Design parameter evaluation method for cell assembly structure

Abstract

The invention discloses a design parameter evaluation method for a cell assembly structure, and relates to the field of batteries. Calculating equivalent design parameters corresponding to the battery cell monomers according to the design parameters of the battery cell assembly structure; based on the equivalent design parameters of the battery cell monomers and the stress-strain relation function corresponding to each compressible component, calculating the equivalent initial compression thickness and initial compression pressure of each compressible component in an initial compression state through static balance; calculating a free expansion space of the battery cell monomer according to the equivalent design parameters corresponding to the battery cell monomer and the stress-strain relation function corresponding to each compressible component; evaluating the design parameters of the current cell assembly structure based on the free expansion space ratio of the cell monomers and the initial compression pressure intensity of each compressible component in the initial compression state; according to the method, the quantitative index of the free expansion space is introduced, and objective evaluation of the mechanical environment is achieved for the design scheme of the cell assembly structure.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and particularly to a method for evaluating design parameters of a cell assembly structure. Background Art

[0002] In the design of a cell assembly structure (such as a battery module, a battery test tooling, or an overall or partial cell stacking design structure in a battery system), it is necessary to design appropriate space and select suitable compressible components to ensure that the structure can provide a good mechanical environment, accommodate the expansion of lithium batteries during normal long-term use, and apply appropriate pressure to the cells, thereby ensuring the performance of the battery and extending its service life. Traditional design methods face many challenges: due to numerous design parameters and a long cell test cycle, traditional testing methods are difficult to effectively optimize these parameters; in addition, there are differences between previous cell test results and actual designs, which cannot directly guide the design; at the same time, there is a lack of a rapid evaluation method based on mechanical principles, and it is usually necessary to rely on time-consuming and resource-intensive finite element analysis to evaluate design schemes.

[0003] To solve the above technical problems, the present invention provides a method based on mechanical principles, which can quickly and objectively evaluate the mechanical environment of design schemes for different cell assembly structures. By introducing a quantitative index of "free expansion space" and combining the mechanical characteristic curves of compressible components, this method can quickly evaluate the effectiveness of design schemes according to design parameters. This not only simplifies the optimization process of design schemes, enables designers to more easily compare different schemes, but also significantly reduces design time and costs, and improves flexibility and efficiency in the design process. Although the present invention does not directly solve the problem that traditional testing methods are difficult to effectively optimize design parameters, the present invention can quickly screen and evaluate multiple design schemes in the early stage of design, providing strong support for subsequent detailed testing and optimization. This method significantly improves the efficiency of the design process and ensures that the cell assembly structure has excellent mechanical environment and performance during long-term use. Summary of the Invention

[0004] To achieve accurate and rapid evaluation of design schemes for cell assembly structures, the present invention proposes a method for evaluating design parameters of a cell assembly structure, where the cell assembly structure includes one or more stacked cell components, and the cell components include stacked incompressible components, cell monomers, and compressible components; the method includes:

[0005] Based on the compression test data of different types of compressible components in the cell assembly structure, establish a stress-strain relationship function corresponding to each compressible component;

[0006] Calculate the equivalent design parameters corresponding to the cell monomers according to the design parameters of the cell assembly structure;

[0007] Based on the equivalent design parameters of the single battery cell and the stress-strain relationship function corresponding to each compressible component, calculate the equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state through the static equilibrium condition; the equivalent initial compression thickness represents the theoretical thickness value of the compressible component in the initial compression state;

[0008] Calculate the free expansion space of the single battery cell according to the equivalent design parameters corresponding to the single battery cell and the stress-strain relationship function corresponding to each compressible component, and obtain the free expansion space ratio of the single battery cell through normalization processing;

[0009] Evaluate whether the design parameters of the current battery cell assembly structure are reasonable based on the free expansion space ratio of the single battery cell and the initial compression pressure of each compressible component in the initial compression state.

[0010] Furthermore, the establishment of the stress-strain relationship function includes:

[0011] Conduct a compression test on the compressible component, record the strain data corresponding to different pressures, and obtain the compression test data, that is, n pairs of strain values ∈ cp,i of the discrete compressible component and the corresponding stress value, that is, the compression pressure is σ cp,i ; where, i = 1, 2, …, n; n is a positive integer; cp represents the compressible component;

[0012] Construct an m-th order polynomial regression model of the stress-strain relationship through the compression test data; where, m is a positive integer;

[0013] Calculate the polynomial regression coefficient estimation based on the m-th order polynomial regression model;

[0014] Establish the stress-strain relationship function corresponding to the compressible component through the polynomial regression coefficient estimation.

[0015] Furthermore, calculate the equivalent design parameters corresponding to the single battery cell according to the design parameters of the battery cell assembly structure, including:

[0016] According to the preset design parameters of the battery cell assembly structure, set:

[0017] The set of types of compressible components in the battery cell assembly structure is P, the thickness of the i-th single battery cell is t cell,i (i = 1, 2, …, M), the design thickness and uncompressed thickness of the j p -th compressible component of the p-th type of compressible component are respectively The thickness of the k-th incompressible component is t misc,k (k = 1, 2, …, L);

[0018] Based on the content set according to the preset design parameters of the battery cell assembly structure, calculate the equivalent design parameters corresponding to the battery cell monomers. The calculation formula includes:

[0019]

[0020] In the formula, t total represents the equivalent total space of the battery cell monomer, t cell represents the equivalent thickness of the battery cell monomer, t misc represents the equivalent thickness of the incompressible components corresponding to the battery cell monomer, represents the equivalent thickness of the p-th compressible component of the battery cell monomer before compression, represents the equivalent design thickness of the p-th compressible component of the battery cell monomer. M represents the total number of battery cell monomers in the battery cell assembly structure, L represents the total number of incompressible components in the battery cell assembly structure, and N p represents the total number of the p-th compressible component in the battery cell assembly structure.

