Coating preparation device and preparation method of battery diaphragm

Abstract

The invention discloses a coating preparation device and a preparation method of a battery diaphragm, and belongs to the field of secondary batteries, in the coating preparation device, base membrane conveying equipment comprises a plurality of compression rollers which are distributed at intervals and are used for conveying base membranes; the slurry supply equipment provides slurry; the surface of the gravure roller is provided with a plurality of concave liquid taking grooves distributed at intervals in the circumferential direction, and the concave liquid taking grooves are used for extracting slurry from slurry supply equipment and transferring the slurry to the concave liquid taking grooves. The surface of the relief printing roller is provided with a plurality of dispensing bosses arranged in a protruding mode, and the dispensing bosses are used for extracting slurry from the concave liquid taking groove and transferring the slurry to the surface of the base film. The drying equipment is used for receiving and drying the base film with slurry salient points on the surface; and the control equipment is used for controlling the rotation operation of the pressing roller, the gravure roller and the relief roller. According to the coating preparation device, a matrix type adhesive layer is formed on a base film, so that the cohesiveness and the liquid retention performance of the base film are enhanced, and the ventilation increment of the base film is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a coating preparation device and a method for preparing a battery separator. Background Art

[0002] In secondary batteries, battery separators primarily serve to separate the positive and negative electrodes and allow ions to pass freely. Currently, it is hoped that battery separators can bond with both the positive and negative electrode sheets to inhibit movement during expansion, thereby improving the interfacial properties of the battery sheets and increasing the battery's cycle life.

[0003] In related technologies, the battery separator includes a base film and an adhesive layer coated on the surface of the base film. The adhesive layer includes a polymer, an adhesive, a wetting agent, etc. The slurry corresponding to the adhesive layer is sprayed onto the surface of the base film through a rotary spraying device, and then dried and rolled up to obtain a battery separator.

[0004] However, the battery separator provided by the related art has technical problems such as poor adhesion, large air permeability increase, and poor liquid retention. Summary of the Invention

[0005] In view of this, the present invention provides a coating preparation device and a method for preparing a battery separator, which can solve the technical problems of poor adhesion, large air permeability increase, and poor liquid retention of battery separators in related technologies. Specifically, it includes the following technical solutions:

[0006] In one aspect, a coating preparation device is provided, comprising: a base film conveying device, the base film conveying device comprising a plurality of spaced-apart pressing rollers, the plurality of pressing rollers being rotatably arranged and used to convey the base film;

[0007] a slurry supply device, wherein the slurry supply device provides slurry;

[0008] a gravure roller rotatably arranged adjacent to the slurry supply device, the surface of the gravure roller having a plurality of concave liquid extraction grooves spaced apart along the circumferential direction, the gravure roller being used to extract slurry from the slurry supply device and transfer the slurry into the concave liquid extraction grooves;

[0009] A relief roller, the relief roller being rotatably arranged and located between one of the pressure rollers and the gravure roller, the surface of the relief roller having a plurality of raised dot coating bosses, the relief roller being used to extract the slurry from the concave liquid extraction tank through the dot coating bosses and transfer the slurry to the surface of the base film;

[0010] A drying device, the drying device is used to receive the base film having slurry bumps on the surface and dry it;

[0011] A control device is used to control the rotation of the pressing roller, the gravure roller, and the relief roller.

[0012] In some possible implementations, any two adjacent concave liquid collection grooves among the multiple concave liquid collection grooves are parallel to each other, and the length direction of each concave liquid collection groove has an angle with the central axis direction of the gravure roller, and the angle is greater than 0° and less than 90°.

[0013] In some possible implementations, the multiple dot coating bosses cooperate to form a plurality of boss groups, and the multiple boss groups are spaced apart along the circumferential direction of the relief roller. Each of the boss groups includes a plurality of spaced apart dot coating bosses, and the distribution direction of the plurality of spaced apart dot coating bosses has an angle with the central axis direction of the relief roller, and the angle is greater than 0° and less than 90°.

[0014] In some possible implementations, the surface of the dot coating boss facing away from the relief roller is in the shape of a circle, an ellipse, a square, or a polygon with more than 4 sides.

[0015] In some possible implementations, the cross-sectional area of ​​the dot coating boss gradually decreases along the radially outward direction.

[0016] In some possible implementations, the height of the dot coating boss is 1 mm-5 mm, the radial dimension of the dot coating boss away from the surface of the relief roller is 200 μm-1000 μm, and the center distance between any two adjacent dot coating bosses is 250 μm-1200 μm.

