A method and system for predicting cracking and pulverization of polycrystalline NCM electrode particles

Abstract

The application belongs to but is not limited to the technical field of electronic core industry, and discloses a polycrystalline NCM electrode particle cracking and pulverization prediction method and system, which comprises the following steps: constructing an anisotropic polycrystalline fracture phase field model, including a grain boundary phase field equation, a solid mechanics equation, a Li + diffusion equation and a fracture phase field equation; constructing a two-dimensional geometry of a polycrystalline NCM electrode particle, setting required parameters of physical fields, carrying out grid division and setting initial conditions and boundary conditions; using a finite element simulation software to perform numerical solution, and obtaining cracking and pulverization distribution of the polycrystalline NCM electrode particle. + The application considers bidirectional coupling of Li diffusion and mechanical stress, cracking and pulverization and mechanical stress, and uses grain boundary phase field calculation to correct the critical energy release rate, so that the application can accurately reflect the mechanism of cracking and pulverization of the polycrystalline NCM electrode particle, and improve the accuracy of cracking and pulverization prediction.

Description

TECHNICAL FIELD

[0001] The application belongs to but is not limited to the technical field of electronic core industry, and particularly relates to a polycrystalline NCM electrode particle cracking and pulverization prediction method and system. BACKGROUND

[0002] Lithium-ion batteries (LIBs) are widely used in electric vehicles (EVs) due to their high energy density, long cycle life, and low manufacturing cost. Despite the significant progress made in LIBs technology, the energy density remains difficult to meet the requirements of electric vehicles for power batteries. Expanding the limited range of current EVs requires the development of high-energy-density LIBs, among which nickel-rich layered LiNi 1-x-y Co x Mn y O2 cathode (NCM) is considered the most promising cathode candidate material. The energy density of NCM electrodes can be further improved by increasing the Ni content, but the performance enhancement obtained using this method comes at the expense of cycle performance and mechanical stability. During cycling, cracking and pulverization occur in NCM electrode particles, allowing electrolyte to penetrate the interior of the particles. This process has two serious consequences: first, it accelerates the degradation of the electrolyte and the surface of the NCM active material, severely damaging the available capacity and service life of the NCM electrode. Second, it reduces the electrochemical performance of the NCM particles.

[0003] Currently, experimental and simulation studies on polycrystalline NCM electrode particles are not perfect. Most experimental observations use non-in situ methods, ignoring the cracking and propagation process during charging and discharging, and lack of research on the formation mechanism and influencing mechanism of cracks. The simulation methods used are too outdated, often only analyzing the cracking process from the stress angle, and cannot accurately simulate the generation and propagation of cracks.

[0004] Through the above analysis, the problems and defects of the prior art are that the existing simulation methods are too outdated, often only analyzing the cracking process from the stress angle, and cannot accurately simulate the generation and propagation of cracks.

[0005] 1) Lack of prediction accuracy: Traditional electrode particle cracking and pulverization prediction methods are often based on empirical formulas or simplified physical models, making it difficult to accurately reflect the complex behavior of polycrystalline NCM electrode particles during charging and discharging, resulting in inaccurate prediction results.

[0006] 2) Lack of microscale analysis: The cracking and pulverization of polycrystalline NCM electrode particles is a process involving microscale, and traditional methods often have difficulty in analyzing and predicting at the microscale.

[0007] 3) The influence of anisotropy is not considered: polycrystalline materials have anisotropy, i.e. the physical properties in different directions may be different, and the traditional method tends to ignore the influence of this characteristic on cracking and pulverization. SUMMARY

[0008] In view of the problems existing in the prior art, the present application provides a polycrystalline NCM electrode particle cracking and pulverization prediction method and system, which aims to improve the accuracy of polycrystalline NCM electrode particle cracking and pulverization prediction.

[0009] The present application is implemented in the following way: a polycrystalline NCM electrode particle cracking and pulverization prediction method, comprising:

[0010] S1, constructing an anisotropic polycrystalline fracture phase field model, including a grain boundary phase field equation, a solid mechanics equation, Li + diffusion equation and fracture phase field equation;

[0011] S2, constructing a two-dimensional geometry of polycrystalline NCM electrode particles, setting the required parameters of physical fields, performing grid division and setting initial conditions and boundary conditions;

[0012] S3, using finite element simulation software to perform numerical solution, obtaining the cracking and pulverization distribution of polycrystalline NCM electrode particles.

