Current collector composite copper foil film spreading method and device

Abstract

The invention discloses a current collector composite copper foil film spreading method and device, and the method comprises the steps: applying a DC electric field to a current collector composite copper foil, forming an interface charge separation layer, obtaining reference capacitance distribution data, applying a film spreading tension to enable the material layers to generate microscopic displacement, and obtaining capacitance change data. The method comprises the following steps: analyzing and identifying an abnormal adhesion area through time domain difference and sliding window correlation, applying periodic micro-stress disturbance to the abnormal area to establish a stress-capacitance response relation to invert adhesion strength spatial distribution, and periodically recording a capacitance reference value to evaluate the interface adhesion fatigue degree. The device comprises an electric field processing module, a film spreading tension module, a correlation analysis module, a stress disturbance module and a fatigue evaluation module. According to the scheme, real-time dynamic detection and quantitative evaluation of the interlayer adhesion strength in the current collector composite copper foil film spreading process can be realized, the interface adhesion failure and fatigue accumulation state can be effectively identified, and accurate technical support is provided for battery current collector preparation process optimization and product quality control.

Description

Technical Field

[0001] The present invention relates to the technical field of current collector composite copper foil film spreading detection, and in particular to a current collector composite copper foil film spreading method and device. Background Art

[0002] Current collector composite copper foil is a key component of lithium-ion battery anodes. It is a multilayer structure composed of a conductive copper base layer and a functional polymer film layer, formed through a specialized process. The copper base layer performs current collection and conduction functions, while the functional layer provides mechanical protection, enhances electrochemical stability, or performs specific interface modification. This composite structure is designed to maintain excellent electrical conductivity while improving the mechanical strength, surface properties, and electrochemical compatibility deficiencies of traditional single copper foil, thereby meeting the increasingly stringent comprehensive performance requirements of current collectors in high-performance lithium-ion batteries.

[0003] Before practical application, the current collector composite copper foil must undergo a film spreading process to eliminate defects such as internal stress, surface unevenness, and dimensional deviation generated during production and storage and transportation. The film spreading process applies controllable mechanical tension and temperature conditions to enable the composite copper foil to achieve the required flatness, dimensional accuracy, and surface quality standards. However, since the composite copper foil is composed of material layers with different physical and chemical properties, there are significant differences in the response of each layer to mechanical stress and thermal stress during the film spreading process. This difference causes the interface between the layers to be subjected to complex shear stress and normal stress. When the film spreading tension, deformation rate, and temperature change exceed a specific threshold, the difference in elastic modulus and mismatch in thermal expansion coefficient between different material layers will cause interfacial stress concentration, which in turn leads to a local decrease in interlayer adhesion strength or even instantaneous failure, forming micro-delamination or interface slip, which seriously affects the quality stability of the subsequent electrode preparation process and the reliability of the final battery product. Summary of the Invention

[0004] The main purpose of the present 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 film expansion of the current collector composite copper foil to identify the interface adhesion failure and fatigue accumulation state.

[0005] A first aspect of the present invention provides a method for spreading a current collector composite copper foil, the method comprising: A DC electric field is applied to the current collector composite copper foil entering the film extension area, and the charge separation layer is formed at the interface area by utilizing the work function difference between the copper layer and the polymer layer to obtain the interface reference capacitance distribution data; Applying film-stretching tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data; 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 abnormality areas based on a correlation coefficient change trend; Applying periodic microstress perturbations to the abnormal adhesion region, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship; During the film expansion process, the capacitance baseline value in the stress-free state is periodically recorded, and the fatigue-sensitive area is determined based on the adhesion strength spatial distribution data. The capacitance baseline value corresponding to the fatigue-sensitive area is compared with the interface reference capacitance distribution data to obtain the capacitance offset accumulation. The interface adhesion fatigue degree is evaluated based on the capacitance offset accumulation.

[0006] Preferably, applying a DC electric field to the current collector composite copper foil entering the film extension area, utilizing the work function difference between the copper layer and the polymer layer to form a charge separation layer in the interface area, and obtaining interface reference capacitance distribution data, includes: Performing stress distribution measurement on the current collector composite copper foil entering the film spreading area, determining the interface prestress state according to the stress concentration area in the stress distribution measurement results, and obtaining interface stress distribution data; Applying compensation tension to the current collector composite copper foil according to the interface stress distribution data to make the interface prestress state uniform, and obtaining interface layer spacing distribution data at the same time; Calculating an electric field penetration coefficient based on the interfacial layer spacing distribution data, 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 intensity is inversely proportional to the interfacial layer spacing, and obtaining electric field intensity distribution data; Using the electric field intensity distribution data, a charge accumulation region is formed at the microscopic protrusions of the interface, and charge diffusion from the charge accumulation region to the flat region establishes an interface charge gradient to obtain a gradient charge separation layer; 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 interface reference capacitance distribution data.

[0007] Preferably, the electric field penetration coefficient is calculated based on the interfacial layer spacing distribution data, and 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 interfacial layer spacing to obtain the electric field intensity distribution data, including: Calculating the dielectric field strength attenuation coefficient of each region based on the spatial variation characteristics of the interface layer spacing distribution data, and determining the electric field penetration depth corresponding to different layer spacings based on the difference in dielectric constants between the copper layer and the polymer layer to obtain layered electric field penetration coefficient data; Determining an electric field strength compensation factor based on the layered electric field penetration coefficient data, setting a compensation factor greater than 1 for a region where the interfacial layer spacing exceeds the average value, and setting a compensation factor less than 1 for a region where the interfacial layer spacing is lower than the average value, to obtain electric field strength compensation coefficient distribution data; A compensated DC electric field is applied to different regions of the current collector composite copper foil according to the electric field strength compensation coefficient distribution data, and differential adjustment of the electric field strength in each region is achieved by multiplying the electric field strength by the compensation coefficient to obtain electric field strength distribution data.

[0008] Preferably, applying film-stretching tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data, includes: Applying a step-wise film-stretching tension to the current collector composite copper foil to cause the copper layer and the polymer layer to generate differential strain responses, and obtaining interlayer strain difference distribution data based on the differential strain responses; determining interface shear stress distribution data based on the interlayer strain difference distribution data, and using the interface shear stress distribution data to drive interface microscopic displacement to obtain interface displacement vector data; Performing spatial displacement correction on the interface reference capacitance distribution data based on the interface displacement vector data, and calculating instantaneous capacitance distribution data through a response relationship between capacitance value and interface geometry change to obtain dynamic capacitance data; Performing a time series analysis on the dynamic capacitance data, extracting fast response component data and slow response component data of the capacitance change according to the stress relaxation time difference between the copper layer and the polymer layer, and obtaining dual-time-scale capacitance response data; A difference operation is performed on the dual-time-scale capacitance response data and the interface reference capacitance distribution data to obtain interface capacitance change data under the stress.

[0009] Preferably, determining interface shear stress distribution data according to the interlayer strain difference distribution data, and using the interface shear stress distribution data to drive interface microscopic displacement to obtain interface displacement vector data, includes: performing spatial gradient calculation on the interlayer strain difference distribution data, determining an interlayer strain transfer ratio based on a ratio of the elastic modulus of the copper layer to the elastic modulus of the polymer layer, and converting the interlayer strain difference into equivalent shear strain data at the interface through the strain transfer ratio; Calculating the shear stress amplitude of each region based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, determining the spatial distribution direction of the shear stress in combination with the microscopic geometric characteristics of the interface, and obtaining 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 to obtain the interface displacement vector data.

[0010] Preferably, performing time-domain differential 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 abnormality areas based on correlation coefficient change trends include: Performing first-order time-domain difference and second-order time-domain difference processing on the interface capacitance change data under the stress, obtaining an instantaneous capacitance change rate sequence based on the first-order difference data, and obtaining a capacitance change acceleration sequence based on the second-order difference data; performing speed normalization processing on the instantaneous capacitance change rate sequence according to the film spreading speed data, so as to establish a fixed corresponding relationship between the capacitance change rate and the spatial position, thereby obtaining a spatially 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, and performing Pearson correlation calculation on the capacitance change rates in adjacent windows to obtain spatial correlation coefficient distribution data; A local continuity test is performed on the spatial correlation coefficient distribution data, a 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 abnormality area.

[0011] Preferably, applying periodic microstress perturbations to the adhesion abnormality 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 by inverting the spatial distribution of the stress-capacitance response relationship include: Performing frequency sweep microstress excitation on the abnormal adhesion area, determining the interface resonance frequency according to the change in capacitance response amplitude at different excitation frequencies, and obtaining resonance frequency distribution data; Applying periodic microstress perturbations at corresponding frequencies according to the resonant frequency distribution data, and synchronously recording corresponding capacitance response amplitude data and phase delay data in the interface capacitance change data under the stress to obtain 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 difference in damping coefficient between the adhesion abnormality region and the adjacent normal region, and obtaining regional response characteristic data; The regional response characteristic data is spatially coupled corrected, the single-point response characteristics are corrected according to the constraint effect between adjacent regions, and the spatial distribution data of the adhesion strength is obtained by inverting the corrected local stress-capacitance response relationship.

[0012] Preferably, the calculating of the interface damping coefficient based on the complex capacitance response data, establishing a local stress-capacitance response relationship according to the difference in damping coefficient between the adhesion abnormality region and the adjacent normal region, and obtaining the regional response characteristic data include: Separating the real and imaginary components of the capacitance response from the complex capacitance response data, calculating the interface dielectric loss factor according to the ratio of the imaginary component to the real component, and determining the interface damping coefficient data of each region according to the dielectric loss factor; Performing inter-regional comparative calculation on the interface damping coefficient data to obtain the damping coefficient ratio and gradient change rate between the adhesion abnormality region and the adjacent normal region, and dividing the interface response sensitivity level according to the ratio and gradient change rate to obtain interface response sensitivity classification data; Based on the interface response sensitivity classification data, corresponding stress-capacitance response coefficients are allocated to regions with different sensitivity levels, and regionalized stress-capacitance relationships are established through the spatial distribution of the response coefficients to obtain regional response characteristic data.

