Lithium battery diaphragm wet-process line casting system and method

Abstract

The invention discloses a lithium battery diaphragm wet-process line casting system, which comprises a chilling roller, a film penetrating channel allowing a casting piece to penetrate through is formed between the air cooler and the chilling roller, and the air cooler is provided with an air inlet cavity and an air outlet cavity which are communicated with the film penetrating channel; the gas-liquid separator is communicated with a gas outlet cavity pipeline of the air cooler, and a gas conveying device is arranged on the pipeline between the gas-liquid separator and the air cooler; and the condenser is communicated with the gas inlet cavities of the gas-liquid separator and the air cooler. According to the wet-process casting piece system for the lithium battery diaphragm, the two surfaces of the casting piece are synchronously cooled through the air cooler and the chilling roller correspondingly, rapid and uniform cooling of the casting piece is achieved, and the consistency of the thickness of a finished diaphragm product can be improved. And meanwhile, the air flowing to the air cooler is cooled, so that oil mist in the air can be dewed and condensed, the oil mist component in the air is reduced, the temperature of the air blown to the casting piece can be always kept in a lower range, and the cooling effect on the casting piece is ensured.

Description

Technical Field

[0001] The present invention relates to the field of diaphragm production and manufacturing, and further relates to a lithium battery diaphragm wet line casting system. Background Art

[0002] Microporous preparation technology is a core process in the production of lithium-ion battery separators. Its preparation methods are mainly divided into two technical routes: dry method and wet method. Currently, the wet method dominates the market due to its performance advantages. The casting process, as a key link in the wet production process, directly determines the quality and stability of the separator products. In this process, the melt is extruded through the die head and then rapidly cooled by chilled rollers to form it. However, due to the significant difference in cooling rate between the front and back sides of the casting in the traditional process, it is very easy to cause the thickness uniformity of the final product to not meet the standard. Summary of the Invention

[0003] In response to the above technical problems, the purpose of the present invention is to provide a lithium battery diaphragm wet line casting system, which can synchronously cool the two surfaces of the casting, achieve rapid and uniform cooling of the casting, and help improve the consistency of the thickness of the finished diaphragm product.

[0004] In order to achieve the above objectives, the present invention proposes a lithium battery separator wet line casting system, comprising: Chilled rollers; An air cooler is formed with the chill roller to form a membrane passage for allowing the casting to pass through. The air cooler has an air inlet cavity and an air outlet cavity connected to the membrane passage. The air inlet cavity is used to blow air to the surface of the casting, and the air outlet cavity is used to transport the solvent on the surface of the casting to the gas-liquid separator after forming oil mist. A gas-liquid separator is connected to the air outlet pipe of the air cooler, and a gas conveying device is provided on the pipe between the gas-liquid separator and the air cooler; The condenser is communicated with the gas-liquid separator and the air inlet cavity of the air cooler.

[0005] In some embodiments, the air outlet direction of the air inlet cavity is directed along the tangential direction of the chilled roller.

[0006] In some embodiments, the air suction direction of the air outlet cavity is preferably directed along the radial direction of the chilled roller.

[0007] In some embodiments, the air outlet direction of the air inlet cavity and the air intake direction of the air outlet cavity intersect with each other.

[0008] In some embodiments, the air outlet of the air inlet cavity is in the shape of a narrow slit.

[0009] In some embodiments, at least two adsorption / desorption chambers are further included, wherein an adsorbent is provided in the adsorption / desorption chamber, and the adsorption / desorption chamber is disposed on a pipe between the condenser and the cold air nozzle.

[0010] In some embodiments, the adsorption / desorption chamber is further connected to the gas-liquid separator via a pipeline, and a gas delivery device is provided on the pipeline between the adsorption / desorption chamber and the gas-liquid separator.

[0011] In some embodiments, the air cooler includes an air cooler body, in which the air outlet cavity and the air inlet cavity are formed. One end of the air cooler body has an arc surface that matches the shape of the chilling roller, and the arc surface cooperates with the outer peripheral surface of the traction roller to form the membrane penetration channel.

