CN103762325B - A kind of production technology of novel low-cost lithium ion battery PE barrier film - Google Patents

Abstract

The invention discloses a production process of a low-cost lithium-ion battery PE diaphragm, belonging to the field of battery diaphragms. Its production process includes: first, uniformly mix polyethylene and organic solvent to obtain a mixture; respectively extrude, measure, and cast the mixture to obtain an oil-containing film; send the oil-containing film after biaxial stretching into a vacuum drying box, set The organic solvent in the oil-containing film is volatilized at a constant temperature and negative pressure to obtain the primary product of the dry porous film. The volatilized organic solvent enters the exhaust gas adsorption device after cooling, and the adsorbent is selected to adsorb the organic solvent. After the adsorption is completed, the desorption exhaust gas passes through After condensation, it enters the stratification tank, and the separated organic solvent enters the batching system for recycling. This method avoids the solvent extraction and the separation operation of the extraction mixture in the traditional wet process, and the solvent recovered from the waste gas system can continue to enter the batching system for recycling, which greatly reduces the production cost.

Description

A new low-cost lithium-ion battery PE separator production process

technical field

The invention belongs to the field of battery diaphragms, and in particular relates to a production process of a novel low-cost lithium-ion battery PE diaphragm.

Background technique

In recent years, as a high specific energy power source, lithium-ion batteries have been widely used in fields such as portable electronic devices, electric tools, electric vehicles, and energy storage power stations. Diaphragm is one of the important raw materials for batteries. Therefore, lithium The safety of ion batteries has always been a concern. As an important part of the lithium-ion battery, the diaphragm is used to separate the positive electrode from the negative electrode material, allowing ions to pass through and preventing electrons from passing through. The performance of the lithium battery diaphragm determines the interface structure and internal resistance of the battery, which directly affects the capacity of the battery. , cycle and safety performance, the separator with excellent performance plays an important role in improving the overall performance of the battery. The main function of the diaphragm is to separate the positive and negative electrodes of the battery, prevent the two electrodes from contacting and short circuit, and also have the function of allowing electrolyte ions to pass through.

At present, the production methods of lithium-ion battery diaphragm mainly include dry method and wet method. The invention patent CN201010107854.1 applied by Cangzhou Mingzhu Plastic Co., Ltd. discloses a method for preparing lithium-ion battery diaphragm by wet method. The product obtained by this method is The first pass rate is not high. In addition, the traditional wet process also includes solvent extraction and separation of the extraction mixture, which obviously increases the input of production costs.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention proposes a new low-cost lithium-ion battery PE diaphragm preparation method, which does not require solvent extraction and separation of the extraction mixture in the traditional wet process , and the solvent recovered from the waste gas system can continue to enter the batching system for recycling, which greatly reduces the production cost.

Technical scheme of the present invention comprises:

A preparation method of a novel low-cost lithium-ion battery PE diaphragm, comprising the following steps:

a. Ingredients: Weigh 15-50% of polyethylene and 50-85% of organic solvent according to weight percentage, and mix them thoroughly to obtain mixture A;

b. Extrusion and metering: pass the mixture A in step a through an extruder to obtain a high-temperature melt, and the high-temperature melt is accurately metered and then fed into the die;

c. Cast sheet: the high-temperature melt sent into the die in step b flows out from the slit of the die, and is cooled by a chill roller to obtain a cast sheet;

d. Biaxial stretching: preheating the cast sheet obtained in step c to carry out high-temperature biaxial stretching to obtain an oil-containing film;

e. Vacuum drying: send the oil-containing film in step d into a vacuum drying oven, set the temperature and negative pressure to volatilize the organic solvent in the oil-containing film to obtain the primary product of the dry porous film, and the volatilized organic solvent enters the waste gas after cooling The adsorption device uses an adsorbent to adsorb the organic solvent. After the adsorption is completed, it is analyzed, and the desorption waste gas enters the stratified tank after condensation, and the separated organic solvent enters the batching system for recycling;

f, horizontal stretching expansion: the primary product of the porous membrane in step e is expanded by a horizontal stretching machine to obtain a diaphragm;

g. Heat setting and winding: after step f, the expanded separator is heat-set and stress-removed, and then wound by an online winding machine to obtain a lithium-ion battery PE separator.

The organic solvent in the above step a is kerosene or decahydronaphthalene.

In the above step b, the mixture A was passed through a twin-screw extruder with a diameter of 96 mm, an aspect ratio of 52, and a temperature of 130° C. to obtain a high-temperature melt.

In the above step c, the high-temperature melt flowing out of the slit of the die head passes through four chilled rollers with temperatures of 20°C-30°C-30°C-30°C in turn to obtain extruded cast flakes; the extruded cast flakes enter the two-way The synchronous stretching machine obtains an oil-containing film with a longitudinal draw ratio of 5 times and a transverse draw ratio of 5 times.

