Lithium battery short circuit thermal runaway simulation method and temperature research method

Abstract

The invention discloses a lithium battery short circuit thermal runaway simulation method and a temperature research method, which can accurately simulate a lithium battery thermal runaway process. Comprising the following steps: disassembling the lithium battery, taking out the lithium battery, cutting the lithium battery into a positive plate and a negative plate with preset sizes, forming a blank aluminum foil area without a pole material on the positive plate, forming a blank copper foil area without a pole material on the negative plate, and infiltrating a diaphragm of the lithium battery into an electrolyte; sequentially laminating the positive plate, the diaphragm infiltrated with the electrolyte and the negative plate to form a lamination assembly, and enabling a part of the white aluminum foil region to correspond to the position of the negative coating region, a part of the white copper foil region to correspond to the position of the positive coating region, and / or a part of the white aluminum foil region to correspond to the position of the white copper foil region; putting the lamination assembly into an aluminum-plastic film bag, and introducing electrolyte into the aluminum-plastic film bag; marking a short-circuit area required by the short-circuit model on the aluminum-plastic film bag; and forming a preset short-circuit model corresponding to the mark position by using the conductive needle so as to carry out corresponding thermal runaway simulation.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a thermal runaway simulation method and a temperature research method for a lithium battery short circuit. Background Art

[0002] Lithium-ion batteries have become an important energy supply option for mobile electronic devices and electric vehicles due to their high energy density and long life. However, the potential accident hazards of lithium-ion batteries will undermine consumers' confidence in accepting electric vehicles and endanger the safety of people's lives and property. The safety issues of lithium-ion batteries are mainly fires and explosions caused by thermal runaway. In the field of small commercial lithium-ion battery cells (<3A·h) and battery packs (<150W·h), the thermal runaway problem has been met by safety redundancy design. However, for large lithium-ion battery cells (6A·h) and battery stacks (200W·h) for automobiles, the thermal runaway problem is still a challenge. The main reasons are: (1) The high power requirements of electric vehicles limit the use of PTC (positive temperature coefficient element) and other safety devices; (2) Large batteries are inherently more prone to thermal runaway because the increased battery capacity reduces the surface area to volume ratio, which reduces the heat dissipation area per unit volume; (3) The increased battery capacity exacerbates the temperature distribution differences within the battery. Under given surface heat transfer conditions, the uneven battery temperature distribution leads to higher local temperatures and increases the possibility of thermal runaway. Therefore, studying the temperature changes and heat generation characteristics of lithium-ion batteries under needle puncture is of great significance for improving the safety and reliability of batteries.

[0003] The solution of the existing technology: a small commercial 18650 cylindrical ternary lithium-ion battery cell (<4A·h) is penetrated with a needle to simulate an internal short circuit to confirm whether the battery is smoking, catching fire, or rupturing. Under normal conditions, the positive and negative electrodes of the lithium-ion battery are insulated by a polymer insulating film in the organic electrolyte - a diaphragm. In this state, inserting a steel nail into the lithium-ion battery causes a short circuit between the positive and negative electrode sheets, forcing an internal short circuit test. The characteristic of this test method is that the test conditions such as the diameter, material, insertion depth, insertion position, and insertion speed of the steel nail inserted into the battery can be adjusted.

[0004] However, the existing technology still has some problems in this field. First, this experiment uses a single-core test of a 18650 cylindrical ternary lithium-ion monomer. The internal structure of the inserted cell is unknown during the needle puncture test. The existing technology may not be able to accurately simulate the impact of different types of internal short circuits (such as positive electrode layer-negative electrode layer type internal short circuit, positive electrode current collector-negative electrode layer type internal short circuit, etc.) on battery temperature. Therefore, the existing technology still has certain limitations in this field and needs further simplification and improvement. Summary of the invention

[0005] The purpose of the present invention is to provide a thermal runaway simulation method and a temperature research method for a lithium battery short circuit, which can accurately simulate the thermal runaway process of a lithium battery.

