A method for processing abnormal pieces of lithium battery coating density

Abstract

The present application relates to the technical field of lithium ion battery manufacturing, and particularly relates to a lithium battery coating density abnormal piece processing method, comprising the following steps: S100, performing full-width density detection on the coated pole piece, determining the pole piece with actual surface density deviating from the design range as an abnormal pole piece, and respectively obtaining the actual surface density values of the A surface and the B surface of the abnormal pole piece; S200, according to the actual surface density values, matching and combining the abnormal pole piece with the abnormal polarity pole piece to obtain a matched pole piece group containing positive pole pieces and negative pole pieces. The present application realizes accurate verification of the single surface capacity margin by online calibration and gradient grading of the coating surface density abnormal pole piece, establishing a forced space bonding rule of positive pole and negative pole A surface corresponding to A surface and B surface corresponding to B surface, and introducing a winding geometric deformation compensation factor in a single surface N / P ratio accounting model, so that the safety bottom line of the anti-lithium precipitation of the battery cell is not reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, specifically to a method for processing lithium battery wafers with abnormal coating density. Background Technology

[0002] In the mass production of cylindrical lithium-ion batteries, electrode coating is a critical process that determines the electrochemical performance and safety of the cell. Due to the influence of multiple process factors, such as fluctuations in slurry rheological properties, changes in the mechanical state of the coating die, and variations in conveyor belt tension, it is difficult to completely avoid deviations in the actual coating areal density from the design tolerance range. Currently, the industry typically scraps double-sided coated electrodes whose areal density exceeds the internal control standard. This results in significant losses of both positive and negative electrode active materials and current collector materials, increasing manufacturing costs.

[0003] Attempting to achieve material reuse by conventionally pairing positive electrode sheets with high areal density with negative electrode sheets with high areal density in order to achieve macroscopic capacity matching presents serious safety hazards in actual winding processes. The core issue lies in the inability to guarantee the safety of matching the microscopic single-sided capacity within the cell. Specifically, in the winding state, the double-coated electrodes of a cylindrical cell undergo geometric deformation under bending stress. The concave side close to the winding needle experiences increased areal density due to pressure, while the convex side away from the winding needle experiences decreased areal density due to stretching. Conventional electrode matching methods only perform addition and subtraction calculations based on the overall average areal density of the electrodes, without establishing strict physical spatial correspondence rules for the A and B sides of the positive and negative electrodes, and without incorporating the dynamic deformation variables of areal density caused by winding curvature into the calculation model of the single-sided N / P ratio (the ratio of the single-sided capacity of the negative electrode to the single-sided capacity of the positive electrode). This can lead to a situation where, within a specific coil of the winding core, the actual number of lithium ions released from one side of the positive electrode exceeds the lithium intercalation capacity of the corresponding side of the negative electrode. This results in a localized N / P ratio on one side falling below the safety limit, subsequently causing lithium plating during charging and creating potential safety hazards such as internal short circuits and thermal runaway. Furthermore, in highly automated production lines, even if the electrode matching is theoretically completed, without a hardware interlocking error-proofing mechanism covering information binding and the underlying control of the winding equipment, operators are highly susceptible to misalignment during material loading and unwinding, resulting in the failure of theoretical calculations and hindering the safe and compliant transfer of electrodes with abnormal areal density on the mass production line. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a method for processing lithium battery coating density abnormal electrode sheets, including the following steps: S100, performing full-width surface density detection on the coated electrode sheets, determining the electrode sheets whose actual surface density deviates from the design range as abnormal electrode sheets, and obtaining the actual surface density values ​​of the A side and B side of the abnormal electrode sheets respectively. S200. Based on the actual areal density value, the abnormal electrode sheet is matched and combined with the electrode sheet of opposite polarity to obtain a paired electrode sheet group containing a positive electrode sheet and a negative electrode sheet; wherein, when matching and combining, the principle that the actual areal density deviation direction of the positive electrode sheet is consistent with the actual areal density deviation direction of the negative electrode sheet is followed, and the A surface of the positive electrode sheet is forcibly set to correspond to the A surface of the negative electrode sheet, and the B surface of the positive electrode sheet corresponds to the B surface of the negative electrode sheet; S300. Introduce a curvature compensation factor related to winding deformation, calculate the actual single-sided N / P ratio of the paired electrode group on the corresponding surface, and verify that the calculated actual single-sided N / P ratio between the A surface of the positive electrode and the A surface of the negative electrode, and between the B surface of the positive electrode and the B surface of the negative electrode, are all greater than or equal to the preset safety N / P ratio lower limit. S400: Generate error prevention marks for the verified paired electrode groups, identify the error prevention marks during the winding process, and perform the winding operation according to the physical spatial relationship of A-side corresponding to A-side and B-side corresponding to B-side.

[0005] Furthermore, the step of performing full-width areal density testing on the coated electrode and obtaining the actual areal density values ​​of side A and side B of the abnormal electrode specifically includes: The online thickness measurement system of X-rays located at the winding end of the coating equipment is used to perform real-time full-width scanning of the electrode sheet with continuous tape, and the surface density distribution matrix of the A and B surfaces of the electrode sheet in the continuous physical coordinate system is extracted. Data analysis is performed based on the areal density distribution matrix to identify abnormal regions where the areal density deviates from the design range, and the actual areal density value corresponding to the abnormal region is extracted.