[0017] On the other hand, a method for preparing a battery separator is provided, wherein the method for preparing a battery separator uses any of the coating preparation devices described above;

[0018] The preparation method comprises:

[0019] The base film is conveyed by a base film conveying device, and the slurry is provided by a slurry supplying device, wherein the slurry contains a binder in an amount of 2% to 7% by mass and has a viscosity of 30 mPa·s to 500 mPa·s;

[0020] Extracting slurry from the slurry supply device through a rotating gravure roller and transferring it into its concave liquid collection tank;

[0021] Extracting the slurry from the concave liquid collection tank by a rotating relief roller and transferring it to the surface of the base film through a dot coating boss to obtain a base film with slurry convex points on the surface;

[0022] The base film with slurry convex points on the surface is dried by a drying device, so that a plurality of glue points distributed in a matrix and arranged in a convex manner are formed on the surface of the base film.

[0023] In some possible implementations, the slurry includes the following components in the following mass percentages: 8%-16% of a polymer, 2%-7% of a binder, 0.5%-1.5% of a dispersant, 3%-9% of a thickener, 0.1%-0.4% of a wetting agent, and deionized water as the balance;

[0024] The polymer is selected from at least one of polyvinylidene fluoride, hexafluoropropylene-modified polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, and polyethylene oxide;

[0025] In some possible implementations, the binder is selected from at least one of polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, silicone-modified polyacrylate, polyurethane-modified polyacrylate, and methacryloyl epoxy ester.

[0026] In some possible implementations, the slurry satisfies at least one of the following parameters: solid content is 5%-25%, particle size D50 of secondary particles in the slurry is ≤20 μm, and particle size D90 of secondary particles in the slurry is ≤50 μm.

[0027] In some possible implementations, the particle size of the glue dots is 200 μm-1200 μm, the height of the glue dots is 0.5 μm-10 μm, and the center distance between any two adjacent glue dots is 250 μm-1200 μm.

[0028] The beneficial effects of the technical solution provided by the embodiment of the present invention include at least:

[0029] The coating preparation device and battery separator preparation method provided by the embodiment of the present invention are as follows: a base film is conveyed by a base film conveying device, and a slurry is provided by a slurry supply device. The slurry is extracted from the slurry supply device by a rotating gravure roller and transferred to its concave liquid extraction tank. The slurry is extracted from the concave liquid extraction tank by a rotating relief roller and transferred to the surface of the base film through a dot coating boss, thereby obtaining a base film with slurry protrusions on the surface. By designing the physical properties of the slurry, the slurry protrusions can be stably bonded to the base film surface and the surface solidification is completed in a very short time, ensuring the structural stability of the slurry protrusions. Subsequently, the base film with slurry protrusions on the surface is dried by a drying device, forming a plurality of glue dots distributed in a matrix and arranged in a raised manner on the base film surface, thereby preparing a matrix adhesive layer on the base film. The matrix adhesive layer includes a plurality of glue dots distributed in a matrix and arranged in a raised manner. Compared with the adhesive layer continuously applied to the carrier layer, the matrix adhesive layer can significantly increase its contact area with the carrier layer and the electrode, which is beneficial to enhancing the adhesion of the battery separator. This matrix adhesive layer is based on a discrete adhesive dot design that only partially covers the carrier layer, which also helps reduce the air permeability increase of the battery separator and enhance the liquid retention of the battery separator. In summary, this coating preparation device can achieve transfer coating of the slurry to the base film. The formed adhesive dots can be precisely arranged according to a specific pattern, and the morphology of the adhesive dots is highly uniform and consistent, making the matrix adhesive layer composed of adhesive dots have high adhesion, high liquid retention and low air permeability increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic structural diagram of an exemplary coating preparation device provided in an embodiment of the present invention;

[0032] Figure 2 A schematic structural diagram of an exemplary gravure roller provided in an embodiment of the present invention;

[0033] Figure 3 A schematic structural diagram of an exemplary relief roller provided in an embodiment of the present invention.

[0034] The reference numerals are:

[0035] 100. Base film conveying device; 101. Pressing roller;

[0036] 200. Slurry supply equipment;

[0037] 300, gravure roller; 301, concave liquid collection tank;

[0038] 400. Letterpress roller; 401. Dot coating boss;

[0039] 500. Drying equipment;

[0040] 600, control equipment;

[0041] 001. Basement membrane. DETAILED DESCRIPTION

[0042] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0043] An embodiment of the present invention provides a coating preparation device, which can form a matrix adhesive layer on a base film, and the matrix adhesive layer can solve the technical problems existing in the battery separator of the related art.

