Preparation method of battery coating film and battery coating film

Abstract

The invention discloses a preparation method of a battery coating film and the battery coating film, in the spraying step of the preparation method of the battery coating film, by controlling the viscosity and the particle size of slurry, the slurry is made to meet specific process requirements, a premise is provided for uniform coating, meanwhile, the transmission mode of spraying equipment is independent motor transmission, and the cost is low. The dispersing plates of the spraying equipment are arranged in a high-low staggered mode, slurry dispersed by the adjacent dispersing plates is in different planes, collision between the atomized slurry is reduced, the spraying effect of the slurry is improved, and the probability that liquid drops and bright spots are generated on the surface of a film is reduced.

Description

Technical Field

[0001] The invention relates to a preparation method of a battery coating film and the battery coating film, belonging to the technical field of lithium battery diaphragm production. Background Art

[0002] As the global demand for renewable energy and new energy transportation continues to increase, the market demand for lithium battery separators is growing year by year. At the same time, the new energy industry is also facing technological innovation and improvement. The research and development of new materials, the application of new processes, and the optimization of debugging methods are all current research hotspots. At present, coating machine spraying technology is widely used in the preparation and modification process of separators to improve the performance and function of separators. The spraying method can improve the uniformity of separators, adjust the coating thickness, and change the material composition. However, the speed increase of coating equipment, the adjustment of corresponding process parameters of the sprayer, and the dispersion process of the sprayer may affect the spraying quality, which may cause droplets to appear on the membrane surface, thereby affecting the quality of the separator.

[0003] For droplets on the membrane surface, their size, shape and distribution all have an impact on the performance and application of the film. On the one hand, the presence of droplets can change the surface morphology and structure of the film, thereby affecting its wettability, transparency, optical properties, etc. On the other hand, the aggregation or dispersion of droplets may also lead to the inhomogeneity of the film, thus affecting its function and performance.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a battery coating film, so as to solve the technical problem that the membrane surface droplets are easily generated during the spraying process of the prior art diaphragm. At the same time, the present invention also provides a battery coating film prepared by the method.

[0006] The present invention ensures fluidity and stirring performance by limiting the particle size of the material and the viscosity of the slurry, thereby meeting the requirements of uniform coating and providing a prerequisite for the spraying process and improving production efficiency. Therefore, the present invention combines specific slurry requirements with high and low staggered dispersion discs to improve the slurry spraying effect and reduce the probability of droplets and bright spots on the membrane surface.

[0007] The preparation method of the battery coating film of the present invention adopts the following technical scheme: a preparation method of a battery coating film, wherein the preparation steps include preparing a base film, preparing a coating slurry, and coating the slurry on the base film, and the step of coating the slurry on the base film includes: S1. Arrange the dispersion disks of the spraying equipment in sequence on the same side of the membrane surface along the width direction of the membrane, with two adjacent dispersion disks arranged alternately, one high and one low, each dispersion disk being driven by a separate motor, each dispersion disk being equipped with a separate spray window, and the spray window being located in front of the dispersion disk; S2. The prepared coating slurry is transported to the spraying equipment through a slurry pump. When the diaphragm is driven, the spraying equipment is running, and the slurry is atomized under the shear force of the dispersion disk and coated onto the diaphragm membrane surface.

[0008] Each dispersion disc is connected with a separate feed pipe, and each feed pipe is provided with a slurry pump and a flow meter; the slurry pump adopts a vacuum impeller pump; the spray window adopts an inverted triangle, and the spray window area is 40-80mm².

[0009] The adjustable speed range of the slurry pump is 500-3000 r / min. The operation of the slurry pump adjusts the flow rate of the feed pipe within the range of 1000ml / min to 11000ml / min. When the spraying equipment is running stably, the flow rate of the feed pipe is 3000ml / min±5%.

[0010] The height difference between two adjacent dispersion discs is 5-10mm; the distance between the dispersion disc at the lower position and the bottom is 35-40mm, the distance between the dispersion disc at the higher position and the bottom is 40-45mm, the rotation speed of the dispersion disc is 8000-8500r / min, the distance between the spray window and the membrane surface is 20-25mm, and the flow rate of the slurry pump is 4000-4500mL / min.

[0011] The dispersion speed is 1000~1200rpm, the duration is 30~35min, the stirring speed is 20~25rpm, and the duration is 30~35min.

[0012] The slurry includes organic particles, which include one or more of polyacrylic acid resin, polymethyl methacrylate, and fluorine-containing polymer.

