A lithium-ion battery diaphragm wrinkle testing device and wrinkle detection method

Abstract

The present invention relates to the technical field of lithium-ion battery diaphragm materials, and specifically to a lithium-ion battery diaphragm wrinkle testing device and wrinkle detection method, the lithium-ion battery diaphragm wrinkle testing device comprises a water bath, a bearing assembly and a gravity pressing block, the water bath is injected with an organic solution; the bearing assembly is located in the water bath, comprises a first plane plate and a second plane plate, the diaphragm to be tested is clamped between the first plane plate and the second plane plate; the gravity pressing block bears pressure on the bearing assembly. By testing the dry lithium-ion battery diaphragm under the condition of being soaked in an organic solvent, after being clamped by the bearing assembly and statically pressed by the gravity pressing block, and then heated in a water bath, the wrinkles generated by the diaphragm during the organic solution soaking process and the hot pressing process can be effectively simulated, so that the wrinkles generated by the battery diaphragm can be detected in time, the wrinkle resistance of the diaphragm can be evaluated, and the damage of the diaphragm wrinkles to the battery can be effectively prevented.

Description

Technical Field

[0001] The invention relates to the technical field of lithium-ion battery diaphragm materials, and in particular to a lithium-ion battery diaphragm wrinkle testing device and a wrinkle detection method. Background Art

[0002] Currently, the most common commercial lithium-ion battery separators are mainly polyolefin separators, which have dominated the lithium-ion battery market due to their high mechanical strength, good electrochemical stability, uniform pore structure and outstanding cost advantages. Polyolefin separators for lithium-ion batteries are mainly divided into dry-process separators, wet-process separators and ceramic separators. With the increase in the market share of new energy vehicles, the demand for power cells is growing rapidly, and the energy storage market is growing rapidly. Based on this, the dry-process separators are increasing their market share in the energy storage and power battery fields due to their cost and safety advantages.

[0003] Thinning is an inevitable trend in the development of dry-process diaphragms. The application of power-type dry-process diaphragms has gradually changed from the initial 32μm to 25μm, 24μm, and 22μm. Since 2018, the 20μm dry-process diaphragm has gradually matured in the field of power batteries and is moving towards large-scale application of 14μm and 12μm. In the future, the product thickness of dry-process diaphragms will gradually move from 12μm to 10μm and 9μm, but as the thickness of the diaphragm decreases, the probability of wrinkles in the diaphragm increases.

[0004] The reasons why the diaphragm wrinkles are as follows: the dry diaphragm has a fibrous structure, which is divided into a crystalline area and an amorphous area. During the battery filling process, when the electrolyte penetrates the crystalline area and the amorphous area in the diaphragm, the capillary action will cause the diaphragm to bulge at the front end in the direction of liquid flow. After the bulge, when the battery is hot-pressed, a gap will appear between the diaphragm and the electrode, resulting in macroscopic wrinkles. The smaller the thickness of the diaphragm, the more obvious the wrinkle deformation.

[0005] Hazards of diaphragm wrinkles: When the diaphragm is wrinkled, there will be multiple layers of diaphragms at the wrinkles in the interface with the pole piece, resulting in defects in the interface between the diaphragm and the pole piece. The defects will cause uneven distribution of the internal resistance of the battery. Local overcharge or over-discharge may occur in places with low internal resistance, which will affect the consistency and cycle performance of the battery. At the same time, diaphragm wrinkle defects can easily cause high-voltage batteries to catch fire, increase the risk of battery unsafety, and even lead to electric vehicle recalls in severe cases. At present, there is no effective detection method and clear indicators to evaluate the performance of diaphragm wrinkles. In order to prevent the safety risks caused by battery wrinkles, the wrinkle phenomenon of dry diaphragms needs to be detected in advance to prevent it from causing harm to downstream. Summary of the invention

[0006] The purpose of the present invention is to provide a lithium-ion battery separator wrinkle testing device and wrinkle detection method, which can simulate the situation in which the battery separator produces wrinkles in actual use, detect the wrinkle situation, and evaluate the anti-wrinkle performance of the battery separator.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is to provide a lithium-ion battery diaphragm wrinkle testing device, including a water bath, a load-bearing assembly and a gravity pressure block, wherein an organic solution is injected into the water bath; the load-bearing assembly is located in the water bath, and includes a first plane plate and a second plane plate, and the diaphragm to be tested is clamped between the first plane plate and the second plane plate; the gravity pressure block bears pressure on the load-bearing assembly.

[0008] Furthermore, there are multiple gravity pressing blocks, and the overall center of gravity of the multiple gravity pressing blocks and the center of the bearing assembly are located in the same vertical direction.

