A method for detecting foreign matter resistance of a soft package battery

Abstract

The application discloses a soft package battery foreign matter tolerance detection method, and relates to the battery detection field. The battery minimum unit is adopted for detection. The method comprises the following steps: grouping the foreign matter according to attributes and sizes; adjusting test variables, placing the foreign matter between two soft package batteries, adhering the two soft package batteries, and applying pressure to make the two soft package batteries extrude each other; the test variables comprise foreign matter attributes, foreign matter placement positions, foreign matter quantities, foreign matter sizes and applied pressure values; the battery state is analyzed after each time of applying pressure, and the test variable values and the corresponding battery states are recorded; and the test variables comprise foreign matter sizes and applied pressure values. The application is used for detecting the tolerance of different battery cell products to foreign matters, the test is carried out on the minimum unit of the battery, the influence of other non-related factors is maximally excluded, and the detection result is more direct and effective.

Description

Technical Field

[0001] This invention relates to the field of pouch battery testing, and more particularly to a method for testing the foreign object tolerance of pouch batteries. Background Technology

[0002] Soft-pack batteries are widely used in the current market. During the production, processing, assembly, and transportation processes, it is inevitable that some metal impurities will enter the battery. If the metal foreign object is too large or is subjected to a large external impact, it may cause an internal short circuit and lead to danger.

[0003] Current research on metal foreign objects in pouch batteries primarily focuses on controlling and detecting these objects. Testing the battery's tolerance to metal foreign objects mainly refers to commonly used standards such as national, international, and European standards, including IP protection, foreign object resistance testing, and needle penetration testing. There are no clear standards for testing the battery's own tolerance to metal foreign objects.

[0004] 1. Due to differences in the cleanliness control capabilities of each battery manufacturer's production line, the battery's own protection, and the battery's performance, general standards can only detect whether a certain standard has been met, but do not know the tolerance of different products to metallic foreign objects.

[0005] 2. Conventional standard test conditions are relatively simple and mostly short-cycle tests, which cannot be obtained for long-cycle testing.

[0006] 3. Existing products are typically tested at the module or battery pack level, which involves many variables. If failures caused by other factors are found, they cannot be quickly and effectively identified.

[0007] 4. Existing testing standards only address the requirements of current market batteries. As technology advances, testing standards will be adjusted accordingly, and the detection of metallic foreign objects will need to be redone.

[0008] Existing testing standards only assess whether the battery itself meets the standards, and there are no special reference standards for production line cleanliness control and packaging and transportation standards. Summary of the Invention

[0009] To address the challenge of testing the tolerance of pouch batteries to metallic foreign objects, this invention proposes a method for testing the tolerance of pouch batteries to metallic foreign objects.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0011] A method for detecting the foreign object tolerance of a pouch battery, using the smallest cell of the battery for testing, includes the following steps:

[0012] 1) Divide the foreign objects into several test groups from largest to smallest according to their size;

[0013] 2) Test the foreign objects grouped from largest to smallest, including: placing the foreign object between two pouch batteries, pressing the two pouch batteries together and applying pressure to squeeze the two pouch batteries towards each other, applying pressure values ​​from largest to smallest in sequence, and holding the pressure value for a preset time for each application.

[0014] 3) Analyze the battery status after each pressure application and record the test data and corresponding battery status;

[0015] 4) If there are unqualified battery conditions after the current testing group applies pressure, reduce the size of the foreign object and repeat steps 2) and 3).

[0016] Specifically, steps 2) and 3) include: determining the foreign object's properties, its location, and quantity, and then executing:

[0017] Several groups of foreign objects, ranging in size from large to small, are subjected to pressures ranging from large to small. The battery status is analyzed after each pressure application. If the battery status is qualified after the current group of objects is pressured, the test ends.

[0018] If the battery condition is found to be substandard, test with the next size of foreign object.

[0019] Record the size of the foreign object, the pressure, and the corresponding battery status.

[0020] As a preferred approach, methods for analyzing battery state include:

[0021] After each pressure is applied, visual inspection, electrical performance testing, aluminum-plastic film testing, and electrode testing are performed in sequence. If any step fails to meet the requirements, the next foreign object size or pressure is changed for testing.

[0022] The methods for performing visual inspection, electrical performance testing, aluminum-plastic film testing, and electrode inspection in sequence include:

[0023] Visually inspect for any damage. If damage is found, record the battery status, as well as the current foreign object's attributes, location, size, and quantity. End the current inspection and proceed to the next foreign object size or pressure level for the next round of pressure application and inspection.

