PP (Polypropylene) capsule filter element for filtering lithium battery slurry as well as preparation and application of PP capsule filter element

Abstract

The invention provides a PP capsule filter element for filtering lithium battery slurry, preparation and application. The method comprises the following steps: S11, providing a PP filter membrane, wherein the air permeability range of the PP filter membrane is 2800m < 2 > / s-5200m < 2 > / s; s12, winding the PP filter membrane into a hollow cylinder, and then welding at a seam to form a hollow PP coiled material column; s13, the hollow PP coiled material column is cut into multiple sections according to the preset size; s14, a first end cover and a second end cover are provided, the two ends of the hollow PP coiled material column are subjected to end sealing treatment through the first end cover and the second end cover, and the first end cover is provided with a first through hole communicating with the hollow pipeline; and S15, the hollow PP coiled material column with the sealed end is sealed in a shell to form the PP capsule filter element, the shell comprises a water inlet and a water outlet, the water outlet is communicated with the first through hole, a water passing channel is formed between the hollow PP coiled material column and the shell, and the water passing channel is communicated with the water inlet.

Description

Technical Field

[0001] This application relates to the field of filter element manufacturing technology, and in particular to a PP capsule filter element for lithium battery slurry filtration, its preparation and application. Background Technology

[0002] In the manufacturing process of lithium-ion batteries, in order to ensure the continuous and effective operation of coating, it is necessary to filter the positive and negative electrode slurries to intercept large particles.

[0003] CN206214865U discloses a filter element for filtering lithium battery slurry. The filter element has a three-layer structure, consisting of a stainless steel support body, a stainless steel filter screen with a specific mesh size, and a polypropylene fixed outer mesh from the inside out. The support body, filter screen, and fixed outer mesh are coaxially arranged. Both the support body and the fixed outer mesh are hollow structures. The filter screen is wrapped around the surface of the support body by manual wrapping and is fixed by the fixed outer mesh. The stainless steel support body has annular grooves on the outer walls at both ends, threaded holes on the inner wall, and an open cylindrical wall in the middle.

[0004] However, this filter cartridge uses a single layer of polypropylene, relying on the thickness direction to intercept particles; the filtration accuracy is determined solely by the basis weight / pore size of the felt, making it impossible to create a gradient capture within the same filter cartridge. This results in large particles larger than 100 μm directly impacting the surface, forming a "filter cake" on the surface in a short time, causing a rapid increase in pressure differential, thus significantly reducing the lifespan of a single cartridge (NCM 523 slurry, solid content 55%, flow rate 3 L / min). -1 (Measured data). Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by providing a PP capsule filter element for lithium battery slurry filtration, its preparation, and its application.

[0006] The technical solution of this application is implemented as follows: This invention provides a method for preparing a PP capsule filter element for lithium battery slurry filtration, comprising: S11, a PP (polypropylene) filter membrane is provided, wherein the air permeability range of the PP filter membrane is 2800 μm. 2 / s~5200m 2 / s, the flexural strength of the PP filter membrane is 45N / 5cm~420N / 5cm, the elongation at break of the PP filter membrane is 16%~40%, and the hardness of the PP filter membrane is 0.03mN~9mN; S12, the PP filter membrane is wound into a hollow cylinder, and then welded at the seam to form a hollow PP roll column; S13, the hollow PP roll column is cut into multiple segments according to a predetermined size; S14, a first end cap and a second end cap are provided to seal both ends of the hollow PP roll column. The first end cap has a first through hole that connects to the hollow pipe. S15, the end-sealed hollow PP roll column is sealed in the shell to form a PP capsule filter element, wherein the shell includes an inlet and an outlet, and the outlet is connected to the first through hole, and a water passage is formed between the hollow PP roll column and the shell, and the water passage is connected to the inlet.

