WO2024044897A1

WO2024044897A1 - Swelling-resistant polyester composite film, and preparation method therefor and use thereof

Info

Publication number: WO2024044897A1
Application number: PCT/CN2022/115544
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 swelling-resistant polyester composite film. The swelling-resistant polyester composite film comprises a core layer, a surface layer A and a surface layer B, wherein the surface layer A and the surface layer B are respectively located on the two side surfaces of the core layer. The surface layer A and the surface layer B each independently comprise the following raw materials in percentages by mass: 88-97% of a polyester material, and 3-12% of an additive. The core layer comprises the following raw materials in percentages by mass: 95-99% of a polyester material, and 1-5% of an additive. The additives in the surface layer A, the surface layer B and the core layer each comprise a nucleating agent, the contents of the nucleating agents in the surface layer A and the surface layer B are both higher than that of the nucleating agent in the core layer, and the mass percentage of the nucleating agents in the respective additives of the surface layer A and the surface layer B is not less than 50%.

Description

Swelling-resistant polyester composite film and its preparation method and application

Technical field

The present application relates to the technical field of electrochemical devices, and in particular to a swelling-resistant polyester composite membrane and its preparation method and application.

Background technique

Electricity storage performance is an important indicator for evaluating batteries. As the new energy industry has an increasingly urgent demand for high-energy-density batteries, composite current collectors based on polymer membranes have received widespread attention and application. The composite current collector uses a polymer polymer film as a base film, and is prepared by attaching metal materials to the front and back sides of the base film to form metal layers through methods such as physical vapor deposition. Battery pole pieces can be obtained by coating active material slurry on one side or both sides of the composite current collector. Compared with traditional battery pole pieces, battery pole pieces containing composite current collectors are relatively low-quality, and their application in batteries is beneficial to meet the demand for high energy density performance.

The most commonly used polymer-based film for composite current collectors is polyester film. However, when the composite current collector comes into contact with the battery electrolyte, the traditional polyester film will swell. Even if there is a metal layer on the surface of the polyester film, Since there are many pores on the surface of the metal layer, the battery electrolyte can still penetrate into the metal layer and contact the polyester film, causing it to swell. The continuous penetration of the battery electrolyte will gradually destroy the structure of the polyester film, thus affecting the stability of the composite current collector.

Contents of the invention

According to various embodiments of the present application, a swelling-resistant polyester composite film and its preparation method and application are provided.

The first aspect of this application provides a swelling-resistant polyester composite film. The polyester composite film includes a core layer, a surface layer A and a surface layer B, wherein the surface layer A and the surface layer B are respectively located on both sides of the core layer. ;

In terms of mass percentage, the raw materials of the surface layer A and the surface layer B each independently include: 88% to 97% polyester material and 3% to 12% additives, and the raw materials of the core layer include: 95% to 99% Polyester material and 1% to 5% additives;

The additives in the surface layer A, the surface layer B and the core layer all include nucleating agents, and the content of the nucleating agent in the surface layer A and the surface layer B is higher than that of the nucleating agent in the core layer. content, and the mass percentage of the nucleating agent in the surface layer A and the surface layer B in the respective additives is not less than 50%.

In some embodiments, the polyester material includes polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene 2,6-naphthalate (PTN) ), polyethylene 2,6-naphthalate (PEN), polytrimethylene terephthalate (PTT), poly1,4-cyclohexanedimethanol terephthalate (PCT), polyp Ethylene glycol phthalate-1,4-cyclohexanedimethanol ester (PETG), polybutylene 2,6-naphthalate (PBN), polybutylene 2,5-furandicarboxylate, One or more of polyarylate (PAR) and polybutylene adipate terephthalate (PBAT) and their derivatives.

In some embodiments, the thickness of the surface layer A and the surface layer B are equal, and the thickness of the surface layer A and the surface layer B each independently accounts for 5% to 15% of the thickness of the polyester composite film, The thickness of the core layer accounts for 70% to 90% of the thickness of the polyester composite film.

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

In some embodiments, the additives further include one or more of antioxidants, slip agents and antistatic agents.

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

The slip agent includes one or more of calcium carbonate, titanium dioxide, diatomaceous earth, talc, acrylate, silicon dioxide, siloxane and kaolin;

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

A second aspect of this application provides a method for preparing a swelling-resistant polyester composite film. The preparation method includes the following steps:

Preparing polyester slices A: The polyester slices A are obtained by mixing the raw materials of surface layer A and then sequentially undergoing melt extrusion and molding slice processing;

Preparing polyester slices B: The polyester slices B are obtained by mixing the raw materials of the core layer and then sequentially undergoing melt extrusion and molding slice processing;

Preparing polyester slices C: The polyester slices C are obtained by mixing the raw materials of surface layer B and then sequentially undergoing melt extrusion and molding slice processing;