[0013] Preferably, the method includes periodically recording a capacitance reference value in a stress-free state during the film spreading process, determining a fatigue-sensitive area 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 a capacitance offset accumulation, and evaluating the degree of interface adhesion fatigue based on the capacitance offset accumulation, including: determining an adhesion strength classification threshold based on the intensity gradient change in the adhesion strength spatial distribution data, marking areas where the adhesion strength is below a preset threshold as highly sensitive areas, and marking areas where the adhesion strength is within the threshold range as moderately sensitive areas, thereby obtaining fatigue sensitivity classification data corresponding to the fatigue sensitive areas; During the film expansion process, periodically recording the capacitance reference values of the highly sensitive area and the medium sensitive area in a stress-free state at preset time intervals, and establishing time series capacitance reference value data according to the recording time sequence; Comparing the timing capacitance reference value data with the interface reference capacitance distribution data point by point, obtaining capacitance offset at each time point, and performing weighted accumulation calculation on the capacitance offset according to a time weight coefficient, obtaining capacitance offset accumulation; Performing spatial correlation analysis on the capacitance offset accumulation, identifying fatigue propagation paths based on differences in offset accumulation between adjacent regions, and correcting the offset accumulation of each region using the propagation paths to obtain a corrected capacitance offset accumulation; The fatigue degree is graded according to the comparison result of the corrected capacitance offset accumulation amount and the preset fatigue threshold. The area where the accumulation amount exceeds the threshold is determined as a severe fatigue area, and the area where the accumulation amount is close to the threshold is determined as a moderate fatigue area, thereby obtaining the interface adhesion fatigue degree assessment result.

[0014] A second aspect of the present invention provides a current collector composite copper foil film spreading device, the current collector composite copper foil film spreading device comprising: The electric field processing module is used to apply a DC electric field to the current collector composite copper foil entering the film extension area, forming a charge separation layer in the interface area by utilizing the work function difference between the copper layer and the polymer layer to obtain interface reference capacitance distribution data; A film spreading tension module is used to apply film spreading tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtain interface capacitance change data under stress based on the interface reference capacitance distribution data; a correlation analysis module for performing time-domain differential 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 abnormality areas based on correlation coefficient change trends; a stress perturbation module, configured to apply periodic microstress perturbations to the adhesion abnormality region, establish a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtain adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship; The fatigue assessment module is used to periodically record the capacitance reference value in the stress-free state during the film expansion 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 capacitance offset accumulation, and assess the interface adhesion fatigue degree based on the capacitance offset accumulation.

[0015] The technical solution provided in the embodiment of the present application utilizes the naturally existing work function difference between the copper layer and the polymer layer in the current collector composite copper foil, and forms a stable charge separation layer in the interface area by applying a DC electric field. The key to this process lies in the differentiated response of different materials to the electric field: the copper layer, as a good conductor, quickly reaches potential equilibrium, while the polymer layer forms a bound charge layer at the interface due to its dielectric properties. The formation of the charge separation layer provides a highly sensitive "sensing basis" for subsequent detection, and any slight change in the interface geometry or physical state will cause a significant change in the capacitance value. By obtaining the interface benchmark capacitance distribution data, a reference standard for the entire detection system was established.

[0016] Under the action of film tension, the different material layers of the composite copper foil deform differentially due to differences in elastic modulus, causing microscopic relative displacement between the layers. This displacement directly changes the geometric configuration of the interface capacitor. Because capacitance is inversely proportional to distance, small changes in interlayer distance are amplified into significant capacitance change signals. When the interface adhesion strength is sufficient, the interlayer displacement is mainly manifested as elastic deformation, and the capacitance changes show regular fluctuations. However, when the adhesion strength decreases, microscopic slippage or local separation occurs at the interface, resulting in discontinuous jumps in the capacitance value. By continuously monitoring the interface capacitance change data under stress, abnormal adhesion conditions can be captured in real time.

[0017] The interface capacitance change data is processed by time domain difference to obtain a capacitance change rate sequence, which reflects the dynamic characteristics of the interface response. Normal adhesion interfaces show a highly correlated response under stress, that is, there is a strong positive correlation between the capacitance change rates at adjacent time points. When the interface begins to show adhesion degradation, this correlation gradually weakens, which is manifested as a decrease in the correlation coefficient in the sliding window correlation analysis. By tracking the trend of the correlation coefficient, areas where the correlation is interrupted can be identified, which correspond 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 and can automatically adapt to the differences between different batches of materials.

[0018] Periodic microstress perturbations are applied to identified areas of abnormal adhesion, and the capacitance response amplitude is monitored to establish a stress-capacitance response relationship. Regions with high adhesion strength produce smaller interface deformations and correspondingly smaller capacitance changes under the same stress; conversely, regions with low adhesion strength produce larger deformations and capacitance changes. By analyzing the spatial distribution of the stress-capacitance response relationship, the spatial distribution of adhesion strength can be inverted. This inversion process, based on the coupled relationship between the mechanical and electrical properties of the interface, converts differences in capacitance response into a quantitative assessment of adhesion strength.

[0019] Interface adhesion fatigue is a gradual cumulative process, which manifests as irreversible changes in the interface microstructure. The present invention quantitatively evaluates the cumulative degree of adhesion fatigue by periodically recording the capacitance baseline value in the stress-free state and comparing it with the initial baseline. After the interface undergoes repeated stress cycles, even in the stress-free state, its capacitance value cannot be completely restored to the initial state, and there is a small residual offset. This offset directly reflects the cumulative damage to the interface microstructure. By establishing identification criteria for fatigue-sensitive areas and focusing on monitoring the cumulative amount of capacitance offset in areas with low adhesion strength, a predictive assessment of the interface fatigue state can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1 Schematic diagram of an embodiment of a method for spreading a current collector composite copper foil according to an embodiment of the present invention; Figure 2 Schematic diagram of an embodiment of a current collector composite copper foil film spreading device in an embodiment of the present invention; Figure 3 This is a schematic diagram of a portion of the structure of the current collector composite copper foil film spreading device according to an embodiment of the present invention; Figure 4 for Figure 3 Another perspective diagram of the structure in .

[0022] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0025] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, "and / or" in the full text includes three solutions. Taking A and / or B as an example, it includes technical solution A, technical solution B, and technical solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, and must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] An embodiment of the present application provides a method for spreading a current collector composite copper foil. Figure 1 A flow chart of a method for spreading a current collector composite copper foil according to an embodiment of the present application. In this embodiment, the method includes: See also Figure 1 , applying a DC electric field to the current collector composite copper foil entering the film extension area, using the work function difference between the copper layer and the polymer layer to form a charge separation layer in the interface area, and obtaining the interface reference capacitance distribution data; In one embodiment of the present invention, applying a DC electric field to the current collector composite copper foil entering the film extension area, utilizing the work function difference between the copper layer and the polymer layer to form a charge separation layer in the interface area, and obtaining interface reference capacitance distribution data, includes: Performing stress distribution measurement on the current collector composite copper foil entering the film spreading area, determining the interface prestress state according to the stress concentration area in the stress distribution measurement results, and obtaining interface stress distribution data; Applying compensation tension to the current collector composite copper foil according to the interface stress distribution data to make the interface prestress state uniform, and obtaining interface layer spacing distribution data at the same time; Calculating an electric field penetration coefficient based on the interfacial layer spacing distribution data, 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 intensity is inversely proportional to the interfacial layer spacing, and obtaining electric field intensity distribution data; Using the electric field intensity distribution data, a charge accumulation region is formed at the microscopic protrusions of the interface, and charge diffusion from the charge accumulation region to the flat region establishes an interface charge gradient to obtain a gradient charge separation layer; 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 interface reference capacitance distribution data.

[0027] The following is a detailed description of the steps involved in the above embodiment: When measuring the stress distribution of the current collector composite copper foil entering the film-unrolling area, a laser speckle interferometer was used, with measurement points 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, at a 45° angle and for 50 milliseconds. The speckle pattern was captured by a CCD camera and phase-compared with a reference image. Stress concentration areas are defined as regions where the stress exceeds 1.5 times the average stress. When the measurement shows a stress of 350 MPa and an average stress of 200 MPa, this region is considered a stress concentration area. The interfacial prestress state is the internal stress that remains at the interface between the copper layer and the polymer layer during the winding and storage process of the composite copper foil. The data acquisition system stores the stress values at all measurement points and generates a two-dimensional stress distribution map. The map uses different colors to represent stress levels, with red areas indicating high stress and blue areas indicating low stress, thus generating the interfacial stress distribution data. This precise identification of stress distribution provides an accurate basis for subsequent tension compensation, preventing uneven stress from interfering with the electric field treatment effect.

[0028] Based on the interfacial stress distribution data, a segmented tension control system applies compensating tension to the current collector composite copper foil. This system consists of eight independent tension rollers evenly spaced across the width of the copper foil. Each roller is equipped with a servo motor and force sensor, achieving a control accuracy of ±1N. The system calculates the required compensating tension based on the stress values in each region of the stress distribution map: target tension = standard tension + (target stress - measured stress) × conversion factor, where the conversion factor is 0.5N / MPa. For example, if the measured stress in a region is 150MPa and the target stress is 200MPa, the compensating tension is 25N. The interfacial interlayer spacing distribution data refers to the actual spatial distribution of the distance between the copper and polymer layers. The ultrasonic thickness gauge transmits 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: (echo time difference × sound velocity) / 2. The sound velocity for the copper layer is 5900m / s, and the sound velocity for the polymer layer is 2300m / s. The measurement accuracy is 0.1 micron. Homogenization reduces stress differences that originally exceeded 100MPa to within 20MPa. This differentiated tension control can effectively eliminate stress inhomogeneity and create ideal interface conditions for subsequent electric field processing.

[0029] The electric field penetration coefficient (EPC) is calculated based on interlayer spacing data. This coefficient describes the propagation ability of an electric field in a multilayer composite material. The calculation process involves substituting the measured copper layer thickness of 10 microns, the polymer layer thickness of 3 microns, and the interlayer spacing of 2 microns into the formula. The dielectric constant of the copper layer is set to 1, and the dielectric constant of the polymer layer is set to 3. The calculated EPC is K = 1 / (1 + 3 × 10 / 3) = 0.091. The adaptive DC electric field application utilizes 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 limit is 10mA. The electric field strength in each region is adjusted based on the interlayer spacing data: EPC = baseline EPC × (average interlayer spacing / actual interlayer spacing), with the baseline EPC set to 200V / μm. When the interlayer spacing in a region is 1.5 microns, the EPC 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 regulation ensures that different areas receive similar charge injection effects, avoiding the problem of uneven processing caused by a fixed electric field strength.

[0030] Using the electric field intensity distribution data, charge accumulation areas are formed at the microscopic protrusions on the interface. The microscopic protrusions on the interface are micron-sized protrusions caused by uneven calendering during the composite process. The height of the microscopic protrusions detected by atomic force microscopy is 0.8-1.5 microns, and the density is 20-50 per square millimeter. Under the action 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 800-1000V / μm. When it exceeds the polymer breakdown threshold of 500V / μm, local breakdown occurs, forming a conductive channel, and the charge density reaches 10 -6 C / cm 2 Charge diffusion is achieved through dipole reorientation of the polymer chain, with a diffusion coefficient of 10 -12 cm 2 / s, the diffusion distance from the aggregation area to the surrounding flat area is 5-10 microns, and the diffusion time is about 100 milliseconds. The interface charge gradient refers to the charge density from 10 in the aggregation area to -6 C / cm 2 10 to the flat area -8 C / cm 2 The linear decrease with a gradient of 10 -7 C / cm 3 The thickness of the gradient charge separation layer is one-third the thickness of the polymer layer, approximately 1 micron. This gradient distribution has higher detection sensitivity than a uniform distribution. When the interface shifts by 0.1 micron, the capacitance changes by 0.5 pF, which is 5 times higher than the 0.1 pF of a uniform distribution.