[0006] In order to achieve the above-mentioned object, the present invention provides a method for simulating thermal runaway of a lithium battery short circuit, comprising: disassembling the lithium battery, taking out and cutting the positive electrode sheet and the negative electrode sheet of a preset size, forming a blank aluminum foil area without electrode material on the first area of ​​the positive electrode sheet, and forming a blank copper foil area without electrode material on the second area of ​​the negative electrode sheet, so that the positive electrode sheet is composed of a blank aluminum foil area and a positive electrode coating area, and the negative electrode sheet is composed of a blank copper foil area and a negative electrode coating area; providing a lithium battery diaphragm of a preset size, and soaking the diaphragm of the lithium battery in an electrolyte; stacking the positive electrode sheet, the diaphragm soaked in the electrolyte, and the negative electrode sheet in sequence to form a stacking assembly, wherein the diaphragm separates the positive electrode sheet and the negative electrode sheet to prevent the The positive electrode sheet and the negative electrode sheet are in short-circuit contact, and a plurality of combinations of the position of part of the blank aluminum foil area corresponding to the position of the negative electrode coating area, the position of part of the blank copper foil area corresponding to the position of the positive electrode coating area, the position of part of the blank aluminum foil area corresponding to the position of part of the blank copper foil area, and the position of part of the positive electrode coating area corresponding to the position of part of the negative electrode coating area are achieved; the stacking assembly is placed in an aluminum-plastic film bag; an electrolyte is introduced into the aluminum-plastic film bag to ensure ion conduction in the aluminum-plastic film bag; the short-circuit area required for the short-circuit model is marked on the aluminum-plastic film bag; a conductive needle is used to pierce the corresponding marked position along the stacking direction of the stacking assembly to form a preset short-circuit model, so as to perform corresponding thermal runaway simulation.

[0007] Preferably, the lithium battery to be disassembled is a fully charged lithium battery. Fully charged disassembly needs to be carried out in a temperature and humidity controlled environment. In addition, the electrolyte needs to be sealed better than operating under temperature and humidity controlled conditions.

[0008] Preferably, after the electrolyte is poured into the aluminum-plastic film bag, a clip is used to clamp the opening of the aluminum-plastic film bag and other outer edge areas except the opening to fix the position of the stacking assembly relative to the aluminum-plastic film bag.

[0009] More preferably, the clip is a metal clip, which is clamped on the aluminum-plastic film bag through an insulating spacer paper and is insulated from the aluminum-plastic film bag. It has low cost, is easy to operate, and does not affect the thermal runaway simulation of the lithium battery.

[0010] Preferably, the marking position includes a first marking area where the projections of the positive electrode sheet and the negative electrode sheet overlap and are offset from the first area and the second area, a second marking area where the negative electrode sheet does not overlap with the projection of the positive electrode sheet and is offset from the first area and the second area, a third marking area where the projections of the positive electrode sheet and the negative electrode sheet overlap and correspond to the first area, and a fourth marking area where the projections of the positive electrode sheet and the negative electrode sheet overlap and correspond to the second area.

[0011] Preferably, the area ratio of the blank aluminum foil area to the positive electrode coating area is less than or equal to 1:5, and the area ratio of the blank copper foil area to the negative electrode coating area is less than or equal to 1:25. This further improves the accuracy of thermal runaway simulation.

[0012] Preferably, the lithium battery is a 18650 cylindrical ternary lithium-ion battery cell.

[0013] Preferably, the projection of the negative electrode sheet covers the projection of the positive electrode sheet, the projection of the diaphragm covers the projection of the negative electrode sheet, one end of the positive electrode sheet and the negative electrode sheet are aligned, and the blank aluminum foil area and the blank copper foil area are respectively located at the two ends of the positive electrode sheet and the negative electrode sheet. This solution allows the position of the positive electrode sheet in the width direction to be adjusted relative to the negative electrode sheet as needed when the sheet assembly is stacked, so as to form a variety of markable puncture points for short-circuit models.

[0014] Preferably, the positive electrode sheet, negative electrode sheet and separator are in the shape of long strips with wider width than long length, and the separator is wider than the negative electrode sheet and longer than or equal to the negative electrode sheet, and the negative electrode sheet is wider than the positive electrode sheet and longer than or equal to the positive electrode sheet.

[0015] Preferably, the tail of one end of the negative electrode sheet is coated with anode and cathode to form an anode and cathode coated area with electrode materials on one side, which not only allows more short-circuit model simulations but also makes the simulation environment closer to the original environment of the lithium battery.

[0016] Preferably, after the electrolyte is introduced into the aluminum-plastic film bag, the aluminum-plastic film bag is also sealed.