[0044] As attached Figure 1 As shown, the coating preparation device includes: a base film conveying device 100, a slurry supply device 200, a gravure roller 300, a relief roller 400, a drying device 500, and a control device 600. The base film conveying device 100 includes a plurality of pressure rollers 101 spaced apart, which are rotatably arranged and used to convey the base film. The slurry supply device 200 is used to provide slurry. The gravure roller 300 is rotatably arranged adjacent to the slurry supply device 200. Figure 2 As shown, the surface of the gravure roller 300 has a plurality of concave liquid collection grooves 301 spaced apart along the circumferential direction. The gravure roller 300 is used to extract the slurry from the slurry supply device 200 and transfer it to the concave liquid collection grooves 301. The relief roller 400 is rotatably arranged and is located between one of the pressure rollers 101 and the gravure roller 300. Figure 3 As shown, the surface of the relief roller 400 has a plurality of raised dot-coating projections 401. The relief roller 400 is used to extract slurry from the concave liquid extraction tank 301 via the dot-coating projections 401 and transfer it to the surface of the base film. The drying device 500 is used to receive the base film with the slurry dots on its surface and dry it. The control device 600 is used to control the rotation of the pressing roller 101, the gravure roller 300, and the relief roller 400.

[0045] The coating preparation device provided by the embodiment of the present invention, when used, is used to convey the base film through the base film conveying device 100, and to provide slurry through the slurry supply device 200. The slurry is extracted from the slurry supply device 200 by the rotating gravure roller 300 and transferred to its concave liquid collection tank 301. The slurry is extracted from the concave liquid collection tank 301 by the rotating relief roller 400 and transferred to the surface of the base film through the dot coating boss 401, thereby obtaining a base film with slurry convex points on the surface. By designing the physical properties of the slurry, the slurry convex points can be stably bonded to the surface of the base film, and the surface curing is completed in a very short time, ensuring the structural stability of the slurry convex points. Subsequently, the base film with slurry convex points on the surface is dried by the drying device 500, forming a plurality of glue points distributed in a matrix and arranged in a raised manner on the surface of the base film, thereby preparing a matrix adhesive layer on the base film. The matrix adhesive layer comprises multiple raised adhesive dots arranged in a matrix. Compared to an adhesive layer applied continuously to the carrier layer, this matrix adhesive layer significantly increases its contact area with the carrier layer and the electrode, thereby enhancing the adhesion of the battery separator. This matrix adhesive layer, based on a discrete adhesive dot design that only partially covers the carrier layer, also helps reduce the battery separator's air permeability and enhances its liquid retention.

[0046] In summary, the coating preparation device enables the slurry to be transferred to the base film. The formed glue dots can be precisely arranged according to a specific rule, and the morphology of the glue dots is highly uniform and consistent, so that the matrix adhesive layer composed of glue dots has high adhesion, high liquid retention and low air permeability increment.

[0047] The following is an exemplary description of the composition and function of each component involved in the coating preparation device.

[0048] With respect to the base film conveying device 100, the film conveying device includes a plurality of pressure rollers 101 distributed at intervals, and the plurality of pressure rollers 101 are distributed in sequence along the conveying path of the base film. The rotating pressure rollers 101 drive the base film to move in translation, so as to enable the base film to move smoothly from the initial position to the drying device 500. For example, when the conveying path of the base film is a straight path, the plurality of pressure rollers 101 are distributed at intervals along the same straight direction. When the conveying path of the base film is a curved path, the plurality of pressure rollers 101 can be respectively located at different bending points of the curved path. The number of pressure rollers 101 can be 2, 3, 4, 5 or more, and can be adaptively designed according to the actual conveying path.

[0049] The slurry supply device 200 has a accommodating chamber for accommodating the slurry. For example, the slurry supply device 200 has an opening that communicates with the accommodating chamber. The gravure roller 300 can partially enter the accommodating chamber of the slurry supply device 200 through the opening to contact the slurry. For example, the slurry supply device 200 is in the shape of a cylinder with an opening at the top. The slurry supply device 200 is located below the gravure roller 300, and a portion of the surface of the gravure roller 300 enters the accommodating chamber of the slurry supply device 200 through the top opening of the slurry supply device 200.

[0050] As for the gravure roller 300, the gravure roller 300 can be rotatably arranged on the adjacent side of the slurry supply device 200. The surface of the gravure roller 300 has a plurality of concave liquid collection grooves 301 distributed at intervals along the circumferential direction. When in use, some of the concave liquid collection grooves 301 of the gravure roller 300 enter the accommodating cavity of the slurry supply device 200 and contact the slurry. The slurry enters the concave liquid collection grooves 301. As the gravure roller 300 rotates, all the concave liquid collection grooves 301 thereon can be filled with slurry and contact the relief roller 400 during the subsequent rotation process.

