PEM water electrolysis hydrogen production membrane electrode coating method

Abstract

The invention belongs to the technical field of PEM (proton exchange membrane) water electrolysis hydrogen production, and particularly relates to a PEM water electrolysis hydrogen production membrane electrode coating method. The method comprises the following steps: step 1, dynamically pretreating coating slurry; 2, stable tension conveying of the proton exchange membrane; 3, double-sided synchronous slit coating is carried out; step 4, carrying out first OCT online detection in the coating process; 5, three-stage gradient drying and curing; step 6, after drying, carrying out OCT real-time detection and closed-loop adjustment for the second time; and step 7, winding a coated finished product. The problems of low single-side dispersion efficiency, uneven thickness, defect detection lag, transfer wrinkles and the like of a traditional coating process are solved.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane (PEM) electrolysis of water to produce hydrogen, specifically involving the optimization and improvement of the coating preparation process of membrane electrode (CCM), and more specifically involving a coating method for PEM electrolysis of water to produce hydrogen membrane electrode. Background Technology

[0002] PEM (Polymer Electrolysis Membrane) has become a core technology for green hydrogen production due to its advantages of fast start-up, high electrolysis efficiency, high product purity, and flexible adaptability to fluctuating renewable energy sources such as photovoltaics and wind power. The membrane electrode assembly (MEA), as the "heart" of the PEM electrolyzer, directly determines the electrolyzer's performance—the uniformity of the coating, the tightness of the interlayer bonding, the adequacy of catalyst dispersion, and the appropriate porosity all affect the electrolyzer's hydrogen evolution efficiency, current density, and long-term operational stability. Currently, common MEA production processes mainly involve catalyst slurry preparation, proton exchange membrane coating to form a catalyst coated membrane (CCM), hot-pressing a gas diffusion layer, and laminating a frame membrane. Among these, there are many coating processes for the catalyst layer of the MEA, commonly including thermal transfer printing, partial direct coating, and roll-to-roll CCM coating technologies.

[0003] The current membrane electrode coating process suffers from the following key technical challenges, hindering mass production quality and efficiency: 1. Drying step: Setting a single temperature parameter leads to both efficiency and quality defects; In the drying step after coating the membrane electrode, the existing technology uses a single temperature setting (usually 80-150℃). Under this parameter setting, the rapid evaporation of solvent will cause a series of problems: first, the proton exchange membrane will swell, curl, become porous, crack, and wrinkle on the surface; second, the interlayer peel strength of the coating will decrease. Especially in the case of double-sided coating, a single drying will reduce the adhesion between the first coating and the substrate, resulting in delamination during subsequent overcoating. The root cause of the drawback is the sudden heating and cooling environment caused by a single temperature, which disrupts the phase separation equilibrium of the ionomer.

[0004] 2. Coating steps: Inadequate adaptation of traditional coating methods and parameters leads to poor uniformity; In the slurry coating step, existing technologies mostly use slit coating and do not adapt and control variables such as slurry viscosity fluctuations and uneven tension of proton exchange membrane substrates. Due to insufficient parameter control, this process results in coating thickness deviations of more than ±5μm. Problems caused by thickness deviation: excessive thickness in some areas will increase the resistance to proton conduction, while excessive thinness in some areas will lead to insufficient catalyst and incomplete hydrogen evolution reaction. The root cause of the drawbacks is that traditional coating methods have limited process precision and lack dynamic adaptation and adjustment of slurry characteristics and substrate conditions.

[0005] 3. Quality inspection steps: Offline sampling methods lead to inspection delays and wasted costs; Existing technologies employ "offline sampling inspection" (such as section thickness measurement and electron microscope observation) in the coating quality inspection step. This inspection method cannot capture real-time defects (such as pinholes, scratches, and abrupt changes in thickness) during the coating process. By the time problems are discovered during offline inspection, a large number of defective products have already been generated, leading to a significant increase in production costs. The root cause of the drawbacks is that the non-real-time nature of offline sampling inspection and the limitations of sampling coverage make it impossible to synchronously match dynamic defects in the coating process.

[0006] 4. Hot pressing composite step: Lack of parameter coordination control leads to poor composite consistency; In the existing technology, the thickness and uniformity of the coating in the hot-pressing composite step between membrane electrode layers are not precisely controlled, and the hot-pressing parameters (such as temperature, pressure and time) are not adapted to the coating state. This parameter control method makes it easy for the coatings on both sides to misalign, causing fluctuations in the overall resistance of the membrane electrode, which ultimately affects the operational stability of the electrolyzer. The root cause of the defects is that the initial coating parameters and the subsequent hot-pressing transfer parameters lack coordinated control logic, and the coating thickness uniformity does not meet the requirements of the composite process. Summary of the Invention

[0007] The purpose of this invention is to address the problems of traditional coating processes, such as "low single-sided discrete efficiency, uneven thickness, delayed defect detection, and transport wrinkles." By optimizing the equipment and processes through "dynamic slurry adaptation, stable substrate delivery, simultaneous double-sided coating, seamless drying, real-time detection and adjustment, curing and winding, and hot-pressing lamination," a continuous and high-precision coating production chain is formed. This invention proposes an improved membrane electrode coating process with high precision, high efficiency, and low loss.

[0008] In particular, it integrates catalyst coating uniformity control, gradient drying parameter optimization, and industrial-grade online detection technology to achieve double-sided direct coating, making it especially suitable for large-scale, high-precision membrane electrode mass production scenarios.

