Battery cell module design evaluation system and method based on stress-strain data

Abstract

The invention discloses a battery cell module design evaluation system and method based on stress-strain data. The system comprises a plurality of battery cells; the end plates are arranged at two ends of the battery cell; the silica gel foam is arranged between the battery cell and the end plate; the pre-tightening force equipment is used for applying pre-tightening force to the battery cell; the pressure sensor is used for measuring the expansion force of the battery cell; a battery management system (BMS); the pressure sensor is electrically connected with a battery management system (BMS) and transmits measured expansive force data to the BMS; the BMS is used for collecting data, monitoring the state of the battery, recording the stress-strain data of the battery cell under different pre-tightening forces, and obtaining a stress-strain data prediction model. Different pre-tightening forces are applied to the battery cell under different working conditions to obtain a stress-strain data model and predict the expansion condition of the module, so that a basis can be provided for the structural design of the module, and the design accuracy is improved; potential problems are found through simulation in the initial stage of product design, an improvement scheme is optimized in time, and the product research and development cycle is effectively shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery testing, and relates to a cell module design evaluation system and method based on stress and strain data. Background Art

[0002] In the field of battery technology, cells and modules, as the core components of a battery system, the stability of their performance and the cycle life directly affect the reliability and service life of the entire battery system. Therefore, the accurate evaluation of the cycle life of cells / modules is a key link in the battery R & D, design, and production processes.

[0003] Currently, the commonly used method for testing the cycle life of cells / modules in the industry is mainly to fix the cells / modules by applying a fixed pre-tightening force, and then simulate the actual use conditions for cyclic charge and discharge testing to evaluate their cycle life. However, this traditional testing method has many limitations. On the one hand, the time required for this testing method is extremely long. Since it is necessary to completely simulate the charge and discharge cycles of cells / modules during actual use until their performance significantly decays, the entire process may require thousands or even tens of thousands of charge and discharge cycles, resulting in a testing period of several months or even several years. Such a long testing time not only increases the R & D cost but also seriously delays the product's market launch cycle, putting the enterprise at a disadvantage in the market competition. On the other hand, this long-cycle testing method cannot provide effective data support for the design work at the initial design stage. During the R & D and design stage of battery products, it is necessary to carry out various tasks such as structural design, thermal management design, and electrical design based on the performance parameters of cells / modules. However, due to the inability of the traditional testing method to obtain cycle life data in a timely manner, designers often have to estimate based on experience and theoretical models during the design process, lacking the verification of actual test data. This may lead to problems such as unqualified performance and short life in the actual use of the designed battery products, increasing the design risk and R & D cost of the products.

[0004] In addition, the existing fixed pre-tightening force fixing method may not be able to fully simulate the stress conditions of cells / modules during actual use. In actual applications, cells / modules are subjected to various complex external forces, such as vibration, shock, and thermal stress caused by temperature changes. However, the fixed pre-tightening force may not fully consider these factors, resulting in a certain deviation between the test results and the actual use conditions, further affecting the accuracy of the evaluation of the cycle life of cells / modules.

[0005] In summary, the existing test methods for the cycle life of battery cells / modules have problems such as long test time, inability to provide data support in the initial design stage, and incomplete simulation conditions, making it difficult to meet the requirements of rapid R & D and design optimization of battery products. Therefore, it is necessary to develop a test method that can quickly and accurately evaluate the cycle life of battery cells / modules in the initial design stage to improve the R & D efficiency and quality of battery products. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the existing test methods for the cycle life of battery cells / modules, such as long test time, inability to provide data support in the initial design stage, and incomplete simulation conditions, and to provide a design evaluation system and method for battery cell modules based on stress-strain data.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A design evaluation system for battery cell modules based on stress-strain data, comprising:

[0009] A plurality of battery cells;

[0010] End plates arranged at both ends of the battery cells;

[0011] Silicone foam placed between the battery cells and the end plates;

[0012] A pre-tightening force device for applying a pre-tightening force to the battery cells;

[0013] A pressure sensor for measuring the expansion force of the battery cells;

[0014] A battery management system BMS; wherein, the pressure sensor is electrically connected to the battery management system BMS for transmitting the measured expansion force data to the battery management system BMS; the battery management system BMS is used for collecting data and monitoring the battery state, and obtaining a stress-strain data prediction model by recording the stress-strain data of the battery cells under different pre-tightening forces to guide the preliminary structural design.

