Apparatus and process for reducing stress and surface defects in wet separator membranes

Abstract

The application discloses a device and a process for reducing internal stress and surface defects of a wet diaphragm, which comprises an inlet water removal device, a diaphragm flattening device and an outlet liquid removal device. The inlet water removal device is arranged inside the inlet of an extraction tank and is used for scraping off the oil-water mixture brought out from the water seal liquid by inertia on the surface of the diaphragm. The outlet liquid removal device is arranged outside the outlet of the extraction tank and is used for scraping off the extractant brought out by inertia on both sides of the diaphragm. The diaphragm flattening device is symmetrically arranged on both sides of the inside of the extraction tank and is used for clamping the diaphragm on both sides to apply a transverse tension to the diaphragm. The diaphragm flattening device comprises a clamp roller, a bottom plate and a sliding adjustment mechanism. The sliding adjustment mechanism comprises a sliding rail, a sliding block and a driving gear set. The driving gear set can drive the sliding block to move on the sliding rail and then drive the two sets of clamp rollers to move. The application can eliminate the internal stress generated in the transmission process of the diaphragm, thereby effectively realizing the production of a low internal stress wet diaphragm and reducing the defects in the production process of the diaphragm.

Description

Technical Field

[0001] This invention relates to an apparatus and process for reducing internal stress and surface defects in wet-process separators, belonging to the field of lithium battery separator manufacturing. Background Technology

[0002] Lithium-ion batteries are mainly composed of four key materials: positive electrode, negative electrode, electrolyte, and separator. The separator, a crucial material in battery production, primarily functions to isolate the positive and negative electrodes, preventing internal short circuits, and providing a channel for ion transfer between them, ensuring the completion of the lithium-ion charging and discharging process. Under abnormal conditions, the separator can automatically close its pores to block ion transfer, preventing safety accidents.

[0003] Currently, there are two main types of diaphragms on the market: wet process and dry process. In the wet process, the equipment stretches the castings and diaphragms under different temperatures, directions, and tension levels. According to the principle of force and energy transfer, the force and energy generated by the equipment will eventually accumulate in the diaphragm and cannot be released. This will eventually become internal stress inside the diaphragm, which will lead to cracking, curling, or changes in material dimensions in the next production process.

[0004] Secondly, the current wet-process membrane production process mainly involves: casting → longitudinal stretching → transverse stretching 1 → extraction → transverse stretching 2 → winding → primary slitting → packaging. In the extraction section, the oil film, after longitudinal and transverse stretching, directly enters the extraction tank. To prevent leakage or evaporation of the extractant, a water seal is installed at the extraction inlet. After passing through the water seal, the oil film surface carries a large amount of oil-water mixture. During membrane operation, this mixture is carried into the entire extraction section, potentially forming oil spots on the roller surface in the drying section. Contact between the membrane and these oil spots causes continuous bright spots. Furthermore, after the membrane passes through the extraction section, the pore-forming agent occupying spaces in the oil film is replaced by the extractant, causing the membrane to shrink and alter its stress state. Simultaneously, the temperature difference between the extraction and stretching processes leads to stress accumulation within the membrane during continuous operation.

[0005] Therefore, firstly, separators with internal stress will crack or curl during processing, leading to a decrease in the pass rate of separator products; secondly, if such separators with residual strong internal stress are used to produce lithium-ion batteries, the batteries may deform during charging and discharging, and the battery safety performance cannot be guaranteed.

[0006] In summary, in order to reduce losses for separator manufacturers and enhance battery safety, it is imperative to design and develop a production process that reduces internal stress and surface defects in wet-process separators, and that can effectively solve the problems in existing separator production processes. Summary of the Invention

