Splicing design method of dissimilar material cushion pad and battery pack

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a dissimilar material cushion splicing design method and a battery pack. Comprising the following steps: calculating to obtain a minimum expansion gap T0 required by a single battery cell; calculating the total tolerance + / -H of the grouped monomers in the length direction; calculating the minimum thickness T1 required by the cushion pad; obtaining the maximum bearable force F0 of the large surface of the single battery cell; determining the area S1 of left and right edge strips and the area S2 of upper and lower edge strips of the cushion pad; calculating a force value F1 applied to the battery cell by the left and right edge strips at the moment, and verifying F1lt; f0; calculating the thickness T3 of the buffer pad and the compression ratio W2 of the left and right edge strips under the harsh working condition, calculating the force value F2 applied to the battery cell by the left and right edge strips at the moment, and verifying F2lt; f0. According to the method, the experience design of the cushion pad is converted into the accurate quantitative design, and the problem that the performance adaptability of an existing cushion pad made of a single material is insufficient is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a method for splicing heterogeneous material buffer pads and a battery pack. Background Technology

[0002] In recent years, with the rapid development of the new energy vehicle industry, the safety, reliability, and service life of power battery packs have received increasing attention. During vehicle operation, battery packs need to cope with vibration, impact, and volume changes (mainly expansion and contraction) of the cells during charge and discharge cycles. Therefore, buffer pads are usually placed between cells, between cells and end plates, or between cells and the casing to absorb mechanical stress, provide buffer protection, and maintain the relative positional stability between cells.

[0003] Currently, most common battery pack cushioning pads are integrated structures made of a single material (such as silicone, foam, or rubber). While this design can meet basic cushioning needs to some extent, the different cushioning performance requirements at different locations within the battery pack (e.g., the large surface of the cell needs to evenly distribute pressure and allow for expansion gaps, while the edge areas may need to prevent welding spatter or glue overflow) mean that a single material often cannot achieve optimal performance under all operating conditions. This results in limited overall cushioning effect, low material utilization, and even affects the long-term cycle performance of the cell.

[0004] Furthermore, the design and selection of existing buffer pads largely rely on experience or simplified mechanical models, lacking a systematic and quantitative design methodology. Under the combined influence of multiple factors such as cell size tolerances, cumulative tolerances of the pack, assembly space fluctuations, and cell expansion characteristics, traditional design methods struggle to accurately coordinate key parameters such as buffer pad thickness, material hardness, and contact area, easily leading to the following problems: insufficient buffer pad thickness, failing to adequately absorb cell expansion and resulting in excessive stress on the cells; excessive thickness, causing assembly space constraints and even hindering assembly; material selection mismatch with local functions, such as using overly soft materials in areas requiring high support or overly hard materials in areas requiring flexibility; and insufficient design redundancy, failing to cover extreme or beyond-limit operating conditions (such as accumulated assembly errors and equipment precision deviations), affecting the overall safety and reliability of the battery pack. Summary of the Invention

[0005] The purpose of this invention is to provide a design method for splicing heterogeneous material buffer pads and a battery pack, which can provide a buffer pad solution with refined and quantitative design based on the functional requirements of different areas inside the battery pack, so as to improve the adaptability, reliability and economy of the buffer pad, and at the same time provide systematic support for the safety redundancy design of the battery pack.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for designing and splicing dissimilar material cushioning pads, comprising the following steps:

[0008] S1: Based on the thickness D1 and minimum expansion rate W1 of a single cell, calculate the minimum expansion gap T0 required for a single cell, T0 = D1 × W1%.

[0009] S2: Based on the thickness tolerance of individual battery cells, the thickness tolerance of buffer pads, and the thickness tolerance of assembled structural components.

[0010] The total tolerance ±H in the length direction after the individual units are grouped is calculated.

[0011] S3: Based on the module's theoretical installation length L0, maximum installation length L1, and the tolerance ±H obtained in step S2, calculate the minimum thickness T1 required for the buffer pad under the extreme working condition where the installation space is the largest and the group's free length is the shortest, and ensure that T1 > T0.