[0009] Therefore, the present invention provides a method for coating a PEM electrolysis water-to-hydrogen membrane electrode, the method comprising: Step 1: Dynamic pretreatment of coating slurry; Control the ambient temperature so that the temperature fluctuation of the anode slurry and cathode slurry is within 6℃; Control the viscosity of the anode slurry and cathode slurry to keep them stable at 100-500 mPa·s with fluctuations within 100 mPa·s; Step 2: Stable delivery via proton exchange membrane tension; The proton exchange membrane is installed on the roll-to-roll unroller, and the initial tension fluctuation is controlled to be within 4N. Step 3: Double-sided simultaneous slot coating; The anode slurry and cathode slurry obtained in step 1 are respectively fed to the coating head for double-sided coating, and the coating thickness is monitored in real time. Step 4: First OCT online inspection during the coating process; Two sweep frequency optical coherence tomography (OCT) devices were used to scan in real time at a distance after the anode slurry coating head and the cathode slurry coating head, respectively, and to continuously scan along the coating width direction. Optionally: If the test fails and the parameters are adjusted, test again; Step 5: Three-stage gradient drying and curing; After coating and passing inspection, the semi-finished product enters a three-stage series drying device for drying. Step 5-1: Pre-drying: Temperature 35-60℃, hot air velocity 1-2 m / s; Step 5-2: Shaping and drying: Temperature 75-150℃, hot air velocity 2-3 m / s; Step 5-3: Curing and drying: temperature 35-60℃, cooling fan speed 1-1.5 m / s; Step 6: After drying, perform a second OCT real-time detection and closed-loop adjustment; Two frequency-sweeping optical coherence tomography (OCT) devices were used to detect in real time the dry film thickness, overall thickness uniformity, interlayer bonding state, and surface smoothness of the coating after double-sided drying. If the test fails, a closed-loop adjustment is performed; Step 7: Coating the finished product and then winding it up.

[0010] As a preferred embodiment, the above-mentioned PEM electrolysis water production hydrogen membrane electrode coating method further includes: step 8: hot pressing composite.

[0011] As a preferred embodiment, in the above-mentioned PEM electrolysis water-to-hydrogen membrane electrode coating method, in step 3, the slit outlet width of the double-sided synchronous slit coating is 0.1-0.3 mm, the coating pressure is 0.1-0.3 MPa, and the coating speed is 0-10 m / min and not 0.

[0012] As a preferred embodiment, in the above-mentioned PEM electrolysis water-to-hydrogen membrane electrode coating method, step 4 includes detecting parameters such as wet film thickness uniformity and surface defects. Wet film thickness uniformity: deviation must be ≤ ±1 μm; surface defects: include at least one of pinholes, scratches, and bubbles, with an identification size ≥ 50 μm.

[0013] As a preferred embodiment, in the above-mentioned PEM electrolysis water production hydrogen membrane electrode coating method, in step 5, the pre-drying process involves the semi-finished product remaining for 4-7 minutes; the shaping and drying process involves the semi-finished product remaining for 5-8 minutes; and the curing and drying process involves the semi-finished product remaining for 3-6 minutes.

[0014] As a preferred embodiment, in the above-mentioned PEM electrolysis water-to-hydrogen membrane electrode coating method, in step 6, the dry film thickness is 5-30 μm / surface; the overall thickness uniformity is ≤ ±2 μm; the interlayer bonding state is free of delamination and bubbles; and the surface smoothness is Ra ≤ 0.5 μm.

[0015] As a preferred embodiment, the above-mentioned PEM electrolysis water production hydrogen membrane electrode coating method further includes step 6 as follows: if the dry film thickness is detected to be excessive, the system automatically records the corresponding membrane segment position and adjusts the hot pressing pressure of that area during subsequent hot pressing. If there is interlayer delamination or large area of ​​air bubbles, it is judged as unqualified, marked and rejected.

[0016] As a preferred embodiment, in the above-mentioned PEM electrolysis water-to-hydrogen membrane electrode coating method, step 7, the fluctuation range of the winding tension is controlled to be within 2N.

[0017] As a further preferred embodiment, the above-mentioned PEM electrolysis water-to-hydrogen membrane electrode coating method includes: Step 1: Dynamic pretreatment of coating slurry; First, prepare the anode and cathode slurries required for the membrane electrode; The anode slurry and cathode slurry are injected into different slurry storage tanks, and the ambient temperature is controlled to keep the slurry temperature fluctuation within 6°C. The online viscometer in the storage tank is activated to monitor the slurry viscosity in real time and stabilize the slurry viscosity at 300±50mPa·s. After ensuring that the slurry is uniform and free of particle agglomeration, the slurry is transported to the feed port of the dual-station coating head through the heat preservation device. Step 2: Stable delivery via proton exchange membrane tension; First, the proton exchange membrane is plasma cleaned to remove surface oil and impurities, and then it is installed on the roll-to-roll unwinding rollers, controlling the initial tension fluctuation range within 4N; start the drive motor of the roll-to-roll conveying system; the tension sensor on the guide roller monitors the substrate tension in real time to ensure that the substrate is conveyed to the coating station with constant tension and uniform speed. Step 3: Double-sided simultaneous slot coating; Adjust the position of the dual-station slit coating head: arrange the two coating heads on the upper and lower sides of the substrate; transport the anode slurry and cathode slurry prepared in step 1 to the dual-station coating head through the constant pressure feeding tank, start double-sided coating according to the preset program, and monitor the coating thickness in real time. Step 4: First OCT online inspection during the coating process; Two sweep frequency optical coherence tomography (OCT) devices are used to scan in real time at a distance after the anode slurry coating head and the cathode slurry coating head, respectively, and to continuously scan along the coating width direction. The defect identification module compares the detection data with the preset threshold: if the detection is unqualified, the parameters are adjusted and the detection is performed again. Detection parameters: uniformity of wet film thickness of coating, surface defects; detection data is transmitted to the control system in real time; Step 5: Three-stage gradient drying and curing; After coating and passing inspection, the semi-finished product enters a three-stage series drying unit. The drying process parameters are set as follows: Step 5-1: Pre-drying: Temperature 40-60℃, hot air velocity 1-2 m / s; Step 5-2: Shaping and drying: Temperature 80-150℃, hot air velocity 2-3 m / s; Step 5-3: Curing and drying: temperature 40-60℃, cooling fan speed 1-1.5 m / s; Step 6: After drying, perform a second OCT real-time detection and closed-loop adjustment; Two frequency-sweeping optical coherence tomography (OCT) devices were used to detect in real time the dry film thickness, overall thickness uniformity, interlayer bonding state, and surface smoothness of the coating after double-sided drying. If the dry film thickness is detected to be excessive, the system will automatically record the corresponding film segment position and adjust the hot pressing pressure of that area during subsequent hot pressing. If there is interlayer delamination or large area of ​​air bubbles, it is judged as unqualified, marked and rejected; Step 7: Coating the finished product and then winding it up; Control the winding tension fluctuation range to within 2N; optionally including: Step 8: Hot pressing composite.