[0007] The purpose of this invention is to provide an apparatus and process for reducing internal stress and membrane surface defects in wet-process diaphragms, thereby overcoming the shortcomings of the existing technology.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] On one hand, the present invention provides an apparatus for reducing internal stress and membrane surface defects in wet-process diaphragms, comprising an inlet dewatering device, a diaphragm flattening device, and an outlet liquid removal device. The inlet dewatering device is located inside the inlet of the extraction tank and is used to scrape off the oil-water mixture carried out from the water seal liquid due to inertia on the diaphragm surface. The outlet liquid removal device is located outside the outlet of the extraction tank and is used to scrape off the extractant carried out from both sides of the diaphragm due to inertia. The diaphragm flattening devices are symmetrically arranged in pairs on both sides inside the extraction tank. The diaphragm flattening devices are used to clamp the diaphragm on both sides and apply lateral tension to the diaphragm. It includes two sets of parallel clamping rollers, a base plate, and a sliding adjustment mechanism. The sliding adjustment mechanism includes a slide rail, a slider, and a drive gear set. The slide rail is mounted on the base plate, the slider is slidably mounted on the slide rail, the two sets of clamping rollers are connected to the slider, and the drive gear set drives the slider to move on the slide rail, thereby driving the two sets of clamping rollers to move.

[0010] Furthermore, the drive gear set includes a rack, a gear, and a gear shaft. The rack is mounted on the base plate, the gear is mounted on the bottom end of the gear shaft and meshes with the rack, the gear shaft is vertically mounted on the slider via a bearing, and a crossbar is mounted on the upper end of the gear shaft.

[0011] Furthermore, the base plate is installed at one end of the stiffening plate, and a welding plate is fixedly connected to the other end of the stiffening plate, with a main fixing plate fixed on the welding plate.

[0012] Furthermore, the ends of the clamping rollers are provided with guide chamfers to facilitate the entry of the diaphragm between the two rollers, and the two sets of clamping rollers are clamped by springs.

[0013] Furthermore, the inlet dewatering device includes a dewatering roller and a dewatering roller base, wherein the dewatering roller can be lifted and lowered on the dewatering roller base.

[0014] Furthermore, the diameter of the dewatering roller is 120-200mm, the length is the same as the extraction roller of the extraction tank, the surface finish is ≥13, and after installation, the center position of the dewatering roller is 0-100mm lower than the center of the first roller at the inlet of the extraction tank.

[0015] Furthermore, the dewatering roller base is equipped with a scale and a lifting frame, which drives the dewatering roller to move up and down. The lifting frame adopts a scissor-type structure.

[0016] Furthermore, the outlet liquid removal device includes two liquid removal rollers and a liquid removal roller base, and the surfaces of the two liquid removal rollers are covered with fluororubber or silicone rubber.

[0017] Furthermore, the diameter of the liquid removal roller is 100-200mm, the length is the same as the extraction roller of the extraction tank, the surface finish is ≥13, and the two liquid removal rollers are arranged one above the other and installed at a certain angle.

[0018] On the other hand, the present invention also provides a process for reducing internal stress and membrane surface defects in wet-process diaphragms, which involves extraction by installing the aforementioned device in an extraction tank, and the steps are as follows:

[0019] Step 1: After stretching and shaping, the diaphragm enters the extraction inlet water seal tank, passes below the liquid surface at the inlet end, and then enters the extraction tank from the outlet of the water seal tank.

[0020] Step 2: After the diaphragm exits from the water seal tank outlet, it first passes through the inlet dewatering device. The dewatering roller scrapes off the oil-water mixture remaining on the diaphragm surface. During or before scraping, the position of the dewatering roller can be adjusted horizontally and vertically to adjust the angle of contact between the diaphragm and the roller, thereby adjusting the magnitude of the friction.

[0021] Step 3: After the diaphragm passes through the inlet dehydration device, it moves up and down in the extraction tank. At this time, the clamping rollers of the diaphragm flattening device apply lateral tension to the diaphragm to eliminate the shrinkage internal stress caused by the disappearance of the pore-forming agent during the extraction process.

[0022] Step 4: After being flattened in multiple stages, the diaphragm comes to the extraction outlet. Due to inertia, the diaphragm coming out of the outlet carries the extractant. At this time, the extractant on both sides of the diaphragm is scraped off by the outlet liquid removal device.

[0023] Step 5: After multiple stages of flattening and liquid removal, the diaphragm enters the drying oven for drying.

[0024] The beneficial effects of this invention are: by adding clamping rollers, this invention can eliminate the internal force of the diaphragm, and the device has a simple structure and low cost. The internal stress generated by the diaphragm during the transmission process will be eliminated, thereby effectively realizing the production of low internal stress wet diaphragms; at the same time, this device can effectively flatten the diaphragm, and also reduce defects in the diaphragm production process.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the installation of the device of the present invention;

[0027] Figure 2This is a schematic diagram of the inlet dewatering device of the present invention;

[0028] Figure 3 This is a front view of the diaphragm flattening device of the present invention;

[0029] Figure 4 This is a side view of the diaphragm flattening device of the present invention;

[0030] Figure 5 This is a top view of the diaphragm flattening device of the present invention;

[0031] Figure 6 This is a schematic diagram of the outlet liquid removal device of the present invention.

