Pole piece thickness control method

Abstract

According to the pole piece thickness control method, a dynamic regulation and control mechanism is constructed by detecting the thickness of a pole piece in real time and calculating the thickness deviation in real time, once the thickness deviation is larger than a preset threshold value, a system can give out an instruction in real time, a rolling mechanism is driven to adjust a roll gap, and it is ensured that the rolling thickness of the follow-up pole piece is stable and consistent; the requirements on the thickness consistency and stability of the pole piece are met, so that the product defects are reduced, and the product qualification rate is improved; reworking and scrapping are reduced, the production cost is reduced, meanwhile, the downtime is shortened, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a method for controlling electrode thickness. Background Technology

[0002] Secondary batteries achieve repeated charging and discharging by allowing lithium or sodium ions to move between the positive and negative electrodes. They offer advantages such as economy and environmental friendliness, and are widely used in consumer electronics, electric vehicles, and other fields. A secondary battery consists of a positive electrode, a separator, and a negative electrode. The rolling thickness of the electrode affects the compaction density, consistency, and stability of the product, thus requiring strict control over the rolling thickness. However, current electrode processing technologies often fail to meet the requirements for thickness consistency and stability. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide an electrode thickness control method that enables stable and consistent electrode thickness after roll forming, effectively improving product yield.

[0004] Specifically, the present invention provides a method for controlling electrode thickness, comprising the following steps: (1) Multiple rolling mechanisms are used to roll the electrode sheet multiple times in sequence; (2) The electrode sheet after being rolled multiple times is subjected to real-time thickness detection to obtain the actual thickness value; (3) Calculate the absolute value of the difference between the actual thickness value and the preset target thickness value to obtain the thickness deviation; (4) If the thickness deviation is less than or equal to the preset threshold, a qualified electrode sheet is obtained, and the roll gap parameters are determined; (5) If the thickness deviation is greater than the preset threshold, the roll gap of the rolling mechanism is adjusted in real time according to the thickness deviation, and the thickness deviation of the electrode after multiple rolling is checked again to see if it is less than or equal to the preset threshold. If not, this step is repeated until the electrode thickness is qualified.

[0005] This invention establishes a dynamic control mechanism by real-time detection of electrode thickness and real-time calculation of thickness deviation. Once the thickness deviation exceeds a preset threshold, the system will issue a real-time command to drive the rolling mechanism to adjust the roller gap, ensuring that the subsequent rolling thickness of the electrode is stable and consistent, meeting the requirements for electrode thickness consistency and stability, thereby reducing product defects, improving product qualification rate, reducing rework and scrap, lowering production costs, and reducing downtime, thus improving production efficiency.

[0006] According to some embodiments of the present invention, the process of sequentially rolling an electrode sheet multiple times using multiple rolling mechanisms includes: sequentially rolling the electrode sheet using n rolling mechanisms for a first rolling, a second rolling, ..., an nth rolling, where n is an integer from 2 to 5; and defining the adjustment amount of the roll gap of the n rolling mechanisms as d1, d2, ..., dn. n The unit is μm; real-time adjustment of the roll gap of the roller pressing mechanism includes any one of the following situations: (1) The roll gap of the n roller pressing mechanisms is adjusted in real time, d1≥d2≥……≥d n ; (2) The roll gap of part of the roller pressing mechanism is adjusted in real time, from d1 to d i Both are 0, d i+1 ≥d i+2 ≥……≥d n , where i is an integer from 1 to n-1.

[0007] According to some embodiments of the present invention, for the case (1), the method satisfies one of the following conditions: (1) n is 2, d1:d2 = (6-8) : (2-4); (2) n is 3, d1:d2:d3 = (4-6) : (2-4) : (1-3).

[0008] According to some embodiments of the present invention, for the case (2), i is n-1.

[0009] According to some embodiments of the present invention, the preset threshold is in the range of 0~0.5μm and is not 0.

[0010] According to some embodiments of the present invention, the preset rolling pressure amounts for the first rolling, the second rolling, ..., the nth rolling are sequentially defined as h1, h2, ..., h... n The unit is μm, where h1, h2, ..., h n They decrease sequentially, and h1, h2, ..., h n The sum is equal to the difference between the initial thickness of the electrode sheet before rolling and the preset target thickness value.

