Flying cleaning process for thinning area of battery pole piece

Abstract

The invention discloses a flying cleaning process for a thinning area of a battery pole piece, and relates to the technical field of laser processing. The method comprises the following steps: S1, selecting a homogenized DOE lens for a pulse laser and / or a continuous laser, arranging the homogenized DOE lens on an external light path, adjusting the angle of the lens to enable laser to vertically and smoothly pass through the center of the homogenized DOE lens, and rotating the homogenized DOE lens to adjust the angle of a shaped light spot to an area to be cleaned after light is emitted; s2, cleaning upper-layer graphite of the coating layer of the thinned area by adopting a continuous laser / pulse laser until the copper foil is slightly exposed, and uniformly cleaning the thinned area; and S3, cleaning the residual bottom layer graphite of the coating layer in the thinned area by using a pulse laser. The cleaning process is simple and reliable, the yield of the laser cleaning thinned area can be effectively improved, the lossless cleaning effect is achieved, and meanwhile the laser cleaning efficiency can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly to a flying cleaning process for the thinning area of battery electrode sheets. Background Art

[0002] During the production process of lithium battery electrode sheets, due to the fluid characteristics of the slurry, semi-circular thinning areas are likely to form at the coating starting point, ending point, and both sides. The thickness and compaction density in this area are uneven, which will cause uneven current distribution during the charge and discharge process of the battery, accelerate the polarization phenomenon, and trigger problems such as abnormal growth of the SEI film, lithium precipitation, and dendritic lithium formation. Therefore, laser cleaning is required to remove the coating in the thinning area. Existing technologies usually use pulsed lasers or continuous lasers for separate cleaning. However, this cleaning method has low efficiency and low cleaning yield, and may cause the coexistence of damage and residue. Summary of the Invention

[0003] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a flying cleaning process for the thinning area of battery electrode sheets, which can improve the efficiency and yield of laser cleaning the thinning area.

[0004] The present invention provides the following technical solutions:

[0005] The present invention provides a flying cleaning process for the thinning area of battery electrode sheets, which includes the following steps:

[0006] S1. Select a homogenizing DOE lens for the pulsed laser and / or continuous laser, install it on the external optical path, adjust the lens angle so that the laser passes vertically and smoothly through the center of the homogenizing DOE lens, and rotate the homogenizing DOE lens after the light exits to adjust the angle of the shaped light spot to the area to be cleaned;

[0007] S2. Use the continuous laser / pulsed laser to clean the upper layer of graphite in the coating layer of the thinning area until the copper foil is slightly exposed, and clean the thinning area evenly;

[0008] S3. Use the pulsed laser to clean the remaining bottom layer of graphite in the coating layer of the thinning area.

[0009] Further, the thickness of the upper layer of graphite is 2 / 3 of the graphite thickness in the thinning area.

[0010] Further, the upper layer of graphite is cleaned by the method of stepped cleaning and / or segmented filling cleaning.

[0011] Further, the stepped cleaning includes dividing the upper layer of graphite in the coating layer of the thinning area into multiple layers of graphite according to the thickness, and then cleaning layer by layer.

[0012] Preferably, the stepwise cleaning includes dividing the upper-layer graphite of the coating layer in the thinning area into three layers for cleaning. The cleaning of the first layer of graphite includes removing 50-60% of the graphite in the upper-layer graphite of the coating layer in the thinning area; the cleaning of the second layer of graphite includes removing 70-80% of the remaining graphite in the upper-layer graphite of the coating layer in the thinning area; the third-layer cleaning completely removes the upper-layer graphite of the coating layer in the thinning area, achieving the effect of non-destructive cleaning.

[0013] Further, the segmented filling type cleaning includes longitudinally segmenting the upper-layer graphite of the coating layer in the thinning area according to the thickness, and then performing segmented cleaning.

[0014] Preferably, in the segmented filling type cleaning, the filling spacing of the segment with a larger thickness of the coating layer in the thinning area is greater than that of the segment with a smaller thickness, matching the problem of different thicknesses of the material, and improving the phenomenon of color change in layers on the cleaning surface.

[0015] Preferably, the segmented cleaning includes longitudinally dividing the coating layer in the thinning area into three thickness gradient regions, namely a thin region, a medium-thick region, and a thick region. The width of the thin region is defined as extending 1.5 mm inward from the edge of the coating layer in the thinning area; the width of the medium-thick region is defined as extending 1.0 mm inward from the termination end of the thin region, that is, in the range of 1.5 mm to 2.5 mm from the edge of the coating layer in the thinning area; the width of the thick region is defined as extending 0.5 mm inward from the termination end of the medium-thick region, that is, in the range of 2.5 mm to 3.0 mm from the edge of the coating layer in the thinning area; the filling spacing of the medium-thick region is 0.08 mm - 0.15 mm; the filling spacing of the thick region is 0.05 mm - 0.1 mm.

