Flexible polyester film and its manufacturing method, composite current collector, battery and electronic product

Abstract

The present application relates to a flexible polyester film and its manufacturing method, a composite current collector, a battery, and an electronic product. [Means] The flexible polyester film contains, by mass, 96.90 to 99.49 parts of polyester, 0.5 to 3 parts of polyol, and 0.01 to 0.1 part of an active metal compound.

Description

[Technical Field]

[0001] The present application relates to the technical field of polymeric materials, in particular to flexible polyester films and their manufacturing methods, composite current collectors, batteries and electronic products. [Background technology]

[0002] Currently, composite current collectors made of polymer films are widely used in the new energy industry, boasting features such as low cost, light weight, and excellent internal insulation. These features enable their application in batteries to reduce battery costs while improving the energy density and safety of the battery. The manufacturing process for composite current collectors made of polymer films typically involves forming a metal layer on the polymer film. However, in the conventional process of manufacturing composite current collectors using polyester film as a base film, the relatively poor mechanical properties of the base film make the film prone to fracture during the formation of the metal layer, resulting in a low yield rate of composite current collectors and poor mechanical performance of the manufactured composite current collectors. Summary of the Invention [Problem to be solved by the invention]

[0003] In light of this, it is necessary to provide a flexible polyester film that can improve the mechanical performance of polyester films, reduce the film breakage rate during the production of current collectors, and improve the mechanical performance of composite current collectors, as well as a manufacturing method thereof, a composite current collector, a battery, and an electronic product. [Means for solving the problem]

[0004] In a first aspect, the present application provides a flexible polyester film comprising, by weight, 96.90 to 99.49 parts of a polyester, 0.5 to 3 parts of a polyol, and 0.01 to 0.1 parts of an active metal compound.

[0005] In some examples, the polyol comprises one or more of diethylene glycol, polyethylene glycol, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, heptaglycerin, octaglycerin, nonaglycerin, and decaglycerin.

[0006] In some embodiments, the active metal compounds include one or more of titanium-based compounds, antimony-based compounds, and germanium-based compounds.

[0007] In some embodiments, the titanium-based compound includes one or more of titanium dioxide, potassium fluorotitanate, tetrabutyl titanate, and titanium complexes; the antimony-based compound includes one or more of diantimony trioxide, antimony acetate, and antimony ethoxide; and the germanium-based compound includes one or more of germanium dioxide, germanium monoxide, sodium germanate, and potassium germanate.

[0008] In some embodiments, the polyester comprises one or more of 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-furanoate and its derivatives, polybutylene adipate terephthalate and its derivatives, polycyclohexane 1,4-dimethylene terephthalate and its derivatives, polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate and its derivatives.

[0009] In one embodiment, the weight average molecular weight of the polyester is 25,000 to 40,000 Da.

[0010] In one embodiment, the molecular weight distribution of the polyester is 1.5 to 2.5.

[0011] In one embodiment, the flexible polyester film has a crystallinity of 5% to 20%.

[0012] In a second aspect, the present application further provides a method for producing a flexible polyester film, comprising: mixing and melting, by mass, 96.90 to 99.49 parts of a polyester, 0.5 to 3 parts of a polyol, and 0.01 to 0.1 parts of an active metal compound to obtain a molten material; and stretching the molten material.

[0013] In one embodiment thereof, the stretching is biaxial stretching.

[0014] In one embodiment, the biaxial stretching includes at least one of asynchronous stretching in the machine direction and the transverse direction and synchronous stretching in the machine direction and the transverse direction.

[0015] In a third aspect, the present application further provides a composite current collector comprising any of the flexible polyester films described above and a conductive layer located on at least one surface of the flexible polyester film.

[0016] In a fourth aspect, the present application further provides a battery comprising any of the composite current collectors described above.

[0017] In a fifth aspect, the present application further provides an electronic product comprising the battery described above.

