CN114725612B - High-toughness lithium ion battery blending diaphragm and preparation method thereof - Google Patents

Abstract

The invention provides a high-toughness lithium-ion battery blend separator and a preparation method thereof. The separator is composed of a solid material with micropores. The preparation method at least includes: pretreatment of toughened polymer; mixing the solid material at high speed Mixing in the machine; the mixed materials and plasticizer are processed through the extrusion process, and then through the stretching process, extraction, heat setting, and winding processes to obtain a high-tenacity lithium-ion battery blend separator. In the present invention, the toughening polymer is introduced into the separator system through a blending method, and the toughening polymer and polyethylene form a homogeneous system through the promotion of pretreatment, compatibilizer, strong mechanical force and plasticizer. The separator obtained by the invention has high puncture resistance and is less likely to be punctured by lithium dendrites in the lithium ion battery, which greatly improves the safety of the lithium ion battery.

Description

A high-toughness lithium-ion battery blend separator and its preparation method

Technical field

The present invention relates to the technical field of lithium batteries, and in particular to a high-tenacity lithium-ion battery blend separator and a preparation method thereof.

Background technique

With the rapid development of the new energy industry, people's demand for high-performance energy storage equipment is soaring. Lithium-ion batteries have the advantages of small size, high energy density, long cycle life, no memory effect, high average output voltage, and small self-discharge, and have become the most widely used secondary batteries at present.

The main components of a lithium-ion battery include the positive electrode, negative electrode, electrolyte and separator. The separator functions to separate the positive and negative electrodes to prevent battery short circuit, provide lithium ion transmission channels, and store electrolyte. However, during the use of lithium-ion batteries, due to uneven current and uneven electrode surfaces, lithium dendrites will inevitably be generated. If the generated lithium dendrites pierce the separator, it will cause a short circuit in the battery and the battery temperature will rise sharply. High, it is easy to cause fires, explosions and other safety accidents. Therefore, it is very important to develop a high-toughness lithium-ion battery separator and improve the puncture resistance of the separator to improve battery safety.

In view of this, it is necessary to improve the lithium battery separators in the prior art to solve the above problems.

Contents of the invention

The first object of the present invention is to provide a high-tenacity lithium-ion battery blend separator to solve the problem of low puncture resistance of the separator and avoid the occurrence of battery short circuit problems caused by lithium dendrites piercing the separator.

In order to achieve the above object, the present invention provides a high-toughness lithium-ion battery blend separator. The high-toughness lithium-ion battery blend separator is composed of a solid material with micropores. The solid material is polyethylene, toughened polymer A homogeneous mixture of compounds and compatibilizers.

In some embodiments, the component composition ratio of the solid material is: polyethylene: 74% to 95%, toughening polymer: 4% to 25%, and compatibilizer: 0.4 to 2.5%.

In some embodiments, the number average molecular weight of the polyethylene is between 800,000 g/mol and 1.9 million g/mol.

In some embodiments, the toughening polymer is one or both of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the VA content of the ethylene-vinyl acetate copolymer is between 8wt Between %~28wt%.

In some embodiments, the compatibilizer is one or more of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, and styrene-butadiene-styrene triblock copolymer.

The second object of the present invention is to disclose a method for preparing a high-toughness lithium-ion battery blend separator, and prepare a lithium-ion battery blend separator with excellent performance through biaxial stretching.

In order to achieve the above objectives, the present invention provides a method for preparing a highly tough lithium-ion battery blend separator, which includes the following steps:

Step 1: Extrude the toughened polymer and plasticizer through an extruder and then pelletize to obtain the toughened polymer pretreatment material;

Step 2: Place polyethylene, toughened polymer pretreatment material, and compatibilizer in a high-speed mixer and mix evenly to obtain a mixed material;

Step 3: Add the mixed material prepared in Step 2 to the extruder, inject white oil into the extruder, and extrud and cast it through the T-shaped die to the chill roller to obtain cast flakes;

Step 4: Use a synchronous biaxial stretching machine to biaxially stretch the cast sheet obtained in step 3 to obtain an oil-containing film;

Step 5: Extract the oil-containing film obtained in Step 4 with an extraction agent to obtain a wet film;

Step 6: Let the wet film obtained in Step 5 stand at room temperature in a ventilated place, fix it with a clamping mold and then heat-set it. Finally, go through a winding process to obtain a high-toughness lithium-ion battery blend separator.

