Method for removing surface passivation layer of lithium-containing strip and controlling surface quality

Abstract

The application discloses a method for removing surface passivation layer of lithium-containing strip and controlling surface quality, and comprises the following steps: providing a lithium-containing strip with a surface passivation layer to be removed; providing a supporting roller; providing a cylindrical brush arranged in parallel with the supporting roller; winding the lithium-containing strip around the supporting roller in an inert gas environment or a low dew point environment, and arranging the surface passivation layer to be removed opposite to the cylindrical brush; adjusting the distance between the cylindrical brush and the supporting roller, so that the cylindrical brush is in contact with the surface passivation layer to be removed; and rotating the cylindrical brush to generate a relative speed difference between the cylindrical brush and the strip, so as to remove the surface passivation layer of the strip. The method can remove various types of passivation layer materials such as lithium oxide and lithium carbonate on the surface of the lithium-containing strip, can be processed in a roll-to-roll batch mode, has good processing effect, high production efficiency and good product consistency.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to a method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality. Background Technology

[0002] Lithium metal is a rare element with a density of 0.534 g / cm³. 3 Lithium is the lightest metal. It has a melting point of 180.54℃ and a boiling point of 1317℃. It is soft, tough, ductile, chemically active, has a high negative potential and high specific energy, and can react with a large number of inorganic and organic reagents, reacting very violently with water. During production, storage, and transportation, it reacts with water vapor, oxygen, carbon dioxide, nitrogen, etc., in the air, forming a surface passivation layer containing various substances such as lithium oxide, lithium carbonate, lithium hydroxide, and lithium nitride on the surface of lithium-containing strips. These passivation layers or impurities can adversely affect the performance of lithium-containing strips used in batteries or other processes, and therefore need to be removed.

[0003] Currently, commonly used methods for removing passivation layers include chemical solvent reaction and plasma etching. However, these are not suitable for treating the passivation layer on the surface of lithium-containing strips. Due to the extreme reactivity of lithium metal and the complex and diverse materials of the surface passivation layer, chemical solvent reaction methods cannot remove various materials and may even leave residual solvent components that introduce new impurities. Patents CN117711922A and CN116536670A mention methods for removing the surface passivation layer using plasma. However, even existing low-temperature plasma technology still has relatively high temperatures, which can still cause the extremely reactive lithium metal to react with the surrounding gas and introduce new impurities. On the other hand, plasma is effective in removing organic impurities, but its effect on impurities such as lithium oxide, lithium carbonate, and lithium nitride is not significant.

[0004] In view of this, the present invention provides a method for removing the passivation layer on the surface of lithium-containing strip with controllable surface quality. By using a mechanical roller brush, the roller brush depth and speed can be precisely controlled, thereby achieving precise control over the passivation layer removal depth and surface roughness. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple, reliable method for removing the passivation layer on the surface of lithium metal with controllable surface quality.

[0006] The objective of this invention can be achieved through the following technical solutions.

[0007] A method for removing a passivation layer from the surface of a lithium-containing strip with controllable surface quality includes: providing a lithium-containing strip, the surface of which has a passivation layer to be removed; providing a support roller, the support roller comprising a roller sleeve, a bearing, and a support shaft, the roller sleeve being freely rotatable around the support shaft; providing a cylindrical brush, the cylindrical brush being arranged parallel to the support roller, the cylindrical brush being rotatable around its own axis under the drive of a driving element; in an inert gas environment or a low dew point environment, passing the lithium-containing strip around the support roller, with the side of the passivation layer to be removed facing the cylindrical brush, and adjusting... The distance between the cylindrical brush and the support roller is adjusted so that the cylindrical brush contacts the side of the surface to be removed from the passivation layer. When the cylindrical brush rotates, a relative speed difference is generated between it and the strip, thereby removing the passivation layer from the strip surface. At least one of the support roller and the cylindrical brush has a distance fine-tuning function, which can adjust the center distance between the cylindrical brush and the support roller, that is, the distance at which the cylindrical brush presses on the support roller can be finely adjusted. The lithium-containing strip is passed between the support roller and the cylindrical brush by the strip take-up and unwinding device, and the passivation layer removal treatment of the lithium-containing strip is continuously performed.

