A diaphragm powder drop test method and test device

Abstract

The invention discloses a diaphragm powder loss testing method. The method comprises the following steps: selecting a coated diaphragm with an area of ​​A0, laying the coated diaphragm flat and fixed on a loading platform, and contacting the coated diaphragm with the upper surface of a test receiver electrically connected to a resistance tester; measuring the coating diaphragm resistance R0 by contacting the coating with a probe electrically connected to the resistance tester, and calculating the coating diaphragm surface resistance R0'; blowing air through an air blowing device to impact the coating and remove powder attached to the diaphragm, measuring the powder loss diaphragm resistance R1, and calculating the powder loss diaphragm surface resistance R1'; selecting an uncoated diaphragm with an area of ​​A2, measuring the uncoated diaphragm resistance R2, and calculating the uncoated diaphragm surface resistance R2'; and finally calculating the diaphragm powder loss rate by using the formula (R0'-R1') / (R0'-R2')*100%. The invention adopts a resistance testing method to measure the diaphragm powder loss rate, has small error and high precision, and can be used to formulate a diaphragm powder loss detection standard. The invention also discloses a diaphragm powder loss testing device.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragm production, and in particular to a diaphragm powder loss testing method and a testing device thereof. Background Art

[0002] In the lithium-ion battery industry, separators are a crucial component. Slurry coating plays a crucial role in producing functional separators. However, different slurry formulations exhibit significant variations in their adhesion to the separator. Poor coating quality results in powder shedding. Large particles can puncture the separator during the hot pressing phase of the battery cell, causing a direct short circuit between the positive and negative electrodes. Therefore, the quality of the separator surface coating directly impacts the production quality of lithium-ion battery cells.

[0003] At present, the diaphragm industry has not clearly established a standard for diaphragm powder loss detection. The conventional detection method is to use fingers to wipe the diaphragm surface with a certain pressure, and judge the degree of diaphragm powder loss based on the color depth of the powder sticking on the fingers. This has the following problems: 1. Different people use different forces, and the judgment results are different; 2. The roughness of different people's fingers is different, and the possibility of touching white powder is different, and the judgment results are different; 3. The degree of powder loss is judged by the depth of color, which has a large subjective human error; the diaphragm powder loss detection disclosed in the prior art adopts a weighing method, which characterizes the degree of diaphragm powder loss by weighing the mass difference before and after the friction between the diaphragm and the friction block; however, the fluctuation deviation of this mass difference is large, and there is a large measurement error. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention provides a diaphragm powder loss testing method and a testing device thereof, which adopts a resistance testing method to measure the diaphragm powder loss rate. This method tests the surface resistance of coated diaphragms, powder loss diaphragms and uncoated diaphragms, and calculates the powder loss rate using the surface resistance. The test has small error and high accuracy, and can be used to formulate standards for diaphragm powder loss detection.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A diaphragm powder loss testing method comprises the following steps:

[0007] Step 1: Measure the surface resistance of the coating diaphragm. Select a coating diaphragm with an area of ​​A0, lay the coating diaphragm flat on a loading platform, and make the coated side of the coating diaphragm face upward. The lower surface of the coating diaphragm is in contact with the upper surface of a test receiver electrically connected to a resistance tester. The coating diaphragm resistance R0 is measured by contacting a probe electrically connected to the resistance tester with the upper surface of the coating. The coating diaphragm surface resistance R0' is calculated using the formula: diaphragm surface resistance R0' = R0 / A0;

[0008] Step 2: Measure the surface resistance of the powder-shedding diaphragm. Use an air blowing device to blow air to impact the coating and remove the powder attached to the diaphragm. The probe contacts the upper surface of the coating after the airflow impact to measure the surface resistance R1 of the powder-shedding diaphragm. The surface resistance R1' of the powder-shedding diaphragm after the airflow impact is calculated using the formula: diaphragm surface resistance R1' = R1 / A0.

[0009] Step 3: Measure the surface resistance of the uncoated diaphragm. Select an uncoated diaphragm with an area of ​​A1, lay the uncoated diaphragm flat on the loading platform, and make the lower surface of the uncoated diaphragm contact the upper surface of the test receiver. Measure the uncoated diaphragm resistance R2 by contacting the probe with the upper surface of the uncoated diaphragm. Calculate the uncoated diaphragm surface resistance R2' using the formula: diaphragm surface resistance R2' = R2 / A1.