In step d, the bidirectional stretching can be bidirectional stepwise stretching or bidirectional simultaneous stretching.

In the above step e, the temperature of the drying oven is 100°C, the negative pressure is below -80KPa, and the adsorbent is activated carbon fiber.

In the above step f, the draw ratio of the draw machine is 1.2 times, and the temperature of the draw machine is 120°C.

In the above step g, the heat setting temperature is 125°C.

Beneficial technical effects brought by the present invention:

The present invention proposes a preparation method of a novel low-cost lithium-ion battery PE separator. Compared with the prior art, in the selection of raw materials, the present invention uses polyethylene and organic solvents as raw materials, and the organic solvent is selected from kerosene or decahydronaphthalene. , due to the low boiling point of kerosene and decahydronaphthalene, it is easy to volatilize in the vacuum drying step; in the preparation process, compared with the traditional wet process, this method avoids solvent extraction and extraction mixture in the traditional wet process The separation operation, and the solvent recovered from the exhaust gas system can continue to enter the batching system for recycling, which greatly reduces the production cost.

detailed description

The present invention proposes a new low-cost lithium-ion battery PE diaphragm preparation method. In order to make the advantages and technical solutions of the present invention more prominent, the present invention will be further clearly and completely described below in conjunction with specific embodiments.

The selected raw materials of the present invention can be purchased through commercial channels, and the properties of the selected raw materials of the present invention are described as follows:

Polyethylene: It is a kind of thermoplastic resin obtained by polymerization of ethylene. In industry, it also includes copolymers of ethylene and a small amount of α-olefin. Polyethylene is odorless, non-toxic, feels like wax, and has excellent low temperature resistance. Good chemical stability, resistant to most acid and alkali erosion, insoluble in common solvents at room temperature, low water absorption, excellent electrical insulation performance; the polyethylene of the present invention includes ultra-high molecular weight polyethylene with a molecular weight of 1 million to 1.5 million and a molecular weight lower than 1 million high-density polyethylene.

The present invention, a kind of preparation method of novel low-cost lithium-ion battery PE diaphragm, comprises the following steps:

Step 1, batching step: weigh 15-50% of polyethylene and 50-85% of organic solvent according to the weight percentage. The organic solvent of the present invention is preferably kerosene or decahydronaphthalene, and polyethylene and kerosene or decahydronaphthalene are fully mixed. Mixture A is obtained;

Step 2. Extrusion and metering steps: pass the mixture A in step 1 through a twin-screw extruder with a diameter of 96mm, an aspect ratio of 52, and a temperature of 130°C to obtain a high-temperature melt, and the high-temperature melt is accurately obtained by a melt pump Feed into the die head after metering;

Step 3, casting step: the high-temperature melt sent into the die in step 2 flows out from the slit of the die, and the high-temperature melt flowing out of the slit of the die passes through the temperature in turn at 20°C-30°C-30°C Extruded cast flakes were obtained after four chilled rolls at -30°C; the extruded cast flakes entered a bidirectional synchronous stretching machine to obtain an oil-containing film with a longitudinal draw ratio of 4.5 times and a transverse draw ratio of 5 times;

Step 4. Vacuum drying step: send the oil-containing film in step 3 into a vacuum drying oven, set the temperature at 100°C, and the negative pressure below -80KPa to volatilize the organic solvent in the oil-containing film to obtain the primary product of dry porous film , the volatilized organic solvent enters the exhaust gas adsorption device after cooling, and selects an adsorbent to adsorb the organic solvent. After the adsorption is completed, it is analyzed, and the desorbed exhaust gas enters the stratified tank after condensation, and the separated organic solvent enters the batching system for recycling;

Step 5, horizontal stretching expansion: the primary product of the porous film in step 4 is expanded by a horizontal stretching machine to obtain a diaphragm. The horizontal stretching ratio of the horizontal stretching machine is 1.2 times, and the temperature of the horizontal stretching machine is 120 ° C;

Step 6. Heat setting and winding: the expanded separator in step 5 is heat set at a temperature of 125° C., and after stress is removed, it is wound by an online winding machine to obtain a lithium-ion battery PE separator.