[0032] The markings in the diagram are as follows: 1-Water seal tank, 2-Extraction tank, 3-Inlet dewatering device, 301-Dewatering roller base, 302-Dewatering roller, 303-Lifting frame, 304-Slide rail, 305-Coupling, 4-Diaphragm flattening device, 401-Base plate, 402-Clamping roller, 403-Slider, 404-Slide rail, 405-Gear, 406-Rack, 407-Gear shaft, 408-Crossbar, 409-Firming plate, 410-Welding plate, 411-Main fixing plate, 412-Guide chamfer, 413-Spring, 5-Outlet liquid removal device, 501-Liquid removal roller, 502-Liquid removal roller base. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] like Figure 1 As shown, an apparatus for reducing internal stress and surface defects in wet-process diaphragms includes an inlet dewatering device 3, a diaphragm flattening device 4, and an outlet liquid removal device 5. The inlet dewatering device 3 is located inside the inlet of the extraction tank 2 and is used to scrape off the oil-water mixture carried out from the water seal liquid due to inertia on the diaphragm surface. The outlet liquid removal device 5 is located outside the outlet of the extraction tank 2 and is used to scrape off the extractant carried out from both sides of the diaphragm due to inertia. The diaphragm flattening devices 4 are symmetrically arranged in pairs on both sides inside the extraction tank 2 and are used to clamp the diaphragm on both sides to apply lateral tension to the diaphragm.

[0036] like Figure 2As shown, the inlet dewatering device 3 includes a dewatering roller 302 and a dewatering roller base 301. The dewatering roller 302 is vertically and vertically mounted on the dewatering roller base 301. The diameter of the dewatering roller 302 is 120-200mm, its length is the same as the extraction roller in the extraction tank, and its surface finish is ≥13. After installation, the center position of the dewatering roller 302 is 0-100mm lower than the center of the first roller at the inlet of the extraction tank. The dewatering roller base 301 is equipped with a scale and a lifting frame 303. The lifting frame 303 drives the dewatering roller to move up and down. Specifically, the lifting frame 303 adopts an existing scissor-type structure. The inlet dewatering device 3 effectively scrapes off the oil-water mixture carried out from the water seal fluid due to inertia on the surface of the oil film by the reverse friction force generated between the diaphragm and the dewatering roller 302 during the diaphragm operation, reducing diaphragm defects caused by the oil-water mixture being carried into the later stage.

[0037] like Figures 3 to 5 As shown, the diaphragm flattening device 4 includes two sets of parallel clamping rollers 402, a base plate 401, and a sliding adjustment mechanism. The sliding adjustment mechanism includes a slide rail 404, a slider 403, and a drive gear set. The slide rail 404 is mounted on the base plate 401, and the slider 403 is slidably mounted on the slide rail 404. The two sets of clamping rollers 402 are connected to the slider 403. The drive gear set drives the slider 403 to move on the slide rail 404, thereby driving the two sets of clamping rollers 402 to move.

[0038] Specifically, the drive gear set includes a rack 406, a gear 405, and a gear shaft 407. The rack 406 is mounted on a base plate 401. The gear 405 is mounted on the bottom end of the gear shaft 407 and meshes with the rack 406. The gear shaft 407 is vertically mounted on the slider 403 via a bearing, and a crossbar 408 is mounted on the upper end of the gear shaft 407. The base plate 401 is mounted on one end of a rib 409, and a welding plate 410 is fixedly connected to the other end of the rib 409. A main fixing plate 411 is fixed on the welding plate 410.

[0039] Preferably, the end of the clamping roller 402 is provided with a guide chamfer 412 to facilitate the entry of the diaphragm into the space between the two rollers, and the two sets of clamping rollers are clamped by springs 413.

