Ceramic separator for batteries

Abstract

The embodiment of the present application provides a kind of ceramic separator for battery.The present application relates to the technical field of battery.A kind of ceramic separator for battery, including base film and the ceramic layer of being arranged in at least one side of base film, ceramic layer includes ceramic particle and binder, the curling rate of ceramic separator is less than 2%.The curling rate of the separator is low, and the test method provided by the application for the ceramic separator for battery can accurately detect the curling degree of the separator.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a ceramic separator for batteries. Background Technology

[0002] The separator in a lithium-ion battery is a core material in the battery cell. During the battery manufacturing process, the separator needs to be wound or stacked in a low-humidity environment. However, in a low-humidity environment, the separator is prone to curling due to internal stress release or anisotropic deformation. A separator with a severe degree of curling can lead to poor alignment of the battery cell winding, difficulty in inserting the electrode, and even short circuits and other safety issues. Therefore, providing a separator product with low curling characteristics in a low-humidity environment is crucial to ensuring the stability and safety of battery cell manufacturing.

[0003] Currently, although coating the base membrane with a ceramic layer is used to suppress separator deformation, this method has limited effectiveness in suppressing curling. Furthermore, existing ceramic separator products lack quantitative control over the degree of curling, resulting in significant differences in curling performance between different batches. The production end cannot clearly define what degree of curling meets the requirements of the battery cell manufacturing process, and quality control also lacks a unified acceptable curling rate threshold as a basis for quality release. In summary, the overall curling rate of existing ceramic separator products for batteries is relatively high. Summary of the Invention

[0004] This application provides a diaphragm with low curl rate.

[0005] In a first aspect, the ceramic separator for batteries provided in this application includes a base membrane and a ceramic layer disposed on at least one side of the base membrane. The ceramic layer includes ceramic particles and a binder, and the curvature of the ceramic separator is less than 2%.

[0006] In one possible implementation, the thickness of the base film is 4~8 μm.

[0007] In one possible implementation, the average thickness of the ceramic layer is 0.8 μm to 1.2 μm.

[0008] In one possible implementation, the mass ratio of ceramic particles to binder is (50~150):(2~10).

[0009] In one possible implementation, the base membrane comprises a polyethylene porous membrane and / or a polypropylene porous membrane.

[0010] The curl rate is obtained by testing the following method: obtaining a first diaphragm sample of a preset shape and the first area of ​​the first diaphragm sample, wherein the preset shape is an isosceles right triangle;

[0011] The first diaphragm sample was placed in a preset environment for humidity equilibration treatment;

[0012] Under a preset environment, multiple first vertices of the first diaphragm sample are fixed on a horizontal plane. After the curling stabilizes, a curled sample is obtained, where the first vertex is the acute angle vertex of the first diaphragm sample.

[0013] The curling area was determined based on the first diaphragm sample and the curled sample.

[0014] Divide the curled area by the first area to obtain the curling rate of the first diaphragm sample. The curling rate is used to indicate the degree of curling of the first diaphragm sample under a preset environment.

[0015] In one possible implementation, determining the curling area based on the first diaphragm sample and the curled sample includes:

[0016] Determine the projected area of ​​the curled sample on the horizontal plane;

[0017] The difference between the first area and the projected area is determined as the curled area.

[0018] In one possible implementation, determining the curling area based on the first diaphragm sample and the curled sample includes:

[0019] Determine the curl information of the curled specimen, which is used to indicate the projected dimensions of the multiple right-angled sides of the curled specimen on the horizontal plane;

[0020] Based on the curling information, the curling area is determined.

[0021] In one possible implementation, determining the curling information of the curled sample includes:

[0022] Under a preset environment, curled samples were obtained at multiple moments after the curling had stabilized.

[0023] For each moment, determine the first distance and the second distance of the curled sample. The first distance is the linear distance of the projection of the first right-angled side of the curled sample along its original length direction onto the horizontal plane, and the second distance is the linear distance of the projection of the second right-angled side of the curled sample along its original length direction onto the horizontal plane.

[0024] The first mean of the first distance at each time point and the second mean of the second distance at each time point are determined as the curl information.

[0025] In one possible implementation, under a preset environment, the curled sample is acquired at multiple time points after the curl has stabilized, including:

[0026] Under a preset environment, the state of the part of the first diaphragm sample other than the multiple first vertices is set as the preset state, which is a state without external force constraints.

[0027] Obtain curled samples at multiple time points;

[0028] Obtain curled samples at multiple time points, including:

[0029] The first diaphragm sample is placed in a preset environment and left to stand for a preset first time to obtain the curled sample at the first moment after the curling is stabilized.

[0030] Continue at a preset second time interval to obtain curled samples at times other than the first moment after curling has stabilized;

[0031] Based on the curling information, the curling area is determined, including:

[0032] Determine the first product between the first mean and the second mean;

[0033] Multiply the first product by the target value to obtain the curled area.

[0034] This application provides a method for detecting the curling of a ceramic separator for batteries, which can accurately detect the degree of curling of the separator.

[0035] Secondly, embodiments of this application provide a method for detecting the curling of a ceramic separator for batteries, including:

[0036] Obtain a first diaphragm sample with a preset shape and a first area of ​​the first diaphragm sample. The preset shape is an isosceles right triangle.

[0037] The first diaphragm sample was placed in a preset environment for humidity equilibration treatment;

[0038] Under a preset environment, multiple first vertices of the first diaphragm sample are fixed on a horizontal plane. After the curling stabilizes, a curled sample is obtained, where the first vertex is the acute angle vertex of the first diaphragm sample.

[0039] The curling area was determined based on the first diaphragm sample and the curled sample.

[0040] Divide the curled area by the first area to obtain the curling rate of the first diaphragm sample. The curling rate is used to indicate the degree of curling of the first diaphragm sample under a preset environment.

[0041] In one possible implementation, determining the curling area based on the first diaphragm sample and the curled sample includes:

[0042] Determine the projected area of ​​the curled sample on the horizontal plane;

[0043] The difference between the first area and the projected area is determined as the curled area.

[0044] In one possible implementation, determining the curling area based on the first diaphragm sample and the curled sample includes:

[0045] Determine the curl information of the curled specimen, which is used to indicate the projected dimensions of the multiple right-angled sides of the curled specimen on the horizontal plane;

[0046] Based on the curling information, the curling area is determined.

[0047] In one possible implementation, determining the curling information of the curled sample includes:

[0048] Under a preset environment, curled samples were obtained at multiple moments after the curling had stabilized.

