Composite polyester film and its manufacturing method and use

Abstract

The present application relates to a composite polyester film. [Means] The composite polyester film comprises a first polyester layer, a second polyester layer, and a third polyester layer, the first polyester layer and the third polyester layer being located on opposite surfaces of the second polyester layer, respectively, and the raw materials for the first polyester layer, the second polyester layer, and the third polyester layer each independently contain, by mass%, 97.0% to 99.9% polyester material and 0.1% to 3.0% additive, the polyester material in the first polyester layer and the third polyester layer each having a terminal carboxyl group content of 40 to 100 mol / t, and the polyester material in the second polyester layer having a terminal carboxyl group content of 5 to 30 mol / t.

Description

[Technical Field]

[0001] This application relates to the field of batteries, and in particular to composite polyester films and their manufacturing methods and uses. [Background technology]

[0002] Metallized polymer films are widely used in fields such as electronics, packaging, and printing due to their excellent conductivity, barrier properties, flexibility, and light weight. Metallized polymer film products include composite current collectors, thin-film electrodes, aluminum-plated packaging films, and printed thin films. Composite current collectors are typically manufactured by physical vapor deposition (PVD) of metal materials onto the surface of a thin polymer film, such as polypropylene, polyethylene, or polyester. Compared to conventional current collectors, composite current collectors offer advantages such as low cost, light weight, and excellent internal insulation. These features enable their application in batteries to reduce battery costs and improve battery energy density and safety. The base film of composite current collectors is typically polyester film. However, due to the low surface tension of polyester film and the high surface tension of the surface metal layer, the adhesion between the two is poor. Even if the polyester film surface is treated with a corona process, the degree of improvement in the surface tension of the polyester film is limited, and the surface tension of corona-treated polyester film is unstable. Summary of the Invention [Problem to be solved by the invention]

[0003] According to various embodiments of the present application, composite polyester films and methods for making and using the same are provided. [Means for solving the problem]

[0004] The present application provides the following technical solutions.

[0005] The present application provides a composite polyester film comprising a first polyester layer, a second polyester layer, and a third polyester layer, the first polyester layer and the third polyester layer are respectively located on opposite surfaces of the second polyester layer; the first polyester layer, the second polyester layer, and the third polyester layer each independently contain, by mass %, 97.0% to 99.9% of a polyester material and 0.1% to 3.0% of an additive; The composite polyester film is provided, wherein the content of terminal carboxyl groups in the polyester material in the first polyester layer and the third polyester layer is both 40 to 100 mol / t, and the content of terminal carboxyl groups in the polyester material in the second polyester layer is 5 to 30 mol / t.

[0006] In some embodiments, the raw materials for manufacturing the first polyester layer, the second polyester layer, and the third polyester layer each independently contain, in mass %, 99.0% to 99.8% polyester material and 0.2% to 1.0% additive.

[0007] In some embodiments, the content of terminal carboxyl groups in the polyester material of the first polyester layer and the third polyester layer is both 50 to 100 mol / t, and the content of terminal carboxyl groups in the polyester material of the second polyester layer is 10 to 25 mol / t.

[0008] In some embodiments, the polyester material comprises one or more of polyethylene-2,6-naphthalenedicarboxylate (PEN), polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate (PETG), polyethylene terephthalate (PET), polycyclohexane 1,4-dimethylene terephthalate (PCT), polypropylene-2,6-naphthalenedicarboxylate (PTN), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene adipate terephthalate (PBAT), polybutylene-2,6-naphthalenedicarboxylate (PBN), polybutylene-2,5-furanoate, polyarylate (PAR), and derivatives thereof.

[0009] In some embodiments, the additives include one or more of a nucleating agent, an antioxidant, a lubricant, and an antistatic agent; Preferably, the nucleating agent comprises one or more of sodium carbonate, triphenyl phosphate, polycaprolactone, benzophenone, aluminum oxide, copper oxide, magnesium oxide, zinc oxide, barium sulfate, magnesium stearate, and sodium benzoate; Preferably, the antioxidant comprises one or more of bisphenol A phosphite and phosphonate esters; Preferably, the lubricant comprises one or more of titanium dioxide, silica, siloxane, calcium carbonate, diatomaceous earth, talc powder, kaolin, and acrylic esters; Preferably, the antistatic agent comprises one or more of polyethylene glycol, glycerin, polyglycerin, polyether ester, carbon black, graphite and conductive fibers.

