Off-line secondary synchronous stretching equipment for wet-process lithium ion diaphragm

Abstract

The invention discloses an off-line secondary synchronous stretching device for a wet-process lithium ion diaphragm, and relates to the technical field of wet-process lithium ion battery thin film processing, and the off-line secondary synchronous stretching device for the wet-process lithium ion diaphragm performs off-line secondary synchronous stretching on a wet-process lithium ion battery thin film subjected to primary stretching. The production line sequentially comprises an unwinding unit, a two-way synchronous stretching machine, a traction unit and a winding unit according to a processing procedure, a lithium ion battery film penetrates through a stretching inlet in the two-way synchronous stretching machine, sequentially passes through the heating stretching section and the cooling shaping section in the transmission processing direction of the lithium ion battery film, and is subjected to heating stretching and then cooling shaping until the lithium ion battery film penetrates through a stretching outlet in the two-way synchronous stretching machine; and entering the traction unit. The preparation method has the advantages that the strength and modulus of the membrane material are greatly improved, and the elongation at break of the membrane material is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of wet-process lithium-ion battery film processing, and in particular to an off-line secondary synchronous stretching device for a wet-process lithium-ion diaphragm. Background Art

[0002] Wet-process lithium-ion battery film is one of the important component films that must be used in current liquid lithium-ion batteries, especially power batteries and high-end 3C digital batteries.

[0003] The conventional method for preparing the existing wet-process lithium-ion separator by biaxial stretching is to use plasticizing extrusion casting, single asynchronous or synchronous stretching, extraction drying, longitudinal shaping, and winding. The biaxial (MD / TD) ratio of the single asynchronous stretching or synchronous stretching biaxial stretching does not exceed 10 / 10 times.

[0004] In the prior art, during the stretching process, excessive transverse stretching ratio will cause the middle part of the film to sag significantly due to gravity, which may easily cause serious problems such as film scratching the equipment and uneven transverse force. For single synchronous stretching, the aforementioned problems similar to those of single asynchronous stretching exist in the transverse direction. In addition, for the longitudinal stretching in the bidirectional synchronous stretching equipment, the longitudinal ratio is achieved by changing the spacing of the chain clips. Calculated based on the initial clip spacing of 0.025m, the longitudinal ratio must reach 100 times, and the maximum spacing between the two chain clips must reach 2.5m. If the spacing is too large, the film will be concave in the middle, which is not conducive to heating. It will also bring great marginal effects and it will be impossible to produce qualified films.

[0005] Therefore, the current mainstream single asynchronous or synchronous stretching equipment process cannot achieve ultra-high ratio stretching of the film, generally staying below 100 times; and the film obtained by low stretching ratio has the problems of insufficient strength and small modulus. In view of this, a wet lithium ion diaphragm offline secondary synchronous stretching equipment is proposed to solve the above-mentioned technical problems. Summary of the invention

[0006] The present application provides an off-line secondary synchronous stretching device for a wet-process lithium-ion diaphragm, which has the advantages of greatly improving the strength and modulus of the membrane material and reducing the elongation at break of the membrane material.

[0007] The present application provides a wet-process lithium-ion membrane offline secondary synchronous stretching device, which adopts the following technical solution: A wet-process lithium-ion membrane offline secondary synchronous stretching device, which performs secondary synchronous stretching on a wet-process lithium-ion battery film that has been stretched once, and includes an unwinding unit, a bidirectional synchronous stretching machine, a traction unit, and a winding unit in sequence according to the processing procedures; The bidirectional synchronous stretching machine is provided with several sections, and the lithium-ion battery film passes through the stretching entrance on the bidirectional synchronous stretching machine, and passes through the heating stretching section and the cooling shaping section in sequence along the transmission processing direction of the lithium-ion battery film, which are used for heating and stretching first, and then cooling and shaping, until passing through the stretching exit on the bidirectional synchronous stretching machine and entering the traction unit.

[0008] By adopting the above technical scheme, through the secondary synchronous stretching of the bidirectional synchronous stretching machine, and based on heating and stretching first, and then cooling and shaping, the problem of sagging of the lithium-ion battery film due to gravity during the stretching process is solved, and the problem of limited stretching ratio of a single set of synchronous bidirectional stretching or a single set of asynchronous stretching equipment is solved, and a maximum regional stretching ratio of 100*100 times is achieved, so as to obtain a lithium-ion battery film with high strength and large modulus.

