Production method of lithium ion battery diaphragm, lithium ion battery diaphragm and application
By adjusting the ratio of the raw materials for preparation of lithium-ion battery separator to white oil and the stretching process, combining the attachment method of the calendering roller or cold air knife and soft bellows, the stretching process is optimized, and the problem of extremely poor breathable value of the lithium-ion battery separator is solved, and the performance consistency and breathability of the product are improved.
Patent Information
- Application Number
- CN202510477345.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2025-07-25
AI Technical Summary
The extremely difference in breathable value of lithium-ion battery separators during production is large, resulting in poor consistency of product performance, especially when coating and processing, it is difficult to meet the consistency requirements of breathable value.
By adjusting the ratio of raw materials and white oil for lithium-ion battery separator, and controlling the screw extrusion amount and speed ratio during the screw extrusion process, combined with the attachment method of the calendering roller or cold air knife to the soft bellows, longitudinal and secondary lateral stretching are performed, the stretching ratio and temperature are controlled, and the uniformity of the stretching process is optimized.
It effectively reduces the extreme air permeability value of the lithium-ion battery separator, improves the performance consistency of the product, and ensures the uniformity and breathability of the separator.
Smart Images
Figure CN120376878A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of lithium-ion batteries, and particularly to a production method of a lithium-ion battery separator, a lithium-ion battery separator and an application. Background Art
[0002] After the winding of the lithium-ion battery separator is completed, physical property tests such as air permeability are carried out. In the transverse direction of the product, an air permeability point is tested every 10 cm or 20 cm, forming 20 - 40 data values. The range of these data is basically between 10 - 50 seconds. Especially when producing high-air-permeability products, a "high in the middle and low on both sides" bowl-shaped air permeability value will particularly occur, and the range reaches more than 50 seconds, even more than 100 seconds, resulting in poor product performance consistency. Especially when the product is applied to coating processing, different formula slurries need to be replaced to meet the air permeability consistency. How to reduce the range of the air permeability value of the lithium-ion battery separator and improve the product performance consistency of the lithium-ion battery separator has become a problem to be solved. Summary of the Invention
[0003] (1) Technical Problems to be Solved
[0004] The present application provides a lithium-ion battery separator, a preparation method and an application thereof, which solve the problems of reducing the range of the air permeability value of the lithium-ion battery separator and improving the product performance consistency of the lithium-ion battery separator.
[0005] (2) Technical Solutions
[0006] In a first aspect, the present application provides a production method of a lithium-ion battery separator, including:
[0007] Adding raw materials for preparing the lithium-ion battery separator with a mass ratio of 15 - 28% and white oil with a mass ratio of 72 - 85% into a screw extruder for melt extrusion, and the ratio of the screw extrusion amount to the rotation speed is 3.5 - 5.0;
[0008] Attaching the sheet extruded from the die head of the screw extruder to a chill roll through a calender roll or a cold air knife and a soft air box to obtain a cast sheet;
[0009] After longitudinally stretching and extracting the cast sheet in sequence, then performing secondary transverse stretching, and obtaining the lithium-ion battery separator after traction and winding. The stretching ratio of the longitudinal stretching is 8.0 - 9.7, and the stretching temperature of the secondary transverse stretching is 120 - 126 °C.
[0010] Further, the molecular weight of the raw materials for preparing the lithium-ion battery separator is 580,000 - 600,000.
[0011] Further, the mass ratio of the raw materials for preparing the lithium-ion battery separator is 28%, and the mass ratio of the white oil is 72%.
[0012] Further, the ratio of the screw extrusion amount to the rotational speed is 3.5.
[0013] Further, the draw ratio of the longitudinal stretching is 9.7.
[0014] Further, the stretching temperature of the secondary transverse stretching is 126 °C.
[0015] In a second aspect, the present application provides a lithium-ion battery separator prepared based on the production method of the lithium-ion battery separator described above.