[0009] Furthermore, the lithium-ion battery diaphragm wrinkle testing device also includes a pad, which is located at the bottom end of the water bath, and the bearing assembly is located on the pad.

[0010] Furthermore, there are multiple cushion blocks, and the overall center of the multiple cushion blocks, the overall center of gravity of the multiple gravity pressure blocks and the center of the bearing assembly are all located in the same vertical direction.

[0011] Furthermore, the orthographic projection surfaces of the first plane plate and the second plane plate completely cover the orthographic projection surface of the diaphragm to be tested.

[0012] Furthermore, the present application also provides a lithium-ion battery separator wrinkle detection method, using the above-mentioned test device, the detection method steps are as follows:

[0013] Cut the diaphragm to be tested according to the preset size;

[0014] The diaphragm to be tested is sandwiched between the first flat plate and the second flat plate and then directly placed in a water bath;

[0015] Placing a gravity pressing block on the load-bearing component;

[0016] Slowly pour the organic solvent into the water bath, and stop adding the organic solvent at least when the organic solvent covers the supporting component;

[0017] The water bath heating temperature is set to simulate the environment of the diaphragm in the heating process. When the temperature of the organic solvent is detected to reach the specified temperature, the timing starts; when the timing time reaches the preset time, the water bath heating is stopped and the organic solvent is emptied;

[0018] After the temperature of the water bath has dropped, the load-bearing assembly is taken out and the diaphragm to be tested therein is taken out for natural drying. After the diaphragm to be tested is dried, the diameter of the wrinkles thereon is measured with a ruler, and the number of wrinkles is recorded.

[0019] Furthermore, before placing the bearing assembly in the water bath, a plurality of pads are placed at the bottom of the water bath, and after the pads are placed stably, the bearing assembly is placed directly on the pads.

[0020] Furthermore, there are multiple gravity pressing blocks. When placing the gravity pressing blocks, the gravity pressing blocks are first placed at the center of the load-bearing component, and then the remaining gravity pressing blocks are successively placed at the edge positions of the load-bearing component.

[0021] Furthermore, the first plane plate and the second plane plate are made of glass plates of equal size, and the diaphragm to be tested is sandwiched between the two glass plates with its edge not protruding from the edge of the glass plates.

[0022] Furthermore, in the step of placing the support assembly in the water bath, a space is left between the edge of the support assembly and the side wall of the water bath to avoid direct contact.

[0023] The beneficial effects of the present invention are:

[0024] 1. By testing the dry lithium-ion battery diaphragm under the condition of being soaked in organic solvent, clamped by the load-bearing component and statically pressed by the gravity block, and then heated in a water bath, the wrinkles generated by the diaphragm during the organic solution soaking process and the hot pressing process can be effectively simulated, which is convenient for timely detection of wrinkles on the battery diaphragm, and the anti-wrinkle performance of the diaphragm can be evaluated, which can effectively prevent the damage of diaphragm wrinkles to the battery.

[0025] 2. The wrinkle test device also includes a pad, which is located at the bottom of the water bath, and the bearing assembly is located on the pad. By setting the pad, the bearing assembly can be prevented from directly contacting the bottom of the water bath, so that the diaphragm to be tested is fully immersed in the organic solution for water bath heating, so that the diaphragm to be tested is heated evenly, effectively ensuring the test environment.

[0026] 3. The orthographic projection surfaces of the first plane plate and the second plane plate completely cover the orthographic projection surface of the diaphragm to be tested, so as to avoid the diaphragm to be tested from curling and warping during the test, thereby affecting the accuracy of the test.

[0027] 4. Currently, there is no effective method for detecting diaphragm wrinkles. In the lithium-ion battery diaphragm wrinkle detection method of the present application, the use environment of the battery diaphragm is first simulated to test it to cause wrinkles, and then the wrinkles are measured. This can intuitively simulate the conditions for the diaphragm to wrinkle in the battery, and the wrinkle condition of the diaphragm can be tested in advance, and the anti-wrinkle performance of the diaphragm can be evaluated, effectively preventing the damage of diaphragm wrinkles to the battery. The above wrinkle detection method fills the gap in the detection of diaphragm wrinkles and is representative. In addition, the test device is simple and easy to obtain, and the detection method is simple to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic diagram of the overall structure of a lithium-ion battery separator wrinkle testing device provided in Example 1 of the present invention;

[0030] Figure 2 A step diagram of a lithium-ion battery separator wrinkle detection method provided in Example 2 of the present invention.