[0021] Furthermore, the static equilibrium condition is: for any component η stacked in the battery cell assembly structure, at its interface, that is, on the contact surface between the component η and the adjacent component, the resultant force of the internal stress of the component and the external acting force is zero; where η = 1, 2,..., N parts ; N parts represents the total number of components inside the battery cell assembly structure; the components are incompressible components, battery cell monomers, and compressible components.

[0022] Furthermore, calculate the equivalent initial compression thickness and initial compression pressure of each compressible component under the initial compression state through static equilibrium, specifically including:

[0023] Set the stress of the component η stacked in the battery cell assembly structure in the stacking thickness direction as σ η , and according to the set stress σ η Use the static equilibrium condition to construct the force balance formulas at the upper interface and the lower interface of the component η respectively as:

[0024] σ η-1 A = σ η A (η = 2, 3,..., N parts );

[0025] σ η A = σ η+1 A (η = 1, 2,..., N parts -1);

[0026] In the formula, A represents the cross-sectional area of the component in the stacking direction;

[0027] Assume that the initial compression pressure of the components stacked within the entire cell assembly structure from the outside is σ 0 , based on the initial compression pressure σ 0 and the force balance formula at the upper interface and the lower interface of component η, the initial compression pressure of the p-th compressible component is obtained equal to σ 0 ;

[0028] Set the strain value of the p-th compressible component under the action of the initial compression pressure as strain value The calculation formula is:

[0029] In the formula, represents the equivalent initial compression thickness of the p-th compressible component corresponding to the single cell;

[0030] According to the stress-strain relationship function corresponding to the p-th compressible component The stress-strain relationship formula of the p-th compressible component is obtained as:

[0031] According to the calculation formula of the strain value and the stress-strain relationship formula of the p-th compressible component, the first equation is obtained: For each compressible component p ∈ P, a corresponding first equation is obtained. Set the number of elements in set P as M P , then a total of M P first equations are obtained;

[0032] According to the spatial relationship of the components within the cell assembly structure in the stacking direction, the second equation is established:

[0033]

[0034] By simultaneously solving the M P first equations and the second equation, the equivalent initial compression thickness of each compressible component in the initial compression state and the initial compression pressure σ 0 are solved.

[0035] Further, assume that the initial compression pressure of the components stacked within the entire cell assembly structure from the outside is σ 0 , and based on the initial compression pressure σ 0 and the force balance formula at the upper interface and the lower interface of component η, the initial compression pressure of the p-th compressible component is obtained equal to σ 0 , including:

[0036] Based on the initial compression pressure σ of the components stacked within the entire cell assembly structure 0 , the force equations for the upper and lower boundaries in the stacking direction are respectively set as follows:

[0037] σ 0 A = σ 1 A; where σ 1 represents the initial compression pressure of the first component in the stacking direction;

[0038] In the formula, represents the initial compression pressure of the last component in the stacking direction;

[0039] According to the force balance formula at the upper interface and the lower interface of component η, and the force equations for the upper and lower boundaries in the stacking direction, the initial compression pressure of each component within the cell assembly structure in the stacking direction is obtained, and the obtaining formula is: σ η = σ 0 (η = 1, 2, …, N parts );

[0040] Based on the obtained formula, the initial compression pressure of the p-th compressible component is equal to σ 0 :

[0041] In the formula, represents the initial compression pressure of the p-th compressible component.

[0042] Furthermore, for a component η that is not the topmost one, the upper interface refers to the contact surface between this component and the adjacent component above it; for the topmost component η = 1, the upper interface is the top surface of this component;

[0043] For a component η that is not the bottommost one, the lower interface refers to the contact surface between this component and the adjacent component below it; for the bottommost component η = N parts , the lower interface is the bottom surface of this component.

[0044] Furthermore, according to the equivalent design parameters corresponding to the cell unit and the stress-strain relationship function corresponding to each type of compressible component, the free expansion space of the cell unit is calculated, including:

[0045] By setting the stress-strain relationship function corresponding to the p-th compressible component as the following is obtained:

[0046]

[0047] In the formula, σ th represents the compression pressure criterion, Indicates the thickness when the p-th compressible component is compressed to the compression pressure criterion σ th ;

[0048] Based on the thickness when the p-th compressible component is compressed to the compression pressure criterion σ th ; Construct a calculation equation for the free expansion space of the single cell:

[0049] In the formula, t free represents the free expansion space of the single cell; the free expansion space t free represents the expandable space of the single cell from the initial state to before the external pressure reaches the preset compression pressure criterion during its normal use; the external pressure is the unit area reaction force exerted by the outside world on the components stacked in the cell assembly structure;

[0050] Obtain the free expansion space ratio corresponding to the single cell through standardization processing. The acquisition formula is:

[0051] In the formula, represents the free expansion space ratio.

[0052] Furthermore, based on the free expansion space ratio of the single cell and the initial compression pressure of each compressible component in the initial compression state, evaluate whether the design parameters of the current cell assembly structure are reasonable. Specifically:

[0053] Set the lower limit requirement value of the free expansion space ratio and the standard range of the initial compression pressure;

[0054] Judge whether the free expansion space ratio of the single cell is less than the lower limit requirement value If so, it means that the design parameters of the current cell assembly structure are unreasonable;

[0055] Judge whether the initial compression pressure of each compressible component in the initial compression state, that is, the initial compression pressure σ 0 is within the standard range. If not, it means that the design parameters of the current cell assembly structure are unreasonable.

