Pole piece processing method

Abstract

The invention discloses a pole piece processing method. The pole piece processing method comprises the following steps: rolling a coated pole piece by adopting a rolling mechanism; wherein the rolling mechanism comprises an upper roller and a lower roller, and a roller gap is formed between the upper roller and the lower roller; wherein before rolling, the cylinder bending pressure of the upper roller and the cylinder bending pressure of the lower roller are adjusted, so that the cylinder bending pressure of the lower roller is smaller than the cylinder bending pressure of the upper roller. The cylinder bending pressure of the lower roller is controlled to be smaller than that of the upper roller, so that deflection deviation of the upper roller and the lower roller can be accurately compensated, strip breakage can be reduced, production efficiency is improved, production cost is reduced, and product quality is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to an electrode processing method. Background Technology

[0002] Secondary batteries, due to their high energy density, long cycle life, and environmental friendliness, have been widely used in new energy vehicles, energy storage systems, and portable electronic devices. Electrodes are the core component of secondary batteries. During the continuous production process of electrode rolling and slitting, strip breakage is the most common and serious production failure. Sudden breakage of the electrode under tension can force the production line to stop, reduce production efficiency, increase production costs, and affect product quality. Therefore, it is necessary to improve the strip breakage problem that occurs in processes such as rolling and slitting. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one object of this invention is to provide an electrode processing method that can effectively solve the problem of electrode breakage during the production process.

[0004] Specifically, the present invention provides an electrode processing method, comprising the following steps: A roller pressing mechanism is used to roll the coated electrode sheet; wherein, the roller pressing mechanism includes an upper roller and a lower roller, and a roller gap is provided between the upper roller and the lower roller; Before rolling, the bending cylinder pressure of the upper and lower rolls is adjusted so that the bending cylinder pressure of the lower roll is less than that of the upper roll.

[0005] When subjected to working pressure, the upper and lower rolls are prone to deflection deformation, resulting in a roll gap that is wider in the middle and narrower on both sides, leading to uneven compaction of the electrode sheet in the width direction. Related technologies utilize bending cylinders on the upper and lower rolls to apply a reverse bending force, precisely compensating for deflection deviations and ensuring a consistent roll gap along the width direction. Typically, the bending cylinder pressures of the upper and lower rolls are set to be the same. However, because the bending cylinder pressure of the lower roll is in the opposite direction to the rolling force on the electrode sheet, there is a partial cancellation between the bending cylinder pressure of the lower roll and the rolling force on the electrode sheet. Therefore, the preset bending cylinder pressure of the lower roll is actually partially "wasted." This portion not only fails to adjust the deformation of the lower roll but can also cause some areas of the electrode sheet to break due to excessive force (this phenomenon does not occur with the upper roll). Based on this discovery, the present invention reduces the bending cylinder pressure of the lower roll, making the bending cylinder pressure of the lower roll less than that of the upper roll. This not only accurately compensates for the deflection deviation of the upper and lower rolls, but also reduces the occurrence of strip breakage during the roll pressing and slitting process, thereby improving production efficiency, reducing production costs, and improving product quality.

[0006] According to some embodiments of the present invention, the bending cylinder pressure of the upper roll is denoted as p1, the bending cylinder pressure of the lower roll is denoted as p2, and 1 < p1 / p2 ≤ 2.

[0007] According to some embodiments of the present invention, 5 MPa ≤ p1 ≤ 10 MPa.

[0008] According to some embodiments of the present invention, before rolling, it is detected whether the upper roll and the lower roll are arranged in parallel; if they are not parallel, they are adjusted.

[0009] According to some embodiments of the present invention, the coated electrode sheet includes a coated area and an uncoated area, the coated area including a coating; before rolling, the method further includes: passing the coated electrode sheet through a roller device; corresponding to the uncoated area, n straightening layers are wound on the roller body of the roller device; the ratio of the total thickness of the n straightening layers to the thickness of the coating is (1-1.2):1.

[0010] According to some embodiments of the present invention, the material of the straightening layer includes Teflon.

[0011] According to some embodiments of the present invention, the n straightening layers are stacked sequentially, and the maximum distance between the same side edges of two adjacent straightening layers along the axial direction of the roller body is less than 0.5 mm; preferably, the edges of two adjacent straightening layers are flush.

