Dispensing diaphragm, preparation method thereof and battery

Abstract

A plurality of coating points are respectively arranged on two sides of the dispensing diaphragm, the coating points are periodically arranged, the periodic arrangement is that a single-side minimum coating point repeating unit is respectively staggered with the TD direction and the MD direction by the same angle, and the difference of the coating point coverage rate of a double-side coating point superposition structure after double-side superposition is more than 0% and less than 10%. The invention further discloses a manufacturing method of the dot-coated separator and a battery comprising the dot-coated separator. And in the spot-coated diaphragms at different double-sided overlapping positions, the thickness consistency is realized, and the battery also has good electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of lithium battery separator technology, specifically to a lithium battery dot-coated separator with misalignment consistency, its preparation method, and the battery thereof. Background Technology

[0002] Currently, mass-produced diaphragm coating processes mainly include roller coating and spray coating. In recent years, dot coating has gained attention and is gradually being applied due to its better consistency and lower slurry consumption. Current dot coating processes primarily employ a three-roller coating process: a gravure roller, a rubber roller, and a back roller. The slurry is sequentially transferred onto the diaphragm surface between these three rollers. The rubber roller has a special raised dot structure on its surface, so the dot-coated diaphragm surface exhibits the same texture as the raised dots on the rubber roller surface. Compared to the randomness of spray coating dots, dot coating allows for flexible customization of the shape, size, and structure of the surface coating dots, resulting in better consistency on the diaphragm surface.

[0003] Most known dot-coated separators use circular dot designs on their surface, arranged in a square pattern. When the separator is dot-coated on both sides, the superposition of the dot patterns on the first side (A side) and the second side (B side) is highly complex, significantly impacting thickness consistency and consequently affecting battery performance. In other words, when the separator uses a traditional square dot arrangement, the dot structure varies considerably depending on the superposition position of the dots on both sides, resulting in different dot coverage rates and affecting separator thickness consistency and battery electrochemical performance.

[0004] In order to improve the technical defects of dot-coated diaphragms in double-sided dot-coating processes, it is urgent to develop a dot-coated diaphragm with a similar dot structure after the double-sided coating dots are superimposed at different superposition positions. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the main objective of the present invention is to provide a dot-coated separator, its preparation method and battery, so as to improve the thickness uniformity of the dot-coated separator and improve the electrochemical performance of the battery.

[0006] In a first aspect, in some embodiments of the present invention, a dot-coated diaphragm is provided, wherein each of the two sides of the dot-coated diaphragm includes a plurality of coating dots, wherein the plurality of coating dots are arranged periodically, wherein the periodic arrangement is such that the smallest repeating unit of the coating dot on one side is offset by the same angle from the TD direction and the MD direction, and the difference in coating dot coverage of the double-sided coating dot superposition structure after double-sided superposition is greater than 0% and less than 10%.

[0007] In some embodiments of the present invention, when the shape of the coating dot, the diameter of the coating dot, the distance between the centers of adjacent coating dots, and the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions are all the same, under different superposition positions of the double-sided coating dots, the difference in coating dot coverage of the double-sided coating dot superposition structure after double-sided superposition is less than 5%. The minimum superposition repeating unit of the double-sided coating dot superposition structure is arranged periodically, and the minimum superposition repeating unit includes at least one of a circle and a hexagon.

[0008] In some embodiments of the present invention, when the shape of the coating dot, the diameter of the coating dot, the distance between the centers of adjacent coating dots, the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions are all the same, the difference in coating dot coverage of the double-sided coating dot superposition structure after double-sided superposition is less than 1.5% under different superposition positions of the double-sided coating dots.

[0009] In some embodiments of the present invention, the single-sided minimum coating dot repeating unit is offset from the TD direction and the MD direction by the same angle, which means that among the multiple coating dots on a single side, the included angle formed by three adjacent coating dots is offset from the TD direction and the MD direction by the same angle.

[0010] In some embodiments of the present invention, the formula for calculating the coverage of the coating dots is as follows: ,

[0011] The area of ​​the adhesive coating after the two sides are superimposed is only counted once for the overlapping part.

[0012] In some embodiments of the present invention, the formula for calculating the coverage of the coating dots is as follows: .

[0013] In some embodiments of the present invention, when any of the following conditions are different: the shape of the coating dot, the diameter of the coating dot, the distance between the centers of adjacent coating dots, the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions, the coating dot coverage rate after double-sided superposition is in the range of 1% to 80% under different superposition positions of the double-sided coating dots.

[0014] In some embodiments of the present invention, the single-sided minimum repeating unit of the smear includes at least one of a triangle, an equilateral triangle, a quadrilateral, a rhombus, a square, a hexagon, and a regular hexagon. In some embodiments of the present invention, the shape of the smear includes a circular smear, but is not limited thereto.

[0015] This invention provides a dot-coated diaphragm. When any one of the following is different: dot shape, dot diameter, spacing between the centers of adjacent dots, or misalignment angle between the minimum dot repeating unit and the TD and MD directions, and at different stacking positions, the coverage rate of the double-sided superimposed dot coating is statistically analyzed. The resulting Span value is ≤0.1. The formula for calculating the Span value is: Span = (D... 90- D 10 ) / D 50 D 10 D 50 and D 90 The coverage rates of the double-sided overlay coating points are the cumulative coverage rates of 10%, 50%, and 90%.

[0016] In some embodiments of the present invention, on one side of the dot-coated diaphragm, the plurality of coating dots satisfy at least one of the following conditions: (a) Dot shape: round, oval or nearly round; (b) The diameter of the coating spot is 100μm~600μm; (c) Spacing between the centers of adjacent coating dots: 200μm~800μm; and (d) The smallest repeating unit is offset from the TD and MD directions by the following angles: the angle is acute and the range of the offset angle is 0.1° to 45°.

