuring that the simulation accuracy and stability under medium-high temperature conditions are not significantly affected by the correction of low-temperature parameters. Second, under medium-high temperature and low-temperature conditions, the polarization effects of lithium batteries show significant differences. Therefore, during the parameter adjustment process, the medium-high temperature and low-temperature parameters can be corrected using the same charge and discharge rate for optimization, thereby simplifying the adjustment process, avoiding the complexity brought by the interaction between temperature and rate, and obtaining a better rate performance simulation model.

[0114] Through the above parameter adjustment, efficient optimization under different working conditions (temperature and rate) can be achieved. Using the obtained full three-dimensional electro-thermal coupling simulation model, the simulation values of the terminal voltage and temperature can be obtained; comparing the simulation values of the terminal voltage and temperature with the experimental values, if the error is less than or equal to the set threshold, the best full three-dimensional electro-thermal coupling simulation model can be obtained; otherwise, the key sensitive parameters are corrected until the error is less than or equal to the set threshold.

[0115] Embodiment

[0116] In this embodiment, taking an 1800mAh wound 18650 lithium iron phosphate battery as an example, a full three-dimensional electro-thermal coupling simulation model of the lithium battery is constructed.

[0117] The first step: Disassemble the 1800mAh wound 18650 lithium iron phosphate battery to obtain the components of the lithium battery, including the positive electrode, negative electrode, separator, positive current collector, and negative current collector, and measure the geometric parameters of each component.

[0118] Table 1 Geometric parameters of each component of the battery

[0119]

[0120] The second step: Construct a wound unit structure according to the length and thickness of each component of the lithium battery. The wound unit structure is stacked in the order of "positive current collector - positive electrode - separator - negative electrode - negative current collector - negative electrode - separator - positive electrode", starting from the positive current collector, winding from the inside out, so that the positive current collector can be directly connected to the positive electrode tab; using the negative current collector as the end, and the negative current collector is directly connected to the negative electrode tab; for the wound unit structure, see Figure 2 . Stretch the wound unit structure according to the width of each component of the lithium battery to obtain a full three-dimensional geometric model of the lithium battery; in the COMSOL Multiphysics software, construct a full three-dimensional electro-thermal coupling simulation model of the lithium battery according to the electrochemical mathematical model, heat transfer and heat dissipation mathematical model, and full three-dimensional geometric model of the lithium battery.

[0121] Step 3: Adjust the parameters of the full three-dimensional electro-thermal coupling simulation model of the lithium battery to obtain the optimal full three-dimensional electro-thermal coupling simulation model of the lithium battery under different working conditions;

[0122] Construct a P2D model based on the thickness of each component of the lithium battery, the electrochemical mathematical model of the lithium battery, and the heat transfer and heat dissipation mathematical models; based on the experimental data of the terminal voltage and temperature rise of the lithium battery, quickly optimize the parameters of the P2D model to ensure that the P2D model can accurately reflect the actual working state of the lithium battery; transfer the optimized parameters of the P2D model to the full three-dimensional electro-thermal coupling simulation model of the lithium battery, and based on the parameter adjustment strategy of "first medium and high temperature, then low temperature", perform secondary optimization on the key sensitive parameters in the full three-dimensional electro-thermal coupling simulation model of the lithium battery to obtain the optimal full three-dimensional electro-thermal coupling simulation model of the lithium battery. The key sensitive parameters include the solid-phase diffusion coefficient of lithium ions The liquid-phase diffusion coefficient of lithium ions The reaction rate constant k eff 、The electrolyte conductivity κ eff 、The liquid-phase volume fraction ε e 、The particle radius R of the electrode material s And the convective heat transfer coefficient h. The first four parameters are corrected for temperature according to the Arrhenius formula. The liquid-phase diffusion coefficient of lithium ions And the electrolyte conductivity κ eff Are obtained by fitting a polynomial about the electrolyte concentration c from the interpolation data built in the COMSOL software. The key sensitive parameters after the preliminary identification and optimization of the P2D model are shown in Table 2.