[0007] As a further improvement, the air permeability of the PP filter membrane is 2850~2950 μm. 2 / s, 3450~3550m 2 / s, 3600~3700m 2 / s, 3850~3950m 2 / s, 4100~4200m 2 / s, 4350~4450m 2 / s, 4650~4750m 2 / s, 5100~5200m 2 / s; the unit area mass of the PP filter membrane is 95~105g / m². 2 70~80g / m 2 55~65g / m 2 45~55g / m 2 38~42g / m 2 28~32g / m 2 18~22g / m 2 8~12g / m 2 The flexural strengths of the PP filter membranes are as follows: 380~420 N / 5cm, 260~280 N / 5cm, 230~240 N / 5cm, 165~175 N / 5cm, 125~135 N / 5cm, 90~100 N / 5cm, 60~70 N / 5cm, and 45~55 N / 5cm; the elongation at break of the PP filter membranes is as follows: 38~40%. 35~37%, 33~34%, 29~31%, 25~28%, 23~24%, 20~21%, 16~18%; the corresponding hardnesses of the PP filter membranes are 6~9mN, 3.5~4.5mN, 2.0~3.0mN, 1.4~1.8mN, 0.8~1.2mN, 0.5~0.7mN, 0.15~0.25mN, and 0.03~0.06mN, respectively.

[0008] As a further improvement, in step S14, the first end cap and the second end cap are integrally formed as circular sheet structures that are adapted to the two end faces of the hollow PP roll column, and are welded to the two end faces of the hollow PP roll column by hot-melt welding around the periphery of the circular sheet structure for end sealing.

[0009] As a further improvement, the outer diameter of the hollow PP roll column is defined as r, and the inner diameter of the shell is defined as R, wherein 1.5 × r ≥ R ≥ 1.1 × r.

[0010] As a further improvement, R is 1.2xr.

[0011] As a further improvement, the housing consists of a cylindrical body and a cover that mates with the cylindrical body, and the cylindrical body and the cover are sealed by hot-melt welding.

[0012] As a further improvement, the PP filter membrane is formed from filaments with a diameter of 37 micrometers. The present invention further provides a PP capsule filter element for filtering lithium battery slurry, wherein the PP capsule filter element is prepared by the above-described method.

[0013] The present invention further provides an application of the above-mentioned PP capsule filter element in lithium battery slurry filtration.

[0014] The advantages or beneficial effects of the above technical solutions include at least the following: The present invention provides a PP capsule filter element for lithium battery slurry filtration, its preparation, and its application. The air permeability of the PP filter membrane in the filter element is in the range of 2800 μm. 2 / s to 5200m 2 / s, thus effectively filtering particles of 5μm~200μm in lithium battery slurry; in addition, under the same operating conditions, the pressure difference rise rate of the filter element of the present invention is reduced by 82%, thereby significantly extending its service life, which is about 4-6 times that of the prior art. Furthermore, the PP capsule filter element used for lithium battery slurry filtration, its preparation and application are all carried out by hot melt welding, completely eliminating epoxy adhesive and meeting the "zero adhesive" specifications of power battery customers; after soaking in DMC for 72 hours, the total organic carbon (TOC) detected by ICP-MS is <5 ppm, which is lower than the 47 ppm of the adhesive sample in CN206214865U.

[0015] Finally, the filter element of the present invention has a smooth surface, an elongation at break of 16%~40%, a flexural strength of 45N / 5cm~420N / 5cm, and can withstand 100 cycles of 0.4 MPa reverse pulse; the particle residue rate after cleaning is <1%, enabling more than 10 cycles of use, which greatly reduces the cost of use. Attached Figure Description

[0016] The accompanying drawings illustrate exemplary embodiments of the present application and, together with the description thereof, serve to explain the principles of the present application. These drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification.

[0017] Figure 1 A flowchart illustrating the preparation method of a PP capsule filter element for lithium battery slurry filtration provided in an embodiment of the present invention is shown.

[0018] Figure 2 This diagram illustrates the liquid flow direction during use of a PP capsule filter element for lithium battery slurry filtration provided in an embodiment of the present invention.

[0019] Figure 3 The bar chart shows the particle distribution of the PP capsule filter element for lithium battery slurry filtration provided in the embodiment of the present invention at various particle sizes before filtration.