[0031] The gradient charge separation layer is temperature-corrected. The temperature coefficient of the polymer layer's dielectric constant is -0.002 / °C. The infrared thermal imager captures temperature images at 30 frames per second, with a spatial resolution of 0.1mm and a temperature resolution of 0.1°C. The temperature correction is calculated using a linear compensation algorithm: Corrected capacitance = measured capacitance × [1 - 0.002 × (measured temperature - 25°C)]. The data processor calculates and stores the correction results in real time. For example, if the temperature at the measurement point is 32°C and the measured capacitance is 98pF, the corrected capacitance is 98 × [1 - 0.002 × (32 - 25°C)] = 96.6pF. The interface reference capacitance distribution data is a temperature-corrected capacitance matrix divided into a 2mm x 2mm grid. Each grid point contains three parameters: capacitance, temperature, and position coordinates. Capacitance measurements are performed using an LCR bridge with a measurement frequency of 1kHz, an integration time of 100ms, and a measurement accuracy of 0.01pF. An automatic zeroing function eliminates systematic errors. After data collection is complete, a capacitance distribution contour map is generated, serving as a zero-point reference for all subsequent capacitance change measurements. By establishing an accurate baseline capacitance distribution, a reliable reference standard is provided for subsequent adhesion strength testing. Temperature compensation accuracy of ±0.05pF ensures that test results are unaffected by temperature fluctuations, significantly improving test accuracy and reproducibility.

[0032] In one embodiment of the present invention, the electric field penetration coefficient is calculated based on the interfacial layer spacing distribution data, and 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 interfacial layer spacing to obtain the electric field intensity distribution data, including: Calculating the dielectric field strength attenuation coefficient of each region based on the spatial variation characteristics of the interface layer spacing distribution data, and determining the electric field penetration depth corresponding to different layer spacings based on the difference in dielectric constants between the copper layer and the polymer layer to obtain layered electric field penetration coefficient data; Determining an electric field strength compensation factor based on the layered electric field penetration coefficient data, setting a compensation factor greater than 1 for a region where the interfacial layer spacing exceeds the average value, and setting a compensation factor less than 1 for a region where the interfacial layer spacing is lower than the average value, to obtain electric field strength compensation coefficient distribution data; A compensated DC electric field is applied to different regions of the current collector composite copper foil according to the electric field strength compensation coefficient distribution data, and differential adjustment of the electric field strength in each region is achieved by multiplying the electric field strength by the compensation coefficient to obtain electric field strength distribution data.

[0033] The following is a detailed description of the steps involved in the above embodiment: The dielectric field attenuation coefficient for each region is calculated based on the spatial variation characteristics of the interlayer spacing distribution data. This spatial variation refers to the numerical differences and changing trends of the interlayer spacing at different locations. The interlayer spacing distribution data is then analyzed using a data processing system to perform spatial gradient analysis. The dielectric field attenuation coefficient is a physical parameter that describes the degree to which an electric field decreases in intensity when passing through a multilayer dielectric. The calculation process involves taking the interlayer spacing values at two adjacent measurement points, calculating the ratio of their difference to the distance, and then combining this with the dielectric loss parameter of the material to determine the attenuation coefficient. For example, if the interlayer spacing in a region changes from 2.0 microns to 2.5 microns over a distance of 5 mm, the spatial gradient is 0.1 microns / mm. Combined with the dielectric loss tangent of the polymer layer of 0.02, the dielectric field attenuation coefficient for this region is calculated to be 0.002 / micron. The electric field penetration depth refers to the depth at which an electric field can effectively penetrate the composite copper foil and exert an effect at the interface. Different interlayer spacings correspond to different penetration depths: a 1.5 micron interlayer spacing results in a penetration depth of 1.2 microns, while a 3.0 micron interlayer spacing results in a penetration depth of 2.8 microns. The layered electric field penetration coefficient data is obtained by dividing the entire composite copper foil into a 2 mm x 2 mm grid and calculating the corresponding penetration coefficient for each grid, forming a spatial distribution matrix. This refined penetration coefficient calculation accurately reflects the electric field propagation characteristics of different regions and eliminates the problem of uneven electric field distribution caused by differences in material thickness.

[0034] When determining the electric field strength compensation factor based on layered electric field penetration coefficient data, the compensation factor is a correction factor used to adjust the electric field strength in each region to achieve uniform charge injection. The determination process involves calculating the arithmetic mean of the interlayer spacing at all measurement points as a baseline value. For example, the average interlayer spacing is 2.2 microns. The actual interlayer spacing in each region is then compared point by point with the average. For regions where the interlayer spacing exceeds the average, a compensation factor greater than 1 is set to enhance the electric field strength. The specific value is determined by the percentage of excess: for example, a region with an interlayer spacing of 2.8 microns, exceeding the average by 27%, corresponds to a compensation factor of 1.3. For regions with interlayer spacing below the average, a compensation factor less than 1 is set to weaken the electric field strength: for example, a region with an interlayer spacing of 1.8 microns, falling 18% below the average, corresponds to a compensation factor of 0.8. The electric field strength compensation coefficient distribution data is a two-dimensional array of all compensation factors arranged by spatial location. Each element in the array contains the location coordinates and the corresponding compensation coefficient value. This differentiated compensation strategy effectively overcomes the impact of uneven thickness of the composite copper foil on charge injection, ensuring similar charge density across regions.

[0035] To apply a compensated DC electric field to different regions of the current collector composite copper foil based on the electric field intensity 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 x 2 mm. The product of the electric field intensity and the compensation coefficient is calculated using a digital signal processor: the processor reads the baseline electric field intensity of 200 V / μm and the compensation coefficient for each region, performing a real-time multiplication to calculate the adjusted electric field intensity. For example, if the compensation coefficient for a region is 1.3, the actual electric field intensity in that region is 200 × 1.3 = 260 V / μm; for a region with a compensation coefficient of 0.8, the actual electric field intensity is 200 × 0.8 = 160 V / μm. Differentiated adjustment of the electric field intensity in each region is achieved by independently controlling the output voltage of each electrode, with a voltage adjustment accuracy of ±1 V and a response time of less than 10 milliseconds. The electric field intensity distribution data records the final applied electric field intensity 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.

[0036] Please continue reading Figure 1 , applying film extension tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data; In one embodiment of the present invention, applying film extension tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data, includes: Applying a step-wise film-stretching tension to the current collector composite copper foil to cause the copper layer and the polymer layer to generate differential strain responses, and obtaining interlayer strain difference distribution data based on the differential strain responses; determining interface shear stress distribution data based on the interlayer strain difference distribution data, and using the interface shear stress distribution data to drive interface microscopic displacement to obtain interface displacement vector data; Performing spatial displacement correction on the interface reference capacitance distribution data based on the interface displacement vector data, and calculating instantaneous capacitance distribution data through a response relationship between capacitance value and interface geometry change to obtain dynamic capacitance data; Performing a time series analysis on the dynamic capacitance data, extracting fast response component data and slow response component data of the capacitance change according to the stress relaxation time difference between the copper layer and the polymer layer, and obtaining dual-time-scale capacitance response data; A difference operation is performed on the dual-time-scale capacitance response data and the interface reference capacitance distribution data to obtain interface capacitance change data under the stress.

[0037] The following is a detailed description of the steps involved in the above embodiment: Stepwise tension is applied to the current collector composite copper foil. This refers to a method of gradually increasing tension according to preset time intervals and force gradients during the film-rolling process, as opposed to the traditional method of applying a fixed tension all at once. A servo motor-driven tension control system is used, consisting of four tension rollers, each equipped with a torque sensor and a position encoder. The tension application program is programmed as follows: 50N at 0 seconds, increasing to 60N at 2 seconds, 70N at 4 seconds, and so on, increasing by 10N every 2 seconds for a total of 15 steps, reaching and maintaining the target tension of 150N at 28 seconds. Differential strain response refers to the phenomenon in which the copper and polymer layers deform to varying degrees under the same tension due to their different elastic moduli: the copper layer has an elastic modulus of 110 GPa, and the polymer layer has an elastic modulus of 3 GPa. Strain measurement utilizes 5mm-long resistance strain gauges. A pair of strain gauges is placed every 20mm across the width of the copper foil, attached to the copper and polymer layers, for a total of 16 pairs. The strain gauges were bonded using conductive silver adhesive at a temperature of 60°C and a curing time of 30 minutes. The signal conditioning circuit employed an INA125 precision instrumentation amplifier with a 1000x amplification factor. The output voltage range of 0-10V corresponds to a strain range of 0-0.01. Data acquisition utilized a 16-bit ADC with a sampling frequency of 100Hz, and a strain resolution of 1 microstrain per channel. For example, at a tension of 100N, the strain in the copper layer is 800 microstrain, the strain in the polymer layer is 25,000 microstrain, and the strain difference is 24,200 microstrain. Interlayer strain difference distribution data is stored according to the measurement point number and the corresponding strain difference value. The data is formatted as a CSV file containing three columns: timestamp, location coordinates, and strain difference value. This stepped tension application method allows the entire loading process to be completed within 15 seconds, preventing damage to the interface caused by transient impacts. Furthermore, high-precision strain difference distribution data is obtained with a time resolution of 0.01 seconds.

[0038] When determining the interface shear stress distribution data based on the interlayer strain difference distribution data, the interface shear stress is the tangential stress generated at the interface due to the strain difference between the copper layer and the polymer layer. The calculation adopts the composite material interlayer shear theory: the shear stress is equal to the strain difference multiplied by the interface equivalent shear modulus, where the interface equivalent shear modulus is determined by nanoindentation test. The nanoindentation test uses a Berkovich diamond indenter, and the indentation depth is controlled at 200 nanometers to ensure the test interface area. The loading rate is 10 micronewtons / second and the maximum load is 500 micronewtons. The test was repeated 10 times in the interface area, and the average interface shear modulus was measured to be 8.2GPa with a standard deviation of 0.5GPa. The shear stress calculation formula is: τ=Δε×G, where τ is the interface shear stress, Δε is the interlayer strain difference, and G is the interface shear modulus 8.2GPa. For example, when the interlayer strain difference at a certain position is 0.02, the interface shear stress is 0.02×8.2×10 9 Pa = 164 MPa. The interface micro displacement is calculated using shear deformation theory: the displacement is equal to the shear stress divided by the interface shear stiffness. The interface shear stiffness is determined by the interface thickness and shear modulus, and the value is G / h, where h is the thickness of the interface transition layer, which is about 0.5 microns. Therefore, the shear stiffness is 1.64×10 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 Pa / (1.64×10 13 N / m 3 ) = 10 nanometers. Interface displacement vector data is stored in three-dimensional coordinate form: (x, y, δx, δy), where x and y are position coordinates, and δx and δy are the displacement components in the X and Y directions. This calculation method, based on material mechanics theory, ensures the physical rationality and calculation accuracy of shear stress and displacement data.

