Test method for inhibiting thermal runaway diffusion of battery cell module through battery explosion-proof box

Abstract

The invention relates to a test method for inhibiting thermal runaway diffusion of a battery cell module by a battery explosion-proof box. The test method comprises the following steps: S1, preparing the battery explosion-proof box; s2, preparing a to-be-tested battery cell module; s3, respectively installing a temperature sensor and a voltage sensor on two sides of the heating sheet, and installing a temperature sensor on each surface outside the explosion-proof box; s4, carrying out a thermal runaway test on the to-be-tested cell module, and obtaining a time-dependent temperature change curve and a time-dependent voltage change curve of the cell module provided with the heating sheet, and a time-dependent temperature change curve of each monitoring point on the outer side of the box body; and S5, observing whether flames and bursts are separated out in the test process and whether the pressure of the box body can be normally relieved, standing for more than 48 hours after the test is finished, opening the box under the condition of ensuring safety, and checking whether the structure of the box body is intact. The method is simple and easy to implement, the understanding and research of the whole process of triggering the thermal runaway diffusion of the battery cell module are enhanced, and the test of the protective performance of the battery packaging box and the targeted improvement of a packaging scheme are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of battery transportation and storage safety testing, and in particular relates to a test method for a battery explosion-proof box to suppress thermal runaway diffusion of a battery core module. Background Art

[0002] Waste lithium batteries belong to the ninth category of dangerous goods. The electrolyte in waste lithium batteries is flammable. If it encounters a fire source during storage, transportation, and handling, it will cause an explosion or fire, causing serious losses; there may be a short circuit between the positive and negative electrodes in waste lithium batteries, causing the battery to overheat and explode; the electrolyte and metal elements in lithium batteries are toxic, causing harm to the environment and human health. Therefore, waste lithium batteries need to follow professional transportation and storage requirements, that is, the requirements of P911 and LP906 of the 40-20 edition of the International Maritime Dangerous Goods Code to ensure safety.

[0003] At the same time, when lithium batteries are subjected to thermal abuse, electrical abuse (overcharging, over-discharging, internal short circuit, etc.) or mechanical abuse (extrusion, puncture, collision, etc.), thermal runaway and explosion and fire are prone to occur, which in turn causes the spread of thermal runaway at the module and pack levels, which can easily cause casualties and property losses.

[0004] Therefore, a method for testing the thermal runaway suppression effect of a battery explosion-proof box is needed. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a test method for a battery explosion-proof box to inhibit the spread of thermal runaway of a battery cell module, so as to solve the current lack of research on the effect of battery explosion-proof boxes on inhibiting thermal runaway, and provide guidance for the design and production of explosion-proof boxes for waste lithium batteries.

[0006] The present invention solves the technical problem by the following technical solutions:

[0007] A test method for a battery explosion-proof box to inhibit thermal runaway diffusion of a battery module, the method comprising the following steps:

[0008] S1. Prepare a battery explosion-proof box: an energy-absorbing layer is arranged in the inner packaging box of the explosion-proof box, an adsorption layer and a flame-retardant and heat-insulating layer are arranged in the outer packaging box of the explosion-proof box, pressure relief holes are arranged around the outer packaging box, a sealing unit is arranged between the outer packaging box body and the box cover, and a leakage collection unit is arranged at the bottom of the outer packaging box;

[0009] S2. Prepare the battery cell modules to be tested: the battery cell modules to be tested include a first module (1), a second module (2), a third module (3), a fourth module (4), a fifth module (5), a sixth module (6), a seventh module (7), an eighth module (8), a ninth module (9), a tenth module (10), an eleventh module (11), a twelfth module (12), a thirteenth module (13), a fourteenth module (14) and a fifteenth module (15); the battery cell modules to be tested are arranged in order, with three modules forming a row, and heating plates are installed on two of the battery cell modules to be tested;

[0010] S3, installing temperature sensors and voltage sensors on the battery explosion-proof boxes on both sides of the heating plate;

[0011] S4. Start the heating device to heat the cell module to be tested, perform a thermal runaway test on the cell module to be tested, and continuously heat the trigger object at its maximum power to trigger the cell module, obtain the temperature change curve over time, the voltage change curve over time of the cell module with the heating plate installed, and the temperature change curve over time of each monitoring point outside the battery explosion-proof box. When thermal runaway occurs or the temperature of the monitoring point reaches 300°C, stop triggering;

[0012] S5. Observe whether there is any flame or ejecta during the test, and whether the explosion-proof box can release pressure normally. After the test, let it stand for more than 48 hours to ensure safety and conduct unpacking inspection to check whether the explosion-proof box structure is intact.