In conjunction with specific embodiments, further explain as follows:

Example 1:

A preparation method of a novel low-cost lithium-ion battery PE diaphragm, comprising the following steps:

Step 1. Ingredients: Weigh 70Kg of polyethylene powder and 396.67Kg of decahydronaphthalene, respectively, and pour them into the stirring tank (the stirrer is in the form of double ribbons) for full stirring to obtain the mixture A, which is set aside;

Step 2. Extrusion and metering steps: Mixture A passes through a twin-screw extruder with a diameter of 96mm, an aspect ratio of 52, and a temperature of 130°C to obtain a uniform high-temperature melt, and the high-temperature melt is accurately metered by a melt pump before entering In the die head;

Step 3, casting step: the high-temperature melt flowing out from the slit of the die head passes through four chilling rollers with temperatures of 20°C-30°C-30°C-30°C in sequence to obtain extruded cast pieces;

Step 4. Stretching step: Extrude the cast sheet into a bidirectional synchronous stretching machine to obtain an oil-containing film with a longitudinal draw ratio of 4.5 times and a transverse draw ratio of 5 times. The preheating temperature is 120°C, the stretching temperature is 125°C, and the cooling and setting temperature 30°C;

Step 5. Vacuum drying step: the stretched oil-containing film enters a vacuum drying oven, the temperature of the drying oven is 100°C, the negative pressure is controlled below -80KPa, the decahydronaphthalene in the film is volatilized, and the primary product of the dry porous film is obtained. The decahydronaphthalene that comes out is cooled to 60°C by the surface cooler and then enters the exhaust gas adsorption device. Activated carbon fiber is used as the adsorbent to absorb the decahydronaphthalene, and then 0.1MPa saturated water vapor is introduced to desorb the decahydronaphthalene from the surface of the carbon fiber. Down, the desorption waste gas enters the layered tank after being condensed, and the separated decahydronaphthalene enters the batching system for recycling;

Step 6. Horizontal drawing expansion step: the obtained dry porous film primary product is expanded by a horizontal drawing machine to obtain a diaphragm. The horizontal drawing ratio of the horizontal drawing machine is 1.2 times, and the temperature of the horizontal drawing machine is 120 ° C;

Step 7: Heat setting and winding steps: After the expanded diaphragm passes through a high-temperature heat setting device, the thermal stress inside the diaphragm is removed. The heat setting temperature is 125°C. After removing the stress, the three-layer diaphragm is wound by an online winding machine to obtain lithium Ion battery PE separator.

Example 2:

Step 1. Ingredients: Weigh 70Kg of polyethylene powder and 70Kg of decahydronaphthalene respectively, and pour them together into the stirring tank (the stirrer is in the form of double ribbons) for full stirring to obtain the mixture A, which is set aside;

Step 2. Extrusion and metering steps: Mixture A passes through a twin-screw extruder with a diameter of 96mm, an aspect ratio of 52, and a temperature of 130°C to obtain a uniform high-temperature melt, and the high-temperature melt is accurately metered by a melt pump before entering In the die head;

Step 3, casting step: the high-temperature melt flowing out from the slit of the die head passes through four chilling rollers with temperatures of 20°C-30°C-30°C-30°C in sequence to obtain extruded cast pieces;

Step 4. Stretching step: Extrude the cast sheet into a bidirectional synchronous stretching machine to obtain an oil-containing film with a longitudinal draw ratio of 4.5 times and a transverse draw ratio of 5 times. The preheating temperature is 120°C, the stretching temperature is 125°C, and the cooling and setting temperature 30°C;

Step 5. Vacuum drying step: the stretched oil-containing film enters a vacuum drying oven, the temperature of the drying oven is 100°C, the negative pressure is controlled below -80KPa, the decahydronaphthalene in the film is volatilized, and the primary product of the dry porous film is obtained. The decahydronaphthalene that comes out is cooled to 60°C by the surface cooler and then enters the exhaust gas adsorption device. Activated carbon fiber is used as the adsorbent to absorb the decahydronaphthalene, and then 0.1MPa saturated water vapor is introduced to desorb the decahydronaphthalene from the surface of the carbon fiber. Down, the desorption waste gas enters the layered tank after being condensed, and the separated decahydronaphthalene enters the batching system for recycling;

Step 6. Horizontal drawing expansion step: the obtained dry porous film primary product is expanded by a horizontal drawing machine to obtain a diaphragm. The horizontal drawing ratio of the horizontal drawing machine is 1.2 times, and the temperature of the horizontal drawing machine is 120 ° C;

Step 7: Heat setting and winding steps: After the expanded diaphragm passes through a high-temperature heat setting device, the thermal stress inside the diaphragm is removed. The heat setting temperature is 125°C. After removing the stress, the three-layer diaphragm is wound by an online winding machine to obtain lithium Ion battery PE separator.