[0039] When spatially correcting the interface reference capacitance distribution data based on the interface displacement vector data, the correction process is based on the principle of parallel-plate capacitors. Capacitive sensor calibration experiments were conducted using a precision translation stage and a high-precision capacitance meter. A standard parallel-plate capacitor was mounted on a nanometer-scale precision translation stage with a resolution of 1 nanometer and a capacitance meter with an accuracy of 0.001 pF. During the calibration process, the stage was moved from 0 to 500 nanometers in steps of 10 nanometers. The capacitance value was measured 10 times at each position and the average value was taken to generate a capacitance-displacement calibration curve. The calibration results show that capacitance is inversely proportional to 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. During the correction calculation, the interface displacement is subtracted from the reference interlayer spacing: d = d0 - δ, where δ is the interface displacement. For example, if the baseline interlayer spacing is 2.0 microns, the interface displacement is 10 nanometers, the corrected interlayer spacing is 1.99 microns, and the baseline capacitance is 100 pF, the corrected capacitance is 100 × 2.0 / 1.99 = 100.5 pF. Transient capacitance distribution data is acquired using a 64-channel capacitance measurement system, each channel equipped with an independent AC excitation source and synchronous detector, an excitation frequency of 1 kHz, an excitation amplitude of 1 V, and a measurement resolution of 0.01 pF. The data acquisition frequency is 50 Hz, acquiring 3200 capacitance data points per second. Dynamic capacitance data is stored in a timestamp-tagged three-dimensional array format: [time][X coordinate][Y coordinate] = [capacitance value]. Data files use a binary format to improve storage efficiency. This calibration curve-based correction method ensures the accuracy of capacitance calculations, with displacement resolution reaching the nanometer level.

[0040] When performing time-series analysis of dynamic capacitance data, digital signal processing methods were used to separate response components at different time scales. A fourth-order Butterworth high-pass filter was used to extract the fast-response component. The filter parameters were set as follows: a cutoff frequency of 10 Hz, a passband ripple of less than 0.1 dB, and a stopband attenuation greater than 40 dB. The filter was converted from the analog prototype to a digital filter using a bilinear transformation method, with a sampling frequency of 200 Hz to meet the requirements of the Nyquist theorem. A fourth-order Butterworth low-pass filter was used to extract the slow-response component. The filter was implemented using a cascaded two-stage structure, with each stage consisting of two delays, five multipliers, and four adders. Step response testing determined the relaxation time of the copper layer to be 50 microseconds, while the relaxation time of the polymer layer was 0.8 seconds, a 16,000-fold difference. The filtering process is as follows: the original dynamic capacitance signal is simultaneously input into 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, the capacitance signal at a certain measurement point contains a 20Hz fast oscillation (amplitude 2pF) and a 0.5Hz slow variation (amplitude 8pF). After filtering, the fast-response component extracts a 2pF 20Hz signal, and the slow-response component extracts an 8pF 0.5Hz signal. The dual-time-scale capacitance response data is stored in the format of [time][position][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, with a filtering accuracy of 0.01pF.

[0041] When performing difference calculations on the dual-time-scale capacitance response data and the interface reference capacitance distribution data, a parallel computing architecture is used to improve processing efficiency. The difference calculation is performed on a GPU-accelerated processor that contains 1024 parallel computing cores, each responsible for the calculation of one measurement point. The calculation process is as follows: for each spatial position (i, j), read the reference capacitance value C0(i, j), the fast response capacitance value C 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, if the baseline capacitance at position (5, 8) is 100pF, the fast-response capacitance is 102pF at a certain moment, 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 high-speed memory in a 5-dimensional array format: [X coordinate][Y coordinate][time][fast-response difference][slow-response difference]. Data compression uses a lossless algorithm with a compression ratio of 3:1. The interface capacitance change data under stress generates approximately 50MB of data per second, and the storage system uses a RAID array to ensure data security and access speed. This efficient parallel computing and storage solution can process large amounts of capacitance data in real time with a computational latency of less than 20 milliseconds, providing timely and accurate capacitance change information for subsequent real-time adhesion strength analysis.

[0042] In one embodiment of the present invention, 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 microscopic displacement to obtain interface displacement vector data includes: performing spatial gradient calculation on the interlayer strain difference distribution data, determining an interlayer strain transfer ratio based on a ratio of the elastic modulus of the copper layer to the elastic modulus of the polymer layer, and converting the interlayer strain difference into equivalent shear strain data at the interface through the strain transfer ratio; Calculating the shear stress amplitude of each region based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, determining the spatial distribution direction of the shear stress in combination with the microscopic geometric characteristics of the interface, and obtaining 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 to obtain the interface displacement vector data.

[0043] The following is a detailed description of the steps involved in the above embodiment: When calculating the spatial gradient of interlaminar strain difference distribution data, this involves performing differential operations on the strain difference data along the length and width of the copper foil to obtain the spatial rate of change of the strain difference. The calculation uses the central difference method: the strain difference values of three adjacent measurement points are selected, and the gradient at the midpoint is equal to the difference between the two values divided by the distance between them. For example, if the strain difference at position 10 mm is 0.015, at position 20 mm is 0.018, and at position 30 mm is 0.021, then the spatial gradient at position 20 mm is (0.021 - 0.015) / (30 - 10) = 0.0003 / mm. The interlaminar strain transfer ratio is a dimensionless parameter that describes the efficiency of strain transfer between different material layers. According to composite material mechanics theory, the transfer ratio is equal to the inverse of the ratio of the elastic moduli of the two materials. The elastic modulus of the copper layer is 110 GPa, and the elastic modulus of the polymer layer is 3 GPa. The modulus ratio is 36.7, so the interlaminar strain transfer ratio is 1 / 36.7 = 0.027. The equivalent shear strain data is the actual shear strain value at the interface obtained by correcting the interlaminar strain difference by the transfer ratio. The calculation method is: Equivalent shear strain = interlaminar strain difference × strain transfer ratio × spatial gradient correction factor. The spatial gradient correction factor is determined by the spatial variation of the strain difference; a larger gradient indicates a larger correction factor, 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 factor is 1.1, the equivalent shear strain is 0.018 × 0.027 × 1.1 = 0.00053. This strain transfer calculation method based on the elastic modulus ratio accurately reflects the true strain state of the composite interface and eliminates strain distribution distortion caused by differences in material properties.

[0044] When calculating the shear stress amplitude of each region based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, the equivalent shear modulus is a material parameter that describes the ability of the interface region to resist shear deformation, and is measured by a dynamic mechanical analyzer. The test uses a shear fixture to apply a sinusoidal shear load at a frequency of 1 Hz with an amplitude of 10% of the interface yield strength. The test temperature is 25°C, and the interface equivalent shear modulus is measured to be 6.8 GPa. The shear stress amplitude is calculated using the linear elastic relationship: shear stress = equivalent shear strain × equivalent shear modulus. For example, when the equivalent shear strain of a certain region is 0.00053, the shear stress amplitude is 0.00053×6.8×10 9Pa = 3.6 MPa. Interface microgeometry refers to the micromorphological features formed at the interface due to the composite process, including surface roughness, microprotrusions, and texture orientation. An atomic force microscope was used to scan the interface region with a scanning range of 100 μm × 100 μm and a resolution of 1 nm to obtain three-dimensional morphological data. Analysis results revealed a periodic corrugated structure at the interface, with the corrugations oriented in the direction of copper foil rolling, a wavelength of 50-80 μm, and a height of 200-500 nm. The spatial distribution direction of shear stress is determined by the interface microgeometry: at the corrugation peaks, the shear stress is distributed perpendicular to the corrugations, while at the corrugation valleys, the shear stress is distributed parallel to the corrugations. The interface shear stress distribution data is represented as a vector field, with each measurement point containing two parameters: the shear stress amplitude and the azimuth angle. The azimuth angle is referenced to the copper foil rolling direction as 0°. This stress analysis method, combined with microgeometry, accurately describes the true stress state of the interface and takes into account the influence of interface morphology on stress distribution.

[0045] When using interface shear stress distribution data as the driving load for interface displacement, the driving load refers to the external force or stress that causes interface displacement. The interface shear stress acts directly on the interface to produce shear deformation. Interface adhesion impedance is a parameter that describes the ability of an interface to resist relative displacement and consists of two components: elastic impedance and viscous impedance. Elastic impedance is measured through an interface peel test: using a 180° peel tester at a peel speed of 50 mm / min, the interface peel strength was measured to be 15 N / mm, which converts to a shear impedance of 8.5 × 10 6 N / m 2 The viscous impedance was determined by creep testing: the displacement was measured over time under a constant shear stress of 3 MPa, and the viscous impedance coefficient was fitted to be 2.3×10 4 N·s / m 2 The mechanical equilibrium relationship is based on the force balance condition at the interface: the shear driving force is equal to 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, the shear stress at a certain location is 3.6 MPa, and the elastic resistance is 8.5×10 6 N / m 2 , the viscous impedance is 2.3×10 4 N·s / m 2 When the action time is 0.1 seconds, the displacement is 3.6×10 6 / (8.5×10 6 +2.3×10 4 / 0.1) = 0.14 microns. Interface displacement vector data contains both magnitude and direction information. The displacement direction aligns with the shear stress direction and is represented as a three-dimensional vector (x, y, z), where x and y represent the displacement components within the interface plane and z represents the normal displacement component. This displacement calculation method, based on mechanical equilibrium, accurately predicts the true displacement response of the interface under shear load, providing precise geometric change parameters for subsequent capacitance change analysis.

[0046] Please continue reading Figure 1 , 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 abnormality areas based on a correlation coefficient change trend; In one embodiment of the present invention, performing time-domain differential 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 abnormality areas based on correlation coefficient change trends include: Performing first-order time-domain difference and second-order time-domain difference processing on the interface capacitance change data under the stress, obtaining an instantaneous capacitance change rate sequence based on the first-order difference data, and obtaining a capacitance change acceleration sequence based on the second-order difference data; performing speed normalization processing on the instantaneous capacitance change rate sequence according to the film spreading speed data, so as to establish a fixed corresponding relationship between the capacitance change rate and the spatial position, thereby obtaining a spatially 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, and performing Pearson correlation calculation on the capacitance change rates in adjacent windows to obtain spatial correlation coefficient distribution data; A local continuity test is performed on the spatial correlation coefficient distribution data, a 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 abnormality area.