[0016] Further, the air permeability difference of the lithium-ion battery separator is 6 - 7 seconds.
[0017] In a third aspect, the present application provides the application of the lithium-ion battery separator obtained by the production method of the lithium-ion battery separator described above or the lithium-ion battery separator described above in the field of lithium-ion batteries.
[0018] (3) Beneficial effects
[0019] The above technical solutions of the present application have the following advantages:
[0020] The production method of the lithium-ion battery separator provided by the present application can reduce the breakage during the melting and processing of the molecular weight and ensure the uniformity of the subsequent stretching process by increasing the addition ratio of white oil and reducing the ratio of the screw extrusion amount to the rotational speed. By attaching the sheet extruded from the die head of the screw extruder to the chill roll through a calender roll or a cold air knife and a soft air box, a single casting attachment mode can be avoided, and uneven cooling crystallization on both sides of the separator, resulting in uneven subsequent stretching, can be prevented. By reducing the draw ratio of the longitudinal stretching, the difference between the middle and both sides of the separator can be reduced. By reducing the stretching temperature of the secondary transverse stretching, the tortuosity of the pores formed in the middle part of the separator can be reduced. By this method, the air permeability difference of the lithium-ion battery separator can be reduced, and the product performance consistency of the lithium-ion battery separator can be improved.
[0021] It can be understood that the beneficial effects of the above second and third aspects can refer to the relevant descriptions in the above first aspect and will not be repeated here. Description of the drawings
[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0023] Figure 1Flow chart of the production method of the lithium-ion battery separator provided by this application;
[0024] Figure 2 Schematic diagram of calender roll attachment provided by this application;
[0025] Figure 3 Schematic diagram of cold air knife and soft air box attachment provided by this application. Detailed implementation manners
[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer, the following further elaborates on this application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.
[0027] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression means any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) among a, b, or c", or, "at least one (item) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.
[0028] It should be understood that in various embodiments of this application, the magnitudes of the serial numbers of the above processes do not mean the order of execution. Some or all steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.
[0029] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms of "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.
[0030] The weights of the relevant components mentioned in the specification of the embodiments of this application not only can refer to the specific contents of each component, but also can represent the proportional relationship of the weights between each component. Therefore, as long as the contents of the relevant components in the specification of the embodiments of this application are enlarged or reduced in proportion, they are within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass described in the specification of the embodiments of this application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.
[0031] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.
[0032] The embodiments of the present application provide a production method for a lithium-ion battery separator, as Figure 1 shown, including the following steps:
[0033] Adding raw materials for preparing a lithium-ion battery separator with a mass ratio of 15-28% and white oil with a mass ratio of 72-85% into a screw extruder for melt extrusion, and the ratio of the screw extrusion amount to the rotation speed is 3.5-5.0;
[0034] Attaching the sheet extruded from the die head of the screw extruder to a chill roll through a calender roll or a cold air knife and a soft air box to obtain a cast sheet;
[0035] After longitudinally stretching and extracting the cast sheet in sequence, then performing secondary transverse stretching, and obtaining a lithium-ion battery separator after traction and winding. The stretching ratio of the longitudinal stretching is 8.0-9.7, and the stretching temperature of the secondary transverse stretching is 120-126 °C.
[0036] Under the condition of meeting production, the addition ratio of white oil can be increased to 72-85%, and the ratio of the screw extrusion amount to the rotation speed, i.e., the Q / NS value, can be reduced to 3.5-5.0, so as to reduce the breakage during the melt processing of the molecular weight and ensure the uniformity of the subsequent stretching process. As Figure 2 and Figure 3 shown, the attachment method of the sheet to the chill roll adopts a calender mode or a cold air knife + soft air box attachment method, avoiding a single casting attachment mode to prevent uneven cooling and crystallization on both sides of the separator, resulting in uneven subsequent stretching.
