Composite diaphragm

Abstract

The utility model relates to the technical field of batteries, in particular to a composite diaphragm. The composite diaphragm comprises a base membrane and a composite coating located on the surface of at least one side of the base membrane, the composite coating comprises a heat-resistant layer, a strip-shaped coating and a bonding layer, the strip-shaped coating comprises a first strip-shaped structure and a second strip-shaped structure, the first strip-shaped structure is an inorganic ceramic layer, and the second strip-shaped structure is a polymer layer; the heat-resistant layer is located on the surface of the base film, the surface, away from the base film, of the heat-resistant layer is provided with a coating area and a blank area, the coating area is provided with the strip-shaped coating, and the bonding layer is located on the surface, away from the base film, of the strip-shaped coating and the surface of the blank area. Through cooperation of all the layers, the heat resistance, the bonding performance and the liquid storage performance of the composite diaphragm can be improved, and the capacity retention ratio, the cycle performance and the safety performance of the battery can be improved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and more specifically, to a composite separator. Background Technology

[0002] As one of the four major components of lithium batteries, the separator's performance directly affects the cell's performance. Therefore, functional separators have attracted much attention. For example, coating the separator with an inorganic ceramic layer can improve its overall thermal shrinkage performance; to improve the adhesion between the electrode and the separator, a layer of polyvinylidene fluoride (PVDF) is often sprayed onto the separator. These functional separators solve some of the separator's defects, but they also lead to some performance degradation. For instance, when coating with a ceramic layer, a full-coverage heat-resistant ceramic layer is required, which worsens the separator's overall permeability and reduces its liquid storage performance; the adhesion between the sprayed PVDF and the electrode is relatively weak, and the overall cell rigidity is still insufficient, requiring further improvement.

[0003] In view of the above, this utility model is hereby proposed. Utility Model Content

[0004] One objective of this invention is to provide a composite separator that has excellent heat resistance, adhesion, and liquid storage properties, which can improve the battery's capacity retention, cycle performance, and safety performance.

[0005] In order to achieve the above-mentioned objectives of this utility model, the following technical solution is adopted:

[0006] A composite membrane includes a base membrane and a composite coating located on at least one surface of the base membrane. The composite coating includes a heat-resistant layer, a strip-shaped coating, and an adhesive layer. The strip-shaped coating includes a first strip-shaped structure and a second strip-shaped structure, wherein the first strip-shaped structure is an inorganic ceramic layer and the second strip-shaped structure is a polymer layer. The heat-resistant layer is located on the surface of the base membrane. The surface of the heat-resistant layer away from the base membrane is provided with a coating area and a blank area. The strip-shaped coating is disposed in the coating area. The adhesive layer is located on the surface of the strip-shaped coating away from the base membrane and on the surface of the blank area.

[0007] In some embodiments, the angle θ between the first strip structure and the second strip structure and the width direction of the base film satisfies: 0°... <x≤45°。

[0008] In some embodiments, the first strip structure and the second strip structure are distributed in parallel at equal intervals on the surface of the heat-resistant layer.

[0009] In some embodiments, the angle θ between the first strip structure and the second strip structure and the width direction of the base film satisfies: 0°... <x≤35°。

[0010] In some embodiments, the distance between any adjacent first strip structure and / or second strip structure is 400–600 μm.

[0011] In some embodiments, the widths of the first strip structure and the second strip structure are 200–400 μm.

[0012] In some embodiments, the distance between any adjacent first strip structure and / or second strip structure is 450–550 μm; the width of the first strip structure and the second strip structure is 250–350 μm.

[0013] In some implementations, the ratio of the number a of the first strip structure to the number b of the second strip structure satisfies: 1 ≤ a : b ≤ 10, where a and b are integers from 1 to 10.

[0014] In some embodiments, the thickness h1 of the first strip structure is 1.5 to 3.5 μm, and the thickness h2 of the second strip structure is 3 to 5 μm.

[0015] In some embodiments, the difference between the thickness h2 of the second strip structure and the thickness h1 of the first strip structure satisfies: h2-h1=1.5μm.

[0016] In some embodiments, the adhesive layer is a porous polymer layer.