[0047] The following is a detailed description of the steps involved in the above embodiment: When performing first-order and second-order time-domain differencing on the interface capacitance change data under stress, first-order time-domain differencing involves performing a single differential operation on the time series data, calculating the difference between the data at adjacent time points to obtain the rate of change information. This process uses a forward differencing method: two adjacent data points separated by a time interval of 0.02 seconds are selected. The first-order difference is equal to 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 at time t = 1.0 seconds is 102.5 pF and at time t = 1.02 seconds is 102.8 pF, the first-order difference at that time point is (102.8 - 102.5) / 0.02 = 15 pF / s. The instantaneous capacitance rate of change series 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. The second-order time-domain differencing is performed again on the first-order difference result to obtain the rate of change. The calculation method is: take two adjacent first-order difference values, divide their difference by the time interval to get the second-order difference. For example, when t=1.0 seconds, the first-order difference is 15pF / s, and when t=1.02 seconds, it is 18pF / s, then the second-order difference is (18-15) / 0.02=150pF / s 2 The capacitance change acceleration sequence is a time series of all second-order differential values, describing the acceleration or deceleration trend of the capacitance change rate. Data processing uses 32-bit floating-point operations to ensure calculation accuracy, and the processor uses a digital signal processor (DSP) chip with an operating frequency of 200MHz. This time-domain differential processing can extract the dynamic change characteristics in the original capacitance data, highlighting the instantaneous response information of the interface state change. At the same time, it captures the turning points of the change trend through second-order differentials, thereby improving the sensitivity of anomaly detection.

[0048] When performing speed normalization on the instantaneous capacitance change rate series based on the film roll speed data, the film roll speed data refers to the linear velocity variation of the current collector composite copper foil during the roll roll process. This velocity data is converted by measuring the tension roller speed using a photoelectric encoder. The encoder resolution is 10,000 pulses / rev, and the tension roller diameter is 200 mm, resulting in a calculated speed resolution of 0.063 mm / s. The roll roll speed fluctuates during the roll roll process, typically ranging from 45-55 m / min, with an average of 50 m / min. Speed normalization normalizes the capacitance change rate data according to the roll roll speed to eliminate the impact of speed fluctuations on the capacitance change rate. The normalization calculation method is to multiply the instantaneous capacitance change rate at each moment by the ratio of the actual roll roll speed to the reference speed at that moment. For example, if the instantaneous capacitance change rate at a certain moment is 15 pF / s, the actual roll roll speed is 48 m / min, and the reference speed is 50 m / min, the normalized capacitance change rate is 15 × (48 / 50) = 14.4 pF / s. The fixed spatial position correspondence relationship means that the same capacitance change rate value corresponds to the same spatial position through speed normalization, without being affected by time changes. The spatially normalized capacitance change rate sequence is to rearrange the normalized capacitance change rate according to the corresponding spatial position to form 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 0.1mm. This speed normalization process can eliminate the interference of film expansion speed fluctuations on capacitance data analysis, ensure that the capacitance change characteristics at the spatial position are not affected by time factors, and improve the accuracy of subsequent correlation analysis.

[0049] 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 window length can be dynamically adjusted based on data characteristics, as opposed to a fixed-length window. The window length adjustment is based on the fluctuation amplitude in the capacitance change acceleration sequence: when the acceleration fluctuation amplitude is large, a smaller window is used to improve spatial resolution; when the fluctuation amplitude is small, a larger window is used to improve statistical stability. The fluctuation amplitude is calculated by the standard deviation: the standard deviation is calculated by taking the acceleration values of 10 consecutive data points, and the standard deviation is greater than 100pF / s. 2 The window length is set to 20 data points, and the standard deviation is 50-100pF / s 2 The window length is 30 data points when the current is less than 50pF / s. 2 The window length is 40 data points. For example, the standard deviation of the acceleration of capacitance change in a certain area is 120pF / s 2, the corresponding window length is 20 data points, which is equivalent to a spatial length of 2mm. Pearson correlation calculation refers to calculating the degree of linear correlation between the capacitance change rate data in adjacent sliding windows. The calculation process is: take the capacitance change rate data of two adjacent windows, calculate their mean and standard deviation respectively, and then calculate the covariance. The Pearson correlation coefficient is equal to the covariance divided by the product of two standard deviations. The correlation coefficient range is -1 to 1. A value close to 1 indicates a strong positive correlation, a value close to 0 indicates no correlation, and a value close to -1 indicates a strong negative correlation. For example, the capacitance change rate correlation coefficient of two adjacent windows is 0.85, indicating that the capacitance changes in the two regions are highly consistent. The spatial correlation coefficient distribution data is a distribution graph formed by arranging the correlation coefficients of all adjacent window pairs according to their spatial positions. The data format is spatial coordinates and corresponding correlation coefficient values. This adaptive window correlation analysis can automatically adjust the analysis accuracy according to the complexity of the interface state, provide high spatial resolution in areas where the interface changes drastically, and maintain statistical reliability in stable areas.

[0050] When performing a local continuity test on spatial correlation coefficient distribution data, the test involves analyzing the continuity of the correlation coefficients of adjacent spatial regions to identify locations where the correlation changes suddenly. This test utilizes spatial gradient analysis: the ratio of the difference in the correlation coefficients between adjacent measurement points to their spatial distance is calculated to obtain the spatial gradient of the correlation coefficient. The gradient is calculated using the central difference method: the correlation coefficients of three adjacent measurement points are selected, and the gradient at the midpoint is equal to the difference between the values of the two preceding and following points divided by twice the distance between them. For example, if the correlation coefficients at position 10 mm are 0.90, at position 12 mm are 0.85, and at position 14 mm are 0.82, then the spatial gradient at position 12 mm is (0.82-0.90) / (14-10) = -0.020 / mm. A correlation break occurs when the absolute value of the spatial gradient exceeds a preset threshold of 0.015 / mm, which, based on statistical analysis, is determined to effectively identify 95% of adhesion anomalies. The interruption area identification process is as follows: scan the spatial gradients of all measurement points. When the absolute values of the gradients of more than three consecutive measurement points exceed the threshold, the area is marked as a correlation interruption area. For example, the absolute values of the gradients of four consecutive measurement points within the range of 20-26mm are 0.018 / mm, 0.021 / mm, 0.019 / mm, and 0.017 / mm, respectively, all exceeding the threshold of 0.015 / mm. Therefore, the area is marked as a correlation interruption area. The adhesion abnormality area refers to the spatial area where the interface adhesion strength deviates significantly from the normal level, which is determined by the identification of the correlation interruption area. The marking process records the spatial coordinates and range of the correlation interruption area into the abnormal area database, including information such as the starting position, end position, and degree of abnormality. This continuity inspection method based on spatial gradients can accurately locate the position of abnormal changes in the interface adhesion state, with detection accuracy reaching the millimeter level, providing an accurate target area for subsequent quantitative analysis.

[0051] Please continue reading Figure 1 , applying periodic micro-stress perturbations to the adhesion abnormality area, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship; In one embodiment of the present invention, applying periodic microstress perturbations to the adhesion abnormality region, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship include: Performing frequency sweep microstress excitation on the abnormal adhesion area, determining the interface resonance frequency according to the change in capacitance response amplitude at different excitation frequencies, and obtaining resonance frequency distribution data; Applying periodic microstress perturbations at corresponding frequencies according to the resonant frequency distribution data, and synchronously recording corresponding capacitance response amplitude data and phase delay data in the interface capacitance change data under the stress to obtain 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 difference in damping coefficient between the adhesion abnormality region and the adjacent normal region, and obtaining regional response characteristic data; The regional response characteristic data is spatially coupled corrected, the single-point response characteristics are corrected according to the constraint effect between adjacent regions, and the spatial distribution data of the adhesion strength is obtained by inverting the corrected local stress-capacitance response relationship.

[0052] The following is a detailed description of the steps involved in the above embodiment: Frequency-swept microstress excitation is performed on areas of abnormal adhesion. This excitation method involves continuously varying the excitation frequency within a predetermined frequency range while simultaneously applying a small, constant-amplitude stress load. The excitation system utilizes a piezoelectric ceramic driver with a thickness of 2 mm, a maximum displacement of 10 microns, and a response frequency range of 0.1 Hz to 1000 Hz. The frequency sweep begins at 1 Hz and sweeps logarithmically to 500 Hz. The excitation duration at each frequency point is 2 seconds, and the excitation amplitude is controlled at 0.5 MPa to ensure no damage to the interface structure. The capacitance response amplitude variation refers to the change in interface capacitance at different excitation frequencies. The excitation signal and capacitance response signal are synchronously measured using a lock-in amplifier. The lock-in amplifier has a time constant of 0.1 seconds and a dynamic reserve of 80 dB, enabling accurate extraction of weak capacitance change signals from noise. The interface resonant frequency is the frequency at which the interface system resonates and the capacitance response amplitude reaches a local maximum. The identification method is to scan the capacitance response amplitude of all frequency points and find the frequency corresponding to the amplitude peak. At the same time, the peak is required to be at least 20% higher than the response amplitude of the adjacent frequency points. For example, the capacitance response amplitude of a certain adhesion abnormality area is 3.2pF at 85Hz, and 2.1pF and 2.3pF at 80Hz and 90Hz respectively. Then 85Hz is the interface resonance frequency of this area. The resonance frequency distribution data is a distribution diagram formed by arranging the resonance frequencies of each adhesion abnormality area according to spatial position. The data format contains the area coordinates and the corresponding resonance frequency values. This sweeping frequency excitation method can accurately identify the dynamic response characteristics of each abnormal area. The difference in resonance frequency directly reflects the change in the interface adhesion state, providing key frequency parameters for subsequent quantitative analysis.

[0053] Based on the resonant frequency distribution data, periodic microstress perturbations are applied at corresponding frequencies. Periodic microstress perturbations refer to alternating stress loads repeatedly applied at a defined frequency and amplitude. The perturbation frequency is set to the interface resonant frequency corresponding to each region, the perturbation amplitude is maintained constant at 0.5 MPa, and the perturbation waveform is a sinusoidal wave with a duration of 10 seconds to obtain stable response data. The piezoelectric actuator is controlled by a function generator with an output voltage amplitude of ±10 V and a frequency accuracy of 0.01 Hz. Capacitive response amplitude data, which refers to the amplitude of the capacitance change under periodic perturbations, is obtained through synchronous sampling: the sampling frequency is set to 20 times the excitation frequency to comply with the sampling theorem, and the sampling time is 10 seconds. 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 between the excitation and response signals is calculated. The time delay corresponding to the correlation function peak is multiplied by the excitation frequency and then by 360° to obtain the phase delay angle. For example, if a region is excited at 85Hz and has a capacitance response amplitude of 3.2pF and a phase delay of 25°, the complex capacitance response of that region can be expressed as 3.2∠25°pF. Complex capacitance response data is a complex number that combines 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 resonant frequency-based periodic excitation method maximizes the interface response signal, improving measurement accuracy and signal-to-noise ratio. The phase information obtained can also reveal the damping characteristics of the interface.