[0017] In a second aspect, embodiments of the present invention provide a battery comprising the dot-coated separator provided in any of the embodiments of the first aspect.

[0018] Thirdly, embodiments of the present invention provide a method for manufacturing a dot-coated diaphragm, comprising: forming a plurality of periodically arranged coating dots on both sides of the diaphragm using a dot-coating method, wherein the periodic arrangement is such that the minimum repeating unit of the single-sided coating dots is offset by the same angle from the TD direction and the MD direction, wherein when the shape of the coating dots, the diameter of the coating dots, the distance between the centers of adjacent coating dots, and the offset angle of the minimum repeating unit of the coating dots from the TD direction and the MD direction are all the same, under different superposition positions of the double-sided coating dots, the difference in the coating dot coverage of the double-sided coating dot superposition structure is greater than 0% and less than 10%, wherein the minimum superposition repeating unit of the double-sided coating dot superposition structure is periodically arranged, and the minimum superposition repeating unit includes at least one of a circle and a hexagon.

[0019] In some embodiments of the present invention, prior to using the dot-coating method, a base film is further formed on both sides of the diaphragm, wherein the material of the base film includes at least one of a polyolefin-based film and a ceramic film. In some embodiments of the present invention, the porous substrate includes a polymer film, a multilayer polymer film, a nonwoven fabric, or nanofibers, wherein the polymer film, multilayer polymer film, or nonwoven fabric is formed from any one or more of the following polymers: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyphenylene terephthalamide, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, or polynaphthalene.

[0020] In some embodiments of the present invention, a plurality of coating dots arranged periodically are formed on both sides of the diaphragm, forming a mirror-image symmetrical arrangement of the coating dots. The axis of symmetry includes at least one of the TD direction, MD direction, or the angle bisector of the MD and TD directions. In the aforementioned mirror-image symmetrical arrangement, the flip angle includes, but is not limited to, 0 degrees to 180 degrees. Optionally, the flip angle is 180 degrees.

[0021] In some embodiments of the present invention, the dot coating method includes at least one of the following: rubber roller transfer method and direct coating with printing roller.

[0022] In some embodiments of the present invention, a plurality of coating dots arranged periodically are formed on both sides of the diaphragm, wherein the coating is performed twice by a single-sided coating machine or once by a double-sided coating machine.

[0023] In some embodiments of the present invention, in the manufacturing method of the dot-coated diaphragm, the smallest repeating unit of the single-sided coating is offset by the same angle from the TD direction and the MD direction, respectively. This means that among the multiple coatings on a single side, the included angle formed by three adjacent coatings is offset by the same angle from the TD direction and the MD direction, respectively.

[0024] In some embodiments of the present invention, the formula for calculating the coverage rate of the coating dots in the method for manufacturing the dot-coated diaphragm is as follows: ,

[0025] The area of ​​the adhesive coating after the two sides are superimposed is only counted once for the overlapping part.

[0026] In some embodiments of the present invention, the formula for calculating the coverage rate of the coating dots in the method for manufacturing the dot-coated diaphragm is as follows: .

[0027] In some embodiments of the present invention, in the manufacturing method of the dot-coated diaphragm, when any of the following conditions are different: dot shape, dot diameter, spacing between the centers of adjacent dots, and misalignment angle between the minimum dot repeating unit and the TD and MD directions, the dot coverage rate after double-sided superposition is in the range of 1% to 80% under different superposition positions of the double-sided dots.

[0028] In some embodiments of the present invention, in the method for manufacturing a dot-coated diaphragm, the single-sided minimum dot repeating unit includes at least one of a triangle, an equilateral triangle, a quadrilateral, a rhombus, a square, a hexagon, and a regular hexagon.

[0029] In some embodiments of the present invention, in the method for manufacturing a dot-coated diaphragm, the smallest repeating unit of a single-sided coating dot is rhomboid.

[0030] In some embodiments of the present invention, when any one of the following is different: the shape of the coating dot, the diameter of the coating dot, the spacing between the centers of adjacent coating dots, or the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions, and when the frequency of the double-sided superimposed coating dot coverage is statistically analyzed at different superimposed positions, the Span value after the statistics is ≤0.1, wherein the formula for calculating the Span value is: Span=(D 90- D 10 ) / D 50 , D 10 D 50 and D 90 The coverage rates of the double-sided overlay coating points are the cumulative coverage rates of 10%, 50%, and 90%.

[0031] In some embodiments of the present invention, in the method for manufacturing the dot-coated diaphragm, the material of the plurality of coating dots is selected from at least one of the following: vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trichloroethylene copolymer, polymethyl methacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, polyvinyl alcohol ether, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene copolymer, and polyvinylidene fluoride. In some embodiments of the present invention, the material of the plurality of coating dots is selected from at least one of PVDF, PMMA, and PAA.