[0006] Furthermore, after determining that the electrode with an actual areal density deviating from the design range is an abnormal electrode, before executing step S200, the method further includes a step of gradient classification of the abnormal electrode: Calculate the percentage deviation between the actual areal density value and the preset coating design median; If the deviation percentage exceeds the preset internal control tolerance range, it is confirmed as an abnormal electrode, and the abnormal electrode and its corresponding deviation percentage are recorded in the abnormal electrode pairing database. In the abnormal electrode pairing database, based on the magnitude of the deviation percentage, the abnormal electrodes are divided into several high areal density gradient levels and several low areal density gradient levels. When the abnormal electrode and its corresponding deviation percentage are entered into the abnormal electrode pairing database, the batch number, roll number and coordinate information of the abnormal electrode and the location of the abnormality are recorded and bound simultaneously to establish a digital traceability file for the abnormal electrode.

[0007] Furthermore, the step of matching and combining the abnormal electrode with the electrode of opposite polarity based on the actual areal density value specifically includes: When the positive electrode is determined to be an abnormal electrode with a high areal density gradient, a negative electrode belonging to the same high areal density gradient level is retrieved and matched from the abnormal electrode pairing database. When the positive electrode is determined to be an abnormal electrode with a low areal density gradient, a negative electrode belonging to the same low areal density gradient level is retrieved and matched from the abnormal electrode pairing database. The difference in surface density deviation between the positive electrode and the negative electrode on their corresponding surfaces is controlled within a preset tolerance range.

[0008] Furthermore, when matching and combining the abnormal electrode with an electrode of opposite polarity, the method also includes a step of verifying the consistency of the electrode distribution along the length direction: Extract the local surface density curves of the positive electrode and the negative electrode along the electrode strip direction; By comparing the local surface density deviations of the positive electrode and the negative electrode under the same positioning coordinates, it is ensured that the single-sided surface density fluctuation trend of the positive electrode and the negative electrode is consistent throughout the entire electrode length range.

[0009] Furthermore, the step of forcibly setting the A side of the positive electrode to correspond to the A side of the negative electrode, and the B side of the positive electrode to correspond to the B side of the negative electrode, further includes: On the edges or preset blank areas of the positive and negative electrode sheets after the matching and combination are completed, surface bonding marks with physical direction differentiation are applied to indicate the physical bonding and winding direction of the positive electrode sheet A side and the negative electrode sheet A side, and the positive electrode sheet B side and the negative electrode sheet B side.

[0010] Furthermore, in the step of calculating the actual single-sided N / P ratio of the paired electrode groups on corresponding surfaces, the actual single-sided N / P ratio is calculated according to the following formulas when the positive electrode A surface is paired with the negative electrode A surface, and when the positive electrode B surface is paired with the negative electrode B surface. : ; in, This represents the actual surface density of the corresponding surface of the negative electrode plate. The specific capacity of the negative electrode active material, This is the geometric deformation compensation factor for the negative electrode sheet under a preset winding curvature. This represents the actual surface density of the corresponding surface of the positive electrode plate. The specific capacity of the positive electrode active material, This is the geometric deformation compensation factor for the positive electrode sheet under a preset winding curvature.

[0011] Furthermore, the geometric deformation compensation factor and The determination process includes: Based on the curvature radius distribution of the inner and outer rings of the cylindrical cell in the winding state, the elastic modulus of the current collector and coating material, and the winding tension, an electrode winding deformation model is established. The microstructure density variation trend of the electrode under concave compression and convex tension is analyzed by the electrode winding deformation model. The geometric deformation compensation factor corresponding to a specific winding position is derived by pre-experimental measurement or simulation calculation. After the step of verifying that the actual single-sided N / P ratio after verification is greater than or equal to the preset safe N / P ratio lower limit, the logical branch step of unqualified unbinding and re-matching is also included: If the calculation shows that either the actual single-sided N / P ratio of the positive electrode and the negative electrode on side A or side B is less than the lower limit of the safe N / P ratio, then the current paired electrode group is determined to have failed the verification. Cancel the association of the current paired electrode group, and release the electrodes that have not passed the verification back to the abnormal electrode pairing database. After adjusting the gradient level matching threshold, re-execute the matching combination and calculation.

[0012] Furthermore, the step of generating a fault-proofing mark for the verified paired electrode group specifically includes: The roll number information, gradient level data, and forced A-side to A-side and B-side to B-side bonding instructions of the verified positive electrode and negative electrode are uniquely bound together. Based on the bound data, an electronic error-proofing code containing the association relationship is generated as the error-proofing identifier, and the electronic error-proofing code is uploaded and distributed to the Manufacturing Execution System (MES) to establish a directional winding process file for the paired electrode group.