[0051] The relief roller 400 is rotatably disposed between one of the pressure rollers 101 and the gravure roller 300, and is in contact with both the pressure roller 101 and the gravure roller 300. As the relief roller 400 rotates, the dot coating bosses 401 thereon enter the concave liquid extraction tank 301 to extract the slurry. The dot coating bosses 401 carrying the slurry then contact the surface of the driven base film during the subsequent rotation process, thereby transferring the slurry to the surface of the base film in the form of slurry dots.

[0052] In some examples, the diameter and thickness of the gravure roller 300 and the relief roller 400 are the same, so that the two are matched and work together.

[0053] The drying device 500 is used to receive the base film having slurry bumps on its surface and dry it. For example, the drying device 500 can be an oven.

[0054] In the embodiment of the present invention, the rotation of the pressure roller 101, the gravure roller 300, and the relief roller 400 is controlled by the control device 600. The control device 600 can control the speed, rotation direction, etc. of the corresponding rollers to achieve stable and controllable dot coating operations.

[0055] In some implementations, such as the attached Figure 2 As shown, any two adjacent concave liquid collection grooves 301 among the multiple concave liquid collection grooves 301 are parallel to each other, and there is an angle between the length direction of each concave liquid collection groove 301 and the central axis direction of the gravure roller 300, and the angle is greater than 0° and less than 90°. For example, the value range of the angle can be 30°-60°, that is, the concave liquid collection grooves 301 are arranged at an angle.

[0056] On the one hand, the presence of the aforementioned angle helps increase the contact area and contact time between the concave liquid extraction groove 301 and the slurry during rotation, more effectively extracting the slurry from the slurry supply device 200, improving the slurry transfer efficiency, and ensuring that sufficient slurry is transferred to the surface of the base film to form stable slurry bumps. On the other hand, it also helps to make the slurry more evenly distributed on the surface of the base film when it is extracted by the dot coating boss 401 of the relief roller 400. Due to the consistent inclination angle of the liquid extraction groove, the flow characteristics of the slurry during the transfer process are relatively stable, which is conducive to forming slurry bumps of relatively consistent size and shape on the surface of the base film, thereby making the final matrix adhesive layer more uniform and improving the consistency of the bonding performance of the battery separator.

[0057] Furthermore, based on the arrangement of the concave liquid collection tank 301 as above, as shown in the attached Figure 3 As shown, multiple dot coating bosses 401 cooperate to form multiple boss groups, and the multiple boss groups are spaced apart along the circumferential direction of the relief roller 400. Each boss group includes multiple spaced dot coating bosses 401, and the distribution direction of the multiple spaced dot coating bosses 401 forms an angle with the central axis direction of the relief roller 400. The angle is greater than 0° and less than 90°. For example, the value range of the angle can be 30°-60°. In other words, the distribution direction of the multiple dot coating bosses 401 in the boss group is arranged obliquely. Furthermore, the angle between the distribution direction of the multiple spaced dot coating bosses 401 and the central axis direction of the relief roller 400 is equal to the angle between the length direction of the concave liquid collection groove 301 and the central axis direction of the gravure roller 300. In this way, the relief roller 400 and the gravure roller 300 work together to achieve the purpose of optimizing the above-mentioned effect.

[0058] In some examples, the shape of the surface of the dot coating boss 401 facing away from the relief roller 400 is circular, elliptical, square, or a polygon with more than 4 sides. Accordingly, the projection shape of the glue dots formed on the surface of the base film on the base film can be circular, elliptical, square, or a polygon with more than 4 sides, wherein the polygons involved above can be regular polygons, including but not limited to regular pentagons, regular hexagons, etc.

[0059] For the plurality of dot coating bosses 401 , the shapes of their surfaces facing away from the relief roller 400 may be the same or different, depending on actual needs.

[0060] In some examples, the cross-sectional area of ​​the dot coating boss 401 gradually decreases in the radially outward direction, wherein the cross-sectional area of ​​the dot coating boss 401 is the cross-sectional area of ​​the surfaces of the dot coating boss 401 that are parallel to the surfaces of the dot coating boss 401 that are in contact with the relief roller 400. In other words, the radial dimension of the dot coating boss 401 gradually decreases from the end of the dot coating boss 401 that is in contact with the relief roller 400 to the end of the dot coating boss 401 that is away from the relief roller 400. This not only facilitates accurate slurry collection and efficient slurry release, but also helps to stabilize the service life of the dot coating boss 401 under frequent use.