[0049] For each moment, determine the first distance and the second distance of the curled sample. The first distance is the linear distance of the projection of the first right-angled side of the curled sample along its original length direction onto the horizontal plane, and the second distance is the linear distance of the projection of the second right-angled side of the curled sample along its original length direction onto the horizontal plane.

[0050] The first mean of the first distance at each time point and the second mean of the second distance at each time point are determined as the curl information.

[0051] In one possible implementation, under a preset environment, the curled sample is acquired at multiple time points after the curl has stabilized, including:

[0052] Under a preset environment, the state of the part of the first diaphragm sample other than the multiple first vertices is set as the preset state, which is a state without external force constraints.

[0053] Obtain curled samples at multiple times.

[0054] In one possible implementation, acquiring the curled sample at multiple moments includes:

[0055] The first diaphragm sample is placed in a preset environment and left to stand for a preset first time to obtain the curled sample at the first moment after the curling is stabilized.

[0056] Continue at a preset second time interval to obtain the curled sample at a time other than the first moment after the curling has stabilized.

[0057] In one possible implementation, determining the curl area based on curl information includes:

[0058] Determine the first product between the first mean and the second mean;

[0059] Multiply the first product by the target value to obtain the curled area.

[0060] In one possible implementation, obtaining a first diaphragm sample of a predetermined shape includes:

[0061] Obtain a second diaphragm sample, the second diaphragm sample including the first diaphragm sample;

[0062] The second diaphragm sample is cut along a preset direction to obtain a first diaphragm sample of a preset shape.

[0063] In one possible implementation, the preset ambient humidity is 1.5% to 2.5%, and the duration of the humidity balancing process is greater than or equal to a preset third duration of 30 minutes.

[0064] Thirdly, embodiments of this application provide a device for testing the curling of a ceramic separator for batteries, comprising: an acquisition module, a first processing module, a second processing module, a determination module, and a third processing module, wherein...

[0065] The acquisition module is used to acquire a first diaphragm sample of a preset shape and a first area of ​​the first diaphragm sample. The preset shape is an isosceles right triangle.

[0066] The first processing module is used to place the first diaphragm sample in a preset environment for humidity balancing treatment.

[0067] The second processing module is used to fix multiple first vertices of the first diaphragm sample on a horizontal plane under a preset environment. After the curling is stable, a curled sample is obtained, where the first vertex is the acute angle vertex of the first diaphragm sample.

[0068] A determination module is used to determine the curling area based on the first diaphragm sample and the curled sample;

[0069] The third processing module is used to divide the curled area by the first area to obtain the curling rate of the first diaphragm sample. The curling rate is used to indicate the degree of curling of the first diaphragm sample under a preset environment.

[0070] This application provides a ceramic separator for batteries. A ceramic layer containing ceramic particles and a binder is formed on the surface of a base film. The rigid framework of the ceramic particles suppresses anisotropic shrinkage of the base film in low-humidity environments. Simultaneously, the binder firmly anchors the ceramic particles to the base film surface, enhancing the overall structural stability of the coating and base film. This reduces the degree of separator curling in low-humidity environments, achieving a curl rate of less than 2%, overcoming the generally high curl rate of existing ceramic separator products. This less than 2% curl rate threshold ensures good flatness of the separator during winding or stacking processes, avoiding issues such as poor cell alignment, difficulty in electrode embedding, and short circuits caused by curling. Furthermore, it provides a clear and unified quality release standard for both production and quality control, improving the consistency and safety of cell manufacturing. Attached Figure Description

[0071] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0072] Figure 1 A schematic flowchart illustrating a method for detecting the curling of a ceramic separator for batteries, provided in an embodiment of this application;

[0073] Figure 2 A method for determining the curled area provided in this application embodiment;

[0074] Figure 3 A schematic diagram illustrating a method for placing a first diaphragm sample according to an embodiment of this application;

[0075] Figure 4 A schematic diagram illustrating a method for determining a first distance and a second distance provided in an embodiment of this application;

[0076] Figure 5 This is a schematic diagram of the structure of a battery ceramic separator curl detection device provided in an embodiment of this application.

[0077] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0078] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0079] This application provides a diaphragm with low curl rate.

[0080] In a first aspect, the ceramic separator for batteries provided in this application includes a base membrane and a ceramic layer disposed on at least one side of the base membrane. The ceramic layer includes ceramic particles and a binder, and the curvature of the ceramic separator is less than 2%.

[0081] In one possible implementation, the thickness of the base film is 4~8 μm.

[0082] In one possible implementation, the average thickness of the ceramic layer is 0.8 μm to 1.2 μm.

[0083] In one possible implementation, the mass ratio of ceramic particles to binder is (50~150):(2~10).

[0084] In one possible implementation, the base membrane comprises a polyethylene porous membrane and / or a polypropylene porous membrane.

[0085] The curl rate is obtained by testing the following method: obtaining a first diaphragm sample of a preset shape and the first area of ​​the first diaphragm sample, wherein the preset shape is an isosceles right triangle;

[0086] The first diaphragm sample was placed in a preset environment for humidity equilibration treatment;

[0087] Under a preset environment, multiple first vertices of the first diaphragm sample are fixed on a horizontal plane. After the curling stabilizes, a curled sample is obtained, where the first vertex is the acute angle vertex of the first diaphragm sample.

[0088] The curling area was determined based on the first diaphragm sample and the curled sample.

[0089] Divide the curled area by the first area to obtain the curling rate of the first diaphragm sample. The curling rate is used to indicate the degree of curling of the first diaphragm sample under a preset environment.

[0090] In one possible implementation, determining the curling area based on the first diaphragm sample and the curled sample includes:

[0091] Determine the projected area of ​​the curled sample on the horizontal plane;

[0092] The difference between the first area and the projected area is determined as the curled area.

[0093] In one possible implementation, determining the curling area based on the first diaphragm sample and the curled sample includes:

[0094] Determine the curl information of the curled specimen, which is used to indicate the projected dimensions of the multiple right-angled sides of the curled specimen on the horizontal plane;

[0095] Based on the curling information, the curling area is determined.

[0096] In one possible implementation, determining the curling information of the curled sample includes:

[0097] Under a preset environment, curled samples were obtained at multiple moments after the curling had stabilized.

[0098] For each moment, determine the first distance and the second distance of the curled sample. The first distance is the linear distance of the projection of the first right-angled side of the curled sample along its original length direction onto the horizontal plane, and the second distance is the linear distance of the projection of the second right-angled side of the curled sample along its original length direction onto the horizontal plane.