[0009] Preferably, the heating and stretching section and the cooling and shaping section of the bidirectional synchronous stretching machine are respectively provided with a heating oven and a cooling oven, and the temperature accuracy of the heating oven is ±0.5°C, and the wind speed uniformity is ±1m / s.

[0010] By adopting the above technical solution, the temperature of the heating oven can be controlled accurately to ±0.5℃, ensuring that the lithium-ion battery film is always in the optimal heating state during the stretching process; this precise control improves the flexibility of the film and allows the molecular chains to be fully active, thereby stretching smoothly; in addition, the wind speed uniformity is ±1m / s, ensuring uniform flow of hot air to avoid local overheating or insufficient heating; this uniformity makes the surface temperature of the film consistent, thereby improving the overall quality and performance of the lithium-ion battery film.

[0011] Preferably, the unwinding unit comprises a supporting frame and an unwinding frame for unwinding the lithium-ion battery film, and the lithium-ion battery film passes through a floating roller and a traction roller arranged on the supporting frame alternately in sequence.

[0012] By adopting the above technical solution, the floating roller is designed to float up and down to adapt to the tension changes of lithium-ion battery film. Its main function is to reduce friction during unwinding, reduce film damage, and maintain its smooth operation. The floating roller effectively reduces friction and avoids damage or deformation caused by friction, thereby ensuring smooth unwinding of the film; and the traction roller ensures that the film is released at a consistent speed and tension by applying a stable traction force; the combination of the floating roller and the traction roller allows real-time adjustment of tension during the unwinding process, ensuring the consistency of the production process and reducing downtime and debugging time.

[0013] Preferably, the traction unit comprises a mounting frame, on which a plurality of heating rollers, cooling rollers and vacuum rollers are arranged; the stretched lithium-ion battery film passes through the heating rollers, cooling rollers and vacuum rollers alternately in sequence.

[0014] By adopting the above technical solution, the traction unit helps to improve the comprehensive performance of the lithium-ion battery film through the synergistic effect of the heating roller, the cooling roller and the vacuum roller, and ensures its reliability and stability in the subsequent processing process.

[0015] Preferably, a thickness gauge is provided on the mounting frame, and the thickness gauge is located between the heating roller and the cooling roller.

[0016] By adopting the above technical solution, the thickness gauge can measure the thickness of the lithium-ion battery film instantly when it passes through without causing any damage to the film; the instrument is located between the heating roller and the cooling roller, and can measure the film after it is heated but not yet cooled, so as to take into account the thermal expansion effect; and measurement after heating and stretching helps to capture thickness changes in time so as to adjust production parameters in real time; by monitoring the film thickness, defective products can be discovered in time, thereby ensuring the consistency and quality of the lithium-ion battery film.

[0017] Preferably, a trimming assembly is provided on the mounting frame; a waste edge winder is provided on the trimming assembly, and the trimming assembly is located between the cooling roller and the vacuum roller.

[0018] By adopting the above technical solution, the configuration of the trimming assembly and the waste edge winder improves the final quality of the lithium-ion battery film, while improving production efficiency and film utilization; this design realizes a more refined and efficient production process.

[0019] Preferably, the winding unit comprises a winding frame, on which a transmission roller, a flattening roller, a tension measuring roller and a contact roller are sequentially arranged.

[0020] By adopting the above technical solution, the winding unit is set up automatically; the efficiency of the winding process is improved, manual intervention is reduced, and production efficiency is improved; the flattening roller and tension measuring roller ensure the flatness and proper tension of the film, thereby avoiding subsequent product defects and improving the quality of the final product.

[0021] Preferably, a method for stretching a secondary synchronous stretching system is based on the above-mentioned wet lithium ion membrane offline secondary synchronous stretching equipment, and the stretching step includes: S1: rolling up the formed cast sheet into a roll by longitudinal stretching, transverse stretching, and longitudinal and transverse synchronous stretching to obtain a once-stretched lithium-ion battery film; S2: The primary stretched lithium-ion battery film is passed through an offline secondary synchronous stretching device to achieve an ultra-high ratio stretching with a longitudinal and transverse product relationship.