[0024] If the battery is not damaged, test its electrical performance, insulation, and withstand voltage performance to see if they are up to standard. If they are not up to standard, record the battery status, as well as the current foreign object's properties, location, size, and quantity. End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing.

[0025] If the test is successful, proceed with the aluminum-plastic film test. If the test fails, record the battery status, as well as the current foreign object properties, location, size, and quantity. End the current test and proceed with the next foreign object size or pressure level for the next round of pressure application and testing.

[0026] If the test is successful, perform electrode testing. If the test is unsuccessful, record the battery status, as well as the current foreign object's properties, location, size, and quantity. End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing.

[0027] If the test is successful, record the battery status, as well as the current foreign object attributes, location, size, and quantity, and end the current test.

[0028] The method of changing to the next foreign object size or pressure for the next round of pressure application and testing includes: if all pressure values ​​of the current test group have been applied and there is an unqualified battery state, then change to the next foreign object size.

[0029] If there are still untested pressure values ​​in the current test group, and the analysis score is unqualified after applying the current pressure value, then switch to the next lower pressure level for testing, until all pressure tests are completed before moving on to the next test group.

[0030] As a preferred option, the aluminum-plastic film testing method includes: black box testing, used to confirm whether there are penetrating cracks in the aluminum layer.

[0031] ① Place the aluminum-plastic film in a dark environment; ② Illuminate the test area of ​​the aluminum-plastic film with a beam of light; ③ Observe whether the light source passes through.

[0032] Therefore, the testing methods for aluminum-plastic film include: acid washing test, used to confirm the order of damage to the aluminum-plastic film. The structure of aluminum-plastic film includes an outer nylon layer -> an aluminum layer -> an inner PP layer.

[0033] ① Take a sample of aluminum-plastic film that transmits light through a black box test;

[0034] ②Drip hydrochloric acid into the outer nylon layer and the inner PP layer respectively;

[0035] ③ Observe whether bubbles are produced.

[0036] As a preferred option, the electrode inspection method includes: checking each layer for pits or damage, and recording the depth of pits and the length of cracks in damage.

[0037] As a preferred option, the number, properties, or placement of foreign objects can be changed before proceeding with the detection according to steps 2)-4).

[0038] As a preferred embodiment, the foreign object placement locations include at least: the positive and negative terminals of the battery cell, and the middle position of the battery cell; the corresponding number of foreign objects includes at least three, namely at least one each at the positive and negative terminals of the battery cell, and at least one at the middle position of the battery cell.

[0039] The beneficial effects of this invention are:

[0040] The purpose of this invention is to provide a method for testing the tolerance of pouch batteries to metallic foreign objects, used to test the tolerance of different battery cell products to foreign objects. By testing at the smallest battery unit, the influence of other irrelevant factors is minimized, resulting in more direct and effective test results. Testing based on the smallest battery unit (cell) allows the test results to be used as a reference for modules and battery packs, offering significant advantages in terms of testing time and cost.

[0041] At the same time, the test method takes into account the impact of long-term testing conditions and comprehensively evaluates the effects of different metallic foreign objects on the battery. Moreover, this test method can detect the product's tolerance limit to metallic foreign objects to the greatest extent, which is of great reference value for the adjustment of standards and regulations in the future.

[0042] Moreover, placing particles of the same size in different locations under the same pressure helps to identify weak points in the battery cell, facilitating overall improvement and optimization, and can also provide reference support for the analysis of other potential causes of failure.

[0043] Furthermore, the testing method and equipment mentioned in this invention are simple to operate and will not affect the project cycle or cost of conventional development, providing strong guidance for production line cleanliness control and packaging and transportation standards.

[0044] Furthermore, this invention evaluates the relevant performance of a product through the simplest stress test. The testing conditions proceed from the surface to the core, from the overall to the specific, with a simple process and high efficiency. The test conditions are evaluated based on product characteristics and application conditions, simulating the product's performance under application conditions to the greatest extent, truly reflecting the product's actual tolerance, and making the test results more effective. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 Conventional pouch battery structure;

[0047] Figure 2 A schematic diagram showing a foreign object between two batteries;

[0048] Figure 3 This is a flowchart of the testing method;

[0049] Figure 4 A schematic diagram of the preferred placement location for foreign objects. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0051] The typical structure of a pouch cell, from the outside in, consists of: 1. an aluminum-plastic film, 2. a separator and electrodes, and 3. an electrolyte. Figure 1 As shown.