[0013] Further, in the step S1, the grain boundary phase field equation is used to calculate the corrected critical energy release rate inside the polycrystalline NCM electrode particles, the solid mechanics equation is used to calculate the stress and elastic strain energy density distribution, the Li + diffusion equation is used to calculate the Li + concentration distribution, and the fracture phase field equation is used to calculate the cracking and pulverization distribution.

[0014] Further, in the step S2, the two-dimensional geometry of polycrystalline NCM electrode particles is drawn by the Voronoi diagram algorithm; the physical parameters set include Young's modulus, Poisson's ratio, density, temperature, Li + diffusion rate, maximum Li + concentration, reference Li + concentration, grain boundary phase field length parameter, fracture phase field length parameter, grain boundary critical energy release rate, primary particle energy release rate, unit concentration volume change, partial molar volume, and all primary particle crystal orientations; the grid division adopts triangular grid, and the maximum grid size is set to 0.02 μm; the initial conditions include grain boundary phase field initial value, Li + diffusion initial concentration, solid mechanics initial displacement, and fracture phase field initial value; the boundary conditions include grain boundary phase field Dirichlet boundary condition, Li + diffusion flux, and solid mechanics free boundary condition.

[0015] Further, in the step S2, for each primary particle in the polycrystalline NCM electrode particle, an independent spatial coordinate system is constructed, and the orientation of the coordinate system is the primary particle crystal direction.

[0016] Further, in the step S3, two solving steps are adopted to numerically solve the model. The first step is to stably solve the grain boundary phase field equation to obtain the modified critical energy release rate distribution and store it. The second step is to transiently solve the solid mechanics equation, the Li+diffusion equation and the fracture phase field equation, and the solution stored in the first step is transmitted to the second step as the numerical value of the critical energy release rate.

[0017] The grain boundary phase field equation constructed in S1 is:

[0018]

[0019] wherein p is the grain boundary phase field order parameter, l p is the grain boundary phase field length parameter, represents the Hamiltonian operator. The modified critical energy release rate G p can be written as

[0020] G p = g(p)G c_G ++((1-g(p))G c_GB

[0021] wherein g(p) = (1-p) 2 , G c_G is the critical energy release rate of the grain, and G c_GB is the critical energy release rate of the grain boundary.

[0022] Specifically, the solid mechanics equation constructed in S1 is:

[0023]

[0024] wherein is the Hamiltonian operator, and C(d) represents the modified elastic stiffness tensor;

[0025] ε e represents the elastic strain tensor:

[0026] ε e = ε - ε c ,

[0027] ε is the total strain tensor;

[0028] ε c is the chemical strain tensor:

[0029] ε c = (c - c ref )β ij,

[0030] β ij is the unit concentration volume change of anisotropy;

[0031] c represents Li + concentration, c ref represents the reference Li + concentration.

[0032] In the formula, the expression of the modified elastic stiffness tensor C(d) is:

[0033]

[0034] Wherein, C0 is the elastic stiffness tensor of normal material, k0 is the bulk modulus, I is the unit matrix, sign - is the sign function, ε e is the elastic strain tensor, tr(ε e ) is the trace of ε e ;

[0035] g(d) is the phase field degeneration function:

[0036] g(d) = (1-d) 2 +k,

[0037] k is a numerical calculation stability parameter.

[0038] The Li + diffusion equation constructed in S1 is:

[0039]

[0040] Wherein, J is the Li + molar flux per unit area per unit time, D represents the diffusion rate of Li + , represents the Hamiltonian operator, Ω ij represents the partial molar volume, R represents the ideal gas constant, T represents the Kelvin temperature, c represents the Li + concentration, c max represents the maximum Li + concentration that the material can accommodate, σ h represents the hydrostatic stress.

[0041] The fracture phase field equation constructed in S1 is:

[0042]

[0043] Wherein, G pis the modified critical energy release rate of the polycrystalline NCM electrode particle material; d is a broken phase field order parameter, d = 1 represents that the material is completely damaged, d = 0 represents that the material is intact (i.e. no failure), and 0 < d < 1 represents a transition state; l d represents a length parameter of the broken phase field, represents a Hamiltonian operator, H is defined as a historical maximum tensile strain energy density:

[0044] H = max Ψ e (t)

[0045] wherein, Ψ e (t) represents a tensile elastic strain energy density, and its expression is:

[0046]

[0047] wherein, g(d) is a phase field degradation function, ε e is an elastic strain tensor, C0 is an elastic stiffness tensor of a normal material, ε vol is an elastic strain volume component, ε dev is an elastic strain deviatoric component, and tr(ε e ) is a trace of ε e .

