Test method and test device for cell protection layer

Abstract

The invention provides a testing method and a testing device for a battery cell protection layer, and relates to the technical field of battery manufacturing, the battery cell protection layer is arranged between an out-of-control battery cell and a to-be-tested battery cell, and the testing method comprises the following steps: selecting a plurality of groups of battery cell protection layers of which the thicknesses are sequentially increased at equal multiplying power; placing a plurality of groups of battery cell protection layers between the out-of-control battery cell and the to-be-tested battery cell, and obtaining the maximum average temperature of the to-be-tested battery cell corresponding to each group of battery cell protection layer; data of the to-be-detected battery cells which are subjected to thermal runaway are removed, the maximum average temperatures of multiple groups of to-be-detected battery cells which are not subjected to thermal runaway are fitted, and a thickness formula is obtained; and according to the maximum average temperature of the to-be-measured cell at the short-circuit moment corresponding to the maximum thickness of thermal runaway, in combination with a thickness formula, obtaining the minimum safe thickness of the cell protection layer. According to the test method of the battery cell protection layer, the minimum safety thickness of the battery cell protection layer can be obtained, the use reliability of the battery cell protection layer is ensured, the use safety of the battery pack is improved, and the use effect is better.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to a test method for a cell protective layer and a test apparatus for a cell protective layer using the test method. Background Technology

[0002] With the improvement of people's living standards, automobiles have become an indispensable means of transportation in daily life. Existing vehicles can be equipped with lithium-ion battery packs as their power source, and with the advancement of the electric vehicle industry, the safety of lithium-ion battery packs has become fundamental to the industry's development. When a cell in the battery pack experiences thermal runaway, it releases a huge amount of heat, creating conditions conducive to thermal abuse and easily leading to the spread of thermal runaway within the lithium-ion battery pack. Therefore, a protective layer with heat insulation and flame retardant capabilities must be installed inside the lithium-ion battery pack to effectively prevent the spread of thermal runaway.

[0003] The material and thickness of the protective layer affect its barrier effect, which in turn affects the safety of its use. When the protective layer is too thin, its barrier effect is poor, which makes it unable to effectively curb the spread of thermal runaway in lithium-ion battery packs, affecting the reliability of the protective layer and the safety of lithium-ion batteries. There is room for improvement. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a testing method for the cell protective layer, which can determine the minimum safe thickness of the cell protective layer, ensure the reliability of the cell protective layer in use, and thus improve the safety of the battery pack.

[0005] According to an embodiment of the present invention, a test method for a cell protective layer is provided between a runaway cell and a cell under test. The test method includes:

[0006] Multiple sets of cell protective layers with thicknesses increasing sequentially at equal ratios were selected;

[0007] Multiple sets of the cell protection layers are placed between the runaway cell and the cell under test, and the maximum average temperature of the cell under test corresponding to each set of cell protection layers is obtained.

[0008] Data from the tested battery cells that experienced thermal runaway were discarded, and the maximum average temperature of multiple sets of tested battery cells that did not experience thermal runaway was fitted to obtain the thickness formula.

[0009] Based on the maximum average temperature of the cell under test at the moment of short circuit corresponding to the maximum thickness of thermal runaway, and in conjunction with the thickness formula, the minimum safe thickness of the cell's protective layer is obtained.

[0010] According to the test method of the cell protective layer of the present invention, the thickness formula can be obtained by fitting the maximum average temperature of multiple sets of cells under test, and the minimum safe thickness of the cell protective layer can be obtained by combining the maximum average temperature of the cell under test at the short circuit moment corresponding to the maximum thickness of thermal runaway. This can ensure the reliability of the cell protective layer, avoid the spread of thermal runaway in the battery pack, improve the safety of the battery pack, and have better performance and wider applicability.

[0011] The method for testing the cell protective layer according to some embodiments of the present invention further includes:

[0012] After placing each set of the cell protection layer between the runaway cell and the cell under test, the real-time voltage of the cell under test is detected respectively;

[0013] The thermal runaway state of the battery cell under test is determined based on the voltage change of the real-time voltage.

[0014] According to some embodiments of the present invention, the method for testing the cell protective layer, wherein determining the thermal runaway state of the cell under test based on the voltage change of the real-time voltage includes:

[0015] When the drop in real-time voltage is greater than 20% of the available window value of the cell under test, the cell under test is determined to be in a thermal runaway state.

[0016] When the drop in real-time voltage is less than or equal to 20% of the available window value of the cell under test, it is determined that the cell under test has not thermally runaway.