[0054] When calculating the interface damping coefficient based on complex capacitance response data, the interface damping coefficient is a dimensionless parameter that describes the energy dissipation capacity of the interface system. It is calculated as the ratio of the imaginary to real parts of the complex capacitance response data. The calculation method is: the damping coefficient is equal to the imaginary part of the capacitance response divided by the real part, then divided by 2π. For example, if the real part of the complex capacitance response in a certain region is 2.9pF and the imaginary part is 1.4pF, the damping coefficient is 1.4 / (2.9×2π)=0.077. The local stress-capacitance response relationship is the quantitative relationship between stress load and capacitance response within a local region. It is established by comparing the damping coefficients of the adhesion anomaly region with those of the adjacent normal region. The establishment process is as follows: a normal region within 5mm of the adhesion anomaly region is selected as a reference, its complex capacitance response is measured under the same excitation conditions, and the corresponding damping coefficient is calculated. The difference in damping coefficient 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 significant. For example, the damping coefficient of the abnormal region is 0.077, while that of the adjacent normal region is 0.045, resulting in a ratio of 1.71, indicating that the damping characteristics of the abnormal region are significantly higher than those of the normal region. Regional response characteristic data, including parameters such as the damping coefficient, response amplitude, phase delay, and the difference ratio with the normal region for each region, are stored in a data table. This response relationship analysis method based on damping coefficient differences can quantitatively assess the differences in interface state between different regions. Changes in the damping coefficient directly reflect the changing trend of adhesion strength.

[0055] Spatial coupling correction is performed on regional response characteristic data. This refers to a data processing method that corrects single-point measurement results by taking into account the mutual influence between adjacent regions. The constraint effect between adjacent regions refers to the fact that, due to material continuity, the deformation of one region constrains the surrounding regions, affecting their actual response characteristics. The strength of the constraint effect is determined by the distance between regions and the stiffness difference: the closer the distance, the stronger the constraint effect, and the greater the stiffness difference, the more pronounced the constraint effect. The correction algorithm uses a weighted averaging method: With the target region as the center, all measurement points within a 3mm radius are selected and weighted according to the inverse of the distance, with closer distances increasing the weight. For example, if the original damping coefficient of the target region is 0.077, the damping coefficients of the four adjacent regions are 0.045, 0.052, 0.048, and 0.041, respectively. The corresponding distances are 1mm, 1.5mm, 2mm, and 2.5mm, and the weights are 1.0, 0.67, 0.5, and 0.4, respectively. The corrected damping coefficient is the weighted average of the product of the damping coefficients of each region and the weights. The corrected local stress-capacitance response relationship is used to recalculate the stress-load-capacitance response curve using the corrected damping coefficient. Inverse calculation refers to the process of reversely calculating the interfacial adhesion strength based on the measured capacitance response data and the known stress-capacitance response relationship. The calculation uses a linear relationship: the adhesion strength is equal to the corrected damping coefficient multiplied by the conversion coefficient plus the reference strength value. The conversion coefficient was determined through comparative testing of standard adhesion strength specimens. Five sets of standard composite copper foil specimens with different adhesion strengths were prepared: 5 MPa, 10 MPa, 15 MPa, 20 MPa, and 25 MPa. Their actual adhesion strengths were measured using a 180° peel tester. Dynamic capacitance tests were then performed on these standard specimens to obtain the corresponding damping coefficient data. The least squares method was used to fit the linear relationship between the damping coefficient and adhesion strength, resulting in a conversion coefficient of 85 MPa and a reference strength of 2 MPa. For example, if the corrected damping coefficient for a region is 0.074, the calculated adhesion strength is 0.074 × 85 + 2 = 8.3 MPa. Adhesion strength spatial distribution data is a distribution diagram formed by arranging the adhesion strength values calculated by inversion for each region according to their spatial position. The data has an accuracy of 0.1 MPa and a spatial resolution of 1 mm. This spatial coupling correction method eliminates interference from the mutual influence of adjacent regions on the measurement results, obtaining more accurate single-point adhesion strength values. The correction accuracy can be improved by 15-20%, significantly improving the accuracy of adhesion strength distribution assessment.

[0056] In one embodiment of the present invention, the calculation of the interface damping coefficient based on the complex capacitance response data, the establishment of a local stress-capacitance response relationship based on the difference in damping coefficient between the adhesion abnormality region and the adjacent normal region, and the acquisition of regional response characteristic data include: Separating the real and imaginary components of the capacitance response from the complex capacitance response data, calculating the interface dielectric loss factor according to the ratio of the imaginary component to the real component, and determining the interface damping coefficient data of each region according to the dielectric loss factor; Performing inter-regional comparative calculation on the interface damping coefficient data to obtain the damping coefficient ratio and gradient change rate between the adhesion abnormality region and the adjacent normal region, and dividing the interface response sensitivity level according to the ratio and gradient change rate to obtain interface response sensitivity classification data; Based on the interface response sensitivity classification data, corresponding stress-capacitance response coefficients are allocated to regions with different sensitivity levels, and regionalized stress-capacitance relationships are established through the spatial distribution of the response coefficients to obtain regional response characteristic data.

[0057] The following is a detailed description of the steps involved in the above embodiment: When separating the real and imaginary components of the complex capacitance response data, the real component refers to the portion of the complex capacitance response that is in phase with the excitation signal and reflects the energy storage characteristics of the interface. The imaginary component refers to the portion that is orthogonal to the excitation signal and reflects the energy dissipation characteristics of the interface. This separation process utilizes complex arithmetic: the complex capacitance response data is represented as A+jB, where A is the real component, B is the imaginary component, and j is the imaginary unit. Data processing utilizes a 32-bit floating-point digital signal processor, achieving component separation through trigonometric operations: the real component equals the response amplitude multiplied by the cosine of the phase angle, and the imaginary component equals the response amplitude multiplied by the sine of the phase angle. For example, if the complex capacitance response amplitude for a region is 3.2pF and the phase angle is 25°, the real component is 3.2×cos(25°)=2.9pF, and the imaginary component is 3.2×sin(25°)=1.35pF. The dielectric loss factor of an interface is a dimensionless parameter that describes the degree of energy loss in interface materials under an alternating electric field. It is calculated by dividing the imaginary component by the real component. A larger loss factor indicates a greater energy dissipation capacity of the interface, while a smaller loss factor indicates a greater energy storage capacity. For example, the dielectric loss factor of the region described above is 1.35 / 2.9 = 0.466. The interface damping coefficient data is converted from the dielectric loss factor to obtain the interface damping characteristic parameter. The conversion relationship is: 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, a dielectric loss factor of 0.466 corresponds to an interface damping coefficient of 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 can accurately quantify the energy dissipation characteristics of the interface. Changes in the dielectric loss factor directly reflect changes in the adhesion state of the interface, with the loss factor increasing significantly when the adhesion strength decreases.

[0058] Inter-regional comparison of interface damping coefficient data involves numerically comparing and statistically analyzing the damping coefficient of an abnormal adhesion region with that of adjacent normal regions. The comparison method utilizes paired comparison: for each abnormal adhesion region, the three nearest 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 abnormal region by the baseline value. A ratio greater than 1 indicates that the damping of the abnormal region is higher than that of the normal region, while a ratio less than 1 indicates that the damping of the abnormal region is lower than that of the normal region. For example, if the damping coefficient of an abnormal 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, a parameter that describes the spatial variation of the damping coefficient, is calculated by selecting two adjacent measurement points at the boundary of the abnormal region and dividing the difference in damping coefficient by the spatial distance. For example, at the boundary of the abnormal region, the damping coefficient changes from 0.045 to 0.074 over a distance of 2 mm, and the gradient change rate is (0.074-0.045) / 2 = 0.0145 / mm. The interface response sensitivity level is a classification system for interface states that is graded based on the combination of the damping coefficient ratio and the gradient change rate. It is divided into three levels: high sensitivity, medium sensitivity, and low sensitivity. The grading standard is: areas with a ratio greater than 1.5 and a gradient change rate greater than 0.01 / mm are classified as high sensitivity, areas 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 areas 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 grading data is stored as 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 the damping characteristics. The division of sensitivity levels directly corresponds to different degrees of adhesion strength changes, providing a scientific basis for subsequent differentiated processing.

[0059] When assigning corresponding stress-capacitance response coefficients to areas of different sensitivity levels based on the interface response sensitivity grading data, the stress-capacitance response coefficient is a physical parameter that describes the degree of capacitance change caused by a unit stress change, and its unit is pF / MPa. The assignment of the response coefficient is based on the sensitivity level and the calibration experiment results: the stress-capacitance response test of standard specimens at different adhesion strengths is used to determine the response coefficient range corresponding to each sensitivity level. The response coefficient of the high-sensitivity level area is set to 2.5-3.0pF / MPa, the medium-sensitivity level area is set to 1.8-2.2pF / MPa, and the low-sensitivity level area is set to 1.2-1.5pF / MPa. The specific values are determined by the linear interpolation method: within the coefficient range of each level, linear interpolation calculations are performed based on the specific values of the damping coefficient ratio. For example, the damping coefficient ratio of a highly sensitive area is 1.64. Within the high-sensitivity ratio 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. The regionalized stress-capacitance relationship refers to the quantitative relationship between stress and capacitance changes established using different response coefficients in different spatial regions. The relationship is expressed as: the change in capacitance equals the change in stress multiplied by the response coefficient of the corresponding region. The spatial distribution of the response coefficient is generated into a continuous spatial distribution map using an interpolation algorithm: using bilinear interpolation, the response coefficient of any point in space is calculated based on the response coefficient values of known measurement points. Regional response feature data includes parameters such as sensitivity level, response coefficient, damping coefficient ratio, gradient change rate, etc. for each region. It is stored in a structured data table format, with each row corresponding to a region and each column corresponding to a feature parameter. This differentiated response coefficient allocation method based on sensitivity grading can accurately reflect the differences in response characteristics of areas with different adhesion states. The spatial distribution of the response coefficient provides precise conversion parameters for the subsequent quantitative calculation of adhesion strength. The calculation accuracy is 25-30% higher than that of the traditional uniform response coefficient method.

[0060] Please continue reading Figure 1 During the film expansion process, the capacitance reference value in the stress-free state is periodically recorded, the fatigue-sensitive area is determined based on 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 based on the capacitance offset accumulation.

