Thermal runaway test system and method

Abstract

The invention relates to a thermal runaway test system and method. The thermal runaway test system comprises a controller, power supply equipment and a thermal runaway test device, the thermal runaway test device comprises a plurality of test branches connected in parallel, and each test branch comprises a sample cell, a heating device, a temperature acquisition device and a fire-resistant wire; the heating device is attached to the sample cell and is connected with the fire-resistant wire; the temperature acquisition device is attached to the sample cell and is connected with the controller; the fire-resistant wires of the plurality of test branches are connected in parallel and are connected with power supply equipment; the controller is connected with the power supply equipment, and is used for controlling the power supply equipment to output initial power, so that the power supply equipment enables the heating device to heat the sample battery cells through the fire-resistant wires, obtains the battery cell temperatures of the plurality of sample battery cells from the plurality of temperature acquisition devices, and adjusts the power output by the power supply equipment according to the plurality of battery cell temperatures; and the thermal runaway is triggered. By adopting the application, a battery cell heating mode required by airworthiness regulations can be met, and thermal runaway is successfully triggered.

Description

Technical Field

[0001] This application relates to the field of battery cell technology, and in particular to a thermal runaway testing system and method. Background Technology

[0002] With the mature application of lithium-ion cells in the new energy vehicle market, using lithium-ion cells as battery cells for aircraft has become a new application direction. Unlike the thermal runaway test standards for battery cells in the automotive industry, the airworthiness regulations have higher requirements for the thermal runaway test standards for battery cells: on the one hand, it requires the entire battery pack to be heated to trigger or all cells to be heated to trigger; on the other hand, it requires the temperature rise rate during the heating trigger process to be within the range of 5~20℃ / min.

[0003] Therefore, there is an urgent need to develop a device for testing thermal runaway of aviation battery cells. Summary of the Invention

[0004] Therefore, it is necessary to provide a thermal runaway test system and method that can meet airworthiness regulations and successfully trigger thermal runaway in order to address the above-mentioned technical problems.

[0005] In a first aspect, this application provides a thermal runaway test system, which includes a controller, a power supply device, and a thermal runaway test apparatus. The thermal runaway test apparatus includes multiple test branches connected in parallel, and each test branch includes a sample cell, a heating device, a temperature acquisition device, and a fire-resistant wire.

[0006] The heating element is attached to the sample battery cell and connected to the refractory wire;

[0007] The temperature acquisition device is attached to the sample cell and connected to the controller;

[0008] The fire-resistant wires of multiple test branches are connected in parallel and connected to the power supply equipment;

[0009] The controller is connected to the power supply equipment. The controller is used to control the initial output power of the power supply equipment so that the power supply equipment can heat the sample battery cell through the refractory wire and obtain the battery cell temperature of multiple sample battery cells from multiple temperature acquisition devices. The controller adjusts the output power of the power supply equipment according to the multiple battery cell temperatures until thermal runaway is triggered.

[0010] In one embodiment, the heating device includes a heating wire wound in a spiral manner around the sample cell with a pitch range of 10±0.1 mm. The winding area covers 2 / 3 of the cell height and is centrally symmetrical along the cell height direction.

[0011] In one embodiment, the heating wire is made of Cr20Ni80, has a maximum operating temperature of 1200°C, a diameter range of 0.6±0.006 mm, and a length range of 800±10 mm / wire.

[0012] In one embodiment, the heating wire is attached to the surface of the battery cell using insulating adhesive tape;

[0013] The temperature acquisition device is fixed to the surface of the battery cell using insulating adhesive tape.

[0014] In one embodiment, the insulating fixing tape is made of acrylic adhesive with a thickness ranging from 0.06±0.01mm, a maximum short-time temperature resistance of 400℃, and a flame retardant rating of UL94 V-0.

[0015] In one embodiment, the refractory wire and the heating wire lead-out end are cross-wound and connected, the contact resistance at the connection point is ≤0.02mΩ, and it is wrapped with Teflon tape.

[0016] In one embodiment, the Teflon tape is made of polytetrafluoroethylene with a dielectric constant of 2.6 and a maximum short-time temperature resistance of 400°C.

[0017] In one embodiment, the diameter of the internal copper wire of the fire-resistant wire ranges from 0.6 to 0.7 mm, and the fire-resistant layer of the fire-resistant wire is made of synthetic mica tape with a maximum temperature resistance of 1200°C.

