Salient point structure for point coating plate roller

Abstract

The salient point structure comprises a circular truncated cone, a third cylinder and a fourth cylinder which are sequentially arranged from bottom to top, the circular truncated cone is gradually shrunk from bottom to top, the diameter of the top face of the circular truncated cone is equal to that of the third cylinder, and the diameter of the fourth cylinder is smaller than that of the third cylinder. The top of the fourth cylinder is a cambered surface, and the salient point structure is an axisymmetric structure. On the basis of solving the problem of edge missing of the coating points, the completeness of the coating points is remarkably enhanced, meanwhile, the edge regularity is greatly improved, the forms of the coating points better conform to the process standard, the coating points are more uniform and consistent, the occurrence of weak points on the surface of a coating film is reduced, and the safety performance is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery separators, and particularly relates to a convex point structure for a point coating version roller. BACKGROUND

[0002] With the rapid development of new energy automobile and electronic equipment markets, the market demand for lithium batteries as efficient energy storage elements continues to grow. The safety and performance of lithium batteries are crucial to the development of the entire industry, and the performance of the separator, as one of the key components of the lithium battery, directly affects the safety, cycle life and energy density of the battery.

[0003] The main role of the separator is to isolate the positive and negative electrodes of the battery to prevent short circuits, while allowing lithium ions to pass through to form a charge and discharge circuit. In order to improve the performance of the separator, a scheme of coating a slurry on the surface of the base film to form a coating is generally adopted. The thermal stability, mechanical strength, puncture resistance and liquid retention of the coated separator are significantly improved compared to the base film, thereby prolonging the cycle life of the battery and enhancing safety.

[0004] However, there are still many problems to be solved in the current separator coating technology. For example, the emerging point coating process often has irregular coating point morphology and back-drawing during coating operation. These problems not only have adverse effects on the performance of the separator, but also may cause safety risks such as battery short circuit and thermal runaway.

[0005] Based on the above needs, it is necessary to fundamentally solve the problems existing in the current point coating process of the separator, thereby providing reliable technical support for the high-quality production of lithium battery separators. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a convex point structure.

[0007] Another purpose of the present application is to provide a point coating version roller.

[0008] The purpose of the present application is achieved by the following technical solutions.

[0009] A convex point structure is one of the following three structures:

[0010] Structure one, the convex point structure comprises, from bottom to top, a circular truncated cone, a first cylinder and a second cylinder, the circular truncated cone is tapered from bottom to top, the top surface diameter of the circular truncated cone is equal to the diameter of the first cylinder, one side of the first cylinder and the second cylinder in the height direction is on the same vertical plane, and the diameter of the second cylinder is smaller than the diameter of the first cylinder;

[0011] Structure 2, the convex structure includes: a frustum and a truncated cylinder arranged sequentially from bottom to top. The frustum tapers from bottom to top, and the diameter of the top surface of the frustum is equal to the diameter of the truncated cylinder.

[0012] Structure 3, the convex structure includes: a frustum, a third cylinder and a fourth cylinder arranged sequentially from bottom to top. The frustum tapers from bottom to top. The diameter of the top surface of the frustum is equal to the diameter of the third cylinder. The diameter of the fourth cylinder is smaller than the diameter of the third cylinder. The top of the fourth cylinder is an arc surface. The convex structure described in Structure 3 is an axisymmetric structure.

[0013] In the above technical solution, the height of the frustum is 430~590μm, the top diameter of the frustum is 450~600μm, and the bottom diameter of the frustum is 650~1200.12μm.

[0014] In the above technical solution, the distance between the highest point of the arc surface and the bottom surface of the fourth cylinder is 90~150μm (preferably 100~130μm).

[0015] In the above technical solution, the diameter of the second cylinder is 250~350μm, the height of the first cylinder is 30~90μm, and the height of the second cylinder is 30~90μm (preferably 50~70μm).

[0016] In the above technical solution, the height of the lower side of the oblique cylinder is 30~90μm, and the height of the higher side of the oblique cylinder is 100~120μm.

[0017] In the above technical solution, the diameter of the fourth cylinder is 350~420μm, and the height of the third cylinder is 30~90μm.

[0018] A dot-coating roller includes: a roller body and a plurality of protrusions evenly distributed on the surface of the roller body, each of the protrusions being a protrusion structure.