[0032] This invention provides a dot-coated separator with double-sided misalignment consistency, wherein the coating dots exhibit a novel periodic arrangement. Specifically, the smallest repeating unit of the single-sided coating dot on both sides of the separator is misaligned by the same angle with the TD and MD directions, respectively. Furthermore, the double-sided coating dots of the dot-coated separator present a mirror-reversed symmetrical distribution structure. When the shape, diameter, spacing between the centers of adjacent coating dots, and misalignment angle of the smallest repeating unit with the TD and MD directions are all the same, the double-sided coating dots, after being superimposed at different superposition positions, exhibit a structurally similar double-sided coating dot superposition pattern. Moreover, the coating dot coverage does not show significant changes at different double-sided superposition positions, and the thickness consistency of the dot-coated separator also exhibits good performance, regardless of the superposition position of the double-sided coating dots. In this way, the thickness consistency of the separator and the electrochemical performance of the battery are improved, which helps to reduce the impact of separator thickness variations on battery performance. In addition, the friendliness and convenience of process development are greatly improved, as there is no need to strictly require alignment of the starting positions of the double-sided coating dots, which is conducive to improving the standardization of product manufacturing. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a double-sided perspective overlay diagram of the dot-coated diaphragm provided in an embodiment of the present invention; Figure 2A This is a schematic diagram of the first side of the dot-coated diaphragm provided in an embodiment of the present invention; Figure 2B This is a schematic diagram of the second side of the dot-coated diaphragm provided in an embodiment of the present invention; Figure 2C To undertake Figure 2A and Figure 2B ,in Figure 2C To illustrate the double-sided coating of the dot-coated diaphragm, the double-sided coating superposition structure is shown. Figure 3 This is a schematic diagram of a single-sided minimum coating dot repeating unit provided in an embodiment of the present invention. It is shown that the single-sided minimum coating dot repeating unit is offset from the TD direction and the MD direction by the same angle. The single-sided minimum coating dot repeating unit is a plurality of coating dots existing on at least one side of the dot-coated diaphragm.

[0035] Figure 4 This is a schematic diagram of a single-sided minimum coating dot repeating unit provided in an embodiment of the present invention, which illustrates that the coating dot distribution on side A is obtained by mirror flipping and translation to obtain the coating dot distribution on side B.

[0036] Figure 5 A process flow diagram of the preparation method of the dot-coated diaphragm provided in the embodiment of the present invention; Figure 6 This is a schematic diagram of the minimum superimposed repeating unit provided in an embodiment of the present invention, illustrating that a complex number of minimum superimposed repeating units are observed in a dot-coated diaphragm. The minimum superimposed repeating unit includes circular units and hexagonal units. The circular frame and hexagonal frame in the figure (for illustration only) are used to indicate the positions of the aforementioned circular units and hexagonal units, respectively. Figure 7 This is a schematic diagram showing the coverage distribution of double-sided superimposed coating dots arranged in a square for comparison. Figure 8 This is a schematic diagram of the coverage distribution of staggered double-sided superimposed coating dots provided in an embodiment of the present invention; Icons: 100 - Dot coating diaphragm; 200 - Dot coating diaphragm; 300 - Single-sided minimum dot repeating unit; 400 - Dot distribution on surface A; 500 - Dot distribution on surface B; S510 - Step; S520 - Step; 600 - Dot coating diaphragm; 601 - Circular unit; 602 - Hexagonal unit. Detailed Implementation

[0037] To make the above and / or other objects, effects, and features of the present invention more apparent and understandable, preferred embodiments are described in detail below: See Figure 1 The main objective of this invention is to provide a dot-coating diaphragm 100, wherein the coating dots on one side and the other side of the diaphragm are superimposed on both sides to form a double-sided coating dot superposition structure. Specifically, Figure 1 The double-sided coating overlay structure is obtained by treating the diaphragm as a virtual plane and projecting the coating dots on one side and the coating dots on the other side of the diaphragm onto this virtual plane. It can also be understood that... Figure 1 The double-sided dotted superposition structure in the image was observed when the diaphragm plane was transparent.

[0038] In some embodiments, the double-sided coating dot superposition structure is a staggered and consistent double-sided coating dot superposition structure.

[0039] See also Figure 2A , Figure 2B and Figure 2C As shown in the figure, both sides of the dot-coated diaphragm 200 include multiple coating dots arranged in a periodic pattern (e.g., ...). Figure 2A and Figure 2BAs shown, these are the dot arrangement structures on one and the other side of the dot-coated diaphragm, respectively. When the dot shape, dot diameter, spacing between the centers of adjacent dots, and the misalignment angle between the minimum dot repeating unit and the TD and MD directions are all the same, the double-sided dot superposition structure of the dot-coated diaphragm remains approximately the same under different dot superposition positions (e.g., ...). Figure 2C As shown, this is a double-sided coating dot stacking structure that, even at different stacking positions, still produces a similar dot stacking pattern. The dot coverage is essentially the same (the difference in dot coverage is greater than 0% and less than 10%), and is largely independent of the stacking position of the double-sided coating dots. The minimum stacking repeating unit of the double-sided coating dot stacking structure is periodically arranged, and the minimum stacking repeating unit includes at least one of a circle and a hexagon. Figure 2C The double-sided coating overlay structure is obtained by treating the diaphragm as a virtual plane and projecting the coating dots on one side and the coating dots on the other side of the diaphragm onto this virtual plane. It can also be understood that... Figure 2C The double-sided dotted superposition structure in the image was observed when the diaphragm plane was transparent.

[0040] In some embodiments, the aforementioned substantially the same coverage rate means that the difference in coverage rate is greater than 0% and less than 10%, preferably less than 5%, and more preferably less than 1.5%.

[0041] In some embodiments, the aforementioned periodic arrangement refers to the single-sided minimum coating dot repeating unit being offset by the same angle from both the TD and MD directions, where MD is the conveyor belt direction or transverse direction of the diaphragm, and TD is the tangential direction or longitudinal direction of the dotting roller. Specifically, as... Figure 3 As shown, the single-sided minimum coating dot repeating unit 300 (taking the rhombus formed by the arrangement of four coating dots as an example) is offset by the same angle with the TD direction and the MD direction, respectively. This refers to the single-sided minimum coating dot repeating unit among multiple coating dots on a single surface, where the included angle formed by three adjacent coating dots is offset by the same angle (such as angle a°) with the TD direction and the MD direction, respectively.