[0017] In some embodiments, the thickness h3 of the adhesive layer is 2 to 4 μm, and h3 > h1.

[0018] In some embodiments, the porosity of the adhesive layer is 40% to 60%.

[0019] In some embodiments, the heat-resistant layer is a ceramic layer.

[0020] In some embodiments, the thickness of the heat-resistant layer is 0.4 to 1.0 μm.

[0021] In some embodiments, the thickness of the base film is 5–20 μm.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0023] The composite separator of this invention features a heat-resistant layer that enhances the overall heat resistance of the separator, ensuring its integrity even at high temperatures. The heat-resistant layer incorporates a discontinuous strip coating composed of two parts: a first strip structure made of inorganic ceramic material, which provides support during hot pressing of the separator and electrode sheets, creating more liquid storage space; and a second strip structure made of polymer, which acts as an adhesive to the electrode sheets during hot pressing, increasing the density of the separator and electrode sheets after hot pressing. An adhesive layer further enhances the adhesion between the separator and electrode sheets, thus ensuring the rigidity of the battery cell. Through the synergy of these layers, the composite separator's heat resistance, adhesion, and liquid storage performance are improved, which is beneficial for enhancing the battery's capacity retention, cycle performance, and safety. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the overall structure of the composite diaphragm in Examples 1 to 5 of this utility model;

[0026] Figure 2 This is a top view schematic diagram of the strip-shaped coating in this utility model.

[0027] Figure label:

[0028] 1-Base film, 2-Heat resistant layer, 3-First strip structure, 4-Second strip structure, 5-Adhesive layer, 6-Blank area. Detailed Implementation

[0029] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and defined, the terms "arranged", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0031] A composite separator, comprising a base film and a composite coating located on at least one surface of the base film, the composite coating comprising a heat-resistant layer, a strip coating, and an adhesive layer, the strip coating comprising a first strip structure and a second strip structure, the first strip structure being an inorganic ceramic layer, and the second strip structure being a polymer layer; the heat-resistant layer is located on the surface of the base film, and a coating area and a blank area are provided on the surface of the heat-resistant layer away from the base film, the strip coating is provided in the coating area, and the adhesive layer is located on the surface of the strip coating away from the base film and the surface of the blank area.

[0032] In the composite separator of the present utility model, the heat-resistant layer can improve the overall heat resistance level of the separator, ensuring that the separator can still maintain good integrity at high temperatures; the discontinuous strip coating provided on the heat-resistant layer consists of two parts. One part is the first strip structure with inorganic ceramic material, which plays a supporting role when the separator is hot-pressed with the electrode sheet, creating more liquid storage space for the coated separator; the other part is the second strip structure with polymer, which plays an adhesive role with the electrode sheet when the separator is hot-pressed with the electrode sheet, increasing the compactness after the separator and the electrode are hot-pressed; the adhesive layer can further improve the adhesion of the separator to the electrode sheet, thereby ensuring the hardness of the battery cell. Through the cooperation of each layer, the heat resistance performance, adhesion performance, and liquid storage performance of the composite separator can be improved, which is beneficial to improving the capacity retention rate, cycle performance, and safety performance of the battery.

[0033] In some embodiments, the included angle x between each of the first strip structure and the second strip structure and the width direction of the base film satisfies: 0 < x ≤ 45°, such as 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, etc., or the range value between any two of them. Preferably, the included angle x between each of the first strip structure and the second strip structure and the width direction (TD direction) of the base film satisfies: 0 < x ≤ 35°, and more preferably, 0 < x ≤ 35°. The included angle x between the first strip structure and the second strip structure and the width direction of the base film satisfying the above range is beneficial to improving the comprehensive electrochemical performance of the composite separator. When preparing a wound battery cell for liquid injection, the liquid injection time is shortened and the efficiency is improved. On the other hand, the design of the twill can well release the stress generated in the inner layer during the winding of the battery cell, making the performance of the battery cell relatively stable.

