Polyester release film for lithium battery diaphragm and preparation system thereof

Abstract

The utility model discloses a polyester release film for a lithium battery diaphragm, which comprises a PET (polyethylene terephthalate) base film, a release agent layer and an active coating, the release agent layer is positioned on one side of the PET base film, the active coating is positioned on the other side of the PET base film, the thickness of the PET base film is 12-25 mu m, the thickness of the release agent layer is 0.1-1 mu m, and the thickness of the active coating is 1-5 mu m. The utility model further provides a preparation system of the polyester release film for the lithium battery diaphragm. According to the preparation system, the steps of large-scale production of the high-quality polyester release film for the lithium battery diaphragm, heat treatment, coating, drying, curing and the like can be matched with one another, it is guaranteed that all performance indexes of the film meet the requirements, continuous automatic production can be achieved through the whole equipment system, and the production efficiency is greatly improved.

Description

Technical Field

[0001] This utility model relates to a polyester release film for lithium battery separators and its preparation system. Background Technology

[0002] Release film is a crucial component in the production and use of lithium-ion battery separators. During production, it's typically used in steps such as coating, drying, and cutting. It prevents direct contact between the separator and production equipment or other materials, reducing adhesion and damage. When multiple separator layers are stacked, the release film prevents adhesion between layers, ensuring they don't stick together during storage and transportation. The release film is easily removed during separator cutting and shaping, ensuring the separator's integrity and performance. Using release film simplifies the production process, improves efficiency, and reduces scrap rates. Therefore, a release film specifically designed to match the production and usage environments of lithium-ion battery separators is needed.

[0003] No existing technology has documented or provided examples of the application of such a dedicated release film. Furthermore, there is no existing technology documenting the manufacturing technology or preparation system related to this release film. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide a polyester release film for lithium battery separators and its preparation system, so as to reduce or avoid the problems mentioned above.

[0005] To solve the above-mentioned technical problems, this utility model proposes a polyester release film for lithium battery separators, which is composed of a PET base film, a release agent layer on one side of the PET base film, and an active coating on the other side of the PET base film. The thickness of the PET base film is 12-25μm, the thickness of the release agent layer is 0.1-1μm, and the thickness of the active coating is 1-5μm.

[0006] This invention also proposes a preparation system for polyester release film for lithium battery separators, including a feed reel for conveying PET base film; a first tension adjusting wheel assembly is provided downstream of the feed reel; the PET base film is conveyed from the feed reel through the first tension adjusting wheel assembly into a hot air circulating oven; the PET base film after being processed in the hot air circulating oven is conveyed to a first coating machine; the PET base film after being coated with an active coating liquid in the first coating machine is further conveyed to a dryer; the PET base film after being processed in the dryer is further flipped and conveyed to a second coating machine; the PET base film after being coated with a release agent in the second coating machine is further conveyed to an oven; the release film after being cured in the oven is further conveyed through the second tension adjusting wheel assembly and finally conveyed to a winding machine.

[0007] Preferably, the hot air circulating oven is set to operate at a temperature of 80℃-120℃ and the heat treatment time is 30-60 minutes.

[0008] Preferably, the first coating machine includes a first coating roller located below the PET base film, the lower part of the first coating roller being immersed in the coating liquid in the first coating tank; a first agitator is provided in the first coating tank.

[0009] Preferably, the dryer is set to operate at a temperature of 40°C-60°C and the drying time is 30-60 minutes.

[0010] Preferably, a first rotating wheel is provided between the first coating machine and the dryer, and a second rotating wheel is provided between the dryer and the second coating machine. After the PET base film is output from the first coating machine, it turns 90 degrees through the first rotating wheel, and then the PET base film is output from the dryer and turns 90 degrees in the same direction through the second rotating wheel.

[0011] Preferably, the second coating machine includes a second coating roller located below the PET base film, the lower part of the second coating roller being immersed in the release agent in the second coating tank; a second agitator is provided in the second coating tank.

