WO2024050726A1

WO2024050726A1 - Flexible polyester film and preparation method therefor, composite current collector, battery and electronic product

Info

Publication number: WO2024050726A1
Application number: PCT/CN2022/117600
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: 2022-09-07
Filing date: 2022-09-07
Publication date: 2024-03-14

Abstract

The present application relates to a flexible polyester film and a preparation method therefor, a composite current collector, a battery and an electronic product. The flexible polyester film comprises the following components in parts by mass: 96.90-99.49 parts of polyester, 0.5-3 parts of a polyol and 0.01-0.1 parts of an active metal compound.

Description

Flexible polyester film and preparation method thereof, composite current collector, battery and electronic products

Technical field

This application relates to the technical field of polymer materials, and in particular to a flexible polyester film and its preparation method, composite current collectors, batteries and electronic products.

Background technique

At present, composite current collectors based on polymer membranes are widely used in the new energy industry. They have the characteristics of low cost, light weight, and good internal insulation. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and safety of the battery when used in batteries. The preparation process of a composite current collector based on a polymer film usually results in the formation of a metal material layer on the polymer film. However, in the traditional process of preparing a composite current collector using a polyester film as the base film, due to the relatively poor mechanical properties of the base film, it is prone to membrane rupture during the formation of the metal material layer, resulting in a poor yield rate of the composite current collector. is low, and the mechanical properties of the prepared composite current collector are poor.

Contents of the invention

Based on this, it is necessary to provide a flexible polyester film and its preparation method, composite current collector, battery and electronic products, which can improve the mechanical properties of the polyester film, reduce the membrane rupture rate during the preparation process of the current collector, and improve the composite current collector. mechanical properties.

In the first aspect, this application provides a flexible polyester film, which includes the following components by mass: 96.90 to 99.49 parts of polyester, 0.5 to 3 parts of polyol, and

0.01 part to 0.1 part of active metal compound.

In some embodiments, the polyols include diethylene glycol, polyethylene glycol, two polyglycerols, three polyglycerols, four polyglycerols, five polyglycerols, six polyglycerols, seven polyglycerols, eight polyglycerols, and nine polyglycerols. One or more of glycerin and decaglycerol.

In some embodiments, the active metal compound includes one or more of titanium-based compounds, antimony-based compounds, and germanium-based compounds.

In some embodiments, the titanium-based compound includes one or more of titanium dioxide, potassium fluorotitanate, tetrabutyl titanate, and titanium complex; the antimony-based compound includes antimony trioxide, antimony acetate , one or more of antimony ethanol; the germanium-based compound includes one or more of germanium dioxide, germanium monoxide, sodium germanate, and potassium germanate.

In some embodiments, the polyester includes polyethylene terephthalate and its derivatives, polytrimethylene terephthalate and its derivatives, polybutylene terephthalate and its derivatives , polyethylene naphthalate and its derivatives, polytrimethylene naphthalate and its derivatives, polybutylene naphthalate and its derivatives, polybutylene 2,5-furandicarboxylate and Its derivatives, polybutylene adipate terephthalate and its derivatives, poly1,4-cyclohexanedimethanol terephthalate and its derivatives, polyethylene terephthalate -One or more of 1,4-cyclohexanedimethanol ester and its derivatives.

In one embodiment, the weight average molecular weight of the polyester is 25,000 to 40,000 Da.

In one embodiment, the polyester has a molecular weight distribution of 1.5 to 2.5.

In one embodiment, the flexible polyester film has a crystallinity of 5% to 20%.

In a second aspect, this application also provides a method for preparing a flexible polyester film, including:

Mix and melt 96.90 to 99.49 parts by mass of polyester, 0.5 to 3 parts of polyol and 0.01 to 0.1 part of active metal compound to obtain molten material;

The molten material is stretched.

In one embodiment, the stretching is bidirectional stretching.

