A method and apparatus for spreading composite copper foil with current collector

Abstract

This invention discloses a method and apparatus for spreading a current collector composite copper foil. The method includes applying a DC electric field to the current collector composite copper foil to form an interfacial charge separation layer and obtain reference capacitance distribution data; applying spreading tension to induce micro-displacement between material layers and obtain capacitance change data; identifying adhesion anomaly regions through time-domain difference and sliding window correlation analysis; applying periodic micro-stress perturbation to the anomaly regions to establish a stress-capacitance response relationship and invert the spatial distribution of adhesion strength; and periodically recording the reference capacitance value to assess the degree of interfacial adhesion fatigue. The apparatus includes an electric field processing module, a spreading tension module, a correlation analysis module, a stress perturbation module, and a fatigue assessment module. This solution can achieve real-time dynamic detection and quantitative assessment of interfacial adhesion strength during the current collector composite copper foil spreading process, effectively identify interfacial adhesion failure and fatigue accumulation state, and provide precise technical support for optimizing battery current collector manufacturing processes and controlling product quality.

Description

Technical Field

[0001] This invention relates to the field of current collector composite copper foil spreading detection technology, and in particular to a current collector composite copper foil spreading method and apparatus. Background Technology

[0002] Current collector composite copper foil is a key component of the negative electrode in lithium-ion batteries. It is a multilayer structure material composed of a conductive copper base layer and a functional polymer thin film layer through a special process. The copper base layer performs current collection and conduction, while the functional layers provide mechanical protection, enhanced electrochemical stability, or specific interface modification. This composite structure design aims to improve upon the shortcomings of traditional single copper foil in terms of mechanical strength, surface properties, and electrochemical compatibility while maintaining excellent conductivity, thereby meeting the increasingly stringent comprehensive performance requirements of current collectors in high-performance lithium-ion batteries.

[0003] Before practical application, current collector composite copper foil must undergo a spreading process to eliminate defects such as internal stress, surface unevenness, and dimensional deviations generated during production and storage. The spreading process applies controlled mechanical tension and temperature conditions to achieve the required flatness, dimensional accuracy, and surface quality standards for the composite copper foil. However, because the composite copper foil is composed of layers of materials with different physicochemical properties, the responses of each layer to mechanical and thermal stresses during the spreading process vary significantly. This difference leads to complex shear and normal stresses at the interlayer interfaces. When the spreading tension, deformation rate, and temperature changes exceed certain thresholds, the differences in elastic modulus and mismatches in thermal expansion coefficients between the different material layers cause interfacial stress concentration, resulting in a local decrease in interlayer adhesion strength or even instantaneous failure, forming micro-delamination or interfacial slippage. This severely affects the quality stability of subsequent electrode fabrication processes and the reliability of the final battery product. Summary of the Invention

[0004] The main objective of this invention is to solve the technical problem of how to detect and quantitatively evaluate the changes in adhesion strength between multilayer structures in real time during the high-speed spreading process of current collector composite copper foil, so as to identify interfacial adhesion failure and fatigue accumulation state.

[0005] The first aspect of this invention provides a method for spreading a composite copper foil with a current collector, the method comprising:

[0006] A DC electric field is applied to the current collector composite copper foil entering the film spreading area. By utilizing the work function difference between the copper layer and the polymer layer, a charge separation layer is formed in the interface region to obtain the interface reference capacitance distribution data.

[0007] Apply film tension to the current collector composite copper foil to induce microscopic relative displacement between different material layers, and obtain the interface capacitance change data under stress based on the interface reference capacitance distribution data.

[0008] The interface capacitance change data is processed by time-domain difference to obtain a capacitance change rate sequence. Sliding window correlation analysis is performed on the capacitance change rate sequence, and adhesion anomaly regions are identified based on the trend of correlation coefficient changes.

[0009] Periodic micro-stress perturbation is applied to the adhesion anomaly region, and a stress-capacitance response relationship is established based on the corresponding capacitance response amplitude in the interface capacitance change data. The spatial distribution data of adhesion strength is obtained by inverting the spatial distribution of the stress-capacitance response relationship.

[0010] During the film spreading process, the capacitance reference value under stress-free conditions is recorded periodically. The fatigue-sensitive area is determined based on the spatial distribution data of adhesion strength. The capacitance reference value corresponding to the fatigue-sensitive area is compared with the interface reference capacitance distribution data to obtain the cumulative capacitance offset. The degree of interface adhesion fatigue is evaluated based on the cumulative capacitance offset.

[0011] Preferably, the step of applying a DC electric field to the current collector composite copper foil entering the spreading region, and using the work function difference between the copper layer and the polymer layer to form a charge separation layer in the interface region to obtain interface reference capacitance distribution data, includes:

[0012] Stress distribution of the current collector composite copper foil entering the film spreading area is measured, and the interface prestress state is determined based on the stress concentration area in the stress distribution measurement results to obtain interface stress distribution data.

[0013] Based on the interface stress distribution data, a compensating tension is applied to the current collector composite copper foil to achieve uniformity of the interface prestress state, and at the same time, the interface interlayer spacing distribution data is obtained.

[0014] Based on the interface layer spacing distribution data, the electric field penetration coefficient is calculated. An adaptive DC electric field is applied to the current collector composite copper foil according to the electric field penetration coefficient, so that the electric field intensity is inversely proportional to the interface layer spacing, and the electric field intensity distribution data is obtained.

[0015] The electric field intensity distribution data is used to form a charge accumulation region at the microscopic protrusions of the interface. The charge gradient of the interface is established by the charge diffusion from the charge accumulation region to the flat area, thus obtaining a gradient charge separation layer.

[0016] The gradient charge separation layer is subjected to temperature correction processing, and the capacitance value is corrected according to the temperature coefficient of the dielectric constant of the polymer layer to obtain the interface reference capacitance distribution data.

[0017] Preferably, the step of calculating the electric field penetration coefficient based on the interface interlayer spacing distribution data, and applying an adaptive DC electric field to the current collector composite copper foil according to the electric field penetration coefficient, so that the electric field strength is inversely proportional to the interface interlayer spacing, to obtain the electric field strength distribution data, includes:

[0018] Based on the spatial variation characteristics in the interface layer spacing distribution data, the dielectric field strength attenuation coefficient of each region is calculated, and the electric field penetration depth corresponding to different layer spacings is determined by combining the difference in dielectric constants of the copper layer and the polymer layer, thus obtaining the layered electric field penetration coefficient data.

[0019] Based on the layered electric field penetration coefficient data, the electric field strength compensation factor is determined. A compensation factor greater than 1 is set for regions where the interlayer spacing exceeds the average value, and a compensation factor less than 1 is set for regions where the interlayer spacing is lower than the average value, thereby obtaining the electric field strength compensation coefficient distribution data.

[0020] Based on the electric field strength compensation coefficient distribution data, a compensated DC electric field is applied to different regions of the current collector composite copper foil. The electric field strength of each region is adjusted differently by multiplying the electric field strength with the compensation coefficient, thus obtaining the electric field strength distribution data.

[0021] Preferably, the step of applying film tension to the current collector composite copper foil to induce microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data, includes:

[0022] A stepped film tension is applied to the current collector composite copper foil to induce differential strain responses in the copper layer and the polymer layer, and interlayer strain difference distribution data is obtained based on the differential strain responses.

[0023] Based on the interlayer strain difference distribution data, the interface shear stress distribution data is determined, and the interface shear stress distribution data is used to drive the interface micro-displacement to obtain the interface displacement vector data.

[0024] Based on the interface displacement vector data, the interface reference capacitance distribution data is spatially displacement corrected, and the instantaneous capacitance distribution data is calculated by the response relationship between capacitance value and interface geometry change, thus obtaining dynamic capacitance data.

[0025] Time-series analysis was performed on the dynamic capacitance data, and fast response component data and slow response component data of capacitance change were extracted based on the difference in stress relaxation time between the copper layer and the polymer layer to obtain dual-time-scale capacitance response data.

[0026] The difference between the dual-time-scaled capacitance response data and the interface reference capacitance distribution data is calculated to obtain the interface capacitance change data under stress.

[0027] Preferably, the step of determining the interface shear stress distribution data based on the interlaminar strain difference distribution data, and using the interface shear stress distribution data to drive the interface micro-displacement to obtain interface displacement vector data, includes:

[0028] Spatial gradient calculation is performed on the interlayer strain difference distribution data. The interlayer strain transfer ratio is determined based on the ratio of the elastic modulus of the copper layer to the elastic modulus of the polymer layer. The interlayer strain difference is then converted into equivalent shear strain data at the interface through the strain transfer ratio.

[0029] Based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, the shear stress amplitude of each region is calculated, and the spatial distribution direction of the shear stress is determined by combining the micro-geometric characteristics of the interface, thus obtaining the interface shear stress distribution data.

[0030] Using the interface shear stress distribution data as the driving load for interface displacement, the actual displacement response is calculated based on the mechanical balance relationship between interface adhesion impedance and shear driving force, thus obtaining interface displacement vector data.

[0031] Preferably, the step of performing time-domain difference processing on the interface capacitance change data to obtain a capacitance change rate sequence, performing sliding window correlation analysis on the capacitance change rate sequence, and identifying adhesion anomaly regions based on the trend of correlation coefficient changes includes:

[0032] The interface capacitance change data under stress is processed by first-order time-domain difference and second-order time-domain difference. The instantaneous capacitance change rate sequence is obtained from the first-order difference data, and the capacitance change acceleration sequence is obtained from the second-order difference data.

[0033] Based on the film spreading speed data, the instantaneous capacitance change rate sequence is normalized to establish a fixed correspondence between the capacitance change rate and spatial position, thus obtaining a spatially normalized capacitance change rate sequence.

[0034] An adaptive sliding window is set for the spatially normalized capacitance change rate sequence. The window length is dynamically adjusted according to the fluctuation amplitude in the capacitance change acceleration sequence. Pearson correlation is calculated for the capacitance change rate in adjacent windows to obtain spatial correlation coefficient distribution data.

[0035] The spatial correlation coefficient distribution data is subjected to a local continuity test. Based on the spatial gradient change of the correlation coefficient, the correlation interruption region is identified and marked as an adhesion anomaly region.

[0036] Preferably, the step of applying periodic micro-stress perturbation to the adhesion anomaly region, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining the spatial distribution data of adhesion strength through the spatial distribution inversion of the stress-capacitance response relationship includes:

[0037] The adhesion abnormality region was subjected to frequency sweep micro-stress excitation, and the interface resonance frequency was determined based on the change in capacitance response amplitude under different excitation frequencies, thus obtaining resonance frequency distribution data.

[0038] Based on the resonant frequency distribution data, periodic micro-stress disturbances are applied at the corresponding frequencies, and the capacitance response amplitude data and phase delay data corresponding to the interface capacitance change data under the stress are recorded simultaneously to obtain complex capacitance response data.

[0039] The interface damping coefficient is calculated based on the complex capacitance response data. The local stress-capacitance response relationship is established based on the difference in damping coefficients between the adhesion abnormal region and the adjacent normal region, and the regional response characteristic data is obtained.

[0040] Spatial coupling correction is performed on the regional response characteristic data, and the single-point response characteristics are corrected according to the constraint effect between adjacent regions. The spatial distribution data of adhesion strength is obtained by inversion calculation through the corrected local stress-capacitance response relationship.

[0041] Preferably, the step of calculating the interface damping coefficient based on the complex capacitance response data, establishing a local stress-capacitance response relationship based on the difference in damping coefficients between the adhesion anomalous region and the adjacent normal region, and obtaining regional response characteristic data includes:

[0042] The real and imaginary components of the capacitance response are separated from the complex capacitance response data. The interface dielectric loss factor is calculated based on the ratio of the imaginary component to the real component. The interface damping coefficient data of each region is determined by the dielectric loss factor.

[0043] The interface damping coefficient data is compared between regions to obtain the ratio of damping coefficients and gradient change rate between the adhesion abnormal region and the adjacent normal region. The interface response sensitivity level is divided according to the ratio and gradient change rate to obtain interface response sensitivity classification data.

[0044] Based on the interface response sensitivity classification data, corresponding stress-capacitance response coefficients are assigned to regions with different sensitivity levels. Regionalized stress-capacitance relationships are established through the spatial distribution of response coefficients to obtain regional response characteristic data.

[0045] Preferably, the process of periodically recording the capacitance reference value under stress-free conditions during film spreading, determining fatigue-sensitive areas based on the adhesion strength spatial distribution data, comparing the capacitance reference value corresponding to the fatigue-sensitive area with the interface reference capacitance distribution data to obtain the cumulative capacitance offset, and evaluating the degree of interface adhesion fatigue based on the cumulative capacitance offset includes:

[0046] Based on the intensity gradient change in the spatial distribution data of adhesion strength, an adhesion strength grading threshold is determined. Areas with adhesion strength below the preset threshold are marked as high-sensitivity areas, and areas with adhesion strength within the threshold range are marked as medium-sensitivity areas, thereby obtaining fatigue sensitivity grading data corresponding to the fatigue-sensitive areas.