[0037] Under the premise of meeting production requirements, the stretching ratio of the longitudinal stretching can be reduced to 8.0-9.7, because the stretching process is not an accurate uniform stretching, and there are differences between the middle and both sides, and the greater the ratio, the greater the difference. The stretching temperature of the secondary transverse stretching is controlled below 130 °C, such as 120-126 °C. The higher the temperature, the easier it is to stretch the middle part, the greater the tortuosity of the formed pores, and the relatively higher the air permeability value.
[0038] The currently commonly used improvement solutions are to reduce the median air permeability (the lower the median, the smaller the range), trim the edges at the extraction outlet, or increase the edge trimming width before winding. This method can control the range of air permeability values within 50 seconds without reducing the median air permeability and reducing the edge trimming at the extraction outlet, thereby improving the consistency of the physical and chemical properties of the lithium-ion battery separator. The above is the improvement solution for the "high in the middle and low on both sides" bowl-shaped air permeability value. For the "low in the middle and high on both sides" air permeability shape, the improvement direction is opposite to the above solution.
[0039] In some embodiments, the molecular weight of the raw materials for preparing the lithium-ion battery separator is 580,000 - 600,000.
[0040] In some embodiments, the mass ratio of the raw materials for preparing the lithium-ion battery separator is 28%, and the mass ratio of the white oil is 72%.
[0041] In some embodiments, the ratio of the screw extrusion amount to the rotation speed is 3.5.
[0042] In some embodiments, the stretching ratio of the longitudinal stretching is 9.7.
[0043] In some embodiments, the stretching temperature of the secondary transverse stretching is 126 °C.
[0044] The following is illustrated with specific embodiments.
[0045] It should be noted that the raw materials for preparing the lithium-ion battery separator used in the following examples and comparative examples are the commonly used existing raw materials for preparing the lithium-ion battery separator, and their molecular weight is 600,000.
[0046] Example 1
[0047] Add the raw materials for preparing the lithium-ion battery separator with a mass ratio of 28% and white oil with a mass ratio of 72% to the screw extruder for melting and extrusion, and the ratio of the screw extrusion amount to the rotation speed is 3.5;
[0048] Attach the sheet extruded from the die head of the screw extruder to the chill roll through the calender roll to obtain a cast film;
[0049] After longitudinally stretching and extracting the cast film in sequence, then perform secondary transverse stretching, and obtain the lithium-ion battery separator after traction and winding. The stretching ratio of the longitudinal stretching is 9.7, and the stretching temperature of the secondary transverse stretching is 126 °C.
[0050] After testing, the air permeability range of the lithium-ion battery separator is 7 seconds.
[0051] Example 2
[0052] Add the raw materials for preparing the lithium-ion battery separator with a mass ratio of 20% and white oil with a mass ratio of 80% to the screw extruder for melting and extrusion, and the ratio of the screw extrusion amount to the rotation speed is 4.0;
[0053] The sheet extruded from the die head of the screw extruder is attached to a chilled roller by means of a cold air knife and a soft bellows to obtain a cast sheet;
[0054] The cast sheet is sequentially longitudinally stretched and extracted, and then transversely stretched for a second time, and then pulled and rolled to obtain a lithium-ion battery separator. The stretching ratio of the longitudinal stretching is 9.0, and the stretching temperature of the secondary transverse stretching is 120°C.
[0055] After testing, the extreme air permeability of lithium-ion battery separators was found to be 6 seconds.
[0056] Comparative Example
[0057] 30% by weight of raw materials for preparing lithium-ion battery separators and 70% by weight of white oil are added into a screw extruder for melt extrusion, and the ratio of the screw extrusion volume to the speed is 3;
[0058] The sheet extruded from the die head of the screw extruder is attached to a chilled roller by a casting roller to obtain a cast sheet;
[0059] The cast sheet is sequentially longitudinally stretched and extracted, and then transversely stretched for a second time, and then pulled and rolled to obtain a lithium-ion battery separator. The stretching ratio of the longitudinal stretching is 12.2, and the stretching temperature of the secondary transverse stretching is 132°C.