[0012] Preferably, the oven is set to operate at a temperature of 80℃-120℃ and the curing time is 30-60 minutes.

[0013] The preparation system described in this application can ensure the large-scale production of high-quality polyester release films for lithium battery separators. The heat treatment, coating, drying and curing steps work together to ensure that the various performance indicators of the film meet the requirements. The entire equipment system can achieve continuous automated production, which greatly improves production efficiency. Attached Figure Description

[0014] The accompanying drawings are intended only to illustrate and explain this application and do not limit the scope of this utility model.

[0015] Figure 1 The diagram shown is a structural schematic of a polyester release film for lithium battery separators according to a specific embodiment of the present invention.

[0016] Figure 2 The diagram shown is a structural schematic of a system for preparing a polyester release film for lithium battery separators according to a specific embodiment of the present invention. Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, specific embodiments are now described with reference to the accompanying drawings. Identical components are denoted by the same reference numerals.

[0018] like Figure 1As shown, this invention proposes a polyester release film for lithium battery separators, comprising a PET base film 100, a release agent layer 20 on one side of the PET base film 100, and an active coating 30 on the other side of the PET base film 100. In one specific embodiment, the thickness of the PET base film 100 is 12-25 μm, the thickness of the release agent layer 20 is 0.1-1 μm, and the thickness of the active coating 30 is 1-5 μm.

[0019] In one specific embodiment, the polyester release film for lithium battery separators of the present invention can be prepared by the following steps. For example, firstly, the PET base film is placed in a hot air circulating oven for heat treatment, with the temperature set at 80℃-120℃ and the heat treatment time at 30-60 minutes. During the treatment, it is ensured that the temperature is uniformly distributed to avoid local deformation of the film.

[0020] Pre-heat treatment can first improve the crystallinity of the PET base film, thereby enhancing its mechanical strength and high-temperature resistance, and improving the overall structural stability of the film; it also helps eliminate internal stress that may be generated during film preparation, thus improving the film's flexibility and resistance to deformation; and it can improve the PET film's resistance to chemical media, extending its service life in electrolyte environments. Secondly, it can improve the adhesion between the PET base film and the release agent coating during the subsequent coating and curing process, ensuring that the release agent is not easily detached under high-temperature environments.

[0021] Then, the prepared active coating solution is evenly coated on one side of the heat-treated PET base film and dried at 40℃-60℃ for 30-60 minutes to ensure that the coating is uniform and free of moisture.

[0022] Next, a release agent is coated on the other side of the PET base film and cured to obtain a release agent layer. The specific steps are as follows: the release agent coating liquid is coated on the other side of the PET base film using a coating machine, and the coated release film is placed in a temperature-controlled oven for curing to form a release agent layer. The curing temperature is set at 80℃-120℃ and the curing time is 30-60 minutes.

[0023] Remove the release film from the oven and allow it to cool at room temperature.

[0024] In one specific embodiment, the active coating liquid constituting the active coating 30 can be prepared from the following raw materials in parts by weight: 10-20 parts by weight of polyvinyl alcohol (PVA), 80-90 parts by weight of deionized water, and 0.5-2 parts by weight of polyvinyl alcohol ether. The polyvinyl alcohol can be PVA-117 or PVA-124, which are produced by companies such as Dow Chemical Company (USA), Eisman (Switzerland), and Kuraray Co., Ltd. (Japan).

[0025] The specific preparation process of the reactive coating solution is as follows: Add 10-20 parts by weight of PVA to 80-90 parts by weight of deionized water, and stir at 60°C for 1-2 hours until the PVA is completely dissolved, forming a transparent gel-like liquid. Add 0.5-2 parts by weight of polyvinyl alcohol ether to the liquid, and continue stirring for 30-60 minutes to obtain the reactive coating solution. Cool the prepared reactive coating solution to room temperature and store it in a clean container for later use.