[0018] As a more specific preferred embodiment, the above-mentioned PEM electrolysis water-to-hydrogen membrane electrode coating method can be: Step 1: Dynamic pretreatment of coating slurry; First, prepare two core catalyst layer slurries required for the membrane electrode: one is the proton exchange membrane side anode slurry (which can be called catalyst slurry a), which is prepared by mixing an iridium-containing composite catalyst and perfluorosulfonic acid resin with a propylene glycol / deionized water mixed solvent (solid content 8%-12%) and dispersing for 60 min; the other is the cathode slurry (which can be called catalyst slurry b), which is prepared by mixing a platinum-based catalyst (such as Pt / C) and perfluorosulfonic acid resin with the above-mentioned type of propylene glycol / deionized water mixed solvent (solid content 8%-12%) and dispersing for 50 min.

[0019] The basic ratio of the two slurries can be referenced as "Ir / Pt noble metal catalyst: ionomer: solvent = 1:2:7" (the mass ratio can be adjusted according to actual needs). Catalyst slurries a and b are injected into different slurry storage tanks. The ambient temperature is controlled to stabilize the slurry temperature at 17-27℃, preferably at 25±2℃. This temperature is the optimal temperature for ionomer dissolution, avoiding slurry agglomeration due to excessively low temperatures and excessive solvent evaporation due to excessively high temperatures. The online viscometer in the storage tank (detection accuracy ±5 mPa·s, detection frequency 1 time / 10s) is activated to monitor the slurry viscosity in real time. If the viscosity is >350 mPa·s, the slurry is too thick. Use an ultrasonic disperser to disperse the slurry while reducing the flow rate of the variable frequency slurry pump. Improve the viscosity by enhancing dispersion and reducing the feed rate. If the viscosity is <250 mPa·s, reduce the power of the ultrasonic disperser and increase the flow rate of the variable frequency slurry pump. Finally, stabilize the slurry viscosity at 300±50 mPa·s. Continue pretreatment for 10 minutes to ensure that the slurry is uniform and free of particle agglomeration. Then, turn on the variable frequency slurry pump and transport the slurry through the heated pipeline (25±2℃) to the feed port of the dual-station coating head.

[0020] In step 1, the "heat tracing pipe" is replaced with "insulation cotton wrapped around the conveying pipe". The insulation cotton (5 mm thick, made of glass wool) is less expensive than the heat tracing pipe and can maintain the temperature fluctuation of the slurry inside the pipe ≤ ±3℃.

[0021] Step 2: Stable delivery via proton exchange membrane tension; The specific implementation process is as follows: First, the sulfonic acid proton exchange membrane (such as Nafion 212) is plasma cleaned (processing time 30-60s) to remove surface oil and impurities. Then, the proton exchange membrane roll (e.g., 500 mm wide, 25 μm thick) is installed on the roll-to-roll unwinding roller, and the initial tension fluctuation is controlled within 4N. The drive motor of the roll-to-roll conveying system is started, and the substrate conveying speed is set: if the target coating thickness is 0.5 μm, the speed is set to 3 m / min; if the target thickness is 1 μm, the speed is set to 5 m / min. The tension sensor on the guide roller (accuracy ±0.5N) monitors the substrate tension in real time to ensure that the substrate is conveyed to the coating station with constant tension and uniform speed.

[0022] In step 2, a tension of 6±2N is suitable for proton exchange membranes with a thickness of 20-30μm, while 8±2N is suitable for 25μm membranes, preventing the thin membrane from stretching due to excessive tension. The conveying speed can be reduced from 3-5m / min to 2-4m / min. Although this reduces production efficiency (a 20% reduction), it reduces vibration of the substrate during conveying and improves coating alignment accuracy. This ensures constant tension conveying of the substrate, without slack or stretching, meeting basic accuracy requirements.

[0023] Step 3: Double-sided simultaneous slot coating; Specific implementation process: Adjust the position of the dual-station slit coating head: Arrange the two coating heads on the upper and lower sides of the substrate, adjusting the vertical spacing to 30-180 μm (adapted to the thickness of the proton exchange membrane: 30-120 μm spacing is suitable for proton exchange membranes with a thickness of 20-25 μm, 30-80 μm for thin films, and 80-180 μm for thick films) to avoid excessive spacing causing slurry dripping. Set the slit outlet width to 0.1-0.3 mm. Transport the catalyst slurries a and b prepared in step 1 to the dual-station coating head via a constant pressure feeding tank (with a built-in agitator to prevent sedimentation), and start coating according to the preset program: set the coating speed to 0.8-1.2 m / min and the coating pressure to 0.1-0.3 MPa (0.1-0.25 MPa pressure is suitable for slurries with a viscosity of 280-320 mPa·s, and 0.15-0.3 MPa is suitable for slurries with a viscosity of 300±50 mPa·s). The slurry concentration (mPa·s) ensures continuous slurry extrusion. The coating weight per unit area fluctuates by ≤±0.1 g / cm². 2 (Anode 0.7-1.1 g / cm) 2 Cathode 0.3-0.6 g / cm 2 Even with this method, the catalyst layer activity requirements are still met, with a double-sided alignment error ≤ ±1.5μm. Simultaneously, a variable frequency precision gear pump (flow accuracy ±0.05mL / min) is used to adjust the feed rate. The material is uniformly coated on both sides of the proton exchange membrane, performing a double-sided coating process. The specific parameter matching logic is as follows: when the substrate conveying speed is 0.8m / min, the corresponding coating pressure is 0.15MPa and the pump flow rate is 1.2mL / min; when the speed increases to 1.2m / min, the pressure is simultaneously increased to 0.3MPa and the flow rate is adjusted to 1.8mL / min, ensuring that the slurry coating amount (wet weight) per unit area remains stable at 0.6-1.0 g / cm³ on the anode (upper side). 2 Cathode (bottom side): 0.2-0.5 g / cm³ 2 .

[0024] Between the substrate entry and the coating head position, the upper and lower coating heads synchronously spray slurry. The coating head position sensor monitors the film transfer speed and the coating head spacing in real time to ensure that the wet film thickness is controlled within 20-30μm. If the spacing deviation is >±10μm, the coating head lifting mechanism is automatically adjusted to ensure that the centers of the double-sided coating are aligned, and the alignment error is controlled within ±0.5μm. During the coating process, the substrate tension is continuously monitored. If fluctuations occur, the coating speed is simultaneously fine-tuned to ensure the coordination of "speed-pressure-flow".

