Secondary battery tab life prediction method

Abstract

The application provides a secondary battery tab life prediction method, comprising the following steps: S10: providing a plurality of test samples and preparing corrosive solutions with different moisture contents; S20: injecting the corrosive solutions into sealed containers of the plurality of test samples respectively; S30: aging the first group of test samples at the same temperature and aging the second group of test samples at different temperatures; S40: recording the failure times of the test samples; and S50: establishing a prediction function relationship between the tab life and the temperature and the moisture content in the test samples according to the test data of the first group of test samples and the test data of the second group of test samples. The secondary battery tab life prediction method can predict the life of the tab, thereby providing a reliable evaluation method and standard for the screening of the raw materials of the tab in the process of the development and design of the battery cell.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for predicting the lifespan of the tabs in a soft-pack lithium-ion secondary battery. Background Technology

[0002] Currently, rechargeable batteries are widely used in 3C digital products, electric vehicles, and other fields. Among them, pouch lithium-ion rechargeable batteries are widely used in the new energy industry due to their advantages such as high energy density, light weight, good safety, and flexible size.

[0003] The tabs of a pouch lithium-ion secondary battery typically consist of a metal substrate (usually aluminum or nickel-plated copper) and tab adhesive applied to the metal substrate. The metal substrate is generally bonded to the aluminum-plastic film adhesive layer inside the pouch casing via thermal fusion bonding, thus achieving a seal between the tabs and the pouch casing. The sealing performance of the tabs is crucial to the performance of the pouch lithium-ion secondary battery; however, in actual use, the sealing performance of the tabs can be affected by the operating environment.

[0004] The main reasons for tab failure are as follows: (1) Structural failure: The thermal expansion coefficients of the metal substrate and the tab adhesive are different. After long-term use (especially in high-temperature environments), the tab adhesive is prone to deformation, resulting in the tab delamination. (2) Thermal failure: The materials inside the battery cell undergo physical and chemical reactions at high temperatures to produce gas, which increases the internal pressure of the battery cell and causes the tab to delaminate. (3) Corrosion failure: The electrolyte, positive and negative electrode materials, trace amounts of moisture, trace amounts of hydrofluoric acid, etc., present inside the battery cell cause the tab to be chemically and electrochemically corroded. The tab adhesive swells when it comes into contact with organic solvents and ages and deteriorates, causing the tab to delaminate. (4) Physical external force failure: The battery cell is subjected to external vibration, pulling force, etc. during use, which causes delamination. (5) The influence of the tab and the aluminum-plastic film top seal: After encapsulation, the tab adhesive and the aluminum-plastic film adhesive layer fuse together. The top seal affects the thickness of the tab adhesive and the bonding surface between the tab adhesive and the metal substrate (i.e., poor encapsulation). When the tabs fail, the cell's sealing performance deteriorates, allowing external air and moisture to enter the cell through the failed tab location. This can affect the cell's normal operation and even cause thermal runaway. Therefore, ensuring the sealing performance of the tabs is of paramount importance.

[0005] Currently, the evaluation items for electrodes include appearance, size, electrolyte peel strength, and permeability. However, these evaluation items cannot predict the future service life of electrodes in soft-pack lithium-ion secondary batteries, nor can they provide accurate guidance and evaluation standards for the selection of electrode raw materials during the cell development and design process. Summary of the Invention

[0006] The purpose of this invention is to provide a method for predicting the lifespan of secondary battery tabs, which can predict the lifespan of tabs and thus provide a reliable evaluation method and standard for screening tab raw materials during the cell development and design process.

[0007] One embodiment of the present invention provides a method for predicting the lifespan of a secondary battery tab, comprising the following steps:

[0008] S10: Provide multiple test samples and prepare corrosive solutions with different moisture contents; each test sample includes a sealed container and a tab sample disposed in the sealed container, the tab sample being a tab with tab adhesive, and at least one tab sample in the sealed container of each test sample;

[0009] S20: The corrosive solution is injected into the sealed containers of the multiple test samples respectively, and then the sealed containers of the test samples are sealed; wherein, the multiple test samples are divided into two groups, the sealed containers of the first group of test samples are injected with corrosive solutions of different moisture contents, and the sealed containers of the second group of test samples are injected with corrosive solutions of the same moisture content.

[0010] The sealed containers of the test samples in the second group are filled with a corrosive solution with the same moisture content, as long as the error between the moisture content of each test sample in the second group is controlled within ±1%.

[0011] S30: The test samples in the first group are aged at the same temperature, and the test samples in the second group are aged at different temperatures.

[0012] S40: Record the failure time of each test sample, wherein the failure of the test sample is the debonding of the tab adhesive and the tab;

[0013] S50: Based on the test data of the first group of test samples and the test data of the second group of test samples, establish a predictive function relationship between the electrode life and temperature and the moisture content in the test samples.

[0014] In one possible implementation, in step S10 above, the sealed containers of each of the test samples are of the same size, and the number of tab samples in the sealed containers of each of the test samples is the same.

[0015] In one possible implementation, during step S20 above, when the corrosive solution is injected into the sealed container of the test sample, the corrosive solution in the sealed container needs to immerse the tab sample.

[0016] Another embodiment of the present invention provides a method for predicting the lifespan of a secondary battery tab, comprising the following steps:

[0017] S10: Provide multiple test samples and prepare corrosive solutions with different moisture contents; the test sample is a soft-pack battery cell without electrolyte injection, the test sample includes a shell and a battery cell encapsulated in the shell, the battery cell is provided with tabs, and the tabs are sealed to the shell by tab adhesive;

[0018] S20: The corrosive solution is injected into the shells of the multiple test samples respectively, and then the shells of each test sample are sealed; wherein, the multiple test samples are divided into two groups, the shells of the first group of test samples are injected with corrosive solutions of different moisture contents, and the shells of the second group of test samples are injected with corrosive solutions of the same moisture content.