[0026] In another specific embodiment, the release agent constituting the release agent layer 20 of the present invention can be prepared from the following raw materials in parts by weight: 50-70 parts by weight of polyvinyl fluoride (PVDF), 30-50 parts by weight of polyether ether ketone (PEEK), 0.5-1 parts by weight of butylated hydroxytoluene (BHT), 1-3 parts by weight of phthalate, and 100-200 parts by weight of N-methylpyrrolidone (NMP).

[0027] The specific preparation process of the release agent is as follows: In a clean mixing container, add 50-70 parts by weight of PVDF and 30-50 parts by weight of PEEK powder, and stir for 30-60 minutes to uniformly disperse the two polymers. Add 100-200 parts by weight of NMP to the mixture and stir with a stirrer until completely dissolved to form a uniform gel-like coating solution. Continue to add 0.5-1 parts by weight of BHT and 1-3 parts by weight of phthalate to the solution, and continue stirring for 30-60 minutes to obtain the release agent coating solution.

[0028] Corresponding to the above-described preparation process, this application proposes a system specifically designed for the preparation of the aforementioned polyester release film, such as... Figure 2 The diagram shown is a structural schematic of a system for preparing a polyester release film for lithium battery separators according to a specific embodiment of the present invention.

[0029] As shown in the figure, the preparation system of this utility model includes a feed reel 1 for conveying PET base film 100, used to hold large rolls of PET base film 100. To prevent the PET base film 100 from wrinkling or breaking during conveying, a first tension adjusting wheel assembly 2 is provided downstream of the feed reel 1. The PET base film 100 is conveyed from the feed reel 1 through the first tension adjusting wheel assembly 2 into the hot air circulating oven 3. The tension adjusting wheel assembly 2 adjusts according to the film thickness and speed to ensure a stable supply.

[0030] The hot air circulating oven 3 is used to heat-treat the PET base film 100 with hot air, eliminating internal stress and enhancing the crystallinity and mechanical strength of the base film. The hot air circulating oven 3 is set to operate at a temperature of 80℃-120℃ for 30-60 minutes.

[0031] The PET base film 100, after being processed by the hot air circulating oven 3, is conveyed to the first coating machine 4 for coating one side of the PET base film 100 with an active coating liquid. In the specific embodiment shown in the figure, the first coating machine 4 includes a first coating roller 41 located below the PET base film 100. The lower part of the first coating roller 41 is immersed in the coating liquid in the first coating tank 42, and the rotation of the first coating roller 41 is used to bring the coating liquid in the first coating tank 42 to the lower surface of the PET base film 100. In order to maintain the uniformity of the coating liquid, a first stirrer 43 is provided in the first coating tank 42.

[0032] After being coated with the active coating liquid by the first coating machine 4, the PET base film 100 is further conveyed to the dryer 5 for drying the active coating, ensuring no moisture residue and a uniform and firm coating. The dryer 5 is set to operate at a temperature of 40℃-60℃ for 30-60 minutes.

[0033] After being processed by the dryer 5, the PET base film 100 is further flipped and conveyed to the second coating machine 6 for coating the other side of the PET base film 100 with a release agent. In order to achieve coating on the other side of the PET base film 100, this application sets two flipping rollers to perform a flipping operation on the PET base film. Specifically, a first flipping roller 44 is set between the first coating machine 4 and the dryer 5, and a second flipping roller 64 is set between the dryer 5 and the second coating machine 6. After the PET base film 100 is output from the first coating machine 4, it makes a 90-degree turn by the first flipping roller 44. Then, the PET base film 100 is output from the dryer 5 and makes another 90-degree turn in the same direction by the second flipping roller 64. Through the two 90-degree turning operations of the two flipping rollers, the flipping of the PET base film 100 is finally achieved.