[0012] According to some embodiments of the present invention, before rolling, the method further includes: unwinding the electrode sheet to be rolled; before unwinding, aligning the first end of the electrode sheet to be rolled with the last end of the electrode sheet in the previous rolling and attaching multiple adhesive tapes; the multiple adhesive tapes are arranged in parallel; the maximum distance between the end edges of two adjacent parallel adhesive tapes along the length direction of the tapes is less than 0.5 cm.

[0013] According to some embodiments of the present invention, the plurality of tapes are of the same length; the lengths of the plurality of tapes are 5cm-10cm respectively.

[0014] According to some embodiments of the present invention, after the tape is pasted and before unwinding, the method further includes: checking whether the end edges of the plurality of tapes are aligned, wherein the alignment standard is: the maximum distance between the end edges of two adjacent parallel tapes along the tape length direction is less than 0.5 cm; if they are not aligned, adjustments are made.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a cross-sectional view of an exemplary roller device with a straightening layer wound around it according to the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of the electrode roll joint of the present invention.

[0018] Figure label: 100. Roller device; 110. Roller body; 120. Straight-pull layer; 200. First end of electrode sheet; 300. Last end of electrode sheet; 400. Belt. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. "Multiple" means two or more. Throughout this document, the terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0023] Secondary batteries, due to their high energy density, long cycle life, and environmental friendliness, have been widely used in new energy vehicles, energy storage systems, and portable electronic devices. Electrodes are the core component of secondary batteries. During the continuous production process of electrode rolling and slitting, strip breakage is the most common and serious production failure. Sudden breakage of the electrode under tension can force the production line to stop, reduce production efficiency, increase production costs, and affect product quality. Therefore, it is necessary to improve the strip breakage problem that occurs in processes such as rolling and slitting.

[0024] Therefore, the present invention provides an electrode processing method, comprising the following steps: A roller pressing mechanism is used to roll the coated electrode sheet; wherein, the roller pressing mechanism includes an upper roller and a lower roller, and a roller gap is provided between the upper roller and the lower roller; Before rolling, the bending cylinder pressure of the upper and lower rolls is adjusted so that the bending cylinder pressure of the lower roll is less than that of the upper roll.

[0025] When subjected to working pressure, the upper and lower rolls are prone to deflection deformation, resulting in a roll gap that is wider in the middle and narrower on both sides, leading to uneven compaction of the electrode sheet in the width direction. Related technologies utilize bending cylinders on the upper and lower rolls to apply a reverse bending force, precisely compensating for deflection deviations and ensuring a consistent roll gap along the width direction. Typically, the bending cylinder pressures of the upper and lower rolls are set to be the same. However, because the bending cylinder pressure of the lower roll is in the opposite direction to the rolling force on the electrode sheet, there is a partial cancellation between the bending cylinder pressure of the lower roll and the rolling force on the electrode sheet. Therefore, the preset bending cylinder pressure of the lower roll is actually partially "wasted." This portion not only fails to adjust the deformation of the lower roll but can also cause some areas of the electrode sheet to break due to excessive force (this phenomenon does not occur with the upper roll). Based on this discovery, the present invention reduces the bending cylinder pressure of the lower roll, making the bending cylinder pressure of the lower roll less than that of the upper roll. This not only accurately compensates for the deflection deviation of the upper and lower rolls, but also reduces the occurrence of strip breakage, thereby improving production efficiency, reducing production costs, and improving product quality.

[0026] In some embodiments, the upper and lower rolls each include a bending cylinder. After the coated electrode sheet passes through the roll gap between the upper and lower rolls, it is compacted by the rolls. The upper and lower rolls are prone to deflection deformation under working pressure. By applying a reverse bending force to the rolls through the bending cylinder, the deflection deviation can be precisely compensated, ensuring that the roll gap remains consistent along its width. The method for adjusting the bending cylinder pressure is well known to those skilled in the art and will not be described in detail here.

[0027] In some embodiments, the bending cylinder pressure of the upper roll is denoted as p1, and the bending cylinder pressure of the lower roll is denoted as p2, where 1 < p1 / p2 ≤ 2. Controlling p1 / p2 to be less than or equal to 2 can effectively reduce the occurrence of strip breakage, while preventing the lower roll deflection deformation from being unable to recover due to p2 being too small. Controlling p1 / p2 to be greater than 1 can accurately compensate for the deflection deviation between the upper and lower rolls, preventing strip breakage due to p2 being too large.