[0016] Preferably, the light spot is selected from one of a square, a long strip, a circle, and an annulus.

[0017] Preferably, the size of the light spot is (40 μm - 100 μm) × (100 μm - 250 μm).

[0018] Preferably, a gap of 0.5 - 0.8 mm is reserved between the cleaning area and the copper foil edge.

[0019] The present invention also discloses a laser processing system, which includes a continuous laser, a pulsed laser, and a homogenizing DOE lens. Two homogenizing DOE lenses are provided and are respectively arranged on the optical circuits of the continuous laser and the pulsed laser.

[0020] Preferably, a die-cutting station is provided at the rear end of the laser processing system. After the cleaning of the thinning area is completed, the tab can be immediately die-cut out, realizing the integration of cleaning and die-cutting. The laser cleaning of the thinning area + die-cutting to form the pole piece ensures the ultra-high consistency of the process starting from the pole piece.

[0021] The present invention has the following technical effects:

[0022] The present invention adds a homogenizing DOE lens suitable for high-power lasers in a laser processing system, which can shape Gaussian light into flat-top light with extremely high energy distribution uniformity from the center to the edge. The energy distribution of its light spot is uniform, which can avoid the influence caused by uneven thickness of the coating layer in the thinning area, make the cleaning surface smoother, and has low damage to metals, and can clean the substances on the metal surface more uniformly; the shape of the light spot can be adjusted as needed, the area of the light spot can be increased, and the cleaning efficiency can be improved; due to the good energy consistency of the flat-top light spot, its cleaning compatibility is higher, and no breakdown, no surface damage, and no thermal deformation can be achieved after multiple cleanings. By first using a continuous laser / pulsed laser combined with a homogenizing DOE lens to clean the upper layer of graphite in the thinning area, and then using a pulsed laser to clean the bottom layer of graphite in the thinning area, the cleaning efficiency can be improved, and at the same time, the effect of non-destructive cleaning of the thinning area can be achieved. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic diagram of the layered cleaning process provided in Embodiment 2 of the present invention.

[0025] Figure 2 It is a schematic diagram of segmented cleaning provided in Embodiment 3 of the present invention.

[0026] Figure 3 It is another perspective schematic diagram of segmented cleaning provided in Embodiment 3 of the present invention.

[0027] Figure 4 It is a microscopic effect diagram of cleaning provided in Embodiment 2 of the present invention.

[0028] Figure 5 It is a microscopic effect diagram of cleaning provided in Comparative Example 1 of the present invention.

[0029] Explanation of the labels in the figure: 1 - damage; 2 - residue; 3 - coating layer in the thinning area; 4 - first layer of graphite; 5 - second layer of graphite; 6 - bottom layer of graphite; 7 - thin area; 8 - medium-thick area; 9 - thick area. Detailed Embodiments

[0030] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] It should be understood that when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0032] Specifically, the flying cleaning process for the thinned area of the battery electrode sheet in the specific implementation manner of the present invention may include the following steps:

[0033] Step 1: Pull out the QBH head (Quartz Block Head) of the continuous laser, check the lens at the QBH output end to ensure that the lens is intact and clean, and then align and insert the QBH head into the collimator head and lock it.

[0034] Step 2: After connecting the laser head of the continuous laser, adjust the optical path to find the focal point. Use the control card for BOX and high-precision calibration to meet the dimensional accuracy requirements.

[0035] Step 3: Install the pulsed laser, adjust the optical path to find the focal point, use the control card for BOX and high-precision calibration to meet the dimensional accuracy requirements.

[0036] Step 4: Select homogenizing DOE lenses of appropriate sizes for the two lasers respectively, install them on the external optical path, adjust the lens angle so that the laser passes vertically and smoothly through the center of the DOE lens, and rotate the DOE after the light exits to adjust the shaped light spot to an appropriate angle.

[0037] Step 5: According to the cleaning speed of the laser, change the switch-on and switch-off delays of the two lasers, remove the acceleration and deceleration sections, align the left and right ends, change the length and width, and set a drawing file with a size of 50×3.5 mm.

[0038] Step 6: Use the continuous laser station to wash away the upper layer of graphite (the thickness accounts for 2 / 3 of the thickness of the thinned area) in a segmented filling or stepped cleaning manner until the copper foil is slightly exposed, and make the thinned area cleaner and more uniform.