[0013] Moreover, the battery cell module to be tested in S2 is pre-conditioned by charge-discharge cycles according to GB 38031-2020, and then charged so that its SOC finally reaches 95% to 100%.

[0014] Moreover, the installation area of ​​the heating plate is smaller than the area of ​​the contact surface with the battery core.

[0015] Moreover, the battery explosion-proof box packaging requirements of S1 must meet the requirements of P911 and LP906 of the International Maritime Dangerous Goods Code, 40-20 edition.

[0016] Moreover, during the S4 test, the temperature of the outer surface of the explosion-proof box shall not exceed 100°C. An instantaneous temperature rise to 200°C is within an acceptable range. If it exceeds 100°C, evaluate the temperature trend within 10 minutes. If the temperature can be controlled not to continue to rise and fall back to within 100°C during this period, it is acceptable. There will be no fire outside the explosion-proof box, and sporadic flames from the heating point holes of the sample in this test are within an acceptable range. There shall be no ejecta precipitated from the explosion-proof box. After the test, the package structure must be intact and the container pressure relief system must be able to work normally.

[0017] Moreover, the heating plates in S2 are respectively installed at the center and corners of the explosion-proof box, namely the eighth module and the thirteenth module.

[0018] Moreover, in the S3, the voltage and temperature of the trigger object battery cell are monitored to determine whether thermal runaway occurs in the trigger object; the battery cell modules adjacent to the trigger battery cell module are monitored to determine whether heat diffusion occurs in the battery module; when monitoring the voltage, the original circuit should not be changed; when heating is triggered, the temperature sensor is arranged on the side away from heat conduction, that is, installed on the opposite side of the heating device.

[0019] Moreover, the determination conditions for thermal runaway diffusion are that (1) and (3) are satisfied at the same time or (2) and (3) are satisfied at the same time: (1) the trigger object produces a voltage drop, and the drop value exceeds 25% of the initial voltage; (2) the temperature at the monitoring point reaches the maximum operating temperature specified by the manufacturer; (3) the temperature rise rate dT / dt at the monitoring point is ≥1°C / s and lasts for more than 3s.

[0020] The positive effects that the present invention can produce are:

[0021] The present invention places the battery module to be tested with the heating plate installed at one of the center and corners of the bottom of the explosion-proof box, respectively, and installs temperature sensors and voltage sensors on both sides of the heating plate, and temperature sensors on each surface of the outside of the explosion-proof box. A thermal runaway test is performed on the battery module to be tested at the center, and the temperature-time curve, voltage-time curve, and temperature-time curve of the battery module with the heating plate installed are obtained. It is observed whether there is flame and ejection precipitation during the test, and whether the box can be depressurized normally. After the test is completed, it is left to stand for more than 48 hours to ensure that the box is unpacked and checked under safe conditions to see if the box structure is intact. The method for suppressing the thermal runaway diffusion of the battery module in the battery explosion-proof box is simple and easy, which strengthens the understanding and research of the entire process of triggering the thermal runaway diffusion of the battery module, strengthens the research on the effect of suppressing thermal runaway of the battery explosion-proof box, and provides guidance for the design and production of explosion-proof boxes for waste lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the placement of 15 groups of battery cell modules for testing in a box according to an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the installation positions of the heating plate, the temperature sensor, and the voltage sensor installed in the battery module provided by the embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the installation position of the temperature sensor installed outside the box provided by an embodiment of the present invention;

[0025] Figure 4is a curve diagram showing the temperature variation over time of an eighth module equipped with a heating plate provided in an embodiment of the present invention;

[0026] Figure 5 is a curve diagram of voltage variation over time of an eighth module equipped with a heating plate provided in an embodiment of the present invention;

[0027] Figure 6 It is a curve diagram of the temperature variation over time of the electric module with the heating plate installed (but not started) provided in the embodiment of the present invention;

[0028] Figure 7 is a curve diagram of voltage variation over time of a thirteenth module with a heater installed (but not started) provided in an embodiment of the present invention;

[0029] Figure 8 is a curve diagram of the temperature change of the monitoring point outside the box over time provided by an embodiment of the present invention;

[0030] Fig. 9 It is an exhaust pressure relief diagram of the box pressure relief hole provided by an embodiment of the present invention;