In one embodiment, the bidirectional stretching includes at least one of longitudinal and transverse asynchronous stretching and longitudinal and transverse synchronous stretching.

In a third aspect, the present application also provides a composite current collector, including: a flexible polyester film as described in any one of the above and a conductive layer located on at least one surface of the flexible polyester film.

In a fourth aspect, the present application also provides a battery, including the composite current collector as described in any one of the above.

In a fifth aspect, this application also provides an electronic product, including the above-mentioned battery.

The components of the above-mentioned flexible polyester film include polyester, polyol and active metal compound. In preparing flexible polyester films from raw materials including polyester, polyol and active metal compounds, the polyol can play a bridging role and react with the carboxyl or hydroxyl groups at the end of the polyester to promote further polymerization of the polyester polymer, thus To improve the mechanical properties of the base material, the active metal compound catalyzes the polycondensation reaction between polyester molecules and between polyester and polyol, thereby improving the mechanical properties of the polyester film. This application can further obtain flexible polyester with good mechanical properties. membrane.

The above-mentioned composite current collector has good mechanical properties, can reduce the membrane rupture rate during the preparation process of the composite current collector, and improve the yield of finished products.

Description of the drawings

In order to more clearly explain the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to describe the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting any creative effort.

Figure 1 is a flow chart of a method for preparing a flexible polyester film according to an embodiment of the present application;

Figure 2 is a schematic structural diagram of a composite current collector provided by an embodiment of the present application. Explanation of reference signs

1. First protective layer; 2. First conductive layer; 3. Composite polyester film; 4. Second conductive layer; 5. Second protective layer.

Detailed ways

In order to make the above objects, features and advantages of the present application more obvious and easy to understand, the specific implementation modes of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described here. Those skilled in the art can make similar improvements without violating the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

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 "and/or" includes any and all combinations of one or more of the associated listed items.

In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

One embodiment of the present application provides a flexible polyester film, which includes the following components by mass: 96.90 to 99.49 parts of polyester, 0.5 to 3 parts of polyol, and

0.01 part to 0.1 part of active metal compound.

In the chemical reaction of polyester synthesis, the mixed components undergo in-situ solid-phase polycondensation to improve the mechanical properties of the polyester film. The mass fraction of polyol is 0.5 to 3 parts; polyol plays a bridging role in the in-situ solid-phase polycondensation reaction, reacting with the carboxyl or hydroxyl groups at the end of the polyester to promote further polymerization of the polyester molecules, thereby improving the Mechanical properties of the substrate. When the polyol content is too low, the effect of promoting the polymerization of polyester molecules is not good; when the polyol content is too high, the proportion of single-end reactions increases, making it difficult to further increase the degree of polymerization of polyester molecules; and the polyol content is too high. , will reduce the film-forming properties and stability of the polyester film. Active metal compounds catalyze the polycondensation reaction between polyester molecules and between polyester and polyol, improving the mechanical properties of the polyester film. Active metal compounds catalyze the polycondensation reaction between polyester molecules and between polyester and polyol, improving the mechanical properties of the polyester film. The mass fraction of the active metal compound is 0.01 to 0.1 parts; when the content is too low, the effect of catalyzing the polycondensation reaction between polyester molecules and between polyester and polyol is not good; when the content is too high, the solid phase If the degree of polycondensation reaction is too high, the flexibility of the polyester film will become worse and the elongation at break will decrease, which will lead to an increase in the membrane rupture rate during the preparation of the composite current collector. Within the range of the mass fraction of each component of the present application, a flexible polyester film with good mechanical properties can be obtained.

In some embodiments, the flexible polyester film includes the following mass percentages of each component: 96.90% to 99.49% polyester, 0.5% to 3% polyol, and

0.01% ~ 0.1% active metal compound.

In one embodiment, the raw materials of the flexible polyester film are the following mass percentage components: 96.90% to 99.49% polyester, 0.5% to 3% polyol, and

0.01% ~ 0.1% active metal compound.