[0018] The components of the flexible polyester film include polyester, polyol, and active metal compound. According to the present application, during the production of flexible polyester film from raw materials including polyester, polyol, and active metal compound, the polyol plays a role of cross-linking, reacting with the carboxyl or hydroxyl groups at the polyester terminals to promote further polymerization of the polyester polymer, thereby improving the mechanical properties of the substrate, and 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. Furthermore, the present application provides a flexible polyester film with good mechanical properties. [Effects of the Invention]

[0019] The composite current collector has good mechanical properties, which can reduce the film breakage rate during the manufacturing process of the composite current collector and increase the yield. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a flowchart of a method for manufacturing a flexible polyester film according to an embodiment of the present application. [Figure 2] 1 is a structural schematic diagram of a composite current collector according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to more clearly describe the technical solutions of the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. The drawings in the following description are only some embodiments of the present invention, and it is obvious that those skilled in the art can further derive other drawings from these drawings without creative work.

[0022] In order to make the above-mentioned objects, features, and advantages of the present application more clear and understandable, specific embodiments of the present application will be described in detail below with reference to the drawings. In the following description, many specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other forms different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present application, and the present application is not limited by the specific examples disclosed below.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Terms used herein are for the purpose of describing specific examples only and are not intended to limit the scope of this application. As used herein, the term "and / or" includes any and all combinations of one or more associated items.

[0024] Additionally, the terms "first" and "second" are merely for descriptive purposes and are not to be understood as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature qualified as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of this application, unless otherwise clearly and specifically limited, "plurality" means at least two, e.g., two, three, etc.

[0025] In one embodiment of the present application, there is provided a flexible polyester film comprising, by weight, 96.90 to 99.49 parts of a polyester, 0.5 to 3 parts of a polyol, and 0.01 to 0.1 parts of an active metal compound.

[0026] During the chemical reaction of polyester synthesis, the mixed components undergo in situ solid-state polycondensation, improving the mechanical properties of the polyester film. The polyol is used in an amount of 0.5 to 3 parts by weight. The polyol acts as a crosslinker during the in situ solid-state polycondensation reaction, reacting with the carboxyl or hydroxyl groups at the polyester end points to promote further polymerization of the polyester molecules and thereby improving the mechanical properties of the substrate. If the polyol content is too low, it is less effective at promoting polymerization of the polyester molecules. If the polyol content is too high, the proportion of polyol at one end increases, making it difficult to further increase the degree of polymerization of the polyester molecules. If the polyol content is too high, the film-forming properties and stability of the polyester film are reduced. The active metal compound catalyzes the polycondensation reactions between polyester molecules and between polyester and polyol, thereby improving the mechanical properties of the polyester film. The active metal compound catalyzes the polycondensation reactions between polyester molecules and between polyester and polyol, thereby improving the mechanical properties of the polyester film. The active metal compound is present in an amount of 0.01 to 0.1 parts by weight. If the amount is too low, the effect of catalyzing the polycondensation reaction between polyester molecules and between the polyester and polyol is poor. If the amount is too high, the degree of solid-state polycondensation reaction is too high, resulting in poor flexibility of the polyester film and a reduced elongation at break, which in turn increases the film breakage rate during the production of the composite current collector. Within the range of the amount of each component by weight in the present application, a flexible polyester film with good mechanical properties can be obtained.

[0027] In some embodiments, the flexible polyester film comprises, by weight, 96.90% to 99.49% polyester, 0.5% to 3% polyol, and 0.01% to 0.1% active metal compound.

[0028] In one embodiment, the raw materials for the flexible polyester film consist of, by mass, 96.90% to 99.49% polyester, 0.5% to 3% polyol, and 0.01% to 0.1% active metal compound.

[0029] In some examples, the polyol comprises one or more of diethylene glycol, polyethylene glycol, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, heptaglycerin, octaglycerin, nonaglycerin, and decaglycerin.

[0030] In some embodiments, the active metal compounds include one or more of titanium-based compounds, antimony-based compounds, and germanium-based compounds.