In some embodiments, in step one, the extrusion temperature is between 100°C and 140°C, and the screw speed of the extruder is between 130rpm and 150rpm;

In step two, the rotating speed of the flying knife of the high-speed mixer is between 550r/min and 830r/min, and the rotating speed of the barrel of the high-speed mixer is between 9r/min and 12r/min. The mixing time of the machine is between 30min and 45min;

In step three, the temperature of the chill roller is between 10°C and 25°C;

In step four, the biaxial stretching temperature is between 115°C and 125°C, and the biaxial stretching stretching ratio is between 6 and 8 times;

In step five, the extraction time is between 2min and 4min;

In step six, the heat setting temperature is between 90°C and 130°C, and the heat setting time is between 0.5min and 2min.

In some embodiments, in step one, the mass ratio of the components of the toughened polymer pretreatment material is 50wt% to 65wt% of the toughened polymer and 35wt% to 50wt% of the plasticizer, and the plasticizer is One or more of white oil, mineral oil, soybean oil, toluene and xylene.

In some embodiments, in step three, the component mass ratio of the cast sheet is 18wt% to 30wt% of solid material, 70wt% to 82wt% of plasticizer, and the thickness of the cast sheet is between 700 μm and 1000 μm. .

In some embodiments, in step five, the extraction agent is one or more of dichloromethane, chloroform, benzene, carbon disulfide, and ethanol.

Compared with the prior art, the beneficial effects of the present invention are: the present invention introduces toughening polymer into the separator system, and it is difficult to form a homogeneous system between the polar toughening polymer and non-polar polyethylene. The toughened polymer is pretreated through extrusion and granulation processes to achieve early dispersion of the toughened polymer in the plasticizer, which provides the necessary foundation for the subsequent uniform dispersion of the toughened polymer in the separator system. The non-polar segment of the compatibilizer has a strong interaction with polyethylene, and the interaction between the polar segment of the compatibilizer and the toughened polymer is strong. Its existence promotes the interaction between the toughened polymer and polyethylene. interaction between. In addition, under the action of plasticizer, the mechanical force of high-speed mixer and twin-screw extruder provide favorable conditions for achieving good compatibility between toughened polymer and polyethylene, so that toughened polymer and polyethylene The entanglements are formed between the molecular chains, which improves the toughness of the modified separator, thereby obtaining higher puncture resistance and the elongation at break is also improved. The puncture resistance of the separator prepared by the invention is ≥500g, and the elongation at break is ≥95%. The separator is not easily punctured by lithium dendrites generated during the use of lithium ion batteries, thereby improving the safety of lithium ion batteries.

Description of the drawings

Figure 1 is a process flow chart of the preparation method of the high-toughness lithium-ion battery blend separator of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the various embodiments shown in the accompanying drawings. However, it should be noted that these embodiments do not limit the invention. Those of ordinary skill in the art may make functional, method or structural modifications based on these embodiments. Equivalent transformations or substitutions are within the scope of the present invention.

Example 1

A high-toughness lithium-ion battery blend separator. The high-toughness lithium-ion battery blend separator is composed of a solid material with micropores. The solid material is a homogeneous mixture of polyethylene, toughened polymers and compatibilizers. . The component proportions of the solid material are: polyethylene: 74% to 95%, toughening polymer: 4% to 25%, and compatibilizer: 0.4 to 2.5%.

Wherein, the number average molecular weight of the polyethylene is between 800,000 g/mol and 1.9 million g/mol. The toughening polymer is one or both of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the VA content of the ethylene-vinyl acetate copolymer is between 8wt% and 28wt%. . The compatibilizer is one or more of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, and styrene-butadiene-styrene triblock copolymer.