[0018] In one embodiment, the gaps between adjacent sample cells are filled with potting compound, which is then cured at room temperature.

[0019] In one embodiment, the potting compound is an addition-curing two-component silicone rubber with a volume resistivity ≥1×10⁻⁶. 13 Ω.cm, thermal conductivity ≤0.2W / mK, flame retardant rating UL94 V-0.

[0020] Secondly, this application provides a thermal runaway testing method, applied to a controller in a thermal runaway testing system as described in any one of the first aspects, the method comprising:

[0021] The power supply equipment of the thermal runaway test system is controlled to output initial power so that multiple heating devices in the thermal runaway test system can heat multiple sample cells;

[0022] Obtain the cell temperature of multiple sample cells;

[0023] The power output of the power supply equipment is adjusted based on the cell temperature of multiple sample cells until thermal runaway is triggered.

[0024] In one embodiment, adjusting the output power of the power supply device based on the cell temperature of multiple sample cells includes:

[0025] Determine whether preset conditions are met based on the cell temperatures of multiple sample cells; wherein the preset conditions include at least two sample cells having a temperature rise rate greater than a temperature rise rate threshold and a duration exceeding a first duration threshold, the average temperature rise rate of multiple sample cells exceeding the temperature rise rate range, and at least two sample cells having a cell voltage lower than a preset voltage threshold, and / or at least two sample cells having a cell temperature exceeding a preset temperature threshold and a duration exceeding a second duration threshold.

[0026] If the preset conditions are not met, the power supply equipment is controlled to increase the output power by a preset step size.

[0027] In the aforementioned thermal runaway system and method, the thermal runaway test system includes a controller, a power supply device, and a thermal runaway test apparatus. The thermal runaway test apparatus includes multiple test branches connected in parallel. Each test branch includes a sample battery cell, a heating device, a temperature acquisition device, and a refractory wire. The controller controls the power supply device to output initial power. The power supply device heats the sample battery cell through the refractory wire using the heating device. Subsequently, the controller obtains the battery cell temperatures of multiple sample battery cells from multiple temperature acquisition devices and adjusts the power output of the power supply device according to the multiple battery cell temperatures until thermal runaway is triggered. The thermal runaway test system provided in this application embodiment can perform parallel heating for all battery cells, which not only reduces the risk of heating device burnout due to heat concentration during heating, but also simplifies the sample preparation process, facilitates disassembly and assembly, does not affect post-test disassembly and observation, and is applicable to thermal runaway tests of battery cells of different specifications. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the thermal runaway test system in one embodiment;

[0030] Figure 2 This is a schematic diagram of the thermal runaway test system in another embodiment;

[0031] Figure 3 This is a flowchart illustrating a thermal runaway method in one embodiment;

[0032] Figure 4 This is a flowchart illustrating the steps for adjusting the output power of a power supply device in one embodiment.

[0033] Figure 5This is a schematic diagram of power and cell temperature in one embodiment. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0036] With the mature application of lithium-ion cells in the new energy vehicle market, using lithium-ion cells as battery cells for aircraft has become a new application direction. Unlike the thermal runaway test standards for battery cells in the automotive industry, the airworthiness regulations have higher requirements for the thermal runaway test standards for battery cells: on the one hand, it requires the entire battery pack to be heated to trigger or all cells to be heated to trigger; on the other hand, it requires the temperature rise rate during the heating trigger process to be within the range of 5~20℃ / min.

[0037] Regarding the triggering method for thermal runaway testing of battery cells, airworthiness regulations provide three options: Option 1, installing one or more heating devices inside the battery pack to heat all cells; Option 2, installing heating devices around the battery pack for overall heating; and Option 3, placing the battery pack in an environmental chamber for heating. Since Options 2 and 3 involve heating externally to the battery pack, heat conduction occurs from the outside in, resulting in a low rate of temperature rise for the cells, affecting the condition of other components, and causing uneven heating of the cells; therefore, these options are not recommended. For Option 1, currently, heating wires are wound in series around each cell; however, this can easily lead to problems such as large deformation of the heating wires in localized circuits, decreased strength at high temperatures, and burnout.