[0012] In some embodiments, the liquid outlets of the gas-liquid separator and the condenser are both connected to a temporary storage tank through pipes, and a filter is provided on the pipe between the gas-liquid separator and the temporary storage tank.

[0013] The present invention also provides a wet line casting method for lithium battery separators, which comprises the following steps: The high-temperature melt extruded from the die is rapidly cooled to below the glass transition temperature by a chilled roller, so that the melt is transformed from a viscous flow state to an amorphous solid casting sheet; Low-temperature gas is transported to the surface of the casting through the air inlet cavity of the air cooler 3 to reduce the surface temperature of the casting on the side away from the chilling roller. At the same time, the solvent on the surface of the casting is transformed into oil mist through the gas conveying device and then sent to the gas-liquid separator. Most of the oil mist is separated from the air by the gas-liquid separator, and the oil mist in the air is recovered by the condenser. The air is cooled and flows to the air inlet cavity of the air cooler 3 to perform air intake and exhaust circulation in the air cooler 3.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The lithium battery diaphragm wet casting line system and method proposed in the present invention, on the one hand, synchronously cools the two surfaces of the casting through an air cooler and a chill roller, thereby achieving rapid and uniform cooling of the casting, which helps to improve the thickness consistency of the finished diaphragm product. On the other hand, the air cooler can perform suction and exhaust cycles, and the wind field in the diaphragm wet casting line plant will not be turbulent, which can stabilize the temperature and humidity in the plant and prevent the physical and chemical properties of the finished diaphragm product from being affected by changes in local temperature and humidity in the plant. On the other hand, the air flowing into the air inlet chamber of the air cooler is cooled by a condenser, and the cooling can cause condensation and aggregation of oil mist in the air, reducing the oil mist component in the air, preventing environmental pollution caused by the escape of oil mist into the plant, and can also keep the temperature of the air blown to the casting within a relatively low range, ensuring the cooling effect on the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The preferred embodiments will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0016] Figure 1 It is a structural schematic diagram of a lithium battery separator wet line casting system according to one embodiment of the present invention.

[0017] Figure 2 It is a structural schematic diagram of an air cooler of a lithium battery diaphragm wet casting system according to one embodiment of the present invention.

[0018] Description of Figure Numbers: Die head 1; chill roller 2; air cooler 3; air cooler body 31; air inlet cavity 311; air outlet cavity 312; first gas conveying device 4; gas-liquid separator 5; condenser 6; adsorption / desorption chamber 7; second gas conveying device 8; temporary storage tank 9. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0020] Please refer to Figure 1 and Figure 2 A lithium battery separator wet casting system according to one embodiment of the present invention includes a chill roller 2 and an air cooling device. The chill roller 2 and the air cooling device are respectively used to cool the front and back surfaces of the casting sheet 10, thereby achieving rapid and uniform cooling of the casting sheet 10. It will be understood that the front and back surfaces of the casting sheet 10 are two opposing surfaces of the casting sheet 10. In this embodiment, the front surface of the casting sheet 10 refers to the surface of the casting sheet 10 close to the chill roller 2, and the back surface of the casting sheet 10 refers to the surface of the casting sheet 10 away from the chill roller 2.

[0021] Chill roller 2 is used to cool the cast sheet 10. It rapidly cools the high-temperature melt extruded from die head 1 to below its glass transition temperature, transforming the melt from a viscous flow state into an amorphous solid cast sheet 10, thereby preventing crystallization from affecting subsequent stretching. Chill roller 2 contains a circulating cooling medium, such as water or oil. Heat exchange between the cooling medium and chill roller 2 maintains a stable temperature, ensuring efficient cooling of the front surface of the cast sheet 10.

[0022] The air cooling device includes an air cooler 3 , a gas-liquid separator 5 and a condenser 6 .

[0023] The air cooler 3 is disposed outside the chill roller 2 and is used to cool the back surface of the slab 10. This embodiment achieves rapid and uniform cooling of the slab 10 by synchronously cooling both surfaces of the slab 10 through the air cooler 3 and the chill roller 2, thereby improving the thickness consistency of the finished diaphragm.