[0022] By adopting the above technical scheme, the stretching method of the secondary synchronous stretching system is to stretch through transverse hole expansion; ensure that the lithium-ion battery film has an appropriate porosity; adopt transverse and longitudinal bidirectional shrinkage treatment and heat setting methods to replace the traditional transverse unidirectional shrinkage, thereby enhancing the bidirectional heat shrinkage stability of the film in the longitudinal and transverse directions.

[0023] Preferably, a high-strength and high-modulus wet-process lithium-ion battery film is prepared using the secondary synchronous stretching system stretching method.

[0024] By adopting the above technical scheme, a large-ratio stretching is achieved by setting up an offline secondary single-stage or multi-stage synchronous stretching machine; the method provided in this application can greatly increase the regional stretching ratio to 10,000 times, thereby greatly improving the orientation, crystallization, fine denier of microfibers, and specific strength of the membrane lithium-ion battery film, reducing the elongation at break of the membrane lithium-ion battery film, and forming a wet-process lithium-ion battery film with ultra-high strength and ultra-high modulus.

[0025] Preferably, the high-strength and high-modulus wet-process lithium-ion battery film has a thickness range of 2 to 100 μm, an air permeability range of 10-300 s / in2*100 cc, a tensile strength range of 300-2000 MPa, a specific puncture strength range of 50-300 gf / μm, a porosity range of 25-75%, and a modulus range of 2 GPa to 30 GPa.

[0026] By adopting the above technical scheme, the high-strength and high-modulus wet-process lithium-ion battery film has a specific thickness, air permeability, tensile strength, puncture strength, porosity and modulus range, so that the wet-process lithium-ion battery film after secondary stretching shows significant advantages in performance, safety, applicability, cycle life, etc., providing a good foundation for the application and further development of lithium-ion batteries.

[0027] In summary, this application has the following beneficial effects: 1. The stretching method of the secondary synchronous stretching system is to stretch by lateral hole expansion; ensure that the lithium-ion battery film has an appropriate porosity; adopt a transverse and longitudinal bidirectional shrinkage treatment and heat setting method to replace the traditional transverse unidirectional shrinkage, thereby enhancing the bidirectional heat shrinkage stability of the film in the longitudinal and transverse directions.

[0028] 2. By setting up an offline secondary single-stage or multi-stage synchronous stretching machine, high-ratio stretching is achieved; the method provided in this application can greatly increase the regional stretching ratio to 10,000 times, thereby greatly improving the orientation, crystallization, fine denier of microfibers, and specific strength of the membrane lithium-ion battery film, reducing the elongation at break of the membrane lithium-ion battery film, and forming a wet-process lithium-ion battery film with ultra-high strength and ultra-high modulus.

[0029] 3. The high-strength and high-modulus wet-process lithium-ion battery film has a specific thickness, air permeability, tensile strength, puncture strength, porosity and modulus range, so that the wet-process lithium-ion battery film after secondary stretching shows significant advantages in performance, safety, applicability, cycle life, etc., providing a good foundation for the application and further development of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 2 is a schematic diagram of the main structure of the off-line secondary synchronous stretching device for wet-process lithium-ion membrane in this embodiment; Figure 2 It is a schematic diagram of the internal structure of the bidirectional synchronous stretching machine in this embodiment; Figure 3 is a schematic diagram of the internal structure of the unwinding unit in this embodiment; Figure 4 is a schematic diagram of the internal structure between the traction unit and the winding unit in this embodiment; Figure 5 2 is a schematic diagram of the top view of the off-line secondary synchronous stretching device for wet-process lithium-ion membrane in this embodiment; Explanation of the reference numerals: 1. unwinding unit; 101. supporting frame; 102. unwinding frame; 103. floating roller; 104. pulling roller; 105. deviation correction mechanism; 2. bidirectional synchronous stretching machine; 3. pulling unit; 301. mounting frame; 302. heating roller; 303. cooling roller; 304. vacuum roller; 305. thickness gauge; 306. trimming assembly; 307. defect detection unit; 308. waste edge winder; 4. winding unit; 401. winding frame; 402. transmission roller; 403. flattening roller; 404. tension measuring roller; 405. contact roller; 5. heating oven; 6. cooling oven; 7. stretching inlet; 8. stretching outlet. DETAILED DESCRIPTION

