Detection system for nondestructively and intelligently testing defects of finished naked battery cell

Abstract

The invention provides a nondestructive intelligent detection system for testing the defects of a finished naked battery cell, which comprises a feeding machine, a battery cell code scanning device, an optical appearance detection module, an X-ray nondestructive detection module, an electrical function detection module, an equipment system data processing center and an automatic result judgment module, and the detection modules work cooperatively to automatically execute all operation steps. Automatically judging a test result, and automatically uploading and storing the test result; the production stability and the traceability of test steps and test data can be improved, the operation is simple and convenient, the manual operation procedures of personnel inspection, test result judgment, test data storage and the like are solved, and the labor cost and the quality cost caused by fatigue operation errors of personnel are greatly saved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery testing technology, and in particular to a non-destructive intelligent testing system for defects in finished bare battery cells. Background Technology

[0002] With the rapid development of lithium batteries, especially in the existing lithium battery finished product manufacturing technology, the detection of defects in bare cells is crucial. Non-destructive intelligent testing of finished bare cell defects refers to the online detection of the appearance, performance, and safety of finished bare cells before the cells are sorted and used in the pack. Non-destructive intelligent testing of finished bare cell defects is a production stage test for appearance and performance safety, and it tests the finished bare cells produced by the cell factory for defects in appearance and performance safety.

[0003] Currently, there is no suitable testing system for the appearance and performance safety of finished bare battery cells. This results in a limited range of testing methods for the appearance and performance safety of finished bare battery cells, making it inconvenient for users to selectively implement tests according to their needs and failing to improve testing efficiency. Therefore, there is an urgent need for a testing system for the appearance and performance safety defects of finished bare battery cells to solve this problem in the existing technology. Summary of the Invention

[0004] This invention provides a non-destructive intelligent testing system for defects in finished bare battery cells. It automatically executes all operation steps, automatically judges test results, and automatically uploads and saves test results. It can improve production stability, ensure the traceability of test steps and test data, and is simple and convenient to operate. It eliminates manual operation processes such as personnel inspection, test result judgment, and test data storage, and greatly saves labor costs and quality costs caused by personnel fatigue and operation errors.

[0005] To address the aforementioned issues, this invention provides a non-destructive intelligent testing system for defects in finished bare battery cells, comprising a feeding machine, a cell scanning device, an optical appearance inspection module, an X-ray non-destructive testing module, an electrical function testing module, an equipment system data processing center, and an automatic result determination module, connected to a feeding port and a sorting and traceability module;

[0006] The optical appearance inspection module includes visible light multi-angle imaging and near-infrared transmission difference film on / under film, multi-angle structured light and photometric stereo detection device, striped grating and 3D contour, time-division exposure, multispectral fusion and production line cycle organization.

[0007] The X-ray non-destructive testing module includes DR rapid screening, CT three-dimensional quantitative analysis, and online CT index reference: X-ray non-destructive testing is used to visualize the inside of the package through DR / CT, identifying electrode alignment, overhang, interlayer misalignment, wrinkles, solder joint defects / missing solder joints, and housing dimensions; online CT improves scanning efficiency to the second level, enabling production line cycle time matching and full inspection;

[0008] The electrical and functional testing module includes insulation withstand voltage and leakage current devices, DC internal resistance, AC impedance EIS and micro short circuit rapid screening, to detect insulation withstand voltage, leakage current, DC internal resistance / ESR, AC impedance (EIS) tests, and to locate electrical defects such as micro short circuits, abnormal internal resistance and / or self-discharge.

[0009] A further approach involves the visible light multi-angle imaging: multiple sets of visible light sources and cameras are arranged on the same side of the detection surface, the light areas are staggered, a large incident angle (60°~80°) is used to highlight the morphological changes caused by particles / bubbles in the film, and a small incident angle (5°~15°) is used to enhance the shadow and edge response of surface pits; the camera and light area coincide and online high-speed acquisition improves the detection rate and stability of pits / scratches / film damage.

[0010] A further proposed solution is the DR rapid screening: an X-ray source emits penetrating rays, and an imaging system receives the attenuation differences to form a two-dimensional projection, allowing real-time observation of electrode alignment, winding / stacking status, solder joint quality, and housing dimensions; suitable for high-speed sampling or as a pre-screening step for online CT.

[0011] A further solution involves using near-infrared transmission to determine whether the object is above or below the film: a dual-pathway system is set up with visible light and near-infrared (800-900nm). Utilizing the certain penetrability of infrared light through the encapsulation film, two images are obtained: "surface morphology" and "internal transmission". At the same suspected location, if the infrared transmission image shows an anomaly while the visible light surface image is not significant, or if the grayscale distribution characteristics are combined (e.g., high grayscale values ​​in the region indicate bubbles, while low grayscale values ​​in the center and high grayscale values ​​around the edges indicate foreign objects), it can be determined as a foreign object / bubble under the film, significantly reducing false detections.