[0099] The first mean of the first distance at each time point and the second mean of the second distance at each time point are determined as the curl information.

[0100] In one possible implementation, under a preset environment, the curled sample is acquired at multiple time points after the curl has stabilized, including:

[0101] Under a preset environment, the state of the part of the first diaphragm sample other than the multiple first vertices is set as the preset state, which is a state without external force constraints.

[0102] Obtain curled samples at multiple time points;

[0103] Obtain curled samples at multiple time points, including:

[0104] The first diaphragm sample is placed in a preset environment and left to stand for a preset first time to obtain the curled sample at the first moment after the curling is stabilized.

[0105] Continue at a preset second time interval to obtain curled samples at times other than the first moment after curling has stabilized;

[0106] Based on the curling information, the curling area is determined, including:

[0107] Determine the first product between the first mean and the second mean;

[0108] Multiply the first product by the target value to obtain the curled area.

[0109] It should be noted that the method and apparatus for detecting the curling of a ceramic separator for batteries provided in this application can be used in the field of battery technology, or in any field other than battery technology. The application field of the method and apparatus for detecting the curling of a ceramic separator for batteries in this application is not limited.

[0110] It should be noted that in the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, it does not mean that the applicant has used or necessarily used the solution.

[0111] The separator of a lithium-ion battery is a porous insulating film placed between the positive and negative electrodes of the lithium battery. It allows lithium ions to pass through and prevents the positive and negative electrodes from directly contacting and short-circuiting. It is the core material for cell safety and cycle life.

[0112] In battery manufacturing, separators need to be wound or stacked in a low-humidity environment. However, in low humidity, separators are prone to curling due to internal stress release or anisotropic deformation. Severe curling can lead to poor cell alignment, difficulty in electrode insertion, and even short circuits, posing safety risks. Therefore, providing a separator product with low curling characteristics in low-humidity environments is crucial for ensuring the stability and safety of cell manufacturing. Curling refers to the upward warping, edge curling, and planar deformation of the separator due to internal stress release and anisotropic contraction under low humidity conditions.

[0113] Currently, although coating the base membrane with a ceramic layer is used to suppress separator deformation, this method has limited effectiveness in suppressing curling. Furthermore, existing ceramic separator products lack quantitative control over the degree of curling, resulting in significant differences in curling performance between different batches. The production end cannot clearly define what degree of curling meets the requirements of the battery cell manufacturing process, and quality control also lacks a unified acceptable curling rate threshold as a basis for quality release. In summary, the overall curling rate of existing ceramic separator products for batteries is relatively high.

[0114] To address the aforementioned issues, this application provides a ceramic separator for batteries, comprising a base membrane and a ceramic layer disposed on at least one side of the base membrane, the ceramic layer comprising ceramic particles and a binder, and the curvature of the ceramic separator being less than 2%.

[0115] In the aforementioned ceramic separator for batteries, a ceramic layer containing ceramic particles and a binder is formed on the surface of the base film. The rigid framework of the ceramic particles suppresses the anisotropic shrinkage of the separator base film in low-humidity environments. Simultaneously, the binder firmly anchors the ceramic particles to the base film surface, enhancing the overall structural stability of the coating and base film. This reduces the degree of separator curling in low-humidity environments, achieving a curl rate of less than 2%, overcoming the generally high curl rate of existing ceramic separator products. This less than 2% curl rate threshold ensures good flatness of the separator during winding or stacking processes, preventing issues such as poor cell alignment, difficulty in electrode embedding, and short circuits caused by curling. Furthermore, it provides a clear and unified quality release standard for both production and quality control, improving the consistency and safety of cell manufacturing.

[0116] Furthermore, currently, the degree of membrane curling can be detected by suspending a long strip of membrane sample and observing or directly measuring the warp height of the membrane's edge. However, in the above methods, it is difficult to quantify the curling tendency of the membrane in a free state, and the influence of membrane anisotropy (e.g., MD and TD) on the curling behavior is ignored. Therefore, the above methods may not be accurate in detecting the degree of membrane curling.

[0117] To address the aforementioned issues, this application provides a method for detecting the curling of a ceramic separator for batteries. The method involves obtaining a first separator sample with a preset shape and a first area of ​​the first separator sample. The preset shape is an isosceles right triangle. The first separator sample is placed in a preset environment and subjected to humidity balancing treatment. Under the preset environment, multiple first vertices of the first separator sample are fixed on a horizontal plane. After the curling stabilizes, a curled sample is obtained, where the first vertices are acute angle vertices of the first separator sample. Based on the first separator sample and the curled sample, the curled area is determined. The curled area is divided by the first area to obtain the curling rate, which indicates the degree of curling of the first separator sample under the preset environment.

[0118] In the above method, the first diaphragm sample, which is an isosceles right triangle, is used for curl detection. Leveraging the structural characteristics of the triangle's two acute vertices corresponding to the orthogonal directions MD and TD of the first diaphragm sample, the method can take into account the differential shrinkage deformation caused by the anisotropy of the first diaphragm sample. Furthermore, by fixing the acute vertices of the first diaphragm sample to a horizontal plane and stabilizing the curled state after humidity equilibrium, the curl rate is calculated by comparing the first area and the curled area of ​​the first diaphragm sample. This solves the problem that traditional long strip samples only observe the edge warping height, cannot quantify the overall free-state curling trend, and ignore bidirectional deformation differences. It can intuitively and quantitatively characterize the overall planar warping and edge curling of the first diaphragm sample, accurately reflecting the true curling trend of the first diaphragm sample under low humidity conditions. This improves the accuracy and comprehensiveness of diaphragm curl detection, providing a reliable quantitative basis for adjusting process parameters and selecting diaphragm materials in cell winding and stacking processes. It also reduces safety and yield problems caused by diaphragm curl during production, such as cell short circuits and stacking misalignments.

[0119] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0120] Figure 1 This is a schematic flowchart illustrating a method for detecting the curling of a ceramic separator for batteries, provided in an embodiment of this application. Please refer to... Figure 1 As shown, the method may include the following steps:

[0121] S101. Obtain a first diaphragm sample with a preset shape and a first area of ​​the first diaphragm sample. The preset shape is an isosceles right triangle.

[0122] The execution subject of this application embodiment can be a manual test or an electronic device, or it can be a battery ceramic separator curl detection device installed in an electronic device. The battery ceramic separator curl detection device can be implemented by software or by a combination of software and hardware.

