A method and apparatus for measuring the warping amount of a lithium-ion battery separator

Abstract

This invention discloses a method and apparatus for measuring the warpage of a lithium-ion battery separator. The method involves moving a laser displacement sensor horizontally above a reference plate, with the direction of movement perpendicular to the length direction of the reference plate. The laser emission end of the laser displacement sensor is vertically downward, and the distance between the reference plate and the laser displacement sensor is measured simultaneously during the movement. Then, a separator sample is placed on the reference plate, and the laser displacement sensor moves above the separator sample, while the distance between the separator and the laser displacement sensor is measured simultaneously. Finally, the difference between two distances recorded by the laser displacement sensor at the same position is calculated, thus obtaining the difference in the MD direction and the TD direction of the separator. The maximum values ​​of the difference in the MD direction and the TD direction are the warpage amounts of the separator in the MD and TD directions, respectively.

Description

Technical Field

[0001] This invention relates to a method and device for measuring the warping amount of a lithium-ion battery separator, belonging to the field of lithium battery separator testing technology. Background Technology

[0002] As a crucial material in lithium-ion batteries, the separator's performance and flatness directly impact battery performance and lifespan. On one hand, the separator undergoes deformation during the winding process; on the other hand, regional thickness variations within the separator cause natural edge curling in single-layer separators without external force. This curling can lead to wrinkles during battery winding, short-circuiting the positive and negative electrodes and causing a short circuit. Furthermore, the curled separator can prevent flattening during coating, resulting in incomplete coating (the base film surface is not covered with slurry), affecting battery performance. Therefore, an accurate and efficient detection method is needed to control and adjust the curling amount at the front end to prevent defects at the battery end.

[0003] Announcement No. CN108604657B, entitled "Method for Measuring the Curvature Amount of a Diaphragm, Slitting Device and Curvature Amount Measuring Device," discloses a device and method for measuring the curvature amount of a diaphragm strip. This method involves applying tension along the length of the diaphragm strip parallel to its long side while measuring the curvature amount of the side of the diaphragm strip parallel to its long side. Although slitting the diaphragm is not required before measurement, the diaphragm is subjected to tension from the winding and conveying sections during measurement, which can affect the accuracy of the measurement of the diaphragm curl-up amount.

[0004] An existing technology has a method for detecting the warpage of PCB (printed circuit board) by using a pair of displacement sensors to detect the PCB sample passing through it and calculating the warpage using software. However, this test method requires the test object to be continuously moved. For diaphragms with a thickness of less than 20 micrometers, the diaphragm is easily affected by external factors during the movement process, which can cause the edges to warp, resulting in unreliable test results. Therefore, this method for detecting the warpage of PCB is not suitable for diaphragm testing. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for measuring the warping amount of lithium-ion battery separators, in order to solve the problem that the measurement methods in the prior art are inaccurate or unsuitable for separators with a thickness of micrometers.

[0006] The method for measuring the warping amount of a lithium-ion battery separator of the present invention adopts the following technical solution: A method for measuring the warping amount of a lithium-ion battery separator includes the following steps: (1) placing a reference plate horizontally and keeping the upper surface of the reference plate horizontal; (2) moving a laser displacement sensor horizontally above the reference plate, the direction of movement of the laser displacement sensor being perpendicular to the length direction of the reference plate, the laser emitting end of the laser displacement sensor being vertically downward, and measuring the distance between the reference plate and the laser displacement sensor while the laser displacement sensor is moving, and recording the real-time measured distance value while the laser displacement sensor is moving; (3) cutting a certain length of separator sample along the MD direction of the separator, and cutting the separator sample according to the MD direction and TD direction respectively. Place the membrane flat on the reference plate so that the MD direction or TD direction of the diaphragm is parallel to the moving direction of the laser displacement sensor; (4) The laser displacement sensor moves above the diaphragm sample. The direction of the laser displacement sensor is perpendicular to the length direction of the reference plate. The laser emitting end of the laser displacement sensor is vertically downward. While the laser displacement sensor moves, the distance between the diaphragm and the laser displacement sensor is measured. While the laser displacement sensor moves, the distance value measured in real time is recorded; (5) Calculate the distance difference recorded at the same position in steps (2) and (4) to obtain the difference in the MD direction and the difference in the TD direction. The maximum values ​​of the difference in the MD direction and the difference in the TD direction are the amount of the diaphragm tilted in the MD direction and the TD direction, respectively.

