Digital printing production method for insulating coating on surface of lithium battery

Abstract

The invention provides a lithium battery surface insulation coating digital printing production method, which comprises the steps of UV digital coating, mapping relation establishment, finished product detection, good product grading blanking and defective product repair treatment, and is characterized in that a printing station for executing each surface of a battery and a plurality of nozzles for executing current surface printing are grouped and numbered; and forming a mapping relation table among the printing station, the nozzle and each surface of the battery. When a finished product is detected, the defect type and the bad position information of the insulating coating are obtained, the mapping relation table is inquired according to the defect type and the bad position information, the information of the printing station and the spray head generating the defects is obtained, and then the process parameters of the corresponding printing station and the spray head are adjusted according to the defect type, so that the product defects are found in time; and the function of automatically responding to the defect is realized, so that the production waste is avoided.

Description

Technical Field

[0001] This application belongs to the technical field of battery production. More specifically, it relates to a digital printing production method for the surface insulation coating of lithium batteries. Background Art

[0002] The rapid development of the new energy vehicle market and the energy storage market has promoted the improvement of the insulation performance requirements for the outer shell of lithium batteries. With the significant increase in working voltage and energy density, the traditional PET blue film insulation solution has begun to fail to meet higher-level safety requirements. The bonding performance of the PET blue film is weak. Especially after long-term use, the bonding performance of the PET blue film's back glue decreases due to environmental factors, posing a safety hazard in high-voltage platform vehicles. There are a large number of defects such as bubbles under the film, foreign particles, and uneven film coating in the PET film during the coating production process, resulting in low yield and cost waste. The above defects will also cause potential risks such as local overheating, piercing of the insulation film, and shedding of the insulation film during the service life of the battery.

[0003] To solve the problem of the preparation of the battery surface insulation coating, the common process paths in the industry include: powder spraying, UV painting, and UV digital coating. Among them, the UV digital coating process has significant advantages over powder spraying and painting processes in terms of coating thickness uniformity control, raw material utilization rate, production environment, energy consumption, etc. However, the existing production lines for the preparation of battery surface insulation coatings are not intelligent enough to detect product defects in a timely manner or cannot react in a timely manner when product defects are detected, resulting in production waste. Summary of the Invention

[0004] The purpose of the present invention is to provide a digital printing production method for the surface insulation coating of lithium batteries, aiming to solve the problem of the poor effect of the existing insulation spraying method.

[0005] To achieve the above purpose, the technical solution adopted in this application is: to provide a digital printing production method for the surface insulation coating of lithium batteries, including: UV digital coating, coating an insulation coating on each surface of the battery and curing the insulation coating; Establishing a mapping relationship, grouping and numbering each printing station of the battery being executed and multiple nozzles executing the printing of the current surface to form a mapping relationship table between the printing stations, nozzles, and each surface of the battery; Finished product inspection, detecting the insulation coating on the battery surface to obtain the defect type and bad position information of the insulation coating. According to the defect type and bad position information, query the mapping relationship table to obtain the information of the printing station and nozzle that caused the defect, so as to adjust the process parameters of the corresponding printing station and nozzle according to the defect type; Quality determination: The batteries are classified into qualified and unqualified products according to the results of finished product inspection. The qualified products are sorted and cut, and the unqualified products are repaired. After passing the repair, the above steps are repeated.

[0006] Optionally, the UV digital coating includes: Taking pictures of each surface of the battery to be printed to obtain bright areas and dark areas. The bright areas are the highly reflective areas on the battery surface, and the dark areas are the low reflective areas outside the battery. Using the bright areas and the dark areas to identify the edge and corner areas and flat areas of the battery to obtain the contour information of the battery, and performing inkjet printing and crosslinking curing on the battery surface according to the contour information of the battery to obtain an insulating coating.

[0007] Optionally, the performing inkjet printing on the battery surface according to the contour information of the battery includes: Full-surface printing: covering the edge and corner areas and flat areas on the battery surface with insulating paint; Partial printing: performing supplementary spraying of insulating paint on the edge and corner areas of the battery to form an insulating coating with a preset thickness on the edge and corner areas of the battery.

[0008] Optionally, the partial printing includes: Printing and curing the edge and corner areas to form an additional coating with a certain thickness on the edge and corner areas; or the printing control system controls the injection amount of insulating paint in the edge and corner areas to be greater than that in the flat areas; or injecting insulating paint into the edge and corner areas through a spray valve or dispensing process and pre-curing to form a local insulating coating in advance.