[0010] Step 4: Calculate the diaphragm powder loss rate using the formula (R0'- R1') / (R0'- R2')*100%. Use the resistance test method to measure the diaphragm powder loss rate. This method first measures the surface resistance of the coated diaphragm, then measures the surface resistance of the coated diaphragm after air blowing, and then measures the surface resistance of the uncoated diaphragm. Finally, the powder loss rate is calculated. The test error is small and the accuracy is high, which can be used to formulate the standard for diaphragm powder loss detection.

[0011] As a preferred solution, in step 1 and step 2, the position of the coating membrane on the loading platform remains unchanged before and after the blowing device blows, and the test point where the probe contacts the coating is the same.

[0012] As a preferred solution, the marking line includes a transverse marking line and a longitudinal marking line, and the intersection of the transverse marking line and the longitudinal marking line is the test point.

[0013] As a preferred solution, in step 1, step 2 and step 3, multiple test points are used to measure the average surface resistance of the diaphragm.

[0014] As a preferred solution, the probe is a retractable probe.

[0015] As a preferred solution, in step 1, a diaphragm placement position is provided on the object-carrying platform, and a positioning structure is provided to fix the diaphragm to be tested laid flat on the diaphragm placement position.

[0016] As a preferred solution, the positioning structure is a plurality of suction cups distributed at the diaphragm placement position, and the openings of the suction cups face upward.

[0017] As a preferred solution, in step 2, the angle between the blowing direction of the air nozzle on the blowing device and the diaphragm is 30° to 60°, and the distance between the air nozzle and the diaphragm is 2 cm to 20 cm.

[0018] A diaphragm powder loss testing device includes a loading platform and a resistance tester, wherein a diaphragm placement position is provided on the loading platform, the resistance tester is electrically connected to a probe and a test receiver corresponding to the probe, the test receiver is provided at the diaphragm placement position, and a blowing device for blowing air to the diaphragm placed on the test receiver is provided above the diaphragm placement position.

[0019] As a preferred solution, it further includes a probe mounting plate, a plurality of probes are distributed on one side of the probe mounting plate, and the plurality of probes are electrically connected to the resistance tester.

[0020] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, a resistance test method is used to measure the powder loss rate of the diaphragm. This method first measures the surface resistance of the coated diaphragm, then measures the surface resistance of the powder loss diaphragm after blowing the coated diaphragm, and then measures the surface resistance of the uncoated diaphragm. Finally, the powder loss rate is calculated using the surface resistance. The test error is small and the accuracy is high, and it can be used to formulate standards for diaphragm powder loss detection; the air flow is directly hit against the diaphragm coating by blowing with a nozzle instead of the friction action of the traditional friction block, which can effectively avoid the influence of the friction block material, wear degree, etc. on the friction effect; the diaphragm is kept in a taut state by setting a positioning structure, so that the test data is more valid; and a telescopic probe is set and the buffering effect of the probe is used to avoid excessive pressure and damage to the coating when the probe contacts the coating, thereby improving the test quality.

[0021] In order to more clearly illustrate the structural features, technical means and specific objectives and functions achieved by the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the method steps of an embodiment of the present invention;

[0023] Figure 2 1 is a schematic structural diagram of a testing device according to an embodiment of the present invention;

[0024] Figure 3 1 is a schematic structural diagram of a resistance tester according to an embodiment of the present invention;

[0025] Figure 4 is a top view schematically showing a diaphragm to be tested placed on a stage according to an embodiment of the present invention;

[0026] Figure 5 1. It is a schematic diagram of the assembly of the nozzle, mounting slide, lifting seat and connecting shaft according to an embodiment of the present invention;

[0027] Figure 6 It is a schematic diagram of the air blowing of the air nozzle according to an embodiment of the present invention.