[0047] During the film spreading process, the capacitance reference values ​​of the high-sensitivity region and the medium-sensitivity region under stress-free conditions are recorded periodically at preset time intervals, and time-series capacitance reference value data is established according to the recording time sequence.

[0048] The time-series capacitance reference value data and the interface reference capacitance distribution data are compared and calculated point by point to obtain the capacitance offset at each time point. The capacitance offset is then weighted and accumulated according to the time weight coefficient to obtain the cumulative capacitance offset.

[0049] Spatial correlation analysis is performed on the accumulated capacitance offset. The fatigue propagation path is identified based on the difference in accumulated offset between adjacent regions. The accumulated offset of each region is corrected through the propagation path to obtain the corrected accumulated capacitance offset.

[0050] The fatigue level is graded based on the comparison between the cumulative amount of the corrected capacitor offset and the preset fatigue threshold. Areas with a cumulative amount exceeding the threshold are identified as severely fatigued areas, and areas with a cumulative amount close to the threshold are identified as moderately fatigued areas, thus obtaining the interface adhesion fatigue level assessment result.

[0051] A second aspect of the present invention provides a current collector composite copper foil spreading device, the current collector composite copper foil spreading device comprising:

[0052] The electric field processing module is used to apply a DC electric field to the current collector composite copper foil entering the film spreading area, and to form a charge separation layer in the interface region by utilizing the work function difference between the copper layer and the polymer layer, thereby obtaining interface reference capacitance distribution data.

[0053] The film tension module is used to apply film tension to the current collector composite copper foil, so as to generate microscopic relative displacement between different material layers, and obtain the interface capacitance change data under stress based on the interface reference capacitance distribution data.

[0054] The correlation analysis module is used to perform time-domain difference processing on the interface capacitance change data to obtain a capacitance change rate sequence, perform sliding window correlation analysis on the capacitance change rate sequence, and identify adhesion anomaly regions based on the trend of correlation coefficient changes.

[0055] The stress disturbance module is used to apply periodic micro-stress disturbance to the adhesion abnormal area, establish a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtain the spatial distribution data of adhesion strength through the spatial distribution inversion of the stress-capacitance response relationship.

[0056] The fatigue assessment module is used to periodically record the capacitance reference value under stress-free conditions during the film spreading process, determine the fatigue-sensitive area based on the adhesion strength spatial distribution data, compare the capacitance reference value corresponding to the fatigue-sensitive area with the interface reference capacitance distribution data to obtain the cumulative capacitance offset, and assess the degree of interface adhesion fatigue based on the cumulative capacitance offset.

[0057] The technical solution provided in this application utilizes the inherent work function difference between the copper layer and the polymer layer in a current collector composite copper foil to form a stable charge separation layer in the interface region by applying a DC electric field. The key to this process lies in the differentiated responses of the different materials to the electric field: the copper layer, as a good conductor, quickly reaches potential equilibrium, while the polymer layer, due to its dielectric properties, forms a bound charge layer at the interface. The formation of the charge separation layer provides a highly sensitive "sensing basis" for subsequent detection; any small change in the interface geometry or physical state will cause a significant change in the capacitance value. By obtaining the interface reference capacitance distribution data, a reference standard for the entire detection system is established.

[0058] Under the influence of film tension, the different material layers of the composite copper foil undergo differential deformation due to differences in their elastic moduli, leading to microscopic relative displacement between the layers. This displacement directly alters the geometry of the interfacial capacitor. Since capacitance is inversely proportional to distance, minute changes in interfacial distance are amplified into significant capacitance changes. When the interfacial adhesion strength is sufficient, the interfacial displacement mainly manifests as elastic deformation, and the capacitance change exhibits regular fluctuations. However, when the adhesion strength decreases, microscopic slippage or local separation occurs at the interface, resulting in discontinuous jumps in capacitance values. By continuously monitoring the interfacial capacitance changes under stress, real-time detection of adhesion anomalies can be achieved.

[0059] After time-domain difference processing, the interfacial capacitance change data yields a capacitance change rate sequence, which reflects the dynamic characteristics of the interfacial response. Normally adhered interfaces exhibit a highly correlated response under stress, meaning there is a strong positive correlation between the capacitance change rates at adjacent time points. As adhesion degradation begins, this correlation gradually weakens, manifested as a decrease in the correlation coefficient in sliding window correlation analysis. By tracking the trend of the correlation coefficient, regions of correlation interruption can be identified, corresponding to abnormal changes in adhesion strength. The advantage of this method is that it does not rely on absolute capacitance values ​​but is based on the inherent regularity of capacitance changes, automatically adapting to differences between different batches of materials.

[0060] Periodic micro-stress perturbations were applied to identified adhesion anomaly regions, and the stress-capacitance response relationship was established by monitoring the capacitance response amplitude. Regions with high adhesion strength exhibited smaller interfacial deformation and corresponding smaller capacitance changes under the same stress; conversely, regions with low adhesion strength produced larger deformation and capacitance changes. By analyzing the spatial distribution characteristics of the stress-capacitance response relationship, the spatial distribution of adhesion strength could be deduced. This deduction process is based on the coupling relationship between interfacial mechanical and electrical properties, transforming differences in capacitance response into a quantitative assessment of adhesion strength.

[0061] Interfacial adhesion fatigue is a gradual cumulative process, manifested as irreversible changes in the interfacial microstructure. This invention quantitatively assesses the degree of adhesion fatigue accumulation by periodically recording the capacitance baseline value under stress-free conditions and comparing it with an initial baseline. After repeated stress cycles, even under stress-free conditions, the capacitance value of the interface cannot completely recover to its initial state, exhibiting a slight residual shift. This shift directly reflects the cumulative damage to the interfacial microstructure. By establishing identification criteria for fatigue-sensitive regions and focusing on monitoring the cumulative capacitance shift in areas with low adhesion strength, a predictive assessment of the interfacial fatigue state can be achieved. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0063] Figure 1 This is a schematic diagram of an embodiment of the current collector composite copper foil spreading method in this invention;

[0064] Figure 2 This is a schematic diagram of one embodiment of the current collector composite copper foil spreading device of the present invention;

[0065] Figure 3 This is a partial structural schematic diagram of the current collector composite copper foil spreading device in an embodiment of the present invention;

[0066] Figure 4 for Figure 3 A schematic diagram of the structure from another perspective.

[0067] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0070] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the term "and / or" throughout the text includes three solutions; taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that simultaneously satisfies A and B. Furthermore, the technical solutions of various embodiments can be combined with each other, provided that they are feasible for those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0071] One embodiment of this application provides a method for spreading a composite copper foil film using a current collector. Figure 1 This is a flowchart illustrating a method for spreading composite copper foil with a current collector according to an embodiment of this application. In this embodiment, the method includes:

[0072] Please see Figure 1 A DC electric field is applied to the current collector composite copper foil entering the film spreading area. The difference in work function between the copper layer and the polymer layer is used to form a charge separation layer in the interface region to obtain the interface reference capacitance distribution data.

[0073] In one embodiment of the present invention, the step of applying a DC electric field to the current collector composite copper foil entering the spreading region, and forming a charge separation layer in the interface region by utilizing the work function difference between the copper layer and the polymer layer to obtain interface reference capacitance distribution data includes:

[0074] Stress distribution of the current collector composite copper foil entering the film spreading area is measured, and the interface prestress state is determined based on the stress concentration area in the stress distribution measurement results to obtain interface stress distribution data.

[0075] Based on the interface stress distribution data, a compensating tension is applied to the current collector composite copper foil to achieve uniformity of the interface prestress state, and at the same time, the interface interlayer spacing distribution data is obtained.

[0076] Based on the interface layer spacing distribution data, the electric field penetration coefficient is calculated. An adaptive DC electric field is applied to the current collector composite copper foil according to the electric field penetration coefficient, so that the electric field intensity is inversely proportional to the interface layer spacing, and the electric field intensity distribution data is obtained.

[0077] The electric field intensity distribution data is used to form a charge accumulation region at the microscopic protrusions of the interface. The charge gradient of the interface is established by the charge diffusion from the charge accumulation region to the flat area, thus obtaining a gradient charge separation layer.

[0078] The gradient charge separation layer is subjected to temperature correction processing, and the capacitance value is corrected according to the temperature coefficient of the dielectric constant of the polymer layer to obtain the interface reference capacitance distribution data.

[0079] The following is a detailed description of the steps involved in the above embodiments:

[0080] When measuring the stress distribution of the current collector composite copper foil entering the spreading area, a laser speckle interferometer was used, with a measurement point set every 5 mm along the length of the copper foil. The laser emitted a helium-neon laser with a wavelength of 632.8 nm, an illumination angle of 45°, and an illumination time of 50 milliseconds. The speckle image was captured by a CCD camera and compared with a reference image for phase analysis. Stress concentration areas refer to regions where the stress value exceeds 1.5 times the average stress. When the measurement shows a stress of 350 MPa in a certain area while the average stress is 200 MPa, this area is considered a stress concentration area. The interface prestress state refers to the residual internal stress state at the interface between the copper layer and the polymer layer during the winding and storage of the composite copper foil. The data acquisition system stores the stress values ​​of all measurement points and generates a two-dimensional stress distribution map. Different colors are used to represent stress magnitude in the map, with red areas representing high stress and blue areas representing low stress, thus obtaining the interface stress distribution data. This accurate stress distribution identification provides a precise basis for subsequent compensation tension application, avoiding interference from stress inhomogeneity on the electric field processing effect.

[0081] Based on the interface stress distribution data, a segmented tension control system is used to apply compensating tension to the current collector composite copper foil. This system comprises eight independent tension rollers evenly distributed along the width of the copper foil. Each tension roller is equipped with a servo motor and a force sensor, with a control accuracy of ±1N. The system calculates the required compensating tension based on the stress value of each region in the stress distribution diagram: Target tension = Standard tension value + (Target stress - Measured stress) × Conversion factor, where the conversion factor is 0.5N / MPa. For example, if the measured stress in a certain region is 150MPa and the target stress is 200MPa, then the compensating tension is 25N. The interface interlayer spacing distribution data refers to the spatial distribution of the actual distance between the copper layer and the polymer layer. An ultrasonic thickness gauge emits ultrasonic pulses at a frequency of 5MHz, and the receiver records the echo time. The interlayer spacing is calculated based on the difference in sound velocity: Interlayer spacing = (Echo time difference × Sound velocity) / 2. The sound velocity in the copper layer is 5900m / s, and in the polymer layer it is 2300m / s, with a measurement accuracy of 0.1 micrometers. Homogenization processing refers to reducing the stress difference from more than 100MPa to less than 20MPa. This differentiated tension control can effectively eliminate stress inhomogeneity and create ideal interface conditions for subsequent electric field processing.

[0082] The electric field penetration coefficient, which describes the propagation ability of the electric field in multilayer composite materials, is calculated based on the interlayer spacing distribution data. The specific calculation process is as follows: Substituting the measured copper layer thickness of 10 μm, polymer layer thickness of 3 μm, and interlayer spacing of 2 μm into the calculation formula, with the dielectric constant of the copper layer set to 1 and the dielectric constant of the polymer layer set to 3, the electric field penetration coefficient K is calculated as K = 1 / (1 + 3 × 10 / 3) = 0.091. An adaptive DC electric field is applied using a 16-channel programmable DC power supply, with each channel independently controlling an electrode region. The power supply output voltage range is 0-1000V, and the current is limited to 10mA. The electric field intensity in each region is adjusted according to the interlayer spacing data: Electric field intensity = Reference electric field intensity × (Average interlayer spacing / Actual interlayer spacing), with the reference electric field intensity set to 200V / μm. When the interlayer spacing in a certain region is 1.5 μm, the electric field intensity in that region is 200 × (2 / 1.5) = 267V / μm. The electric field application time is 500 milliseconds to ensure sufficient charge injection. This adaptive electric field adjustment ensures that different regions achieve similar charge injection effects, avoiding the uneven processing problems caused by a fixed electric field strength.

[0083] Using electric field intensity distribution data, charge accumulation regions were formed at the microscopic protrusions at the interface. These microscopic protrusions are micrometer-sized bumps caused by uneven calendering during the composite process. Atomic force microscopy analysis revealed heights of 0.8-1.5 micrometers and a density of 20-50 protrusions per square millimeter. Under the influence of the electric field, the electric field intensity at the tip of the protrusion is 3-5 times higher than that in the flat area, reaching 800-1000 V / μm. When this exceeds the polymer breakdown threshold of 500 V / μm, local breakdown occurs, forming conductive channels with a charge density reaching 102. -6C / cm 2 Charge diffusion is achieved through the reorientation of dipoles in the polymer molecular chains, with a diffusion coefficient of 10. -12 cm 2 / s, the diffusion distance from the aggregation region to the surrounding flat area is 5-10 micrometers, and the diffusion time is about 100 milliseconds. The interfacial charge gradient refers to the charge density from 10 in the aggregation region to 10 in the flat area. -6 C / cm 2 Towards the flat area 10 -8 C / cm 2 The linear decrease has a gradient slope of 10. -7 C / cm 3 The gradient charge separation layer is one-third the thickness of the polymer layer, approximately 1 micrometer. This gradient distribution has higher detection sensitivity compared to a uniform distribution; when the interface shifts by 0.1 micrometers, the capacitance change reaches 0.5 pF, which is 5 times higher than the 0.1 pF of a uniform distribution.