[0042] In some embodiments, when the dot shape, dot diameter, spacing between the centers of adjacent dots, and misalignment angle between the minimum dot repeating unit and the TD and MD directions are all the same, when the first and second dot dots of the dot-coated separator are superimposed at any angle, the resulting double-sided dot superposition structure (double-sided dot superposition morphology) is approximately similar and the dot coverage is approximately the same. In some embodiments, when the dot shape, dot diameter, spacing between the centers of adjacent dots, and misalignment angle between the minimum dot repeating unit and the TD and MD directions are all the same, the double-sided dot-coated separator at different superposition positions has consistent thickness, and the battery containing it has good electrochemical performance. This improves the thickness consistency of the separator and the electrochemical performance of the battery, reducing the impact of separator thickness variations on battery performance. Furthermore, it significantly improves the friendliness of process development, lowers the process threshold, and enhances convenience, eliminating the need for strict alignment of the starting positions of the double-sided dots, thus promoting product standardization.

[0043] In some embodiments, when the shape of the coating dot, the diameter of the coating dot, the distance between the centers of adjacent coating dots, and the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions are all the same, the double-sided coating dot superposition structure after double-sided superposition is approximately the same, and is basically independent of the superposition position of the A and B sides.

[0044] In some embodiments, the formula for calculating the coverage of the coating dots is as follows: ,

[0045] The area covered by the double-sided coating is counted only once for the overlapping areas. In some embodiments, the double-sided coating coverage percentage (%) represents the total coverage percentage.

[0046] In some embodiments, the formula for calculating the coverage of the coating dots is as follows: .

[0047] In some embodiments, regarding the coverage calculation method, taking a rhombus as an example of the single-sided minimum coating dot repeating unit, since there are four sectors formed by the intersection of circular coating dots in the internal area of ​​the rhombus, the coverage is the sum of the areas of the sectors inside the rhombus divided by the area of ​​the rhombus. On this basis, further calculations are performed to obtain the double-sided superimposed coating dot coverage.

[0048] As an example, when any of the following conditions are different: dot shape, dot diameter, spacing between the centers of adjacent dots, or misalignment angle between the minimum dot repeating unit and the TD and MD directions, the dot coverage of the double-sided dot-coated diaphragm after double-sided superposition can range from 1%, 2%, 5%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 20%, 30%, 40%, 45%, 50%, 55%, 60%, 70%, or 80%, but is not limited to these. Optionally, the dot coverage ranges from 1% to 80%.

[0049] In some embodiments, the single-sided minimum coating dot repeating unit in the dot-coated diaphragm of the present invention is different from the traditional square arrangement. Instead, it adopts a bidirectional deformed single-sided minimum coating dot repeating unit, wherein the single-sided minimum coating dot repeating unit is offset from the TD direction and the MD direction by the same angle.

[0050] In some embodiments, in order to obtain a double-sided dot-coated diaphragm with consistent double-sided misalignment, the double-sided coating dots of the dot-coated diaphragm are arranged in a mirror-reversed symmetrical distribution.

[0051] like Figure 4 As shown, it is a schematic diagram of the smallest repeating unit of single-sided coating, illustrating that the coating distribution 400 on side A is obtained by mirror flipping and translation to obtain the coating distribution 500 on side B.

[0052] In some embodiments, the double-sided coating dots of the dot-coated membrane are arranged in a mirror-reversed symmetrical distribution. On one side of the dot-coated membrane, the minimum repeating units are arranged periodically along the MD and TD directions until the entire membrane surface is covered. On the other side of the dot-coated membrane, the periodic arrangement of the minimum repeating units is similar to that on one side, wherein the double-sided coating dots are arranged in a mirror-reversed symmetrical distribution, with the axis of symmetry being either a horizontal flip or a vertical reversal along the TD or MD directions.

[0053] Optionally, the single-sided minimum repeating unit includes at least one of a triangle, equilateral triangle, quadrilateral, rhombus, square, hexagon, and regular hexagon, but is not limited thereto. Optionally, the single-sided minimum repeating unit is a rhombus.

[0054] As an example, the single-sided minimum repeating unit of the paint dot is a rhombus.

[0055] In some embodiments, the material of the multiple coating dots is selected from at least one of the following: vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trichloroethylene copolymer, polymethyl methacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, polyvinyl alcohol ether, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene copolymer, and polyvinylidene fluoride.

[0056] In some embodiments, the material of the multiple coating dots includes at least one of PVDF, PMMA and PAA, but is not limited thereto.

[0057] In some embodiments, the material of the base film with multiple coating dots includes at least one of aramid, polyolefin-based film, and ceramic film, but is not limited thereto. In some embodiments, the porous substrate includes a polymer film, a multilayer polymer film, a nonwoven fabric, or nanofibers, wherein the polymer film, multilayer polymer film, or nonwoven fabric is formed from any one or more of the following polymers: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyphenylene terephthalamide, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletheretherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, or polynaphthalene.

[0058] Another objective of this invention is to provide a dot-coated diaphragm, wherein when any of the following factors are different: dot shape, dot diameter, spacing between the centers of adjacent dots, or misalignment angle between the minimum dot repeating unit and the TD and MD directions, and when the coverage rate of the double-sided superimposed dot is statistically analyzed at different superposition positions, the Span value is ≤0.1 after statistical analysis. The formula for calculating the Span value is: Span = (D... 90- D 10 ) / D 50 D 10 D 50 and D 90 The cumulative coverage distribution is represented by the double-sided overlay coverage corresponding to 10%, 50%, and 90%.