[0011] According to some embodiments of the present invention, the method satisfies one of the following conditions: (1) n is 2, h1:h2 = (6-8):(2-4); (2) n is 3, h1:h2:h3 = (4-6):(2-4):(1-3).

[0012] According to some embodiments of the present invention, the actual thickness value is fed back to the thickness closed-loop device, which calculates the thickness deviation and drives the roller pressing mechanism to adjust the roller gap.

[0013] According to some embodiments of the present invention, the rolls of the rolling mechanism are cleaned at predetermined time intervals, the predetermined time intervals being 4h-8h.

[0014] According to some embodiments of the present invention, a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the rolling mechanism is maintained at a preset bending value; the preset pressure of the bending cylinder is 10 bar - 50 bar.

[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. Detailed Implementation

[0016] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0017] 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.

[0018] 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.

[0019] Secondary batteries achieve repeated charging and discharging by allowing lithium or sodium ions to move between the positive and negative electrodes. They offer advantages such as economy and environmental friendliness, and are widely used in consumer electronics, electric vehicles, and other fields. A secondary battery consists of a positive electrode, a separator, and a negative electrode. The rolling thickness of the electrode affects the compaction density, consistency, and stability of the product, thus requiring strict control over the rolling thickness. However, current electrode processing technologies often fail to meet the requirements for thickness consistency and stability.

[0020] To address the aforementioned issues, this invention proposes a method for controlling electrode thickness. This method ensures that the thickness of the electrode after roll forming is stable and consistent, effectively improving the product qualification rate.

[0021] Specifically, the present invention provides a method for controlling electrode thickness, comprising the following steps: (1) Multiple rolling mechanisms are used to roll the electrode sheet multiple times in sequence; (2) The electrode sheet after being rolled multiple times is subjected to real-time thickness detection to obtain the actual thickness value; (3) Calculate the absolute value of the difference between the actual thickness value and the preset target thickness value to obtain the thickness deviation; (4) If the thickness deviation is less than or equal to the preset threshold, a qualified electrode sheet is obtained, and the roll gap parameters are determined; (5) If the thickness deviation is greater than the preset threshold, the roll gap of the rolling mechanism is adjusted in real time according to the thickness deviation, and the thickness deviation of the electrode after multiple rolling is checked again to see if it is less than or equal to the preset threshold. If not, this step is repeated until the electrode thickness is qualified.

[0022] This invention establishes a dynamic control mechanism by real-time detection of electrode thickness and real-time calculation of thickness deviation. Once the thickness deviation exceeds a preset threshold, the system will issue a real-time command to drive the rolling mechanism to adjust the roller gap, ensuring that the subsequent rolling thickness of the electrode is stable and consistent, meeting the requirements for electrode thickness consistency and stability, thereby reducing product defects, improving product qualification rate, reducing rework and scrap, lowering production costs, and reducing downtime, thus improving production efficiency.

[0023] In this invention, "actual thickness value" refers to the thickness value obtained by measuring the thickness of the electrode after the last rolling process, which involves multiple rolling processes.

[0024] In this invention, the rolling mechanism includes upper and lower rollers, and the "roll gap" refers to the minimum clearance between the upper and lower rollers. The electrode sheet to be rolled passes through the roll gap, thereby being rolled.

[0025] In this invention, the "preset target thickness value" can be formulated according to the actual rolling thickness specifications of the machine and actual needs.

[0026] In this invention, if the thickness deviation is less than or equal to a preset threshold, a qualified electrode sheet is obtained, and the roll gap parameters are determined. The determined roll gap parameters can be used in the subsequent rolling of the electrode sheet.

[0027] In this invention, the statement "re-detecting the thickness deviation of the electrode sheet after multiple roll pressings" should be understood as the subsequent unrolled electrode sheet being rolled after the adjusted roll gap, and then the thickness deviation of the resulting electrode sheet is detected.

[0028] In some embodiments, a thickness tester can be used to detect the thickness of the electrode sheet after multiple rolling processes in real time to obtain the actual thickness value.

