Salient point structure and dispensing plate roller

Abstract

The invention discloses a salient point structure and a dispensing plate roller, the dispensing plate roller comprises a roller body and a plurality of salient points uniformly distributed on the surface of the roller body, each salient point is a salient point structure, each salient point structure comprises a circular truncated cone, a first cylinder and a second 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 first cylinder, one side of the first cylinder and one side of the second cylinder in the height direction are located on the same vertical face, and the diameter of the second cylinder is smaller than that of the first cylinder. 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 and 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, in the emerging point coating process, irregular coating point morphology and back-drawing often occur 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] The convex point structure comprises, from bottom to top, a circular truncated cone and an oblique truncated cylinder, the circular truncated cone is tapered from bottom to top, and the top surface diameter of the circular truncated cone is equal to the diameter of the oblique truncated cylinder;

[0012] The convex point structure comprises, from bottom to top, a circular truncated cone, a third cylinder and a fourth 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 third cylinder, the diameter of the fourth cylinder is smaller than that of the third cylinder, and the top of the fourth cylinder is an arc surface.

[0013] In the above technical solution, the height of the circular truncated cone is 430-590 mu m, the top surface diameter of the circular truncated cone is 450-600 mu m, and the bottom surface diameter of the circular truncated cone is 650-1200.12 mu m.

[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 90-150 mu m (preferably 100-130 mu m).

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

[0016] In the above technical solution, the height of the lower side of the oblique truncated cylinder is 30-90 mu m, and the height of the higher side of the oblique truncated cylinder is 100-120 mu m.

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

[0018] A dot coating roll comprises a roll body and a plurality of convex points uniformly distributed on the surface of the roll body, each of the convex points being a convex point structure.

[0019] In the above technical solution, the convex points are arranged in a matrix on the surface of the roll body, and the distance between the center points of every two adjacent convex points is 580-780 mu m.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The convex point structure of the present application reduces the extrusion effect of the dot coating roll during the slurry transfer process, accurately solves the key problem of missing edges of the coating dots, and lays a foundation for subsequent improvement of the performance of the coated film.

[0022] 2. The present application significantly enhances the integrity of the coating point and greatly improves the edge regularity on the basis of solving the problem of missing edge of the coating point, so that the coating point morphology is more in line with the process standard, the coating point is more uniform, the appearance of weak points on the coating film surface is reduced, and the safety performance is increased.

[0023] 3. When the convex point structure is structure one, the height of the second cylinder is 50-70 μm, and the coating point in the obtained coating film is complete; when the convex point structure is structure two, the height of the lower side of the truncated cylinder is 30-90 μm, and the height of the higher side of the truncated cylinder is 100-120 μm, and the coating point in the obtained coating film is complete; when the convex point structure is structure three, the distance between the highest point of the arc surface and the bottom surface of the fourth cylinder is 100-130 μm, and the coating point in the obtained coating film is complete. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The appearance of the coating film obtained by coating with the point coating roll of Comparative Example 1;

[0025] Figure 2 The appearance of the coating film obtained by coating with the point coating roll of Comparative Example 1;

[0026] Figure 3 The schematic diagram of the convex point structure in Example 1;

[0027] Figure 4 The schematic diagram of the convex point structure in Example 2;

[0028] Figure 5 The schematic diagram of the convex point structure in Example 3;

[0029] Figure 6 The schematic diagram of the convex point structure in Comparative Example 1;

[0030] Figure 7 The mechanism diagram of forming a deformed coating point (crescent shape);

[0031] Figure 8 The appearance of the coating film obtained by coating with the point coating roll of Example 1;

[0032] Figure 9 The appearance of the coating film obtained by coating with the point coating roll of Example 2;

[0033] Figure 10 The appearance of the coating film obtained by coating with the point coating roll of Example 3;

[0034] Figure 11 The appearance of the coating film obtained by coating with the point coating roll of Example 4;

[0035] Figure 12Appearance of the coating film obtained by coating the point coating version of Example 5 with a roll;

[0036] Figure 13 Appearance of the coating film obtained by coating the point coating version of Example 6 with a roll;

[0037] Figure 14 Appearance of the coating film obtained by coating the point coating version of Example 7 with a roll;

[0038] Figure 15 Appearance of the coating film obtained by coating the point coating version of Example 8 with a roll;

[0039] Figure 16 Appearance of the coating film obtained by coating the point coating version of Example 9 with a roll;

[0040] Figure 17 Appearance of the coating film obtained by coating the point coating version of Comparative Example 1 with a roll;

[0041] Figure 18 Partial schematic view of the point coating version.