A method for preparing a high-toughness lithium-ion battery blend separator, including the following steps:

Step 1: Extrude the toughened polymer and plasticizer through the extruder and then pelletize to obtain the toughened polymer pretreatment material. The extrusion temperature is between 100°C and 140°C. The screw speed of the extruder is Between 130rpm and 150rpm;

Step 2: Place polyethylene, toughened polymer pretreatment material, and compatibilizer in a high-speed mixer and mix evenly to obtain a mixed material. The flying knife speed of the high-speed mixer is between 550r/min and 830r/min. , the barrel speed of the high-speed mixer is between 9r/min and 12r/min, and the mixing time of the high-speed mixer is between 30min and 45min;

Step 3: Add the mixed material prepared in Step 2 to the extruder, inject white oil into the extruder, extrud and cast it through the T-shaped die to the chill roller, and obtain the temperature of the cast sheet and chill roller. Between 10℃～25℃;

Step 4: Use a synchronous biaxial stretching machine to biaxially stretch the cast sheet prepared in Step 3 to obtain an oil-containing film. The biaxial stretching temperature is between 115°C and 125°C, and the biaxial stretching stretch ratio is between 6 and 6. Between 8 times;

Step 5: Extract the oil-containing film obtained in Step 4 with an extraction agent to obtain a wet film. The extraction time is between 2 minutes and 4 minutes;

Step 6: Let the wet film obtained in Step 5 stand in a ventilated place at room temperature, fix it with a clamping mold and then heat-set it. The heat-setting temperature is between 90℃~130℃, and the heat-setting time is between 0.5min~ Within 2 minutes, a high-toughness lithium-ion battery blend separator is finally produced through a winding process.

In the above preparation process, the mass ratio of the components of the toughened polymer pretreatment material in step one is 50wt% to 65wt% of the toughened polymer and 35wt% to 50wt% of the plasticizer, and the plasticizer is white oil. , mineral oil, soybean oil, one or more of toluene and xylene; in step three, the component mass ratio of the cast sheet is 18wt% to 30wt% of solid material and 70wt% to 82wt% of plasticizer. The thickness of the cast piece is between 700 μm and 1000 μm; in step five, the extraction agent is one or more of methylene chloride, chloroform, benzene, carbon disulfide, and ethanol.

In this embodiment, polyethylene with a number average molecular weight of 1.5 million g/mol, ethylene-vinyl acetate copolymer with a VA content of 9 wt%, maleic anhydride-grafted polyethylene as the compatibilizer, and white oil are used as the compatibilizer. Plasticizer, choose methylene chloride as the extraction agent;

Weigh 50% of ethylene-vinyl acetate copolymer and 50% of white oil respectively according to mass percentage. The extruder temperature is 105°C and the screw speed is 150 rpm. After extruding the ethylene-vinyl acetate copolymer-white oil strip, cut it through Granulate with a granulator to obtain ethylene-vinyl acetate copolymer pretreatment material;

According to mass percentage, take 20.90% polyethylene, 2.18% ethylene-vinyl acetate copolymer pretreated material, 0.02% maleic anhydride grafted polyethylene, and 76.90% white oil. The treatment materials and compatibilizer are mixed evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 750r/min, the barrel speed is 9r/min, and the mixing time is 35min. The obtained mixed material and white oil are passed through a twin-screw extruder. Extrusion, extrusion and casting through T-shaped die to the chill roller, the temperature of the chill roller is 18°C, to obtain a cast sheet with a thickness of 750 μm;

Biaxially stretch the cast sheet through a synchronous biaxial stretching machine at a stretching temperature of 125°C and a stretching ratio of 6 times to obtain an oil-containing film; extract the oil-containing film with dichloromethane for 2 minutes to obtain a wet film; The film was allowed to stand in a ventilated place at room temperature, fixed with a clamping mold, and then heat-set at 130°C for 1 minute. After a winding process, a high-tenacity lithium-ion battery blend separator was obtained.