[0123] In one possible implementation, the preset shape is a geometric shape set for uniform test conditions, amplifying curling behavior, and facilitating measurement and calculation. The preset shape is a right triangle; for example, it is an isosceles right triangle. The lengths of the two right-angled sides of the first diaphragm sample can both be 100 millimeters (mm), and the length of the hypotenuse can be 100 mm. mm.

[0124] In one possible implementation, the first diaphragm sample refers to a standard sample cut from the diaphragm roll for this curling test.

[0125] In one possible implementation, the first area refers to the initial area of ​​the first diaphragm sample after cutting, before any curling or deformation occurs.

[0126] In one possible implementation, the lengths of the two right-angled sides of the first diaphragm sample can first be determined, and then the first area can be determined based on the lengths of the two right-angled sides. For example, if the preset shape is an isosceles right triangle and the length of each of the two right-angled sides of the first diaphragm sample is 100 mm, then the first area is (1 / 2 × 100 × 100) mm. 2 That is, 5000mm 2 .

[0127] In some implementations, obtaining a first diaphragm sample of a predetermined shape may include:

[0128] A second diaphragm sample is obtained, which includes the first diaphragm sample; the second diaphragm sample is cut along a preset direction to obtain a first diaphragm sample of a preset shape.

[0129] In one possible implementation, the second separator sample is a ceramic separator roll for lithium-ion batteries to be tested.

[0130] In one possible implementation, the bevel of the first diaphragm sample is cut in a direction perpendicular to MD, where MD refers to the direction along the production line during the production of the first diaphragm sample, also known as the longitudinal or length direction.

[0131] In one possible implementation, the two right-angled sides of the cut first diaphragm sample are at a 45° angle to the machine direction. This cutting method can simultaneously reflect the stress release characteristics of the first diaphragm sample in both the machine direction and the transverse direction, enhancing the sensitivity to the anisotropic curling behavior of the material. Here, the transverse direction refers to the direction perpendicular to the machine direction, i.e., the width direction during diaphragm production, or it can be understood as perpendicular to the material feeding direction.

[0132] In one possible implementation, a wrinkle-free, stain-free, and deformation-free area can be selected from the middle of the second diaphragm sample. Using a pre-shaped mold, the sample is cut perpendicular to the machine direction using a cutter or laser cutting method, ensuring that the hypotenuse of the pre-shaped shape is perpendicular to the machine direction and the two right-angled sides are at 45° to the machine direction, thus obtaining the first diaphragm sample. Cutting the second diaphragm sample using a cutter or laser cutting method can result in neat cut edges without tensile deformation.

[0133] In this way, by cutting the second diaphragm sample into the first diaphragm sample of a preset shape, the degree of curling can be detected, which can amplify the curling behavior of the first diaphragm sample due to stress release in a low humidity environment, making the effect of curling easy to observe and quantify.

[0134] Furthermore, by cutting the second diaphragm sample along a predetermined direction, a first diaphragm sample is obtained. The right-angled edge of the first diaphragm sample forms a 45° angle with the machine direction, which can simultaneously reflect the difference in thermal shrinkage of the first diaphragm sample in both the machine direction and the transverse direction. For example, if the shrinkage rate of the first diaphragm sample in the machine direction is higher than that in the transverse direction, the difference in the projected size of the right-angled edge after cutting will be more obvious. This allows for a more accurate differentiation of the contribution of material anisotropy to the curling behavior, providing data support for coating structure optimization.

[0135] S102. Place the first diaphragm sample in a preset environment and perform humidity balancing treatment.

[0136] In some implementations, the preset environment is a dry environment, and the duration of humidity balancing processing is greater than or equal to a preset third duration.

[0137] In one possible implementation, the preset environment can be a low-humidity, dry room temperature environment. For example, the preset environment refers to an environment with humidity of 1.5% to 2.5% and a preset temperature (such as 25 degrees Celsius, °C). This environment is the environment for battery processing. Performing humidity balancing treatment in this environment can accurately quantify the degree of membrane curling in the battery environment.

[0138] In one possible implementation, the third duration refers to the minimum processing time required for the first diaphragm sample to adapt to the preset environment and for its internal moisture and ambient humidity to reach equilibrium. For example, the third duration is 30 minutes.

[0139] In one possible implementation, humidity balancing treatment refers to placing the first diaphragm sample in a preset environment for a preset third time to allow the first diaphragm sample to reach the humidity state of the preset environment, and also to stabilize the internal stress of the first diaphragm sample and eliminate the influence of historical environmental factors on the test results.

[0140] In one possible implementation, during the humidity balancing process of the first diaphragm sample, the first diaphragm sample is kept flat, wrinkle-free, and free from external force constraints, so as to ensure that the subsequent curling behavior is determined only by the characteristics of the diaphragm itself.

[0141] In this way, by performing sufficient humidity balancing treatment on the first diaphragm sample, the internal moisture content of the sample can be made consistent with the ambient humidity, avoiding differences in local stress release caused by moisture gradients. For example, if the diaphragm is not sufficiently balanced, its edges may curl prematurely due to excessively rapid local drying, causing the measurement results to deviate from the intrinsic characteristics of the diaphragm. Therefore, humidity balancing treatment can eliminate testing errors caused by changes in ambient humidity, ensuring a stable curling state of the first diaphragm sample and accurate test results.

[0142] S103. Under a preset environment, fix multiple first vertices of the first diaphragm sample on a horizontal plane. After the curling stabilizes, a curled sample is obtained, where the first vertex is the acute angle vertex of the first diaphragm sample.

[0143] In one possible implementation, the first vertex refers to the two acute vertices of the first diaphragm sample, where the acute vertices are vertices with an angle less than 90°. For example, if the shape of the first diaphragm sample is an isosceles right triangle, then the first vertex is the two 45° vertices of the first diaphragm sample.

[0144] In one possible implementation, curl stability means that after the first diaphragm sample has been placed for a certain period of time, the curl shape no longer changes significantly over time, and the deformation reaches an equilibrium state.

[0145] In this way, by placing the first diaphragm sample in a preset environment, the interference of moisture on the expansion and stress release of the first diaphragm sample can be eliminated, so that the subsequent determination of the curl rate can focus more on the dimensional stability of the first diaphragm sample characteristics.

[0146] S104. Determine the curling area based on the first diaphragm sample and the curled sample.