[0048] The polycrystalline NCM electrode particle two-dimensional geometry constructed in S2 is generated by using a Voronoi diagram algorithm, the generated two-dimensional polycrystalline geometry is a circle with a radius of 5 μm, the internal primary particles are irregular hexagons with an average particle size of 0.57 μm, and the size and shape are random.

[0049] The polycrystalline NCM electrode particle two-dimensional geometry grid constructed in S2 is divided by using a triangular grid, the maximum grid size is set to 0.02 μm, the constructed grid contains a total of 508636 triangular regions, and the degree of freedom is 5.1 million during simulation calculation.

[0050] The physical parameters set in S2 are: Young's modulus E = 120 GPa, Poisson's ratio v = 0.3, density p = 4.14 g / cm 3 , temperature T = 300 K, Li + diffusion rate D = 7 x 10 -15 m 2 / s, maximum Li + concentration c max = 35164 mol / m 3 , reference Li + concentration c max = 31648 mol / m 3 , grain boundary phase field length parameter l p = 0.05 μm, and broken phase field length parameter l d=0.05μm, grain boundary critical energy release rate G c_GB =2N / m, energy release rate of first-order particles G c_G =10 N / m. The volume change per unit concentration and the partial molar volume are anisotropic, with the volume change per unit concentration set as: β a =β b =0.597cm 3 / mol, β c =1.052cm 3 / mol. The partial molar volume is set as: Ω a =Ω b =1.79cm 3 / mol, Ω c =3.16cm 3 / mol. All primary particle crystal orientations are randomly generated and set using a script;

[0051] The initial conditions set in S2 are: the initial value of the grain boundary phase field is set to 0, and Li... + The initial diffusion concentration was set to 31648 mol / m³. 3 The initial displacement in solid mechanics is set to no displacement, and the initial value of the fracture phase field is set to 0; the boundary conditions set in S2 are: Dirichlet boundary conditions are set for the grain boundaries of polycrystalline NCM electrode particles in the grain boundary phase field, and the value is set to 1; Li + The flux size of the polycrystalline NCM electrode particles in the diffusion equation is set to 7.33 × 10⁻⁶. -5 mol / (m 2 ·s); In solid mechanics, polycrystalline NCM electrode particles adopt free boundary conditions.

[0052] Furthermore, in step S3, the cracking and pulverization distribution of the polycrystalline NCM electrode particles is a distribution of the fracture phase field order parameter.

[0053] Another object of the present invention is to provide a polycrystalline NCM electrode particle cracking and pulverization prediction system for implementing the aforementioned polycrystalline NCM electrode particle cracking and pulverization prediction method, comprising:

[0054] The model building module is used to construct an anisotropic polycrystalline fracture phase-field model, including grain boundary phase-field equations, solid mechanics equations, and Li... + Diffusion equation and fracture phase field equation;

[0055] The two-dimensional geometry construction module is used to construct the two-dimensional geometry of polycrystalline NCM electrode particles, set the parameters required for the physical field, perform mesh generation, and set initial and boundary conditions.

[0056] The numerical solution module is used to perform numerical solutions using finite element simulation software to obtain the cracking and pulverization distribution of polycrystalline NCM electrode particles.

[0057] Another object of the present application is to provide a computer device comprising a memory and a processor, the memory storing a computer program, the computer program being executed by the processor to cause the processor to perform the steps of the polycrystalline NCM electrode particle cracking and pulverization prediction method.

[0058] Another object of the present application is to provide a computer-readable storage medium storing a computer program, the computer program being executed by a processor to cause the processor to perform the steps of the polycrystalline NCM electrode particle cracking and pulverization prediction method.

[0059] Another object of the present application is to provide an information data processing terminal for implementing the polycrystalline NCM electrode particle cracking and pulverization prediction system.