Example 2

In this embodiment, polyethylene with a number average molecular weight of 1.7 million g/mol is selected, ethylene-octene copolymer is selected as the toughening polymer, maleic anhydride grafted polypropylene is selected as the compatibilizer, and mineral oil is selected as the plasticizer. , choose chloroform as the extraction agent;

Weigh 60% of ethylene-octene copolymer and 40% of mineral oil respectively according to mass percentage. The extruder temperature is 130°C and the screw speed is 130 rpm. After extruding the ethylene-octene copolymer-mineral oil sample, pass it through the pelletizer. Granulate to obtain ethylene-octene copolymer pretreatment material;

According to mass percentage, take 18.24% polyethylene, 2.02% ethylene-octene copolymer pretreated material, 0.01% maleic anhydride grafted polypropylene, and 79.73% mineral oil. Combine the polyethylene and ethylene-octene copolymer pretreated material. , the compatibilizer is mixed evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 800r/min, the barrel speed is 10r/min, and the mixing time is 30min. The obtained mixed material and mineral oil are extruded through a twin-screw extruder. , extruded and cast through a T-shaped die to the chill roller, the temperature of the chill roller is 20°C, and the cast sheet is obtained, with a thickness of 800 μm;

The cast sheet was biaxially stretched using a synchronous biaxial stretching machine at a stretching temperature of 122°C and a stretching ratio of 7 times to obtain an oily film; the oily film was extracted with chloroform for 3 minutes to obtain a wet film; the wet film was obtained The film is allowed to stand in a ventilated place at room temperature, fixed with a clamping mold, and then heat-set at 120°C for 1 minute. After a winding process, a high-tenacity lithium-ion battery blend separator is obtained.

Example 3

In this embodiment, polyethylene with a number average molecular weight of 1.2 million g/mol, an ethylene-vinyl acetate copolymer with a VA content of 18 wt%, and a styrene-butadiene-styrene triblock copolymer are used as the compatibilizer. Agent, choose xylene as plasticizer, choose ethanol as extraction agent;

Weigh 55% of ethylene-vinyl acetate copolymer and 45% of xylene according to mass percentage. The extruder temperature is 115°C and the screw speed is 140 rpm. After extruding the ethylene-vinyl acetate copolymer-xylene spline, cut it through Granulate with a granulator to obtain ethylene-vinyl acetate copolymer pretreatment material;

According to mass percentage, take 20.35% polyethylene, 6.52% ethylene-vinyl acetate copolymer pretreated material, 0.03% styrene-butadiene-styrene triblock copolymer, and 73.10% xylene. Combine polyethylene, ethylene - Mix the vinyl acetate copolymer pretreatment material and compatibilizer evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 650r/min, the barrel speed is 10r/min, and the mixing time is 40min. The obtained mixed material is mixed with the second Toluene is extruded through a twin-screw extruder, extruded through a T-shaped die and cast to a chill roller. The chill roller temperature is 15°C to obtain a cast flake with a thickness of 800 μm;

Biaxially stretch the cast sheet through a synchronous biaxial stretching machine at a stretching temperature of 120°C and a stretching ratio of 8 times to obtain an oily film; extract the oily film with ethanol for 3.5 minutes to obtain a wet film; Let it stand in a ventilated place at room temperature. After fixing it with a clamping mold, it is heat-set at 110°C for 1.5 minutes. After a rolling process, a high-toughness lithium-ion battery blend separator is produced.

Example 4

In this embodiment, polyethylene with a number average molecular weight of 1 million g/mol is selected, ethylene-octene copolymer is selected as the toughening polymer, and styrene-butadiene-styrene triblock copolymer is selected as the compatibilizer. Use toluene as the plasticizer and carbon disulfide as the extraction agent;

Weigh 65% of ethylene-octene copolymer and 35% of toluene respectively according to mass percentage. The extruder temperature is 135°C and the screw speed is 130 rpm. After extruding the ethylene-octene copolymer-toluene spline, it is granulated through a pelletizer. , obtain ethylene-octene copolymer pretreatment material;

According to mass percentage, take 20.80% polyethylene, 7.96% ethylene-octene copolymer pretreated material, 0.04% styrene-butadiene-styrene triblock copolymer, and 71.20% toluene. The olefin copolymer pretreatment material and compatibilizer are mixed evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 600r/min, the barrel speed is 12r/min, and the mixing time is 40min. The obtained mixed material and toluene are passed through the twin-screw Extruded by an extruder, extruded and cast through a T-shaped die to a chill roller with a chill roller temperature of 13°C to obtain a cast sheet with a thickness of 900 μm;

Biaxially stretch the cast sheet through a synchronous biaxial stretching machine at a stretching temperature of 118°C and a stretching ratio of 8 times to obtain an oil-containing film; extract the oil-containing film with carbon disulfide for 4 minutes to obtain a wet film; put the wet film in Let it stand in a ventilated place at room temperature. After fixing it with a clamping mold, it is heat-set at 90°C for 2 minutes. After a rolling process, a high-toughness lithium-ion battery blend separator is produced.

