CN108405716A - A kind of Surface Texture milling method of current collector aluminum foil - Google Patents

Abstract

The present invention provides a texture rolling method of current collector aluminum foil, comprising the following steps: step 100, roughening the surface of the roll by using a pulsed laser, and forming a texture pattern composed of independent circular units distributed and arranged on the surface of the roll Appearance; step 200, prepare the aluminum foil to be rolled, and copy the texture appearance of the roll surface to the surface of the aluminum foil through the rolling process. The invention utilizes the characteristic of the center symmetry of the circular unit, and can obtain better isotropy of surface roughness by controlling the distribution of the circular unit. The extrusions on the surface of the aluminum foil concentrate to form protrusions, which have a stronger "mortise and tenon" connection effect and stronger coating adhesion. The aluminum foil is produced by the rolling production method, and the extrusion of the pits on the surface of the aluminum foil is completely converted into a protrusion, without material loss, and has better mechanical properties than etched aluminum foil. The pits on the surface of the aluminum foil have good consistency in depth, can avoid local thinning of the aluminum foil, and have better mechanical properties than the existing roughened and rolled aluminum foil.

Description

A kind of surface texture rolling method of current collector aluminum foil

technical field

The invention belongs to the field of batteries, in particular to a surface texture rolling method for current collector aluminum foil used in lithium ion batteries and double-layer capacitors.

Background technique

Aluminum foil is used as a current collector for lithium ion batteries and electric double layer capacitors. In lithium-ion batteries, the surface of aluminum foil is coated with a coating containing positive active materials to form the positive electrode. The adhesion between the coating and the current collector affects the internal resistance, high-rate discharge performance and cycle life of the battery. In order to improve the adhesion between the current collector and the coating, the surface of the aluminum foil is usually roughened to increase the contact area between the two. In electric double layer capacitors, the surface of the current collector aluminum foil also needs to be coated with a coating containing porous carbon and other materials to make electrodes, and the surface roughening of the aluminum foil is also conducive to improving the performance of the electric double layer capacitor.

In the prior art, etching is often used to roughen the surface of the aluminum foil. Surface roughening methods such as etching have certain requirements on the crystal structure of the aluminum foil, which will increase the cost of the aluminum foil. At the same time, the uniformity of the thickness of the aluminum foil after etching will become poor. , the mechanical properties are reduced, which increases the difficulty of electrode preparation.

Combining the surface roughening of the aluminum foil with the rolling process, it is an ideal solution to roughen the surface of the aluminum foil during the production stage of the aluminum foil. In the prior art, it is proposed that the surface of the roll is shot peened and then chrome-plated, and then the surface of the aluminum foil is roughened by rolling. However, due to the random shape of the roll surface formed by shot peening and other similar roughening methods, the roughness uniformity is poor, and the abnormally high peaks on the roll surface are likely to cause local thinning of the aluminum foil and affect the strength of the aluminum foil. The anisotropic difference in surface roughness will also make the adhesion between the coating and the aluminum foil directional. Obviously, the existing surface roughening methods of aluminum foil cannot meet the requirements of using aluminum foil as a current collector and must be optimized.

Contents of the invention

The purpose of the present invention is to provide a surface texture rolling method for current collector aluminum foil used in lithium ion batteries and double layer capacitors.

In particular, the present invention provides a texture rolling method of current collector aluminum foil, comprising the following steps:

Step 100, using a pulsed laser to roughen the surface of the roll to form a texture morphology composed of independent circular units distributed and arranged on the surface of the roll;

Step 200, preparing the aluminum foil to be rolled, and copying the texture topography of the roll surface to the surface of the aluminum foil through the rolling process.

In one embodiment of the present invention, the circular unit includes an annular protruding ring and a pit surrounded by the protruding ring.

In one embodiment of the present invention, the diameter of the circular unit is 50-100 μm.

In one embodiment of the present invention, the center-to-center distance of the circular units is 50-200 μm.

In one embodiment of the present invention, the circular unit on the surface of the roll is copied to the surface of the aluminum foil to form a convex shape surrounded by an annular groove, and the convex ring of the circular unit forms a convex shape on the surface of the aluminum foil. Formed after extrusion.

In one embodiment of the present invention, the depth of the annular groove on the surface of the aluminum foil is 2.5-5 μm.