[0061] In some examples, the dot coating bosses 401 meet the following physical parameters: the height of the dot coating bosses 401 is 1mm-5mm, the radial dimension of the dot coating bosses 401 away from the surface of the relief roller 400 is 200μm-1000μm, and the center distance between any two adjacent dot coating bosses 401 is 250μm-1200μm.

[0062] The height of the dispensing bosses 401 is configured to ensure reliable and precise transfer of the glue dots to the base film surface. The radial dimension of the dispensing bosses 401, facing away from the relief roller 400, corresponds to the particle size of the glue dots, facilitating the formation of glue dots with a particle size of 50μm-1200μm. This prevents the glue particles from being too large, thereby allowing them to be evenly and densely distributed on the carrier layer. It also prevents the glue particles from being too small, thereby allowing the matrix adhesive layer to provide sufficient bonding area.

[0063] The center distance between any two adjacent dot coating bosses 401 corresponds to the center distance between any two adjacent glue dots, so that the pore structure formed by multiple glue dots is conducive to the rapid penetration and diffusion of the electrolyte, and can also keep the electrolyte in the pores through capillary action, preventing the electrolyte from drying up and losing, improving the battery's liquid retention, and extending the battery life.

[0064] For any of the coating preparation devices mentioned above, the material of the relief roller 400 is selected from EPDM, styrene-butadiene rubber, butyl rubber, nitrile rubber, or chloroprene rubber. Correspondingly, the material of the dot coating boss 401 is also as described above. This makes the dot coating boss 401 have good elasticity, which facilitates the accurate transfer of the slurry to the base film surface and avoids excessive pressure when contacting the pressure roller 101, which may cause deformation or damage to the base film. In addition, the relief roller 400 made of the above material also facilitates the smooth demolding of the slurry bumps.

[0065] On the other hand, an embodiment of the present invention further provides a method for preparing a battery separator, which adopts any of the coating preparation devices mentioned above.

[0066] The preparation method of the battery separator comprises:

[0067] The base film is conveyed by the base film conveying device, and the slurry is provided by the slurry supplying device. The slurry contains a binder with a mass percentage of 2%-7% and a viscosity of the slurry of 30mPa·s-500mPa·s.

[0068] The slurry is extracted from the slurry supply device by the rotating gravure roller and transferred to its concave liquid collection tank.

[0069] The slurry is extracted from the concave liquid collection tank by a rotating relief roller and transferred to the surface of the base film through a dot coating boss to obtain a base film with slurry convex points on the surface.

[0070] The base film with slurry convex points on the surface is dried by a drying device to form a plurality of glue points distributed in a matrix and arranged in a convex manner on the surface of the base film.

[0071] The preparation method of the battery separator provided by the embodiment of the present invention is based on the use of the coating preparation device involved above. When used, the base film is conveyed by the base film conveying device, and the slurry is provided by the slurry supply device. The slurry is extracted from the slurry supply device by a rotating gravure roller and transferred to its concave liquid collection tank. The slurry is extracted from the concave liquid collection tank by a rotating relief roller and transferred to the surface of the base film through a dot coating boss, thereby obtaining a base film with slurry protrusions on the surface. By designing the physical properties of the slurry, the slurry protrusions can be stably bonded to the surface of the base film and the surface curing is completed in a very short time, ensuring the structural stability of the slurry protrusions. Subsequently, the base film with slurry protrusions on the surface is dried by a drying device, forming a plurality of glue dots distributed in a matrix and arranged in a raised manner on the surface of the base film, thereby preparing a matrix adhesive layer on the base film.

[0072] The matrix adhesive layer includes a plurality of adhesive dots distributed in a matrix and arranged in a raised manner. Compared with the adhesive layer continuously applied to the carrier layer, the matrix adhesive layer can significantly increase its contact area with the carrier layer and the pole piece, which is beneficial to enhancing the adhesion of the battery separator. The matrix adhesive layer is based on a discrete adhesive dot design and only partially covers the carrier layer. It is also beneficial to reduce the air permeability increment of the battery separator and enhance the liquid retention of the battery separator. In summary, this preparation method enables the slurry to be transferred to the base film. The formed adhesive dots can be precisely arranged according to a specific rule, and the morphology of the adhesive dots is highly uniform and consistent, so that the matrix adhesive layer composed of adhesive dots has high adhesion, high liquid retention and low air permeability increment.

