A safety performance test method of a soft package battery cell

Abstract

The application discloses a kind of safety performance test methods of soft package battery, the method comprises: the soft package battery of full charge is placed on platform;Soft package battery rim is hit by using rim hammering method;Until smoke or fire phenomenon appears or no tab rim is all hammered finished.This application utilizes the characteristics that tab rim is more prone to unevenness, burr and other defects, and the positive and negative tab overhang exists in the edge part of battery, and the edge part of battery is hammered, which can trigger the safety boundary of battery more easily than other methods, and can better represent the destructive effect of soft package battery safety out of control.Therefore, it can better guide battery research and development.

Description

Technical Field

[0001] This invention relates to the field of pouch cells, and more particularly to a method for testing the safety performance of pouch cells. Background Technology

[0002] Based on the type of outer sealing material, battery cells can be classified into three categories: pouch cells, prismatic aluminum-cased cells, and cylindrical cells. There are various methods for testing the safety performance of battery cells, including overcharging, needle penetration, and fire testing. Among these, needle penetration is the most severe test method.

[0003] The purpose of safety performance testing is twofold: first, to determine the safety boundaries of the battery cell, i.e., under what circumstances a safety accident will occur; second, to assess the destructive impact of a battery cell experiencing a safety runaway, which is the most important objective of safety testing. It serves as a crucial means to verify whether the battery cell's safety design meets standards and to optimize its development. However, even the most severe nail penetration tests sometimes fail to trigger the battery cell's safety boundaries and do not reveal the destructive impact of a safety runaway.

[0004] Based on this, the present invention proposes a test method that can more effectively trigger the safety boundary of pouch cells and fully demonstrate the damage situation after safety runaway, so as to better guide research and development optimization. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a safety performance testing method for pouch cells. This method is based on edge hammering. This invention utilizes the fact that unevenness, burrs, and other defects are more likely to occur at the edges of the electrode sheets, as well as the characteristic that the positive and negative electrode sheets are misaligned (overhang) at the edges of the cell. Hammering the edges of the cell can trigger a safety runaway of the cell most easily compared to other methods, thereby providing better guidance for cell research and development.

[0006] The technical solution adopted in this invention is as follows: A method for testing the safety performance of a pouch cell includes: Place the fully charged pouch cells on the platform; The edges of the soft-pack battery cells are struck using an edge-hammering method. Continue until smoke or fire appears, or until all the edges of the infinite loop are completely hammered.

[0007] In the above technical solution, furthermore, the striking sequence of the edge hammering is arbitrarily combined along the edge of the infinite loop.

[0008] Furthermore, the hammering can be done with a metal hammer, rubber hammer, wooden hammer, or plastic hammer.

[0009] Furthermore, except for the first hammer blow, each hammer blow on each edge must partially overlap with the previous hammer blow.

[0010] Furthermore, the striking surface of the hammerhead can be either flat or convex.

[0011] Furthermore, all hammering points on each edge must cover the entire area of ​​that edge; the next edge can only be hammered after the previous edge has been hammered.

[0012] Furthermore, each hammer blow must cause the cell to deform by more than 10% along the thickness direction perpendicular to the platform.

[0013] Furthermore, the hammer marks on the battery cell must meet the following requirements: the length in the direction of the edge of the battery cell must be greater than the length in the direction of the vertical edge, and the length in the direction of the vertical edge must be greater than or equal to 5mm, to ensure that the internal core of the battery cell is hammered.

[0014] The beneficial effects of this invention are: This invention provides a method for triggering the safety boundary of a pouch cell: edge hammering. Since edge hammering is performed at the location where the cell is most likely to fail (the edge of the electrode), compared with tests such as needle penetration, the edge hammering method can not only trigger the boundary of the pouch cell more easily, but also better characterize the destructive impact when the pouch cell runs out of safety control. Attached Figure Description

[0015] Figure 1 It is a single-sided output tab soft-pack battery cell; Figure 2 It is a double-sided tab soft-pack battery cell. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the tools and materials used in the following examples are commercially available.

[0018] In order to fully demonstrate the damage caused by the safety loss of a battery cell, the present invention provides a method that can trigger the safety boundary of a pouch cell and demonstrate the damage caused by the safety loss: edge hammering.

[0019] This invention is achieved through the following technical solution: like Figure 1 As shown, for a single-sided tab soft-pack battery cell, the other three edges besides the edge with the tab are labeled as edge A, edge B, and edge C, respectively.

[0020] like Figure 2 As shown, for a double-sided tab soft-pack battery cell, the other two edges besides the two sides with tabs are marked as edge A and edge B, respectively.

[0021] After placing the fully charged pouch cell on the platform, strike the edge of the cell with a hammer. For a single-sided tab pouch cell, the striking sequence can be any combination of the three edges: A, B, and C; for a double-sided tab pouch cell, the striking sequence can be any combination of the two edges: A and B.