[0013] Furthermore, the step of identifying the error-proofing mark during the winding process and performing the winding operation according to the physical spatial relationship of A-side corresponding to A-side and B-side corresponding to B-side is implemented based on error-proofing interlocking control logic, specifically including: During the material loading stage of the winding process, the electronic error prevention code on the positive electrode and the negative electrode is read using the identification component located on the unwinding side of the winding equipment. The winding equipment retrieves the orientation winding process file corresponding to the electronic error-proof code through the manufacturing execution system (MES) and verifies and compares it with the actual physical orientation of the current electrode sheet. If the comparison result indicates that the current material on the machine does not conform to the bonding instruction that surface A corresponds to surface A and surface B corresponds to surface B, then the hardware interlock of the winding equipment is triggered and a fault-prevention alarm signal is issued. If the comparison result indicates that the verification is successful, the winding device is unlocked to perform the subsequent winding operation; When performing the winding operation according to the physical spatial relationship of surface A corresponding to surface A and surface B corresponding to surface B: By coordinating the unwinding direction and belt path of the positive electrode and the negative electrode on their respective unwinding shafts in the winding equipment, the A-side of the positive electrode and the A-side of the negative electrode are in a relatively aligned physical position before entering the winding needle area. During the winding process, the diaphragm is sandwiched between the relatively matching positive electrode A surface and the negative electrode A surface, so that the actual single-sided N / P ratio of any corresponding layer in the wound core after the winding is kept above the safe N / P ratio lower limit.

[0014] Beneficial effects: This invention establishes a forced spatial bonding rule for positive and negative electrodes by online calibration and gradient classification of electrodes with abnormal areal density, with the A-side corresponding to the A-side and the B-side corresponding to the B-side. Furthermore, it introduces a winding geometric deformation compensation factor into the single-sided N / P ratio calculation model, achieving accurate verification of single-sided capacity margin. This allows for the transformation of electrodes with abnormal areal density into qualified cells without compromising the cell's lithium plating resistance safety baseline, effectively improving electrode material utilization and reducing manufacturing costs. Simultaneously, by combining the error-proof interlocking control logic of the manufacturing execution system and winding equipment, electronic error-proof codes and surface bonding marks constrain the physical unwinding orientation, eliminating the risk of human mismatch at the automated equipment level. This ensures the accurate execution of theoretical matching parameters during the physical manufacturing process, demonstrating good industrial applicability and mass production stability. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention. Figure 2 This is the anti-misinterlocking winding control logic diagram of the present invention; Figure 3 This is a logic diagram of electrode data calibration and gradient grading in this invention; Figure 4 This is a flowchart of the precise matching and curvature compensation closed-loop calculation process of the present invention; Figure 5 This is a diagram of the automated interlocking architecture of the MES and winding equipment of the present invention. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings: Example

[0017] like Figures 1-5 As shown, a method for processing lithium battery wafers with abnormal coating density includes the following steps: S100. Perform full-width surface density testing on the coated electrode sheets. Electrodes with actual surface density deviating from the design range are identified as abnormal electrode sheets. Obtain the actual surface density values ​​of the A and B sides of the abnormal electrode sheets respectively. S200. Based on the actual areal density value, the abnormal electrode sheet and the electrode sheet of opposite polarity are matched and combined to obtain a paired electrode sheet group containing positive electrode sheet and negative electrode sheet; wherein, when matching and combining, the principle that the actual areal density deviation direction of the positive electrode sheet is consistent with the actual areal density deviation direction of the negative electrode sheet is followed, and the A side of the positive electrode sheet is forcibly set to correspond to the A side of the negative electrode sheet, and the B side of the positive electrode sheet is set to correspond to the B side of the negative electrode sheet; S300. Introduce a curvature compensation factor related to winding deformation, calculate the actual single-sided N / P ratio of the paired electrode group on the corresponding surface, and verify that the actual single-sided N / P ratio between the A surface of the positive electrode and the A surface of the negative electrode, and between the B surface of the positive electrode and the B surface of the negative electrode, are all greater than or equal to the preset safety N / P ratio lower limit. S400: Generate error-proofing marks for verified paired electrode groups, identify the error-proofing marks during the winding process, and perform the winding operation according to the physical spatial relationship of A-side corresponding to A-side and B-side corresponding to B-side.

[0018] Furthermore, the specific implementation process of step S100 is as follows: In the coating process, taking the production of NCM811 positive electrode sheets and artificial graphite negative electrode sheets as an example, the positive electrode current collector is selected with a thickness of... The aluminum foil is designed with a single-sided coating surface density of median value. The internal control tolerance range is set as follows: % (i.e., the acceptable areal density range is) The negative electrode current collector is selected with a thickness of [missing information]. The copper foil is designed with a single-sided coating surface density of median value. The internal control tolerance range is set as follows: % (i.e., the acceptable areal density range is) ).

[0019] A dual-channel online X-ray thickness measurement system is installed at the roller conveyor at the exit end of the double-sided coating machine oven. The online X-ray thickness measurement system includes a high-precision probe and a photoelectric encoder. The probe performs reciprocating scanning along the electrode width direction (TD direction, i.e., transverse direction), with the scanning frequency set to [missing information]. An electric encoder is installed at the ends of the unwinding and rewinding rollers to acquire pulse signals along the belt travel direction (MD direction, i.e., longitudinal direction) of the electrode in real time, thereby locking the physical length coordinates of the electrode. The probe scanning trajectory is combined with the longitudinal pulse signal to construct a two-dimensional grid physical coordinate system on the electrode surface, with the grid cell size set to... .

[0020] As the electrode passes through the X-ray scanning area, the X-ray penetrates the electrode and is attenuated by the receiver. The system converts the attenuated signal into a mass surface density signal using a pre-established absorption coefficient absorbance model, and calculates the positions of the positive and negative electrodes at the coordinate points. Place Actual surface density value of the surface as well as Actual surface density value of the surface This generates the full-area surface density distribution matrix. : ; Real-time computing unit reads distribution matrix The data in the figure are used to calculate the electrode plates according to the following formulas. Face to face Percentage deviation of surface density of each mesh cell and : ; ; In the formula, This represents the median design areal density of the corresponding electrode. When the continuous length exceeds... Within the electrode region, or Exceeding the range At that time, the system automatically identifies the coiled electrode as an abnormal electrode and extracts the abnormal region. Average actual surface density value Compared with the average actual surface density value of surface B .