[0031] Fig.10 This is a diagram of unpacking inspection after the box test provided by the embodiment of the present invention is completed;

[0032] Fig.11 This is a comparison diagram before and after the fire-resistant and thermal insulation performance test of the closed composite sandwich panel made of a stainless steel plate, which is the basic material of the box body provided by an embodiment of the present invention;

[0033] Fig.12 This is a comparison diagram of the fire-resistant and thermal insulation performance of the galvanized steel plate, the basic material of the box body provided by the embodiment of the present invention, before and after the test;

[0034] Fig.13 This is a comparison diagram of the high temperature resistance performance of the aluminum silicate braided rope, a box sealing structural material provided by an embodiment of the present invention, before and after the test;

[0035] Fig.14 This is a comparison chart of the box sealing structure material provided by an embodiment of the present invention, a woven tin foil + flame retardant cotton before and after the high temperature resistance test;

[0036] Fig.15 This is a comparison chart before and after the high temperature resistance test of the box sealing structure material provided by the embodiment of the present invention, aluminum silicate braided rope + braided tin foil + flame retardant cotton;

[0037] Fig.16 Schematic diagram of a fire-blocking performance testing device for a box fire-blocking net provided in an embodiment of the present invention;

[0038] Fig.17This is a comparison diagram before and after the fire-blocking performance test of the box fire-blocking net 1 (SUS304 stainless steel corrugated disc with a diameter of 152 mm, a wave height of 10 mm, and a fire-blocking gap of 7 mm) provided in an embodiment of the present invention;

[0039] Fig.18 This is a comparison diagram before and after the fire-blocking performance test of the box fire-blocking net 2 (SUS304 stainless steel corrugated disc with a diameter of 129 mm, a wave height of 15 mm, and a fire-blocking gap of 1.5 mm) provided in an embodiment of the present invention;

[0040] Fig.19 Schematic diagram of a dust filtering performance test device for a fire-blocking net of a box provided in an embodiment of the present invention;

[0041] Fig. 20 This is a comparison chart before and after the dust filtration performance test of the box fire-blocking net 2 (SUS304 stainless steel corrugated disc with a diameter of 129 mm, a wave height of 15 mm, and a fire-blocking gap of 1.5 mm) provided in an embodiment of the present invention;

[0042] Fig.21 This is a test phenomenon diagram of the entire process of triggering thermal runaway of a battery cell provided by an embodiment of the present invention;

[0043] Fig. 22 It is a curve diagram of temperature and voltage variation over time of a thermal runaway test of a battery cell provided in an embodiment of the present invention;

[0044] Fig.23 It is an unpacking inspection diagram of a past test provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0046] The present invention will be further described below in conjunction with the embodiments.

[0047] like Figures 1 to 8 As shown, a test method for a battery explosion-proof box to inhibit the thermal runaway diffusion of a battery module, the innovation of which is that the steps of the method are:

[0048] S1: Prepare a battery explosion-proof box, which should have insulation, airtightness, pressure relief, filtration, and flame and ejection suppression devices and functions.

[0049] S2: Prepare the battery module to be tested. The battery module to be tested needs to be charged to ensure that the SOC of the test battery module is 95%-100%. The test uses a flat heating device to install heating plates on the two groups of battery modules. One of the battery modules to be tested with heating plates installed is placed at the center of the bottom of the explosion-proof box, and the other is placed at the corner of the bottom of the explosion-proof box.

[0050] The heating power selection of the heating device of the present invention is shown in Table 1.

[0051] Table 1

[0052] Trigger object electric energy Wh Maximum power of heating device W E＜100 30-300 100≤E＜400 300-1000 400≤E＜800 300-2000 E≥800 ＞600

[0053] S3: Install temperature sensors and voltage sensors on both sides of the heating plate, and install temperature sensors on each external surface of the explosion-proof box.

[0054] S4: Perform a thermal runaway test on the battery module to be tested at the center, and obtain the temperature change curve over time, the voltage change curve over time of the battery module with the heater installed, and the temperature change curve over time of each monitoring point outside the box.

[0055] S5: Observe whether there is any flame or ejected material during the test and whether the box can release pressure normally. After the test, let it stand for more than 48 hours, and perform an unpacking inspection under safe conditions to check whether the box structure is intact.

