Design method of battery module

Abstract

The design method of the battery module comprises the following steps: S1, calculating a battery module gap; s2, calculating a compression ratio interval of the buffer material, and searching a CFD stress interval corresponding to the compression ratio interval; s3, calculating a pre-tightening force range interval of the battery module, comparing the pre-tightening force range interval with a target pre-tightening force interval of the battery module, if the pre-tightening force of the battery module is not within the target pre-tightening force range, adjusting the design parameters according to the adjusting rule, and repeatedly checking the pre-tightening force until the pre-tightening force meets the requirement; s4, calculating the compression increase rate of the buffer material; s5, the upper limit of the EOL compression ratio of the buffer material is calculated, and the CFD stress corresponding to the upper limit of the EOL compression ratio is found; and S6, calculating the expansion force of the battery module, and comparing the expansion force with the upper limit J of the expansion force of the battery cell: if the expansion force is greater than or equal to the upper limit J of the expansion force of the battery cell, adjusting the design parameters, re-checking the expansion force until the expansion force design meets the requirement, and re-checking the pre-tightening force. The problems of low battery module design and production efficiency and high quality control cost are solved.

Description

Technical Field

[0001] The invention belongs to the field of batteries, and in particular relates to a design method for a battery module. Background Art

[0002] As the core component of the new energy industry, the performance of lithium-ion power batteries directly determines the development of the new energy industry. During the charging and discharging process of lithium-ion batteries, the positive and negative electrode materials continuously release lithium, resulting in changes in the volume of particles, which in turn causes changes in the thickness of the battery cells, which will directly affect the service life and number of cycles of the battery. As the battery ages, the battery expands in the middle and late stages of its life, causing the thickness to increase, the internal resistance of the battery cells to increase, and the capacity to decay. Studies have shown that applying a certain preload to the battery can ensure that the various components in the battery module are tightly connected, prevent loosening or deformation during use, improve the conductivity and heat dissipation performance of the battery module, thereby improving its overall performance, and can also slow down the expansion of the battery and increase the battery life. Therefore, in the design of the battery module, it is very important to check the BOL preload and EOL expansion force of the battery module.

[0003] At present, the control of preload force in the prior art usually uses a preloading tool to clamp the battery cell to the theoretical size, and then the module is finalized. This will inevitably lead to the problem that the battery is crushed and there is no expansion space, which will cause battery safety hazards; or the module is difficult to install in the box after the module is preloaded and packaged. When implementing the preload force method, it is necessary to accurately control the size of the clamping force and the amount of deformation. Excessive clamping force may cause damage or deformation of the battery cell, while too small clamping force may not ensure close contact between the battery cells. There are many factors affecting the packaging preload force, mainly the compression amount and CFD stress of the buffer material between the battery cells. If it is not checked, it may take several experiments to barely draw a conclusion, which greatly reduces the efficiency of battery module design and production. It may even lead to the inability to accurately evaluate the performance and safety of the battery module during the design stage, thereby hindering the optimization and improvement of the battery module design, or the quality of the produced battery modules is uneven, increasing the difficulty and cost of quality control. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a design method for a battery module to solve the problems of low design and production efficiency of the battery module and high quality control cost.

[0005] The basic solution provided by the present invention is a method for designing a battery module, which specifically includes the following steps:

[0006] S1: Calculate the battery module gap X based on the material parameters of the battery module;

[0007] S2: Calculate the compression rate interval [E1, E2] of the buffer material, and find the CFD stress interval [F1, F2] corresponding to the compression rate interval [E1, E2] according to the CFD stress curve data of the buffer material corresponding to the compression rate interval [E1, E2] of the buffer material;

[0008] S3: Calculate the battery module preload range [G1, G2] based on the CFD stress range [F1, F2], and compare the battery module preload range [G1, G2] with the battery module target preload range [H1, H2]:

[0009] If the target preload force lower limit H1 is less than the battery module preload force lower limit G1, and the target preload force upper limit H2 is greater than the battery module preload force upper limit G2, the preload force design meets the requirements; otherwise, adjust the design parameters according to the preload force parameter adjustment rules, and repeat steps S1 to S5 until the preload force design meets the requirements;