[0025] Step 4: First OCT online inspection during the coating process; Two swept-source optical coherence tomography (OCT) devices (resolution ≤ 1 μm, 50 Hz at a speed of 3 m / min, 100 Hz at a speed of 5 m / min) are used to scan at a short distance behind the upper and lower coating heads respectively, and continuous scanning is carried out along the coating width direction (detection range 50 - 100 mm). The defect recognition module compares the detected data with the preset threshold: Detection parameters: Focus on detecting the wet film thickness uniformity of the coating (deviation ≤ ±1 μm), surface defects (such as pinholes, scratches, bubbles, defects with a size ≥ 50 μm need to be identified); the detected data is transmitted to the control system in real time. If unqualified items are found, the system will automatically stop and trigger the adjustment of the parameters of the corresponding coating head (such as adjusting the coating pressure, slit width). After the parameters are calibrated, the coating is restarted. If the detected pinholes / scratches exceed the standard: Immediately trigger an audible and visual alarm, suspend the feeding of the corresponding coating head, and manually check for slurry impurities or coating head blockage problems; within 10 s after the parameter adjustment, the OCT probe detects again. After confirming that the coating is qualified, the coating is resumed, forming a "detection - adjustment - verification" closed loop.

[0026] Qualified standard: When the wet film thickness of the coating is within the range of 20 - 50 μm and there are no continuous defect points ≥ 50 μm, it is judged as qualified and proceeds to the next step; unqualified products are automatically cut and removed (cutting length ≥ 100 mm to avoid defect extension). The first OCT probe is placed behind the upper coating head.

[0027] Step 5: Three - stage gradient drying and curing; The semi - finished product of the "proton exchange membrane - double - sided catalytic layer" after coating is conveyed through a transition roller with a Teflon - coated surface (diameter 50 mm, roller spacing 100 mm). The Teflon material prevents the coating from sticking. The semi - finished products that pass the inspection enter a three - stage series drying device, each section with a length of 1 - 1.5 m, equipped with independent temperature and air velocity control systems. The drying process parameters are set as follows: Step 5 - 1: Pre - heating zone 5 (pre - drying): Temperature 35 - 60 °C, hot air velocity 1 - 2 m / s, the semi - finished product stays for 4 - 7 min, mainly to slowly remove 45 - 60% of the solvent in the volatile slurry, avoid rapid heating causing swelling of the membrane body, and avoid rapid crust formation on the coating surface; Step 5 - 2: Constant - rate zone 6 (shaping drying): Temperature 75 - 100 °C, hot air velocity 2 - 3 m / s, infrared auxiliary heating is turned on, the semi - finished product stays for 5 - 8 min, further remove the remaining 35 - 50% of the solvent in the volatile matter, make the coating cured and initially bonded to the substrate; Step 5 - 3: Falling - rate zone 7 (curing drying): Temperature 35 - 60 °C, cooling fan velocity 1 - 1.5 m / s, the semi - finished product stays for 3 - 6 min, remove the remaining solvent, and at the same time increase the hardness of the coating, avoid coating cracking caused by thermal stress; The three-stage gradient drying and curing process solves the problems of coating peeling and film swelling.

[0028] If OCT testing shows that the coating thickness is >30μm, the dwell time in the constant speed zone will be automatically extended by 1-3 minutes to ensure that the thick coating is fully cured.

[0029] Step 6: After drying, perform a second OCT real-time detection and closed-loop adjustment; Using the same two OCT scanning probes as in step 4 (aligned with the upper and lower coatings respectively), the dry film thickness (target 5-30 μm / side), overall thickness uniformity (deviation ≤ ±2 μm), interlayer bonding state (no delamination, bubbles), and surface smoothness (roughness Ra ≤ 0.5 μm) of the double-sided dried coating are detected. The scanning and detection parameters are set as in step 4 to achieve full coverage of the coating without blind spots. Feedback mechanism: If the dry film thickness exceeds the standard (e.g., ≥30 μm or ≤5 μm on one side), the system automatically records the corresponding film segment position, and adjusts the hot-pressing pressure of that area during subsequent hot pressing. If interlayer delamination or large-area bubbles (≥100 μm) are present, the coating is deemed unqualified, marked, and removed.

[0030] Step 7: Coating the finished product and then winding it up; The specific implementation process is as follows: After drying and curing, the coated finished product (double-sided coating thickness 0.5-20μm, flatness Ra≤0.2μm) is conveyed to the roll-to-roll take-up roller; the take-up tension is set to 8±1N (consistent with the substrate tension during coating), the take-up motor is started, and the correction mechanism (accuracy ±0.1mm) is activated at the same time. The take-up position is adjusted according to the substrate edge detection signal to prevent the finished product from deviating; each roll has a take-up length of 100m. After the take-up is completed, the coating parameters (date, speed, thickness, viscosity) of the roll are recorded and marked on the label for subsequent quality traceability.

[0031] Step 8: Hot pressing lamination; Specific implementation process: Preliminary data association: Call the dry film thickness data (0.5-20μm on one side) and uniformity parameters (deviation ≤ ±2μm) from the second OCT detection in step 6, and establish the adaptation logic between hot pressing parameters and coating state: If the coating thickness on one side is >20μm, the hot pressing parameters are set according to the high thickness range; if the thickness is ≤20μm, the parameters are set according to the normal range.

[0032] Precise alignment: A visual positioning system (accuracy ±0.05mm) is used to align the GDL with the double-sided coated film prepared in step 7, ensuring that the alignment deviation between the edge of the GDL and the edge of the coating is ≤0.1mm, so as to avoid local resistance abnormalities caused by misalignment.

[0033] Collaborative hot pressing parameter control: Place the aligned components in the hot press and perform hot pressing according to the following parameters: Standard setting (coating thickness ≤ 20μm): temperature 120-160℃, pressure 1.0-2.0MPa, time 120-250s; High thickness setting (coating thickness > 20μm): temperature 160-190℃, pressure 1.5-2.5MPa, time 200-350s (extended time ensures full adhesion of thick coatings). During hot pressing, activate the pressure gradient control system to linearly decrease the pressure from the center to the edge (gradient 0.1 MPa / cm), avoiding damage to the membrane material caused by pressure concentration at the edges.