[0034] In the illustrated embodiment, the second coating machine 6 includes a second coating roller 61 located below the PET base film 100. The lower part of the second coating roller 61 is immersed in the release agent in the second coating tank 62, and is used to transfer the release agent in the second coating tank 62 to the lower surface of the PET base film 100 by the rotation of the second coating roller 61. In order to maintain the uniformity of the release agent, a second agitator 63 is provided in the second coating tank 62.

[0035] The PET base film 100, coated with release agent by the second coating machine 6, is further conveyed to the oven 7 for curing the base film coated with release agent, thereby improving the stability and durability of the release layer. The oven 7 is set to operate at a temperature of 80℃-120℃, with a curing time of 30-60 minutes.

[0036] After curing in oven 7, the release film is further conveyed through the second tension adjusting roller group 8, and finally to the winding machine 9, which winds the coated and cured release film into rolls for subsequent processing and use. The second tension adjusting roller group 8 is also designed to prevent air bubbles or wrinkles from forming during the winding process.

[0037] The preparation system described in this application can ensure the large-scale production of high-quality polyester release films for lithium battery separators. The heat treatment, coating, drying and curing steps work together to ensure that the various performance indicators of the film meet the requirements. The entire equipment system can achieve continuous automated production, which greatly improves production efficiency.

[0038] The polyester release film prepared using the preparation system of this application has the following performance parameters:

[0039] Tensile strength: 100-120MPa, elongation at break: 250-600%.

[0040] Heat distortion temperature: No deformation occurs within 160-250℃. It exhibits good resistance to acids, alkalis, and electrolytes. Chemical corrosion resistance test: No significant swelling or degradation occurs in lithium battery electrolyte.

[0041] Moisture permeability: 1-3 g / m 2 ·day, possesses excellent permeability.

[0042] The active coating has a hydrophilic contact angle of 20-50°, exhibiting excellent hydrophilicity and improving battery performance.

[0043] The active coating exhibits good adhesion in scratch tests and will not peel off during use, maintaining the overall performance of the release film.

[0044] The release force of the release agent layer is less than 20 g / cm, ensuring smooth peeling of the release film from the lithium battery separator during production and use without adhesion or resistance. In tape testing, the adhesion between the release agent layer and the PET base film is greater than 20 N / cm, preventing detachment during use. The release agent exhibits good resistance to lithium battery electrolytes (LiPF6, LiBF4 solutions), with no degradation or swelling observed in the battery environment. It passes chemical compatibility testing. The heat distortion temperature of the release agent layer is greater than 250℃, remaining stable without deformation or degradation under high-temperature conditions, ensuring reliability within the battery's operating temperature range. The coefficient of friction of the release agent layer is 0.1-0.3, a low coefficient that helps reduce friction between the film and battery components, improving production efficiency and reducing resistance during battery assembly. The air permeability of the release agent layer is 1-5 g / m³. 2 • Day allows electrolyte permeation and prevents gas buildup on the membrane.

[0045] Example 1

[0046] Preparation steps:

[0047] A PET base film with a thickness of 12μm was selected.

[0048] The PET base film was heat-treated at 80°C for 30 minutes.

[0049] Preparation of active coating solution: Add 10 parts by weight of PVA to 80 parts by weight of deionized water, stir at 60°C for 1 hour, then add 0.5 parts by weight of polyvinyl alcohol ether and continue stirring for 30 minutes.

[0050] The drying temperature after coating was set to 40℃ for 30 minutes. The thickness of the active coating was 1μm.

[0051] The other side is coated with a release agent, which consists of 50 parts by weight of PVDF, 30 parts by weight of PEEK, 0.5 parts by weight of BHT, 1 part by weight of phthalate and 100 parts by weight of NMP.

[0052] The curing conditions were 80℃ for 30 minutes. The release agent layer thickness was 0.1μm.

[0053] Effect:

[0054] The release force is approximately 18 g / cm.

[0055] Tensile strength is 100 MPa, elongation at break is 250%, and moisture permeability is 3 g / m³. 2 ·day.