In one embodiment of the present invention, the width of the annular groove on the surface of the aluminum foil is 10-20 μm.

In one embodiment of the present invention, the height of the protrusions on the surface of the aluminum foil is 1.5-4 μm.

In one embodiment of the present invention, the depth of the annular groove on the surface of the aluminum foil and the dispersion coefficient of the surface roughness Ra are both less than 0.1.

In one embodiment of the present invention, by adjusting the texture parameters of the roll surface in the step 100, and adjusting the rolling parameters in the step 200, it is realized that the regulation affects the adhesion performance between the aluminum foil surface and the coating and Surface roughness of aluminum foil mechanical properties.

Compared with the existing aluminum foil rolling surface roughening method, the method of the present invention can prepare an aluminum foil with a specific surface texture morphology, and the aluminum foil has the following advantages:

1. Since the circular unit has the characteristic of central symmetry, by controlling the distribution of the circular unit, better isotropy of surface roughness can be obtained, that is, the isotropy of the adhesion performance between the coating and the aluminum foil.

2. The extrusion on the surface of the aluminum foil concentrates to form a bulge, which has a stronger "mortise and tenon" connection effect and stronger adhesion.

3. The aluminum foil passes through the rolling production method, and the extrudates of the grooves on the surface of the aluminum foil are completely converted into protrusions, without material loss, and have better mechanical properties than etched aluminum foil.

4. The groove depth on the surface of the aluminum foil is consistent, which can avoid local thinning of the aluminum foil, and has better mechanical properties than the existing roughened and rolled aluminum foil.

5. By adjusting the texture parameters of the aluminum foil surface, combined with the rolling process, the adhesion performance between the aluminum foil surface and the coating and the mechanical properties of the aluminum foil can be regulated, so that the comprehensive performance of the current collector aluminum foil can be optimized.

Description of drawings

Fig. 1 is a schematic flow chart of a texture rolling method according to an embodiment of the present invention;

Fig. 2 is a schematic structural view of the circular unit on the surface of the roll and the annular unit rolled on the surface of the aluminum foil in one embodiment of the present invention;

Fig. 3 is the surface photograph of aluminum foil raw material in one embodiment of the present invention;

Fig. 4 is a surface photo of the aluminum foil texture after rolling in an embodiment of the aluminum foil shown in Fig. 2;

Fig. 5 is a surface photo of the aluminum foil texture after rolling in another embodiment of the aluminum foil shown in Fig. 2;

Fig. 6 is the typical peel strength of the positive electrode sheet made of the aluminum foil before and after texture rolling in the embodiment of the aluminum foil shown in Fig. 2;

Figure 7 is a representative tensile curve of the aluminum foil before and after texture rolling for the embodiment of the aluminum foil shown in Figure 2 .

Detailed ways

As shown in Figure 1, a texture rolling method of a current collector aluminum foil according to an embodiment of the present invention is characterized in that it comprises the following steps:

Step 100, using a pulsed laser to roughen the surface of the roll to form a texture morphology composed of independent circular units distributed and arranged on the surface of the roll;

In this step, the surface of the roll is firstly ground with a cylindrical grinder, and then the roll is placed on a lathe or a similar rotary mechanism, and the distribution of independent circular units on the roll surface is achieved by controlling the roll speed, lead screw pitch and pulse laser frequency. The texture formed by arrangement. The circular unit can be any structure with an independent shape, so as to form an array structure on the surface of the roll, so that the surface of the rolled aluminum foil has a regular surface shape.

Step 200, preparing the aluminum foil to be rolled, and copying the texture topography of the roll surface to the surface of the aluminum foil through the rolling process.

The rolls are assembled on the rolling mill, the surface texture rolling is carried out on the current collector aluminum foil, and the texture topography on the surface of the roll is squeezed and copied to the surface of the aluminum foil.

This embodiment utilizes the characteristic of the center of symmetry of the circular units, and by controlling the distribution of the circular units, better isotropy of surface roughness can be obtained, that is, the isotropy of the adhesion performance between the coating and the aluminum foil. Moreover, rolling with uniformly shaped circular units can keep the depth of grooves on the surface of the aluminum foil consistent, avoiding local thinning of the aluminum foil, and has better mechanical properties than the existing roughened rolled aluminum foil.