In some embodiments, the polyol includes diethylene glycol, polyethylene glycol, two polyglycerols, three polyglycerols, four polyglycerols, five polyglycerols, six polyglycerols, seven polyglycerols, eight polyglycerols, nine polyglycerols, One or more polyglycerols.

In some embodiments, the titanium-based compound includes one or more of titanium dioxide, potassium fluorotitanate, tetrabutyl titanate, and titanium complex; the antimony-based compound includes antimony trioxide, antimony acetate, and antimony ethanol. One or more of the germanium-based compounds include one or more of germanium dioxide, germanium monoxide, sodium germanate, and potassium germanate. In the high-temperature vacuum environment during the preparation of the composite current collector, the active metal compound catalyzes the polycondensation reaction between polyester polymers and between polyester and diethylene glycol, improving the mechanical properties of the polyester film in situ.

In some embodiments, the polyester includes polyethylene terephthalate and its derivatives, polytrimethylene terephthalate and its derivatives, polybutylene terephthalate and its derivatives, poly Ethylene naphthalate and its derivatives, polytrimethylene naphthalate and its derivatives, polybutylene naphthalate and its derivatives, polybutylene 2,5-furandicarboxylate and its derivatives Materials, polybutylene adipate terephthalate and its derivatives, poly1,4-cyclohexanedimethanol terephthalate and its derivatives, polyethylene terephthalate-1 , one or more of 4-cyclohexanedimethanol ester and its derivatives.

In one embodiment, the polyester has a weight average molecular weight of 25,000 to 40,000 Da. A weight average molecular weight that is too low will lead to poor mechanical properties of the polyester film, and a weight average molecular weight that is too high will lead to poor film-forming properties. Within this weight average molecular weight range, the polyester film can have both good mechanical properties and good film forming properties. Optionally, the polyester has a weight average molecular weight of 29,000 to 36,000 Da. Further optionally, the weight average molecular weight of the polyester is 29000Da, 30000Da, 31000Da, 32000Da, 33000Da, 34000Da, 35000Da or 36000Da

In one embodiment, the polyester has a molecular weight distribution of 1.5 to 2.5. A molecular weight distribution that is too low will lead to poor film-forming properties, and a molecular weight distribution that is too high will lead to poor mechanical properties of the polyester film. Within this molecular weight distribution range, the polyester film can have both good mechanical properties and good film-forming properties. Optionally, the polyester has a molecular weight distribution of 1.7 to 2.3. Further optionally, the polyester has a molecular weight distribution of 1.7, 1.8, 1.9, 2.0, 2.1, 2.2 or 2.3.

In one embodiment, the flexible polyester film has a crystallinity of 5% to 20%. Since the solid-phase polycondensation reaction occurs in the amorphous region of the polymer, if the crystallinity is too high, the proportion of the amorphous region will decrease, thereby hindering the occurrence of the solid-phase polycondensation reaction, resulting in limited improvement in the mechanical properties of the polyester film and composite current collector; If the crystallinity is too low and the proportion of invisible regions is too high, the polymer will be easily deoriented during the preparation of the current collector, resulting in a decrease in mechanical properties. Within this crystallinity range, the prepared flexible polyester film has good mechanical properties. Alternatively, the flexible polyester film has a crystallinity of 5%, 8%, 10%, 12%, 15%, 18% or 20%.

An embodiment of the present application also provides a method for preparing a flexible polyester film. Referring to Figure 1, the preparation method includes:

S10: Mix and melt 96.90 to 99.49 parts of polyester, 0.5 to 3 parts of polyol and 0.01 to 0.1 parts of active metal compounds by mass to obtain molten material;

S20: Stretch the molten material.

In some embodiments, the preparation method of the flexible polyester film includes the following steps:

(1) Mix and melt 96.90% to 99.49% polyester, 0.5% to 3% polyol and 0.01% to 0.1% active metal compound by mass to obtain molten material;

(2) Stretch the molten material.