[0007] Before starting steps (2) and (4), initial position calibration is performed. Specifically, the laser displacement sensor is moved horizontally so that the laser point of the laser displacement sensor is moved to the edge of the reference plate until the laser point is tangent to the edge of the reference plate. Then, the spacing measurement steps (2) and (4) are performed.

[0008] After calculating the difference in the MD direction and the difference in the TD direction, the warping curves of the diaphragm in the MD direction and the TD direction are plotted.

[0009] In step (3), the diaphragm sample is placed on the reference plate, and the edge of the diaphragm sample is aligned with the edge of one side of the reference plate.

[0010] When detecting the warping amount in the MD direction, the distance the laser displacement sensor moves in steps (2) and (4) is equal to the width of the diaphragm in the MD direction; when detecting the warping amount in the TD direction, the distance the laser displacement sensor moves in steps (2) and (4) is equal to the width of the diaphragm in the TD direction.

[0011] In step (3), the length of the diaphragm sample is 15cm.

[0012] The lithium-ion battery separator warpage measurement device of the present invention adopts the following technical solution: A lithium-ion battery separator warpage measurement device includes a measuring platform and a reference plate. A horizontally set reference rod is provided on the measuring platform, and support platforms are respectively provided on both sides of the measuring platform. The middle part of the reference plate is located below the reference rod and there is a gap between the reference plate and the reference rod. The two ends of the reference plate are respectively supported on the upper surfaces of the two support platforms. The upper surface of the reference plate is a horizontal plane for placing the separator. A laser displacement sensor that moves horizontally along the reference rod is provided on the reference rod. The laser emitting end of the laser displacement sensor is set vertically downward. A driving mechanism for driving the laser displacement sensor to move is connected to the laser displacement sensor. The laser displacement sensor emits laser light towards the reference plate or the separator sample placed on the reference plate and records the distance between the laser displacement sensor and the laser point. The laser displacement sensor is connected to the control system and sends the detected distance data to the control system. The control system calculates the detected distance data to obtain the separator warpage amount.

[0013] The support frame is equipped with horizontally arranged support rollers, the axis of which is parallel to the moving direction of the laser displacement sensor, and the reference plate is placed on the support rollers.

[0014] The support rollers are steel rollers; one support frame has one steel roller, and another support frame has three steel rollers.

[0015] The beneficial effects of the present invention are: The present invention adopts a detection method in which the laser displacement sensor moves while the object being tested remains stationary. During the testing process, the instrument does not contact the object being tested, and the diaphragm is not damaged or subjected to pressure throughout the process, thus avoiding the problem of diaphragm deformation during the detection process and greatly reducing the impact of the detection method on the detection results. Before each test, the warpage of the reference plate is first measured, followed by the test of the diaphragm sample. The actual warpage of the diaphragm is determined by the absolute value of the difference between the two tests. This operation is performed for each measurement to eliminate the influence of reference plate deformation on the final test results. During testing with this invention, the diaphragm is not affected by external forces, and the influence of reference plate deformation on the test is also avoided, resulting in accurate warpage detection results.

[0016] After the lifting amount is detected, the separators are evaluated and screened based on the measured lifting amount. This avoids the separators from not being able to flatten during the coating process, which would lead to incomplete coating and affect battery performance. It also prevents separators with large lifting amounts from entering the production line, where they may wrinkle during winding, causing short circuits between the positive and negative electrodes and resulting in battery short circuits. Meanwhile, separators that do not exceed the standard can be used normally, avoiding product waste. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a lithium-ion battery separator warping measurement device according to an embodiment of the present invention; Figure 2 yes Figure 1 A plan view.