[0010] The present invention provides a method for producing the above-mentioned composite polyester film, Step S1, in which polyester chips 1, 2, and 3 are produced, respectively, by mass %, of polyester chips 1, 2, and 3, each of which is independently produced from 97.0% to 99.9% polyester material and 0.1% to 3% additive, wherein the content of terminal carboxyl groups of the polyester material in polyester chips 1 and 3 is 40 to 100 mol / t, and the content of terminal carboxyl groups of the polyester material in polyester chip 2 is 5 to 30 mol / t; Step S2 of producing a molten polyester material having a first polyester layer, a second polyester layer and a third polyester layer, wherein the first polyester layer, the second polyester layer and the third polyester layer are produced by the polyester chip 1, the polyester chip 2 and the polyester chip 3 in order, and the first polyester layer and the third polyester layer are respectively located on both sides of the second polyester layer; and step S3 of sequentially subjecting the molten polyester material to a molding process and a heat treatment.

[0011] The present application further provides a metallized polyester film comprising: a substrate layer including the composite polyester film or the composite polyester film produced by the production method; and a metal layer provided on at least one surface of the substrate layer.

[0012] In some embodiments, the metal layer has a thickness of 20 to 2000 nm.

[0013] In some embodiments, the material of the metal layer comprises one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0014] The present application further provides a composite current collector comprising the metallized polyester film.

[0015] In some embodiments, the composite current collector further includes a protective layer disposed on the surface of the metal layer of the metallized polyester film.

[0016] In some embodiments, the protective layer has a thickness of 10 to 150 nm.

[0017] In some embodiments, the material of the protective layer includes one or more of nickel, chromium, a nickel-based alloy, a copper-based alloy, 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.

[0018] Furthermore, the present application further provides an electrode piece including the above composite current collector.

[0019] Furthermore, the present application further provides an electrochemical device including the electrode strip.

[0020] Still further, the present application further provides a power consuming device including the electrochemical device described above.

[0021] The details of one or more embodiments of the application are set forth in the description below. Other features, objects, and advantages of the application will become apparent from the description and claims. DETAILED DESCRIPTION OF THE INVENTION

[0022] The technical solution of the present application will be explained clearly and completely below with reference to specific examples. It is clear that the described examples are only some of the examples of the present application, and do not include all of the examples. All other examples that can be obtained by those skilled in the art based on the examples of the present application without paying creative labor fall within the scope of protection of the present application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used herein are only for describing specific examples and are not intended to limit the scope of the present application. The term "one or more" as used herein includes any and all combinations of one or more associated items.

[0024] In this application, technical features described in an open format include closed technical solutions consisting of the listed features, and also include open technical solutions including the listed features.

[0025] In this application, unless otherwise specified, any numerical range within the range is considered continuous and inclusive of the minimum and maximum values ​​within the range, as well as each value between such minimum and maximum values. Furthermore, when a range refers to integers, it also includes each integer between the minimum and maximum values ​​within the range. Furthermore, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges contained therein.

[0026] According to one embodiment of the present application, there is provided a composite polyester film comprising a first polyester layer, a second polyester layer, and a third polyester layer, a first polyester layer and a third polyester layer are respectively located on opposite surfaces of the second polyester layer; the manufacturing raw materials of the first polyester layer, the second polyester layer, and the third polyester layer each independently contain, by mass%, 97.0% to 99.9% of a polyester material and 0.1% to 3.0% of an additive; The composite polyester film is provided in which the content of terminal carboxyl groups in the polyester material of the first polyester layer and the third polyester layer is both 40 to 100 mol / t, and the content of terminal carboxyl groups in the polyester material of the second polyester layer is 5 to 30 mol / t.