[0024] In this embodiment, a membrane-penetrating channel is formed in the gap between the air cooler 3 and the chilling roller 2 for the casting sheet 10 to pass through. The depth of the membrane-penetrating channel is greater than the thickness of the casting sheet 10, so that the casting sheet 10 can pass through the membrane-penetrating channel without contacting the air cooler 3, thereby avoiding the air cooler 3 scratching the casting sheet 10 due to the relative movement between the casting sheet 10 and the air cooler 3, and helping to keep the membrane surface of the casting sheet 10 intact.

[0025] The air cooler 3 in this embodiment is configured to not only exhaust air but also intake it. It includes a main body 31 having an arcuate surface that matches the shape of the chilled roller 2. This arcuate surface, in conjunction with the outer circumference of the chilled roller 2, forms the transmembrane passage. The main body also includes an air outlet cavity 312 and an air inlet cavity 311, both communicating with the transmembrane passage.

[0026] Low-temperature air can be blown toward the surface of the slab 10 through the air outlet of the air inlet cavity 311 to cool the slab 10. The air outlet direction of the air inlet cavity 311 is preferably tangential to the chill roller 2. This reduces the impact on the surface of the slab 10 while allowing the air to flow along the surface of the slab 10. During the flow, the air fully exchanges heat with the slab 10, thereby improving the cooling efficiency of the slab 10.

[0027] Air is suctioned from the surface of the slab 10 through the air inlet of the air outlet cavity 312 to reduce the amount of white oil on the surface of the slab 10. The air outlet cavity 312 preferably directs air suction radially along the chill roll 2 to maximize removal of high-boiling-point solvents (such as paraffin oil) from the surface of the slab 10, reducing the solvent content on the surface of the slab 10 and the subsequent degreasing workload. It also prevents solvent from dripping from the slab 10, keeping the floor near the slab rolls clean.

[0028] In this embodiment, the outlet of the air inlet cavity 311 is a narrow, slit-like structure that extends along the length of the air cooler body 31, that is, along the axial direction of the chill roller 2. The length of the outlet of the air inlet cavity 311 is comparable to the width of the cast sheet 10. It is understood that the term "slit-like" in this embodiment of the present invention refers to a long hole with a relatively narrow width and a relatively long shape. The slit-like outlet of the air inlet cavity 311 in this embodiment allows the air ejected through the outlet of the air inlet cavity 311 to have a high exhaust pressure, which maintains contact between the cast sheet 10 and the chill roller 2 and prevents the cast sheet 10 from being lifted.

[0029] During operation of the air cooler 3, negative pressure is applied to the air cooler 3 via the first gas delivery device 4. Due to the pressure differential, the solvent on the surface of the casting slab 10 within the transmembrane channel forms an oil mist. The oil mist and air then move toward the air outlet cavity 312, passing through the cavity 312 and entering the gas-liquid separator 5 via a pipe. The gas-liquid separator 5 separates most of the oil mist from the air. A small portion of the oil mist and air, after leaving the gas-liquid separator 5, undergoes cooling and / or further gas-liquid separation before entering the air inlet cavity 311. The surface of the casting slab 10 is purged from the air outlet of the air inlet cavity 311, thereby completing the air intake and exhaust cycle of the air cooler 33.

[0030] In some embodiments, the air cooler 3 includes air inlet cavities 311 and air outlet cavities 312 arranged alternately along the circumference of the chill roller 2. Two of the air inlet cavities 311 are located at the two side edges of the air cooler and have only one air outlet. The remaining air inlet cavities 311 have two air outlets, and these two air outlets point in opposite directions. The air outlet directions of two adjacent air inlet cavities are opposite, so that the solvent on the surface of the casting in the cooling chamber 312 can be blown toward the air outlet cavities 312, thereby improving the oil removal efficiency of the air outlet cavities 312. In addition, by providing the alternating air inlet cavities 311 and air outlet cavities 312, sufficient heat exchange between the cold air and the casting can be achieved, ensuring the cooling effect on the casting.