[0012] A further solution is that the CT three-dimensional quantitative method involves using a horizontal CT scanner to perform continuous angular scanning of the battery cell and reconstruct three-dimensional volume data. The electrode area is extracted by slicing, and combined with image enhancement and deep learning models, the height difference (over-hang), inter-slice gap, and morphological anomalies of adjacent positive and negative electrode endpoints are automatically measured. Compared with 2D, CT can present the internal structure from multiple layers and angles, reducing misjudgments / missed judgments caused by electrode interference and projection occlusion, and supports online second-level detection and full-size measurement.

[0013] A further proposed solution is to specify the following online CT indicators: repeatability measurement accuracy (GR&R) ≤ 10%, detection efficiency ≥ 36 PPM, false positive rate < 0.5%, detection accuracy < 0.03 mm, and single cell detection time ≤ 3.5 s, to meet the quality control requirements for high-speed production of stacked cells.

[0014] A further solution is to apply a gradually increasing DC high voltage (e.g., gradually increasing from 0 to a set value U) to the bare cell or assembly, maintain it for a certain period of time, and monitor whether the leakage current is lower than the threshold. The parameter design needs to consider the charging current and gradual increase time caused by stray capacitance. After the test, discharge is performed to avoid misjudgment and ensure safety.

[0015] A further solution is that the AC impedance EIS is: a small amplitude sinusoidal current excitation is applied to a single chip or module, the voltage response is collected at multiple frequency points, the impedance modulus |Z|, phase θ, real part Zre, and imaginary part Zim are calculated, and the equivalent circuit fitting is combined to evaluate SOC / aging and consistency, which is suitable for R&D and production line sampling inspection.

[0016] A further solution is the rapid screening of micro-short circuits: using high-voltage pulses + high-speed sampling (such as capacitor energy storage and discharge, sampling frequency 15-20kHz), comparing the measured current with the standard value under a set voltage level, and determining that there is a risk of micro-short circuit if the current exceeds the threshold, which is used for rapid control of sampling before and after liquid injection and during the process.

[0017] A further solution is to organize the production line cycle time as follows: on cylindrical, square, and pouch cells of different shapes, through multi-station parallel operation and multi-angle synchronous acquisition within the station, to achieve full inspection of six sides and directional high-resolution observation of key parts of the pole / explosion-proof valve, covering different production capacity levels of 24-240PPM.

[0018] The beneficial effects of this invention are as follows: it includes a feeding machine, a cell scanning device, an optical appearance inspection module, an X-ray non-destructive testing module, an electrical function testing module, an equipment system data processing center, and an automatic result determination module. Specific advantages are as follows:

[0019] 1. After the bare battery cells are loaded, the cells automatically stop at the testing station according to the testing station track. Only one testing personnel is needed. The system automatically tests and judges each item according to the set testing process. Products that pass the test automatically flow into the qualified temporary storage area. The test data is uploaded to the engineering MES&PLM system in real time.

[0020] 2. This invention automatically executes all operation steps, automatically judges test results, automatically performs tests according to the test steps, and automatically uploads and saves test results;

[0021] 3. This invention can improve production stability and the traceability of testing steps and data. It is simple and convenient to operate, eliminating manual processes such as personnel inspection, test result judgment, and test data storage, greatly saving labor costs and quality costs caused by operator fatigue and errors. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the working principle of an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the assembled three-dimensional structure according to an embodiment of the present invention;

[0024] Figure 3 This is a top view schematic diagram of the structure of an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the overall appearance structure of an embodiment of the present invention.

[0026] Figure Labels

[0027] 1. X-ray non-destructive testing module; 2. Micro-short circuit rapid screening; 3. Insulation withstand voltage and leakage current; 4. Feeding connection port; 5. Electrical function testing module; 6. Equipment working warning light; 7. Near-infrared transmission discrimination of membrane above / below; 8. Optical appearance inspection module; 9. Visible light multi-angle imaging; 10. Cell barcode scanning; 11. Feeding connection port; 12. Equipment system data processing center; 13. MES / PLM data upload interface; 14. DR rapid screening; 15. CT three-dimensional quantitative analysis; 16. Online CT index reference; 17. Cell testing conveyor track; 18. Equipment outer shell shielding cover. Detailed Implementation

[0028] To better understand the technical content of the present invention, the technical solution of the present invention will be further described and explained below with reference to the accompanying drawings and specific embodiments, but is not limited thereto.