[0015] The magnitude of the pre-tightening force is limited by the material of the battery cell housing. The upper limit value of the pre-tightening force is determined based on the material of the battery cell housing, and after calculating and setting a safety redundancy according to the material, the upper limit of the pre-tightening force is set.

[0016] The pre-tightening force device applies a series of pre-tightening forces that change from small to large to the battery cells. The pre-tightening force increases sequentially at a fixed interval, starting from zero pre-tightening force, and then gradually increasing the pre-tightening force according to the set interval until the pre-determined upper limit of the pre-tightening force is reached; during the application of the pre-tightening force, the pressure sensor is used to record in real time the change data of the expansion force and the deformation amount data of the battery cells under different pre-tightening forces, and upload the data to the battery management system BMS in a timely manner for subsequent analysis and processing.

[0017] The expansion force is specifically calculated by the following formula:

[0018] F1 = XSOC + Y*(T - 25) + Zln(C / 100 + 1)

[0019] Where, F1 is the expansion force, X is the expansion coefficient of the battery cell, SOC is the state of charge, Y is the temperature coefficient, Z is the aging logarithmic coefficient, T is the temperature, and C is the number of cycles;

[0020] The pre-tightening force is specifically:

[0021] F2 ≥ F1×COSθ - μF3

[0022] Where, F2 is the pre-tightening force, θ is the direction of the expansion force, μ is the friction coefficient between the battery cell and the housing, and F3 is the minimum pressure to maintain the contact of the electrode sheet.

[0023] The battery management system BMS is used to collect data and monitor the battery state. By recording the stress-strain data of the battery cell under different pre-tightening forces, a stress-strain data prediction model is obtained, specifically:

[0024] Data sorting: From the data recorded by the battery management system BMS, filter out the expansion force data and deformation data corresponding to different pre-tightening force conditions; sort the filtered data, and extract the working condition information, pre-tightening force value, expansion force measurement value, and deformation measurement value to form a structured data set;

[0025] Model input: Take the extracted working condition information and pre-tightening force value as input variables, and the deformation measurement value as the output variable, and input them into a preset data fitting model; the data fitting model uses the least squares method to optimize the parameters;

[0026] Curve fitting: Perform fitting processing on the data input into the model by the least squares method, and adjust the model parameters to minimize the error between the predicted deformation and the actual deformation; according to the fitting result, generate a data curve with the working condition and pre-tightening force as the input and the corresponding deformation as the output;

[0027] Data prediction: Based on the fitted data curve, input specific working condition conditions and pre-tightening force values, and calculate and output the corresponding predicted expansion force value and predicted deformation value; the predicted expansion force value is obtained by indirectly associating the relationship between the working condition, pre-tightening force, and deformation through the data curve. <U+

[0028] A method for evaluating the design of a battery cell module based on stress-strain data includes the following steps:

[0029] Determine the upper limit value of the pre-tightening force according to the material of the battery cell housing. After calculating and setting the safety redundancy according to the material, set the upper limit of the pre-tightening force;

[0030] Apply a series of pre-tightening forces of different magnitudes to the battery cell using a pre-tightening force device. The pre-tightening force gradually increases at intervals until the determined upper limit of the pre-tightening force is reached; and use a pressure sensor to record the data of the expansion force change and the deformation amount data of the battery cell under different pre-tightening forces, and upload these data to the battery management system BMS;

[0031] Under the condition of keeping the pre-tightening force unchanged, conduct charge and discharge tests on the battery cell at various different rates. During the test process, record the expansion force data and the deformation amount data of the battery cell;

[0032] From the data recorded in the battery management system BMS, sort out the expansion force data and the deformation data of the battery cell under different pre-tightening force conditions, and extract the key data related to the test conditions, pre-tightening force, expansion force, and deformation;

[0033] Input the extracted data into the stress-strain data prediction model to obtain the data curve of the deformation amount of the battery cell under the given working conditions and pre-tightening force conditions;

[0034] According to the data curve, input specific working conditions and pre-tightening force values, and then obtain the corresponding expansion force and deformation amount data.