[0147] In some implementations, determining the curled area based on the first diaphragm sample and the curled sample may include:

[0148] Determine the projected area of ​​the curled sample on the horizontal plane; the difference between the first area and the projected area is determined as the curled area.

[0149] In one possible implementation, an image acquisition device can be used to take a picture of the curled sample vertically facing the horizontal plane. The closed projection contour of the curled sample on the horizontal plane can be extracted by an image contour recognition algorithm, thereby calculating the projected area. Then, the difference between the first area and the projected area can be calculated, and the difference can be determined as the curled area.

[0150] It is understandable that after the first diaphragm sample curls and warps, it will detach from the horizontal plane and arch upwards, and the projected area of ​​the plane will be smaller than the area of ​​the initial intact plane (i.e., the first area). The greater the difference between the two, the greater the total deformation of the diaphragm warping and curling. Therefore, the area difference can be used to quantitatively characterize the size of the deformation area caused by curling.

[0151] S105. Divide the curled area by the first area to obtain the curling rate of the first diaphragm sample. The curling rate is used to indicate the degree of curling of the first diaphragm sample under a preset environment.

[0152] In one possible implementation, the curling rate refers to a value calculated by the ratio of the projected area after curling to the initial area. It can be a percentage or a decimal value, used to quantitatively, uniformly, and intuitively represent the degree of curling of the diaphragm under a preset environment. The larger the curling rate, the greater the degree of curling of the first diaphragm sample; the smaller the curling rate, the smaller the degree of curling of the first diaphragm sample.

[0153] For example, the curl rate can be expressed as: C=S1 / S2×100%, where S1 represents the curled area and S2 represents the first area.

[0154] In this embodiment, a first diaphragm sample with a preset shape and a first area of ​​the first diaphragm sample are obtained. The preset shape is an isosceles right triangle. The first diaphragm sample is placed in a preset environment and subjected to humidity balancing treatment. In the preset environment, multiple first vertices of the first diaphragm sample are fixed on a horizontal plane. After the curling stabilizes, a curled sample is obtained, where the first vertex is the acute vertex of the first diaphragm sample. Based on the first diaphragm sample and the curled sample, the curled area is determined. The curled area is divided by the first area to obtain the curling rate, which is used to indicate the degree of curling of the first diaphragm sample in the preset environment.

[0155] In the above method, the first diaphragm sample, which is an isosceles right triangle, is used for curl detection. Leveraging the structural characteristics of the triangle's two acute vertices corresponding to the orthogonal directions MD and TD of the first diaphragm sample, the method can take into account the differential shrinkage deformation caused by the anisotropy of the first diaphragm sample. Furthermore, by fixing the acute vertices of the first diaphragm sample to a horizontal plane and stabilizing the curled state after humidity equilibrium, the curl rate is calculated by comparing the first area and the curled area of ​​the first diaphragm sample. This solves the problem that traditional long strip samples only observe the edge warping height, cannot quantify the overall free-state curling trend, and ignore bidirectional deformation differences. It can intuitively and quantitatively characterize the overall planar warping and edge curling of the first diaphragm sample, accurately reflecting the true curling trend of the first diaphragm sample under low humidity conditions. This improves the accuracy and comprehensiveness of diaphragm curl detection, providing a reliable quantitative basis for adjusting process parameters and selecting diaphragm materials in cell winding and stacking processes. It also reduces safety and yield problems caused by diaphragm curl during production, such as cell short circuits and stacking misalignments.

[0156] Based on the above embodiments, it can also be achieved through, as follows: Figure 2 The method for determining the curl area, for example, Figure 2 A method for determining the curled area provided in this application embodiment, such as Figure 2 As shown, the method includes:

[0157] S201. Determine the curling information of the curled sample. The curling information is used to indicate the projected dimensions of the multiple right-angled sides of the curled sample on the horizontal plane.

[0158] In one possible implementation, the curling information is used as geometric measurement data to indicate the degree of curling of the first diaphragm sample. In this embodiment, the curling information can be the projected straight-line distance between the multiple right-angled edges of the first diaphragm sample along their original direction on a horizontal plane after curling. Here, the horizontal plane refers to a flat reference plane used to place and fix the diaphragm sample during the testing process, serving as a unified measurement reference.

[0159] In one possible implementation, the projected dimension refers to the length of the straight line formed by the vertical projection of the edge of the first diaphragm sample onto the horizontal reference plane after it has curled up.

[0160] In some implementations, determining the curling information of the curled sample includes:

[0161] Under a preset environment, the curled sample is acquired at multiple time points after the curling has stabilized. For each time point, a first distance and a second distance of the curled sample are determined. The first distance is the straight-line distance of the projection of the first right-angled side of the curled sample along its original length direction onto the horizontal plane, and the second distance is the straight-line distance of the projection of the second right-angled side of the curled sample along its original length direction onto the horizontal plane. The first average of the first distance at each time point and the second average of the second distance at each time point are determined as the curling information.

[0162] In one possible implementation, the first distance refers to the projected straight-line distance on the horizontal plane formed by the right-angled side of the first diaphragm sample along its original length direction, from the right-angle vertex to the farthest point of the curled edge. The original length direction refers to the straight-line direction where the right-angled side of the first diaphragm sample is located when it is not deformed. The projected straight-line distance refers to the straight-line length between the vertical projection points of the curled edge of the first diaphragm sample on the horizontal reference plane, which is not affected by the height of the curl, and is used to indicate the degree of horizontal shrinkage of the first diaphragm sample.

[0163] In one possible implementation, the second distance refers to the projected straight-line distance on a horizontal plane formed by the other right-angled side of the first diaphragm sample along its original length direction, from the right-angle vertex to the farthest point of the curled edge.

[0164] In one possible implementation, for each moment, the first distance can be obtained by measuring the straight-line distance between the farthest projection point of the curled edge along the original length direction of the first right-angled side, starting from the right-angle vertex, using a vernier caliper or optical measurement system. Alternatively, the second distance can be obtained by measuring the straight-line distance between the farthest projection point of the curled edge along the original length direction of the other right-angled side, starting from the same right-angle vertex, using a vernier caliper or optical measurement system. The accuracy of the vernier caliper and optical measurement system is greater than or equal to 0.1 mm.

[0165] In one possible implementation, the first mean refers to the arithmetic mean of the first distances measured at multiple times, used to eliminate single-shot errors, and the second mean refers to the arithmetic mean of the second distances measured at multiple times.