[0027] Conventional polyester films have a surface polarity of 35 mN / m, which is significantly different from the surface polarity of metal materials. To address this issue, the surface of polyester films is typically modified using a corona treatment. However, this method has the following shortcomings: (1) While ensuring that the mechanical properties of the polyester film are not significantly affected, the surface tension of corona-treated polyester films is generally 35-50 mN / m. Compared to untreated polyester films, the improvement in surface tension is limited, and the difference with the surface tension of metal materials (over 100 mN / m) is still significant, resulting in an insufficient bonding effect between the two. (2) The surface tension of corona-treated polyester films is unstable; after standing for a certain period of time, the surface tension decreases and eventually approaches the surface tension of untreated polyester film, resulting in storage instability.

[0028] To address the above technical problems, the present application provides a composite polyester film in which polyester materials with a high content of terminal carboxyl groups are selected for the first and third polyester layers to create a polar surface rich in carboxyl groups, thereby improving the adhesive performance of the composite polyester film, maintaining the adhesive performance of the composite polyester film essentially unchanged after storage for a certain period of time, and improving the bonding strength between the composite polyester film and the metal layer. If the content of terminal carboxyl groups in the polyester materials in the first and third polyester layers is too low, the surface adhesive performance of the composite polyester film will be poor, and if the content of terminal carboxyl groups in the polyester materials in the first and third polyester layers is too high, it will affect the stability of the composite polyester film during film formation and use. The polyester material in the second polyester layer is primarily intended to ensure the main body performance of the composite polyester film and does not require high adhesiveness. Therefore, a polyester material with a relatively low content is selected for the second polyester layer in this application. If the terminal carboxyl group content of the polyester material in the second polyester layer is too high, it will affect the stability during film formation and use. If the content is too low, the polyester material will be easily decomposed during melt extrusion, resulting in poor performance of the resulting composite polyester film.

[0029] In some embodiments, the raw materials for manufacturing the first polyester layer, the second polyester layer, and the third polyester layer each independently contain, in weight percent, 99.0% to 99.8% polyester material and 0.2% to 1.0% additive.

[0030] If the content of the additive in the first polyester layer, the second polyester layer, and the third polyester layer is too low, the effect of the additive will not be apparent, whereas if the content of the additive in the first polyester layer, the second polyester layer, and the third polyester layer is too high, the film-forming properties will be affected during film formation, making defects more likely to form.

[0031] In some embodiments, the additive is particulate and has an average particle size of 0.01 to 1.5 μm.

[0032] In some embodiments, the additive is a particulate material, the average particle size of the additive is 0.02 to 0.5 μm, and the average particle size (d) of the particulate material and the corresponding thickness (t) of the first polyester layer, second polyester layer, and third polyester layer satisfy t≧0.3d.

[0033] If the average particle size of the particles is too small, the effect will not be apparent. If the average particle size of the particles is too large, defects are likely to form during film formation. The reason for making the film layer thickness at least 30% of the average particle size is to prevent defects in the film layer due to the film layer thickness not matching the particle size.

[0034] In some embodiments, the terminal carboxyl group content of the polyester material in the first polyester layer and the third polyester layer is both 50 to 100 mol / t, and the terminal carboxyl group content of the polyester material in the second polyester layer is 10 to 25 mol / t.

[0035] It should be understood that the content of terminal carboxyl groups in the polyester material in the first polyester layer and the third polyester layer may be any value between 50 and 100 mol / t, such as 50 mol / t, 55 mol / t, 60 mol / t, 65 mol / t, 70 mol / t, 75 mol / t, 80 mol / t, 85 mol / t, 90 mol / t, 95 mol / t, or 100 mol / t, and the content of terminal carboxyl groups in the polyester material in the second polyester layer may be any value between 10 and 25 mol / t, such as 10 mol / t, 12 mol / t, 14 mol / t, 16 mol / t, 18 mol / t, 20 mol / t, 22 mol / t, 24 mol / t, or 25 mol / t.

[0036] In some embodiments, the polyester material comprises one or more of polyethylene-2,6-naphthalenedicarboxylate (PEN), polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate (PETG), polyethylene terephthalate (PET), polycyclohexane 1,4-dimethylene terephthalate (PCT), polypropylene-2,6-naphthalenedicarboxylate (PTN), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene adipate terephthalate (PBAT), polybutylene-2,6-naphthalenedicarboxylate (PBN), polybutylene-2,5-furanoate, polyarylate (PAR), and derivatives thereof.

