Method for testing aperture of diaphragm through hole

Abstract

The invention relates to the technical field of diaphragm testing, and provides a diaphragm through hole diameter testing method which comprises the following steps: preparing a diaphragm sample with a preset size; wetting the diaphragm sample to a saturated state through wetting liquid, and pressing the diaphragm sample into the sample groove; the diaphragm sample placed in the sample groove is tested through the lithium ion battery diaphragm aperture analyzer according to preset parameters, and the wetting test result of the diaphragm sample is obtained. According to the diaphragm through hole diameter testing method, high-value equipment such as a scanning electron microscope and a section polishing instrument does not need to be purchased, sample preparation is simple, the testing period is short, the labor hour and the testing cost are reduced, the pressure needed by testing is small, the testing precision is high, the good testing effect is achieved, and diaphragm research and development and production quality control are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of diaphragm testing, and in particular to a method for testing the aperture of a diaphragm through hole. Background Art

[0002] Lithium-ion batteries are widely used because of their advantages such as high voltage, high capacity, long cycle life and no memory effect. For lithium-ion batteries, the characteristics of the diaphragm material and related processing technology have a great influence on their performance. Among them, the influence of the diaphragm through-hole diameter on the battery is mainly reflected in the impact on voltage, safety, internal resistance and self-discharge rate. For example, if the diaphragm through-hole diameter is too large, the self-discharge rate of the lithium battery will be accelerated, thereby reducing the voltage consistency of the battery; the higher the permeability of the diaphragm, the greater the internal resistance of the battery. For this reason, controlling the size of the diaphragm through-hole diameter is of great significance for maintaining stable battery performance and extending battery life.

[0003] At present, the methods for testing the aperture of diaphragm through-holes in the industry include electron microscopy, bubble point method and water pressure method. Among them, the electron microscopy method is to observe the diaphragm sample under SEM (scanning electron microscope) and analyze the aperture size and distribution through SEM images. This method has high equipment purchase costs and a relatively complicated sample preparation process. Since the diaphragm sample is not conductive, the diaphragm sample needs to be gold-sprayed for shooting the plane, which may cause damage to the diaphragm holes. The cross-section shooting also requires argon ion polishing using a cross-section polisher, which has high testing costs and a long testing cycle.

[0004] The bubble point method uses the porous nature of the membrane to form bubbles in the liquid to characterize the size of the membrane pores. Since the formation of bubbles takes time, the test time of this method is relatively long, resulting in increased test costs. The water pressure method uses pressure to squeeze water into the sample, including through holes and blind holes. The two types of holes cannot be distinguished, and the test data is not accurate enough to evaluate battery performance. At the same time, excessive pressure will cause damage to the diaphragm sample. If the pressure is too low, water cannot fully enter and all pores cannot be detected.

[0005] Therefore, the diaphragm through-hole diameter testing method in the prior art has the problems of high testing cost, low testing safety, and low testing accuracy, which is not conducive to improving the accuracy of battery performance evaluation. Summary of the invention

[0006] In view of this, the present invention aims to provide a method for testing the aperture of a diaphragm through hole, which is beneficial to improving the test accuracy and achieving the purpose of reducing costs and shortening the test cycle.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A method for testing the aperture of a diaphragm through hole comprises the following steps:

[0009] preparing membrane samples of preset sizes;

[0010] Wetting the membrane sample to a saturated state with a wetting liquid and pressing it into a sample groove;

[0011] The membrane sample placed in the sample slot is tested by a lithium-ion battery membrane pore size analyzer with preset parameters to obtain a wetness test result of the membrane sample.

[0012] Furthermore, preparing the diaphragm sample of the preset size also includes the following steps:

[0013] Select a flat and wrinkle-free diaphragm, and cut the diaphragm according to the preset size; select a flat and wrinkle-free dust-free paper or non-woven fabric, and cut the dust-free paper or non-woven fabric according to the preset size; stack the diaphragm of the preset size on the dust-free paper or non-woven fabric of the preset size to obtain the diaphragm sample.

[0014] Furthermore, the diaphragm is cut by a sampler; the sampler and / or the sample tank are made of corrosion-resistant stainless steel.

[0015] Furthermore, the preset size includes a diameter size D of the diaphragm sample, and the diameter size D is between 1-3 cm.

[0016] Furthermore, the wetting liquid uses Gemini surfactant.