[0028] In some specific embodiments, the value of p1 / p2 can be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.

[0029] In some embodiments, 5 MPa ≤ p1 ≤ 10 MPa. This can accurately compensate for the deflection deviation of the upper and lower rolls, reduce the occurrence of strip breakage, effectively avoid the deflection deviation not being compensated due to p1 being too small, and at the same time avoid the strip breakage caused by p being too large.

[0030] In some specific embodiments, p1 can be 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa or 10 MPa.

[0031] In some embodiments, before rolling, it is checked whether the upper and lower rolls are parallel. If they are not parallel, they are adjusted. During adjustment, it is ensured that the rotation axes of the upper and lower rolls are parallel. As a result, the roll gap between the upper and lower rolls remains uniform, making the electrode sheet compaction uniform in the width direction and improving the uniformity of the electrode sheet thickness.

[0032] In some embodiments, the coated electrode includes a coated area and an uncoated area. The coated area includes a coating layer. The coating layer is disposed on the current collector. Typically, the coating layer includes an active material layer, such as a negative electrode active material layer or a positive electrode active material layer. The coating layer may also include other functional coatings, which can be configured according to actual needs and will not be described in detail here.

[0033] In some embodiments, before rolling, the method further includes passing the coated electrode sheet through a roller-passing device. The roller-passing device can provide guidance for the electrode sheet and prevent it from going astray.

[0034] In some embodiments, corresponding to the uncoated area, n layers of straightening layers 120 are wound on the roller body 110 of the roller device 100, such as... Figure 1As shown. By winding a straightening layer on a portion of the roller body of the roller-passing device, the radial diameter of this portion can be increased. During the passing through the roller, the coated area of ​​the electrode contacts the roller body, and the uncoated area of ​​the electrode contacts the straightening layer. The straightening layer plays a supporting role for the uncoated area, thereby improving the flatness of the electrode after passing through the roller, reducing electrode wrinkles, and thus reducing the breakage phenomenon caused by electrode wrinkles during rolling.

[0035] The number of straightening layers, n, is determined by the thickness of the coating and the thickness of a single straightening layer. Specifically, n can be 1-20 layers, such as 1, 5, 10, 15, or 20. In some embodiments, the ratio of the total thickness of the n straightening layers to the thickness of the coating is (1-1.2):1. Thus, the straightening layers provide excellent support for the uncoated areas of the electrode, reducing electrode wrinkles. Specifically, the ratio of the total thickness of the n straightening layers to the thickness of the coating can be 1:1, 1.1:1, or 1.2:1.

[0036] In some embodiments, the material of the straightening layer includes Teflon. Using Teflon tape wrapped around the rollers of the roller-passing device provides excellent support for the uncoated areas of the electrode sheet. Furthermore, the Teflon tape has good adhesion, is not easily detached, and is stable and reusable.

[0037] In some embodiments, such as Figure 1 As shown, n straightening layers 120 are stacked sequentially. The maximum distance L between the same-side edges of two adjacent straightening layers along the axial direction of the roller body is less than 0.5 mm. Therefore, the edges of adjacent layers are aligned as much as possible. Compared to stepped stacking, this invention provides better support for the uncoated area of ​​the electrode sheet, effectively reducing wrinkles after passing through the roller and thus reducing electrode breakage. Preferably, the edges of two adjacent straightening layers are flush, such as... Figure 1 As shown in the dashed box. This provides better support for the uncoated areas of the electrode, resulting in better wrinkle removal.

[0038] In some specific embodiments, the maximum distance L between the same-side edges of two adjacent straightening layers along the axial direction of the roller body can be 0, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm.

[0039] In some embodiments, before rolling, the method further includes unwinding the electrode sheet to be rolled. Before unwinding, the first end 200 of the electrode sheet to be rolled is aligned with the last end 300 of the electrode sheet in the previous rolling process, and multiple strips of adhesive tape 400 are attached, such as... Figure 2As shown. Typically, coated electrode sheets are prepared in coil form after the winding process. Before subsequent rolling processes, the electrode sheets need to be unwound. For continuous production, the next electrode coil needs to be connected to the previous one before the previous coil is unwound. This requires aligning the beginning of the next electrode sheet to be rolled with the end of the previous one being rolled, and applying multiple strips of tape at the joint. This achieves continuous production. In this article, "electrode coil" refers to the coil formed after the coated electrode sheets have undergone the winding process.