[0010] S4: Calculate the compression increase rate P of the buffer material;

[0011] S5: calculating the EOL compression rate upper limit Q of the buffer material according to the compression increase rate P of the buffer material, and finding the CFD stress R corresponding to the EOL compression rate upper limit Q according to the CFD stress curve data of the buffer material corresponding to the EOL compression rate upper limit Q of the buffer material;

[0012] S6: Calculate the expansion force U of the battery module based on the CFD stress R, and compare the expansion force U of the battery module with the upper limit J of the battery cell expansion force:

[0013] If the expansion force U is less than the upper limit J of the battery cell expansion force, the design meets the requirements. Otherwise, adjust the design parameters according to the expansion force parameter adjustment rules, repeat steps S4 to S6 until the expansion force design meets the requirements, and recheck the preload force.

[0014] Preferably, in step S1, the material parameters include the design length A of the module, the end plate thickness B, and the cell thickness C, and the battery module gap X includes the gap X1 between the cell and the end plate, and the gap X2 between the cells. The battery module gap X is calculated according to the design length A of the module, the end plate thickness B, and the cell thickness C;

[0015] The design length A of the module has the following relationship:

[0016] A=L a ±T a

[0017] Where, L a is the theoretical length of the battery module, T a is the battery module length tolerance;

[0018] The end plate thickness B has the following relationship:

[0019] B=L b ±T b

[0020] Where, L b is the theoretical thickness of the end plate, T b is the end plate thickness tolerance;

[0021] The cell thickness C has the following relationship:

[0022] C=L c ±T c

[0023] Where, L c is the theoretical length of the battery module, T c is the battery module length tolerance.

[0024] Further preferably, the battery module gap X is calculated according to the following calculation formula:

[0025]

[0026] Where N a is the number of battery modules, N b is the number of end plates, N c is the number of cells, L a is the theoretical length of the battery module, L b is the theoretical thickness of the end plate, L c is the theoretical thickness of the cell, T a is the battery module length tolerance, T b is the end plate thickness tolerance, T c is the cell thickness tolerance, N x The amount of buffer material.

[0027] Preferably, in step S2, the calculation formula of the compression rate interval [E1, E2] of the buffer material is as follows:

[0028]

[0029] Where, E2 is the upper limit of the compression rate of the buffer material, L d is the theoretical thickness of the buffer material, T d is the thickness tolerance of the buffer material, L x is the theoretical gap of the battery module, T x is the battery module gap tolerance;

[0030]

[0031] Where, E1 is the lower limit of the compression rate of the buffer material, L d is the theoretical thickness of the buffer material, Td is the thickness tolerance of the buffer material, L x is the theoretical gap of the battery module, T x is the battery module gap tolerance.

[0032] Preferably, in step S3, the preload force parameter adjustment rule includes adjusting the battery module material parameters and the battery module assembly size parameters. The preload force parameter adjustment rule is to adjust the battery module material parameters first. If the preload force still does not meet the requirements, the battery module assembly size parameters are adjusted.

[0033] Further preferably, the theoretical value, tolerance value and contact area of ​​the buffer material of each material of the battery module material parameters, when adjusting the battery module material parameters in the preload force parameter adjustment rule, the theoretical value of the material is adjusted first, then the tolerance value is adjusted, and finally the contact area of ​​the buffer material is adjusted.

[0034] Preferably, in step S4, the calculation formula of the buffer material compression increase rate P is as follows:

[0035] P=L c ×K / L d

[0036] Where, L c is the theoretical thickness of the battery cell, L d is the theoretical thickness of the buffer material, and K is the expansion rate of the battery cell.

[0037] Preferably, the calculation formula of the upper limit Q of the EOL compression rate of the buffer material in step S5 is as follows:

[0038] Q=P+E2

[0039] Where P is the compression increase rate of the buffer material, and E2 is the upper limit of the compression rate of the buffer material.

[0040] The principles and advantages of the present invention are:

[0041] 1. By checking the BOL preload force and EOL expansion force of the battery module, accurate data on the performance and safety of the battery module is provided, providing strong support for the design and optimization of the battery module; through verification, close contact between the battery cells and between the battery cells and the module frame can be ensured during the assembly process of the battery module, preventing structural damage caused by poor contact, thereby improving the safety performance of the battery module.

