Triggering method for battery thermal diffusion test

Abstract

The invention discloses a triggering method for a battery thermal diffusion test. The triggering method for the battery thermal diffusion test comprises the following steps: removing a positive active material in a preset defect area on a positive plate of a tested battery; removing the diaphragm of the test battery in a preset removal area; blocking the anode current collector of the test battery leaked from the preset removal area and the preset defect area by using an insulating phase change material to form a specially-made test battery; forming a thermal diffusion test device by the specially-made test battery and a standard test battery; and heating the thermal diffusion test device by adopting a heating device to change the phase of the insulating phase change material into a liquid state, so that the special test battery is short-circuited to trigger the thermal runaway of the thermal diffusion test device. By adopting the scheme, the influence of the triggering mode on the thermal diffusion test result is reduced, so that the obtained thermal diffusion test result is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of battery testing, and in particular to a triggering method for battery thermal diffusion testing. Background Art

[0002] With the development of science and technology, batteries are increasingly used in various fields, such as electronic products, electric vehicles, energy storage systems, etc. Therefore, the thermal stability of batteries has become particularly important. Battery thermal diffusion testing came into being in this context. It is a method for testing the thermal stability of batteries under high temperature conditions. Thermal diffusion testing is of great significance to ensure the safe use of batteries, improve battery performance and promote the development of battery technology.

[0003] At present, when performing a battery thermal diffusion test, it is necessary to trigger the thermal runaway of the battery. Existing triggering methods for the battery thermal diffusion test include heating sheet triggering, overcharge triggering, and needle puncture triggering.

[0004] When the battery thermal runaway occurs due to the triggering of the heating sheet, the triggering time is long, which causes the initial heat release time of the battery to be prolonged. At the same time, some substances (electrolyte) involved in the thermal runaway reaction in the battery leak, affecting the energy released during the thermal runaway of the battery. In addition, when the heating sheet is used for triggering, the battery shell on the side of the heating sheet is heated to a higher temperature, losing its strength at the normal operating temperature of the battery, and it is impossible to accurately evaluate the thermal diffusion protection capability of the entire package. When overcharging triggers thermal runaway of the battery, the input energy is large and a large amount of gas is produced in the early stage of overcharging, causing the electrolyte to leak from the explosion-proof valve, affecting the energy released during the thermal runaway of the battery. When the thermal runaway of the battery is triggered by acupuncture, it is impossible to test the battery in the middle of the battery pack, and the acupuncture damages the battery shell. The thermal runaway battery has a smoke release point other than the explosion-proof valve, and it is also difficult to accurately evaluate the thermal diffusion protection capability of the battery system.

[0005] In summary, the current triggering methods for battery thermal diffusion tests have a significant impact on the thermal diffusion test results, and there is a problem that the obtained thermal diffusion test results are not accurate enough. Summary of the invention

[0006] The present invention provides a triggering method for a battery thermal diffusion test, so as to reduce the influence of a triggering mode on a thermal diffusion test result, so as to obtain a more accurate thermal diffusion test result.

[0007] According to one aspect of the present invention, a triggering method for a battery thermal diffusion test is provided, which is used for the thermal diffusion test of a battery, wherein the battery comprises a battery cell, wherein the battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode active material and a positive electrode current collector, wherein the positive electrode active material is located between the separator and the positive electrode current collector, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material, wherein the negative electrode active material is located between the separator and the negative electrode current collector, and wherein the triggering method for the battery thermal diffusion test comprises:

[0008] Removing the positive electrode active material in the preset defect area on the positive electrode sheet of the test battery, so that the positive electrode current collector opposite to the preset defect area leaks out;

[0009] Removing the separator of the test battery located in a preset removal area, wherein the preset removal area is opposite to the preset defect area;

[0010] The positive electrode current collector leaking from the preset removal area and the preset defect area of ​​the test battery is sealed with an insulating phase change material to form a special test battery, wherein the insulating phase change material is immiscible with the electrolyte and the phase change temperature from solid to liquid is greater than or equal to 40° C. and less than or equal to 90° C.;

[0011] The special test battery and the standard test battery form a thermal diffusion test device;

[0012] The thermal diffusion test device is heated by a heating device to change the insulating phase change material into a liquid state, so that the special test battery is short-circuited to trigger thermal runaway of the thermal diffusion test device, wherein the deviation between the maximum heating temperature of the heating device and the self-heating temperature of the battery is less than a preset temperature deviation.

[0013] In an optional embodiment of the present invention, the area of ​​the preset removal area is greater than or equal to the area of ​​the preset defect area, and the area of ​​the preset defect area is greater than or equal to 1 mm 2 And less than or equal to 2000mm 2 .

[0014] In an optional embodiment of the present invention, before removing the positive electrode active material in the preset defective area on the positive electrode sheet of the test battery, the method further includes:

[0015] Determine the battery type of the test battery;

[0016] The area of ​​the preset defective region is determined based on the battery type.