[0012] S4: Obtain the maximum withstand force F0 of a single battery cell on a large surface area;

[0013] S5: Determine the areas S1 of the left and right side strips and S2 of the top and bottom side strips of the cushioning pad;

[0014] S6: Select different materials for the left and right side strips and the top and bottom side strips respectively. The compressibility A1 of the left and right side strip material is greater than that of the top and bottom side strip material.

[0015] S7: Based on the minimum installation length L2 and tolerance ±H of the module, calculate the thickness T2 of the buffer pad and the compression ratio W1 of the left and right side strips under the extreme working condition of minimum installation space and longest free length of the group, and calculate the force F1 exerted by the left and right side strips on the cell at this time, and verify F1. <F0;

[0016] S8: Based on the theoretical installation length L0 of the module, reduce the preset safety margin Y, calculate the thickness T3 of the buffer pad and the compression ratio W2 of its left and right side strips under more severe working conditions, and calculate the force F2 exerted by the left and right side strips on the battery cell at this time, and verify F2. <F0。

[0017] Preferably, in step S2, the formula for calculating the total tolerance ±H is:

[0018]

[0019] Where N1 is the number of individual battery cells, ±H1 is the thickness tolerance of individual battery cells; N2 is the number of buffer pads, ±H2 is the thickness tolerance of buffer pads; N3, ±H3... are the number and thickness tolerance of other grouped structural components, respectively.

[0020] Preferably, in step S3, the minimum thickness T1 of the buffer pad is calculated using the following formula:

[0021] L1=D1×N1+T1×N2+D3×N3+…-H

[0022]

[0023] Where N1 is the number of individual battery cells, N2 is the number of buffer pads, and D3, N3... are the thickness and number of other grouped structural components.

[0024] Preferably, in step S7, the calculation process of the force value F1 includes:

[0025] a) Calculate the thickness T2: L2=D1×N1+T2×N2+D3×N3+…+H;

[0026]

[0027] b) Calculate the compression ratio W1: W1 = (T1 - T2) / T1 × 100%;

[0028] c) Obtain the corresponding pressure P1 based on the compression ratio W1 and the compression characteristic curves of the selected left and right side strip materials;

[0029] d) Calculate the force value F1: F1 = P1 × S1.

[0030] Preferably, in step S6, the material of the upper and lower edge strips is selected from MPP or DPF foam material, and the material of the left and right edge strips is selected from rubber material with a Shore hardness of 35A to 50A.

[0031] Preferably, in step S8, the safety margin Y is determined based on the accuracy of the equipment used for assembling the battery module into the box.

[0032] The present invention also discloses a battery pack, including a housing and at least one battery cell assembly placed therein. The housing is provided with a crossbeam and a longitudinal beam forming a battery cell receiving cavity. The battery cell assembly includes a plurality of parallel battery cells, buffer pads located between adjacent battery cells and at both ends of the battery cells, and end plates located at both ends of the battery cell assembly. The buffer pads are heterogeneous material splicing buffer pads designed using the design method described above.

[0033] Preferably, the dissimilar material splicing buffer pad includes:

[0034] The left and right side bars are used to provide the main expansion buffer, and the top and bottom side bars are functionally distinct from the left and right side bars;

[0035] The left and right strips are made of a first material, and the top and bottom strips are made of a second material, wherein the compressibility of the first material is greater than that of the second material.

[0036] Preferably, the first material is hard rubber, and the second material is MPP or DPF foam material.

[0037] Preferably, the buffer pad is fixedly connected to the battery cell and end plate by adhesive bonding.

[0038] The beneficial effects of this invention are as follows: By introducing a dissimilar material splicing design system based on the differentiated performance requirements of different regions of the battery pack, and combining it with a multi-dimensional quantitative calculation method covering expansion gaps, group tolerances, compression ratios, and force values, this invention achieves a transformation from empirical design to precise quantitative design of the buffer pad, effectively solving the problem of insufficient performance adaptability of existing single-material buffer pads. This method not only significantly improves the adaptability and reliability of the buffer pad through "on-demand allocation" of material selection and structural layout, but also covers extreme and ultra-extreme working conditions through system safety redundancy verification. Thus, while ensuring the safety of the battery cells under stress, it improves the overall lifespan and safety of the battery pack, while achieving efficient material utilization and reducing production costs. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall structure of a battery pack including a spliced ​​buffer pad made of dissimilar materials, provided by an embodiment of the present invention;