[0017] According to some embodiments of the present invention, the method for testing the cell protective layer, wherein obtaining the maximum average temperature of the cell under test corresponding to each group of cell protective layers includes:

[0018] The temperature at multiple locations on the side of the battery cell under test facing the runaway battery cell is detected;

[0019] Calculate the average value based on the temperature measured at multiple locations;

[0020] The calculated average value is taken as the maximum average temperature.

[0021] According to some embodiments of the present invention, the test method for the cell protective layer is provided, wherein the thickness formula is y = ax^3 + bx^2 + cx + d; where x is the thickness of the cell protective layer and y is the maximum average temperature of the cell protective layer at the thickness corresponding to x.

[0022] The method for testing the cell protective layer according to some embodiments of the present invention further includes:

[0023] Obtain the maximum heat insulation benefit value of the protective layer of each group of cells;

[0024] Determine the relationship between the maximum insulation benefit value and the set insulation benefit value;

[0025] The maximum profit thickness is determined based on the judgment result.

[0026] According to some embodiments of the present invention, the method for testing the cell protective layer, wherein obtaining the maximum heat insulation benefit value of each group of the protective layers includes:

[0027] Differentiating the thickness formula yields the formula for the thermal insulation value;

[0028] Based on the thickness value of the cell protective layer and the heat insulation formula, the maximum heat insulation benefit value of the protective layer corresponding to the thickness value is calculated.

[0029] According to some embodiments of the present invention, the method for testing the cell protective layer includes determining the relationship between the maximum heat insulation benefit value and the set heat insulation benefit value, which includes:

[0030] Take the absolute value of the maximum insulation benefit;

[0031] Compare the absolute value with the set insulation benefit value;

[0032] When the absolute value is less than the set insulation benefit value, the thickness value at this time is taken as the maximum benefit thickness.

[0033] The present invention also proposes a testing device for the protective layer of battery cells.

[0034] The testing apparatus for the cell protective layer according to an embodiment of the present invention employs the testing method for the cell protective layer described in any one of the above claims, the testing apparatus comprising:

[0035] Test housing;

[0036] The test cell and at least one runaway cell are installed in the test housing, and each of the test cells and each runaway cell is provided with a temperature detection element.

[0037] A cell protective layer is installed between the cell under test and the runaway cell;

[0038] A trigger, the trigger being used to trigger thermal runaway of the runaway battery cell.

[0039] According to some embodiments of the present invention, the battery cell protective layer testing device is provided with multiple temperature detection elements for both the battery cell under test and the runaway battery cell, and the multiple temperature detection elements are distributed at intervals on the same side of the battery cell under test or the runaway battery cell.

[0040] And / or, the trigger is constructed as a mechanical trigger, an electrical trigger, or a thermal trigger.

[0041] The testing device and method for the battery cell protective layer described above have the same advantages over the prior art, and will not be repeated here.

[0042] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0043] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0044] Figure 1 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 1 ;

[0045] Figure 2 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 2 ;

[0046] Figure 3 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 3 ;

[0047] Figure 4 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 4 ;

[0048] Figure 5 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 5 ;

[0049] Figure 6 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 6 ;

[0050] Figure 7 This is a flowchart illustrating the testing method for the cell protective layer according to an embodiment of the present invention. Figure 7 ;

[0051] Figure 8 This is a schematic diagram of the structure of a test device for the cell protective layer according to an embodiment of the present invention. Figure 1 ;

[0052] Figure 9 This is a schematic diagram of the structure of a test device for the cell protective layer according to an embodiment of the present invention. Figure 2 ;

[0053] Figure 10 This is a schematic diagram of the structure of a test device for the cell protective layer according to an embodiment of the present invention. Figure 3 .

[0054] Figure label:

[0055] Test device 100,

[0056] Test housing 1, mounting cavity 11, through hole 12, cell under test 2, uncontrolled cell 3, positive electrode 31, negative electrode 32, cell protective layer 4, temperature detection component 5, trigger component 6. Detailed Implementation

[0057] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0058] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0059] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0060] The following is for reference. Figures 1-7 The test method for the cell protective layer according to an embodiment of the present invention can be used to determine the minimum safe thickness of the cell protective layer 4, ensure the reliability of the cell protective layer 4, and thus improve the safety of the battery pack.

[0061] like Figures 1-7 As shown, according to an embodiment of the present invention, a test method for a cell protective layer 4 is provided between a runaway cell 3 and a cell 2 under test. The test method includes:

[0062] S1. Select multiple sets of cell protective layers 4 with thicknesses increasing at equal ratios;

[0063] S2. Place multiple sets of cell protection layers 4 between the runaway cell 3 and the cell under test 2, and obtain the maximum average temperature of the cell under test 2 corresponding to each set of cell protection layers 4.