[0029] like Figures 1 to 4 As shown in the specific embodiment of the present invention, a non-destructive intelligent testing system for defects in finished bare battery cells includes a feeding machine, a battery cell scanning device 10, an optical appearance inspection module 8, an X-ray non-destructive testing module 1, an electrical function testing module 5, an equipment system data processing center 12, and an automatic result judgment module, connected to a feeding port 4 and a sorting and traceability module.

[0030] The optical appearance inspection module 8 includes visible light multi-angle imaging 9 and near-infrared transmission difference film on / under film, multi-angle structured light and photometric three-dimensional inspection device, stripe grating and 3D contour, time-division exposure, multispectral fusion and production line cycle organization;

[0031] X-ray non-destructive testing module 1 includes DR rapid screening 14, CT three-dimensional quantitative 15 and online CT index reference 16: X-ray non-destructive testing is used to see through the inside of the package through DR / CT to identify electrode alignment, overhang, interlayer misalignment, wrinkles, solder joint cold / missing solder, and housing size; online CT improves scanning efficiency to the second level, realizing production line cycle matching and full inspection;

[0032] The electrical and functional testing module 5 includes an insulation withstand voltage and leakage current device 3, a DC internal resistance, AC impedance EIS and a micro short circuit rapid screening 2, which detects insulation withstand voltage, leakage current, DC internal resistance / ESR, AC impedance (EIS) tests, and locates electrical defects such as micro short circuits, abnormal internal resistance and / or self-discharge.

[0033] Furthermore, visible light multi-angle imaging 9: Multiple sets of visible light sources and cameras are arranged on the same side of the detection surface, and the light areas are staggered. A large incident angle (about 60° to 80°) is used to highlight the morphological changes caused by particles / bubbles in the film, and a small incident angle (about 5° to 15°) is used to enhance the shadow and edge response of surface pits. The camera and light area coincide and online high-speed acquisition improves the detection rate and stability of pits / scratches / film damage.

[0034] Furthermore, DR rapid screening 14: The X-ray source emits penetrating rays, and the imaging system receives the attenuation difference to form a two-dimensional projection, allowing real-time observation of electrode alignment, winding / stacking status, solder joint quality, and housing size; suitable for high-speed sampling or as a pre-screening step for online CT.

[0035] Furthermore, near-infrared transmission discrimination of above / below film 7: A dual-pathway system of visible light + near-infrared (approximately 800-900nm) is set up. Utilizing the certain penetrability of infrared light through the encapsulation film, two images of "surface morphology + internal transmission" are obtained. At the same suspected location, if the infrared transmission image shows an anomaly while the visible light surface image is not significant, or combined with grayscale distribution characteristics (such as high pixel grayscale in the region indicating bubbles, and low grayscale in the center and high grayscale around the edges indicating foreign objects), it can be determined as a foreign object / bubble under the film, significantly reducing false detections.

[0036] Furthermore, CT 3D quantitative analysis 15: Horizontal CT performs continuous angle scanning of the battery cell and reconstructs 3D volume data, extracts electrode areas by slicing, and automatically measures the height difference (over-hang), inter-slice gap, and morphological anomalies of adjacent positive and negative electrode endpoints by combining image enhancement and deep learning models. Compared with 2D, CT can present the internal structure from multiple layers and angles, reduce misjudgments / missed judgments caused by electrode interference and projection occlusion, and support online second-level detection and full-size measurement.

[0037] Furthermore, the online CT indicator reference 16: The online CT solution has a repeatability measurement accuracy GR&R ≤ 10%, detection efficiency ≥ 36 PPM, false positive rate < 0.5%, detection accuracy < 0.03 mm, and single cell detection time ≤ 3.5 s, which meets the quality control requirements of high-speed production of stacked cells.

[0038] Furthermore, insulation withstand voltage and leakage current 3: Apply a slowly increasing DC high voltage (e.g., slowly increasing from 0 to a set value U) to the bare cell or assembly, maintain it for a certain time, and monitor whether the leakage current is lower than the threshold; the parameter design needs to consider the charging current and slow-up time caused by stray capacitance, and discharge after testing to avoid misjudgment and ensure safety.

[0039] Furthermore, AC impedance EIS: Apply a small amplitude sinusoidal current excitation to a single chip or module, collect voltage response at multiple frequency points, calculate impedance modulus |Z|, phase θ, real part Zre, and imaginary part Zim, and combine with equivalent circuit fitting to evaluate SOC / aging and consistency, suitable for R&D and production line sampling inspection.