[0052] Testing is performed using the smallest battery cell, including the following steps:

[0053] 1) Divide the foreign objects into several groups from largest to smallest according to their size;

[0054] 2) Test the foreign objects grouped from largest to smallest, including: placing a foreign object 4 between two pouch batteries 3, pressing the two pouch batteries together and applying pressure to squeeze them towards each other, applying pressure values ​​from largest to smallest sequentially, and holding the pressure value for a preset time each time, such as... Figure 2 As shown in (a) and (b), the pressure holding time can be selected based on experience, for example, 10 seconds, but longer or shorter times are also possible.

[0055] 3) Analyze the battery status after each pressure application and record the test data and corresponding battery status;

[0056] 4) After the current testing group applies pressure, if there is an unqualified battery condition, reduce the size of the foreign object and repeat steps 2) and 3).

[0057] Specifically, steps 2) and 3) include: determining the foreign object's properties, its location, and quantity, and then executing:

[0058] Several groups of foreign objects, ranging in size from large to small, are subjected to pressures ranging from large to small. The battery status is analyzed after each pressure application. If the battery status is qualified after the current group of objects is pressured, the test ends.

[0059] If the battery condition is found to be substandard, test with the next size of foreign object.

[0060] Record the size of the foreign object, the pressure, and the corresponding battery status.

[0061] For a specific example, first determine the properties of the foreign object (such as material properties), such as copper particles, determine the placement location, such as the middle and both sides of the battery cell, determine the number of foreign objects to be three, and place one in each of the three locations.

[0062] Among them, the foreign matter properties are selected based on the particles that may appear during the production process of soft-pack batteries, such as copper and aluminum particles. The size and structure of these particles are also adjusted according to different production lines.

[0063] The identified foreign objects are divided into several groups according to size. The test begins with the largest foreign object. Following the steps above, the foreign object is placed between two pouch cells, and pressure is applied to press the two pouch cells together. The pressure is applied sequentially from high to low. After each pressure application, the battery status is analyzed, and the data is recorded, for example, in Table 1 below.

[0064] Table 1

[0065]

[0066] Table 1 shows the lateral parameters as the size of the foreign object from largest to smallest. If the foreign object is an irregular particle, the maximum size of the two longitudinal points when it is naturally placed on a plane can be used as the size of the foreign object. Other measurement methods are not excluded.

[0067] Table 1 shows the vertical parameters as pressure values ​​from largest to smallest. Experiments were conducted sequentially according to this table, and the battery status was recorded as either qualified (yes) or unqualified (no).

[0068] If any foreign object size in the current group fails to meet the requirements, the test must be continued with a smaller foreign object size. If there are both acceptable and unacceptable pressure values ​​in the same group of foreign object sizes, once an acceptable pressure value is found, the test for the current group can be terminated directly, and the test for the next group of foreign object sizes can begin.

[0069] The qualified and unqualified battery conditions mentioned above are analyzed in the following way:

[0070] After each pressure is applied, visual inspection, electrical performance testing, aluminum-plastic film testing, and electrode testing are performed in sequence. If any step fails to meet the requirements, the next foreign object size or pressure is changed for testing.

[0071] The main impact of foreign metal particles inside a battery is that, under pressure, they can cut through the aluminum-plastic film on the battery surface, causing leakage or internal short circuits. When pressure is applied in the presence of metal particles, damage to the battery cell will most directly manifest as poor appearance and insulation. If the battery performs well under the above tests, further disassembly and evaluation are necessary for more accurate testing. Therefore, after visual inspection and electrical performance testing, the battery needs to be disassembled for further analysis.

[0072] The specific methods for conducting visual inspection, electrical performance testing, aluminum-plastic film testing, and electrode testing in sequence are as follows: Figure 3 ,include:

[0073] a. Visually inspect for any damage. If damaged, record the battery status, as well as the current foreign object's attributes, location, size, and quantity.

[0074] End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing.

[0075] If the battery is not damaged, b. check whether the electrical performance, insulation and withstand voltage performance are up to standard. If they are not up to standard, record the battery status, as well as the current foreign object properties, location, size and quantity.

[0076] End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing.

[0077] If it passes, c. perform aluminum-plastic film testing; if it fails, record the battery status, as well as the current foreign object properties, location, size, and quantity.

[0078] End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing.

[0079] If it passes, d. perform electrode testing; if it fails, record the battery status, as well as the current foreign object properties, location, size, and quantity.

[0080] End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing.