[0017] The present invention also provides a temperature research method for thermal runaway of lithium battery short circuit, and thermal runaway simulation is performed according to the thermal runaway simulation method of lithium battery short circuit; when the conductive needle pierces, the temperature of the puncture position is recorded using a thermal imager; the aluminum-plastic film bag is disassembled, the diaphragm is removed, and the size of the heat shrinkage holes left by the puncture on the diaphragm is detected; and a temperature research is performed based on the size of the heat shrinkage holes and the detected temperature.

[0018] Compared with the prior art, the present invention disassembles the positive and negative electrodes in the lithium battery and cuts them, and then uses a diaphragm soaked in electrolyte to separate the positive and negative electrodes and form a laminate structure. Through the misalignment of the positive and negative electrodes and the misalignment of the blank areas of the electrodes, marking points for various short-circuit simulations are formed on the laminate structure, and various thermal runaway simulations can be realized. On the other hand, the present invention soaks the laminate structure in electrolyte and wraps it with aluminum-plastic film bags, which can effectively keep warm during thermal runaway simulations, and the simulation accuracy is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention Flowchart of the thermal runaway simulation method for lithium battery short circuit.

[0020] Figure 2 is a cross-sectional view of a lamination assembly in one embodiment of the present invention.

[0021] Figure 3 is a cross-sectional view of a lamination assembly in another embodiment of the present invention.

[0022] Figure 4 is a cross-sectional view of a lamination assembly in yet another embodiment of the present invention.

[0023] Figure 5 is a cross-sectional view of a lamination assembly in yet another embodiment of the present invention.

[0024] Figure 6 It is a top view of a lamination assembly in accordance with an embodiment of the present invention.

[0025] Figure 7 It is a structural diagram of the laminate assembly of the present invention being loaded into an aluminum-plastic film bag.

[0026] Figure 8 It is a structural diagram of the diaphragm removed from the aluminum-plastic film bag after the thermal runaway simulation of the present invention. DETAILED DESCRIPTION

[0027] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0028] refer to Figure 1 The present invention discloses a method for simulating thermal runaway of a lithium battery short circuit, comprising steps S1 to S9.

[0029] S1, disassemble the lithium battery, take out and cut the positive electrode sheet 20 and the negative electrode sheet 30 into preset sizes.

[0030] Preferably, the lithium battery to be disassembled is a fully charged lithium battery, which is convenient for subsequent temperature research on thermal runaway. Wherein, the lithium battery is a 18650 cylindrical ternary lithium-ion battery cell.

[0031] The lithium battery is disassembled in an environment within a preset temperature range and a preset humidity range.

[0032] S2, forming a blank aluminum foil area 201 without electrode material (electrode coating) on ​​the first area of ​​the positive electrode sheet 20, so that the positive electrode sheet 20 consists of the blank aluminum foil area 201 and the positive electrode coating area 202. The positive electrode coating area 202 is an area where positive electrode coating is laid.

[0033] Wherein, the area ratio of the blank aluminum foil area 201 to the positive electrode coating area 202 is less than or equal to 1:25.

[0034] refer to Figure 2 , blank aluminum foil areas 201 without coating are formed at both ends of the positive electrode sheet 20, and the first area is located at both ends of the positive electrode sheet 20. Among them, there is no coating on the front and back sides of the aluminum foil layer at both ends of the positive electrode sheet 20, so that there is no electrode material layer of the positive electrode sheet 20 in the projection direction of the blank aluminum foil area 201. The positive electrode sheet 20 includes an aluminum foil layer 21 and an electrode material layer 22 located on both sides of the aluminum foil layer 21. Of course, in contrast to this, the first area can also be only one and located at one end of the width direction of the positive electrode sheet 20 or in the middle area of ​​the width direction. The first area can also be composed of a plurality of and spaced apart in the middle of the width direction of the positive electrode sheet 20, or partially located in the middle of the width direction of the positive electrode sheet 20, partially located at one end of the width direction of the positive electrode sheet 20, and partially located in the middle of the width direction of the positive electrode sheet 20.

[0035] S3, forming a blank copper foil area 301 without electrode material on the second area of ​​the negative electrode sheet 30 so that the negative electrode sheet 30 consists of the blank copper foil area 301 and the negative electrode coating area 302. The negative electrode coating area 302 is an area for laying negative electrode coating.

