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CN115926389A - High-strength polyester-based film, preparation method thereof and application thereof in composite current collector - Google Patents

High-strength polyester-based film, preparation method thereof and application thereof in composite current collector Download PDF

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Publication number
CN115926389A
CN115926389A CN202211509980.9A CN202211509980A CN115926389A CN 115926389 A CN115926389 A CN 115926389A CN 202211509980 A CN202211509980 A CN 202211509980A CN 115926389 A CN115926389 A CN 115926389A
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molecular weight
current collector
based film
strength polyester
polyester
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夏建中
朱中亚
李学法
张国平
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Yangzhou Nanopore Innovative Materials Technology Ltd
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Yangzhou Nanopore Innovative Materials Technology Ltd
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Priority to PCT/CN2022/139619 priority patent/WO2024113432A1/en
Publication of CN115926389A publication Critical patent/CN115926389A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)

Abstract

The invention discloses a high-strength polyester-based film, a preparation method thereof and application thereof in a composite current collector, and relates to the technical field of current collectors. The raw materials of the high-strength polyester base film comprise a polyethylene terephthalate white chip A and a polyethylene terephthalate white chip B; the preparation method comprises the following steps: (1) mixing the two materials thoroughly; (2) Heating and melting the mixed materials to form a melt, and extruding to prepare a cast sheet; (3) Longitudinally stretching the cast sheet along the advancing direction of a machine conveying mechanism; and (4) then entering a transverse oven unit for transverse stretching. The high-strength polyester base film prepared by the method has the characteristics of high strength and high elongation, and the puncture resistance of the composite current collector can be greatly improved, so that the safety of the battery under extreme conditions such as impact and impact is improved.

Description

High-strength polyester-based film, preparation method thereof and application thereof in composite current collector
Technical Field
The invention relates to the technical field of current collectors, in particular to a high-strength polyester-based film, a preparation method thereof and application thereof in a composite current collector.
Background
At present, a composite current collector based on a polymer film is widely concerned and applied in the new energy industry. The preparation process of the composite current collector is generally as follows: a layer of metal (aluminum, copper and the like) material is deposited on a high molecular film (such as polypropylene, polyethylene, polyesters and the like) by adopting a Physical Vapor Deposition (PVD) method, and the surface metallized film with certain conductivity is prepared and is the composite current collector. Compared with the traditional current collector, the composite current collector based on the polymer film has the characteristics of low cost, light weight, good internal insulation and the like. The characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and the safety of the battery when the composite current collector is applied to the battery.
However, the polymer film used in the composite current collector in the prior art is not specially developed for the application of battery materials, but is directly selected from mature films in other industries, such as packaging, capacitors and the like. In the packaging and capacitor industries, due to different application requirements, various requirements are put forward on the light transmittance, food safety, insulativity and the like of the film. In order to meet these requirements, the use of additives has to be increased or limited, or there are trade-offs in the preparation process for technical specifications that cannot be taken into account.
Therefore, the mature films in the existing industry are not ideal base film materials for composite current collectors, especially for puncture-resistant composite current collectors. And because of the addition of certain additives, the composite current collector prepared by using the films has the phenomena of low strength, weak binding force, easy powder falling, insufficient fusing speed and the like. Meanwhile, the tensile strength of the polyester base film used in the traditional industry in the machine advancing direction (MD) and the Transverse Direction (TD) is lower than 300MPa, while the tensile strength of the current collector industry in all directions is required to be higher than 300MPa, and particularly, when the current collector is deformed to a certain extent, for example, 10%, the tensile strength of the film in all directions is higher than 140MPa; further, in the elastic deformation range, for example, 2.5% deformation, the tensile strength of the film in all directions is greater than or equal to 100MPa.
In view of the above, it is urgent to develop a polymer thin film suitable for a composite current collector in the battery industry.
Disclosure of Invention
The invention aims to provide a high-strength polyester-based film, a preparation method thereof and application thereof in a composite current collector, so as to solve the problems in the background technology. The polyester-based film prepared by the invention has the characteristics of high strength and high elongation, and the puncture resistance of the composite current collector can be greatly improved, so that the safety of the battery under extreme conditions such as impact and impact is improved.