Example 5

In this embodiment, polyethylene with a number average molecular weight of 800,000 g/mol, ethylene-vinyl acetate copolymer with a VA content of 24 wt%, maleic anhydride-grafted polypropylene as the compatibilizer, and soybean oil are used. Plasticizer, use methylene chloride as the extraction agent;

Weigh 50% of ethylene-vinyl acetate copolymer and 50% of soybean oil respectively according to mass percentage. The extruder temperature is 110°C and the screw speed is 140 rpm. After extruding the ethylene-vinyl acetate copolymer-soybean oil sample, cut it through Granulate with a granulator to obtain ethylene-vinyl acetate copolymer pretreatment material;

According to mass percentage, take 21.56% polyethylene, 12.83% ethylene-vinyl acetate copolymer pretreated material, 0.05% maleic anhydride grafted polypropylene, and 65.56% soybean oil. The treatment materials and compatibilizer are mixed evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 780r/min, the barrel speed is 12r/min, and the mixing time is 35min. The obtained mixed material and soybean oil are passed through a twin-screw extruder. Extrusion, extrusion and casting through T-shaped die to the chill roller, the temperature of the chill roller is 18°C, to obtain a cast sheet with a thickness of 850 μm;

Biaxially stretch the cast sheet through a synchronous biaxial stretching machine at a stretching temperature of 118°C and a stretching ratio of 7 times to obtain an oil-containing film; extract the oil-containing film with methylene chloride for 3 minutes to obtain a wet film; The film was left to stand in a ventilated place at room temperature, fixed with a clamping mold, and then heat-set at 90°C for 1.5 minutes. After a winding process, a high-toughness lithium-ion battery blend separator was obtained.

Example 6

In this embodiment, polyethylene with a number average molecular weight of 1.8 million g/mol, ethylene-vinyl acetate copolymer with a VA content of 28 wt%, maleic anhydride-grafted polyethylene as the compatibilizer, and white oil are used as the compatibilizer. For plasticizers, benzene is used as the extraction agent;

Weigh 55% of ethylene-vinyl acetate copolymer and 45% of white oil respectively according to mass percentage. The extruder temperature is 115°C and the screw speed is 150 rpm. After extruding the ethylene-vinyl acetate copolymer-white oil sample, cut it through Granulate with a granulator to obtain ethylene-vinyl acetate copolymer pretreatment material;

According to mass percentage, take 22.50% polyethylene, 13.57% ethylene-vinyl acetate copolymer pretreated material, 0.07% maleic anhydride grafted polyethylene, and 63.86% white oil. The treated materials and compatibilizer are mixed evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 820r/min, the barrel speed is 12r/min, and the mixing time is 30min. The obtained mixed material and white oil are passed through a twin-screw extruder. Extrusion, extrusion and casting through T-shaped die to the chill roller, the temperature of the chill roller is 20°C, to obtain a cast sheet with a thickness of 950 μm;

Biaxially stretch the cast sheet through a synchronous biaxial stretching machine at a stretching temperature of 120°C and a stretching ratio of 7 times to obtain an oil-containing film; extract the oil-containing film with benzene for 3.5 minutes to obtain a wet film; Let it stand in a ventilated place at room temperature, fix it with a clamping mold, and heat set it at 100°C for 1 minute. After a rolling process, a high-toughness lithium-ion battery blend separator is produced.

Comparative example 1

Polyethylene with a number average molecular weight of 1.5 million g/mol is selected, white oil is selected as the plasticizer, and methylene chloride is selected as the extractant; the polyethylene and white oil are extruded through a twin-screw extruder, in which polyethylene accounts for the total 23% of the mass, and white oil accounts for 77% of the total mass. It is extruded through a T-shaped die and cast to the chill roller. The temperature of the chill roller is 18°C to obtain a cast sheet with a thickness of 750 μm; it is processed through a synchronous biaxial stretching machine. The cast sheet is biaxially stretched at a stretching temperature of 125°C and a stretching ratio of 6 times to obtain an oil-containing film; the oil-containing film is extracted with dichloromethane for 2 minutes to obtain a wet film; the wet film is allowed to stand in a ventilated place at room temperature. Place it, fix it with a clamping mold, heat set it at 130°C for 1 minute, and then go through a rolling process to prepare the lithium-ion battery separator.