[0020] Figure 4 The bar chart shows the particle distribution of the PP capsule filter element for lithium battery slurry filtration provided in the embodiment of the present invention at various particle sizes after filtration. Detailed Implementation

[0021] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this application. It should be understood that the drawings and embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0022] It should be noted that, where there is no conflict, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] The names of the messages or information exchanged between multiple devices in the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0024] Reference Figure 1This invention provides a method for preparing a PP capsule filter element for lithium battery slurry filtration, comprising the following steps: S11, a PP filter membrane (polypropylene filter membrane) 10 is provided, wherein the air permeability range of the PP filter membrane 10 is 2800 μm. 2 / s~5200m 2 / s, the flexural strength of the PP filter membrane 10 is 45N / 5cm to 420N / 5cm, the elongation at break of the PP filter membrane 10 is 16% to 40%, and the hardness of the PP filter membrane 10 is 0.03mN to 9mN.

[0025] Preferably, the air permeability of the PP filter membrane can be 2850~2950 μm. 2 / s, 3450~3550m 2 / s, 3600~3700m 2 / s, 3850~3950m 2 / s, 4100~4200m 2 / s, 4350~4450m 2 / s, 4650~4750m 2 / s, 5100~5200m 2 / s; the corresponding unit area mass is 95~105g / m². 2 70~80g / m 2 55~65g / m 2 45~55g / m 2 38~42g / m 2 28~32g / m 2 18~22g / m 2 8~12g / m 2 The corresponding bending strengths are: 380~420N / 5cm, 260~280N / 5cm, 230~240N / 5cm, 165~175N / 5cm, 125~135N / 5cm, 90~100N / 5cm, 60~70N / 5cm, 45~55N / 5cm; the corresponding elongation at break are: 38~40%, 35~37%, 33~34%, 29~31%, 25~28%, 23~24%, 20~21%, 16~18%; the corresponding hardnesses are: 6~9mN, 3.5~4.5mN, 2.0~3.0mN, 1.4~1.8mN, 0.8~1.2mN, 0.5~0.7mN, 0.15~0.25mN, 0.03~0.06mN.

[0026] S12, the PP filter membrane 10 is wound into a hollow cylinder, and then welded at the seam 110 to form a hollow PP roll column 11. The number of winding layers is not specific; for example, it can be 10 to 100 layers, and can be produced according to the required precision.

[0027] In step S12, a hollow PP roll column 11 is radially formed into a hollow channel 112, the diameter of which is 10mm to 100mm. Preferably, the diameter of the hollow channel 112 is 40mm to 80mm. In one embodiment, the diameter of the hollow channel 112 is 65mm.

[0028] The welding can be achieved through hot melt welding.

[0029] Preferably, during the winding process, a mesh support can be further added between the two layers of PP filter membrane 10, so that the mesh support serves as a support for the PP filter membrane 10. The mesh support can be at least partially disposed between the two layers of PP filter membrane 10, which can effectively increase the dirt-holding capacity of the filter element.

[0030] S13, the hollow PP roll column 11 is cut into multiple segments according to a predetermined size.

[0031] In step S13, the cutting method is not limited. It can be cut by a knife or by laser heating, etc. There are no restrictions here.

[0032] S14, a first end cap 12 and a second end cap 13 are provided, wherein the first end cap 12 has a first through hole 120 communicating with the hollow pipe 112, and the two ends of the hollow PP roll column 11 are end-sealed by the first end cap 12 and the second end cap 13.