Example 3:

Step 1. Ingredients: Weigh 70Kg of polyethylene powder and 330Kg of decahydronaphthalene respectively, and pour them together into the stirring tank (the stirrer is in the form of double ribbons) and stir thoroughly to obtain the mixture A, which is set aside;

Step 2. Extrusion and metering steps: Mixture A passes through a twin-screw extruder with a diameter of 96mm, an aspect ratio of 52, and a temperature of 130°C to obtain a uniform high-temperature melt, and the high-temperature melt is accurately metered by a melt pump before entering In the die head;

Step 3, casting step: the high-temperature melt flowing out from the slit of the die head passes through four chilling rollers with temperatures of 20°C-30°C-30°C-30°C in sequence to obtain extruded cast pieces;

Step 4. Stretching step: Extrude the cast sheet into a bidirectional synchronous stretching machine to obtain an oil-containing film with a longitudinal draw ratio of 4.5 times and a transverse draw ratio of 5 times. The preheating temperature is 120°C, the stretching temperature is 125°C, and the cooling and setting temperature 30°C;

Step 5. Vacuum drying step: the stretched oil-containing film enters a vacuum drying oven, the temperature of the drying oven is 100°C, the negative pressure is controlled below -80KPa, the decahydronaphthalene in the film is volatilized, and the primary product of the dry porous film is obtained. The decahydronaphthalene that comes out is cooled to 60°C by the surface cooler and then enters the exhaust gas adsorption device. Activated carbon fiber is used as the adsorbent to absorb the decahydronaphthalene, and then 0.1MPa saturated water vapor is introduced to desorb the decahydronaphthalene from the surface of the carbon fiber. Down, the desorption waste gas enters the layered tank after being condensed, and the separated decahydronaphthalene enters the batching system for recycling;

Step 6. Horizontal drawing expansion step: the obtained dry porous film primary product is expanded by a horizontal drawing machine to obtain a diaphragm. The horizontal drawing ratio of the horizontal drawing machine is 1.2 times, and the temperature of the horizontal drawing machine is 120 ° C;

Step 7: Heat setting and winding steps: After the expanded diaphragm passes through a high-temperature heat setting device, the thermal stress inside the diaphragm is removed. The heat setting temperature is 125°C. After removing the stress, the three-layer diaphragm is wound by an online winding machine to obtain lithium Ion battery PE separator.

Example 4:

The difference from Example 1 is that in step 5, the organic solvent is kerosene.

It should be understood that under the enlightenment of the present invention, those skilled in the art can also make various modifications such as replacement and simple combination without departing from the protection scope of the claims of the present invention. The scope should be governed by the appended claims.

Claims (6)

1. a preparation method of low-cost lithium-ion battery PE diaphragm, is characterized in that comprising the following steps: a. Ingredients: Weigh 15-50% of polyethylene and 50-85% of organic solvent according to the weight percentage, and mix them fully to obtain mixture A. The organic solvent is kerosene or decahydronaphthalene; b. Extrusion and metering: pass the mixture A in step a through an extruder to obtain a high-temperature melt, and the high-temperature melt is accurately metered and then fed into the die; c. Cast sheet: the high-temperature melt sent into the die in step b flows out from the slit of the die, and is cooled by a chill roller to obtain a cast sheet; d. Biaxial stretching: preheating the cast sheet obtained in step c to carry out high-temperature biaxial stretching to obtain a film containing an organic solvent; e. Vacuum drying: send the film containing the organic solvent in step d into a vacuum drying oven, set the temperature and negative pressure to volatilize the organic solvent in the film to obtain the primary product of the dry porous film, and cool the volatilized organic solvent Enter the exhaust gas adsorption device, select the adsorbent to adsorb the organic solvent, desorb after the adsorption is completed, the desorbed exhaust gas enters the stratified tank after condensation, and the separated organic solvent enters the batching system for recycling. The pressure is below -80KPa, and the adsorbent is activated carbon fiber; f, horizontal stretching expansion: the primary product of the porous membrane in step e is expanded by a horizontal stretching machine to obtain a diaphragm; g. Heat setting and winding: after step f, the expanded separator is heat-set and stress-removed, and then wound by an online winding machine to obtain a lithium-ion battery PE separator. 2. The preparation method according to claim 1, characterized in that: in the step b, the mixture A passes through a twin-screw extruder with a diameter of 96mm, an aspect ratio of 52, and a temperature of 130°C to obtain a high-temperature melt. 3. The preparation method according to claim 1, characterized in that in step c, the high-temperature melt flowing out from the slit of the die head successively passes through four stages with temperatures of 20°C-30°C-30°C-30°C. After a chill roll, extruded cast sheet is obtained; the extruded cast sheet enters a bidirectional stretching machine to obtain a film containing an organic solvent with a longitudinal draw ratio of 4.5 times and a transverse draw ratio of 5 times. 4. The preparation method according to claim 1, characterized in that: in step d, the biaxial stretching is bidirectional stepwise stretching or bidirectional simultaneous stretching. 5. The preparation method according to claim 1, characterized in that: in the step f, the draw ratio of the draw machine is 1.2 times, and the temperature of the draw machine is 120°C. 6. The preparation method according to claim 1, characterized in that: in the step g, the heat-setting temperature is 125°C.