[0073] Among them, in order to ensure that the slurry bumps formed by the slurry can be reliably transferred to the base film, the slurry can contain a binder with a mass percentage of 2%-7% and the viscosity of the slurry is 30mPa·s-500mPa·s. Such a setting of the slurry is conducive to the slurry bumps being bonded to the surface of the base film at room temperature, and can be initially solidified in a very short time (that is, the solvent on the surface of the slurry bumps evaporates quickly, so that its surface is formed to maintain the shape, and the slurry bumps are in a semi-dry state), ensuring that the slurry bumps maintain structural stability during the subsequent drying process to form glue dots, thereby achieving precise transfer of the glue dot morphology.

[0074] For the adhesive, its mass percentage in the glue dot can be any of the following values ​​or an interval consisting of two of the values: 2%, 3%, 4%, 5%, 6%, 7%, etc.

[0075] In some examples, the adhesive is an acrylic adhesive, which can be selected from at least one of polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, silicone-modified polyacrylate, polyurethane-modified polyacrylate, and methacryloyl epoxy ester.

[0076] The above-mentioned adhesive can not only further enhance the adhesion of the adhesive layer (for example, achieving stable bonding with the carrier layer and the polymer through the carboxylic acid group), but also help to form an elastic network to inhibit deformation cracking, further reduce the air permeability of the diaphragm, and also help to enhance the liquid retention rate.

[0077] In addition, the above-mentioned acrylic binder not only helps to enhance the adhesion between the glue dots and the base film, but also has a significant regulatory effect on the process of polymer primary particles (i.e., single polymer powder particles) agglomerating into secondary particles (i.e., agglomerate particles formed by the agglomeration of multiple primary particles). It converts the random agglomeration of polymer primary particles into controllable, high-strength, functionalized secondary particles through the triple effects of dispersion regulation (anti-agglomeration), interface bridging (strong structure), and gradient function (excellent performance). It can not only solve the problem of "easy to break and uneven porosity" of traditional agglomerates, but also the carboxyl active groups of the binder give the secondary particles complex functions such as interface bonding, ion conduction, and liquid retention and locking, which is beneficial to improving the cycle life of the diaphragm.

[0078] In some examples, the viscosity of the slurry may be between 100 mPa·s and 500 mPa·s, including but not limited to 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s, 350 mPa·s, 400 mPa·s, 450 mPa·s, and 500 mPa·s. By controlling the viscosity and curing amount of the slurry, the amount of slurry applied by the dispensing boss each time can be controlled, thereby controlling the height and other morphologies of the formed glue dots.

[0079] In some examples, the slurry includes the following components in the following mass percentages: 8%-16% polymer, 2%-7% binder, 0.5%-1.5% dispersant, 3%-9% thickener, 0.1%-0.4% wetting agent, and deionized water as the balance.

[0080] By improving the composition of the glue points in the matrix adhesive layer, the polymer is in the form of micron-sized powder and is in a bonding state when the temperature is higher than its glass transition temperature, thereby realizing its bonding function. Specific amounts of binder, dispersant, thickener and wetting agent are added thereto. The various components act synergistically. The binder cooperates with the polymer to further enhance the adhesion of the matrix adhesive layer. The dispersant can effectively inhibit polymer agglomeration. The wetting agent is beneficial to reducing the surface energy of the glue points and promoting capillary filling of the electrolyte. The thickener cooperates with the polymer to form a cross-linked network to accommodate the electrolyte. The above is beneficial to enhancing the adhesion and liquid retention performance of the matrix adhesive layer and reducing the air permeability increment of the battery separator.

[0081] The polymer is applied to the matrix adhesive layer to form the main body of the adhesive particles, providing suitable bonding force and mechanical strength. For the polymer, its mass percentage in the adhesive point can be any of the following values ​​or an interval consisting of two of the following values: 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, etc.

[0082] The glass transition temperature T g -50℃~100℃, for example, some polymers that meet this requirement can be selected from polyvinylidene fluoride (PVDF), hexafluoropropylene modified polyvinylidene fluoride

[0083] At least one of (PVDF-HPF), polymethyl methacrylate (PMMA), polyacrylonitrile, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, and polyethylene oxide.

[0084] The above polymers are polar or contain polar groups, which not only facilitates stable and reliable bonding between the battery separator and the carrier layer and the electrode, but also helps improve compatibility with the electrolyte to obtain a stronger liquid retention rate.

[0085] The dispersant serves to disperse the colloid particles and prevent them from agglomerating. Its mass percentage in the slurry can be any of the following values ​​or an interval consisting of two of them: 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc.