[0081] If the test is successful, e. record the battery status, as well as the current foreign object attributes, location, size, and quantity, and end the current test.

[0082] The method of changing to the next foreign object size or pressure for the next round of pressure application and testing includes: if all pressure values ​​of the current test group have been applied, then change to the next foreign object size;

[0083] If there are still untested pressure values ​​in the current test group, switch to the next lower pressure setting for testing, and continue testing until all pressures have been tested before replacing the foreign object with the next set.

[0084] Furthermore, it is understandable that if the battery condition is qualified after applying all pressure values ​​in the current group, the current test can be ended directly. If the battery condition is qualified after applying the current pressure value in the current group, but there are still unqualified battery conditions after applying the previous pressure value, the test can proceed directly to the next group when a qualified condition is found.

[0085] The above-mentioned detection methods can be implemented in different ways. This embodiment introduces one preferred solution:

[0086] (1) Aluminum-plastic film testing is used to detect whether the aluminum-plastic film is damaged. The method used in this embodiment includes: black box testing, which is used to confirm whether there is a through crack in the aluminum layer. ① Place the aluminum-plastic film in a dark environment; ② Illuminate the area to be tested on the aluminum-plastic film with a beam of strong light; ③ Observe whether the light source passes through. If it passes through, it means that there is damage.

[0087] (2) Pickling test, used to confirm the order of damage to aluminum-plastic film, wherein the aluminum-plastic film from the outside to the inside is the outer nylon layer -> aluminum layer -> inner PP layer.

[0088] ① Take a sample of aluminum-plastic film that transmits light through a black box test;

[0089] ②Drip hydrochloric acid into the outer nylon layer and the inner PP layer respectively;

[0090] ③ Observe whether bubbles are produced.

[0091] The aluminum layer will react with hydrochloric acid to produce hydrogen gas: 2Al + 6HCl = 2AlCl3 + 3H2↑, while the nylon and PP layers will not. If bubbles are produced, it can be determined that the nylon and PP layers are damaged.

[0092] As a preferred method, the detection method for the electrode and the diaphragm includes: detecting whether each layer has pits or damage, and recording the depth and crack length.

[0093] After disassembling the battery, if the previous tests are all passed, and the electrode sheets and separator also meet the requirements, the parameters of the foreign object pits on the surface of the pouch cell can be recorded to provide a reference for the subsequent pit standard setting. For example, if a 1000μm foreign object particle is used for testing, and all indicators meet the requirements after testing, the pouch cell quality is qualified. Then the pit depth on the surface of the pouch cell can be determined to be 500 micrometers. This value should be recorded to provide a reference for the subsequent pit standard setting. As a preferred foreign object placement scheme, at least the following locations are included: such as... Figure 4 The positive and negative terminals of the battery cell are 3-1 and 3-2, and the middle terminal of the battery cell is 3-3. The number of foreign objects is at least three, namely at least one at each of the positive and negative terminals of the battery cell and at least one at the middle terminal of the battery cell.

[0094] After prolonged operation, batteries will swell to varying degrees, and the internal pressure will increase, usually in the middle of the battery. Therefore, it is preferable to place metal particles (foreign objects) at the location of maximum swelling.

[0095] At the same time, the possibility of short circuits at the positive and negative terminals of the battery is also a key concern. If different products require evaluation of the sealing or other edge positions, microparticles can also be placed.

[0096] Setting the initial maximum pressure:

[0097] The pressure setting takes into account two aspects: first, the internal pressure that the battery product itself is designed to withstand; and second, the test data of the product at the module or battery pack level (such as swelling cycle, fast charging cycle, etc.).

[0098] Since the testing conditions range from stringent to general, the first foreign objects to pass all tests are those with the largest particle size and the largest pressure that the battery can withstand. Considering that batteries will swell to some extent during use, and there is generally a minimum pressure assessment within the module or battery pack, this proposal suggests prioritizing the adjustment of the size of metal particles. The specific tolerance limit will be considered based on the application requirements of different battery products.

[0099] In this embodiment, the foreign matter is mainly evaluated as metallic particles, but other non-metallic foreign matter is not excluded.

[0100] Furthermore, it should be noted that all equivalent or simple variations made to the methods and principles described in this invention are included within the scope of protection of this invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of this invention or exceed the scope defined in these claims, all of which should fall within the scope of protection of this invention.