[0040] In some specific embodiments, such as Figure 2 As shown, multiple tapes are arranged in parallel. The maximum distance D between the end edges of two adjacent parallel tapes along the tape's length is less than 0.5 cm. "End edge of the tape" refers to the end edge of the tape along its length. "End edges of two adjacent parallel tapes" refers to the end edges of two adjacent parallel tapes located on the same side. Arranging multiple tapes in parallel is more conducive to tape alignment. Because the tape has a certain thickness, if the tapes are not evenly spaced and the distance between their end edges is too large, it will cause uneven stress on the electrode at the end edges of the tapes, easily leading to tape breakage. Controlling the alignment of the multiple tapes helps reduce tape breakage. As a specific example, the maximum distance D between the end edges of two adjacent parallel tapes along the tape's length is 0, 0.1 cm, 0.2 cm, 0.3 cm, 0.4 cm, or 0.5 cm.

[0041] In some embodiments, the multiple tapes are of the same length. This makes it easier to align and adhere the multiple tapes.

[0042] In some embodiments, the lengths of the multiple adhesive tapes can be 5cm-10cm, for example, 5cm, 6cm, 7cm, 8cm, 9cm, or 10cm. This allows the first end of the next electrode to be rolled to be effectively bonded to the last end of the previous electrode being rolled, preventing the tape from being too short and resulting in weak bonding, while also avoiding waste due to excessively long tapes.

[0043] In some embodiments, after applying the tape and before unwinding, the method further includes: checking whether the end edges of the plurality of tapes are aligned. The alignment standard is that the maximum distance D between the end edges of two adjacent parallel tapes along the tape length direction is less than 0.5 cm. If they are not aligned, adjustments are made until they are aligned. After applying the tape and before unwinding, the tape alignment is checked again. If there is a large difference in the end edges, adjustments are needed to ensure that the tapes are aligned before unwinding and rolling, thereby reducing tape breakage.

[0044] In some embodiments, the coated electrode is obtained by applying a coating slurry to the current collector. Before coating, it is necessary to check whether the areal density of the foil used for the current collector is lower than a threshold. If the areal density of the foil is found to be lower than the threshold before coating, the foil is used for coating. After the coating length exceeds a predetermined length (e.g., 30 meters), the areal density is checked again. If the areal density is still lower than the threshold, the coating of the foil needs to be terminated. By controlling the foil material, the probability of tape breakage during the rolling process after coating is reduced.

[0045] In some embodiments, the electrode sheets, after being rolled by the rolling mechanism, pass through multiple rollers to a slitting mechanism for slitting. Afterwards, the slitted electrode sheets are wound up.

[0046] The electrode processing method of the present invention can reduce product defects and improve the pass rate; reduce rework and scrap, and reduce production costs; reduce downtime and rework, and improve production efficiency.

[0047] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0048] Test method for tape breakage defect rate in positive electrode rolling process: Roll forming failure refers to the breakage of the electrode sheet during the rolling process. The defect rate of the positive electrode sheet due to breakage during the rolling process is calculated as follows: (Weight of positive electrode sheets with breakage during rolling process ÷ Weight of positive electrode sheets in one battery ÷ Output per shift) × 10 6 During the rolling process, when the positive electrode sheet breaks, some of it falls to the ground and comes into contact with it. This portion of the positive electrode sheet needs to be cut off, and the weight of this cut-off portion is the weight of the positive electrode sheet in the interrupted rolling process. The shift's output refers to the number of batteries produced per unit of time.

[0049] The defect rate of the positive electrode sheet during the rolling process can be divided into the following four levels: defect rate ≤1300ppm is excellent; 1300ppm < defect rate ≤2000ppm is good; 2000ppm < defect rate ≤2800ppm is medium; defect rate >2800ppm is poor.

[0050] Example 1 (1) After the coated positive electrode sheet is unwound, it passes through the roller and enters the rolling position, where it is rolled by the rolling mechanism.

[0051] (a) Before the electrode is rolled, adjust the upper and lower rollers so that they are parallel.

[0052] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 10 MPa, p2 is 5 MPa, and p1 / p2 = 2.