[0061] In one embodiment of the present invention, periodically recording a capacitance reference value in a stress-free state during film expansion, determining a fatigue-sensitive area 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 a capacitance offset accumulation, and evaluating the degree of interface adhesion fatigue based on the capacitance offset accumulation includes: determining an adhesion strength classification threshold based on the intensity gradient change in the adhesion strength spatial distribution data, marking areas where the adhesion strength is below a preset threshold as highly sensitive areas, and marking areas where the adhesion strength is within the threshold range as moderately sensitive areas, thereby obtaining fatigue sensitivity classification data corresponding to the fatigue sensitive areas; During the film expansion process, periodically recording the capacitance reference values of the highly sensitive area and the medium sensitive area in a stress-free state at preset time intervals, and establishing time series capacitance reference value data according to the recording time sequence; Comparing the timing capacitance reference value data with the interface reference capacitance distribution data point by point, obtaining capacitance offset at each time point, and performing weighted accumulation calculation on the capacitance offset according to a time weight coefficient, obtaining capacitance offset accumulation; Performing spatial correlation analysis on the capacitance offset accumulation, identifying fatigue propagation paths based on differences in offset accumulation between adjacent regions, and correcting the offset accumulation of each region using the propagation paths to obtain a corrected capacitance offset accumulation; The fatigue degree is graded according to the comparison result of the corrected capacitance offset accumulation amount and the preset fatigue threshold. The area where the accumulation amount exceeds the threshold is determined as a severe fatigue area, and the area where the accumulation amount is close to the threshold is determined as a moderate fatigue area, thereby obtaining the interface adhesion fatigue degree assessment result.

[0062] The following is a detailed description of the steps involved in the above embodiment: When determining the adhesion strength grading threshold based on the intensity gradient variation in the spatial distribution of adhesion strength data, the intensity gradient refers to the spatial rate of change of adhesion strength, obtained by calculating the ratio of the adhesion strength difference between adjacent measurement points to their distance. The gradient is calculated using the central difference method: the adhesion strength values of three adjacent measurement points are selected, and the gradient at the middle point is equal to the difference between the values of the two preceding and following points divided by twice the distance between them. For example, if the adhesion strength at a position of 10 mm is 12 MPa, at a position of 12 mm is 15 MPa, and at a position of 14 mm is 18 MPa, then the intensity gradient at a position of 12 mm is (18-12) / (14-10) = 1.5 MPa / mm. The adhesion strength grading threshold is the critical value of adhesion strength used to distinguish different levels of fatigue sensitivity. It is determined by statistically analyzing the adhesion strength data of all measurement points. The threshold is determined by calculating the 25th percentile of the adhesion strength data as the lower threshold and the 75th percentile as the upper threshold. For example, after the adhesion strength of 100 measurement points is sorted, the 25th value is 8MPa and the 75th value is 18MPa, then the low threshold is 8MPa and the high threshold is 18MPa. Highly sensitive areas refer to areas where the adhesion strength is lower than the low threshold. These areas are more prone to fatigue damage under the action of film stress due to their low adhesion strength. Medium-sensitive areas refer to areas where the adhesion strength is between the low threshold and the high threshold. These areas have a moderate fatigue risk. The fatigue sensitivity grading data corresponding to the fatigue-sensitive area is stored in the form of area coordinates and sensitivity level identifiers (H for high sensitivity, M for medium sensitivity, and L for low sensitivity). The data format is a CSV file containing four columns of information: 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 of different batches of composite copper foils. The accuracy of sensitivity grading reaches more than 92%, providing accurate target area identification for subsequent fatigue monitoring.

[0063] During the film rollout process, the capacitance baseline values of the highly sensitive and moderately sensitive areas in the stress-free state are periodically recorded at preset intervals. This interval, set every 30 seconds based on the characteristics of the rollout process, captures the slow evolution of fatigue accumulation while minimizing data generation. The stress-free state refers to a state in which the rollout tension is temporarily released to zero. The tension control system reduces the tension to 0 N at the time of recording and maintains it for 5 seconds to ensure a natural interface state. The capacitance baseline values are recorded using a high-precision LCR bridge with a measurement frequency of 1 kHz and a measurement time of 1 second. Three measurements are repeated at each measurement point and the average is taken to improve accuracy. The recording process involves the data acquisition system automatically releasing the tension at preset intervals, triggering the capacitance measurement system to measure the capacitance of all highly sensitive and moderately sensitive areas. After the measurements are completed, the rollout tension is restored to normal. For example, the capacitance baseline value of a highly sensitive area at minute 0 is 98.5 pF, at minute 0.5 is 98.3 pF, and at minute 1 is 98.1 pF, showing a gradually decreasing trend. Time-series capacitance baseline data is a chronological arrangement of the capacitance baseline values of each sensitive area at different time points. The data is structured as a three-dimensional array: [area number][time point][capacitance value]. The data is stored in HDF5 format to support efficient access to time-series data. This periodic recording method can track the dynamic development of interface fatigue with a time resolution of 30 seconds, which is sufficient to capture the key changes in fatigue accumulation.

[0064] When performing a point-by-point comparison between the time-series capacitance baseline data and the interface reference capacitance distribution data, this comparison involves a one-to-one numerical comparison of 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 region, the capacitance value at that moment is read from the time-series capacitance baseline data, and the initial reference value at the corresponding location is read from the interface reference capacitance distribution data. The two values are then subtracted to obtain the capacitance offset. For example, if the initial reference capacitance of a region is 100.0pF and the capacitance value at the first minute is 99.7pF, the capacitance offset at that moment is 99.7-100.0 = -0.3pF. The time weight coefficient is a weighting factor that reflects the cumulative contribution of fatigue at different time points. Based on fatigue damage theory, early damage has a greater impact on subsequent fatigue development, so the weight coefficient for earlier time points is higher. The weight coefficient uses an exponential decay function: W(t) = exp(-t / τ), where W(t) is the weight coefficient at time t and τ is the time constant, which is 300 seconds. For example, the weight coefficient for the first minute (t=60 seconds) is exp(-60 / 300) = 0.819, and the weight coefficient for the fifth minute (t=300 seconds) is exp(-300 / 300) = 0.368. Weighted accumulation calculation multiplies the capacitance offset at each time point by the corresponding time weight coefficient and then sums the results: Cumulative value = Σ(offset × weight coefficient). For example, if the offsets for the first three time points in a region are -0.3pF, -0.5pF, and -0.8pF, respectively, and the corresponding weight coefficients are 0.90, 0.819, and 0.741, the cumulative capacitance offset is (-0.3 × 0.90) + (-0.5 × 0.819) + (-0.8 × 0.741) = -1.466pF. This weighted accumulation method accurately reflects the time-dependence and cumulative characteristics of fatigue damage. The weight function is designed based on the physical laws of material fatigue, making fatigue assessment results more realistic.

[0065] When performing spatial correlation analysis on capacitance offset accumulation, spatial correlation analysis refers to studying the interrelationships and influence patterns of capacitance offset accumulation between adjacent regions. The analysis method utilizes a spatial autocorrelation algorithm: the correlation coefficient between the offset accumulation of each region and its eight surrounding regions is calculated. 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 expansion on the interface. It is identified by analyzing the gradient direction of the offset accumulation between adjacent regions. This identification method involves calculating the spatial gradient vector of the offset accumulation for each region. The gradient direction represents the possible path for fatigue propagation, and the magnitude of the gradient reflects the propagation speed. For example, if the offset accumulation of a region is -2.1pF, its adjacent region to the right is -1.8pF, and its adjacent region below is -1.9pF, the gradient vector points to the lower right, indicating that fatigue is propagating from that region to the lower right. Propagation path correction involves adjusting the offset cumulative values for each region based on fatigue propagation patterns: the cumulative value for the region at the start of the propagation path remains unchanged; the cumulative value for the region in the middle of the propagation path is multiplied by a propagation coefficient of 1.2; and the cumulative value for the region at the end of the propagation path remains unchanged. The corrected capacitance offset cumulative value is the cumulative value after propagation path correction, more accurately reflecting the actual status 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 value accounts for the mutual influence between regions, improving the accuracy of fatigue assessment by 15-20%.

[0066] Fatigue severity is graded based on the comparison of the corrected capacitance offset cumulative value with a preset fatigue threshold. The preset fatigue threshold is a critical value of the cumulative value determined based on fatigue test data and used to distinguish different degrees of fatigue. The threshold is determined through a standard fatigue test: 20 composite copper foil specimens with different fatigue levels were prepared and subjected to cyclic loading to different fatigue stages. The cumulative capacitance offset was measured. Statistical analysis revealed a severe fatigue threshold of -3.0pF and a moderate fatigue threshold of -1.5pF. Fatigue severity is graded using a three-level classification: areas with a corrected capacitance offset cumulative value less than -3.0pF are classified as severe fatigue, indicating that they are close to fatigue failure; areas with cumulative values between -3.0pF and -1.5pF are classified as moderate fatigue, indicating significant fatigue damage but not yet reaching a critical level; and areas with cumulative values greater than -1.5pF are classified as mild fatigue or normal. The comparison process is performed on a region-by-region basis: the data processing system reads the corrected capacitance offset cumulative value of each region, compares it 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 interface adhesion fatigue assessment are displayed as a spatial distribution map, with different fatigue levels represented by different colors: red indicates severe fatigue, yellow indicates moderate fatigue, and green indicates normal fatigue. This cumulative threshold-based grading method accurately identifies different fatigue states, with a fatigue prediction accuracy exceeding 88%, providing a reliable technical basis for film spreading process optimization and quality control.

[0067] The above describes the method for spreading the current collector composite copper foil according to the embodiment of the present invention. The following describes the device for spreading the current collector composite copper foil according to the embodiment of the present invention. Figure 2 An embodiment of the current collector composite copper foil film spreading device of the present invention includes: The electric field processing module 101 is used to apply a DC electric field to the current collector composite copper foil entering the film extension area, forming a charge separation layer in the interface area by utilizing the work function difference between the copper layer and the polymer layer to obtain interface reference capacitance distribution data; The film spreading tension module 102 is used to apply film spreading tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtain interface capacitance change data under stress based on the interface reference capacitance distribution data; a correlation analysis module 103 for 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 abnormality areas based on correlation coefficient change trends; a stress perturbation module 104 for applying periodic microstress perturbations to the adhesion abnormality region, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship; The fatigue assessment module 105 is used to periodically record the capacitance reference value in the stress-free state during the film expansion 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 capacitance offset accumulation, and assess the degree of interface adhesion fatigue based on the capacitance offset accumulation.