[0166] In one possible implementation, the first distances at multiple times can be summed and averaged to obtain a first mean, and the second distances at multiple times can be summed and averaged to obtain a second mean. The first mean and the second mean can then be combined as the curly information.

[0167] In this way, since the curling shape of the diaphragm may fluctuate in the short term due to the difference in local stress release under low humidity environment, by sampling the first diaphragm sample after the curling has stabilized at multiple times, measuring the horizontal projection distance of the two right-angled sides and calculating the average value, the random error (such as environmental disturbance) and reading fluctuation caused by a single measurement can be reduced, the accuracy, stability and repeatability of the curling information can be improved, and the obtained curling information can truly and objectively reflect the curling deformation characteristics of the first diaphragm sample, providing reliable data support for subsequent accurate calculation of the curling rate.

[0168] In some implementations, acquiring curled samples at multiple moments after curling has stabilized, under a preset environment, may include:

[0169] Under a preset environment, the state of the portion of the first diaphragm sample other than the multiple first vertices is set to a preset state, which is a state without external force constraints; and the curled sample at multiple times is obtained.

[0170] In one possible implementation, the preset state means that, except for the two fixed acute vertices, all other regions are not subject to external forces such as pressing, stretching, clamping, or obstruction, and can be completely free to deform, warp, and shrink.

[0171] In one possible implementation, the state without external force constraints means that the first diaphragm sample is only subjected to gravity, with no external mechanical force applied to the membrane surface, the internal stress can be completely released, and the curling behavior is entirely determined by the material's own properties.

[0172] In one possible implementation, multiple first vertices (i.e. two acute vertices) of the first diaphragm sample are gently fixed on a horizontal plane using a lightweight clamp. The fixing point only covers the area of ​​the vertices and does not affect the free deformation of the membrane surface. The part of the first diaphragm sample other than the two acute vertices is set to a preset state. At this time, the right-angled vertices, the two right-angled sides, and the hypotenuse are all in a free and unrestrained state, and can freely bend upward, shrink inward, and deform.

[0173] For example, Figure 3 The following explanation uses the example of an isosceles right triangle as the shape of the first diaphragm sample. Figure 3 A schematic diagram illustrating a method for placing a first diaphragm sample according to an embodiment of this application is shown below. Figure 3 As shown, the first diaphragm sample includes vertex A, vertex B and vertex C. Vertex A and vertex B are both acute vertices, vertex C is a right-angled vertex. Vertex A and vertex B are both fixed to the horizontal plane by a lightweight clamp. Vertex C and other parts of the first diaphragm sample are not constrained by external forces. The vertically downward direction is the machine direction.

[0174] It should be noted that the shrinkage deformation of the first diaphragm sample can only occur horizontally along the length of the right-angled sides. The deformation displacement is concentrated at the right-angled vertex at the free end, resulting only in upward warping vertical deformation. There is no mechanical condition for the two right-angled sides to bend towards each other and converge towards the middle. Therefore, the two right-angled sides will only shrink horizontally along their respective length directions, and there will be no phenomenon of the two right-angled sides simultaneously curling and converging towards the center of the triangle. In addition, since the two right-angled sides are at 45° with the MD direction, each right-angled side simultaneously bears two sets of shrinkage stresses in the machine direction and the transverse direction. After the two sets of stress vectors are superimposed, the resultant force points vertically upward in a direction away from the horizontal plane. The stress release path is only the lifting of the right-angled vertex, and there will be no horizontal resultant force pointing towards the inside of the triangle. Therefore, the two right-angled sides will only shorten synchronously and warp upward at the free end, and will not bend and converge towards each other.

[0175] For example, Figure 4 The following explanation uses the example of an isosceles right triangle as the shape of the first diaphragm sample. Figure 4 A schematic diagram illustrating a method for determining a first distance and a second distance provided in an embodiment of this application, as shown below. Figure 4 As shown, the first diaphragm sample includes vertex D, vertex E, vertex F, vertex G, region A, region B, edge A, and edge B. Region A is a part of the region of the initial uncurled first diaphragm sample. Region A and region B together form the region of the initial uncurled first diaphragm sample. Region B is the projected region of the first diaphragm sample after curing (i.e., the curled sample). Vertex G and vertex E are both the farthest points of the curled edges. The first distance is the length of edge A, and the second distance is the length of edge B.

[0176] In some implementations, curled samples are acquired at multiple time points, including:

[0177] The first diaphragm sample is placed in a preset environment and left to stand for a preset first time to obtain a curled sample at the first moment after the curling has stabilized; the curled sample is then left at a preset second time interval to obtain a curled sample at a time other than the first moment after the curling has stabilized.

[0178] In one possible implementation, the preset first duration is the shortest settling time required for the first diaphragm sample to reach a curled stable state from its initial flat state; for example, the first duration is 10 minutes.

[0179] In one possible implementation, the first moment refers to the time point at which the first measurement is performed after the first diaphragm sample has reached curling stability.

[0180] In one possible implementation, continuing to take a second preset time interval means that after the measurement is completed at the first moment, the curled sample that has been curled up is obtained again at a preset second time interval to obtain multiple sets of data under stable conditions.

[0181] In one possible implementation, the first fixed diaphragm sample can be placed in a preset environment and left to stand for a preset first time to allow the internal stress of the diaphragm to be fully released and the curling shape to no longer change significantly, thus obtaining the curled sample at the first moment after the curling has stabilized.

[0182] In one possible implementation, after the first moment, a preset second time interval (e.g., 1 minute) can be maintained to sequentially obtain the curled sample at the second and third moments. It should be noted that the number of times the curled sample is obtained after the first moment can be preset, for example, the number of times the first diaphragm sample is obtained is 2.

[0183] In this way, by fixing multiple first vertices of the first diaphragm sample and keeping the rest in a free state without external force constraints, and waiting for a first time period under a preset environment to allow the diaphragm to curl up to a stable state, and then acquiring curled samples at multiple time intervals with a second time period as the interval, the internal stress of the diaphragm can be fully released, making the diaphragm curling shape real and stable. At the same time, sampling at multiple time periods can effectively reduce the error caused by a single measurement, improve the accuracy, consistency and reliability of curling information acquisition, and provide a reliable and stable data foundation for the subsequent determination of the curling rate.

[0184] Furthermore, by fixing the two acute-angled vertices and allowing the right-angled vertices to curl freely, the curling of the first diaphragm sample can be driven only by internal stress rather than by external clamping force interference, thus more realistically simulating the free deformation of the diaphragm in a low-humidity environment. In addition, by making the part outside the acute-angled vertices a state without external force constraints, the edge stress concentration of the first diaphragm sample can be avoided, making the curling shape of the right-angled vertices closer to the stress release process in actual applications.