[0009] Optionally, the crosslinking curing includes: Pre-curing: irradiating the insulating paint on the battery surface with the first UV light to make the insulating paint lose fluidity and form a pre-cured layer; Final curing: irradiating the pre-cured layer with the second UV light to further complete the photoinitiated crosslinking curing reaction of the pre-cured layer until the insulating paint reaches the final stable form to form the insulating coating.

[0010] Optionally, the finished product inspection includes one or several of coating thickness detection, appearance inspection, coating insulation withstanding voltage performance test, and color detection.

[0011] Optionally, the coating thickness detection includes: measuring the thickness of the insulating coating by the photothermal infrared method in the edge and corner areas, and measuring the thickness of the insulating coating by the infrared spectroscopic interferometer in the flat areas. When the thickness data exceeds the set threshold, the printing control system corrects the process parameters of the corresponding printing station and nozzle according to the mapping table.

[0012] Optionally, the appearance inspection includes: obtaining a product image using a 2.5D optical imaging system, identifying defects in the product image in combination with a deep learning algorithm, and performing position location, quantification, and classification determination on the defects.

[0013] Optionally, the insulation withstanding voltage performance test includes: performing insulation impedance and withstanding voltage tests by contacting the surface of the insulation coating with conductive electrodes. If there is insufficient impedance or withstanding voltage breakdown failure, determine which surface of the battery the defect appears on through the test station, and the printing control system corrects the process parameters of the corresponding printing station and nozzle according to the mapping relation table.

[0014] Optionally, during the repair process of defective products, determine the position and type of defects on the product according to the feedback defect and defective position information, and perform corresponding repair processing on the defective positions according to the defect type; and / or, surface pre-treatment is also included before UV digital coating, and the surface pre-treatment includes one or more of laser cleaning, plasma gas cleaning, sandblasting and shot peening, chemical reagent cleaning, and dry ice cleaning.

[0015] The beneficial effects of the digital printing production method for the surface insulation coating of lithium batteries provided in this application are as follows: Compared with the prior art, in this application, the printing stations for each surface of the battery and multiple nozzles for printing the current surface are grouped and numbered to form a mapping relation table between the printing stations, nozzles, and each surface of the battery. During the finished product inspection, obtain the defect type and defective position information of the insulation coating, query the mapping relation table according to the defect type and defective position information to obtain the information of the printing station and nozzle where the defect occurs, and then adjust the process parameters of the corresponding printing station and nozzle according to the defect type, so as to realize the function of timely detecting product defects and automatically reacting to the defect, avoiding production waste. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic flow chart of the digital printing production method for the surface insulation coating of lithium batteries provided in the embodiments of this application; Figure 2 It is a schematic diagram of the insulation coating thickness on the battery surface in the uncompensated state of the edge; Figure 3 It is a schematic diagram of the insulation coating thickness on the battery surface in the compensated state of the edge. Detailed Embodiments

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer and more understandable, the following further details this application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0019] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0020] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to this application.

[0021] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality" means two or more, unless otherwise specifically defined.

[0022] In the related field, with the substantial increase in working voltage and energy density, the traditional PET blue film insulation solution begins to fail to meet higher-level safety requirements. The bonding performance of the PET blue film is weak. Especially after long-term use, the bonding performance of the PET blue film's back glue decreases due to environmental factors, posing a safety hazard in high-voltage platform vehicles. There are a large number of defects such as bubbles under the film, foreign particles, and uneven film coating in the PET film coating production process, and the low yield rate causes cost waste. The above defects will also cause potential risks such as local overheating, puncture of the insulation film, and detachment of the insulation film during the service life cycle of the battery.

[0023] To solve the above problems, the UV digital spraying process is usually adopted. However, the existing UV digital spraying production line is not intelligent enough, cannot detect product defects in time or cannot react in time when product defects are detected, resulting in production waste.

[0024] In view of this, this application provides a digital printing production method for the surface insulation coating of lithium batteries. Please refer to Figures 1 - 3, the digital printing production method of the insulating coating on the surface of the lithium battery provided by the embodiments of the present application will be described below.

