Device and process for reducing internal stress and membrane surface defects of wet process membrane

Abstract

The invention discloses a device and a process for reducing internal stress and membrane surface defects of a wet process membrane, the device comprises an inlet water removal device, a membrane flattening device and an outlet liquid removal device, the inlet water removal device is arranged in an inlet of an extraction tank and is used for scraping an oil-water mixture brought out from a water seal liquid due to inertia on the surface of the membrane, and the outlet liquid removal device is used for removing the membrane surface defects; the outlet liquid removing device is arranged on the outer side of an outlet of the extraction tank and used for scraping an extracting agent brought out by inertia from the two sides of a diaphragm, and the diaphragm flattening devices are symmetrically arranged on the two sides of the interior of the extraction tank in pairs and used for clamping the two sides of the diaphragm to apply transverse tension to the diaphragm, and each diaphragm flattening device comprises a clamping roller, a bottom plate and a sliding adjusting mechanism; the sliding adjusting mechanism comprises a sliding rail, a sliding block and a driving gear set, and the driving gear set can drive the sliding block to move on the sliding rail so as to drive the two sets of clamping rollers to move. The internal stress generated in the transmission process of the diaphragm can be eliminated, so that the production of the low-internal-stress wet diaphragm is effectively realized, and the defects in the diaphragm production process are reduced.

Description

Technical Field

[0001] The invention relates to a device and a process for reducing internal stress and membrane surface defects of a wet-process diaphragm, and belongs to the field of lithium battery diaphragm production and manufacturing. Background Art

[0002] Lithium batteries are mainly composed of four key materials: positive electrode, negative electrode, electrolyte, and diaphragm. The diaphragm, as a key material in battery production, is mainly used to isolate the positive and negative electrodes, avoid short circuits inside the battery, provide channels for ion transfer between the positive and negative electrodes, and ensure the completion of the lithium ion charging and discharging process. Under abnormal conditions, the diaphragm can automatically close the pores to isolate ion transfer and avoid safety accidents.

[0003] At present, there are two main types of diaphragms on the market: wet method and dry method. In the wet method, during the production process, the equipment will stretch the casting and diaphragm in different directions and under different temperatures and tension conditions. According to the principle of force and energy transmission, the force and energy generated by the equipment will eventually accumulate in the diaphragm and cannot be released, eventually becoming internal stress that remains inside the diaphragm, causing the diaphragm product to crack, curl or change in material size in the next production process.

[0004] Secondly, the current wet-process diaphragm production process is mainly: casting → longitudinal stretching → transverse stretching 1 → extraction → transverse stretching 2 → winding → primary slitting → packaging; in the extraction section, the oil film that has been stretched longitudinally and transversely directly enters the extraction tank. In order to prevent the extractant from leaking or volatilizing, a water seal is set at the extraction entrance. After the oil film passes through the water seal, a large amount of oil-water mixture will be carried on the surface. During the operation of the diaphragm, the oil-water mixture will be carried into the entire extraction section with the diaphragm, and may eventually form oil spots on the roller surface from the diaphragm to the drying section. After the diaphragm contacts the oil spots, the diaphragm will produce continuous bright spots. In addition, after the diaphragm passes through the extraction section, the pore-forming agent that occupies the position in the oil film is replaced by the extractant, and the diaphragm will shrink, and then the state of stress on the diaphragm will change; at the same time, the temperature during the extraction process is different from the temperature during the stretching process. Therefore, during the continuous operation of the diaphragm, stress will accumulate inside the diaphragm.

[0005] Therefore, firstly, the diaphragm with internal stress will crack or curl during the processing, resulting in a decrease in the qualified rate of the diaphragm products; secondly, if the diaphragm with strong residual internal stress is used to produce lithium-ion batteries, it may cause the battery to deform during the charging and discharging process, and the battery safety performance cannot be guaranteed.

[0006] In summary, in order to reduce the losses of diaphragm manufacturers and enhance the safety performance of batteries, it is imperative to design and develop a production process that reduces the internal stress and membrane surface defects of wet-process diaphragms, and it must be able to effectively solve the problems in the existing diaphragm production process. Summary of the invention

[0007] The object of the present invention is to provide a device and process for reducing internal stress and membrane surface defects of a wet-process diaphragm, so as to overcome the shortcomings of the current prior art.