[0018] In the figure: 1-measuring platform, 2-reference plate, 3-reference rod, 4-laser displacement sensor, 5-support platform, 6-support roller, 7-diaphragm sample. Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] The present invention relates to a method for measuring the warping amount of a lithium-ion battery separator, which employs, as follows: Figures 1 to 2 The measuring device includes a measuring stand 1 and a reference plate 2. A horizontally positioned reference rod 3 is mounted on the measuring stand 1. Support stands 5 are located on both sides of the measuring stand 1. The middle of the reference plate 2 is located below the reference rod 3 and is spaced apart from it. Both ends of the reference plate 2 are supported on the upper surfaces of the two support stands 5. The upper surface of the reference plate 2 is a horizontal plane for placing the diaphragm. A laser displacement sensor 4, which moves horizontally along the reference rod 3, is mounted on the reference rod 3. The laser emitting end of the laser displacement sensor 4 is vertically downward. The upper part is connected to a drive mechanism for driving the laser displacement sensor 4 to move. The method for measuring the amount of lithium-ion battery separator warping includes the following steps: (1) placing the reference plate 2 on two support frames 5 and keeping the upper surface of the reference plate 2 horizontal; (2) the drive mechanism drives the laser displacement sensor 4 to move horizontally along the reference rod 3, so that the laser point of the laser displacement sensor 4 moves to the edge of one side of the reference plate 2 until the laser point is tangent to the edge of the reference plate 2; (3) the drive mechanism drives the laser displacement sensor 4 to move toward the other side of the reference plate 2, and the laser displacement sensor 4 moves... Simultaneously measure the distance between the reference plate 2 and the laser displacement sensor 4. While the laser displacement sensor 4 moves, it sends the real-time measured distance value to the control system. (4) Cut a certain length of diaphragm sample 7 along the MD direction of the diaphragm. The length of the diaphragm sample is 15cm. Place the diaphragm sample flat on the reference plate 2 in the MD direction and TD direction respectively, so that the MD direction or TD direction of the diaphragm is parallel to the moving direction of the laser displacement sensor 4. Then repeat step (2). (5) Drive the laser displacement sensor 5 to move towards the other side of the reference plate 2. While the laser displacement sensor 5 moves, measure the distance between the diaphragm sample 7 and the laser displacement sensor 5. While the laser displacement sensor 5 moves, it sends the real-time measured distance value to the control system. (6) Use the control system to calculate the distance difference recorded at the same position in steps (3) and (5), so as to obtain the MD direction difference and the TD direction difference. After the control system calculates the MD direction difference and the TD direction difference, draw the curve of the diaphragm in the MD direction and the TD direction. The maximum values ​​of the MD direction difference and the TD direction difference are the diaphragm in the MD direction and the TD direction, respectively.

[0021] When detecting the warping amount in the MD direction, the distance the laser displacement sensor moves in steps (3) and (5) is equal to the width of the diaphragm in the MD direction; when detecting the warping amount in the TD direction, the distance the laser displacement sensor moves in steps (3) and (5) is equal to the width of the diaphragm in the TD direction.

[0022] In step (4), the diaphragm sample can be placed on the reference plate, and the edge of the diaphragm sample should be aligned with the edge of one side of the reference plate. If the diaphragm sample is placed in the middle of the reference plate, the distance between the diaphragm sample and the two sides of the reference plate can be recorded first.

[0023] The control system can use a Siemens laser ranging system, and the specific operation process is as follows: A: Turn on the instrument power knob, and it will automatically enter the initial screen. Click "Enter System" to enter the measurement screen. B: Place the reference plate horizontally on the support roller, ensuring that both ends of the reference plate are supported by the support roller, and keep the reference plate flat with the roller surface; C: Parameter settings: Select "Median Value Reference" for the measurement reference mode, and select the measurement width according to the actual width; D: After setting the parameters, the drive mechanism moves the laser point to the right edge of the reference plate, making the laser point tangent to the reference edge. Click on laser measurement, and the laser displacement sensor starts automatic measurement. During measurement, results higher than the median reference value are displayed as positive values, and results lower than the median reference value are displayed as negative values. E: After the test is completed, the difference in the intermediate trend chart is the test value; F: Place the sample flat on the test reference plate in the MD and TD directions respectively, repeat step D, and record the difference in the MD direction and the difference in the TD direction, which are the diaphragm test values. G: After the test is completed, the absolute value of the difference between the diaphragm test value and the reference plate test value is used to measure the actual diaphragm warping amount.