[0086] For example, some suitable dispersants are selected from at least one of sodium hexametaphosphate, triethyl phosphate, sodium polyacrylate, ammonium polyacrylate, polyethylene glycol, polyvinyl alcohol, naphthalenesulfonic acid condensate, sodium cellulose sulfonate, and sodium lignin sulfonate. These dispersants can synergize with other components in the particles to achieve a good dispersion effect.

[0087] The thickener forms a cross-linked network within the particles after curing, maintaining their structural shape. This contributes to the membrane's fluid retention and air permeability. The mass percentage of the thickener in the slurry can be any of the following values, or a range consisting of two of these values: 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc.

[0088] Some suitable thickeners are selected from at least one of sodium hydroxymethyl cellulose (NaCMC) and xanthan gum, for example, sodium hydroxymethyl cellulose. When preparing the granules, the sodium hydroxymethyl cellulose can be pre-mixed with water to form a sodium hydroxymethyl cellulose glue solution with a mass concentration of 0.5% to 1%. Subsequently, the sodium hydroxymethyl cellulose glue solution and other components are dissolved in water to form a slurry.

[0089] Wetting agents can reduce the surface tension of the adhesive particles, ensuring wettability between the matrix adhesive layer, the carrier layer, and the electrode, which is beneficial for improving the adhesion of the diaphragm. The mass percentage of the wetting agent in the slurry can be any of the following values ​​or a range of two of these values: 0.1%, 0.2%, 0.3%, 0.4%, etc.

[0090] Some suitable wetting agents can be selected from at least one of polyether wetting agents, silicone and polyether mixture wetting agents, and alcohol alkoxylate wetting agents. Among them, polyether wetting agents can be, for example, fatty alcohol polyoxyethylene ether (lauryl alcohol polyoxyethylene ether, etc.), polyoxyethylene polyoxypropylene block copolymer (poloxamer, etc.), silicone and polyether mixture wetting agents can be, for example, the commercially available product Digo Wet 270, Evonik Wet 290, etc., and alcohol alkoxylate wetting agents can be, for example, isotridecanol polyoxyethylene ether, etc.

[0091] As mentioned above, in order to further improve the adhesion and liquid retention of the matrix adhesive layer and reduce its air permeability increment, the particle size of the glue dots can be 200μm-1200μm, the height of the glue dots can be 0.5μm-10μm, and the center distance between any two adjacent glue dots can be 250μm-1200μm.

[0092] Furthermore, the amount of glue applied to the matrix glue layer on the surface of the carrier layer is 0.3 g / m 2 -1.5g / m 2, with a coverage rate of 20%-80%. The glue coating weight refers to the mass of the matrix adhesive layer per unit area, while the coverage rate refers to the percentage of the projected area of ​​multiple adhesive dots on the carrier layer's surface area. By limiting the glue coating weight and adhesive layer coverage rate, the battery separator's adhesion and liquid retention properties can be further optimized, while also reducing its air permeability gain.

[0093] Furthermore, the polymer particle size D50 can be set to 0.5 μm-50 μm, where the polymer particle size is also the primary particle size. The slurry must meet at least one of the following parameters: solids content of 5%-25%, secondary particle size D50 ≤ 20 μm, and secondary particle size D90 ≤ 50 μm. The secondary particles in the slurry are obtained by agglomeration of polymer powder.

[0094] By limiting the polymer powder particle size and the physical properties of the slurry, the morphology of the glue particles can be effectively controlled, allowing the glue dots to have a particle size of 200μm-1200μm, a height of 0.5μm-10μm, and a center-to-center distance of 250μm-1200μm between any two adjacent glue dots. Furthermore, the amount of glue applied and the coverage of the matrix glue layer can be easily controlled.

[0095] For any of the battery separators mentioned above, the base film can be a polyethylene-based film (abbreviated as PE-based film) or a polypropylene-based film (abbreviated as PP-based film). Both polyethylene-based films and polypropylene-based films have good chemical stability, high mechanical strength, excellent electrical insulation properties, suitable pore structure and pore size distribution, and are easy to process and shape, giving the battery separator excellent comprehensive performance.

[0096] It is not ruled out that other functional layers may be further provided on the surface of the base film, such as a nanofiber layer, a ceramic layer, etc. When the base film surface has a functional layer, a matrix adhesive layer is formed on the surface of the functional layer, and a suitable base film can be selected according to actual needs.