[0019] In the above technical solution, the protrusions are arranged in a matrix on the surface of the roller, and the distance between the center points of every two adjacent protrusions is 580~780μm.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The raised dot structure proposed in this invention reduces the squeezing effect of the dot coating roller during the slurry transfer process, precisely overcomes the key problem of missing coating dot edges, and lays the foundation for improving the performance of the subsequent coating film;

[0022] 2. Based on solving the problem of missing edges of coating points, this invention significantly enhances the integrity of coating points, while greatly improving edge regularity, making the shape of coating points more in line with process standards, making coating points more uniform and consistent, reducing the occurrence of weak points on the surface of the coating film, and increasing safety performance.

[0023] 3. When the convex structure is structure one, the coating points in the obtained coating film are complete only when the height of the second cylinder is 50~70μm; when the convex structure is structure two, the coating points in the obtained coating film are complete when the height of the lower side of the oblique cylinder is 30~90μm and the height of the higher side of the oblique cylinder is 100~120μm; when the convex structure is structure three, the coating points in the obtained coating film are complete only when the distance between the highest point of the arc surface and the bottom surface of the fourth cylinder is 100~130μm. Attached Figure Description

[0024] Figure 1 The appearance of the coating film obtained by the dot-coating roller of Comparative Example 1;

[0025] Figure 2 The appearance of the coating film obtained by the dot-coating roller of Comparative Example 1;

[0026] Figure 3 This is a schematic diagram of the convex structure in Example 1;

[0027] Figure 4 This is a schematic diagram of the convex structure in Example 2;

[0028] Figure 5 This is a schematic diagram of the convex structure in Example 3;

[0029] Figure 6 This is a schematic diagram of the convex structure in Comparative Example 1;

[0030] Figure 7 A diagram illustrating the mechanism by which deformed coating points (crescent-shaped morphology) are formed;

[0031] Figure 8 The appearance of the coating film obtained by the dot-coating roller of Example 1;

[0032] Figure 9 The appearance of the coating film obtained by the dot-coating roller of Example 2;

[0033] Figure 10 The appearance of the coating film obtained by the dot-coating roller of Example 3;

[0034] Figure 11 The appearance of the coating film obtained by the dot-coating roller of Example 4;

[0035] Figure 12The appearance of the coating film obtained by the dot-coating roller of Example 5;

[0036] Figure 13 The appearance of the coating film obtained by the dot-coating roller of Example 6;

[0037] Figure 14 The appearance of the coating film obtained by the dot-coating roller of Example 7;

[0038] Figure 15 The appearance of the coating film obtained by the dot-coating roller of Example 8;

[0039] Figure 16 The appearance of the coating film obtained by the dot-coating roller of Example 9;

[0040] Figure 17 The appearance of the coating film obtained by the dot-coating roller of Comparative Example 1;

[0041] Figure 18 This is a partial schematic diagram of the dot coating roller.

[0042] 1: Roller body, 2: Protrusion, 3: Frustum, 4: First cylinder, 5: Second cylinder, 6: Oblique cylinder, 7: Third cylinder, 8: Fourth cylinder, 9: Fifth cylinder. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0044] The preparation method of the dot-coating slurry in the following examples and comparative examples includes: at room temperature, deionized water and a dispersant are mixed and stirred in a double planetary mixer for 10 minutes until homogeneous (the stirring speed is 20 rpm and the rotation speed is 1500 rpm). First, polyvinylidene fluoride-hexafluoropropylene copolymer (powder) is added and stirred for 60 minutes until homogeneous (the stirring speed is 20 rpm and the rotation speed is 1500 rpm). Then, a thickener and a binder are added sequentially and stirred for 20 minutes until homogeneous (the stirring speed is 20 rpm and the rotation speed is 1500 rpm), resulting in a dot-coating slurry (viscosity 400 cp, solid content 18 wt%). The ratio of dispersant, polyvinylidene fluoride-hexafluoropropylene copolymer (powder), thickener, and binder, by mass parts, is 0.02:2:1.1:1. The dispersant is ammonium polyacrylate (SN5027), the thickener is carboxymethyl cellulose, and the binder is styrene-butadiene rubber.

[0045] Thickness increment: The difference between the thickness of the coated film and the thickness of the base film.