[0008] The thickness t of the passivation layer removed from the lithium-containing strip and / or the surface roughness Sa of the lithium-containing strip after the passivation layer is removed are controlled by adjusting at least one of the following: the length L' of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip, the brush bristle diameter d, and the center distance L between the cylindrical brush and the support roller.

[0009] in, ,

[0010] Where ν is the conveying speed of the lithium-containing strip, D is the diameter of the cylindrical brush, and n is the rotational speed of the cylindrical brush.

[0011] The depth at which the passivation layer on the surface of the lithium-containing strip is removed can be adjusted by adjusting the distance between the cylindrical brush and the support roller. The deeper the cylindrical brush is pressed into the lithium-containing strip, the deeper the passivation layer on the surface of the lithium-containing strip is removed.

[0012] The surface roughness of lithium-containing strips can be controlled by adjusting the stiffness of the cylindrical brush bristles. The finer the bristles, the softer the bristles, and the longer the friction length per unit length of the cylindrical brush relative to the roller brush, the smoother the surface of the lithium-containing strip. Conversely, the coarser the bristles, the stiffer the bristles, and the shorter the friction length per unit length of the cylindrical brush relative to the roller brush, the rougher the surface of the lithium-containing strip.

[0013] Optionally, the distance fine-tuning function is achieved by providing a fine-tuning component on at least one of the support roller and the cylindrical brush, the fine-tuning component consisting of a cylinder and a fine-tuning mechanism.

[0014] Optionally, the fine-tuning component is located at both ends of the cylindrical brush, that is, one end is located at the bearing seat of the power transmission shaft and the other end is located at the positioning tip; this allows the cylindrical brush to move closer to or further away from the support roller.

[0015] Optionally, the fine-tuning component is located at the roller fixing seats at both ends of the support roller assembly, which can make the support rollers move closer to or further away from the cylindrical brush.

[0016] Optionally, the bristles of the cylindrical brush are made of any of the following materials: nylon (PA), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene (PE), and animal hair (pig bristles, horse bristles, wool).

[0017] Optionally, the diameter of the bristles of the cylindrical brush is between 0.08 mm and 1 mm.

[0018] Optionally, the cylindrical brush rotates in the same direction as the supporting roller, and the linear velocity of the cylindrical brush at the point of contact with the lithium-containing strip is opposite to the direction of the belt travel.

[0019] Optionally, the ratio of the rotational speed of the cylindrical brush to the rotational speed of the supporting roller is greater than 1.

[0020] Optionally, the positioning accuracy of the center distance adjustment between the cylindrical brush and the support roller is between 0.5 and 10 μm.

[0021] Optionally, the working area of ​​the support roller and the cylindrical brush is also provided with a dust suction or dust collection device.

[0022] Optionally, the inert gas environment is an inert gas chamber in which moisture and oxygen are removed internally.

[0023] Optionally, the dew point in the low dew point environment is less than -20°C.

[0024] The technical solution of the present invention has at least one of the following advantages:

[0025] 1. The method of the present invention has a wide range of applications and can remove any type of passivation layer;

[0026] 2. The thickness of the passivation layer can be adjusted at the micrometer level, allowing for precise control of the passivation layer removal thickness;

[0027] 3. By controlling the hardness of the brush bristles and the relative rotation speed of the cylindrical brush, the surface roughness of the lithium-containing strip after the passivation layer is removed can be controlled; a rough or smooth surface can be obtained as needed.

[0028] 4. The strip is continuously processed in a roll-to-roll manner using a mechanical roller brush, resulting in high production efficiency and stable and consistent product quality after processing. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the working principle of the method of the present invention.