[0056] Furthermore, the incompressible component is a rigid component, and the compressible component is a foam or a flexible heat insulation pad.

[0057] Compared with the prior art, the present invention has at least the following beneficial effects:

[0058] (1) The present invention calculates the equivalent design parameters corresponding to each single cell according to the design parameters of the cell assembly structure; based on the equivalent design parameters of the single cell and the stress-strain relationship function corresponding to each compressible component, the equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state are calculated through static equilibrium; the free expansion space of the single cell is calculated according to the equivalent design parameters corresponding to the single cell and the stress-strain relationship function corresponding to each compressible component; based on the free expansion space ratio of the single cell and the initial compression pressure of each compressible component in the initial compression state, it is evaluated whether the design parameters of the current cell assembly structure are reasonable; that is, the present invention quickly makes an objective evaluation of the mechanical environment of the design scheme of the cell assembly structure by introducing the quantitative index of "free expansion space" and combining the stress-strain relationship curve of the compressible component, which significantly reduces the design time and design cost and improves the flexibility and efficiency in the design process;

[0059] (2) The present invention establishes the stress-strain relationship function of each compressible component and calculates the thickness and pressure of the compressible component in the initial compression state by using the static equilibrium condition, ensuring that the single cell has sufficient expansion space and suitable pressure environment in the assembly structure, which helps to improve the overall performance and reliability of the cell assembly structure and extend the service life of the battery;

[0060] (3) Traditional design methods usually rely on long-term cell tests or time-consuming and resource-intensive finite element analysis to evaluate and optimize the design scheme, while the design parameter evaluation method based on mechanical principles provided by the present invention reduces the dependence on tests and finite element analysis, thereby reducing the design cost and accelerating the development cycle;

[0061] (4) The present invention ensures that the influence of all components in the same cell assembly structure on the free expansion space of the cell can be correctly considered by adopting equivalent design parameters (such as the t cell of the single cell and the equivalent thickness t misc of the incompressible component), and can complete the calculation of the free expansion space t free of all single cells at one time. Such equivalent and unified parameters not only simplify the calculation, but also ensure that all single cells have similar working conditions and sufficient expansion space in the cell assembly structure;

[0062] (5) The method of the present invention can flexibly adjust the design parameters according to actual needs, enabling designers to quickly evaluate the effectiveness of multiple schemes under different design conditions, which enhances the flexibility in the design process and meets the requirements of different application scenarios.

[0063] In summary, by introducing a design parameter evaluation method based on mechanical principles, the present invention significantly improves the efficiency and accuracy of the design of the battery cell assembly structure. It not only reduces the design time and cost, but also enhances the flexibility and reliability during the design process, ensuring that the battery cell assembly structure has excellent mechanical environment and performance during long-term use. These technical effects jointly promote the optimized design of the battery cell assembly structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 FIG. is a flowchart of a design parameter evaluation method for a battery cell assembly structure according to an embodiment of the present invention;

[0065] Figure 2 FIG. is a stacking diagram of each component within a battery cell assembly structure according to an embodiment of the present invention;

[0066] Figure 3 FIG. is a schematic diagram of the force analysis of component η according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0067] The following are specific embodiments of the present invention in combination with the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0068] Embodiment 1

[0069] In order to quickly screen and evaluate multiple design schemes in the early stage of design and significantly improve the efficiency of the design process, as Figure 1 shown, the present invention proposes a design parameter evaluation method for a battery cell assembly structure. The battery cell assembly structure includes one or more stacked battery cell components, and the battery cell components include stacked incompressible components, battery cell monomers, and compressible components. In this embodiment, the incompressible component is a rigid component, and the rigid component can be a separator, other metal or plastic hard components; the compressible component is a component made of foam, flexible heat insulation pad, or other compressible materials;

[0070] It should be noted that the incompressible component can mainly provide physical protection for the battery cell, prevent external impacts, vibrations, and other mechanical damages, and provide appropriate heat transfer conditions for the battery cell, which is particularly important in battery cell assembly structures used in vehicles or other dynamic environments. The incompressible component plays a key supporting role in the design of the battery cell assembly structure, ensuring the stability and rigidity of the structure, thereby preventing the displacement or deformation of the battery cell monomers during assembly and use. This design not only helps to ensure the overall performance and safety of the battery cell assembly structure, but also enhances its reliability and durability in various application environments.

[0071] Meanwhile, compressible components are also particularly important in the battery assembly structure, mainly reflected in providing buffer protection, absorbing the expansion of battery cells, ensuring mechanical stability, and preventing heat diffusion. Specifically, as compressible materials, compressible components can effectively absorb and disperse energy when the battery cell assembly structure is subjected to external impacts or vibrations, thereby reducing physical damage to individual battery cells and improving the anti-vibration performance of the entire assembly structure. In addition, as the battery expands and contracts during charge and discharge cycles, the compressible components can provide necessary free expansion space for individual battery cells, preventing performance degradation or safety hazards caused by excessive extrusion. At the same time, the compressible components can also apply appropriate pre-tightening forces during initial installation to ensure that individual battery cells remain in a fixed position throughout their life cycle, avoiding displacement or loosening. Finally, the compressible components have good heat insulation performance, which can slow down the heat transfer from a thermally out-of-control battery cell to adjacent battery cells and prevent the spread of thermal runaway. Through these functions, the compressible components not only enhance the reliability and safety of the battery assembly structure, but also extend the service life of the battery and ensure its long-term stable operation.