[0038] To address the aforementioned problems, this application provides a thermal runaway testing system. The system includes a controller, a power supply, and a thermal runaway testing device. The device comprises multiple parallel-connected test branches, each including a sample battery cell, a heating element, a temperature acquisition device, and a refractory wire. The controller controls the power supply to output initial power, which heats the sample battery cell via the refractory wire. Subsequently, the controller acquires the cell temperatures of multiple sample batteries from the temperature acquisition devices and adjusts the power output of the power supply based on these temperatures until thermal runaway is triggered. The thermal runaway testing system provided in this application can perform parallel heating of all battery cells, reducing the risk of heating element burnout due to concentrated heat during heating. Furthermore, the system simplifies sample preparation, facilitates disassembly and assembly, does not affect post-test observation, and is suitable for thermal runaway testing of battery cells of different specifications.

[0039] In one exemplary embodiment, such as Figure 1 As shown, a thermal runaway testing system is provided. The thermal runaway testing system includes a controller 10, a power supply 20, and a thermal runaway testing device 30. The thermal runaway testing device 30 includes multiple test branches connected in parallel. Each test branch includes a sample battery cell 301, a heating element 302, a temperature acquisition device 303, and a refractory wire 304. The heating element 302 is attached to the sample battery cell 301 and connected to the refractory wire 304. The temperature acquisition device 303 is attached to the sample battery cell 301 and connected to the controller 10 (see the dotted line in the figure). The fire-resistant wires 304 of each test branch are connected in parallel and connected to the power supply equipment 20 (see solid line in the figure); the controller 10 is connected to the power supply equipment 20. The controller 10 is used to control the power supply equipment 20 to output the initial power so that the power supply equipment 20 heats the sample cell 301 through the heating device 302 via the fire-resistant wires 304, and obtains the cell temperature of multiple sample cells 301 from multiple temperature acquisition devices 303, and adjusts the power output of the power supply equipment 20 according to the multiple cell temperatures until thermal runaway is triggered.

[0040] In this embodiment, for each test branch, a heating device 302 is attached to a sample battery cell 301, and the heating device 302 is connected to a refractory wire 304; a temperature acquisition device 303 is attached to a sample battery cell 301. Furthermore, the refractory wires 304 of multiple test branches are connected in parallel to obtain a thermal runaway test device 30. Then, the temperature acquisition device 303 is connected to a controller 10, the refractory wires 304 are connected to a power supply device 20, and the power supply device 20 is connected to the controller 10 to obtain a thermal runaway test system.

[0041] During the thermal runaway test, the controller 10 controls the power supply device 20 to output initial power. Since the heating device 302 is connected to the power supply device 20 via a refractory wire 304, it heats the sample battery cell 301 after the power supply device 20 outputs initial power. The temperature of the sample battery cell 301 gradually increases, and the temperature acquisition device 303 collects the battery temperature and transmits it to the controller 10. The controller 10 determines whether thermal runaway has been triggered based on the battery temperatures of multiple sample battery cells 301. If thermal runaway has not been triggered, the controller 10 adjusts the output power of the power supply device 20 to further heat the sample battery cell 301, increasing its temperature. Thermal runaway is triggered only when the battery temperatures of multiple sample battery cells 301 are determined to be the cause, at which point the controller 10 stops the power supply device 20 from operating.

[0042] During the test, the initial power output of the power supply device 20 and the power output after each adjustment can be recorded, as well as the time interval between two adjacent adjustments, the cell temperature and heating rate of sample cell 301, the cell temperature of sample cell 301 at the time of thermal runaway, and the heating time from the start of heating to triggering thermal runaway, etc. After thermal runaway, sample cell 301 can be disassembled for inspection and analysis. By combining the various data recorded during the test and the disassembly results after thermal runaway, various performance characteristics of sample cell 301 can be determined, providing a reference for evaluating the performance of cells of the same batch and / or model as sample cell 301.

[0043] It should be noted that the role of thermal runaway testing is not limited to the examples above. In practical applications, thermal runaway testing can also guide the design and manufacturing of battery cells, or be applied to other aspects.

[0044] In some embodiments, the heating device 302 may include a PTC (Positive Temperature Coefficient) heating element, a ceramic heating element, and a heating wire, etc. The temperature acquisition device 303 may be a type K thermocouple.