[0037] It should be understood that polyester materials include, but are not limited to, any one of polyethylene-2,6-naphthalenedicarboxylate (PEN), polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate (PETG), polyethylene terephthalate (PET), polycyclohexane 1,4-dimethylene terephthalate (PCT), polypropylene-2,6-naphthalenedicarboxylate (PTN), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene adipate terephthalate (PBAT), polybutylene-2,6-naphthalenedicarboxylate (PBN), polybutylene-2,5-furanoate, polyarylate (PAR), and derivatives thereof; The polyester material includes, but is not limited to, polyethylene-2,6-naphthalenedicarboxylate (PEN), polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate (PETG), polyethylene terephthalate (PET), polycyclohexane 1,4-dimethylene terephthalate (PCT), polypropylene-2,6-naphthalenedicarboxylate (PTN), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polybutylene adipate terephthalate (PBAT), polybutylene-2,6-naphthalenedicarboxylate (PBN), polybutylene-2,5-furanoate, polyarylate (PAR), and mixtures of two or more of these derivatives in any ratio.

[0038] In some embodiments, the intrinsic viscosity of the polyester material in the first polyester layer, the second polyester layer, and the third polyester layer is 0.600 to 0.850 dL / g.

[0039] In some embodiments, the intrinsic viscosity of the polyester material in the first polyester layer, the second polyester layer, and the third polyester layer is 0.700 to 0.800 dL / g.

[0040] If the intrinsic viscosity of the polyester materials in the first, second, and third polyester layers is too low, the average molecular weight of the composite polyester film will be low, resulting in poor mechanical properties.If the intrinsic viscosity of the polyester materials in the first, second, and third polyester layers is too high, the average molecular weight of the composite polyester film will be high, resulting in poor film-forming properties and a tendency for the film to break.

[0041] In some embodiments, the additives include one or more of a nucleating agent, an antioxidant, a lubricant, and an antistatic agent; Preferably, the nucleating agent comprises one or more of sodium carbonate, triphenyl phosphate, polycaprolactone, benzophenone, aluminum oxide, copper oxide, magnesium oxide, zinc oxide, barium sulfate, magnesium stearate, and sodium benzoate; Preferably, the antioxidant comprises one or more of bisphenol A phosphite and phosphonate esters; Preferably, the lubricant comprises one or more of titanium dioxide, silica, siloxane, calcium carbonate, diatomaceous earth, talc powder, kaolin, and acrylic esters; Preferably, the antistatic agent comprises one or more of polyethylene glycol, glycerin, polyglycerin, polyetherester, carbon black, graphite and conductive fibers.

[0042] It should be understood that nucleating agents include, but are not limited to, any one of sodium carbonate, triphenyl phosphate, polycaprolactone, benzophenone, aluminum oxide, copper oxide, magnesium oxide, zinc oxide, barium sulfate, magnesium stearate, and sodium benzoate, or nucleating agents include, but are not limited to, a mixture of two or more of sodium carbonate, triphenyl phosphate, polycaprolactone, benzophenone, aluminum oxide, copper oxide, magnesium oxide, zinc oxide, barium sulfate, magnesium stearate, and sodium benzoate in any ratio.

[0043] It should be understood that the antioxidant includes, but is not limited to, any one of bisphenol A phosphite and phosphonate esters, or the antioxidant includes, but is not limited to, a mixture of bisphenol A phosphite and phosphonate esters in any ratio.

[0044] It should be understood that the lubricant includes, but is not limited to, any one of titanium dioxide, silica, siloxane, calcium carbonate, diatomaceous earth, talc powder, kaolin, and acrylic acid esters, or the lubricant includes, but is not limited to, a mixture of two or more of titanium dioxide, silica, siloxane, calcium carbonate, diatomaceous earth, talc powder, kaolin, and acrylic acid esters in any ratio.

[0045] The substances included in the nucleating agents, lubricants, and antistatic agents are classified according to their primary function, and may also have other auxiliary functions. For example, magnesium oxide, zinc oxide, aluminum oxide, and copper oxide according to the present application are primarily used as nucleating agents, but also have an antistatic function. Similarly, calcium carbonate and talc powder according to the present application are primarily used as lubricants, but also have a function similar to that of a nucleating agent. Polyethylene glycol according to the present application primarily has an antistatic function and also has a function similar to that of a nucleating agent.