[0053] (c) Before the electrode is rolled, 10 straightening layers are wound on the roller in front of the rolling mechanism. The material of the straightening layer is Teflon. The 10 straightening layers are stacked. The ratio of the total thickness of the 10 straightening layers to the thickness of the coating on the electrode is 1:1. The maximum distance L between the same side edges of two adjacent straightening layers along the axial direction of the roller body is 0, that is, the edges of two adjacent straightening layers are flush.

[0054] (2) Before the previous electrode is unwound, the first end of the next electrode to be rolled is joined with the tail end of the previous electrode being rolled and multiple tapes are pasted at the joint. The multiple tapes are arranged in parallel, and the maximum distance D between the end edges of two adjacent parallel tapes along the tape length direction is 0. The lengths of the multiple tapes are the same and are all 5cm.

[0055] (3) After applying the tape at the joint and before unwinding, check whether the end edges of the multiple tapes are aligned. The alignment standard is: the maximum distance between the end edges of two adjacent parallel tapes along the length of the tape should be less than 0.5cm. If they are not aligned, adjust them until they are aligned. After alignment, continue unwinding for subsequent rolling.

[0056] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0057] Example 2 (1) Same as step (1) in Example 1.

[0058] (a) Same as step (a) in Example 1.

[0059] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 10 MPa, p2 is 6.7 MPa, and p1 / p2 = 1.5.

[0060] (c) Same as step (c) in Example 1.

[0061] (2) Same as step (2) in Example 1.

[0062] (3) Same as step (3) in Example 1.

[0063] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0064] Example 3 (1) Same as step (1) in Example 1.

[0065] (a) Same as step (a) in Example 1.

[0066] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 10 MPa, p2 is 9 MPa, and p1 / p2 = 1.1.

[0067] (c) Same as step (c) in Example 1.

[0068] (2) Same as step (2) in Example 1.

[0069] (3) Same as step (3) in Example 1.

[0070] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0071] Example 4 (1) Same as step (1) in Example 1.

[0072] (a) Same as step (a) in Example 1.

[0073] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 5 MPa, p2 is 2.5 MPa, and p1 / p2 = 2.

[0074] (c) Same as step (c) in Example 1.

[0075] (2) Same as step (2) in Example 1.

[0076] (3) Same as step (3) in Example 1.

[0077] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0078] Example 5 (1) Same as step (1) in Example 1.

[0079] (a) Same as step (a) in Example 1.

[0080] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 12 MPa, p2 is 6 MPa, and p1 / p2 = 2.

[0081] (c) Same as step (c) in Example 1.

[0082] (2) Same as step (2) in Example 1.

[0083] (3) Same as step (3) in Example 1.

[0084] Testing revealed that the breakage rate of the positive electrode sheet during the rolling process was good.

[0085] Example 6 (1) Same as step (1) in Example 1.

[0086] (a) Same as step (a) in Example 1.

[0087] (b) Same as step (b) in Example 1.

[0088] (c) Before the electrode is rolled, 12 straightening layers are wound on the roller in front of the rolling mechanism. The material of the straightening layer is Teflon. The 12 straightening layers are stacked. The ratio of the total thickness of the 12 straightening layers to the thickness of the coating on the electrode is 1:1.2. The maximum distance L between the same side edges of two adjacent straightening layers along the axial direction of the roller body is 0, that is, the edges of two adjacent straightening layers are flush.

[0089] (2) Same as step (2) in Example 1.

[0090] (3) Same as step (3) in Example 1.

[0091] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0092] Example 7 (1) Same as step (1) in Example 1.

[0093] (a) Same as step (a) in Example 1.

[0094] (b) Same as step (b) in Example 1.

[0095] (c) Before the electrode is rolled, eight straightening layers are wound on the roller in front of the rolling mechanism. The material of the straightening layers is Teflon. The eight straightening layers are stacked. The ratio of the total thickness of the eight straightening layers to the thickness of the coating on the electrode is 1:0.8. The maximum distance L between the same side edges of two adjacent straightening layers along the axial direction of the roller body is 0, that is, the edges of two adjacent straightening layers are flush.

[0096] (2) Same as step (2) in Example 1.

[0097] (3) Same as step (3) in Example 1.

[0098] Testing revealed that the breakage rate of the positive electrode sheet during the rolling process was good.

[0099] Example 8 (1) Same as step (1) in Example 1.

[0100] (a) Same as step (a) in Example 1.

[0101] (b) Same as step (b) in Example 1.