[0017] In an optional embodiment of the present invention, the determining the area of ​​the preset defect region based on the battery type includes at least one of the following:

[0018] When the battery type is a ternary battery, the area of ​​the preset defect area is greater than or equal to 30mm 2 And less than or equal to 150mm 2 ;

[0019] When the battery type is a lithium iron battery, the area of ​​the preset defect area is greater than or equal to 800mm 2 And less than or equal to 1500mm 2 .

[0020] In an optional embodiment of the present invention, when the area of ​​the preset defect area is less than 50 mm 2 , the area of ​​the preset removal region is greater than the area of ​​the preset defect region by a preset percentage, and the preset percentage is 10%.

[0021] In an optional embodiment of the present invention, after the insulating phase change material is used to seal the positive electrode current collector of the test battery leaking from the preset removal area and the preset defect area, the method further includes:

[0022] A fixing device is used to relatively fix the insulating phase change material and the positive electrode current collector.

[0023] In an optional embodiment of the present invention, the fixing device includes at least one of paraffin and insulating tape.

[0024] In an optional embodiment of the present invention, the specially made test cell has a large surface;

[0025] The distance between the preset defect area and the large surface of the specially made test battery is less than or equal to a preset distance, wherein the preset distance is 1 / 4 of the thickness of the specially made test battery;

[0026] Accordingly, the step of heating the thermal diffusion test device with a heating device to change the insulating phase change material into a liquid state includes:

[0027] The heating device is arranged on the large surface of the special test battery;

[0028] The heating device is controlled to generate heat so that the insulating phase change material changes into a liquid state.

[0029] In an optional embodiment of the present invention, the triggering method of the battery thermal diffusion test further includes at least one of the following:

[0030] The heating device comprises a heating plate;

[0031] The preset temperature deviation is 20°C;

[0032] The insulating phase change material is paraffin;

[0033] The thickness of the insulating phase change material is less than 0.3 mm;

[0034] The heating time of the heating device is less than 10 minutes.

[0035] In an optional embodiment of the present invention, the removing of the positive electrode active material in the preset defective area on the positive electrode sheet of the test battery includes:

[0036] After the hot pressing process in the preparation process of the battery cell of the test battery, the positive electrode active material in the preset defect area on the positive electrode sheet of the battery cell is removed, so that the positive electrode current collector corresponding to the preset defect area leaks out;

[0037] Alternatively, when the test battery is a same-side-output battery, the test battery is discharged to 0% SOC and then the battery shell of the test battery is disassembled to obtain a battery cell, and the positive electrode active material in a preset defect area on the positive electrode sheet of the battery cell is removed to allow the positive electrode current collector opposite to the preset defect area to leak out.

[0038] In an optional embodiment of the present invention, the removing of the positive electrode active material in the preset defective area on the positive electrode sheet of the battery cell includes:

[0039] Using a tool to scrape away the positive electrode active material in the preset defect area on the positive electrode sheet of the battery cell;

[0040] Alternatively, NMP solvent is used to wipe away the positive electrode active material in the preset defective area on the positive electrode sheet of the battery cell.

[0041] The technical solution of the embodiment of the present invention is to first remove the positive electrode active material in the preset defect area of ​​the test battery, then remove the diaphragm in the preset removal area of ​​the test battery, and then use an insulating phase change material to seal the positive electrode collector leaking from the preset removal area and the preset defect area of ​​the test battery to form a special test battery, and finally combine the special test battery and the standard test battery to form a thermal diffusion test device, and use a heating device to heat the thermal diffusion test device to make the insulating phase change material phase change into a liquid state, so that the special test battery is short-circuited to trigger thermal runaway of the thermal diffusion test device.

[0042] Since the phase change temperature of the insulating phase change material from solid to liquid is greater than or equal to 40°C and less than or equal to 90°C, and the deviation between the maximum heating temperature of the heating device and the self-heating temperature of the battery is less than the preset temperature deviation, the thermal runaway of the thermal diffusion test device can be triggered at a relatively low temperature, avoiding the reduction of the strength of the battery shell due to external reasons, and there is no need to physically damage the battery shell; at the same time, the input energy is small, avoiding excessive energy input to the battery and causing the battery thermal runaway process to deviate from the actual situation; in addition, the trigger position can be located at any position of the thermal diffusion test device, and only the position of the preset defect area and the position of the special test battery in the thermal diffusion test device need to be adjusted. Finally, the internal short circuit form is used to trigger the thermal runaway of the battery, taking into account the internal defects that may exist in the battery manufacturing process, which is more in line with the actual thermal runaway situation that may occur. The effect of reducing the influence of the triggering method on the thermal diffusion test results is achieved, so that the obtained thermal diffusion test results are more accurate.