Preparing molten polyester material: After the polyester slice A, the polyester slice B and the polyester slice C are sequentially subjected to crystallization treatment and drying treatment, they are added to different twin-screw extruders respectively, and undergo melt extrusion. After processing, molten polyester material is obtained;

Preparing a polyester composite film: The molten polyester material is sequentially cast, stretched and heat treated to obtain a polyester composite film including the surface layer A, the core layer and the surface layer B. The surface layer A and The surface layer B is located on both sides of the core layer respectively;

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

In some embodiments, the heat treatment includes the following steps:

(1) Raise the temperature to 130~160℃ and process for 0.5~20 minutes;

(2) Raise the temperature to 160~220℃ and process for 0.5~30 minutes;

(3) Cool down to 130~160℃ and process for 0.5~20 minutes;

(4) Cool down to 70~110℃ and process for 0.5~20min.

A third aspect of the present application provides a composite current collector. The composite current collector includes a base layer and a metal conductive layer. The metal conductive layer is provided on at least one surface of the base layer. The base layer includes the above-mentioned polyester composite. film or a polyester composite film prepared by the above preparation method.

In some embodiments, the composite current collector further includes a protective layer disposed on at least one of two surfaces with opposite thicknesses of the metal conductive layer itself.

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

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.

A fourth aspect of the present application provides an electrode pole piece, including an active material layer and the above-mentioned composite current collector. The active material layer is located on at least one surface of the composite current collector close to the metal conductive layer.

A fifth aspect of the present application provides a battery, including a positive electrode piece and a negative electrode piece, and at least one of the positive electrode piece and the negative electrode piece is the above-mentioned electrode piece.

A sixth aspect of this application provides an electronic device, including 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 swelling-resistant polyester composite film. The polyester composite film includes a core layer, and surface layers A and B respectively provided on both sides of the core layer;

In terms of mass percentage, the raw materials of surface layer A and surface layer B each independently include: 88% to 97% polyester material and 3% to 12% additives. The raw materials of the core layer include: 95% to 99% polyester material and 1%. ~5% additives;

The additives in the surface layer A, the surface layer B and the core layer all include nucleating agents. The contents of the nucleating agents in the surface layer A and the surface layer B are higher than the content of the nucleating agent in the core layer, and the nucleating agents in the surface layer A and the surface layer B The mass percentage of the additives in the respective additives shall not be less than 50%.

A polyester composite film is used as the base film to prepare a composite current collector. Usually, a metal conductive layer is formed on the surface of the polyester composite film. Since there are some tiny pores such as pinholes inside the metal conductive layer, the battery electrolyte flows from this layer. The pores penetrate into the base film of the polyester composite film, causing the polyester composite film to swell and affecting the stability of the composite current collector. Although the solvent resistance of the polyester composite film can be improved by increasing the crystallinity of the polyester composite film, the increased crystallinity will make the polyester composite film brittle, resulting in an increase in the membrane rupture rate of the polyester composite film during the preparation process.

In order to take advantage of the improved solvent resistance of the polyester composite film caused by high crystallinity and balance the problem of increased film rupture rate of the polyester composite film caused by high crystallinity, this application creatively provides a swelling-resistant polyester composite film. film, the polyester composite film includes surface layer A, core layer and surface layer B. By regulating the content of crystallization nucleating agent in each layer, the crystallinity of surface layer A and surface layer B is relatively high, and the crystallinity of the core layer is relatively low, with Surface layer A and surface layer B with higher crystallinity can improve the solvent resistance of the polyester composite film, and the core layer with lower crystallinity can make the polyester composite film flexible, thereby helping to reduce film breakage during the film production process. Rate. The composite current collector prepared using the polyester composite film as the base film has excellent stability.

In some embodiments, polyester materials include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene 2,6-naphthalate (PTN), Polyethylene 2,6-naphthalate (PEN), polytrimethylene terephthalate (PTT), poly1,4-cyclohexanedimethanol terephthalate (PCT), polyterephthalate Ethylene glycol formate-1,4-cyclohexane dimethanol (PETG), polybutylene 2,6-naphthalenedicarboxylate (PBN), polybutylene 2,5-furandicarboxylate, polyarylene glycol ester (PAR) and polybutylene adipate terephthalate (PBAT) and one or more of their derivatives.