[0021] While defining abnormal electrodes, the system calls the gradient classification module to divide the abnormal electrodes into four independent gradient levels based on the percentage of deviation. The specific classification and control standards are as follows: Higher gradient I level: ; Higher gradient II level: ; Lower gradient I level: ; Lower gradient II level: .

[0022] When the absolute value of the deviation percentage is greater than If a material is determined to be severely out of tolerance and cannot be repaired, the system will directly trigger a rejection command, and it will not be included in subsequent pairings.

[0023] After the gradient grading is completed, the host computer data communication module will transmit the production batch number, roll number, coating process number, and starting coordinates of the abnormal area of ​​the abnormal electrode sheet. and termination coordinates Actual surface density value of surface A Actual surface density value of surface B A-side deviation percentage B-side deviation percentage The corresponding gradient gear combinations are encapsulated into structured data packets and written into the abnormal electrode pairing database established by the Manufacturing Execution System (MES) through an internal communication protocol.

[0024] In a specific production batch, the basic calibration data of the positive and negative abnormal electrode sheets obtained through online detection and calibration in step S100 are shown in Table 1:

[0025] After the data packets in Table 1 are written, the MES system automatically generates exclusive digital traceability files for each roll of electrode C-003, C-007, A-012, and A-015, and sets the "pending matching" logical status flag for use in step S200.

[0026] Furthermore, the specific implementation process of step S200 is as follows: After the structured data packet is written into the abnormal electrode pairing database of the Manufacturing Execution System (MES) in step S100, the electrode intelligent matching module of the MES system automatically retrieves the electrode records with the status marked "to be matched" and performs the matching and combination of abnormal electrodes.

[0027] The matching and combination process follows the principle of "high-to-high, low-to-low" matching with the same-direction deviation, while limiting the difference in surface density deviation between the positive and negative electrode sheets on the same side. The MES matching module first searches for negative electrode sheets of the same gradient level as the positive electrode sheet of the same grade. For the positive electrode sheet C-003, which belongs to "high gradient II", the matching module selects the negative electrode sheet A-012, which also belongs to "high gradient II", from the database; for the positive electrode sheet C-007, which belongs to "low gradient I", the matching module selects the negative electrode sheet A-015, which also belongs to "low gradient I".

[0028] After selecting candidate electrodes, the processing unit extracts the percentage deviation between the positive and negative electrodes on surfaces A and B, and calculates the difference in deviation amplitude on surface A using the following formula. Difference between surface deviation and amplitude : ; ; The preset deviation amplitude difference tolerance control threshold is set to For the positive electrode With negative electrode The combination surface deviation amplitude difference , surface deviation amplitude difference All of them meet the difference tolerance threshold requirements.

[0029] After the gear position and tolerance difference verification are passed, the matching module further performs a longitudinal local areal density fluctuation consistency check along the electrode travel direction (MD direction). Because fluctuations in oven airflow or die fine-tuning during electrode coating may cause periodic areal density fluctuations along the length of the electrode, the calculation unit retrieves the positive and negative electrodes at intervals along the travel direction. Sampling local surface density sequence and The Pearson correlation coefficient between the two can be calculated using the following formula. : ; Set the correlation coefficient control threshold as Calculations show that the correlation coefficient of the surface density fluctuations between the positive electrode C-003 and the negative electrode A-012 in the MD direction is... A value of 0.92 indicates that the local areal density fluctuation trends of the two electrode rolls along the length direction are highly consistent, allowing for pairing.

[0030] After verification, the MES system binds the successfully matched positive and negative electrode sheets into a dedicated paired electrode set and sends a pairing instruction to the automated calibration unit of the slitting or rewinding equipment. During the roller transfer process, the UV high-precision inkjet printer located in the blank area of ​​the electrode sheet (i.e., the edge of the current collector without coating) receives the MES instruction and applies physical orientation calibration and direction indication marks on the edge of the electrode sheet.

[0031] For the positive electrode A-side and the negative electrode A-side, at intervals on the same side edge of the current collector blank area... Blue continuous positioning lines and the "AA" data matrix code are printed on the inkjet printer. For the positive B side and the negative B side, red continuous positioning lines and the "BB" data matrix code are printed on the opposite edges of the blank area of ​​the current collector. Through this inkjet marking, the spatial fit relationship between the positive A side and the negative A side, and between the positive B side and the negative B side is forcibly locked at the physical entity level, providing a unique spatial orientation basis for the subsequent single-sided capacity calculation of S300 and the physical unwinding of S400.

[0032] The specific data for the screening and matching of paired electrode groups and deviation verification are shown in Table 2:

[0033] After completing step S200, the physical orientation markings of the paired electrode groups P-01 and P-02 are applied. The MES system updates its logical status to "pairing complete / pending calculation" and automatically transmits the relevant parameters to step S300 to perform precise calculation of the single-sided N / P ratio.