[0046] The present invention provides a method for producing the above-mentioned composite polyester film, Step S1, in which polyester chips 1, 2, and 3 are produced, respectively, by mass %, polyester chips 1, 2, and 3 are each independently produced from 97.0% to 99.9% polyester material and 0.1% to 3% additive, wherein the content of the terminal carboxyl group of the polyester material in polyester chips 1 and 2 is 40 to 100 mol / t, and the content of the terminal carboxyl group of the polyester material in polyester chip 3 is 5 to 30 mol / t; Step S2 of producing a molten polyester material having a first polyester layer, a second polyester layer and a third polyester layer, the first polyester layer, the second polyester layer and the third polyester layer being produced by polyester chip 1, polyester chip 2 and polyester chip 3 in order, wherein the first polyester layer and the third polyester layer are respectively located on both sides of the second polyester layer; and step S3 of sequentially subjecting the molten polyester material to a molding process and a heat treatment.

[0047] The raw material for producing the first polyester layer is polyester chip 1, the raw material for producing the second polyester layer is polyester chip 2, and the raw material for producing the third polyester layer is polyester chip 3.

[0048] In some embodiments, the molding process of step S3 includes the following steps:

[0049] (1) Slab: In step S2, the molten polyester material is cast onto a slab roll, and after passing through the slab roll and water cooling treatment, a slab is obtained.

[0050] (2) Longitudinal stretching: The above-mentioned cast piece is preheated at 70 to 100°C, and then longitudinally stretched at a ratio of (3 to 5):1 under conditions of 80 to 120°C to obtain a film piece, which is then heat-set at 165 to 180°C and cooled at 30 to 50°C.

[0051] (3) Transverse stretching: The film pieces are preheated at 80 to 120°C, then transversely stretched at a ratio of (3 to 5):1 at 90 to 140°C, heat-set at 150 to 250°C, and cooled at 80 to 150°C.

[0052] In some embodiments, the heat treatment process of step S3 includes Stage I, in which the heat treatment temperature is 130 to 160°C and the heat treatment time is 0.5 to 2 minutes, Stage II, in which the heat treatment temperature is 160 to 220°C and the heat treatment time is 0.5 to 5 minutes, and Stage III, in which the heat treatment temperature is 130 to 160°C and the heat treatment time is 0.5 to 2 minutes.

[0053] It should be understood that the heat treatment temperature in Stage I and Stage III may be any value between 130 and 160° C., such as 130° C., 134° C., 138° C., 140° C., 144° C., 148° C., 150° C., 154° C., 158° C., or 160° C. The heat treatment temperature in Stage II may be any value between 160 and 220° C., such as 160° C., 165° C., 170° C., 175° C., 180° C., 185° C., 190° C., 195° C., 200° C., 205° C., 210° C., 215° C., or 220° C. The heat treatment times in Steps I, II, and III may be any value between 0.5 and 2 minutes, for example, 0.5 minutes, 0.7 minutes, 0.9 minutes, 1.1 minutes, 1.3 minutes, 1.5 minutes, 1.7 minutes, 1.9 minutes, or 2.0 minutes. The heat treatment is intended to reduce the thermal shrinkage rate of the film pieces and improve the stretching strength of the film pieces by removing residual stress and appropriately improving the crystallinity of the film pieces.

[0054] The present application further provides a metallized polyester film comprising a substrate layer including the composite polyester film or the composite polyester film produced by the production method, and a metal layer provided on at least one surface of the substrate layer.

[0055] In some embodiments, the thickness of the metal layer is between 20 and 2000 nm.

[0056] In some embodiments, the material of the metal layer includes one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, and silver.

[0057] It should be understood that the thickness of the metal layer may be any value between 20 and 2000 nm, for example, 20 nm, 50 nm, 150 nm, 250 nm, 350 nm, 450 nm, 550 nm, 650 nm, 750 nm, 850 nm, 950 nm, 1050 nm, 1150 nm, 1250 nm, 1350 nm, 1450 nm, 1550 nm, 1650 nm, 1750 nm, 1850 nm, 1950 nm, 2000 nm.