[0043] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 is a schematic structural diagram of a battery provided by an embodiment of the present invention;

[0046] Figure 2 A flowchart of a method for triggering a battery thermal diffusion test provided in Embodiment 1 of the present invention;

[0047] Figure 3 A schematic diagram of the structure of a positive electrode sheet processing provided in the first embodiment of the present invention;

[0048] Figure 4 A schematic diagram of the structure of a special test battery provided in Example 1 of the present invention;

[0049] Figure 5 A schematic diagram of the structure of a thermal diffusion test device provided in Example 1 of the present invention;

[0050] Figure 6 A flowchart of a method for triggering a battery thermal diffusion test provided in Embodiment 2 of the present invention;

[0051] Figure 7 This is a flow chart of a method for triggering a battery thermal diffusion test provided in Embodiment 3 of the present invention.

[0052] Among them: 1. Battery cell; 11. Positive electrode sheet; 111. Positive electrode active material; 112. Positive electrode current collector; 12. Negative electrode sheet; 121. Negative electrode current collector; 122. Negative electrode active material; 13. Diaphragm; 2. Preset defect area; 3. Preset removal area; 4. Insulating phase change material; 5. Heating device; 7. Temperature measuring point; 8. Special test battery; 81. Large surface; 9. Standard test battery. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0054] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0055] Embodiment 1

[0056] Embodiment 1 of the present invention provides a triggering method for a battery thermal diffusion test. This embodiment can be applied to a battery thermal diffusion test, such as Figure 1 As shown, the battery for heat diffusion includes a battery cell 1, the battery cell 1 includes a positive electrode sheet 11, a negative electrode sheet 12 and a separator 13, the separator 13 is arranged between the positive electrode sheet 11 and the negative electrode sheet 12, the positive electrode sheet 11 includes a positive electrode active material 111 and a positive electrode collector 112, the positive electrode active material 111 is located between the separator 13 and the positive electrode collector 112, the negative electrode sheet 12 includes a negative electrode collector 121 and a negative electrode active material 122, the negative electrode active material 122 is located between the separator 13 and the negative electrode collector 121, Figure 2 A flowchart of a method for triggering a battery thermal diffusion test provided in the first embodiment of the present invention, such as Figure 2-Figure 5 As shown, the triggering method of the battery thermal diffusion test includes:

[0057] S110 , removing the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the test battery, so that the positive electrode current collector 112 opposite to the preset defect area 2 leaks out.

[0058] Among them, the test battery is a battery that needs to be tested for thermal diffusion. The type of test battery is different, and the positive electrode active material 111 will also be different. The positive electrode active material 111 can be any of NCM, NCA, LFP and other lithium-ion battery positive electrode materials, which is subject to the specific battery that needs to be tested for thermal diffusion. The preset defect area 2 refers to the area on the positive electrode sheet 11 where the positive electrode active material 111 needs to be removed. There are many ways to remove the positive electrode active material 111. For example, the positive electrode active material 111 in the preset defect area 2 can be scraped off with a tool, or the positive electrode active material 111 in the preset defect area 2 can be wiped off with a solvent. The solvent can preferably be an NMP solvent, which is not specifically limited here, but is just an example. Since the positive electrode active material 111 is located on the positive electrode collector 112, after the positive electrode active material 111 in the preset defect area 2 is scraped off, the positive electrode collector 112 opposite to the preset defect area 2 will leak out from the preset defect area 2.

[0059] Since it is necessary to operate the positive electrode sheet 11 of the test battery, in specific applications, the positive electrode sheet 11 of the test battery can be operated during the preparation process of the battery cell 1 of the test battery, or the positive electrode sheet 11 of the test battery can be operated after the test battery has been manufactured. No specific limitation is made here, it is just an example.

[0060] In one embodiment, the removal of the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the test battery includes: after the hot pressing process in the preparation process of the battery cell 1 of the test battery, the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 is removed, so that the positive electrode collector 112 opposite to the preset defect area 2 leaks out. When there is a hot pressing process in the preparation process of the battery cell 1 of the test battery, the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 after the hot pressing process can prevent the test battery from short-circuiting during the preparation process. Specifically, if the positive electrode sheet 11 of the test battery is operated during the preparation process of the battery cell 1 of the test battery, the battery cell 1 of the test battery does not undergo a drying process and uses a normal temperature or low temperature small current formation process.

[0061] In some alternative embodiments, the removal of the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the test battery includes: when the test battery is a same-side output column battery, the test battery is discharged to 0% SOC and then the battery shell of the test battery is disassembled to obtain the battery cell 1, and the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 is removed, so that the positive electrode current collector 112 opposite to the preset defect area 2 leaks out. Among them, when the test battery has been prepared, the battery cell 1 of the test battery is usually located in the battery shell, so it is necessary to disassemble the battery shell of the test battery to obtain the battery cell 1 inside the battery shell, and then remove the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1. Specifically, a tool can be used to break the battery shell 1-2mm below the cover plate weld of the battery shell to take out the battery cell 1.