[0034] In some embodiments, the first strip structure and the second strip structure are distributed in parallel at equal intervals on the surface of the heat-resistant layer. In some embodiments, the first strip structure and the second strip structure are distributed at intervals. In some embodiments, the distance between any adjacent first strip structure and / or second strip structure is 400-600 μm, for example, 400 μm, 430 μm, 450 μm, 480 μm, 500 μm, 550 μm, 580 μm, 600 μm, etc., or any value between the two, preferably 450-550 μm.

[0035] In some embodiments, the widths of the first strip structure and the second strip structure are 200 to 400 μm, such as 200 μm, 250 μm, 300 μm, 350 μm, 380 μm, 400 μm, or any value between the two, preferably 250 to 350 μm.

[0036] In some embodiments, the ratio of the number 'a' of the first strip structure to the number 'b' of the second strip structure satisfies: 1 ≤ a:b ≤ 10, where a and b are integers from 1 to 10, and a:b is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. Preferably, 1 ≤ a:b ≤ 5.

[0037] In some embodiments, the thickness h1 of the first strip structure is 1.5–3.5 μm, such as 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or any value between the two, preferably 2–3 μm; the thickness h2 of the second strip structure is 3–5 μm, such as 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any value between the two, preferably 3.5–4.5 μm. Furthermore, the difference between the thickness h2 of the second strip structure and the thickness h1 of the first strip structure satisfies: h2 - h1 = 1.5 μm.

[0038] The first and second strip structures have suitable spacing, width, quantity ratio and thickness, which are more conducive to improving the liquid storage performance and adhesion performance of the composite diaphragm.

[0039] In some embodiments, in the first strip structure, the ceramic layer is conventional alumina, boehmite, zirconium oxide, magnesium hydroxide, or a solid electrolyte, and the particle size D50 of the ceramic particles is 0.5–0.8 μm. In some embodiments, the ceramic layer comprises ceramic particles, an adhesive (e.g., polyacrylic acid, polyacrylamide, polyacrylate, or SBR), and a wetting agent, and the mass content of the ceramic particles is above 80%.

[0040] In some embodiments, the polymer layer in the second strip structure can be a PVDF layer or a PMMA (polymethyl methacrylate) layer, and the particle size D50 of the polymer particles is 2–4 μm. In some embodiments, the polymer layer comprises polymer particles, an adhesive (e.g., polyacrylonitrile, polyacrylate, or SBR), and a dispersant, and the mass content of the polymer particles is greater than 80%.

[0041] In some embodiments, the adhesive layer is a porous polymer layer. The porous polymer layer is a conventional material. In some embodiments, the polymer in the polymer layer is PVDF or PMMA, or a combination of PVDF and PMMA. In some embodiments, the adhesive layer also contains ceramic particles, such as alumina, boehmite, zirconium oxide, magnesium hydroxide, or a solid electrolyte. The thickness h3 of the adhesive layer is 2–4 μm, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm, or 4 μm, or any value between the two, preferably 2.5–3.5 μm. And h3 > h1. In some embodiments, the porosity of the adhesive layer is 40%–60%, for example, 40%, 45%, 50%, 55%, or 60%, preferably 45%–55%. An adhesive layer with suitable thickness and porosity is more conducive to improving the adhesion between the separator and the electrode sheet, thereby ensuring the rigidity of the battery cell.

[0042] In some embodiments, the heat-resistant layer is a ceramic layer. The ceramic layer is a conventional ceramic layer. The ceramic material in the ceramic layer is, for example, alumina, boehmite, zirconium oxide, magnesium hydroxide, or a solid electrolyte. In some embodiments, the particle size D50 of the ceramic material is 0.2–0.3 μm. In some embodiments, the heat-resistant layer also contains an adhesive (polyacrylic acid or polyacrylamide or a mixture of both, with an adhesive Tg greater than 100°C) and a wetting agent. In some embodiments, the thickness of the heat-resistant layer is 0.4–1.0 μm, for example, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, etc. The above-mentioned heat-resistant layer maintains high heat resistance even at relatively thin thicknesses, resulting in good thermal shrinkage performance of the diaphragm at high temperatures and a small increase in the diaphragm's permeability.

[0043] In some embodiments, the base film is a conventional PP (polypropylene), PE (polyethylene), or PP / PE composite film. The thickness of the base film is 5–20 μm, for example, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, etc.