[0031] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content. Example

[0032] The present invention discloses an off-line secondary synchronous stretching device for wet-process lithium-ion diaphragm, which performs secondary synchronous stretching on a wet-process lithium-ion battery film that has been stretched once. Figure 1 As shown, according to the processing steps, it includes an unwinding unit 1, a bidirectional synchronous stretching machine 2, a traction unit 3 and a winding unit 4 in sequence.

[0033] Through secondary synchronous stretching, the problem of sagging of lithium-ion battery film due to gravity during the stretching process is solved, and the problem of limited stretching ratio of a single set of synchronous bidirectional stretching or a single set of asynchronous stretching equipment is solved. The maximum regional stretching ratio of 100*100 times is achieved to obtain a film with high strength and large modulus.

[0034] Since the secondary synchronous stretching is carried out in an offline form, the process is short, the process adjustment is simple, the film quality is better, and it can meet the differentiated needs of customers; the production speed is high, and the production capacity is effectively improved compared to the one-time stretching method. One set of offline synchronous stretching machines can serve the coordinated use of 3-4 one-time stretching machines.

[0035] like Figure 2 As shown, the bidirectional synchronous stretching machine 2 is provided with several stretching entrances 7 on the bidirectional synchronous stretching machine 2, and passes through the heating stretching section and the cooling shaping section in sequence along the transmission processing direction of the lithium-ion battery film, which are used for heating and stretching first, and then cooling and shaping, until passing through the stretching exit 8 on the bidirectional synchronous stretching machine 2 and entering the traction unit 3.

[0036] The lithium-ion battery film first passes through the heating zone. The increased temperature makes the molecular chain activity of the film more active and more flexible. At this stage, the lithium-ion battery film is stretched to adjust its physical and chemical properties. After heating, the lithium-ion battery film is cooled to quickly fix its stretched shape. This is a process in which the lithium-ion battery film is cooled under appropriate temperature conditions to achieve shaping. This stage ensures the dimensional stability of the lithium-ion battery film. The biaxially stretched film then enters the traction unit 3 to ensure its transmission stability before winding. Winding unit 4: Finally, the shaped lithium-ion battery film is wound into a roll.

[0037] Secondary synchronous stretching can further improve the mechanical strength, ductility and electrochemical properties of lithium-ion battery films, thereby improving the overall performance of the battery; through synchronous stretching, the physical properties of lithium-ion battery films in all directions can be made more uniform, thereby improving the reliability of the battery; after cooling and shaping, the lithium-ion battery film can be effectively prevented from shrinking or deforming due to temperature changes in subsequent production and use; the continuous operation mode of the whole set of equipment improves production efficiency and reduces manpower and time costs; the wet process may bring less environmental burden than the dry process, especially in the use of solvents; in this way, secondary synchronous stretching not only optimizes the characteristics of lithium-ion battery separators, but also provides technical support for the high performance of batteries.

[0038] Through secondary synchronous stretching, the problem of sagging of lithium-ion battery film due to gravity during the stretching process is solved, and the problem of limited stretching ratio of a single set of synchronous bidirectional stretching or a single set of asynchronous stretching equipment is solved. The maximum regional stretching ratio of 100*100 times is achieved to obtain a lithium-ion battery film with high strength and large modulus.

[0039] like Figure 2 As shown, the heating and stretching section and the cooling and shaping section of the bidirectional synchronous stretching machine 2 are respectively provided with a heating oven 5 and a cooling oven 6, the temperature accuracy of the heating oven 5 is ±0.5°C, and the temperature of the heating oven 5 is controlled within a high-precision range of ±0.5°C, which can ensure that the lithium-ion battery film is always kept at the optimal heating temperature during the stretching process; precise temperature control can effectively improve the flexibility of the lithium-ion battery film, so that its molecular chains can be fully active during the stretching process, thereby achieving smooth stretching; the wind speed uniformity is ±1m / s; ensuring that the hot air can flow evenly during the heating process to avoid local overheating or insufficient heating; this uniformity helps to make the surface temperature of the lithium-ion battery film consistent, thereby improving the overall quality and performance of the lithium-ion battery film.