[0068] Figure 3 and Figure 4 It is a mechanical support platform for the current collector composite copper foil film spreading device, which is used to carry the current collector composite copper foil and provide basic tension application function. The mechanical support platform includes two tension application units 1 located on both sides of the width direction of the current collector composite copper foil, each tension application unit 1 has an upper and lower roller 11, and the rollers 11 are driven to rotate by a motor 12 respectively. The current collector composite copper foil is located between the upper and lower rollers 11 and is clamped. The two tension application units 1 can be movably set on the guide rail 2, and by adjusting the distance between the two tension application units 1, current collector composite copper foils of different widths can be adapted. Since the mechanical support platform is a relatively common structure, the focus of this application is on the improvement of the method, so the platform will not be described in detail here.

[0069] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for spreading a current collector composite copper foil, characterized in that: include: A DC electric field is applied to the current collector composite copper foil entering the film extension area, and the charge separation layer is formed at the interface area by utilizing the work function difference between the copper layer and the polymer layer to obtain the interface reference capacitance distribution data; Applying film-stretching tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data; 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 abnormality areas based on a correlation coefficient change trend; Applying periodic microstress perturbations to the abnormal adhesion region, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship; During the film expansion process, the capacitance baseline value in the stress-free state is periodically recorded, and the fatigue-sensitive area is determined based on the adhesion strength spatial distribution data. The capacitance baseline value corresponding to the fatigue-sensitive area is compared with the interface reference capacitance distribution data to obtain the capacitance offset accumulation. The interface adhesion fatigue degree is evaluated based on the capacitance offset accumulation.

2. The method for spreading a current collector composite copper foil according to claim 1, characterized in that: The method of applying a DC electric field to the current collector composite copper foil entering the film extension 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 includes: Performing stress distribution measurement on the current collector composite copper foil entering the film spreading area, determining the interface prestress state according to the stress concentration area in the stress distribution measurement results, and obtaining interface stress distribution data; Applying compensation tension to the current collector composite copper foil according to the interface stress distribution data to make the interface prestress state uniform, and obtaining interface layer spacing distribution data at the same time; Calculating an electric field penetration coefficient based on the interfacial layer spacing distribution data, 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 intensity is inversely proportional to the interfacial layer spacing, and obtaining electric field intensity distribution data; Using the electric field intensity distribution data, a charge accumulation region is formed at the microscopic protrusions of the interface, and charge diffusion from the charge accumulation region to the flat region establishes an interface charge gradient to obtain a gradient charge separation layer; 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 interface reference capacitance distribution data.

3. The method for spreading a current collector composite copper foil according to claim 2, characterized in that: The electric field penetration coefficient is calculated based on the interface layer spacing distribution data, and 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 to obtain the electric field intensity distribution data, including: Calculating the dielectric field strength attenuation coefficient of each region based on the spatial variation characteristics of the interface layer spacing distribution data, and determining the electric field penetration depth corresponding to different layer spacings based on the difference in dielectric constants between the copper layer and the polymer layer to obtain layered electric field penetration coefficient data; Determining an electric field strength compensation factor based on the layered electric field penetration coefficient data, setting a compensation factor greater than 1 for a region where the interfacial layer spacing exceeds the average value, and setting a compensation factor less than 1 for a region where the interfacial layer spacing is lower than the average value, to obtain electric field strength compensation coefficient distribution data; A compensated DC electric field is applied to different regions of the current collector composite copper foil according to the electric field strength compensation coefficient distribution data, and differential adjustment of the electric field strength in each region is achieved by multiplying the electric field strength by the compensation coefficient to obtain electric field strength distribution data.

4. The method for spreading a current collector composite copper foil according to claim 1, wherein: The step of applying film-stretching tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtaining interface capacitance change data under stress based on the interface reference capacitance distribution data, includes: Applying a step-wise film-stretching tension to the current collector composite copper foil to cause the copper layer and the polymer layer to generate differential strain responses, and obtaining interlayer strain difference distribution data based on the differential strain responses; determining interface shear stress distribution data based on the interlayer strain difference distribution data, and using the interface shear stress distribution data to drive interface microscopic displacement to obtain interface displacement vector data; Performing spatial displacement correction on the interface reference capacitance distribution data based on the interface displacement vector data, and calculating instantaneous capacitance distribution data through a response relationship between capacitance value and interface geometry change to obtain dynamic capacitance data; Performing a time series analysis on the dynamic capacitance data, extracting fast response component data and slow response component data of the capacitance change according to the stress relaxation time difference between the copper layer and the polymer layer, and obtaining dual-time-scale capacitance response data; A difference operation is performed on the dual-time-scale capacitance response data and the interface reference capacitance distribution data to obtain interface capacitance change data under the stress.

5. The method for spreading a current collector composite copper foil according to claim 4, characterized in that: Determining interface shear stress distribution data based on the interlayer strain difference distribution data, and using the interface shear stress distribution data to drive interface microscopic displacement to obtain interface displacement vector data, includes: performing spatial gradient calculation on the interlayer strain difference distribution data, determining an interlayer strain transfer ratio based on a ratio of the elastic modulus of the copper layer to the elastic modulus of the polymer layer, and converting the interlayer strain difference into equivalent shear strain data at the interface through the strain transfer ratio; Calculating the shear stress amplitude of each region based on the equivalent shear strain data and the equivalent shear modulus of the composite copper foil interface, determining the spatial distribution direction of the shear stress in combination with the microscopic geometric characteristics of the interface, and obtaining 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 to obtain the interface displacement vector data.

6. The method for spreading a current collector composite copper foil according to claim 1, characterized in that: The method 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 an abnormal adhesion area based on a correlation coefficient change trend includes: Performing first-order time-domain difference and second-order time-domain difference processing on the interface capacitance change data under the stress, obtaining an instantaneous capacitance change rate sequence based on the first-order difference data, and obtaining a capacitance change acceleration sequence based on the second-order difference data; performing speed normalization processing on the instantaneous capacitance change rate sequence according to the film spreading speed data, so as to establish a fixed corresponding relationship between the capacitance change rate and the spatial position, thereby obtaining a spatially 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, and performing Pearson correlation calculation on the capacitance change rates in adjacent windows to obtain spatial correlation coefficient distribution data; A local continuity test is performed on the spatial correlation coefficient distribution data, a 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 abnormality area.

7. The method for spreading a current collector composite copper foil according to claim 1, characterized in that: Applying periodic microstress perturbations to the abnormal adhesion area, establishing a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtaining adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship, includes: Performing frequency sweep microstress excitation on the abnormal adhesion area, determining the interface resonance frequency according to the change in capacitance response amplitude at different excitation frequencies, and obtaining resonance frequency distribution data; Applying periodic microstress perturbations at corresponding frequencies according to the resonant frequency distribution data, and synchronously recording corresponding capacitance response amplitude data and phase delay data in the interface capacitance change data under the stress to obtain 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 difference in damping coefficient between the adhesion abnormality region and the adjacent normal region, and obtaining regional response characteristic data; The regional response characteristic data is spatially coupled corrected, the single-point response characteristics are corrected according to the constraint effect between adjacent regions, and the spatial distribution data of the adhesion strength is obtained by inverting the corrected local stress-capacitance response relationship.

8. The method for spreading a current collector composite copper foil according to claim 7, characterized in that: The calculating of the interface damping coefficient based on the complex capacitance response data, establishing a local stress-capacitance response relationship according to the difference in damping coefficient between the adhesion abnormal area and the adjacent normal area, and obtaining regional response characteristic data include: Separating the real and imaginary components of the capacitance response from the complex capacitance response data, calculating the interface dielectric loss factor according to the ratio of the imaginary component to the real component, and determining the interface damping coefficient data of each region according to the dielectric loss factor; Performing inter-regional comparative calculation on the interface damping coefficient data to obtain the damping coefficient ratio and gradient change rate between the adhesion abnormality region and the adjacent normal region, and dividing the interface response sensitivity level according to the ratio and gradient change rate to obtain interface response sensitivity classification data; Based on the interface response sensitivity classification data, corresponding stress-capacitance response coefficients are allocated to regions with different sensitivity levels, and regionalized stress-capacitance relationships are established through the spatial distribution of the response coefficients to obtain regional response characteristic data.

9. The method for spreading a current collector composite copper foil according to claim 1, wherein: The method includes periodically recording a capacitance reference value in a stress-free state during the film spreading process, determining a fatigue-sensitive area 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 a capacitance offset accumulation, and evaluating the degree of interface adhesion fatigue based on the capacitance offset accumulation, including: determining an adhesion strength classification threshold based on the intensity gradient change in the adhesion strength spatial distribution data, marking areas where the adhesion strength is below a preset threshold as highly sensitive areas, and marking areas where the adhesion strength is within the threshold range as moderately sensitive areas, thereby obtaining fatigue sensitivity classification data corresponding to the fatigue sensitive areas; During the film expansion process, periodically recording the capacitance reference values of the highly sensitive area and the medium sensitive area in a stress-free state at preset time intervals, and establishing time series capacitance reference value data according to the recording time sequence; Comparing the timing capacitance reference value data with the interface reference capacitance distribution data point by point, obtaining capacitance offset at each time point, and performing weighted accumulation calculation on the capacitance offset according to a time weight coefficient, obtaining capacitance offset accumulation; Performing spatial correlation analysis on the capacitance offset accumulation, identifying fatigue propagation paths based on differences in offset accumulation between adjacent regions, and correcting the offset accumulation of each region using the propagation paths to obtain a corrected capacitance offset accumulation; The fatigue degree is graded according to the comparison result of the corrected capacitance offset accumulation amount and the preset fatigue threshold. The area where the accumulation amount exceeds the threshold is determined as a severe fatigue area, and the area where the accumulation amount is close to the threshold is determined as a moderate fatigue area, thereby obtaining the interface adhesion fatigue degree assessment result.

10. A current collector composite copper foil film spreading device, characterized in that: The current collector composite copper foil film spreading device adopts the current collector composite copper foil film spreading method according to any one of claims 1 to 9, and the current collector composite copper foil film spreading device comprises: The electric field processing module is used to apply a DC electric field to the current collector composite copper foil entering the film extension area, forming a charge separation layer in the interface area by utilizing the work function difference between the copper layer and the polymer layer to obtain interface reference capacitance distribution data; A film spreading tension module is used to apply film spreading tension to the current collector composite copper foil to generate microscopic relative displacement between different material layers, and obtain interface capacitance change data under stress based on the interface reference capacitance distribution data; a correlation analysis module for performing time-domain differential 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 abnormality areas based on correlation coefficient change trends; a stress perturbation module, configured to apply periodic microstress perturbations to the adhesion abnormality region, establish a stress-capacitance response relationship based on the corresponding capacitance response amplitude in the interface capacitance change data, and obtain adhesion strength spatial distribution data by inverting the spatial distribution of the stress-capacitance response relationship; The fatigue assessment module is used to periodically record the capacitance reference value in the stress-free state during the film expansion 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 capacitance offset accumulation, and assess the interface adhesion fatigue degree based on the capacitance offset accumulation.

Images