[0046] Coating amount: The weight of the coating on a unit area of ​​the coated film.

[0047] Positive electrode adhesion: The coated film and the positive electrode sheet were each cut into samples with a length * width of 60mm * 25mm. The coated surface of the film was attached to the positive electrode sheet, and the samples were placed under a hot press for hot pressing (hot pressing parameters: 1000Kgf, 80℃, preheating for 1s, hot pressing for 1s). The force required to separate the coated film from the positive electrode sheet was then tested to obtain the positive electrode adhesion. The positive electrode material in the positive electrode sheet is lithium iron phosphate.

[0048] The base film is a 9μm thick PE base film. It should be noted that base films of other thicknesses can also be used.

[0049] The material of the protrusion 2 is one or a mixture of nitrile rubber (NBR), fluororubber (FKM), and polyurethane rubber (PU), and specifically nitrile rubber in this invention.

[0050] Example 1

[0051] like Figure 18 and Figure 3 As shown, a dot-coating roller includes: a roller body 1 and a plurality of protrusions 2 evenly distributed on the surface of the roller body 1. The protrusions 2 are arranged in a matrix on the surface of the roller body 1. The roller body 1 is a cylindrical cavity. The distance between the center points of every two adjacent protrusions 2 in the transverse and longitudinal directions of the rectangular array is 680 μm. Each protrusion 2 is a protrusion structure, wherein each protrusion structure includes: a frustum 3, a first cylinder 4 and a second cylinder 5 arranged sequentially from bottom to top. The frustum 3 tapers from bottom to top, and the top surface of the frustum 3 is straight. The diameter of the first cylinder 4 is equal to the diameter of the second cylinder 5. The first cylinder 4 and the second cylinder 5 are on the same vertical plane on one side (right side) in the height direction. The diameter of the second cylinder 5 is smaller than the diameter of the first cylinder 4. The diameter of the second cylinder 5 is 320 μm. The height of the first cylinder 4 is 60 μm. The height of the second cylinder 5 is 60 μm. The height of the frustum 3 is 530 μm. The top diameter of the frustum 3 is 450 μm. The bottom diameter of the frustum 3 is 1200.12 μm.

[0052] The design advantage of the convex structure in Example 1 is that there is a depression (notch) on one side of the convex structure. During the coating process, the convex points on the surface of the dot coating roller are compressed and produce elastic deformation. The presence of this depression can reduce the squeezing effect of the edge position on the slurry.

[0053] Example 2

[0054] like Figure 18 and Figure 4As shown, a dot-coating roller includes: a roller body 1 and a plurality of protrusions 2 evenly distributed on the surface of the roller body 1. The protrusions 2 are arranged in a matrix on the surface of the roller body 1. The roller body 1 is a cylindrical cavity. The distance between the center points of every two adjacent protrusions 2 in the transverse and longitudinal directions of the rectangular array is 680 μm. Each protrusion 2 is a protrusion structure, wherein each protrusion structure includes: a frustum 3 and a truncated cylinder 6 arranged sequentially from bottom to top. The frustum 3 tapers from bottom to top. The diameter of the top surface of the frustum 3 is equal to the diameter of the truncated cylinder 6. The height of the lower side of the truncated cylinder 6 is 90 μm, and the height of the higher side is 120 μm. The height, top surface diameter, and bottom surface diameter of the frustum 3 are the same as in Embodiment 1.

[0055] The design advantages of the convex structure in Example 2 are basically the same as those in Example 1. The same principle is to adjust one side of the convex structure so that the height of one side of the convex structure is lower than that of the other side, thereby reducing the squeezing effect of the convex on the slurry during the rotation of the dot coating roller.

[0056] Example 3

[0057] like Figure 18 and Figure 5 As shown, a dot-coating roller includes: a roller body 1 and a plurality of protrusions 2 evenly distributed on the surface of the roller body 1. The protrusions 2 are arranged in a matrix on the surface of the roller body 1. The roller body 1 is a cylindrical cavity. The distance between the center points of every two adjacent protrusions 2 in the transverse and longitudinal directions of the rectangular array is 680 μm. Each protrusion 2 is a protrusion structure, wherein each protrusion structure includes: a frustum 3, a third cylinder 7, and a fourth cylinder 8 arranged sequentially from bottom to top. The frustum 3 tapers from bottom to top. The diameter of the top surface of the frustum 3 is equal to the diameter of the third cylinder 7. The diameter of the fourth cylinder 8 is smaller than the diameter of the third cylinder 7. The top of the fourth cylinder 8 is an arc surface. The distance between the highest point of the arc surface and the bottom surface of the fourth cylinder 8 is 120 μm. The diameter of the fourth cylinder 8 is 420 μm. The height of the third cylinder 7 is 60 μm. The height, top surface diameter, and bottom surface diameter of the frustum 3 are the same as in Embodiment 1.