[0031] Description of reference numerals:

[0032] 1. Water bath; 11. Organic solvent; 2. Carrying assembly; 21. First plane plate; 22. Second plane plate; 3. Gravity pressure block; 4. Cushion block; 5. Diaphragm to be tested. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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 are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1

[0038] Reference Figure 1 A lithium-ion battery diaphragm wrinkle test device provided as an embodiment of the present invention includes a water bath 1, a bearing assembly 2 and a gravity pressing block 3, wherein an organic solvent 11 is injected into the water bath 1; the bearing assembly 2 is located in the water bath 1, and the bearing assembly 2 includes a first plane plate 21 and a second plane plate 22, and a diaphragm 5 to be tested is sandwiched between the first plane plate 21 and the second plane plate 22; the gravity pressing block 3 bears pressure on the bearing assembly 2.

[0039] By testing the dry lithium-ion battery diaphragm under the condition of being soaked in an organic solvent 11, and then being clamped by the support component 2 and statically pressed by the gravity pressing block 3 and then heated in a water bath, the wrinkles generated by the diaphragm during the organic solution soaking process and the hot pressing process can be effectively simulated, which facilitates the timely detection of wrinkles on the battery diaphragm, can evaluate the anti-wrinkle performance of the diaphragm, and can effectively prevent the damage of diaphragm wrinkles to the battery.

[0040] Specifically, the wrinkle test device also includes a pad 4, which is located at the bottom of the water bath 1, and the bearing assembly 2 is located on the pad 4. By providing the pad 4, the bearing assembly 2 can be prevented from directly contacting the bottom of the water bath 1, so that the diaphragm 5 to be tested is fully immersed in the organic layer for water bath heating, so that the diaphragm 5 to be tested is evenly heated, and the test environment is effectively guaranteed. The orthographic projection surface of the first plane plate 21 and the second plane plate 22 completely covers the orthographic projection surface of the diaphragm 5 to be tested. In this embodiment, the first plane plate 21 and the second plane plate 22 are made of glass plates of equal size, and the surface of the glass plates is flat and smooth, which can be better pressed and fitted with the diaphragm 5 to be tested. The diaphragm 5 to be tested is sandwiched between the two glass plates and the edge does not protrude from the edge of the glass plate, so as to avoid the diaphragm 5 to be tested from curling and warping during the test and affecting the accuracy of the test.

[0041] As a variable embodiment, the first plane plate 21 and the second plane plate 22 may also be structures of unequal size, and it is only necessary to ensure that the orthographic projection surface of the first plane plate 21 and the second plane plate 22 completely covers the orthographic projection surface of the diaphragm 5 to be tested.

[0042] In this embodiment, there are multiple gravity blocks 3, and the center of gravity of the multiple gravity blocks 3 and the center of the load-bearing assembly 2 are located in the same vertical direction. There are also multiple cushion blocks 4, and the overall center of the multiple cushion blocks 4, the overall center of gravity of the multiple gravity blocks 3 and the center of the load-bearing assembly 2 are all located in the same vertical direction. On the one hand, the stability of the placement of the load-bearing assembly 2 can be ensured to avoid tipping over. On the other hand, the pressure of the gravity blocks 3 on the load-bearing assembly 2 is also relatively uniform, so that the diaphragm 5 to be tested is evenly compressed, effectively simulating the conditions of the diaphragm wrinkling in the battery. The organic solvent 11 uses anhydrous ethanol, which is low-cost, easy to obtain, and pollution-free.

[0043] Example 2

[0044] As a lithium ion battery diaphragm wrinkle detection method provided by an embodiment of the present invention, the test device described in Example 1 is used. The lithium ion battery diaphragm wrinkle test device is described in detail in Example 1, so it is not repeated here. The detection method steps are as follows:

[0045] S10: cutting the diaphragm 5 to be tested according to a preset size;

[0046] S20: The diaphragm 5 to be tested is sandwiched between the first flat plate 21 and the second flat plate 22 and then directly placed in the water bath 1;

[0047] S30: placing the gravity pressing block 3 on the bearing assembly 2;

[0048] S40: slowly pouring the organic solvent 11 into the water bath 1, and stopping the addition of the organic solvent 11 at least when the organic solvent 11 covers the supporting component 2;

[0049] S50: Setting the water bath heating temperature to simulate the environment of the diaphragm in the heating process, and starting the timing when it is detected that the temperature of the organic solvent 11 reaches the specified temperature; when the timing time reaches the preset time, stopping the water bath heating and draining the organic solvent 11;

[0050] S60: After the temperature of the water bath 1 drops, the bearing assembly 2 is taken out and the diaphragm 5 to be tested therein is taken out for natural drying. After the diaphragm 5 to be tested is dried, the diameter of the wrinkles on the diaphragm 5 is measured with a ruler, and the number of wrinkles is recorded.