[0044] In some embodiments, the method for preparing the composite separator includes: preparing a composite coating on one or both surfaces of a base membrane. Specifically, first, a heat-resistant material is coated on the surface of the base membrane to prepare a heat-resistant layer; then, a strip-shaped ceramic layer and a polymer layer are coated on the surface of the heat-resistant layer to obtain a first strip-shaped structure and a second strip-shaped structure, thus preparing a strip-shaped coating; finally, a polymer material is coated on the surface of the strip-shaped coating to obtain an adhesive layer. It should be noted that the coating and other processes involved in the preparation of the composite separator are all existing conventional preparation processes, and are not limited as long as the corresponding coating can be obtained. For example, the heat-resistant layer can be prepared by roller coating, the strip-shaped coating can be prepared by twill roller coating, and the adhesive layer can be prepared by roller coating.

[0045] The following explanation, in conjunction with specific embodiments, further clarifies the situation.

[0046] Example 1

[0047] A composite membrane, such as Figure 1 and Figure 2 As shown, the composite coating includes a base film 1 and a composite coating located on one side of the base film 1. The composite coating includes a heat-resistant layer 2, a strip coating, and an adhesive layer 5. The strip coating includes a first strip structure 3 and a second strip structure 4. The first strip structure 3 is an inorganic ceramic layer (alumina layer), and the second strip structure 4 is a polymer layer (PVDF layer). The heat-resistant layer 2 is located on the surface of the base film 1. The surface of the heat-resistant layer 2 away from the base film 1 is provided with a coating area and a blank area 6. The coating area is provided with a strip coating. The adhesive layer 5 is located on the surface of the strip coating away from the base film 1 and on the surface of the blank area 6.

[0048] The first strip structure 3 and the second strip structure 4 are evenly spaced and parallel on the surface of the heat-resistant layer 2. The angle x between each of the first strip structure 3 and the second strip structure 4 and the length direction of the base film 1 is 25°. The distance between any two adjacent first strip structures 3 and / or second strip structures 4 is 500 μm. The width of each first strip structure 3 and second strip structure 4 is 300 μm. The ratio of the number a of the first strip structures 3 to the number b of the second strip structures 4 is a:b = 3, where a is 6 and b is 2. The thickness h1 of the first strip structure 3 is 2.5 μm, and the thickness h2 of the second strip structure 4 is 4 μm.

[0049] The adhesive layer 5 is a porous polymer layer (PVDF layer) with a thickness h3 of 3 μm and a porosity of 50%.

[0050] The heat-resistant layer 2 is a ceramic layer (alumina layer) with a thickness of 0.5μm.

[0051] Base film 1 is made of PE and has a thickness of 8μm.

[0052] Example 2

[0053] A composite membrane, such as Figure 1 and Figure 2 As shown, the composite coating includes a base film 1 and a composite coating located on one side of the base film 1. The composite coating includes a heat-resistant layer 2, a strip coating, and an adhesive layer 5. The strip coating includes a first strip structure 3 and a second strip structure 4. The first strip structure 3 is an inorganic ceramic layer (zirconia layer), and the second strip structure 4 is a polymer layer (PMMA layer). The heat-resistant layer 2 is located on the surface of the base film 1. The surface of the heat-resistant layer 2 away from the base film 1 is provided with a coating area and a blank area 6. The coating area is provided with a strip coating. The adhesive layer 5 is located on the surface of the strip coating away from the base film 1 and on the surface of the blank area 6.

[0054] The first strip structure 3 and the second strip structure 4 are evenly spaced and parallel on the surface of the heat-resistant layer 2. The angle x between each of the first strip structure 3 and the second strip structure 4 and the length direction of the base film 1 is 35°. The distance between any two adjacent first strip structures 3 and / or second strip structures 4 is 550 μm. The width of the first strip structure 3 and the second strip structure 4 is 400 μm. The ratio of the number a of the first strip structures 3 to the number b of the second strip structures 4 is a:b = 4, where a is 8 and b is 2. The thickness h1 of the first strip structure 3 is 3 μm, and the thickness h2 of the second strip structure 4 is 4.5 μm.