[0036] Wherein, the area ratio of the blank copper foil area 301 to the negative electrode coating area 302 is less than or equal to 1:25.

[0037] refer to Figure 2 , the negative electrode sheet 30 forms a blank copper foil area 301 without pole material at the tail of both ends, and the second area is located at both ends of the negative electrode sheet 30. The negative electrode sheet 30 includes a copper foil layer 31 and pole material layers 32 located on both sides of the copper foil layer 21. Of course, in contrast to this, the second area can also be only one and located at one end or the middle area of ​​the negative electrode sheet 30. The second area can also be composed of multiple and spaced in the middle of the width direction of the negative electrode sheet 30, or partially located in the middle of the width direction of the negative electrode sheet 30, partially located at one end of the width direction of the negative electrode sheet 30, and partially located in the middle of the width direction of the negative electrode sheet 30.

[0038] S4, providing a lithium battery separator 10 of a preset size, and soaking the lithium battery separator 10 with electrolyte, so that during subsequent lamination, the positive electrode sheet 20 and the negative electrode sheet 30 can be firmly attached to the separator 10 with the help of the electrolyte.

[0039] refer to Figure 6 In this embodiment, the positive electrode sheet 20, the negative electrode sheet 30 and the separator 10 are in the shape of long strips, and the separator 10 is wider and longer than the negative electrode sheet 30, and the negative electrode sheet 30 is wider and longer than the positive electrode sheet 20. The projection of the negative electrode sheet 30 covers the projection of the positive electrode sheet 20, the projection of the separator 10 covers the projection of the negative electrode sheet 30, and the blank aluminum foil area 201 and the blank copper foil area 301 are respectively arranged at two ends of the separator 10 that are far away from each other.

[0040] S5, stacking the positive electrode sheet 20, the diaphragm 10 soaked in electrolyte and the negative electrode sheet 30 in sequence to form a stacking assembly, the diaphragm 10 spacing the positive electrode sheet 20 and the negative electrode sheet 30 to prevent the positive electrode sheet 20 and the negative electrode sheet 30 from short-circuiting contact, part of the first area and the second area are staggered, part of the first area and the second area are corresponding, and at least two combinations of one blank aluminum foil area 201 corresponding to the negative electrode coating area 302, one blank copper foil area 301 corresponding to the positive electrode coating area 202, one blank aluminum foil area 201 corresponding to a blank copper foil area 301, and part of the negative electrode coating area and part of the positive electrode coating area 202 corresponding to each other are achieved.

[0041] refer to Figure 2 The blank aluminum foil area 201 corresponds to the negative electrode coating area 302 , the blank aluminum foil area 201 corresponds to the blank copper foil area 301 , and part of the negative electrode coating area 301 and part of the positive electrode coating area 202 correspond to each other.

[0042] refer to Figure 3 and Figure 4 In another embodiment, the tail of one end of the negative electrode sheet 30 forms a blank copper foil area 301 without a pole material, and the other end forms a positive and negative electrode coating area 303 for anode and cathode coating. Among them, one side of the copper foil layer 31 of the positive and negative electrode coating area 303 has a pole material layer 32 and the other side does not have a pole material layer 32. The pole material layer 32 of the positive and negative electrode coating area 303 can be located on the side of the copper foil layer 31 adjacent to the separator 10 (such as Figure 3 As shown), it can also be located on the side of the copper foil layer 32 away from the diaphragm 10 (as shown Figure 4 As shown). At this time, a blank aluminum foil area 201 corresponds to a positive and negative coating area 303. A blank aluminum foil area 201 corresponds to the negative electrode coating area 302, and part of the negative electrode coating area 301 corresponds to part of the positive electrode coating area 202.

[0043] refer to Figure 5 In another embodiment, a blank copper foil area 301 is formed at both ends of the negative electrode sheet 30, and a positive and negative coating area 303 is formed at a position adjacent to the blank copper foil area 301 at one end. The coating layer 32 of the positive and negative coating area 303 can be located on the side of the copper foil layer 31 adjacent to the diaphragm 10, or on the side of the copper foil layer 32 away from the diaphragm 10. At this time, a blank aluminum foil area 201 corresponds to a positive and negative coating area 303, a blank aluminum foil area 201 corresponds to a blank copper foil area 301, a blank aluminum foil area 201 corresponds to a negative electrode coating area 302, and part of the negative electrode coating area 301 corresponds to part of the positive electrode coating area 202.