[0045] In the above embodiments, the thermal runaway test system can perform parallel heating for all battery cells, which not only reduces the risk of heating devices burning out due to concentrated heat during the heating process, but also simplifies the sample preparation process, facilitates test disassembly and assembly, does not affect the disassembly and observation after the test, and is suitable for thermal runaway tests of battery cells of different specifications.

[0046] In an exemplary embodiment, the heating device 302 includes a heating wire that is spirally wound around the sample cell 301 with a pitch range of 10±0.1mm. The winding area covers 2 / 3 of the cell height and is centrally symmetrical along the cell height direction.

[0047] Taking sample cell 301 as a cylindrical cell as an example, the heating device 302 uses a heating wire, which is spirally wound around the cylindrical cell. The uniform pitch and the fact that the winding area covers most of the sample cell 301 contribute to more uniform heat conduction, enabling the sample cell 301 to heat up at a uniform rate.

[0048] In some embodiments, the heating wire is made of Cr20Ni80, has a maximum operating temperature of 1200°C, a diameter range of 0.6±0.006 mm, and a length range of 800±10 mm / wire.

[0049] Having the same resistance value for the heating wires in multiple test branches ensures consistent heating power across them. The maximum operating temperature of the heating wires, 1200℃, guarantees they won't burn out in the event of thermal runaway, thus preventing them from interfering with the observation of test results.

[0050] In one exemplary embodiment, such as Figure 2 As shown, the heating wire is attached to the surface of the battery cell using insulating adhesive tape 305; the temperature acquisition device 303 is also attached to the surface of the battery cell using insulating adhesive tape 305. It should be noted that the connection relationship between the controller 10 and the power supply device 20 is not shown in the figure.

[0051] By using insulating fixing tape 305 to fix the heating wire to the surface of the battery cell and the temperature acquisition device 303 to the surface of the battery cell, the reliability of the thermal runaway test device can be improved, ensuring that heat does not diffuse to the surroundings during the heating process, resulting in uniform heating, high efficiency, and accurate battery cell temperature.

[0052] In some embodiments, the insulating fixing tape 305 is made of acrylic adhesive with a thickness ranging from 0.06±0.01mm, a maximum short-time temperature resistance of 400℃, and a flame retardant rating of UL94 V-0.

[0053] The maximum short-time temperature resistance of the insulating fixing tape 305 reaches 400℃, which is much higher than the normal heating-triggered thermal runaway temperature of the battery cell (about 200-250℃ for ternary lithium and about 250-300℃ for lithium iron phosphate). This can avoid the introduction of other uncontrollable variables (such as the risk of heating wire burnout, short circuit, and fire of the triggering device), and has high reliability.

[0054] Among them, UL94 V-0 is the highest flame retardant rating for vertical burning tests of plastic materials, representing that the material has extremely strong self-extinguishing ability and is a core access standard for safety-critical components in electronics, electrical appliances, automobiles and other industries.

[0055] It should be noted that the material of the insulating fixing tape 305 can be adjusted according to the actual situation of the sample cell 301, and the thickness range can also be adjusted accordingly.

[0056] In one exemplary embodiment, such as Figure 2 As shown, the fire-resistant wire 304 is cross-wound with the heating wire lead-out end, the contact resistance at the connection point is ≤0.02mΩ, and it is wrapped with Teflon tape 306. The connection relationship between the controller 10 and the power supply equipment 20 is not shown in the figure.

[0057] In related technologies, heating wires are wound in series around each sample cell, which can easily lead to large deformation in local circuits and a decrease in strength at high temperatures, resulting in burnout. This application addresses this problem by using a parallel connection structure for the heating wires. However, concentrated heating can easily occur at the connection points, causing the heating wires to burn out if the heating time is slightly longer than the material's melting point. Therefore, this application further improves upon this by using a fire-resistant wire 304 to connect the heating wires, with a contact resistance of ≤0.02mΩ at the connection point. The fire-resistant wire 304 is then connected to the power supply device 20. This reduces the problem of concentrated heating at the connection points and lowers the risk of the heating wires burning out over long heating times.

[0058] Wrapping the connection between the fire-resistant wire 304 and the heating wire with Teflon tape 306 can insulate the connection and prevent local overheating and short circuit risks caused by vibration during transportation.