[0033] It is understood that through the end-sealing treatment of the first end cap 12 and the second end cap 13, one end of the end-sealing treatment is sealed, and the other end is connected to the first through hole 120, thereby forming a water channel. The end-sealing treatment can be achieved by snap-fit, adhesive, or hot-melt welding, etc., and is not limited here. Preferably, the end-sealing treatment can be achieved by hot-melt welding. Specifically, the first end cap 12 and the second end cap 13 are generally circular plate-shaped structures adapted to the two end faces of the hollow PP roll column 11. Therefore, they can be welded to the two end faces of the hollow PP roll column 11 by hot-melt welding around the perimeter of the circular plate-shaped structure. In order to improve the welding strength of hot-melt welding, preferably, cross-patterned energy-conducting ribs are injection molded on the end faces of the first end cap 12 and the second end cap 13, wherein the rib height is 0.25 mm, the top width is 0.15 mm, the cross angle is 60°, and the surface knurling depth is 0.10 mm. The textured valleys of the energy-conducting ribs can lock the melt, reducing flash by more than 55% while simultaneously meeting the TOC ≤ 5ppm requirement. During welding, a "bite" followed by "melt" method is used. Specifically, the first stage is 30 µm, 1.5 s, allowing the cross-shaped ribs to "bite" into the main body; the second stage is 45 µm, 3.5 s, completing the melting; the total time is 5 s, 28% shorter than the constant amplitude 7 s, resulting in a 30% reduction in heat-affected zone thickness and a 1.8-fold increase in fatigue life. Furthermore, a servo motor can be used to drive the welding head, changing the pressure curve to a three-step pattern of 0.35 MPa --> 0.20 MPa --> 0.30 MPa; the staged pressure reduction allows the melt to fully wet the textured valleys, followed by pressure increase to expel air bubbles, reducing porosity from 3.2% to 0.4%, and achieving a leak-free seal at 1.0 MPa for 30 min.

[0034] S15, the end-sealed hollow PP roll column 11 is sealed in the housing to form a PP capsule filter element. The housing includes an inlet 151 and an outlet 150, with the outlet 150 communicating with a first through hole 120. A water passage 140 is formed between the hollow PP roll column 11 and the housing, and the water passage 140 communicates with the inlet 151. In other embodiments, a vent 142 may be further included to remove gas from the filter element.

[0035] Preferably, the outer diameter of the hollow PP roll column 11 is defined as r, and the inner diameter of the shell is defined as R, where R > r. More preferably, 1.5 × r ≥ R ≥ 1.1 × r. In one embodiment, R is 1.2 × r, which can form a good water passage space. Generally speaking, the narrower the flow channel, the greater the resistance. However, in this invention, when the gap is about 0.2 r, the fluid is forced to form a thin annular high-speed shear layer, continuously thinning the "concentration polarization-filter cake" on the filter element surface; the equivalent filtration resistance decreases, the overall pressure difference decreases instead of increasing, and the resistance decreases. In addition, a narrow gap of about 0.2 r will generate 0.4–0.8 ms -1 With the local tangential velocity, particles larger than 200 µm are "thrown" back into the main fluid in the annular gap, with only 10% getting stuck in the weld or end cap dead corner; while with wide gaps (>0.5 r), this proportion is as high as 60%. As a result, the lifespan of a single hollow PP roll column 11 can be increased by more than 20% (wide gap = 0.5 r), and the accumulation of large particles visible to the naked eye during disassembly and inspection almost disappears.

[0036] In one embodiment, the housing comprises a cylindrical body 14 and a cover 15 that mates with the cylindrical body 14. The cylindrical body 14 is used to accommodate the hollow PP roll column 11. The outlet 150 and the inlet 151 are located at the same end of the cylindrical body 14. The cylindrical body 14 and the cover 15 can be sealed together by heat fusion welding, threads, or other snap fasteners.

[0037] Please see Figure 2 As shown, this embodiment of the invention further provides a PP capsule filter element for lithium battery slurry filtration obtained by the above method, comprising: The housing includes an inlet 151 and an outlet 150; A hollow PP roll column 11 is housed in the housing. The hollow PP roll column 11 has a hollow pipe 112, and a water passage 140 is formed between the hollow PP roll column 11 and the housing, which communicates with the water inlet 151. The hollow PP roll column 11 is formed by winding PP filter membrane and then welding it at the seam 110. A first end cap 12 and a second end cap 13 are sealed at both ends of the hollow PP roll column 11. The first end cap 12 has a first through hole 120 that communicates with the hollow pipe 112 and the first through hole 120 communicates with the water outlet 150.

[0038] The air permeability range of the PP filter membrane is 2800 μm. 2 / s to 5200m 2 / s, and the corresponding bending strength is 45N / 5cm~420N / 5cm, the corresponding elongation at break is 16%~40%, and the corresponding hardness is 0.03mN~9mN.