[0030] Figure 2 This is an isometric view of the apparatus for removing the passivation layer from the surface of lithium-containing strips, which can be used in this invention.

[0031] Figure 3 yes Figure 2 A diagram showing the dust collection cover after it has been removed.

[0032] Figure 4 yes Figure 3 A schematic diagram of the top view.

[0033] Drawing number explanation: 100 Lithium-containing strip; 110 Passivation layer; L Center distance between cylindrical brush and support roller; 200 Brush assembly; 210 Drive element; 220 Bearing housing; 230 Power transmission shaft; 240 Coupling; 250 Drive pin; 260 Positioning center; 270 Center fixing seat; 280 Tightening cylinder; 290 Cylindrical brush; 300 Support roller assembly; 310 Support roller; 311 Support shaft; 312 Roller sleeve; 320 Roller fixing seat; 330 Adjustable cylinder; 340 Fine adjustment assembly; 400 Dust collection hood; 410 Dust suction port. Detailed Implementation

[0034] Specific embodiments of the present invention are described below. It should be understood that, without departing from the scope or spirit of the present invention, those skilled in the art can conceive of various other embodiments and make modifications thereto based on the teachings of this disclosure. Therefore, the following specific embodiments are not intended to be limiting.

[0035] In the description of this invention, it should be understood that the terms "upper" and "lower" are used only for the convenience of describing this invention and simplifying the description, and therefore should not be construed as limiting this invention.

[0036] refer to Figure 1 , Figure 1The diagram illustrates the working principle of the method of the present invention. The surface of the lithium-containing strip 100 typically forms a passivation layer 110 containing various impurities due to the reactive nature of lithium metal and its reaction with various components in the air. This complex passivation layer usually has adverse effects during the use of the lithium-containing strip, and therefore needs to be removed. In an inert gas environment or a low dew point environment, the lithium-containing strip 100 is routed around the support roller 310, with the side of the lithium-containing strip 100 having the passivation layer 110 facing the cylindrical brush 290. By adjusting the center distance L between the cylindrical brush and the support roller, the depth to which the cylindrical brush 290 is pressed into the lithium-containing strip 100 can be adjusted, thereby adjusting the thickness of the removed passivation layer 100. When removing the passivation layer 110 on the lithium-containing strip 100, the lithium-containing strip 100 passes around the support roller 310, and the support roller 310 rotates under the drive of the lithium-containing strip 100; the cylindrical brush 290 rotates in the same direction as the support roller 310 under the drive of the drive element, and the linear velocity direction of the cylindrical brush 290 is opposite to the running direction of the lithium-containing strip 100.

[0037] The method for removing the passivation layer from the surface of lithium-containing strip with controllable surface quality according to the present invention can be performed using the following apparatus for removing the passivation layer from the surface of lithium-containing strip. The apparatus includes: a brush assembly comprising a driving element and a cylindrical brush, the driving element driving the cylindrical brush to rotate; and a support roller assembly comprising a support roller, a roller mounting base, and a fine-tuning component. The support roller is arranged parallel to the cylindrical brush, and the center distance between the support roller and the cylindrical brush can be adjusted by the fine-tuning component. The support roller consists of a support shaft, a roller sleeve, and a bearing. The roller sleeve is fixedly connected to the support shaft via the bearing, allowing the roller sleeve to rotate around the support shaft. The support roller is fixedly connected to the fine-tuning component via the roller mounting base, and adjusting the fine-tuning component can move the support roller closer to or further away from the cylindrical brush. The apparatus is installed in an inert gas environment or a low dew point environment.

[0038] The apparatus for removing the passivation layer on the surface of lithium-containing strips will be described in detail below with reference to specific embodiments.

[0039] refer to Figures 2 to 3 The apparatus for removing the passivation layer from the lithium-containing strip includes: a brush assembly 200, a support roller assembly 300, and a dust collection hood 400.