In order to achieve the purpose, the invention provides the following technical scheme:
the invention firstly provides a high-strength polyester base film, and the raw materials of the high-strength polyester base film comprise a polyethylene terephthalate white chip A and a polyethylene terephthalate white chip B;
the molecular weight dispersion coefficient of the polyethylene terephthalate white chip A is =1.7 +/-0.5, and any one of the following conditions is satisfied:
(1) Weight average molecular weight Mw =33000 ± 2000;
(2) Number average molecular weight Mn =19000 ± 1000;
(3) The Z-average molecular weight Mz =60000 ± 3000;
the molecular weight dispersion coefficient of the polyethylene terephthalate white chip B is =1.9 +/-0.5, and any one of the following conditions is satisfied:
(1) Weight average molecular weight Mw =50000 ± 5000;
(2) Number average molecular weight Mn =30000 ± 3000;
(3) Z-average molecular weight Mz =90000 ± 3000.
Preferably, the mass ratio of the ethylene terephthalate white chip A to the ethylene terephthalate white chip B is in the range of 99-90.
Preferably, GPC test is carried out on the mixture of the ethylene terephthalate white chip A and the ethylene terephthalate white chip B, and a molecular weight distribution curve of the mixture is obtained; integrating the part with the molecular weight Mw of more than 75000 and less than 200000 to obtain an integral area Delta S; the proportion of the obtained Delta S in the integral area of the whole curve is between 15 and 35 percent.
Further, the thickness of the high-strength polyester base film is 2-6 um, and the ultimate tensile strength in the longitudinal direction and the transverse direction is more than or equal to 300Mpa; when the deformation reaches 10%, the tensile strength in the longitudinal direction and the tensile strength in the transverse direction are both more than or equal to 140Mpa, and the elongation at break is both more than or equal to 80%; when the deformation reaches 2.5%, the tensile strength in the longitudinal direction and the tensile strength in the transverse direction are both more than or equal to 100Mpa, and the elongation at break is both more than or equal to 80%.
The invention also provides a preparation method of the high-strength polyester-based film, which comprises the following steps:
(1) Weighing a polyethylene terephthalate white slice A and a polyethylene terephthalate white slice B, and fully mixing the two slices;
(2) Heating and melting the mixed materials in the step (1) to form a melt, and extruding to prepare a cast sheet;
(3) Carrying out longitudinal stretching treatment on the cast sheet prepared in the step (2), wherein the longitudinal stretching ratio is 1:4-1:5;
(4) And (4) transversely stretching the cast sheet prepared in the step (3) to obtain the high-strength polyester base film, wherein the transverse stretching ratio is 1:4-1:5.
Preferably, in the treatment process of the step (2), the casting temperature is 220-270 ℃, the temperature of a cooling roller is 20-35 ℃, the extrusion rate is 50-100m/min, and the speed of the cooling roller is 50-100m/min.
Preferably, the temperature of the longitudinal stretching treatment in the step (3) is 115 to 130 ℃, and the temperature of the transverse stretching treatment in the step (4) is 230 to 260 ℃.
The invention also provides a composite current collector, which structurally comprises a supporting layer and metal layers respectively arranged on the surfaces of the two sides of the supporting layer, wherein the supporting layer is the high-strength polyester base film, and the thickness of each metal layer is 0.8-1.5 um.
Preferably, the metal layer is one of copper, copper alloy, aluminum or aluminum alloy.
More preferably, a protective layer is arranged on the surface of the metal layer far away from the high-strength polyester base film, and the protective layer is coated by the following method:
(1) Uniformly dispersing the carbon nano tubes into N-methyl pyrrolidone (NMP) solution to prepare coating liquid;
(2) Uniformly coating the coating liquid prepared in the step (1) on the surface of the metal layer, wherein the coating thickness is 10-100um;
(3) And (3) drying the composite current collector prepared in the step (2) at the temperature of 90-110 ℃.
It should be noted that the coating thickness is not the thickness after drying at 90-110 ℃; wherein the thickness after drying at 90-110 ℃ is the thickness of the protective layer, and the coating thickness refers to the thickness when the coating liquid is uniformly coated on the surface of the metal layer.