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

[0009] On the one hand, the present invention provides a device for reducing internal stress and membrane surface defects of a wet-process diaphragm, which includes 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 to scrape off the oil-water mixture brought out of the water sealing liquid on the surface of the diaphragm due to inertia. The outlet liquid removal device is arranged outside the outlet of the extraction tank, and is used to scrape off the extractant brought out on both sides of the diaphragm due to inertia. The diaphragm flattening devices are symmetrically arranged on both sides of the interior of the extraction tank. The diaphragm flattening device is used to clamp both sides of the diaphragm to apply lateral tension to the diaphragm. It includes two groups of clamping rollers, a bottom plate and a sliding adjustment mechanism arranged in parallel. The sliding adjustment mechanism includes a slide rail, a slider and a driving gear set. The slide rail is installed on the bottom plate, and the slider is slidably installed on the slide rail. The two groups of clamping rollers are connected to the slider, and the driving gear set drives the slider to move on the slide rail and then drives the two groups of clamping rollers to move.

[0010] Furthermore, the driving 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 through a bearing, and a cross bar is installed on the upper end of the gear shaft.

[0011] Furthermore, the bottom plate is installed on one end of the rib plate, and the other end of the rib plate is fixedly connected to a welding plate, and a total fixing plate is fixed on the welding plate.

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

[0013] Furthermore, the inlet dewatering device comprises a dewatering roller and a dewatering roller base, and the dewatering roller is installed on the dewatering roller base in a liftable manner.

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

[0015] Furthermore, the dewatering roller base is provided with a scale and a lifting frame, and the dewatering roller is driven to move up and down by the lifting frame, and 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 wrapped with fluororubber or silicone rubber.

[0017] Furthermore, the diameter of the liquid removal roller is 100-200 mm, the length is consistent with the extraction roller of the extraction tank, the surface finish is ≥ level 13, and the two liquid removal rollers are arranged up and down and installed at a certain angle.

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

[0019] Step 1: The stretched and shaped 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 the water seal tank outlet, it first passes through the inlet water removal device, and the water removal roller scrapes the oil-water mixture remaining on the diaphragm membrane surface; during or before scraping, the position of the water removal roller can be adjusted horizontally and vertically to adjust the contact angle between the diaphragm and the roller, thereby adjusting the magnitude of the friction force;

[0021] Step 3, after the diaphragm passes through the inlet water removal device, it is driven up and down in the extraction tank. At this time, the diaphragm is subjected to lateral tension by the clamping roller of the diaphragm flattening device to eliminate the shrinkage internal stress of the diaphragm caused by the disappearance of the pore-forming agent during the extraction process;

[0022] Step 4: After being flattened for multiple stages, the diaphragm reaches the extraction outlet. The diaphragm coming out of the outlet carries the extractant due to inertia. 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 a drying furnace for drying.

[0024] The beneficial effects of the present invention are as follows: the present invention can eliminate the internal force of the diaphragm by adding a clamping roller, 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-process diaphragms; at the same time, the device can achieve effective flattening of the diaphragm and can also reduce defects in the diaphragm production process.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 2It is a structural schematic diagram of the inlet water removal device of the present invention;

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

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

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

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

[0032] Marked in the figure: 1-water seal tank, 2-extraction tank, 3-inlet water removal device, 301-water removal roller base, 302-water removal roller, 303-lifting frame, 304-slide rail, 305-coupling, 4-diaphragm flattening device, 401-bottom plate, 402-clamping roller, 403-sliding block, 404-slide rail, 405-gear, 406-rack, 407-gear shaft, 408-cross bar, 409-rib 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 DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Embodiment 1

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

[0036] like Figure 2As shown, the inlet water removal device 3 includes a water removal roller 302 and a water removal roller base 301, and the water removal roller 302 can be lifted and lowered on the water removal roller base 301. The diameter of the water removal roller 302 is 120-200mm, and the length is consistent with the extraction roller of the extraction tank. The surface finish is ≥ level 13. After installation, the center position height of the water removal roller 302 is 0-100mm lower than the center of the first roller at the entrance of the extraction tank. The water removal roller base 301 is provided with a scale and a lifting frame 303, and the water removal roller is driven to move up and down by the lifting frame 303. Specifically, the lifting frame 303 adopts an existing scissor-type structure. The inlet water removal device 3 can effectively scrape off the oil-water mixture brought out of the water sealing liquid due to inertia on the surface of the oil film through the reverse friction force generated by the water removal roller 302 during the operation of the diaphragm, thereby reducing the diaphragm defects caused by the oil-water mixture being brought into the rear section.