In this embodiment, the surface roughness that affects the adhesion performance between the surface of the aluminum foil and the coating and the mechanical properties of the aluminum foil can be regulated by adjusting the texture parameters and rolling parameters of the roll surface, so that the comprehensive performance of the current collector aluminum foil reaches optimal.

As shown in Figure 2, in one embodiment of the present invention, the specific circular unit can include an annular convex ring, and a pit surrounded by the convex ring inside the convex ring; the diameter of the circular unit can be 50- 100 μm; the center-to-center distance between adjacent circular units may be 50-200 μm.

Under the above-mentioned structure, the circular unit on the surface of the roll is copied to the surface of the aluminum foil to form a shape surrounded by an annular groove and a convex shape in the middle, which is formed by extruding the surface of the aluminum foil by the bead of the circular unit; wherein , the depth of the annular groove on the surface of the aluminum foil can be 2.5-5 μm, the width of the annular groove can be 10-20 μm, and the height of the protrusion can be 1.5-4 μm. Under this structure, the depth of the annular groove on the surface of the aluminum foil and the dispersion coefficient of the surface roughness Ra (that is, the ratio of the standard deviation to the average) are both less than 0.1.

During the rolling process, each independent circular unit 3 on the surface of the roll 1 will be copied to the surface of the aluminum foil 2 to form a corresponding independent annular unit 4, wherein the annular bead 31 on the surface of the roll 1 is copied to the surface of the aluminum foil 2 to form an annular groove 41 , the pit 32 on the surface of the roll 1 accommodates the extrusion of the annular groove 41 on the surface of the aluminum foil 2 to form a protrusion 42 on the surface of the aluminum foil 2 . After texture rolling, the diameter 43 of the independent circular unit 4 on the surface of the aluminum foil 2 is the same as the diameter 33 of the independent circular unit 3 on the surface of the roll 1, and the distance 6 between the independent circular unit 4 on the surface of the aluminum foil 2 is the same as that of the independent circular unit 3 on the surface of the roll 1. The spacing 5 of the shape unit 3 is the same. When the surface texture rolling process is added after the aluminum foil finish rolling process, the average thickness of the aluminum foil 2 remains unchanged, and the width 44 of the annular groove 41 on the surface of the aluminum foil 2 is only related to the rolling force. When the texture rolling process is combined with the finishing rolling process of the aluminum foil, there is relative sliding between the roll and the aluminum foil, and the width 44 of the annular groove 41 on the surface of the aluminum foil 2 is related to the sliding amount between the roll and foil.

In this embodiment, the extrusions on the surface of the aluminum foil are concentrated to form protrusions, which have a stronger "tenon-tenon" connection effect and stronger adhesion performance. The aluminum foil is produced by rolling, and the extrusion of the annular groove on the surface of the aluminum foil is completely converted into a protrusion in the middle, without material loss, and has better mechanical properties than etched aluminum foil.

Example 1

The 1235 aluminum foil with a thickness of 16 μm is selected for double-sided texture rolling. The rolling process only replicates the surface texture of roll 1 without changing the average thickness of aluminum foil 2. The height of the annular bead 31 of the independent circular unit 3 on the surface of the roll 1 is between 6 and 7 μm, and the depth of the central pit 32 of the independent circular unit 3 on the surface of the roll 1 is between 6 and 7 μm. The diameter 33 of the independent circular unit 3 is 70 μm, the center distance 5 of the independent circular unit 3 on the surface of the roll 1 is 70 μm, the edges of the independent circular unit 3 on the surface of the roll 1 are tangent, and the surface roughness Ra of the roll 1 is 2.6 Between ~2.7 μm, the dispersion coefficients of the height of the annular bead 31 on the surface of the roll 1 and the roughness Ra are both less than 0.1.

The surface shape of the aluminum foil raw material is shown in Figure 3, and the surface shape of the aluminum foil 2 after texture rolling is shown in Figure 4. According to the difference in rolling force, the height of the annular bead 31 on the surface of the roll 1 is closer to the ring shape on the surface of the aluminum foil 2. The replication rate of the depth of the groove 41 is between 30% and 70%, and the replication rate of the depth of the pit 32 on the surface of the roll 1 to the height of the protrusion 42 on the surface of the aluminum foil 2 is between 30% and 50%. The replication ratio of the surface roughness Ra to the surface roughness Ra of the aluminum foil 2 is 30%-60%, and the dispersion coefficients of the annular groove on the surface of the aluminum foil 2 and the roughness Ra are both less than 0.1.