[0055] The adhesive layer 5 is a porous polymer layer (PMMA layer) with a thickness h3 of 3.5 μm and a porosity of 55%.

[0056] The heat-resistant layer 2 is a ceramic layer (zirconia layer) with a thickness of 0.8μm.

[0057] Base film 1 is made of PE and has a thickness of 10 μm.

[0058] Example 3

[0059] A composite membrane, such as Figure 1 and Figure 2 As shown, the composite coating includes a base film 1 and a composite coating located on one side of the base film 1. The composite coating includes a heat-resistant layer 2, a strip coating, and an adhesive layer 5. The strip coating includes a first strip structure 3 and a second strip structure 4. The first strip structure 3 is an inorganic ceramic layer (alumina layer), and the second strip structure 4 is a polymer layer (PVDF layer). The heat-resistant layer 2 is located on the surface of the base film 1. The surface of the heat-resistant layer 2 away from the base film 1 is provided with a coating area and a blank area 6. The coating area is provided with a strip coating. The adhesive layer 5 is located on the surface of the strip coating away from the base film 1 and on the surface of the blank area 6.

[0060] The first strip structure 3 and the second strip structure 4 are evenly spaced and parallel on the surface of the heat-resistant layer 2. The angle x between each of the first strip structure 3 and the second strip structure 4 and the length direction of the base film 1 is 15°. The distance between any two adjacent first strip structures 3 and / or second strip structures 4 is 450 μm. The width of each first strip structure 3 and second strip structure 4 is 250 μm. The ratio of the number a of the first strip structures 3 to the number b of the second strip structures 4 is a:b = 5, where a is 10 and b is 2. The thickness h1 of the first strip structure 3 is 2 μm, and the thickness h2 of the second strip structure 4 is 3.5 μm.

[0061] The adhesive layer 5 is a porous polymer layer (PVDF layer) with a thickness h3 of 2.5 μm and a porosity of 45%.

[0062] The heat-resistant layer 2 is a ceramic layer (alumina layer) with a thickness of 0.6μm.

[0063] Base film 1 is made of PE and has a thickness of 9μm.

[0064] Example 4

[0065] A composite membrane, such as Figure 1 and Figure 2 As shown, the composite coating includes a base film 1 and a composite coating located on one side of the base film 1. The composite coating includes a heat-resistant layer 2, a strip coating, and an adhesive layer 5. The strip coating includes a first strip structure 3 and a second strip structure 4. The first strip structure 3 is an inorganic ceramic layer (alumina layer), and the second strip structure 4 is a polymer layer (PVDF layer). The heat-resistant layer 2 is located on the surface of the base film 1. The surface of the heat-resistant layer 2 away from the base film 1 is provided with a coating area and a blank area 6. The coating area is provided with a strip coating. The adhesive layer 5 is located on the surface of the strip coating away from the base film 1 and on the surface of the blank area 6.

[0066] The first strip structure 3 and the second strip structure 4 are evenly spaced and parallel on the surface of the heat-resistant layer 2. The angle x between each of the first strip structure 3 and the second strip structure 4 and the length direction of the base film 1 is 10°. The distance between any two adjacent first strip structures 3 and / or second strip structures 4 is 400 μm. The width of the first strip structure 3 and the second strip structure 4 is 200 μm. The ratio of the number a of the first strip structures 3 to the number b of the second strip structures 4 is a:b = 3, where a is 9 and b is 3. The thickness h1 of the first strip structure 3 is 3.5 μm, and the thickness h2 of the second strip structure 4 is 5 μm.

[0067] The adhesive layer 5 is a porous polymer layer (PVDF layer) with a thickness h3 of 4 μm and a porosity of 40%.

[0068] The heat-resistant layer 2 is a ceramic layer (alumina layer) with a thickness of 1μm.

[0069] The base film 1 is made of PE and has a thickness of 12μm.