[0056] It exhibits good thermal stability, remaining stable at 175℃. It also demonstrates excellent resistance to acids, alkalis, and electrolytes. Chemical corrosion resistance tests show no significant swelling or degradation in LiPF6 and LiBF4 solutions.

[0057] The active coating has a hydrophilic contact angle of 20° and exhibits good adhesion in scratch tests. It will not peel off during use and can maintain the overall performance of the release film.

[0058] The adhesion between the release agent layer and the PET base film is 25 N / cm; the heat deformation of the release agent layer is 263℃; the coefficient of friction of the release agent layer is 0.1; and the air permeability of the release agent layer is 1 g / m³. 2 ·day.

[0059] Example 2

[0060] Preparation steps:

[0061] A PET base film with a thickness of 18μm was selected.

[0062] Heat treatment was performed in a hot air circulating oven at 100°C for 45 minutes.

[0063] Preparation of active coating solution: Add 15 parts by weight of PVA to 85 parts by weight of deionized water, stir at 60°C for 1.5 hours, then add 1 part by weight of polyvinyl alcohol ether, and continue stirring for 45 minutes.

[0064] The drying temperature after coating is 50℃, and the drying time is 45 minutes. The thickness of the active coating is 3μm.

[0065] The release agent coated on the other side consists of 60 parts by weight of PVDF, 40 parts by weight of PEEK, 0.75 parts by weight of BHT, 2 parts by weight of phthalate and 150 parts by weight of NMP.

[0066] The curing temperature is 100℃, and the curing time is 45 minutes. The thickness of the release agent layer is 0.5μm.

[0067] Effect:

[0068] With a release force of 12g / cm, it is suitable for the production of lithium battery separators.

[0069] The tensile strength is 110 MPa, the elongation at break is 300%, and the moisture permeability is 2.5 g / m². 2 ·day.

[0070] It exhibits good thermal stability, remaining stable at 180℃. It also demonstrates excellent resistance to acids, alkalis, and electrolytes. Chemical corrosion resistance tests show no significant swelling or degradation in LiPF6 and LiBF4 solutions.

[0071] The active coating has a hydrophilic contact angle of 36° and exhibits good adhesion in scratch tests. It will not peel off during use and can maintain the overall performance of the release film.

[0072] The adhesion between the release agent layer and the PET base film is 23 N / cm; the heat deformation of the release agent layer is 259℃; the coefficient of friction of the release agent layer is 0.3; and the air permeability of the release agent layer is 3 g / m³. 2 ·day.

[0073] Example 3

[0074] Preparation steps:

[0075] A PET base film with a thickness of 25μm was selected.

[0076] Heat treatment at 120℃ for 60 minutes.

[0077] Add 20 parts by weight of PVA to 90 parts by weight of deionized water, stir at 70°C for 2 hours, then add 2 parts by weight of polyvinyl alcohol ether and continue stirring for 60 minutes.

[0078] The drying temperature after coating is 60℃, and the drying time is 60 minutes. The thickness of the active coating is 5μm.

[0079] The release agent solution on the other side consists of 70 parts by weight of PVDF, 50 parts by weight of PEEK, 1 part by weight of BHT, 3 parts by weight of phthalate and 200 parts by weight of NMP.

[0080] The curing temperature is 120℃, and the curing time is 60 minutes. The thickness of the release agent layer is 1μm.

[0081] Effect:

[0082] Release force is less than 10g / cm, making it suitable for high-temperature production environments.

[0083] The tensile strength is 120 MPa, the elongation at break is 450%, and the moisture permeability is 1.8 g / m². 2 ·day.

[0084] It exhibits excellent thermal stability, showing no deformation at 250℃. It also demonstrates good resistance to acids, alkalis, and electrolytes. Chemical corrosion resistance tests show no significant swelling or degradation in LiPF6 and LiBF4 solutions.

[0085] The active coating has a hydrophilic contact angle of 50° and exhibits good adhesion in scratch tests. It will not peel off during use and can maintain the overall performance of the release film.