[0031] In this embodiment, a membrane-penetrating channel is formed between the chilling roller 2 and the air cooler 3 to allow the casting 10 to pass through. In order to ensure the cooling effect of the air cooler 3 on the casting 10, the air cooler 3 needs to be close enough to the casting 10, that is, the depth of the membrane-penetrating channel is slightly greater than the thickness of the casting 10. Since the specifications of the diaphragm produced by the diaphragm wet process line can be adjusted, that is, when the thickness of the diaphragm product changes, the thickness of the casting 10 needs to be reset, so the gap between the air cooler 3 and the chilling roller 2 should be adjustable. Based on this, in this embodiment, the air cooler 3 is connected to a driving mechanism, and is driven by the driving mechanism to move closer to or away from the chilling roller 2. The movement of the air cooler 3 can be linear movement, swinging, or other forms of movement, which are not limited in this embodiment. As an example, the driving mechanism can drive the air cooler 3 to perform linear movement, and the driving mechanism can adopt a power device such as a cylinder or a hydraulic cylinder.

[0032] The air outlet of the air outlet cavity 312 of the air cooler 3 is connected to the pipe 101. The pipe 101 and the pipe 102 are pipes that connect the air outlet of the air outlet cavity 312 and the air inlet of the gas-liquid separator 5 via the first gas conveying device 4. The air containing oil mist flows from the side of the air cooler 3 to the side of the gas-liquid separator 5 through the first gas conveying device 4 via the pipe 101 and the pipe 102.

[0033] The gas-liquid separator 5 is a device for separating oil mist from air. The structure of the gas-liquid separator 5 is not limited in this embodiment. As an example, the gas-liquid separator 5 can be a cyclone separator. The main features of the cyclone separator are simple structure, great operational flexibility, and high efficiency. It is a novel, efficient, energy-saving, long-term operation and economical separation device. The working principle is to rely on the rotational motion caused by the tangential introduction of airflow and the density difference between the gas and liquid phases. The centrifugal force generated by the high-speed rotation of the fluid in the cyclone separator causes the denser liquid to gradually move downward and eventually be discharged through the liquid outlet of the cyclone separator, while the less dense air is forced upward and eventually discharged through the gas outlet of the cyclone separator.

[0034] Incompletely melted polymer particles may precipitate from the surface of the casting slab 10. When the air outlet cavity 312 of the air cooler 3 draws air, these particles are drawn into the cyclone separator and discharged through the liquid outlet at the bottom of the cyclone separator. To prevent particles from entering the temporary storage tank 9, a filter can be installed downstream of the liquid outlet of the cyclone separator to separate the particles. To ensure filtering performance, the filter can be cleaned or replaced regularly.

[0035] In this embodiment, after the first gas delivery device 4 is activated, it draws air from the transmembrane channel, creating a negative pressure therein. Influenced by atmospheric pressure, the air cooler 3 generates a suction force on the membrane surface of the casting slab 10. Air and the solvent on the membrane surface of the casting slab 10 enter the air outlet cavity 312 and are forcibly transported to the gas-liquid separator 5. After gas-liquid separation in the gas-liquid separator 5, a small amount of oil mist and air flows to the condenser 6.

[0036] Condenser 6 is a device that cools the oil mist and air transported through gas-liquid separator 5. Connected to condenser 6 is a pipe 103, which connects the air outlet of gas-liquid separator 5 and the air inlet of condenser 6. In pipe 103, air containing oil mist flows from gas-liquid separator 5 to condenser 6. Condenser 6 includes a cooler disposed in a sealed chamber. The cooler can be a heat exchanger with fins that cools the air and oil mist using a circulating coolant or cooling water as the cooling medium. It is understood that the cooler can also be an electronic cooler equipped with a Peltier element, for example. Within condenser 6, some of the oil mist condenses and collects on the cooler, where it is recovered.