[0024] After measurement, the test value H is determined by taking the absolute value of the maximum and minimum values ​​that is the largest. The specific process is as follows: First, test the reference plate. If the warping of the reference plate at a certain position is H1, place the diaphragm on the reference plate and measure it. The value measured at the same position of the diaphragm is H2. Finally, the warping at that point is H = ABS(H1-H2). If H is less than the set standard, the warping meets the requirements. If H is greater than the set standard, the warping does not meet the requirements.

[0025] This invention uses a laser displacement sensor to monitor the movement distance and generate a separator lift curve. A lift standard can be established, and separators can be evaluated and screened based on the measured lift. This avoids separator lift causing incomplete coating during the coating process, which could affect battery performance. It also prevents separators with excessive lift from entering the production line, where wrinkles during winding could lead to short circuits between the positive and negative electrodes. Separators that do not exceed the standard are used normally, avoiding product waste. This method is accurate, reliable, and simple to operate, and has been applied to Panasonic products.

[0026] An embodiment of the present invention provides a measuring device for measuring the amount of lithium-ion battery separator warping, such as... Figures 1 to 2 As shown, the lithium-ion battery separator warping measurement device of this embodiment includes a measuring platform 1 and a reference plate 2. The measuring platform 1 is provided with a horizontally arranged reference rod 3. Supporting platforms 5 are respectively provided on both sides of the measuring platform 1. The middle part of the reference plate 2 is located below the reference rod 3 and there is a gap between the reference plate 2 and the reference rod 3. The two ends of the reference plate 2 are respectively supported on the upper surfaces of the two supporting platforms 5. The upper surface of the reference plate 2 is a horizontal plane for placing the separator. A laser displacement sensor 4 is provided on the reference rod 3 and moves horizontally along the reference rod. The laser emitting end of the laser displacement sensor 4 is set vertically downward. A driving mechanism for driving the laser displacement sensor 4 to move is connected to the laser displacement sensor 4. The driving mechanism is not shown in the figure. It can be a form in which a motor drives a lead screw and nut mechanism to drive the laser displacement sensor to move.

[0027] In this embodiment, the support frame 5 is provided with a horizontally arranged support roller 6, the axis of which is parallel to the moving direction of the laser displacement sensor 4, and the reference plate 2 is placed on the support roller 6. The support roller 6 is a steel roller, with one steel roller on one support frame and three steel rollers on another support frame.

[0028] The laser displacement sensor 4 is used to emit a laser to the reference plate 2 or the diaphragm sample 7 placed on the reference plate 2, and to record the distance between the laser displacement sensor and the laser point. The laser displacement sensor is connected to the control system (not shown in the figure) and sends the detected distance data to the control system. The control system calculates the diaphragm warping amount after processing the detected distance data.

[0029] Diaphragm warpage is used to describe the degree of curvature of a planar object in space. Numerically, it is defined as the distance between the two points where the measured object has the largest difference in height relative to the reference plate. Diaphragm warpage in the MD direction: The distance between the two points where the laser displacement sensor scans the diaphragm sample along the TD direction and has the largest difference in height relative to the reference plate. Diaphragm warpage in the TD direction: The distance between the two points where the laser displacement sensor scans the diaphragm sample along the MD direction and has the largest difference in height relative to the reference plate.

[0030] In practical use, the drive mechanism first moves the laser displacement sensor from one side of the reference plate to the other. While moving, the laser displacement sensor measures the distance between itself and the reference plate, sending the real-time distance measurement to the control system. Then, the diaphragm sample to be tested is placed on the reference plate (the distance between the diaphragm sample and both sides of the reference plate can be recorded). The drive mechanism moves the laser displacement sensor from one side of the reference plate to the other, measuring the distance between itself and the diaphragm sample. The control system calculates the distance difference recorded at the same position during the two distance measurements; the maximum value is the diaphragm warping amount. After calculating the difference, the system simultaneously plots the distance difference curve, thus obtaining the profile curve of the diaphragm sample.