It will be understood that the polyester material may include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene 2,6-naphthalate (PTN), poly(trimethylene 2,6-naphthalate), 2,6-Ethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), poly1,4-cyclohexanedimethanol terephthalate (PCT), polyterephthalate Ethylene glycol ester-1,4-cyclohexanedimethanol (PETG), polybutylene 2,6-naphthalenedicarboxylate (PBN), polybutylene 2,5-furandicarboxylate, polyarylate (PAR) and polybutylene adipate terephthalate (PBAT) and any of their derivatives; polyester materials can also include polyethylene terephthalate (PET), poly Butylene terephthalate (PBT), polytrimethylene 2,6-naphthalate (PTN), polyethylene 2,6-naphthalate (PEN), polytrimethylene terephthalate ( PTT), poly1,4-cyclohexanedimethanol terephthalate (PCT), polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG), poly2,6 -Butylene naphthalate (PBN), polybutylene 2,5-furandicarboxylate, polyarylate (PAR) and polybutylene adipate terephthalate (PBAT) and their derivatives A mixture obtained by mixing a variety of substances in any proportion.

In some embodiments, the thickness of surface layer A and surface layer B are equal, the thickness of surface layer A and surface layer B each independently accounts for 5% to 15% of the thickness of the polyester composite film, and the thickness of the core layer accounts for 5% to 15% of the thickness of the polyester composite film. The percentage is 70% to 90%.

Alternatively, the thickness of surface layer A and surface layer B both accounts for 5% of the thickness of the polyester composite film, and the thickness of the core layer accounts for 90% of the thickness of the polyester composite film; or the thickness of surface layer A and surface layer B Both account for 10% of the thickness of the polyester composite film, and the thickness of the core layer accounts for 80% of the thickness of the polyester composite film; or the thickness of surface layer A and surface layer B both account for the thickness of the polyester composite film. 15%, the thickness of the core layer accounts for 70% of the thickness of the polyester composite film.

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

In some embodiments, the additives further include one or more of antioxidants, slip agents, and antistatic agents.

The slip agent includes one or more of calcium carbonate, titanium dioxide, diatomaceous earth, talc, acrylate, silica, siloxane and kaolin;

Antistatic agents include one or more of glycerol, polyethylene glycol, polyglycerol, polyether ester, graphite, carbon black and conductive fibers.

It should be explained that substances are divided into nucleating agents, slip agents and antistatic agents according to their main functions. In addition to their main functions, some of these substances also have auxiliary functions. For example: although zinc oxide, aluminum oxide, magnesium 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.

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

S100. Preparing polyester slice A: Polyester slice A is obtained by mixing the raw materials of surface layer A and then sequentially undergoing melt extrusion and molding slice processing;

S200. Preparing polyester slice B: Polyester slice B is obtained by mixing the raw materials of the core layer and then sequentially undergoing melt extrusion and molding slice processing;

S300. Preparing polyester slice C: Polyester slice C is obtained by mixing the raw materials of surface layer B and then sequentially undergoing melt extrusion and molding slice processing;

S400. Preparation of molten polyester material: After crystallizing and drying polyester chips A, polyester chips B and polyester chips C, they are added to different twin-screw extruders respectively, and after melt extrusion processing, we obtain Molten polyester material;

S500. Preparation of polyester composite film: The molten polyester material is sequentially cast, stretched and heat treated to obtain a polyester composite film including surface layer A, core layer and surface layer B. Surface layer A and surface layer B are located on both sides of the core layer respectively. on the side surface;

Alternatively, when preparing molten polyester material by melt extrusion, the extrusion amount ratio of surface layer A, core layer and surface layer B is (5%~15%): (70%~90%): (5%~15% ).

In some embodiments, the stretching process includes longitudinal stretching, the process conditions of longitudinal stretching include a stretching ratio of (3-4.5):1, and a stretching temperature of 80-120°C.

Optionally, the stretching ratio of longitudinal stretching is 3:1, 3.5:1, 4:1 or 4.5:1, etc., and the stretching temperature can be 80°C, 85°C, 90°C, 95°C, 105°C, 110°C ℃, 115℃ or 120℃, etc.

In some embodiments, the stretching process also includes transverse stretching, and the process conditions of transverse stretching include a stretching ratio of (3-4.5):1, and a stretching temperature of 90-140°C.

Optionally, the stretching ratio of transverse stretching is 3:1, 3.5:1, 4:1 or 4.5:1, etc., and the stretching temperature can be 80°C, 85°C, 90°C, 95°C, 105°C, 110°C ℃, 115℃ or 120℃, etc.

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

It should be noted that the crystallization treatment temperature can be 130°C, 133°C, 136°C, 139°C, 143°C, 146°C, 149°C, 153°C, 158°C, 160°C, 164°C, 168°C, 170°C, 177 ℃ or 185 ℃, or other values between 130 and 185 ℃; the crystallization treatment time can be 20min, 25min, 35min, 45min, 55min, 65min, 75min, 85min, 95min, 105min, 115min, 125min or 130min, or It can be other values between 20 and 130min; the drying temperature can be 130℃, 133℃, 135℃, 138℃, 143℃, 146℃, 149℃, 152℃, 155℃, 160℃, 163℃, 168 ℃, 170 ℃ or 175 ℃, or other values between 130 and 175 ℃; the drying treatment time can be 110min, 120min, 125min, 130min, 140min, 145min, 150min, 160min, 170min, 180min, 190min, 200min, 220min, 240min, 260min, 280min or 300min, or other values between 110 and 300min.