[0034] This application avoids mechanical damage (such as curling, cracking, and surface wrinkling) to the ultrathin proton exchange membrane during the drying process, while inhibiting the swelling of the proton membrane and improving the interlayer adhesion of the coating to avoid delamination problems during double-sided coating. This application solves the problems of large coating thickness deviation and insufficient uniformity in traditional coating processes, and controls the coating thickness tolerance of the membrane electrode within ±2μm, thereby avoiding the problems of increased proton conduction resistance due to excessive local thickness and insufficient catalyst and incomplete hydrogen evolution reaction due to excessive local thinness. This application solves the problem of how to increase the detection rate of defects (such as pinholes, scratches, and abrupt changes in thickness) in the coating process to over 99%, while reducing the scrap rate to below 3%, thus avoiding the problem of a large number of non-conforming products and cost waste caused by the lag in offline sampling and inspection. This application addresses how to improve the structural consistency of the membrane electrode after hot-pressing composite, thereby increasing the electrolysis efficiency by 5%-8%, and ensuring that the stability performance degradation rate of the membrane electrode during long-term operation (1000h) is <10%, thus avoiding the problems of overall resistance fluctuation of the membrane electrode and decreased operation stability of the electrolytic cell caused by coating misalignment and mismatch of hot-pressing parameters.

[0035] Compared with the prior art, this application has at least the following beneficial effects: I. A continuous and simple coating process for simultaneous roll-to-roll double-sided slit coating is adopted: a dual-station slit coating head adapted to the width of the proton exchange membrane (corresponding to the upper and lower sides of the proton exchange membrane respectively) is configured to form a closed-loop linkage with the roll-to-roll unwinding mechanism and the rewinding mechanism; wherein, each slit coating head is equipped with an independent slurry supply system (adapted to the viscosity characteristics of the catalyst layer slurry) to ensure that a uniform ultrathin catalyst layer can be formed on both sides of the proton exchange membrane during continuous transport.

[0036] Second, a three-stage gradient drying unit (preheating zone - constant speed zone - deceleration zone) is directly connected after the double-sided coating station, achieving slow solvent evaporation through gradient changes in temperature and air velocity. This forms an integrated process of "roll-to-roll unwinding → double-sided synchronous slot coating → continuous gradient drying → roll-to-roll rewinding," eliminating the need for secondary alignment and transfer operations after traditional single-sided coating. It leverages the advantages of slot extrusion coating—high capacity, low material waste, and stable process—while simplifying intermediate steps in the membrane electrode coating process through its "double-sided synchronous + continuous connection" structural design.

[0037] III. Constructing an OCT online detection and real-time feedback closed-loop system: Optical coherence tomography (OCT) detection modules are set up after the coating process and before and after the drying process to collect coating thickness, porosity distribution and surface / internal defect data in real time; the detection data is transmitted to the coating control system, and when the detection value exceeds the preset threshold, the system automatically adjusts parameters such as coating speed and slurry supply.

[0038] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0039] Figure 1 A process flow diagram of a specific embodiment of a PEM electrolysis water production hydrogen membrane electrode coating method is shown; Figure 2 The membrane electrode obtained in Example 1 is shown; Figure 3 A comparison diagram of polarization curves for Example 1 and Comparative Examples 1-2 is shown; Explanation of reference numerals in the attached figures: 1-First coating head, 2-First sweep frequency optical coherence tomography (OCT) device, 3-Second coating head, 4-Second sweep frequency OCT device, 5-Preheating zone, 6-Constant speed zone, 7-Slowing-down zone, 8-Third sweep frequency OCT device, 9-Fourth sweep frequency OCT device, 10-Hot pressing, 11-Membrane electrode. Detailed Implementation

[0040] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0041] In this embodiment of the invention, the coating uses an existing double-sided coating device, supplemented by four sweep frequency optical coherence tomography (OCT) devices for real-time scanning; the drying uses an existing drying device assembled into a three-stage series drying device, which respectively constitutes a preheating zone 5, a constant speed zone 6, and a deceleration zone 7.

[0042] Example 1 This embodiment provides a method for coating a PEM electrolysis water-to-hydrogen membrane electrode. (See also...) Figure 1 The method includes: Step 1: Dynamic pretreatment of coating slurry; First, prepare two core catalyst layer slurries required for the membrane electrode: one is the anode slurry on the proton exchange membrane side (which can be called catalyst slurry a), which is prepared by mixing an iridium-containing composite catalyst and perfluorosulfonic acid resin with a propylene glycol / deionized water mixed solvent (10% solid content) and dispersing for 60 min; the other is the cathode slurry (which can be called catalyst slurry b), which is prepared by mixing a platinum-based catalyst (Pt / C) and perfluorosulfonic acid resin with the above-mentioned propylene glycol / deionized water mixed solvent (10% solid content) and dispersing for 50 min.

[0043] The basic mixing ratio of the two slurries is referenced as "Ir / Pt noble metal catalyst: ionomer: solvent = 1:2:7". Catalyst slurries a and b are injected into separate slurry storage tanks. The ambient temperature is controlled to stabilize the slurry temperature at 25±2℃, which is the optimal temperature for ionomer dissolution, avoiding slurry agglomeration due to excessively low temperatures and excessive solvent evaporation due to excessively high temperatures. The online viscometer in the storage tank (detection accuracy ±5 mPa·s, detection frequency 1 time / 10s) is activated to monitor the slurry viscosity in real time. If the viscosity is >350 mPa·s, the slurry is too thick. Use an ultrasonic disperser to disperse the slurry while reducing the flow rate of the variable frequency slurry pump. Improve the viscosity by enhancing dispersion and reducing the feed. If the viscosity is <250 mPa·s, reduce the power of the ultrasonic disperser and increase the flow rate of the variable frequency slurry pump. Finally, stabilize the slurry viscosity at 300±50 mPa·s. Continue pretreatment for 10 minutes to ensure that the slurry is uniform and free of particle agglomeration. Then, turn on the variable frequency slurry pump and transport the slurry through the heated pipeline (25±2℃) to the feed inlet of the dual-station coating head (first coating head 1 and second coating head 3).

[0044] Step 2: Stable delivery via proton exchange membrane tension; The specific implementation process is as follows: First, the sulfonic acid proton exchange membrane (Nafion 212) is plasma cleaned (processing time 45s) to remove surface oil and impurities. Then, the proton exchange membrane roll (500 mm wide, 25 μm thick) is installed on the roll-to-roll unwinding rollers, and the initial tension is set to 8±2N through the control system. The drive motor of the roll-to-roll conveying system is started, and the substrate conveying speed is set to 1 m / min. The tension sensor (accuracy ±0.5N) on the guide roller monitors the substrate tension in real time to ensure that the substrate is conveyed to the coating station with constant tension and uniform speed.