[0040] Furthermore, the micro-short circuit rapid screening method 2 uses high-voltage pulse + high-speed sampling (such as capacitor energy storage and discharge, sampling frequency 15-20kHz). Under the set voltage level, the measured current is compared with the standard value. If the current exceeds the threshold, it is determined that there is a micro-short circuit risk. This method is used for rapid control of sampling before and after liquid injection and during the process.

[0041] Furthermore, production line cycle organization: On cylindrical, square, and pouch cells of different shapes, multi-station parallel operation and multi-angle synchronous acquisition within the station are used to achieve full inspection of six sides and directional high-resolution observation of key parts of the pole / explosion-proof valve, covering different production capacity levels of 24-240PPM.

[0042] Furthermore, the complementary use of electrical testing and optical / X-ray methods can effectively identify potential problems such as internal short circuits and electrical performance degradation without damaging the sample.

[0043] The invention also includes a working warning light 6, a feeding port 11, a MES / PLM data upload interface 13, a cell detection and conveying track 17, and a device housing shield 18.

[0044] This invention provides a non-destructive intelligent testing system for detecting defects in finished bare battery cells, as detailed below:

[0045] I. Optical Appearance and Multispectral Imaging Principle: Optical Appearance: Utilizing visible light and near-infrared imaging, combined with multi-angle / coaxial / dark field / strip light sources and line scan cameras, images of the battery cell casing, encapsulation film, electrode, edges, etc. are acquired to detect wrinkles, pits, foreign objects, bubbles, cracks, deformation, mixed materials, character defects, etc., and can distinguish between defects on / under the film.

[0046] A. Visible light multi-angle imaging 9: Multiple sets of visible light sources and cameras are arranged on the same side of the detection surface, and the light areas are staggered. A large incident angle (about 60° to 80°) is used to highlight the morphological changes caused by particles / bubbles in the film, and a small incident angle (about 5° to 15°) is used to enhance the shadow and edge response of surface pits. The camera and light area are aligned and online high-speed acquisition is performed to improve the detection rate and stability of pits / scratches / film damage.

[0047] B. Near-infrared transmission discrimination of on-film / under-film 7: Set up a dual-path system of visible light + near-infrared (about 800-900nm), and take advantage of the certain penetrability of infrared light through the encapsulation film to obtain two images of "surface morphology + internal transmission"; at the same suspected location, if the infrared transmission image is abnormal and the visible light surface image is not significant, or combined with gray-scale distribution characteristics (such as high pixel gray-scale in the area indicates bubbles, low gray-scale in the center and high gray-scale around the perimeter indicates foreign objects), it can be determined as a foreign object / bubble under the film, which significantly reduces false detections.

[0048] C. Line Scanning and Motion Control: A line scan camera and encoder are synchronized to ensure strict overlap between the scan line and the light area; stable imaging of moving battery cells is achieved, adapting to multi-faceted inspection stations and meeting the requirements of high-speed online full-scale appearance inspection. This approach has been validated in the differentiation of on / under-film defects and the identification of pits and foreign objects in coated battery cells, and is suitable for the appearance quality inspection of various battery cell shapes, including square, cylindrical, and pouch cells.

[0049] II. Principles of X-ray and Industrial CT Non-destructive Testing: X-ray non-destructive testing: DR / CT is used to see through the inside of the package and identify electrode alignment, overhang, interlayer misalignment, wrinkles, solder joint defects / missing solder joints, and housing dimensions, etc.; online CT improves scanning efficiency to the second level, realizing production line cycle matching and full inspection.

[0050] A.DR Rapid Screening 14: The X-ray source emits penetrating rays, and the imaging system receives the attenuation difference to form a two-dimensional projection, allowing real-time observation of electrode alignment, winding / stacking status, solder joint quality, housing size, etc.; suitable for high-speed sampling or as a pre-screening step for online CT.

[0051] B. CT 3D Quantitative 15: Horizontal CT performs continuous angular scanning of the battery cell and reconstructs 3D volume data. It extracts the electrode area by slicing and combines image enhancement and deep learning models to automatically measure the height difference (over-hang), inter-slice gap and morphological anomalies of adjacent positive and negative electrode endpoints. Compared with 2D, CT can present the internal structure from multiple layers and angles, reduce misjudgment / missed judgment caused by electrode interference and projection occlusion, and support online second-level detection and full-size measurement.

[0052] C. Online CT Indicator Reference 16: The online CT solution has a repeatability measurement accuracy GR&R ≤ 10%, detection efficiency ≥ 36 PPM, false positive rate < 0.5%, detection accuracy < 0.03 mm, and single cell detection time ≤ 3.5 s, which meets the quality control requirements of high-speed production of stacked cells.

[0053] D. The above method enables intuitive and quantifiable assessment of internal defects, representing a capability upgrade path from 2D to 3D / CT.