[0051] Specifically, in step S10 , the preset size may be 50 cm×80 cm, and may be specifically set according to the size of the water bath 1 .

[0052] In step S20, the first plane plate 21 and the second plane plate 22 are made of equal-sized glass plates, and the surface of the glass plates is flat and smooth, which can be better pressed and fitted with the diaphragm to be tested 5. The diaphragm to be tested 5 is sandwiched between the two glass plates and the edge does not protrude from the edge of the glass plate, so as to avoid the diaphragm to be tested 5 from curling and warping during the test and affecting the accuracy of the test. Before placing the bearing assembly 2 in the water bath 1, a plurality of pads 4 are placed at the bottom of the water bath 1, and the bearing assembly 2 is directly placed on the pads 4 after the pads 4 are placed steadily. By setting the pads 4, the bearing assembly 2 can be prevented from directly contacting the bottom of the water bath 1, so that the diaphragm to be tested 5 is fully immersed in the organic easy to be heated in a water bath, so that the diaphragm to be tested 5 is heated evenly, and the test environment is effectively guaranteed. Among them, the pads 4 can also be fixed on the bottom wall of the water bath 1 by bonding. In the process of placing the bearing assembly 2 in the water bath 1, there is space between the edge of the bearing assembly 2 and the side wall of the water bath 1 to avoid direct contact.

[0053] In step S30, there are multiple gravity pressing blocks 3. When placing the gravity pressing blocks 3, first place the gravity pressing block 3 at the center of the load-bearing assembly 2, and then place the remaining gravity pressing blocks 3 at the edge of the load-bearing assembly 2, which can effectively prevent the gravity pressing blocks 3 from overturning the load-bearing assembly 2. After the gravity pressing blocks 3 are placed, it is ensured that the overall center of the multiple cushion blocks 4, the overall center of gravity of the multiple gravity pressing blocks 3, and the center of the load-bearing assembly 2 are all located in the same vertical direction. On the one hand, the stability of the placement of the load-bearing assembly 2 can be ensured to avoid tipping over. On the other hand, the pressure of the gravity pressing blocks 3 on the load-bearing assembly 2 is also relatively uniform, so that the diaphragm 5 to be tested is evenly compressed, effectively simulating the condition of the diaphragm wrinkling in the battery.

[0054] In step S40, the side wall of the water bath 1 is provided with scale lines, and the organic solvent 11 is anhydrous ethanol, which is low in cost, easy to obtain, and pollution-free. In this step, the addition of the organic solvent 11 can be stopped when the anhydrous ethanol submerges the load-bearing component 2 and is 5-10 scale lines higher than the load-bearing component. Considering the boiling of anhydrous ethanol heated in a water bath, the anhydrous ethanol should not only submerge the load-bearing component 2, but also be slightly higher than the load-bearing component 2, so as to ensure that the diaphragm 5 to be tested on the load-bearing component 2 is effectively heated in a water bath.

[0055] In step S50, the water bath heating temperature can be set to 60°, which can simulate the environment of the diaphragm in the hot pressing process. When the ethanol temperature in the water bath pot 1 reaches 60° during the heating process, the timing starts. The preset duration of the timing time is 30 minutes, that is, after 30 minutes of timing, the water bath heating is stopped and the anhydrous ethanol is emptied. In the process of emptying the anhydrous ethanol, burns should be prevented.

[0056] In step S60, although the anhydrous ethanol has been emptied, the temperature of the water bath 1 and the bearing assembly 2 is still high. Therefore, after waiting for the temperature of the water bath 1 and the bearing assembly 2 to drop, the bearing assembly 2 is taken out and the diaphragm 5 to be tested is taken out for natural drying. Natural drying means placing the diaphragm at room temperature without any drying treatment and waiting for automatic drying. After the diaphragm 5 to be tested is dried, the diameter of the wrinkles on it is measured with a ruler, and the number of wrinkles is recorded. The standard of wrinkles can be formulated according to the size of the diaphragm, the diameter of the wrinkles and the number of wrinkles in the test, and then it is judged whether the wrinkle standard of the current diaphragm 5 to be tested meets the standard.