[0064] S3. Data of the test cell 2 that has thermal runaway are removed, and the maximum average temperature of multiple test cells 2 that have not thermal runaway is fitted to obtain the thickness formula.

[0065] S4. Based on the maximum average temperature of the cell 2 under test at the short circuit moment corresponding to the maximum thickness of thermal runaway, and combined with the thickness formula, obtain the minimum safe thickness of the cell protective layer 4.

[0066] The cell protection layer 4 is installed inside the battery pack, which contains multiple cells that can form a battery module, ensuring the reliability of the battery pack's power supply. The cell protection layer 4 can be set between two adjacent cells to isolate them. When the battery pack is in use, the cells may be subjected to extreme situations such as large impact forces, excessively high operating temperatures, or excessive power charging and discharging. In such cases, a short circuit may occur inside the cell, leading to thermal runaway. The cell protection layer 4 can isolate the cells that have experienced thermal runaway from the normal cells, thereby preventing the spread of thermal runaway and improving the safety of the battery pack.

[0067] Specifically, the testing method for the cell protection layer can test the thickness of the cell protection layer 4 of different battery packs to select a cell protection layer 4 of appropriate thickness, ensuring the reliability of the cell protection layer 4. Multiple sets of cell protection layers 4 with progressively increasing thickness can be selected, such as three, four, or five sets of cell protection layers 4 with progressively increasing thickness, so that the thickness difference between adjacent sets of cell protection layers 4 is the same. In this embodiment, six sets of cell protection layers 4 can be selected, and the thicknesses of the six sets of cell protection layers are selected as 1mm, 2mm, 3mm, 4mm, 5mm, and 6mm, respectively. That is, in this embodiment, the thickness difference between adjacent sets of cell protection layers 4 is 1mm. In actual settings, the thickness difference between adjacent sets of cell protection layers 4 can also be set to 2mm, 3mm, or 4mm, etc., which can be selected according to actual setting requirements.

[0068] The six sets of cell protection layers 4 are respectively recorded as U, V, W, X, Y, and Z. A runaway cell 3 and a cell under test 2 can be set. The user can trigger thermal runaway of the runaway cell 3 through electrical, thermal, or mechanical triggering. Multiple sets of cell protection layers 4 can be set between the runaway cell 3 and the cell under test 2. When the runaway cell 3 experiences thermal runaway, the user can monitor the cell under test 2 in real time to obtain the maximum average temperature of the cell under test 2 corresponding to each set of cell protection layers 4, which can be recorded as T. U T V T W T X T Y T Z .

[0069] Furthermore, the barrier effects of multiple sets of cell protective layers 4 vary during testing. When the thickness of the cell protective layer 4 does not meet the barrier requirements, the heat from the runaway cell 3 can be conducted to the cell under test 2 through the cell protective layer 4, leading to thermal runaway of the cell under test 2. In this case, the maximum average temperature corresponding to the cell protective layer 4 of that thickness is the failure data and needs to be discarded. That is, if the cell under test 2 experiences thermal runaway when the thickness of the cell protective layer 4 is 1mm and 2mm, then T... U and T V After eliminating the non-thermal runaway cells, the maximum average temperature corresponding to the remaining protective layer 4 of the cells that have not experienced thermal runaway is fitted to determine the T value. W T X T Y T Z A fitting process is performed to obtain the thickness formula.

[0070] Furthermore, among multiple sets of thermal runaway data, the set with the largest thickness of the cell protective layer 4 was selected, and the maximum average temperature of the tested cell 2 at the moment of thermal runaway, i.e., the moment a short circuit occurred inside the tested cell 2, was recorded. This maximum average temperature was recorded as T. isc By substituting the maximum average temperature at the moment of short circuit into the thickness formula, the thickness of the cell protection layer 4 at that moment can be calculated, which is the minimum safe thickness of the cell protection layer 4. If the thickness of the cell protection layer 4 is set to be less than or equal to this thickness, the cell 2 under test will experience thermal runaway. If the thickness of the cell protection layer 4 is set to be greater than this thickness, the cell 2 under test will not experience thermal runaway. Therefore, the thickness of the cell protection layer can be set according to this minimum safe thickness to ensure the reliability of the cell protection layer and thus improve the safety of the battery pack.

[0071] All battery cells used in the test must be fully charged, i.e., 100% SOC.