[0019] The shells of the test samples in the second group are injected with a corrosive solution with the same water content, as long as the error between the water content of each test sample in the second group is controlled within ±1%.

[0020] S30: The test samples in the first group are aged at the same temperature, and the test samples in the second group are aged at different temperatures.

[0021] S40: Record the failure time of each test sample, wherein the failure of the test sample is caused by leakage at the tab and detachment between the tab adhesive and the tab.

[0022] S50: Based on the test data of the first group of test samples and the test data of the second group of test samples, establish a predictive function relationship between the electrode life and temperature and the moisture content in the test samples.

[0023] In one feasible approach, in step S20 above, after sealing the casing of each test sample, each test sample is further charged and discharged; the number of charge-discharge cycles for each test sample remains consistent, and the final SOC state of each test sample remains consistent. Maintaining consistent final SOC state for each test sample includes controlling the error between the final SOC values ​​of each test sample to within ±5%.

[0024] In one feasible manner, in step S20 above, the first group of test samples includes multiple first sub-test sample groups, each first sub-test sample group includes at least one test sample, and the shells of each first sub-test sample group are injected with corrosive solutions of different moisture contents; the second group of test samples includes multiple second sub-test sample groups, each second sub-test sample group includes at least one test sample, and the shells of each second sub-test sample group are injected with corrosive solutions of the same moisture content.

[0025] After sealing the shells of each of the test samples, clamps are used to clamp each of the first sub-test sample groups and each of the second sub-test sample groups on both sides along the thickness direction of the test sample, ensuring that the clamping force on each of the first sub-test sample groups and each of the second sub-test sample groups is the same.

[0026] In one feasible manner, in step S10 above, the corrosive solution is an electrolyte for secondary batteries, and the water content in the test sample is less than or equal to 1%.

[0027] In one feasible manner, in step S30 above, the aging treatment temperature of the test sample is less than or equal to 100°C.

[0028] In one feasible manner, in step S30 above, the number of test samples in the second group is at least three, and the temperature gradient of the aging treatment between each test sample in the second group is 2℃-20℃.

[0029] In one feasible approach, in step S30 above, the test sample is aged using an aging treatment device, which is an oven.

[0030] In one feasible implementation, the above S50 step specifically includes:

[0031] Under the condition of the same aging temperature but different moisture contents in the test samples, a curve fitting was performed based on the corresponding data of moisture content and failure time of the test samples to establish a functional relationship between tab life and moisture content in the test samples; under the condition of different aging temperatures but the same moisture content in the test samples, a curve fitting was performed based on the corresponding data of aging temperature and failure time of the test samples to establish a functional relationship between tab life and temperature; then, based on the functional relationships between tab life and moisture content in the test samples, and the functional relationships between tab life and temperature, a predictive functional relationship between tab life and temperature and moisture content in the test samples was established.

[0032] In one feasible approach, the predicted functional relationship between the electrode life and temperature and the moisture content in the test sample in step S50 above is as follows:

[0033] Y = Y1 * e a*(X-X1) *e b*(t-t1) ;

[0034] Where Y is the tab life, X is the moisture content in the test sample, t is the temperature, e is the natural logarithm, a is the moisture content coefficient, b is the temperature coefficient, and Y1 is the failure time of the test sample when the moisture content in the test sample is X1 and the temperature is t1.

[0035] The present invention provides a method for predicting the lifespan of secondary battery tabs. This method involves dividing test samples into two groups: one group with different moisture contents in a corrosive solution and the same aging temperature, and the other with the same moisture content in the corrosive solution but different aging temperatures. Single-variable experiments are conducted to obtain the relationships between tab lifespan and temperature, and between tab lifespan and moisture content in the corrosive solution. This allows for the establishment of a predictive function for tab lifespan based on these relationships. According to this predictive function, the lifespan of the tabs can be predicted, providing a reliable evaluation method and standard for selecting tab raw materials during the cell development and design process. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the test sample in an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of the structure of the test sample in another embodiment of the present invention.

[0038] Figure 3 This is a graph showing the functional relationship between the tab failure time and the water content in the electrolyte in Embodiment 1 of the present invention.

[0039] Figure 4 This is a graph showing the functional relationship between tab failure time and aging temperature in Embodiment 1 of the present invention.

[0040] Figure 5 This is a graph showing the functional relationship between the tab failure time and the moisture content in the cell sample in Embodiment 2 of the present invention.

[0041] Figure 6 This is a graph showing the functional relationship between tab failure time and aging temperature in Embodiment 2 of the present invention.

[0042] In the diagram: 1-Test sample, 11-Taper, 12-Taper adhesive, 13-Sealed container, 14-Battery cell, 15-Casing. Detailed Implementation

[0043] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0044] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0045] The directional terms such as "up," "down," "left," "right," "front," "back," "top," and "bottom" (if present) used in the specification and claims of this invention are defined by the position of the structures in the drawings and the relative positions of the structures, and are only for the clarity and convenience of expressing the technical solution. It should be understood that the use of directional terms should not limit the scope of protection claimed by this invention.

[0046] An embodiment of the present invention provides a method for predicting the lifespan of secondary battery tabs (including but not limited to lithium-ion secondary battery tabs), comprising the following steps:

[0047] S10: Provide multiple test samples 1 and prepare corrosive solutions with different moisture contents; such as Figure 1 As shown, each test sample 1 includes a sealed container 13 and a tab sample placed inside the sealed container 13. The tab sample is a tab 11 with tab adhesive 12 (that is, the tab adhesive 12 is attached to the tab 11 to obtain the tab sample). Each test sample 1 has at least one tab sample in the sealed container 13.