In the step (1) of the coating method of the protective layer, the mass ratio of the carbon nano tube to the nitrogen methyl pyrrolidone solution is 1:1000 to 1:500.
compared with the prior art, the invention has the beneficial effects that:
(1) The special polyester base film with high strength and high elongation at break is prepared by the invention, so that the special requirements of the composite current collector industry on the polyester film are met. The preparation method selects the polyester resin slices with specific molecular weight and molecular weight distribution to be blended with a small amount of high molecular weight polyester, particularly limits the high molecular components which account for less components but have obvious influence on the performance, and completes the preparation of the polyester base film by matching with a stretching process.
(2) The composite current collector has high adhesion between the surface metal and the polyester base film, and effectively avoids the problem that the metal layer is stripped or falls off from the polyester base film, thereby prolonging the service life of the composite current collector and a battery using the composite current collector.
Drawings
FIG. 1 is a molecular weight distribution chart of the mixture obtained in step (1) of the present invention.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings and examples. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The first embodiment provides a high strength polyester-based film, wherein the weight average molecular weight Mw of polyethylene terephthalate (PET) white chip a as the host material of the polyester-based film formulation is 33000, the number average molecular weight Mn is 19000, the z average molecular weight Mz is 59000, and the molecular weight distribution coefficient is 1.74;
polyethylene terephthalate (PET) ester white chips B as an auxiliary material for polyester-based film formulations had a weight average molecular weight Mw of 55000, a number average molecular weight Mn of 33000, a z average molecular weight Mz of 93000, and satisfied a molecular weight distribution coefficient of 1.67.
The preparation method of the high-strength polyester-based film comprises the following steps:
(1) The host material (i.e., polyester chip a) and the auxiliary material (i.e., polyester chip B) were mixed at a mass ratio of 92 to 8, and subjected to GPC testing, as Δ S =30%, as shown in fig. 1;
(2) Adding the mixed material obtained in the step (1) into a double-screw extruder, heating and melting the mixed material to form a melt, and then feeding the melt into a coat hanger type single-runner die head to extrude a cast sheet; wherein the casting temperature is 220 ℃, the cooling roller temperature is 20 ℃, the extrusion speed is 50m/min, and the cooling roller speed is 50m/min;
(3) Carrying out longitudinal stretching treatment on the cast sheet obtained in the step (2) along the advancing direction of a machine conveying mechanism, wherein the longitudinal stretching ratio is 1:4; the temperature of longitudinal stretching treatment is 120 ℃;
(4) Then entering a transverse oven unit for transverse stretching, wherein the transverse stretching ratio is 1:4, and preparing the biaxially oriented polyester film with the final thickness of 4.5 um; the temperature of the transverse oven unit was 240 ℃.
The film was found to have a tensile strength of 380MPa in the MD direction, an elongation at break of 80%, a tensile strength of 350MPa in the TD direction, an elongation at break of 90%, a tensile strength of 170MPa in the P10 direction (when the amount of deformation reached 10%) in the MD direction, 130MPa in the P2.5 direction (when the amount of deformation reached 2.5%), 170MPa in the P10 direction (when the amount of deformation reached 10%) in the TD direction, and 130MPa in the P2.5 direction (when the amount of deformation reached 2.5%).
The second embodiment also provides a method for preparing a composite negative current collector from a polyester-based film:
A. firstly, preparing a metal conducting layer: placing the polyester basal membrane which is prepared in the embodiment 1 and has the surface cleaned in a vacuum evaporation cabin, melting and evaporating high-purity copper wires (the purity is more than 99.99%) in a metal evaporation chamber at the high temperature of 1400-2000 ℃, and depositing evaporated metal atoms on two surfaces of a high-molecular basal membrane through a cooling system in a vacuum coating chamber to form a copper metal conducting layer with the thickness of 1.0 micron;
B. and secondly, preparing a protective layer: uniformly dispersing 1g of graphene into 999g of N-methyl pyrrolidone (NMP) solution by an ultrasonic dispersion method to prepare a coating liquid with the solid content of 0.1wt.%, uniformly coating the coating liquid on the surface of the metal conductive layer by a die head coating process, wherein the coating amount is controlled at 80 micrometers, and finally drying at 100 ℃.