[0039] Preferably, the air permeability of the PP filter membrane 10 is 2850~2950 μm. 2 / s, 3450~3550m 2 / s, 3600~3700m 2 / s, 3850~3950m 2 / s, 4100~4200m 2 / s, 4350~4450m 2 / s, 4650~4750m 2 / s, 5100~5200m 2 / s; the unit area mass of the PP filter membrane 10 is 95~105g / m². 2 70~80g / m 2 55~65g / m 2 45~55g / m 2 38~42g / m 2 28~32g / m 2 18~22g / m 2 8~12g / m 2 The flexural strengths of the PP filter membrane 10 are as follows: 380~420 N / 5cm, 260~280 N / 5cm, 230~240 N / 5cm, 165~175 N / 5cm, 125~135 N / 5cm, 90~100 N / 5cm, 60~70 N / 5cm, and 45~55 N / 5cm; the elongation at break of the PP filter membrane 10 is as follows: 38~40%. The hardness of the PP filter membrane 10 is 35-37%, 33-34%, 29-31%, 25-28%, 23-24%, 20-21%, and 16-18%, respectively; the hardness of the PP filter membrane 10 is 6-9 mN, 3.5-4.5 mN, 2.0-3.0 mN, 1.4-1.8 mN, 0.8-1.2 mN, 0.5-0.7 mN, 0.15-0.25 mN, and 0.03-0.06 mN, respectively. More preferably, in one embodiment, the air permeability of the PP filter membrane can be 2900 m. 2 / s, 3500m 2 / s, 3660m 2 / s, 3900m 2 / s, 4150m 2 / s, 4400m 2 / s, 4700m 2 / s or 5150m 2 / s.

[0040] The PP capsule filter element provided by this invention is mainly used to filter large particles in lithium battery slurry. Therefore, the air permeability of the PP filter membrane needs to meet the above conditions.

[0041] However, in order to further improve the service life of the PP capsule filter element, other performance parameters of the PP filter membrane are shown in Table 1.

[0042] Table 1 shows the material parameters of different types of PP filter membranes.

[0043] As can be seen from the table above, the air permeability of the PP filter membrane is 2900m. 2 / s, 3500m 2 / s, 3660m 2 / s, 3900m 2 / s, 4150m 2 / s, 4400m 2 / s, 4700m 2 / s, 5150m 2 / s; their unit area mass corresponds to 100g / m² 2 75g / m 2 60g / m 2 50g / m 2 40g / m 2 30g / m 2 20g / m 2 10g / m 2 The flexural strengths are 400N / 5cm, 270N / 5cm, 235N / 5cm, 170N / 5cm, 127N / 5cm, 96N / 5cm, 67N / 5cm, and 49N / 5cm, respectively. The elongation at break is 39%, 37%, 34%, 31%, 27%, 24%, 21%, and 17%, respectively. The hardness is 8mN, 4mN, 2.5mN, 1.5mN, 1mN, 0.6mN, 0.2mN, and 0.05mN, respectively. All PP filter membranes are made of 37-micron diameter threads. The outer layer has a hardness of 8 mN, while the inner layer has a hardness of 0.05 mN. After hot pressing, the compression rebound of each layer is different, automatically filling the 0.05–0.1 mm assembly gap to avoid leakage. This ensures that no visible bypass penetration is achieved under 1.0 MPa static pressure for 30 minutes.

[0044] Example: In this embodiment of the invention, an A3 type PP filter membrane is used, and different winding turns are controlled to filter battery slurry with different particle sizes, as shown in Table 1.

[0045]

[0046] Test example: Please see Figure 3-4 As shown, Figure 3 This shows the particle distribution of lithium battery slurry at various particle sizes before filtration. Figure 4 The figure shows the particle distribution of lithium battery slurry at various particle sizes after filtration. As can be seen from the figure, the PP capsule filter element provided by this invention can achieve a filtration efficiency of over 50% for particles smaller than 100 micrometers, and over 85% for particles larger than 100 micrometers; and has a 100% interception and filtration efficiency for particles larger than 150 micrometers.