[0045] Step 3: Double-sided simultaneous slot coating; Adjust the position of the dual-station slit coating head: Two sets of coating heads (first coating head 1 and second coating head 3) are arranged on the upper and lower sides of the substrate, with the vertical spacing adjusted to 75 μm (to match the thickness of the proton exchange membrane), and the slit outlet width set to 0.2 mm. The catalyst slurries a and b prepared in step 1 are transported to the dual-station coating head via a constant-pressure feed tank (with a built-in stirrer to prevent sedimentation). Coating is started according to the preset program: the coating speed is set to 1 m / min, the coating pressure is controlled at 0.2 MPa, and the feed rate is adjusted by a variable frequency precision gear pump (flow accuracy ±0.05 mL / min), setting the feed flow rate to 1.5 mL / min. The slurry is evenly coated on both sides of the proton exchange membrane for double-sided coating. The slurry coating amount (wet weight) per unit area is stabilized at 0.8 g / cm³ on the anode (upper side). 2 Cathode (bottom side) 0.4 g / cm 2 .

[0046] Between the substrate entry and the coating head position, the upper and lower coating heads synchronously spray slurry. The coating head position sensor monitors the film transfer speed and the coating head spacing in real time to ensure that the wet film thickness is controlled within 20±2μm. If the spacing deviation is >±10μm, the coating head lifting mechanism is automatically adjusted to ensure that the centers of the double-sided coating are aligned, and the alignment error is controlled within ±0.5μm. During the coating process, the substrate tension is continuously monitored. If fluctuations occur, the coating speed is simultaneously fine-tuned to ensure the coordination of "speed-pressure-flow".

[0047] Step 4: First OCT online inspection during the coating process; Two sweeping optical coherence tomography (OCT) devices (first sweeping OCT device 2 and second sweeping OCT device 4) (resolution ≤1μm, 50Hz at a speed of 3 m / min, and 100Hz at a speed of 5 m / min) were used to scan a short distance behind the coating head on the upper and lower sides, respectively, and to continuously scan along the coating width direction (detection range 50mm). The defect identification module compared the detection data with a preset threshold. Detection parameters: Focus on detecting the wet film thickness uniformity of the coating (deviation ≤ ±1μm), surface defects (such as pinholes, scratches, bubbles, defects with a size ≥ 50μm need to be identified); the detection data is transmitted to the control system in real time. If unqualified items are found, the system automatically stops and triggers parameter adjustment of the corresponding coating head (such as adjusting coating pressure, slit width). After the parameters are calibrated, the coating is restarted. If the pinhole / scratch exceeds the standard: immediately trigger an audible and visual alarm, pause the feeding of the corresponding coating head, and manually check for slurry impurities or coating head blockage problems; within 10s after parameter adjustment, the OCT probe detects again. After confirming that the coating is qualified, the coating is resumed, forming a "detection - adjustment - verification" closed loop.

[0048] Qualified standard: If the wet film thickness of the coating is within the range of 20 ± 2μm and there are no continuous defect points ≥ 50μm, it is judged as qualified and proceeds to the next step; unqualified products are automatically cut and removed (cutting length ≥ 100mm to avoid defect extension). The first OCT probe is placed behind the upper coating head.

[0049] Step 5: Three - stage gradient drying and curing; The semi - finished product of the "proton exchange membrane - double - sided catalytic layer" after coating is conveyed through a transition roller with a surface - plated Teflon (diameter 50 mm, roller spacing 100 mm). The Teflon material prevents coating adhesion. The semi - finished products that pass the inspection enter a three - stage series drying device, each section with a length of 1 m, equipped with independent temperature and air velocity control systems. The drying process parameters are set as follows: Step 5 - 1: Pre - heating zone 5 (pre - drying): Temperature 60°C, hot air velocity 1 m / s, the semi - finished product stays for 4 min; Step 5 - 2: Constant - rate zone 6 (shaping drying): Temperature 90°C, hot air velocity 2 m / s, infrared auxiliary heating is turned on, the semi - finished product stays for 5 min; Step 5 - 3: Falling - rate zone 7 (curing drying): Temperature 40°C, cooling fan velocity 1 m / s, the semi - finished product stays for 3 min to remove the remaining solvent, and at the same time increase the coating hardness to avoid coating cracking caused by thermal stress; If the OCT detection shows that the coating thickness > 30μm, automatically extend the residence time in the constant - rate zone by 1 - 3 min to ensure full curing of the thick coating.

[0050] Step 6: Conduct a second real - time OCT detection and closed - loop adjustment after drying; Using the same two OCT scanning probes as in step 4 (aimed at the upper and lower coatings respectively) (third-scan optical coherence tomography device 8 and fourth-scan optical coherence tomography device 9), the dry film thickness (target 20 μm / side), overall thickness uniformity (deviation ≤ ±2 μm), interlayer bonding state (no delamination, bubbles), and surface smoothness (roughness Ra ≤ 0.5 μm) of the double-sided dried coating were detected. The scanning and detection parameters were set as in step 4 to achieve full coverage of the coating without blind spots. Feedback mechanism: if the dry film thickness exceeds the standard (single-sided film thickness not within the range of 20 ± 5 μm), the system automatically records the corresponding film segment position, and adjusts the hot-pressing pressure of that area during subsequent hot pressing; if interlayer delamination or large-area bubbles (≥100 μm) exist, the coating is judged as unqualified, marked, and discarded.

[0051] Step 7: Coating the finished product and then winding it up; The specific implementation process is as follows: After drying and curing, the coated finished product (double-sided coating thickness 40μm, flatness Ra≤0.2μm) is conveyed to the roll-to-roll take-up roller; the take-up tension is set to 8±1N, the take-up motor is started, and the correction mechanism (accuracy ±0.1mm) is activated at the same time. The take-up position is adjusted according to the substrate edge detection signal to avoid the finished product from deviating; the take-up length of each roll is 100m. After the take-up is completed, the coating parameters (date, speed, thickness, viscosity) of the roll are recorded and marked on the label for subsequent quality traceability.

[0052] Step 8: Hot pressing lamination; Preliminary data association: Call the dry film thickness data and uniformity parameters (deviation ≤ ±2μm) from the second OCT detection in step 6 to establish the adaptation logic between hot pressing parameters and coating state.