[0035] The specific operation of conducting charge and discharge tests on the battery cell at various different rates under the condition of keeping the pre-tightening force unchanged and recording the expansion force data and the deformation amount data of the battery cell during the test process is as follows:

[0036] Fix the battery cell on the test device and make it in the set pre-tightening force state, and keep this pre-tightening force state unchanged during the whole test process;

[0037] In the order from low to high, conduct charge and discharge tests on the battery cell in the set pre-tightening force state at different charge and discharge rates. The charge and discharge rate represents the proportional relationship between the charge and discharge current magnitude of the battery cell and its rated capacity, and different rates correspond to different charge and discharge speeds;

[0038] During the charge and discharge test at each rate, record the expansion force data of the battery cell in real time; at the same time, record the deformation amount data of the battery cell during the charge and discharge process at different rates.

[0039] The specific operation of sorting out the expansion force data and the deformation data of the battery cell under different pre-tightening force conditions from the data recorded in the battery management system BMS and extracting the key data related to the test conditions, pre-tightening force, expansion force, and deformation is as follows:

[0040] Export a file containing all relevant data during the test from the Battery Management System (BMS). The data includes timestamp, pre-tightening force value, expansion force measurement value, and deformation measurement value. Check the exported data and remove or correct significantly incorrect or abnormal data points. Classify and organize the data into different intervals or groups according to different levels of pre-tightening force.

[0041] Expansion force and deformation data extraction: From each pre-tightening force interval or group, extract the corresponding expansion force measurement value, and associate the expansion force data with the corresponding timestamp and pre-tightening force value to form an expansion force data set. From each pre-tightening force interval or group, extract the corresponding deformation measurement value, and associate the deformation data with the corresponding timestamp and pre-tightening force value to form a deformation data set.

[0042] Key data extraction and organization: Extract the working condition information during the test, including test temperature, test environment humidity, and the initial state of the battery cell.

[0043] For each pre-tightening force value, calculate or extract the corresponding average expansion force value to form a relationship data set between pre-tightening force and expansion force. For each pre-tightening force value, calculate or extract the corresponding average deformation value to form a relationship data set between pre-tightening force and deformation.

[0044] Integrate the extracted test working condition data, pre-tightening force - expansion force relationship data, and pre-tightening force - deformation relationship data to form a comprehensive data set.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The cell module design evaluation system based on stress-strain data in the present invention can obtain a stress-strain data model by applying different pre-tightening forces to the cell under different working conditions and predict the expansion of the module, which can provide an accurate basis for the module structure design, significantly improve the design accuracy; can simulate and discover potential problems in the initial stage of product design, optimize and improve the scheme in a timely manner, avoid rework and modification in the later stage, effectively shorten the product R & D cycle; helps to take measures to deal with cell expansion in advance, reasonably design structures such as buffering, fixing, and heat dissipation, enhance the reliability of the product under different working conditions, reduce the failure rate, and extend the service life; can reduce the actual test times and scale, discover design defects in advance to avoid material waste and repeated production, reduce the R & D cost, and improve the economic benefits of the enterprise; can also select materials reasonably and optimize the structure layout based on accurate prediction, achieve the maximum utilization of materials, reduce the weight and volume of the module, improve the space utilization rate, optimize resource utilization, and conform to the development trend of energy conservation and environmental protection. Description of the Drawings

[0047] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0048] Figure 1 Structural diagram of the battery cell module design evaluation system based on stress-strain data of the present invention;

[0049] Figure 2 Flowchart of the battery cell module design evaluation method based on stress-strain data of the present invention. Detailed implementation manners

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0051] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0052] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0053] The following will further describe the present invention in detail in conjunction with the drawings:

[0054] See Figure 1 , which is a structural diagram of a battery cell module design evaluation system based on stress-strain data in the present invention, including: a plurality of battery cells; end plates provided at both ends of the battery cells; silica gel foam placed between the battery cells and the end plates; a pre-tightening force device for applying a pre-tightening force to the battery cells; a pressure sensor for measuring the expansion force of the battery cells; a battery management system BMS; wherein, the pressure sensor is electrically connected to the battery management system BMS for transmitting the measured expansion force data to the battery management system BMS; the battery management system BMS is used for collecting data and monitoring the battery state, and obtaining a stress-strain data prediction model by recording the stress-strain data of the battery cells under different pre-tightening forces to guide the preliminary structural design.

[0055] The magnitude of the pre-tightening force is limited by the material of the battery cell casing. The upper limit value of the pre-tightening force is determined based on the material of the battery cell casing. After calculating and setting the safety redundancy according to the material, the upper limit of the pre-tightening force is set.