[0048] S20: The corrosive solution is injected into the sealed containers 13 of multiple test samples 1 respectively, and then the sealed containers 13 of each test sample 1 are sealed; wherein, the multiple test samples 1 are divided into two groups, the sealed containers 13 of the first group of test samples 1 are injected with corrosive solutions of different moisture contents, and the sealed containers 13 of the second group of test samples 1 are injected with corrosive solutions of the same moisture content.

[0049] S30: The first group of test samples 1 is aged at the same temperature, and the second group of test samples 1 is aged at different temperatures.

[0050] S40: Record the failure time of each test sample 1. The failure of test sample 1 is the debonding between tab adhesive 12 and tab 11.

[0051] S50: Based on the test data of the first group of test samples 1 and the test data of the second group of test samples 1, establish a predictive function relationship between the electrode life and temperature and the moisture content in test sample 1.

[0052] The secondary battery tab life prediction method provided in this embodiment divides the test sample 1 into two groups. These two groups are tested under different conditions: one with different water content in the corrosive solution and the same aging temperature, and the other with the same water content in the corrosive solution and different aging temperatures. Single-variable experiments are conducted to obtain the relationship between tab life and temperature, and between tab life and water content in the corrosive solution. A predictive function relationship between tab life and temperature and water content in the corrosive solution is then established. Based on this predictive function relationship, the lifespan of the tabs can be predicted, thus providing a reliable evaluation method and standard for selecting tab raw materials during the cell development and design process.

[0053] Meanwhile, this method for predicting the lifespan of secondary battery tabs directly uses tab samples (i.e., unpackaged to form a soft-pack cell) for testing, thereby obtaining a predictive function relationship between tab lifespan and temperature and moisture content in test sample 1. This method is not only simple to operate, but also saves costs.

[0054] In one implementation, the sealing container 13 in step S10 above can be an aluminum-plastic bag, a PP bottle, or the like. The sealing containers 13 for each test sample 1 are of the same size, and the number of tab samples in each sealing container 13 is the same, thereby ensuring consistent test conditions and improving the accuracy of the test.

[0055] In one implementation, in step S10 above, the corrosive solution is an electrolyte for secondary batteries, specifically an electrolyte for lithium-ion secondary batteries. The water content in test sample 1 is less than or equal to 1% (when the sealed container 13 is in a dry state, the water content in test sample 1 is the same as the water content in the corrosive solution; when the sealed container 13 itself contains a certain amount of water before the liquid is injected, the water content in test sample 1 is the sum of the water content in the corrosive solution and the water content in the sealed container 13 itself); wherein, 1% = 10000ppm.

[0056] In one implementation, the preparation of corrosive solutions with different moisture contents in step S10 specifically includes: preparing multiple portions of corrosive solutions with different moisture contents and multiple portions of corrosive solutions with the same moisture content, wherein the weight of each portion of the corrosive solution is substantially the same. In one implementation, the weight difference between the portions of the corrosive solutions is controlled within 5%; or within 2-5%; or within 3-4%; or within 2-5%; or within 3-5%; or within 2-4%. In step S20, the injection of the corrosive solutions into the sealed containers 13 of multiple test samples 1 specifically includes: injecting multiple portions of corrosive solutions with different moisture contents and multiple portions of corrosive solutions with the same moisture content into the sealed containers 13 of multiple test samples 1.

[0057] As one implementation method, in step S20 above, when injecting the corrosive solution into the sealed container 13 of the test sample 1, the corrosive solution in the sealed container 13 needs to submerge the tab sample, and the error in the amount of corrosive solution injected into the sealed container 13 of each test sample 1 is less than 5%, thereby ensuring consistent test conditions and improving the accuracy of the test.

[0058] As one implementation method, in step S30 above, test sample 1 is placed in an oven for aging treatment. The oven is set to a temperature of less than or equal to 100°C (that is, the aging treatment temperature of test sample 1 is less than or equal to 100°C). Under the premise of ensuring test safety and smooth test progress, the higher the aging temperature, the shorter the failure time of the tab, thereby accelerating the test or tab screening process.

[0059] In one implementation, in step S30 above, the number of test samples 1 in the second group is at least three, and the temperature gradient of aging treatment (i.e., the temperature difference between each test sample 1) between each test sample 1 in the second group is 2℃-20℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 4℃-18℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 5℃-15℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 7℃-13℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 9℃-11℃.

[0060] As one implementation method, the above-mentioned step S40 specifically includes:

[0061] Periodically (e.g., every 4 hours), remove test sample 1 from the oven and cool it to room temperature. Then open the sealed container 13, remove the tab sample from the sealed container 13, wipe it dry with a non-woven cloth, and observe whether there is any delamination between the tab adhesive 12 and the tab 11. If delamination occurs, record the time of delamination (i.e., the failure time of test sample 1). If no delamination occurs, put the tab sample back into the sealed container 13, and then put test sample 1 back into the oven to continue aging.

[0062] In one implementation, the operations of steps S10, S20, S30 and S40 are all carried out in a drying room, where the dew point is less than or equal to -30°C.

[0063] As one implementation method, the above-mentioned step S50 specifically includes:

[0064] Under the condition of the same aging temperature but different moisture contents in test sample 1, a curve fitting was performed based on the corresponding data of moisture content and failure time of test sample 1 to establish the functional relationship between tab life and moisture content in test sample 1. Under the condition of different aging temperatures but the same moisture content in test sample 1, a curve fitting was performed based on the corresponding data of aging temperature and failure time of test sample 1 to establish the functional relationship between tab life and temperature. Then, based on the functional relationship between tab life and moisture content in test sample 1, as well as the functional relationship between tab life and temperature, a predictive functional relationship between tab life and temperature and moisture content in test sample 1 was established.