[0054] III. Electrical and Functional Testing Principles: Electrical and Functional Testing: Conduct tests such as insulation withstand voltage, leakage current, DC internal resistance / ESR, and AC impedance (EIS) to locate electrical defects such as micro-short circuits, abnormal internal resistance, and self-discharge.

[0055] A. Insulation withstand voltage and leakage current 3: Apply a slowly increasing DC high voltage (e.g., slowly increasing from 0 to the set value U) to the bare cell or assembly, maintain it for a certain time, and monitor whether the leakage current is lower than the threshold. The parameter design should take into account the charging current and slow-up time caused by stray capacitance. Discharge after the test to avoid misjudgment and ensure safety.

[0056] B. DC Internal Resistance / ESR and Functional Items: The internal resistance / ESR and consistency are evaluated by measuring voltage drop and current response using the pulse / load method; combined with capacity, self-discharge and aging strategies, individuals with micro-short circuits and abnormal internal resistance are screened out.

[0057] C. AC Impedance EIS: Apply a small amplitude sinusoidal current excitation to a single chip or module, collect voltage response at multiple frequency points, calculate impedance modulus |Z|, phase θ, real part Zre, and imaginary part Zim, and combine with equivalent circuit fitting to evaluate SOC / aging and consistency. Suitable for R&D and production line sampling inspection.

[0058] D. Micro-short circuit rapid screening 2: High voltage pulse + high speed sampling (such as capacitor energy storage and discharge, sampling frequency 15-20kHz) is used to compare the measured current with the standard value under the set voltage level. If the current exceeds the threshold, it is determined that there is a micro-short circuit risk. This is used for rapid control of sampling before and after liquid injection and during the process.

[0059] E. Electrical testing complements optical / X-ray testing, enabling effective identification of potential hazards such as internal short circuits and electrical performance degradation without damaging the sample.

[0060] 4. Configuration and Applicable Scenarios

[0061]

[0062]

[0063] I. Principle of Online Inspection of Battery Cell Optical Appearance and Multispectral Imaging

[0064] 1. Overall Architecture and Process:

[0065] Online inspection integrating optical appearance and multispectral imaging typically operates on a multi-station circular line: loading and positioning → multi-angle / multispectral imaging (including visible light, near-infrared, stripe / structured light, coaxial / dark field, etc.) → online / near real-time reconstruction and AI inference → sorting and traceability. To cover differences between "on-film / under-film" and "surface / near-surface" areas, visible light + near-infrared (approximately 800-900nm) dual-path co-location acquisition is often used, collaborating with 2D / 2.5D / 3D measurement stations to form a complementary evidence chain. Engineering case studies show that cell appearance inspection has achieved an accuracy of 0.015-0.02mm and an efficiency of 24-240PPM, validating the mass production feasibility of this approach.

[0066] 2. Optical appearance imaging principle

[0067] A. Multi-angle structured lighting and photometric stereo: Large incident angles (approximately 60°-80°) enhance edge and height variations, while small incident angles (approximately 5°-15°) create dark areas that highlight particles / pits. Combined with photometric stereo to obtain normal vectors and height maps, this method stably presents morphological features such as pits, scratches, film breaks, and deformations. For the interface between the metal shell and the coating, coaxial / strip lighting is used to suppress strong reflections, ensuring accurate edge positioning.

[0068] B. Striped grating and 3D contour: For the six sides and edges of the coated battery cell, a striped grating projection + 3D contour instrument is used to obtain sub-millimeter level contours, solving the detection problems of wrinkles, bubbles, leakage, foreign objects, pits, scratches and other reflective materials.

[0069] C. Time-sharing exposure and multispectral fusion: For subtle color changes and material differences, time-sharing exposure / multispectral light source (including near-infrared) is used to acquire multiple complementary images in one or small step cycles, improving the detection rate and distinguishability of foreign objects, bubbles and color difference defects on / under the film.

[0070] D. Production line cycle organization: On cells of different shapes such as cylindrical, square, and pouch, multi-station parallel operation and multi-angle synchronous acquisition within the station are used to achieve full inspection of six sides and directional high-resolution observation of key parts such as poles / explosion-proof valves. Typical solutions have covered different production capacity levels of 24-240PPM.

[0071] 3. Multispectral imaging principle and cell adaptation

[0072] A. Band selection and physical mechanism: Visible light (approximately 400-700nm) is sensitive to surface texture, color and printed markings; near-infrared light (approximately 800-900nm) has a certain degree of penetration into the encapsulation film, which can form a dual-path evidence of "surface morphology + internal transmission", which is helpful in distinguishing foreign objects / scratches on the film from foreign objects / bubbles under the film; in scenarios such as tabs / PP films, the spectral transmission characteristics can be used to suppress film reflection and enhance the contrast under the film.