[0102] (c) Before the electrode is rolled, 14 straightening layers are wound on the roller in front of the rolling mechanism. The material of the straightening layer is Teflon. The 14 straightening layers are stacked. The ratio of the total thickness of the 14 straightening layers to the thickness of the coating on the electrode is 1:1.4. The maximum distance L between the same side edges of two adjacent straightening layers along the axial direction of the roller body is 0, that is, the edges of two adjacent straightening layers are flush.

[0103] (2) Same as step (2) in Example 1.

[0104] (3) Same as step (3) in Example 1.

[0105] Testing revealed that the breakage rate of the positive electrode sheet during the rolling process was good.

[0106] Example 9 (1) Same as step (1) in Example 1.

[0107] (a) Same as step (a) in Example 1.

[0108] (b) Same as step (b) in Example 1.

[0109] (c) Before the electrode is rolled, 10 straightening layers are wound on the roller in front of the rolling mechanism. The material of the straightening layer is Teflon. The 10 straightening layers are stacked. The ratio of the total thickness of the 10 straightening layers to the thickness of the coating on the electrode is 1:1. The maximum distance L between the same side edges of two adjacent straightening layers along the axial direction of the roller body is 1mm.

[0110] (2) Same as step (2) in Example 1.

[0111] (3) Same as step (3) in Example 1.

[0112] According to the test, the defect rate of broken strips of positive electrode sheets in the rolling process is medium.

[0113] Example 10 (1) Same as step (1) in Example 1.

[0114] (a) Same as step (a) in Example 1.

[0115] (b) Same as step (b) in Example 1.

[0116] (c) Same as step (c) in Example 1.

[0117] (2) Before the previous electrode is unwound, the first end of the next electrode to be rolled is joined with the tail end of the previous electrode being rolled, and multiple tapes are pasted at the joint. The multiple tapes are arranged in parallel, and the maximum distance D between the end edges of two adjacent parallel tapes along the tape length direction is 0.5cm. The lengths of the multiple tapes are the same and are all 5cm.

[0118] (3) Same as step (3) in Example 1.

[0119] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0120] Example 11 (1) Same as step (1) in Example 1.

[0121] (a) Same as step (a) in Example 1.

[0122] (b) Same as step (b) in Example 1.

[0123] (c) Same as step (c) in Example 1.

[0124] (2) Before the previous electrode is unwound, the first end of the next electrode to be rolled is joined with the tail end of the previous electrode being rolled and multiple tapes are pasted at the joint. The multiple tapes are arranged in parallel, and the maximum distance D between the end edges of two adjacent parallel tapes along the tape length direction is 1cm. The lengths of the multiple tapes are the same and are all 5cm.

[0125] (3) Same as step (3) in Example 1.

[0126] According to the test, the defect rate of broken strips of positive electrode sheets in the rolling process is medium.

[0127] Example 12 (1) Same as step (1) in Example 1.

[0128] (a) Same as step (a) in Example 1.

[0129] (b) Same as step (b) in Example 1.

[0130] (c) Same as step (c) in Example 1.

[0131] (2) Before the previous electrode is unwound, the first end of the next electrode to be rolled is joined with the tail end of the previous electrode being rolled, and multiple tapes are pasted at the joint. The multiple tapes are arranged in parallel, and the maximum distance D between the end edges of two adjacent parallel tapes along the tape length direction is 0. The lengths of the multiple tapes are the same and all are 10cm.

[0132] (3) Same as step (3) in Example 1.

[0133] Tests showed that the breakage rate of the positive electrode sheet in the rolling process was excellent.

[0134] Comparative Example 1 (1) Same as step (1) in Example 1.

[0135] (a) Same as step (a) in Example 1.

[0136] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 10 MPa, p2 is 10 MPa, and p1 / p2=1.

[0137] (c) Same as step (c) in Example 1.

[0138] (2) Same as step (2) in Example 1.

[0139] (3) Same as step (3) in Example 1.

[0140] Testing revealed that the breakage rate of the positive electrode sheet was poor during the rolling process.

[0141] Comparative Example 2 (1) Same as step (1) in Example 1.

[0142] (a) Same as step (a) in Example 1.

[0143] (b) Before the electrode is rolled, adjust the bending cylinder pressure of the upper roll and the bending cylinder pressure of the lower roll so that the bending cylinder pressure p2 of the lower roll is less than the bending cylinder pressure p1 of the upper roll, where p1 is 10 MPa, p2 is 12 MPa, and p1 / p2 = 0.8.