[0185] S202. Determine the curl area based on the curl information.

[0186] In some implementations, the curl area is determined based on curl information, including:

[0187] Determine the first product between the first mean and the second mean; multiply the first product by the target value to obtain the curled area.

[0188] In one possible implementation, the first product refers to the value obtained by multiplying the lengths of the two projected right-angled sides after averaging over multiple time intervals, that is, the product of the first mean and the second mean. This product represents the rectangular equivalent area corresponding to the horizontal projection of the rolled-up sample.

[0189] In one possible implementation, the target value is the area conversion factor corresponding to the isosceles right triangle, for example, 1 / 2. Since the geometry of the first diaphragm sample is an isosceles right triangle, and the standard area calculation formula for a triangle is the product of half the area and the lengths of the two right-angled sides, a factor of 1 / 2 is selected as the target value to complete the conversion of the projected triangle area.

[0190] In one possible implementation, the first and second means can be multiplied, and half of the result can be used to determine the area of ​​curvature. For example, the area of ​​curvature can be expressed as: S1 = 1 / 2 × W1 × W2, where W1 represents the first mean and W2 represents the second mean. The area of ​​curvature can be... Figure 3 The area of ​​region B in the example.

[0191] In this way, by determining the curling area through curling information, the curling rate of the first diaphragm sample can be obtained in subsequent steps based on the curling area and the first area. This eliminates the need for complex three-dimensional contour scanning, thereby improving the efficiency of diaphragm curling detection and reducing the cost of diaphragm curling detection.

[0192] In this embodiment, the curling information of the curled sample is determined. The curling information is used to indicate the projected dimensions of multiple right-angled sides of the curled sample on the horizontal plane. Based on the curling information, the curled area is determined. In the above method, by collecting only the projected lengths of two characteristic right-angled sides, averaging measurements at multiple times to eliminate errors from single readings and deformation fluctuations, and directly completing the area conversion based on the inherent geometric coefficients of triangles, there is no need to build complex detection equipment such as image capture, contour recognition, or 3D scanning. This method can balance the accuracy of diaphragm MD and TD bidirectional stress shrinkage characterization, simplify the testing operation process, shorten the detection time, and reduce hardware investment costs. It can also reliably avoid the data drift problem caused by the slow release of diaphragm stress in low humidity environments, achieving low-cost, high-efficiency, and highly repeatable quantitative detection of diaphragm curling.

[0193] It should be noted that the method for detecting the curling of ceramic separators for batteries provided in this application embodiment can be applied to various types of ceramic separators for lithium-ion batteries, including polyethylene, polypropylene, and ceramic-coated separators, and has good versatility.

[0194] In one example, the second separator sample is a boehmite ceramic-coated polyethylene (PE) lithium-ion battery ceramic separator with a base film thickness of 8 micrometers (μm) and a 1 μm thick boehmite ceramic layer coated on one side (the solid mass ratio of ceramic particles to SBR binder is 100:5). A first separator sample A is cut from the second separator sample. The first separator sample A is an isosceles right triangle with each right angle side length of 100 mm. The first separator sample A is then placed in a preset environment and subjected to a 30-minute humidity equilibration treatment. Finally, it is placed using a lightweight clamp. Two acute-angle vertices of the first diaphragm sample A were fixed and placed on a horizontal peeling plate, with the right-angle vertices in a free state. After standing for 15 minutes, the curled state of the first diaphragm sample A stabilized, and the curled sample A at that time (i.e., time A) was obtained. The first distance and the second distance of the curled sample A at that time (i.e., time A) were then determined by a vernier caliper (accuracy of 0.1 mm). After determination, the curled sample B at time B and the curled sample C at time C were obtained at second time intervals. At the same time, the first distance and the second distance of the curled sample B and the first distance and the second distance of the curled sample C were determined in sequence. The results are shown in Table 1.

[0195] Table 1

[0196]

[0197] Among them, 49.73 mm is the first average, 99.87 mm is the second average, and the first area of ​​the first diaphragm sample A before curling was 5000 mm². 2 The curled area, determined based on the first and second means, is (1 / 2 × 49.73 × 99.87) mm. 2 That is, 2483.27mm 2 The curl rate is (2483.27 / 5000×100%), which is 49.67%.

[0198] In another example, the second diaphragm sample is a three-layer PP / PE / PP composite diaphragm with a thickness of 16 μm and a 1 μm thick boehmite ceramic layer coated on one side. The first diaphragm sample B is cut from the second diaphragm sample. The shape of the first diaphragm sample B is an isosceles right triangle with a right angle side length of 100 mm. The subsequent processing of the first diaphragm sample B is the same as that of the first diaphragm sample A. After the first diaphragm sample B is curled and stabilized, the first distance and the second distance at three times (time D, time E and time F) are shown in Table 2.

[0199] Table 2

[0200]

[0201] Among them, 23.83 mm is the first average, 98.70 mm is the second average, and the first area of ​​the first diaphragm sample B before curling was 5000 mm². 2 The curled area, determined based on the first and second mean values, is (1 / 2 × 23.83 × 98.70) mm. 2 That is, 1176.01mm 2 The curl rate was 23.52%.

[0202] As can be seen from the two examples above, under the preset environment, the anti-curling performance of the second diaphragm sample in the second example is better than that of the second diaphragm sample in the first example.

[0203] Figure 5 This is a schematic diagram of a device for detecting the curling of a ceramic separator for batteries, provided in an embodiment of this application. Please refer to... Figure 5 The battery ceramic separator curling detection device 500 includes: an acquisition module 501, a first processing module 502, a second processing module 503, a determination module 504, and a third processing module 505, wherein...

[0204] The acquisition module 501 is used to acquire a first diaphragm sample with a preset shape and a first area of ​​the first diaphragm sample. The preset shape is an isosceles right triangle.

[0205] The first processing module 502 is used to place the first diaphragm sample in a preset environment for humidity balancing treatment.

[0206] The second processing module 503 is used to fix multiple first vertices of the first diaphragm sample on a horizontal plane under a preset environment. After the curling is stabilized, a curled sample is obtained, where the first vertex is the acute angle vertex of the first diaphragm sample.

[0207] Module 504 is used to determine the curling area based on the first diaphragm sample and the curled sample;

[0208] The third processing module 505 is used to divide the curled area by the first area to obtain the curling rate of the first diaphragm sample. The curling rate is used to indicate the degree of curling of the first diaphragm sample under a preset environment.