[0072] As Figure 2 shown, the first battery cell assembly in the figure includes the following stacked in sequence:

[0073] Incompressible component 1, incompressible component 2, battery cell monomer 1, compressible component 11, compressible component 21; where: the first "1" in compressible component 11 represents the first type of compressible component, the "2" in compressible component 21 represents the second type of compressible component, L represents the number of incompressible components in the battery cell assembly structure, M represents the number of battery cell monomers in the battery cell assembly structure, N 1 、N 2 respectively represent the number of the first type of compressible components and the number of the second type of compressible components.

[0074] In addition, in the present invention, the battery cell assembly structure can be an overall or partial battery cell stacking design structure in a battery module, a battery test tooling, and a battery system. Specifically, the battery cell assembly structure is not limited to a complete battery module, but also includes battery toolings for experiments and tests, as well as the battery cell stacking design of any part in the battery system. This broad definition ensures that the method of the present invention can be applied to a variety of different application scenarios, covering all stages from R & D testing to actual product design.

[0075] The method includes:

[0076] According to the compression test data of different types of compressible components in the battery cell assembly structure, establish a stress-strain relationship function corresponding to each compressible component;

[0077] The establishment of the stress-strain relationship function includes:

[0078] Perform a compression test on the compressible component and record the corresponding strain data at different pressures (ensuring that the test covers the entire operating pressure range from low to high) to obtain the compression test data, that is, n pairs of strain values of the discrete compressible component ∈ cp,i and their corresponding stress values, that is, the compression pressure is σ cp,i :

[0079] (∈ cp,1 , σ cp,1 ), (∈ cp,2 , σ cp,2 ), …, (∈ cp,n , σ cp,b )(i = 1, 2, …, n);

[0080] Construct an m - degree polynomial regression model of the stress - strain relationship through the compression test data (where the intercept term is zero):

[0081]

[0082] In the formula, β i represents the regression coefficient, and ε i represents the random error; n and m are positive integers; cp represents the compressible component;

[0083] Based on the m - degree polynomial regression model, use the least - squares method to calculate the estimated polynomial regression coefficients, specifically including:

[0084] Based on the m - degree polynomial regression model, construct the corresponding system of linear equations:

[0085]

[0086] Convert the system of linear equations into a pure matrix representation formula through the pure matrix representation method:

[0087] σ cp = Εβ + ε;

[0088] In the formula:

[0089]

[0090] Use the least - squares method to calculate the estimated polynomial regression coefficients The calculation formula is:

[0091]

[0092] In the formula:

[0093] Establish the stress - strain relationship function corresponding to the compressible component through the estimated polynomial regression coefficients:

[0094]

[0095] In the formula, represents the estimated polynomial regression coefficient of the i-th order polynomial.

[0096] It should be noted that after completing the polynomial regression analysis of the stress-strain relationship of the compressible component, in order to improve the efficiency and accuracy when back-calculating the strain value from the stress, this embodiment adopts a high-resolution method to construct this relationship. Specifically, the strain interval [∈ cp,1 , ∈ cp,n of the compressible component in the compressed state is divided into 1000 equal parts, that is, a fine-grained strain sequence is created. By using the stress-strain relationship function, based on this high-resolution strain sequence, a more accurate and query-efficient stress-strain correspondence table can be established. This method enables obtaining accurate results more quickly when it is necessary to find the corresponding strain value according to a specific stress. And if it is found that for some compressible component materials, the polynomial regression cannot well fit their actual stress-strain behavior, a series of discrete stress-strain points can also be manually specified to more appropriately reflect the behavior characteristics of these materials. When performing the query from stress to strain, if the queried stress value does not exactly lie on the known data points, then linear interpolation or polynomial interpolation methods can be used to estimate the strain value at that point. Both of these interpolation methods can ensure obtaining reasonable approximations during the query process while maintaining the computational efficiency.

[0097] Calculate the equivalent design parameters corresponding to the single cell according to the design parameters of the cell assembly structure; the equivalent design parameters refer to the idealized parameter values obtained through calculation and capable of representing the behavior characteristics of the single cell under actual working conditions.

[0098] Calculating the equivalent design parameters corresponding to the single cell according to the design parameters of the cell assembly structure includes:

[0099] According to the preset design parameters of the cell assembly structure, set:

[0100] The set of types of compressible components in the cell assembly structure is P, the thickness of the i-th single cell is t cell,i (i = 1, 2,..., M), the design thickness and uncompressed thickness of the j p -th compressible component of the p-th type of compressible component are respectively The thickness of the k-th incompressible component is t misc,k (k = 1, 2,..., L);

[0101] Based on the content set according to the preset design parameters of the cell assembly structure, calculate the equivalent design parameters corresponding to the single cell, and the calculation formulas include:

[0102]

[0103] In the formula, t total represents the equivalent total space of the single cell, and t cell represents the equivalent thickness of the single cell, and t misc represents the equivalent thickness of the non-compressible components corresponding to the single cell, represents the equivalent thickness of the p-th compressible component corresponding to the single cell before compression, represents the equivalent designed thickness of the p-th compressible component corresponding to the single cell. M represents the total number of single cells in the cell assembly structure, L represents the total number of non-compressible components in the cell assembly structure, and N p represents the total number of the p-th compressible component in the cell assembly structure.