[0144] (c) Same as step (c) in Example 1.

[0145] (2) Same as step (2) in Example 1.

[0146] (3) Same as step (3) in Example 1.

[0147] Testing revealed that the breakage rate of the positive electrode sheet was poor during the rolling process.

[0148] Results and Discussion: Comparing Example 1 and Comparative Examples 1-2, it can be seen that adjusting the bending cylinder pressure of the upper and lower rolls so that the bending cylinder pressure of the lower roll is less than that of the upper roll helps to reduce the occurrence of strip breakage.

[0149] Comparing Examples 1 and 2-3, it can be seen that as the bending cylinder pressure of the lower roll increases, the strip breakage phenomenon becomes more obvious.

[0150] Comparing Examples 1 and 5, it can be seen that the bending cylinder pressure p1 of the upper roll should not be too high, otherwise it will increase the occurrence of strip breakage.

[0151] Comparing Examples 1 and 6-8, it can be seen that the ratio of the total thickness of the n-layer straightening layer to the thickness of the coating affects the wrinkle removal effect, and thus affects the occurrence of strip breakage.

[0152] Comparing Examples 1 and 9, it can be seen that the maximum distance L between the same-side edges of two adjacent straightening layers along the axial direction of the roller body needs to be controlled within a reasonable range; if it is too large, it will increase the phenomenon of belt breakage.

[0153] Comparing Examples 1 and 10-11, it can be seen that the maximum distance D between the end edges of two adjacent parallel tapes along the tape length direction needs to be controlled within a reasonable range; if it is too large, it will increase the tape breakage phenomenon.

[0154] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0155] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for processing electrode sheets, characterized in that, Includes the following steps: A roller pressing mechanism is used to roll the coated electrode sheet; wherein, the roller pressing mechanism includes an upper roller and a lower roller, and a roller gap is provided between the upper roller and the lower roller; Before rolling, the bending cylinder pressure of the upper and lower rolls is adjusted so that the bending cylinder pressure of the lower roll is less than that of the upper roll.

2. The electrode processing method according to claim 1, characterized in that, The bending cylinder pressure of the upper roll is denoted as p1, and the bending cylinder pressure of the lower roll is denoted as p2, where 1 < p1 / p2 ≤ 2.

3. The electrode processing method according to claim 2, characterized in that, 5 MPa ≤ p1 ≤ 10 MPa.

4. The electrode processing method according to claim 1, characterized in that, Before rolling, check whether the upper and lower rolls are set in parallel. If they are not parallel, adjust them.

5. The electrode processing method according to claim 1, characterized in that, The coated electrode sheet includes a coated area and an uncoated area, and the coated area includes a coating layer; Before rolling, the method further includes: passing the coated electrode sheet through a roller passing device; corresponding to the uncoated area, n straightening layers are wound on the roller body of the roller passing device; the ratio of the total thickness of the n straightening layers to the thickness of the coating is (1-1.2):

1.

6. The electrode processing method according to claim 5, characterized in that, The material of the straightening layer includes Teflon.

7. The electrode processing method according to claim 5, characterized in that, The n straightening layers are stacked sequentially, and the maximum distance between the edges of two adjacent straightening layers on the same side along the axial direction of the roller body is less than 0.5 mm; Preferably, the edges of two adjacent straightening layers are flush.

8. The electrode processing method according to claim 1, characterized in that, Before rolling, the method further includes: unwinding the electrode sheet to be rolled; before unwinding, aligning the first end of the electrode sheet to be rolled with the last end of the electrode sheet in the previous rolling and attaching multiple adhesive tapes; the multiple adhesive tapes are arranged in parallel; the maximum distance between the end edges of two adjacent parallel adhesive tapes along the length of the tapes is less than 0.5 cm.

9. The electrode processing method according to claim 8, characterized in that, The multiple tapes are of the same length; The lengths of the multiple tapes range from 5cm to 10cm.

10. The electrode processing method according to claim 8, characterized in that, After the tape is applied and before unwinding, the method further includes: checking whether the end edges of the multiple tapes are aligned. The alignment standard is that the maximum distance between the end edges of two adjacent parallel tapes along the tape length direction is less than 0.5 cm; if they are not aligned, adjustments are made.

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