[0044] S6, reference Figure 7 , putting the laminate assembly into an aluminum-plastic film bag. In the embodiment, the aluminum-plastic film bag is a rectangular bag, and the aluminum-plastic film bag has openings on three sides and one side is open.

[0045] S7, introducing sufficient electrolyte into the aluminum-plastic film bag to ensure ion conduction in the aluminum-plastic film bag.

[0046] refer to Figure 7 Preferably, after the electrolyte is poured into the aluminum-plastic film bag, a clip is used to clamp the opening of the aluminum-plastic film bag and other outer edge areas except the opening to fix the position of the stacking assembly relative to the aluminum-plastic film bag.

[0047] More preferably, the clip is a metal clip, which is clamped on the aluminum-plastic film bag through an insulating spacer paper and is insulated from the aluminum-plastic film bag. It has low cost, is easy to operate, and does not affect the thermal runaway simulation of the lithium battery.

[0048] Preferably, after the electrolyte is introduced into the aluminum-plastic film bag, the aluminum-plastic film bag is also sealed, which can be sealed with a tape or a thermoplastic sealing machine. Figure 5 As shown, it is also possible not to seal. Figure 5 In the test, only a clip is used to clamp the aluminum-plastic film bag from its opening. At this time, the blank aluminum foil area 201 and the blank copper foil area 301 need to be arranged on the side away from the opening of the aluminum-plastic film bag, and then the aluminum-plastic film bag is slightly tilted during the test to prevent the electrolyte from flowing out.

[0049] S8, marking the short-circuit area required by the short-circuit model on the aluminum-plastic film bag to form an area mark.

[0050] refer to Figure 3The marking position includes a first marking area 401 overlapping with the projection of the positive electrode sheet 20 and the negative electrode sheet 30 and staggered with the blank aluminum foil area 201 and the blank copper foil area 301, a second marking area 402 overlapping with the projection of the negative electrode sheet 30 and the positive electrode sheet 20 and corresponding to the blank aluminum foil area 201 and the blank copper foil area 301, a third marking area 403 overlapping with the projection of the positive electrode sheet 20 and the negative electrode sheet 30 and corresponding to the blank aluminum foil area 201 and staggered with the blank copper foil area 301, a fourth marking area 404 overlapping with the projection of the positive electrode sheet 20 and the negative electrode sheet 30 and corresponding to the blank copper foil area 301 and staggered with the blank aluminum foil area 201, and a fifth marking area 405 overlapping with the projection of the positive electrode sheet 20 and the negative electrode sheet 30 and corresponding to the blank aluminum foil area 201 and the positive and negative coating area 303.

[0051] S9, using a conductive needle to pierce the corresponding marked position along the lamination direction of the lamination assembly to form a preset short-circuit model to perform a corresponding thermal runaway simulation.

[0052] Among them, the use of the electrolyte in the above steps is carried out under temperature and humidity controlled conditions.

[0053] The conductive needle may be a steel needle, or a combined structure consisting of an insulating material and a gold-plated layer.

[0054] Specifically, refer to Figures 2 to 5 , use a conductive needle to pierce the laminate assembly from the first marking area 401, and the conductive needle pierces the positive electrode coating area 202 of the positive electrode sheet 20, the separator 10, and the negative electrode coating area 302 of the negative electrode sheet 30 in turn, short-circuiting the positive electrode coating area 202 and the negative electrode coating area 302 together to form a positive electrode layer-negative electrode layer internal short circuit. Since the conductivity of the positive and negative electrode materials of the battery is significantly lower than that of the metal material, the positive electrode-negative electrode conductivity is the worst among the short circuit types, and its heat generation capacity is very low. At the same time, since the thermal conductivity of the positive and negative electrode materials of the battery is also significantly lower than that of the metal material, the heat dissipation capacity of the positive electrode-negative electrode internal short circuit is also very poor. Although the heat dissipation capacity of the positive electrode-negative electrode internal short circuit is very poor, due to its low heat generation capacity, the heating (temperature rise) effect of the positive electrode-negative electrode internal short circuit on the battery is generally weak.