[0062] On the basis of the above embodiment, the method of removing the positive electrode active material 111 from the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 includes:

[0063] A tool is used to scrape away the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1. The tool may be a cutter, for example, a ceramic knife may be used to scrape away the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1, or other tools may be used.

[0064] In another alternative embodiment, the removing of the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 includes:

[0065] The positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 is wiped off with an NMP solvent. The NMP solvent refers to N-methylpyrrolidone. Since an NMP solvent is usually used in battery production, the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the battery cell 1 is wiped off with an NMP solvent to prevent the introduction of other impurities.

[0066] S120 , removing the separator 13 of the test battery located in the preset removal area 3 , wherein the preset removal area 3 is opposite to the preset defect area 2 .

[0067] The preset removal area 3 refers to the area on the diaphragm 13 that needs to be removed. The diaphragm 13 can be cut with a tool to cut the diaphragm 13 at the corresponding position of the preset removal area 3. Preferably, a ceramic knife can be used to scratch a corresponding mark on the diaphragm 13 along the edge of the preset removal area 3, and then the diaphragm 13 at the corresponding position of the preset removal area 3 can be cut. The area of ​​the preset removal area 3 can be the same as or different from the area of ​​the preset defect area 2. The area of ​​the preset removal area 3 can be greater than or equal to the area of ​​the preset defect area 2, or it can be less than the area of ​​the preset defect area 2. Figure 4 In the example, the area of ​​the preset removal region 3 is the same as the area of ​​the preset defect region 2.

[0068] Since the preset removal area 3 is opposite to the preset defect area 2, the positive electrode current collector 112 leaking from the preset defect area 2 will also leak from the preset removal area 3. When the area of ​​the preset removal area 3 is different from the area of ​​the preset defect area 2, the area of ​​the positive electrode current collector 112 leaking from the preset defect area 2 and the area of ​​the positive electrode current collector 112 leaking from the preset removal area 3 may be the same or different. For example, when the area of ​​the preset removal area 3 is greater than or equal to the area of ​​the preset defect area 2, the area of ​​the positive electrode current collector 112 leaking from the preset defect area 2 and the area of ​​the positive electrode current collector 112 leaking from the preset removal area 3 are the same. When the area of ​​the preset removal area 3 is smaller than the area of ​​the preset defect area 2, the area of ​​the positive electrode current collector 112 leaking from the preset defect area 2 will be greater than the area of ​​the positive electrode current collector 112 leaking from the preset removal area 3.

[0069] S130, using insulating phase change material 4 to seal the positive electrode current collector 112 of the test battery leaking from the preset removal area 3 and the preset defect area 2 to form a special test battery 8, wherein the insulating phase change material 4 is immiscible with the electrolyte and the phase change temperature from solid to liquid is greater than or equal to 40°C and less than or equal to 90°C.

[0070] Among them, the special test battery 8 refers to a test battery in which the positive electrode active material 111 of the preset defect area 2 is removed by the above scheme, and the diaphragm 13 of the preset removal area 3 is removed, and the positive electrode current collector 112 of the test battery leaking from the preset removal area 3 and the preset defect area 2 is blocked by the insulating phase change material 4. The insulating phase change material 4 refers to a non-conductive phase change material, and the phase change material (PCM-Phase Change Material) refers to a substance that changes the state of matter and can provide latent heat under constant temperature. The process of changing physical properties is called a phase change process, and the phase change material will absorb or release a large amount of latent heat at this time. The phase change material has the ability to change its physical state within a certain temperature range, and the temperature at which the phase change material changes its physical state is the phase change temperature. Since there is an electrolyte in the battery, if the insulating phase change material 4 and the electrolyte are miscible, it will lose its function, so the insulating phase change material 4 and the electrolyte are not miscible.

[0071] S140, the special test battery 8 and the standard test battery 9 form a thermal diffusion test device.

[0072] Among them, the standard test battery 9 refers to the battery used for the thermal diffusion test this time without the above operation, and the thermal diffusion test device refers to the device for the thermal diffusion test. Since the battery is usually used in conjunction with other batteries when in use, a single battery is usually not tested during the thermal diffusion test, so the special test battery 8 and the standard test battery 9 are combined into a thermal diffusion test device for the convenience of overall testing. Preferably, when the special test battery 8 is obtained by disassembling and modifying the prepared test battery, the battery cell 1 of the special test battery 8 can be reassembled using a new battery shell of the same model, and the cover plate and the battery shell are welded by laser welding. Before welding, the electrolyte on the cover plate should be wiped clean and a suitable method should be used to make the overlapped part of the battery shell and the cover plate to prevent the laser from entering the battery during welding and causing the electrolyte to burn. In addition, a small current is applied to charge the special test battery 8 to the group voltage. Then the special test battery 8 and the standard test battery 9 are combined into a thermal diffusion test device.