[0042] 2. By simultaneously checking the BOL preload and EOL expansion force of the battery module, we can have a more comprehensive understanding of the state of the battery module under actual working conditions, ensure that the mutual influence between the two is fully considered, avoid the interaction effect that is ignored due to separate verification, and improve the accuracy of the overall verification; compared with the method of separately verifying in the prior art, this method can reduce the number of repeated adjustment experiments, reduce the time and labor costs of repeated operations, and effectively improve the design and production efficiency of the battery module; through simultaneous verification, we can more accurately evaluate whether the design and manufacturing process of the battery module are reasonable, timely discover and solve design defects, optimize product performance, effectively improve the quality of the battery module, and reduce the difficulty and cost of quality control; and ensure the stability and consistency of the preload and expansion force throughout the life cycle of the battery module, reducing system instability caused by changes in a single factor; more complete data records can be generated to facilitate subsequent analysis and problem tracking, and improve data consistency and traceability.

[0043] 3. During the verification process, reasonable parameter adjustment rules are used to give priority to adjusting the battery module material parameters in the preload force parameter adjustment and the expansion force parameter adjustment, and then the battery module assembly size parameters are adjusted. This can reduce human operation errors and improve the accuracy of the verification results. At the same time, it simplifies the verification and adjustment steps, reduces unnecessary repeated operations, and improves work efficiency. Reasonable parameter adjustment rules can be flexibly adjusted according to different working conditions and environmental conditions to ensure that the battery module can work normally under various conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a flow chart of the present invention;

[0045] Figure 2 It is a structural schematic diagram of the battery module of the present invention;

[0046] Figure 3 It is a structural front view of the battery module of the present invention. DETAILED DESCRIPTION

[0047] The following is further described in detail through specific implementation methods:

[0048] The specific implementation process is as follows: Figures 1 to 3 , a battery module design method, specifically comprising the following steps:

[0049] S1: Calculate the battery module gap X according to the material parameters of the battery module, including the design length A of the module, the thickness B of the end plate, the thickness C of the battery cell, the thickness of the double-sided adhesive tape, the thickness of the spray adhesive, and the thickness of other insulation materials, etc.

[0050] In this embodiment, the structure of the battery module is as follows: Figures 2 to 3As shown, the battery module includes a battery cell 2, an end plate 1, and a buffer material 3. The material parameters include the design length A of the module, the thickness B of the end plate, and the thickness C of the battery cell; the gap X of the battery module includes the gap X1 between the battery cell and the end plate, and the gap X2 between the battery cells; wherein the design length A of the module has the following relationship:

[0051] A=L a ±T a ;

[0052] Where, L a is the theoretical length of the battery module, T a is the battery module length tolerance;

[0053] In this embodiment, the design length of the module is A = 667 ± 1.5 mm;

[0054] The end plate thickness B has the following relationship:

[0055] B=L b ±T b ;

[0056] Where, L b is the theoretical thickness of the end plate, T b is the end plate thickness tolerance;

[0057] In this embodiment, the end plate thickness B = 14 ± 0.2 mm;

[0058] The cell thickness C has the following relationship:

[0059] C=L c ±T c ;

[0060] Where, L c is the theoretical length of the battery module, T c is the battery module length tolerance;

[0061] In this embodiment, the cell thickness C = 50 ± 0.3 mm;

[0062] Calculate the battery module gap X according to the following calculation formula based on the module design length A, end plate thickness B, and cell thickness C:

[0063]

[0064] Where N a is the number of battery modules, N b is the number of end plates, N c is the number of cells, L a is the theoretical length of the battery module, L b is the theoretical thickness of the end plate, L c is the theoretical thickness of the cell, T ais the battery module length tolerance, T b is the end plate thickness tolerance, T c is the cell thickness tolerance, N x The amount of buffer material.

[0065] In this embodiment, the number of battery modules N a is 1, the number of end plates is N b is 2, the number of cells is N c is 20, and the battery module gap X = 3 ± 1.35 mm.

