Extraction device for reducing number of wrinkle bright lines in wet diaphragm extraction

Abstract

The invention discloses an extraction device for reducing the number of wrinkled bright lines in wet diaphragm extraction, the device comprises a plurality of groove bodies which are sequentially arranged from front to back, the first groove body is a partition groove, and the second groove body and the groove body at the rear side of the second groove body are extraction grooves; according to the diaphragm extraction movement direction, the depth of the tank body of the first extraction tank is lower than that of the tank body of the second extraction tank, and the depth of the tank body of the second extraction tank is lower than that of the tank body of the third extraction tank; except the first extraction tank, each extraction tank is provided with an overflow outlet for the extraction agent to flow out, and the top height of the overflow outlet of any extraction tank is lower than that of the overflow outlet of the extraction tank on the rear side, so that the extraction agent can flow into the extraction tank on the front side through overflow to form counter-current extraction; at least one lower guide roller is arranged in the lower part of each extraction tank, and at least one upper guide roller is arranged above each extraction tank. By adopting the device disclosed by the invention, the number of wrinkled bright lines during wet-process lithium battery diaphragm extraction can be reduced to two or less, and even the wrinkled bright lines are completely eliminated.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery separator technology, specifically relating to an extraction device that reduces the number of wrinkles and bright lines in wet separator extraction. Background Technology

[0002] Lithium-ion batteries, as an important means of modern energy storage, consist of core components including positive electrode materials, negative electrode materials, electrolyte, and separator. The separator is a crucial component; its main function is to separate the positive and negative electrodes, preventing direct contact that could lead to short circuits and safety issues. Simultaneously, the separator provides a channel for electrolyte ions, ensuring their free movement, which is essential for the battery's charging and discharging processes.

[0003] As a core component of lithium batteries, the quality of the separator has a decisive impact on battery performance. An ideal separator must possess five key characteristics: uniform thickness (ensuring consistent electric field within the cell), excellent mechanical properties (resisting manufacturing and operational stresses), outstanding permeability (creating efficient ion channels), stable physicochemical properties (resistant to electrolyte corrosion and dimensionally constant), and high safety (high-temperature closed-cell flame retardancy). Extraction of wrinkles and bright lines during the wet process can cause closed-cell phenomena on the separator surface, potentially leading to three risks: localized short circuits at the bright lines, failure of the cell to pass the high-voltage insulation test (Hi-pot test), and material scrapping and reduced yield. Therefore, strictly controlling such defects is a crucial measure to improve the long-term operational reliability of the separator, reduce safety risks, and ultimately achieve a synergistic enhancement of the overall performance and safety of the battery system.

[0004] The wet-process separator extraction process is carried out in an extraction tank containing an extractant (dichloromethane). An oil film containing oil (paraffin oil) enters the extraction tank, and the oil is extracted from the oil film by the extractant. To ensure complete extraction of the oil film, multiple extraction tanks are typically used, with the oil film passing through them sequentially. The extractant enters from the last extraction tank and exits from the first, continuously entering and exiting at a constant flow rate. In existing extraction devices, the depth of each extraction tank is uniform. To achieve extraction with a smaller extractant circulation volume, CN 212383225 U (Suzhou Jieli New Energy Materials Co., Ltd., 2020.6.3) discloses an extraction device for wet-process lithium-ion battery separators. This device lowers the bottom of the front extraction tank and deepens the first two extraction tanks, increasing the capacity and extraction ability of the front extraction tank. This allows extraction to be achieved with a smaller dichloromethane circulation volume, saving extractant usage and improving extraction efficiency. However, this device does not reduce or decrease the number of bright lines and wrinkles in the wet-process separator extraction process.

[0005] Therefore, there is an urgent need to develop an extraction device to solve the problem of extracting wrinkles and bright lines in wet-process diaphragm products, and to improve the technical problem of extracting wrinkles and bright lines in wet-process diaphragm products. Summary of the Invention

[0006] The present invention relates to an extraction apparatus that reduces the number of wrinkles and bright lines in wet membrane extraction.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention claims protection for an extraction device that reduces the number of wrinkles and bright lines in wet membrane extraction. The device includes multiple tanks arranged sequentially from front to back, the first tank being a partition tank, and the second and subsequent tanks being extraction tanks.