[0056] The test method for thermal runaway diffusion of the battery module of this embodiment is to install heating plates on the eighth and thirteenth modules after charging the battery modules, and place them in the middle and bottom corners of the explosion-proof box, respectively. At the same time, temperature sensors and voltage sensors are installed on the two battery modules with heating plates, and temperature sensors are installed above the pressure relief holes around the outside of the explosion-proof box and on the top and bottom surfaces. After the test preparation is completed, the heating device is started on the eighth module to be tested to conduct a thermal runaway diffusion test. The thirteenth module is a standby and will be activated when the eighth module fails to trigger thermal runaway. Observe the temperature change curves over time and the voltage change curves over time to determine whether the eighth module and the thirteenth module have thermal runaway; observe the temperature change curves over time at each temperature monitoring point outside the box to see if it exceeds 100°C; observe whether there is flame and ejection during the entire test process; observe whether the pressure relief hole can release pressure normally and whether the box structure is intact; after the test, conduct an unpacking inspection to check whether the pressure relief hole is blocked, whether the box structure is intact and can be opened normally, and check whether there are traces of ejection residues inside and outside the explosion-proof box and the outside of the inner packaging box. The battery explosion-proof box suppresses the thermal runaway diffusion of the battery module, strengthens the understanding and research of the entire process of triggering the thermal runaway diffusion of the battery module, strengthens the research on the effect of battery explosion-proof boxes in suppressing thermal runaway, and provides guidance for the design and production of explosion-proof boxes for waste lithium batteries.

[0057] In step S4, according to the temperature-time variation curve and the voltage-time variation curve, as shown in FIG. Figure 4-7 As shown, it is used as the basis for determining whether the eighth module and the thirteenth module have thermal runaway. In this embodiment, the temperature rise and voltage drop of the eighth module or the thirteenth module are used as the main criteria for determining whether the eighth module or the thirteenth module has thermal runaway.

[0058] In step S2, the eighth module and the thirteenth module each include 12 cells. Figure 2 As shown, thermal runaway occurs in cell 6 or cell 7. By triggering thermal runaway in the two cells in the middle of the eighth module or the thirteenth module (i.e., the cells on both sides of the heating plate), the thermal runaway can spread from the middle of the eighth module or the thirteenth module to both ends and then to the surrounding areas, thereby improving the accuracy of the test method for thermal runaway diffusion of the cell module, and effectively simulating the hazards that occur in actual situations, which is helpful for verifying the explosion-proof function of the explosion-proof box in a practical manner.

[0059] In step S4, the two battery cells of the eighth module are heated to cause thermal runaway of the eighth module, and the thirteenth module is a spare module. This embodiment triggers thermal runaway of the battery cells on both sides of the heating plate by heating to improve and enhance the efficiency and effect of the thermal runaway diffusion test method of the battery cell module. Of course, thermal runaway of the battery cell can also be triggered by extrusion, acupuncture, etc., but because the battery cell module is placed in a packaging box, it is inconvenient to operate and does not conform to the situation that may occur during actual transportation, so it is not selected.

[0060] In order to observe the temperature and voltage changes of the cells on both sides of the heating plate, Figure 2 As shown, the two sides of the heating plates of the eighth and thirteenth modules are selected as collection points. The temperature is collected at the yellow icon in the figure, and the voltage is collected at the "+-" position. 10 data are recorded per second. The data of temperature and voltage changes over time are collected, and the temperature change curve and voltage change curve of the eighth and thirteenth modules are obtained.

[0061] like Figure 4 , Figure 5 As shown, when the eighth module was tested for 36 minutes and 50 seconds, it was detected that the temperature rose sharply and the voltage dropped sharply. According to the thermal runaway judgment standard, the thermal runaway response has been triggered at this time, and the heating device will not be started for the thirteenth module.

[0062] like Figure 6 , Figure 7As shown in the figure, the temperature of the 13th module rose sharply and the voltage dropped sharply at 87 minutes into the test. According to the thermal runaway judgment standard, the thermal runaway reaction was triggered at this time. It also proves that after the thermal runaway of the eighth module cell was triggered, it spread to both sides and the surroundings, thus triggering the thermal runaway of the surrounding module cells.

[0063] like Figure 8 As shown, the monitoring point on the top of the box is T1, the monitoring point on the bottom is T2, and the monitoring points around the box are T3-T12. The positions of the surrounding monitoring points are all directly above the pressure relief hole. The temperature change data of T1-T12 over time are collected to obtain the box temperature change curve over time.