[0073] S150, using a heating device 5 to heat the thermal diffusion test device to change the insulating phase change material 4 into a liquid state, so that the special test battery 8 is short-circuited to trigger thermal runaway of the thermal diffusion test device, wherein the deviation between the maximum heating temperature of the heating device 5 and the battery self-heating temperature is less than a preset temperature deviation.

[0074] Among them, the battery self-heating temperature is the starting temperature at which the test battery begins to self-generate heat. The battery self-heating temperature can be obtained through testing, and specifically can be measured through the ARC test of the test battery. The maximum heating temperature refers to the maximum temperature heated by the heating device 5. The heating device 5 refers to a device that can be used to heat an object. In a specific embodiment, the heating device 5 includes a heating plate. By attaching the heating plate to the thermal diffusion test device, the thermal diffusion test device can be heated. In another specific embodiment, the heating device 5 includes an ultrasonic heating device 5, which heats the thermal diffusion device by ultrasound.

[0075] The preset temperature deviation is the deviation range between the maximum heating temperature of the heating device 5 and the self-heating temperature of the battery. Optionally, the preset temperature deviation is 15°C-20°C. Preferably, the preset temperature deviation is 20°C, that is, the maximum heating temperature of the heating device 5 is within ±20°C of the self-heating temperature of the battery, thereby being able to trigger thermal runaway of the thermal diffusion test device at a relatively low temperature.

[0076] Since the insulating phase change material 4 can change from solid to liquid when the phase change temperature is reached, the positive electrode current collector 112 blocked by the insulating phase change material 4 will leak out and contact the negative electrode sheet 12, causing the special test battery 8 to short-circuit, thereby triggering thermal runaway of the thermal diffusion test device.

[0077] The above scheme first removes the positive electrode active material 111 of the preset defect area 2 of the test battery, then removes the diaphragm 13 of the preset removal area 3 of the test battery, and then uses the insulating phase change material 4 to seal the positive electrode current collector 112 of the test battery leaking from the preset removal area 3 and the preset defect area 2 to form a special test battery 8, and finally the special test battery 8 and the standard test battery 9 are combined into a thermal diffusion test device, and the heating device 5 is used to heat the thermal diffusion test device to make the insulating phase change material 4 phase change into liquid, so that the special test battery 8 is short-circuited to trigger the thermal runaway of the thermal diffusion test device.

[0078] Since the phase change temperature of the insulating phase change material 4 from solid to liquid is greater than or equal to 40°C and less than or equal to 90°C, and the deviation between the maximum heating temperature of the heating device 5 and the self-heating temperature of the battery is less than the preset temperature deviation, the thermal runaway of the thermal diffusion test device can be triggered at a relatively low temperature, avoiding the reduction of the strength of the battery shell due to external reasons, and there is no need to physically damage the battery shell; at the same time, the input energy is small, avoiding excessive energy input to the battery and causing the battery thermal runaway process to deviate from the actual situation; in addition, the trigger position can be located at any position of the thermal diffusion test device, and only the position of the preset defect area 2 and the position of the special test battery 8 in the thermal diffusion test device need to be adjusted. Finally, the battery thermal runaway is triggered in the form of an internal short circuit, taking into account the internal defects that may exist in the battery manufacturing process, which is more in line with the actual thermal runaway situation that may occur. The effect of reducing the influence of the triggering method on the thermal diffusion test results is achieved, so that the obtained thermal diffusion test results are more accurate.

[0079] In an optional embodiment of the present invention, the area of ​​the preset removal region 3 is greater than or equal to the area of ​​the preset defect region 2, so that the positive electrode collector 112 located in the preset defect region 2 on the positive electrode sheet 11 can fully leak out from the preset removal region 3, so as to facilitate the subsequent short circuit contact with the negative electrode sheet 12 to trigger thermal runaway.

[0080] Based on the above embodiment, the area of ​​the preset defect area 2 is greater than or equal to 1 mm 2 And less than or equal to 2000mm 2 Among them, an overly large preset defect area 2 increases the degree of thermal runaway, making the thermal runaway too severe and deviating too much from the actual thermal runaway situation that may occur, making the test meaningless. An overly small preset defect area 2 may cause the thermal runaway trigger to fail. By making the area of ​​the preset defect area 2 greater than or equal to 1mm 2 And less than or equal to 2000mm 2 , which can make the thermal diffusion test results more accurate while preventing the success rate of thermal triggering from being too low.

[0081] On the basis of the above embodiment, when the area of ​​the preset defect area 2 is less than 50mm 2 The area of ​​the preset removal region 3 is greater than the area of ​​the preset defect region 2 by a preset percentage, which is 10%, thereby increasing the success rate of triggering thermal runaway.