[0040] The diaphragm flattening device allows for manual adjustment of the slider's position on the slide rail, enabling the clamping rollers to move left and right according to the diaphragm width. This device is installed laterally on both sides of the middle of the extraction tank, along the direction of diaphragm movement. The contact distance between the diaphragm and the clamping rollers is approximately 50-100mm from the edge. By using the clamping rollers to laterally flatten the diaphragm, it effectively releases the internal stress generated by the diaphragm's retraction after the extraction of the pore-forming agent, reducing diaphragm wrinkling and facilitating the precipitation of the pore-forming agent.

[0041] like Figure 6As shown, the outlet liquid removal device includes two liquid removal rollers 501 and a liquid removal roller base 502. The surfaces of the two liquid removal rollers 501 are covered with fluororubber or silicone rubber. The diameter of the liquid removal rollers 501 is 100-200mm, the length is the same as the extraction roller of the extraction tank, and the surface finish is ≥13. The two liquid removal rollers 501 are arranged vertically and installed at a certain angle, so that the two rollers scrape off the extractant carried out by inertia from both sides of the diaphragm in opposite directions. The use of rubber material for the liquid removal rollers 501 can effectively avoid condensation caused by the temperature difference of the roller surface due to the evaporation of the extractant, and reduce the membrane surface defects caused by water vapor condensation on the roller surface after the roller surface temperature drops due to the evaporation of the extractant.

[0042] Example 2

[0043] A process for reducing internal stress and surface defects in wet-process membranes involves extraction using the apparatus described in Example 1 within an extraction tank. The steps are as follows:

[0044] Step 1: After stretching and shaping, the diaphragm enters the extraction inlet water seal tank, passes below the liquid surface at the inlet end, and then enters the extraction tank from the outlet of the water seal tank.

[0045] Step 2: After the diaphragm exits from the water seal tank outlet, it first passes through the inlet dewatering device. The dewatering roller scrapes off the oil-water mixture remaining on the diaphragm surface. During or before scraping, the position of the dewatering roller can be adjusted horizontally and vertically to adjust the angle of contact between the diaphragm and the roller, thereby adjusting the magnitude of the friction.

[0046] Step 3: After the diaphragm passes through the inlet dehydration device, it moves up and down in the extraction tank. After the pore-forming agent in the diaphragm is extracted and precipitated after passing through the extraction liquid, the diaphragm shrinks. At this time, the clamping rollers of the diaphragm flattening device apply lateral tension to the diaphragm to eliminate the shrinkage internal stress caused by the disappearance of the pore-forming agent during the extraction process.

[0047] Step 4: After being flattened in multiple stages, the diaphragm comes to the extraction outlet. Due to inertia, the diaphragm coming out of the outlet carries the extractant. At this time, the extractant on both sides of the diaphragm is scraped off by the outlet liquid removal device.

[0048] Step 5: After multiple stages of flattening and liquid removal, the diaphragm enters the drying oven for drying.

[0049] This invention introduces a scraping and flattening device. The specific process flow is as follows: The stretched oil film is drawn into the extraction device. Due to the high viscosity of paraffin oil, the complexity of the extraction process increases significantly. This process removes moisture from the diaphragm surface through the inlet reverse dehydration roller, increasing the contact area between the diaphragm and the extractant. The reverse tension applied to the diaphragm by the flattening roller at the inlet of each extraction tank eliminates the shrinkage stress caused by the disappearance of the pore-forming agent during the extraction process. When the diaphragm reaches the extraction outlet, the extractant carried away by inertia is scraped off by the heated reverse dehydration roller device, effectively reducing extractant loss and diaphragm defects caused by pore-forming agent residue on the extractant surface carried away by the diaphragm's inertia.

[0050] In summary, the wet-process diaphragm prepared using this extraction process fundamentally eliminates the causes of residual stress and surface defects within the diaphragm, effectively reducing internal stress and surface defects. Furthermore, the inlet dewatering device, diaphragm flattening device, and outlet liquid removal device can be used in combination or separately to achieve different effects.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the scope of protection of the present invention in any way, and all technical solutions obtained by equivalent substitution or other means fall within the scope of protection of the present invention. Parts not covered in this invention are the same as or can be implemented using existing technology.