[0040] The brush assembly 200 comprises a drive element 210, a bearing housing 220, a power transmission shaft 230, a coupling 240, a drive pin 250, a positioning center 260, a center fixing seat 270, a clamping cylinder 280, and a cylindrical brush 290. Both ends of the cylindrical brush 290 are connected to the power transmission shaft 230 and the positioning center 260, respectively. At least one end of the cylindrical brush 290 on the power transmission shaft 230 has a groove that mates with the drive pin 250. The drive pin 250 passes through the power transmission shaft 230 and connects with the groove of the cylindrical brush 290 to transmit rotational motion. The power transmission shaft 230 is rotatably fixed to the bearing housing 220 via a bearing (not shown in the figure). One end of the power transmission shaft 230 is connected to the cylindrical brush 290 to transmit power, and the other end is connected to the drive element 210 via the coupling 240. The positioning tip 260 located at the other end of the cylindrical brush 290 is fixedly connected to the clamping cylinder 280 through the tip fixing seat 270. The clamping cylinder 280 can reciprocate along the axis of the cylindrical brush 290. When the clamping cylinder 280 moves away from the cylindrical brush 290, the positioning tip 260 is disengaged from the cylindrical brush 290, and the cylindrical brush 290 can be replaced or removed at this time. When the clamping cylinder 280 moves closer to the cylindrical brush 290, the clamping cylinder 280 drives the positioning tip 260 to clamp the cylindrical brush 290.

[0041] The support roller assembly 300 consists of a support roller 310, a roller fixing seat 320, an adjustable cylinder 330, and a fine-tuning component 340. The support roller 310 comprises at least a support shaft 311, a bearing (not shown in the figure), and a roller sleeve 312. The roller sleeve 312 is fixedly connected to the support shaft 311 via the bearing and can rotate around the axis of the support shaft 311. Both ends of the support shaft 311 of the support roller 310 are fixedly connected to the adjustable cylinder 330 via the roller fixing seat 320. The adjustable cylinder 330 can drive the support roller 310 closer to or further away from the brush assembly 200. A fine-tuning component 340 is also provided on the adjustable cylinder 330, which can achieve micron-level adjustment precision, accurately controlling or limiting the center distance L between the cylindrical brush 290 and the support roller 310.

[0042] The dust collection hood 400 covers at least the working area of ​​the cylindrical brush 290 and the support roller assembly 300, and the dust collection hood 400 is also provided with a suction port 410. The dust collection hood 400 is connected to the pipe of a vacuum cleaner (not shown in the figure) through the suction port 410, thereby collecting the passivation layer powder that rolls off the brush.

[0043] It should be understood that the apparatus described in this invention for removing the passivation layer from the surface of lithium-containing strips is a functional component corresponding to the method of this invention, and is only a part of the equipment. A complete apparatus for removing the passivation layer from the surface of lithium-containing strips should also include necessary unwinding and rewinding components.

[0044] refer to Figures 1 to 4 The specific operation of the method of the present invention is as follows: First, preparation work for threading the tape. The lithium-containing tape 100 to be processed is unwound by the unwinding assembly (not shown in the figure) and passes around the support roller 310 in the support roller assembly 300, with one side of the passivation layer 110 in the lithium-containing tape 100 away from the support roller 310. The processed lithium-containing tape 100 is then wound up by the winding assembly (not shown in the figure). Then, according to the process parameters such as the thickness of the passivation layer to be removed and the surface roughness, the fine-tuning assembly 340 is adjusted to maintain a reasonable center distance L between the support roller 310 and the cylindrical brush 290. Finally, the equipment is started, and the unwinding assembly, the winding assembly, and the device for removing the passivation layer on the surface of the lithium-containing tape in the present invention all start to operate. The passivation layer 110 on the lithium-containing tape 100 is removed under the action of the rotating roller brush of the cylindrical brush 290.