[0066] S2: Calculate the compression rate interval [E1, E2] of the buffer material according to the battery module gap X, and find the CFD stress interval [F1, F2] corresponding to the compression rate interval [E1, E2] according to the CFD stress curve data of the buffer material corresponding to the compression rate interval [E1, E2]. In this embodiment, the buffer material is foam.

[0067] In step S2, the calculation formula of the compression rate interval [E1, E2] of the buffer material is as follows:

[0068]

[0069] Where, E2 is the upper limit of the compression rate of the buffer material, L d is the theoretical thickness of the buffer material, T d is the thickness tolerance of the buffer material, L x is the theoretical gap of the battery module, T x is the battery module gap tolerance;

[0070]

[0071] Where, E1 is the lower limit of the compression rate of the buffer material, L d is the theoretical thickness of the buffer material, T d is the thickness tolerance of the buffer material, L x is the theoretical gap of the battery module, T x is the battery module gap tolerance.

[0072] Among them, the battery module theoretical gap L x The following relationship exists:

[0073]

[0074] Where N a is the number of battery modules, N b is the number of end plates, N c is the number of cells, L a is the theoretical length of the battery module, L b is the theoretical thickness of the end plate, L cis the theoretical thickness of the battery cell, N x The amount of buffer material.

[0075] Battery module gap tolerance T x The following relationship exists:

[0076]

[0077] Where N a is the number of battery modules, N b is the number of end plates, N c is the number of cells, T a is the battery module length tolerance, T b is the end plate thickness tolerance, T c is the cell thickness tolerance, N x The amount of buffer material.

[0078] In this embodiment, the theoretical thickness of the buffer material is L d is 4, the buffer material thickness tolerance T d is 0.4, the upper limit E2 of the compression rate of the buffer material is 30%, the lower limit E1 of the compression rate of the buffer material is 20%, [E1, E2] = [20%, 30%];

[0079] According to the CFD stress curve data of the foam corresponding to the compression rate range [20%, 30%] of the cushioning material, the CFD stress range [F1, F2] corresponding to the compression rate range [E1, E2] is found to be [0.03MPa, 0.9MPa].

[0080] S3: Calculate the battery module preload range [G1, G2] based on the CFD stress range [F1, F2], and compare the battery module preload range [G1, G2] with the battery module target preload range [H1, H2]:

[0081] If the target preload force lower limit H1 is less than the battery module preload force lower limit G1, and the target preload force upper limit H2 is greater than the battery module preload force upper limit G2, the preload force design meets the requirements; otherwise, adjust the design parameters according to the preload force parameter adjustment rules, and repeat steps S1 to S5 until the preload force design meets the requirements;

[0082] The battery module preload range [G1, G2] is calculated according to the formula G=F×S, wherein the lower limit of the battery module preload range is calculated according to the following formula:

[0083] G1=F1×S

[0084] Where G1 is the lower limit of the preload range of the battery module, F1 is the lower limit of the CFD stress range corresponding to the compression rate range [E1, E2], and S is the contact area between the buffer material and the battery cell;

[0085] The upper limit of the battery module preload range is calculated according to the following formula:

[0086] G2=F2×S

[0087] Where G2 is the upper limit of the preload range of the battery module, F2 is the upper limit of the CFD stress range corresponding to the compression rate range [E1, E2], and S is the contact area between the buffer material and the battery cell.

[0088] According to the calculation results, the battery module preload range can be determined as [G1, G2] = [1200N, 3600N].

[0089] In this embodiment, the target preload force interval of the battery module is set to [H1, H2] = [1000N, 5000N], and the calculated preload force range of the battery module is within the target preload force interval, so the preload force design meets the requirements.

[0090] In step S3, the preload force parameter adjustment rule includes the adjustment of the battery module material parameters and the battery module assembly size parameters. The preload force parameter adjustment rule is to give priority to adjusting the battery module material parameters. If the preload force still does not meet the requirements, the battery module assembly size parameters are adjusted. The battery module materials include end plates, battery cells, and buffer materials. The battery module material parameters include the theoretical value, tolerance value, and buffer material contact area of ​​each material. When adjusting the battery module material parameters in the preload force parameter adjustment rule, the theoretical value of the material is adjusted first, then the tolerance value is adjusted, and finally the buffer material contact area is adjusted.