[0025] A digital printing production method for the insulating coating on the surface of a lithium battery, comprising: UV digital painting, coating an insulating coating on each surface of the battery and curing the insulating coating; Establishing a mapping relationship, grouping and numbering the printing stations for each surface of the battery to be executed and multiple nozzles for printing the current surface, and forming a mapping relationship table between the printing stations, nozzles and each surface of the battery; Final product inspection, inspecting the insulating coating on the surface of the battery to obtain the defect type and defective position information of the insulating coating, querying the mapping relationship table according to the defect type and defective position information, and obtaining the information of the printing station and nozzle that cause the defect, so as to adjust the process parameters of the corresponding printing station and nozzle according to the defect type; Quality determination, classifying the batteries into good products and defective products according to the results of the final product inspection, sorting and discharging the good products, repairing the defective products, and repeating the above steps after the defective products are repaired successfully.

[0026] In the present application, the printing stations for each surface of the battery to be executed and multiple nozzles for printing the current surface are grouped and numbered to form a mapping relationship table between the printing stations, nozzles and each surface of the battery. During the final product inspection, the defect type and defective position information of the insulating coating are obtained, and according to the defect type and defective position information, the mapping relationship table is queried to obtain the information of the printing station and nozzle that cause the defect, and then the process parameters of the corresponding printing station and nozzle are adjusted according to the defect type, so as to realize the closed-loop management of the automated production process and reduce the production waste caused by the situation that the discovery is not timely or the reaction cannot be made in time when the defect is found.

[0027] For example, if the final product inspection station identifies that several identical defects appear at a certain position of the battery at the same time, it can automatically feedback to the UV digital painting station. The printing control system can query the corresponding printing station and nozzle information through the mapping relationship table according to the position information of the defect, and then change the process parameters of the corresponding printing station and nozzle to avoid generating more defective products. Another example is that the final product inspection station identifies an unacceptable defect at a specific position of the battery. The printing control system can transmit the position information of the defect to the defective product repair station. The defective product repair station can execute specific repair treatment processes according to the defect type while retaining the coatings of the remaining parts without defects, so as to realize precise repair of defective products.

[0028] In some embodiments of the present application, for each surface of the square shell battery (the same applies to cylindrical batteries), the printing stations of each surface and the multiple nozzles that complete the printing of this surface are grouped and numbered to form a mapping relationship table between the stations + nozzles of the entire printer and the surfaces of the product. When the finished product inspection station identifies a printing defect in a specific area of a specific surface, the printing control system queries through the mapping relationship table to obtain the information of the printing station and nozzle where the abnormality occurs, so as to locate which nozzle of which printing station in the upstream printing equipment has an abnormality, and then adjusts its process parameters accordingly to achieve the closed-loop management of the automated production process and reduce production waste caused by untimely discovery or the inability to respond in a timely manner when a defect is found.

[0029] In some embodiments of the present application, for the detected defects, the printing control system can set different processing methods according to the type of the defect (such as an ink shortage stripe running through the entire plane) or the quantification result (the thickness unevenness exceeding a specific area). For example, attempt to adjust the printing area (the print head is translated to change the area of the printing work), or perform an automatic cleaning and maintenance operation on the nozzles, or directly alarm to interrupt production to prompt the need for manual intervention.

[0030] In some embodiments of the present application, the specific steps of the UV digital coating include: Take pictures of each surface of the battery to be printed to obtain bright areas and dark areas. The bright areas are the highly reflective areas on the surface of the battery, and the dark areas are the low reflective areas outside the battery. Use the bright areas and the dark areas to identify the edge and corner areas and flat areas of the battery to obtain the contour information of the battery, and perform inkjet printing and crosslinking curing on the surface of the battery according to the contour information of the battery to obtain an insulating coating.

[0031] Specifically, each face of the battery is photographed through a vision guidance system. The edge of the battery product is illuminated by a light source to form a bright area feature, while the area outside the product forms a dark area feature. The contour area is identified through the contrast between light and dark. The edges and corners of the battery reflect more light, forming bright areas (when the gray value is greater than the set value, it can be determined as a bright area), the area outside the battery reflects less light, forming dark areas (when the gray value is less than the set value, it can be determined as a dark area), and the area on the battery surface except for the edges and corners is a flat area. Therefore, through the determination of bright areas and dark areas, the edge and corner areas and the flat area of the battery can be identified, thereby obtaining the contour information of the battery. After identifying the contour, the template can be set according to the contour position to determine the structural position where coating avoidance is required inside. After the printing control system transmits the relevant control information to the digital printing system for execution, accurate coating production on the product surface can be achieved. Through the vision guidance system, the specific contour details and dimensions of each product can be identified, effectively reducing the waste of overspray outside the product contour and improving the appearance quality, and realizing compatibility with the digital printing system within a certain size range to achieve the function of rapid production changeover.