[0028] Description of the accompanying drawings:

[0029] 10-Loading platform; 11-Diaphragm placement position; 12-Suction cup; 13-Blowing device;

[0030] 14-Nozzle mounting bracket; 15-Nozzle; 16-Guide rail; 17-Connecting shaft;

[0031] 18-Mounting slide; 19-Adjusting screw; 20-Lifting seat; 30-Resistance tester;

[0032] 31-test receiver; 32-probe mounting plate; 33-probe; 40-diaphragm;

[0033] 41-test point; 42-horizontal marking line; 43-vertical marking line. DETAILED DESCRIPTION

[0034] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the position or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0035] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0036] like Figure 1-6 As shown, the present invention discloses a diaphragm powder loss testing method, comprising the following steps:

[0037] Step 1: Measure the surface resistance of the coated diaphragm 40. Select a coated diaphragm 40 with an area of ​​A0, lay the coated diaphragm 40 flat on the loading platform 10, and make the coated side of the coated diaphragm 40 face upward. The lower surface of the coated diaphragm 40 is in contact with the upper surface of the test receiver 31 electrically connected to the resistance tester 30. The resistance R0 of the coated diaphragm 40 is measured by contacting the probe 33 electrically connected to the resistance tester 30 with the upper surface of the coating. The surface resistance R0' of the coated diaphragm 40 is calculated using the formula: R0' = R0 / A0.

[0038] Step 2: Measure the surface resistance of the powder-shedding diaphragm 40. The air blowing device 13 blows air to impact the coating and remove the powder attached to the diaphragm 40. The probe 33 contacts the upper surface of the coating after the airflow impact to measure the resistance R1 of the powder-shedding diaphragm 40. The surface resistance R1' of the powder-shedding diaphragm 40 after the airflow impact is calculated using the formula: R1' = R1 / A0.

[0039] Step 3: Measure the surface resistance of the uncoated diaphragm 40. Select an uncoated diaphragm 40 with an area of ​​A1, lay the uncoated diaphragm 40 flat on the loading platform 10, and make the lower surface of the uncoated diaphragm 40 contact the upper surface of the test receiver 31. The resistance R2 of the uncoated diaphragm 40 is measured by contacting the probe 33 with the upper surface of the uncoated diaphragm 40. The surface resistance R2' of the uncoated diaphragm 40 is calculated using the formula: diaphragm 40 surface resistance R2' = R2 / A1;

[0040] Step 4: Calculate the powder loss rate of the diaphragm 40 using the formula (R0'- R1') / (R0'- R2')*100%.

[0041] In step 1 and step 2, the position of the coating membrane 40 on the loading platform 10 remains unchanged before and after the blowing device 13 blows air, and the test point 41 where the probe 33 contacts the coating is the same.

[0042] In step one and step three, before testing, marking lines are set on the side of the diaphragm 40 to be tested facing the probe 33. The marking lines include multiple transverse marking lines 42 and multiple longitudinal marking lines 43. The intersection of the transverse marking lines 42 and the longitudinal marking lines 43 is the test point 41, and the distance between two adjacent test points 41 is 0.5 cm to 2.5 cm.

[0043] In step 1, step 2, and step 3, the average surface resistance of the diaphragm 40 is measured using multiple test points 41 .

[0044] The probe 33 is a retractable probe 33 . By providing the retractable probe 33 , the buffering effect of the probe 33 is utilized to prevent the probe 33 from excessively pressing and damaging the coating when in contact with the coating, thereby improving the test quality.

[0045] In step one, a diaphragm placement position 11 is provided on the loading platform 10, and the diaphragm placement position 11 is provided with a positioning structure for fixing the diaphragm 40 to be tested laid flat on the diaphragm placement position 11. The positioning structure is a plurality of suction cups 12 distributed on the diaphragm placement position 11, and the openings of the suction cups 12 face upward.

[0046] In step 2, the angle between the blowing direction of the nozzle 15 on the blowing device 13 and the diaphragm 40 is 30° to 60°, the distance h between the nozzle 15 and the diaphragm 40 is 2cm to 20cm, and the air supply volume of the nozzle 15 is 0.025 m 3 / s~0.25 m 3 / s, corresponding to a wind speed of 0.5m / s to 50m / s, and a moving speed of the air nozzle 15 of 0.01m / s to 0.5m / s. The air supply volume of the air nozzle 15 is adjusted to remove powder attached to the diaphragm 40.