[0086] The adhesion between the release agent layer and the PET base film is 26 N / cm; the heat deformation of the release agent layer is 255℃; the coefficient of friction of the release agent layer is 0.2; and the air permeability of the release agent layer is 2 g / m³. 2 ·day.

[0087] Comparative Example 1

[0088] Preparation steps:

[0089] A PET base film with a thickness of 12μm was selected.

[0090] The PET base film was heat-treated at 80°C for 30 minutes.

[0091] Preparation of the active coating solution: Add 10 parts by weight of PVA to 80 parts by weight of deionized water and stir at 60°C for 1 hour. Do not add polyvinyl alcohol ether.

[0092] The drying temperature after coating was set to 40℃ for 30 minutes. The thickness of the active coating was 1μm.

[0093] The other side is coated with a release agent, which consists of 50 parts by weight of PVDF, no PEEK added, 0.5 parts by weight of BHT, 1 part by weight of phthalate and 100 parts by weight of NMP.

[0094] The curing conditions were 80℃ for 30 minutes. The release agent layer thickness was 0.1μm.

[0095] Effect:

[0096] It has poor release properties, and the release film and the diaphragm surface are prone to sticking together and are not easy to separate.

[0097] The tensile strength is 80 MPa, the elongation at break is 200%, the thermal stability is poor, and the film deforms severely at 140℃.

[0098] Swelling and degradation phenomena occur in LiPF6 and LiBF4 solutions.

[0099] The hydrophilic contact angle of the active coating is 11°, and the active coating shows signs of peeling off during scratch testing.

[0100] The adhesion between the release agent layer and the PET base film is 103 N / cm; the heat deformation of the release agent layer is 152℃; the coefficient of friction of the release agent layer is 10.9; and the air permeability of the release agent layer is 0.01 g / m³. 2 ·day.

[0101] Comparative Example 2

[0102] Preparation steps:

[0103] A PET base film with a thickness of 18μm was selected.

[0104] Heat treatment was performed in a hot air circulating oven at 100°C for 45 minutes.

[0105] Preparation of active coating solution: Add 15 parts by weight of PVA to 85 parts by weight of deionized water and stir at 60°C for 1.5 hours. Do not add polyvinyl alcohol ether.

[0106] The drying temperature after coating is 50℃, and the drying time is 45 minutes. The thickness of the active coating is 3μm.

[0107] The release agent coated on the other side consists of 60 parts by weight of PVDF, 40 parts by weight of PEEK, no BHT added, 2 parts by weight of phthalate and 150 parts by weight of NMP.

[0108] The curing temperature is 100℃, and the curing time is 45 minutes. The thickness of the release agent layer is 0.5μm.

[0109] Effect:

[0110] The release force is 25 g / cm, which leads to severe adhesion between the diaphragm and the release film surface.

[0111] The tensile strength is 90 MPa, the elongation at break is 250%, the moisture permeability is low, and the heat distortion temperature is 150℃.

[0112] Swelling and degradation phenomena occur in LiPF6 and LiBF4 solutions.

[0113] The active coating has a hydrophilic contact angle of 13°, and the active coating peels off during the scratch test.

[0114] The adhesion between the release agent layer and the PET base film is 56 N / cm; the heat deformation of the release agent layer is 170℃; the coefficient of friction of the release agent layer is 5.7; and the air permeability of the release agent layer is 0.02 g / m³. 2 ·day.

[0115] Comparative Example 3

[0116] Preparation steps:

[0117] A 25μm PET base film was used, and the heat treatment temperature was relatively low, only 60℃, for 20 minutes.

[0118] The coating process was not standardized, the drying temperature was too low (only 30℃), and the drying time was insufficient (20 minutes). The thickness of the active coating was 5μm.

[0119] The release agent used consists of 50 parts by weight of PVDF and 100 parts by weight of NMP. The thickness of the release agent layer is 1 μm.