[0059] In some embodiments, the material of Teflon tape 306 is polytetrafluoroethylene, with a dielectric constant of 2.6 and a maximum short-time temperature resistance of 400°C. It should be noted that in practical applications, other insulating and heat-resistant tapes can also be used instead of Teflon tape.

[0060] In some embodiments, the diameter of the internal copper wire of the fire-resistant wire 304 ranges from 0.6 to 0.7 mm, and the fire-resistant layer of the fire-resistant wire 304 is made of synthetic mica tape with a maximum temperature resistance of 1200°C.

[0061] In one exemplary embodiment, such as Figure 2 As shown, the gaps between adjacent sample cells 301 are filled with potting compound 307, which is cured at room temperature. The connection relationship between the controller 10 and the power supply device 20 is not shown in the figure.

[0062] Encapsulating resin 307 is filled between adjacent sample cells 301 and cured at room temperature. The filling and curing of encapsulating resin 307 helps to fix the temperature acquisition device 303, preventing it from becoming loose during transportation and assembly, thus improving the temperature sampling accuracy.

[0063] In some embodiments, potting compound 307 is an addition-cured two-component silicone rubber with a volume resistivity ≥1×10⁻⁶. 13 Ω.cm, thermal conductivity ≤0.2W / mK, flame retardant rating UL94 V-0.

[0064] Encapsulant 307 can also effectively isolate oxygen, ensuring that the test equipment inside the package will not ignite after the cell thermal runaway, thereby improving the safety of the thermal runaway test system.

[0065] In one exemplary embodiment, such as Figure 3 As shown, a thermal runaway test method is provided. Taking the application of this method to the controller in the thermal runaway test system of the above embodiment as an example, it can include the following steps:

[0066] Step 401: Control the power supply equipment of the thermal runaway test system to output initial power so that multiple heating devices in the thermal runaway test system can heat multiple sample cells.

[0067] Taking a 20Ah cylindrical battery cell as an example, the controller controls the initial power output of the power supply equipment to be 380W. The power supply equipment is connected to the heating wire via a heat-resistant wire. After the power supply equipment outputs the initial power, the heating wire will heat up, thereby heating the sample battery cell.

[0068] Step 402: Obtain the cell temperature of multiple sample cells.

[0069] The controller can acquire the cell temperature of each sample cell from various temperature acquisition devices. In some embodiments, the acquisition frequency of the temperature acquisition devices can be 1 Hz.

[0070] Step 403: Adjust the output power of the power supply equipment according to the cell temperature of multiple sample cells until thermal runaway is triggered.

[0071] The controller determines whether the temperature rise rate of each sample cell is within the range of 5~20℃ / min based on the cell temperatures of multiple sample cells. If the temperature rise rate of the sample cell is outside this range, the controller adjusts the output power of the power supply equipment. For example, if the temperature rise rate of the sample cell is less than 5℃ / min, the controller increases the output power of the power supply equipment; if the temperature rise rate of the sample cell is greater than 20℃ / min, the controller decreases the output power of the power supply equipment.

[0072] By adjusting the output power of the power supply equipment, the temperature rise rate of the sample cells is made to meet the requirements of airworthiness regulations. When all sample cells trigger thermal runaway, the controller shuts down the power supply equipment.

[0073] In the above embodiments, the power supply equipment of the thermal runaway test system outputs initial power to enable multiple heating devices in the thermal runaway test system to heat multiple sample cells; the cell temperatures of the multiple sample cells are acquired; and the power output of the power supply equipment is adjusted according to the cell temperatures of the multiple sample cells until thermal runaway is triggered. The technical solution of this application embodiment can perform parallel heating for all cells, which not only meets the experimental requirements of airworthiness regulations, but also reduces the risk of heating devices burning out due to heat concentration during the heating process.

[0074] In one exemplary embodiment, such as Figure 4 As shown, in the above embodiment, "adjusting the output power of the power supply device according to the cell temperature of multiple sample cells" may include the following steps:

[0075] Step 501: Determine whether the preset conditions are met based on the cell temperature of multiple sample cells.

[0076] The preset conditions include at least two sample cells having a temperature rise rate greater than a temperature rise rate threshold and a duration exceeding a first duration threshold, multiple sample cells having an average temperature rise rate exceeding a temperature rise rate range, at least two sample cells having a cell voltage lower than a preset voltage threshold, and / or at least two sample cells having a cell temperature exceeding a preset temperature threshold and a duration exceeding a second duration threshold.