[0064] Except for the temperature at the bottom of the box, the temperatures at the other monitoring points began to rise when the eighth module battery cell triggered thermal runaway for the first time, and then there was a short temperature drop trend. As the thermal runaway diffused, the temperature rose again and remained for a relatively long time. However, due to the insulation effect of the box, the temperature outside the box never exceeded 100°C, and as the thermal runaway diffusion reaction ended, the temperature gradually fell back to room temperature. The temperature trend at the bottom of the box gradually accumulated, with the highest temperature being 117°C. After all the thermal runaway diffusion in the box ended, it slowly fell back to room temperature.

[0065] like Fig. 9 As shown in A, after the battery cell triggers thermal runaway, the box will release gas through the pressure relief hole. As the thermal runaway of the battery module spreads, the concentration of the gas released by the pressure relief in the box increases, such as Fig. 9 As shown in Figure B, there is a continuous release. With the end of the thermal runaway diffusion reaction, the concentration of the released gas gradually decreases. The box structure has not changed, the pressure relief hole is not blocked, and the exhaust pressure relief structure is reasonably designed.

[0066] During the test, observations were made in the observation room, which was equipped with high-definition cameras in four directions to record the whole scene at a 45-degree angle. During the test, no ejection or flame precipitation occurred. There were sporadic flame precipitation in the pressure relief hole, which was within the acceptable range.

[0067] After 48 hours of the test, open the box for inspection under safe conditions. Fig.10 A. Fig.10 As shown in B, the outer and inner packaging boxes of the explosion-proof box are both in good condition and can be opened normally; no traces of ejected objects were found inside and outside the outer box of the explosion-proof box or outside the inner packaging box; Fig.10 As shown in D, all battery modules experienced thermal runaway reactions, and 15 modules experienced thermal runaway reactions 180 times in total; Fig.10 As shown in C, the internal adsorption device has obvious effect and effectively adsorbs a large amount of reaction particles. The pressure relief hole is not blocked and can continue to work normally. A leakage collection tank is set at the bottom of the explosion-proof box and there is no leakage.

[0068] In step S1, the prepared battery explosion-proof box should have obvious fire resistance and heat insulation performance, so the heat insulation and fire resistance performance tests are carried out on the selection of basic materials: after the material is roughly screened, sample 1 is selected: 300*300mm SUS304 stainless steel plate closed composite sandwich panel, such as Fig.11 As shown in A, and sample 2: 300*300mm galvanized steel plate, such as Fig.12 As shown in A, a comparative test is conducted. The test tool is a flame cutting machine. Test method: Fix the sample with a fixture to ensure that the distance between the flame cutting machine's nozzle and the test sample is 80mm, adjust the fuel size and measure the temperature of the flame contact point and 5mm above and below it to 1150±50℃ through a temperature measuring instrument, and record the test data. Test phenomenon: Sample 1: As shown in Fig.11 As shown in B, as the flame roasting time increases, the front test area of ​​the stainless steel composite plate gradually turns red, and the surface delamination occurs without burning through, but the flame retardant cotton in the middle is not damaged; the temperature of the back of the stainless steel composite plate exceeds 100℃ at around 8min54s, and reaches 112.4℃ at around 9min35s. Please see the table below for the time-temperature table of thermal insulation performance test. Sample 2: Fig.12 The flame shown in B was burned for less than 3 minutes, the front of the galvanized steel composite plate was burned through, and part of the flame retardant cotton in the middle was burned off, and the temperature of the back was higher than 100℃, and the test ended. At a high temperature of 1150℃, stainless steel showed good high temperature resistance, and the stainless steel composite plate showed good thermal insulation performance; the galvanized plate was burned through at this temperature, which was slightly inferior to stainless steel in high temperature resistance.

[0069] Table 2

[0070]