[0037] The bottoms of the gas-liquid separator 5 and condenser 6 are connected to pipes 108 and 109, respectively. Pipe 108 connects the liquid outlet of the gas-liquid separator 5 to the liquid inlet of the temporary storage tank. In pipe 108, the solvent flows from the gas-liquid separator 5 to the temporary storage tank 9. Pipe 109 connects the liquid outlet of the condenser 6 to the liquid inlet of the temporary storage tank 9. In pipe 109, paraffin oil flows from the condenser 6 to the temporary storage tank 9. The temporary storage tank 9 is a tank for collecting solvent.

[0038] The condenser 6 is also connected to a pipe 104 , which is a pipe between the condenser 6 and the adsorption / desorption device. In the pipe 104 , the oil mist flows from the condenser 6 side to the adsorption / desorption device side.

[0039] In this embodiment, the condenser 6 can lower the temperature of the air after heat exchange, so that the air blown onto the surface of the slab 10 is always maintained within a relatively low temperature range, thereby ensuring a cooling effect on the back of the slab 10. At the same time, the temperature of the air containing the oil mist flowing to the adsorption and desorption device is relatively low. In a low-temperature environment, the kinetic energy of the oil mist molecules is reduced, making them more easily captured by the micropores on the surface of the adsorbent in the desorption tank, thereby improving the adsorption efficiency of the adsorbent.

[0040] The adsorption / desorption device is used to absorb oil mist from the air and desorb previously adsorbed oil mist. The device includes at least two adsorption / desorption chambers 7, each containing an adsorbent for adsorbing oil mist from the air. The present invention does not impose any specific restrictions on the material of the adsorbent; as long as it can adsorb oil mist without chemically reacting with it and can also desorb oil mist after heating, it is sufficient. For example, the adsorbent material can be selected from activated carbon, zeolite, and the like. One or more of these materials can be used.

[0041] The adsorption / desorption chamber 7 is connected to a pipe 105 and a pipe 106. The pipe 105 is a pipe connecting the air outlet of the adsorption / desorption chamber 7 and the air inlet of the air inlet cavity 311 of the air cooler 3. In the pipe 105, air flows from the adsorption / desorption chamber 7 to the air cooler 3. The pipes 106 and 107 are pipes connecting the adsorption / desorption chamber 7 and the gas-liquid separator 5 via the second gas conveying device 8. In the pipes 106 and 107, the desorbed oil mist flows from the adsorption / desorption chamber 7 to the gas-liquid separator 5 for secondary recovery. It can be understood that while one of the adsorption / desorption chambers 7 is undergoing adsorption treatment, the adsorbent in the other adsorption / desorption chamber 7 can be desorbed. After a specified period of time, continuous adsorption of the oil mist can be achieved by alternating between adsorption and desorption treatments.

[0042] The following specifically describes a casting method using the above-mentioned lithium battery separator wet casting system, which includes the following steps: The high-temperature melt extruded from the die head 1 is rapidly cooled to below the glass transition temperature by the chill roller 2, so that the melt is transformed from a viscous flow state to an amorphous solid casting sheet; Low-temperature gas is transported to the surface of the casting through the air outlet of the air inlet chamber 311 of the air cooler 3 to reduce the surface temperature of the casting on the side away from the chilling roller 2. At the same time, the oil mist formed by the solvent on the surface of the casting is transported into the gas-liquid separator 5 through the air outlet of the air outlet chamber of the air cooler 3 through the first gas conveying device 4. Most of the oil mist is separated from the air by the gas-liquid separator 5, and the residual oil mist in the air is recovered by the condenser, and the air is cooled. The cooled air flows to the air inlet chamber 311 of the air cooler 3 to perform air intake and exhaust circulation in the air cooler 3.

[0043] In summary, the lithium battery diaphragm wet casting line system and method proposed in this embodiment, on the one hand, synchronously cools the two surfaces of the casting through the air cooler and the chill roller, thereby achieving rapid and uniform cooling of the casting, which helps to improve the consistency of the thickness of the finished diaphragm product. On the other hand, the air cooler 3 can perform an intake and exhaust cycle, and the wind field in the diaphragm wet casting line factory will not be disturbed, which can stabilize the temperature and humidity in the factory and prevent the physical and chemical properties of the finished diaphragm product from being affected by changes in local temperature and humidity in the factory. On the other hand, the air flowing to the air inlet chamber 311 of the air cooler 3 is cooled by the condenser. The cooling can cause the oil mist in the air to condense and condense, reducing the oil mist component in the air, preventing the oil mist from escaping into the factory and causing environmental pollution, and can also keep the temperature of the air blown to the casting within a relatively low range, ensuring the cooling effect on the casting.