[0073] B. Dual-path same-site acquisition: Acquire visible light and near-infrared images in the same field of view / exposure sequence. Through pixel-level alignment and feature fusion, construct a joint criterion of "surface + near-surface" to reduce false positives / false negatives.

[0074] C. Online Applications and Expansion: Deep fusion of multispectral and 2D / 3D technologies has achieved stable results in addressing challenges such as blue film appearance in battery cells, electrode contamination, and foreign matter under the PP membrane of explosion-proof valves. In the module / pack stage, visible light + near-infrared fusion is also used to cover various types of defects such as shell scratches, electrode oxidation, and sealant integrity, verifying cross-process transferability.

[0075] 4. Key Engineering Implementation Points for Online Detection

[0076] A. Light source and camera configuration: For different materials and defect spectra, coaxial, ring, dark field, bar, and stripe projection light sources are used in combination; the camera side adopts a hybrid area array + line array to balance area coverage and high-speed scanning, and liquid lens is introduced when necessary to achieve millisecond-level focusing to adapt to zoom scenarios such as electrode tabs.

[0077] B. Reflectivity and Material Compatibility: For highly reflective / semi-transparent materials such as blue film, top cover metal, and explosion-proof valve PP film, high dynamic imaging, polarization, frequency division / time division exposure and spectral filtering are used to stably obtain discernible grayscale / texture / height features.

[0078] C. Adaptive control and data consistency: By adaptive light source intensity and exposure control, combined with image validity verification (empty frame / size / alignment) and dynamic bit depth mapping (such as normalizing and fusing 8-bit grayscale and 16-bit height map), the impact of environmental and incoming material fluctuations on imaging quality is reduced, and the robustness and cycle stability of the algorithm are improved.

[0079] Speed-accuracy trade-off: In parallel pipelines of 2D / 2.5D / 3D+multispectral, ROI priority and angle / layer limit strategies are applied based on defect risk and region of interest. Fine scan verification is triggered when necessary to ensure high-confidence judgment is completed within seconds.

[0080] II. Implementation Scheme of Online CT for Battery Cells

[0081] 1. Overall Architecture and Beat Design

[0082] The system consists of an X-ray source (cone beam / microfocus) + rotating / stationary imaging chain + high-speed reconstruction (GPU) + AI detection + MES linkage. After the battery cells are loaded and positioned at the workstation, they enter the CT scan. Reconstruction and AI judgment are performed in parallel to output sorting signals. To match the production line cycle time, the mainstream solution adopts a horizontal structure, with the battery cells stationary and only the imaging system rotating, avoiding the ghosting and safety risks caused by high-speed moving battery cells. It is also equipped with independent multi-channel workstations to ensure that loading / unloading and scanning do not interfere with each other. Publicly available mass production indicators show that the online CT has achieved single-piece inspection ≤3.5s, inspection efficiency ≥36PPM, repeatability GR&R ≤10%, false negative rate 0%, false positive rate <0.5%, and inspection accuracy <0.03mm, meeting the requirements for high-speed online full inspection of stacked battery cells.

[0083] 2. Hardware selection and optical path layout

[0084] A. X-ray source and detector: Select a 225kV cone beam source (compatible with most battery cells) or a higher power microfocus / liquid metal target source (pursuing higher resolution and shorter exposure) based on the battery cell size and material; the detector needs to have high dynamic range and high frame rate, and support area scan / line scan modes.

[0085] B. Motion and Structure: For stacked cells, horizontal CT is preferred (cells remain stationary, turntable / detector scans around). If necessary, multiple light sources such as coaxial / dark field / strip / near infrared can be used to suppress reflections and enhance inter-slice contrast.

[0086] C. Speed ​​vs. accuracy trade-off: Using linear CT (replacing mechanical rotation with linear scanning) can further increase speed, achieving an online full inspection capability of approximately 30 PPM, which is suitable for extreme time-lapse scenarios.

[0087] Safety shielding: The entire machine must be placed in a lead room / shielded chamber and equipped with interlocks, dose monitoring and emergency stop to meet the 24-hour safe operation requirements of the production line.

[0088] 3. Scanning and Reconstruction Process

[0089] A. Scanning strategy: For stacked / wound cells, set a low-dose pre-scan + triggered fine scan according to the process cycle; for high-risk processes (such as after liquid injection, before and after formation), the sampling density can be increased.

[0090] B. Reconstruction and AI Enhancement: FDK / iterative reconstruction combined with GPU acceleration is used to achieve image output in seconds; AI modules such as image convolution filtering, subpixel measurement, and intelligent recognition of positive and negative electrodes are introduced to directly output quantitative results such as electrode alignment, overhang, number of layers, wrinkles, and shell size, reducing manual intervention and misjudgment.