Comparative example 2

Polyethylene with a number average molecular weight of 1.7 million g/mol was selected, ethylene-octene copolymer was selected as the toughening polymer, maleic anhydride grafted polypropylene was selected as the compatibilizer, mineral oil was selected as the plasticizer, and three Methyl chloride is used as the extraction agent; polyethylene, ethylene-octene copolymer, maleic anhydride-grafted polypropylene and mineral oil are extruded through an extruder, in which polyethylene accounts for 18.24% of the total mass, and ethylene-octene copolymer Pretreatment material 2.02%, maleic anhydride grafted polypropylene 0.01%, mineral oil accounting for 79.73% of the total mass, extruded through a T-shaped die and cast to the chill roller, the temperature of the chill roller is 20°C, and the cast piece is obtained. The thickness of the sheet is 800 μm; the cast sheet is biaxially stretched using a synchronous biaxial stretching machine at a stretching temperature of 122°C and a stretching ratio of 7 times to obtain an oily film; the oily film is extracted with chloroform for 3 minutes to obtain a wet film. film; let the wet film stand in a ventilated place at room temperature, fix it with a clamping mold, heat set it at 120°C for 1 minute, and then go through a winding process to obtain a high-toughness lithium-ion battery blend separator.

Comparative example 3

Select polyethylene with a number average molecular weight of 1.2 million g/mol, ethylene-vinyl acetate copolymer with a VA content of 18 wt%, xylene as the plasticizer, and ethanol as the extraction agent; weigh the ethylene separately according to mass percentage. - Vinyl acetate copolymer 55%, xylene 45%, extruder temperature 115°C, screw speed 140rpm, after extruding ethylene-vinyl acetate copolymer-xylene spline, pelletize through a pelletizer to obtain ethylene - Vinyl acetate copolymer pretreatment material; take 20.35% polyethylene, 6.55% ethylene-vinyl acetate copolymer pretreatment material, and 73.10% xylene according to mass percentage. The treated materials are mixed evenly in a high-speed mixer. The flying knife speed of the high-speed mixer is 650r/min, the barrel speed is 10r/min, and the mixing time is 40min. The obtained mixed material and xylene are extruded through a twin-screw extruder. The T-shaped die is extruded and cast to the chill roller. The chill roller temperature is 15°C to obtain a cast sheet with a thickness of 800 μm. The cast sheet is biaxially stretched through a synchronous biaxial stretching machine at a stretching temperature of 120°C. The oil-containing film is obtained at a magnification of 8 times; the oil-containing film is extracted with ethanol for 3.5 minutes to obtain a wet film; the wet film is left to stand in a ventilated place at room temperature, fixed with a clamping mold, and heat set at 110°C for 1.5 minutes. , a high-toughness lithium-ion battery blend separator is produced after a winding process.

Table 1 Comparison of performance of separators prepared in various embodiments

project Puncture resistance (g) Tensile strength(MPa) Elongation at break (%) Example 1 552.49 210.55 96.13 Example 2 662.71 230.38 99.37 Example 3 567.44 216.71 95.74 Example 4 688.32 222.57 98.28 Example 5 636.24 223.76 95.27 Example 6 711.93 242.57 100.89 Comparative example 1 384.55 169.12 66.73 Comparative example 2 424.15 197.22 72.91 Comparative example 3 454.154 213.76 70.28

It can be seen from Table 1 that the puncture resistance, tensile strength, and elongation at break of the separator prepared by the present invention are better than those of the separator prepared by the comparative example. As a result, by adding toughening polymers to the separator system, pretreating the toughened polymers, and adding compatibilizers, the toughness of the separator can be improved, and a high-toughness lithium-ion battery blend separator can be obtained. Puncture resistance.

Applying the separator prepared by the present invention to a lithium-ion battery can reduce the risk of the separator being punctured by lithium dendrites and improve the safety of the lithium-ion battery.