[0084] Temperature correction was applied to the gradient charge separation layer. The temperature coefficient of the polymer layer's dielectric constant was -0.002 / ℃. An infrared thermal imager acquired 30 temperature images per second, with a spatial resolution of 0.1 mm and a temperature resolution of 0.1℃. The temperature correction calculation employed a linear compensation algorithm: corrected capacitance = measured capacitance × [1 - 0.002 × (measured temperature - 25)]. The data processor calculated and stored the correction results in real time. For example, if the measured temperature was 32℃ and the measured capacitance was 98 pF, the corrected capacitance would be 98 × [1 - 0.002 × (32 - 25)] = 96.6 pF. The interface reference capacitance distribution data refers to the capacitance value matrix divided into 2 mm × 2 mm grids after temperature correction. Each grid point contains three parameters: capacitance value, temperature value, and location coordinates. Capacitance measurement used an LCR bridge with a measurement frequency of 1 kHz, an integration time of 100 ms, and a measurement accuracy of 0.01 pF. Automatic zeroing eliminated system errors. After data acquisition, a capacitance distribution contour map is generated, serving as a zero-point reference for all subsequent capacitance change detections. By establishing an accurate baseline capacitance distribution, a reliable reference standard is provided for subsequent adhesion strength testing. The temperature compensation accuracy reaches ±0.05pF, ensuring that the test results are not affected by temperature fluctuations, significantly improving detection accuracy and reproducibility.

[0085] In one embodiment of the present invention, the step of calculating the electric field penetration coefficient based on the interface layer spacing distribution data, and applying an adaptive DC electric field to the current collector composite copper foil according to the electric field penetration coefficient, such that the electric field strength is inversely proportional to the interface layer spacing, to obtain the electric field strength distribution data, includes:

[0086] Based on the spatial variation characteristics in the interface layer spacing distribution data, the dielectric field strength attenuation coefficient of each region is calculated, and the electric field penetration depth corresponding to different layer spacings is determined by combining the difference in dielectric constants of the copper layer and the polymer layer, thus obtaining the layered electric field penetration coefficient data.

[0087] Based on the layered electric field penetration coefficient data, the electric field strength compensation factor is determined. A compensation factor greater than 1 is set for regions where the interlayer spacing exceeds the average value, and a compensation factor less than 1 is set for regions where the interlayer spacing is lower than the average value, thereby obtaining the electric field strength compensation coefficient distribution data.

[0088] Based on the electric field strength compensation coefficient distribution data, a compensated DC electric field is applied to different regions of the current collector composite copper foil. The electric field strength of each region is adjusted differently by multiplying the electric field strength with the compensation coefficient, thus obtaining the electric field strength distribution data.

[0089] The following is a detailed description of the steps involved in the above embodiments:

[0090] When calculating the dielectric field attenuation coefficient for each region based on the spatial variation characteristics of the interlayer spacing distribution data, the spatial variation characteristics refer to the numerical differences and trends in the interlayer spacing at different locations. A data processing system performs spatial gradient analysis on the interlayer spacing distribution data. The dielectric field attenuation coefficient is a physical parameter describing the degree of intensity reduction of an electric field as it passes through multiple layers of dielectric material. The calculation process involves taking the interlayer spacing values ​​of two adjacent measurement points, calculating the ratio of their difference to the distance to obtain the spatial gradient, and then combining this with the dielectric loss parameters of the material to determine the attenuation coefficient. For example, if the interlayer spacing in a certain region changes from 2.0 micrometers to 2.5 micrometers (a distance of 5 millimeters), the spatial gradient is 0.1 micrometers / millimeter. Combined with the dielectric loss tangent of the polymer layer (0.02), the dielectric field attenuation coefficient for this region is calculated to be 0.002 / micrometer. The electric field penetration depth refers to the depth to which the electric field can effectively penetrate the composite copper foil and exert its effect at the interface. Different interlayer spacings correspond to different penetration depths: a 1.5-micrometer interlayer spacing results in a penetration depth of 1.2 micrometers, and a 3.0-micrometer interlayer spacing results in a penetration depth of 2.8 micrometers. The layered electric field penetration coefficient data is obtained by dividing the entire composite copper foil into a 2 mm × 2 mm grid, calculating the corresponding penetration coefficient for each grid, and forming a spatial distribution matrix. This refined penetration coefficient calculation can accurately reflect the electric field propagation characteristics in different regions and eliminate the problem of uneven electric field distribution caused by differences in material thickness.

[0091] When determining the electric field strength compensation factor based on the layered electric field penetration coefficient data, the compensation factor is a correction coefficient used to adjust the electric field strength in each region to achieve uniform charge injection. The determination process is as follows: Calculate the arithmetic mean of the interlayer spacing at all measurement points as a baseline value, for example, an average interlayer spacing of 2.2 micrometers. Then, compare the actual interlayer spacing of each region with the average value point by point. For regions where the interlayer spacing exceeds the average value, a compensation factor greater than 1 is set to enhance the electric field strength. The specific value is determined by the excess ratio: for example, if the interlayer spacing in a region is 2.8 micrometers, exceeding the average by 27%, the corresponding compensation factor is set to 1.3. For regions where the interlayer spacing is below the average value, a compensation factor less than 1 is set to weaken the electric field strength: for example, if the interlayer spacing in a region is 1.8 micrometers, below the average by 18%, the corresponding compensation factor is set to 0.8. The electric field strength compensation coefficient distribution data is a two-dimensional array formed by arranging all compensation factors according to their spatial positions. Each element in the array contains the position coordinates and the corresponding compensation coefficient value. This differentiated compensation strategy can effectively overcome the influence of the non-uniformity of the composite copper foil thickness on the charge injection effect, ensuring that each region obtains a similar charge density.

[0092] When applying compensated DC electric fields to different regions of the current collector composite copper foil based on electric field strength compensation coefficient distribution data, a multi-channel programmable DC power supply system is used. This system contains 64 independent control channels, each corresponding to an electrode region with an electrode size of 2 mm × 2 mm. The product of electric field strength and compensation coefficient is implemented through a digital signal processor: the processor reads the reference electric field strength of 200 V / μm and the compensation coefficient of each region, and performs real-time multiplication to obtain the adjusted electric field strength. For example, when the compensation coefficient of a certain region is 1.3, the actual electric field strength of that region is 200 × 1.3 = 260 V / μm; for a region with a compensation coefficient of 0.8, the actual electric field strength is 200 × 0.8 = 160 V / μm. Differential adjustment of the electric field strength in each region is achieved by independently controlling the output voltage of each electrode, with a voltage adjustment accuracy of ±1V and a response time of less than 10 milliseconds. The electric field strength distribution data records the final applied electric field strength value for each electrode region, as well as the corresponding voltage, current, and power parameters. This precise regional electric field control can compensate for the geometric inhomogeneity of the composite copper foil, achieve uniform charge injection across the entire interface region, and significantly improve the accuracy and reliability of subsequent capacitance detection.

[0093] Please continue reading. Figure 1 Apply film tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtain the interface capacitance change data under stress based on the interface reference capacitance distribution data.

[0094] In one embodiment of the present invention, applying film tension to the current collector composite copper foil to induce microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data, includes:

[0095] A stepped film tension is applied to the current collector composite copper foil to induce differential strain responses in the copper layer and the polymer layer, and interlayer strain difference distribution data is obtained based on the differential strain responses.

[0096] Based on the interlayer strain difference distribution data, the interface shear stress distribution data is determined, and the interface shear stress distribution data is used to drive the interface micro-displacement to obtain the interface displacement vector data.

[0097] Based on the interface displacement vector data, the interface reference capacitance distribution data is spatially displacement corrected, and the instantaneous capacitance distribution data is calculated by the response relationship between capacitance value and interface geometry change, thus obtaining dynamic capacitance data.

[0098] Time-series analysis was performed on the dynamic capacitance data, and fast response component data and slow response component data of capacitance change were extracted based on the difference in stress relaxation time between the copper layer and the polymer layer to obtain dual-time-scale capacitance response data.

[0099] The difference between the dual-time-scaled capacitance response data and the interface reference capacitance distribution data is calculated to obtain the interface capacitance change data under stress.

[0100] The following is a detailed description of the steps involved in the above embodiments:

[0101] When applying stepped tension to the current collector composite copper foil, stepped tension refers to the method of gradually increasing tension according to a preset time interval and force gradient during the film spreading process, which differs from the traditional method of applying a fixed tension all at once. Specifically, a tension control system driven by a servo motor is used. The system includes four tension rollers, each equipped with a torque sensor and a position encoder. The tension application program is set as follows: 50N is applied at second 0, increasing to 60N at second 2, increasing to 70N at second 4, and so on, increasing by 10N every 2 seconds, for a total of 15 steps, reaching the target tension of 150N at second 28 and maintaining it. Differential strain response refers to the phenomenon that the copper layer and polymer layer deform to different degrees under the same tension due to their different elastic moduli. The elastic modulus of the copper layer is 110GPa, and the elastic modulus of the polymer layer is 3GPa. Strain measurement uses resistance strain gauges with a grid length of 5 mm. A pair of strain gauges is arranged every 20 mm along the width of the copper foil, attached to the surfaces of the copper layer and polymer layer respectively, for a total of 16 pairs of strain gauges. Strain gauges are bonded using conductive silver adhesive at 60℃ with a curing time of 30 minutes. The signal conditioning circuit employs an INA125 precision instrumentation amplifier with a magnification of 1000x and an output voltage range of 0-10V corresponding to a strain range of 0-0.01. Data acquisition utilizes a 16-bit ADC converter with a sampling frequency of 100Hz and a strain resolution of 1 microstrain per channel. For example, at a tension of 100N, the copper layer strain is 800 microstrains, the polymer layer strain is 25000 microstrains, and the strain difference is 24200 microstrains. The interlayer strain difference distribution data is stored according to the measurement point number and corresponding strain difference value in a CSV file format, containing three columns: timestamp, location coordinates, and strain difference value. This stepped tension application method can complete the entire loading process within 15 seconds, avoiding damage to the interface from instantaneous impacts, while obtaining high-precision strain difference distribution data with a time resolution of 0.01 seconds.

[0102] When determining the interfacial shear stress distribution based on interlaminar strain difference distribution data, the interfacial shear stress is the tangential stress generated at the interface due to the strain difference between the copper and polymer layers. The calculation employs the interlaminar shear theory of composite materials: shear stress equals the strain difference multiplied by the interfacial equivalent shear modulus, which is determined by nanoindentation testing. The nanoindentation test uses a Berkovich diamond indenter, with an indentation depth controlled at 200 nm to ensure the test interface area, a loading rate of 10 μN / s, and a maximum load of 500 μN. The test was repeated 10 times in the interface area, and the average interfacial shear modulus was measured to be 8.2 GPa, with a standard deviation of 0.5 GPa. The shear stress calculation formula is: τ = Δε × G, where τ is the interfacial shear stress, Δε is the interlaminar strain difference, and G is the interfacial shear modulus (8.2 GPa). For example, when the interlaminar strain difference at a certain location is 0.02, the interfacial shear stress is 0.02 × 8.2 × 10⁻⁶. 9Pa = 164 MPa. The interfacial micro-displacement is calculated using shear deformation theory: the displacement equals the shear stress divided by the interfacial shear stiffness. The interfacial shear stiffness is determined by the interfacial thickness and shear modulus, and its value is G / h, where h is the thickness of the interfacial transition layer, approximately 0.5 micrometers. Therefore, the shear stiffness is 1.64 × 10⁻⁶. 13 N / m 3 The displacement calculation formula is: δ = τ / K, where δ is the interface displacement and K is the interface shear stiffness. When the shear stress is 164 MPa, the interface displacement is 164 × 10⁻⁶. 6 Pa / (1.64×10 13 N / m 3 =10 nanometers. Interface displacement vector data is stored in three-dimensional coordinates: (x, y, δx, δy), where x and y are position coordinates, and δx and δy are displacement components in the X and Y directions, respectively. This calculation method based on materials mechanics theory ensures the physical rationality and computational accuracy of the shear stress and displacement data.