In some embodiments, heat treatment includes the following steps:

(1) Raise the temperature to 130~160℃ and process for 0.5~20 minutes;

(2) Raise the temperature to 160~220℃ and process for 0.5~30 minutes;

(3) Cool down to 130~160℃ and process for 0.5~20 minutes;

(4) Cool down to 70~110℃ and process for 0.5~20min.

The heat treatment process provided by this application can improve the crystallinity of the polyester composite film, thereby further improving the solvent resistance of the polyester composite film. It should be noted that the temperature of the heat treatment step (1) can be 130°C, 135°C, 140°C, 145°C, 150°C, 155°C or 160°C, or other values between 130 and 160°C; the heat treatment step The treatment time of (1) can be 0.5min, 1min, 6min, 12min, 18min or 20min, or other values between 0.5 and 20min; the temperature of heat treatment step (2) can be 160℃, 165℃, 170℃ , 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C or 220°C, or other values between 160°C and 220°C; heat treatment step (2) The treatment time can be 0.5min, 1min, 6min, 12min, 18min, 24min or 30min, or other values between 0.5 and 20min; the temperature of the heat treatment step (3) can be 130℃, 135℃, 140℃, 145 ℃, 150℃, 155℃ or 160℃, or other values between 130 and 160℃; the processing time of heat treatment step (3) can be 0.5min, 1min, 6min, 12min, 18min or 20min, or it can be Other values between 0.5~20min; the temperature of heat treatment step (4) can be 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃ or 110℃, or it can be 70~ Other values between 110°C; the treatment time of heat treatment step (4) can be 0.5min, 1min, 6min, 12min, 18min or 20min, or other values between 0.5 and 20min.

The application also provides a composite current collector. The composite current collector includes a base layer and a metal conductive layer. The metal conductive layer is provided on at least one surface of the base layer. The base layer includes the above-mentioned polyester composite film or the polyester composite film prepared by the above-mentioned preparation method. Polyester composite film.

When the composite current collector prepared based on the above polyester composite film comes into contact with the electrolyte, the surface layer A and the surface layer B have a certain degree of solvent resistance, which prevents the penetration of the electrolyte from causing damage to the structure of the polyester composite film and improves the stability of the composite current collector. .

In some embodiments, the thickness of the base layer is 1-20 μm. It can be understood that the thickness of the base layer may be 1 μm, 2.5 μm, 4 μm, 6 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm or 20 μm, or other values between 1 and 20 μm.

In some embodiments, the thickness of the metal conductive layer is 500-2000 nm; preferably 800-1300 nm. It should be noted that the thickness of the metal conductive layer can be 500nm, 550nm, 600nm, 700nm, 750nm, 800nm, 850nm, 900nm, 1050nm, 1200nm, 1250nm, 1300nm, 1450nm, 1500nm, 1600nm, 1750nm, 1850nm m, 1900nm or 2000nm, The thickness of the metal conductive layer can also be other values between 500 and 2000 nm.

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

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

It should be explained that the protective layer provided on the surface of the metal conductive layer in this application is used to prevent the metal conductive layer from being chemically corroded or physically damaged, which is beneficial to ensuring the stability of the composite current collector. Optionally, the materials of the two metal conductive layers may be the same or different.

In some embodiments, the thickness of the protective layer ranges from 10 to 150 nm. It can be understood that the thickness of the protective layer can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm or 150nm, or other thickness between 10 and 150nm. value.

In some embodiments, the thickness of the protective layer ranges from 20 to 100 nm. It can be understood that the thickness of the protective layer can be 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, or other values between 20 and 100nm.

In some embodiments, the preparation method of the protective layer includes, but is not limited to, one or more of physical vapor deposition, in-situ molding, and coating. Among them, the vapor deposition method is preferably vacuum evaporation and magnetron sputtering. The injection method; the in-situ forming method is preferably the method of forming a metal oxide passivation layer in situ on the surface of the metal conductive layer; the coating method is preferably the die coating method, the blade coating method and the extrusion coating method.

This application also provides an electrode pole piece, which includes an active material layer and the above-mentioned composite current collector. The active material layer is located on at least one surface of the composite current collector close to the metal conductive layer.

This application also provides a battery, including a positive electrode piece and a negative electrode piece, and at least one of the positive electrode piece and the negative electrode piece is the above-mentioned electrode piece.

This application also provides an electronic device, including the above-mentioned battery.

The embodiments of the present application will be described in detail below with reference to examples.