[0065] As one implementation method, in step S50 above, the predictive function relationship between the electrode life and temperature and the moisture content in test sample 1 is as follows:

[0066] Y = Y1 * e a*(X-X1) *e b*(t-t1) ;

[0067] Where Y is the tab life, X is the moisture content in test sample 1, t is the temperature, e is the natural logarithm, a is the moisture content coefficient, and b is the temperature coefficient; Y1 is the failure time of test sample 1 when the moisture content in test sample 1 is X1 and the temperature is t1. That is, Y, X, and t are all variables, where X and t are independent variables and Y is the dependent variable; a, b, Y1, X1, and t1 can all be obtained from experimental data, and their calculation process can be referred to in Examples 1 and 2 below.

[0068] Another embodiment of the present invention provides a method for predicting the lifespan of secondary battery tabs, comprising the following steps:

[0069] S10: Provide multiple test samples 1 and prepare corrosive solutions with different moisture contents; such as Figure 2 As shown, test sample 1 is a soft-pack battery cell without electrolyte injection. Test sample 1 includes a housing 15 and a battery cell 14 encapsulated in the housing 15. The battery cell 14 is provided with tabs 11 and tab adhesive 12. The tabs 11 and the housing 15 are sealed by the tab adhesive 12. One end of the tab 11 is connected to the battery cell 14, and the other end of the tab 11 extends out of the housing 15.

[0070] S20: The corrosive solution is injected into the shells 15 of multiple test samples 1, and then the shells 15 of each test sample 1 are sealed. The multiple test samples 1 are divided into two groups. The shells 15 of the first group of test samples 1 are injected with corrosive solutions of different moisture contents, and the shells 15 of the second group of test samples 1 are injected with corrosive solutions of the same moisture content. The error between the moisture content of each test sample 1 in the second group is controlled within ±1% (specifically, the moisture in the test sample 1 generally comes partly from the corrosive solution and partly from the electrode in the cell 14; the moisture content of the electrode in the cell 14 is generally related to its storage environment. The moisture content of the electrode in the cell 14 of each test sample 1 is basically the same. Therefore, when controlling the moisture content of each test sample 1 in the second group to be within the error range, it is generally only necessary to ensure that the moisture content of the corrosive solution injected into each test sample 1 in the second group is within the error range).

[0071] S30: The first group of test samples 1 is aged at the same temperature, and the second group of test samples 1 is aged at different temperatures.

[0072] S40: Record the failure time of each test sample 1. The failure of test sample 1 is that leakage occurs at tab 11 and the tab adhesive 12 delaminates from tab 11.

[0073] S50: Based on the test data of the first group of test samples 1 and the test data of the second group of test samples 1, establish a predictive function relationship between the electrode life and temperature and the moisture content in test sample 1.

[0074] Specifically, this method for predicting the lifespan of secondary battery tabs uses pouch cells (i.e., the tabs to be tested are made into pouch cells) for testing, which can simulate the real working state of pouch cells, thereby improving the accuracy and reliability of the test.

[0075] In one embodiment, in step S10 above, the housing 15 is an aluminum-plastic film.

[0076] As one implementation method, in step S10 above, when the electrode to be tested is made into a soft-pack battery cell, the soft-pack battery cell can be made according to the normal production process, or the size of the aluminum-plastic film can be lengthened and widened to increase the sealing width of the soft-pack battery cell according to the test requirements; the soft-pack battery cell can be heat-sealed once or multiple times during packaging.

[0077] In one implementation, in step S10 above, the corrosive solution is an electrolyte for secondary batteries, specifically an electrolyte for lithium-ion secondary batteries. The water content in test sample 1 is less than or equal to 1% (when the battery cell 14 inside the casing 15 is in a dry state, the water content in test sample 1 is the same as the water content in the corrosive solution; when the battery cell 14 inside the casing 15 already contains a certain amount of moisture before being injected with the electrolyte, the water content in test sample 1 is the sum of the water content in the corrosive solution and the water content in the battery cell 14). Specifically, the formula for calculating the water content in test sample 1 is: Total water content = (Weight of the battery cell electrode * Moisture content concentration of the electrode + Weight of the corrosive solution * Moisture content concentration of the corrosive solution) / (Weight of the battery cell electrode + Weight of the corrosive solution). The moisture content of the electrode and the moisture content concentration of the corrosive solution can be expressed in ppm, as calculated and used in the embodiments of this application.

[0078] In one implementation, step S10 above, the preparation of corrosive solutions with different moisture contents specifically includes: preparing multiple portions of corrosive solutions with different moisture contents and multiple portions of corrosive solutions with the same moisture content, wherein the weight of each portion of corrosive solution is substantially the same. In one implementation, the weight difference between each portion of corrosive solution is controlled within 5%. In step S20 above, the injection of the corrosive solution into the shells 15 of multiple test samples 1 specifically includes: injecting multiple portions of corrosive solutions with different moisture contents and multiple portions of corrosive solutions with the same moisture content into the shells 15 of multiple test samples 1.

[0079] As one implementation method, in step S20 above, after sealing the casing 15 of each test sample 1, each test sample 1 is also charged and discharged to simulate the charging and discharging process of the soft-pack battery cell during normal operation, further improving the accuracy and reliability of the test. Simultaneously, the number of charge-discharge cycles for each test sample 1 is kept consistent, and after the charging and discharging ends, the final SOC state of each test sample 1 is kept consistent (where SOC refers to the state of charge of the battery, i.e., the ratio of the current remaining capacity of the battery to the battery capacity; SOC = 0 when the battery is fully discharged, and SOC = 100% when the battery is fully charged). The error between the final SOC values ​​of each test sample 1 is controlled within ±5%; or the error between the final SOC values ​​of each test sample 1 is controlled within ±3%; or the error between the final SOC values ​​of each test sample 1 is controlled within ±1% (for example, the final charge of each test sample 1 is fully charged, half-charged, or empty), thereby ensuring consistent test parameters.