[0059] The span value represents the distribution span of the double-sided superimposed coating coverage rate calculated by frequency statistics at different superimposed positions when any of the following factors are different: coating shape, coating diameter, spacing between the centers of adjacent coating points, and misalignment angle between the minimum coating repeating unit and the TD and MD directions.

[0060] In some embodiments, the plurality of coating dots satisfy at least one of the following conditions: (a) Dot shape: round, oval or nearly round; (b) The diameter of the coating spot is 100μm~600μm; (c) Spacing between the centers of adjacent coating dots: 200μm ~ 800μm; and (d) The smallest repeating unit is offset from the TD and MD directions by the following angles: the angle is acute and the range of the offset angle is 0.1° to 45°.

[0061] Another object of the present invention is to provide a battery comprising the dot-coated separator as described above.

[0062] like Figure 5 As shown, another objective of the present invention is to provide a method for manufacturing a dot-coated diaphragm, comprising: S510, a bottom film is formed on both sides of the diaphragm, wherein the material of the bottom film includes at least one of a polyolefin-based film and a ceramic film.

[0063] S520, using a dot coating method, multiple coating dots with a periodic arrangement are formed on both sides of the diaphragm. The periodic arrangement is such that the smallest repeating unit of the single-sided coating dot is offset by the same angle from the TD direction and the MD direction. When the shape of the coating dot, the diameter of the coating dot, the distance between the centers of adjacent coating dots, and the offset angle of the smallest repeating unit from the TD direction and the MD direction are all the same, the double-sided coating dot superposition structure after double-sided superposition is approximately the same, the coating dot coverage is basically the same, and the difference in coating dot coverage is greater than 0% and less than 10%. The smallest superposition repeating unit of the double-sided coating dot superposition structure is periodically arranged, and the smallest superposition repeating unit includes at least one of a circle and a hexagon.

[0064] In some embodiments, the dot coating method includes at least one of rubber roller transfer and direct coating with printing roller.

[0065] In some embodiments, step S320 involves either two coatings using a single-sided coating machine or a single coating using a double-sided coating machine.

[0066] In some embodiments, the single-sided minimum coating dot repeating unit is offset by the same angle from the TD direction and the MD direction, respectively. This means that among the multiple coating dots on a single side, the included angle formed by three adjacent coating dots is offset by the same angle from the TD direction and the MD direction, respectively.

[0067] like Figure 6As shown in the schematic diagram of the minimum superimposed repeating unit provided in the embodiment of the present invention, it is illustrated that a plurality of minimum superimposed repeating units are observed in the dot coating diaphragm 600. The minimum superimposed repeating units include circular units 601 and hexagonal units 602. At the same time, the dot coating diaphragm 600 presents a repeating structure with the aforementioned circular unit 601 as the center and surrounded by 6 hexagonal units 602. The aforementioned structure is distributed throughout the entire dot coating diaphragm 600.

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0069] The above-described embodiments of the present invention are illustrated by the following examples: Table 1. Dot-coated diaphragms of the Examples and Comparative Examples

[0070] The formula for calculating the coverage rate of the single-sided diaphragm coating is as follows: ,

[0071] In the formula, D is the diameter of the coating point, L is the diameter of the center of the circle, and α is the acute angle within the smallest repeating unit formed by the single-sided coating points.

[0072] Example 1 In this embodiment, the dot-coated diaphragm is dot-coated using a rubber roller transfer method. Multiple coating dots with a periodic arrangement are formed on both sides of the diaphragm. The main material of the coating dots is PVDF, the shape of the coating dots is circular, the diameter of the coating dots is 200μm, and the distance between the centers of adjacent coating dots is 460μm. The smallest repeating unit of the coating dots on one side is rhomboid, with rhomboid angles of 72.1° and 107.9°. Notably, multiple repeating units of the smallest repeating units on one side have the same misalignment angle, that is, the smallest repeating unit of the coating dots on one side is misaligned with MD and TD by the same angle of 8.95° (the calculation method is 90°-72.1°=17.9°, 17.9° divided by 2). The coating dots are symmetrically distributed along the angle bisector of MD / TD. The coating dots on side A of the dot-coated diaphragm are obtained by extending the aforementioned repeating units of the smallest repeating units on one side along the direction of the angle bisector of MD / TD.

[0073] Next, the arrangement of the dots on surface B is similar to that on surface A, obtained by mirroring and flipping the dots on surface A, with the axis of symmetry in the TD direction and the rotation angle being 180°.

[0074] Furthermore, the coating dots on side B and side A can be randomly overlapped, and the resulting double-sided coating dot superposition structure is basically the same.

[0075] In addition, the dot-coated separator of this embodiment is used to prepare a battery.

[0076] Example 2 The preparation method is roughly the same as in Example 1, except that the dot-coated diaphragm in this example is coated by direct coating with a roller. The diameter of the coating dot is 300 μm, and the distance between the centers of adjacent coating dots is 553 μm. In addition, the included angle formed by three adjacent coating dots in the single-sided minimum coating dot repeating unit is 67.2°. The single-sided minimum coating dot repeating unit is offset from MD and TD by the same angle by 11.4° (the calculation method is 90°-67.2°=22.8°, 22.8° divided by 2). The double-sided coating dots are symmetrically distributed along the TD direction.

[0077] Example 3 The preparation method is roughly the same as in Example 1, except that the diameter of the coating dot is 400 μm, the distance between the centers of adjacent coating dots is 624 μm, the included angle formed by three adjacent coating dots in the single-sided minimum coating dot repeating unit is 57.4°, and the single-sided minimum coating dot repeating unit is misaligned with MD and TD by the same angle of 16.3°.