Example 1

Among the raw materials in this embodiment, the polyester material is commercial polyethylene terephthalate (PET), with an intrinsic viscosity of 0.697dL/g and a molecular weight distribution of 2.1; the additives are antioxidant 1222 and magnesium stearate. , alumina and silica (size 30-100nm), among which magnesium stearate and alumina are nucleating agents.

Prepare swelling-resistant polyester composite membrane according to the following method:

S1. Preparation of polyester slices

PET masterbatch, antioxidant 1222, magnesium stearate, alumina and silica are mixed in sequence according to the mass percentage of 96%, 1%, 1%, 1%, 1%, heated, melted, extruded and shaped into slices Prepare polyester chips A;

Mix PET masterbatch, antioxidant 1222, alumina and silica in sequence according to the mass percentage of 97%, 1%, 1% and 1%, and then heat, melt extrusion and shape slices to prepare polyester slices B;

PET masterbatch, antioxidant 1222, magnesium stearate, alumina and silica are mixed in sequence according to the mass percentage of 96%, 1%, 1%, 1%, 1%, heated, melted, extruded and shaped into slices Prepare polyester slice C;

S2. Crystal drying treatment

Add polyester slices A, polyester slices B and polyester slices C into the crystallizer, process at 140°C for 40 minutes, and transport the crystallized polyester slices A, polyester slices B and polyester slices C to the drying tower. Within, dry at 150℃ for 160min;

S3. Preparation of molten polyester material

Add the polyester slices A, polyester slices B and polyester slices C obtained in step S2 into different twin-screw extruders, heat and melt at 280°C, and then extrudate through the die with the help of a metering pump to obtain molten polyester material. , wherein the extrusion amounts of surface layer A, core layer and surface layer B are controlled at 10%: 80%: 10% (mass ratio);

S4. Preparation of polyester composite film

S4.1. Casting sheet: Cast the molten polyester material onto the casting roller, and then form it through the casting roller and water-cooling cooling treatment to obtain the cast sheet. The thickness of the cast sheet is 96 μm;

S4.2. Longitudinal stretching: Preheat the cast sheet in step S4.1 at 90°C, and then stretch it longitudinally at 110°C. The longitudinal stretching ratio is 4:1. After stretching, stretch it at 170°C. Perform heat setting treatment and then cool and form at 40°C;

S4.3. Transverse stretching: Preheat the longitudinally processed cast sheet at 90°C, and then stretch it transversely at 120°C. The transverse stretching ratio is 4:1. After stretching, stretch it at 170°C. Perform heat setting treatment, then cool and form at 100°C to obtain a film;

S4.4. Perform heat treatment on the film obtained in step S4.3 according to the following steps:

(1) Raise the temperature to 140°C and process for 2 minutes;

(2) Raise the temperature to 190°C and process for 5 minutes;

(3) Cool down to 140°C and process for 2 minutes;

(4) Cool down to 90°C and process for 2 minutes;

S4.5. 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 obtain a 6 μm polyester composite film.

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

(1) Preparation of metal conductive layer: Place the prepared polyester composite film in a vacuum evaporation chamber, and melt and evaporate the high-purity copper wire (purity greater than 99.99%) in the metal evaporation chamber at a high temperature of 1400 to 2000°C. The final metal atoms pass through the cooling system in the vacuum coating chamber and are deposited on both surfaces of the polyester composite film to form a copper metal conductive layer with a thickness of 1 μm;

(2) Preparation of protective layer: uniformly disperse 1g of graphene into 999g of nitrogen methylpyrrolidone (NMP) solution by ultrasonic dispersion, prepare a coating liquid with a solid content of 0.1wt%, and then apply it through a die. In the process, the coating liquid is evenly applied to the surface of the above-mentioned copper metal conductive layer, and finally dried at 100°C, where the coating amount is controlled at 80 μm.

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

(1) Preparation of metal conductive layer: Place the prepared polyester composite film in a vacuum evaporation chamber, and melt and evaporate the high-purity aluminum wire (purity greater than 99.99%) in the metal evaporation chamber at a high temperature of 1300 to 2000°C. The final metal atoms pass through the cooling system in the vacuum coating chamber and are deposited on both surfaces of the polyester composite film to form an aluminum metal conductive layer with a thickness of 1 μm;

(2) Preparation of protective layer: Use ultrasonic dispersion method to uniformly disperse 1g carbon nanotubes into 999g nitrogen methylpyrrolidone (NMP) solution, prepare a coating liquid with a solid content of 0.1wt%, and then apply it through a die The process is to evenly apply the coating liquid to the surface of the metal conductive layer, and finally dry it at 100°C, where the coating amount is controlled at 90 μm.

Example 2

The difference between this embodiment and Example 1 is that the percentages of the nucleating agents magnesium stearate and aluminum oxide in surface layer A and surface layer B are increased, that is, the raw materials of polyester chips A and polyester chips C in step S1 are independently included. : 94% PET masterbatch, 1% antioxidant 1222, 2% magnesium stearate, 2% alumina and 1% silica.