[0013] Preferably, the particle size of the organic particles is less than 5 microns, the slurry viscosity is 50-150 mPa.s, and the slurry solid content is 5%-15%.

[0014] Preferably, the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, and a copolymer of vinylidene fluoride and hexafluoropropylene.

[0015] Preferably, the present invention adopts a vacuum vane pump to replace the diaphragm pump of the prior art, thereby improving the stability of the feed and further reducing the droplets on the membrane surface.

[0016] Preferably, the spray window adopts an inverted triangle shape, and excess slurry can flow out along the bottom of the inverted triangle window to avoid large-area leakage of slurry and facilitate the recovery of excess slurry.

[0017] Preferably, each dispersion disk is connected to a separate feed pipe, and the flow rate can be adjusted by a separately provided slurry pump.

[0018] The present invention upgrades the transmission mode of the spraying equipment from the belt drive of the prior art to a single motor drive, which is more suitable for dispersed atomization under high-speed conditions. Each dispersion disk is controlled individually by a motor, corresponding to different areas of the spraying diaphragm, so that the rotation speed of each dispersion disk can be set to an appropriate value according to the spraying effect of each area; the dispersion disks of the spraying equipment are arranged in a high and low staggered arrangement, and the slurry dispersed by adjacent dispersion disks is in different planes, which reduces the collision between the atomized slurries and avoids the formation of droplets on the membrane surface.

[0019] The beneficial effects of the present invention are: The present invention significantly improves the existing membrane spray droplet defects. At the same time, the limitation of slurry viscosity improves the condensation of bleaching powder on site, and it is more convenient and quick for operators to clean up the site. The present invention improves the membrane surface droplets from the following aspects: (1) Controlling the slurry viscosity avoids the factors that cause the formation of membrane surface droplets due to excessively high slurry viscosity; (2) The dispersion disc is driven separately to avoid the problem of poor atomization effect caused by poor transmission effect; (3) The dispersion discs are arranged in a staggered manner, and the slurry dispersed by adjacent dispersion discs is in different planes, reducing the collision between the atomized slurries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the arrangement of the dispersion disk in the spraying step of the present invention; DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. Example 1

[0022] A method for preparing and spraying a lithium battery separator coating slurry according to an embodiment of the present invention comprises a coating slurry preparation step and a spraying step. (1) The coating slurry preparation step is: The organic particles of the present application are preferably fluorine-containing polymers, and the fluorine-containing polymers include at least one of polyvinylidene fluoride homopolymer PVDF, polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, and polyvinylidene fluoride-trifluoroethylene copolymer PVDF-TrFE. In this embodiment, polyvinylidene fluoride homopolymer PVDF is used.

[0023] 1.1. Arrange the dispersion discs of the spraying equipment on the same side of the membrane surface along the width direction of the membrane, and alternately arrange two adjacent dispersion discs, one high and one low, with a height difference of 5-10mm. Each dispersion disc is driven by a separate motor, and each dispersion disc is equipped with a separate spray window; the spray window adopts an inverted triangle, and the spray window area is 50mm².

[0024] 1.2. The slurry in the finished product tank is transported to the spraying equipment through the slurry pump. When the diaphragm is driven, the spraying equipment is running, and the slurry is atomized under the shear force of the dispersion disk and coated on the diaphragm membrane surface. The slurry pump adopts a vacuum impeller pump. The slurry pump can adjust the speed range of 500-3000 rpm, the flow stability is 3000ml / min±5%, the lower limit of the flow is 1000ml / min, and the upper limit of the flow is 11000ml / min.

[0025] In the present embodiment, when there is no droplet on the membrane surface, the height position range of the dispersion disk is: the distance between the dispersion disk at a low position and the bottom is 35-40mm, the distance between the dispersion disk at a high position and the bottom is 40-45mm, the rotation speed of the dispersion disk is 8000-8500r / min, the distance between the spray window and the membrane surface is 20-25mm, and the flow rate of the slurry pump is 4000-4500mL. In the present embodiment, the distance between the dispersion disk at a low position and the bottom is 36mm, the distance between the dispersion disk at a high position and the bottom is 42mm, the rotation speed of the dispersion disk is 8000r / min, the distance between the spray window and the membrane surface is 20mm, and the flow rate of the slurry pump is 4000mL.

[0026] Comparative Example 1 The preparation steps of the coating slurry are the same as those in Example 1. In the spraying step of the coating slurry, the dispersion disk height is 40 mm. The remaining steps are the same as those in Example 1. At this time, the problem with the membrane surface is that there are many droplets on the membrane surface.