[0029] In some embodiments, using multiple rolling mechanisms to sequentially roll the electrode sheet multiple times includes: using n rolling mechanisms to sequentially perform a first rolling, a second rolling, ..., an nth rolling, where n is an integer from 2 to 5. As a specific example, n can be 2, 3, 4, or 5. Considering economic and time costs, n is preferably 2 or 3. This achieves the desired electrode thickness while protecting the electrode structure and ensuring stable electrode performance. Too few rolling cycles, such as a single rolling, can easily lead to irreversible damage to the electrode sheet due to high pressure, degrading its performance. Too many rolling cycles result in increased costs, longer rolling times, and decreased production efficiency.

[0030] In some embodiments, the adjustment amounts of the roll gaps of the n roll pressing mechanisms are sequentially defined as d1, d2, ..., d... n The unit is μm. The adjustment amount refers to the absolute value of the difference between the adjusted roll gap size and the initial roll gap size. The method for adjusting the roll gap of the rolling mechanism is well known to those skilled in the art. For example, if the target thickness of the electrode is 160 μm, and the actual thickness of the electrode after multiple rolling processes is 163 μm, there is a thickness deviation of 3 μm. Assuming a preset threshold of 0.5 μm, since the thickness deviation is greater than the preset threshold, the roll gap needs to be adjusted. For example, only the roll gap size of the last rolling mechanism (i.e., the nth rolling mechanism) is adjusted, with an adjustment amount of 3 μm, while the roll gap sizes of other rolling mechanisms remain unchanged. If the thickness deviation is greater than 5 μm, the roll gap sizes of multiple rolling mechanisms can be adjusted using a "coarse adjustment followed by fine adjustment" method, d1, d2, ..., d... n The sum equals the thickness deviation. For example, when the thickness deviation is 23μm, the gap between the rolls of the last two rolling mechanisms can be adjusted, with the adjustment amounts being 20μm and 3μm respectively.

[0031] Electrode thickness control typically involves adjusting the roller gap (mechanical manual adjustment or servo motor electric adjustment) to control the electrode thickness, prioritizing a "coarse adjustment followed by fine adjustment" approach. First, coarsely adjust to the target thickness ±0.02mm; then finely adjust using pressure or a thickness closed-loop device (for every 0.5MPa increase in pressure, the thickness decreases by approximately 0.003-0.005mm, requiring equipment calibration).

[0032] Real-time adjustment of the roll gap of the roller pressing mechanism includes any one of the following situations: (1) The roll gap of the n roller pressing mechanisms is adjusted in real time, d1≥d2≥……≥d n ; (2) The roll gap of part of the roller pressing mechanism is adjusted in real time, from d1 to d i Both are 0, d i+1 ≥d i+2 ≥……≥dn , where i is an integer from 1 to n-1.

[0033] Case (1) involves adjusting the gap between all rollers in the roller pressing mechanism and following the principle of coarse adjustment followed by fine adjustment. This step-by-step adjustment is used to eliminate the thickness deviation of the electrode sheet, thereby obtaining an electrode sheet with consistent and stable thickness.

[0034] Scenario (2) involves adjusting the roll gap of some of the rolling mechanisms. When there are many rolling mechanisms or to save time, the roll gap of only some of the rolling mechanisms can be adjusted, usually the roll gap of the rolling mechanisms that are later in the sequence. This can improve production efficiency and save time costs.

[0035] In some specific embodiments, for scenario (1), the method satisfies one of the following conditions: (1) n is 2, d1:d2 = (6-8) : (2-4); (2) n is 3, d1:d2:d3 = (4-6) : (2-4) : (1-3).

[0036] The roller gap adjustment follows the principle of coarse adjustment first and then fine adjustment. Optimizing the proportional relationship between the roller gap adjustment amounts of different roller pressing mechanisms is beneficial to further improve the consistency and stability of electrode thickness.

[0037] As a specific example, when n is 2, d1:d2 can be 6:4, 6.5:3.5, 7:3, 7.5:2.5 or 8:2.

[0038] As a specific example, when n is 3, d1:d2:d3 can be 4:3:3, 5:3:2, 5:4:1 or 6:3:1.