The series of detailed descriptions listed above are only specific descriptions of feasible implementations of the present invention. They are not intended to limit the protection scope of the present invention. Any equivalent implementations or implementations that do not depart from the technical spirit of the present invention are not intended to limit the protection scope of the present invention. All changes should be included in the protection scope of the present invention.

In addition, it should be understood that although this specification is described in terms of implementations, not each implementation only contains an independent technical solution. This description of the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole. , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (8)

1. A method for preparing a high-toughness lithium-ion battery blended separator, characterized in that the high-toughness lithium-ion battery blended separator is composed of a solid material with micropores, and the solid material is polyethylene, toughened polymer Homogeneous mixture of substance and compatibilizer; The preparation method of the high-toughness lithium-ion battery blend separator includes the following steps: Step 1: Extrude the toughened polymer and plasticizer through an extruder and then pelletize to obtain the toughened polymer pretreatment material; Step 2: Place polyethylene, toughened polymer pretreatment material, and compatibilizer in a high-speed mixer and mix evenly to obtain a mixed material; Step 3: Add the mixed material prepared in Step 2 to the extruder, inject white oil into the extruder, and extrud and cast it through the T-shaped die to the chill roller to obtain cast flakes; Step 4: Use a synchronous biaxial stretching machine to biaxially stretch the cast sheet obtained in step 3 to obtain an oil-containing film; Step 5: Extract the oil-containing film obtained in Step 4 with an extraction agent to obtain a wet film; Step 6: Let the wet film obtained in Step 5 stand in a ventilated place at room temperature, fix it with a clamping mold and then heat-set it. Finally, go through a winding process to obtain a high-toughness lithium-ion battery blend separator; In step one, the extrusion temperature is between 100°C and 140°C, and the screw speed of the extruder is between 130rpm and 150rpm; In step two, the rotating speed of the flying knife of the high-speed mixer is between 550r/min and 830r/min, and the rotating speed of the barrel of the high-speed mixer is between 9r/min and 12r/min. The mixing time of the machine is between 30min and 45min; In step three, the temperature of the chill roller is between 10°C and 25°C; In step four, the biaxial stretching temperature is between 115°C and 125°C, and the stretching ratio of the biaxial stretching is between 6 and 8 times; In step five, the extraction time is between 2min and 4min; In step six, the heat setting temperature is between 90°C and 130°C, and the heat setting time is between 0.5min and 2min. 2. The preparation method of high-toughness lithium-ion battery blend separator according to claim 1, characterized in that the component composition ratio of the solid material is: polyethylene: 74% to 95%, toughening polymer: 4 %～25%, compatibilizer: 0.4～2.5%. 3. The method for preparing a high-toughness lithium-ion battery blend separator according to claim 1, wherein the number average molecular weight of the polyethylene is between 800,000 g/mol and 1.9 million g/mol. 4. The method for preparing a high-toughness lithium-ion battery blend separator according to claim 1, wherein the toughening polymer is one of ethylene-vinyl acetate copolymer, ethylene-octene copolymer or Two types, the VA content of the ethylene-vinyl acetate copolymer is between 8wt% and 28wt%. 5. The preparation method of high-toughness lithium-ion battery blend separator according to claim 1, characterized in that the compatibilizer is maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, styrene-butylene More than one type of diene-styrene triblock copolymer. 6. The method for preparing a high-toughness lithium-ion battery blend separator according to claim 1, characterized in that, in step one, the component mass ratio of the toughened polymer pretreatment material is 50wt% to toughened polymer. 65wt%, plasticizer 35wt% ~ 50wt%, the plasticizer is one or more of white oil, mineral oil, soybean oil, toluene and xylene. 7. The method for preparing a high-toughness lithium-ion battery blend separator according to claim 1, characterized in that in step three, the component mass ratio of the cast sheet is 18wt% to 30wt% of solid material and 70wt of plasticizer. %～82wt%, and the thickness of the cast piece is between 700μm～1000μm. 8. The preparation method of high-tenacity lithium-ion battery blend separator according to claim 1, characterized in that, in step five, the extraction agent is one of methylene chloride, chloroform, benzene, carbon disulfide, and ethanol. above.