[0091] In another embodiment, the target preload force interval of the battery module is set to [H1, H2] = [2000N, 5000N], and the calculated preload force range of the battery module is not within the target preload force interval, so the preload force design does not meet the requirements.

[0092] According to the preload force parameter adjustment rules, adjust the theoretical thickness L of the buffer material d is 4.5mm, recalculate the preload force:

[0093] The compression rate range of the cushioning material [E1, E2] = [29%, 37%];

[0094] The CFD stress interval [F1, F2] is [0.03MPa, 0.9MPa] = [0.08MPa, 0.12MPa];

[0095] The preload force range of the battery module is [G1, G2] = [3200N, 4800N], which is within the target preload force range [H1, H2] = [2000N, 5000N], so the adjusted design meets the preload force design requirements.

[0096] S4: Calculate the compression increase rate P of the buffer material according to the expansion size M of the battery cell and the theoretical thickness of the buffer material;

[0097] The calculation formula of the expansion size M of the battery cell is as follows:

[0098] M=K×L c

[0099] Where, L c is the theoretical thickness of the battery cell, K is the expansion rate of the battery cell;

[0100] The calculation formula of the compression increase rate P of the cushioning material is as follows:

[0101] P=M / L d

[0102] Where M is the expansion size of the battery cell, L d It is the theoretical thickness of the cushioning material.

[0103] In this embodiment, the theoretical thickness of the buffer material is L d =4mm, the theoretical thickness of the battery cell is L c =50mm, the cell expansion rate K = 1%, so the cell expansion size = 0.5mm, the buffer material compression increase rate P = 12.5%.

[0104] S5: calculating the EOL compression rate upper limit Q of the buffer material according to the compression increase rate P of the buffer material, and finding the CFD stress R corresponding to the EOL compression rate upper limit Q according to the CFD stress curve data of the buffer material corresponding to the EOL compression rate upper limit Q of the buffer material;

[0105] The calculation formula of the upper limit Q of the EOL compression rate of the buffer material in step S5 is as follows:

[0106] Q=P+E2

[0107] Where P is the compression increase rate of the buffer material, and E2 is the upper limit of the compression rate of the buffer material.

[0108] In this embodiment, the upper limit of the EOL compression rate of the buffer material is Q=12.5%+30%=42.5%.

[0109] According to the CFD stress curve data of the foam, the corresponding CFD stress R is found to be 0.5Mpa.

[0110] S6: Calculate the expansion force U of the battery module based on the CFD stress R, and compare the expansion force U of the battery module with the upper limit J of the battery cell expansion force:

[0111] If the expansion force U is less than the upper limit J of the battery cell expansion force, the design meets the requirements. Otherwise, adjust the design parameters according to the expansion force parameter adjustment rules, repeat steps S4 to S6 until the expansion force design meets the requirements, and recheck the preload force.

[0112] The calculation formula of the expansion force U of the battery module is as follows:

[0113] U=R×S

[0114] Where R is the CFD stress corresponding to the upper limit Q of EOL compression rate, and S is the contact area between the buffer material and the battery cell;

[0115] In this embodiment, the upper limit of the expansion force of the battery cell J=40000N, and the expansion force of the battery module U=0.5×40000=20000N. This expansion force is less than the upper limit of the expansion force of the battery cell J, so the design meets the requirements.

[0116] The expansion force parameter adjustment rule includes prioritizing the adjustment of the battery module material parameters, including sequentially adjusting the theoretical values, tolerance values, and contact areas of the end plates, battery cells, and buffer materials. When the expansion force requirements are still not met after adjusting the battery module material parameters, the battery module assembly size parameters are adjusted.