The third embodiment also provides a method for preparing a composite positive current collector from a polyester-based film:
A. firstly, preparing a metal conducting layer: placing the polyester basal membrane which is prepared in the embodiment 1 and has the surface cleaned in a vacuum evaporation cabin, melting and evaporating high-purity aluminum wires (the purity is more than 99.99%) in a metal evaporation chamber at the high temperature of 1300-2000 ℃, and depositing evaporated metal atoms on two surfaces of a high-molecular basal membrane through a cooling system in a vacuum coating chamber to form an aluminum metal conducting layer with the thickness of 1.0 micron;
B. and secondly, preparing a protective layer: uniformly dispersing 1g of carbon nanotubes into 999g of N-methyl pyrrolidone (NMP) solution by an ultrasonic dispersion method to prepare a coating liquid with the solid content of 0.1wt.%, uniformly coating the coating liquid on the surface of the metal conductive layer by a die head coating process, wherein the coating amount is controlled at 90 micrometers, and finally drying at 100 ℃.
Example 2
The first embodiment provides a high strength polyester-based film, wherein the weight average molecular weight Mw of polyethylene terephthalate (PET) white chip a as the host material of the polyester-based film formulation is 33000, the number average molecular weight Mn is 19000, the z average molecular weight Mz is 59000, and the molecular weight distribution coefficient is 1.74;
polyethylene terephthalate (PET) ester white chips B as an auxiliary material for the polyester-based film formulation had a weight average molecular weight Mw of 50000, a number average molecular weight Mn of 30000, a z average molecular weight Mz of 90000, and satisfied a molecular weight distribution coefficient of 1.67.
The preparation method of the high-strength polyester-based film comprises the following steps:
(1) The main material (i.e. polyester chip a) and the auxiliary material (i.e. polyester chip B) were mixed in a mass ratio of 95;
(2) Adding the premix obtained in the step (1) into a double-screw extruder, heating, melting and mixing to form a melt, and then feeding the melt into a coat hanger type single-runner die head to extrude a casting sheet; wherein the casting temperature is 250 ℃, the temperature of a cooling roller is 28 ℃, the extrusion speed is 75m/min, and the speed of the cooling roller is 75m/min;
(3) Carrying out longitudinal stretching treatment on the cast sheet obtained in the step (2) along the advancing direction of a machine conveying mechanism, wherein the longitudinal stretching ratio is 1:4; the temperature of the longitudinal stretching treatment is 125 ℃;
(4) Then entering a transverse oven unit for transverse stretching, wherein the transverse stretching ratio is 1:4, and preparing the biaxially oriented polyester film with the final thickness of 4.5 um; the temperature of the transverse oven unit was 250 ℃.
The film was found to have a tensile strength in the MD of 350MPa, an elongation at break of 90%, a tensile strength in the TD of 330MPa, an elongation at break of 100%, a tensile strength in the MD of P10 (when the amount of deformation reached 10%) of 160MPa, a tensile strength in P2.5 (when the amount of deformation reached 2.5%) of 120MPa, a tensile strength in the TD of P10 (when the amount of deformation reached 10%) of 160MPa, and a tensile strength in the P2.5 (when the amount of deformation reached 2.5%) of 120MPa.
The second embodiment also provides a method for preparing a composite negative current collector from a polyester-based film:
A. firstly, preparing a metal conducting layer: placing the polyester basal membrane which is prepared in the embodiment 2 and has the surface cleaned in a vacuum evaporation cabin, melting and evaporating high-purity copper wires (the purity is more than 99.99%) in a metal evaporation chamber at the high temperature of 1400-2000 ℃, and depositing evaporated metal atoms on two surfaces of a high-molecular basal membrane through a cooling system in a vacuum coating chamber to form a copper metal conducting layer with the thickness of 0.8 micron;
B. then, preparing a protective layer: uniformly dispersing 1g of graphene into 599g of N-methyl pyrrolidone (NMP) solution by an ultrasonic dispersion method to prepare a coating liquid with the solid content of 0.17wt.%, uniformly coating the coating liquid on the surface of the metal conductive layer by a die coating process, wherein the coating amount is controlled at 70 micrometers, and finally drying at 90 ℃.