Claims

1. A device for reducing internal stress and surface defects in wet-process diaphragms, characterized in that, The extraction tank includes an inlet dehydration device, a diaphragm flattening device, and an outlet dehydration device. The inlet dehydration device is located inside the inlet of the extraction tank and is used to scrape away the oil-water mixture carried out from the water seal fluid by inertia from the diaphragm surface. The inlet dehydration device includes a dehydration roller and a dehydration roller base. The dehydration roller is vertically and flexibly mounted on the dehydration roller base, which is equipped with a scale and a lifting frame. The lifting frame drives the dehydration roller to move up and down. The outlet dehydration device is located outside the outlet of the extraction tank and is used to scrape away the extractant carried out by inertia from both sides of the diaphragm. The outlet dehydration device includes two dehydration rollers and a dehydration roller base. The surfaces of the two dehydration rollers... The membrane is covered with fluororubber or silicone rubber. The diaphragm flattening devices are symmetrically arranged in pairs on both sides of the inside of the extraction tank. The diaphragm flattening devices are used to clamp the two sides of the diaphragm and apply lateral tension to the diaphragm. They include two sets of parallel clamping rollers, a base plate, and a sliding adjustment mechanism. The sliding adjustment mechanism includes a slide rail, a slider, and a drive gear set. The slide rail is mounted on the base plate, and the slider is slidably mounted on the slide rail. The two sets of clamping rollers are connected to the slider. The drive gear set drives the slider to move on the slide rail, thereby driving the two sets of clamping rollers to move. The ends of the clamping rollers are provided with guide chamfers to facilitate the diaphragm entering between the two rollers, and the two sets of clamping rollers are clamped by springs.

2. The device for reducing internal stress and membrane surface defects in wet-process diaphragms according to claim 1, characterized in that, The drive gear set includes a rack, a gear, and a gear shaft. The rack is mounted on a base plate, the gear is mounted on the bottom end of the gear shaft and meshes with the rack, the gear shaft is vertically mounted on the slider via a bearing, and a crossbar is mounted on the upper end of the gear shaft.

3. The device for reducing internal stress and membrane surface defects in wet-process diaphragms according to claim 1, characterized in that, The base plate is installed at one end of the stiffening plate, and a welding plate is fixedly connected to the other end of the stiffening plate. A main fixing plate is fixed on the welding plate.

4. The device for reducing internal stress and membrane surface defects in wet-process diaphragms according to claim 1, characterized in that, The diameter of the dewatering roller is 120-200mm, the length is the same as the extraction roller of the extraction tank, the surface finish is ≥13, and after installation, the center position of the dewatering roller is 0-100mm lower than the center of the first roller at the inlet of the extraction tank.

5. The device for reducing internal stress and membrane surface defects in wet-process diaphragms according to claim 1, characterized in that, The lifting frame adopts a scissor-type structure.

6. The device for reducing internal stress and membrane surface defects in wet-process diaphragms according to claim 1, characterized in that, The diameter of the liquid removal roller is 100-200mm, the length is the same as the extraction roller of the extraction tank, the surface finish is ≥13, and the two liquid removal rollers are arranged one above the other and installed at a certain angle.

7. A process for reducing internal stress and surface defects in wet-process diaphragms, characterized in that, Extraction is performed by installing the apparatus as described in any one of claims 1 to 6 in an extraction tank, with the following steps: Step 1: After stretching and shaping, the diaphragm enters the extraction inlet water seal tank, passes below the liquid surface at the inlet end, and then enters the extraction tank from the outlet of the water seal tank. Step 2: After the diaphragm exits from the water seal tank outlet, it first passes through the inlet dewatering device. The dewatering roller scrapes off the oil-water mixture remaining on the diaphragm surface. During or before scraping, the position of the dewatering roller can be adjusted horizontally and vertically to adjust the angle of contact between the diaphragm and the roller, thereby adjusting the magnitude of the friction. Step 3: After the diaphragm passes through the inlet dehydration device, it moves up and down in the extraction tank. At this time, the clamping rollers of the diaphragm flattening device apply lateral tension to the diaphragm to eliminate the shrinkage internal stress caused by the disappearance of the pore-forming agent during the extraction process. Step 4: After being flattened in multiple stages, the diaphragm comes to the extraction outlet. Due to inertia, the diaphragm coming out of the outlet carries the extractant. At this time, the extractant on both sides of the diaphragm is scraped off by the outlet liquid removal device. Step 5: After multiple stages of flattening and liquid removal, the diaphragm enters the drying oven for drying.

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