[0082] Embodiment 2

[0083] Figure 6A flowchart of a triggering method for a battery thermal diffusion test provided in Embodiment 2 of the present invention. The relationship between this embodiment and the above-mentioned embodiment is that Embodiment 1 is improved. Optionally, before removing the positive electrode active material 111 of the preset defect area 2 on the positive electrode sheet 11 of the test battery, it also includes: determining the battery type of the test battery; determining the area of ​​the preset defect area 2 based on the battery type, based on this, such as Figure 4-Figure 6 As shown, the triggering method of the battery thermal diffusion test includes:

[0084] S210: Determine the battery type of the test battery.

[0085] Among them, the battery types are divided into ternary batteries and iron-lithium batteries. The positive electrode material of the ternary battery is NCM (nickel cobalt manganese) or NCA (nickel cobalt aluminum), and the positive electrode material of the iron-lithium battery is LFP (lithium iron phosphate)

[0086] S220: Determine the area of ​​the preset defect region 2 based on the battery type.

[0087] Among them, ternary batteries and iron-lithium batteries differ in their ability to resist temperature. Under high temperature conditions, ternary batteries will decompose at 200°C, while the decomposition temperature of iron-lithium batteries is 800°C. Therefore, iron-lithium batteries are more resistant to high temperatures and less likely to catch fire, which also shows that iron-lithium batteries have better safety. The thermal stability of ternary batteries is poor, so for ternary batteries, only a small area of ​​the positive electrode collector 112 needs to leak out to short-circuit and cause thermal runaway. The thermal stability of iron-lithium batteries is better, so for iron-lithium batteries, a large area of ​​the positive electrode collector 112 needs to leak out to short-circuit and cause thermal runaway. When the preset defect area 2 is larger, the leakage area of ​​the positive electrode collector 112 is larger, so the area of ​​the preset defect area 2 can be determined according to the battery type, so that the thermal diffusion test results are more accurate.

[0088] In a specific embodiment, the area of ​​the preset defect area 2 is determined based on the battery type, including: when the battery type is a ternary battery, the area of ​​the preset defect area 2 is greater than or equal to 30mm 2 And less than or equal to 150mm 2 Preferably, the area of ​​the preset defect area 2 is 100 mm 2 . This can prevent the thermal runaway from being too severe and deviating too much from the actual thermal runaway situation while triggering the thermal runaway of the ternary battery.

[0089] In a specific embodiment, the area of ​​the preset defect area 2 is determined based on the battery type, including: when the battery type is a lithium iron battery, the area of ​​the preset defect area 2 is greater than or equal to 800mm 2 And less than or equal to 1500mm 2Preferably, the preset defect area 2 is 1000mm 2 . This can prevent the thermal runaway from being too severe and deviating too much from the actual thermal runaway situation while triggering the thermal runaway of the lithium iron battery.

[0090] S230 , removing the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the test battery, so that the positive electrode current collector 112 opposite to the preset defect area 2 leaks out.

[0091] S240 , removing the separator 13 of the test battery located in the preset removal area 3 , where the preset removal area 3 is opposite to the preset defect area 2 .

[0092] S250, using insulating phase change material 4 to seal the positive electrode current collector 112 of the test battery leaking from the preset removal area 3 and the preset defect area 2 to form a special test battery 8, wherein the insulating phase change material 4 is immiscible with the electrolyte and the phase change temperature from solid to liquid is greater than or equal to 40°C and less than or equal to 90°C.

[0093] S260, the special test battery 8 and the standard test battery 9 form a thermal diffusion test device.

[0094] S270, using a heating device 5 to heat the thermal diffusion test device to change the insulating phase change material 4 into a liquid state, so that the special test battery 8 is short-circuited to trigger thermal runaway of the thermal diffusion test device, wherein the deviation between the maximum heating temperature of the heating device 5 and the battery self-heating temperature is less than a preset temperature deviation.

[0095] Embodiment 3

[0096] Figure 7 A flowchart of a triggering method for a battery thermal diffusion test provided in the third embodiment of the present invention. The relationship between this embodiment and the above embodiment is that the second embodiment is improved. Optionally, after the insulating phase change material 4 is used to block the positive electrode current collector 112 of the test battery leaking from the preset removal area 3 and the preset defect area 2, it also includes: using a fixing device to relatively fix the insulating phase change material 4 and the positive electrode current collector 112. Based on this, Figure 4 , Figure 5 and Figure 7 As shown, the triggering method of the battery thermal diffusion test includes:

[0097] S310: Determine the battery type of the test battery.

[0098] S320: Determine the area of ​​the preset defect region 2 based on the battery type.

[0099] S330 , removing the positive electrode active material 111 in the preset defect area 2 on the positive electrode sheet 11 of the test battery, so that the positive electrode current collector 112 opposite to the preset defect area 2 leaks out.