[0209] The device for detecting the curling of a ceramic separator for batteries provided in this application embodiment can perform the technical solution shown in the above method embodiment. Its implementation principle and beneficial effects are similar, and will not be described again here.

[0210] In one possible implementation, the determining module 504 is specifically used for:

[0211] Determine the projected area of ​​the curled sample on the horizontal plane;

[0212] The difference between the first area and the projected area is determined as the curled area.

[0213] In one possible implementation, the determining module 504 is specifically used for:

[0214] Determine the curl information of the curled specimen, which is used to indicate the projected dimensions of the multiple right-angled sides of the curled specimen on the horizontal plane;

[0215] Based on the curling information, the curling area is determined.

[0216] In one possible implementation, the determining module 504 is specifically used for:

[0217] Under a preset environment, curled samples were obtained at multiple moments after the curling had stabilized.

[0218] For each moment, determine the first distance and the second distance of the curled sample. The first distance is the linear distance of the projection of the first right-angled side of the curled sample along its original length direction onto the horizontal plane, and the second distance is the linear distance of the projection of the second right-angled side of the curled sample along its original length direction onto the horizontal plane.

[0219] The first mean of the first distance at each time point and the second mean of the second distance at each time point are determined as the curl information.

[0220] In one possible implementation, the determining module 504 is specifically used for:

[0221] Under a preset environment, the state of the part of the first diaphragm sample other than the multiple first vertices is set as the preset state, which is a state without external force constraints.

[0222] Obtain curled samples at multiple times.

[0223] In one possible implementation, the determining module 504 is specifically used for:

[0224] The first diaphragm sample is placed in a preset environment and left to stand for a preset first time to obtain the curled sample at the first moment after the curling is stabilized.

[0225] Continue at a preset second time interval to obtain the curled sample at a time other than the first moment after the curling has stabilized.

[0226] In one possible implementation, the determining module 504 is specifically used for:

[0227] Determine the first product between the first mean and the second mean;

[0228] Multiply the first product by the target value to obtain the curled area.

[0229] In one possible implementation, the acquisition module 501 is specifically used for:

[0230] Obtain a second diaphragm sample, the second diaphragm sample including the first diaphragm sample;

[0231] The second diaphragm sample is cut along a preset direction to obtain a first diaphragm sample of a preset shape.

[0232] In one possible implementation, the preset environment is a dry environment, and the duration of the humidity balancing process is greater than or equal to a preset third duration.

[0233] The device for detecting the curling of a ceramic separator for batteries provided in this application embodiment can perform the technical solution shown in the above method embodiment. Its implementation principle and beneficial effects are similar, and will not be described again here.

[0234] In the embodiments provided in this application, it should be understood that the disclosed methods can be implemented in other ways. For example, the division of modules is merely a logical functional division; in actual implementation, there may be other division methods. For instance, multiple modules may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or modules, and may be electrical, mechanical, or other forms.

[0235] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The unit composed of the above modules can be implemented in hardware or in the form of hardware plus software functional units.

[0236] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A ceramic separator for batteries, characterized in that, It includes a base membrane and a ceramic layer disposed on at least one side of the base membrane, the ceramic layer comprising ceramic particles and a binder, the ceramic membrane having a curl rate of less than 2%.

2. The ceramic separator for batteries according to claim 1, characterized in that, The thickness of the base film is 4~8μm.

3. The ceramic separator for batteries according to claim 1, characterized in that, The average thickness of the ceramic layer is 0.8 μm to 1.2 μm.

4. The ceramic separator for batteries according to claim 1, characterized in that, The mass ratio of the ceramic particles to the binder is (50~150):(2~10).

5. The ceramic separator for batteries according to claim 1, characterized in that, The base membrane includes polyethylene porous membranes and / or polypropylene porous membranes.

6. The ceramic separator for batteries according to claim 1, characterized in that, The curl rate was obtained by testing using the following method: Obtain a first diaphragm sample with a preset shape and a first area of ​​the first diaphragm sample, wherein the preset shape is an isosceles right triangle; The first diaphragm sample was placed in a preset environment for humidity balancing treatment; Under the preset environment, multiple first vertices of the first diaphragm sample are fixed on a horizontal plane. After the curling is stabilized, a curled sample is obtained. The first vertex is the acute angle vertex of the first diaphragm sample. Based on the first diaphragm sample and the curled sample, the curled area is determined; Dividing the curled area by the first area yields the curling rate of the first diaphragm sample, which indicates the degree of curling of the first diaphragm sample under the preset environment.

7. The ceramic separator for batteries according to claim 6, characterized in that, Determining the curled area based on the first diaphragm sample and the curled sample includes: Determine the projected area of ​​the curled sample on the horizontal plane; The difference between the first area and the projected area is determined as the curled area.

8. The ceramic separator for batteries according to claim 6, characterized in that, Determining the curled area based on the first diaphragm sample and the curled sample includes: Determine the curling information of the curled sample, the curling information being used to indicate the projected dimensions of the multiple right-angled sides of the curled sample on a horizontal plane; Based on the curling information, the curling area is determined.

9. The ceramic separator for batteries according to claim 8, characterized in that, Determining the curling information of the curled sample includes: Under a preset environment, curled samples were obtained at multiple moments after the curling had stabilized. For each moment, a first distance and a second distance of the curled sample are determined. The first distance is the projected straight-line distance of the first right-angled side of the curled sample along its original length direction on the horizontal plane, and the second distance is the projected straight-line distance of the second right-angled side of the curled sample along its original length direction on the horizontal plane. The first mean of the first distance at each time point and the second mean of the second distance at each time point are determined as curl information.

10. The ceramic separator for batteries according to claim 9, characterized in that, The process of acquiring curled samples at multiple moments after curling has stabilized under a preset environment includes: Under a preset environment, the state of the portion of the first diaphragm sample other than the plurality of first vertices is set as a preset state, which is a state without external force constraints. Obtain curled samples at multiple time points; The acquisition of curled samples at multiple times includes: The first diaphragm sample is placed in a preset environment and left to stand for a preset first time to obtain the curled sample at the first moment after the curling is stabilized. Continue at a preset second time interval to obtain curled samples at times other than the first moment after curling has stabilized; Determining the curl area based on the curl information includes: Determine the first product between the first mean and the second mean; Multiply the first product by the target value to obtain the curled area.

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