[0032] In the prior art, referring to Figure 2 , due to the geometric features of the edges and corners of the battery housing and the surface tension factor of the insulating coating, when the insulating coating is sprayed onto the edge surface, it will instantaneously tend to gather towards the flat areas on both sides of the edge, resulting in insufficient coating thickness in the middle part of the edge arc. Such a microstructure makes the insulating coating unable to meet the electrical performance requirements of insulation withstand voltage. The area with a thin insulating coating will be preferentially broken down by high voltage.

[0033] To compensate for the weak conductivity of the insulating coating in the edge and corner areas, in this application, the insulating coating in the edge and corner areas is compensated to increase the coating thickness at the thinnest point (as shown in Figure 3 ) so that it can meet the requirement of the minimum conductive thickness for insulation withstand voltage.

[0034] In some embodiments of this application, the printing steps of the insulating coating include: Full-surface printing, covering the edge, corner areas, and flat area on the surface of the battery with the insulating coating; Local printing, spraying the insulating coating on the edge and corner areas of the battery to form an insulating coating with a preset thickness (a thickness preset in advance, at which the insulating coating can meet the insulation withstand voltage requirement) in the edge and corner areas of the battery.

[0035] By locally printing the insulating coating on the edge and corner areas of the battery, the insulating coating in the edge and corner areas is compensated to increase the insulating coating thickness at the thinnest point so that it can meet the insulation withstand voltage requirement.

[0036] In some embodiments of the present application, full-surface printing can be performed first, and then local printing can be performed on the edge and top corner regions. In some other embodiments of the present application, local printing on the edge and top corner regions can also be performed first, and then full-surface printing can be performed.

[0037] In some embodiments of the present application, local printing can also be performed multiple times, such as 2 times, 3 times, etc. The number of local printing times depends on the requirements of the insulation withstand voltage performance for the thinnest coating, or the influence of the geometric features of the edges and top corners on the ink hanging thickness. For example, for a smoother and rounder edge, the difference in thickness between the middle region and the planar region will be slightly smaller, and for a sharper edge, the difference in thickness between the middle region and the planar region will be larger, and more local printing times may be required.

[0038] In some embodiments of the present application, local printing is achieved by printing and curing the edge and top corner regions to form an additional coating of a certain thickness on the edge and top corner regions.

[0039] In some other embodiments of the present application, local printing is achieved by controlling the insulation coating ejection amount in the edge and top corner regions to be greater than that in the planar region through a printing control system. The implementation method can be to delete the pixel points in the planar region according to certain rules in the printed image (also called "dot extraction") so that the number and density of pixel points in the planar region are less than those in the edge and top corner regions. It can also be through image gray level setting, making the gray level of the planar region smaller and the gray level of the edge and top corner regions larger. When printing, a smaller gray level calls a smaller ink droplet, and a larger gray level calls a larger ink droplet, which can also form a difference in the insulation coating ejection amount to compensate for the thickness of the edge and top corner regions.

[0040] In some other embodiments of the present application, local printing is achieved by spraying the insulation coating onto the edge and top corner regions through a glue spraying valve or a dispensing process and pre-curing to form a local insulation coating in advance.

[0041] Table 1 Comparison of the thicknesses of the thinnest positions in different local printing states of edges

[0042] Table 1 shows the thickness comparison of the thinnest positions after three different edges in Examples 1 - 3 without local printing and with 1, 2, and 3 times of local printing respectively. From the data in the table, it can be seen that by using the local printing method, the insulation coating in the edge and top corner regions can be effectively compensated to increase the thickness of the insulation coating at the thinnest point so that it can meet the insulation withstand voltage requirements, and the more times of local printing, the greater the thickness of the insulation coating.

[0043] In some embodiments of the present application, the steps for crosslinking and curing the insulation coating printed on the product surface include: Pre-curing: Using UV light irradiation to make the insulating coating printed on the battery surface lose fluidity and form preliminary curing. Final curing: Using UV light irradiation to fully complete photo-initiated crosslinking curing of the insulating coating on the battery surface, making the insulating coating reach the final stable form and form an insulating coating.