[0080] As one implementation, in step S20 above, after charging and discharging each test sample 1, high-temperature insulating tape is applied to the portion of the tab 11 extending beyond the housing 15. The high-temperature insulating tape can be transparent tape (transparent tape facilitates observation of whether leakage occurs at the tab). By attaching high-temperature insulating tape to the protruding portion of the tab 11, leakage of the test sample 1 can be prevented (the test sample 1 may be placed in an oven while charged for aging; the high-temperature insulating tape can prevent the exposed tab 11 from contacting the oven or other test samples 1 and causing leakage), and it can also prevent the tabs 11 of other normal test samples 1 from being corroded from the outside when a test sample 1 leaks (multiple test samples 1 may be placed in the same oven).

[0081] In one implementation, in step S20 above, the first group of test samples 1 includes multiple first sub-test sample groups, each first sub-test sample group includes at least one test sample 1, and corrosive solutions with different moisture contents are injected into the shell 15 of each first sub-test sample group; the second group of test samples 1 includes multiple second sub-test sample groups, each second sub-test sample group includes at least one test sample 1, and corrosive solutions with the same moisture content are injected into the shell 15 of each second sub-test sample group.

[0082] After sealing the casing 15 of each test sample 1, clamps (not shown) are used to clamp each first sub-test sample group and each second sub-test sample group on both sides along the thickness direction of the test sample 1, ensuring that the clamping force on each first sub-test sample group and each second sub-test sample group is the same. This simulates the state of the pouch cells after they are assembled into a battery module (after the pouch cells are assembled into a battery module, multiple pouch cells are stacked, so the sides of the pouch cells will be subjected to a certain amount of compressive force in actual use), thereby improving the accuracy and reliability of the test. When fixing the clamps, a torque wrench with the same torque can be used to fix the clamps, thus ensuring that the clamping force on each first sub-test sample group and each second sub-test sample group is the same.

[0083] For example, the first group of test samples 1 includes three first sub-test sample groups, each of which includes two test samples 1. Corrosive solutions with different moisture contents are injected into the shell 15 of each first sub-test sample group. Corrosive solutions with the same moisture content are injected into the two test samples 1 in each first sub-test sample group (that is, corrosive solutions with different moisture contents are injected into the shell 15 of test samples 1 in different first sub-test sample groups, while corrosive solutions with the same moisture content are injected into the shell 15 of test samples 1 in the same first sub-test sample group). The second group of test samples 1 includes three second sub-test sample groups, each of which includes two test samples 1. Corrosive solutions with the same moisture content are injected into the shell 15 of each second sub-test sample group. After sealing the shell 15 of each test sample 1, two test samples 1 from each first sub-test sample group are stacked together to obtain three first stacks; and two test samples 1 from each second sub-test sample group are stacked together to obtain three second stacks; clamps are used to clamp the two sides of the three first stacks and the three second stacks respectively, ensuring that the clamping force on each first stack and each second stack is the same (when the number of test samples 1 in the first sub-test sample group and the second sub-test sample group is one, there is no need to stack them, and the clamps can be used to clamp the two sides of the single test sample 1 in each sub-test sample group directly).

[0084] As one implementation method, in step S30 above, test sample 1 is placed in an oven for aging treatment, and the oven is set at a temperature less than or equal to 100°C (that is, the aging treatment temperature of test sample 1 is less than or equal to 100°C). Under the premise of ensuring test safety and smooth test progress, the higher the aging temperature, the shorter the failure time of the tab, thereby accelerating the test or tab screening process.

[0085] In one implementation, in step S30 above, the number of test samples 1 in the second group is at least three, and the temperature gradient of aging treatment (i.e., the temperature difference of each test sample 1) between each test sample 1 in the second group is 2℃-20℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 5℃-17℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 7℃-15℃; or the temperature gradient of aging treatment between each test sample 1 in the second group is 9℃-13℃.

[0086] As one implementation method, the above-mentioned step S40 specifically includes:

[0087] Periodically (e.g., every 4 hours), remove test sample 1 from the oven and check for leakage at the tab 11. If no leakage is found, put test sample 1 back into the oven for continued aging; if leakage is found, disassemble test sample 1 promptly to confirm that the leakage is caused by delamination between the tab adhesive 12 and the tab 11, and record the time of delamination (i.e., the failure time of test sample 1).

[0088] In one implementation, the operations of steps S10, S20, S30 and S40 are all carried out in a drying room, where the dew point is less than or equal to -30°C.

[0089] As one implementation method, the above-mentioned step S50 specifically includes:

[0090] Under the condition of the same aging temperature but different moisture contents in test sample 1, a curve fitting was performed based on the corresponding data of moisture content and failure time of test sample 1 to establish the functional relationship between tab life and moisture content in test sample 1. Under the condition of different aging temperatures but the same moisture content in test sample 1, a curve fitting was performed based on the corresponding data of aging temperature and failure time of test sample 1 to establish the functional relationship between tab life and temperature. Then, based on the functional relationship between tab life and moisture content in test sample 1, as well as the functional relationship between tab life and temperature, a predictive functional relationship between tab life and temperature and moisture content in test sample 1 was established.

[0091] As one implementation method, in step S50 above, the predictive function relationship between the electrode life and temperature and the moisture content in test sample 1 is as follows:

[0092] Y = Y1 * e a*(X-X1) *e b*(t-t1) ;

[0093] Where Y is the tab life, X is the moisture content in test sample 1, t is the temperature, e is the natural logarithm, a is the moisture content coefficient, and b is the temperature coefficient; Y1 is the failure time of test sample 1 when the moisture content in test sample 1 is X1 and the temperature is t1. That is, Y, X, and t are all variables, with X and t being independent variables and Y being the dependent variable; a, b, Y1, X1, and t1 can all be obtained from experimental data.