[0100] S340 , removing the diaphragm 13 of the test battery located in the preset removal area 3 , where the preset removal area 3 is opposite to the preset defect area 2 .

[0101] S350, using insulating phase change material 4 to seal the positive electrode current collector 112 of the test battery leaking from the preset removal area 3 and the preset defect area 2, and using a fixing device to relatively fix the insulating phase change material 4 and the positive electrode current collector 112 to form a special test battery 8, wherein the insulating phase change material 4 is immiscible with the electrolyte and the phase change temperature from solid to liquid is greater than or equal to 40°C and less than or equal to 90°C.

[0102] The fixing device refers to a device that can relatively fix the insulating phase change material 4 and the positive electrode current collector 112. By setting the fixing device, it is possible to prevent the special test battery 8 from short-circuiting during transportation or grouping.

[0103] In a specific embodiment, the fixing device includes paraffin wax. Paraffin wax can be dripped on the corners of the insulating phase change material 4 to fix the insulating phase change material 4 on the diaphragm 13 or on the foil material, which is the material for making the positive electrode sheet 11, so as to prevent the special test battery 8 from short circuiting during transportation or grouping.

[0104] In a specific embodiment, the fixing device includes an insulating tape. The insulating tape can be pasted on the corners of the insulating phase change material 4 to fix the insulating phase change material 4 on the diaphragm 13 or the foil.

[0105] S360, the special test battery 8 and the standard test battery 9 form a thermal diffusion test device.

[0106] S370, using a heating device 5 to heat the thermal diffusion test device to change the insulating phase change material 4 into a liquid state, so that the special test battery 8 is short-circuited to trigger thermal runaway of the thermal diffusion test device, wherein the deviation between the maximum heating temperature of the heating device 5 and the battery's self-heating temperature is less than a preset temperature deviation.

[0107] In an optional embodiment of the present invention, the insulating phase change material 4 is paraffin; specifically, the paraffin can be heated and melted and then dripped onto a metal plate to solidify to form a paraffin sheet. When the area of ​​the preset defect region 2 is the same as the area of ​​the preset removal region 3, the paraffin sheet is cut to the size of the preset defect region 2. If the area of ​​the preset defect region 2 is smaller than the preset removal region 3, the paraffin sheet is cut to the size of the preset removal region 3. Then the paraffin sheet is placed in the space formed by the area of ​​the preset defect region 2 and the preset removal region 3, and finally a fixing device is used to relatively fix the insulating phase change material 4 and the positive electrode current collector 112. This can prevent the special test battery 8 from short-circuiting during transportation or grouping, and can also melt the paraffin sheet at a low temperature during the thermal trigger test to cause the special test battery 8 to short-circuit, thereby triggering thermal runaway.

[0108] In an optional embodiment of the present invention, the thickness of the insulating phase change material 4 is less than 0.3 mm. An overly thick insulating phase change material 4 will reduce the success rate of triggering thermal runaway. By making the thickness of the insulating phase change material 4 less than 0.3 mm, the success rate of triggering thermal runaway can be prevented from being low. Specifically, when the insulating phase change material 4 is paraffin, the thickness of the paraffin is less than 0.3 mm.

[0109] In an optional embodiment of the present invention, the heating time of the heating device 5 is less than 10 minutes, which can ensure that the special test battery 8 directly thermally runs away due to internal short circuit at a relatively low temperature, and at the same time, the input energy is small, avoiding excessive energy input to the battery, which may cause the battery thermal runaway process to deviate from the actual situation.

[0110] In an optional embodiment of the present invention, the special test battery 8 has a large surface 81. The large surface 81 refers to the stacking direction of the special test battery 8 in the thermal diffusion test device.

[0111] The distance between the preset defect area 2 and the large surface 81 of the special test battery 8 is less than or equal to a preset distance, wherein the preset distance is 1 / 4 of the thickness of the special test battery 8 .

[0112] Accordingly, the step of heating the thermal diffusion test device with the heating device 5 to change the insulating phase change material 4 into a liquid state includes:

[0113] The heating device 5 is disposed on the large surface 81 of the special test battery 8 .

[0114] The heating device 5 is controlled to generate heat so that the insulating phase change material 4 changes into a liquid state.

[0115] Among them, since the heating device 5 is arranged on the large surface 81 of the special test battery 8, by making the distance between the preset defect area 2 and the large surface 81 of the special test battery 8 less than or equal to the preset distance, wherein the preset distance is 1 / 4 of the thickness of the special test battery 8, the success rate of triggering thermal runaway can be increased.