[0040] Figure 2 yes Figure 1 A top view of the internal structure of the battery pack housing;

[0041] Figure 3 yes Figure 1 A schematic diagram of the cell assembly structure within a cell housing cavity;

[0042] Figure 4 This is a three-dimensional structural diagram of the dissimilar material splicing buffer pad used in an embodiment of the present invention;

[0043] Figure 5 This is a flowchart of the dissimilar material buffer pad splicing design method of the present invention;

[0044] The labels in the diagram are explained as follows:

[0045] 1. Housing; 11. Crossbeam; 12. Longitudinal beam; 101. Cell housing cavity; 2. Cell assembly; 21. Cell; 22. Dissimilar material splicing buffer pad; 23. End plate; 201. Top edge strip; 202. Bottom edge strip; 203. Left side strip; 204. Right side strip. Detailed Implementation

[0046] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0047] Reference Figure 5 The flowchart shown illustrates a specific implementation of this design method, which includes the following steps:

[0048] Step 1: Determine the minimum expansion gap T0 required for a single battery cell.

[0049] Obtain the design thickness D1 (e.g., 52.72 mm) of a single battery cell and its minimum volumetric expansion rate W1% (e.g., 2%) that may occur during charge-discharge cycles. Calculate the minimum theoretical gap required to ensure free expansion of the cell without excessive compression using the formula T0 = D1 × W1%. For example, T0 = 52.72 mm × 2% = 1.054 mm.

[0050] Step 2: Calculate the cumulative tolerance ±H in the length direction after the modules are assembled.

[0051] Considering production batch fluctuations, collect the thickness tolerances of individual battery cells (±H1, e.g., ±0.3mm), buffer pad thickness tolerances (±H2, e.g., ±0.1mm), and thickness tolerances of other structural components such as end plates (±H3, e.g., ±0.3mm). Calculate the number of battery cells (N1, e.g., 16), buffer pads (N2, e.g., 15), and end plates (N3, e.g., 2) within a module. Calculate the overall cumulative tolerance using the sum-of-squares formula: ±H=±√[N1×(±H1)] 2 +N2×(±H2) 2 +N3×(±H3) 2 Using this example, ±H≈±2.770mm.

[0052] Step 3: Calculate and verify the minimum design thickness T1 of the cushioning pad.

[0053] Based on the overall battery pack layout, obtain the theoretical length L0 (e.g., 875.72mm), the maximum allowable installation length L1 (e.g., 876.72mm), and the minimum installation length L2 (e.g., 874.72mm) of the module installation space. In the worst-case scenario where the installation space is at its maximum (L1) and the free length of the group is at its minimum (nominal size minus tolerance H), the minimum required thickness T1 of the buffer pad is calculated using the formula L1 = D1 × N1 + T1 × N2 + D3 × N3 + ... - H. The calculated T1 is approximately 1.133mm, which is rounded to 1.2mm based on commonly used material specifications. It must be verified that T1 > T0 (i.e., 1.2mm > 1.054mm) to ensure that the reserved gap is greater than the minimum expansion requirement of the battery cell; otherwise, the input parameters need to be adjusted and the calculation recalculated.

[0054] Step 4: Obtain the cell mechanical performance limit F0.

[0055] Obtain the maximum allowable pressure F0 (e.g., 5000N) that the large surface (i.e. the plane in contact with the buffer pad) can withstand from the cell's technical specifications. This value serves as the safe upper limit for the load applied to the buffer pad under all subsequent operating conditions.

[0056] Step 5: Determine the areas S1 and S2 of the buffer pad edge strips.

[0057] According to the structural design of the cushioning pad (e.g.) Figure 4 Measure or calculate the total effective bearing area S1 of the left and right edge strips (203, 204) and the total effective bearing area S2 of the top and bottom edge strips (201, 202). For example, if the dimensions of a single left and right edge strip are 83mm × 5mm, then S1 = 83 × 5 × 2 = 830mm. 2 .

[0058] Step Six: Selecting Dissimilar Materials.