[0055] refer to Figure 2 and Figure 5, use a conductive needle to pierce the laminate assembly from the second marking area 402, and the conductive needle sequentially pierces the aluminum foil layer 21 of the blank aluminum foil area 201, the diaphragm 10, and the copper foil layer 31 of the blank copper foil area 301, short-circuiting the aluminum foil layer 21 and the copper foil layer 31 to form a positive electrode current collector aluminum-negative electrode current collector copper internal short circuit. Since the metal material has good electrical conductivity, the aluminum-copper internal short circuit has a strong electrical conductivity and a high heat generation capacity. At the same time, since the metal material has good thermal conductivity, the overall heat dissipation capacity of the aluminum-copper internal short circuit is very strong. Although the heat generation capacity of the aluminum-copper internal short circuit is very high, due to its strong heat dissipation capacity, the heat can be dissipated in time, so overall, the aluminum-copper internal short circuit has a strong heating effect on the battery, but it is lower than the aluminum-negative electrode internal short circuit.

[0056] refer to Figure 2 and Figure 3 , use a conductive needle to pierce the laminate assembly from the third marking area 403, and the conductive needle pierces the aluminum foil layer 21 of the blank aluminum foil area 201, the separator 10, the electrode material layer 32, the copper foil layer 31, and the electrode material layer 32 of the negative electrode coating area 302 in turn, forming a positive electrode current collector aluminum-negative electrode layer internal short circuit. Although the conductivity of the negative electrode material is much lower than that of the metal material, it is still significantly higher than that of the positive electrode material. Therefore, although the conductivity of the aluminum-negative electrode internal short circuit is worse than that of the aluminum-copper internal short circuit, it is higher than the positive electrode-negative electrode internal short circuit and the positive electrode copper internal short circuit, and its heat generation capacity is relatively strong. The thermal conductivity of the negative electrode material is much lower than that of the metal material, and the thermal conductivity of aluminum is lower than that of copper, resulting in poor overall heat dissipation capacity of the aluminum-negative electrode internal short circuit. Because the heat generation capacity of the aluminum-negative electrode internal short circuit is strong and the heat dissipation capacity is poor, the aluminum-negative electrode internal short circuit has a strong heating effect on the battery.

[0057] refer to Figure 5 , use a conductive needle to pierce the laminate assembly from the fourth marking area 404, and the conductive needle pierces the electrode material layer 22, aluminum foil layer 21, electrode material layer 22, and copper foil layer 31 of the blank copper foil area 301 of the positive electrode coating area 202 in turn, forming a positive electrode layer-negative electrode current collector copper internal short circuit. Limited by the conductivity of the battery positive electrode material, the conductivity of the positive electrode-copper internal short circuit is poor, so the heat generation capacity of the positive electrode-copper internal short circuit is low. The thermal conductivity of the positive electrode material is much lower than that of the metal material, but due to the strong thermal conductivity of copper, the overall heat dissipation capacity of the positive electrode-copper internal short circuit is better. Because the heat generation capacity of the positive electrode-copper internal short circuit is low and the heat dissipation capacity is good, the heating effect of the positive electrode-copper internal short circuit on the battery is very weak.

[0058] refer to Figures 4 to 5 , use a conductive needle to pierce the laminated assembly from the fifth marking area 405, and the conductive needle sequentially pierces the aluminum foil layer 21 of the blank aluminum foil area 201, the separator 10, the copper foil layer 31 of the cation and cathode coating area 303, and the electrode material layer 32, forming an internal short circuit between the positive electrode collector aluminum and the negative electrode collector copper, and then contacts the electrode material layer 32 of the negative electrode sheet 30, resulting in a violent reaction with strong heat generation capacity.

[0059] The present invention also discloses a temperature research method for short-circuit thermal runaway of a lithium battery, which includes steps S100 to S400.

[0060] S100, performing thermal runaway simulation according to the thermal runaway simulation method for a short circuit of a lithium battery.

[0061] S200, when the conductive needle pierces, use a thermal imager to record the temperature of the puncture location.

[0062] S300, reference Figure 8 , disassemble the aluminum-plastic film bag, remove the diaphragm 10, and detect the size of the heat shrinkage holes left by acupuncture on the diaphragm 10.

[0063] S400, performing a temperature study based on the size of the heat shrinkage holes and the detection temperature. The specific method of performing the temperature study based on the size of the heat shrinkage holes and the detection temperature is set by the technicians themselves, and the technicians can summarize the rules for verification, and conduct research by associating the size of the heat shrinkage holes with the detection temperature.