[0058] In some embodiments, the method for producing the metal layer includes, but is not limited to, one or more of physical vapor deposition, plating, and electroless plating, where physical vapor deposition includes, but is not limited to, one or more of resistance heating vacuum evaporation, electron beam heating vacuum evaporation, laser heating vacuum evaporation, and magnetron sputtering.

[0059] In some embodiments, a metal layer is provided on the surface of each of the first polyester layer and the third polyester layer of the composite polyester film.

[0060] In this case, the materials of the metal layers on the surfaces of the first polyester layer and the third polyester layer are the same.

[0061] The present application further provides a composite current collector comprising the metallized polyester film.

[0062] In some embodiments, the composite current collector further comprises a protective layer disposed on the surface of the metal layer of the metallized polyester film.

[0063] In some embodiments, the thickness of the protective layer is 10 to 150 nm.

[0064] In some embodiments, the material of the protective layer comprises 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.

[0065] It should be understood that the thickness of the protective layer may be any value between 10 and 150 nm, for example, 10 nm, 16 nm, 26 nm, 36 nm, 46 nm, 56 nm, 66 nm, 76 nm, 86 nm, 96 nm, 106 nm, 116 nm, 126 nm, 136 nm, 146 nm, 150 nm.

[0066] When the same composite current collector has two protective layers, the materials of the two protective layers may be the same or different, and the thicknesses of the two protective layers may be equal or unequal. The disposed protective layer is used to prevent the metal layer from being chemically corroded or physically damaged.

[0067] In some embodiments, the method for manufacturing the protective layer includes at least one of a physical vapor deposition method, an in-situ casting method, and a coating method, wherein the physical vapor deposition method includes at least one of a vacuum evaporation method and a magnetron sputtering method, the in-situ casting method may be a method for in-situ forming a metal oxide blunting layer on the surface of the metal layer, and the coating method may be at least one of a die coating method, a knife coating method, and a squeeze coating method.

[0068] Furthermore, the present application further provides an electrode piece including the above composite current collector.

[0069] It should be understood that the electrode pieces according to the present application may be either positive or negative electrode pieces. The method for manufacturing the electrode pieces is well known to those skilled in the art, and is not particularly limited in the present application.

[0070] Furthermore, the present application further provides an electrochemical device including the electrode piece.

[0071] The electrochemical device according to the present application is not particularly limited and may include any device that causes an electrochemical reaction. In some embodiments, the electrochemical device may include, but is not limited to, a lithium ion secondary battery, a lithium metal secondary battery, a lithium ion polymer secondary battery, or a lithium polymer secondary battery.

[0072] Still further, the present application further provides a power consuming device including the electrochemical device described above.

[0073] The power consumption device according to the present application is not particularly limited and may include, but is not limited to, smart home appliances, mobile phones, computers, or electric vehicles.

[0074] The present invention will be described in more detail below with reference to specific examples and comparative examples.

[0075] Measurement method:

[0076] (1) Surface tension measurement: The initial surface tension of the composite polyester film and the surface tension after 3 months were measured according to the Chinese national standard GB / T 14216-2008. The surface tension of the composite polyester film immediately after production was defined as the initial surface tension, and the surface tension of the composite polyester film after 3 months of storage was measured, and the resulting surface tension was defined as the surface tension after 3 months of storage.

[0077] (2) Adhesion strength measurement: A layer of Permacel P-94 double-sided tape was attached to a 1 mm thick aluminum foil, and a composite positive electrode current collector / composite negative electrode current collector was attached to the double-sided tape. A layer of ethylene-acrylic acid copolymer thin film (DuPont Nurcel 0903, 50 μm thick) was then coated on the composite positive electrode current collector / composite negative electrode current collector. After that, a 1.3 × 10 5 N / m 2 The sample was then hot-pressed at 120°C for 10 seconds, cooled to room temperature, and cut into 150mm x 15mm pieces. Finally, the ethylene-acrylic acid copolymer thin film of the sample piece was fixed to the upper jig of a tensile machine, and the remaining part was fixed to the lower jig. After fixing, the two were peeled at an angle of 180° at a rate of 100mm / min, and the peel force, i.e., the adhesive strength between the composite positive electrode current collector / composite negative electrode current collector and the metal layer, was measured.