[0103] When performing spatial displacement correction on the interface reference capacitance distribution data based on interface displacement vector data, the correction process is based on the principle of a parallel-plate capacitor. The capacitance sensor calibration experiment was conducted using a precision displacement stage and a high-precision capacitance measuring instrument: a standard parallel-plate capacitor was mounted on a nanometer-level precision displacement stage with a resolution of 1 nanometer, and the capacitance measuring instrument had an accuracy of 0.001 pF. During calibration, the displacement stage moved from 0 to 500 nanometers in steps of 10 nanometers, and the capacitance value was measured 10 times at each position, with the average value taken to obtain the capacitance-displacement calibration curve. The calibration results show that the capacitance is inversely proportional to the distance: C = C0 × d0 / d, where C is the corrected capacitance, C0 is the reference capacitance, d0 is the reference distance, and d is the corrected distance. In the correction calculation, the interface displacement is subtracted from the reference layer spacing: d = d0 - δ, where δ is the interface displacement. For example, with a baseline interlayer spacing of 2.0 micrometers and an interface displacement of 10 nanometers, the corrected interlayer spacing is 1.99 micrometers. When the baseline capacitance is 100 pF, the corrected capacitance is 100 × 2.0 / 1.99 = 100.5 pF. Instantaneous capacitance distribution data acquisition utilizes a 64-channel capacitance measurement system, with each channel equipped with an independent AC excitation source and synchronous detector. The excitation frequency is 1 kHz, the excitation amplitude is 1 V, and the measurement resolution is 0.01 pF. The data acquisition frequency is 50 Hz, acquiring 3200 capacitance data points per second. Dynamic capacitance data storage uses a timestamped three-dimensional array format: [time][X coordinate][Y coordinate] = [capacitance value]. The data file uses a binary format to improve storage efficiency. This calibration curve-based correction method ensures the accuracy of capacitance calculation, achieving a displacement resolution at the nanometer level.

[0104] When performing time-series analysis on dynamic capacitance data, digital signal processing methods are used to separate response components at different time scales. Fast response component extraction employs a 4th-order Butterworth high-pass filter with the following parameters: cutoff frequency 10Hz, passband ripple less than 0.1dB, and stopband attenuation greater than 40dB. The filter is converted from an analog prototype to a digital filter using a bilinear transform method, with a sampling frequency of 200Hz to meet the Nyquist theorem requirements. Slow response component extraction uses a 4th-order Butterworth low-pass filter with a cutoff frequency of 1Hz, and other parameters identical to the high-pass filter. The filter implementation adopts a cascaded two-stage structure, with each stage containing two delay units, five multipliers, and four adders. The copper layer relaxation time was determined to be 50 microseconds through step response testing, while the polymer layer relaxation time was 0.8 seconds, a difference of 16,000 times. The filtering process is as follows: the original dynamic capacitance signal is simultaneously input to high-pass and low-pass filters. The high-pass filter outputs a fast-response component, reflecting the instantaneous response characteristics of the copper layer; the low-pass filter outputs a slow-response component, reflecting the delayed response characteristics of the polymer layer. For example, if the capacitance signal at a certain measurement point contains a 20Hz fast oscillation (amplitude 2pF) and a 0.5Hz slow change (amplitude 8pF), after filtering, the fast-response component extracts the 20Hz signal of 2pF, and the slow-response component extracts the 0.5Hz signal of 8pF. The dual-time-scale capacitance response data is stored in the format of [time][location][fast response value, slow response value], with a data update frequency of 50Hz. This digital filtering method can accurately separate the response characteristics of different material layers, achieving a filtering accuracy of 0.01pF.

[0105] When performing difference calculations between the dual-time-scaled capacitance response data and the interface reference capacitance distribution data, a parallel computing architecture is employed to improve processing efficiency. The difference calculation is performed on a GPU-accelerated processor containing 1024 parallel computing cores, with each core responsible for calculating one measurement point. The calculation process is as follows: for each spatial location (i,j), the reference capacitance value C0(i,j) and the fast response capacitance value C are read. fast (i,j,t) and slow response capacitance C slow (i,j,t), calculate the difference ΔC fast (i,j,t)=C fast (i,j,t)-C0(i,j) and ΔC slow (i,j,t)=C slow(i,j,t)-C0(i,j). For example, the reference capacitance at position (5,8) is 100pF. At a certain moment, the fast response capacitance is 102pF and the slow response capacitance is 108pF. Then, the fast response difference is 2pF and the slow response difference is 8pF. The calculation results are stored in real time in a high-speed memory in a 5-dimensional array: [X coordinate][Y coordinate][Time][Fast response difference][Slow response difference]. Data compression uses a lossless compression algorithm with a compression ratio of 3:1. The interface capacitance change data under stress generates approximately 50MB of data per second. The storage system uses a RAID array to ensure data security and access speed. This efficient parallel computing and storage scheme can process large amounts of capacitance data in real time with a calculation latency of less than 20 milliseconds, providing timely and accurate capacitance change information for subsequent real-time adhesion strength analysis.

[0106] In one embodiment of the present invention, the step of determining interface shear stress distribution data based on the interlaminar strain difference distribution data, and using the interface shear stress distribution data to drive interface micro-displacement to obtain interface displacement vector data includes:

[0107] Spatial gradient calculation is performed on the interlayer strain difference distribution data. The interlayer strain transfer ratio is determined based on the ratio of the elastic modulus of the copper layer to the elastic modulus of the polymer layer. The interlayer strain difference is then converted into equivalent shear strain data at the interface through the strain transfer ratio.

[0108] Based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, the shear stress amplitude of each region is calculated, and the spatial distribution direction of the shear stress is determined by combining the micro-geometric characteristics of the interface, thus obtaining the interface shear stress distribution data.

[0109] Using the interface shear stress distribution data as the driving load for interface displacement, the actual displacement response is calculated based on the mechanical balance relationship between interface adhesion impedance and shear driving force, thus obtaining interface displacement vector data.

[0110] The following is a detailed description of the steps involved in the above embodiments:

[0111] When calculating the spatial gradient of interlayer strain difference distribution data, the spatial gradient calculation refers to performing differential operations on the strain difference data distributed along the length and width of the copper foil to obtain the spatial rate of change of the strain difference. The calculation process uses the central difference method: the strain difference values ​​of three adjacent measurement points are selected, and the gradient of the intermediate point is equal to the difference between the values ​​of the two points divided by the distance interval. For example, the strain difference at position 10mm is 0.015, at position 20mm it is 0.018, and at position 30mm it is 0.021, then the spatial gradient at position 20mm is (0.021-0.015) / (30-10)=0.0003 / mm. The interlayer strain transfer ratio is a dimensionless parameter describing the efficiency of strain transfer between different material layers. According to the theory of composite material mechanics, the transfer ratio is equal to the reciprocal of the ratio of the elastic moduli of the two materials. The elastic modulus of the copper layer is 110GPa, and the elastic modulus of the polymer layer is 3GPa, with a modulus ratio of 36.7. Therefore, the interlayer strain transfer ratio is 1 / 36.7=0.027. Equivalent shear strain data is the actual shear strain value at the interface obtained by correcting the interlaminar strain difference using a strain transfer ratio. The calculation method is: Equivalent shear strain = Interlaminar strain difference × Strain transfer ratio × Spatial gradient correction coefficient. The spatial gradient correction coefficient is determined based on the spatial variation of the strain difference; the larger the gradient, the larger the correction coefficient, ranging from 0.8 to 1.2. For example, if the interlaminar strain difference at a certain location is 0.018, the strain transfer ratio is 0.027, and the spatial gradient correction coefficient is 1.1, then the equivalent shear strain is 0.018 × 0.027 × 1.1 = 0.00053. This strain transfer calculation method based on the elastic modulus ratio can accurately reflect the true strain state of the composite material interface, eliminating the strain distribution distortion caused by differences in material properties.

[0112] When calculating the shear stress amplitude in each region based on equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, the equivalent shear modulus, a material parameter describing the interface region's resistance to shear deformation, is measured using a dynamic mechanical analyzer. The test employed a shear fixture, applying a sinusoidal shear load at a frequency of 1 Hz, with an amplitude of 10% of the interface yield strength. The test temperature was 25℃, and the measured equivalent shear modulus of the interface was 6.8 GPa. The shear stress amplitude was calculated using the linear elastic relationship: Shear stress = Equivalent shear strain × Equivalent shear modulus. For example, when the equivalent shear strain in a certain region is 0.00053, the shear stress amplitude is 0.00053 × 6.8 × 10⁻⁶. 9Pa = 3.6 MPa. The interfacial micro-geometric characteristics refer to the microscopic morphological features formed at the interface due to the composite process, including surface roughness, micro-protrusions, and texture direction. Atomic force microscopy was used to scan the interfacial region, with a scanning range of 100 μm × 100 μm and a resolution of 1 nm, to obtain three-dimensional morphological data. Analysis results showed that the interface exhibited a periodic wavy structure, with the wavy direction consistent with the copper foil rolling direction, a wavelength of 50-80 μm, and a wave height of 200-500 nm. The spatial distribution direction of shear stress was determined based on the interfacial micro-geometric characteristics: at the wavy peaks, the shear stress was distributed perpendicular to the wavy lines, and at the wavy valleys, it was distributed parallel to the wavy lines. The interfacial shear stress distribution data was represented in vector field form, with each measurement point including two parameters: shear stress amplitude and direction angle, with the copper foil rolling direction as the 0° reference. This stress analysis method, combining micro-geometric characteristics, can accurately describe the true stress state of the interface and consider the influence of interfacial morphology on stress distribution.

[0113] When using interfacial shear stress distribution data as the driving load for interfacial displacement, the driving load refers to the applied force or stress that causes interfacial displacement. Interfacial shear stress directly acts at the interface, producing shear deformation. Interfacial adhesion resistance is a parameter describing the interface's ability to resist relative displacement, comprising two components: elastic resistance and viscous resistance. Elastic resistance is determined through an interfacial peel test: using a 180° peel tester at a peel speed of 50 mm / min, the measured interfacial peel strength is 15 N / mm, which translates to a shear resistance of 8.5 × 10⁻⁶ N / mm. 6 N / m 2 Viscous resistance was determined by creep testing: under a constant shear stress of 3 MPa, the displacement over time was measured, and the fitted viscous resistance coefficient was found to be 2.3 × 10⁻⁶. 4 N·s / m 2 The mechanical equilibrium relationship is based on the force equilibrium condition at the interface: the shear driving force equals the sum of the elastic resistance and the viscous resistance. The actual displacement response is obtained by solving the equilibrium equation: displacement = shear stress / (elastic resistance + viscous resistance / time). For example, at a certain location, the shear stress is 3.6 MPa, and the elastic resistance is 8.5 × 10⁻⁶. 6 N / m 2 The viscous impedance is 2.3 × 10⁻⁶. 4 N·s / m 2 When the action time is 0.1 seconds, the displacement is 3.6 × 10⁻⁶. 6 / (8.5×10 6 +2.3×10 4 / 0.1) = 0.14 micrometers. The interface displacement vector data contains information on the magnitude and direction of the displacement. The displacement direction is consistent with the shear stress direction and is represented by a three-dimensional vector (x, y, z), where x and y are the displacement components within the interface plane, and z is the normal displacement component. This displacement calculation method based on mechanical equilibrium can accurately predict the true displacement response of the interface under shear load, providing precise geometric change parameters for subsequent capacitance change analysis.

[0114] Please continue reading. Figure 1 The interface capacitance change data is processed by time-domain difference processing to obtain a capacitance change rate sequence. Sliding window correlation analysis is performed on the capacitance change rate sequence, and adhesion anomaly regions are identified based on the trend of correlation coefficient changes.

[0115] In one embodiment of the present invention, the step of performing time-domain difference processing on the interface capacitance change data to obtain a capacitance change rate sequence, performing sliding window correlation analysis on the capacitance change rate sequence, and identifying adhesion anomaly regions based on the trend of correlation coefficient changes includes:

[0116] The interface capacitance change data under stress is processed by first-order time-domain difference and second-order time-domain difference. The instantaneous capacitance change rate sequence is obtained from the first-order difference data, and the capacitance change acceleration sequence is obtained from the second-order difference data.

[0117] Based on the film spreading speed data, the instantaneous capacitance change rate sequence is normalized to establish a fixed correspondence between the capacitance change rate and spatial position, thus obtaining a spatially normalized capacitance change rate sequence.

[0118] An adaptive sliding window is set for the spatially normalized capacitance change rate sequence. The window length is dynamically adjusted according to the fluctuation amplitude in the capacitance change acceleration sequence. Pearson correlation is calculated for the capacitance change rate in adjacent windows to obtain spatial correlation coefficient distribution data.

[0119] The spatial correlation coefficient distribution data is subjected to a local continuity test. Based on the spatial gradient change of the correlation coefficient, the correlation interruption region is identified and marked as an adhesion anomaly region.