The third embodiment also provides a method for preparing a composite positive current collector from a polyester-based film:
A. firstly, preparing a metal conductive layer: placing the polyester basal membrane which is prepared in the embodiment 2 and has the surface cleaned in a vacuum evaporation cabin, melting and evaporating high-purity aluminum wires (the purity is more than 99.99%) in a metal evaporation chamber at the high temperature of 1300-2000 ℃, and depositing evaporated metal atoms on two surfaces of a high-molecular basal membrane through a cooling system in a vacuum coating chamber to form an aluminum metal conducting layer with the thickness of 0.8 micron;
B. then, preparing a protective layer: 1g of carbon nano tubes are uniformly dispersed into 599g of N-methyl pyrrolidone (NMP) solution by an ultrasonic dispersion method to prepare a coating liquid with the solid content of 0.17wt.%, then the coating liquid is uniformly coated on the surface of the metal conducting layer by a die head coating process, wherein the coating amount is controlled at 80 micrometers, and finally the drying is carried out at 90 ℃.
Example 3
The first embodiment provides a high strength polyester-based film, wherein the weight average molecular weight Mw of polyethylene terephthalate (PET) white chip a as the host material of the polyester-based film formulation is 33000, the number average molecular weight Mn is 19000, the z average molecular weight Mz is 59000, and the molecular weight distribution coefficient is 1.74;
polyethylene terephthalate (PET) ester white chips B as an auxiliary material for the polyester-based film formulation had a weight average molecular weight Mw of 45000, a number average molecular weight Mn of 27000, a z average molecular weight Mz of 87000, and satisfied a molecular weight distribution coefficient of 1.67.
The preparation method of the high-strength polyester-based film comprises the following steps:
(1) The main material (i.e. polyester chip a) and the auxiliary material (i.e. polyester chip B) were mixed in a mass ratio of 97% to 3, and subjected to GPC testing, Δ S =15%;
(2) Adding the premix obtained in the step (1) into a double-screw extruder, heating, melting and mixing to form a melt, and then feeding the melt into a coat hanger type single-runner die head to extrude a casting sheet; the casting temperature is 270 ℃, the cooling roller temperature is 35 ℃, the extrusion speed is 100m/min, and the cooling roller speed is 100m/min;
(3) Carrying out longitudinal stretching treatment on the cast sheet obtained in the step (2) along the advancing direction of a machine conveying mechanism, wherein the longitudinal stretching ratio is 1:4; the temperature of the longitudinal stretching treatment is 130 ℃;
(4) Then entering a transverse oven unit for transverse stretching, wherein the transverse stretching ratio is 1:4, and preparing the biaxially oriented polyester film with the final thickness of 4.5 um; the temperature of the transverse oven unit was 260 ℃.
The film was found to have a tensile strength in the MD of 310MPa, an elongation at break of 100%, a tensile strength in the TD of 300MPa, an elongation at break of 110%, a tensile strength in the P10 (when the amount of deformation reached 10%) in the MD of 140MPa, a tensile strength in the P2.5 of 100MPa, a tensile strength in the P10 (when the amount of deformation reached 10%) in the TD of 140MPa, and a tensile strength in the P2.5 of 100MPa.
The second embodiment also provides a method for preparing a composite negative current collector from a polyester-based film:
A. firstly, preparing a metal conductive layer: placing the polyester base film prepared in the embodiment 3 and subjected to surface cleaning treatment in a cabin body of vacuum evaporation, melting and evaporating high-purity copper wires (the purity is more than 99.99%) in a metal evaporation chamber at the high temperature of 1400-2000 ℃, and depositing evaporated metal atoms on two surfaces of a high-molecular base film through a cooling system in a vacuum coating chamber to form a copper metal conducting layer with the thickness of 1.5 micrometers;
B. then, preparing a protective layer: 1g of graphene is uniformly dispersed into 799g of N-methyl pyrrolidone (NMP) solution by an ultrasonic dispersion method to prepare a coating liquid with the solid content of 0.125wt.%, and then the coating liquid is uniformly coated on the surface of the metal conductive layer by a die coating process, wherein the coating amount is controlled at 90 micrometers, and finally, the metal conductive layer is dried at 110 ℃.