[0027] Comparative Example 2 The preparation steps of the coating slurry are the same as those in Example 1. In the spraying step of the coating slurry, the distance between the dispersion disk at a low position and the bottom is 45 mm, and the distance between the dispersion disk at a high position and the bottom is 50 mm. The remaining steps are the same as those in Example 1. At this time, the problem on the membrane surface is coating accumulation and an increase in black spots.

[0028] Comparative Example 3 The preparation steps of the coating slurry are the same as those in Example 1, and the spraying steps of the coating slurry are the same as those in Comparative Example 1. In the spraying step of the coating slurry, the rotation speed of the dispersion disk is 6000r / min, and the flow rate of the slurry pump between the spray window and the membrane surface is 3000mL. The remaining steps are the same as those in Example 1. The problem with the membrane surface is that the number of droplets on the membrane surface is reduced, but the gram weight of the diaphragm is insufficient.

[0029] The present invention improves the transmission method of the existing dispersion disc through belts and bearings. The dispersion discs are driven by a single motor, and the dispersion discs can rotate independently without affecting each other, thereby reducing the generation of droplets due to poor slurry atomization effect caused by poor bearing rotation or belt slippage. The existing dispersion discs are distributed at the same horizontal position. When the flow rate is large and the slurry to be atomized is large, the probability of slurry droplets colliding increases. The present invention optimizes the distribution of the dispersion discs and adopts a high-low staggered distribution method. The arrangement of the dispersion discs is as follows: Figure 1 As shown, each dispersion disc is equipped with a separate spray window. The slurry dispersed by adjacent dispersion discs is in different planes, which greatly reduces the probability of slurry droplet collision and improves the problem of droplets on the membrane surface. The spray window is located in front of the dispersion disc. The spray window adopts an inverted triangle shape. The dispersion disc spray area is about 50mm².

[0030] The present invention adopts a vacuum impeller pump to replace the diaphragm pump in the prior art, adapts to the feeding requirements of high-flow products, and ensures feeding stability.

Claims

1. A method for preparing a battery coating film, the preparation steps comprising providing a base film and a coating slurry and coating the slurry on the base film, characterized in that: The steps of coating the slurry on the base film include: S1. Arrange the dispersion disks of the spraying equipment in sequence on the same side of the membrane surface along the width direction of the membrane, with two adjacent dispersion disks arranged alternately, one high and one low, each dispersion disk being driven by a separate motor, each dispersion disk being equipped with a separate spray window, and the spray window being located in front of the dispersion disk; S2. The coating slurry is transported to the spraying equipment through a slurry pump. When the diaphragm is driven, the spraying equipment is running, and the slurry is atomized under the shear force of the dispersion disk and coated onto the diaphragm membrane surface.

2. The method for preparing a battery coating film according to claim 1, characterized in that: Each dispersion disc is connected with a separate feed pipe, and each feed pipe is provided with a slurry pump and a flow meter.

3. The method for preparing a battery coating film according to claim 1, characterized in that: The slurry pump adopts a vacuum impeller pump; the spray window adopts an inverted triangle, and the spray window area is 40-80mm².

4. The method for preparing a battery coating film according to claim 2, characterized in that: The adjustable speed range of the slurry pump is 500-3000 r / min. The operation of the slurry pump adjusts the flow rate of the feed pipe within the range of 1000ml / min to 11000ml / min. When the spraying equipment is running stably, the flow rate of the feed pipe is 3000ml / min±5%.

5. The method for preparing a battery coating film according to claim 1, characterized in that: The height difference between two adjacent dispersion discs is 5-10mm; the distance between the dispersion disc at the lower position and the bottom is 35-40mm, and the distance between the dispersion disc at the higher position and the bottom is 40-45mm.

6. The method for preparing a battery coating film according to claim 1, characterized in that: The rotation speed of the dispersion disk is 8000-8500r / min, the distance between the spray window and the membrane surface is 20-25mm, and the flow rate of the slurry pump is 4000-4500mL / min.

7. The method for preparing a battery coating film according to claim 1, characterized in that: The slurry includes organic particles.

8. The method for preparing a battery coating film according to claim 7, characterized in that: The particle size of the organic particles is less than 5 microns, the slurry viscosity is 50-150 mpa.s, and the slurry solid content is 5%-15%.

9. A battery coating film, characterized in that: The battery coating film is prepared by the preparation method described in any one of claims 1-8.

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