[0071] In step S1, the prepared battery explosion-proof box must have good fire resistance and sealing effect, so the fire resistance and high temperature resistance performance tests are carried out on the selection of sealing materials. After preliminary selection based on the high temperature resistance of the material, sample 1 is selected: aluminum silicate braided rope, such as Fig.13 As shown in A, sample 2: woven tin foil + flame retardant cotton, such as Fig.14 As shown in A, sample 3: aluminum silicate braided rope + braided tin foil + flame retardant cotton, such as Fig.15 As shown in A, a comparative test was conducted. The test tool was a flame cutting machine. Test method: Fix the sample with a fixture to ensure that the distance between the flame cutting machine's nozzle and the test sample is 80mm, adjust the fuel size and measure the temperature of the flame contact point and 5mm above and below it to 1150±50℃ through a temperature measuring instrument, and record the test data. Test phenomenon: Sample 1: The aluminum silicate braided rope was not burned. After cooling and removal, it was found that the material became hard, brittle, and easy to break. The burning part shrank by 50%, such as Fig.13As shown in B; Sample 2: The woven tin foil on the surface of the composite fire-resistant board was burned through in less than 5 seconds of flame baking, and the combined material was severely burned and damaged in about 21 seconds. Fig.14 As shown in B; Sample 3: The aluminum silicate braided rope on the surface of the composite sealing rope was not burned off, and the roasted part was hardened and brittle, but no burn-through or cracks appeared. After the test was completed and cooled, the hardened part was broken off, and it was found that the internal material was intact and not damaged. Fig.15 As shown in B. Sample 3 can withstand direct flame roasting at about 1150±50℃, and after roasting, it will harden, become brittle, shrink, etc. The sealing rope wrapped by aluminum silicate braided rope can withstand flame roasting while protecting the inner layer material. It is a good sealing, flame retardant and fire-resistant composite material.

[0072] In step S1, the prepared battery explosion-proof box must have good filtering and pressure relief functions, which requires that the pressure relief hole can not only relieve pressure but also block fire. After preliminary screening of the fire-blocking nets on the market, sample one was selected: a SUS304 stainless steel corrugated disc-shaped fire-blocking net with a diameter of 152mm, a wave height of 10mm, and a fire-blocking gap of 7mm; sample two: a SUS304 stainless steel corrugated disc-shaped fire-blocking net with a diameter of 129mm, a wave height of 15mm, and a fire-blocking gap of 1.5mm. The fire-blocking performance test was carried out in accordance with GB 5908-2005 "Petroleum Storage Tank Flame Arrestor" and GB 13347-2010 "Petroleum Gas Pipeline Flame Arrestor" standards. The schematic diagram of the fire-blocking performance test device of the fire-blocking net is shown in the figure. Fig.16 As shown in the figure: 1. black background board; 2. test platform; 3. fixture 2; 4. flame cutting machine; 5. fire-blocking net; 6. fixture 1; 7. flammable paper; 8. photographic recording equipment.

[0073] A flame cutter is set at 60mm on the left end of the fire-blocking net to provide flames, and a flammable test paper with an ignition point of about 100℃ is set at 50mm on the right end to test the length of the flame. The fire-blocking net, flame cutter and flammable test paper are at the same test level; a photographic recording device is set at 100mm in front of the fire-blocking net to record and observe the test phenomena; a black background board is set at 100mm behind the fire-blocking net to facilitate the observation of the test phenomena; the test is carried out at normal temperature and pressure, and the safety performance of the flame cutter needs to be tested before the test starts; at the start of the test, the flame cutter, the photographic recording device are turned on in turn Equipment and timer, each test rotate the flame cutting machine, so that the flame dynamically roasts the fire barrier net, and the flame and the fire barrier net can be at different angles such as 90°, 60°, 45°, etc.; each test lasts for 10s, and after 10s, the flame cutting machine is moved away, and the next round of testing is carried out after the fire barrier net cools down; monitor whether the photographic recording equipment records and monitors the flame, and whether the flammable test paper on the right side is ignited. Once a flame emerges and the flammable test paper on the right side is ignited, the test is over and the fire barrier net fails to block the fire. If the fire barrier net can block the fire every time and there is no permanent deformation or damage after the test, the fire barrier net meets the fire barrier requirements. Test results: Sample 1: Rotate the flame cutting machine, the flame passes through the fire barrier net, and the flame beam is dispersed and reduced in size by 50%. The flammable paper at the rear is ignited, and the fire barrier fails. Fig.17 As shown; Sample 2: Turn the flame cutting machine, the flame is dispersed and does not pass through the fire-blocking net. There is no obvious phenomenon of flammable paper behind it, and the fire blocking is successful. Fig.18 A. Fig.18 As shown in B. The fire-blocking gap of the fire-blocking net of sample 1 is much larger than that of the fire-blocking net of sample 2, which can only disperse the power and size of the flame, but cannot effectively prevent the flame from escaping.