The third embodiment also provides a method for preparing a composite positive current collector from a polyester-based film:
A. firstly, preparing a metal conductive layer: placing the polyester basal membrane which is prepared in the embodiment 3 and has the surface cleaned in a vacuum evaporation cabin, melting and evaporating high-purity aluminum wires (the purity is more than 99.99%) in a metal evaporation chamber at the high temperature of 1300-2000 ℃, and depositing evaporated metal atoms on two surfaces of a high-molecular basal membrane through a cooling system in a vacuum coating chamber to form an aluminum metal conducting layer with the thickness of 1.5 microns;
B. then, preparing a protective layer: 1g of carbon nanotubes are uniformly dispersed into 799g of N-methyl pyrrolidone (NMP) solution by an ultrasonic dispersion method to prepare a coating liquid with the solid content of 0.125wt.%, and then the coating liquid is uniformly coated on the surface of the metal conductive layer by a die coating process, wherein the coating amount is controlled at 100 micrometers, and finally the drying is carried out at 110 ℃.
Comparative example 1
This comparative example is substantially the same as the method of manufacturing the composite current collector in example 1, except that the weight average molecular weight Mw =25000, the number average molecular weight Mn =13000, and the z average molecular weight Mz =57000 of the polyethylene terephthalate (PET) white chip, which is an auxiliary material of the polyester-based film formulation, satisfy the molecular weight dispersion coefficient =1.92. In addition, the host material and the auxiliary material described in 2 were mixed in a mass ratio of 92, Δ S =12% by GPC test.
Preparing a biaxially oriented polyester film with the final thickness of 4.5um by using an MD direction stretching ratio of 1; the P10 tensile strength (when the deformation amount reaches 10%) in the MD direction is 125Mpa; the tensile strength of P2.5 was 92MPa, the tensile strength of P10 in TD direction (when the amount of deformation reached 10%) was 118MPa, and the tensile strength of P2.5 was 90MPa.
As can be seen from the above data, the transverse and machine direction tensile strengths of the polyester base film are much lower than those of the base film obtained in example 1, and the tensile strengths of P10 and P2.5 are also significantly lower than those of example 1.
Comparative example 2
Commercially available 6um pure copper foil is used as the current collector.
Comparative example 3
Commercially available 13um pure aluminum foil was used as the current collector.
Test example
(1) With reference to GB/T10004-2008, the obtained current collectors of examples 1 to 3 and comparative examples 1 to 3 were subjected to a puncture resistance test, and the test results are shown in table 1 below:
TABLE 1
Figure BDA0003968864280000101
As can be seen from the data in table 1, the composite current collector prepared using the high-strength high-elongation-at-break polyester-based film has a puncture strength much greater than that of the conventional pure copper foil and pure aluminum foil current collectors.
In conclusion, the polyester base film prepared by the preparation method has the characteristics of high strength and high elongation at break, and the composite current collector prepared by the polyester base film has puncture resistance far higher than that of the traditional pure copper foil and pure aluminum foil current collectors, so that the safety of the battery under extreme conditions such as impact and impact can be improved; and the polyester base film has strong adhesive force with the metal conducting layer, and can effectively prevent the metal layer from peeling or falling off from the polyester base film, thereby prolonging the service life of the composite current collector and the battery using the composite current collector.
While the embodiments of the invention have been described in detail, it is not intended to limit the invention to the exact construction and operation illustrated and described, and it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made herein without departing from the spirit and scope of the invention.

Claims (10)

1. A high-strength polyester-based film is characterized in that raw materials of the high-strength polyester-based film comprise a polyethylene terephthalate white chip A and a polyethylene terephthalate white chip B;
the molecular weight dispersion coefficient of the polyethylene terephthalate white chip A is =1.7 +/-0.5, and any one of the following conditions is satisfied:
(1) Weight average molecular weight Mw =33000 ± 2000;
(2) Number average molecular weight Mn =19000 ± 1000;
(3) The Z-average molecular weight Mz =60000 ± 3000;
the molecular weight dispersion coefficient of the polyethylene terephthalate white chip B is =1.9 +/-0.5, and any one of the following conditions is satisfied:
(1) Weight average molecular weight Mw =50000 ± 5000;
(2) Number average molecular weight Mn =30000 ± 3000;
(3) Z-average molecular weight Mz =90000 ± 3000.