[0060] In combination with the above technical solutions and the technical problems solved, the technical solutions to be protected by the present application have the following advantages and positive effects:

[0061] (1) The method for predicting polycrystalline NCM electrode particle cracking and pulverization constructed by the present application considers the bidirectional coupling of Li + diffusion and mechanical stress, cracking and pulverization and mechanical stress, and uses grain boundary phase field calculation to correct the critical energy release rate, so that the present application can accurately reflect the mechanism of polycrystalline NCM electrode particle cracking and pulverization, and improve the accuracy of cracking and pulverization prediction.

[0062] (2) The method for predicting polycrystalline NCM electrode particle cracking and pulverization constructed by the present application is more specific and concrete, the results of cracking and pulverization can be displayed through a two-dimensional cloud chart, and the process of cracking and pulverization can be dynamically displayed. At the same time, the stress distribution, Li + concentration distribution inside the polycrystalline NCM electrode particle during the cracking and pulverization process can also be dynamically displayed.

[0063] (3) The method for predicting polycrystalline NCM electrode particle cracking and pulverization constructed by the present application is universal and suitable for accurately predicting the cracking and pulverization of polycrystalline NCM electrode particles under different geometries, different materials and different working conditions.

[0064] (4) The method for predicting polycrystalline NCM electrode particle cracking and pulverization constructed by the present application can be used to explore inhibition strategies, and the effect of inhibiting cracking and pulverization can be achieved by changing the geometric size and shape distribution of primary particles and secondary particles, or by structure regulation.

[0065] (5) The geometric model used in the method for predicting polycrystalline NCM electrode particle cracking and pulverization constructed by the present application can be a SEM image of a real particle, so the present application can be used for real polycrystalline NCM electrode particle inspection and detection work.

[0066] The method for predicting the cracking and pulverization of polycrystalline NCM electrode particles constructed by the present application can accurately predict the cracking and pulverization of polycrystalline NCM electrode particles in the charging and discharging process, and has the advantages of using a more accurate physical model and improving the accuracy of prediction.

[0067] (1) The expected income and commercial value of the technical solution of the present application after transformation are:

[0068] The technical solution of the present application can be used for the design and testing of lithium ion battery positive electrode materials, can greatly reduce the consumption of real experiments, or can be used as an auxiliary means of real experiments. Ultimately, the cost of the design and testing of lithium ion battery positive electrode materials is reduced.

[0069] (2) The technical solution of the present application fills the technical gap in the industry at home and abroad:

[0070] The method for predicting the cracking and pulverization of polycrystalline NCM electrode particles constructed by the present application is the first in the industry, which combines previous technical solutions at home and abroad, and constructs a more accurate and more complex physical model, greatly improving the accuracy of prediction.

[0071] (3) The technical solution of the present application solves a technical problem that people have been eager to solve but have failed to succeed:

[0072] The method for predicting the cracking and pulverization of polycrystalline NCM electrode particles constructed by the present application solves a technical problem, i.e. accurately predicting the cracking and pulverization of polycrystalline NCM electrode particles. The prediction accuracy of previous prediction models is far from meeting the actual requirements. The prediction accuracy of the present application is greatly improved.

[0073] Thirdly, the method for predicting the cracking and pulverization of polycrystalline NCM (lithium nickel cobalt manganese oxide) electrode particles constructed by the present application integrates phase field model, solid mechanics, Li + diffusion and other physical equations, providing a powerful tool for accurately predicting the cracking and pulverization of polycrystalline NCM electrode particles. The following is the technical problem solved by the method and the significant technical progress obtained:

[0074] 1) Improve prediction accuracy: by constructing an anisotropic polycrystalline fracture phase field model, the present application can comprehensively consider the influence of factors such as grain boundaries, solid mechanics, Li + diffusion on the cracking and pulverization of electrode particles, thereby improving the accuracy of prediction.

[0075] 2) Realize microscale analysis: by numerically solving the two-dimensional geometric model of polycrystalline NCM electrode particles, the present application can analyze the stress, strain and Li +The concentration distribution and other parameters provide more detailed and in-depth information for cracking and pulverization prediction.

[0076] 3) Consider the influence of anisotropy: by introducing the concepts of modified elastic stiffness tensor and phase field degradation function, the invention can fully consider the influence of anisotropy of polycrystalline materials on cracking and pulverization, making the prediction results more in line with the actual situation.