[0104] It should be noted that the initial compression amount of the compressible component (i.e., the change of the compressible component from the original uncompressed state to the compressed state after installation) and the initial compression pressure (i.e., the pressure borne by the compressible component in the compressed state after installation) are one of the key indicators affecting the mechanical environment of the cells in the cell assembly structure. These parameters are directly related to the minimum pressure and mechanical safety of the cells during operation. If the compressible component is not correctly compressed or an inappropriate minimum pressure is applied, it may lead to a decline in cell performance or potential safety hazards.

[0105] When the design of the cell assembly structure includes multiple layers of different types of compressible components, each compressible component will have different compression behaviors under the action of the same external pressure due to its unique physical properties (such as hardness, elastic modulus, etc.). However, these properties are generally not considered in the design, and only the designed thickness is roughly given according to the space. Therefore, the equivalent designed thickness of the p-th compressible component corresponding to the single cell usually does not equal the actual thickness of the compressible component in the initial compressed state. To accurately evaluate the actual working conditions of the single cell, it is necessary to calculate the equivalent initial compression thickness and the initial compression pressure σ 0 of each compressible component in the initial compressed state.

[0106] In addition, considering that the stiffness of the single cell is much greater than that of the compressible component and the initial compression pressure is small, some reasonable simplified assumptions can be made in the calculation process to simplify the analysis and improve the calculation efficiency. Specifically:

[0107] 1. The deformation of the single cell is negligible

[0108] Since the stiffness of the single battery cell is much greater than that of the compressible component material, this means that when a relatively small initial compression pressure is applied, the deformation of the battery cell is extremely small and can almost be ignored. Therefore, in the calculation, it can be directly assumed that the single battery cell does not undergo significant deformation, which simplifies the problem from a three-dimensional complex non-linear problem to a more easily handled one-dimensional problem.

[0109] 2. The external constraint is a rigid constraint

[0110] It is further assumed that the external constraint on the battery cell assembly structure is rigid, that is, the boundary conditions are fixed and unchanged. This means that in the force analysis, the elastic or plastic deformation of the external constraint itself does not need to be considered, thus greatly simplifying the mechanical analysis of the boundary.

[0111] 3. Uniform pressure distribution

[0112] It is assumed that the pressure received by the stacked components is uniformly distributed. This assumption means that inside the battery cell assembly, the pressure at each position is equal and there is no local stress concentration phenomenon. This idealized pressure distribution model can greatly simplify the establishment and solution process of the static equilibrium equation.

[0113] 4. The Poisson's ratio effect is ignored

[0114] For the incompressible components, single battery cells and compressible components in the stacked components, it is assumed that the influence of their Poisson's ratio (that is, the ratio of the transverse strain to the longitudinal strain when the material is subjected to unidirectional tension or compression) on the overall behavior can be ignored. This is because, in this context, the main concern is the behavior of the material along the compression direction rather than the transverse expansion or contraction. In addition, when the pressure is small, the Poisson's ratio effect of the compressible component itself is also small and has little influence on the result, so the calculation can be simplified without affecting the accuracy of the final conclusion.

[0115] Through these reasonable assumptions, without affecting the key calculation results, the mathematical model of the complex interaction between the compressible component and the battery cell assembly structure can be simplified, making the analysis more intuitive and efficient. These assumptions are particularly applicable to the initial design stage or situations where different design schemes need to be quickly evaluated.

[0116] Based on the above assumptions:

[0117] Based on the equivalent design parameters of the single battery cell and the stress-strain relationship function corresponding to each compressible component, the equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state are calculated through the static equilibrium condition; the equivalent initial compression thickness represents the theoretical thickness value of the compressible component in the initial compression state;

[0118] By establishing the stress-strain relationship function for each compressible component and using the static equilibrium condition to calculate the thickness and pressure of the compressible component in the initial compression state, it is ensured that the single cell has sufficient expansion space and a suitable pressure environment in the assembly structure, which helps to improve the overall performance and reliability of the cell assembly structure and extend the service life of the battery.

[0119] The static equilibrium condition is: for any component η stacked in the cell assembly structure, at its interface, that is, on the contact surface between the component η and the adjacent component, the resultant force of the internal stress of the component and the external force is zero; where η = 1, 2, …, N parts ; N parts represents the total number of components inside the cell assembly structure; the components are incompressible components, single cells, and compressible components.

[0120] Calculate the equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state through static equilibrium, specifically including:

[0121] As Figure 3 shown, set the stress of the component η stacked in the cell assembly structure in the stacking thickness direction as σ η , according to the set stress σ η Use the static equilibrium condition to construct the force balance formulas at the upper interface and the lower interface of the component η respectively as:

[0122] σ η-1 A = σ η A (η = 2, 3, …, N parts );

[0123] σ η A = σ η+1 A (η = 1, 2, …, N parts - 1);

[0124] In the formula, A represents the cross-sectional area of the component in the stacking direction;

[0125] Assume that the initial compression pressure of the components stacked in the entire cell assembly structure by the outside is σ 0 , according to the initial compression pressure σ 0 , the force balance formulas at the upper interface and the lower interface of the component η, obtain the initial compression pressure of the p-th compressible component equal to σ 0 ; specifically including:

[0126] Based on the initial compression pressure σ 0 of the components stacked in the entire cell assembly structure by the outside, respectively set the force equations at the upper boundary and the lower boundary in the stacking direction:

[0127] σ0 A = σ 1 A;

[0128] In the formula, σ 1 represents the initial compression pressure of the first component in the stacking direction;

[0129]

[0130] In the formula, represents the initial compression pressure of the last component in the stacking direction;

[0131] According to the force balance formula at the upper interface and the lower interface of component η, and the force equations at the upper and lower boundaries in the stacking direction, obtain the initial compression pressure of each component in the stacking direction within the battery cell assembly structure. The obtaining formula is:

[0132] σ η = σ 0 (η = 1, 2,..., N parts );

[0133] Based on the said obtaining formula, obtain the initial compression pressure of the p-th compressible component equal to σ 0 :

[0134]

[0135] In the formula, represents the initial compression pressure of the p-th compressible component.