[0031] In some embodiments, the titanium-based compound includes one or more of titanium dioxide, potassium fluorotitanate, tetrabutyl titanate, and titanium complexes; the antimony-based compound includes one or more of diantimony trioxide, antimony acetate, and antimony ethoxide; and the germanium-based compound includes one or more of germanium dioxide, germanium monoxide, sodium germanate, and potassium germanate. In the high-temperature and vacuum environment during the manufacturing process of the composite current collector, the active metal compound catalyzes polycondensation reactions between polyester polymers and between polyester and diethylene glycol, improving the mechanical performance of the polyester film in situ.

[0032] In some examples, polyesters include one or more of 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-furanoate and its derivatives, polybutylene adipate terephthalate and its derivatives, polycyclohexane 1,4-dimethylene terephthalate and its derivatives, polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate and its derivatives.

[0033] In one embodiment, the weight-average molecular weight of the polyester is 25,000 to 40,000 Da. If the weight-average molecular weight is too low, the mechanical properties of the polyester film will be poor, and if the weight-average molecular weight is too high, the film-formability will be poor. Within this weight-average molecular weight range, the polyester film can have both good mechanical properties and good film-formability. Preferably, the weight-average molecular weight of the polyester is 29,000 to 36,000 Da. More preferably, the weight-average molecular weight of the polyester is 29,000 Da, 30,000 Da, 31,000 Da, 32,000 Da, 33,000 Da, 34,000 Da, 35,000 Da, or 36,000 Da.

[0034] In one embodiment, the molecular weight distribution of the polyester is 1.5 to 2.5. If the molecular weight distribution is too low, film-forming properties will be poor, and if the molecular weight distribution is too high, the mechanical properties of the polyester film will be poor. Within this molecular weight distribution range, the polyester film can have good mechanical properties as well as good film-forming properties. Preferably, the molecular weight distribution of the polyester is 1.7 to 2.3. More preferably, the molecular weight distribution of the polyester is 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, or 2.3.

[0035] In one embodiment, the flexible polyester film has a crystallinity of 5% to 20%. Because solid-state polycondensation reactions occur in the amorphous regions of the polymer, if the crystallinity is too high, the proportion of amorphous regions is reduced, hindering the progress of the solid-state polycondensation reaction, thereby limiting the improvement in the mechanical performance of the polyester film and composite current collector. If the crystallinity is too low, the proportion of amorphous regions is too high, making the polymer more susceptible to deorientation during current collector production, resulting in reduced mechanical performance. Within this crystallinity range, the flexible polyester film produced has good mechanical performance. Preferably, the crystallinity of the flexible polyester film is 5%, 8%, 10%, 12%, 15%, 18%, or 20%.

[0036] An embodiment of the present application further provides a method for producing a flexible polyester film, and referring to FIG. 1, the method includes: S10, which is a mixture of 96.90 to 99.49 parts by mass of polyester, 0.5 to 3 parts by mass of polyol, and 0.01 to 0.1 parts by mass of an active metal compound, and melts the mixture to obtain a molten material; and S20, drawing the molten material.

[0037] In some embodiments, a method for producing a flexible polyester film includes: (1) mixing and melting 96.90% to 99.49% by mass of polyester, 0.5% to 3% by mass of polyol, and 0.01% to 0.1% by mass of active metal compound to obtain a molten material; (2) drawing the molten material.

[0038] In some embodiments, the stretching is biaxial stretching.

[0039] In some embodiments, the biaxial stretching comprises at least one of asynchronous stretching in the machine and transverse directions and synchronous stretching in the machine and transverse directions.

[0040] In one embodiment, the biaxial stretching includes at least one of asynchronous stretching in the machine direction, transverse direction, and machine direction, and synchronous stretching in the machine direction and transverse direction followed by secondary stretching in the machine direction.

[0041] One embodiment of the present application further provides a composite current collector comprising any of the flexible polyester films described above and a conductive layer disposed on at least one surface of the flexible polyester film.

[0042] A composite current collector manufactured using a flexible polyester film as a base film layer has good mechanical properties, which can reduce the film breakage rate during the manufacturing of the composite current collector and increase the yield.