In some embodiments, the stretching is bidirectional stretching.

In some embodiments, the bidirectional stretching includes at least one of longitudinal and transverse asynchronous stretching and longitudinal and transverse synchronous stretching.

In one embodiment, the biaxial stretching includes at least one of asynchronous stretching in the longitudinal and transverse directions and synchronous stretching in the longitudinal and transverse directions - secondary stretching in the longitudinal direction.

An embodiment of the present application also provides a composite current collector, including: a flexible polyester film as described above and a conductive layer located on at least one surface of the flexible polyester film.

The composite current collector prepared with a flexible polyester film as the base film layer has good mechanical properties, can reduce the membrane rupture rate during the preparation process of the composite current collector, and improve the yield.

In some embodiments, the composite current collector further includes a protective layer located on a surface of the conductive layer away from the flexible polyester film.

In one embodiment, the thickness of the conductive layer is 500-2000 nm. Optionally, the thickness of the conductive layer is 700-1200nm. Further optionally, the thickness of the conductive layer is 700nm, 800nm, 900nm, 1000nm, 1100nm or 1200nm.

In one embodiment, the thickness of the protective layer is 10-150 nm. Optionally, the thickness of the protective layer is 10nm, 30nm, 50nm, 70nm, 100nm, 120nm or 150nm.

In one embodiment, the thickness of the protective layer is less than or equal to 10% of the thickness of the conductive layer. Optionally the thickness of the protective layer is 1%, 3%, 5%, 7% or 10% of the thickness of the conductive layer.

In one embodiment, referring to Figure 2, the composite current collector includes: a flexible polyester film 3, a first conductive layer 2 and a second conductive layer 4 respectively located on two opposite surfaces of the flexible polyester film, and a first conductive layer located far away from the first conductive layer. The first protective layer 1 on the surface of the flexible polyester film, and the second protective layer 5 on the surface of the second conductive layer away from the flexible polyester film.

In one embodiment, the thickness of the flexible polyester film is greater than 1 micron. Optionally, the thickness of the flexible polyester film is 2 to 20 microns. The smaller the thickness of the polyester film, the greater its ability to promote the improvement of the energy density of the composite current collector. At the same time, the smaller the thickness of the polyester film, the greater the difficulty of production and the lower the yield rate. Within the thickness range of the polyester film, a polyester film with a high ability to promote the energy density increase of the composite current collector can be obtained while taking into account production difficulty and yield rate. Further optionally, the thickness of the flexible polyester film is 2 microns, 5 microns, 8 microns, 10 microns, 15 microns or 20 microns.

In one embodiment, the material of the conductive layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

In one embodiment, the conductive layer is prepared by one or more of physical vapor deposition, electroplating, and chemical plating. Optionally, physical vapor deposition includes: resistance heating vacuum evaporation, electron beam heating vacuum evaporation, laser heating vacuum evaporation, and magnetron sputtering.

In one embodiment, 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, and Ketjen black. , one or more of carbon nanoquantum dots, carbon nanotubes, carbon nanofibers, and graphene.

In one embodiment, the protective layer is prepared by one or more of physical vapor deposition, chemical vapor deposition, in-situ molding, and coating. Optionally, physical vapor deposition is selected from vacuum evaporation or magnetron sputtering; chemical vapor deposition is selected from atmospheric pressure chemical vapor deposition or plasma enhanced chemical vapor deposition; in-situ forming is selected from in-situ formation of metal oxide on the surface of the conductive layer The method of physical passivation layer; the coating method is selected from die coating, blade coating, and extrusion coating.

An embodiment of the present application provides a battery, including: any of the above composite current collectors.

An embodiment of the present application also provides an electronic product, including: the above-mentioned battery.

The following are specific examples.

