WO2024044901A1

WO2024044901A1 - Solvent-resistant enhanced polyester film, preparation method therefor, composite current collector and use

Info

Publication number: WO2024044901A1
Application number: PCT/CN2022/115555
Authority: WO
Inventors: 朱中亚; 王帅; 夏建中; 李学法; 张国平
Original assignee: 扬州纳力新材料科技有限公司
Priority date: 2022-08-29
Filing date: 2022-08-29
Publication date: 2024-03-07

Abstract

The present application relates to a solvent-resistant enhanced polyester film. The solvent-resistant enhanced polyester film comprises a core layer, and a first surface layer and a second surface layer which are respectively arranged on two sides of the core layer; the first surface layer and the second surface layer are prepared from the following raw materials in percentage by mass: 70%-97% of a polyester material, 2%-25% of a crystallization auxiliary material and 1%-5% of an additive; and the core layer is prepared from the following raw materials in percentage by mass: 95%-99% of a polyester material and 1%-5% of an additive. The crystallization auxiliary material comprises one or more of poly(2,6-dimethyl-1,4-phenylene oxide), polycarbonate, polypropylene, maleic anhydride-grafted polypropylene, glycidyl methacrylate-grafted polypropylene and derivatives thereof.

Description

Solvent-resistant reinforced polyester film, preparation method thereof, composite current collector and use

Technical field

This application relates to the field of energy storage technology, in particular to a solvent-resistant reinforced polyester film, its preparation method, composite current collector and use.

Background technique

At present, composite current collectors based on polymer films are widely used in the new energy industry. The preparation process of the composite current collector is usually: using physical vapor deposition (PVD) method to deposit polymer films (such as polypropylene, polyethylene, polyethylene, etc.) A layer of metal (aluminum, copper, etc.) material is deposited on the ester. The preparation of a surface metallized film with certain electrical conductivity is a composite current collector. Compared with traditional current collectors, composite current collectors based on polymer films have the characteristics of low cost, light weight and good internal insulation. Applying this composite current collector to batteries can reduce the cost of the battery and improve the performance of the battery. energy density and safety.

Among the many composite current collectors based on polymer films, composite current collectors based on polyester films are the most common. However, there are often pores (such as pinholes) inside the metal layer of composite current collectors based on polyester films, which cause the polyester base film to come into contact with the battery electrolyte during use, causing the polyester base film to swell and affecting the stability of the composite current collector. sex.

Contents of the invention

According to various embodiments of the present application, a solvent-resistant enhanced polyester film that can improve the swelling resistance of the polyester film in battery electrolyte and thereby improve the stability of the composite current collector, its preparation method, and the composite current collector are provided. Fluids and uses.

A solvent-resistant enhanced polyester film, the polyester film includes a core layer, and a first surface layer and a second surface layer respectively provided on both sides of the core layer;

The raw material compositions of the first surface layer and the second surface layer independently include: 70% to 97% polyester material, 2% to 25% crystallization auxiliary materials and 1% to 5% additives in terms of mass percentage;

The raw material composition of the core layer includes, in terms of mass percentage: 95% to 99% polyester material and 1% to 5% additives;

The crystallization auxiliary materials include poly2,6-dimethyl-1,4-phenyl ether, polycarbonate, polypropylene, maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene and their One or more of the derivatives.

In some embodiments, the polyester material includes PET (polyethylene terephthalate), PEN (polyethylene 2,6-naphthalate), PBT (polybutylene terephthalate) alcohol ester), PCT (poly 1,4-cyclohexanedimethanol terephthalate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol ester), PTN (polyethylene terephthalate-1,4-cyclohexanedimethanol ester), 2,6-Trimethylene naphthalate), PTT (Polytrimethylene terephthalate), PBN (Polybutylene 2,6-naphthalate), PBAT (Polybutylene adipate terephthalate) ester), PAR (polyarylate), polybutylene 2,5-furandicarboxylate and one or more of their derivatives.

In some embodiments, the additives in the core layer, the first skin layer and the second skin layer each independently include one of a nucleating agent, an antioxidant, a slip agent and an antistatic agent, or Several kinds.

In some embodiments, the nucleating agent includes magnesium oxide, zinc oxide, aluminum oxide, copper oxide, barium sulfate, benzophenone, sodium carbonate, sodium benzoate, triphenyl phosphate, magnesium stearate, and polyhexane One or more lactones.

In some embodiments, the antioxidant includes one or more of bisphenol A phosphite and phosphonate.

In some embodiments, the slip agent includes one or more of titanium dioxide, silica, calcium carbonate, talc, kaolin, diatomaceous earth, siloxane and acrylate.

In some embodiments, the antistatic agent includes one or more of carbon black, graphite, glycerol, polyglycerol, polyethylene glycol, polyether ester and conductive fiber.