[0136] For a component η that is not the topmost one, the upper interface refers to the contact surface between this component and the adjacent component above it; for the topmost component η = 1, the upper interface is the top surface of this component;

[0137] For a component η that is not the bottommost one, the lower interface refers to the contact surface between this component and the adjacent component below it; for the bottommost component η = N parts , the lower interface is the bottom surface of this component.

[0138] Set the strain value of the p-th compressible component under the action of the initial compression pressure as strain value The calculation formula of is:

[0139] In the formula, represents the equivalent initial compression thickness of the p-th compressible component corresponding to the battery cell monomer;

[0140] According to the stress-strain relationship function corresponding to the p-th compressible component Obtain the stress-strain relationship formula of the p-th compressible component as:

[0141] According to the calculation formula of the strain value and the stress-strain relationship formula of the p-th compressible component, the first equation is obtained:

[0142] For each compressible component p ∈ P, a corresponding first equation is obtained. Assuming the number of elements in set P is M P , then a total of M P first equations are obtained;

[0143] According to the spatial relationship of each component in the stacking direction within the battery cell assembly structure, the second equation is established:

[0144]

[0145] By simultaneously solving the M P first equations and the second equation, the equivalent initial compression thickness and the initial compression pressure σ 0 of each compressible component in the initial compression state are obtained.

[0146] Specifically, the "equivalent initial compression thickness" refers to an idealized and simplified representation of the compression thickness of the compressible component corresponding to the battery cell monomer obtained through calculation after considering the stress-strain relationship functions of the battery cell monomer and each compressible component and the overall design parameters of the battery cell assembly, aiming to reflect the real behavior of the compressible component in the initial compression state.

[0147] In this embodiment, the initial compression pressure is used as one of the evaluation indicators for the battery cell assembly structure design scheme (the initial compression pressure is basically the lowest pressure during the battery cell life cycle, because as the battery cell is used, the irreversible expansion of the battery cell will cause the pressure on the battery cell to gradually increase. Therefore, having a reasonable initial compression pressure is one of the conditions for the battery cell to have good performance). According to the initial compression pressure σ 0 , it can be known the lowest pressure that the battery cell experiences in the battery cell assembly structure during its life cycle. This is very important for optimizing the battery cell assembly structure design, because it can help engineers understand whether the compressible component can provide the lowest pressure condition that can meet the good performance of the battery cell while ensuring appropriate mechanical stability under the given design parameters.

[0148] In addition, the equivalent initial compression thickness can be used as a reference indicator for the battery cell assembly structure design. Using the equivalent initial compression thickness It is possible to evaluate the compression amount and compression ratio of each compressible component under the initial compression pressure condition. In the design of complex battery cell assembly structures that apply multiple different compressible components, this can effectively help engineers understand the compression conditions of various compressible components under complex compressible component combinations, so as to select appropriate compressible components and their uncompressed thicknesses, ensuring that each compressible component has an appropriate thickness under the initial compression pressure and can meet the requirements of production tolerances.

[0149] Calculate the free expansion space of the battery cell monomer according to the equivalent design parameters corresponding to the battery cell monomer and the stress-strain relationship function corresponding to each compressible component, and obtain the free expansion space ratio of the battery cell monomer through standardization processing;

[0150] Calculate the free expansion space of the battery cell monomer according to the equivalent design parameters corresponding to the battery cell monomer and the stress-strain relationship function corresponding to each compressible component, including:

[0151] By setting the stress-strain relationship function corresponding to the p-th compressible component as Get:

[0152]

[0153] In the formula, σ th represents the compression pressure criterion, represents the thickness of the p-th compressible component when compressed to the compression pressure criterion σ th ;

[0154] Based on the thickness th of the p-th compressible component when compressed to the compression pressure criterion σ Construct the calculation equation for the free expansion space of the battery cell monomer:

[0155]

[0156] In the formula, t free represents the free expansion space of the battery cell monomer; the free expansion space t free represents the expandable space of the battery cell monomer during its normal use, from the initial state to before the external pressure reaches the preset compression pressure criterion; the external pressure is the unit area reaction force exerted by the outside world on the components stacked in the battery cell assembly structure;

[0157] In the present invention, by adopting equivalent design parameters (such as t cell of the battery cell monomer and the equivalent thickness t misc of the incompressible component), it is ensured that the influence of all components within the same battery cell assembly structure on the free expansion space of the battery cell can be correctly considered, and the free expansion space t free of all battery cell monomers can be completed at one time.For the calculation, such equivalent and unified parameters not only simplify the calculation but also ensure that all single battery cells have similar working conditions and sufficient expansion space in the assembly structure.

[0158] Obtain the free expansion space ratio corresponding to the single battery cell through standardization. The acquisition formula is:

[0159]

[0160] In the formula, represents the free expansion space ratio.

[0161] It should be noted that due to the differences in the design of single battery cells in different battery cell assembly structures, the thickness of single battery cells may vary, and the required free expansion space roughly changes proportionally with the battery cell thickness. Therefore, in this embodiment, the free expansion space is standardized to obtain the free expansion space ratio to evaluate the mechanical environment of single battery cells in different battery cell assembly structures.