[0040] The function of the cooling oven 6 is to quickly reduce the temperature of the lithium-ion battery film by controlling the temperature and air flow rate, ensuring that it is quickly shaped under optimal cooling conditions; similar to the heating stage, the uniformity and rate of cooling are crucial to the shape retention and physical properties of the lithium-ion battery film; high-precision control of temperature and wind speed enables the lithium-ion battery film to avoid thermal stress and structural deformation during the heating and cooling process, thereby improving the consistency and quality of the final lithium-ion battery film; precise temperature control helps to stabilize the electrochemical properties of the battery film and improve the charging and discharging efficiency and cycle life of the lithium-ion battery.

[0041] like Figure 3 As shown, specifically, the unwinding unit 1 includes a supporting frame 101 and an unwinding frame 102 for unwinding the lithium-ion battery film. The function of the unwinding frame 102 is to support and control the unwinding of the lithium-ion battery film to ensure that the film does not relax or curl during the unwinding process; the lithium-ion battery film passes through the floating roller 103 and the traction roller 104 arranged on the supporting frame 101 alternately in turn.

[0042] like Figure 3As shown, the floating roller 103 floats up and down on the supporting frame 101, and this design can adapt to the tension change of the lithium-ion battery film; the main function of the floating roller 103 is to reduce the friction of the lithium-ion battery film during unwinding, reduce the damage of the lithium-ion battery film, and at the same time maintain the smooth operation of the lithium-ion battery film through its floating characteristics; the design of the floating roller 103 effectively reduces the friction of the lithium-ion battery film, avoids the damage or deformation of the lithium-ion battery film caused by friction, thereby ensuring the smooth unwinding of the lithium-ion battery film.

[0043] like Figure 3 As shown, the traction roller 104 is responsible for applying a stable traction force to the lithium-ion battery film to ensure that the lithium-ion battery film is released at a consistent speed and tension; the traction roller 104 is connected to the motor to control its speed, thereby affecting the unwinding speed of the lithium-ion battery film; the combination of the floating roller 103 and the traction roller 104 enables real-time adjustment of the tension during the unwinding process of the lithium-ion battery film to ensure the consistency of the lithium-ion battery film in the entire production process, thereby reducing downtime and debugging time.

[0044] like Figure 3 As shown, the unwinding unit 1 conveys the lithium-ion battery film into the device along the center; the control of the temperature accuracy and wind speed uniformity of the heating oven 5 can ensure the uniformity of the lithium-ion battery film during stretching.

[0045] like Figure 3 As shown, the stretching inlet 7 of the bidirectional synchronous stretching machine 2 is provided with a correcting mechanism 105, which can effectively detect and correct the displacement of the lithium-ion battery film, ensure that the lithium-ion battery film remains flat during the stretching process, and avoid waves or wrinkles; through the precise alignment of the lithium-ion battery film, the correcting mechanism 105 can reduce the loss caused by the unevenness of the lithium-ion battery film and optimize the material utilization rate.

[0046] like Figure 4 As shown, specifically, the traction unit 3 includes a mounting frame 301, on which a plurality of heating rollers 302, cooling rollers 303, and vacuum rollers 304 are arranged; the stretched lithium-ion battery film passes through the heating rollers 302, cooling rollers 303, and vacuum rollers 304 alternately in sequence, like Figure 4 As shown, the heating roller 302 relaxes the molecular chains of the lithium-ion battery film by providing appropriate heat, thereby improving its plasticity; this process helps to improve the uniformity and structure of the lithium-ion battery film, ensuring that a good stretching effect can be obtained in subsequent processes; the lithium-ion battery film achieves heat transfer through contact with the heating roller 302, promoting the required physical changes; through heating, the flexibility of the lithium-ion battery film is enhanced, which helps to obtain a higher stretching ratio.