In some embodiments, the first surface layer and the second surface layer have the same thickness, and the thicknesses of the first surface layer, the core layer and the second surface layer account for the thickness of the polyester film as a percentage of 5% to 20% and 60% to 90%, respectively. %, 5%~20%.

This application also provides a preparation method for the above-mentioned solvent-resistant reinforced polyester film, which includes the following steps:

The raw materials of the first surface layer, the core layer and the second surface layer are independently mixed, and sequentially undergo heating, melt extrusion and molding and slicing processes to prepare the first polyester chips, the second polyester chips and the third polyester chips respectively. ;

The first polyester chip, the second polyester chip and the third polyester chip are crystallized and dried separately and sequentially, and then added to different twin-screw extruders. After heating, melting and extrusion processing, a melt mixture is obtained. material;

The molten mixture is sequentially subjected to sheet casting, stretching and heat treatment to obtain a polyester film;

The polyester film includes the core layer, the first surface layer and the second surface layer, and the first surface layer and the second surface layer are located on both sides of the core layer;

In some embodiments, the crystallization temperature during the crystallization process is 130-185°C, and the crystallization time is 20-130 min; the drying temperature during the drying process is 130-175°C, and the drying time is 110～300min.

In some embodiments, the heat treatment process includes the following steps: the first stage: raising the temperature to 130-160°C, and treating for 0.5-20 minutes; the second stage: raising the temperature to 160-220°C, and treating for 0.5-30 minutes; the third stage: Lower the temperature to 130~160℃ and process for 0.5~20min; the fourth stage: lower the temperature to 70~110℃ and process for 0.5~20min.

Further, the present application provides a composite current collector, which includes a support layer and a metal layer disposed on at least one surface of the support layer. The support layer includes the above-mentioned polyester film or is produced by the above-mentioned preparation method. of polyester film.

In some embodiments, the composite current collector further includes a protective layer, which is disposed on a surface of the metal layer away from the support layer;

Optionally, the material of the protective layer includes nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, Ketjen black, One or more of carbon nanoquantum dots, carbon nanotubes, carbon nanofibers and graphene.

In some embodiments, the thickness of the protective layer ranges from 10 to 150 nm.

In some embodiments, the thickness of the protective layer ranges from 20 to 100 nm.

Further, the present application provides an electrode, which electrode includes the above composite current collector.

Furthermore, the present application provides a battery including the above composite current collector.

In addition, this application also provides an electrical device, which includes the above-mentioned battery.

The details of one or more embodiments of the application are set forth in the description below. Other features, objects and advantages of the application will become apparent from the description and claims.

Detailed ways

The technical solution of the present application will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing specific embodiments only and is not intended to limit the application. As used herein, the term "one or more" includes any and all combinations of one or more of the associated listed items.

One embodiment of the present application provides a solvent-resistant enhanced polyester film. The polyester film includes a core layer, and a first surface layer and a second surface layer respectively provided on both sides of the core layer;

Crystallization auxiliary materials include poly2,6-dimethyl-1,4-phenyl ether, polycarbonate, polypropylene, maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene and their derivatives one or more of them.

The key factor affecting the solvent resistance of the polyester film is the crystallinity of the polyester material. Polyester films with high crystallinity have better solvent resistance due to their smaller free volume. However, increasing the crystallinity of the polyester film will cause the polyester film to become brittle, leading to an increase in the membrane rupture rate of the polyester film during the preparation process. In order to take advantage of the improved solvent resistance of the polyester film brought by high crystallinity and balance the problem of increased membrane rupture rate of the polyester film caused by high crystallinity, the present application provides a solvent-resistant enhanced polyester film, which The first surface layer and the second surface layer of the polyester film are made of polyester material, crystallization auxiliary materials and additives. The first surface layer and the second surface layer have a high degree of crystallinity. The core layer between the first surface layer and the second surface layer is The crystallinity is lower than the two. The first surface layer and the second surface layer with higher crystallinity provide the polyester film with solvent resistance, and the core layer with lower crystallinity provides flexibility as the main body of the polyester film, thereby reducing the membrane rupture rate during the film production process. , to achieve stable production of polyester film. Using the above-mentioned polyester film as the base film to prepare a composite current collector can effectively solve the problem of instability of the composite current collector during battery application caused by the electrolyte-swollen base film.

It can be understood that the crystallization auxiliary materials may include PPO (poly 2,6-dimethyl-1,4-phenyl ether), PC (polycarbonate), PP (polypropylene), PP-g-MA (maleic anhydride) Any one of grafted polypropylene), PP-g-GMA (glycidyl methacrylate grafted polypropylene) and their derivatives, including PPO (poly 2,6-dimethyl-1, 4-phenylene ether), PC (polycarbonate), PP (polypropylene), PP-g-MA (maleic anhydride grafted polypropylene), PP-g-GMA (glycidyl methacrylate grafted polypropylene) ) and their derivatives in any proportion.