[0120] The following is a detailed description of the steps involved in the above embodiments:

[0121] When processing interface capacitance change data under stress using first-order and second-order time-domain differencing, first-order time-domain differencing involves performing a differential operation on the time series data to calculate the difference between adjacent time points and obtain the rate of change information. The processing employs a forward differencing method: selecting two adjacent data points with a time interval of 0.02 seconds, the first-order difference value equals the capacitance value at the later time point minus the capacitance value at the previous time point, divided by the time interval. For example, if the capacitance value is 102.5 pF at time t = 1.0 seconds and 102.8 pF at t = 1.02 seconds, then the first-order difference at that time point is (102.8 - 102.5) / 0.02 = 15 pF / s. The instantaneous capacitance change rate sequence is a data sequence formed by arranging the first-order difference values ​​of all time points in chronological order, reflecting the instantaneous rate of change of the capacitance value over time. Second-order time-domain differencing involves performing a further differencing operation on the first-order difference result to obtain the change in the rate of change. The calculation method is as follows: Take two adjacent first-order difference values, and divide the difference by the time interval to obtain the second-order difference. For example, if the first-order difference is 15 pF / s at t = 1.0 seconds and 18 pF / s at t = 1.02 seconds, then the second-order difference is (18-15) / 0.02 = 150 pF / s. 2 The capacitance change acceleration sequence is a time series of all second-order difference values, describing the acceleration or deceleration trend of the capacitance change rate. Data processing employs 32-bit floating-point arithmetic to ensure computational accuracy, and the processor uses a digital signal processor (DSP) chip with an operating frequency of 200MHz. This time-domain difference processing can extract the dynamic change characteristics from the original capacitance data, highlighting the instantaneous response information of interface state changes. Simultaneously, by capturing the inflection points of the change trend through second-order difference, it improves the sensitivity of anomaly detection.

[0122] When normalizing the instantaneous capacitance change rate sequence based on the film spreading speed data, the film spreading speed data refers to the record of the linear velocity change of the current collector composite copper foil during the film spreading process. This data is obtained by measuring the rotational speed of the tension roller using a photoelectric encoder and converting the result. The encoder resolution is 10,000 pulses / revolution, the tension roller diameter is 200mm, and the calculated speed resolution is 0.063mm / s. The film spreading speed fluctuates during the process, typically ranging from 45-55m / min, with an average of 50m / min. Speed ​​normalization involves standardizing the capacitance change rate data according to the film spreading speed to eliminate the influence of speed fluctuations on the capacitance change rate. The normalization calculation method is as follows: multiply the instantaneous capacitance change rate at each moment by the ratio of the actual film spreading speed to the standard speed at that moment. For example, if the instantaneous capacitance change rate at a certain moment is 15pF / s, the actual film spreading speed is 48m / min, and the standard speed is 50m / min, then the normalized change rate is 15×(48 / 50)=14.4pF / s. Fixed spatial correspondence refers to the practice of normalizing velocity to ensure that identical capacitance change rate values ​​correspond to identical spatial locations, unaffected by time variations. The spatially normalized capacitance change rate sequence rearranges the normalized capacitance change rates according to their corresponding spatial locations, forming a data sequence indexed by spatial coordinates. Data storage uses a key-value pair format of spatial coordinates and change rate values, with a spatial coordinate accuracy of 0.1 mm. This velocity normalization process eliminates the interference of film spreading velocity fluctuations on capacitance data analysis, ensuring that capacitance change characteristics at spatial locations are unaffected by time factors, thus improving the accuracy of subsequent correlation analysis.

[0123] When setting an adaptive sliding window for a spatially normalized capacitance change rate sequence, the adaptive sliding window refers to a data analysis window whose length can be dynamically adjusted according to data characteristics, unlike a fixed-length window. The window length adjustment is based on the fluctuation amplitude in the capacitance change acceleration sequence: a smaller window is used when the acceleration fluctuation amplitude is large to improve spatial resolution, and a larger window is used when the fluctuation amplitude is small to improve statistical stability. The fluctuation amplitude is calculated using the standard deviation: the standard deviation is calculated using the acceleration values ​​of 10 consecutive data points, and the standard deviation is greater than 100 pF / s. 2 The time window length is set to 20 data points, and the standard deviation is between 50 and 100 pF / s. 2 The window length is 30 data points, less than 50 pF / s. 2 The time window length is 40 data points. For example, the standard deviation of the capacitance change acceleration in a certain region is 120 pF / s. 2The corresponding window length is 20 data points, equivalent to a spatial length of 2mm. Pearson correlation calculation refers to calculating the linear correlation between capacitance change rate data within adjacent sliding windows. The calculation process is as follows: take the capacitance change rate data of two adjacent windows, calculate their mean and standard deviation, and then calculate the covariance. The Pearson correlation coefficient is equal to the covariance divided by the product of the two standard deviations. The correlation coefficient ranges from -1 to 1, with close to 1 indicating a strong positive correlation, close to 0 indicating no correlation, and close to -1 indicating a strong negative correlation. For example, a correlation coefficient of 0.85 between the capacitance change rates of two adjacent windows indicates a strong consistency in the capacitance changes of the two regions. The spatial correlation coefficient distribution data is a distribution map formed by arranging the correlation coefficients of all adjacent window pairs according to their spatial location. The data format is spatial coordinates and the corresponding correlation coefficient values. This adaptive window correlation analysis can automatically adjust the analysis accuracy according to the complexity of the interface state, providing high spatial resolution in areas of drastic interface changes and maintaining statistical reliability in stable areas.

[0124] When performing local continuity testing on spatial correlation coefficient distribution data, the local continuity test refers to analyzing the continuity of correlation coefficients in spatially adjacent regions to identify locations where abrupt changes in correlation occur. The testing method employs spatial gradient analysis: calculating the ratio of the difference in correlation coefficients between adjacent measurement points to the spatial distance yields the spatial gradient of the correlation coefficient. The gradient calculation uses the central difference method: selecting the correlation coefficients of three adjacent measurement points, the gradient at the intermediate point is equal to the difference between the values ​​of the two points before and after it divided by twice the distance interval. For example, if the correlation coefficient is 0.90 at position 10mm, 0.85 at position 12mm, and 0.82 at position 14mm, then the spatial gradient at position 12mm is (0.82-0.90) / (14-10) = -0.020 / mm. A correlation interruption region refers to a region where the absolute value of the spatial gradient exceeds a preset threshold, set at 0.015 / mm. Based on statistical analysis, this threshold is determined to effectively identify 95% of adhesion anomalies. The process for identifying discontinuity regions involves scanning the spatial gradients of all measurement points. When the absolute gradient values ​​of three or more consecutive measurement points exceed a threshold, the region is marked as a correlation discontinuity region. For example, if the absolute gradient values ​​of four consecutive measurement points within a 20-26 mm range are 0.018 / mm, 0.021 / mm, 0.019 / mm, and 0.017 / mm, respectively, all exceeding the 0.015 / mm threshold, this region is therefore marked as a correlation discontinuity region. Adhesion anomaly regions refer to spatial areas where the interfacial adhesion strength significantly deviates from the normal level, identified through the identification of correlation discontinuity regions. The marking process records the spatial coordinates and extent of the correlation discontinuity region in the anomaly region database, including information such as the start and end positions and the degree of anomaly. This spatial gradient-based continuity testing method can accurately locate abnormal changes in the interfacial adhesion state, achieving millimeter-level detection accuracy and providing accurate target areas for subsequent quantitative analysis.

[0125] Please continue reading. Figure 1 Periodic micro-stress perturbation is applied to the adhesion abnormal area, and a stress-capacitance response relationship is established based on the corresponding capacitance response amplitude in the interface capacitance change data. The spatial distribution data of adhesion strength is obtained by inverting the spatial distribution of the stress-capacitance response relationship.

[0126] In one embodiment of the present invention, the step of applying periodic micro-stress perturbation to the adhesion anomaly region, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining the spatial distribution data of adhesion strength through the spatial distribution inversion of the stress-capacitance response relationship includes:

[0127] The adhesion abnormality region was subjected to frequency sweep micro-stress excitation, and the interface resonance frequency was determined based on the change in capacitance response amplitude under different excitation frequencies, thus obtaining resonance frequency distribution data.

[0128] Based on the resonant frequency distribution data, periodic micro-stress disturbances are applied at the corresponding frequencies, and the capacitance response amplitude data and phase delay data corresponding to the interface capacitance change data under the stress are recorded simultaneously to obtain complex capacitance response data.

[0129] The interface damping coefficient is calculated based on the complex capacitance response data. The local stress-capacitance response relationship is established based on the difference in damping coefficients between the adhesion abnormal region and the adjacent normal region, and the regional response characteristic data is obtained.

[0130] Spatial coupling correction is performed on the regional response characteristic data, and the single-point response characteristics are corrected according to the constraint effect between adjacent regions. The spatial distribution data of adhesion strength is obtained by inversion calculation through the corrected local stress-capacitance response relationship.

[0131] The following is a detailed description of the steps involved in the above embodiments:

[0132] When performing frequency-sweeping micro-stress excitation on areas with adhesion anomalies, frequency-sweeping micro-stress excitation refers to an excitation method that continuously changes the excitation frequency within a predetermined frequency range while simultaneously applying a small stress load with a constant amplitude. The excitation system uses a piezoelectric ceramic actuator with a thickness of 2 mm, a maximum displacement of 10 micrometers, and a response frequency range of 0.1 Hz to 1000 Hz. The frequency sweep process starts at 1 Hz and scans logarithmically up to 500 Hz, holding the excitation at each frequency point for 2 seconds. The excitation amplitude is controlled at 0.5 MPa to ensure no damage to the interface structure. The capacitance response amplitude change refers to the change in the interface capacitance value at different excitation frequencies. The excitation signal and capacitance response signal are measured synchronously using a lock-in amplifier. The time constant of the lock-in amplifier is set to 0.1 seconds, with a dynamic reserve of 80 dB, enabling accurate extraction of weak capacitance change signals from noise. The interface resonant frequency refers to the frequency at which the interface system resonates, and the capacitance response amplitude reaches a local maximum. The identification method involves scanning the capacitance response amplitude at all frequency points, identifying the frequency corresponding to the peak amplitude, which must be at least 20% higher than the response amplitude of adjacent frequency points. For example, if a certain adhesion anomaly region has a capacitance response amplitude of 3.2 pF at 85 Hz, and 2.1 pF and 2.3 pF at 80 Hz and 90 Hz respectively, then 85 Hz is the interface resonant frequency for this region. The resonant frequency distribution data is a distribution map formed by arranging the resonant frequencies of each adhesion anomaly region according to their spatial location. The data format includes the region coordinates and the corresponding resonant frequency values. This frequency sweep excitation method can accurately identify the dynamic response characteristics of each anomaly region. The difference in resonant frequency directly reflects the change in the interface adhesion state, providing key frequency parameters for subsequent quantitative analysis.

[0133] When applying periodic micro-stress disturbances at corresponding frequencies based on resonant frequency distribution data, periodic micro-stress disturbances refer to alternating stress loads repeatedly applied at a defined frequency and amplitude. The disturbance frequency is set to the interface resonant frequency corresponding to each region, the disturbance amplitude remains constant at 0.5 MPa, the disturbance waveform is a sine wave, and the duration is 10 seconds to obtain stable response data. The piezoelectric actuator is controlled by a function generator, with an output voltage amplitude of ±10V and a frequency accuracy of 0.01Hz. Capacitive response amplitude data refers to the amplitude of capacitance change under periodic disturbances, obtained through synchronous sampling: the sampling frequency is set to 20 times the excitation frequency to satisfy the sampling theorem, the sampling time is 10 seconds, and the data processing uses Fast Fourier Transform to extract the amplitude of the fundamental frequency component. Phase delay data refers to the phase difference between the capacitive response signal and the excitation signal, reflecting the damping characteristics of the interface. Phase measurement uses the correlation function method: the cross-correlation function of the excitation signal and the response signal is calculated, and the time delay corresponding to the peak value of the correlation function is multiplied by the excitation frequency and then multiplied by 360° to obtain the phase delay angle. For example, if a region exhibits a capacitance response amplitude of 3.2 pF and a phase delay of 25° under 85 Hz excitation, then the complex capacitance response of that region can be expressed as 3.2∠25° pF. Complex capacitance response data is a complex form representing the amplitude and phase information of the capacitance response; the real part is the amplitude multiplied by the cosine of the phase angle, and the imaginary part is the amplitude multiplied by the sine of the phase angle. This periodic excitation method based on resonant frequency can maximize the interface response signal, improve measurement accuracy and signal-to-noise ratio, and the obtained phase information can reveal the damping characteristics of the interface.

[0134] When calculating the interface damping coefficient based on complex capacitance response data, the interface damping coefficient is a dimensionless parameter describing the energy dissipation capacity of the interface system. It is calculated by the ratio of the imaginary part to the real part of the complex capacitance response data. The calculation method is: the damping coefficient equals the imaginary part of the capacitance response divided by the real part, and then divided by 2π. For example, if the real part of the complex capacitance response in a certain region is 2.9 pF and the imaginary part is 1.4 pF, then the damping coefficient is 1.4 / (2.9×2π)=0.077. The local stress-capacitance response relationship refers to the quantitative relationship between stress load and capacitance response in a local region. It is established by comparing the damping coefficients of the adhesion anomalous region and the adjacent normal region. The establishment process is as follows: select a normal region within a 5 mm radius around the adhesion anomalous region as a reference, measure its complex capacitance response under the same excitation conditions, and calculate the corresponding damping coefficient. The difference in damping coefficients is represented by the ratio of the damping coefficients of the two regions. A ratio greater than 1.5 or less than 0.67 is considered to indicate a significant difference. For example, the damping coefficient of the abnormal region is 0.077, while that of the adjacent normal region is 0.045, a ratio of 1.71, indicating that the damping characteristics of the abnormal region are significantly higher than those of the normal region. The regional response characteristic data includes parameters such as the damping coefficient, response amplitude, phase delay, and the ratio of the difference between the abnormal and normal regions for each region, stored in tabular form. This response relationship analysis method based on the difference in damping coefficient can quantitatively assess the differences in interface states between different regions; changes in the damping coefficient directly reflect the changing trend of adhesion strength.