[0047] like Figure 4 As shown, the cooling roller 303 quickly reduces the temperature of the lithium-ion battery film to ensure that the lithium-ion battery film maintains a stable shape and size after stretching; this process helps to lock the molecular structure of the lithium-ion battery film and enhance its mechanical properties; by quickly removing the heat from the lithium-ion battery film, it prevents it from over-softening or deformation; after cooling, the physical properties of the lithium-ion battery film are locked to enhance its mechanical strength and chemical stability.

[0048] like Figure 4 As shown, the vacuum roller 304 can remove surface moisture or bubbles when the lithium-ion battery film passes through, thereby ensuring the surface quality and adhesion of the lithium-ion battery film; by operating in a vacuum environment, the interference of external air is reduced, thereby improving the overall performance and consistency of the lithium-ion battery film; removing surface bubbles and moisture reduces the risk of defects in the lithium-ion battery film in subsequent processes and improves the qualified rate of finished products.

[0049] like Figure 4 As shown, in summary, the traction unit 3 helps to improve the comprehensive performance of the lithium-ion battery film through the synergistic effect of the heating roller 302, the cooling roller 303 and the vacuum roller 304, and ensures its reliability and stability in the subsequent processing process.

[0050] like Figure 4 As shown, a thickness gauge 305 is arranged on the mounting frame 301. The thickness gauge 305 is a non-contact thickness gauge 305 of any one of laser thickness measurement, optical measurement or ultrasonic measurement, and can measure the thickness of the lithium-ion battery film in real time when it passes through, without causing any damage to the lithium-ion battery film; the thickness gauge 305 is located between the heating roller 302 and the cooling roller 303; it can measure the lithium-ion battery film after it has been heated but not yet cooled, so as to ensure that the measurement result takes into account the thermal expansion effect that may be generated during the heating process; after the lithium-ion battery film has been heated and stretched, it is measured again, which helps to capture the thickness change of the lithium-ion battery film in time for real-time adjustment; by real-time monitoring of the thickness of the lithium-ion battery film, it is possible to timely discover defective products in the production process to ensure the consistency and quality of the lithium-ion battery film.

[0051] like Figure 4As shown, a trimming assembly 306 is provided on the mounting frame 301; a waste edge winder 308 is provided on the trimming assembly 306; the trimming assembly 306 cuts the edge of the lithium-ion battery film by a mechanical cutter or laser cutting technology to remove the waste edge that exceeds the specified size; this is usually performed after the lithium-ion battery film has cooled and reached a certain stability; the waste edge generated by the trimming will be collected by the winder to ensure the cleanliness of the production environment and facilitate subsequent processing and recycling; the trimming assembly 306 is located between the cooling roller 303 and the vacuum roller 304; after the lithium-ion battery film passes through the cooling roller 303 03, its temperature is reduced and its shape is stable, which is suitable for precise edge cutting; it is arranged before the vacuum roller 304 to ensure that the cut lithium-ion battery film maintains a good shape and size before entering the vacuum environment, avoiding the impact of uneven edges on subsequent processes; through precise edge cutting, the defects and uneven parts on the surface of the lithium-ion battery film can be removed, thereby improving the appearance and performance of the final lithium-ion battery film; the setting of the edge cutting component 306 between the cooling roller 303 and the vacuum roller 304 can effectively integrate edge cutting and waste edge winding into the production process, thereby reducing the connection time between processes.

[0052] In summary, the configuration of the trimming assembly 306 and the waste edge winder 308 not only improves the final quality of the lithium-ion battery film, but also effectively improves the overall production efficiency and the utilization rate of the lithium-ion battery film; through this design, a more refined and efficient production process can be achieved.

[0053] like Figure 4 As shown, a defect detection unit 307 is disposed on the mounting frame 301 , and the defect detection unit 307 is located at the output end of the mounting frame 301 .

[0054] like Figure 4 As shown, the defect detection unit 307 is usually equipped with a variety of sensors, such as photoelectric sensors, image recognition cameras, laser sensors, etc.; these sensors monitor the surface of the produced lithium-ion battery film in real time to detect possible defects; through real-time detection, defective lithium-ion battery films can be discovered and removed in time, thereby improving the overall lithium-ion battery film quality and meeting customer needs.