In some embodiments, polyester materials include PET (polyethylene terephthalate), PEN (polyethylene 2,6-naphthalate), PBT (polybutylene terephthalate) ), PCT (poly 1,4-cyclohexanedimethanol terephthalate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol ester), PTN (poly2, Trimethylene 6-naphthalate), PTT (polytrimethylene terephthalate), PBN (polybutylene 2,6-naphthalate), PBAT (polybutylene adipate terephthalate) , PAR (polyarylate), polybutylene glycol 2,5-furandicarboxylate and one or more of their derivatives.

It can be understood that the polyester material can be PET (polyethylene terephthalate), PEN (polyethylene 2,6-naphthalate), PBT (polybutylene terephthalate) , PCT (poly 1,4-cyclohexanedimethanol terephthalate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol), PTN (poly 2,6 -Trimethylene naphthalate), PTT (polytrimethylene terephthalate), PBN (polybutylene 2,6-naphthalate), PBAT (polybutylene adipate terephthalate), Any one of PAR (polyarylate), polybutylene furandicarboxylate and their derivatives, or PET (polyethylene terephthalate), PEN (poly2 , 6-ethylene naphthalate), PBT (polybutylene terephthalate), PCT (poly 1,4-cyclohexanedimethanol terephthalate), PETG (polyterephthalate) Ethylene glycol formate-1,4-cyclohexanedimethanol), PTN (polytrimethylene 2,6-naphthalate), PTT (polytrimethylene terephthalate), PBN (polytrimethylene 2,6-naphthalate) Butylene naphthalate), PBAT (polybutylene adipate terephthalate), PAR (polyarylate) and polybutylene 2,5-furandicarboxylate and their derivatives Mixtures of various types in any proportion.

In some embodiments, the additives in the core layer, the first skin layer and the second skin layer each independently include one or more of a nucleating agent, an antioxidant, a slip agent and an antistatic agent.

In some embodiments, nucleating agents include magnesium oxide, zinc oxide, aluminum oxide, copper oxide, barium sulfate, benzophenone, sodium carbonate, sodium benzoate, triphenyl phosphate, magnesium stearate, and polycaprolactone one or more of them.

In some embodiments, the antioxidant includes one or more of bisphenol A phosphite and phosphonate esters.

In some embodiments, the slip agent includes one or more of titanium dioxide, silica, calcium carbonate, talc, kaolin, diatomaceous earth, silicone and acrylate.

It should be explained that the substances included in nucleating agents, slip agents and antistatic agents are only classified according to the main function played by the substance. In addition, the substance also has other auxiliary functions. For example: although magnesium oxide, zinc oxide, aluminum oxide and copper oxide in this application are mainly used as nucleating agents, they also have antistatic effects; similarly, calcium carbonate and talc powder in this application are mainly used as slip agents. , but it also has a nucleating agent-like effect; the main function of polyethylene glycol in this application is antistatic, and in addition, it also has a nucleating agent-like effect.

In some embodiments, the thickness of the first surface layer and the second surface layer are equal, and the thickness of the first surface layer, the core layer and the second surface layer account for the thickness of the polyester film as a percentage of 5% to 20%, 60% to 90%, respectively. 5%~20%.

Optionally, the thickness of the first surface layer, the core layer and the second surface layer may account for 5%, 90%, and 5% of the thickness of the polyester film in sequence; the thickness of the first surface layer, the core layer, and the second surface layer may account for The percentages of the film thickness can be 8%, 84%, and 8% in sequence; the thicknesses of the first surface layer, the core layer, and the second surface layer can be 10%, 80%, and 10% in the thickness of the polyester film; the first surface layer , the percentages of the thickness of the core layer and the second surface layer to the thickness of the polyester film can be 15%, 70%, and 15% in sequence; the thicknesses of the first surface layer, the core layer, and the second surface layer can be in sequence as a percentage of the thickness of the polyester film. 20%, 60%, 20%.

This application also provides a preparation method for the above-mentioned polyester film, which includes the following steps:

The molten mixture is sequentially cast, stretched and heat treated to obtain a polyester film;

The polyester film includes a core layer, a first surface layer and a second surface layer, and the first surface layer and the second surface layer are located on both sides of the core layer;

In some embodiments, the crystallization temperature during the crystallization process is 130-185°C, and the crystallization time is 20-130 min; the drying temperature during the drying process is 130-175°C, and the drying time is 110-300 min.

Understandably, the crystallization treatment temperature may be 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C or 185°C, etc., and the crystallization treatment time may be It is 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min or 130min, etc. The drying temperature can be 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160 ℃, 165 ℃, 170 ℃ or 175 ℃, etc., the drying treatment time can be 110min, 130min, 150min, 170min, 190min, 210min, 230min, 250min, 270min, 290min or 300min, etc.