[0039] In some specific embodiments, for case (2), i is n-1. In other words, only the roll gap of the last rolling mechanism is adjusted, thereby quickly eliminating thickness deviations, improving production efficiency, and saving time.

[0040] In some embodiments, the preset threshold is in the range of 0~0.5μm and is not 0. The smaller the preset threshold, the higher the thickness consistency and stability of the qualified electrode, but the preset threshold should not be set too small.

[0041] As a specific example, the preset threshold can be 0.1μm, 0.2μm, 0.3μm, 0.4μm or 0.5μm.

[0042] In some embodiments, the preset rolling pressure amounts of the first rolling, the second rolling, ..., the nth rolling are sequentially defined as h1, h2, ..., h... nThe unit is μm, where h1, h2, ..., h n They decrease sequentially, and h1, h2, ..., h n The sum equals the difference between the initial thickness of the electrode before rolling and the preset target thickness. Rolling amount refers to the difference between the electrode thickness before and after rolling. Multiple rolling operations on the electrode help protect its structural integrity and ensure stable performance. The design of the rolling amount for the rolling mechanism follows a principle of starting with a large amount and gradually decreasing it to ensure stable electrode thickness and performance.

[0043] In some embodiments, the method satisfies one of the following conditions: (1) n is 2, h1:h2 = (6-8):(2-4); (2) n is 3, h1:h2:h3 = (4-6):(2-4):(1-3).

[0044] Optimize the ratio between the preset rolling pressure amounts of the rolling mechanism to ensure the stability of the electrode structure during large-amplitude rolling and to achieve consistent electrode thickness during small-amplitude fine rolling. This avoids damage to the electrode structure caused by excessive single rolling amplitude and achieves the target electrode thickness with as few rolling cycles as possible, thereby improving production efficiency.

[0045] As a specific example, when n is 2, two rolling mechanisms are used to roll the electrode sheet twice in sequence, and h1:h2 can be 6:4, 6.5:3.5, 7.5:2.5 or 8:2.

[0046] As a specific example, when n is 3, three rolling mechanisms are used to roll the electrode sheet three times in sequence, and h1:h2:h3 can be 4:3:3, 5:3:2, 5:4:1 or 6:3:1.

[0047] In some embodiments, the actual thickness value is fed back to the thickness closed-loop device, which calculates the thickness deviation and drives the roller pressing mechanism to adjust the roller gap.

[0048] A thickness closed-loop system typically consists of a thickness sensor, a controller, and an actuator. The thickness sensor monitors the thickness of the target object in real time, converting physical thickness changes into processable signals such as electrical signals, and feeds this information back to the controller. The controller compares the received actual thickness signal with the preset target thickness and calculates the thickness deviation. Then, based on a preset control algorithm, such as a PID control algorithm, the controller outputs a corresponding control signal to the actuator. The actuator adjusts the roll gap according to the control signal, thereby achieving precise thickness control. Thus, the thickness closed-loop device can detect and adjust the electrode thickness in real time.

[0049] In some embodiments, the rolls of the rolling mechanism are cleaned at predetermined time intervals, which are 4-8 hours. During rolling, the coatings on the electrode surface (such as ternary materials for the positive electrode and graphite for the negative electrode) may adhere to the roll surface. Residual coatings or impurities can accumulate on the roll surface, causing localized narrowing of the roll gap. This can result in thinner electrodes at corresponding locations, disrupting the thickness consistency of the entire roll, and thickness fluctuations directly affect the battery's capacity and rate performance. Therefore, it is necessary to clean the roll surface regularly. As a specific example, the predetermined time interval can be 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.

[0050] In some embodiments, a bending cylinder is used to adjust the bending degree of the rolls in the rolling mechanism, maintaining the bending degree of the rolls at a preset bending value; the preset pressure of the bending cylinder is 10 bar - 50 bar. When the rolls are pressing the electrode sheet, they are subjected to a radial "rolling force," which causes the rolls to naturally bulge towards the center. This natural bending results in a roll gap that is wider in the middle and narrower at the edges, ultimately making the electrode sheet thicker in the middle and thinner at the edges, severely affecting the uniformity of the electrode sheet thickness. The bending cylinder can counteract this natural bending by applying a counterforce, maintaining the bending degree of the rolls at the preset bending value. As a specific example, the preset pressure of the bending cylinder is 10 bar, 20 bar, 30 bar, 40 bar, or 50 bar. The bending degree of the rolls can be selected according to actual production needs, as is well known to those skilled in the art.