[0057] Currently, there is no effective method for detecting diaphragm wrinkles. In the lithium-ion battery diaphragm wrinkle detection method of the present application, the use environment of the battery diaphragm is first simulated to test it to make it wrinkle, and then the wrinkle condition is measured. This can intuitively simulate the conditions for the diaphragm to wrinkle in the battery, and the wrinkle condition of the diaphragm can be tested in advance, and the anti-wrinkle performance of the diaphragm can be evaluated, effectively preventing the damage of diaphragm wrinkles to the battery. The above wrinkle detection method fills the gap in the detection of diaphragm wrinkles and is representative. In addition, the test device is simple and easy to obtain, and the detection method is simple to operate.

[0058] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium-ion battery separator wrinkle test device, characterized in that: include: A water bath (1) into which an organic solution is injected; A bearing assembly (2) is located in the water bath (1), comprising a first plane plate (21) and a second plane plate (22), wherein the diaphragm to be tested (5) is sandwiched between the first plane plate (21) and the second plane plate (22); A gravity pressing block (3) is placed on the bearing assembly (2); Slowly pouring an organic solvent (11) into a water bath (1), and stopping the addition of the organic solvent (11) when the organic solvent (11) at least covers the supporting component (2); The water bath heating temperature is set to simulate the environment of the diaphragm in the heating process. When it is detected that the temperature of the organic solvent (11) reaches the specified temperature, the timing is started; when the timing time reaches the preset time, the water bath heating is stopped and the organic solvent (11) is emptied.

2. The lithium-ion battery separator wrinkle testing device according to claim 1, characterized in that: There are a plurality of gravity pressing blocks (3), and the overall center of gravity of the plurality of gravity pressing blocks (3) and the center of the bearing assembly (2) are located in the same vertical direction.

3. The lithium-ion battery separator wrinkle testing device according to claim 2, characterized in that: It also comprises a cushion block (4), wherein the cushion block (4) is located at the bottom end of the water bath pot (1), and the bearing assembly (2) is located on the cushion block (4).

4. The lithium-ion battery separator wrinkle testing device according to claim 3, characterized in that: There are a plurality of cushion blocks (4), and the overall center of the plurality of cushion blocks (4), the overall center of gravity of the plurality of gravity pressure blocks (3) and the center of the bearing assembly (2) are all located in the same vertical direction.

5. The lithium-ion battery separator wrinkle testing device according to any one of claims 1 to 4, characterized in that: The orthographic projection surfaces of the first plane plate (21) and the second plane plate (22) completely cover the orthographic projection surface of the diaphragm (5) to be tested.

6. A method for detecting wrinkles in a lithium-ion battery separator, characterized in that: Using the test device described in any one of claims 1 to 5, the detection method steps are as follows: Cutting the diaphragm (5) to be tested according to a preset size; The diaphragm to be tested (5) is clamped between the first plane plate (21) and the second plane plate (22) and then directly placed in the water bath (1); Placing the gravity pressing block (3) on the bearing assembly (2); Slowly pouring an organic solvent (11) into a water bath (1), and stopping the addition of the organic solvent (11) when the organic solvent (11) at least covers the supporting component (2); The water bath heating temperature is set to simulate the environment of the diaphragm in the heating process, and when it is detected that the temperature of the organic solvent (11) reaches a specified temperature, the timing is started; when the timing time reaches a preset time, the water bath heating is stopped and the organic solvent (11) is emptied; After the temperature of the water bath (1) drops, the support assembly (2) is taken out and the diaphragm (5) to be tested therein is taken out for natural drying. After the diaphragm (5) to be tested is dried, the diameter of the wrinkles on the diaphragm (5) is measured with a ruler and the number of wrinkles is recorded.

7. The lithium-ion battery separator wrinkle detection method according to claim 6, characterized in that: Before placing the supporting component (2) in the water bath (1), a plurality of pads (4) are placed at the bottom of the water bath (1). After the pads (4) are placed stably, the supporting component (2) is directly placed on the pads (4).

8. The lithium-ion battery separator wrinkle detection method according to claim 7, characterized in that: There are multiple gravity pressing blocks (3). When placing the gravity pressing blocks (3), the gravity pressing blocks (3) are first placed at the center of the bearing assembly (2), and then the remaining gravity pressing blocks (3) are successively placed at the edge of the bearing assembly (2).

9. The lithium-ion battery separator wrinkle detection method according to claim 6, characterized in that: The first plane plate (21) and the second plane plate (22) are made of glass plates of equal size, and the diaphragm (5) to be tested is sandwiched between the two glass plates with its edge not protruding from the edge of the glass plates.

10. The lithium-ion battery separator wrinkle detection method according to claim 6, characterized in that: In the step of placing the supporting component (2) in the water bath (1), a space is left between the edge of the supporting component (2) and the side wall of the water bath (1) to avoid direct contact.

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