In some embodiments, the heat treatment process includes the following steps: the first stage: raising the temperature to 130-160°C, and treating for 0.5-20 minutes; the second stage: raising the temperature to 160-220°C, and treating for 0.5-30 minutes; the third stage: cooling to 130~160℃, process for 0.5~20min; the fourth stage: lower the temperature to 70~110℃, process for 0.5~20min.

The heat treatment process can greatly affect the crystallinity of the polyester film. By rationally designing the heat treatment process steps, the crystallinity of the polyester film can be further improved, thereby improving the solvent resistance of the polyester film.

It should be noted that the temperature of the first stage can be 130℃, 132℃, 135℃, 140℃, 143℃, 146℃, 150℃, 153℃, 156℃ or 160℃, etc., and the processing time of the first stage can be It can be 0.5min, 5min, 10min, 15min or 20min, etc.; the temperature of the second stage can be 160℃, 170℃, 180℃, 190℃, 200℃, 210℃ or 220℃, etc., and the processing time of the second stage can be 0.5min, 5min, 10min, 15min, 20min, 25min or 30min, etc.; the temperature of the third stage can be 130℃, 133℃, 136℃, 140℃, 143℃, 146℃, 150℃, 153℃, 156℃ or 160℃, etc., the second stage processing time can be 0.5min, 5min, 10min or 15min, etc.; the fourth stage temperature can be 70℃, 80℃, 90℃, 100℃ or 110min, etc., the second stage processing time It can be 0.5min, 5min, 10min, 15min or 20min, etc.

Further, the present application provides a composite current collector, which includes a support layer and a metal layer provided on at least one surface of the support layer. The support layer is made of the above-mentioned polyester film or the polyester film produced by the above-mentioned preparation method. become.

In some embodiments, taking into account the application requirements of the composite current collector and the difficulty and cost of the preparation process, the thickness of the support layer is set to 1 to 20 μm. Alternatively, the thickness of the support layer may be 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm. It should be explained that the purpose of providing the metal layer is to conduct electricity. When metal layers are provided on both surfaces of the support layer, the two metal layers can be made of the same material or different materials.

In some embodiments, the material of the metal layer includes, but is not limited to, one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium and silver.

In some embodiments, the thickness of the metal layer ranges from 500 to 2000 nm.

Understandably, the thickness of the metal layer may be 500nm, 650nm, 700nm, 800nm, 950nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1550nm, 1600nm, 1650nm, 1700nm, 1800nm, 1850nm, 1900nm , 1950nm or 2000nm, etc.

In some embodiments, the thickness of the metal layer ranges from 800 to 1300 nm.

Understandably, the thickness of the metal layer may be 800nm, 850nm, 900nm, 950nm, 1000nm, 1050nm, 1100nm, 1150nm, 1200nm, 1250nm or 1300nm, etc.

In some embodiments, the preparation method of the metal layer includes, but is not limited to, one or more of physical vapor deposition, electroplating, and chemical plating; optionally, the preparation method of the metal layer includes, but is not limited to, resistance heating vacuum. One or more of evaporation method, electron beam heating vacuum evaporation method, laser heating vacuum evaporation method and magnetron sputtering method.

In some embodiments, the composite current collector further includes a protective layer, which is disposed on the surface of the metal layer away from the support layer; optionally, the material of the protective layer includes but is not limited to nickel, chromium, nickel-based alloys, and copper-based alloys. , one or more of copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, Ketjen black, carbon nanoquantum dots, carbon nanotubes, carbon nanofibers and graphene .

The purpose of providing a protective layer on the surface of the metal layer in this application is to prevent the metal layer from being chemically corroded or physically damaged. When the same polyester film is provided with two protective layers, the materials of the two protective layers may be the same or different. Optionally, the material of the protective layer includes but is not limited to nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, cobalt oxide, etc. One or more of piano black, carbon nanometer quantum dots, carbon nanotubes, carbon nanofibers and graphene.

When the same polyester film is provided with two protective layers, the thicknesses of the two protective layers may be consistent or inconsistent. Alternatively, the thickness of the protective layer may be 10nm, 13nm, 20nm, 25nm, 30nm, 32nm, 40nm, 47nm, 50nm, 54nm, 60nm, 68nm, 70nm, 74nm, 80nm, 86nm, 90nm, 95nm, 100nm, 110nm, 115nm, 120nm, 123nm, 130nm, 137nm, 140nm, 144nm or 150nm, etc.

When the same polyester film is provided with two protective layers, the thicknesses of the two protective layers may be consistent or inconsistent. Alternatively, the thickness of the protective layer may be 20nm, 25nm, 30nm, 32nm, 40nm, 47nm, 50nm, 54nm, 60nm, 68nm, 70nm, 74nm, 80nm, 86nm, 90nm, 95nm or 100nm, etc.

Further, the present application provides an electrode, which includes the above composite current collector.

Furthermore, this application also provides a battery, which includes the above-mentioned electrode.