[0037] like Figures 3 to 5 As shown, the diaphragm flattening device 4 includes two groups of parallelly arranged 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 driving gear set, the slide rail 404 is installed on the base plate 401, the slider 403 is slidably installed on the slide rail 404, the two groups of clamping rollers 402 are connected to the slider 403, and the driving gear set drives the slider 403 to move on the slide rail 404 and then drives the two groups of clamping rollers 402 to move.

[0038] Specifically, the driving gear set includes a rack 406, a gear 405 and a gear shaft 407. The rack 406 is mounted on the bottom plate 401. The gear 405 is mounted at 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 through a bearing, and a crossbar 408 is mounted on the upper end of the gear shaft 407. The bottom plate 401 is mounted on one end of the rib plate 409, and the other end of the rib plate 409 is fixedly connected to a welding plate 410, and a total fixing plate 411 is fixed on the welding plate 410.

[0039] Preferably, the ends of the clamping rollers 402 are provided with guide chamfers 412 for facilitating the membrane to enter between the two rollers, and the two sets of clamping rollers are clamped by springs 413 .

[0040] The membrane flattening device can manually adjust the position of the slider on the slide rail, and then realize the left and right movement of the clamping roller according to the width of the membrane. The device is installed on both sides of the middle of the extraction tank along the direction of the membrane. The contact distance between the membrane and the clamping roller is about 50-100mm from the edge. The membrane is flattened horizontally by the clamping roller, which can effectively release the internal stress generated by the membrane shrinkage after the pore-forming placeholder is extracted, reduce the formation of wrinkles on the membrane, and facilitate the precipitation of the pore-forming agent.

[0041] like Figure 6As shown, the outlet deliquidation device comprises two deliquidation rollers 501 and a deliquidation roller base 502, and the surfaces of the two deliquidation rollers 501 are wrapped with fluororubber or silicone rubber. The diameter of the deliquidation roller 501 is 100-200 mm, and the length is consistent with the extraction roller of the extraction tank, and the surface finish is ≥13 level. The two deliquidation rollers 501 are arranged up and down and installed at a certain angle, so that the two rollers can scrape the extractant brought out by inertia on both sides of the diaphragm in opposite directions. The deliquidation rollers 501 are made of rubber material, which can effectively avoid condensed water caused by the roller surface temperature difference caused by the volatilization of the extractant, and reduce the membrane surface defects caused by the condensation of water vapor on the roller surface after the roller surface temperature is reduced due to the volatilization of the extractant.

[0042] Embodiment 2

[0043] A process for reducing internal stress and membrane surface defects of a wet-process diaphragm, wherein the device described in Example 1 is installed in an extraction tank for extraction, and the steps are as follows:

[0044] Step 1: The stretched and shaped 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 the water seal tank outlet, it first passes through the inlet water removal device, and the water removal roller scrapes the oil-water mixture remaining on the diaphragm membrane surface; during or before scraping, the position of the water removal roller can be adjusted horizontally and vertically to adjust the contact angle between the diaphragm and the roller, thereby adjusting the magnitude of the friction force;

[0046] Step 3: After the diaphragm passes through the inlet water removal device, it is driven 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 diaphragm is subjected to a lateral tension by the clamping roller of the diaphragm flattening device to eliminate the shrinkage internal stress of the diaphragm caused by the disappearance of the pore-forming agent during the extraction process;

[0047] Step 4: After being flattened for multiple stages, the diaphragm reaches the extraction outlet. The diaphragm coming out of the outlet carries the extractant due to inertia. 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 a drying furnace for drying.

[0049] The process of the present invention introduces a scraping and flattening device, and the specific process flow is: the stretched oil film is pulled into the extraction device. Since the viscosity of the paraffin oil is too high, the process complexity in the extraction process increases in large proportion. This process removes moisture on the surface of the diaphragm through the inlet reverse water removal roller, thereby 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 internal stress of the diaphragm caused by the disappearance of the pore-forming agent during the extraction process; when the diaphragm runs to the extraction outlet, the extractant carried away by inertia passes through the heated reverse liquid removal roller device and is scraped away, which can effectively reduce the loss of the extractant and reduce the diaphragm defects caused by the pore-forming agent residues on the surface of the extractant brought out by the inertia of the diaphragm movement.