[0047] like Figure 2-6 As shown, the present invention also discloses a diaphragm 40 powder loss testing device, including a loading platform 10 and a resistance tester 30, wherein a diaphragm placement position 11 is provided on the loading platform 10, and the resistance tester 30 is electrically connected to a probe 33 and a test receiver 31 corresponding to the probe 33, and the test receiver 31 is provided at the diaphragm placement position 11, and a blowing device 13 for blowing air to the diaphragm 40 placed on the test receiver 31 is provided above the diaphragm placement position 11. During the test, the diaphragm 40 to be tested is laid flat on the diaphragm placement position 11 and the test receiver 31 is in contact with the lower surface of the diaphragm 40, and the probe 33 is in contact with the coating on the upper surface of the diaphragm 40.

[0048] It also includes a probe mounting plate 32, and a plurality of probes 33 are distributed on one side of the probe mounting plate 32. The plurality of probes 33 are electrically connected to the resistance tester 30. The plurality of probes 33 are distributed in a matrix on the probe mounting plate 32, and each of the probes 33 corresponds one-to-one to a test point 41. By setting up a plurality of probes 33 and adopting a matrix distribution arrangement, the resistance values ​​of multiple diaphragms 40 can be measured at one time during the test, and the average surface resistance value can be quickly calculated, making the test convenient and efficient.

[0049] The blowing device 13 includes a nozzle 15 mounting frame 14 provided on the loading platform 10, and the nozzle 15 mounting frame 14 is movably provided with a nozzle 15 and a nozzle 15 driving assembly (not shown) for driving the nozzle 15 to move back and forth. The nozzle 15 is connected to an air supply unit (not shown), and the blowing direction of the nozzle 15 is horizontally and perpendicularly to the movement direction of the nozzle 15.

[0050] The nozzle 15 mounting frame 14 is movably provided with a mounting slide 18. The nozzle 15 driving assembly includes a screw and a motor for controlling the rotation of the screw. The screw extends in the front-to-back direction and is rotatably connected to the mounting slide 18. The nozzle 15 is provided on the mounting slide 18 and can move in the front-to-back direction with the mounting slide 18. By arranging the screw and the motor, the nozzle 15 can automatically blow air on the coating with good uniformity, thereby improving the accuracy of the test data.

[0051] The left and right sides of the mounting slide 18 are provided with a lifting seat 20 and an adjusting screw 19. The lifting seat 20 is movably connected to the mounting slide 18 up and down, and the adjusting screw 19 extends vertically and is screwed into the lifting seat 20. The two ends of the air nozzle 15 are rotatably connected to the corresponding lifting seat 20 through a connecting shaft 17. The connecting shaft 17 allows the air nozzle 15 to stay at any position. When adjusting, the air nozzle 15 can be manually rotated to rotate around the connecting shaft 17 to adjust the angle of the air nozzle 15. Rotating the adjusting screw drives the lifting seat 20 to move up and down to adjust the height of the air nozzle 15, thereby achieving different blowing requirements and effects. In addition, the blowing intensity of the air nozzle 15 can be controlled by adjusting the air supply volume of the air supply unit to achieve different blowing effects.

[0052] The nozzle 15 mounting frame 14 is provided with a guide rail 16 extending in the front-to-back direction, and the mounting slide 18 is slidably connected to the guide rail 16 via a slider.

[0053] The following steps are used to test the powder loss rate of the diaphragm:

[0054] A 7μm PE membrane was used as the uncoated membrane, and slurry A (easy to shed powder) and slurry B (not easy to shed powder) were selected as the coating. Resistance test conditions: the test temperature was 25°C, the relative humidity was 50%, and the air volume was 0.1 m 3 / s, the distance between the nozzle 15 and the diaphragm is 4cm, the moving speed of the nozzle 15 is 0.02m / s, and the angle between the blowing direction and the diaphragm is 45°. The test results are shown in Table 1:

[0055] Table 1:

[0056] plan <![CDATA[Air delivery volume (m 3 / s)]]> Distance between nozzle 15 and diaphragm 40 (cm) Nozzle 15 moving speed (m / s) Angle between blowing direction and diaphragm 40° (°) Slurry type <![CDATA[Area A0 (m 2 )]]> <![CDATA[Area A1 (m 2 )]]> <![CDATA[R0(GΩ)]]> <![CDATA[R1(GΩ)]]> <![CDATA[R2(GΩ)]]> Fan drop rate (%) Option 1 0.1 4 0.02 45 Slurry A 0.01 0.01 7.65 6.42 6.23 86.6 Option 2 0.1 4 0.02 45 Slurry B 0.01 0.01 7.36 7.23 6.23 11.5

[0057] Powder loss rate qualification standard: The powder loss rate of the diaphragm is less than 30% to be qualified. As can be seen from Table 1, the powder loss rate of the coated diaphragm using slurry A in Scheme 1 is greater than 30%, and the powder loss rate of the coated diaphragm using slurry B in Scheme 2 is less than 30%. This test method can accurately reflect that slurry A is easy to powder, while slurry B is not easy to powder. Therefore, this test method can accurately measure the powder loss rate of the diaphragm.