Example 1

A flexible polyester film is prepared using polyethylene terephthalate (PET), diethylene glycol and potassium fluotitanate with a weight average molecular weight of 30,000 and a molecular weight distribution of 2.0. The mass percentages of the three raw materials are as follows: 99.49%, 0.5%, 0.01%. The polyester film is prepared using a melt-biaxial stretching method, which includes the following steps: crystal drying - melt extrusion - casting - longitudinal stretching - transverse stretching - heat setting. A flexible polyester film with a thickness of 6 microns and a crystallinity of 20% was prepared.

Using the prepared flexible polyester film as the base film layer to prepare a composite current collector includes the following steps:

(1) Preparation of the conductive layer: Place the flexible polyester film prepared above in a vacuum evaporation chamber, and melt and evaporate the aluminum wire in the metal evaporation chamber with a purity greater than 99.99% at a high temperature of 1500°C. The metal atoms after evaporation After the cooling system in the vacuum coating chamber, it is deposited on the upper and lower surfaces of the flexible polyester film to form an aluminum metal conductive layer with a thickness of 1 micron.

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

Example 2

Example 2 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.47%, 0.5%, and 0.03%.

Example 3

Embodiment 3 is basically the same as Embodiment 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.45%, 0.5%, and 0.05%.

Example 4

Example 4 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.43%, 0.5%, and 0.07%, respectively.

Example 5

Embodiment 5 is basically the same as Embodiment 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.41%, 0.5%, and 0.09%.

Example 6

Embodiment 6 is basically the same as Embodiment 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.4%, 0.5%, and 0.1%.

Example 7

Example 7 is basically the same as Example 4, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 98.93%, 1.0%, and 0.07%.

Example 8

Example 8 is basically the same as Example 4, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 97.93%, 2.0%, and 0.07%, respectively.

Example 9

Embodiment 9 is basically the same as Embodiment 4, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 96.93%, 3.0%, and 0.07%.

Example 10

Example 10 is basically the same as Example 8, except that the weight average molecular weight of PET in the flexible polyester film is 25,000, and the molecular weight distribution is 2.0.

Example 11

Example 11 is basically the same as Example 8, except that the weight average molecular weight of PET in the flexible polyester film is 35,000, and the molecular weight distribution is 2.0.

Example 12

Example 12 is basically the same as Example 8, except that the weight average molecular weight of PET in the flexible polyester film is 40,000 and the molecular weight distribution is 2.0.

Example 13

The example is basically the same as Example 11, except that the weight average molecular weight of PET in the flexible polyester film is 35,000, and the molecular weight distribution is 1.5.

Example 14

Example 14 is basically the same as Example 11, except that the weight average molecular weight of PET in the flexible polyester film is 35,000, and the molecular weight distribution is 2.5.

Example 15

Example 15 is basically the same as Example 11, except that the crystallinity of the flexible polyester film is 15%.

Example 16

Example 16 is basically the same as Example 11, except that the crystallinity of the flexible polyester film is 10%.

Example 17

Example 17 is basically the same as Example 11, except that the crystallinity of the flexible polyester film is 5%.

Comparative example 1

Comparative Example 1 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 100%, 0%, and 0%.

Comparative example 2

Comparative Example 2 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.495%, 0.5%, and 0.005%.

Comparative example 3

Comparative Example 3 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.35%, 0.5%, and 0.15%.

Comparative example 4

Comparative Example 4 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 99.69%, 0.3%, and 0.01%.

Comparative example 5

Comparative Example 5 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluotitanate in the flexible polyester film are: 96.79%, 3.2%, and 0.01%.

Comparative example 6

Comparative Example 6 is basically the same as Example 1, except that the weight average molecular weight of PET in the flexible polyester film is 23,000, and the molecular weight distribution is 2.0.

Comparative example 7

Comparative Example 7 is basically the same as Example 1, except that the weight average molecular weight of PET in the flexible polyester film is 42,000 and the molecular weight distribution is 2.0.