[0059] Selection should be based on functional differences: the left and right side strips primarily function to absorb cell expansion and provide cushioning, requiring materials with good compressibility (i.e., relatively soft) (such as hard rubber with a Shore hardness of 50A); the top and bottom side strips mainly serve auxiliary functions such as positioning, splash prevention, or adhesive blocking, and can be made of relatively harder or higher-density materials (such as DPF dual-density foam). After selection, it must be confirmed that the compressibility A1 of the left and right side strip materials is greater than the compressibility A2 of the top and bottom side strip materials.

[0060] Step 7: Verify the safety of the installation under the most stringent conditions.

[0061] Calculate the actual thickness T2 of the buffer pad after compression under the extreme condition of "minimum installation space (L2)" and "maximum free length of the group (nominal size plus tolerance H)". Solve using the formula L2=D1×N1+T2×N2+D3×N3+…+H, and we get T2≈0.682mm.

[0062] Calculate the compression ratio of the left and right side strips under this working condition: W1=(T1-T2) / T1×100%=(1.2-0.682) / 1.2×100%≈31.80%.

[0063] Based on the stress-strain curves of the selected left and right side strip materials (50A hard rubber), find the pressure P1 (e.g., 0.5525 MPa) corresponding to a compression ratio of 31.80%.

[0064] Calculate the total force exerted on the battery cell by the left and right side strips at this time: F1=P1×S1=0.5525MPa×830mm 2 ≈458.6N.

[0065] It is necessary to verify that F1 < F0 (i.e., 458.6 N < 5000 N) to ensure the safety of the battery cells under the tightest assembly state.

[0066] Step Eight: Verify the safety under extreme working conditions (assembly error).

[0067] Considering the possible over-tolerance in actual assembly, a safety margin Y is set (for example, according to the precision of the equipment for putting into the box, the total assembly tolerance Y = 4 mm is set). Subtract Y from L0 to simulate an extreme working condition with a smaller installation space than the designed one.

[0068] Calculate the thickness T3 of the buffer pad under this working condition: L0 - Y = D1×N1 + T3×N2 + D3×N3 + … + H, and solve to get T3 ≈ 0.482 mm.

[0069] Calculate the compression ratio: W2 = (T1 - T3) / T1×100% ≈ 59.83%.

[0070] Check the material curve to obtain the corresponding pressure P2 (for example, 1.745 MPa), and calculate the force value F2 = P2×S1 ≈ 1448.4 N.

[0071] Finally, verify that F2 < F0 (1448.4 N < 5000 N). If it is satisfied, the entire design passes the verification; if not, it is necessary to return to Step Six to reselect a softer material or optimize the area of the side strip.

[0072] Refer to Figures 1 to 4 , and the specific implementation manner of the battery pack designed by applying the above method is as follows:

[0073] The battery pack includes a box body 1 and a plurality of battery cell groups 2 arranged therein. Inside the box body 1, a plurality of battery cell accommodation cavities 101 for accommodating the battery cell groups 2 are separated by cross beams 11 and longitudinal beams 12.

[0074] Each battery cell group 2 includes a plurality of battery cells 21 arranged side by side in the thickness direction, and dissimilar material splicing buffer pads 22 arranged between every two adjacent battery cells 21 and between the two ends of the battery cell group and the end plates 23. The buffer pads 22 are fixedly connected to the large surfaces of the battery cells 21 and the end plates 23 by means of adhesives, etc.

[0075] The key dissimilar material splicing buffer pad 22 (such as Figure 4 ) is spliced by four parts: an upper side strip 201, a lower side strip 202, a left side strip 203, and a right side strip 204. In this embodiment, the left side strip 203 and the right side strip 204 are made of hard rubber (such as 50A) and are responsible for providing the main expansion buffer; while the upper side strip 201 and the lower side strip 202 are made of DPF foam and mainly play an auxiliary positioning and protection role. This splicing structure realizes the "demand-based distribution" of material properties and ensures its reliability and safety under various working conditions through the aforementioned quantitative design method.