[0009] According to the direction of the diaphragm extraction movement, the depth of the first extraction tank is lower than the depth of the second extraction tank, and the depth of the second extraction tank is lower than the depth of the third extraction tank.

[0010] Except for the first extraction tank, each of the extraction tanks has an overflow outlet for the extractant to flow out. The top height of the overflow outlet of any extraction tank is lower than the top height of the overflow outlet of the extraction tank behind it, so that the extractant can flow into the extraction tank in front of it through the overflow, forming countercurrent extraction. The bottom of the last extraction tank is provided with an extractant inlet, and the overflow outlet of the first extraction tank is provided with an extractant discharge pipe.

[0011] Each extraction tank has at least one lower guide roller in its lower part to guide the diaphragm and immerse it below the liquid surface, and at least one upper guide roller in its upper part to draw the extracted diaphragm out from above the liquid surface.

[0012] Furthermore, the partition groove is used to block the volatilization and dispersion of the gaseous extractant in the rear extraction tank and the tension conduction of the diaphragm; the upper wall of the partition groove is provided with a gaseous extractant outlet, which is connected to an exhaust device for discharging and recovering the gaseous extractant; the bottom of the partition groove is provided with an extractant stratification drainage tank for stratifying the extractant; the extractant discharge pipe at the overflow outlet of the first extraction tank is connected to the extractant stratification drainage tank.

[0013] Furthermore, the number of extraction tanks is 3-15 (for example, it can be 3, 5, 7, 9, 11, 13, or 15).

[0014] Furthermore, the third extraction tank has the same depth as any of the extraction tanks behind it.

[0015] Furthermore, two adjacent extraction tanks are separated by a partition, and the overflow outlet is formed on the upper surface of the partition. The upper surface of the rear partition is higher than the upper surface of the front partition.

[0016] Furthermore, the width of each groove is equal.

[0017] Furthermore, the height of the bottom of the partition tank may be equal to or different from the height of the bottom of the first extraction tank behind it.

[0018] Furthermore, the depth of the first extraction tank is half the depth of the second extraction tank; the depth of the second extraction tank is two-thirds the depth of the third extraction tank.

[0019] The first tank of the multi-stage extraction device designed in this invention is a partition tank, without any built-in liquid or extractant. It is used to prevent the volatilization and escape of gaseous extractant in subsequent tanks (extraction tanks) and to block the tension conduction of the diaphragm. The extractant enters from the end extraction tank and is conveyed forward to the first extraction tank through overflow. The extractant discharge pipe at the overflow outlet of the first extraction tank is connected to the extractant stratified discharge tank for recovering the extractant overflowing from the first extraction tank. The partition tank is independent of the extractant circulation path and is gas-phase isolated only by a gaseous extractant recovery device.

[0020] The multi-stage extraction device of the present invention achieves the purpose of stepped extraction by reducing the depth of the first and second extraction tanks, which significantly reduces the extraction rate of paraffin oil in the diaphragm at the extraction inlet (first and second extraction tanks), reduces the diaphragm shrinkage rate of the extraction inlet rollers, and at the same time, the reduction of tank depth helps to reduce the force surface of the extractant flow on the diaphragm, reduce the operating resistance of the diaphragm at the extraction inlet, thereby reducing extraction wrinkles.

[0021] The beneficial effects of this invention are:

[0022] Existing extraction devices can produce more than six wrinkled bright lines during transverse extraction, which cannot be completely eliminated. The device of this invention can reduce the number of wrinkled bright lines during wet lithium battery separator extraction to two or less, or even eliminate them completely. Attached Figure Description

[0023] Figure 1 A three-dimensional structural diagram of an extraction device for solving the problem of wrinkled bright lines in wet membrane extraction.

[0024] Figure 2 Internal structure diagram of the extraction device used to solve the problem of wrinkled bright lines in wet diaphragm extraction.