[0022] Preferably, the hammer is a metal hammer, a rubber hammer, or other similar heavy object.

[0023] Except for the first hammer blow, each hammer blow on each edge must partially overlap with the previous hammer blow.

[0024] Preferably, the striking surface of the hammer head can be a flat surface or a convex surface.

[0025] All hammering points on each edge must cover the entire area of ​​that edge; the next edge can only be hammered after the previous edge has been hammered.

[0026] Hammering force requirement: Each hammer blow must cause a deformation of more than 10% in the cell thickness (in the direction perpendicular to the platform).

[0027] Hammer marks on battery cells must be longer along the edge of the cell than along the vertical edge.

[0028] The conditions for ending the edge hammering test are: the appearance of smoke or fire, or the completion of hammering all the edges of the endless tab.

[0029] Example 1: Ten lithium iron phosphate pouch cells (model IFP13151227-50Ah) with single-sided tabs were fully charged and placed on a flat cement slab. The three edges of the tabless were then hammered sequentially with a hammer until smoke or fire appeared, or until all three edges were hammered. The results of the edge hammering test were statistically analyzed.

[0030] Comparative Example 1: Ten lithium iron phosphate pouch cells with a single-sided output tab, model IFP13151227-50Ah, were fully charged and tested according to "6.3.5 Needle Penetration Test" in "GB 43854-2024 Safety Technical Specification for Lithium-ion Batteries for Electric Bicycles". The test results of the needle penetration test were statistically analyzed.

[0031] Example 2: Ten lithium iron phosphate pouch cells (model IFP12145250-50Ah) with dual-sided tabs were fully charged and placed on a flat cement slab. The two edges of the tabless were then hammered sequentially with a hammer until smoke or fire appeared, or until all three edges were hammered. The results of the edge hammering test were statistically analyzed.

[0032] Comparative Example 2: Ten lithium iron phosphate pouch cells with dual-sided tabs, model IFP12145250-50Ah, were fully charged and tested according to "6.3.5 Needle Penetration Test" in GB 43854-2024 Safety Technical Specification for Lithium-ion Batteries for Electric Bicycles. The test results of the needle penetration test were statistically analyzed.

[0033] The experimental results are shown in Table 1: Table 1 Results of the experiments in the examples and comparative examples Example 1 and Comparative Example 1 are test results for single-sided tab cells. The test results show that the proportion of smoke and fire after the new method (edge ​​hammering) test increased, indicating that the new method is more likely to trigger the safety boundary of the pouch cell.

[0034] Example 2 and Comparative Example 2 present the test results for cells with dual-sided tabs. The test results show that the new method (edge ​​hammering) resulted in an increased proportion of smoke and fire after the test, indicating that the new method is more likely to trigger the safety boundaries of pouch cells.

[0035] As shown in Table 1, compared with the comparative example (needle penetration), the number of pouch cells emitting smoke and catching fire increased after edge hammering. This indicates that edge hammering is more likely to trigger the safety boundary of pouch cells and better characterizes the destructive impact after a safety failure. This is mainly because the edges of the positive and negative electrodes contain more electrode defects, such as burrs, cracks, and unevenness. Additionally, the outer shell of the pouch cell is a flexible aluminum-plastic film, making the edges the most vulnerable to safety failures. Edge hammering is a safety test specifically targeting the edges of pouch cells, thus more easily triggering edge safety failures.

[0036] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for testing the safety performance of a pouch cell, characterized in that, include: Place the fully charged pouch cells on the platform; The edges of the soft-pack battery cells are struck using an edge-hammering method. Continue until smoke or fire appears, or until all the edges of the infinite loop are completely hammered.

2. The safety performance testing method for pouch cells according to claim 1, characterized in that, The striking sequence of the edge hammering is a random combination along the edge of the infinite loop.

3. The safety performance testing method for pouch cells according to claim 1, characterized in that, The hammering can be done with a metal hammer, rubber hammer, wooden hammer, or plastic hammer.

4. The safety performance testing method for pouch cells according to claim 1, characterized in that, Except for the first hammer blow, each hammer blow on each edge must partially overlap with the previous hammer blow.

5. The safety performance testing method for pouch cells according to claim 1, characterized in that, The striking surface of the hammer head can be flat or convex.

6. The safety performance testing method for pouch cells according to claim 1, characterized in that, All hammering points on each edge must cover the entire area of ​​that edge; the next edge can only be hammered after the previous edge has been hammered.

7. The safety performance testing method for pouch cells according to claim 1, characterized in that, Each hammer blow must cause the cell to deform by more than 10% along the thickness direction perpendicular to the platform.

8. The safety performance testing method for pouch cells according to claim 1, characterized in that, The hammer marks on the battery cell must meet the following requirement: the length along the edge of the battery cell must be greater than the length along the vertical edge.

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