[0162] Based on the free expansion space ratio of the single battery cell and the initial compression pressure of each compressible component in the initial compression state, evaluate whether the design parameters of the current battery cell assembly structure are reasonable. Specifically:

[0163] Set the lower limit requirement value of the free expansion space ratio and the standard range of the initial compression pressure;

[0164] Judge whether the free expansion space ratio of the single battery cell is less than the lower limit requirement value If so, it indicates that the design parameters of the current battery cell assembly structure are unreasonable;

[0165] Judge whether the initial compression pressure of each compressible component in the initial compression state, that is, the initial compression pressure σ 0 is within the standard range [σ 0,min , σ 0,max . If not, it indicates that the design parameters of the current battery cell assembly structure are unreasonable. Among them, σ 0,min represents the minimum value of the standard range, and σ 0,max represents the maximum value of the standard range.

[0166] The specific evaluation logic is shown in Table 1 below:

[0167] Table 1:

[0168]

[0169]

[0170] The present invention calculates the equivalent design parameters corresponding to each single battery cell according to the design parameters of the battery cell assembly structure; based on the equivalent design parameters of the single battery cell and the stress-strain relationship function corresponding to each compressible component, the equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state are calculated through static equilibrium; the free expansion space of the single battery cell is calculated according to the equivalent design parameters corresponding to the single battery cell and the stress-strain relationship function corresponding to each compressible component; based on the free expansion space ratio of the single battery cell and the initial compression pressure of each compressible component in the initial compression state, it is evaluated whether the design parameters of the current battery cell assembly structure are reasonable; that is, the present invention introduces a quantitative index of "free expansion space" and combines the stress-strain relationship curve of the compressible component to quickly and objectively evaluate the mechanical environment of the design scheme of the battery cell assembly structure, which significantly reduces the design time and cost and improves the flexibility and efficiency in the design process.

[0171] In summary, the present invention significantly improves the efficiency and accuracy of the design of the battery cell assembly structure by introducing a design parameter evaluation method based on mechanical principles. It not only reduces the design time and cost, but also improves the flexibility and reliability in the design process, ensuring that the battery cell assembly structure has excellent mechanical environment and performance during long-term use. These technical effects jointly promote the optimized design of the battery cell assembly structure.

[0172] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0173] In addition, in the present invention, descriptions such as "first", "second", "one" are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0174] In the present invention, unless otherwise clearly specified and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0175] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A design parameter evaluation method for a battery cell assembly structure, characterized in that: The battery cell assembly structure includes one or more stacked battery cell components, and the battery cell components include stacked incompressible components, battery cell monomers, and compressible components; the method includes: According to the compression test data of different types of compressible components in the battery assembly structure, the stress-strain relationship function corresponding to each compressible component is established; Calculate the equivalent design parameters corresponding to the cell monomer according to the design parameters of the cell assembly structure; Based on the equivalent design parameters of the battery cell and the stress-strain relationship function corresponding to each compressible component, the equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state are calculated by static equilibrium conditions; the equivalent initial compression thickness represents the theoretical thickness value of the compressible component in the initial compression state; The free expansion space of the cell is calculated according to the equivalent design parameters corresponding to the cell and the stress-strain relationship function corresponding to each compressible component, and the free expansion space ratio of the cell is obtained through standardization processing; Based on the free expansion space ratio of the battery cell and the initial compression pressure of each compressible component in the initial compression state, the rationality of the design parameters of the current battery cell assembly structure is evaluated.

2. A design parameter evaluation method for a battery cell assembly structure according to claim 1, characterized in that: The establishment of stress-strain relationship function includes: Perform compression test on the compressible component, record the corresponding strain data under different pressures, and obtain the compression test data, that is, the strain value ∈ of n pairs of discrete compressible components cp,i And the corresponding stress value, that is, the compression pressure, is σ cp,i ; Wherein, i = 1, 2, ..., n; n is a positive integer; cp represents a compressible component; An m-order polynomial regression model of stress-strain relationship is constructed through compression test data; wherein m is a positive integer; Calculate polynomial regression coefficient estimates based on the m-order polynomial regression model; The stress-strain relationship function corresponding to the compressible component is established through polynomial regression coefficient estimation.

3. A design parameter evaluation method for a battery cell assembly structure according to claim 2, characterized in that: The equivalent design parameters corresponding to the cell monomer are calculated according to the design parameters of the cell assembly structure, including: According to the preset cell assembly structure design parameters, set: The set of compressible component types in the cell assembly structure is P, and the thickness of the i-th cell is t cell,i (i=1,2,…,M), the jth compressible component of the pth type p The design thickness and uncompressed thickness of the compressible parts are The thickness of the kth incompressible component is t misc,k (k=1,2,…,L); Based on the contents set according to the preset cell assembly structure design parameters, the equivalent design parameters corresponding to the cell monomer are calculated. The calculation formula includes: In the formula, t total Represents the equivalent total space of the battery cell, t cell Indicates the equivalent thickness of the battery cell, t misc Indicates the equivalent thickness of the incompressible parts of the cell. It represents the equivalent thickness of the pth compressible component corresponding to the cell when it is not compressed. represents the equivalent design thickness of the pth compressible component corresponding to the cell, M represents the total number of cell monomers in the cell assembly structure, L represents the total number of incompressible components in the cell assembly structure, N p Represents the total number of p-th compressible components in the battery cell assembly structure.