[0051] In some embodiments, before multiple rolling processes, the electrode thickness control method further includes: unwinding and correcting the electrode roll to be rolled on the unwinding mechanism. This ensures that the electrode to be rolled remains centered and aligned before entering the rolls, preventing subsequent rolling quality defects and production interruptions caused by electrode misalignment.

[0052] In some embodiments, after real-time adjustment of the roll gap of the rolling mechanism, the electrode thickness control method further includes: using a CCD camera to perform process correction on the rolled electrode. This accurately corrects the positional deviation of the rolled electrode, ensuring precise alignment with subsequent slitting, winding, and other processes, while also linking with quality inspection to prevent the accumulation of deviations that could lead to batch defects.

[0053] In some embodiments, after the process correction, the electrode thickness control method further includes: slitting and winding the rolled electrode. This process transforms the wide electrode into narrow strips that meet the requirements of cell winding, and winds them into regular rolls for subsequent storage, handling, and precise docking with the winding process.

[0054] 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.

[0055] Example 1 (1) Unwind and correct the negative electrode sheet roll to be rolled on the unwinding mechanism. The initial thickness of the negative electrode sheet is 300 μm.

[0056] (2) The first roller pressing mechanism is used to perform the first roller pressing on the electrode. The preset roller pressing amount is h1, h1 = 91μm.

[0057] (3) The electrode is rolled a second time using a second rolling mechanism. The preset rolling amount is h2, h2 = 49 μm, and h1:h2 = 6.5:3.5. After the second rolling, the target thickness of the electrode is 160 μm.

[0058] (4) The thickness of the electrode sheet after the second rolling is detected in real time using a thickness tester, and the measured actual thickness value (163 μm) is fed back to the thickness closed-loop device. The thickness closed-loop device calculates the absolute value of the difference between the actual thickness value and the target thickness value (160 μm) online to obtain the thickness deviation (3 μm); the thickness deviation is compared with the preset threshold (0.5 μm), and the result is that the thickness deviation is greater than the preset threshold. The thickness closed-loop device adjusts the roll gap of the second rolling mechanism in real time according to the thickness deviation and the preset threshold (the adjustment amount of the roll gap is equal to the thickness deviation) until the thickness deviation is less than the preset threshold.

[0059] (5) Use CCD to correct the polarity of the electrode.

[0060] (6) After the electrode sheets are rolled, they are slit and then wound up.

[0061] During the rolling process, the rolls of the first and second rolling mechanisms are cleaned every 6 hours. Specifically, the rolls are cleaned every 3 hours with a lint-free cloth soaked in alcohol.

[0062] In this embodiment, a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 30 bar.

[0063] CPK = min[(USL-X) / 3σ, (X-LSL) / 3σ]; where USL represents the upper limit of the specification, LSL represents the lower limit of the specification, X represents the sample mean, and σ represents the sample standard deviation.

[0064] The Cpk value is a standard for measuring the thickness of the electrode sheet during roll forming. The higher the Cpk value, the better the consistency and stability of the electrode sheet thickness. The calculated Cpk value in this embodiment is 1.37.

[0065] Example 2 The electrode was processed according to the method described in Example 1, except that in step 2, h1 = 84 μm, and in step 3, h2 = 56 μm, and h1:h2 = 6:4.

[0066] In this embodiment, the Cpk value is 1.38.

[0067] Example 3 The electrode was processed according to the method described in Example 1, except that in step 2, h1 = 112 μm, and in step 3, h2 = 28 μm, and h1:h2 = 8:2.

[0068] In this embodiment, the Cpk value is 1.39.

[0069] Example 4 (1) Unwind and correct the negative electrode sheet roll to be rolled on the unwinding mechanism. The initial thickness of the negative electrode sheet is 300 μm.