[0043] In some embodiments, the composite current collector further comprises a protective layer located on a surface of the conductive layer remote from the flexible polyester film.

[0044] In one embodiment, the conductive layer has a thickness of 500 to 2000 nm. Preferably, the conductive layer has a thickness of 700 to 1200 nm. More preferably, the conductive layer has a thickness of 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, or 1200 nm.

[0045] In one embodiment, the thickness of the protective layer is 10 to 150 nm. Preferably, the thickness of the protective layer is 10 nm, 30 nm, 50 nm, 70 nm, 100 nm, 120 nm, or 150 nm.

[0046] In one embodiment, the thickness of the protective layer is 10% or less of the thickness of the conductive layer, and preferably 1%, 3%, 5%, 7% or 10% of the thickness of the conductive layer.

[0047] In one embodiment, referring to FIG. 2 , a composite current collector includes a flexible polyester film 3, a first conductive layer 2 and a second conductive layer 4 located on two opposing surfaces of the flexible polyester film, respectively, a first protective layer 1 located on the surface of the first conductive layer remote from the flexible polyester film, and a second protective layer 5 located on the surface of the second conductive layer remote from the flexible polyester film.

[0048] In one embodiment, the flexible polyester film has a thickness of 1 micron or more. Preferably, the thickness of the flexible polyester film is 2 to 20 microns. The thinner the polyester film, the greater its ability to promote an improvement in the energy density of the composite current collector. At the same time, the thinner the polyester film, the greater the difficulty of production and the lower the yield rate. Within this thickness range of the polyester film, it is possible to obtain a polyester film that has a high ability to promote an improvement in the energy density of the composite current collector while achieving both the ease of production and the yield rate. More preferably, the thickness of the flexible polyester film is 2 microns, 5 microns, 8 microns, 10 microns, 15 microns, or 20 microns.

[0049] In one embodiment thereof, the material of the conductive layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0050] In one embodiment, the conductive layer is fabricated by one or more of physical vapor deposition, electroplating, and electroless plating, preferably physical vapor deposition including resistive evaporation, electron beam evaporation, laser evaporation, and magnetron sputtering.

[0051] In one embodiment, the material of the protective layer includes one or more of nickel, chromium, nickel-based alloys, copper-based alloys, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, ketjen black, carbon nano quantum dots, carbon nanotubes, carbon nanofibers, and graphene.

[0052] In one embodiment, the protective layer is formed by one or more of physical vapor deposition, chemical vapor deposition, in-situ casting, and coating. Preferably, the physical vapor deposition is selected from vacuum evaporation or magnetron sputtering, the chemical vapor deposition is selected from atmospheric pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, the in-situ casting is selected from a method of in-situ forming a metal oxide dulling layer on the surface of the conductive layer, and the coating method is selected from die coating, knife coating, and squeeze coating.

[0053] One embodiment of the present application provides a battery comprising any of the composite current collectors described above.

[0054] An embodiment of the present application further provides an electronic product including the battery described above. [Example]

[0055] The following is a specific example.

[0056] Example 1 A flexible polyester film was produced using polyethylene terephthalate (PET) with a weight-average molecular weight of 30,000 and a molecular weight distribution of 2.0, diethylene glycol, and potassium fluorotitanate as raw materials. The mass percentages of the three raw materials were 99.49%, 0.5%, and 0.01%, respectively. The polyester film was produced using the melt-biaxial stretching method, which included the steps of crystal drying, melt extrusion, casting, longitudinal stretching, transverse stretching, and heat setting. A flexible polyester film with a thickness of 6 microns and a crystallinity of 20% was produced.

[0057] The resulting flexible polyester film was used as a base film layer to manufacture a composite current collector, which included the following steps.

[0058] (1) Preparation of conductive layer: The flexible polyester film prepared above was placed in a vacuum deposition chamber, and aluminum wire with a purity of over 99.99% in the metal evaporation chamber was melted and evaporated at a high temperature of 1500°C. The evaporated metal atoms passed through the cooling system in the vacuum deposition chamber and were deposited on the top and bottom surfaces of the flexible polyester film, forming an aluminum metal conductive layer with a thickness of 1 micron.