Comparative example 8

Comparative Example 8 is basically the same as Example 1, except that the weight average molecular weight of PET in the flexible polyester film is 30,000, and the molecular weight distribution is 1.3.

Comparative example 9

Comparative Example 9 is basically the same as Example 1, except that the weight average molecular weight of PET in the flexible polyester film is 30,000, and the molecular weight distribution is 2.7.

Comparative example 10

Comparative Example 10 is basically the same as Example 1, except that the crystallinity of the flexible polyester film is 22%.

Comparative example 11

Comparative Example 11 is basically the same as Example 1, except that the crystallinity of the flexible polyester film is 3%.

The mass percentage content of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film in Examples 1 to 17 and Comparative Examples 1 to 11, the weight average molecular weight and molecular weight distribution of PET in the flexible polyester film, and the flexible polyester film The list of process parameters such as crystallinity is as follows in Table 1:

Table 1

The composite current collectors prepared in Examples 1 to 17 and Comparative Examples 1 to 11 were tested for mechanical properties, including tensile strength, elongation at break, and membrane rupture rate during the preparation process. The tensile strength and elongation at break of composite current collectors are tested according to the national standard GB/T 1040.3-2006, where MD represents the longitudinal direction and TD represents the transverse direction. The test results are shown in Table 2 below:

Table 2

The flexible polyester films prepared in Examples 1 to 17 and Comparative Examples 1 to 11 were tested for their mechanical properties before and after preparing composite current collectors, including tensile strength, elongation at break, and membrane rupture rate during the preparation process. The flexible polyester film after preparing the composite current collector is obtained through the following steps: soak the composite current collector in a 1% NaOH solution for 20 minutes, then clean it with pure water, and then dry it at 60°C. The tensile strength and elongation at break of flexible polyester films are tested according to the national standard GB/T 1040.3-2006, where MD represents the longitudinal direction and TD represents the transverse direction. The test results are shown in Table 3 below:

table 3

It can be seen from the test results in Table 2 and Table 3 above:

(1) Comparing Examples 1 to 6 and Comparative Examples 1 to 3, it can be concluded that by increasing the content of the active metal compound within the range of the fraction of the active metal compound protected by the claims, the flexible polyester after the composite current collector is prepared The tensile strength of the film increases and the elongation at break decreases. The tensile strength and elongation at break of the prepared composite current collector show the same trend. When it exceeds the scope of the claims, the tensile strength of the flexible polyester film after preparing the composite current collector and the prepared composite current collector decreases.

(2) Comparing Examples 4, 7 to 9, and Comparative Examples 4 to 5, it can be concluded that by increasing the content of diethylene glycol within the range of the percentage of the claimed polyol, the flexibility of the composite current collector can be improved The tensile strength of the polyester film first increased and then decreased, and the elongation at break decreased first and then increased. The tensile strength and elongation at break of the prepared composite current collector showed the same trend. When exceeding the scope of the claims, the tensile strength of the flexible polyester film after preparing the composite current collector and the prepared composite current collector are reduced.

(3) Comparing Examples 8, 10 to 12, and Comparative Examples 6 to 7, it can be concluded that within the weight average molecular weight range of the claimed polyester, the weight average molecular weight of PET is increased, and the flexibility after preparing the composite current collector is The tensile strength and elongation at break of the polyester film increased, and the tensile strength and elongation at break of the prepared composite current collector showed the same trend. When it exceeds the scope of the claims, the tensile strength of the flexible polyester film after preparing the composite current collector and the prepared composite current collector are reduced.

(4) Comparing Examples 11, 13 to 14, and Comparative Examples 8 to 9, it can be concluded that within the molecular weight distribution range protected by the claims, the molecular weight distribution of PET is increased and the stretchability of the flexible polyester film after preparing the composite current collector is The tensile strength first increased and then decreased, and the elongation at break increased. The tensile strength and elongation at break of the prepared composite current collector showed the same trend. Beyond the scope of the claims, the tensile strength of the flexible polyester film after preparing the composite current collector and the prepared composite current collector are reduced.