[0120] Effect:

[0121] The demolding effect is poor, with a release force of 30g / cm, making it unsuitable for high-temperature production.

[0122] The tensile strength is 70 MPa, the elongation at break is 150%, the diaphragm strength is insufficient, the heat distortion temperature is 120℃, and it cannot maintain stability at high temperatures.

[0123] Swelling and degradation phenomena occur in LiPF6 and LiBF4 solutions.

[0124] The hydrophilic contact angle of the active coating is 9°, and the active coating shows signs of peeling off during scratch testing.

[0125] The adhesion between the release agent layer and the PET base film is 65 N / cm; the heat deformation of the release agent layer is 166℃; the coefficient of friction of the release agent layer is 4.8; and the air permeability of the release agent layer is 0.03 g / m³. 2 ·day.

[0126] Summarize:

[0127] These three specific embodiments and three comparative embodiments demonstrate that the present invention has significant advantages in improving the release properties, corrosion resistance, thermal stability, and mechanical properties of the diaphragm. The comparative embodiments, however, show that when the composition of the active coating and release agent changes, or when heat treatment conditions change, the release film is prone to adhesion and breakage during the diaphragm production process, and its performance is significantly inferior to the technical solution of the present invention.

[0128] Those skilled in the art should understand that although the present invention has been described with reference to multiple embodiments, not every embodiment contains only one independent technical solution. This description is provided merely for clarity; those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of the present invention.

[0129] The above description is merely an illustrative embodiment of this utility model and is not intended to limit the scope of this utility model. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this utility model should fall within the protection scope of this utility model.

Claims

1. A polyester release film for lithium battery separators, comprising a PET base film, a release agent layer on one side of the PET base film, and an active coating layer on the other side of the PET base film, characterized in that, The thickness of the PET base film is 12-25μm, the thickness of the release agent layer is 0.1-1μm, and the thickness of the active coating is 1-5μm.

2. A system for preparing a polyester release film for lithium battery separators, characterized in that, The preparation system includes a feed reel for conveying PET base film; a first tension adjusting wheel assembly is provided downstream of the feed reel; the PET base film is conveyed from the feed reel through the first tension adjusting wheel assembly into a hot air circulating oven; the PET base film after being processed in the hot air circulating oven is conveyed to a first coating machine; the PET base film after being coated with an active coating liquid in the first coating machine is further conveyed to a dryer; the PET base film after being processed in the dryer is further flipped and conveyed to a second coating machine; the PET base film after being coated with a release agent in the second coating machine is further conveyed to an oven; the release film after being cured in the oven is further conveyed through the second tension adjusting wheel assembly and finally conveyed to a winding machine.

3. The preparation system as described in claim 2, characterized in that, The hot air circulating oven is set to operate at 80℃-120℃, with a heat treatment time of 30-60 minutes.

4. The preparation system according to claim 2, characterized in that, The first coating machine includes a first coating roller located below the PET base film, the lower part of the first coating roller being immersed in the coating liquid in the first coating tank; a first agitator is provided in the first coating tank.

5. The preparation system as described in claim 2, characterized in that, The dryer is set to operate at a temperature of 40℃-60℃ and a drying time of 30-60 minutes.

6. The preparation system according to claim 2, characterized in that, A first rotating roller is installed between the first coating machine and the dryer, and a second rotating roller is installed between the dryer and the second coating machine. After the PET base film is output from the first coating machine, it turns 90 degrees through the first rotating roller. Then, after the PET base film is output from the dryer, it turns 90 degrees in the same direction through the second rotating roller.

7. The preparation system according to claim 2, characterized in that, The second coating machine includes a second coating roller located below the PET base film, the lower part of which is immersed in a release agent in a second coating tank; a second agitator is provided in the second coating tank.

8. The preparation system according to claim 2, characterized in that, The oven is set to operate at 80℃-120℃, and the curing time is 30-60 minutes.

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