[0091] C. Online Capabilities: The system supports real-time acquisition of production data and cloud / local visualization, facilitating process traceability and quality closed-loop management.

[0092] 4. CT Determination and Quantification of Critical Defects

[0093] A. Electrode alignment and overhang: CT can complete the three-dimensional quantification of positive and negative electrode overhang and inter-slice alignment angle in a single scan, avoiding misjudgment caused by layer obstruction in 2D fluoroscopy; alignment deviation, abnormal number of electrodes, inter-slice misalignment, etc. can be reliably identified.

[0094] B. Wrinkles and Foreign Objects: Provides high-contrast imaging of electrode wrinkles, inclusions / metallic foreign objects, enabling the localization of minute anomalies and assessment of their impact on safety and performance.

[0095] C. Welding and Packaging: Non-destructive evaluation of porosity, cold solder joints, and insufficient penetration in laser or ultrasonic welding of tabs / buses; rapid detection of potential metal particle contamination in finished products.

[0096] D. Aging and Deformation: Electrode expansion, internal void expansion, and interlayer gap changes can still be observed non-destructively after formation / cycling, providing data for process and structural optimization.

[0097] 5. Integration with production lines and data closed loop

[0098] A. System Integration: Online CT and MES / PLC are linked to achieve automatic loading / unloading, sorting, SPC statistics and traceability; through the equipment-side AI platform (such as IMAS Cloud) and cloud-based model management, the algorithm is continuously iterated with new samples to reduce false alarms and adapt to new models / new materials.

[0099] B. Process closed loop: By integrating data such as overhang, alignment, internal resistance / air tightness sampling, etc., a closed-loop control of "detection-analysis-parameter optimization-re-inspection" is formed to steadily improve yield and consistency.

[0100] C. Production line implementation trend: Online CT is moving from spot checks to full inspections and is being integrated with vision + X-Ray / AI whole line solutions, becoming a core link in the quality control of power batteries and energy storage batteries.

[0101] The advantages of this invention compared to the prior art are:

[0102] 1) The system adopts the WINDOS platform as its operating architecture. A self-developed host computer controls the X-ray inspection equipment system via Ethernet (TCP / IP, GigE Vision, PROFINET) and USB through the X-ray source controller. It directly reads stored data using a USB MSC, uses a USB-CDC for line inspection of optical multispectral imager parameters and trigger control, and transmits images via Ethernet (TCP / UDP) or connects to the host computer software. This is used for logic design processing and issuing commands to the issuing mechanism. The various modules work collaboratively to solve the problems of existing testing systems for the appearance, performance, and safety defects of bare battery cells.

[0103] 2) This invention significantly reduces labor costs at production line testing stations. Traditional manual testing requires testing nine major items, each with its own corresponding testing equipment. To prevent confusion, three testing stations are needed. With this invention, only one testing personnel is required. After the bare cells are loaded, they automatically stop at the testing station according to the pre-set testing procedure. The system automatically tests and judges each item according to the pre-set procedure. Qualified products automatically flow into the qualified temporary storage area, and test data is uploaded to the engineering MES & PLM system in real time.

[0104] 3) This invention significantly improves the testing efficiency of the finished bare battery cell defect testing station. Taking the example of a system without this testing system, three stations and three sets of testing instruments are required, and testing a single finished battery cell for defects takes 6 minutes. This invention automatically executes all operation steps, automatically judges test results, automatically tests nine test items according to the test steps, and automatically uploads and saves the test results. The entire testing time is only [time missing].

[0105] 4) This invention improves production stability and the traceability of testing procedures and data. Traditional testing is prone to errors, misjudgments, and product damage. With this invention, employees only need to load the finished bare battery cells. This invention provides a non-destructive intelligent testing system for defects in finished bare battery cells, which is simple and convenient to operate. This system greatly reduces manual processes such as personnel inspection, test result judgment, and test data storage, significantly saving labor costs and quality costs caused by operator fatigue and errors.

[0106] The above description is only a preferred embodiment of this patent and does not limit the scope of this patent. Any equivalent structural or procedural transformations made using the description and drawings, whether directly or indirectly applied to other related technical fields, shall fall within the scope of protection of this patent.