Claims

1. A method for testing the foreign object tolerance of a pouch battery, characterized in that, Testing is performed using the smallest battery cell, including the following steps: 1) Divide the foreign objects into several test groups from largest to smallest according to their size; 2) Test the foreign objects grouped from largest to smallest, including: placing the foreign object between two pouch batteries, pressing the two pouch batteries together and applying pressure to squeeze the two pouch batteries towards each other, applying pressure values ​​from largest to smallest in sequence, and holding the pressure value for a preset time for each application. 3) Analyze the battery status after each pressure application and record the test data and corresponding battery status; Methods for analyzing battery status include: After each pressure is applied, visual inspection, electrical performance testing, aluminum-plastic film testing, and electrode testing are performed in sequence. If any step fails to meet the requirements, the next foreign object size or pressure is changed for testing. The aluminum-plastic film testing method includes: acid washing test, used to confirm the damage sequence of the aluminum-plastic film. The structure of the aluminum-plastic film includes an outer nylon layer -> an aluminum layer -> an inner PP layer. ① Take a sample of aluminum-plastic film that transmits light through a black box test; ②Drip hydrochloric acid into the outer nylon layer and the inner PP layer respectively; ③ Observe whether bubbles are produced; 4) If there are unqualified battery conditions after the current testing group applies pressure, reduce the size of the foreign object and repeat steps 2) and 3).

2. The method for detecting foreign object tolerance of a soft-pack battery according to claim 1, characterized in that, Steps 2) and 3) specifically include: determining the foreign object's properties, its location, and quantity, and then executing: Several groups of foreign objects, ranging in size from large to small, are subjected to pressures ranging from large to small. The battery status is analyzed after each pressure application. If the battery status is qualified after the current group of objects is pressured, the test ends. If the battery condition is found to be substandard, test with the next size of foreign object. Record the size of the foreign object, the pressure, and the corresponding battery status.

3. The method for detecting foreign object tolerance of a soft-pack battery according to claim 1, characterized in that, The methods for performing visual inspection, electrical performance testing, aluminum-plastic film testing, and electrode testing in sequence include: Visually inspect for any damage. If damage is found, record the battery status, as well as the current foreign object's attributes, location, size, and quantity. End the current inspection and proceed to the next foreign object size or pressure level for the next round of pressure application and inspection. If the battery is not damaged, test its electrical performance, insulation, and withstand voltage performance to see if they are up to standard. If they are not up to standard, record the battery status, as well as the current foreign object's properties, location, size, and quantity. End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing. If the test is successful, proceed with the aluminum-plastic film test. If the test fails, record the battery status, as well as the current foreign object properties, location, size, and quantity. End the current test and proceed with the next foreign object size or pressure level for the next round of pressure application and testing. If the test is successful, perform electrode testing. If the test is unsuccessful, record the battery status, as well as the current foreign object's properties, location, size, and quantity. End the current test and change to the next foreign object size or pressure for the next round of pressure application and testing. If the test is successful, record the battery status, as well as the current foreign object attributes, location, size, and quantity, and end the current test.

4. The method for detecting foreign object tolerance of a soft-pack battery according to claim 3, characterized in that, The method of changing to the next foreign object size or pressure for the next round of pressure application and testing includes: if all pressure values ​​of the current test group have been applied and there is an unqualified battery state, then change to the next foreign object size; If there are still untested pressure values ​​in the current test group, and the analysis score is unqualified after applying the current pressure value, then switch to the next lower pressure level for testing, until all pressure tests are completed before moving on to the next test group.

5. The method for detecting foreign object tolerance of a soft-pack battery according to claim 1, characterized in that, The aluminum-plastic film testing method includes: a black box test, used to confirm whether there are penetrating cracks in the aluminum layer. ① Place the aluminum-plastic film in a dark environment; ② Illuminate the test area of ​​the aluminum-plastic film with a beam of light; ③ Observe whether the light source passes through.

6. The method for detecting foreign object tolerance of a soft-pack battery according to claim 1, characterized in that, The method for testing electrodes includes: checking each layer for pits or damage, recording the depth of pits and the length of cracks in damaged layers.

7. The method for detecting foreign object tolerance of a soft-pack battery according to claim 1, characterized in that, After changing the number, properties, or placement of foreign objects, perform the detection according to steps 2)-4).

8. The method for detecting foreign object tolerance of a soft-pack battery according to claim 1, characterized in that, The placement of foreign objects includes at least the positive and negative terminals of the battery cell and the middle position of the battery cell; the corresponding number of foreign objects includes at least three, namely at least one at each of the positive and negative terminals of the battery cell and at least one at the middle position of the battery cell.

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