[0072] According to the test method of the cell protective layer of the present invention, the thickness formula can be obtained by fitting the maximum average temperature of multiple sets of cells 2 under test, and the minimum safe thickness of the cell protective layer 4 can be obtained by combining the maximum average temperature at the short circuit moment corresponding to the maximum thickness of thermal runaway. In this way, the reliability of the cell protective layer 4 can be guaranteed, the spread of thermal runaway in the battery pack can be avoided, the safety of the battery pack can be improved, the performance can be better, and the application range can be wider.

[0073] In some embodiments, such as Figure 2 As shown, the testing method for the cell protective layer also includes:

[0074] S31. After placing each group of cell protection layers 4 between the runaway cell 3 and the cell to be tested 2, the real-time voltage of the cell to be tested 2 is detected respectively.

[0075] S32. Determine the thermal runaway state of the cell under test 2 based on the real-time voltage change.

[0076] Specifically, temperature detection elements 5 can be set on both the cell under test 2 and the runaway cell 3 to monitor the temperature of the cell under test 2 and the runaway cell 3 in real time. There can be multiple runaway cells 3, that is, two, three or four runaway cells 3, etc. In this embodiment, there are two runaway cells 3, which are arranged in sequence. The cell under test 2 is set on one side of one of the two runaway cells 3, and a cell protection layer 4 is set between it and the runaway cell 3. Thermal runaway can be triggered on the runaway cell 3 that is far away from the cell under test 2. Subsequently, due to the large amount of heat released by the runaway cell 3, the runaway cell 3 that is close to the cell under test 2 is also triggered to thermal runaway. After the runaway cell 3 has completed thermal runaway, it is allowed to stand for a while. During this process, the temperature of the runaway cell 3 can be monitored in real time by the temperature detection elements 5 to determine whether the runaway cell 3 has thermal runaway. The real-time voltage of the cell under test 2 can also be detected.

[0077] Before a battery cell experiences thermal runaway, an internal short circuit will occur. Even if a battery cell with an internal short circuit does not ultimately burn or explode, it still carries the risk of thermal runaway. Therefore, any battery cell exhibiting an internal short circuit is considered a thermal runaway battery cell. If, during the experiment, the real-time voltage value of the tested battery cell 2 changes, indicating a short circuit, then the tested battery cell 2 has experienced thermal runaway. In this case, the thickness of the protective layer 4 corresponding to this set of experiments does not meet the barrier requirements, and the thickness of the protective layer 4 in this set of experiments can be removed from the fitted data to ensure the reliability of the fitted results.

[0078] In some embodiments, such as Figure 3 As shown, the thermal runaway state of the tested cell 2 is determined based on the real-time voltage change, including:

[0079] S321. When the real-time voltage drop is greater than 20% of the available window value of the cell under test 2, it is determined that the cell under test 2 is in a thermal runaway state.

[0080] S322. When the real-time voltage drop is less than or equal to 20% of the available window value of the cell under test 2, it is determined that the cell under test 2 has not thermally runaway.

[0081] Specifically, the battery cell has a voltage availability window value. The battery cell voltage availability window value refers to the range between the lowest voltage (discharge cut-off voltage) and the highest voltage (charge cut-off voltage) that the battery cell can use under normal operating conditions. Voltages higher or lower than the voltage availability window value will affect the safety, lifespan and performance of the battery cell. During the experiment, when the runaway battery cell 3 experiences thermal runaway, it can conduct heat to the battery cell protective layer 4, and the voltage of the battery cell 2 under test can be monitored in real time during this process.

[0082] Furthermore, when the real-time voltage of the cell under test 2 drops and the drop exceeds 20% of the available window value of the cell under test 2, it is determined that a short circuit has occurred inside the cell under test 2, and thus the cell under test 2 is in a state of thermal runaway. At this time, the thickness of the cell protective layer 4 does not meet the effective barrier thickness, and the thickness of the cell protective layer 4 can be removed from the fitted data. If the real-time voltage of the cell under test 2 is less than or equal to 20% of the available window value of the cell under test 2 during the test, it is determined that the cell under test 2 is not in thermal runaway. At this time, the thickness of the cell protective layer 4 meets the effective barrier thickness, and the thickness can be recorded for use in fitting the thickness formula to ensure the accuracy of the thickness formula.

[0083] In some embodiments, such as Figure 4 As shown, the maximum average temperature of the tested cell 2 corresponding to each group of cell protective layers 4 includes:

[0084] S21. Detect the temperature at multiple locations on the side of the battery cell 2 facing the runaway battery cell 3;

[0085] S22. Calculate the average value based on the temperature detected at multiple locations;

[0086] S23. Use the calculated average value as the maximum average temperature.