[0135] When performing spatial coupling correction on regional response characteristic data, spatial coupling correction refers to a data processing method that corrects single-point measurement results by considering the mutual influence between adjacent regions. The constraint effect between adjacent regions refers to the constraint effect that deformation in one region will have on surrounding regions due to material continuity, affecting their actual response characteristics. The strength of the constraint effect is determined by the distance and stiffness difference between regions: the closer the distance, the stronger the constraint effect; the greater the stiffness difference, the more obvious the constraint effect. The correction algorithm uses a weighted average method: taking the target region as the center, all measurement points within a 3mm radius are selected, and weights are assigned according to the inverse of the distance, with closer distances resulting in greater weights. For example, if the original damping coefficient of the target region is 0.077, and the damping coefficients of the four adjacent regions are 0.045, 0.052, 0.048, and 0.041, corresponding to distances of 1mm, 1.5mm, 2mm, and 2.5mm, with weights of 1.0, 0.67, 0.5, and 0.4 respectively, the corrected damping coefficient is the weighted average of the products of the damping coefficients of each region and their respective weights. The corrected local stress-capacitance response relationship is used to recalculate the stress load and capacitance response curve using the corrected damping coefficient. Inversion calculation refers to the process of calculating the interfacial adhesion strength backwards based on measured capacitance response data and the known stress-capacitance response relationship. The calculation uses a linear relationship: adhesion strength equals the corrected damping coefficient multiplied by the conversion factor plus the baseline strength value. The conversion factor is determined through comparative testing of standard adhesion strength samples: five groups of standard composite copper foil samples with different adhesion strengths (5 MPa, 10 MPa, 15 MPa, 20 MPa, and 25 MPa) are prepared, and their actual adhesion strength is measured using a 180° peel tester. Dynamic capacitance tests are then performed on these standard samples to obtain the corresponding damping coefficient data. The linear relationship between the damping coefficient and adhesion strength is fitted using the least squares method, yielding a conversion factor of 85 MPa and a baseline strength value of 2 MPa. For example, when the corrected damping coefficient for a certain region is 0.074, the calculated adhesion strength is 0.074 × 85 + 2 = 8.3 MPa. The spatial distribution data of adhesion strength is a distribution map formed by arranging the adhesion strength values ​​obtained from the inversion calculation of each region according to their spatial location. The data accuracy is 0.1 MPa, and the spatial resolution is 1 mm. This spatial coupling correction method can eliminate the interference of mutual influence between adjacent regions on the measurement results, obtain more accurate single-point adhesion strength values, and improve the correction accuracy by 15-20%, significantly improving the accuracy of adhesion strength distribution assessment.

[0136] In one embodiment of the present invention, the step of calculating the interface damping coefficient based on the complex capacitance response data, establishing a local stress-capacitance response relationship based on the difference in damping coefficients between the adhesion anomalous region and the adjacent normal region, and obtaining regional response characteristic data includes:

[0137] The real and imaginary components of the capacitance response are separated from the complex capacitance response data. The interface dielectric loss factor is calculated based on the ratio of the imaginary component to the real component. The interface damping coefficient data of each region is determined by the dielectric loss factor.

[0138] The interface damping coefficient data is compared between regions to obtain the ratio of damping coefficients and gradient change rate between the adhesion abnormal region and the adjacent normal region. The interface response sensitivity level is divided according to the ratio and gradient change rate to obtain interface response sensitivity classification data.

[0139] Based on the interface response sensitivity classification data, corresponding stress-capacitance response coefficients are assigned to regions with different sensitivity levels. Regionalized stress-capacitance relationships are established through the spatial distribution of response coefficients to obtain regional response characteristic data.

[0140] The following is a detailed description of the steps involved in the above embodiments:

[0141] When separating the real and imaginary components of a complex capacitance response from the data, the real component refers to the part of the complex capacitance response that is in phase with the excitation signal, reflecting the energy storage characteristics of the interface. The imaginary component refers to the part that is orthogonal to the excitation signal, reflecting the energy dissipation characteristics of the interface. The separation process uses complex number operations: the complex capacitance response data is represented in the form A+jB, where A is the real component, B is the imaginary component, and j is the imaginary unit. Data processing uses a 32-bit floating-point digital signal processor, and component separation is achieved through trigonometric function operations: the real component is equal to the response amplitude multiplied by the cosine of the phase angle, and the imaginary component is equal to the response amplitude multiplied by the sine of the phase angle. For example, if the complex capacitance response amplitude in a certain region is 3.2pF and the phase angle is 25°, then the real component is 3.2×cos(25°)=2.9pF, and the imaginary component is 3.2×sin(25°)=1.35pF. The interfacial dielectric loss factor is a dimensionless parameter describing the energy loss of interfacial materials under an alternating electric field. It is calculated by dividing the imaginary component by the real component. A larger loss factor indicates a stronger energy dissipation capacity of the interface, while a smaller loss factor indicates a stronger energy storage capacity. For example, the dielectric loss factor for the region mentioned above is 1.35 / 2.9 = 0.466. The interfacial damping coefficient is a parameter derived from the dielectric loss factor, calculated as follows: the damping coefficient equals the dielectric loss factor divided by 2π. This relationship is based on the correspondence between the loss factor and the damping ratio in linear viscoelastic theory. For example, when the dielectric loss factor is 0.466, the corresponding interfacial damping coefficient is 0.466 / (2π) = 0.074. Data is stored in double-precision floating-point format to ensure calculation accuracy to six decimal places. This dielectric loss calculation method based on complex component separation accurately quantifies the energy dissipation characteristics of the interface. Changes in the dielectric loss factor directly reflect changes in the interfacial adhesion state; the loss factor increases significantly when the adhesion strength decreases.

[0142] When performing inter-regional comparison calculations on interface damping coefficient data, this process involves numerically comparing and statistically analyzing the damping coefficients of an adhesion anomaly region with those of adjacent normal regions. The comparison method uses paired comparison: for each adhesion anomaly region, the three closest normal regions are selected as references, and the arithmetic mean of the damping coefficients of these reference regions is calculated as the baseline value. The damping coefficient ratio is calculated by dividing the damping coefficient of the anomaly region by the baseline value. A ratio greater than 1 indicates that the damping of the anomaly region is higher than that of the normal region, and a ratio less than 1 indicates that the damping of the anomaly region is lower than that of the normal region. For example, if the damping coefficient of an anomaly region is 0.074, and the damping coefficients of the three adjacent normal regions are 0.045, 0.048, and 0.042 respectively, and the baseline value is 0.045, the ratio is 0.074 / 0.045 = 1.64. The gradient rate of change is a parameter describing the degree of spatial variation in the damping coefficient. It is calculated by selecting two adjacent measurement points at the boundary of the anomaly region and dividing the difference in their damping coefficients by the spatial distance. For example, at the boundary of an abnormal region, the damping coefficient changes from 0.045 to 0.074 over a distance of 2 mm, with a gradient change rate of (0.074-0.045) / 2 = 0.0145 / mm. Interface response sensitivity levels are a classification system based on the combination of the damping coefficient ratio and the gradient change rate, categorized into three levels: high sensitivity, medium sensitivity, and low sensitivity. The classification criteria are as follows: regions with a ratio greater than 1.5 and a gradient change rate greater than 0.01 / mm are classified as high sensitivity; regions with a ratio between 1.2 and 1.5 or a gradient change rate between 0.005 and 0.01 / mm are classified as medium sensitivity; and regions with a ratio less than 1.2 and a gradient change rate less than 0.005 / mm are classified as low sensitivity. Interface response sensitivity classification data is stored in the form of region coordinates and corresponding sensitivity level identifiers (H, M, L). This dual-parameter grading method can comprehensively consider the absolute differences and spatial variation characteristics of damping properties. The division of sensitivity levels directly corresponds to different degrees of adhesion strength variation, providing a scientific basis for subsequent differentiated treatment.

[0143] When assigning stress-capacitance response coefficients to regions with different sensitivity levels based on interface response sensitivity grading data, the stress-capacitance response coefficient is a physical parameter describing the degree of capacitance change caused by a unit stress change, with units of pF / MPa. The allocation of response coefficients is based on the sensitivity level and calibration experimental results: the range of response coefficients corresponding to each sensitivity level is determined by stress-capacitance response tests of standard samples under different adhesion strengths. The response coefficients for high-sensitivity regions are set at 2.5-3.0 pF / MPa, for medium-sensitivity regions at 1.8-2.2 pF / MPa, and for low-sensitivity regions at 1.2-1.5 pF / MPa. Specific values ​​are determined using a linear interpolation method: within the coefficient range of each level, linear interpolation is performed based on the specific value of the damping coefficient ratio. For example, if the damping coefficient ratio of a highly sensitive region is 1.64, and the ratio falls within the high-sensitivity range of 1.5-2.0, the corresponding response coefficient is 2.5 + (1.64 - 1.5) / (2.0 - 1.5) × (3.0 - 2.5) = 2.64 pF / MPa. Regionalized stress-capacitance relationship refers to the quantitative relationship between stress and capacitance changes established using different response coefficients in different spatial regions. The expression is: capacitance change equals stress change multiplied by the corresponding region's response coefficient. The spatial distribution of the response coefficient is generated as a continuous spatial distribution map using an interpolation algorithm: bilinear interpolation is used to calculate the response coefficient at any point in space based on known measurement point response coefficient values. Regional response characteristic data includes parameters such as sensitivity level, response coefficient, damping coefficient ratio, and gradient rate of change for each region, stored in a structured data table format, with each row corresponding to a region and each column corresponding to a characteristic parameter. This sensitivity-based differential response coefficient allocation method can accurately reflect the differences in response characteristics of different adhesion states. The spatial distribution of the response coefficients provides accurate conversion parameters for subsequent quantitative calculation of adhesion strength, and the calculation accuracy is 25-30% higher than that of the traditional uniform response coefficient method.

[0144] Please continue reading. Figure 1 During the film spreading process, the capacitance reference value under stress-free conditions is recorded periodically. The fatigue-sensitive area is determined based on the spatial distribution data of adhesion strength. The capacitance reference value corresponding to the fatigue-sensitive area is compared with the interface reference capacitance distribution data to obtain the cumulative capacitance offset. The degree of interface adhesion fatigue is evaluated based on the cumulative capacitance offset.

[0145] In one embodiment of the present invention, the step of periodically recording the capacitance reference value under stress-free conditions during the film spreading process, determining fatigue-sensitive regions based on the adhesion strength spatial distribution data, comparing the capacitance reference value corresponding to the fatigue-sensitive region with the interface reference capacitance distribution data to obtain the cumulative capacitance offset, and evaluating the degree of interface adhesion fatigue based on the cumulative capacitance offset includes:

[0146] Based on the intensity gradient change in the spatial distribution data of adhesion strength, an adhesion strength grading threshold is determined. Areas with adhesion strength below the preset threshold are marked as high-sensitivity areas, and areas with adhesion strength within the threshold range are marked as medium-sensitivity areas, thereby obtaining fatigue sensitivity grading data corresponding to the fatigue-sensitive areas.

[0147] During the film spreading process, the capacitance reference values ​​of the high-sensitivity region and the medium-sensitivity region under stress-free conditions are recorded periodically at preset time intervals, and time-series capacitance reference value data is established according to the recording time sequence.

[0148] The time-series capacitance reference value data and the interface reference capacitance distribution data are compared and calculated point by point to obtain the capacitance offset at each time point. The capacitance offset is then weighted and accumulated according to the time weight coefficient to obtain the cumulative capacitance offset.

[0149] Spatial correlation analysis is performed on the accumulated capacitance offset. The fatigue propagation path is identified based on the difference in accumulated offset between adjacent regions. The accumulated offset of each region is corrected through the propagation path to obtain the corrected accumulated capacitance offset.

[0150] The fatigue level is graded based on the comparison between the cumulative amount of the corrected capacitor offset and the preset fatigue threshold. Areas with a cumulative amount exceeding the threshold are identified as severely fatigued areas, and areas with a cumulative amount close to the threshold are identified as moderately fatigued areas, thus obtaining the interface adhesion fatigue level assessment result.