[0077] 4) Optimize industrial applications: the prediction method of the invention can provide important information about the cracking and pulverization of electrode particles for battery manufacturers, helping them optimize battery design and manufacturing processes, and improve the cycle life and safety of batteries.

[0078] 5) Promote scientific research: the prediction method of the invention also provides a new research tool for researchers, helping them better understand the cracking and pulverization mechanism of polycrystalline NCM electrode particles, and promote scientific research progress in related fields. BRIEF DESCRIPTION OF DRAWINGS

[0079] Figure 1 is a polycrystalline NCM electrode particle cracking and pulverization prediction method provided by the embodiment of the invention;

[0080] Figure 2 is a polycrystalline NCM electrode particle cracking and pulverization prediction method flowchart provided by the embodiment of the invention;

[0081] Figure 3 is a two-dimensional geometric diagram of polycrystalline NCM electrode particles provided by the embodiment of the invention;

[0082] Figure 4 is a polycrystalline NCM electrode particle cracking and pulverization distribution evolution process diagram provided by the embodiment of the invention;

[0083] Figure 5 is a polycrystalline NCM electrode particle cracking and pulverization evolution process diagram under different primary particle sizes provided by the embodiment of the invention;

[0084] Figure 6 is a polycrystalline NCM electrode particle cracking and pulverization evolution process diagram under different secondary particle sizes provided by the embodiment of the invention;

[0085] Figure 7 is a polycrystalline NCM electrode particle cracking and pulverization result comparison diagram provided by the embodiment of the invention;

[0086] Figure 8 is a polycrystalline NCM electrode particle cracking and pulverization prediction system structure diagram provided by the embodiment of the invention. DETAILED DESCRIPTION

[0087] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0088] In view of the problems in the prior art, the present application provides a polycrystalline NCM electrode particle cracking and pulverization prediction method and system, which will be described in detail below with reference to the accompanying drawings.

[0089] Two specific industrial application embodiments of the present prediction method are related to the design and maintenance of lithium-ion batteries, especially the optimization of battery performance for electric vehicles and portable electronic devices:

[0090] Embodiment one: electric vehicle battery performance optimization

[0091] 1) Application background:

[0092] The battery performance of electric vehicles directly affects the driving range and service life of the vehicle. Polycrystalline NCM electrode materials are widely used in electric vehicle batteries because they can provide higher energy density. However, electrode particles are prone to cracking and pulverization during charging and discharging, affecting the cycle life and safety of the battery.

[0093] 2) Application method:

[0094] Using the prediction method of the present application, electric vehicle manufacturers can predict the cracking and pulverization behavior of electrodes under different designs and use conditions through simulation models. By adjusting the charging strategy in the battery management system and the use environment, the battery performance can be optimized and its service life can be extended.

[0095] Embodiment two: portable electronic device battery maintenance

[0096] 1) Application background:

[0097] Portable electronic devices such as smartphones and laptops have very high requirements for battery reliability and maintenance. The health status of the battery directly affects the service life of the device and the user's experience.

[0098] 2) Application method:

[0099] Using the method of the present application, device manufacturers can simulate the performance of the battery under different use patterns and environmental conditions during the design phase. In addition, by predicting the cracking and pulverization trend, manufacturers can set more appropriate battery maintenance reminders in advance, helping users effectively manage battery use and avoid sudden failures caused by battery mechanical failure.

[0100] In both embodiments above, by accurately predicting the cracking and pulverization trend of polycrystalline NCM electrode particles in practical applications, the performance and safety of lithium-ion batteries can be significantly improved. This predictive capability not only helps optimize battery design but also provides important information for daily battery maintenance and performance management.

[0101] like Figure 1 and Figure 2 As shown, the method for predicting cracking and pulverization of polycrystalline NCM electrode particles constructed in this invention mainly includes:

[0102] S1, Construct an anisotropic polycrystalline fracture phase-field model, including grain boundary phase-field equations, solid mechanics equations, and Li + Diffusion equation and fracture phase field equation.

[0103] S2, construct the two-dimensional geometry of the polycrystalline NCM electrode particles, set the required parameters for the physical field, perform mesh generation, and set initial and boundary conditions.

[0104] S3. Numerical solution was performed using finite element simulation software to obtain the cracking and pulverization distribution of polycrystalline NCM electrode particles.