[0055] like Figure 4 As shown, the traction unit 3 includes a heating roller 302, a cooling roller 303, a vacuum roller 304, a trimming mechanism, a waste edge winder 308, a thickness measuring unit, and a defect detection unit 307. The lithium-ion battery film that has undergone secondary stretching is longitudinally shaped in the traction unit 3, and the relevant quality indicators are checked, and the excess waste edges are cut off.

[0056] like Figure 4As shown, specifically, the winding unit 4 includes a winding frame 401 , on which a transmission roller 402 , a flattening roller 403 , a tension measuring roller 404 and a contact roller 405 are sequentially arranged.

[0057] The transmission roller 402 is driven by a motor to ensure smooth transmission of the lithium-ion battery film; it is used to transmit the original lithium-ion battery film from the production line or other equipment to the winding unit 4; the flattening roller 403 is used to flatten the transmitted lithium-ion battery film to eliminate wrinkles and unevenness of the lithium-ion battery film during the transmission process; through appropriate pressure and position adjustment, the lithium-ion battery film is kept in a uniform state to ensure the smooth progress of subsequent processes; the tension measuring roller 404 detects and feedbacks the tension state of the lithium-ion battery film in real time through sensors and control systems to ensure operation within the optimal tension range; it is used to monitor the tension of the lithium-ion battery film during the winding process; the setting of the contact roller 405 can ensure that the lithium-ion battery film is not damaged or twisted during winding; it is used to smoothly wind the flattened and tensioned lithium-ion battery film onto the winding shaft.

[0058] Through the automated roller setting, the entire winding process can be completed efficiently, reducing manual intervention and improving production efficiency; the flattening roller 403 and the tension measuring roller 404 ensure the flatness and proper tension of the lithium-ion battery film, thereby avoiding defects in subsequent products and improving the quality of the final product.

[0059] Double-station winding, the lithium-ion battery film after passing through the traction unit 3 enters the winding unit 4, and through precise tension control, it is effectively flattened for contact or gap winding, which does not ensure that the lithium-ion battery film has a smooth and wrinkle-free appearance, is short, and has a flush end surface.

[0060] The stretching method of the secondary synchronous stretching system of the above-mentioned wet lithium ion diaphragm off-line secondary synchronous stretching equipment comprises: S1: rolling up the formed cast sheet into a roll by longitudinal stretching, transverse stretching, and longitudinal and transverse synchronous stretching to obtain a once-stretched lithium-ion battery film; S2: The once stretched lithium-ion battery film is passed through an offline secondary synchronous stretching device to achieve an ultra-high ratio stretching of the longitudinal and transverse product relationship; bidirectional synchronous stretching (1-10)*(1-10) times refers to 1-10 times in the transverse direction and 1-10 times in the longitudinal direction; Transverse hole expansion and stretching can ensure that the lithium-ion battery film has an appropriate porosity; the transverse and longitudinal bidirectional shrinkage treatment and heat setting abandon the traditional transverse unidirectional shrinkage treatment method, allowing the lithium-ion battery film to be shrunk in the longitudinal and transverse directions at the same time, thereby improving the bidirectional thermal shrinkage stability.

[0061] A high-strength and high-modulus wet-process lithium-ion battery film, which is prepared by stretching using the secondary synchronous stretching system of the above-mentioned wet-process lithium-ion diaphragm offline secondary synchronous stretching equipment; Preferably, the high-strength and high-modulus wet-process lithium-ion battery film has a thickness range of 2 to 100 μm, an air permeability range of 10-300 s / in2*100cc, a tensile strength range of 300-2000 MPa, a specific puncture strength range of 50-300 gf / μm, a porosity range of 25-75%, and a modulus range of 2 GPa to 30 GPa.

[0062] Working principle: The cast sheet is rolled up through a combination of longitudinal, transverse and longitudinal and transverse synchronous stretching to form a once-stretched lithium-ion battery film.

[0063] Then, the once stretched lithium-ion battery film is introduced into the bidirectional synchronous stretching machine 2 through the unwinding unit 1, passes through the heating stretching section and the cooling shaping section in sequence, realizes hot stretching and cooling shaping, and finally enters the traction unit 3 from the stretching outlet 8.