(5) Comparing Examples 11, 15-17, and Comparative Examples 10-11, it can be concluded that within the crystallinity range of the flexible polyester film protected by the claims, the crystallinity of the flexible polyester film can be reduced to prepare a composite current collector. The tensile strength of the flexible polyester film first increased and then decreased, and the elongation at break decreased first and then increased. The tensile strength and elongation at break of the prepared composite current collector showed the same trend. Beyond the scope of the claims, the tensile strength of the flexible polyester film after preparing the composite current collector and the prepared composite current collector are reduced.

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 invention patent. 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 the patent of this application shall be determined by the appended claims, and the description and drawings may be used to interpret the contents of the claims.

Claims

A flexible polyester film is characterized in that it includes the following components in parts by mass: 96.90 to 99.49 parts of polyester, 0.5 to 3 parts of polyol, and 0.01 to 0.1 parts of active metal compounds.
The flexible polyester film according to claim 1, wherein the polyol includes diethylene glycol, polyethylene glycol, two polyglycerol, three polyglycerol, four polyglycerol, five polyglycerol, and six polyglycerol. One or more of heptapolyglycerol, octapolyglycerol, nonapolyglycerol, and decapolyglycerol.
The flexible polyester film according to any one of claims 1 to 2, wherein the active metal compound includes one or more of titanium-based compounds, antimony-based compounds, and germanium-based compounds.
The flexible polyester film according to claim 3, wherein the titanium compound includes one or more of titanium dioxide, potassium fluotitanate, tetrabutyl titanate, and titanium complex;

The antimony-based compound includes one or more of antimony trioxide, antimony acetate, and antimony ethanol;

The germanium-based compound includes one or more of germanium dioxide, germanium monoxide, sodium germanate, and potassium germanate.
The flexible polyester film according to any one of claims 1 to 4, characterized in that the polyester includes polyethylene terephthalate and its derivatives, polytrimethylene terephthalate and its derivatives , polybutylene terephthalate and its derivatives, polyethylene naphthalate and its derivatives, polytrimethylene naphthalate and its derivatives, polybutylene naphthalate and its derivatives , polybutylene 2,5-furandicarboxylate and its derivatives, polybutylene adipate terephthalate and its derivatives, poly1,4-cyclohexane dimethanol terephthalate and one or more of its derivatives, polyethylene terephthalate-1,4-cyclohexanedimethanol ester and its derivatives.
The flexible polyester film according to any one of claims 1 to 5, characterized in that the weight average molecular weight of the polyester is 25,000 to 40,000 Da.
The flexible polyester film according to any one of claims 1 to 6, characterized in that the molecular weight distribution of the polyester is 1.5-2.5.
The flexible polyester film according to any one of claims 1 to 7, characterized in that the crystallinity of the flexible polyester film is 5% to 20%.
A method for preparing a flexible polyester film, which is characterized by including:

Mix and melt 96.90 to 99.49 parts by mass of polyester, 0.5 to 3 parts of polyol and 0.01 to 0.1 part of active metal compound to obtain molten material;

The molten material is stretched.
The method for preparing a flexible polyester film according to claim 9, wherein the stretching is biaxial stretching.
The method for preparing a flexible polyester film according to claim 10, wherein the biaxial stretching includes at least one of longitudinal and transverse asynchronous stretching and longitudinal and transverse synchronous stretching.
A composite current collector, characterized by comprising: the flexible polyester film according to any one of claims 1 to 8 and a conductive layer located on at least one surface of the flexible polyester film.
A battery, characterized by comprising the composite current collector according to claim 12.
An electronic product, characterized by comprising the battery according to claim 13.