[0059] (2) Preparation of the protective layer: 1 g of carbon nanotubes was uniformly dispersed in 999 g of N-methylpyrrolidone (NMP) solution using ultrasonic dispersion to prepare a coating solution with a solid content of 0.1 wt.%, which was then uniformly coated onto the surface of the metal conductive layer using a die coating process, with the coating amount limited to 90 microns, and finally dried at 100°C.

[0060] Example 2 Example 2 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.47%, 0.5%, and 0.03%, respectively.

[0061] Example 3 Example 3 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.45%, 0.5%, and 0.05%, respectively.

[0062] Example 4 Example 4 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.43%, 0.5%, and 0.07%, respectively.

[0063] Example 5 Example 5 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.41%, 0.5%, and 0.09%, respectively.

[0064] Example 6 Example 6 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.4%, 0.5%, and 0.1%, respectively.

[0065] Example 7 Example 7 is basically the same as Example 4, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 98.93%, 1.0%, and 0.07%, respectively.

[0066] Example 8 Example 8 is basically the same as Example 4, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 97.93%, 2.0%, and 0.07%, respectively.

[0067] Example 9 Example 9 is basically the same as Example 4, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 96.93%, 3.0%, and 0.07%, respectively.

[0068] Example 10 Example 10 is basically the same as Example 8, except that the weight average molecular weight of the PET in the flexible polyester film is 25,000 and the molecular weight distribution is 2.0.

[0069] Example 11 Example 11 is basically the same as Example 8, except that the weight average molecular weight of the PET in the flexible polyester film is 35,000 and the molecular weight distribution is 2.0.

[0070] Example 12 Example 12 is basically the same as Example 8, except that the weight average molecular weight of the PET in the flexible polyester film is 40,000 and the molecular weight distribution is 2.0.

[0071] Example 13 This example is basically the same as Example 11, except that the weight average molecular weight of the PET in the flexible polyester film is 35,000 and the molecular weight distribution is 1.5.

[0072] Example 14 Example 14 is basically the same as Example 11, except that the weight average molecular weight of the PET in the flexible polyester film is 35,000 and the molecular weight distribution is 2.5.

[0073] Example 15 Example 15 is essentially the same as Example 11, except that the crystallinity of the flexible polyester film is 15%.

[0074] Example 16 Example 16 is essentially the same as Example 11, except that the crystallinity of the flexible polyester film is 10%.

[0075] Example 17 Example 17 is essentially the same as Example 11, except that the crystallinity of the flexible polyester film is 5%.

[0076] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 100%, 0%, and 0%, respectively.

[0077] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.495%, 0.5%, and 0.005%, respectively.

[0078] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.35%, 0.5%, and 0.15%, respectively.

[0079] Comparative Example 4 Comparative Example 4 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 99.69%, 0.3%, and 0.01%, respectively.

[0080] Comparative Example 5 Comparative Example 5 is basically the same as Example 1, except that the mass percentages of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film are 96.79%, 3.2%, and 0.01%, respectively.

[0081] Comparative Example 6 Comparative Example 6 is basically the same as Example 1, except that the weight average molecular weight of the PET in the flexible polyester film is 23,000 and the molecular weight distribution is 2.0.

[0082] Comparative Example 7 Comparative Example 7 is basically the same as Example 1, except that the weight average molecular weight of the PET in the flexible polyester film is 42,000 and the molecular weight distribution is 2.0.

[0083] Comparative Example 8 Comparative Example 8 is basically the same as Example 1, except that the weight average molecular weight of the PET in the flexible polyester film is 30,000 and the molecular weight distribution is 1.3.

[0084] Comparative Example 9 Comparative Example 9 is basically the same as Example 1, except that the weight average molecular weight of the PET in the flexible polyester film is 30,000 and the molecular weight distribution is 2.7.