[0123] Table 2 Key sensitive parameters after the optimization of the P2D model

[0124]

[0125]

[0126] Input the parameters after the preliminary optimization of the P2D model into the full three-dimensional electro-thermal coupling simulation model of the lithium battery, and select the terminal voltage and temperature to compare and verify the calculation results of the full three-dimensional model and the P2D model. The terminal voltage and temperature change curves of different models are shown in Figure 3 And Figure 4 . It can be seen from the figure that the P2D model has a high degree of coincidence with the changes in the terminal voltage and temperature rise of the full three-dimensional model. The maximum error of the terminal voltage is less than 8 mV, the root mean square error is less than 1.5 mV, the maximum error of the temperature rise is less than 0.25 °C, and the root mean square error is less than 0.1 °C, indicating that the cross-dimensional modeling strategy proposed by the present invention can effectively establish the connection between the P2D model and the full three-dimensional model, ensuring the accuracy of parameter transfer and the simulation efficiency.

[0127] Based on the parameter adjustment strategy of "first medium-high temperature, then low temperature", the key sensitive parameters are optimized for the second time in the full three-dimensional model. Using the obtained full three-dimensional electro-thermal coupling simulation model, the simulation values of the terminal voltage and temperature are obtained; the simulation values of the terminal voltage and temperature are compared with the experimental values. If the error is less than or equal to 5%, the best full three-dimensional electro-thermal coupling simulation model is obtained; otherwise, the key sensitive parameters are corrected until the error is less than or equal to 5%.

[0128] Under the conditions of 25 °C, 0 °C and 1C discharge, the convective heat transfer coefficient is gradually adjusted, and the temperature change curve is as Figure 5 shown. Along the optimization direction of the orange arrow in the figure, the overall temperature rise of the model will gradually decrease. Finally, the convective heat transfer coefficient of the best full three-dimensional electro-thermal coupling simulation model is 37 W / m 2 ·K. Under the conditions of 0 °C and 1C discharge, the activation energies of the positive and negative electrode and electrolyte diffusion coefficients are gradually adjusted, and the terminal voltage change curve is as Figure 6 shown. Along the optimization direction of the orange arrow in the figure, finally, the activation energies of the positive and negative electrode and electrolyte diffusion coefficients and are 78525.7 J / mol, 46000 J / mol and 69000 J / mol respectively. The voltage platform during discharge at 0 °C gradually decreases, accompanied by a decrease in the discharge capacity; under the conditions of 25 °C and 1C discharge, the reaction rate constant is gradually adjusted; under the conditions of 0 °C and 1C discharge, the activation energy of the reaction rate constant is gradually adjusted to determine the positive and negative electrode reaction rate constants k a and k c are 2.4×10 -10 m / s and 3.3×10 - 11 m / s respectively, and the corresponding activation energies and are 35000 J / mol and 25000 J / mol respectively. The terminal voltage change curve for adjusting the reaction rate constant is as Figure 7 shown. Along the optimization direction of the orange arrow in the figure, the voltage platforms during discharge at 25 °C and 0 °C will gradually decrease, and the discharge capacity remains unchanged; under the conditions of 0 °C and 1C discharge, the negative electrode liquid phase volume fraction and the activation energy of the electrolyte conductivity are gradually adjusted. The negative electrode liquid phase volume fraction ε e,a is determined to be 0.55, and the activation energy E ψ _κ eff of the electrolyte conductivity is determined to be 20000 J / mol. The terminal voltage change curve obtained by adjusting the negative electrode liquid phase volume fraction and the activation energy of the electrolyte conductivity is as Figure 8As shown, along the tuning direction of the orange arrow in the figure, at 0°C, the discharge voltage plateau gradually decreases while the discharge capacity remains unchanged. The particle radii of the positive and negative electrode materials are finely adjusted under the discharge conditions of 25°C, 0°C, and 1C to make the battery performance closer to the expectation, and the particle radii R e,a and R e,c are 1.06×10 -6 m and 7.3×10 -8 m respectively. The terminal voltage change curves obtained by adjusting the particle radii of the positive and negative electrode materials are as shown in Figure 9 the figure. Along the tuning direction of the orange arrow in the figure, at 25°C and 0°C, the terminal voltage curves gradually approach the experimental curves in black and pink in the figure.