The crystallization auxiliary materials added to the above-mentioned first surface layer and the second surface layer can improve its crystallinity. The first surface layer and the second surface layer with higher crystallinity provide the polyester film with solvent resistance. The core layer in between is made of polyester material with relatively low crystallinity. The core layer is used as the main body of the polyester film to provide flexibility, thereby reducing the film rupture rate during the film making process and achieving stable production of the polyester film. .

Preparing a composite current collector using the above-mentioned polyester film as a base film can effectively solve the problem of electrolyte swelling of the polyester film base film, so that the above-mentioned composite current collector remains stable during battery application.

The present application will be further described in detail below in conjunction with specific examples and comparative examples. For experimental parameters not specified in the following specific examples, priority is given to the guidelines given in the application documents. You can also refer to experimental manuals in the field or other experimental methods known in the field, or refer to the experimental conditions recommended by the manufacturer. It can be understood that the instruments and raw materials used in the following examples are relatively specific, and in other specific examples, they may not be limited thereto.

Example 1-1

The preparation method of solvent-resistant reinforced polyester film includes the following steps:

S1. According to the mass percentage, 93% PET masterbatch, 5% PPO, 1% antioxidant 1222 and 1% alumina are heated, melted extruded and formed into slices in sequence to prepare the first polyester slice;

S2. According to the mass percentage, 98% PET masterbatch, 1% antioxidant 1222 and 1% alumina are heated, melted extruded and formed into slices in sequence to prepare the second polyester slice;

S3. According to the mass percentage, 93% PET masterbatch, 5% PPO, 1% antioxidant 1222 and 1% alumina are heated, melted extruded and formed into slices in sequence to prepare the third polyester slice;

S4. Transport the first polyester slice, the second polyester slice and the third polyester slice to the crystallizer respectively, and perform crystallization treatment at 140°C for 50 minutes. The ester chips and the third polyester chips are transported to the drying tower respectively and dried at 150°C for 170 minutes;

S5. Add the first polyester slice, the second polyester slice and the third polyester slice into the corresponding twin-screw extruder for heating and melting treatment. The processing temperature is 280°C and extruded through the die with the help of a metering pump. Out, prepare a molten mixture with a first surface layer, a core layer and a second surface layer, the extrusion ratio of the first surface layer, the core layer and the second surface layer is 15%: 70%: 15% (mass ratio), wherein, The first polyester slice forms a first surface layer, the second polyester slice forms a core layer, and the third polyester slice forms a second surface layer;

S6. Preparation of polyester film

S6.1. Casting sheet: Cast the molten mixture prepared in step S5 onto the casting roller, and then form it through the casting roller and water-cooling cooling treatment to obtain a 96 μm thick cast sheet;

S6.2. Longitudinal stretching: Preheat the cast sheet before stretching, and then perform cooling and forming treatment after longitudinal stretching at 110°C. The preheating temperature is 90°C, the longitudinal stretching ratio is 4:1, and the cooling and forming temperature is 40℃;

S6.3. Transverse stretching: Before stretching, preheat the longitudinally treated cast sheet, stretch it transversely at 120°C and then perform cooling and forming treatment to obtain a film. The preheating temperature is 90°C, and the transverse stretching ratio is 4:1, cooling molding temperature is 100℃;

S6.4. Heat-treat the film obtained in step S6.3 according to the following steps: first stage: raise the temperature to 145°C, and treat for 2 minutes; second stage: raise the temperature to 190°C, and treat for 5 minutes; third stage: cool down to 145°C. , process for 2 minutes; the fourth stage: cool to 80°C, process for 2 minutes;

S6.5. Rewinding: The heat-treated film is air-dried and cooled to room temperature, and then enters the rewinding system through the traction system to rewind the film to prepare a polyester film with a thickness of 6 μm.

In the above preparation method of the solvent-resistant reinforced polyester film, the molecular weight distribution of polyethylene terephthalate (PET) selected as the polyester material is 2.1, and its intrinsic viscosity is 0.697dL/g; the crystallization auxiliary material selected is The molecular weight distribution of PPO (poly 2,6-dimethyl-1,4-phenyl ether) is 2.2, and its intrinsic viscosity is 0.675dL/g; the particle size of the alumina used as the nucleating agent is 30 to 100nm.

The preparation method of the composite negative electrode current collector includes the following steps:

(1) Put the above-mentioned polyester film into the vacuum evaporation chamber, and melt and evaporate the high-purity copper wire in the metal evaporation chamber at 1400-2000°C. The purity of the high-purity copper wire is greater than 99.99%. After cooling in the vacuum coating chamber The metal atoms evaporated after the system are deposited on both surfaces of the polyester film to form a copper metal layer with a thickness of 1 μm;

(2) Mix 1g of graphene with 999g of nitrogen methylpyrrolidone (NMP) solution, and use ultrasonic dispersion to fully mix the two evenly. The solid content of the resulting coating liquid is 0.1wt%. Coat through the die The process is to evenly coat the coating liquid on the surface of the above-mentioned copper metal layer (the coating amount is controlled at 80 μm), and then dry it at 100°C to obtain a composite negative electrode current collector.