[0050] In summary, the wet-process diaphragm prepared by the extraction process fundamentally eliminates the residual stress inside the diaphragm and the causes of surface defects, and effectively reduces the internal stress and surface defects of the wet-process diaphragm. At the same time, the three groups of devices, namely the inlet water removal device, the diaphragm flattening device and the outlet liquid removal device, can be used in combination or separately to achieve different effects.

[0051] The above shows and describes 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 protection scope of the present invention in any form, and all technical solutions obtained by equivalent replacement and the like fall within the protection scope of the present invention. The parts not involved in the present invention are the same as the prior art or can be implemented by the prior art.

Claims

1. A device for reducing internal stress and membrane surface defects of a wet-process diaphragm, characterized in that: It includes 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 the extraction tank and is used to scrape off the oil-water mixture brought out of the water sealing liquid due to inertia on the surface of the diaphragm. The outlet liquid removal device is arranged outside the outlet of the extraction tank and is used to scrape off the extractant brought out from the two sides of the diaphragm due to inertia. The diaphragm flattening devices are symmetrically arranged on both sides of the inside of the extraction tank. The diaphragm flattening device is used to clamp the two sides of the diaphragm to apply lateral tension to the diaphragm. It includes two groups of clamping rollers, a bottom plate and a sliding adjustment mechanism arranged in parallel. The sliding adjustment mechanism includes a slide rail, a slider and a driving gear set. The slide rail is installed on the bottom plate, and the slider is slidably installed on the slide rail. The two groups of clamping rollers are connected to the slider. The driving gear set drives the slider to move on the slide rail and then drives the two groups of clamping rollers to move.

2. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 1, characterized in that: The driving gear set includes a rack, a gear and a gear shaft, the rack is installed on the bottom plate, the gear is installed at the bottom end of the gear shaft and meshes with the rack, the gear shaft is vertically installed on the slider through a bearing, and a cross bar is installed at the upper end of the gear shaft.

3. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 1, characterized in that: The bottom plate is installed on one end of the rib plate, and the other end of the rib plate is fixedly connected with a welding plate, and the welding plate is fixed with a total fixing plate.

4. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 1, characterized in that: The ends of the clamping rollers are provided with guide chamfers for facilitating the membrane to enter between the two rollers, and the two groups of clamping rollers are clamped by springs.

5. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 1, characterized in that: The inlet dewatering device comprises a dewatering roller and a dewatering roller base, and the dewatering roller is installed on the dewatering roller base in a liftable manner.

6. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 5, characterized in that: The diameter of the dewatering roller is 120-200mm, the length is consistent with the extraction roller of the extraction tank, the surface finish is ≥ level 13, and after installation, the center position height of the dewatering roller is 0-100mm lower than the center of the first roller at the entrance of the extraction tank.

7. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 5, characterized in that: The dewatering roller base is provided with a scale and a lifting frame, and the dewatering roller is driven to move up and down by the lifting frame, and the lifting frame adopts a scissor-type structure.

8. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 1, characterized in that: The outlet liquid removal device comprises two liquid removal rollers and a liquid removal roller base, and the surfaces of the two liquid removal rollers are wrapped with fluororubber or silicone rubber.

9. The device for reducing internal stress and membrane surface defects of a wet-process diaphragm according to claim 8, characterized in that: The diameter of the liquid removal roller is 100-200 mm, the length is consistent with the extraction roller of the extraction tank, the surface finish is ≥ level 13, and the two liquid removal rollers are arranged up and down and installed at a certain angle.

10. A process for reducing internal stress and membrane surface defects of a wet-process diaphragm, characterized in that: The extraction tank is equipped with the device according to any one of claims 1 to 9 for extraction, and the steps are as follows: Step 1: The stretched and shaped 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 the water seal tank outlet, it first passes through the inlet water removal device, and the water removal roller scrapes the oil-water mixture remaining on the diaphragm membrane surface; during or before scraping, the position of the water removal roller can be adjusted horizontally and vertically to adjust the contact angle between the diaphragm and the roller, thereby adjusting the magnitude of the friction force; Step 3, after the diaphragm passes through the inlet water removal device, it is driven up and down in the extraction tank. At this time, the diaphragm is subjected to lateral tension by the clamping roller of the diaphragm flattening device to eliminate the shrinkage internal stress of the diaphragm caused by the disappearance of the pore-forming agent during the extraction process; Step 4: After being flattened for multiple stages, the diaphragm reaches the extraction outlet. The diaphragm coming out of the outlet carries the extractant due to inertia. 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 a drying furnace for drying.

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