[0056] The pre-tightening force device applies a series of pre-tightening forces that change from small to large to the battery cell. The pre-tightening force increases sequentially at fixed intervals, starting from zero pre-tightening force, and then gradually increasing the pre-tightening force according to the set interval until the pre-determined upper limit of the pre-tightening force is reached; during the application of the pre-tightening force, a pressure sensor is used to record in real time the data of the expansion force change and the deformation amount data of the battery cell under different pre-tightening forces, and the data is uploaded to the battery management system BMS in a timely manner for subsequent analysis and processing.

[0057] The expansion force is specifically calculated by the following formula:

[0058] F1 = XSOC + Y*(T - 25) + Zln(C / 100 + 1)

[0059] Where, F1 is the expansion force, X is the expansion coefficient of the battery cell, SOC is the state of charge, Y is the temperature coefficient, Z is the aging logarithmic coefficient, T is the temperature, and C is the number of cycles;

[0060] The pre-tightening force is specifically:

[0061] F2 ≥ F1×COSθ - μF3

[0062] Where, F2 is the pre-tightening force, θ is the direction of the expansion force, μ is the friction coefficient between the battery cell and the casing, and F3 is the minimum pressure to maintain the contact of the electrode sheet.

[0063] The battery management system BMS is used to collect data and monitor the battery state. By recording the stress-strain data of the battery cell under different pre-tightening forces, a stress-strain data prediction model is obtained, specifically:

[0064] Data arrangement: From the data recorded by the battery management system BMS, filter out the expansion force data and deformation data corresponding to different pre-tightening force conditions; arrange the filtered data, extract the working condition information, pre-tightening force value, expansion force measurement value, and deformation amount measurement value to form a structured data set;

[0065] Model input: Take the extracted working condition information and pre-tightening force value as input variables, and the deformation amount measurement value as the output variable, and input them into a preset data fitting model; the data fitting model uses the least squares method for parameter optimization;

[0066] Curve fitting, the data input into the model is fitted by the least squares method, and the model parameters are adjusted to minimize the error between the predicted deformation and the actual deformation; according to the fitting result, a data curve with operating conditions and pre-tightening force as the input and the corresponding deformation as the output is generated.

[0067] Data prediction, based on the fitted data curve, specific operating conditions and pre-tightening force values are input, and the corresponding predicted expansion force value and predicted deformation value are calculated and output; the predicted expansion force value is obtained by indirectly correlating the relationship between operating conditions, pre-tightening force and deformation through the data curve.

[0068] According to the prediction results of the expansion force and deformation, optimize and guide the preliminary structural design of the battery module, specifically including: reserving an expansion space in the battery module that matches the predicted deformation to prevent the battery cells from being damaged due to expansion; evaluating whether it is necessary to adjust the pre-tightening force setting according to the predicted expansion force value to enhance the stability of the battery cells, while avoiding performance degradation caused by excessive pre-tightening force; designing a structure inside the module to limit the expansion force, such as elastic elements or restraint components, to ensure that the battery cells operate within the normal working range.

[0069] See Figure 2 , which is a flowchart of a design evaluation method for a battery cell module based on stress-strain data in the present invention, and includes the following steps:

[0070] Determine the upper limit value of the pre-tightening force according to the material of the battery cell casing, and set the upper limit of the pre-tightening force after calculating and setting the safety redundancy according to the material.

[0071] Apply a series of pre-tightening forces of different magnitudes to the battery cells using a pre-tightening force device, and the pre-tightening force gradually increases at intervals until the determined upper limit of the pre-tightening force is reached; and use a pressure sensor to record the data of the expansion force change and deformation data of the battery cells under different pre-tightening forces, and upload these data to the battery management system BMS.

[0072] While keeping the pre-tightening force unchanged, perform charge and discharge tests on the battery cells at various different rates. During the test, record the expansion force data and deformation data of the battery cells.

[0073] Specifically:

[0074] Fix the battery cells on the test equipment and make them in the set pre-tightening force state, and keep this pre-tightening force state unchanged during the whole test process;

[0075] In ascending order, perform charge and discharge tests on the battery cells in the set pre-tightening force state at different charge and discharge rates. Among them, the charge and discharge rate represents the ratio of the charge and discharge current magnitude of the battery cells to their rated capacity, and different rates correspond to different charge and discharge speeds;

[0076] During the charge and discharge tests at each rate, the swelling force data of the battery cell is recorded in real time; meanwhile, the deformation data of the battery cell during charge and discharge at different rates is recorded.