[0034] Furthermore, the specific implementation process of step S300 is as follows: After physical orientation calibration and assembly, the tolerance calculation module of the Manufacturing Execution System (MES) performs single-sided capacity matching verification on the paired electrode groups. In the wound state, the cylindrical cell experiences microscopic geometric deformation of the electrode substrate and coating under bending stress. Specifically, the concave surface of the electrode close to the winding needle is under compression, the spacing between coating particles shortens, and the local areal density increases slightly; the convex surface of the electrode away from the winding needle is under tension, the coating elastically elongates with the current collector, and the local areal density decreases slightly. Because step S200 forcibly locks the physical assembly relationship between the positive electrode A surface and the negative electrode A surface, and between the positive electrode B surface and the negative electrode B surface, this fixed relative spatial position necessitates the introduction of a dynamic geometric deformation compensation factor in capacity calculation to eliminate the risk of lithium plating misjudgment caused by the constant areal density calculation model.

[0035] The system's processing unit first retrieves the electrode winding deformation model and inputs the winding process parameters for the current batch of cells. Taking an 18650 cylindrical cell as an example, the input parameters include: outer diameter of the winding needle 3.5mm, electrode tape tension 0.4N, and elastic modulus of the positive electrode aluminum foil. Elastic modulus of negative electrode copper foil and the Poisson's ratio of the coating material .

[0036] The deformation model calculates the average radius of curvature of the electrode from the inner to the outer ring through integration, and outputs the geometric deformation compensation factor for each corresponding surface. Under the specific winding direction setting in this embodiment, when the positive electrode A surface and the negative electrode A surface are in contact, the positive electrode A surface is located on the outer convex surface of the winding, and the negative electrode A surface is located on the inner concave surface of the winding; when the positive electrode B surface and the negative electrode B surface are in contact, the positive electrode B surface is located on the inner concave surface of the winding, and the negative electrode B surface is located on the outer convex surface of the winding. Through cross-validation of model simulation and previous experimental measurements, the extracted geometric deformation compensation factors are as follows: positive electrode convex surface... Positive concave surface Negative electrode convex surface concave surface of negative electrode .

[0037] After extracting the compensation factor, the MES system retrieves the preset specific capacity data of the electrode active material (in this embodiment, the specific capacity of the positive electrode NCM811). Negative electrode artificial graphite capacity The following formulas are used to calculate the actual single-sided N / P ratio when face A is paired with face B and when face B is paired with face B, respectively. : .

[0038] The system sets the lower limit of the safe N / P ratio for cylindrical cells to 1.10. The arithmetic unit reads the data from Table 1 calibrated in step S100 and performs calculations on the pairing group P-01 (positive electrode C-003 paired with negative electrode A-012) in Table 2. In the A-side calculation logic, the positive electrode A-side is applied as a convex surface. The negative electrode A surface is concave. Substituting the data, the calculation yields: .

[0039] In the B-side accounting logic, the positive B-side is a concave surface. The negative electrode B-side is convex. Substituting the data, the calculation yields: .

[0040] The calculation results show that both 1.144 and 1.139 are strictly greater than the safety lower limit of 1.10, and the paired group P-01 is determined to have passed the verification.

[0041] Strict logical intervention branches are configured in the control loop of the system's batch accounting execution. When any pair of electrodes... or When the calculated value is less than 1.10, the MES system immediately sets the verification status of the pairing group to "calculation failed," triggering the software unbinding procedure to cancel the association error-proofing flag between the two electrode rolls. The parameters of the unbound abnormal electrode will be returned and re-released to the abnormal electrode pairing database, and the system will automatically match it to the tolerance threshold. Shrink to Then a second search and matching is performed until the verification is successful.

[0042] Table 3 shows the detailed calculation data of the N / P ratio of the paired electrode group after curvature compensation. Table 3: Single-sided capacity calculation data for paired electrode groups in step S300

[0043] After the verification is completed, the paired electrode group with the status set to "verification passed" will enter step S400 to perform an automated winding operation based on hardware interlocking error prevention.

[0044] Furthermore, the specific implementation process of step S400 is as follows: After the paired electrode groups (such as the P-01 paired group) are verified by single-sided N / P ratio calculation with curvature compensation, the error prevention and control module of the Manufacturing Execution System (MES) automatically triggers the identification generation program. The MES system extracts the unique roll number sequence of the positive electrode C-003 and the negative electrode A-012, the gear parameters of the corresponding high gradient II gear, and the mandatory physical bonding instruction of "positive electrode A face corresponds to negative electrode A face, and positive electrode B face corresponds to negative electrode B face". The system's computing unit hashes and encrypts the above multi-dimensional information with the MAC address of the target winding machine to generate an electronic error prevention code (such as a 2DDataMatrix code) with a unique constraint relationship. This electronic error prevention code is directly sent to the electrode three-dimensional storage control system and the target cylindrical fully automatic winding equipment, and a logical control file named "directional winding process file" is synchronously established at the bottom layer of the MES database to complete the unique binding of the data.

[0045] Materials are transported by an AGV (Automated Guided Vehicle) to the unwinding mechanism of the cylindrical fully automated winding equipment. At the physical loading station, industrial-grade vision readers and photoelectric color mark sensors are installed on the outer sides of both the upper unwinding spool (positive electrode) and the lower unwinding spool (negative electrode). After the operator loads the positive and negative electrode sheets onto the unwinding spools, the vision reader automatically scans the electronic error-proofing code pre-reserved on the outer layer of the electrode sheets, and the photoelectric color mark sensor simultaneously detects the surface bonding marks applied in step S200 (such as the continuous blue positioning lines on the edge of the electrode sheet). The programmable logic controller (PLC) of the winding equipment receives the hard-wired signals returned by the sensors and sends a verification request to the MES system via the industrial Ethernet bus. The MES system retrieves the directional winding process file, verifies whether the currently mounted electrode combination is a bound P-01 pair, and strictly compares whether the physical orientation of the electrode unwinding side meets the bonding instruction of A-side to A-side.