[0042] 1: roll body, 2: convex point, 3: circular truncated cone, 4: first cylinder, 5: second cylinder, 6: oblique truncated cylinder, 7: third cylinder, 8: fourth cylinder, 9: fifth cylinder. DETAILED DESCRIPTION

[0043] The technical solutions of the present application are further illustrated below in conjunction with specific examples.

[0044] The preparation method of the point coating paste in the following examples and comparative examples comprises: mixing deionized water and a dispersant at room temperature, stirring in a double-planetary mixer for 10 min until uniform (the revolution speed of stirring is 20 rpm and the rotation speed is 1500 rpm), adding polyvinylidene fluoride-hexafluoropropylene copolymer (powder) first, stirring for 60 min until uniform (the revolution speed of stirring is 20 rpm and the rotation speed is 1500 rpm), and then sequentially adding a thickening agent and a binder, stirring for 20 min until uniform (the revolution speed of stirring is 20 rpm and the rotation speed is 1500 rpm) to obtain a point coating paste (the viscosity is 400 cp and the solid content is 18 wt %), wherein the ratio of the dispersant, the polyvinylidene fluoride-hexafluoropropylene copolymer (powder), the thickening agent and the binder is 0.02:2:1.1:1 by mass fraction. The dispersant is polyacrylic acid ammonium salt (SN5027), the thickening agent is carboxymethyl cellulose, and the binder is butadiene-styrene rubber.

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

[0046] Coating amount: the weight of the coating on the unit area of the coating film.

[0047] Positive electrode adhesion: cut the coated film and the positive electrode sheet into samples with length * width = 60 mm * 25 mm respectively, adhere the coating surface of the coated film to the positive electrode sheet, and place them under a hot press to perform hot pressing (hot pressing parameters: 1000 Kgf, 80℃, preheating 1s, hot pressing 1s), and then test the force for separating the coated film from the positive electrode sheet 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 PE base film with a thickness of 9 μm. It should be noted that other thicknesses of base films can also be used.

[0049] The material of the convex point 2 is a mixture of one or several of nitrile rubber (NBR), fluororubber (FKM), and polyurethane rubber (PU), and in the present application, it is specifically nitrile rubber.

[0050] Example 1

[0051] As shown in Figure 18 and Figure 3 , a dot coating version roll comprises a roll body 1 and a plurality of convex points 2 distributed on the surface of the roll body 1, the convex points 2 are arranged in a matrix on the surface of the roll body 1, the roll body 1 is a cylindrical cavity, the distance between the center points of every two adjacent convex points 2 in the horizontal and vertical directions of the rectangular matrix is 680 μm, and each convex point 2 is a convex point structure, wherein each convex point structure comprises, from bottom to top, a circular truncated cone 3, a first cylinder 4, and a second cylinder 5, 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 first cylinder 4, one side (the right side) of the first cylinder 4 and the second cylinder 5 in the height direction is on the same vertical plane, 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 circular truncated cone 3 is 530 μm, the top surface diameter of the circular truncated cone 3 is 450 μm, and the bottom surface diameter of the circular truncated cone 3 is 1200.12 μm.

[0052] The design advantage of the convex point structure in Example 1 is that one side of the convex point structure has a recess (notch), and the existence of the recess can reduce the extrusion effect of the slurry at the edge position during the elastic deformation of the convex points on the surface of the dot coating version roll due to compression.

[0053] Example 2

[0054] As shown in 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 point coating roll carry the paste and contact the horizontally placed base film to achieve paste transfer, and after the contact is completed, the protrusions are separated from the base film. In this process, since the base film is horizontally placed, the surface of the conventional point coating roll in contact with the paste is an approximate plane, and the point coating roll is rotating, and the paste is deformed by the extrusion of the protrusions on the surface of the point coating roll. However, in mass production, due to the limited distance from the coating area to the oven, the fast speed of the coating machine, and other factors, the paste cannot recover after being extruded, that is, it is dried, resulting in coating points with Figure 1 and Figure 2 approximately crescent-shaped defects, affecting the thickness consistency of the point coating.

[0074] The point coating rolls of Examples 1-9 and Comparative Example 1 were used for coating, specifically including: using the point coating roll to coat the point coating paste on one side of the base film (coating speed of 10 m / min), and drying at 60°C for 40s, and the corresponding coating films were obtained from the point coating rolls of Examples 1-9 and Comparative Example 1 in turn. The coating films obtained by coating were tested using a Keyence microscope, and the test results are shown in Figures 8~17 .