[0094] The method for predicting the lifespan of secondary battery tabs provided in this invention involves dividing test samples 1 into two groups. These two groups are tested under different conditions: one group has different water content in the corrosive solution and the same aging temperature, and the other group has the same water content in the corrosive solution but different aging temperatures. Single-variable experiments are conducted to obtain the relationship between tab lifespan and temperature, and between tab lifespan and water content in the corrosive solution. This allows for the establishment of a predictive function relationship between tab lifespan and temperature and water content in the corrosive solution. Based on this predictive function relationship, the lifespan of the tabs can be predicted, thus providing a reliable evaluation method and standard for selecting tab raw materials during the cell development and design process.

[0095] Example 1

[0096] The lithium-ion secondary battery tab life prediction method provided in this embodiment includes the following steps:

[0097] S10: Divide the 60 tab samples into 6 portions, each portion containing 10 tab samples. Place the 6 portions of tab samples into 6 250mL PP bottles (keep the PP bottles dry) to obtain 6 test samples for later use.

[0098] Preparation of corrosive solutions: Select lithium-ion electrolyte of model 021-13C produced by Tinci Materials, weigh 6 portions of 150.0g each, with an accuracy of ±0.1g; add 0.000g, 0.030g, 0.075g, 0.150g, 0.150g, and 0.150g of pure water to the 6 portions of lithium-ion electrolyte respectively, to obtain 6 corrosive solutions with water contents of 0ppm, 200ppm, 500ppm, 1000ppm, 1000ppm, and 1000ppm respectively.

[0099] S20: Inject 6 portions of corrosive solution into 6 test sample PP bottles and seal them, ensuring that the corrosive solution completely submerges the tab samples.

[0100] S30: Place the 6 test samples prepared in step S20 into 3 ovens at different temperatures for aging treatment. The oven temperatures are 80℃, 85℃ and 90℃ respectively. Among them, the test samples with water content of 0ppm, 200ppm and 500ppm are placed in the 90℃ oven for aging, and the three test samples with water content of 1000ppm are placed in the 80℃, 85℃ and 90℃ ovens respectively for aging.

[0101] S40: Every 4 hours, remove the test sample from the oven and cool it to room temperature. Then open the PP bottle, remove the tab sample from the PP bottle, wipe it dry with a non-woven cloth, and observe whether there is any delamination between the tab adhesive and the tab. If delamination occurs, record the time of delamination (i.e., the failure time of the test sample); if no delamination occurs, put the tab sample back into the PP bottle, and then put the test sample back into the oven for continued aging. The above steps S10, S20, S30, and S40 are all carried out in a drying room with a dew point of -30℃.

[0102] The recorded data is summarized in the table below:

[0103]

[0104] S50: Based on the data from groups 1 to 4 in the table above, plot the graphs and perform curve fitting to obtain the functional relationship between the tab failure time and the water content in the electrolyte: Y = 247.32e -0.003X Where Y is the tab lifetime (i.e., the tab failure time), X is the water content in the electrolyte, and e is the natural logarithm; its functional relationship curve is shown in Figure 1. Figure 3 As shown in the figure (R is the fitting index).

[0105] Based on the data from groups 4 to 6 in the table above, a graph was plotted and curve fitting was performed to obtain the functional relationship between the tab failure time and the aging temperature: Y = 26315e -0.088*t Where Y is the tab lifetime (i.e., the tab failure time), and t is the temperature; its functional relationship curve is shown in Figure 1. Figure 4 As shown in the figure (R is the fitting index).

[0106] Assuming the electrode samples are screened using the 90℃-1000ppm moisture content method (as shown in Item 4 of the table above), the predicted lifespan of the electrode under conditions of X ppm moisture content in the electrolyte and t℃ long-term operating temperature, based on the functional relationship obtained above, is:

[0107] Y = Y0 * e -0.003*(X-1000) *e -0.088*(t-90) Where Y0 is the lifetime of the tab sample under conditions of 90℃ and 1000ppm moisture content.

[0108] The derivation of the above formula is as follows:

[0109] 1. Given that the lifetime of a tab sample under conditions of 90℃-1000ppm moisture content is Y0, calculate the lifetime of a tab sample under conditions of 90℃-Xppm moisture content, Y1:

[0110] Substituting into the functional relationship for the same temperature but different moisture contents: Y = 247.32e -0.003X ;

[0111] Y0 = 247.32e -0.003*1000 ①;

[0112] Y1 = 247.32e -0.003X ②;

[0113] ② / ①=Y1 / Y0=e -0.003*(X-1000) ;

[0114] Then Y1 = Y0 * e -0.003*(X-1000) ③.

[0115] II. Given that the lifetime of a tab sample at 90℃ and X ppm moisture content is Y1, calculate the lifetime Y of the tab sample at t℃ and X ppm moisture content:

[0116] Substituting the functional relationship for different temperatures and the same moisture content: Y = 26315e -0.088*t ;

[0117] Y1 = 26315e -0.088*90 ④;

[0118] Y = 26315e -0.088*t ⑤;

[0119] ⑤ / ④=Y / Y1=e -0.088*(t-90) ;

[0120] Then Y = Y1*e -0.088*(t-90) ⑥;

[0121] Substituting ③ into ⑥, we get Y = Y0 * e -0.003*(X-1000) *e -0.088*(t-90) .

[0122] The service life of the electrode can be predicted based on the above functional relationship, thereby allowing for the selection of electrode raw materials.

[0123] Example 2

[0124] The lithium-ion secondary battery tab life prediction method provided in this embodiment includes the following steps:

[0125] S10: Prepare 15 battery cell samples from the electrode tabs to be tested, and divide them into 5 groups of 3 battery cell samples in each group. The battery cell sample model is 21AH, and the electrode weight of the battery cell sample is 240.0g. Bake the battery cell samples to remove moisture and set aside for later use.