[0077] From the data recorded in the battery management system BMS, organize the swelling force data and deformation data of the battery cell under different pre-tightening force conditions, and extract the key data related to the test conditions, pre-tightening force, swelling force, and deformation.

[0078] Specifically:

[0079] Export a file containing all relevant data during the test from the battery management system BMS. The data includes timestamp, pre-tightening force value, swelling force measurement value, and deformation measurement value; check the exported data, remove or correct the obvious error or abnormal data points; classify and organize the data into different intervals or groups according to different levels of pre-tightening force;

[0080] Swelling force and deformation data extraction: From each pre-tightening force interval or group, extract the corresponding swelling force measurement value, and associate the swelling force data with the corresponding timestamp and pre-tightening force value to form a swelling force data set; from each pre-tightening force interval or group, extract the corresponding deformation measurement value, and associate the deformation data with the corresponding timestamp and pre-tightening force value to form a deformation data set;

[0081] Key data extraction and organization: Extract the working condition information during the test, including test temperature, test environment humidity, and the initial state of the battery cell;

[0082] For each pre-tightening force value, calculate or extract the corresponding average swelling force value to form a data set of the relationship between pre-tightening force and swelling force; for each pre-tightening force value, calculate or extract the corresponding average deformation value to form a data set of the relationship between pre-tightening force and deformation;

[0083] Integrate the extracted test working condition data, pre-tightening force - swelling force relationship data, and pre-tightening force - deformation relationship data to form a comprehensive data set.

[0084] Input the extracted data into the stress-strain data prediction model to obtain the data curve of the deformation of the battery cell under given working conditions and pre-tightening force conditions.

[0085] According to the data curve, input specific working conditions and pre-tightening force values, and then obtain the corresponding swelling force and deformation data.

[0086] Embodiment

[0087] Taking a square shell battery cell as a reference for relevant data derivation, the magnitude of the pre-tightening force is limited by the material of the battery cell shell (AL3003). Excessive pre-tightening force may cause the shell to deform and affect the internal winding core structure. By referring to the data, the yield strength of the shell is about 145 MPa, and the derivation formula is:

[0088] 1 MPa = 1×10 6 N / m 2 = (1×10 6 N) / (10 4 cm 2 ) = 100 N / cm 2

[0089] 1 kgf = 9.80665 N

[0090] 1 MPa ≈ 10.197 kgf / cm 2

[0091] It is obtained that the force per square centimeter is 1478 N, and the stress area of the large surface of the battery cell is about 12.5 cm 2 . At this time, the upper limit of the force that the outer shell can withstand is about 18475 N. At the same time, the upper limit of the pre-tightening force needs to consider the gas expansion under extreme working conditions and the strength of the material itself. It cannot be directly designed according to the ultimate strength. A 50% redundancy needs to be reserved to ensure the stable operation of the battery cell housing during the life cycle of the battery cell. The upper limit of the pre-tightening force is 9237 N. For the convenience of calculation and data statistics, 9000 N is used as the upper limit here.

[0092] Apply different magnitudes of pre-tightening force to the battery cell through the pre-tightening force device. The pre-tightening force increases from small to large, with an interval of 200 N, from 0 N, 200 N, 400 N... 9000 N. Record the change data of the expansion force and the deformation data under different pre-tightening forces through the pressure sensor, and at the same time upload the data to the BMS system.

[0093] At the same time, under the same pre-tightening force, test the data of 1C, 2C, 5C, and 10C, and sort out the corresponding expansion force data and deformation data.

[0094] Sort out the expansion force data and deformation data under different pre-tightening forces from the data recorded by the BMS. Extract the working conditions, pre-tightening force, expansion force, and deformation data from the data obtained from the above experiments, input them into the model, and obtain a data curve of the corresponding deformation amount by fitting through the least squares method based on the input working conditions and pre-tightening force. Through the obtained data curve, the expansion force and deformation data can be obtained by inputting the working conditions and pre-tightening force, guiding the preliminary structural design, including but not limited to reserving expansion space, increasing the pre-tightening force, and the structure inside the module for restricting the expansion force.