[0078] Comparative Example 1 The preparation method is largely the same as in Example 1, except that the center-to-center distance between adjacent coating dots is 449 μm. Furthermore, the single-sided minimum coating dot repeating unit is square, and the included angle formed by three adjacent coating dots within the single-sided minimum coating dot repeating unit is 90°. There is no misalignment angle within the single-sided minimum coating dot repeating unit, and the double-sided coating dots are not symmetrically distributed. Additionally, the coating dots are arranged in a square pattern, with the lengths of adjacent sides coinciding with both the TD and MD directions without any misalignment angles.

[0079] Comparative Example 2 The preparation method is roughly the same as that of Comparative Example 1, except that the direct coating method using a printing roller is used for dot coating, and the double-sided coating dots are symmetrically distributed along the TD direction.

[0080] Comparative Example 3 The preparation method is roughly the same as that of Comparative Example 1, except that the center-to-center distance between adjacent coating dots is 534 μm, the single-sided minimum coating dot repeating unit is a parallelogram, the acute angle formed by three adjacent coating dots in the single-sided minimum coating dot repeating unit is 45°, the coating dots are arranged in a unidirectional staggered manner, the single-sided minimum coating dot repeating unit is only staggered with the TD direction (staggered angle is 45°), and the double-sided coating dots are symmetrically distributed along the TD direction.

[0081] Comparative Example 4 The preparation method is roughly the same as that of Comparative Example 1, except that the center-to-center distance between adjacent coating dots is 534 μm, the single-sided minimum coating dot repeating unit is a parallelogram, the acute angle formed by three adjacent coating dots in the single-sided minimum coating dot repeating unit is 45°, the coating dots are arranged in a unidirectional staggered manner, the single-sided minimum coating dot repeating unit is only staggered with the MD direction (the staggered angle is 45°), and the double-sided coating dots are symmetrically distributed along the TD direction.

[0082] Test method: (1) Coverage of coating spots after double-sided overlay , The measurement method involves microscopic observation combined with image analysis.

[0083] (2) Single-sided coating coverage .

[0084] Specifically, samples of the diaphragm with double-sided dot coating were taken and observed on the surface of the diaphragm using an optical transmission microscope.

[0085] Next, image binarization is performed using image analysis software (such as ImageJ), in which the coating structure is marked. Subsequently, the software calculates the total coating area (based on a coating diameter of 200μm), thereby calculating the coating coverage.

[0086] Next, images are captured to obtain scanning electron microscope (SEM) images.

[0087] The area of ​​the adhesive coating after the two sides are superimposed is only counted once for the overlapping part.

[0088] (3) Detection of the coating superposition structure Samples of the diaphragm with double-sided dot coating were taken and observed on the coating structure of the diaphragm surface using an optical transmission microscope.

[0089] Next, the similarity or similarity of the dot-overlay structures at different double-sided overlay positions is compared.

[0090] (4) Thickness detection of dot-coated diaphragm The thickness of the diaphragm was measured using a Marl thickness gauge. For the same sample of spot-coated diaphragm, the thickness was measured at three random locations, and the average of the three thicknesses was taken.

[0091] (5) Battery performance testing Cyclic performance: A full cell was made by using a spot-coated separator as the positive and negative electrodes, and its electrochemical performance was tested. The capacity retention rate was recorded after 800 cycles.

[0092] All test results are shown in the table below: Table 2. Test Results

[0093] Note: The total diaphragm area is the same for all examples and comparative examples in Table 2.

[0094] First, as can be seen from Tables 1 and 2, Examples 1-3 are generally superior to the comparative examples in terms of coating coverage after double-sided stacking, similarity of the double-sided coating stacking structure, consistency of separator thickness between different double-sided stacking positions, standard deviation of thickness data over 300 cycles, and electrochemical performance of the battery containing the dot-coated separator. This indicates that the dot-coated separators in the example groups have good thickness consistency. When the influence of separator thickness variation on battery performance is reduced, it is beneficial to improve the electrochemical performance and cycle life of the battery.

[0095] In Examples 1-3, the dot-coated diaphragms with double-sided misalignment consistency exhibit a novel periodic arrangement of coating dots. Specifically, the minimum repeating unit of each coating dot on both sides of the diaphragm is misaligned by the same angle with both the TD and MD directions (also known as bidirectional misalignment arrangement). Furthermore, the double-sided coating dots of the dot-coated diaphragm present a mirror-reversed symmetrical distribution. As shown in Table 2, when the shape, diameter, spacing between the centers of adjacent coating dots, and misalignment angle of the minimum repeating unit with both the TD and MD directions are the same, a structurally similar double-sided coating dot superposition pattern can be observed at different superposition positions. Moreover, the coating dot coverage does not show significant changes at different superposition positions, and the thickness consistency of the dot-coated diaphragm is also good. The results show that the coating dot coverage and thickness of the dot-coated diaphragm with double-sided misalignment consistency remain essentially consistent at different superposition positions, and are largely independent of the superposition position of the double-sided coating dots. This improves the thickness uniformity of the separator and the electrochemical performance of the battery, thereby reducing the impact of separator thickness variations on battery performance. In addition, it greatly enhances the friendliness and convenience of process development, eliminating the need for strict alignment of the starting positions of the double-sided coating dots, which facilitates standardized manufacturing of products.