[0060] After testing, the extreme air permeability of lithium-ion battery separators was found to be 78 seconds.
[0061] The production method of the lithium-ion battery separator provided in the embodiment of the present application can reduce the molecular weight breakage during the melt processing by increasing the addition ratio of white oil and reducing the screw extrusion amount and speed ratio, thereby ensuring the uniformity of the subsequent stretching process. The sheet extruded from the die head of the screw extruder is attached to the chilled roller by a calendering roller or a cold air knife and a soft bellows, which can avoid a single cast attachment mode and prevent uneven cooling and crystallization on both sides of the separator, resulting in uneven subsequent stretching. By reducing the stretching ratio of the longitudinal stretching, the difference between the middle and both sides of the separator is reduced. By reducing the stretching temperature of the secondary transverse stretching, the tortuosity of the hole formed in the middle of the separator is reduced. Through this method, the extreme difference in the air permeability value of the "high in the middle and low on both sides" bowl-shaped air permeability lithium-ion battery separator can be reduced, and the performance consistency of the lithium-ion battery separator product can be improved.
[0062] The embodiment of the present application also provides a lithium-ion battery separator, which is obtained based on the production method of the lithium-ion battery separator as described above.
[0063] In some embodiments, the lithium-ion battery separator has a gas permeability range of 6-7 seconds.
[0064] The embodiment of the present application also provides a lithium-ion battery separator obtained by the production method of the lithium-ion battery separator as described above or the application of the lithium-ion battery separator as described above in the field of lithium-ion batteries.
[0065] The above-described embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or equivalently replace some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application and should all be included in the protection scope of the present application.
Claims
1. A production method of a lithium-ion battery separator, characterized in that, Comprising: Adding raw materials for preparing a lithium-ion battery separator with a mass ratio of 15-28% and white oil with a mass ratio of 72-85% into a screw extruder for melt extrusion, and the ratio of the screw extrusion amount to the rotation speed is 3.5-5.0; Attaching the sheet extruded from the die head of the screw extruder to a chill roll through a calender roll or a cold air knife and a soft air box to obtain a cast sheet; After longitudinally stretching and extracting the cast sheet in sequence, then performing secondary transverse stretching, and obtaining a lithium-ion battery separator after traction and winding. The stretching ratio of the longitudinal stretching is 8.0-9.7, and the stretching temperature of the secondary transverse stretching is 120-126°C.
2. The production method of the lithium-ion battery separator according to claim 1, characterized in that, The molecular weight of the raw materials for preparing the lithium-ion battery separator is 580,000-600,000.
3. The production method of the lithium ion battery separator according to claim 1, characterized in that, The mass ratio of the raw materials for preparing the lithium-ion battery separator is 28%, and the mass ratio of the white oil is 72%.
4. The production method of the lithium-ion battery separator according to claim 1, wherein, The ratio of the screw extrusion amount to the rotation speed is 3.
5.
5. The production method of the lithium-ion battery separator according to claim 1, characterized in that The stretching ratio of the longitudinal stretching is 9.
7.
6. The production method of the lithium-ion battery separator according to claim 1, characterized in that, The stretching temperature of the secondary transverse stretching is 126°C.
7. A lithium-ion battery separator, characterized in that, Obtained based on the production method of the lithium-ion battery separator according to any one of claims 1 to 6.
8. The lithium ion battery separator according to claim 7, characterized in that, The air permeability of the lithium-ion battery separator is extremely poor, being 6-7 seconds.
9. Application of the lithium-ion battery separator obtained by the production method of the lithium-ion battery separator according to any one of claims 1 to 6 or the lithium-ion battery separator according to any one of claims 7 to 8 in the field of lithium-ion batteries.