[0074] In step S1, after the fire barrier performance test of the fire barrier net, the dust filtration performance test is performed. Test method: The schematic diagram of the fire barrier net dust filtration performance test device is as follows Fig.19 As shown in the figure: 1. automatic dust screen; 2. blower; 3. transparent feed tube; 4. fire-blocking net; 5. transparent discharge tube; 6. dust collecting bag; transparent feed and discharge observation pipes are respectively arranged at the left and right ends of the fire-blocking net, and the two pipes have the same diameter and length, 800mm in length and 130mm in diameter; a blower is arranged at the inlet of the feed pipe to provide wind power, and a circular opening is opened just above the pipe 100mm away from the inlet to connect the automatic flour screen to realize the feeding of the test dust, and a dust collecting bag is arranged at the end of the right discharge pipe to collect the test dust filtered and discharged by the fire-blocking net; the dust feed pipe and discharge pipe must be sealed and connected with the fire-blocking net, and the gaps need to be filled with filling materials to ensure that the test is carried out under closed conditions; the test site needs to be carried out in an open, fire-free, dry and cool environment to prevent the occurrence of dust explosion.

[0075] Test sequence: Connect the test equipment as shown in the schematic diagram, and test the dust filtration performance of the fire barrier net of sample 2; at the beginning of the test, turn on the blower, check the airtightness of the test device to prevent dust from flying; after the airtightness inspection is completed, turn on the automatic flour sieve and the timing device in turn; during the test, pay attention to the dust content in the automatic flour sieve and control the amount of dust added; if the inner wall of the discharge pipe is attached to dust and the test phenomenon cannot be observed during the test, use a pipe brush to clean the dust on the inner wall to prevent the test condition from being blocked at the right end; the test is carried out for a total of 12 hours, and the test phenomenon is observed every 1 hour to observe whether the fire barrier net is blocked or the powder output is significantly reduced. If the fire barrier net is obviously blocked or no material is discharged, the test is terminated immediately, the timing is stopped, the fire barrier net is removed, the degree of blockage is observed, and the dust emission time, filtration performance and degree of blockage of the fire barrier net are recorded; turn off the blower and the power supply of the automatic flour sieve, clean the dust on the inner wall of the feed pipe and the discharge pipe, and the test is over. Test results: If Fig. 20 Soon after the test shown in A began, the mesh of the fire barrier net of sample 2 began to be covered with powder. After about 40 minutes, it began to be blocked, such as Fig. 20 As shown in B, around 1h45min, the fire barrier net of sample 2 was obviously clogged, and the test ended. The fire barrier gap of the fire barrier net is small, which easily causes dust to clog the fire barrier holes. It is advisable to use a fire barrier net with a larger fire barrier gap. Combined with the fire barrier performance test results, different specifications of fire barrier nets can be tried to achieve the purpose of fire blocking and filtering. At the same time, a filtering device can be added inside the box to reduce the risk of blockage of the pressure relief hole.

[0076] To ensure that step S4 can be carried out normally, a heating plate and temperature and voltage monitoring points are installed on the single cell, a thermal runaway test is carried out, and the test phenomena are observed. At 69 minutes into the test, the cell begins to produce gas and expand; Fig.21 As shown in A, at 92 minutes, the cell pressure relief valve opens and electrolyte sprays out; Fig.21 As shown in B and 21C, at 206 minutes, the battery cell exploded, sparks and flames sprayed violently, and the time lasted for nearly 2 minutes; Fig.21 D, 21E, the flame gradually decreases until it goes out. According to the temperature voltage change curve over time, Fig. 22 As shown, the time when the temperature rises sharply and the voltage drops sharply is exactly when the test is carried out for 206 minutes, which is consistent with the observed phenomenon. The battery cell has a thermal runaway reaction at this time. The curve chart and the test phenomenon also indirectly prove the judgment criteria for triggering thermal runaway.

[0077] The preparation of battery explosion-proof boxes is a process of continuous trial and error, and the normal pressure relief of the box is an important part of the entire test. The size and number of pressure relief holes are important factors in determining whether the pressure relief holes can work properly. Fig.23 A. Fig.23As shown in B, during the test, the pressure relief hole was blocked and could not work normally, causing the pressure in the box to gradually increase. Fig.23 C. Fig.23 As shown in D, when the pressure reaches a certain value, the relatively weak position of the box, that is, the position where the box cover is opened, is broken. When the box cannot be completely closed, the flame and ejected objects directly rush out of the box, and the test fails.