[0126] Preparation of corrosive solution: Select lithium-ion electrolyte of model 021-13C produced by Tinci Materials, weigh 15 portions, 60.0g / portion, with an accuracy of ±0.1g; add 0.030g of pure water to 3 portions of lithium-ion electrolyte, add 0.060g of pure water to another 3 portions of lithium-ion electrolyte, and do not add pure water to the remaining 9 portions of lithium-ion electrolyte.

[0127] S20: Inject 15 portions of corrosive solution into 15 battery cell samples and seal them.

[0128] S30: All battery cell samples underwent the same formation process and 10 charge-discharge cycles. At the end of the cycle, all battery cell samples were fully discharged, reaching a state of zero charge. Transparent high-temperature tape was applied to the positive and negative terminals of each battery cell sample. Nine battery cell samples containing 0g of pure water were divided into three groups of three. Each group was secured with a clamp using a torque wrench with a torque of 2.0 N*m, and then aged in ovens at 60℃, 70℃, and 80℃. Battery cell samples containing 0.030g and 0.060g of pure water were each divided into two groups, secured with a clamp using a torque wrench with a torque of 2.0 N*m, and aged in an oven at 80℃.

[0129] S40: Every 4 hours, remove the battery cell samples from the oven and check for leakage at the tabs. If leakage is found in one battery cell sample in each group, remove the entire group from the oven, disassemble the leaking battery cell samples, carefully observe the leakage point, and if it is confirmed that the leakage is caused by the separation of the tab adhesive from the tab, record the tab failure time.

[0130] The recorded data is summarized in the table below:

[0131]

[0132] The formula for calculating the total moisture content inside the battery cell in the table above is:

[0133] Total content = (electrode weight * electrode moisture content + electrolyte weight * electrolyte moisture content) / (electrode weight + electrolyte weight).

[0134] For example, the total moisture content inside the battery cell in serial number 1 is [240.0*122+60.0*(10+1000)] / (240.0+60.0)=299.6≈300ppm;

[0135] The total moisture content inside the battery cell in serial number 3 is (240.0*122+60.0*10) / (240.0+60.0)=99.6≈100ppm.

[0136] S50: Based on the data from groups 1 to 3 in the table above, plot the graphs and perform curve fitting to obtain the functional relationship between the tab failure time and the moisture content in the cell sample: Y = 46.886e -0.007X Where Y is the tab lifespan (i.e., the tab failure time), X is the moisture content in the cell sample, and e is the natural logarithm; its functional relationship curve is shown in Figure 1. Figure 5 As shown in the figure (R is the fitting index).

[0137] Based on the data from groups 3 to 5 in the table above, a graph was plotted and curve fitting was performed to obtain the functional relationship between the tab failure time and the aging temperature: Y = 10 6 *e -0.136*t Where Y is the tab lifetime (i.e., the tab failure time), and t is the temperature; its functional relationship curve is shown in Figure 1. Figure 6 As shown in the figure (R is the fitting index).

[0138] Assuming the electrode samples are screened using the moisture content of 80℃-200ppm as specified in Serial No. 2 of the table above, the lifespan of the electrode samples can be predicted using the functional relationship obtained above under the following conditions: Moisture content in electrolyte is X ppm, and long-term operating temperature is t℃.

[0139] Y = Y0 * e -0.007*(X-200) *e -0.136*(t-80) Where Y0 is the lifetime of the electrode sample at 80℃ and 200ppm moisture content.

[0140] The derivation of the above formula is as follows:

[0141] 1. Given that the lifetime of a tab sample at 80℃ and a moisture content of 200ppm is Y0, calculate the lifetime of a tab sample at 80℃ and a moisture content of Xppm, Y1:

[0142] Substituting into the functional relationship for the same temperature but different moisture contents: Y1 = 46.886e -0.007X ;

[0143] Y0 = 46.886e -0.007*200 ①;

[0144] Y1 = 46.886e -0.007X ②;

[0145] ② / ①=Y1 / Y0=e -0.007*(X-200) ;

[0146] Then Y1 = Y0 * e -0.007*(X-200) ③.

[0147] II. Given that the lifetime of a tab sample at 80℃ and a moisture content of X ppm is Y1, calculate the lifetime Y of the tab sample at t℃ and a moisture content of X ppm:

[0148] Substituting the functional relationship for different temperatures and the same moisture content: Y = 10 6 *e -0.136*t ;

[0149] Y1 = 10 6 e -0.136*80 ④;

[0150] Y = 10 6 e -0.136*t ⑤;

[0151] ⑤ / ④=Y / Y1=e -0.136*(t-80) ;

[0152] Then Y = Y1*e -0.136*(t-80) ⑥;

[0153] Substituting ③ into ⑥, we get Y = Y0 * e -0.007*(X-200) *e -0.136*(t-80) .

[0154] In actual use, assuming the long-term operating temperature of the battery cell is 45℃ and the internal moisture content of the battery cell is 100ppm, the lifespan of the tab in the battery cell is approximately 7.1 years.

[0155] Therefore, in this battery cell system, if the required lifespan of the battery cell is t≥20 years, the following method can be used for rapid screening of the electrode raw materials:

[0156] Method 1: The raw materials of the electrode are made into corresponding battery cells and aged at 80℃ (the internal moisture content of the battery cell is 300ppm). The leakage time at the electrode is ≥15 days.

[0157] Method 2: The raw material of the electrode is directly immersed in an electrolyte with a moisture content of 1000ppm and aged at 90℃. The electrode delamination failure time is ≥29 days.