[0070] (2) The electrode is rolled for the first time using the first rolling mechanism. The preset rolling amount is h1, h1 = 70μm.

[0071] (3) Use the second rolling mechanism to roll the electrode a second time. The preset rolling amount is h2, h2 = 42μm.

[0072] (4) The electrode is rolled for the third time using the third rolling mechanism. The preset rolling amount is h3, h3 = 28μm, h1:h2:h3 = 5:3:2. After the third rolling, the target thickness of the electrode is 160μm.

[0073] (5) The thickness of the electrode sheet after the third rolling is detected in real time using a thickness tester, and the measured actual thickness value (163 μm) is fed back to the thickness closed-loop device. The thickness closed-loop device calculates the absolute value of the difference between the actual thickness value and the target thickness value (160 μm) online to obtain the thickness deviation (3 μm); the thickness deviation is compared with the preset threshold (0.5 μm), and the result is that the thickness deviation is greater than the preset threshold. The thickness closed-loop device adjusts the roll gap of the third rolling mechanism in real time according to the thickness deviation and the preset threshold (the adjustment amount of the roll gap is equal to the thickness deviation) until the thickness deviation is less than the preset threshold.

[0074] (6) Use CCD to correct the polarity of the electrode.

[0075] (7) After the electrode sheets are rolled, they are slit and then wound up.

[0076] In this embodiment, a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 30 bar.

[0077] In this embodiment, the Cpk value is 1.69.

[0078] Example 5 The electrode processing is carried out according to the method described in Example 4, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 5:3:2, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0079] In this embodiment, the Cpk value is 1.77.

[0080] Example 6 The electrode processing is carried out according to the method described in Example 4, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 6:3:1, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0081] In this embodiment, the Cpk value is 1.72.

[0082] Example 7 The electrode processing is carried out according to the method described in Example 4, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 5:4:1, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0083] In this embodiment, the Cpk value is 1.83.

[0084] Example 8 The electrode processing is carried out according to the method described in Example 4, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 3:4:5, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0085] The Cpk value in this embodiment is 1.59.

[0086] Example 9 The electrode processing is carried out according to the method described in Example 4, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 7:2:1, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0087] In this embodiment, the Cpk value is 1.58.

[0088] Example 10 (1) Unwind and correct the negative electrode sheet roll to be rolled on the unwinding mechanism. The initial thickness of the negative electrode sheet is 300 μm.

[0089] (2) The electrode is rolled for the first time using the first rolling mechanism. The preset rolling amount is h1, h1 = 70μm.

[0090] (3) Use the second rolling mechanism to roll the electrode a second time. The preset rolling amount is h2, h2 = 42μm.

[0091] (4) The electrode is rolled for the third time using the third rolling mechanism. The preset rolling amount is h3, h3 = 28μm, h1:h2:h3 = 5:3:2. After the third rolling, the target thickness of the electrode is 160μm.

[0092] (5) The thickness of the electrode sheet after the third rolling is detected in real time using a thickness tester, and the measured actual thickness value (180 μm) is fed back to the thickness closed-loop device. The thickness closed-loop device calculates the absolute value of the difference between the actual thickness value and the target thickness value (160 μm) online to obtain the thickness deviation (20 μm); the thickness deviation is compared with the preset threshold (0.5 μm), and the result is that the thickness deviation is greater than the preset threshold. The thickness closed-loop device adjusts the roll gap of the third rolling mechanism in real time according to the thickness deviation and the preset threshold (the adjustment amount of the roll gap is equal to the thickness deviation) until the thickness deviation is less than the preset threshold.

[0093] (6) Use CCD to correct the polarity of the electrode.

[0094] (7) After the electrode sheets are rolled, they are slit and then wound up.

[0095] In this embodiment, a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 30 bar.

[0096] In this embodiment, the Cpk value is 1.68.

[0097] Example 11 The electrode processing is performed according to the method described in Example 10, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 5:3:2, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0098] In this embodiment, the Cpk value is 1.76.

[0099] Example 12 The electrode processing is performed according to the method described in Example 10, except that in step 5, the roll gaps of the first, second, and third rolling mechanisms are adjusted in real time. The adjustment amounts of the roll gaps of the three rolling mechanisms are d1, d2, and d3, respectively, where d1:d2:d3 = 6:3:1, and the sum of d1, d2, and d3 is equal to the thickness deviation.