[0085] Comparative Example 10 Comparative Example 10 is basically the same as Example 1, except that the crystallinity of the flexible polyester film is 22%.

[0086] Comparative Example 11 Comparative Example 11 is basically the same as Example 1, except that the crystallinity of the flexible polyester film is 3%.

[0087] In Examples 1 to 17 and Comparative Examples 1 to 11, the list of process parameters such as the mass % contents of PET, diethylene glycol, and potassium fluorotitanate in the flexible polyester film, the weight average molecular weight of PET in the flexible polyester film, the molecular weight distribution, and the crystallinity of the flexible polyester film are as shown in Table 1.

[0088] [Table 1]

[0089] The composite current collectors manufactured in Examples 1 to 17 and Comparative Examples 1 to 11 were subjected to mechanical performance measurements, including tensile strength, elongation at break, and film breakage rate during manufacturing. The tensile strength and elongation at break of the composite current collectors were measured in accordance with Chinese national standard GB / T1040.3-2006, where MD refers to the machine direction and TD refers to the transverse direction. The measurement results are shown in Table 2.

[0090] [Table 2]

[0091] The mechanical properties of the flexible polyester films produced in Examples 1 to 17 and Comparative Examples 1 to 11 were measured before and after the composite current collector was fabricated, including tensile strength, elongation at break, and film breakage during fabrication. The flexible polyester film after composite current collector fabrication was obtained by the following steps: The composite current collector was immersed in a 1% NaOH solution for 20 minutes, then washed with pure water and dried at 60°C. The tensile strength and elongation at break of the flexible polyester film were measured in accordance with Chinese national standard GB / T1040.3-2006, where MD refers to the machine direction and TD refers to the transverse direction. The measurement results are shown in Table 3.

[0092] [Table 3]

[0093] The measurement results in Tables 2 and 3 above reveal the following:

[0094] (1) Comparing Examples 1 to 6 and Comparative Examples 1 to 3, the following was found. When the content of the active metal compound was increased within the range of the number of parts of the active metal compound claimed in the claims, the tensile strength of the flexible polyester film after the production of the composite current collector increased and the breaking elongation decreased, and the tensile strength and breaking elongation of the produced composite current collector showed the same trend. When the content of the active metal compound was exceeded, the tensile strength of the flexible polyester film after the production of the composite current collector and the produced composite current collector decreased.

[0095] (2) Comparing Examples 4, 7-9 and Comparative Examples 4-5, the following was found. When the diethylene glycol content was increased within the claimed range of polyol parts percentage, the tensile strength of the flexible polyester film after the composite current collector was manufactured first increased and then decreased, and the breaking elongation first decreased and then increased, and the tensile strength and breaking elongation of the manufactured composite current collector showed the same trend. When the claimed range was exceeded, the tensile strength of both the flexible polyester film after the composite current collector was manufactured and the manufactured composite current collector decreased.

[0096] (3) Comparing Examples 8, 10-12 and Comparative Examples 6-7, the following was found. When the weight-average molecular weight of PET was increased within the claimed polyester weight-average molecular weight range, the tensile strength of the flexible polyester film after the composite current collector was manufactured increased and the elongation at break decreased, and the tensile strength and elongation at break of the manufactured composite current collector showed the same trend. When the claimed range was exceeded, the tensile strength of both the flexible polyester film after the composite current collector was manufactured and the manufactured composite current collector decreased.

[0097] (4) Comparing Examples 11, 13-14 and Comparative Examples 8-9, the following was found. When the molecular weight distribution of PET was increased within the claimed molecular weight distribution range, the tensile strength of the flexible polyester film after the composite current collector was manufactured first increased and then decreased, and the breaking elongation increased, and the tensile strength and breaking elongation of the manufactured composite current collector showed the same trend. When the claimed range was exceeded, the tensile strength of both the flexible polyester film after the composite current collector was manufactured and the manufactured composite current collector decreased.