The preparation method of the composite positive electrode current collector includes the following steps:

(1) Put the above-mentioned polyester film into the vacuum evaporation chamber, and melt and evaporate the high-purity aluminum wire in the metal evaporation chamber at 1300-2000°C. The purity of the high-purity aluminum wire is greater than 99.99%. After cooling in the vacuum coating chamber The metal atoms evaporated after the system are deposited on both surfaces of the polyester film to form an aluminum metal layer with a thickness of 1 μm;

(2) Mix 1g of carbon nanotubes and 999g of nitrogen methylpyrrolidone (NMP) solution, and use ultrasonic dispersion to fully mix the two evenly to obtain a coating liquid with a solid content of 0.1wt%, which is coated through the die. The process involves uniformly coating the surface of the above-mentioned metal layer with a coating liquid (the coating amount is controlled at 90 μm), and then drying it at 100°C to obtain a composite positive electrode current collector.

Example 1-2

Basically the same as Example 1-1, the difference is that in steps S1 and S3 of the polyester film preparation method, the content of PPO is increased, that is, the first polyester slice and the third polyester slice are both made of 88% PET masterbatch, Made of 10% PPO, 1% antioxidant 1222 and 1% aluminum oxide.

Example 1-3

Basically the same as Example 1-1, the difference is that in steps S1 and S3 of the polyester film preparation method, the content of PPO is increased, that is, the first polyester slice and the third polyester slice are both made of 83% PET masterbatch, Made of 15% PPO, 1% antioxidant 1222 and 1% aluminum oxide.

Example 2-1

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: the second stage is heated to 190°C, and the treatment time is 10 minutes.

Example 2-2

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: the second stage is heated to 190°C, and the treatment time is 15 minutes.

Example 2-3

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: the second stage is heated to 190°C, and the treatment time is 20 minutes.

Example 2-4

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: the second stage is heated to 170°C, and the treatment time is 5 minutes.

Example 2-5

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: the second stage is heated to 210°C, and the treatment time is 5 minutes.

Example 3-1

It is basically the same as Embodiment 1-2, except that in step S1 and step S3 of the polyester film preparation method of this embodiment, PPO is replaced by PC.

Example 3-2

It is basically the same as Embodiment 1-2, except that in step S1 and step S3 of the polyester film preparation method of this embodiment, PPO is replaced by PP.

Example 3-3

It is basically the same as Example 1-2, except that in step S1 and step S3 of the polyester film preparation method in this example, PPO is replaced by PP-g-MA.

Example 3-4

It is basically the same as Example 1-2, except that in step S1 and step S3 of the polyester film preparation method in this example, PPO is replaced by PP-g-GMA.

Example 4-1

Basically the same as Example 1-1, except that in steps S1 and S3 of the polyester film preparation method, the raw material compositions in the first polyester slice and the third polyester slice both include 70% PET in terms of mass percentage. Masterbatch, 25% PPO, 2.5% antioxidant 1222 and 2.5% alumina;

In step S2 of the polyester film preparation method, the raw material composition in the second polyester slice includes 95% PET masterbatch, 2.5% antioxidant 1222 and 2.5% alumina in terms of mass percentage.

Example 4-2

Basically the same as Example 1-1, except that in steps S1 and S3 of the polyester film preparation method, the raw material compositions in the first polyester slice and the third polyester slice both include 97% PET in terms of mass percentage. Masterbatch, 2% PPO, 0.5% antioxidant 1222 and 0.5% alumina;

In step S2 of the polyester film preparation method, the raw material composition in the second polyester slice includes 99% PET masterbatch, 0.5% antioxidant 1222 and 0.5% alumina in terms of mass percentage.

Comparative example 1-1

Basically the same as Example 1-1, except that in steps S1 and S3 of the polyester film preparation method, the raw material compositions in the first polyester slice and the third polyester slice independently include: in terms of mass percentage: 98% PET masterbatch, 1% antioxidant 1222 and 1% alumina.

Comparative Example 1-2

Basically the same as Example 1-1, except that in steps S1 and S3 of the polyester film preparation method, the raw material compositions in the first polyester slice and the third polyester slice independently include: in terms of mass percentage: 97% PET masterbatch, 1% PPO, 1% antioxidant 1222 and 1% alumina.

Comparative Example 1-3

Basically the same as Example 1-1, except that in steps S1 and S3 of the polyester film preparation method, the raw material compositions in the first polyester slice and the third polyester slice independently include: in terms of mass percentage: 72% PET masterbatch, 26% PPO, 1% antioxidant 1222 and 1% alumina.

Comparative example 2-1

It is basically the same as Example 1-2, except that the heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: no second-stage heat treatment is performed.