[0031] The embodiments and descriptions above are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method of measuring the amount of buckling of a lithium-ion battery separator, characterized by, It uses a lithium-ion battery separator warp measurement device. The measurement device includes a measuring platform and a reference plate. A horizontally set reference rod is provided on the measuring platform. Supporting platforms are provided on both sides of the measuring platform. The middle part of the reference plate is located below the reference rod and there is a gap between the reference rod and the reference plate. The two ends of the reference plate are supported on the upper surfaces of the two supporting platforms. The upper surface of the reference plate is a horizontal plane for placing the separator. A laser displacement sensor that moves horizontally along the reference rod is provided on the reference rod. The laser emission end of the laser displacement sensor is set vertically downward. A driving mechanism for driving the laser displacement sensor to move is connected to the laser displacement sensor. The laser displacement sensor emits laser to the reference plate or the separator sample placed on the reference plate and records the distance between the laser displacement sensor and the laser point. The laser displacement sensor is connected to the control system and sends the detected distance data to the control system. The control system calculates the detected distance value to obtain the separator warp amount. The method for measuring the lithium-ion battery separator warp amount includes the following steps: (1) Place the reference plate horizontally and keep the upper surface of the reference plate horizontal; (2) The laser displacement sensor on the reference plate (2) Move horizontally, the direction of the laser displacement sensor is perpendicular to the length direction of the reference plate, and the laser emission end of the laser displacement sensor is vertically downward. While the laser displacement sensor moves, the distance between the reference plate and the laser displacement sensor is measured. While the laser displacement sensor moves, the distance value measured in real time is recorded. (3) Cut a certain length of diaphragm sample along the MD direction of the diaphragm, and place the diaphragm sample flat on the reference plate in the MD direction and TD direction respectively, so that the MD direction or TD direction of the diaphragm is parallel to the direction of the laser displacement sensor. (4) Move the laser displacement sensor above the diaphragm sample, the direction of the laser displacement sensor is perpendicular to the length direction of the reference plate, and the laser emission end of the laser displacement sensor is vertically downward. While the laser displacement sensor moves, the distance between the diaphragm and the laser displacement sensor is measured. While the laser displacement sensor moves, the distance value measured in real time is recorded. (5) Calculate the distance difference recorded at the same position in steps (2) and (4), so as to obtain the difference in the MD direction and the difference in the TD direction. The maximum values ​​of the difference in the MD direction and the difference in the TD direction are the amount of the diaphragm tilted in the MD direction and the TD direction, respectively.

2. The method of measuring the amount of buckling of a lithium-ion battery separator according to claim 1, wherein: Before starting steps (2) and (4), initial position calibration is performed. Specifically, the laser displacement sensor is moved horizontally so that the laser point of the laser displacement sensor is moved to the edge of the reference plate until the laser point is tangent to the edge of the reference plate. Then, the spacing measurement steps (2) and (4) are performed.

3. The method of claim 1, wherein: After calculating the difference in the MD direction and the difference in the TD direction, the warping curves of the diaphragm in the MD direction and the TD direction are plotted.

4. The method of claim 1, wherein: In step (3), the diaphragm sample is placed on the reference plate, and the edge of the diaphragm sample is aligned with the edge of one side of the reference plate.

5. The method of measuring the amount of buckling of a lithium-ion battery separator of claim 4, wherein: When detecting the warping amount in the MD direction, the distance the laser displacement sensor moves in steps (2) and (4) is equal to the width of the diaphragm in the MD direction.

6. The method of claim 4, wherein: When detecting the warping in the TD direction, the distance the laser displacement sensor moves in steps (2) and (4) is equal to the width of the diaphragm in the TD direction.

7. The method for measuring the warping amount of a lithium-ion battery separator according to claim 1, characterized in that: In step (3), the length of the diaphragm sample is 15cm.

8. The method of claim 1, wherein: The support frame is equipped with horizontally arranged support rollers, the axis of which is parallel to the moving direction of the laser displacement sensor, and the reference plate is placed on the support rollers.

9. The method of claim 8, wherein: The support rollers are steel rollers; one support frame has one steel roller, and another support frame has three steel rollers.

Images