[0039] Step 7: Use the pulsed laser, adjust the parameters, and wash away the remaining graphite residue in the thinned area.

[0040] Step 8: After cleaning out the thinned area, through the die-cutting station at the rear end of the equipment, the tab can be immediately die-cut.

[0041] To more fully understand the technical content of the present invention, the technical solution of the present invention will be further introduced and described below in conjunction with specific embodiments.

[0042] Example 1

[0043] A flying cleaning process for the thinning area of a battery electrode sheet, which comprises the following steps:

[0044] S1. Select appropriate homogenizing DOE lenses for the pulsed laser and the continuous laser, install them on the external optical paths of the pulsed laser and the continuous laser, adjust the lens angle so that the laser passes vertically and smoothly through the center of the homogenizing DOE lens, and rotate the homogenizing DOE lens after the light exits to adjust the angle of the shaped light spot to the area to be cleaned;

[0045] S2. Set a pattern with a size of 50×3.5 mm according to the size of the area to be cleaned in the thinning area;

[0046] S3. Use the continuous laser to clean the upper layer of graphite in the coating layer of the thinning area and divide the upper layer of graphite in the coating layer of the thinning area into three layers for cleaning. For the cleaning of the first layer of graphite, the homogenizing DOE lens is used to shape the light spot of the continuous laser into a square light spot with a size of 100 um×100 um, and 60% of the graphite in the upper layer of graphite in the coating layer of the thinning area is removed, and the cleaning time is 0.23 s; for the cleaning of the second layer of graphite, the homogenizing DOE lens is used to shape the light spot of the continuous laser into a strip-shaped light spot with a size of 40 um×100 um, and 80% of the remaining graphite in the upper layer of graphite in the coating layer of the thinning area is removed, and the cleaning time is 0.2 s; for the third layer of cleaning, the homogenizing DOE lens is used to shape the light spot of the continuous laser into a strip-shaped light spot with a size of 40 um×250 um, and the upper layer of graphite in the coating layer of the thinning area is completely removed, and the cleaning time is 0.1 s; the thickness of the upper layer of graphite accounts for 2 / 3 of the thickness of the coating layer in the thinning area;

[0047] S4. Use the pulsed laser, with a galvanometer scanning speed of 30000 mm / s and a filling pitch of 0.04 - 0.08 mm, to clean the remaining bottom layer of graphite in the coating layer of the thinning area under high-frequency conditions, and the cleaning time is 0.13 s.

[0048] Example 2

[0049] A flying cleaning process for the thinning area of a battery electrode sheet, which comprises the following steps:

[0050] S1. Select an appropriate homogenizing DOE lens for the pulsed laser, install it on the external optical path of the pulsed laser, adjust the lens angle so that the laser passes vertically and smoothly through the center of the homogenizing DOE lens, shape the light spot of the pulsed laser into a square light spot with a size of 100 um×100 um, and rotate the homogenizing DOE lens after the light exits to adjust the angle of the shaped light spot to the area to be cleaned;

[0051] S2. Set up a drawing file with a size of 50×3.5 mm according to the size of the area to be cleaned in the thinning area;

[0052] S3. Use a pulsed laser to clean the upper layer of graphite in the coating layer of the thinning area. As shown in Figure 1 , divide the upper layer of graphite in the coating layer 3 of the thinning area into two layers for cleaning. The cleaning of the first layer of graphite 4 includes removing 60% of the graphite in the upper layer of graphite in the coating layer 3 of the thinning area; the cleaning of the second layer of graphite 5 completely removes the upper layer of graphite in the coating layer 3 of the thinning area. The cleaning of the first layer of graphite 4 and the second layer of graphite 5 is specifically to divide the coating layer 3 of the thinning area into three segments according to the thickness. The width range of the thin area is from the edge of the coating layer 3 of the thinning area to 1.5 mm away from the edge, and the filling spacing is 0.05 - 0.07 mm. The width range of the medium-thick area is from 1.5 mm away from the edge to 2.5 mm away from the edge, and the filling spacing is 0.06 - 0.08 mm. The width range of the thick area is from 2.5 mm away from the edge to 3 mm away from the edge, and the filling spacing is 0.06 - 0.1 mm. The galvanometer scanning speed of both the first layer of graphite 4 and the second layer of graphite 5 is 30000 mm / s, and the cleaning time is 0.21 s. The thickness of the upper layer of graphite accounts for 2 / 3 of the thickness of the coating layer 3 of the thinning area;

[0053] S4. Use a pulsed laser to clean the remaining bottom layer of graphite 6 in the coating layer 3 of the thinning area. The specific cleaning method is to divide the coating layer 3 of the thinning area into three segments according to the thickness. The width range of the thin area is from the edge of the coating layer 3 of the thinning area to 1.5 mm away from the edge, and the filling spacing is 0.05 - 0.07 mm. The width range of the medium-thick area is from 1.5 mm away from the edge to 2.5 mm away from the edge, and the filling spacing is 0.06 - 0.08 mm. The width range of the thick area is from 2.5 mm away from the edge to 3 mm away from the edge, and the filling spacing is 0.06 - 0.1 mm. The galvanometer scanning speed is 30000 mm / s, and the cleaning time is 0.21 s.