[0095] Taking NCM811 as an example, at a state of charge (SOC) of 80%, heat up to 45 °C, and the number of cycles is 500 times

[0096] Formula calculation:

[0097] F1 = 0.75SOC + 0.18×(T - 25) + 5Ln(C / 100 + 1)

[0098] = 60 + 2.7 + 8.96

[0099] = 71.7

[0100] F2 ≥ 71.7×1 - 0.2×10

[0101] ≥ 69.7

[0102] The formula here is to prove the relationship between the pre-tightening force and the expansion force.

[0103] In the present invention, by applying different pre-tightening forces to the battery cells under different working conditions and collecting stress-strain data to construct a data model, it is possible to highly accurately predict the expansion of the module under various actual working conditions. In practical applications, based on the predicted data to guide the module structure design, an appropriate expansion space can be effectively reserved. This can avoid the battery cells being squeezed or even damaged during the charge and discharge process due to insufficient expansion space, thereby prolonging the service life of the battery cells and improving the overall reliability and stability of the battery module. At the same time, reasonably adjusting the pre-tightening force setting according to the predicted value of the expansion force can not only enhance the stability of the battery cells in the module to ensure the normal operation of the battery module, but also prevent excessive pre-tightening force from damaging the battery cells and affecting the battery performance.

[0104] In addition, designing a structure in the module to limit the expansion force can further ensure that the battery cells operate within the normal working range and reduce potential safety hazards caused by expansion, such as short circuits, fires, etc. This helps to improve the safety of the battery module, and can also meet the strict requirements for battery performance and safety in different application scenarios. While improving the performance, safety and reliability of the battery module, it reduces the R & D cost and risk, and promotes the wide application of battery technology in more fields.

[0105] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A cell module design evaluation system based on stress-strain data, characterized in that, Comprising: A plurality of battery cells; End plates disposed at both ends of the battery cells; Silicone foam disposed between the battery cells and the end plates; A pre-tightening force device for applying a pre-tightening force to the battery cells; A pressure sensor for measuring the expansion force of the battery cells; A battery management system BMS; wherein, the pressure sensor is electrically connected to the battery management system BMS for transmitting the measured expansion force data to the battery management system BMS; the battery management system BMS is used for collecting data and monitoring the battery state, and obtaining a stress-strain data prediction model by recording the stress-strain data of the battery cells under different pre-tightening forces to guide the preliminary structural design.

2. The design evaluation system for a battery cell module based on stress-strain data according to claim 1, characterized in that, The magnitude of the pre-tightening force is limited by the material of the battery cell housing. The upper limit value of the pre-tightening force is determined according to the material of the battery cell housing. After calculating and setting the safety redundancy according to the material, the upper limit of the pre-tightening force is set.

3. The design evaluation system for the battery cell module based on stress-strain data according to claim 1, characterized in that, The pre-tightening force device applies a series of pre-tightening forces that change from small to large. The pre-tightening force increases sequentially at a fixed interval, starting from zero pre-tightening force, and then gradually increasing the pre-tightening force according to the set interval until the pre-determined upper limit of the pre-tightening force is reached; During the application of the pre-tightening force, the pressure sensor is used to record in real time the change data of the expansion force and the deformation data of the battery cells under different pre-tightening forces, and upload the data to the battery management system BMS in time for subsequent analysis and processing.

4. The design evaluation system of a battery cell module based on stress-strain data according to claim 1, characterized in that, The expansion force is specifically calculated by the following formula: F1 = XSOC + Y*(T - 25) + Zln(C / 100 + 1) Wherein, F1 is the expansion force, X is the expansion coefficient of the battery cell, SOC is the state of charge, Y is the temperature coefficient, Z is the aging logarithmic coefficient, T is the temperature, and C is the number of cycles; The pre-tightening force is specifically: F2 ≥ F1×COSθ - μF3 Wherein, F2 is the pre-tightening force, θ is the direction of the expansion force, μ is the friction coefficient between the battery cell and the housing, and F3 is the minimum pressure to maintain the contact of the electrode plate.