[0096] In contrast, regarding the square arrangement of Comparative Examples 1 and 2, as shown in Table 2, various non-approximate coating arrangement structures were observed after the double-sided coating dots were superimposed at different positions. Furthermore, the membrane thickness varied significantly under different double-sided coating dot superposition positions, particularly with a large standard deviation in the thickness data from 300 tests, indicating substantial variations in the thickness distribution and a lack of thickness consistency in the comparative examples. Moreover, due to the inconsistency in membrane thickness, the impact of membrane thickness variation on battery electrochemical performance was more significant, resulting in poorer battery performance in the comparative example group.

[0097] In contrast, regarding the unidirectional staggered arrangement of Comparative Examples 3 and 4, even if the single-sided minimum coating dot repeating unit is only staggered by an angle with the TD direction (as in Comparative Example 3), or the single-sided minimum coating dot repeating unit is only staggered by an angle with the MD direction (as in Comparative Example 4), after the double-sided coating dots are superimposed at different superposition positions, as shown in the test results in Table 2, various non-approximate coating dot arrangement structures can be observed. Furthermore, the membrane thickness varies greatly under different double-sided coating dot superposition positions, especially the standard deviation of the thickness data from 300 tests is large, indicating that the thickness distribution of the comparative examples varies greatly and lacks thickness consistency. In addition, due to the inconsistency of membrane thickness, the effect of membrane thickness variation on battery electrochemical performance is more significant, and the battery performance of the comparative example group is poor.

[0098] Further, see Figure 6 This is a schematic diagram of the coverage distribution of double-sided overlapping paint dots arranged in a square (with a sufficiently large sample size, the statistical data covers the aforementioned comparative examples 1 to 2 (square arrangement), and other comparative examples (not shown)). Specifically, double-sided overlapping coverage statistics were performed for different double-sided overlapping situations (the overlapping part was only calculated once). Taking a single-sided coverage rate of 15%, under the square arrangement, it was found that the double-sided overlapping coverage rate distribution was relatively wide, ranging from 15% to 31%, with a large degree of dispersion.

[0099] in, Figure 6 The Y-axis represents the relative intensity, which indicates the proportion of a certain double-sided overlay coverage value in the total sample size.

[0100] Furthermore, the coverage distribution of double-sided overlapping paint dots with unidirectional staggered arrangement is not shown (with a sufficiently large sample size, the statistical data covers the aforementioned comparative examples 3 to 4 (unidirectional staggered arrangement) and other comparative examples (not shown)). Specifically, double-sided overlapping coverage statistics were performed for different double-sided overlapping situations (the overlapping part was only calculated once). Taking a single-sided coverage rate of 15%, under the unidirectional staggered arrangement, it was found that the double-sided overlapping coverage rate distribution was relatively wide, ranging from 15% to 30%, with a large degree of dispersion.

[0101] In contrast, see Figure 7This is a schematic diagram of the staggered double-sided coating coverage distribution (with a sufficiently large sample size, the statistical data covers the aforementioned Examples 1 to 3, as well as other examples (not shown), and all examples have a consistent staggered arrangement of double-sided coating dots). Specifically, double-sided overlapping coverage was statistically analyzed for different double-sided overlapping situations (the overlapping part was only calculated once). Taking a single-sided coverage distribution of 15%, the results show that the corresponding double-sided overlapping coating dot coverage distribution is relatively narrow, only distributed between 28% and 29%, and the data is basically not discrete. Therefore, when the double-sided coating dots of the diaphragm are arranged in a staggered and consistent manner, there is consistency in the coating dot overlapping structure.

[0102] To further illustrate the differences in data dispersion between the comparative example (with square-shaped coating dots), the comparative example (with unidirectional staggered coating dots), and the example (with staggered coating dots), the span values ​​in the statistical distribution of the double-sided superimposed coating coverage are shown below: Wherein, D 10 D 50 and D 90 The span values ​​of the double-sided coating overlay coverage corresponding to 10%, 50%, and 90% of the cumulative coverage distribution are shown in Table 3 below.

[0103] Table 3. Span Values

[0104] Among them, the bidirectional staggered arrangement is where the single-sided minimum coating point repeating unit is staggered by the same angle with both the TD and MD directions. The unidirectional staggered arrangement is where the single-sided minimum coating point repeating unit is staggered only with the TD direction, or the single-sided minimum coating point repeating unit is staggered only with the MD direction.

[0105] The above content involving common knowledge will not be described in detail, as those skilled in the art will understand.

[0106] The embodiments described above are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A dot-coated diaphragm, characterized in that, The dot-coated diaphragm has multiple coating dots on both sides, which are arranged periodically. The periodic arrangement is such that the smallest repeating unit of the coating dot on each side is offset by the same angle from the TD direction and the MD direction. The coating dot superposition structure after the two sides are superimposed has a coating dot coverage difference greater than 0% and less than 10%.

2. The dot-coated diaphragm according to claim 1, characterized in that, When the shape of the dot, the diameter of the dot, the distance between the centers of adjacent dots, and the misalignment angle of the minimum dot repeating unit with respect to the TD and MD directions are all the same, the dot coverage of the double-sided dot superposition structure after double-sided superposition is less than 5% under different superposition positions of the double-sided dot. The minimum superposition repeating unit of the double-sided dot superposition structure is arranged periodically, and the minimum superposition repeating unit includes at least one of a circle and a hexagon.

3. The dot-coated diaphragm according to claim 1, characterized in that, When the shape of the dot, the diameter of the dot, the spacing between the centers of adjacent dots, the minimum dot repeating unit and the misalignment angle of the TD and MD directions are all the same, the difference in dot coverage of the double-sided dot superposition structure after double-sided superposition is less than 1.5% under different superposition positions of the double-sided dots.