[0078] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A test method for a battery explosion-proof box to inhibit the thermal runaway diffusion of a battery module, characterized in that: The steps of the method are: S1. Prepare a battery explosion-proof box: an energy-absorbing layer is arranged in the inner packaging box of the explosion-proof box, an adsorption layer and a flame-retardant and heat-insulating layer are arranged in the outer packaging box of the explosion-proof box, pressure relief holes are arranged around the outer packaging box, a sealing unit is arranged between the outer packaging box body and the box cover, and a leakage collection unit is arranged at the bottom of the outer packaging box; S2. Prepare the battery cell modules to be tested: the battery cell modules to be tested include a first module (1), a second module (2), a third module (3), a fourth module (4), a fifth module (5), a sixth module (6), a seventh module (7), an eighth module (8), a ninth module (9), a tenth module (10), an eleventh module (11), a twelfth module (12), a thirteenth module (13), a fourteenth module (14) and a fifteenth module (15); the battery cell modules to be tested are arranged in order, with three modules forming a row, and heating plates are installed on two of the battery cell modules to be tested; S3, installing temperature sensors and voltage sensors on the battery explosion-proof boxes on both sides of the heating plate; S4. Start the heating device to heat the cell module to be tested, perform a thermal runaway test on the cell module to be tested, and continuously heat the trigger object at its maximum power to trigger the cell module, obtain the temperature change curve over time, the voltage change curve over time of the cell module with the heating plate installed, and the temperature change curve over time of each monitoring point outside the battery explosion-proof box. When thermal runaway occurs or the temperature of the monitoring point reaches 300°C, stop triggering; S5. Observe whether there is any flame or ejecta during the test, and whether the explosion-proof box can release pressure normally. After the test, let it stand for more than 48 hours to ensure safety and conduct unpacking inspection to check whether the explosion-proof box structure is intact.

2. The test method for suppressing thermal runaway diffusion of a battery cell module by using a battery explosion-proof box according to claim 1, characterized in that: The battery cell module to be tested in S2 is pre-conditioned by charge-discharge cycles according to GB 38031-2020, and then charged so that its SOC finally reaches 95% to 100%.

3. The test method for suppressing thermal runaway diffusion of a battery cell module by using a battery explosion-proof box according to claim 1, characterized in that: The installation area of ​​the heating plate is smaller than the area of ​​the contact surface with the battery core.

4. The test method for suppressing thermal runaway diffusion of a battery cell module by a battery explosion-proof box according to claim 1, characterized in that: The battery explosion-proof box packaging requirements of S1 must meet the requirements of P911 and LP906 of the International Maritime Dangerous Goods Code, 40-20 edition.

5. The test method for suppressing thermal runaway diffusion of battery core modules by using a battery explosion-proof box according to claim 1, characterized in that: During the S4 test, the temperature of the outer surface of the explosion-proof box shall not exceed 100°C. An instantaneous temperature rise to 200°C is within the acceptable range. If it exceeds 100°C, evaluate the temperature trend within 10 minutes. If the temperature can be controlled not to continue to rise and fall back to within 100°C during this period, it is acceptable. There will be no fire outside the explosion-proof box, and sporadic flames from the heating point holes of the sample in this test are within the acceptable range. There shall be no ejecta precipitated from the explosion-proof box. After the test, the package structure must be intact and the container pressure relief system must be able to work normally.

6. The test method for suppressing thermal runaway diffusion of a battery cell module by a battery explosion-proof box according to claim 1, characterized in that: The heating plates in S2 are respectively installed at the center and corners of the explosion-proof box, namely the eighth module (8) and the thirteenth module (13).

7. The test method for suppressing thermal runaway diffusion of a battery cell module by a battery explosion-proof box according to claim 1, characterized in that: In the S3, the voltage and temperature of the trigger object battery cell are monitored to determine whether thermal runaway occurs in the trigger object; the battery cell modules adjacent to the trigger battery cell module are monitored to determine whether heat diffusion occurs in the battery module; when monitoring the voltage, the original circuit should not be changed; when heating is triggered, the temperature sensor is arranged on the side away from heat conduction, that is, installed on the opposite side of the heating device.

8. The test method for suppressing thermal runaway diffusion of a battery cell module by a battery explosion-proof box according to claim 1, characterized in that: The determination conditions for thermal runaway diffusion are that (1) and (3) are satisfied at the same time or (2) and (3) are satisfied at the same time: (1) the trigger object produces a voltage drop, and the drop value exceeds 25% of the initial voltage; (2) the temperature at the monitoring point reaches the maximum operating temperature specified by the manufacturer; (3) the temperature rise rate dT / dt at the monitoring point is ≥1°C / s and lasts for more than 3s.

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