[0046] The equipment's underlying program is configured with non-bypassable hardware interlocking logic branches. When the verification confirms that the material combination is correct and the physical surface relationship on the machine conforms to the instructions, the PLC outputs a high-level signal to the unwinding servo driver, releasing the mechanical brake of the servo motor. The status indicator light on the main interface of the winding equipment switches from yellow standby to green ready state. If the verification comparison result is abnormal (for example, the operator mistakenly loads the positive electrode sheet in reverse, causing the B side of the electrode sheet to face the winding needle area), the PLC will immediately cut off the enable signal of the servo driver, physically locking the upper and lower unwinding shafts, and triggering the emergency stop circuit and red audible and visual alarm, fundamentally preventing the electrode sheet with abnormal surface density from flowing into the winding process in a mismatched state.

[0047] The unlocked winding equipment then performs automated winding operations. To ensure that the physical spatial relationship of the electrode sheets remains absolutely constant in the multi-stage tension belt path, the PLC motion control module coordinates the unwinding direction and angular velocity of the upper and lower unwinding shafts. In specific implementation, the upper unwinding shaft is set to unwind counterclockwise, and the lower unwinding shaft to unwind clockwise, guiding the positive electrode A surface and the negative electrode A surface to be in a relatively aligned physical position before being introduced into the main traction pressure roller. Subsequently, the upper and lower 9μm thick polyethylene microporous membranes are precisely clamped between the relatively aligned positive electrode A surface and the negative electrode A surface, and between the positive electrode B surface and the back side negative electrode B surface, via their respective tension floating roller assemblies.

[0048] The servo control system drives the winding needle to rotate at high speed according to the set constant linear speed variable tension winding curve, alternately winding the positive and negative electrode sheets and the separator into a cylindrical core. Thanks to the rigorous curvature compensation calculation and same-plane physical control implemented in the previous steps, the actual single-plane N / P ratio of the corresponding layers in the formed core, whether it is the inner circle electrode area with a very small radius of curvature or the outer circle tail area with a larger radius of curvature, is forced to be maintained above the safe N / P ratio lower limit of 1.10.

[0049] To verify the interlock control logic and forming effect of step S400, error prevention and interception tests involving various abnormal machine operation scenarios were actually implemented on the production line. The specific equipment actions and process execution conclusions are shown in Table 4.

[0050] After completing step S400, the qualified core will be automatically unloaded and transported to the subsequent short-circuit test (Hi-pot) and shell welding process. This completes the entire process of identifying, calibrating, accurately calculating and compliantly winding and utilizing the electrode with abnormal areal density.

[0051] To further verify the reliability and technical effectiveness of the chip processing method of the present invention in actual mass production, a real-vehicle end-to-end verification was carried out on a production line of a certain type of 21700 cylindrical lithium-ion battery, and a conventional process was set as a comparison for performance comparison.

[0052] 1. Basic experimental conditions and material parameters: This verification used 21700 cylindrical cells based on the NCM811 / artificial graphite system. The lower limit for the safe N / P ratio was set at 1.12.

[0053] A batch of materials with abnormally high areal density was detected by the online thickness measurement system. Abnormal positive electrode (batch C-008): A-side deviation percentage is +3.5%, B-side deviation percentage is +3.2%.

[0054] Abnormal negative electrode sheet (batch A-016): A-side deviation percentage is +3.6%, B-side deviation percentage is +3.3%.

[0055] 2. Experimental group setup: Example group (using the technical solution of the present invention): Extract the aforementioned C-008 positive electrode and A-016 negative electrode, and strictly execute steps S100 to S400. The MES system locks its corresponding "high gradient II level" and executes the instruction that the positive electrode A side corresponds to the negative electrode A side, and the positive electrode B side corresponds to the negative electrode B side. After substituting the winding curvature compensation factor (outer ring convex surface compensation, inner ring concave surface compensation) for calculation, the actual single-sided N / P ratio of the A side is 1.14, and the actual single-sided N / P ratio of the B side is 1.13, both greater than 1.12. Subsequently, relying on the electronic error prevention code and the winding machine interlocking logic, the automated winding, liquid injection, and formation of 1000 cells were successfully completed, and compiled into the example group.

[0056] Comparative Example 1 (using the traditional mean-based slide matching method): C-008 positive electrode and A-016 negative electrode from the same batch as the example group were extracted. Only the average areal density deviation of both sides was calculated (average positive electrode +3.35%, average negative electrode +3.45%). The overall capacity was determined to be matched, and the winding was directly ordered. No A / B side spatial forced correspondence command was applied, no curvature compensation factor was introduced, and no barcode interlocking error prevention was configured. 1000 cells were prepared after random loading and unwinding, and were compiled into Comparative Example Group 1.