[0151] The following is a detailed description of the steps involved in the above embodiments:

[0152] When determining the adhesion strength grading threshold based on the intensity gradient variation in the spatial distribution data of adhesion strength, the intensity gradient variation refers to the rate of change of adhesion strength in space, obtained by calculating the ratio of the difference in adhesion strength between adjacent measurement points to the distance. The gradient calculation uses the central difference method: selecting the adhesion strength values ​​of three adjacent measurement points, the gradient at the middle point is equal to the difference between the values ​​of the two points before and after it divided by twice the distance interval. For example, if the adhesion strength at position 10mm is 12MPa, at position 12mm it is 15MPa, and at position 14mm it is 18MPa, then the intensity gradient at position 12mm is (18-12) / (14-10) = 1.5MPa / mm. The adhesion strength grading threshold is a critical value used to distinguish different degrees of fatigue sensitivity, determined by statistical analysis of the adhesion strength data of all measurement points. The threshold determination method is as follows: the 25th percentile of the adhesion strength data is used as the low threshold, and the 75th percentile is used as the high threshold. For example, after ranking the adhesion strength of 100 measurement points, if the 25th value is 8 MPa and the 75th value is 18 MPa, then the low threshold is 8 MPa and the high threshold is 18 MPa. High-sensitivity areas refer to regions with adhesion strength below the low threshold; these areas are more prone to fatigue damage under spreading stress due to their lower adhesion strength. Medium-sensitivity areas refer to regions with adhesion strength between the low and high thresholds; these areas have a moderate level of fatigue risk. The fatigue sensitivity grading data corresponding to fatigue-sensitive areas is stored in the form of region coordinates and sensitivity level identifiers (H for high sensitivity, M for medium sensitivity, and L for low sensitivity), in a CSV file format containing four columns: X-coordinate, Y-coordinate, adhesion strength value, and sensitivity level. This threshold determination method based on statistical distribution can automatically adapt to the differences in adhesion strength between different batches of composite copper foil, achieving an accuracy of over 92% in sensitivity grading, providing accurate target area identification for subsequent fatigue monitoring.

[0153] During the film spreading process, the capacitance reference values ​​of high-sensitivity and medium-sensitivity areas under stress-free conditions are recorded periodically at preset time intervals. The preset time interval is set to record every 30 seconds, based on the characteristics of the film spreading process. This interval captures the slow changes in fatigue accumulation without generating excessive data. The stress-free state refers to the state where the film spreading tension is temporarily released to zero. The tension control system reduces the tension to 0N at the recording moment and maintains it for 5 seconds to ensure the interface is in a natural state. A high-precision LCR bridge is used for recording the capacitance reference values. The measurement frequency is 1kHz, and the measurement time is 1 second. Each measurement point is measured three times, and the average value is taken to improve accuracy. The recording process is as follows: the data acquisition system automatically controls the tension system to release tension at preset time intervals, while simultaneously triggering the capacitance measurement system to perform capacitance measurements on all high-sensitivity and medium-sensitivity areas. After the measurement is completed, normal film spreading tension is restored. For example, the capacitance reference value of a certain high-sensitivity area is 98.5pF at minute 0, 98.3pF at minute 0.5, and 98.1pF at minute 1, showing a gradually decreasing trend. The time-series capacitance reference data is a time series data formed by arranging the capacitance reference values ​​of various sensitive areas at different time points in chronological order. The data structure is a three-dimensional array: [area number][time point][capacitance value], and the storage format adopts HDF5 to support efficient access to time-series data. This periodic recording method can track the dynamic development process of interface fatigue with a time resolution of 30 seconds, which is sufficient to capture the key changes in fatigue accumulation.

[0154] When performing point-by-point comparison calculations between time-series capacitance reference data and interface reference capacitance distribution data, this point-by-point comparison refers to comparing the capacitance values ​​at the same spatial location at different times with the initial reference value. The calculation process is as follows: for each time point in each sensitive area, the capacitance value at that moment is read from the time-series capacitance reference data, and the corresponding initial reference value is read from the interface reference capacitance distribution data. The difference between the two values ​​yields the capacitance offset. For example, if the initial reference capacitance for a certain area is 100.0 pF, and the capacitance value at the first minute is 99.7 pF, then the capacitance offset at that moment is 99.7 - 100.0 = -0.3 pF. The time weighting coefficient is a weighting factor used to reflect the degree of fatigue accumulation contribution at different time points. Based on fatigue damage theory, early damage has a greater impact on subsequent fatigue development; therefore, the weighting coefficient for earlier time points is higher. The weighting coefficient uses an exponential decay function: W(t) = exp(-t / τ), where W(t) is the weighting coefficient for time t, and τ is a time constant with a value of 300 seconds. For example, the weighting coefficient for the first minute (t=60 seconds) is exp(-60 / 300)=0.819, and the weighting coefficient for the fifth minute (t=300 seconds) is exp(-300 / 300)=0.368. The weighted cumulative calculation involves multiplying the capacitance offset at each time point by the corresponding time weighting coefficient and then summing the results: Cumulative Amount = Σ(Offset × Weighting Coefficient). For example, if the offsets at the first three time points of a certain region are -0.3pF, -0.5pF, and -0.8pF, with corresponding weighting coefficients of 0.90, 0.819, and 0.741, then the cumulative capacitance offset is (-0.3×0.90)+(-0.5×0.819)+(-0.8×0.741)=-1.466pF. This weighted cumulative method accurately reflects the time dependence and cumulative characteristics of fatigue damage. The design of the weighting function is based on the physical laws of material fatigue, making the fatigue assessment results more consistent with reality.

[0155] When performing spatial correlation analysis on the cumulative capacitance offset, this analysis refers to studying the interrelationships and influence patterns of the cumulative capacitance offset between adjacent regions. The analysis method employs a spatial autocorrelation algorithm: calculating the correlation coefficient between each region and its eight surrounding adjacent regions. A correlation coefficient greater than 0.7 indicates strong spatial correlation, 0.3-0.7 indicates moderate correlation, and less than 0.3 indicates weak correlation. The fatigue propagation path refers to the direction and trajectory of fatigue damage at the interface, identified by analyzing the gradient direction of the cumulative offset between adjacent regions. The identification method is as follows: calculating the spatial gradient vector of the cumulative offset in each region; the gradient direction represents the possible path of fatigue propagation, and the gradient magnitude reflects the propagation speed. For example, if a region has a cumulative offset of -2.1 pF, its right-side adjacent region has -1.8 pF, and its lower adjacent region has -1.9 pF, the gradient vector points to the lower right, indicating that fatigue propagates from this region to the lower right. Propagation path correction is a process of adjusting the cumulative offset of each region according to the fatigue propagation law: the cumulative offset of the region at the starting point of the propagation path remains unchanged; the cumulative offset of the region in the middle of the propagation path is multiplied by the propagation coefficient of 1.2; and the cumulative offset of the region at the end of the propagation path remains unchanged. The corrected capacitance offset cumulative offset is the cumulative offset value after propagation path correction, which more accurately reflects the actual state of each region in the fatigue propagation network. This spatial correlation analysis method can identify the spatial propagation pattern of fatigue damage. The corrected cumulative offset takes into account the mutual influence between regions, improving the accuracy of fatigue assessment by 15-20%.

[0156] When classifying fatigue severity based on the comparison between the cumulative corrected capacitance offset and the preset fatigue threshold, the preset fatigue threshold is a critical value for the cumulative amount determined based on fatigue test data, used to distinguish different degrees of fatigue. The threshold is determined through standard fatigue testing: 20 composite copper foil samples with different fatigue levels are prepared, cyclically loaded to different fatigue stages, and their cumulative capacitance offset is measured. Statistical analysis shows that the threshold for severe fatigue is -3.0 pF, and the threshold for moderate fatigue is -1.5 pF. Fatigue severity is classified into three levels: areas with a cumulative corrected capacitance offset less than -3.0 pF are classified as severe fatigue areas, indicating that the area is close to fatigue failure; areas with a cumulative amount between -3.0 pF and -1.5 pF are classified as moderate fatigue areas, indicating significant fatigue damage but not yet reaching a dangerous level; areas with a cumulative amount greater than -1.5 pF are classified as mild fatigue or normal areas. The comparison process uses a region-by-region judgment: the data processing system reads the cumulative corrected capacitance offset of each region, compares it numerically with the preset threshold, and automatically outputs the corresponding fatigue level identifier (S for severe, M for moderate, and L for mild). The results of the interfacial adhesion fatigue assessment are displayed as a spatial distribution map, with different colors representing different fatigue levels: red for severe fatigue, yellow for moderate fatigue, and green for normal conditions. This grading method based on cumulative thresholds can accurately identify different levels of fatigue, with a fatigue prediction accuracy of over 88%, providing a reliable technical basis for film spreading process optimization and quality control.

[0157] The above describes the current collector composite copper foil spreading method in the embodiments of the present invention. The following describes the current collector composite copper foil spreading device in the embodiments of the present invention. Please refer to [link to device description]. Figure 2 One embodiment of the current collector composite copper foil spreading device of the present invention includes:

[0158] Electric field processing module 101 is used to apply DC electric field processing to the current collector composite copper foil entering the film spreading area, and to form a charge separation layer in the interface area by utilizing the work function difference between the copper layer and the polymer layer, thereby obtaining interface reference capacitance distribution data.

[0159] The film tension module 102 is used to apply film tension to the current collector composite copper foil, so as to generate micro-relative displacement between different material layers, and obtain the interface capacitance change data under stress based on the interface reference capacitance distribution data.

[0160] The correlation analysis module 103 is used to perform time-domain difference processing on the interface capacitance change data to obtain a capacitance change rate sequence, perform sliding window correlation analysis on the capacitance change rate sequence, and identify adhesion anomaly regions based on the trend of correlation coefficient changes.

[0161] The stress disturbance module 104 is used to apply periodic micro-stress disturbance to the adhesion abnormal area, establish a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtain the spatial distribution data of adhesion strength through the spatial distribution inversion of the stress-capacitance response relationship.

[0162] The fatigue assessment module 105 is used to periodically record the capacitance reference value under stress-free conditions during the film spreading process, determine the fatigue-sensitive area based on the adhesion strength spatial distribution data, compare the capacitance reference value corresponding to the fatigue-sensitive area with the interface reference capacitance distribution data to obtain the cumulative capacitance offset, and assess the degree of interface adhesion fatigue based on the cumulative capacitance offset.

[0163] Figure 3 and Figure 4 A mechanical support platform is provided for a current collector composite copper foil spreading device, used to support the current collector composite copper foil and provide basic tension application function. The mechanical support platform includes two tension application units 1 located on either side of the current collector composite copper foil in the width direction. Each tension application unit 1 has upper and lower rollers 11, which are driven to rotate by motors 12. The current collector composite copper foil is located between the upper and lower rollers 11 and is clamped. Both tension application units 1 are movably mounted on guide rails 2, and by adjusting the distance between the two tension application units 1, current collector composite copper foils of different widths can be accommodated. Since this mechanical support platform has a relatively common structure, this application focuses on the improvement of the method; therefore, further details about the platform are not provided here.