Example 3

The difference between this embodiment and Example 1 is that the percentages of the nucleating agents magnesium stearate and aluminum oxide in surface layer A and surface layer B are increased, that is, the raw materials of polyester chips A and polyester chips C in step S1 are independently included. : 92% PET masterbatch, 1% antioxidant 1222, 3% magnesium stearate, 3% alumina and 1% silica.

Example 4

The difference between this embodiment and Example 1 is that the percentages of the nucleating agents magnesium stearate and aluminum oxide in surface layer A and surface layer B are increased, that is, the raw materials of polyester chips A and polyester chips C in step S1 are independently included. : 90% PET masterbatch, 1% antioxidant 1222, 4% magnesium stearate, 4% alumina and 1% silica.

Example 5

The difference between this embodiment and Example 1 is that the percentages of the nucleating agents magnesium stearate and aluminum oxide in surface layer A and surface layer B are increased, that is, the raw materials of polyester chips A and polyester chips C in step S1 are independently included. : 88% PET masterbatch, 1% antioxidant 1222, 5% magnesium stearate, 5% alumina and 1% silica.

Example 6

The difference between this embodiment and Embodiment 3 is that the heat treatment process step (2) of step S4.4 is adjusted to: the temperature is raised to 190°C, and the treatment time is 10 minutes.

Example 7

The difference between this embodiment and Embodiment 3 is that the heat treatment process step (2) of step S4.4 is adjusted to: the temperature is raised to 190°C, and the treatment time is 15 minutes.

Example 8

The difference between this embodiment and Embodiment 3 is that the heat treatment process step (2) of step S4.4 is adjusted to: the temperature is raised to 190°C, and the treatment time is 20 minutes.

Example 9

The difference between this embodiment and Embodiment 3 is that the heat treatment process step (2) of step S4.4 is adjusted to: the temperature is raised to 190°C, and the treatment time is 25 minutes.

Example 10

The difference between this embodiment and Embodiment 3 is that the heat treatment process step (2) of step S4.4 is adjusted to: the temperature is raised to 170°C, and the treatment time is 5 minutes.

Example 11

The difference between this embodiment and Embodiment 3 is that the heat treatment process step (2) of step S4.4 is adjusted to: the temperature is raised to 220°C, and the treatment time is 5 minutes.

Example 12

The difference between this embodiment and Example 1 is that in step S1, the raw materials of polyester chips A and polyester chips C independently include: 97% PET masterbatch, 1% antioxidant 1222, 1% magnesium stearate and 1% silica, the raw materials of polyester chip B include: 95% PET masterbatch, 1% antioxidant 1222, 1% alumina and 3% silica.

Example 13

The difference between this embodiment and Example 1 is that the raw materials of polyester chip B include: 99% PET masterbatch, 0.5% antioxidant 1222 and 0.5% silica.

Comparative example 1

The difference between this comparative example and Example 1 is that in step S1, the raw materials of polyester chips A and polyester chips C independently include: 86% PET masterbatch, 1% antioxidant 1222, 6% magnesium stearate, 6% alumina and 1% silica.

Comparative example 2

The difference between this comparative example and Example 1 is that in step S1, the raw materials of polyester chips A and polyester chips C independently include: 96% PET masterbatch, 1.5% antioxidant 1222, 0.5% magnesium stearate, 1% alumina and 1% silica.

Comparative example 3

The difference between this comparative example and Example 1 is that in step S1, the raw materials of polyester chips A and polyester chips C independently include: 96% PET masterbatch, 1% antioxidant 1222, 1% magnesium stearate, 0.5% alumina and 1.5% silica.

Comparative example 4

The difference between this comparative example and Example 1 is that in step S1, the raw materials of polyester slice B include: 94% PET masterbatch, 1% antioxidant 1222, 4% alumina and 1% silica.

Comparative example 5

The difference between this comparative example and Example 1 is that in step S1, the raw materials of polyester chip B include: 99.5% PET masterbatch and 0.5% alumina.

Comparative example 6

The difference between this comparative example and Example 1 is that the raw materials of polyester chips A, polyester chips B and polyester chips C include: 100% PET masterbatch.

Comparative example 7

The difference between this comparative example and Example 1 is that the heat treatment process in step S4.4 of the polyester composite film preparation method is adjusted to: step (2) is not performed.

Comparative example 8

The difference between this comparative example and Example 1 is that the heat treatment process in step S4.4 of the polyester composite film preparation method is adjusted to: in step (2), the temperature is raised to 150°C and treated for 5 minutes.

Comparative example 9

The difference between this comparative example and Example 1 is that the heat treatment process in step S4.4 of the polyester composite film preparation method is adjusted to: in step (2), the temperature is raised to 230°C and treated for 5 minutes.