[0087] Specifically, a temperature detection element 5 can be set on the same side of each runaway cell 3 and the cell under test 2. The temperature detection element 5 can be set as a thermocouple. The temperature detection element 5 can detect the real-time temperature of the runaway cell 3 and the cell under test 2. Multiple temperature detection elements 5 are set on the same side of each runaway cell 3 and the cell under test 2. The multiple temperature detection elements 5 are distributed at intervals, and the positions of the temperature detection elements 5 on each runaway cell 3 and the cell under test 2 are the same to avoid errors and ensure the accuracy of the measurement results. Setting a temperature detection element 5 on each runaway cell 3 can monitor the thermal runaway state of the runaway cell 3.

[0088] Furthermore, the temperature is detected at multiple locations on the side of the battery cell 2 facing the runaway battery cell 3. This means temperature detection can be performed at two, three, or four locations on the side of the battery cell 2 facing the runaway battery cell 3. In this embodiment, five locations can be selected for temperature detection, and these locations are recorded as T1, T2, T3, T4, and T5 respectively. The average of the temperature data from multiple locations is then used to obtain the maximum average temperature T of the battery cell 2 under test. ave That is, T ave = (T1+T2+T3+T4+T5) / 5, which ensures the accuracy of the test results.

[0089] In some embodiments, the thickness formula is y = ax^3 + bx^2 + cx + d, where x is the thickness of the cell protective layer 4 and y is the maximum average temperature of the cell protective layer 4 at the thickness corresponding to x.

[0090] Specifically, the maximum average temperature of a set of battery cells 2 under test can be obtained for each of the battery cell protective layers 4 with different thicknesses. During the experiment, multiple sets of battery cell protective layers 4 are set for testing, so multiple sets of maximum average temperatures of battery cells 2 under test can be obtained. The maximum average temperature data of battery cells 2 under test that cause thermal runaway is removed, and the thickness formula can be obtained by fitting the remaining sets of maximum average temperature data of battery cells 2 under test. The thickness formula is y=ax^3+bx^2+cx+d. In this embodiment, the thickness formula is selected as a cubic function. In actual settings, the thickness formula can also be set as a quadratic function or a quartic function, etc. The larger the highest degree, the more accurate the result. It can be selected according to the needs.

[0091] Furthermore, in the thickness formula y = ax^3 + bx^2 + cx + d, x is the thickness of the cell protective layer 4, and y is the maximum average temperature of the cell protective layer 4 at the thickness corresponding to x. That is, when x is selected as 3mm, y is T. W When calculating the minimum safe thickness, y = T isc Substituting these values ​​into the thickness formula, we can then obtain the corresponding minimum safe thickness x. cpWhere a, b, and c are curve constants fitted from multiple sets of maximum average temperatures, and the values ​​of a, b, and c are different depending on the obtained maximum average temperature.

[0092] In some embodiments, such as Figure 5 As shown, the testing method for the cell protective layer also includes:

[0093] S5. Obtain the maximum heat insulation benefit value of each group of battery cell protective layer 4;

[0094] S6. Determine the relationship between the maximum insulation benefit value and the set insulation benefit value;

[0095] S7. Obtain the maximum profit thickness based on the judgment result.

[0096] Specifically, the maximum heat insulation benefit value of each group of battery cell protective layers 4 can be obtained by modifying the thickness formula. The thickness of multiple groups of battery cell protective layers 4 is set to increase at an equal ratio, so that the thickness difference between adjacent groups of battery cell protective layers 4 is equal. The maximum heat insulation benefit value is the increase in heat blocking effect caused by increasing the thickness of the battery cell protective layer 4 by a thickness difference. The maximum heat insulation benefit value of each group of battery cell protective layers 4 can be calculated by the modified thickness formula, and the maximum heat insulation benefit value is compared with the set heat insulation benefit value. That is, the relationship between the maximum heat insulation benefit value and the set heat insulation benefit value can be determined. Based on the judgment result, the maximum benefit thickness can be obtained, thereby reducing the setting cost and improving lightweighting. The maximum heat insulation benefit of the thickness can be obtained while ensuring effective heat blocking.

[0097] In some embodiments, such as Figure 6 As shown, obtaining the maximum thermal insulation benefit value for each group of protective layers includes:

[0098] S51. Differentiate the thickness formula to obtain the insulation value formula;

[0099] S52. Based on the formula for the thickness and heat insulation value of the cell protective layer 4, calculate the maximum heat insulation benefit value of the protective layer corresponding to the thickness value.