[0047] Regeneration: First, backwash with 60-70℃ hot water for 3-5 min (to remove 85% of PVDF sludge); then, sonicate with 12-17 wt% food-grade methyl lactate (boiling point 144℃) + 0.2-0.5 wt% quaternary ammonium salt surfactant at 30-50℃ for 5-30 min; finally, recover methyl lactate by closed-circuit flash evaporation (recovery rate 98%, energy consumption reduced by 60% compared to DMC distillation). The final filter cartridge TOC residue is less than 1.8 ppm, lower than the customer limit of 5 ppm.

[0048] Those skilled in the art should understand that the above embodiments are merely for illustrative purposes and are not intended to limit the scope of this application. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of this application.

Claims

1. A method for preparing a PP capsule filter element for lithium battery slurry filtration, characterized in that: include: S11, a PP filter membrane is provided, wherein the air permeability range of the PP filter membrane is 2800 μm. 2 / s~5200m 2 / s, the flexural strength of the PP filter membrane is 45N / 5cm~420N / 5cm, the elongation at break of the PP filter membrane is 16%~40%, and the hardness of the PP filter membrane is 0.03mN~9mN; S12, the PP filter membrane is wound into a hollow cylinder, and then welded at the seam to form a hollow PP roll column; S13, the hollow PP roll column is cut into multiple segments according to a predetermined size; S14, a first end cap and a second end cap are provided to seal both ends of the hollow PP roll column. The first end cap has a first through hole that connects to the hollow pipe. S15, the end-sealed hollow PP roll column is sealed in the shell to form a PP capsule filter element, wherein the shell includes an inlet and an outlet, and the outlet is connected to the first through hole, and a water passage is formed between the hollow PP roll column and the shell, and the water passage is connected to the inlet.

2. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 1, characterized in that: The air permeability of the PP filter membrane is 2850~2950 μm. 2 / s, 3450~3550m 2 / s, 3600~3700m 2 / s, 3850~3950m 2 / s, 4100~4200m 2 / s, 4350~4450m 2 / s, 4650~4750m 2 / s, 5100~5200m 2 / s; the unit area mass of the PP filter membrane is 95~105g / m². 2 70~80g / m 2 55~65g / m 2 45~55g / m 2 38~42g / m 2 28~32g / m 2 18~22g / m 2 8~12g / m 2 The flexural strengths of the PP filter membranes are as follows: 380~420 N / 5cm, 260~280 N / 5cm, 230~240 N / 5cm, 165~175 N / 5cm, 125~135 N / 5cm, 90~100 N / 5cm, 60~70 N / 5cm, and 45~55 N / 5cm; the elongation at break of the PP filter membranes is as follows: 38~40%. 35~37%, 33~34%, 29~31%, 25~28%, 23~24%, 20~21%, 16~18%; the corresponding hardnesses of the PP filter membranes are 6~9mN, 3.5~4.5mN, 2.0~3.0mN, 1.4~1.8mN, 0.8~1.2mN, 0.5~0.7mN, 0.15~0.25mN, and 0.03~0.06mN, respectively.

3. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 1, characterized in that: In step S14, the first end cap and the second end cap are integrally formed as circular sheet structures that fit the two end faces of the hollow PP roll column, and are welded to the two end faces of the hollow PP roll column by hot-melt welding along the periphery of the circular sheet structure for end sealing.

4. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 3, characterized in that: Cross-shaped energy-conducting ribs are injection molded onto the end faces of the first and second end caps. During the welding process, welding is performed by first biting and then melting.

5. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 1, characterized in that: The outer diameter of the hollow PP roll column is defined as r, and the inner diameter of the shell is defined as R, wherein 1.5 × r ≥ R ≥ 1.1 × r.

6. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 4, characterized in that: R is 1.2xr.

7. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 1, characterized in that: The shell consists of a cylindrical body and a cover that mates with the cylindrical body, and the cylindrical body and the cover are sealed by hot-melt welding.

8. The method for preparing a PP capsule filter element for lithium battery slurry filtration according to claim 1, characterized in that: The PP filter membrane is made of filaments with a diameter of 37 micrometers.

9. A PP capsule filter element for lithium battery slurry filtration, characterized in that: The PP capsule filter element is prepared by the method described in any one of claims 1-8.

10. An application of the PP capsule filter element as described in claim 9 in lithium battery slurry filtration.

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