Comparative example 10

The difference between this comparative example and Example 1 is that the heat treatment process in step S4.4 of the polyester composite film preparation method is adjusted to: raise the temperature to 180°C in step (2) and process for 0.4 minutes.

Comparative example 11

The difference between this comparative example and Example 1 is that the heat treatment process in step S4.4 of the polyester composite film preparation method is adjusted to: in step (2), the temperature is raised to 180°C and treated for 32 minutes.

Test Example 1 Elastic modulus, swelling and crystallinity testing

1. Elastic modulus test method: The lower the elastic modulus, the softer the polyester composite film is; the higher the elastic modulus, the brittle the polyester composite film is. Therefore, the elastic modulus can reflect the flexibility and elasticity of the polyester composite film. The test method of modulus refers to GB/T 1040.1-2018.

2. Swelling degree test method: Cut the prepared polyester composite film, composite positive electrode current collector and composite negative electrode current collector into 20cm × 20cm samples, record the circumference of the sample as C ₁ , and then place it in the electrolyte at 65°C Soak in medium for 48 hours. Record the circumference of the sample after soaking as C ₂ . Calculate the swelling degree SD of the sample according to the following formula:

SD=(C ₂ -C ₁ )/C ₁ ×100%,

Among them, the formula of the electrolyte is shown in Table 1. 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 in the additive It refers to the percentage of its mass to the total mass of solvent and additives. Based on the total amount of solvent and additives, the concentration of vinylene carbonate is 2wt%, and the total concentration of ethylene carbonate, ethyl methyl carbonate and vinylene carbonate is 98wt%.

Table 1 Components of electrolyte

3. Crystallinity test method: Tear off the surface layer A or surface layer B from the polyester composite film, and use the differential scanning calorimeter (DSC) method to test the crystallinity of surface layer A or surface layer B. The temperature rise program is: at 30 The temperature was raised to 290°C at a rate of 10°C/min, kept for 3 minutes, and then cooled to 30°C at a rate of 10°C/min. The melting enthalpy (ΔH _f ) is obtained from the tested DSC curve, and the crystallinity X _c is calculated according to 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.

Table 2 Elastic modulus, crystallinity and swelling degree test results

It can be seen from Table 2: ① Compared with Comparative Examples 1 to 11, the polyester composite film prepared in Example 1 and the composite positive electrode current collector and composite negative electrode current collector prepared using it as the base material have better swelling resistance in the electrolyte The performance is significantly improved, and the polyester composite film prepared in Example 1 has good flexibility, which can ensure that the polyester composite film maintains a low membrane rupture rate during the preparation process. ② Observe Examples 1 to 5 and find that when the nucleating agent content in surface layer A and surface layer B is increased, the crystallinity of surface layer A/surface layer B first increases and then decreases, and the elastic modulus of the polyester composite film first increases and then decreases. Preparation The swelling degree of the polyester composite film as well as the composite positive electrode current collector and composite negative electrode current collector prepared as the base material in the electrolyte first decreased and then increased; ③ Observing Examples 6 to 11, it was found that extending the steps of step S4.4 The heat treatment time or the heat treatment temperature in step S4.4 is increased, the crystallinity of surface layer A/surface layer B is improved, and the polyester composite film prepared as well as the composite positive electrode current collector and composite negative electrode current collector prepared as a base material in the electrolyte The degree of swelling is reduced, that is, the solvent swelling resistance is improved.

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 swelling-resistant polyester composite film, characterized in that the polyester composite film includes a core layer, a surface layer A and a surface layer B, wherein the surface layer A and the surface layer B are respectively located on both sides of the core layer;

In terms of mass percentage, the raw materials of the surface layer A and the surface layer B each independently include: 88% to 97% polyester material and 3% to 12% additives, and the raw materials of the core layer include: 95% to 99% Polyester material and 1% to 5% additives;