[0098] (5) Comparing Examples 11, 15-17 and Comparative Examples 10-11, the following was found. When the crystallinity of the flexible polyester film was reduced within the claimed range, the tensile strength of the flexible polyester film after the composite current collector was manufactured first increased and then decreased, and the breaking elongation first decreased and then increased, and the tensile strength and breaking elongation of the manufactured composite current collector showed the same trend. When the crystallinity was exceeded, the tensile strength of both the flexible polyester film after the composite current collector was manufactured and the manufactured composite current collector decreased.

[0099] The technical features of the above-described embodiments can be combined in any manner, and for the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described, but any combination of these technical features should be considered within the scope of the present specification, provided that there is no contradiction.

[0100] The above examples are merely illustrative of some embodiments of the present application, and although the descriptions are specific and detailed, the scope of the claims should not be understood to be limited thereby. Those skilled in the art may further make some modifications and improvements without departing from the concept of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application should be governed by the appended claims, and the specification and drawings can be used to interpret the content of the claims. [Explanation of symbols]

[0101] 1 first protective layer, 2 first conductive layer, 3 composite polyester film, 4 second conductive layer, 5 second protective layer.

Claims

1. The composition comprises, in parts by weight, 96.90 to 99.49 parts of a polyester, 0.5 to 3 parts of a polyol, and 0.01 to 0.1 parts of an active metal compound. A flexible polyester film characterized by:

2. The polyol may comprise one or more of diethylene glycol, polyethylene glycol, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, heptaglycerin, octaglycerin, nonaglycerin, and decaglycerin.

2. The flexible polyester film according to claim 1.

3. The active metal compound includes one or more of a titanium-based compound, an antimony-based compound, and a germanium-based compound.

3. The flexible polyester film according to claim 1, wherein the flexible polyester film is a polyester film having a thickness of 100 nm or less.

4. The titanium-based compound includes one or more of titanium dioxide, potassium fluorotitanate, tetrabutyl titanate, and titanium complexes; The antimony-based compound includes one or more of diantimony trioxide, antimony acetate, and antimony ethoxide; The germanium-based compound includes one or more of germanium dioxide, germanium monoxide, sodium germanate, and potassium germanate.

4. The flexible polyester film according to claim 3.

5. The polyester includes one or more of polyethylene terephthalate and derivatives thereof, polytrimethylene terephthalate and derivatives thereof, polybutylene terephthalate and derivatives thereof, polyethylene naphthalate and derivatives thereof, polytrimethylene naphthalate and derivatives thereof, polybutylene naphthalate and derivatives thereof, polybutylene-2,5-furanoate and derivatives thereof, polybutylene adipate terephthalate and derivatives thereof, polycyclohexane 1,4-dimethylene terephthalate and derivatives thereof, polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate and derivatives thereof; 5. The flexible polyester film according to claim 1.

6. The weight average molecular weight of the polyester is 25,000 to 40,000 Da.

6. The flexible polyester film according to claim 1.

7. The molecular weight distribution of the polyester is 1.5 to 2.

5.

7. The flexible polyester film according to claim 1.

8. The crystallinity of the flexible polyester film is 5% to 20%. The flexible polyester film according to any one of claims 1 to 7.

9. Mixing and melting 96.90 to 99.49 parts by mass of polyester, 0.5 to 3 parts by mass of polyol, and 0.01 to 0.1 parts by mass of active metal compound to obtain a molten material; and drawing the molten material. A method for producing a flexible polyester film.

10. The stretching is biaxial stretching. The method for producing a flexible polyester film according to claim 9 .

11. The biaxial stretching includes at least one of asynchronous stretching in the machine direction and the transverse direction and synchronous stretching in the machine direction and the transverse direction. The method for producing a flexible polyester film according to claim 10 .

12. A flexible polyester film according to any one of claims 1 to 8, comprising: a conductive layer located on at least one surface of the flexible polyester film. A composite current collector characterized by:

13. A composite current collector according to claim 12, A battery characterized by:

14. 14. A battery comprising the battery of claim 13. An electronic product characterized by:

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