[0025] Among them, 1-partition tank, 2-extraction tank, 3-overflow outlet, 4-partition plate, 5-extractant inlet, 6-extractant discharge pipe, 7-lower guide roller, 8-upper guide roller, 9-diaphragm, 10-gas extractant outlet, 11-extractant stratified discharge tank, 12-diaphragm inlet. Detailed Implementation

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Example 1: An extraction device for solving the problem of wrinkles and bright lines in wet membrane extraction.

[0028] like Figure 1 and Figure 2 As shown, an extraction device for reducing the number of wrinkles and bright lines in wet membrane extraction is provided. The device includes nine tanks arranged sequentially from front to back. The width of each tank is equal. The first tank is a partition tank 1, and the second and the tanks behind it are extraction tanks 2.

[0029] Following the direction of the diaphragm extraction movement, the depth of the first extraction tank is lower than the depth of the second extraction tank, and the depth of the second extraction tank is lower than the depth of the third extraction tank; the third extraction tank has the same depth as the other extraction tanks behind it; specifically, the depth of the first extraction tank is half the depth of the second extraction tank; the depth of the second extraction tank is two-thirds the depth of the third extraction tank.

[0030] Except for the first extraction tank, each extraction tank has an overflow outlet 3 for the extractant to flow out. The top height of the overflow outlet of any extraction tank is lower than the top height of the overflow outlet of the extraction tank behind it, so that the extractant can flow into the extraction tank in front through overflow, forming countercurrent extraction. Specifically, two adjacent extraction tanks are separated by a partition 4. The overflow outlet 3 is formed on the upper end face of the partition 4. The upper end face of the rear partition is higher than the upper end face of the front partition. The lower part of the last extraction tank is provided with an extractant inlet 5, and the overflow outlet of the first extraction tank is provided with an extractant discharge pipe 6.

[0031] At least one lower guide roller 7 is provided in the lower part of each extraction tank to guide the diaphragm 9 and immerse it below the liquid surface, and at least one upper guide roller 8 is provided above each extraction tank to draw the extracted diaphragm out from above the liquid surface.

[0032] Furthermore, the partition trough 1 is used to block the volatilization and escape of the gaseous extractant in the subsequent extraction tank 2 and the tension conduction of the diaphragm; a gaseous extractant outlet 10 is provided on the upper wall of the partition trough, which is connected to an exhaust device for discharging and recovering the gaseous extractant, thereby preventing the volatilization and escape of the extractant in the subsequent extraction tanks; the structure of the exhaust device is a conventional structure known to those skilled in the art, and therefore is not shown in the drawings. The bottom of the partition trough 1 is provided with an extractant stratification drainage tank for extractant stratification, and the extractant discharge pipe at the overflow outlet of the first extraction tank is connected to the extractant stratification drainage tank 11. The height of the bottom of the partition trough 1 is equal to the height of the bottom of the first extraction tank 2 behind it.

[0033] The first tank of the multi-stage extraction device designed in this invention is a partition tank, without any built-in liquid or extractant. It is used to prevent the volatilization and escape of gaseous extractant in subsequent tanks (extraction tanks) and to block the tension conduction of the diaphragm. The extractant enters from the end extraction tank and is conveyed forward stage by stage through overflow to the first extraction tank. The extractant discharge pipe at the overflow outlet of the first extraction tank is connected to the extractant stratified discharge tank for recovering the extractant overflowing from the first extraction tank. The partition tank is independent of the extractant circulation path and is gas-phase isolated only through a gaseous extractant recovery device. During extraction, the diaphragm enters the partition tank 2 from the diaphragm inlet 12 located on the partition tank 1, and is then guided into the subsequent extraction tank 2 via the upper guide roller 8 and lower guide roller 7 located in the partition tank 1, undergoing multi-stage extraction.

[0034] The multi-stage extraction device of the present invention achieves the purpose of stepped extraction by reducing the depth of the first and second extraction tanks, which significantly reduces the extraction rate of paraffin oil in the diaphragm at the extraction inlet (first and second extraction tanks), reduces the diaphragm shrinkage rate of the extraction inlet rollers, and at the same time, the reduction of tank depth helps to reduce the force surface of the extractant flow on the diaphragm, reduce the operating resistance of the diaphragm at the extraction inlet, thereby reducing extraction wrinkles.