[0044] It should be noted that the above embodiments can be freely combined as needed. The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lithium battery separator wet line casting system, characterized in that: include: Chilled rollers; An air cooler is formed with the chill roller to form a film-penetrating channel for allowing the casting sheet to pass through. The air cooler has an air inlet cavity and an air outlet cavity connected to the film-penetrating channel. The air inlet cavity is used to blow air to the surface of the casting sheet, and the air outlet cavity is used to suck the solvent on the surface of the casting sheet and transport it to the gas-liquid separator side after the solvent forms oil mist. A gas-liquid separator is connected to the air outlet pipe of the air cooler, and a gas conveying device is provided on the pipe between the gas-liquid separator and the air cooler; The air inlet of the condenser is communicated with the air outlet pipeline of the gas-liquid separator, and the air outlet of the condenser is communicated with the air inlet cavity pipeline of the air cooler.

2. The lithium battery separator wet casting system according to claim 1, characterized in that: The air cooler has the air inlet cavities and the air outlet cavities alternately arranged along the circumference of the chilled roller, wherein two of the air inlet cavities are respectively arranged at the two side edges of the air cooler and have only one air outlet, and the remaining air inlet cavities have two air outlets with opposite air outlet directions, and the air outlet directions of the two adjacent air inlet cavities are opposite.

3. The lithium battery separator wet casting system according to claim 1, characterized in that: The air outlet direction of the air inlet cavity is directed along the tangential direction of the chilled roller.

4. The lithium battery separator wet casting system according to claim 1, characterized in that: The air suction direction of the air outlet cavity is directed along the radial direction of the chill roller.

5. The lithium battery separator wet casting system according to claim 1, characterized in that: The air outlet of the air inlet cavity is in a slit shape.

6. The lithium battery separator wet casting system according to claim 1, characterized in that: It also includes at least two adsorption and desorption chambers, wherein adsorbent is provided in the adsorption and desorption chambers, and the adsorption and desorption chambers are arranged on the pipeline between the condenser and the cold air nozzle.

7. The lithium battery separator wet casting system according to claim 6, characterized in that: The adsorption / desorption chamber is also connected to the gas-liquid separator through a pipeline, and a gas conveying device is provided on the pipeline between the adsorption / desorption chamber and the gas-liquid separator.

8. The lithium battery separator wet casting system according to claim 1, characterized in that: The air cooler includes an air cooler body, in which an air outlet cavity and an air inlet cavity are formed. One end of the air cooler body has an arc surface matching the shape of the chilled roller, and the arc surface cooperates with the outer peripheral surface of the traction roller to form the membrane penetration channel.

9. The lithium battery separator wet casting system according to claim 1, characterized in that: The liquid outlets of the gas-liquid separator and the condenser are both connected to the temporary storage tank through pipelines, and a filter is provided on the pipeline between the gas-liquid separator and the temporary storage tank.

10. A wet line casting method for lithium battery separator, characterized in that: The slab casting system according to any one of claims 1 to 9 is used, and the slab casting method comprises the following steps: The high-temperature melt extruded from the die is rapidly cooled to below the glass transition temperature by a chilled roller, so that the melt is transformed from a viscous flow state to an amorphous solid casting sheet; Low-temperature gas is transported to the surface of the casting through the air inlet cavity of the air cooler to reduce the surface temperature of the casting on the side away from the chill roller. At the same time, the solvent on the surface of the casting is transformed into oil mist through the gas conveying device and then sent to the gas-liquid separator. Most of the oil mist is separated from the air by the gas-liquid separator, and the oil mist in the air is recovered by the condenser, and the air is cooled. The cooled air flows to the air inlet cavity of the air cooler to carry out the air intake and exhaust cycle in the air cooler.

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