[0058] The design advantage of the convex structure in Example 3 is that the top of the convex structure is a raised arched surface, which increases the height of the liquid. During the rotation of the dot coating roller, the center is subjected to a higher extrusion force than the edge, thus reducing the degree of edge extrusion.

[0059] Example 4

[0060] A dot-coating roller is basically the same as in Example 1, except that in Example 4, the height of the second cylinder 5 is 30 μm.

[0061] Example 5

[0062] A dot-coating roller is basically the same as in Example 1, except that in Example 5, the height of the second cylinder 5 is 90 μm.

[0063] Example 6

[0064] A dot-coating roller is basically the same as in Example 2, except that in Example 6, the height of the lower side of the oblique cylinder 6 is 30 μm and the height of the higher side is 120 μm.

[0065] Example 7

[0066] A dot-coating roller is basically the same as in Example 2, except that in Example 7, the height of the lower side of the oblique cylinder 6 is 60 μm and the height of the higher side is 120 μm.

[0067] Example 8

[0068] A dot-coating roller is basically the same as in Example 3, except that in Example 8, the distance between the highest point of the arc surface and the bottom surface of the fourth cylinder 8 is 90 μm.

[0069] Example 9

[0070] A dot-coating roller is basically the same as in Example 3, except that in Example 9, the distance between the highest point of the arc surface and the bottom surface of the fourth cylinder 8 is 150 μm.

[0071] Comparative Example 1

[0072] like Figure 18 and Figure 6 As shown, a dot-coating roller includes: a roller body 1 and a plurality of protrusions 2 evenly distributed on the surface of the roller body 1. The protrusions 2 are arranged in a matrix on the surface of the roller body 1. The roller body 1 is a cylindrical cavity. The distance between the center points of every two adjacent protrusions 2 in the transverse and longitudinal directions of the rectangular array is 680 μm. Each protrusion 2 is a protrusion structure, wherein each protrusion structure includes: a frustum 3 and a fifth cylinder 9 arranged sequentially from bottom to top. The frustum 3 tapers from bottom to top. The diameter of the top surface of the frustum 3 is equal to the diameter of the fifth cylinder 9. The height, top surface diameter, and bottom surface diameter of the frustum 3 are the same as in Embodiment 1. The height of the fifth cylinder 9 is 60 μm.

[0073] The dot-coating roller in Comparative Example 1 is a commonly used type in the prior art. The coating dots on the film obtained using this type of roller are easily deformed, often exhibiting a crescent-shaped morphology. The mechanism of crescent-shaped morphology formation is as follows: Figure 7As shown, the protrusions on the surface of the dot-coating roller carry the slurry and contact the horizontally placed base film to achieve slurry transfer. After contact, the protrusions separate from the base film. During this process, because the base film is horizontally placed, the surface of the conventional dot-coating roller in contact with the slurry is an approximately flat plane, and the dot-coating roller is rotating, causing the slurry to deform under the pressure of the protrusions on the surface of the dot-coating roller. However, in mass production, due to factors such as slurry viscosity, limited distance between the coating area and the drying oven, and high speed of the coating machine, the slurry cannot recover its deformation after being squeezed and is dried, resulting in coating defects such as... Figure 1 and Figure 2 The coating points, which resemble crescent moons, affect the uniformity of the coating thickness.

[0074] The coating process was performed using the dot-coating rollers of Examples 1-9 and Comparative Example 1. Specifically, the process included: applying a dot-coating slurry to one side of the base film using the dot-coating rollers (coating speed 10 m / min), followed by drying at 60°C for 40 s. The corresponding coated films were obtained sequentially using the dot-coating rollers of Examples 1-9 and Comparative Example 1. The coated films were tested using a Keyence microscope, and the test results are as follows: Figures 8~17 Show.