[0064] In the secondary synchronous stretching process, the problem of film sagging due to gravity is solved, thus overcoming the challenge of rate limitation of a single set of synchronous or asynchronous stretching equipment, and achieving a maximum regional stretching rate of 100*100 times. This treatment obtains lithium-ion battery films with high strength and modulus, and achieves an ultra-high rate stretching with a longitudinal and transverse product relationship, that is, bidirectional synchronous stretching of 1-10 times in the transverse direction and 1-10 times in the longitudinal direction.

[0065] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A wet-process lithium-ion membrane offline secondary synchronous stretching device, which performs secondary synchronous stretching on a wet-process lithium-ion battery film that has been stretched once, characterized in that: The process sequence includes an unwinding unit (1), a bidirectional synchronous stretching machine (2), a traction unit (3) and a winding unit (4); The bidirectional synchronous stretching machine (2) is provided with a plurality of stretching inlets (7) on the bidirectional synchronous stretching machine (2), and passes through a heating stretching section and a cooling shaping section in sequence along the transmission processing direction of the lithium ion battery film, for heating and stretching first, and then cooling and shaping, until it passes through a stretching outlet (8) on the bidirectional synchronous stretching machine (2) and enters the traction unit (3); The heating and stretching section and the cooling and shaping section of the bidirectional synchronous stretching machine (2) are respectively provided with a heating oven (5) and a cooling oven (6); the temperature accuracy of the heating oven (5) is ±0.5°C, and the wind speed uniformity is ±1m / s; The traction unit (3) comprises a mounting frame (301), on which a plurality of heating rollers (302), cooling rollers (303), and vacuum rollers (304) are arranged; the stretched lithium-ion battery film passes through the heating rollers (302), cooling rollers (303), and vacuum rollers (304) alternately in sequence.

2. The wet-process lithium-ion membrane off-line secondary synchronous stretching equipment according to claim 1, characterized in that: The unwinding unit (1) comprises a supporting frame (101) and an unwinding frame (102) for unwinding a lithium-ion battery film, and the lithium-ion battery film alternately passes through a floating roller (103) and a traction roller (104) arranged on the supporting frame (101).

3. The wet-process lithium-ion membrane off-line secondary synchronous stretching equipment according to claim 1, characterized in that: A thickness gauge (305) is provided on the mounting frame (301), and the thickness gauge (305) is located between the heating roller (302) and the cooling roller (303).

4. The wet-process lithium-ion membrane off-line secondary synchronous stretching device according to claim 3, characterized in that: A trimming assembly (306) is arranged on the mounting frame (301); a waste edge winding machine (308) is arranged on the trimming assembly (306); and the trimming assembly (306) is located between the cooling roller (303) and the vacuum roller (304).

5. The wet-process lithium-ion membrane off-line secondary synchronous stretching equipment according to claim 1, characterized in that: The winding unit (4) comprises a winding frame (401), on which a transmission roller (402), a flattening roller (403), a tension measuring roller (404) and a contact roller (405) are sequentially arranged.

6. A method for stretching a secondary synchronous stretching system, based on the wet lithium ion membrane offline secondary synchronous stretching equipment according to any one of claims 1 to 5, characterized in that: The stretching steps include: S1: rolling up the formed cast sheet into a roll by longitudinal stretching, transverse stretching, and longitudinal and transverse synchronous stretching to obtain a once-stretched lithium-ion battery film; S2: The primary stretched lithium-ion battery film is passed through an offline secondary synchronous stretching device to achieve an ultra-high ratio stretching with a longitudinal and transverse product relationship.

7. A high-strength and high-modulus wet-process lithium-ion battery film, characterized in that: It is produced by the stretching method using the secondary synchronous stretching system described in claim 6.

8. The high-strength and high-modulus wet-process lithium-ion battery film according to claim 7, characterized in that: The high-strength and high-modulus wet-process lithium-ion battery film has a thickness range of 2 to 100 μm, an air permeability range of 10-300 s / in2*100 cc, a tensile strength range of 300-2000 MPa, a specific puncture strength range of 50-300 gf / μm, a porosity range of 25-75%, and a modulus range of 2 GPa to 30 GPa.

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