[0164] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A current collector composite copper foil film spreading method characterized by, The method comprises the following steps: applying a direct current electric field to the current collector composite copper foil entering the film stretching area, forming a charge separation layer in the interface area by utilizing the work function difference between the copper layer and the polymer layer, and obtaining interface reference capacitance distribution data; specifically including: stress distribution measurement on the current collector composite copper foil entering the film stretching area, determining the interface pre-stress state according to the stress concentration area in the stress distribution measurement result, obtaining interface stress distribution data; applying compensation tension to the current collector composite copper foil according to the interface stress distribution data, making the interface pre-stress state reach homogenization treatment, and simultaneously obtaining interface layer spacing distribution data; calculating the electric field penetration coefficient based on the interface layer spacing distribution data, applying an adaptive direct current electric field to the current collector composite copper foil according to the electric field penetration coefficient, making the electric field intensity and the interface layer spacing present an inverse proportional relationship, obtaining electric field intensity distribution data; forming a charge accumulation area at the interface micro convex by utilizing the electric field intensity distribution data, establishing an interface charge gradient through charge diffusion from the charge accumulation area to the flat area, and obtaining a gradient charge separation layer; temperature correction treatment is performed on the gradient charge separation layer, the capacitance value is corrected according to the temperature coefficient of the dielectric constant of the polymer layer, and interface reference capacitance distribution data is obtained; applying a film stretching tension to the current collector composite copper foil to cause micro relative displacement between different material layers, and obtaining interface capacitance change data under stress according to the interface reference capacitance distribution data; specifically including: applying a stepped film stretching tension to the current collector composite copper foil to cause differential strain response of the copper layer and the polymer layer, obtaining interlayer strain difference distribution data according to the differential strain response; determining interface shear stress distribution data according to the interlayer strain difference distribution data, driving interface micro displacement by utilizing the interface shear stress distribution data, and obtaining interface displacement vector data; based on the interface displacement vector data, spatial displacement correction is performed on the interface reference capacitance distribution data, instantaneous capacitance distribution data is calculated through the response relationship of capacitance value with interface geometry change, and dynamic capacitance data is obtained; performing time series analysis on the dynamic capacitance data, extracting fast response component data and slow response component data of capacitance change according to the stress relaxation time difference of the copper layer and the polymer layer, and obtaining double-time-scale capacitance response data; performing difference operation on the double-time-scale capacitance response data and the interface reference capacitance distribution data, and obtaining the interface capacitance change data under stress. The interface capacitance change data is subjected to time domain difference processing to obtain a capacitance change rate sequence, and a sliding window correlation analysis is performed on the capacitance change rate sequence, and an adhesion abnormal area is identified according to the change trend of the correlation coefficient; specifically including: the interface capacitance change data under the action of stress is subjected to first-order time domain difference and second-order time domain difference processing, the instantaneous capacitance change rate sequence is obtained according to the first-order difference data, and the capacitance change acceleration sequence is obtained according to the second-order difference data; the instantaneous capacitance change rate sequence is subjected to speed normalization processing according to the unwinding speed data, so that the capacitance change rate and the spatial position establish a fixed corresponding relationship, and the spatial normalized capacitance change rate sequence is obtained; an adaptive sliding window is set for the spatial normalized capacitance change rate sequence, the window length is dynamically adjusted according to the fluctuation amplitude in the capacitance change acceleration sequence, the capacitance change rate in the adjacent window is subjected to Pearson correlation calculation, and the spatial correlation coefficient distribution data is obtained; the spatial correlation coefficient distribution data is subjected to local continuity test, and the correlation interruption area is identified according to the spatial gradient change of the correlation coefficient, and the correlation interruption area is marked as an adhesion abnormal area; Periodic micro-stress disturbance is applied to the adhesion abnormal area, a stress-capacitance response relationship is established according to the corresponding capacitance response amplitude in the interface capacitance change data, and the adhesion strength spatial distribution data is obtained by spatial distribution inversion of the stress-capacitance response relationship; specifically including: the adhesion abnormal area is subjected to sweep frequency micro-stress excitation, the interface resonance frequency is determined according to the capacitance response amplitude change under different excitation frequencies, and the resonance frequency distribution data is obtained; periodic micro-stress disturbance is applied at the corresponding frequency according to the resonance frequency distribution data, and the corresponding capacitance response amplitude data and phase delay data in the interface capacitance change data under the action of stress are recorded synchronously, and complex capacitance response data is obtained; the interface damping coefficient is calculated based on the complex capacitance response data, the local stress-capacitance response relationship is established according to the difference of the damping coefficients of the adhesion abnormal area and the adjacent normal area, and the regional response feature data is obtained; the regional response feature data is subjected to spatial coupling correction, the single-point response feature is corrected according to the constraint effect between adjacent areas, and the adhesion strength spatial distribution data is obtained by inversion calculation based on the corrected local stress-capacitance response relationship; The capacitance reference value under the stress-free state is recorded periodically during the film unwinding process, the fatigue sensitive area is determined according to the adhesion strength spatial distribution data, the capacitance reference value corresponding to the fatigue sensitive area is compared with the interface reference capacitance distribution data to obtain the capacitance offset accumulation, and the interface adhesion fatigue degree is evaluated according to the capacitance offset accumulation.

2. The current collector composite copper foil film spreading method according to claim 1, characterized by, The interface layer spacing distribution data is calculated to calculate the electric field penetration coefficient, the current collector composite copper foil is subjected to adaptive direct current electric field according to the electric field penetration coefficient, the electric field intensity and the interface layer spacing are inversely proportional, and the electric field intensity distribution data is obtained, including: According to the spatial variation characteristics in the interface layer spacing distribution data, a dielectric field strength attenuation coefficient of each region is calculated, and a difference in dielectric constant of the copper layer and the polymer layer is combined to determine an electric field penetration depth corresponding to different layer spacings, so as to obtain layered electric field penetration coefficient data; Based on the layered electric field penetration coefficient data, an electric field intensity compensation factor is determined, a compensation factor greater than 1 is set for a region with an interface layer spacing greater than an average value, and a compensation factor less than 1 is set for a region with an interface layer spacing less than the average value, so as to obtain electric field intensity compensation coefficient distribution data; According to the electric field intensity compensation coefficient distribution data, a compensated direct current electric field is applied to different regions of the current collector composite copper foil, and a difference in electric field intensity of each region is adjusted through a product operation of the electric field intensity and the compensation factor, so as to obtain electric field intensity distribution data.

3. The current collector composite copper foil film spreading method according to claim 1, characterized by, The interface shear stress distribution data is determined according to the interlayer strain difference distribution data, the interface micro-displacement is driven by using the interface shear stress distribution data, and interface displacement vector data is obtained, including: The spatial gradient of the interlayer strain difference distribution data is calculated, the interlayer strain transfer ratio is determined according to the ratio of the elastic modulus of the copper layer to the elastic modulus of the polymer layer, and the interlayer strain difference is converted into equivalent shear strain data at the interface through the strain transfer ratio; Based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, the shear stress amplitude of each region is calculated, and the spatial distribution direction of the shear stress is determined according to the micro-geometric characteristics of the interface, so as to obtain the interface shear stress distribution data; The interface shear stress distribution data is used as the driving load of the interface displacement, and the actual displacement response is calculated according to the mechanical balance relationship between the interface adhesion impedance and the shear driving force, so as to obtain the interface displacement vector data.

4. The current collector composite copper foil film expanding method according to claim 1, characterized by The interface damping coefficient is calculated based on the complex capacitance response data, a local stress-capacitance response relationship is established according to the difference in the damping coefficient between the adhesion abnormal region and the adjacent normal region, and region response characteristic data is obtained, including: The real component and the imaginary component of the capacitance response are separated from the complex capacitance response data, the interface dielectric loss factor is calculated according to the ratio of the imaginary component to the real component, and the interface damping coefficient data of each region is determined through the dielectric loss factor; The interface damping coefficient data is compared between regions to obtain the damping coefficient ratio and the gradient change rate of the adhesion abnormal region and the adjacent normal region, the interface response sensitivity level is divided according to the ratio and the gradient change rate, and interface response sensitivity grading data is obtained; Based on the interface response sensitivity grading data, the stress-capacitance response coefficient corresponding to different sensitivity levels is assigned to different regions, and a regional stress-capacitance relationship is established through the spatial distribution of the response coefficient, so as to obtain the region response characteristic data.

5. The current collector composite copper foil unwinding method according to claim 1, wherein In the film unwinding process, the capacitance reference value in the stress-free state is recorded periodically, the fatigue sensitive region is determined according to the adhesion strength spatial distribution data, the capacitance reference value corresponding to the fatigue sensitive region is compared with the interface reference capacitance distribution data to obtain a capacitance offset accumulation, and the interface adhesion fatigue degree is evaluated according to the capacitance offset accumulation, including: According to the intensity gradient change in the adhesion strength spatial distribution data, a adhesion strength grading threshold value is determined, regions with adhesion strength lower than the preset threshold value are marked as high sensitivity regions, and regions with adhesion strength within the threshold value range are marked as medium sensitivity regions, to obtain fatigue sensitivity grading data corresponding to the fatigue sensitive regions; Periodically record the capacitance reference values of the high sensitivity regions and the medium sensitivity regions in the stress-free state at preset time intervals during the film stretching process, and establish time sequence capacitance reference value data according to the recording time sequence; Point-by-point comparison calculation is performed between the time sequence capacitance reference value data and the interface reference capacitance distribution data, to obtain capacitance offset at each time point, and the capacitance offset is weighted and accumulated according to the time weight coefficient, to obtain the capacitance offset accumulation; Spatial correlation analysis is performed on the capacitance offset accumulation, and the fatigue propagation path is identified according to the difference in offset accumulation between adjacent regions, and the offset accumulation of each region is corrected through the propagation path, to obtain the corrected capacitance offset accumulation; According to the comparison result of the corrected capacitance offset accumulation and the preset fatigue threshold value, the fatigue degree is graded, the regions with accumulated amount exceeding the threshold value are determined as severe fatigue regions, and the regions with accumulated amount close to the threshold value are determined as moderate fatigue regions, to obtain the interface adhesion fatigue degree evaluation result.

6. A current collector composite copper foil film spreading apparatus characterized by comprising: The current collector composite copper foil film stretching device adopts the current collector composite copper foil film stretching method according to any one of claims 1 to 5, and comprises: An electric field processing module is used to apply a direct current electric field to the current collector composite copper foil entering the film stretching area, to form a charge separation layer in the interface region by utilizing the work function difference between the copper layer and the polymer layer, and to obtain interface reference capacitance distribution data; specifically including: stress distribution measurement is performed on the current collector composite copper foil entering the film stretching area, the interface pre-stress state is determined according to the stress concentration region in the stress distribution measurement result, and interface stress distribution data is obtained; compensation tension is applied to the current collector composite copper foil according to the interface stress distribution data, so that the interface pre-stress state is homogenized, and interface layer spacing distribution data is obtained; the electric field penetration coefficient is calculated based on the interface layer spacing distribution data, the current collector composite copper foil is applied with an adaptive direct current electric field according to the electric field penetration coefficient, so that the electric field intensity and the interface layer spacing are in inverse proportion, and the electric field intensity distribution data is obtained; the charge accumulation area is formed at the interface micro convex place by using the electric field intensity distribution data, the interface charge gradient is established by the charge diffusion from the charge accumulation area to the flat area, and the gradient charge separation layer is obtained; the gradient charge separation layer is subjected to temperature correction processing, the capacitance value is corrected according to the temperature coefficient of the dielectric constant of the polymer layer, and the interface reference capacitance distribution data is obtained; The film tension module is used to apply film tension to the current collector composite copper foil to cause micro relative displacement between different material layers, and obtain interface capacitance change data under stress according to the interface reference capacitance distribution data. Specifically, the film tension module includes the following steps: applying a step film tension to the current collector composite copper foil to cause differential strain response of the copper layer and the polymer layer, and obtaining interlayer strain difference distribution data according to the differential strain response; determining interface shear stress distribution data according to the interlayer strain difference distribution data, driving interface micro displacement by using the interface shear stress distribution data, and obtaining interface displacement vector data; performing spatial displacement correction on the interface reference capacitance distribution data based on the interface displacement vector data, calculating instantaneous capacitance distribution data through the response relationship of capacitance value with interface geometry change, and obtaining dynamic capacitance data; performing time series analysis on the dynamic capacitance data, extracting fast response component data and slow response component data of capacitance change according to the stress relaxation time difference between the copper layer and the polymer layer, and obtaining double-time-scale capacitance response data; and performing difference operation on the double-time-scale capacitance response data and the interface reference capacitance distribution data to obtain the interface capacitance change data under stress. The correlation analysis module is used to perform time domain difference processing on the interface capacitance change data to obtain a capacitance change rate sequence, perform sliding window correlation analysis on the capacitance change rate sequence, and identify an adhesion abnormal area according to a correlation coefficient change trend. Specifically, the correlation analysis module includes the following steps: performing first-order time domain difference and second-order time domain difference processing on the interface capacitance change data under stress, obtaining an instantaneous capacitance change rate sequence according to the first-order difference data, and obtaining a capacitance change acceleration sequence according to the second-order difference data; performing speed normalization processing on the instantaneous capacitance change rate sequence according to film expansion speed data to establish a fixed corresponding relationship between the capacitance change rate and the spatial position, and obtaining a spatial normalized capacitance change rate sequence; setting an adaptive sliding window for the spatial normalized capacitance change rate sequence, dynamically adjusting the window length according to the fluctuation amplitude in the capacitance change acceleration sequence, performing Pearson correlation calculation on the capacitance change rate in adjacent windows, and obtaining spatial correlation coefficient distribution data; performing local continuity test on the spatial correlation coefficient distribution data, identifying a correlation interruption area according to the spatial gradient change of the correlation coefficient, and marking the correlation interruption area as an adhesion abnormal area. a stress perturbation module for applying periodic micro-stress perturbation to the adhesion abnormal area, establishing a stress-capacitance response relationship according to the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining the adhesion strength spatial distribution data through spatial distribution inversion of the stress-capacitance response relationship; specifically including: performing sweep micro-stress excitation on the adhesion abnormal area, determining the interface resonance frequency according to the capacitance response amplitude change under different excitation frequencies, and obtaining the resonance frequency distribution data; applying periodic micro-stress perturbation at the corresponding frequency according to the resonance frequency distribution data, synchronously recording the corresponding capacitance response amplitude data and phase delay data in the interface capacitance change data under the stress action, and obtaining the complex capacitance response data; calculating the interface damping coefficient based on the complex capacitance response data, establishing a local stress-capacitance response relationship according to the damping coefficient difference between the adhesion abnormal area and the adjacent normal area, and obtaining the regional response characteristic data; performing spatial coupling correction on the regional response characteristic data, correcting the single-point response characteristic according to the constraint effect between adjacent areas, and obtaining the adhesion strength spatial distribution data through the corrected local stress-capacitance response relationship inversion calculation; a fatigue evaluation module for periodically recording the capacitance reference value in the stress-free state during the film unwinding process, determining the fatigue sensitive area according to the adhesion strength spatial distribution data, comparing the corresponding capacitance reference value of the fatigue sensitive area with the interface reference capacitance distribution data to obtain the capacitance offset accumulation, and evaluating the interface adhesion fatigue degree according to the capacitance offset accumulation.

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