[0100] Specifically, the maximum heat insulation benefit value of each group of cell protective layers 4 can be obtained by transforming the thickness formula. The thickness formula can then be differentiated to obtain the heat insulation value formula. The thickness value can be substituted into the heat insulation value formula to obtain the maximum heat insulation benefit value of the cell protective layer 4 at that thickness. In actual calculation, when the calculated maximum heat insulation benefit value is greater than the set heat insulation benefit value, that is, the thickness of the cell protective layer 4 corresponding to the maximum heat insulation benefit value meets the benefit requirement. When the calculated maximum heat insulation benefit value is less than the set heat insulation benefit value, that is, the heat insulation benefit brought by the thickness of the cell protective layer 4 corresponding to the maximum heat insulation benefit value is reduced compared with the heat insulation benefit of the cell protective layer 4 with a thickness less than that, the data of the cell protective layer 4 with a thickness greater than that can be discarded to obtain the thickness with the maximum benefit.

[0101] In some embodiments, such as Figure 7 As shown, the relationship between the maximum insulation benefit value and the set insulation benefit value includes:

[0102] S61. Take the absolute value of the maximum insulation benefit;

[0103] S62. Compare the absolute value and the set insulation benefit value;

[0104] S63. When the absolute value is less than the set insulation benefit value, the thickness value at this time shall be taken as the maximum benefit thickness.

[0105] Specifically, the cell protection layer 4 is used to insulate adjacent cells from heat, so that when one cell experiences thermal runaway, the cell protection layer 4 can isolate the heat generated by the thermal runaway, thereby ensuring the reliability of the remaining cells. When the thickness of the cell protection layer 4 increases by a thickness difference, the temperature value conducted to the remaining cells can be reduced. This is the maximum heat insulation benefit value of the cell protection layer 4 at this thickness. The maximum heat insulation benefit value is a negative number. The absolute value of the maximum heat insulation benefit value is taken, and the absolute value is compared with the set heat insulation benefit value. When the absolute value is less than the set heat insulation benefit value, that is, when the thickness of the cell protection layer 4 increases by a thickness difference, the temperature value conducted to the remaining cells is reduced. At this time, this thickness value is taken as the maximum benefit thickness.

[0106] For example, if the heat insulation benefit value is set to 5℃ / mm, which means that for every 1mm increase in thickness, the temperature conducted to other cells by the cell protection layer 4 can be reduced by 5℃, then if the maximum heat insulation benefit value corresponding to the 4mm thick cell protection layer 4 is greater than 5℃ / mm and the maximum heat insulation benefit value corresponding to the 5mm thick cell protection layer 4 is less than 5℃ / mm, that is, when the thickness of the cell protection layer 4 increases from 4mm to 5mm, the degree of enhancement of its heat insulation effect gradually weakens. Therefore, it is not necessary to use a cell protection layer with a thickness greater than 5mm. Moreover, when the thickness of the cell protection layer 4 is 1mm and 2mm, the cell 2 under test experiences thermal runaway, that is, the minimum safe thickness of the cell protection layer 4 is greater than 2mm. Thus, in this embodiment, the thickness of the cell protection layer 4 can be optimized to 2mm to 5mm.

[0107] Furthermore, when the thickness of the cell protective layer 4 is 2mm, the tested cell 2 will experience thermal runaway, meaning that the 2mm thick cell protective layer 4 cannot effectively block heat transfer. Therefore, the minimum safe thickness of the cell protective layer 4 is between 2mm and 3mm. When the thickness of the cell protective layer 4 increases from 4mm to 5mm, the enhancement of its heat insulation effect gradually weakens. Therefore, the maximum beneficial thickness of the cell protective layer 4 is between 4mm and 5mm. If the target is relatively conservative, the optimization result can be 3mm or 4mm, or less than 5mm and greater than 2mm. This choice can depend on the requirements for the safety factor.

[0108] Among them, each group of cell protective layers 4 without thermal runaway has a safety factor, and the safety factor of each group of cell protective layers 4 without thermal runaway is the maximum average temperature of that group of cell protective layers 4 and T. isc The ratio, i.e., the safety factor for a thickness of 3mm, is T. W With T isc The ratio of .

[0109] The present invention also proposes a testing device 100 for the protective layer of a battery cell.

[0110] The battery cell protective layer testing apparatus 100 according to an embodiment of the present invention employs any of the above-described battery cell protective layer testing methods, such as... Figures 8-10 As shown, the testing device 100 includes: a test housing 1, a cell under test 2, at least one uncontrolled cell 3, a cell protective layer 4, and a trigger 6.