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

[0076] Table 1

[0077]

[0078] As shown in Figure 8 , the coating points of the coating film obtained by the point coating roll of Example 1 have no crescent-shaped morphology, and the thickness distribution of the coating points is uniform, and the diameter consistency is high; as shown in Figure 11 , the coating points of the coating film obtained by the point coating roll of Example 4 have a slight crescent-shaped morphology, which is because reducing the height of the second cylinder 5 enhances the extrusion effect; as shown in Figure 12 , the coating film obtained by the point coating roll of Example 5 does not have a crescent-shaped morphology, but the thickness distribution of the coating points is uneven (the thickness on one side edge is higher), which may be because increasing the height of the second cylinder 5 causes a coupled effect after the paste is separated from the protrusions (that is, during the paste transfer to the film surface, due to the viscosity of the paste, the paste at the concave position cannot complete the transfer synchronously with the paste at other positions), and still cannot obtain coating points with uniform morphology; in Examples 1, 4 and 5, the appearance uniformity of the coating film obtained by the point coating roll of Example 1 is the best.

[0079] As shown in Figure 9 , the coating points of the coating film obtained by the point coating roll of Example 2 have no crescent-shaped morphology, and the thickness distribution of the coating points is uniform, and the diameter consistency is high, as shown in Figure 13 andFigure 14 As shown in FIG. 6, the coating dots of the coating film obtained by coating with the dot coating version roll of Example 6 and Example 7 also have no crescent shape and the thickness distribution of the coating dots is uniform and the diameter consistency is high; as compared with the appearance of Example 2, Example 6, Example 7 and Comparative Example 1, the coating dot morphology of Example 2, Example 6 and Example 7 is obviously improved compared with Comparative Example 1.

[0080] As shown in FIG. 3, the coating dots of the coating film obtained by coating with the dot coating version roll of Example 3 have no obvious crescent shape, but the center height is lower than the edge height, showing a "ring" structure, which may be due to the top of the convex structure being higher than the edge, the center area of the coating process being more extruded by the paste, and showing such structure after drying. Figure 10 Figure 15 and Figure 16 As shown in FIG. 8 and FIG. 9, the coating dots of the coating film obtained by coating with the dot coating version roll of Example 8 and Example 9 both have a downwardly concave appearance in the center area, and the distance between the highest point of the arc surface in the convex structure of Example 9 and the bottom surface of the fourth cylinder 8 is the largest, and the concave is more obvious.

[0081] As shown in FIG. 3, the coating dots of the coating film obtained by coating with the dot coating version roll of Example 3 have no obvious crescent shape, but the center height is lower than the edge height, showing a "ring" structure, which may be due to the top of the convex structure being higher than the edge, the center area of the coating process being more extruded by the paste, and showing such structure after drying. Figure 17

[0082] The test results of the coating film prepared based on the dot coating version roll of Example 1-9 and Comparative Example 1 are shown in Table 2.

[0083] Table 2

[0084]

[0085] The above has made an exemplary description of the present application, it should be explained that, without departing from the core of the present application, any simple modification, change or other equivalent replacement which can not cost creative labor of those skilled in the art falls into the protection scope of the present application.​​

Claims

1. A bump structure, characterized by, The application relates to a roller body (1) and a plurality of convex points (2) uniformly distributed on the surface of the roller body (1), wherein each convex point (2) is the convex point structure as claimed in claim 7. 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 mu m.

2. The bump structure according to claim 1, wherein The application relates to a roller body (1) and a plurality of convex points (2) uniformly distributed on the surface of the roller body (1), wherein each convex point (2) is the convex point structure as claimed in claim 7.

3. The bump structure according to claim 2, 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 mu m.

4. The bump structure according to claim 3, wherein The application relates to a roller body (1) and a plurality of convex points (2) uniformly distributed on the surface of the roller body (1), wherein each convex point (2) is the convex point structure as claimed in claim 7.

5. The bump structure according to claim 4, 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 mu m.

6. The bump structure according to claim 5, wherein The application relates to a roller body (1) and a plurality of convex points (2) uniformly distributed on the surface of the roller body (1), wherein each convex point (2) is the convex point structure as claimed in claim 7.

7. The bump structure according to claim 6, 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 mu m.

8. A spotter roll characterized by, ​ ​ 9. The spotter roll of claim 8, wherein, ​

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