Comparative Example 2-2

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.4 of the polyester film preparation method is adjusted to: the second stage is heated to 225°C, and the treatment time is 5 minutes.

Comparative Example 2-3

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.4 of the polyester film preparation method is adjusted to: the second stage is heated to 155°C, and the treatment time is 5 minutes.

Comparative Example 2-4

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.4 of the polyester film preparation method is adjusted to: the second stage is heated to 190°C, and the treatment time is 0.4 min.

Comparative Example 2-5

Basically the same as Example 1-2, the difference is that the heat treatment process in step S6.4 of the polyester film preparation method is adjusted to: the second stage is heated to 190°C, and the treatment time is 32 minutes.

Comparative example 3

Basically the same as Example 1-1, except that in steps S1 and S3 of the polyester film preparation method, the raw material compositions in the first polyester slice and the third polyester slice independently include: in terms of mass percentage: 98% PET masterbatch, 1% antioxidant 1222 and 1% alumina;

The heat treatment process in step S6.3 of the polyester film preparation method is adjusted to: no second-stage heat treatment is performed.

Test example 1

1. Swelling degree test

Cut the above-mentioned polyester film, composite positive electrode current collector and composite negative electrode current collector into samples of 20cm×20cm respectively. The circumference of the sample is recorded as L ₁ . Soak the sample in the electrolyte at 65°C for 48 hours. After soaking, the circumference of the sample is recorded. is L ₂ , the calculation formula of sample swelling degree SD is as follows:

SD＝(L ₂ -L ₁ )/L ₁ ×100%,

Table 1 shows the formula of the electrolyte. The concentrations of ethylene carbonate, ethyl methyl carbonate and vinylene carbonate in the solvent refer to the percentage of their respective masses to the mass of the solvent. The concentration of vinylene carbonate is 2wt%. That is, the mass of vinylene carbonate accounts for 2% of the total mass of the solvent and additives. Based on the total amount of solvent and additives, the total concentration of ethylene carbonate, ethyl methyl carbonate and vinylene carbonate is 98wt%.

Table 1

2. Crystallinity test

Tear off the first surface layer or the second surface layer of the above-mentioned polyester film, and use the differential scanning calorimeter (DSC) method to test the crystallinity of the first surface layer or the second surface layer. The temperature rising program is: from 10°C/min to 10°C/min. Raise the temperature from 30°C to 290°C, keep it at 290°C for 3 minutes, and then cool down to 30°C at a rate of 10°C/min. The melting enthalpy (△H _f ) is obtained from the tested DSC curve, and the crystallinity X _c is calculated by the following formula:

X _c =△H _f /△H _f ^c ×100%,

Among them, △H _f ^c is the melting enthalpy of PET in the completely crystallized state.

3. Elastic modulus test

The flexibility of the polyester film is characterized by the elastic modulus. The test method of elastic modulus refers to GB/T 1040.1-2018. The lower the elastic modulus, the softer the polyester film. If the elastic modulus is too high, the polyester film will be more brittle. .

The crystallinity, elastic modulus and swelling degree of the polyester film were tested, and the swelling degree of the composite positive electrode current collector and composite negative electrode current collector were tested. The results are shown in Table 2.

Table 2

As can be seen from Table 2, compared with Example 1-1, the crystallinity of the first surface layer/second surface layer of Comparative Example 3 is lower, and the prepared polyester film, composite positive electrode current collector and composite negative electrode current collector have The swelling degree is large, indicating that the crystallization auxiliary material PPO was not added to the first polyester slice and the second polyester slice, and the second stage heat treatment was not performed in step S6.3 of the polyester film preparation method, which greatly affected the first step. The crystallinity of the surface layer/second surface layer affects the swelling degree of the polyester film, composite positive electrode current collector and composite negative electrode current collector;

Compared with Example 1-1 and Example 1-2, Comparative Example 1-1, Comparative Example 1-2, Comparative Example 1-3, Comparative Example 2-1, Comparative Example 2-2 and Comparative Example 2-3 The swelling degree of the polyester film, composite positive electrode current collector and composite negative electrode current collector of Comparative Examples 2-5 is significantly higher. Although the swelling degree of the polyester film, composite positive electrode current collector and composite negative electrode current collector of Comparative Examples 2-5 is small, the polyester The elastic modulus of the film is too large, the polyester film is brittle, and the membrane rupture rate during the film production process is high;

In summary, it can be shown that the polyester film provided by the present application has sufficient flexibility, and the polyester film and the composite positive electrode current collector and composite negative electrode current collector prepared using it as a base material have excellent solvent swelling resistance.

The technical features of the above-described embodiments can be combined in any way. To simplify the description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, All should be considered to be within the scope of this manual.