[0105] The grain boundary phase field equation constructed in S1 is as follows:

[0106]

[0107] Where p is the grain boundary phase field order parameter, l p It is the grain boundary phase field length parameter. Represents the Hamiltonian operator. The corrected critical energy release rate G. p It can be written as

[0108] G p =g(p)G c_G +(1-g(p))G c_GB

[0109] Where g(p)=(1-p) 2 G c_G It is the critical energy release rate of the grain, G c_GB It is the critical energy release rate at the grain boundary.

[0110] Specifically, the solid mechanics equations constructed in S1 are as follows:

[0111]

[0112] in, Here, C(d) is a Hamiltonian operator, and C(d) represents the modified elastic stiffness tensor.

[0113] ε e Represents the elastic strain tensor:

[0114] ε e = ε - ε c ,

[0115] ε is the total strain tensor;

[0116] ε c is the chemical strain tensor:

[0117] ε c = (c - c ref ) β ij ,

[0118] β ij is the anisotropic unit concentration volume change;

[0119] c represents the Li + concentration, c ref represents the reference Li + concentration.

[0120] In the formula, the expression of the modified elastic stiffness tensor C(d) is:

[0121]

[0122] where C0 is the elastic stiffness tensor of the normal material, k0 is the bulk modulus, I is the unit matrix, sign - is the sign function, ε e is the elastic strain tensor, tr(ε e ) is the trace of ε e ;

[0123] g(d) is the phase field degeneration function:

[0124] g(d) = (1 - d) 2 + k,

[0125] k is a numerical calculation stability parameter.

[0126] The Li + diffusion equation constructed in S1 is:

[0127]

[0128] where J is the Li + molar flux per unit area per unit time, D represents the diffusion rate of Li + , represents the Hamiltonian operator, Ω ij represents the partial molar volume, R represents the ideal gas constant, T represents the Kelvin temperature, c represents the Li + concentration, c max represents the maximum Li + concentration that the material can accommodate, σh represents hydrostatic stress.

[0129] The fracture phase field equation constructed in S1 is:

[0130]

[0131] where G p is the modified critical energy release rate of polycrystalline NCM electrode particle material; d is the fracture phase field order parameter, d = 1 represents that the material is completely damaged, d = 0 represents that the material is intact (i.e. no failure), and 0 < d < 1 represents a transition state; l d represents the length parameter of the fracture phase field, represents the Hamiltonian operator, H is defined as the historical maximum tensile strain energy density:

[0132] H = max Ψ e (t)

[0133] where Ψ e (t) represents the tensile elastic strain energy density, and its expression is:

[0134]

[0135] where g(d) is the phase field degradation function, ε e is the elastic strain tensor, C0 is the elastic stiffness tensor of normal material, ε vol is the elastic strain volume component, ε dev is the elastic strain bias component, and tr(ε e ) is the trace of ε e .

[0136] The two-dimensional geometry of the polycrystalline NCM electrode particles constructed in S2 is generated by the Voronoi diagram algorithm, as shown in Figure 3 The generated two-dimensional polycrystalline geometry is circular with a radius of 5 μm, and the internal primary particles are irregular hexagons with an average particle size of 0.57 μm, and the size and shape are random.

[0137] The two-dimensional geometry grid of the polycrystalline NCM electrode particles constructed in S2 is divided by triangular grid, and the maximum grid size is set to 0.02 μm. The constructed grid contains a total of 508636 triangular regions, and the degree of freedom is 5.1 million during simulation calculation.

[0138] The physical parameters set in S2 are: Young's modulus E = 120 GPa, Poisson's ratio v = 0.3, density p = 4.14 g / cm 3 , temperature T = 300 K, Li + diffusion rate D = 7 x 10 -15 m 2 / s, maximum Li +Concentration c max = 35164 mol / m 3 , reference Li + Concentration c max = 31648 mol / m 3 , grain boundary phase field length parameter l p = 0.05 pm, fracture phase field length parameter l d = 0.05 pm, grain boundary critical energy release rate G c_GB = 2 N / m, primary particle energy release rate G c_G = 10 N / m. The unit concentration volume change, partial molar volume are anisotropic, where the unit concentration volume change is set as: b a = b b = 0.597 cm 3 / mol, b c = 1.052 cm 3 / mol. The partial molar volume is set as: w a = w b = 1.79 cm 3 / mol, w c = 3.16 cm 3 / mol. All primary particle crystal orientations are randomly generated and set using scripts;

[0139] The initial conditions set in S2 are: the grain boundary phase field initial value is set to 0, the Li + diffusion initial concentration is set to 31648 mol / m 3 , the solid mechanics initial displacement is set to no displacement, and the fracture phase field initial value is set to 0.