[0097] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A coating preparation device, characterized in that: The coating preparation device comprises: a base film conveying device (100), wherein the base film conveying device (100) comprises a plurality of pressure rollers (101) distributed at intervals, wherein the plurality of pressure rollers (101) are rotatably arranged and used to convey the base film (001); a slurry supply device (200), wherein the slurry supply device (200) provides slurry; a gravure roller (300) rotatably arranged adjacent to the slurry supply device (200), the surface of the gravure roller (300) having a plurality of concave liquid extraction grooves (301) spaced apart along a circumferential direction, the gravure roller (300) being used to extract slurry from the slurry supply device (200) and transfer the slurry into the concave liquid extraction grooves (301); A relief roller (400), the relief roller (400) being rotatably arranged, the relief roller (400) being located between one of the pressure rollers (101) and the gravure roller (300), the surface of the relief roller (400) being provided with a plurality of convexly arranged dot coating bosses (401), the relief roller (400) being used to extract slurry from the concave liquid extraction tank (301) through the dot coating bosses (401) and transfer the slurry to the surface of the base film (001); A drying device (500), the drying device (500) is used to receive a base film (001) having slurry bumps on its surface and dry it; A control device (600) is used to control the rotation of the pressing roller (101), the gravure roller (300), and the relief roller (400).

2. The coating preparation device according to claim 1, characterized in that: Any two adjacent concave liquid-collecting grooves (301) among the plurality of concave liquid-collecting grooves (301) are parallel to each other, and an angle is formed between the length direction of each concave liquid-collecting groove (301) and the central axis direction of the gravure roller (300), and the angle is greater than 0° and less than 90°.

3. The coating preparation device according to claim 2, characterized in that: The plurality of dot coating bosses (401) cooperate to form a plurality of boss groups, the plurality of boss groups are spaced apart along the circumferential direction of the relief roller (400), each of the boss groups comprises a plurality of spaced apart dot coating bosses (401), and the distribution direction of the plurality of spaced apart dot coating bosses (401) has an angle with the central axis direction of the relief roller (400), and the angle is greater than 0° and less than 90°.

4. The coating preparation device according to claim 1, characterized in that: The shape of the surface of the dot coating boss (401) facing away from the relief roller (400) is circular, elliptical, square or polygonal with more than 4 sides.

5. The coating preparation device according to claim 1, characterized in that: Along the radially outward direction, the cross-sectional area of ​​the dot coating boss (401) gradually decreases.

6. The coating preparation device according to claim 4, characterized in that: The height of the dot coating boss (401) is 1 mm to 5 mm, the radial dimension of the dot coating boss (401) away from the surface of the relief roller (400) is 200 μm to 1000 μm, and the center distance between any two adjacent dot coating bosses (401) is 250 μm to 1200 μm.

7. A method for preparing a battery separator, characterized in that: The method for preparing the battery separator adopts the coating preparation device according to any one of claims 1 to 6; The preparation method comprises: The base film (001) is conveyed by a base film conveying device (100), and slurry is provided by a slurry supplying device (200), wherein the slurry contains a binder in an amount of 2% to 7% by mass and has a viscosity of 30 mPa·s to 500 mPa·s; Extracting slurry from the slurry supply device (200) through a rotating gravure roller (300) and transferring the slurry into a concave liquid collection tank (301); Extracting slurry from the concave liquid collection tank (301) by a rotating relief roller (400) and transferring it to the surface of the base film (001) through a dot coating boss (401) to obtain a base film (001) having slurry convex points on the surface; The base film (001) having slurry convex points on the surface is dried by a drying device (500), and a plurality of glue points distributed in a matrix and arranged in a convex manner are formed on the surface of the base film (001).

8. The method for preparing a battery separator according to claim 7, wherein: The slurry comprises the following components in the following mass percentages: 8%-16% of a polymer, 2%-7% of a binder, 0.5%-1.5% of a dispersant, 3%-9% of a thickener, 0.1%-0.4% of a wetting agent, and deionized water as the balance; The polymer is selected from at least one of polyvinylidene fluoride, hexafluoropropylene-modified polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, and polyethylene oxide; The binder is selected from at least one of polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, silicone-modified polyacrylate, polyurethane-modified polyacrylate, and methacryloyl epoxy ester.

9. The method for preparing a battery separator according to claim 8, wherein: The slurry satisfies at least one of the following parameters: solid content is 5%-25%, particle size D50 of secondary particles in the slurry is ≤20 μm, and particle size D90 of secondary particles in the slurry is ≤50 μm.

10. The method for preparing a battery separator according to any one of claims 7 to 9, characterized in that: The particle size of the glue dots is 200 μm-1200 μm, the height of the glue dots is 0.5 μm-10 μm, and the center distance between any two adjacent glue dots is 250 μm-1200 μm.

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