[0100] In this embodiment, the Cpk value is 1.71.

[0101] Example 13 The electrode processing was carried out according to the method described in Example 1, except that the rolls of the first and second rolling mechanisms were cleaned every 4 hours. Specifically, the rolls were cleaned every 3 hours with a lint-free cloth soaked in alcohol.

[0102] In this embodiment, the Cpk value is 1.38.

[0103] Example 14 The electrode processing was carried out according to the method described in Example 1, except that the rolls of the first and second rolling mechanisms were cleaned every 8 hours. Specifically, the rolls were cleaned every 3 hours with a lint-free cloth soaked in alcohol.

[0104] In this embodiment, the Cpk value is 1.36.

[0105] Example 15 The electrode processing was carried out according to the method described in Example 1, except that the rolls of the first and second rolling mechanisms were cleaned every 10 hours. Specifically, the rolls were cleaned every 3 hours with a lint-free cloth soaked in alcohol.

[0106] In this embodiment, the Cpk value is 1.34.

[0107] Example 16 The electrode processing is performed according to the method described in Example 1, except that a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 10 bar.

[0108] In this embodiment, the Cpk value is 1.35.

[0109] Example 17 The electrode processing is performed according to the method described in Example 1, except that a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 50 bar.

[0110] In this embodiment, the Cpk value is 1.46.

[0111] Example 18 The electrode processing is performed according to the method described in Example 1, except that a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 5 bar.

[0112] In this embodiment, the Cpk value is 1.23.

[0113] Example 19 The electrode processing is performed according to the method described in Example 1, except that a bending cylinder is used to adjust the bending degree of the rolls of the rolling mechanism so that the bending degree of the rolls of the first and second rolling mechanisms is maintained at a preset bending value; the preset pressure of the bending cylinder is 70 bar.

[0114] In this embodiment, the Cpk value is 1.28.

[0115] Comparative Example 1 The electrode processing is performed according to the method described in Example 1, except that in step 4, the electrode after the second rolling is offline thickened using a thickness tester. The absolute value of the difference between the measured actual thickness value (163 μm) and the target thickness value (160 μm) is calculated to obtain the thickness deviation (3 μm). This thickness deviation is compared with a preset threshold (0.5 μm), and the result shows that the thickness deviation is greater than the preset threshold. Based on the thickness deviation and the preset threshold, the roll gap of the second rolling mechanism is adjusted by 3 μm to make the thickness deviation less than the preset threshold.

[0116] The Cpk value for this comparative example is 1.17.

[0117] Results and Discussion: By comparing Example 1 and Comparative Example 1, it can be seen that the present invention constructs a dynamic control mechanism by real-time detection of electrode thickness and real-time calculation of thickness deviation. Once the thickness deviation exceeds a preset threshold, the system will issue a command in real time to drive the rolling mechanism to adjust the roller gap, ensuring that the subsequent rolling thickness of the electrode is stable and consistent, meeting the requirements for electrode thickness consistency and stability, thereby reducing product defects, improving product qualification rate, reducing rework and scrap, reducing production costs, and reducing downtime, thereby improving production efficiency.

[0118] Comparing Examples 1 and 4, it can be seen that increasing the number of rolling cycles is beneficial for improving the consistency and stability of the electrode thickness. However, it also increases time costs; therefore, the number of rolling cycles should not be excessive.

[0119] By comparing Examples 4 and Examples 5-7, it can be seen that adjusting the roll gaps of multiple rolling mechanisms simultaneously is more beneficial to improving the consistency and stability of the electrode sheets than adjusting only the roll gap of the last rolling mechanism.

[0120] By comparing Examples 5-7 and Examples 8-9, it can be seen that when adjusting the roll gap of multiple rolling mechanisms, the proportional relationship between the adjustment amounts affects the consistency and stability of the electrode sheets. The preferred proportion between the adjustment amounts of the roll gap of different rolling mechanisms is within the range of this invention.