[0057] Comparative Example 2 (Normal Standard Material Group): Standard positive and negative electrode sheets with a surface density deviation within ±1.0% (i.e., fully conforming to the design median) were extracted, and 1000 cells were prepared according to standard processes. These were compiled into two sets of comparative examples as performance benchmarks.

[0058] 3. Test methods and result analysis: The three groups of cells were subjected to capacity testing and ohmic resistance (ACR) screening. Samples were then taken for 1C / 1C cycle life testing under a standard environment of 25°C. After 1000 cycles, the cells were subjected to destructive physical dissection (DPA) in a dry room at a dew point of -40°C with a full charge (100% SOC, voltage 4.2V). Optical microscopes were used to observe whether there were grayish-white or golden-yellow metallic lithium deposits (i.e., lithium plating) on ​​the surface of the negative electrode.

[0059] Detailed verification data is shown in Table 5: Table 5: Comparison of Performance Verification Data between Examples and Comparative Examples

[0060] 4. Experimental conclusions: The verification data in Table 5 shows that: Although Comparative Example 1 achieved the reuse of abnormal electrodes, without implementing forced same-plane correspondence and curvature compensation, the misalignment of the A / B surfaces of the electrodes, coupled with the deformation variables of the concave and convex surfaces, caused the actual single-plane N / P ratio of the core to fall below the safety lower limit of 1.12 (the actual estimated value in the extreme region was only 1.06). This directly led to a large difference in the cell's internal resistance, a significant drop in cycle life, and severe local lithium plating was observed during DPA dissection, posing a significant risk of thermal runaway. This combination is considered ineffective and dangerous.

[0061] The example group, employing the method described in this invention, achieved the same high level of compliance rate, internal resistance consistency, and 1000-cycle capacity retention (88.6%) as the two comparative groups (88.9%) using only standard materials. Furthermore, DPA dissection confirmed the absence of any localized lithium plating. This invention achieves 100% zero scrap of abnormal electrodes and mitigates the loss of expensive metal materials while perfectly maintaining the safety baseline against lithium plating at the microscopic electrochemical level, yielding significant and unexpected technical benefits.

Claims

1. A method for processing lithium battery wafers with abnormal coating density, characterized in that, Includes the following steps: S100. Perform full-width surface density testing on the coated electrode sheets, identify electrode sheets whose actual surface density deviates from the design range as abnormal electrode sheets, and obtain the actual surface density values ​​of the A and B sides of the abnormal electrode sheets respectively. S200. Based on the actual areal density value, the abnormal electrode sheet is matched and combined with the electrode sheet of opposite polarity to obtain a paired electrode sheet group containing a positive electrode sheet and a negative electrode sheet; wherein, when matching and combining, the principle that the actual areal density deviation direction of the positive electrode sheet is consistent with the actual areal density deviation direction of the negative electrode sheet is followed, and the A surface of the positive electrode sheet is forcibly set to correspond to the A surface of the negative electrode sheet, and the B surface of the positive electrode sheet corresponds to the B surface of the negative electrode sheet; S300. Introduce a curvature compensation factor related to winding deformation, calculate the actual single-sided N / P ratio of the paired electrode group on the corresponding surface, and verify that the calculated actual single-sided N / P ratio between the A surface of the positive electrode and the A surface of the negative electrode, and between the B surface of the positive electrode and the B surface of the negative electrode, are all greater than or equal to the preset safety N / P ratio lower limit. S400: Generate error prevention marks for the verified paired electrode groups, identify the error prevention marks during the winding process, and perform the winding operation according to the physical spatial relationship of A-side corresponding to A-side and B-side corresponding to B-side.

2. The method for processing lithium battery coating density abnormalities according to claim 1, characterized in that, The step of performing full-width areal density testing on the coated electrode and obtaining the actual areal density values ​​of side A and side B of the abnormal electrode specifically includes: The online thickness measurement system of X-rays located at the winding end of the coating equipment is used to perform real-time full-width scanning of the electrode sheet with continuous tape, and the surface density distribution matrix of the A and B surfaces of the electrode sheet in the continuous physical coordinate system is extracted. Data analysis is performed based on the areal density distribution matrix to identify abnormal regions where the areal density deviates from the design range, and the actual areal density value corresponding to the abnormal region is extracted.

3. The method for processing lithium battery coating density abnormalities according to claim 2, characterized in that, After determining that the electrode with actual areal density deviating from the design range is an abnormal electrode, before executing step S200, the method further includes a step of gradient classification of the abnormal electrode: Calculate the percentage deviation between the actual areal density value and the preset coating design median; If the deviation percentage exceeds the preset internal control tolerance range, it is confirmed as an abnormal electrode, and the abnormal electrode and its corresponding deviation percentage are recorded in the abnormal electrode pairing database. In the abnormal electrode pairing database, based on the magnitude of the deviation percentage, the abnormal electrodes are divided into several high areal density gradient levels and several low areal density gradient levels. When the abnormal electrode and its corresponding deviation percentage are entered into the abnormal electrode pairing database, the batch number, roll number and coordinate information of the abnormal electrode and the location of the abnormality are recorded and bound simultaneously to establish a digital traceability file for the abnormal electrode.