[0111] The test cell 2 and at least one runaway cell 3 are installed in the test housing 1. The test cell 2 and each runaway cell 3 are provided with a temperature detection element 5. The cell protection layer 4 is installed between the test cell 2 and the runaway cell 3. The trigger element 6 is used to trigger the thermal runaway of the runaway cell 3.

[0112] Specifically, the testing device 100 is provided with a testing housing 1, and an installation cavity 11 is formed inside the testing housing 1. The remaining structure of the testing device 100 can be installed in the installation cavity 11, so that the testing housing 1 can support and protect the structure inside the testing device 100 and block the external environment to ensure the accuracy of the test results. The testing device 100 is provided with at least one uncontrolled battery cell 3, that is, the uncontrolled battery cell 3 can be set as one, two or three, etc. In this embodiment, the uncontrolled battery cell 3 is set as two. The testing device 100 is also provided with a battery cell 2 under test and a battery cell protective layer 4. The battery cell 2 under test, at least one uncontrolled battery cell 3 and the battery cell protective layer 4 are all disposed in the testing housing 1, and the battery cell protective layer 4 is installed between the battery cell 2 under test and the uncontrolled battery cell 3.

[0113] Furthermore, both the cell under test 2 and each runaway cell 3 are equipped with a temperature detection element 5. The temperature detection element 5 can monitor the thermal runaway state of the runaway cell 3 and obtain the maximum average temperature of the cell under test 2. The testing device 100 is also equipped with a trigger element 6, which can trigger the thermal runaway of the runaway cell 3. That is, during the experiment, the thermal runaway of the runaway cell 3 can be triggered by the trigger element 6, and the real-time voltage of the cell under test 2 can be monitored. When the drop in real-time voltage is greater than 20% of the available window value of the cell under test 2, it is determined that the cell under test 2 is in a thermal runaway state. When the drop in real-time voltage is less than or equal to 20% of the available window value of the cell under test 2, it is determined that the cell under test 2 is not thermally runaway.

[0114] According to the present invention, the testing device 100 for the cell protective layer 4 can obtain the thickness formula by fitting multiple sets of maximum average temperatures of the cells 2 under test, and can obtain the minimum safe thickness of the cell protective layer 4 by combining the maximum average temperature at the short circuit moment corresponding to the maximum thickness of thermal runaway. This can ensure the reliability of the cell protective layer 4, avoid the spread of thermal runaway in the battery pack, improve the safety of the battery pack, and have better performance and wider applicability.

[0115] In some embodiments, both the cell under test 2 and the runaway cell 3 are provided with a plurality of temperature detection elements 5, which are spaced apart on the same side of the cell under test 2 or the runaway cell 3.

[0116] Specifically, such as Figure 10As shown, a temperature detection element 5 can be set on the same side of the cell under test 2 and each runaway cell 3. The temperature detection element 5 can be set as a thermocouple. The temperature detection element 5 can detect the real-time temperature of the runaway cell 3 and the cell under test 2. Multiple temperature detection elements 5 are set on the same side of each cell under test 2 and each runaway cell 3. The multiple temperature detection elements 5 are distributed at intervals, and the positions of the temperature detection elements 5 on the cell under test 2 and each runaway cell 3 are the same to avoid errors and ensure the accuracy of the measurement results. The temperature detection element 5 set on each runaway cell 3 can monitor the thermal runaway state of the runaway cell 3. Since multiple temperature detection elements 5 are set on both the cell under test 2 and the runaway cell 3, the temperature at multiple points can be detected, and the average value is taken to improve the accuracy of the experimental results.

[0117] In other embodiments, the trigger 6 is configured as a mechanical trigger, an electrical trigger, or a thermal trigger.

[0118] Specifically, during the experiment, thermal runaway can be triggered on the runaway cell 3 by triggering element 6, and triggering element 6 can be constructed as a mechanical triggering element, an electrical triggering element, or a thermal triggering element, such as... Figure 8 As shown, the mechanical trigger can be set as a hydraulic trigger, which can squeeze the runaway battery cell 3 to trigger thermal runaway. In actual setup, the end of the hydraulic trigger that contacts the runaway battery cell 3 can be constructed as a hydraulic disc or a needle-like component. The electrical trigger connects wires to the positive terminal 31 and negative terminal 32 of the runaway battery cell 3, and provides overcharging or high-power charging and discharging to the runaway battery cell 3 through the wires to trigger thermal runaway. A through hole 12 can be provided in the test housing 1, through which the wire can extend into the mounting cavity 11 to connect with the runaway battery cell 3, ensuring reliable connection. The thermal trigger is a resistance wire set in the runaway battery cell 3, which continuously heats the runaway battery cell 3 to trigger thermal runaway. The setup is flexible and can be selected according to the actual situation.