2. The high-strength polyester-based film as claimed in claim 1, wherein the mass ratio of the ethylene terephthalate white chip A to the ethylene terephthalate white chip B is in the range of 99-90.
3. The high strength polyester-based film according to claim 1 or 2, wherein a mixture of the ethylene terephthalate white chips a and B is subjected to GPC to obtain a molecular weight distribution curve of the mixture; integrating the part with the molecular weight Mw of more than 75000 and less than 200000 to obtain an integral area Delta S; the proportion of the obtained Delta S in the integral area of the whole curve is between 15 and 35 percent.
4. The high-strength polyester-based film according to claim 3, wherein the high-strength polyester-based film has a thickness of 2-6 um, and ultimate tensile strengths in longitudinal and transverse directions of not less than 300MPa; wherein when the deformation reaches 10%, the tensile strength in the longitudinal direction and the tensile strength in the transverse direction are both more than or equal to 140Mpa, and the elongation at break is both more than or equal to 80%; when the deformation reaches 2.5%, the tensile strength in the longitudinal direction and the tensile strength in the transverse direction are both more than or equal to 100Mpa, and the elongation at break is both more than or equal to 80%.
5. A method for preparing a high-strength polyester-based film according to any one of claims 1 to 4, comprising the steps of:
(1) Weighing a polyethylene terephthalate white slice A and a polyethylene terephthalate white slice B, and fully mixing the two slices;
(2) Heating and melting the mixed material obtained in the step (1) to form a melt, and extruding to prepare a cast sheet;
(3) Performing longitudinal stretching treatment on the cast sheet prepared in the step (2), wherein the longitudinal stretching ratio is 1:4-1:5;
(4) And (4) transversely stretching the cast sheet prepared in the step (3) to obtain the high-strength polyester base film, wherein the transverse stretching ratio is 1:4-1:5.
6. The method for preparing a high strength polyester-based film according to claim 5, wherein the temperature of the longitudinal stretching process of step (3) is 115 to 130 ℃ and the temperature of the transverse stretching process of step (4) is 230 to 260 ℃.
7. A composite current collector is characterized by comprising a supporting layer and metal layers respectively arranged on the surfaces of two sides of the supporting layer, wherein the supporting layer is the high-strength polyester base film according to any one of claims 1 to 4, and the thickness of each metal layer is 0.8 to 1.5 um.
8. The composite current collector of claim 7, wherein the metal layer is one of copper, a copper alloy, aluminum, or an aluminum alloy.
9. The composite current collector of claim 7 or 8, wherein a protective layer is provided on the surface of the metal layer away from the high-strength polyester-based film, and the protective layer is applied by the following method:
(1) Uniformly dispersing the carbon nano tubes into N-methyl pyrrolidone (NMP) solution to prepare coating liquid;
(2) Uniformly coating the coating liquid prepared in the step (1) on the surface of the metal layer, wherein the coating thickness is 10-100um;
(3) And (3) drying the composite current collector prepared in the step (2) at the temperature of 90-110 ℃.
10. The composite current collector of claim 9, wherein in the step (1) of the method for coating the protective layer, the mass ratio of the carbon nanotubes to the nitrogen methyl pyrrolidone solution is 1:1000 to 1:500.
CN202211509980.9A 2022-11-29 2022-11-29 High-strength polyester-based film, preparation method thereof and application thereof in composite current collector Withdrawn CN115926389A (en)

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PCT/CN2022/139619 WO2024113432A1 (en) 2022-11-29 2022-12-16 High-strength polyester base film, and preparation method therefor and use thereof in composite current collector

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JP2004509204A (en) * 2000-09-18 2004-03-25 ビーエーエスエフ　アクチェンゲゼルシャフト Polyester film
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