[0053] Precise alignment: A visual positioning system (accuracy ±0.05mm) is used to align the GDL with the double-sided coated film prepared in step 7, ensuring that the alignment deviation between the edge of the GDL and the edge of the coating is ≤0.1mm, so as to avoid local resistance abnormalities caused by misalignment.

[0054] Collaborative hot pressing parameter control: The aligned components are placed in a hot press at a temperature of 150 ℃ for 120 s and a pressure of 2 MPa. During the hot pressing process, a pressure gradient control system is activated to linearly decrease the pressure from the center to the edge (gradient 0.1 MPa / cm), thus avoiding membrane damage caused by pressure concentration at the edges.

[0055] Figure 2 The membrane electrode obtained in Example 1 is shown. The catalyst layer surface is flat, smooth, uniformly coated, free of dust and bubbles.

[0056] The coating thickness deviation of Example 1 is ≤ ±2μm, the detection rate of defects such as pinholes and scratches is ≥99%, and the production scrap rate is ≤3%. The prepared membrane electrode can basically avoid curling, cracking and surface wrinkling, and the electrolysis efficiency is improved by 5%-8% compared with the traditional ultrasonic spraying process. In the long-term operation test of 1000 hours, the performance decay rate is ≤10%.

[0057] Comparative Example 1 The difference from Example 1 lies in steps 5 and 8.

[0058] The preheating zone (pre-drying) has a temperature of 80 ℃, a hot air velocity of 2 m / s, and a residence time of 4 min for the semi-finished product; the constant speed zone (setting drying) has a temperature of 100 ℃, a hot air velocity of 2 m / s, and a residence time of 6 min for the semi-finished product; the deceleration zone (curing drying) has a temperature of 60 ℃, a cooling fan velocity of 2 m / s, and a residence time of 5 min for the semi-finished product. The hot pressing temperature is 180 ℃, and the time is 80 s.

[0059] Comparative Example 1 showed a coating thickness deviation of ≤±4μm, a defect detection rate of ≥99%, and a production scrap rate of ≤6%. The prepared membrane electrode exhibited slight curling and local cracking, and the electrolysis efficiency was only 3%-6% higher than that of the traditional process. Furthermore, the performance degradation rate was ≤15% during a 1000-hour long-term operation test.

[0060] Comparative Example 2 The difference from Example 1 lies in steps 5 and 8.

[0061] The preheating zone (pre-drying) has a temperature of 80 ℃, a hot air velocity of 2 m / s, and a residence time of 4 min for the semi-finished product; the constant speed zone (setting and drying) has a temperature of 90 ℃, a hot air velocity of 2 m / s, and a residence time of 4 min for the semi-finished product; the deceleration zone (curing and drying) has a temperature of 50 ℃, a cooling fan velocity of 1 m / s, and a residence time of 4 min for the semi-finished product. The hot pressing temperature is 100 ℃, and the time is 200 s.

[0062] Comparative Example 2 has a coating thickness deviation of ≤±4μm, a defect detection rate of ≥99%, and a production scrap rate of ≤8%. The prepared membrane electrode exhibits local swelling and slight delamination, and its electrolysis efficiency is 2%-4% higher than that of the traditional process. Furthermore, its performance degradation rate is ≤20% during a 1000-hour long-term operation test.

[0063] Figure 3 The polarization curves of Example 1 and Comparative Examples 1-2 are shown in comparison. Figure 3 The polarization curves confirmed that Example 1 performed well across the entire current density range (especially >2.0 A / cm²). 2The lowest cell voltage indicates the lowest polarization overpotential and ohmic resistance, confirming its 5%-8% improvement in electrolysis efficiency. Comparative Example 1, due to improper drying process leading to coating cracking, exhibited the fastest voltage rise in the medium-to-high current region, resulting in the worst performance and stability (attenuation rate ≥15μV / h). Comparative Example 2, limited by insufficient interfacial bonding during hot pressing, consistently performed worse than Example 1. The results demonstrate that the gradient drying and synergistic hot pressing process of Example 1 is crucial for obtaining a high-performance membrane electrode.

[0064] Comparative Example 3 The difference from Example 1 is that step 1: dynamic pretreatment of the coating slurry is not performed.

[0065] The viscosity of the slurry can vary by ±100 mPa·s due to temperature fluctuations (±5℃), resulting in subsequent coating thickness fluctuations exceeding ±5μm, which fails to meet the precision requirements of the membrane electrode catalytic layer (0.5-20μm).

[0066] Comparative Example 4 The difference from Example 1 is that step 2: tension stabilization of proton exchange membrane transport is not performed.

[0067] The substrate may stretch or relax due to tension fluctuations, resulting in wrinkles and uneven thickness of the coating during application, with a flatness deviation exceeding 0.05 mm.

[0068] Comparative Example 5 The difference from Example 1 is that step 3 is a single-sided coating.

[0069] After replacing it with traditional single-sided coating, an additional "flip-over-second coating" process is required, which reduces efficiency by 50% and the double-sided alignment error exceeds ±3μm.

[0070] Comparative Example 6 The difference from Example 1 is that step 4 uses traditional offline sampling detection.

[0071] Delayed defect detection can result in at least 50 m of defective semi-finished products and a material waste rate exceeding 15%.

[0072] Comparative Example 7 The difference from Example 1 is that step 5 is omitted.

[0073] Uncured coatings will peel off, and rapid solvent evaporation can cause proton membrane swelling and coating cracking.

[0074] Comparative Example 8 The difference from Example 1 is that step 6 uses traditional offline sampling detection.