4. A design parameter evaluation method for a battery cell assembly structure according to claim 3, characterized in that: The static equilibrium condition is: for any component η stacked in the cell assembly structure, at its interface, i.e., the contact surface between the component η and the adjacent component, the resultant force of the component internal stress and the external force is zero; wherein η=1,2,…,N parts ; N parts Represents the total number of components in the battery cell assembly structure; the components are incompressible components, battery cell monomers and compressible components.

5. A design parameter evaluation method for a battery cell assembly structure according to claim 4, characterized in that: The equivalent initial compression thickness and initial compression pressure of each compressible component in the initial compression state are calculated by static balance, including: Assume that the stress of the stacked components η in the cell assembly structure in the stacking thickness direction is σ η , according to the set stress σ η The force balance formulas at the upper interface of component η and the lower interface of component η are constructed using the static balance condition: s η-1 A=s η A(η=2,3,…,N parts ); s η A=s η+1 A(η=1,2,…,N parts -1); Where A represents the cross-sectional area of ​​the component in the stacking direction; Assuming that the initial compression pressure of the stacked components in the entire battery assembly structure is σ0, the initial compression pressure of the pth compressible component is obtained according to the initial compression pressure σ0, the force balance formula at the upper interface of the component η and the lower interface of the component η is equal to σ0; The strain value of the pth compressible component under the initial compression pressure is set to Strain value The calculation formula is: In the formula, represents the equivalent initial compression thickness of the pth compressible component corresponding to the battery cell; According to the stress-strain relationship function corresponding to the pth compressible component The stress-strain relationship of the pth compressible component is obtained as follows: According to the strain value The calculation formula of and the stress-strain relationship of the pth compressible component give the first equation: For each compressible component p∈P, a corresponding first equation is obtained, and the number of elements in the set P is set to M P , then we get a total of M P The first equation; According to the spatial relationship of the components in the stacking direction in the battery cell assembly structure, the second equation is established: Through Lianli M P The first and second equations are solved to obtain the equivalent initial compression thickness of each compressible component in the initial compression state. and the initial compression pressure σ0.

6. A design parameter evaluation method for a battery cell assembly structure according to claim 5, characterized in that: Assume that the initial compression pressure of the stacked components in the entire battery assembly structure is σ0, and the initial compression pressure of the pth compressible component is obtained based on the initial compression pressure σ0, the force balance formula at the upper interface of the component η and the lower interface of the component η is equal to σ0, including: Based on the initial compression pressure σ0 of the components stacked in the entire battery assembly structure, the force equations of the upper and lower boundaries in the stacking direction are set respectively: σ0A=σ 1 A; where σ 1 represents the initial compression pressure of the first component in the stacking direction; In the formula, Indicates the initial compression pressure of the last component in the stacking direction; According to the force balance formula at the upper interface of component η and the lower interface of component η, and the force equations of the upper boundary and the lower boundary in the stacking direction, the initial compression pressure of each component in the battery cell assembly structure in the stacking direction is obtained, and the formula is: η =σ0(η=1,2,…,N parts ); Based on the acquisition formula, the initial compression pressure of the pth compressible component is obtained: is equal to σ0: In the formula, represents the initial compression pressure of the pth compressible component.

7. A design parameter evaluation method for a battery cell assembly structure according to claim 6, characterized in that: For a non-topmost component η, the upper interface refers to the contact surface between the component and the adjacent component above it; for the topmost component η=1, the upper interface is the top surface of the component; For a non-bottommost component η, the lower interface refers to the contact surface between the component and its lower adjacent component; for the bottommost component η = N parts , the lower interface is the bottom surface of the component.

8. A design parameter evaluation method for a battery cell assembly structure according to claim 3, characterized in that: The free expansion space of the cell is calculated based on the equivalent design parameters of the cell and the stress-strain relationship function of each compressible component, including: By setting the stress-strain relationship function corresponding to the pth compressible component to get: In the formula, σ th represents the compression pressure criterion, represents the compression of the pth compressible component to the compression pressure criterion σ th Thickness at Based on the compression of the pth compressible component to the compression pressure criterion σ th Thickness Construct the calculation equation for the free expansion space of the battery cell: In the formula, t free Represents the free expansion space of the battery cell; the free expansion space t free It indicates the expandable space of the battery cell during its normal use from the initial state to the time when the external pressure reaches the preset compression pressure criterion; the external pressure is the unit area reaction force exerted by the outside world on the stacked components in the battery cell assembly structure; The free expansion space ratio corresponding to the cell monomer is obtained through standardization, and the formula is: In the formula, represents the free expansion space ratio.

9. A design parameter evaluation method for a battery cell assembly structure according to claim 1, characterized in that: Based on the free expansion space ratio of the cell monomer and the initial compression pressure of each compressible component in the initial compression state, the design parameters of the current cell assembly structure are evaluated to see whether they are reasonable. Specifically: Set the lower limit requirement value of the free expansion space ratio Standard range with initial compression pressure; Determine whether the free expansion space ratio of the battery cell is less than the lower limit requirement value If so, it means that the design parameters of the current battery cell assembly structure are unreasonable; It is determined whether the initial compression pressure of each compressible component in the initial compression state, that is, the initial compression pressure σ0, is within the standard range. If not, it indicates that the design parameters of the current battery cell assembly structure are unreasonable.

10. A design parameter evaluation method for a battery cell assembly structure according to any one of claims 1 to 9, characterized in that: The incompressible component is a rigid component, and the compressible component is foam or a flexible thermal insulation pad.

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