The above-described embodiments only express several implementation modes of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

A solvent-resistant enhanced polyester film, characterized in that the polyester film includes a core layer, and a first surface layer and a second surface layer respectively provided on both sides of the core layer;

The raw material compositions of the first surface layer and the second surface layer independently include: 70% to 97% polyester material, 2% to 25% crystallization auxiliary materials and 1% to 5% additives in terms of mass percentage;

The raw material composition of the core layer includes, in terms of mass percentage: 95% to 99% polyester material and 1% to 5% additives;

The crystallization auxiliary materials include poly2,6-dimethyl-1,4-phenyl ether, polycarbonate, polypropylene, maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene and their One or more of the derivatives.
The polyester film according to claim 1, wherein the polyester material includes polyethylene terephthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate Glycol ester, poly1,4-cyclohexanedimethanol terephthalate, polyethylene terephthalate-1,4-cyclohexanedimethanol, polypropylene glycol 2,6-naphthalate Ester, polytrimethylene terephthalate, polybutylene 2,6-naphthalate, polybutylene adipate terephthalate, polyarylate, polybutylene 2,5-furandicarboxylate One or more of esters and their derivatives.
The polyester film according to claim 1 or 2, wherein the additives in the core layer, the first surface layer and the second surface layer each independently include a nucleating agent, an antioxidant, One or more of lubricant and antistatic agent.
The polyester film according to claim 3, wherein the nucleating agent includes magnesium oxide, zinc oxide, aluminum oxide, copper oxide, barium sulfate, benzophenone, sodium carbonate, sodium benzoate, triphenyl phosphate One or more of ester, magnesium stearate and polycaprolactone.
The polyester film according to claim 3 or 4, wherein the antioxidant includes one or more of bisphenol A phosphite and phosphonate ester.
The polyester film according to any one of claims 3 to 5, wherein the slip agent includes titanium dioxide, silicon dioxide, calcium carbonate, talc, kaolin, diatomaceous earth, siloxane and acrylate. one or more of them.
The polyester film according to any one of claims 3 to 6, wherein the antistatic agent includes carbon black, graphite, glycerin, polyglycerol, polyethylene glycol, polyether ester and conductive fiber. one or several kinds.
A method for preparing a solvent-resistant reinforced polyester film, which is characterized by comprising the following steps:

The raw materials of the first surface layer, the core layer and the second surface layer are independently mixed, and sequentially undergo heating, melt extrusion and molding and slicing processes to prepare the first polyester chips, the second polyester chips and the third polyester chips respectively. ;

The first polyester chip, the second polyester chip and the third polyester chip are crystallized and dried separately and sequentially, and then added to different twin-screw extruders. After heating, melting and extrusion processing, a melt mixture is obtained. material;

The molten mixture is sequentially subjected to sheet casting, stretching and heat treatment to obtain a polyester film;

The polyester film includes the core layer, the first surface layer and the second surface layer, and the first surface layer and the second surface layer are located on both sides of the core layer;

The raw material compositions of the first surface layer and the second surface layer independently include: 70% to 97% polyester material, 2% to 25% crystallization auxiliary materials and 1% to 5% additives in terms of mass percentage;

The raw material composition of the core layer includes, in terms of mass percentage: 95% to 99% polyester material and 1% to 5% additives;

The crystallization auxiliary materials include poly2,6-dimethyl-1,4-phenyl ether, polycarbonate, polypropylene, maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene and their One or more of the derivatives.
The preparation method according to claim 8, characterized in that the crystallization temperature during the crystallization process is 130-185°C, the crystallization time is 20-130 min; the drying temperature during the drying process is 130 ~175℃, drying treatment time is 110~300min.
The preparation method according to claim 8 or 9, characterized in that the heat treatment process includes the following steps: first stage: heating to 130-160°C, processing for 0.5-20 minutes; second stage: heating to 160-220°C , process for 0.5~30min; the third stage: cool down to 130~160℃, process for 0.5~20min; the fourth stage: cool down to 70~110℃, process for 0.5~20min.
A composite current collector, characterized in that the composite current collector includes a support layer and a metal layer provided on at least one surface of the support layer, and the support layer includes the polyester according to any one of claims 1 to 7 film or a polyester film prepared by the preparation method according to any one of claims 8 to 10.
The composite current collector according to claim 11, wherein the composite current collector further includes a protective layer, and the protective layer is disposed on a surface of the metal layer away from the support layer;

Optionally, the material of the protective layer includes nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, Ketjen black, One or more of carbon nanoquantum dots, carbon nanotubes, carbon nanofibers and graphene.
The composite current collector according to claim 12, wherein the thickness of the protective layer is 10 to 150 nm.
The composite current collector according to claim 12 or 13, wherein the thickness of the protective layer is 20 to 100 nm.
An electrode, characterized in that the electrode includes the composite current collector according to any one of claims 11 to 14.
A battery, characterized in that the battery includes the electrode according to claim 15.
An electrical device, characterized in that the electrical device includes the battery according to claim 16.