[0140] The boundary conditions set in S2 are: the polycrystalline NCM electrode particle grain boundary in the grain boundary phase field is set to a Dirichlet boundary condition, and the numerical value is set to 1; the Li + diffusion equation is set to 7.33 x 10 -5 mol / (m 2 ·s); the polycrystalline NCM electrode particle in the solid mechanics adopts a free boundary condition.

[0141] In S2, for each primary particle in the polycrystalline NCM electrode particle, an independent spatial coordinate system is constructed, and the orientation of the coordinate system is the primary particle crystal orientation.

[0142] In the step S3, the model is numerically solved by adopting two solving steps. The first step is to stably solve the grain boundary phase field equation to obtain the modified critical energy release rate distribution and store it. The second step is to transiently solve the solid mechanics equation, Li +The diffusion equation and the fracture phase field equation are used to transfer the solution stored in the first step to the second step as the numerical value of the modified critical energy release rate.

[0143] In the step S3, the cracking and pulverization distribution of the polycrystalline NCM electrode particles is the distribution of the fracture phase field order parameter. The evolution of the cracking and pulverization distribution of the polycrystalline NCM electrode particles is shown in Figure 4 The evolution process of the cracking and pulverization of the polycrystalline NCM electrode particles under different primary particle sizes is shown in Figure 5 The evolution process of the cracking and pulverization of the polycrystalline NCM electrode particles under different secondary particle sizes is shown in Figure 6 The cracking and pulverization results of NCM electrode particles with different structures are compared as shown in Figure 7

[0144] As shown in Figure 8 The polycrystalline NCM electrode particle cracking and pulverization prediction system provided by the embodiment of the application comprises:

[0145] The model establishment module is used to construct the anisotropic polycrystalline fracture phase field model, including the grain boundary phase field equation, the solid mechanics equation, the Li + diffusion equation and the fracture phase field equation;

[0146] The two-dimensional geometry construction module is used to construct the two-dimensional geometry of the polycrystalline NCM electrode particles, set the required parameters of the physical field, perform grid division and set the initial conditions and boundary conditions;

[0147] The numerical solution module is used to perform numerical solution using the finite element simulation software to obtain the cracking and pulverization distribution of the polycrystalline NCM electrode particles.

[0148] The application embodiment of the application provides a computer device, the computer device comprises a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the polycrystalline NCM electrode particle cracking and pulverization prediction method.

[0149] The application embodiment of the application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the polycrystalline NCM electrode particle cracking and pulverization prediction method.

[0150] The application embodiment of the application provides an information data processing terminal, which is used to realize the polycrystalline NCM electrode particle cracking and pulverization prediction system.

[0151] ​In addition to the above embodiments, embodiments of the present application also include: (1) predicting the cracking and pulverization of NCM electrode particles with different primary particle average particle sizes, different secondary particle sizes; (2) predicting the cracking and pulverization of NCM electrode particles with different primary particle shapes and arrangement regularities; (3) predicting the cracking and pulverization of NCM electrode particles with special structures, such as core-shell structure.

[0152] Using traditional mechanical models to predict the cracking and pulverization of NCM electrode particles often differs greatly from experimental observations. Traditional mechanical models cannot accurately reflect the concentration of particles inside, and therefore the prediction is inaccurate: (1) it cannot accurately predict whether cracking occurs, (2) it cannot accurately predict the degree of cracking. In contrast, the physical model used in the present application more realistically reflects the physical processes inside the NCM electrode particles, and the prediction results are more consistent with experimental observations. A direct proof is that the present application can directly prove the mechanical superiority of NCM electrode particles with core-shell structure, which is consistent with mainstream experimental observations, as shown in FIG. 1. Figure 7

[0153] It should be noted that the embodiments of the present application can be realized by hardware, software or a combination of software and hardware. The hardware part can be realized by using special logic; the software part can be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or a specially designed hardware. Those skilled in the art can understand that the above devices and methods can be realized by computer executable instructions and / or included in processor control code, such as provided on a carrier medium, such as a magnetic disk, CD or DVD-ROM, a programmable memory, such as a read-only memory (firmware), or a data carrier, such as an optical or electronic signal carrier. The devices of the present application and their modules can be realized by hardware circuits, such as very large scale integrated circuits or gate arrays, semiconductors, such as logic chips, transistors, etc., or programmable hardware devices, such as field programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above hardware circuits and software, such as firmware.