[0058] In summary, the present invention adopts a resistance testing method to measure the powder loss rate of the diaphragm. This method first measures the surface resistance of the coated diaphragm, then measures the surface resistance of the powder loss diaphragm after blowing the coated diaphragm, and then measures the surface resistance of the uncoated diaphragm. Finally, the powder loss rate is calculated using the surface resistance. The test error is small and the accuracy is high, and it can be used to formulate standards for diaphragm powder loss detection. The air flow is blown by a nozzle to directly hit the diaphragm coating to replace the friction action of the traditional friction block, which can effectively avoid the influence of the friction block material, wear degree, etc. on the friction effect; the diaphragm is kept in a taut state by setting a positioning structure, so that the test data is more valid; the telescopic probe is set and the buffering effect of the probe is used to avoid excessive pressure and damage to the coating when the probe contacts the coating, thereby improving the test quality.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical practice of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A diaphragm powder loss test method, characterized in that: The following steps are involved: Step 1: Measure the surface resistance of the coating diaphragm. Select a coating diaphragm with an area of ​​A0, lay the coating diaphragm flat on a loading platform, and make the coated side of the coating diaphragm face upward. The lower surface of the coating diaphragm is in contact with the upper surface of a test receiver electrically connected to a resistance tester. The coating diaphragm resistance R0 is measured by contacting a probe electrically connected to the resistance tester with the upper surface of the coating. The coating diaphragm surface resistance R0' is calculated using the formula: diaphragm surface resistance R0' = R0 / A0; Step 2: Measure the surface resistance of the powder-shedding diaphragm. Use an air blowing device to blow air to impact the coating and remove the powder attached to the diaphragm. The probe contacts the upper surface of the coating after the airflow impact to measure the surface resistance R1 of the powder-shedding diaphragm. The surface resistance R1' of the powder-shedding diaphragm after the airflow impact is calculated using the formula: diaphragm surface resistance R1' = R1 / A0. Step 3: Measure the surface resistance of the uncoated diaphragm. Select an uncoated diaphragm with an area of ​​A1, lay the uncoated diaphragm flat on the loading platform, and make the lower surface of the uncoated diaphragm contact the upper surface of the test receiver. Measure the uncoated diaphragm resistance R2 by contacting the probe with the upper surface of the uncoated diaphragm. Calculate the uncoated diaphragm surface resistance R2' using the formula: diaphragm surface resistance R2' = R2 / A1. Step 4: Calculate the diaphragm powder loss rate using the formula (R0'- R1') / (R0'- R2')*100%; In step 1 and step 2, the position of the coating membrane on the loading platform remains unchanged before and after the blowing device blows, and the test point where the probe contacts the coating is the same; The loading platform is provided with a diaphragm placement position, and the diaphragm placement position is provided with a positioning structure for fixing the diaphragm to be tested laid flat on the diaphragm placement position, and the positioning structure is a plurality of suction cups distributed on the diaphragm placement position, and the openings of the suction cups face upwards; In steps 1, 2, and 3, the average surface resistance of the diaphragm is measured using multiple test points.

2. A diaphragm powder loss testing method according to claim 1, characterized in that: Before the test, marking lines are set on the side of the diaphragm to be tested facing the probe. The marking lines include a transverse marking line and a longitudinal marking line. The intersection of the transverse marking line and the longitudinal marking line is the test point.

3. A diaphragm powder loss testing method according to claim 1, characterized in that: The probe is a retractable probe.

4. A diaphragm powder loss testing method according to claim 1, characterized in that: In step 2, the angle θ between the blowing direction of the air nozzle on the blowing device and the diaphragm is 30° to 60°, and the distance between the air nozzle and the diaphragm is 2 cm to 20 cm.

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