[0129] After the parameter tuning is completed, the full three-dimensional model is experimentally verified, and the simulation results of the terminal voltage and temperature rise are compared with the experimental data under the conditions of 25°C and 0°C respectively. Under 25°C, the simulation results of the terminal voltage and temperature rise during the charge and discharge processes at different rates (0.5C, 0.8C, 1C, 1.2C, 1.5C, 1.8C, 2C) are compared with the experimental results to verify the accuracy of the model. Figure 10 is the comparison between the simulation and experimental results of the terminal voltage during the charge and discharge process at 25°C, Figure 11 is the comparison between the simulation and experimental results of the temperature rise during the charging process at 25°C, Figure 12 is the comparison between the simulation and experimental results of the temperature rise during the charging process at 25°C. The results show that the simulation results are in good agreement with the experimental results at 25°C. The maximum error of the terminal voltage is less than 12 mV, the root mean square error is less than 4 mV, the maximum error of the temperature rise is less than 0.4°C, and the root mean square error is less than 0.17°C. To avoid the influence of extreme loads on the battery, the rate is appropriately reduced at low temperatures. Therefore, at 0°C, the rates of 0.5C, 0.8C, and 1C are selected for charge and discharge verification. Figure 13 is the comparison between the simulation and experimental results of the terminal voltage during the charge and discharge process at 0°C, Figure 14 is the comparison between the simulation and experimental results of the temperature rise during the charging process at 0°C, Figure 15 is the comparison between the simulation and experimental results of the temperature rise during the discharging process at 0°C. The results show that the maximum error of the terminal voltage is less than 10 mV, the root mean square error is less than 3.5 mV, the maximum error of the temperature rise is less than 0.3°C, and the root mean square error is less than 0.14°C. The two are also in good agreement with the experimental data.

[0130] In summary, the parameter tuning strategy proposed by the present invention can accurately and efficiently complete the parameter optimization of the full three-dimensional electrochemical-thermal coupling model of the wound 18650 lithium iron phosphate battery, significantly improving the accuracy and applicability of the model under different working conditions.

[0131] Through the cross-dimensional mapping between the P2D model and the full three-dimensional model, the present invention realizes the preliminary optimization of the full three-dimensional electrochemical-thermal coupling simulation model of lithium batteries. Based on the parameter adjustment strategy of "first medium and high temperature, then low temperature", the accuracy and calculation efficiency of the model are significantly improved. Verified by experimental data, the optimized model can accurately predict the performance of the battery under different working conditions, providing reliable technical support for the research and development and optimization of lithium-ion batteries. When establishing the full three-dimensional electrochemical-thermal coupling simulation model of lithium batteries, since the components of the winding unit structure (such as the positive electrode, negative electrode, separator and current collector) are independent of each other and can effectively reflect the inherent characteristics or intrinsic properties of each layer structure, heat transfer parameters such as thermal conductivity, density and isobaric heat capacity do not need to be normalized and can be directly defined based on the actual physical properties of each layer of material. The heat dissipation process of the battery core is accurately described by defining the heat flux, and the external boundary of the battery core is selected as the heat dissipation boundary condition to accurately characterize its heat dissipation characteristics.

[0132] Through the above method, a full three-dimensional electrochemical-thermal coupling simulation model of lithium batteries is completely constructed. This model can ensure high-precision simulation and analysis of the thermal behavior of the battery (such as temperature distribution, thermal gradient and thermal runaway, etc.) under different working conditions, providing reliable technical support for the thermal management design and safety assessment of the battery.

[0133] Matters not described in the present invention are applicable to the prior art.

Claims

1. A method for constructing a full three-dimensional electrical-thermal coupling simulation model of a wound lithium battery, characterized in that: The following steps are involved: Step 1: Disassemble the wound lithium battery to obtain the components of the lithium battery and measure the geometric parameters of each component; Step 2: Build a full three-dimensional electrical-thermal coupling simulation model of lithium batteries, including geometric model, electrochemical model and thermal model; The winding unit structure is constructed according to the length and thickness of each component of the lithium battery. The winding unit structure is stacked in the order of "positive electrode current collector-positive electrode-diaphragm-negative electrode-negative electrode current collector-negative electrode-diaphragm-positive electrode", and is wound from the inside to the outside with the positive electrode current collector as the starting end, so that the positive electrode current collector is directly connected to the positive electrode ear; the negative electrode current collector is the end, and the negative electrode current collector is directly connected to the negative electrode ear; and the winding unit structure is stretched according to the width of each component of the lithium battery to obtain a full three-dimensional geometric model of the lithium battery; Step 3: Adjust the parameters of the full three-dimensional electrical-thermal coupling simulation model of the lithium battery to obtain the optimal full three-dimensional electrical-thermal coupling simulation model of the lithium battery under different working conditions; A P2D model is constructed, and the parameters of the P2D model are tuned based on the experimental data of the terminal voltage and temperature rise of the lithium battery. The optimized parameters of the P2D model are transferred to the full three-dimensional electro-thermal coupling simulation model of the lithium battery. Based on the parameter adjustment strategy of "medium and high temperature first, then low temperature", the key sensitive parameters are secondary tuned in the full three-dimensional electro-thermal coupling simulation model of the lithium battery. The simulation values ​​of the terminal voltage and temperature are obtained through the simulation model, and the simulation values ​​of the terminal voltage and temperature are compared with the experimental values. If the error is less than or equal to the set threshold, the optimal full three-dimensional electro-thermal coupling simulation model of the lithium battery is obtained; otherwise, the key sensitive parameters are corrected until the error is less than or equal to the set threshold. The key sensitive parameters include the solid phase diffusion coefficient of lithium ions, the liquid phase diffusion coefficient of lithium ions, the reaction rate constant, the electrolyte conductivity, the liquid phase volume fraction, the electrode material particle radius and the convection heat transfer coefficient.