[0121] By comparing Examples 13-15, it can be seen that the cleaning time interval of the rolls affects the consistency and stability of the electrode sheets.

[0122] By comparing Examples 16-17 and Examples 18-19, it can be seen that by controlling the preset pressure of the bending cylinder, the bending degree of the rollers of the rolling mechanism is kept at the preset bending value, which is more conducive to improving the consistency and stability of the electrode thickness.

[0123] 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.

[0124] 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 of controlling the thickness of an electrode sheet, characterized by, The method comprises the following steps: (1) using multiple rolling mechanisms to roll the pole piece multiple times in sequence; (2) detecting the thickness of the pole piece after multiple rolling in real time to obtain an actual thickness value; (3) calculating the absolute value of the difference between the actual thickness value and a preset target thickness value to obtain a thickness deviation; (4) if the thickness deviation is less than or equal to a preset threshold, a qualified pole piece is obtained, and the roll gap parameter is determined; (5) if the thickness deviation is greater than the preset threshold, the roll gap of the rolling mechanism is adjusted in real time according to the thickness deviation, and the thickness deviation of the pole piece after multiple rolling is detected again to determine whether it is less than or equal to the preset threshold, if not, repeat the step until the pole piece thickness is qualified.

2. The pole piece thickness control method according to claim 1, characterized by, Using multiple rolling mechanisms to roll the pole piece multiple times in sequence includes: using n rolling mechanisms to roll the pole piece first, second, …, n times, n is an integer between 2 and 5; The adjustment amounts of the roll gaps of the n roller pressing mechanisms are defined sequentially as d1, d2, ..., d... n The unit is μm; The roll gap of the rolling mechanism is adjusted in real time, including any one of the following cases: (1) Real-time adjustment is made to the roll gap of the n roller mechanisms, d1≥d2≥...≥dn n ; (2) Real-time adjustment is made to the roll gap of part of the roller mechanism, d1 to d i are all 0, d i+1 ≥ d i+2 ≥ … ≥ d n , i is an integer from 1 to n-1.

3. The pole piece thickness control method according to claim 2, characterized by, For case (1), one of the following conditions is met: (1) n is 2, d1:d2 = (6-8) : (2-4); (2) n is 3, d1:d2:d3 = (4-6) : (2-4) : (1-3).

4. The pole piece thickness control method according to claim 2, characterized by, For case (2), i is n-1.

5. The pole piece thickness control method of claim 1, wherein The preset threshold is in the range of 0-0.5μm and is not 0.

6. The pole piece thickness control method according to claim 2, characterized by, The preset rolling amounts of the first rolling, the second rolling, …, the nth rolling are defined as h1, h2, …, hn in sequence, with a unit of μm, wherein h1, h2, …, hn are controlled to decrease in sequence, and the sum of h1, h2, …, hn is equal to the difference between the initial thickness of the pole piece before rolling and the preset target thickness value. n , units of μm, wherein h1, h2, …, hn are controlled to decrease in sequence, and the sum of h1, h2, …, hn is equal to the difference between the initial thickness of the pole piece before rolling and the preset target thickness value. n , units of μm, wherein h1, h2, …, hn are controlled to decrease in sequence, and the sum of h1, h2, …, hn is equal to the difference between the initial thickness of the pole piece before rolling and the preset target thickness value. n ​ 7. The pole piece thickness control method according to claim 6, characterized by, One of the following conditions is met: (1) n is 2, h1:h2 = (6-8):(2-4); (2) n is 3, h1:h2:h3 = (4-6):(2-4):(1-3).

8. The pole piece thickness control method of claim 1, wherein The actual thickness value is fed back to the thickness closed loop device, and the thickness deviation is calculated by the thickness closed loop device and the rolling mechanism is driven to adjust the roll gap.

9. The pole piece thickness control method of claim 1, wherein The roll of the rolling mechanism is cleaned at a predetermined time interval, and the predetermined time interval is 4h-8h.

10. The pole piece thickness control method according to claim 1, characterized by, The bending degree of the roll of the rolling mechanism is adjusted using a bending cylinder, and the bending degree of the roll of the rolling mechanism is kept at a preset bending value; the preset pressure of the bending cylinder is 10 bar-50 bar.