The additives in the surface layer A, the surface layer B and the core layer all include nucleating agents, and the content of the nucleating agent in the surface layer A and the surface layer B is higher than that of the nucleating agent in the core layer. content, and the mass percentage of the nucleating agent in the surface layer A and the surface layer B in the respective additives is not less than 50%.
The polyester composite film according to claim 1, wherein the polyester material includes polyethylene terephthalate, polybutylene terephthalate, poly2,6-naphthalenedicarboxylic acid Propylene glycol ester, polyethylene 2,6-naphthalate, polytrimethylene terephthalate, poly1,4-cyclohexanedimethanol terephthalate, polyethylene terephthalate- 1,4-Cyclohexane dimethanol, polybutylene 2,6-naphthalate, polybutylene 2,5-furandicarboxylate, polyarylate and polybutylene adipate terephthalate One or more of alcohol esters and their derivatives.
The polyester composite film according to claim 1 or 2, characterized in that the thickness of the surface layer A and the surface layer B is equal, and the thickness of the surface layer A and the surface layer B each independently accounts for the thickness of the polyester composite film. The thickness of the composite film accounts for 5% to 15%, and the thickness of the core layer accounts for 70% to 90% of the thickness of the polyester composite film.
The polyester composite film according to any one of claims 1 to 3, wherein the nucleating agent includes zinc oxide, aluminum oxide, magnesium oxide, copper oxide, barium sulfate, sodium carbonate, triphenyl phosphate, One or more of benzophenone, polycaprolactone, magnesium stearate and sodium benzoate.
The polyester composite film according to any one of claims 1 to 4, wherein the additive further includes one or more of antioxidants, slip agents and antistatic agents.
The polyester composite film according to claim 5, wherein the antioxidant includes one or more of phosphonate and bisphenol A phosphite;

The slip agent includes one or more of calcium carbonate, titanium dioxide, diatomaceous earth, talc, acrylate, silicon dioxide, siloxane and kaolin;

The antistatic agent includes one or more of glycerol, polyethylene glycol, polyglycerol, polyether ester, graphite, carbon black and conductive fiber.
A method for preparing a swelling-resistant polyester composite film, characterized in that the preparation method includes the following steps:

Preparing polyester slices A: The polyester slices A are obtained by mixing the raw materials of surface layer A and then sequentially undergoing melt extrusion and molding slice processing;

Preparing polyester slices B: The polyester slices B are obtained by mixing the raw materials of the core layer and then sequentially undergoing melt extrusion and molding slice processing;

Preparing polyester slices C: The polyester slices C are obtained by mixing the raw materials of surface layer B and then sequentially undergoing melt extrusion and molding slice processing;

Preparing molten polyester material: After the polyester slice A, the polyester slice B and the polyester slice C are sequentially subjected to crystallization treatment and drying treatment, they are added to different twin-screw extruders respectively, and undergo melt extrusion. After processing, molten polyester material is obtained;

Preparing a polyester composite film: The molten polyester material is sequentially cast, stretched and heat treated to obtain a polyester composite film including the surface layer A, the core layer and the surface layer B. The surface layer A and The surface layer B is located on both sides of the core layer respectively;

In terms of mass percentage, the raw materials of the surface layer A and the surface layer B each independently include: 88% to 97% polyester material and 3% to 12% additives, and the raw materials of the core layer include: 95% to 99% Polyester material and 1% to 5% additives;

The additives in the surface layer A, the surface layer B and the core layer all include nucleating agents, and the content of the nucleating agent in the surface layer A and the surface layer B is higher than that of the nucleating agent in the core layer. content, and the mass percentage of the nucleating agent in the surface layer A and the surface layer B in the respective additives is not less than 50%.
The preparation method according to claim 7, characterized in that the crystallization treatment temperature is 130-185°C, the crystallization treatment time is 20-130min, the drying treatment temperature is 130-175°C, and the drying treatment The time is 110~300min.
The preparation method according to claim 7 or 8, characterized in that the heat treatment includes the following steps:

(1) Raise the temperature to 130~160℃ and process for 0.5~20 minutes;

(2) Raise the temperature to 160~220℃ and process for 0.5~30 minutes;

(3) Cool down to 130~160℃ and process for 0.5~20 minutes;

(4) Cool down to 70~110℃ and process for 0.5~20min.
A composite current collector, characterized in that the composite current collector includes a base layer and a metal conductive layer, the metal conductive layer is provided on at least one surface of the base layer, the base layer includes any of claims 1 to 6 The polyester composite film described in claim 1 or the polyester composite film prepared by the preparation method described in any one of claims 7 to 9.
The composite current collector according to claim 10, wherein the composite current collector further includes a protective layer, and the protective layer is disposed on at least one of two surfaces of the metal conductive layer with opposite thicknesses.
The composite current collector according to claim 11, wherein the protective layer has at least one of the following characteristics:

(1) The materials of the protective layer include nickel, chromium, copper-based alloys, nickel-based alloys, cobalt oxide, copper oxide, nickel oxide, aluminum oxide, carbon black, carbon nanotubes, acetylene black, graphite, chromium oxide, graphite One or more of cycotjen black, carbon nanofibers and carbon nano-quantum dots;

(2) The thickness of the protective layer is 10 to 150 nm.
An electrode pole piece, characterized by comprising an active material layer and a composite current collector according to any one of claims 10 to 12, the active material layer being located at least on the composite current collector close to the metal conductive layer On the surface.
A battery, characterized in that it includes a positive electrode piece and a negative electrode piece, and at least one of the positive electrode piece and the negative electrode piece is the electrode piece according to claim 13.
An electronic device, characterized by comprising the battery according to claim 14.