[0075] Three coating points were selected from each of the coating films prepared based on the dot-coating rollers of Examples 1-9 and Comparative Example 1 for diameter testing, as shown in Table 1.

[0076] Table 1

[0077]

[0078] like Figure 8 As shown, the coating film obtained by the dot-coating roller of Example 1 has no crescent-shaped coating dots, and the coating dots have a uniform thickness distribution and high diameter consistency; as shown... Figure 11 As shown, the coating dots of the coating film obtained by the dot-coating roller of Example 4 have a slight crescent shape. This is because reducing the height of the second cylinder 5 enhances the extrusion effect; as Figure 12 As shown, the coating film obtained by the dot-coating roller of Example 5 did not exhibit a crescent shape, but the thickness distribution of the coating dots was uneven (the thickness was higher on one side of the edge). This may be because increasing the height of the second cylinder 5 caused a cascading effect after the slurry detached from the protrusion (i.e., during the process of slurry transfer to the film surface, due to the viscosity of the slurry itself, the slurry at the recessed position could not be transferred synchronously with the slurry at other positions), and it was still impossible to obtain coating dots with a uniform shape. Among Examples 1, 4 and 5, the coating film obtained by the dot-coating roller of Example 1 had the best appearance uniformity.

[0079] like Figure 9 As shown, the coating film obtained by the dot-coating roller of Example 2 has no crescent-shaped coating dots, and the thickness distribution of the coating dots is uniform with high diameter consistency. Figure 13 andFigure 14 As shown, the coating spots of the coating films obtained by the dot-coating rollers of Examples 6 and 7 also have no crescent shape and the thickness distribution of the coating spots is uniform and the diameter is highly consistent. Comparing the appearance of Examples 2, 6, 7 and Comparative Example 1, it can be seen that the coating spot morphology of Examples 2, 6 and 7 is significantly improved compared with Comparative Example 1.

[0080] like Figure 10 As shown, the coating dots of the film obtained by the dot-coating roller of Example 3 dot-coating ... Figure 15 and Figure 16 As shown, the coating spots of the coating films obtained by the dot coating rollers of Examples 8 and 9 all exhibit a downward concave appearance in the central area. In the convex structure of Example 9, the distance between the highest point of the arc surface and the bottom surface of the fourth cylinder 8 is the largest, and the concavity is also more obvious.

[0081] like Figure 17 As shown, the coating film obtained by the dot-coating roller of Comparative Example 1 has crescent-shaped coating dots, and the diameter of the coating dots is not very consistent.

[0082] The test results of the coated films prepared based on the dot-coating rollers of Examples 1-9 and Comparative Example 1 are shown in Table 2.

[0083] Table 2

[0084]

[0085] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A bump structure, characterized by, Comprise: A circular truncated cone (3), a third cylinder (7) and a fourth cylinder (8) are sequentially arranged from bottom to top, the circular truncated cone (3) is tapered from bottom to top, the top surface diameter of the circular truncated cone (3) is equal to the diameter of the third cylinder (7), the diameter of the fourth cylinder (8) is smaller than that of the third cylinder (7), the top of the fourth cylinder (8) is an arc surface, and the convex point structure is an axisymmetric structure.

2. The bump structure according to claim 1, wherein The height of the circular truncated cone (3) is 430-590 μm.

3. The bump structure according to claim 2, wherein The top surface diameter of the circular truncated cone (3) is 450-600 μm.

4. The bump structure according to claim 3, wherein The bottom surface diameter of the circular truncated cone (3) is 650-1200.12 μm.

5. The bump structure according to claim 4, wherein The distance between the highest point of the arc surface and the bottom surface of the fourth cylinder (8) is 100-130 μm.

6. The bump structure according to claim 5, wherein The diameter of the fourth cylinder (8) is 350-420 μm.

7. The bump structure according to claim 6, wherein The height of the third cylinder (7) is 30-90 μm.

8. A spotter roll characterized by, Comprise: A roller body (1) and a plurality of convex points (2) uniformly distributed on the surface of the roller body (1), each convex point (2) is the convex point structure of claim 7.

9. The spotter roll of claim 8, wherein, The convex points (2) are arranged in a matrix on the surface of the roller body (1), and the distance between the center points of every two adjacent convex points (2) is 580-780 μm.

Images