[0154] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any modification, equivalent replacement and improvement made by those skilled in the art within the technical scope disclosed by the present application, as long as it is within the spirit and principles of the present application, should be covered within the protection scope of the present application.​

Claims

1. A method for predicting cracking and pulverization of polycrystalline NCM electrode particles, characterized by, The method comprises the steps of: S1, construct an anisotropic polycrystalline fracture phase field model, including crystal boundary phase field equation, solid mechanics equation, Li + diffusion equation and fracture phase field equation; S2, constructing a two-dimensional geometry of the polycrystalline NCM electrode particle, setting required parameters of a physical field, performing mesh division and setting initial conditions and boundary conditions; S3, performing numerical solution using a finite element simulation software to obtain a cracking and pulverization distribution of the polycrystalline NCM electrode particle. In the step S1, the grain boundary phase field equation is used to calculate the modified critical energy release rate inside the polycrystalline NCM electrode particle, the solid mechanics equation is used to calculate the stress, elastic strain energy density distribution, Li + diffusion equation is used to calculate the Li + concentration distribution, and the fracture phase field equation is used to calculate the cracking and pulverization distribution; In the step S2, the polycrystalline NCM electrode particle two-dimensional geometry is drawn by the Voronoi diagram algorithm; the physical parameters set include Young's modulus, Poisson's ratio, density, temperature, Li + diffusion rate, maximum Li + concentration, reference Li + concentration, grain boundary phase field length parameter, fracture phase field length parameter, grain boundary critical energy release rate, primary particle energy release rate, unit concentration volume change, partial molar volume, all primary particle crystal orientations; the triangular grid is used for grid division, and the maximum grid size is set to 0.02 μm; the initial conditions include the grain boundary phase field initial value, Li + diffusion initial concentration, solid mechanics initial displacement, fracture phase field initial value; the boundary conditions include the grain boundary phase field Dirichlet boundary condition, Li + diffusion flux, solid mechanics free boundary condition; In the step S2, for each primary particle in the polycrystalline NCM electrode particle, an independent spatial coordinate system is constructed, and the orientation of the coordinate system is the crystal orientation of the primary particle. In the step S3, the model is solved numerically using two solving steps; the first step is a steady-state solving of the grain boundary phase field equation to obtain the modified critical energy release rate distribution and store it; the second step is a transient solving of the solid mechanics equation, the diffusion equation and the fracture phase field equation, passing the modified critical energy release rate stored in the first step to the second step as the distribution of the critical energy release rate; + G. In the step S3, the cracking and pulverization distribution of the polycrystalline NCM electrode particle is a distribution of a fracture phase field order parameter.

2. A polycrystalline NCM electrode particle cracking and pulverization prediction system for implementing the polycrystalline NCM electrode particle cracking and pulverization prediction method of claim 1, characterized by, The method comprises the steps of: A model establishing module is configured to construct an anisotropic polycrystal fracture phase field model, including a grain boundary phase field equation, a solid mechanics equation, Li + diffusion equation and a fracture phase field equation. a two-dimensional geometry construction module, configured to construct a two-dimensional geometry of the polycrystalline NCM electrode particle, set required parameters of a physical field, perform mesh division and set initial conditions and boundary conditions; a numerical solution module, configured to perform numerical solution using a finite element simulation software to obtain a cracking and pulverization distribution of the polycrystalline NCM electrode particle.

3. A computer device, comprising: The computer device comprises a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the polycrystalline NCM electrode particle cracking and pulverization prediction method according to claim 1.

4. A computer-readable storage medium, characterized in that, The computer program is executed by the processor to make the processor execute the steps of the polycrystalline NCM electrode particle cracking and pulverization prediction method according to claim 1.

5. An information data processing terminal, characterized by The information data processing terminal comprises the polycrystalline NCM electrode particle cracking and pulverization prediction system according to claim 2.

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