[0045] The method of the present invention can control the removal depth of the passivation layer 110 on the surface of the lithium-containing strip 100 and control the surface roughness of the lithium-containing strip 100 after removing the passivation layer 110 by setting different conveyor belt speeds, the hardness of the cylindrical brush bristles, and the rotation speed of the cylindrical brush.

[0046] Assuming the conveying speed of the lithium-containing strip is ν, the diameter of the cylindrical brush is D, and the rotational speed of the cylindrical brush is n, then the length of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip is: .

[0047] In this embodiment, the diameters of the support roller 310 and the cylindrical brush 290 are both 100 mm.

[0048] Table 1 shows the surface roughness values ​​of the lithium-containing strip 100 after removing the passivation layer, obtained under different conditions of conveyor speed ν, cylindrical brush rotation speed n, and cylindrical brush bristle diameter.

[0049] Table 1:

[0050]

[0051] In Table 1: V represents the conveying speed of the lithium-containing strip, n represents the rotational speed of the cylindrical brush, L represents the center distance between the cylindrical brush and the support roller, d represents the diameter of the cylindrical brush bristles, L' represents the calculated length of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip, t represents the thickness of the passivation layer removed from the lithium-containing strip, and Sa represents the surface roughness of the lithium-containing strip after the passivation layer is removed.

[0052] By comparing Examples 1 and 3, and Examples 6 and 8, it can be found that the smaller the distance between the cylindrical brush and the supporting roller, the deeper the passivation layer is removed, and the greater the surface roughness after removing the passivation layer.

[0053] By comparing Examples 1 and 2, and Examples 6 and 7, it can be found that the coarser the diameter of the cylindrical brush bristles, the deeper the passivation layer is removed, and the greater the surface roughness after removing the passivation layer.

[0054] By comparing Examples 1 and 4, and Examples 6 and 9, it can be found that: the longer the length of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip, calculated by the belt speed, brush rotation speed and brush diameter, the deeper the passivation layer is removed, and the smaller the surface roughness after removing the passivation layer.

[0055] By comparing Examples 4 and 5, it can be found that when other parameters remain unchanged, increasing the conveyor speed results in a shorter length of cylindrical brush relative to roller brush friction per unit length of lithium-containing strip, calculated by conveyor speed, brush rotation speed, and brush diameter. This leads to a decrease in the depth of the removed passivation layer and an increase in surface roughness after the passivation layer is removed.

[0056] The above embodiments show that when the center distance L between the cylindrical brush and the supporting roller and the brush diameter d remain constant, the depth of passivation layer removal is not directly related to the belt conveyor speed and the rotational speed of the cylindrical brush. Instead, it is closely related to the calculated friction length of the cylindrical brush relative to the roller brush per unit length of the lithium-containing strip. The longer the friction length of the cylindrical brush relative to the roller brush per unit length of the lithium-containing strip, the deeper the passivation layer is removed, and the smaller the surface roughness after passivation layer removal, i.e., the smoother the surface. The finer the bristle diameter, the softer the bristles; the coarser the bristle diameter, the harder the bristles. When other conditions remain unchanged, the coarser the bristles, the deeper the passivation layer is removed, and the greater the surface roughness after passivation layer removal.

[0057] In summary, the thickness t of the passivation layer removed from the lithium-containing strip is positively correlated with the length L' of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip, positively correlated with the brush diameter d, and negatively correlated with the center distance L between the cylindrical brush and the support roller. This can be expressed as: t∝L'*d / L, and further derived as: t∝nDd / VL. The surface roughness Sa of the lithium-containing strip after passivation layer removal is negatively correlated with the length L' of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip, positively correlated with the brush diameter d, and negatively correlated with the center distance L between the cylindrical brush and the support roller. This can be expressed as: Sa∝d / L'L, and further derived as: Sa∝dV / DnL.