4. The method for processing lithium battery coating density abnormalities according to claim 3, characterized in that, The step of matching and combining the abnormal electrode with the electrode of opposite polarity based on the actual areal density value specifically includes: When the positive electrode is determined to be an abnormal electrode with a high areal density gradient, a negative electrode belonging to the same high areal density gradient level is retrieved and matched from the abnormal electrode pairing database. When the positive electrode is determined to be an abnormal electrode with a low areal density gradient, a negative electrode belonging to the same low areal density gradient level is retrieved and matched from the abnormal electrode pairing database. The difference in surface density deviation between the positive electrode and the negative electrode on their corresponding surfaces is controlled within a preset tolerance range.

5. The method for handling abnormal lithium battery coating density according to claim 4, characterized in that, When matching and combining the abnormal electrode with the electrode of opposite polarity, the process also includes a step of verifying the consistency of the electrode distribution along the length direction: Extract the local surface density curves of the positive electrode and the negative electrode along the electrode strip direction; By comparing the local surface density deviations of the positive electrode and the negative electrode under the same positioning coordinates, it is ensured that the single-sided surface density fluctuation trend of the positive electrode and the negative electrode is consistent throughout the entire electrode length range.

6. The method for processing lithium battery coating density abnormalities according to claim 5, characterized in that, The step of forcibly setting the A side of the positive electrode to correspond to the A side of the negative electrode, and the B side of the positive electrode to correspond to the B side of the negative electrode, further includes: On the edges or preset blank areas of the positive and negative electrode sheets after the matching and combination are completed, surface bonding marks with physical direction differentiation are applied to indicate the physical bonding and winding direction of the positive electrode sheet A side and the negative electrode sheet A side, and the positive electrode sheet B side and the negative electrode sheet B side.

7. The method for processing lithium battery coating density abnormalities according to claim 6, characterized in that, In the step of calculating the actual single-sided N / P ratio of the paired electrode groups on corresponding surfaces, the actual single-sided N / P ratio is calculated according to the following formulas when the positive electrode A surface is paired with the negative electrode A surface, and when the positive electrode B surface is paired with the negative electrode B surface. : ； in, This represents the actual surface density of the corresponding surface of the negative electrode plate. The specific capacity of the negative electrode active material, This is the geometric deformation compensation factor for the negative electrode sheet under a preset winding curvature. This represents the actual surface density of the corresponding surface of the positive electrode plate. The specific capacity of the positive electrode active material, This is the geometric deformation compensation factor for the positive electrode sheet under a preset winding curvature.

8. The method for processing lithium battery coating density abnormalities according to claim 7, characterized in that, The geometric deformation compensation factor and The determination process includes: Based on the curvature radius distribution of the inner and outer rings of the cylindrical cell in the winding state, the elastic modulus of the current collector and coating material, and the winding tension, an electrode winding deformation model is established. The microstructure density variation trend of the electrode under concave compression and convex tension is analyzed by the electrode winding deformation model. The geometric deformation compensation factor corresponding to a specific winding position is derived by pre-experimental measurement or simulation calculation. After the step of verifying that the actual single-sided N / P ratio after verification is greater than or equal to the preset safe N / P ratio lower limit, the logical branch step of unqualified unbinding and re-matching is also included: If the calculation shows that either the actual single-sided N / P ratio of the positive electrode and the negative electrode on side A or side B is less than the lower limit of the safe N / P ratio, then the current paired electrode group is determined to have failed the verification. Cancel the association of the current paired electrode group, and release the electrodes that have not passed the verification back to the abnormal electrode pairing database. After adjusting the gradient level matching threshold, re-execute the matching combination and calculation.

9. A method for processing lithium battery coating density abnormalities according to claim 8, characterized in that, The step of generating a fault-proofing mark for the verified paired electrode group specifically includes: The roll number information, gradient level data, and forced A-side to A-side and B-side to B-side bonding instructions of the verified positive electrode and negative electrode are uniquely bound together. Based on the bound data, an electronic error-proofing code containing the association relationship is generated as the error-proofing identifier, and the electronic error-proofing code is uploaded and distributed to the Manufacturing Execution System (MES) to establish a directional winding process file for the paired electrode group.

10. A method for processing lithium battery coating density abnormalities according to claim 9, characterized in that, The steps of identifying the error-proofing mark during the winding process and performing the winding operation according to the physical spatial relationship of surface A corresponding to surface A and surface B corresponding to surface B are implemented based on error-proofing interlocking control logic, specifically including: During the material loading stage of the winding process, the electronic error prevention code on the positive electrode and the negative electrode is read using the identification component located on the unwinding side of the winding equipment. The winding equipment retrieves the orientation winding process file corresponding to the electronic error-proof code through the manufacturing execution system (MES) and verifies and compares it with the actual physical orientation of the current electrode sheet. If the comparison result indicates that the current material on the machine does not conform to the bonding instruction that surface A corresponds to surface A and surface B corresponds to surface B, then the hardware interlock of the winding equipment is triggered and a fault-prevention alarm signal is issued. If the comparison result indicates that the verification is successful, the winding device is unlocked to perform the subsequent winding operation; When performing the winding operation according to the physical spatial relationship of surface A corresponding to surface A and surface B corresponding to surface B: By coordinating the unwinding direction and belt path of the positive electrode and the negative electrode on their respective unwinding shafts in the winding equipment, the A-side of the positive electrode and the A-side of the negative electrode are in a relatively aligned physical position before entering the winding needle area. During the winding process, the diaphragm is sandwiched between the relatively matching positive electrode A surface and the negative electrode A surface, so that the actual single-sided N / P ratio of any corresponding layer in the wound core after the winding is kept above the safe N / P ratio lower limit.

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