[0064] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. A method for simulating thermal runaway of a lithium battery short circuit, characterized in that: include: The lithium battery is disassembled, and the positive electrode sheet and the negative electrode sheet are taken out and cut into preset sizes, and a blank aluminum foil area without electrode material is formed on the first area of ​​the positive electrode sheet, and a blank copper foil area without electrode material is formed on the second area of ​​the negative electrode sheet, so that the positive electrode sheet consists of a blank aluminum foil area and a positive electrode coating area, and the negative electrode sheet consists of a blank copper foil area and a negative electrode coating area; Providing a lithium battery diaphragm of a preset size, and soaking the lithium battery diaphragm in an electrolyte; The positive electrode sheet, the separator soaked with electrolyte, and the negative electrode sheet are stacked in sequence to form a stacked assembly, wherein the separator separates the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from short-circuiting and contacting each other, and realizes a plurality of combinations of the position of part of the blank aluminum foil area corresponding to the position of the negative electrode coating area, the position of part of the blank copper foil area corresponding to the position of the positive electrode coating area, the position of part of the blank aluminum foil area corresponding to the position of part of the blank copper foil area, and the position of part of the positive electrode coating area corresponding to the position of part of the negative electrode coating area; Putting the laminate assembly into an aluminum-plastic film bag; Introducing electrolyte into the aluminum-plastic film bag to ensure ion conduction in the aluminum-plastic film bag; Marking the short-circuit area required by the short-circuit model on the aluminum-plastic film bag; A conductive needle is used to pierce corresponding marked positions along the lamination direction of the lamination assembly to form a preset short-circuit model to perform corresponding thermal runaway simulation.

2. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 1, characterized in that: After the electrolyte is introduced into the aluminum-plastic film bag, a clip is used to clamp the opening of the aluminum-plastic film bag and other outer edge areas except the opening to fix the position of the stacking assembly relative to the aluminum-plastic film bag.

3. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 2, characterized in that: The clip is a metal clip, which is clamped on the aluminum-plastic film bag through an insulating spacer paper and is insulated from the aluminum-plastic film bag.

4. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 1, characterized in that: The marking positions include a first marking area where the projections of the positive electrode sheet and the negative electrode sheet overlap and are offset from the first area and the second area, a second marking area where the negative electrode sheet does not overlap with the projection of the positive electrode sheet and is offset from the first area and the second area, a third marking area where the projections of the positive electrode sheet and the negative electrode sheet overlap and correspond to the first area, and a fourth marking area where the projections of the positive electrode sheet and the negative electrode sheet overlap and correspond to the second area.

5. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 1, characterized in that: The area ratio of the blank aluminum foil area to the positive electrode coating area is less than or equal to 1:25, and the area ratio of the blank copper foil area to the negative electrode coating area is less than or equal to 1:

25.

6. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 1, characterized in that: The projection of the negative electrode sheet covers the projection of the positive electrode sheet, the projection of the diaphragm covers the projection of the negative electrode sheet, one end of the positive electrode sheet and the negative electrode sheet are aligned, and the blank aluminum foil area and the blank copper foil area are respectively located at the two ends of the positive electrode sheet and the negative electrode sheet.

7. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 6, characterized in that: The positive electrode sheet, negative electrode sheet and separator are in the shape of long strips with greater width than length. The separator is wider than the negative electrode sheet and longer than or equal to the negative electrode sheet, and the negative electrode sheet is wider than the positive electrode sheet and longer than or equal to the positive electrode sheet.

8. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 1, characterized in that: The tail of one end of the negative electrode sheet is coated with cathode and anode to form an cathode and anode coated area with cathode materials on one side.

9. The thermal runaway simulation method for a lithium battery short circuit as claimed in claim 1, characterized in that: After the electrolyte is poured into the aluminum-plastic film bag, the aluminum-plastic film bag is sealed.

10. A temperature research method for short-circuit thermal runaway of lithium batteries, characterized in that: Perform thermal runaway simulation according to the thermal runaway simulation method for lithium battery short circuit according to any one of claims 1 to 9; When the conductive needle pierces, a thermal imager is used to record the temperature of the puncture location; The aluminum-plastic film bag is opened, the diaphragm is removed, and the size of the heat shrinkage holes left by needle puncture on the diaphragm is detected; A temperature study is performed based on the size of the heat shrinkage holes and the detection temperature.

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