[0070] Example 5

[0071] A composite membrane, such as Figure 1 and Figure 2 As shown, the composite coating includes a base film 1 and a composite coating located on one side of the base film 1. The composite coating includes a heat-resistant layer 2, a strip coating, and an adhesive layer 5. The strip coating includes a first strip structure 3 and a second strip structure 4. The first strip structure 3 is an inorganic ceramic layer (alumina layer), and the second strip structure 4 is a polymer layer (PVDF layer). The heat-resistant layer 2 is located on the surface of the base film 1. The surface of the heat-resistant layer 2 away from the base film 1 is provided with a coating area and a blank area 6. The coating area is provided with a strip coating. The adhesive layer 5 is located on the surface of the strip coating away from the base film 1 and on the surface of the blank area 6.

[0072] The first strip structure 3 and the second strip structure 4 are evenly spaced and parallel on the surface of the heat-resistant layer 2. The angle x between each of the first strip structure 3 and the second strip structure 4 and the length direction of the base film 1 is 40°. The distance between any two adjacent first strip structures 3 and / or second strip structures 4 is 600 μm. The width of each first strip structure 3 and second strip structure 4 is 400 μm. The ratio of the number a of the first strip structures 3 to the number b of the second strip structures 4 is a:b = 3, where a is 6 and b is 2. The thickness h1 of the first strip structure 3 is 1.5 μm, and the thickness h2 of the second strip structure 4 is 3 μm.

[0073] The adhesive layer 5 is a porous polymer layer (PVDF layer) with a thickness h3 of 2 μm and a porosity of 60%.

[0074] The heat-resistant layer 2 is a ceramic layer (alumina layer) with a thickness of 0.4μm.

[0075] Base film 1 is made of PP and has a thickness of 7μm.

[0076] Example 6

[0077] A composite diaphragm, which differs from Example 1 in that it includes a base membrane 1 and a composite coating located on both sides of the base membrane 1.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model 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 utility model.

Claims

1. A composite diaphragm, characterized in that, The system includes a base film and a composite coating located on at least one side of the base film. The composite coating includes a heat-resistant layer, a strip coating, and an adhesive layer. The strip coating includes a first strip structure and a second strip structure. The first strip structure is an inorganic ceramic layer, and the second strip structure is a polymer layer. The heat-resistant layer is located on the surface of the base film. The surface of the heat-resistant layer away from the base film is provided with a coating area and a blank area. The strip-shaped coating is provided in the coating area. The adhesive layer is located on the surface of the strip-shaped coating away from the base film and on the surface of the blank area.

2. The composite diaphragm according to claim 1, characterized in that, The angles x between the first strip structure and the second strip structure and the width direction of the base film satisfy: 0 <x≤45°; And / or, the first strip structure and the second strip structure are distributed in parallel at equal intervals on the surface of the heat-resistant layer.

3. The composite diaphragm according to claim 2, characterized in that, The angles x between the first strip structure and the second strip structure and the width direction of the base film satisfy: 0 <x≤35°。 4. The composite diaphragm according to claim 2, characterized in that, The distance between any two adjacent first strip structures and / or second strip structures is 400–600 μm; And / or, the width of the first strip structure and the second strip structure is 200 to 400 μm.

5. The composite diaphragm according to claim 4, characterized in that, The distance between any two adjacent first strip structures and / or second strip structures is 450–550 μm; The widths of the first strip structure and the second strip structure are 250–350 μm.

6. The composite diaphragm according to claim 1, characterized in that, The ratio of the number a of the first strip structure to the number b of the second strip structure satisfies: 1≤a:b≤10, where a and b are integers from 1 to 10.

7. The composite diaphragm according to claim 1, characterized in that, The thickness h1 of the first strip structure is 1.5 to 3.5 μm, and the thickness h2 of the second strip structure is 3 to 5 μm; And / or, the difference between the thickness h2 of the second strip structure and the thickness h1 of the first strip structure satisfies: h2-h1=1.5μm.

8. The composite diaphragm according to claim 7, characterized in that, The adhesive layer is a porous polymer layer; And / or, the thickness h3 of the adhesive layer is 2 to 4 μm, and h3 > h1; And / or, the porosity of the adhesive layer is 40% to 60%.

9. The composite diaphragm according to claim 1, characterized in that, The heat-resistant layer is a ceramic layer; And / or, the thickness of the heat-resistant layer is 0.4 to 1.0 μm.

10. The composite diaphragm according to claim 9, characterized in that, The thickness of the base film is 5–20 μm.

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