[0119] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0120] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for testing a cell protective layer, wherein the cell protective layer (4) is disposed between a runaway cell (3) and a cell under test (2), the testing method comprising: Multiple sets of cell protective layers with thicknesses increasing at equal ratios were selected (4); Multiple sets of the cell protection layers (4) are placed between the runaway cell (3) and the cell under test (2), and the maximum average temperature of the cell under test (2) corresponding to each set of the cell protection layers (4) is obtained. The data of the test cell (2) that is thermally runaway are removed, and the maximum average temperature of multiple test cells (2) that are not thermally runaway is fitted to obtain the thickness formula; Based on the maximum average temperature of the cell under test (2) at the short circuit moment corresponding to the maximum thickness of thermal runaway, and in conjunction with the thickness formula, the minimum safe thickness of the cell protective layer (4) is obtained.

2. The test method for the cell protective layer according to claim 1, characterized in that, Also includes: After placing each set of the cell protection layer (4) between the runaway cell (3) and the cell under test (2), the real-time voltage of the cell under test (2) is detected respectively; The thermal runaway state of the battery cell (2) under test is determined based on the voltage change of the real-time voltage.

3. The test method for the cell protective layer according to claim 2, characterized in that, The step of determining the thermal runaway state of the battery cell (2) under test based on the voltage change of the real-time voltage includes: When the drop in real-time voltage is greater than 20 percent of the available window value of the cell under test (2), the cell under test (2) is determined to be in a thermal runaway state. When the drop in real-time voltage is less than or equal to 20 percent of the available window value of the cell under test (2), it is determined that the cell under test (2) has not thermally runaway.

4. The test method for the cell protective layer according to claim 1, characterized in that, The process of obtaining the maximum average temperature of the cell under test (2) corresponding to each group of cell protective layers (4) includes: The temperature at multiple locations on the side of the cell under test (2) facing the runaway cell (3) is detected; Calculate the average value based on the temperature measured at multiple locations; The calculated average value is taken as the maximum average temperature.

5. The test method for the cell protective layer according to claim 1, characterized in that, The thickness formula is y = ax^3 + bx^2 + cx + d; Where x is the thickness of the cell protective layer (4) and y is the maximum average temperature of the cell protective layer (4) with the thickness corresponding to x.

6. The test method for the cell protective layer according to claim 1, characterized in that, Also includes: Obtain the maximum heat insulation benefit value of each group of cell protective layers (4); Determine the relationship between the maximum insulation benefit value and the set insulation benefit value; The maximum profit thickness is determined based on the judgment result.

7. The test method for the cell protective layer according to claim 6, characterized in that, The process of obtaining the maximum thermal insulation benefit value for each group of protective layers includes: Differentiating the thickness formula yields the formula for the thermal insulation value; Based on the thickness value of the cell protective layer (4) and the heat insulation value formula, the maximum heat insulation benefit value of the protective layer corresponding to the thickness value is calculated.

8. The test method for the cell protective layer according to claim 6, characterized in that, The determination of the relationship between the maximum thermal insulation benefit value and the set thermal insulation benefit value includes: Take the absolute value of the maximum insulation benefit; Compare the absolute value with the set insulation benefit value; When the absolute value is less than the set insulation benefit value, the thickness value at this time is taken as the maximum benefit thickness.

9. A testing device for the protective layer of a battery cell, characterized in that, The test method for the cell protective layer according to any one of claims 1-8, wherein the test apparatus (100) comprises: Test housing (1); The test cell (2) and at least one runaway cell (3) are installed in the test housing (1), and the test cell (2) and at least one runaway cell (3) are provided with a temperature detection element (5). A cell protection layer (4) is installed between the cell under test (2) and the runaway cell (3); Trigger (6), the trigger (6) is used to trigger the thermal runaway of the runaway cell (3).

10. The testing apparatus for the cell protective layer according to claim 9, characterized in that, Both the cell under test (2) and the runaway cell (3) are provided with multiple temperature detection elements (5), and the multiple temperature detection elements (5) are distributed at intervals on the same side of the cell under test (2) or the runaway cell (3); And / or, the trigger (6) is configured as a mechanical trigger, an electrical trigger, or a thermal trigger.

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