[0058] In practical mass production and applications, a relatively high belt speed V is usually required to achieve high production efficiency. Since the diameter D of the cylindrical brush remains essentially constant after the equipment design is finalized, the following conclusion can be drawn:

[0059] If it is necessary to increase the removal depth of the passivation layer, according to t∝nDd / VL, it can be achieved by increasing the rotational speed n of the cylindrical brush, increasing the brush bristle diameter, or decreasing the center distance L between the cylindrical brush and the support roller.

[0060] If it is necessary to reduce the surface roughness Sa, according to Sa∝dV / DnL, it can be achieved by reducing the bristle diameter d (i.e. using a softer brush), increasing the brush rotation speed n, and appropriately increasing the center distance L between the cylindrical brush and the support roller.

[0061] If we want to ensure both the thickness of the passivation layer to be removed and a small surface roughness, according to t∝nDd / VL and Sa∝dV / DnL, we can achieve this by increasing the brush rotation speed n and decreasing the belt speed V; when production efficiency is not affected, we can only increase the brush rotation speed n.

[0062] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for removing the passivation layer from the surface of a lithium-containing strip with controllable surface quality, comprising: A lithium-containing strip is provided, the surface of which has a surface passivation layer to be removed; A support roller is provided, which is composed of a roller sleeve, a bearing and a support shaft, and the roller sleeve can rotate about the support shaft; A cylindrical brush is provided, which is arranged parallel to the support roller, and the cylindrical brush can rotate around its own axis under the drive of the driving element. In an inert gas environment or a low dew point environment, lithium-containing strip is wound around a support roller. The side with the passivation layer to be removed is positioned opposite a cylindrical brush. The distance between the cylindrical brush and the support roller is adjusted so that the cylindrical brush contacts the side with the passivation layer to be removed. When the cylindrical brush rotates, a relative speed difference is generated between it and the strip, thereby removing the passivation layer from the strip surface. At least one of the support roller and the cylindrical brush has a distance fine-tuning function, which can adjust the center distance between the cylindrical brush and the support roller, that is, the distance at which the cylindrical brush presses against the support roller can be finely adjusted. The lithium-containing strip is passed between support rollers and cylindrical brushes by a strip take-up and unwinding device, and the passivation layer of the lithium-containing strip is continuously removed. The thickness t of the passivation layer removed from the lithium-containing strip and / or the surface roughness Sa of the lithium-containing strip after the passivation layer is removed are controlled by adjusting at least one of the following: the length L' of friction between the cylindrical brush and the roller brush per unit length of the lithium-containing strip, the brush bristle diameter d, and the center distance L between the cylindrical brush and the support roller. in, , Where ν is the conveying speed of the lithium-containing strip, D is the diameter of the cylindrical brush, and n is the rotational speed of the cylindrical brush.

2. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The bristles of the cylindrical brush are made of any of the following materials: nylon (PA), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene (PE), and animal hair (pig bristles, horse bristles, wool).

3. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The diameter of the bristles of the cylindrical brush is between 0.08 mm and 1 mm.

4. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The cylindrical brush rotates in the same direction as the supporting roller, and the linear velocity of the cylindrical brush at the point of contact with the lithium-containing strip is opposite to the direction of the belt travel.

5. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The ratio of the rotational speed of the cylindrical brush to the rotational speed of the supporting roller is greater than 1.

6. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The positioning accuracy of the center distance adjustment between the cylindrical brush and the support roller is between 0.5 and 10 μm.

7. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The working area of ​​the support roller and cylindrical brush is also equipped with a dust suction or dust collection device.

8. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The inert gas environment is an inert gas chamber in which moisture and oxygen are removed.

9. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The dew point in the low dew point environment is less than -20°C.

10. The method for removing the passivation layer from the surface of lithium-containing strips with controllable surface quality as described in claim 1, characterized in that, The distance fine-tuning function is achieved by setting a fine-tuning component on at least one of the support roller and the cylindrical brush, the fine-tuning component consisting of a cylinder and a fine-tuning mechanism.

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