Example 2

The 1235 aluminum foil with a thickness of 16 μm is selected for double-sided texture rolling. The rolling process only replicates the surface texture of roll 1 without changing the average thickness of aluminum foil 2. The height of the edge annular bead 31 of the independent circular unit 3 on the surface of the roll 1 is between 4 and 5 μm, the depth of the central pit 32 of the independent circular unit 3 on the surface of the roll 1 is between 5 and 6 μm, and the surface of the roll 1 The diameter of the independent circular unit 3 is 70 μm, the center distance 5 of the independent circular unit 3 on the surface of the roll 1 is 90 μm, the edges of the circular unit 3 on the surface of the roll 1 are separated, and the surface roughness Ra of the roll 1 is between 1.5 and 1.6 μm, the coefficient of dispersion of the height of the annular bead on the surface of the roll 1 and the surface roughness Ra is less than 0.1.

The surface shape of the aluminum foil 2 after texture rolling is shown in Figure 5. According to the different rolling forces, the replication rate of the roughness parameters of the surface texture of the roll 1 to the corresponding parameters of the aluminum foil 2 is 30% to 70%. between. The dispersion coefficient of the annular groove on the surface of the aluminum foil 2 and the roughness Ra is less than 0.1.

In Fig. 6, typical peel strengths of positive electrode sheets made of aluminum foil before and after texture rolling are given. After the texture rolling, the peel strength of the positive electrode sheet is increased by more than 60%, the dispersion of the data is also significantly reduced, and the adhesion performance between the coating and the aluminum foil is obviously improved. In Fig. 7, typical tensile curves of aluminum foils before and after texture rolling are given. The strength of the aluminum foil after texture rolling is basically unchanged, and the elongation is slightly reduced. It has good mechanical properties and can meet the processing requirements of the positive electrode sheet.

So far, those skilled in the art should appreciate that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, without departing from the spirit and scope of the present invention, the disclosed embodiments of the present invention can still be used. Many other variations or modifications consistent with the principles of the invention are directly identified or derived from the content. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims (10)

1. a texture rolling method of current collector aluminum foil, is characterized in that, comprises the steps: Step 100, using a pulsed laser to roughen the surface of the roll to form a texture morphology composed of independent circular units distributed and arranged on the surface of the roll; Step 200, preparing the aluminum foil to be rolled, and copying the texture topography of the roll surface to the surface of the aluminum foil through the rolling process. 2. The texture rolling method according to claim 1, characterized in that, The circular unit includes an annular protruding ring and a pit surrounded by the protruding ring. 3. The texture rolling method according to claim 2, characterized in that, The diameter of the circular unit is 50-100 μm. 4. texture rolling method according to claim 3, is characterized in that, The center-to-center distance of the circular units is 50-200 μm. 5. The texture rolling method according to claim 3, characterized in that, The circular unit on the surface of the roll is replicated on the surface of the aluminum foil to form a convex shape surrounded by an annular groove, which is formed by extrusion from the surface of the aluminum foil. 6. The texture rolling method according to claim 3, characterized in that, The depth of the annular groove on the surface of the aluminum foil is 2.5-5 μm. 7. The texture rolling method according to claim 3, characterized in that, The width of the annular groove on the surface of the aluminum foil is 10-20 μm. 8. The texture rolling method according to claim 3, characterized in that, The height of the protrusions on the surface of the aluminum foil is 1.5-4 μm. 9. The texture rolling method according to claim 3, characterized in that, The depth of the annular groove on the surface of the aluminum foil and the dispersion coefficient of the surface roughness Ra are both less than 0.1. 10. The texture rolling method according to claim 1, characterized in that, By adjusting the texture parameters of the roll surface in the step 100 and adjusting the rolling parameters in the step 200, the surface roughness that affects the adhesion between the aluminum foil surface and the coating and the mechanical properties of the aluminum foil can be adjusted.