[0077] According to airworthiness regulations, if the second and / or third thermal runaway factors are present, in addition to the presence of the first and fourth thermal runaway factors, the cell temperature of multiple sample cells is determined to meet the preset conditions, i.e., thermal runaway heating is successfully triggered.

[0078] For example, 1) Set the temperature rise rate threshold to 1℃ / s and a first duration threshold, and obtain the temperature rise rate of the sample cell through a temperature acquisition device. If the temperature rise rate of ≥2 sample cells is detected to be greater than the temperature rise rate threshold and the duration exceeds the first duration threshold, then it is determined that the sample cell has a first thermal runaway factor.

[0079] 2) The preset voltage threshold is 25% of the rated voltage of the sample cell. The cell voltage of the sample cell is obtained through a voltage sampling line. If ≥2 sample cells are detected with voltages lower than the preset voltage threshold, it is determined that the sample cell has a second thermal runaway factor.

[0080] 3) The preset temperature threshold (maximum operating temperature of the battery cell) is 85℃, and the second duration threshold is 3s. The cell temperature of the sample battery cell is obtained through a temperature acquisition device. If the cell temperature of ≥2 sample battery cells exceeds the preset temperature threshold and the duration exceeds the second duration threshold, it is determined that the sample battery cell has a third thermal runaway factor.

[0081] 4) Set the temperature rise rate range to 5~20℃ / min, acquire the cell temperature of all sample cells through the temperature acquisition device, and calculate the average temperature rise rate of all sample cells. If the detected average temperature rise rate exceeds the temperature rise rate range, it is determined that the sample cell has a fourth thermal runaway factor.

[0082] It should be noted that the temperature rise rate threshold, the first duration threshold, the preset voltage threshold, the preset temperature threshold, the second duration threshold, and the temperature rise rate range can be adjusted according to the actual situation of the sample cell, and are not limited to the above examples.

[0083] Step 502: If the preset conditions are not met, control the power supply equipment to increase the output power according to the preset step size.

[0084] If the preset conditions are not met, it is determined that thermal runaway has not been triggered, and the controller controls the power supply to adjust the power according to a preset step size. For example, the preset step size is 150W. After the power supply outputs an initial power of 380W, the controller acquires the cell temperature of each sample cell at a preset sampling frequency. If it is determined that the cell temperature does not meet the preset conditions, the controller controls the power supply to adjust the output power to 530W. Then, the controller acquires the cell temperature of each sample cell at the preset sampling frequency. If it is determined that the cell temperature still does not meet the preset conditions, the controller controls the power supply to adjust the output power to 680W. This process continues until the controller determines that the cell temperature meets the preset conditions, at which point it controls the power supply to stop working, i.e., disconnect the heating power supply.

[0085] like Figure 5 As shown, the power output of the power supply equipment increases in a stepped manner, and the cell temperature of the sample battery cells gradually rises. The temperature rise rate of the 24 sample battery cells reaches the airworthiness regulation requirement of 5~20℃ / min, and ≥2 cells are detected with a temperature rise rate greater than the temperature rise rate threshold of 1℃ / s, indicating the presence of the aforementioned first and fourth thermal runaway factors. Furthermore, if the cell temperature of ≥2 sample battery cells is detected to be greater than the preset temperature threshold of 85℃ and the duration exceeds the second duration threshold of 3s, then the preset conditions are deemed met, i.e., thermal runaway is successfully triggered. As can be seen from the figure, the thermal runaway test system provided in this application embodiment can successfully trigger thermal runaway while meeting airworthiness regulation requirements.

[0086] It should be noted that, since the resistance of the Cr20Ni80 heating wire increases with temperature, the heating power gradually decreases and tends to stabilize, and the adjustment frequency in the later stages of heating also gradually decreases, making it highly operable.

[0087] In the above embodiments, it is determined whether the preset conditions are met based on the cell temperatures of multiple sample cells; if the preset conditions are not met, the power supply equipment is controlled to increase the output power in preset steps. The technical solution of this application embodiment can gradually adjust the heating power while meeting airworthiness regulations, fully record various data in the thermal runaway test, and provide support for evaluating cell performance and guiding cell design and manufacturing.