[0054] Example 3

[0055] A flying cleaning process for the thinning area of a battery electrode sheet, which includes the following steps:

[0056] S1. Select appropriate homogenizing DOE lenses for the pulsed laser and the continuous laser, install them on the external optical paths of the pulsed laser and the continuous laser, adjust the lens angle so that the laser passes vertically and smoothly through the center of the homogenizing DOE lens, and rotate the homogenizing DOE lens after the light exits to adjust the angle of the shaped light spot to the area to be cleaned;

[0057] ​​S2. Set a drawing file sized 50×3.5 mm according to the size of the area to be cleaned in the thinning area; leave a 0.5-mm gap between the drawing file (area to be cleaned) and the copper foil edge to avoid continuous laser damage to the copper foil.

[0058] S3. Please refer to Figure 2 and Figure 3 and use a continuous laser to clean the upper-layer graphite of the coating layer 3 in the thinning area. Longitudinally divide the coating layer 3 in the thinning area into three thickness gradient regions, namely, a thin region 7, a medium-thick region 8, and a thick region 9. The width of the thin region 7 is defined as extending 1.5 mm inward from the edge of the coating layer in the thinning area, and the filling pitch is 0.08 - 0.1 mm; the width of the medium-thick region 8 is defined as extending 1.0 mm inward from the termination end of the thin region 7, that is, in the range of 1.5 mm to 2.5 mm from the edge of the coating layer 3 in the thinning area, and the filling pitch is 0.1 - 0.15 mm; the width of the thick region 9 is defined as extending 0.5 mm inward from the termination end of the medium-thick region 8, that is, in the range of 2.5 mm to 3.0 mm from the edge of the coating layer 3 in the thinning area, and the filling pitch is 0.15 - 0.2 mm. The total cleaning time is 0.1 s; the thickness of the upper-layer graphite accounts for 2 / 3 of the thickness of the coating layer 3 in the thinning area.

[0059] S4. Use a pulsed laser to clean the remaining bottom-layer graphite of the coating layer 3 in the thinning area. The specific cleaning method is to longitudinally divide the coating layer 3 in the thinning area into three thickness gradient regions, namely, a thin region 7, a medium-thick region 8, and a thick region 9. The width of the thin region 7 is defined as extending 1.5 mm inward from the edge of the coating layer in the thinning area, and the filling pitch is 0.06 - 0.08 mm; the width of the medium-thick region 8 is defined as extending 1.0 mm inward from the termination end of the thin region 7, that is, in the range of 1.5 mm to 2.5 mm from the edge of the coating layer 3 in the thinning area, and the filling pitch is 0.08 - 0.1 mm; the width of the thick region 9 is defined as extending 0.5 mm inward from the termination end of the medium-thick region 8, that is, in the range of 2.5 mm to 3.0 mm from the edge of the coating layer 3 in the thinning area, and the filling pitch is 0.1 - 0.15 mm; the galvanometer scanning speed is 30000 mm / s, and the cleaning time is 0.21 s.

[0060] Comparative Example 1

[0061] In this comparative example, a pulsed laser without a homogenizing DOE lens is used to clean the thinning area, and the galvanometer scanning speed of 30000 mm / s is used. Under the condition of a fundamental frequency and a filling pitch of 0.05 - 0.1 mm, the thinning area is cleaned. In this configuration, it is necessary to clean three times to completely clean it, and the specific cleaning time is 1.2 s.

[0062] To illustrate the technical effects of the present invention, the cleaning completion times of Examples 1 - 3 and Comparative Example 1 are statistically shown in Table 1 below:

[0063] Table 1 Cleaning Time

[0064] Example 1 Example 2 Example 3 Comparative Example 1 Time 0.23s 0.63s 0.31s 1.2s

[0065] As shown in Table 1, the laser cleaning method of the present invention can significantly improve the efficiency. Compared with the cleaning using a pulsed laser without a homogenizing DOE lens, the laser cleaning method of the present invention can shorten the cleaning time to less than 0.7 s.