[0116] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0117] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A triggering method for a battery thermal diffusion test, used for a battery thermal diffusion test, wherein the battery comprises a battery cell, the battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material and a positive electrode current collector, the positive electrode active material is located between the separator and the positive electrode current collector, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material, the negative electrode active material is located between the separator and the negative electrode current collector, characterized in that: The triggering method of the battery thermal diffusion test includes: Removing the positive electrode active material in the preset defect area on the positive electrode sheet of the test battery, so that the positive electrode current collector opposite to the preset defect area leaks out; Removing the separator of the test battery located in a preset removal area, wherein the preset removal area is opposite to the preset defect area; The positive electrode current collector leaking from the preset removal area and the preset defect area of ​​the test battery is sealed with an insulating phase change material to form a special test battery, wherein the insulating phase change material is immiscible with the electrolyte and the phase change temperature from solid to liquid is greater than or equal to 40° C. and less than or equal to 90° C.; The special test battery and the standard test battery form a thermal diffusion test device; The thermal diffusion test device is heated by a heating device to change the insulating phase change material into a liquid state, so that the special test battery is short-circuited to trigger thermal runaway of the thermal diffusion test device, wherein the deviation between the maximum heating temperature of the heating device and the self-heating temperature of the battery is less than a preset temperature deviation.

2. The triggering method for battery thermal diffusion test according to claim 1, characterized in that: The area of ​​the preset removal area is greater than or equal to the area of ​​the preset defect area, and the area of ​​the preset defect area is greater than or equal to 1 mm 2 And less than or equal to 2000mm 2 .

3. The triggering method for battery thermal diffusion test according to claim 2, characterized in that: Before removing the positive electrode active material in the preset defective area on the positive electrode sheet of the test battery, the method further includes: Determine the battery type of the test battery; The area of ​​the preset defective region is determined based on the battery type.

4. The triggering method for battery thermal diffusion test according to claim 3, characterized in that: The determining the area of ​​the preset defect region based on the battery type includes at least one of the following: When the battery type is a ternary battery, the area of ​​the preset defect area is greater than or equal to 30mm 2 And less than or equal to 150mm 2 ; When the battery type is a lithium iron battery, the area of ​​the preset defect area is greater than or equal to 800mm 2 And less than or equal to 1500mm 2 .

5. The triggering method for battery thermal diffusion test according to any one of claims 1 to 4, characterized in that: When the area of ​​the preset defect area is less than 50 mm 2 , the area of ​​the preset removal region is greater than the area of ​​the preset defect region by a preset percentage, and the preset percentage is 10%.

6. The triggering method for battery thermal diffusion test according to any one of claims 1 to 4, characterized in that: After the insulating phase change material is used to seal the positive electrode current collector of the test battery leaking from the preset removal area and the preset defect area, the method further includes: A fixing device is used to relatively fix the insulating phase change material and the positive electrode current collector.

7. The triggering method for battery thermal diffusion test according to claim 6, characterized in that: The fixing device includes at least one of paraffin wax and insulating tape.

8. The triggering method for battery thermal diffusion test according to any one of claims 1 to 4, characterized in that: The specially made test cell has a large surface; The distance between the preset defect area and the large surface of the specially made test battery is less than or equal to a preset distance, wherein the preset distance is 1 / 4 of the thickness of the specially made test battery; Accordingly, the step of heating the thermal diffusion test device with a heating device to change the insulating phase change material into a liquid state includes: The heating device is arranged on the large surface of the special test battery; The heating device is controlled to generate heat so that the insulating phase change material changes into a liquid state.

9. The triggering method for battery thermal diffusion test according to any one of claims 1 to 4, characterized in that: The triggering method of the battery thermal diffusion test also includes at least one of the following: The heating device comprises a heating plate; The preset temperature deviation is 20°C; The insulating phase change material is paraffin; The thickness of the insulating phase change material is less than 0.3 mm; The heating time of the heating device is less than 10 minutes.

10. The triggering method for battery thermal diffusion test according to any one of claims 1 to 4, characterized in that: The method of removing the positive electrode active material in the preset defective area on the positive electrode sheet of the test battery comprises: After the hot pressing process in the preparation process of the battery cell of the test battery, the positive electrode active material in the preset defect area on the positive electrode sheet of the battery cell is removed, so that the positive electrode current collector corresponding to the preset defect area leaks out; Alternatively, when the test battery is a same-side-output battery, the test battery is discharged to 0% SOC and then the battery shell of the test battery is disassembled to obtain a battery cell, and the positive electrode active material in a preset defect area on the positive electrode sheet of the battery cell is removed to allow the positive electrode current collector opposite to the preset defect area to leak out.

11. The triggering method of battery thermal diffusion test according to claim 10, characterized in that: The method of removing the positive electrode active material in the preset defective area on the positive electrode sheet of the battery cell comprises: Using a tool to scrape away the positive electrode active material in the preset defect area on the positive electrode sheet of the battery cell; Alternatively, NMP solvent is used to wipe away the positive electrode active material in the preset defective area on the positive electrode sheet of the battery cell.

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