[0044] Specifically, in some specific embodiments, pre-curing can be carried out by irradiating with UV light having an energy density of 100~2000 mJ / cm² to make the insulating coating printed on the product surface form preliminary curing (only losing liquid fluidity), preventing the insulating coating from flowing further uncontrollably (sagging) to ensure the appearance uniformity of the final coating. Final curing can be carried out by irradiating with UV light having an energy density of 10000~40000 mJ / cm² to fully complete photo-initiated crosslinking curing of the insulating coating on the battery surface, making the insulating coating reach the final stable form.

[0045] In some embodiments of the present application, the finished product inspection includes one or several of coating thickness inspection, appearance inspection, coating insulation withstand voltage performance test, and color inspection.

[0046] In some embodiments of the present application, the coating thickness inspection includes: measuring the thickness of the insulating coating by the photothermal infrared method in the edge and vertex regions, and measuring the thickness of the insulating coating by the infrared spectroscopic interferometer in the plane region. When the thickness data exceeds the set threshold, the printing control system corrects the process parameters of the corresponding printing station and nozzle according to the mapping relation table.

[0047] The photothermal infrared thickness measurement technology can be compatible with irregular measured surfaces (edge arc surfaces, vertices, curved surfaces, etc.), and has little restriction on the installation of the measurement probe (measurement can be carried out within the range of ±70°, which can effectively avoid the interference of mechanical accuracy on the measurement result). In the plane region, the infrared spectroscopic interferometer is used for coating thickness inspection, which can achieve high precision and high sampling frequency, and can realize scribing and scanning measurement of the plane, so as to obtain the coating thickness data on the scribing track. When the thickness data exceeds the set threshold, the printing control system automatically corrects the process parameters of the printing equipment through the mapping relation table. For example, if it is found that the thickness of the insulating coating at a position covered by a certain nozzle in the width direction of a certain surface is lower than the average value, the working voltage of the nozzle can be automatically modified by software for compensation. For example, if it is detected that the thickness of the insulating coating at the edge is much lower than the set threshold, an alarm can be sent to the corresponding station to prompt manual intervention.

[0048] In some embodiments of the present application, the appearance inspection includes: obtaining a product image by using a 2.5D optical imaging system, identifying defects in the product image in combination with a deep learning algorithm, and performing position positioning, quantification, and classification determination on the defects.

[0049] Specifically, the surface features of the product can be imaged by a vision system, and then the defect features in the image can be extracted, classified, and quantified by deep learning algorithms. For example, it can identify whether there are particle protrusions or pits on the coating surface, and whether there is local ink shortage in the printing of the insulating coating. Image recognition is performed by utilizing the differences in gray-scale contrast, morphological features, etc. of the image features formed by different defects under specific exposure conditions. Through algorithm recognition, defects directly related to printing such as ink shortage and frame break can be identified.

[0050] In some embodiments of the present application, the insulation and voltage withstand performance test includes: contacting the surface of the insulating coating through a conductive electrode to perform insulation impedance and voltage withstand tests. If there is insufficient impedance or voltage withstand breakdown failure, the test station is used to determine which surface of the battery the defect appears on, and the printing control system corrects the process parameters of the corresponding printing station and nozzle according to the mapping table.

[0051] In some embodiments of the present application, the frequency of defect occurrence can be set. For example, if 7 (the specific quantity can be set) consecutive defects appear on a certain surface, the printing control system issues an alarm prompt to the printing station of this surface for manual intervention.

[0052] In some embodiments of the present application, during the rework process of defective products, the position and type of the defect on the product are determined according to the feedback defect and defective position information, and the defective position is repaired accordingly according to the defect type. In the prior art, the insulating coatings on all surfaces of defective products are removed by laser cleaning and then reflow printed again. After adopting this solution, when the finished product inspection station detects an unacceptable defect at a specific position, the position information can be transmitted to the defective product rework station, and the printing control system can execute a specific rework process according to the position information of the defect, while retaining the insulating coatings on the remaining defect-free surfaces, thereby achieving precise rework of defective products, saving resources and improving efficiency.

[0053] In some embodiments of the present application, surface pretreatment is also included before UV digital coating, and the surface pretreatment includes but is not limited to laser cleaning, plasma gas cleaning, sandblasting and shot peening, chemical reagent cleaning, and dry ice cleaning.

[0054] In some embodiments of the present application, the surface of the housing is ablated and cleaned by laser, and at the same time, vacuum dust removal is applied to the cleaning position, and then the surface of the housing is subjected to plasma treatment.