[0017] Furthermore, the preset parameters include a test pressure P1; the value of the test pressure P1 is between 0Psi-500Psi.

[0018] Furthermore, the preset parameters include pressurized gas; the high-pressure partial pressure P2 of the pressurized gas is between 3.2Mpa-4Mpa, and the low-pressure partial pressure P3 of the pressurized gas is between 0.6-1Mpa.

[0019] Furthermore, the pressurized gas is nitrogen.

[0020] Furthermore, before the membrane sample is moistened to a saturated state by the moistening liquid and pressed into the sample groove, the following steps are also included:

[0021] The dried membrane sample is pressed into the sample slot; the dried membrane sample placed in the sample slot is tested by the lithium-ion battery membrane pore size analyzer with the preset parameters to obtain the drying test result of the membrane sample.

[0022] Furthermore, before the membrane sample is moistened to a saturated state by the moistening liquid and pressed into the sample groove, the following steps are also included:

[0023] The diaphragm sample is moistened to a semi-saturated state by the wetting liquid and pressed into the sample slot; the diaphragm sample in a semi-saturated state placed in the sample slot is tested by the lithium-ion battery diaphragm pore size analyzer with the preset parameters to obtain a semi-wetting test result of the diaphragm sample.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The method for testing the aperture of the diaphragm through hole described in the present invention uses a lithium-ion battery diaphragm aperture analyzer to test the aperture of the diaphragm through hole. There is no need to purchase high-value equipment such as a scanning electron microscope and a cross-section polisher. Sample preparation is simple, the test cycle is short, and labor hours and test costs are reduced. In addition, the purpose of testing the aperture by the capillary flow method is achieved by using a lithium-ion battery diaphragm aperture analyzer. The pressure required for the test is small and the test accuracy is high. Therefore, it has a good test effect and is beneficial to diaphragm research and development and production quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 A flow chart of a method for testing the aperture of a diaphragm through hole according to an embodiment of the present invention;

[0028] Figure 2 This is a curve chart of test results obtained by the lithium-ion battery membrane pore size analyzer described in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0031] The present embodiment relates to a method for testing the aperture of a diaphragm through hole, which can solve the problems of high testing cost, low testing safety, and low testing accuracy in existing diaphragm through hole diameter testing methods, and is conducive to improving the accuracy of battery performance evaluation.

[0032] In terms of overall design, Figure 1 As shown, the method for testing the aperture of the diaphragm through hole of this embodiment includes the following steps:

[0033] S1. Prepare a diaphragm sample of a preset size;

[0034] S2, wetting the diaphragm sample to a saturated state with a wetting liquid, and pressing it into a sample tank;

[0035] S3. The diaphragm sample placed in the sample slot is tested using a lithium-ion battery diaphragm pore size analyzer with preset parameters to obtain a wetness test result of the diaphragm sample.

[0036] At this time, as designed above, by using a lithium-ion battery diaphragm pore size analyzer to test the diaphragm through-hole aperture, there is no need to purchase high-value equipment such as a scanning electron microscope and a cross-section polisher. The sample preparation is simple, the test cycle is short, and the labor hours and test costs are reduced. In addition, the lithium-ion battery diaphragm pore size analyzer is used to implement the capillary flow method to test the aperture. The test requires a small pressure and has a high test accuracy, which has a good test effect and is beneficial to diaphragm research and development and production quality control.

[0037] Based on the above design ideas, in detail, in this embodiment, during the specific design, the lithium-ion battery diaphragm pore size analyzer can specifically adopt the lithium-ion battery diaphragm pore size analyzer model CFP-1500AE produced by PMI of the United States. At the same time, since the lithium-ion battery diaphragm pore size analyzer is used for testing, non-destructive testing of diaphragm samples can be achieved, which also has the effect of reducing costs to a certain extent.

[0038] In this embodiment, as a preferred implementation form, preparing a diaphragm sample of a preset size also includes the following steps: selecting a flat and wrinkle-free diaphragm, cutting the diaphragm according to a preset size, then selecting a flat and wrinkle-free dust-free paper or non-woven fabric, cutting the dust-free paper or non-woven fabric according to a preset size, and finally stacking the diaphragm of a preset size on the dust-free paper or non-woven fabric of a preset size to obtain a diaphragm sample.