[0075] Delayed defect detection can result in at least 50 m of defective semi-finished products and a material waste rate exceeding 15%.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for coating a PEM (Polymer Electrolysis Membrane) membrane electrode for hydrogen production, characterized in that, The method includes: Step 1: Dynamic pretreatment of coating slurry; Control the ambient temperature so that the temperature fluctuation of the anode slurry and cathode slurry is within 6℃; Control the viscosity of the anode slurry and cathode slurry to keep them stable at 100-500 mPa·s with fluctuations within 100 mPa·s; Step 2: Proton exchange membrane tension stabilizes transport; The proton exchange membrane is installed on the roll-to-roll unroller, and the initial tension fluctuation is controlled to be within 4N. Step 3: Double-sided simultaneous slot coating; The anode slurry and cathode slurry obtained in step 1 are respectively fed to the coating head for double-sided coating, and the coating thickness is monitored in real time. Step 4: First OCT online inspection during the coating process; Two sweep frequency optical coherence tomography (OCT) devices were used to scan in real time at a distance after the anode slurry coating head and the cathode slurry coating head, respectively, and to continuously scan along the coating width direction. Optionally: If the test fails and the parameters are adjusted, test again; Step 5: Three-stage gradient drying and curing; After coating and passing inspection, the semi-finished product enters a three-stage series drying device for drying. Step 5-1: Pre-drying: Temperature 35-60℃, hot air velocity 1-2 m / s; Step 5-2: Shaping and drying: Temperature 75-150℃, hot air velocity 2-3 m / s; Step 5-3: Curing and drying: temperature 35-60℃, cooling fan speed 1-1.5 m / s; Step 6: After drying, perform a second OCT real-time detection and closed-loop adjustment; Two frequency-sweeping optical coherence tomography (OCT) devices were used to detect in real time the dry film thickness, overall thickness uniformity, interlayer bonding state, and surface smoothness of the coating after double-sided drying. If the test fails, a closed-loop adjustment is performed; Step 7: Coating the finished product and then winding it up.

2. The PEM electrolysis water-to-hydrogen membrane electrode coating method according to claim 1, characterized in that, Also includes: Step 8: Hot pressing composite.

3. The PEM electrolysis water-to-hydrogen membrane electrode coating method according to claim 1, characterized in that, In step 3, the slit exit width of the double-sided synchronous slit coating is 0.1-0.3 mm, the coating pressure is 0.1-0.3 MPa, and the coating speed is 0-10 m / min and not 0.

4. The PEM electrolysis water-to-hydrogen membrane electrode coating method according to claim 1, characterized in that, In step 4, the detection parameters include wet film thickness uniformity and surface defects.

5. The PEM electrolysis water-to-hydrogen membrane electrode coating method according to claim 4, characterized in that, Wet film thickness uniformity: deviation must be ≤ ±1μm; Surface defects: including at least one of pinholes, scratches, and bubbles, with a size ≥50μm.

6. The PEM electrolysis water-to-hydrogen membrane electrode coating method according to claim 1, characterized in that, In step 5, pre-drying: the semi-finished product stays for 4-7 minutes; shaping drying: the semi-finished product stays for 5-8 minutes; curing drying: the semi-finished product stays for 3-6 minutes.

7. The method for coating PEM electrolysis water-to-hydrogen membrane electrodes according to claim 1, characterized in that, In step 6, Dry film thickness: 5-30 μm / side; Overall thickness uniformity: deviation ≤ ±2μm; Interlayer bonding state: no delamination, no bubbles; Surface smoothness: Roughness Ra≤0.5μm.

8. The method for coating PEM electrolysis water-to-hydrogen membrane electrodes according to claim 1, characterized in that, Step 6 also includes: If the dry film thickness is detected to be excessive, the system will automatically record the corresponding film segment position and adjust the hot pressing pressure of that area during subsequent hot pressing. If there is interlayer delamination or large area of ​​air bubbles, it is judged as unqualified, marked and rejected.

9. The method for coating PEM electrolysis water-to-hydrogen membrane electrodes according to claim 1, characterized in that, In step 7, the fluctuation range of the winding tension is controlled to be within 2N.

10. The method for coating PEM electrolytic water electrolysis hydrogen production membrane electrode according to claim 1, characterized in that, The method includes: Step 1: Dynamic pretreatment of coating slurry; First, prepare the anode and cathode slurries required for the membrane electrode; The anode slurry and cathode slurry are injected into different slurry storage tanks, and the ambient temperature is controlled to keep the slurry temperature fluctuation within 6°C. The online viscometer in the storage tank is activated to monitor the slurry viscosity in real time and stabilize the slurry viscosity at 300±50mPa·s. After ensuring that the slurry is uniform and free of particle agglomeration, the slurry is transported to the feed port of the dual-station coating head through the heat preservation device. Step 2: Proton exchange membrane tension stabilizes transport; First, the proton exchange membrane is plasma cleaned to remove surface oil and impurities, and then it is installed on the roll-to-roll unwinding rollers, controlling the initial tension fluctuation range within 4N; start the drive motor of the roll-to-roll conveying system; the tension sensor on the guide roller monitors the substrate tension in real time to ensure that the substrate is conveyed to the coating station with constant tension and uniform speed. Step 3: Double-sided simultaneous slot coating; Adjust the position of the dual-station slit coating head: arrange the two coating heads on the upper and lower sides of the substrate; transport the anode slurry and cathode slurry prepared in step 1 to the dual-station coating head through the constant pressure feeding tank, start double-sided coating according to the preset program, and monitor the coating thickness in real time. Step 4: First OCT online inspection during the coating process; Two sweep frequency optical coherence tomography (OCT) devices are used to scan in real time at a distance after the anode slurry coating head and the cathode slurry coating head, respectively, and to continuously scan along the coating width direction. The defect identification module compares the detection data with the preset threshold: if the detection is unqualified, the parameters are adjusted and the detection is performed again. Detection parameters: uniformity of wet film thickness of coating, surface defects; detection data is transmitted to the control system in real time; Step 5: Three-stage gradient drying and curing; After coating and passing inspection, the semi-finished product enters a three-stage series drying unit. The drying process parameters are set as follows: Step 5-1: Pre-drying: Temperature 40-60℃, hot air velocity 1-2 m / s; Step 5-2: Shaping and drying: Temperature 80-150℃, hot air velocity 2-3 m / s; Step 5-3: Curing and drying: temperature 40-60℃, cooling fan speed 1-1.5 m / s; Step 6: After drying, perform a second OCT real-time detection and closed-loop adjustment; Two frequency-sweeping optical coherence tomography (OCT) devices were used to detect in real time the dry film thickness, overall thickness uniformity, interlayer bonding state, and surface smoothness of the coating after double-sided drying. If the dry film thickness is detected to be excessive, the system will automatically record the corresponding film segment position and adjust the hot pressing pressure of that area during subsequent hot pressing. If there is interlayer delamination or large area of ​​air bubbles, it is judged as unqualified, marked and rejected; Step 7: Coating the finished product and then winding it up; Control the winding tension fluctuation range to within 2N; optionally including: Step 8: Hot pressing composite.

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