5. A cell module design evaluation system based on stress-strain data according to claim 1, characterized in that, The battery management system BMS is used for collecting data and monitoring the battery state, and obtaining a stress-strain data prediction model by recording the stress-strain data of the battery cells under different pre-tightening forces. Specifically: [[ID=J17]]Data sorting, from the data recorded by the battery management system BMS, screening out the corresponding expansion force data and deformation data under different pre-tightening force conditions; sorting the screened data, and extracting the working condition information, pre-tightening force value, expansion force measurement value and deformation measurement value to form a structured data set; Model input, taking the extracted working condition information and pre-tightening force value as input variables, and the deformation measurement value as the output variable, and inputting them into a preset data fitting model; the data fitting model uses the least squares method for parameter optimization; Curve fitting, performing fitting processing on the data input into the model by the least squares method, and adjusting the model parameters to minimize the error between the predicted deformation and the actual deformation; According to the fitting result, generating a data curve with the working condition and pre-tightening force as the input and the corresponding deformation as the output; Data prediction, based on the data curve obtained by fitting, input specific working conditions and pre-tightening force values, calculate and output the corresponding predicted expansion force value and predicted deformation value; the predicted expansion force value is obtained by indirectly correlating the relationship between the working conditions, pre-tightening force and deformation through the data curve.

6. A method for evaluating the design of a battery cell module based on stress-strain data, characterized in that It includes the following steps: Determine the upper limit value of the pre-tightening force according to the material of the battery cell housing, calculate and set the safety redundancy according to the material, and then set the upper limit of the pre-tightening force; Use the pre-tightening force device to apply a series of pre-tightening forces of different magnitudes to the battery cell, and the pre-tightening force increases step by step at intervals until the determined upper limit of the pre-tightening force is reached; And use a pressure sensor to record the data of the expansion force change and deformation data of the battery cell under different pre-tightening forces, and upload these data to the battery management system BMS; Under the condition of keeping the pre-tightening force unchanged, conduct charge and discharge tests on the battery cell at various different rates, and record the expansion force data and deformation data of the battery cell during the test; From the data recorded in the battery management system BMS, sort out the expansion force data and deformation data of the battery cell under different pre-tightening force conditions, and extract the key data related to the test working conditions, pre-tightening force, expansion force and deformation; Input the extracted data into the stress-strain data prediction model to obtain the data curve of the deformation of the battery cell under given working conditions and pre-tightening force conditions; According to the data curve, input specific working conditions and pre-tightening force values, and then obtain the corresponding expansion force and deformation data.

7. The design evaluation method of the battery cell module based on stress-strain data according to claim 6, wherein The step of, under the condition of keeping the pre-tightening force unchanged, conducting charge and discharge tests on the battery cell at various different rates, and recording the expansion force data and deformation data of the battery cell during the test, specifically: Fix the battery cell on the test equipment and make it in a set pre-tightening force state, and keep this pre-tightening force state unchanged during the whole test process; In ascending order, sequentially conduct charge and discharge tests on the battery cell in the set pre-tightening force state at different charge and discharge rates. The charge and discharge rate represents the proportional relationship between the charge and discharge current magnitude of the battery cell and its rated capacity, and different rates correspond to different charge and discharge speeds; During the charge and discharge test at each rate, record the expansion force data of the battery cell in real time; at the same time, record the deformation data of the battery cell during the charge and discharge process at different rates.

8. The method for evaluating the design of a battery cell module based on stress-strain data according to claim 6, wherein The step of, from the data recorded in the battery management system BMS, sort out the expansion force data and deformation data of the battery cell under different pre-tightening force conditions, and extract the key data related to the test working conditions, pre-tightening force, expansion force and deformation, specifically: Export a file containing all relevant data during the test from the battery management system BMS. The data includes time stamps, pre-tightening force values, expansion force measurement values, and deformation measurement values; check the exported data, remove or correct obvious error or abnormal data points; classify and sort the data into different intervals or groups according to different levels of the pre-tightening force; Expansion force and deformation data extraction: From each pre-tightening force interval or group, extract the corresponding expansion force measurement values, and associate the expansion force data with the corresponding timestamps and pre-tightening force values to form an expansion force data set; From each pre-tightening force interval or group, extract the corresponding deformation measurement values, and associate the deformation data with the corresponding timestamps and pre-tightening force values to form a deformation data set; Key data extraction and collation: Extract the operating conditions information during the test, including the test temperature, test ambient humidity, and the initial state of the battery cell; For each pre-tightening force value, calculate or extract the corresponding average expansion force value to form a data set of the relationship between pre-tightening force and expansion force; For each pre-tightening force value, calculate or extract the corresponding average deformation value to form a data set of the relationship between pre-tightening force and deformation; Integrate the extracted test operating conditions data, pre-tightening force-expansion force relationship data, and pre-tightening force-deformation relationship data to form a comprehensive data set.

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