[0035] The existing extraction device for wet-process lithium-ion battery separators has the following structure: the first tank (partition tank) is filled with water to prevent the extractant from escaping from the second and subsequent tanks (extraction tanks). The second tank and the subsequent tanks (extraction tanks) have the same height and depth. The extractant enters from the bottom of the last tank, overflows into the second tank (first extraction tank), and then overflows into the extractant stratification drainage tank at the bottom of the partition tank.

[0036] The number of wrinkled bright lines in the lithium battery separator extraction results are shown in Table 1, comparing the two batches of wet lithium battery separator extraction performed using the extraction device in Example 1 with the two batches of extraction performed using an existing extraction device.

[0037] Table 1 compares the extraction efficiency of wet lithium-ion battery separators using the extraction device in Example 1 with existing extraction devices.

[0038] Case Device Horizontal extraction of wrinkled bright lines Bright line regularity Implementation Case 1 The device of the present invention 2 intermittent Implementation Case 2 The device of the present invention 0 / Comparative Example 1 Existing equipment 6 Continuity, indirectness Comparative Example 2 Existing equipment 10 Continuity, indirectness .

[0039] In summary, existing extraction devices can produce more than six wrinkled bright lines during lateral extraction, which cannot be completely eliminated. The device of this invention can reduce the number of wrinkled bright lines during wet lithium battery separator extraction to two or less, or even eliminate them completely.

Claims

1. An extraction apparatus for reducing the number of extraction crease bright lines in a wet separator membrane, characterized by, The device comprises a plurality of tanks arranged in sequence from front to back, the first tank is a partition tank, and the second and the following tanks are extraction tanks; According to the direction of the diaphragm extraction movement, the depth of the tank of the first extraction tank is lower than the depth of the tank of the second extraction tank, and the depth of the tank of the second extraction tank is lower than the depth of the tank of the third extraction tank; Each of the extraction tanks has an overflow outlet for the outflow of the extractant except the first extraction tank, the lower part of the last extraction tank is provided with an extractant inlet, and the overflow outlet of the first extraction tank is provided with an extractant discharge pipe; The lower part of each extraction tank is provided with at least one lower guide roller to guide and immerse the diaphragm below the liquid surface, and the upper part of each extraction tank is provided with at least one upper guide roller to guide the extracted diaphragm out of the liquid surface.

2. The extraction device of claim 1, wherein, The top height of the overflow outlet of any of the extraction tanks is lower than the top height of the overflow outlet of the extraction tank behind it, so that the extractant can flow into the extraction tank in front through overflow, forming countercurrent extraction.

3. The extraction device of claim 1, wherein, The partition tank is used to block the volatilization of gaseous extractant in the extraction tank behind and the tension transmission of the diaphragm.

4. The extraction device of claim 3, wherein, A gaseous extractant outlet is arranged on the upper part of the tank wall of the partition tank, which is connected with an exhaust device for exhausting and recycling gaseous extractant, and the bottom of the partition tank is provided with an extractant layering drain tank for layering the extractant, and the extractant discharge pipe at the overflow outlet of the first extraction tank is connected with the extractant layering drain tank.

5. The extraction device of claim 1, wherein, The number of the extraction tanks is 3-15.

6. The extraction device according to claim 1 or 5, characterized in that The depth of the third extraction tank is the same as that of any extraction tank behind it.

7. The extraction device of claim 1, wherein, Two adjacent extraction tanks are separated by a partition, and the overflow outlet is formed on the upper end face of the partition, and the upper end face height of the partition behind is higher than that of the partition in front.

8. The extraction device of claim 1, wherein, The widths of the tank bodies are equal.

9. The extraction device of claim 1, wherein, The height of the bottom of the partition tank is equal to or not equal to the height of the bottom of the first extraction tank behind it.

10. The extraction device of claim 1, wherein, The depth of the first extraction tank is half of the depth of the second extraction tank, and the depth of the second extraction tank is two-thirds of the depth of the third extraction tank.

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