4. The dot-coated diaphragm according to claim 1, characterized in that, The repetitive unit of the minimum coating point on a single surface is offset by the same angle from the TD direction and the MD direction, respectively. This means that among the multiple coating points on a single surface, the included angle formed by three adjacent coating points is offset by the same angle from the TD direction and the MD direction, respectively.

5. The dot-coated diaphragm according to claim 1, characterized in that, The formula for calculating the coverage rate of the coating dots is as follows: ， The area of ​​the adhesive coating after the two sides are superimposed is only counted once for the overlapping part.

6. The dot-coated diaphragm according to claim 1, characterized in that, The formula for calculating the coverage rate of the coating dots is as follows: 。 7. The dot-coated diaphragm according to claim 5, characterized in that, When any of the following conditions are different: the shape of the coating dot, the diameter of the coating dot, the spacing between the centers of adjacent coating dots, the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions, the coating dot coverage rate after double-sided superposition is in the range of 1% to 80% under different superposition positions of the double-sided coating dots.

8. The dot-coated diaphragm according to claim 1, characterized in that, The single-sided minimum coating repeating unit includes at least one of triangle, equilateral triangle, quadrilateral, rhombus, square, hexagon and regular hexagon.

9. The dot-coated diaphragm according to claim 1, characterized in that, When any of the following factors are different: dot shape, dot diameter, spacing between centers of adjacent dots, or misalignment angle between the minimum dot repeating unit and the TD and MD directions, and frequency statistics are performed on the double-sided dot coverage at different stacking positions, the Span value is ≤0.

1. The formula for calculating the Span value is: Span=(D 90- D 10 ) / D 50 D 10 D 50 and D 90 The coverage rates of the double-sided overlay coating points are the cumulative coverage rates of 10%, 50%, and 90%.

10. The dot-coated diaphragm according to claim 1, characterized in that, The plurality of coating dots satisfy at least one of the following conditions: (a) Dot shape: round, oval or nearly round; (b) The diameter of the coating spot is 100μm~600μm; (c) Spacing between the centers of adjacent coating dots: 200μm~800μm; and (d) The smallest repeating unit is offset from the TD and MD directions by the following angles: the angle is acute and the range of the offset angle is 0.1° to 45°.

11. A battery, characterized in that, Includes the dot-coated diaphragm as described in any one of claims 1 to 10.

12. A method for manufacturing a dot-coated diaphragm as described in any one of claims 1 to 10, characterized in that, The manufacturing method includes: Using a dot coating method, multiple coating dots with a periodic arrangement are formed on both sides of the diaphragm. The periodic arrangement is such that the smallest repeating unit of the single-sided coating dot is offset by the same angle from the TD direction and the MD direction. When the shape of the coating dot, the diameter of the coating dot, the distance between the centers of adjacent coating dots, and the offset angle of the smallest repeating unit from the TD direction and the MD direction are all the same, the difference in coating dot coverage of the double-sided coating dot superposition structure after double-sided superposition is greater than 0% and less than 10% under different superposition positions of the double-sided coating dots. The smallest superposition repeating unit of the double-sided coating dot superposition structure is periodically arranged, and the smallest superposition repeating unit includes at least one of a circle and a hexagon.

13. The manufacturing method according to claim 12, characterized in that, The formation of multiple coating dots with periodic arrangement on both sides of the diaphragm is a double-sided coating dot arrangement structure with mirror-reversed symmetrical distribution, wherein the axis of symmetry includes at least one of the TD direction, MD direction, or the angle bisector of the MD direction and the TD direction.

14. The manufacturing method according to claim 12, characterized in that, The dot coating method includes at least one of the following: rubber roller transfer method and direct coating with printing roller.

15. The manufacturing method according to claim 12, characterized in that, The process involves forming multiple coating dots with a periodic arrangement on both sides of the diaphragm, which can be achieved by applying the coating twice using a single-sided coating machine or by applying it once using a double-sided coating machine.

16. The manufacturing method according to claim 12, characterized in that, The repetitive unit of the minimum coating point on a single surface is offset by the same angle from the TD direction and the MD direction, respectively. This means that among the multiple coating points on a single surface, the included angle formed by three adjacent coating points is offset by the same angle from the TD direction and the MD direction, respectively.

17. The manufacturing method according to claim 12, characterized in that, The formula for calculating the coverage rate of the coating dots is as follows: ， The area of ​​the adhesive coating after the two sides are superimposed is only counted once for the overlapping part.

18. The manufacturing method according to claim 12, characterized in that, The formula for calculating the coverage rate of the coating dots is as follows: 。 19. The manufacturing method according to claim 17, characterized in that, When any of the following conditions are different: the shape of the coating dot, the diameter of the coating dot, the spacing between the centers of adjacent coating dots, the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions, the coating dot coverage rate after double-sided superposition is in the range of 1% to 80% under different superposition positions of the double-sided coating dots.

20. The manufacturing method according to claim 12, characterized in that, The single-sided minimum coating repeating unit includes at least one of triangle, equilateral triangle, quadrilateral, rhombus, square, hexagon and regular hexagon.

21. The manufacturing method according to claim 12, characterized in that, When any of the following factors are different: the shape of the coating dot, the diameter of the coating dot, the spacing between the centers of adjacent coating dots, or the misalignment angle between the minimum coating dot repeating unit and the TD and MD directions, and frequency statistics are performed on the coverage of the double-sided superimposed coating dots at different superposition positions, the Span value after statistics is ≤0.

1. The formula for calculating the Span value is as follows: Span=(D 90- D 10 ) / D 50 D 10 D 50 and D 90 The coverage rates of the double-sided overlay coating points are the cumulative coverage rates of 10%, 50%, and 90%.

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