[0066] To further illustrate the laser cleaning effect of the present invention, the thinned areas after cleaning in Example 2 and Comparative Example 1 were observed microscopically, and the effect diagrams are respectively as Figure 4 and Figure 5 shown. There are defects of residue 2 and damage 1 in the thinned area after cleaning in Comparative Example 1, while there are no defects such as breakdown, surface damage, and thermal deformation in the thinned area after cleaning in Example 2. Therefore, the laser cleaning method of the present invention can significantly improve the cleaning yield of the product.

[0067] In summary, the laser cleaning method of the present invention can significantly improve the cleaning efficiency. After shaping the Gaussian light into a flat-top light using a homogenizing DOE lens, due to the uniform energy distribution, the risk of damaging the copper foil is reduced. Through layer-by-layer cleaning, two lasers can be used for efficient cleaning of the thinned area, further improving the cleaning efficiency.

[0068] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A flying cleaning process for the thinning area of a battery electrode sheet, characterized in that, It includes the following steps: S1. Select a homogenizing DOE lens for the pulsed laser and / or continuous laser, install it on the external optical path, adjust the lens angle so that the laser passes vertically and smoothly through the center of the homogenizing DOE lens, and rotate the homogenizing DOE lens after the light exits to adjust the angle of the shaped light spot to the area to be cleaned; S2. Use a continuous laser / pulsed laser to clean the upper layer of graphite of the coating in the thinning area until the copper foil is slightly exposed, and clean the thinning area evenly; S3. Use a pulsed laser to clean the remaining bottom layer of graphite of the coating in the thinning area.

2. The flying cleaning process for the thinned area of the battery electrode sheet according to claim 1, characterized in that, The thickness of the upper layer of graphite is 2 / 3 of the graphite thickness in the thinning area.

3. The flying cleaning process for the thinned area of the battery electrode sheet according to claim 1, wherein, The upper layer of graphite is cleaned by the method of stepped cleaning and / or segmented filling cleaning.

4. The flying cleaning process for the thinned area of the battery electrode sheet according to claim 3, characterized in that, The stepped cleaning includes dividing the upper layer of graphite of the coating in the thinning area into multiple layers of graphite according to the thickness, and then cleaning layer by layer.

5. The flying cleaning process for the thinning area of the battery electrode sheet according to claim 4, characterized in that, The stepped cleaning includes dividing the upper layer of graphite of the coating in the thinning area into 3 layers for cleaning. The cleaning of the first layer of graphite includes removing 50%-60% of the graphite in the upper layer of graphite of the coating in the thinning area; the cleaning of the second layer of graphite includes removing 70%-80% of the remaining graphite in the upper layer of graphite of the coating in the thinning area; the cleaning of the third layer of graphite includes completely removing the upper layer of graphite of the coating in the thinning area.

6. The flying cleaning process for the thinned area of the battery electrode sheet according to claim 3, characterized in that, The segmented filling cleaning includes longitudinally segmenting the coating in the thinning area according to the thickness, and then performing segmented cleaning.

7. The flying cleaning process for the thinned area of the battery electrode sheet according to claim 6, wherein In the segmented filling cleaning, the filling spacing of the segment with a larger thickness of the coating in the thinning area is greater than that of the segment with a smaller thickness.

8. The flying cleaning process for the thinned area of the battery electrode sheet according to claim 7, characterized in that, The segmented cleaning includes longitudinally dividing the coating in the thinning area into three thickness gradient regions, namely a thin region, a medium-thick region, and a thick region. The width of the thin region is defined as extending 1.5 mm inward from the edge of the coating in the thinning area; the width of the medium-thick region is defined as extending 1.0 mm inward from the end of the thin region, that is, in the range of 1.5 mm to 2.5 mm from the edge of the coating in the thinning area; the width of the thick region is defined as extending 0.5 mm inward from the end of the medium-thick region, that is, in the range of 2.5 mm to 3.0 mm from the edge of the coating in the thinning area; the filling spacing of the thin region is 0.1 mm - 0.2 mm; the filling spacing of the medium-thick region is 0.08 mm - 0.15 mm; the filling spacing of the thick region is 0.05 mm - 0.1 mm.

9. The flying cleaning process for the thinning area of the battery electrode sheet according to claim 1, characterized in that, The light spot is selected from one of a square, a rectangle, a circle, and an annulus.

10. The flying cleaning process for the thinning area of the battery electrode sheet as described in claim 1, wherein, The size of the light spot is (40 μm - 100 μm) × (100 μm - 250 μm).

Images