[0039] The sample slot of this embodiment includes a sample slot bottom plate, a gasket and a sample slot upper plate. In specific implementation, the diaphragm sample (the cut diaphragm is located above the non-woven fabric or dust-free paper) is placed on the sample slot bottom plate, and the gasket is placed above the diaphragm sample, so that the diaphragm sample can be well fixed in the sample slot when the sample slot upper plate and the sample slot bottom plate are buckled together.

[0040] Moreover, in this embodiment, as a preferred implementation form, the diaphragm is cut by the sampler, wherein the sampler and the sample slot are both made of corrosion-resistant stainless steel, such as 304 stainless steel. Of course, in this embodiment, only the sampler or the sample slot can be made of corrosion-resistant stainless steel if necessary.

[0041] In addition, in this embodiment, as a preferred implementation form, the preset size includes the diameter size D of the diaphragm sample, and the diameter size D is between 1-3 cm, for example, the diameter size D can be specifically 1 cm, 1.5 cm or 3 cm, etc. Such a design is not only conducive to pressing the diaphragm sample into the sample slot, but also conducive to ensuring the accuracy of the test results by controlling the size of the test sample.

[0042] Considering the safety of the test, in this embodiment, as a preferred implementation form, the wetting liquid uses Gemini surfactant (gemini surfactant). Gemini surfactant is a high-efficiency, low-toxic, high-performance surfactant. Using Gemini surfactant as a wetting liquid will not pollute the environment. It can also be used to wet the membrane sample to a semi-saturated state or a fully saturated state by utilizing its excellent surface activity, wettability, dispersibility, antistatic and bactericidal properties, which is beneficial to ensure the wettability of the membrane sample and the accuracy of the test results.

[0043] In addition, in this embodiment, as a preferred implementation form, the preset parameters of the lithium-ion battery diaphragm pore size analyzer include a test pressure P1, and the value of the test pressure P1 is between 0Psi-500Psi, for example, it can be specifically 105Psi, 200Psi, 300Psi or 420Psi, etc. In this way, the test can be carried out smoothly without damaging the through-hole aperture of the diaphragm sample.

[0044] At the same time, in this embodiment, as a preferred implementation form, the preset parameters include pressurized gas, the pressurized gas uses nitrogen, and the high pressure partial pressure P2 of the nitrogen is between 3.2Mpa-4Mpa, and the low pressure partial pressure P3 of the nitrogen is between 0.6-1Mpa. The main advantage of this setting is that it can ensure that the test environment is non-oxidized and purified, and avoid the electrolyte and water or oxygen in the air reacting to affect the test structure.

[0045] When taking specific values, the high-pressure partial pressure P2 of nitrogen can be, for example, 3.2 MPa, 3.6 MPa or 4 MPa, and the low-pressure partial pressure P3 of nitrogen can be, for example, 0.6 MPa, 0.8 MPa or 1 MPa, in order to achieve better test results.

[0046] In addition, as a preferred implementation form, in this embodiment, before the membrane sample is moistened to a saturated state by the moistening liquid and pressed into the sample tank, the following steps are also included:

[0047] The dried diaphragm sample is pressed into the sample slot, and then the dried diaphragm sample placed in the sample slot is tested using a lithium-ion battery diaphragm pore size analyzer with preset parameters to obtain the drying test results of the diaphragm sample.

[0048] Secondly, in this embodiment, which is also a preferred implementation form, the following steps are also included before the membrane sample is moistened to a saturated state by the moistening liquid and pressed into the sample tank:

[0049] The diaphragm sample is moistened to a semi-saturated state with a wetting liquid and pressed into a sample slot. Subsequently, the diaphragm sample in a semi-saturated state placed in the sample slot is tested with a lithium-ion battery diaphragm pore size analyzer using preset parameters to obtain a semi-wetting test result of the diaphragm sample.

[0050] In the specific implementation, in this embodiment, the dry diaphragm sample is tested first, then the diaphragm sample soaked in the wetting liquid to a semi-saturated state is tested, and finally the diaphragm sample soaked in the wetting liquid to a fully saturated state is tested. By comparing the three test results, the range of the pore size of the diaphragm sample can be obtained.

[0051] The lithium-ion battery membrane pore size analyzer of this embodiment is based on the capillary flow method to test the pore size. The principle of the capillary flow method to test the pore size is based on the effect of gas-liquid interfacial tension. The pore size is calculated by measuring the pressure required to open the pore, for example Figure 2 As shown, by running the dry and wet curves, three characteristic pore size data of maximum pore size (bubble point pressure), minimum pore size and average pore size are obtained, and the distribution of membrane through-pore size is characterized. Among them, the expression involved is P = [4γcosθ] / D1 for calculation, where P is the test pressure, γ is the liquid surface tension, cosθ is the contact angle, and D1 is the pore throat diameter.