[0076] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for designing splicing cushioning pads made of dissimilar materials, characterized in that, Includes the following steps: S1: Calculate the minimum expansion gap T0 required for a single cell based on the thickness (D1) and minimum expansion rate (W1%) of the single cell, T0 = D1 × W1%. S2: Based on the thickness tolerance of individual cells, the thickness tolerance of buffer pads, and the thickness tolerance of grouped structural components, the total tolerance ±H in the length direction after the cells are grouped together is calculated. S3: Based on the module's theoretical installation length (L0), maximum installation length (L1), and the tolerance ±H obtained in step S2, calculate the minimum thickness T1 required for the buffer pad under the extreme working condition where the installation space is the largest and the group's free length is the shortest, and ensure that T1 > T0. S4: Obtain the maximum withstand force F0 of a single battery cell on a large surface area; S5: Determine the area of ​​the left and right side strips (S1) and the area of ​​the top and bottom side strips (S2) of the cushioning pad; S6: Select different materials for the left and right side strips and the top and bottom side strips respectively. The compressibility (A1) of the material for the left and right side strips is greater than that of the material for the top and bottom side strips (A2). S7: Based on the minimum installation length (L2) and tolerance ±H of the module, calculate the thickness T2 of the buffer pad and the compression ratio (W1) of its left and right side strips under the extreme working condition of minimum installation space and longest free length of the group, and calculate the force F1 exerted by the left and right side strips on the cell at this time, and verify F1. <F0; S8: Based on the theoretical installation length (L0) of the module, reduce the preset safety margin Y, calculate the thickness T3 of the buffer pad and the compression ratio (W2) of its left and right side strips under more severe working conditions, and calculate the force F2 exerted by the left and right side strips on the battery cell at this time, and verify F2. <F0。 2. The design method according to claim 1, characterized in that, In step S2, the formula for calculating the total tolerance ±H is: Where N1 is the number of individual battery cells, ±H1 is the thickness tolerance of individual battery cells; N2 is the number of buffer pads, ±H2 is the thickness tolerance of buffer pads; N3, ±H3... are the number and thickness tolerance of other grouped structural components, respectively.

3. The design method according to claim 1, characterized in that, In step S3, the minimum thickness T1 of the buffer pad is calculated using the following formula: L1=D1×N1+T1×N2+D3×N3+…-H Where N1 is the number of individual battery cells, N2 is the number of buffer pads, and D3, N3... are the thickness and number of other grouped structural components.

4. The design method according to claim 1, characterized in that, In step S7, the calculation process of the force value F1 includes: a) Calculate the thickness T2: L2=D1×N1+T2×N2+D3×N3+…+H; b) Calculate the compression ratio W1: W1 = (T1 - T2) / T1 × 100%; c) Obtain the corresponding pressure P1 based on the compression ratio W1 and the compression characteristic curves of the selected left and right side strip materials; d) Calculate the force value F1: F1 = P1 × S1.

5. The design method according to claim 1, characterized in that, In step S6, the material of the upper and lower edge strips is selected from MPP or DPF foam material, and the material of the left and right edge strips is selected from rubber material with a Shore hardness of 35A to 50A.

6. The design method according to claim 1, characterized in that, In step S8, the safety margin Y is determined based on the accuracy of the equipment used for assembling the battery module into the box.

7. A battery pack comprising a housing (1) and at least one battery cell assembly disposed therein, the housing (1) having a crossbeam (11) and a longitudinal beam (12) forming a battery cell receiving cavity (101), the battery cell assembly comprising a plurality of parallel battery cells (21), buffer pads (22) located between adjacent battery cells (21) and at both ends of the battery cells, and end plates (23) located at both ends of the battery cell assembly, characterized in that, The buffer pad (22) is a non-material spliced ​​buffer pad designed using the design method described in any one of claims 1 to 6.

8. The battery pack according to claim 7, characterized in that, The dissimilar material splicing buffer pad includes: The left side bar (203) and right side bar (204) are used to provide the main expansion buffer, and the upper side bar (201) and lower side bar (202) are functionally distinct from the left and right side bars; The left side strip (203) and the right side strip (204) are made of a first material, and the upper side strip (201) and the lower side strip (202) are made of a second material, wherein the compressibility of the first material is greater than that of the second material.

9. The battery pack according to claim 8, characterized in that, The first material is rigid rubber, and the second material is MPP or DPF foam material.

10. The battery pack according to claim 7, characterized in that, The buffer pad (22) is fixedly connected to the battery cell (21) and the end plate (23) by adhesive bonding.

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