2. The method for constructing a full three-dimensional electrical-thermal coupling simulation model of a wound lithium battery according to claim 1, characterized in that: The electrochemical model includes: The concentration distribution equation of lithium ions in spherical particles is described by Fick's law in the spherical coordinate system: The boundary conditions are: In the formula, c s (x,r,t) represents the lithium ion concentration at the radius r of the spherical particle at coordinate x at time t, is the solid phase diffusion coefficient of lithium ions, R s is the particle radius of the electrode material, j(x,t) is the reaction current density; The concentration distribution equation of lithium ions in the liquid phase is: In the formula, c e (x, t) represents the lithium ion concentration at coordinate x in the liquid phase at time t, ε e is the liquid volume fraction, a s is the specific surface area of ​​solid particles, t + represents the lithium ion migration number, is the liquid phase diffusion coefficient of lithium ions; Based on Ohm's law, the solid phase potential distribution equation in the electrode area is as follows: In the formula, σ eff is the solid phase effective conductivity of the electrode, φ s (x, t) represents the solid phase potential at coordinate x in the electrode region, and F is the Faraday constant; Based on Ohm's law, the liquid potential distribution equation in the electrode area is: In the formula, κ eff is the electrolyte conductivity, φ e (x, t) represents the liquid potential at coordinate x in the electrode region, R represents the ideal gas constant, and T represents the battery temperature; The charge transfer process at the solid-liquid interface is described by the Butler-Volmer equation: h=φ s (x,t)-φ e (x,t)-U ocv (9) Where i0(x,t) is the exchange current density at coordinate x, α a , α c are transfer coefficients, η represents the reaction overpotential, k eff is the reaction rate constant, is the lithium ion concentration on the surface of the electrode solid particles at coordinate x, is the maximum lithium ion concentration in the electrode solid particles, is the reference concentration of liquid lithium ions, U ocv is the open circuit potential of the electrode material; The input quantity of the full three-dimensional electrical-thermal coupling simulation model of lithium batteries is the external current, and its relationship with the charge and discharge current density is as follows: Where I(t) is the external current of the lithium battery at time t, S is the effective area of ​​the electrode, and i(t) is the charge and discharge current density of the lithium battery; The output of the lithium battery, i.e. the terminal voltage, is the boundary solid phase potential difference between the positive and negative electrodes, expressed as: In the formula, is the solid phase potential of the positive electrode close to the positive current collector, is the solid phase potential of the negative electrode close to the negative electrode current collector; The thermal model includes: Assuming that the heat generated inside the lithium battery is evenly distributed, the calculation formula for the heat generation rate per unit volume q inside the lithium battery is as follows: Where V cell is the volume of the battery cell, I is the current, U is the operating voltage, is the temperature coefficient of the battery; For wound lithium batteries, the numerical model equation is established in polar coordinates as follows: In the formula, k r , k θ , k z are the thermal conductivity of lithium batteries in the r, θ, and z directions, ρ and c p is the density and specific heat capacity of lithium battery; According to Newton's law of cooling, the boundary conditions of the lithium battery thermal model are expressed as follows: Where λ is the thermal conductivity of the battery case, n is the radial vector of the battery, h is the convection heat transfer coefficient, and T amb is the temperature of the surrounding fluid, T surf is the battery surface temperature.

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