[0055] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A digital printing production method for the surface insulation coating of a lithium battery, characterized in that, Including: UV digital painting, coating an insulating coating on each surface of the battery and curing the insulating coating; Establishing a mapping relationship, grouping and numbering the printing stations for each surface of the battery to be executed and multiple nozzles for executing the printing of the current surface, and forming a mapping relationship table between the printing stations, nozzles and each surface of the battery; Finished product inspection, inspecting the insulating coating on the battery surface to obtain the defect type and defective position information of the insulating coating, querying the mapping relationship table according to the defect type and defective position information to obtain the information of the printing station and nozzle that caused the defect, so as to adjust the process parameters of the corresponding printing station and nozzle according to the defect type; Quality determination, classifying the batteries into qualified products and unqualified products according to the results of the finished product inspection, sorting and discharging the qualified products, repairing the unqualified products, and repeating the above steps after the repair is qualified.

2. The digital printing production method of the surface insulation coating of the lithium battery according to claim 1, characterized in that, The UV digital painting includes: Taking pictures of each surface of the battery to be printed to obtain a bright area and a dark area. The bright area is the high-reflection area on the battery surface, and the dark area is the low-reflection area outside the battery. Using the bright area and the dark area to identify the edge and corner areas and flat areas of the battery to obtain the contour information of the battery, and performing inkjet printing and crosslinking curing on the battery surface according to the contour information of the battery to obtain an insulating coating.

3. The digital printing production method of the surface insulation coating of the lithium battery according to claim 2, wherein The inkjet printing on the battery surface according to the contour information of the battery includes: Full-surface printing, covering the edge and corner areas and flat areas of the battery surface with insulating paint; Partial printing, performing supplementary spraying of insulating paint on the edge and corner areas of the battery to form an insulating coating with a preset thickness on the edge and corner areas of the battery.

4. The digital printing production method of the surface insulation coating of the lithium battery according to claim 3, wherein, The partial printing includes: Printing and curing the edge and corner areas to form an additional coating with a certain thickness on the edge and corner areas; or the printing control system controls the injection amount of insulating paint in the edge and corner areas to be greater than that in the flat areas; or spraying the insulating paint onto the edge and corner areas through a glue spraying valve or dispensing process and pre-curing to form a partial insulating coating in advance.

5. The digital printing production method of the surface insulation coating of the lithium battery according to claim 2, wherein, The crosslinking curing includes: Pre-curing, using the first UV light to irradiate the insulating paint on the battery surface to make the insulating paint lose fluidity and form a pre-cured layer; Final curing, using the second UV light to irradiate the pre-cured layer to make the pre-cured layer further complete the photoinitiated crosslinking curing reaction until the insulating paint reaches the final stable state to form the insulating coating.

6. The digital printing production method of the surface insulation coating of the lithium battery according to claim 1, characterized in that, The finished product inspection includes one or several of coating thickness detection, appearance inspection, coating insulation withstand voltage performance test and color detection.

7. The digital printing production method of the surface insulation coating of the lithium battery according to claim 6, characterized in that The coating thickness detection includes: measuring the thickness of the insulating coating by the photothermal infrared method in the edge and corner areas, and measuring the thickness of the insulating coating by the infrared spectroscopic interferometer in the flat areas. When the thickness data exceeds the set threshold, the printing control system corrects the process parameters of the corresponding printing station and nozzle according to the mapping relationship table.

8. The digital printing production method of the surface insulation coating of the lithium battery according to claim 6, characterized in that The appearance inspection includes: using a 2.5D optical imaging system to obtain a product image, identifying the defects in the product image by combining a deep learning algorithm, and performing position positioning, quantification and classification determination on the defects.

9. The digital printing production method of the surface insulation coating of the lithium battery according to claim 7, wherein, The insulation withstand voltage performance test includes: conducting insulation impedance and withstand voltage tests by contacting the surface of the insulation coating with conductive electrodes. If there is insufficient impedance or withstand voltage breakdown failure, the test station is used to determine on which surface of the battery the defect appears, and the printing control system corrects the process parameters of the corresponding printing station and nozzle according to the mapping relation table.

10. The digital printing production method of the surface insulation coating of the lithium battery according to claim 1, characterized in that: During the repair process of defective products, the position and type of the defect on the product are determined based on the feedback defect and defect location information, and the defective position is repaired accordingly according to the defect type; and / or, surface pretreatment is also included before UV digital painting, and the surface pretreatment includes one or more of laser cleaning, plasma gas cleaning, sandblasting and shot peening treatment, chemical reagent cleaning, and dry ice cleaning.

Images