Claims

1. A non-destructive intelligent testing system for defects in finished bare battery cells, characterized in that, It includes a feeding machine, a cell scanning device, an optical appearance inspection module, an X-ray non-destructive testing module, an electrical function testing module, an equipment system data processing center and an automatic result judgment module, and connects to the unloading interface and a sorting traceability module; The optical appearance inspection module includes visible light multi-angle imaging and near-infrared transmission difference film on / under film, multi-angle structured light and photometric stereo detection device, striped grating and 3D contour, time-division exposure, multispectral fusion and production line cycle organization. The X-ray non-destructive testing module includes DR rapid screening, CT three-dimensional quantitative analysis, and online CT index reference: X-ray non-destructive testing is used to visualize the inside of the package through DR / CT, identifying electrode alignment, overhang, interlayer misalignment, wrinkles, solder joint defects / missing solder joints, and housing dimensions; online CT improves scanning efficiency to the second level, enabling production line cycle time matching and full inspection; The electrical and functional testing module includes insulation withstand voltage and leakage current devices, DC internal resistance, AC impedance EIS and micro short circuit rapid screening, to detect insulation withstand voltage, leakage current, DC internal resistance / ESR, AC impedance (EIS) tests, and to locate electrical defects such as micro short circuits, abnormal internal resistance and / or self-discharge.

2. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The visible light multi-angle imaging involves arranging multiple sets of visible light sources and cameras on the same side of the detection surface, controlling the light areas to be staggered, using a large incident angle (60°~80°) to highlight the morphological changes caused by particles / bubbles in the film, and using a small incident angle (5°~15°) to enhance the shadow and edge response of surface pits; the camera and light area coincide and online high-speed acquisition improves the detection rate and stability of pits / scratches / film damage.

3. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The DR rapid screening method uses an X-ray source to emit penetrating rays, and an imaging system receives the attenuation differences to form a two-dimensional projection, allowing real-time observation of electrode alignment, winding / stacking status, solder joint quality, and housing dimensions; suitable for high-speed sampling or as a pre-screening step for online CT.

4. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The near-infrared transmission discrimination method for on-film / under-film: A dual-path system of visible light + near-infrared (800-900nm) is set up. Utilizing the certain penetrability of infrared light through the encapsulation film, two images of "surface morphology + internal transmission" are obtained. At the same suspected location, if the infrared transmission image shows an anomaly while the visible light surface image is not significant, or combined with grayscale distribution characteristics (e.g., high pixel grayscale in the region indicates a bubble, low grayscale in the center and high grayscale around the edges indicates a foreign object), it can be determined as an under-film foreign object / bubble, significantly reducing false detections.

5. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The CT three-dimensional quantitative method involves using a horizontal CT scanner to perform continuous angular scanning of the battery cell and reconstruct three-dimensional volume data. The electrode area is extracted by slicing, and combined with image enhancement and deep learning models, the height difference (over-hang), inter-slice gap, and morphological anomalies of adjacent positive and negative electrode endpoints are automatically measured. Compared with 2D, CT can present the internal structure from multiple layers and angles, reducing misjudgments / missed judgments caused by electrode interference and projection occlusion, and supports online second-level detection and full-size measurement.

6. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The online CT specifications are as follows: the online CT solution has a repeatability measurement accuracy (GR&R) of ≤10%, a detection efficiency of ≥36PPM, a false positive rate of <0.5%, a detection accuracy of <0.03mm, and a single cell detection time of ≤3.5s, which meets the quality control requirements for high-speed production of stacked cells.

7. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The insulation withstand voltage and leakage current are as follows: A slowly increasing DC high voltage (from 0 to a set value U) is applied to the bare cell or assembly and maintained for a certain period of time. The leakage current is monitored to see if it is lower than the threshold. The parameter design needs to take into account the charging current and slow-rise time caused by stray capacitance. After the test, the battery is discharged to avoid misjudgment and ensure safety.

8. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The AC impedance EIS: Apply a small amplitude sinusoidal current excitation to a single chip or module, collect voltage response at multiple frequency points, calculate impedance modulus |Z|, phase θ, real part Zre, and imaginary part Zim, and combine with equivalent circuit fitting to evaluate SOC / aging and consistency, suitable for R&D and production line sampling inspection.

9. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The rapid screening for micro-short circuits employs high-voltage pulses and high-speed sampling (e.g., capacitor energy storage and discharge, sampling frequency 15-20kHz). Under a set voltage level, the measured current is compared with the standard value. If the current exceeds the threshold, a micro-short circuit risk is identified. This method is used for rapid control of sampling before, during, and after liquid injection.

10. The non-destructive intelligent testing system for detecting defects in finished bare battery cells as described in claim 1, characterized in that, The production line cycle organization: On cylindrical, square, and pouch cells of different shapes, multi-station parallel operation and multi-angle synchronous acquisition within the station are used to achieve full inspection of six sides and directional high-resolution observation of key parts of the pole / explosion-proof valve, covering different production capacity levels of 24-240PPM.

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