[0158] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for predicting the lifespan of a secondary battery tab, characterized in that, Includes the following steps: S10: Provide multiple test samples and prepare corrosive solutions with different moisture contents; each test sample includes a sealed container and a tab sample disposed in the sealed container, the tab sample being a tab with tab adhesive, and at least one tab sample in the sealed container of each test sample; S20: The corrosive solution is injected into the sealed containers of the multiple test samples respectively, and then the sealed containers of the test samples are sealed; wherein, the multiple test samples are divided into two groups, the sealed containers of the first group of test samples are injected with corrosive solutions of different moisture contents, and the sealed containers of the second group of test samples are injected with corrosive solutions of the same moisture content. S30: The test samples in the first group are aged at the same temperature, and the test samples in the second group are aged at different temperatures. S40: Record the failure time of each test sample, wherein the failure of the test sample is the debonding of the tab adhesive and the tab; S50: Based on the test data of the first group of test samples and the test data of the second group of test samples, establish a predictive function relationship between the electrode life and temperature and the moisture content in the test samples; the predictive function relationship between the electrode life and temperature and the moisture content in the test samples is as follows: Y = Y1*e a*（X-X1） * e b*（t-t1） ; Where Y is the tab life, X is the moisture content in the test sample, t is the temperature, e is the natural logarithm, a is the moisture content coefficient, b is the temperature coefficient, and Y1 is the failure time of the test sample when the moisture content in the test sample is X1 and the temperature is t1.

2. The method for predicting the lifespan of a secondary battery tab as described in claim 1, characterized in that, In step S20 above, when the corrosive solution is injected into the sealed container of the test sample, the corrosive solution in the sealed container needs to immerse the tab sample.

3. A method for predicting the lifespan of a secondary battery tab, characterized in that, Includes the following steps: S10: Provide multiple test samples and prepare corrosive solutions with different moisture contents; the test sample is a soft-pack battery cell without electrolyte injection, the test sample includes a shell and a battery cell encapsulated in the shell, the battery cell is provided with tabs, and the tabs are sealed to the shell by tab adhesive; S20: The corrosive solution is injected into the shells of the multiple test samples respectively, and then the shells of each test sample are sealed; wherein, the multiple test samples are divided into two groups, the shells of the first group of test samples are injected with corrosive solutions of different moisture contents, and the shells of the second group of test samples are injected with corrosive solutions of the same moisture content. S30: The test samples in the first group are aged at the same temperature, and the test samples in the second group are aged at different temperatures. S40: Record the failure time of each test sample, wherein the failure of the test sample is caused by leakage at the tab and detachment between the tab adhesive and the tab. S50: Based on the test data of the first group of test samples and the test data of the second group of test samples, establish a predictive function relationship between the electrode life and temperature and the moisture content in the test samples; the predictive function relationship between the electrode life and temperature and the moisture content in the test samples is as follows: Y = Y1*e a*（X-X1） * e b*（t-t1） ; Where Y is the tab life, X is the moisture content in the test sample, t is the temperature, e is the natural logarithm, a is the moisture content coefficient, b is the temperature coefficient, and Y1 is the failure time of the test sample when the moisture content in the test sample is X1 and the temperature is t1.

4. The method for predicting the lifespan of secondary battery tabs as described in claim 3, characterized in that, In step S20 above, after sealing the shell of each test sample, each test sample is charged and discharged; the number of charge-discharge cycles of each test sample is consistent, and the final SOC state of each test sample is consistent.

5. The method for predicting the lifespan of secondary battery tabs as described in claim 4, characterized in that, In step S10 above, one end of the electrode is connected to the battery cell, and the other end of the electrode extends out of the housing; In step S20 above, after charging and discharging each of the test samples, insulating tape is applied to the portion of the tab that extends out of the housing.

6. The method for predicting the lifespan of secondary battery tabs as described in claim 5, characterized in that, The insulating tape is a transparent tape.

7. The method for predicting the lifespan of secondary battery tabs as described in claim 3, characterized in that, In step S20 above, the first group of test samples includes multiple first sub-test sample groups, each first sub-test sample group includes at least one test sample, and corrosive solutions with different moisture contents are injected into the shell of each first sub-test sample group; the second group of test samples includes multiple second sub-test sample groups, each second sub-test sample group includes at least one test sample, and corrosive solutions with the same moisture content are injected into the shell of each second sub-test sample group. After sealing the shells of each of the test samples, clamps are used to clamp each of the first sub-test sample groups and each of the second sub-test sample groups on both sides along the thickness direction of the test sample, ensuring that the clamping force on each of the first sub-test sample groups and each of the second sub-test sample groups is the same.

8. The method for predicting the lifespan of a secondary battery tab as described in any one of claims 1-7, characterized in that, In step S10 above, the corrosive solution is an electrolyte for secondary batteries, and the water content in the test sample is less than or equal to 1%.

9. The method for predicting the lifespan of a secondary battery tab as described in any one of claims 1-7, characterized in that, In step S30 above, the aging treatment temperature of the test sample is less than or equal to 100°C.

10. The method for predicting the lifespan of a secondary battery tab as described in any one of claims 1-7, characterized in that, The number of test samples in the second group is at least three, and the temperature gradient of the aging treatment between the test samples in the second group is 2℃-20℃.

11. The method for predicting the lifespan of a secondary battery tab as described in any one of claims 1-7, characterized in that, The above S50 steps specifically include: Under the condition of the same aging temperature but different moisture contents in the test samples, a curve fitting was performed based on the corresponding data of moisture content and failure time of the test samples to establish a functional relationship between tab life and moisture content in the test samples; under the condition of different aging temperatures but the same moisture content in the test samples, a curve fitting was performed based on the corresponding data of aging temperature and failure time of the test samples to establish a functional relationship between tab life and temperature; then, based on the functional relationships between tab life and moisture content in the test samples, and the functional relationships between tab life and temperature, a predictive functional relationship between tab life and temperature and moisture content in the test samples was established.

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