[0088] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0089] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0090] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0091] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A thermal runaway testing system, characterized in that, The thermal runaway test system includes a controller, a power supply device, and a thermal runaway test device. The thermal runaway test device includes multiple test branches connected in parallel. Each test branch includes a sample battery cell, a heating device, a temperature acquisition device, and a fire-resistant wire. The heating device is attached to the sample battery cell and connected to the fire-resistant wire; The temperature acquisition device is attached to the sample cell and connected to the controller; The fire-resistant wires of multiple test branches are connected in parallel and connected to the power supply equipment; The controller is connected to the power supply device. The controller is used to control the power supply device to output initial power so that the power supply device heats the sample cell through the fire-resistant wire using the heating device. The controller also acquires the cell temperature of the sample cell from the multiple temperature acquisition devices and adjusts the power output of the power supply device according to the multiple cell temperatures until thermal runaway is triggered.

2. The thermal runaway test system according to claim 1, characterized in that, The heating device includes a heating wire that is wound around the sample cell in a spiral manner with a pitch range of 10±0.1mm. The winding area covers 2 / 3 of the cell height and is centrally symmetrical along the cell height direction.

3. The thermal runaway test system according to claim 2, characterized in that, The heating wire is made of Cr20Ni80, has a maximum operating temperature of 1200℃, a diameter range of 0.6±0.006mm, and a length range of 800±10mm / wire.

4. The thermal runaway test system according to claim 2, characterized in that, The heating wire is fixed to the surface of the battery cell by insulating adhesive tape. The temperature acquisition device is fixed to the surface of the battery cell by insulating adhesive tape.

5. The thermal runaway test system according to claim 4, characterized in that, The insulating fixing tape is made of acrylic adhesive with a thickness ranging from 0.06±0.01mm, a maximum short-time temperature resistance of 400℃, and a flame retardant rating of UL94 V-0.

6. The thermal runaway test system according to claim 2, characterized in that, The refractory wire and the lead-out end of the heating wire are cross-wound and connected, with a contact resistance of ≤0.02mΩ at the connection point, and are wrapped with Teflon tape.

7. The thermal runaway test system according to claim 6, characterized in that, The Teflon tape is made of polytetrafluoroethylene, with a dielectric constant of 2.6 and a maximum short-time temperature resistance of 400°C.

8. The thermal runaway test system according to claim 2, characterized in that, The diameter of the internal copper wire of the fire-resistant wire ranges from 0.6 to 0.7 mm, and the fire-resistant layer of the fire-resistant wire is made of synthetic mica tape with a maximum temperature resistance of 1200℃.

9. The thermal runaway testing system according to any one of claims 1-8, characterized in that, The gaps between adjacent sample cells are filled with potting compound, which is cured at room temperature.

10. The thermal runaway testing system according to claim 9, characterized in that, The potting compound is an addition-curing two-component silicone rubber with a volume resistivity ≥1×10⁻⁶. 13 Ω.cm, thermal conductivity ≤0.2W / mK, flame retardant rating UL94 V-0.

11. A method for thermal runaway testing, characterized in that, The method, applied to a controller in a thermal runaway test system as described in any one of claims 1-10, comprises: The power supply equipment of the thermal runaway test system is controlled to output initial power so that multiple heating devices in the thermal runaway test system can heat multiple sample cells. Obtain the cell temperature of multiple sample cells; The power output of the power supply device is adjusted according to the cell temperature of multiple sample cells until thermal runaway is triggered.

12. The method according to claim 11, characterized in that, The step of adjusting the output power of the power supply device based on the cell temperature of the multiple sample cells includes: Whether a preset condition is met is determined based on the cell temperature of multiple sample cells; wherein the preset condition includes at least two sample cells having a temperature rise rate greater than a temperature rise rate threshold and a duration exceeding a first duration threshold, the average temperature rise rate of multiple sample cells exceeding a temperature rise rate range, and at least two sample cells having a cell voltage lower than a preset voltage threshold, and / or at least two sample cells having a cell temperature exceeding a preset temperature threshold and a duration exceeding a second duration threshold; If the preset conditions are not met, the power supply equipment is controlled to increase its output power by a preset step size.

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