[0052] At this time, combined Figure 2 As shown, the horizontal axis is the test pressure P1, the vertical axis is the ventilation volume, curve 1 is the test result of the dry diaphragm sample, curve 2 is the test result of the diaphragm sample soaked in the wetting liquid to a semi-saturated state, and curve 3 is the test result of the diaphragm sample soaked in the wetting liquid to a saturated state.

[0053] The method for testing the aperture of the diaphragm through hole of the present embodiment does not need to purchase high-value equipment such as scanning electron microscopes and cross-section polishers, which makes sample preparation simple, the test cycle short, and reduces labor hours and test costs. At the same time, the pressure required for the test is small and the test accuracy is high, thereby having a good test effect and being beneficial to diaphragm research and development and production quality control.

[0054] Among them, the capillary flow method is implemented through the lithium-ion battery diaphragm pore size analyzer to test the through-hole diameter. The principle is based on the effect of gas-liquid interface tension and the pore size is calculated by measuring the pressure required for opening the hole. It is a non-destructive testing method that can reduce the testing cost to a certain extent and improve the testing accuracy.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the aperture of a diaphragm through hole, characterized in that: The following steps are involved: preparing a membrane sample of a preset size; Wetting the membrane sample to a saturated state with a wetting liquid and pressing it into a sample groove; The membrane sample placed in the sample slot is tested by a lithium-ion battery membrane pore size analyzer with preset parameters to obtain a wetness test result of the membrane sample.

2. The method for testing the aperture of a diaphragm through hole according to claim 1, characterized in that: The method of preparing the membrane sample of the preset size further comprises the following steps: Select a flat and wrinkle-free diaphragm, and cut the diaphragm according to the preset size; Select a flat, wrinkle-free dust-free paper or non-woven fabric, and cut the dust-free paper or non-woven fabric according to the preset size; The membrane of the preset size is stacked on the dust-free paper or the non-woven fabric of the preset size to obtain the membrane sample.

3. The method for testing the aperture of a diaphragm through hole according to claim 2, characterized in that: cutting the diaphragm by a sampler; The sampler and / or the sample tank are made of corrosion-resistant stainless steel.

4. The method for testing the aperture of a diaphragm through hole according to claim 1, characterized in that: The preset size includes a diameter size D of the diaphragm sample, and the diameter size D is between 1-3 cm.

5. The method for testing the aperture of a diaphragm through hole according to claim 1, characterized in that: The wetting liquid adopts Gemini surfactant.

6. The method for testing the aperture of a diaphragm through hole according to claim 1, characterized in that: The preset parameters include the test pressure P1; The test pressure P1 has a value between 0Psi and 500Psi.

7. The method for testing the aperture of a diaphragm through hole according to claim 1, characterized in that: The preset parameters include pressurized gas; The high-pressure partial pressure P2 of the pressurized gas is between 3.2Mpa and 4Mpa, and the low-pressure partial pressure P3 of the pressurized gas is between 0.6 and 1Mpa.

8. The method for testing the aperture of a diaphragm through hole according to claim 7, characterized in that: The pressurized gas is nitrogen.

9. The method for testing the aperture of a diaphragm through hole according to any one of claims 1 to 8, characterized in that: The method further includes the following steps before wetting the membrane sample to a saturated state with the wetting liquid and pressing the membrane sample into the sample groove: Pressing the dried membrane sample into the sample slot; The diaphragm sample placed in the sample slot and dried is tested by the lithium-ion battery diaphragm pore size analyzer with the preset parameters to obtain a drying test result of the diaphragm sample.

10. The method for testing the aperture of a diaphragm through hole according to any one of claims 1 to 8, characterized in that: The method further includes the following steps before wetting the membrane sample to a saturated state with the wetting liquid and pressing the membrane sample into the sample groove: Wetting the membrane sample to a semi-saturated state with the wetting liquid and pressing it into the sample groove; The diaphragm sample in a semi-saturated state placed in the sample tank is tested by the lithium-ion battery diaphragm pore size analyzer with the preset parameters to obtain a semi-wetting test result of the diaphragm sample.

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