[0117] The above are only embodiments of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for designing a battery module, characterized in that: The specific steps include: S1: Calculate the battery module gap X based on the material parameters of the battery module; S2: Calculate the compression rate interval [E1, E2] of the buffer material, and find the CFD stress interval [F1, F2] corresponding to the compression rate interval [E1, E2] according to the CFD stress curve data of the buffer material corresponding to the compression rate interval [E1, E2] of the buffer material; S3: Calculate the battery module preload range [G1, G2] based on the CFD stress range [F1, F2], and compare the battery module preload range [G1, G2] with the battery module target preload range [H1, H2]: If the target preload force lower limit H1 is less than the battery module preload force lower limit G1, and the target preload force upper limit H2 is greater than the battery module preload force upper limit G2, the preload force design meets the requirements; otherwise, adjust the design parameters according to the preload force parameter adjustment rules, and repeat steps S1 to S3 until the preload force design meets the requirements; S4: Calculate the compression increase rate P of the buffer material; S5: calculating the EOL compression rate upper limit Q of the buffer material according to the compression increase rate P of the buffer material, and finding the CFD stress R corresponding to the EOL compression rate upper limit Q according to the CFD stress curve data of the buffer material corresponding to the EOL compression rate upper limit Q of the buffer material; S6: Calculate the expansion force U of the battery module based on the CFD stress R, and compare the expansion force U of the battery module with the upper limit J of the battery cell expansion force: If the expansion force U is less than the upper limit J of the battery cell expansion force, the design meets the requirements. Otherwise, adjust the design parameters according to the expansion force parameter adjustment rules, repeat steps S4 to S6 until the expansion force design meets the requirements, and recheck the preload force.

2. The method for designing a battery module according to claim 1, characterized in that: In step S1, the material parameters include the design length A of the module, the thickness B of the end plate, and the thickness C of the battery cell. The battery module gap X includes the gap X1 between the battery cell and the end plate, and the gap X2 between the battery cells. The battery module gap X is calculated according to the design length A of the module, the thickness B of the end plate, and the thickness C of the battery cell. The design length A of the module has the following relationship: A=L a ±T a Where, L a is the theoretical length of the battery module, T a is the battery module length tolerance; The end plate thickness B has the following relationship: B=L b ±T b Where, L b is the theoretical thickness of the end plate, T b is the end plate thickness tolerance; The cell thickness C has the following relationship: C=L c ±T c Where, L c is the theoretical length of the battery module, T c is the battery module length tolerance.

3. The method for designing a battery module according to claim 2, characterized in that: Calculate the battery module gap X according to the following formula: Where N a is the number of battery modules, N b is the number of end plates, N c is the number of cells, L a is the theoretical length of the battery module, L b is the theoretical thickness of the end plate, L c is the theoretical thickness of the cell, T a is the battery module length tolerance, T b is the end plate thickness tolerance, T c is the cell thickness tolerance, N x The amount of buffer material.

4. The method for designing a battery module according to claim 1, characterized in that: In step S2, the calculation formula of the compression rate interval [E1, E2] of the buffer material is as follows: Where, E2 is the upper limit of the compression rate of the buffer material, L d is the theoretical thickness of the buffer material, T d is the thickness tolerance of the buffer material, L x is the theoretical gap of the battery module, T x is the battery module gap tolerance; Where, E1 is the lower limit of the compression rate of the buffer material, L d is the theoretical thickness of the buffer material, T d is the thickness tolerance of the buffer material, L x is the theoretical gap of the battery module, T x is the battery module gap tolerance.

5. The method for designing a battery module according to claim 1, characterized in that: In step S3, the preload force parameter adjustment rule includes adjusting the battery module material parameters and the battery module assembly size parameters. The preload force parameter adjustment rule is to adjust the battery module material parameters first. If the preload force still does not meet the requirements, the battery module assembly size parameters are adjusted.

6. The method for designing a battery module according to claim 5, characterized in that: The battery module material parameters include the theoretical value, tolerance value and buffer material contact area of ​​each material. When adjusting the battery module material parameters in the preload force parameter adjustment rule, the theoretical value of the material is adjusted first, then the tolerance value is adjusted, and finally the buffer material contact area is adjusted.

7. The method for designing a battery module according to claim 1, characterized in that: In step S4, the calculation formula of the buffer material compression increase rate P is as follows: P=L c ×K / L d Where, L c is the theoretical thickness of the battery cell, L d is the theoretical thickness of the buffer material, and K is the expansion rate of the battery cell.

8. The method for designing a battery module according to claim 1, characterized in that: The calculation formula of the upper limit Q of the EOL compression rate of the buffer material in step S5 is as follows: Q=P+E2 Where P is the compression increase rate of the buffer material, and E2 is the upper limit of the compression rate of the buffer material.

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