[0078] (3) Measurement of defective rate: The rate of defective products due to breakage of each layer during film formation was measured relative to the total amount of composite polyester film.

[0079] (4) Elastic modulus measurement: To represent the mechanical properties of the composite polyester film, its representative index elastic modulus was evaluated. The evaluation method was based on the national standard GB / T 1040.3-2006.

[0080] Example 1 Material selection: The polyester material in the first and third polyester layers is polyethylene terephthalate (PET), with an intrinsic viscosity of 0.740 dL / g and a molecular weight distribution of 2.2. The PET terminal carboxyl group content is 40 mol / t, and the additives are antioxidant 300 and aluminum oxide (average particle size 0.3 μm).

[0081] The polyester material of the second polyester layer is polyethylene terephthalate (PET), with an intrinsic viscosity of 0.740 dL / g, a molecular weight distribution of 2.2, a terminal carboxyl group content of 20 mol / t, and additives including antioxidant 300 and aluminum oxide (average particle size 0.3 μm).

[0082] S1: Polyester chip 1, polyester chip 2, and polyester chip 3 were produced, each of which was independently produced by heating, melting, mixing, extruding, and shaping 99.4% PET, 0.3% antioxidant 300, and 0.3% aluminum oxide in mass%, where the content of terminal carboxyl groups of the PET in polyester chip 1 and polyester chip 3 was 40 mol / t, and the content of terminal carboxyl groups of the PET in polyester chip 2 was 20 mol / t.

[0083] S2: Polyester chips 1, polyester chips 2, and polyester chips 3 were each sent to a crystallizer, treated at 150°C for 40 minutes, and then sent to a dryer and dried at 155°C for 150 minutes. The dried polyester chips 1, polyester chips 2, and polyester chips 3 were each placed in different twin-screw extruders, heated and melted at 280°C, and extruded through a die using a metering pump to obtain a molten polyester material having a first polyester layer, a second polyester layer, and a third polyester layer. The first polyester layer, the second polyester layer, and the third polyester layer were produced in sequence by polyester chips 1, polyester chips 2, and polyester chips 3, and the first polyester layer and the third polyester layer were located on both sides of the second polyester layer, respectively.

[0084] S3: Forming and heat treatment

[0085] S3.1: Castings The molten polyester material obtained in step S2 was cast onto a slab roll, and was then shaped through a slab roll and water cooling treatment to obtain a slab having a thickness of 96 μm.

[0086] S3.2: Machine direction stretching The cast piece obtained in step S3.1 was preheated at 90°C and then stretched in the longitudinal direction at a ratio of 4:1 at 110°C to obtain a film piece, which was then heat-set at 170°C and cooled and molded at 40°C.

[0087] S3.3: Lateral stretching The film pieces obtained in step S3.2 were preheated at 90°C and then stretched in the transverse direction at a ratio of 4:1 at 120°C. The film pieces were then heat-set at 170°C and cooled and molded at 110°C.

[0088] S3.4: Heat treatment The film pieces obtained in step S3.3 were heat-treated to produce composite polyester films. The heat-treatment process included the following steps:

[0089] Stage I: The heat treatment temperature is 140°C, and the heat treatment time is 0.5 min.

[0090] Stage II: the heat treatment temperature is 160°C, and the heat treatment time is 0.5 min.

[0091] Stage III: the heat treatment temperature is 140°C, and the heat treatment time is 0.5 min.

[0092] A composite positive electrode current collector is manufactured according to the following method.

[0093] (1) Manufacturing of the metal layer After cleaning the surface of the composite polyester film, it was placed in a vacuum deposition chamber. High-purity aluminum wire (purity exceeding 99.99%) in the metal evaporation chamber was melted and evaporated at high temperatures of 1300-2000°C. The evaporated metal atoms passed through the cooling system in the vacuum deposition chamber and were deposited on the two surfaces of the composite polyester film, forming a 1 μm-thick aluminum metal layer.

[0094] (2) Manufacturing the protective layer Using ultrasonic dispersion, 1 g of carbon nanotubes was uniformly dispersed in 999 g of N-methylpyrrolidone (NMP) solution to prepare a coating solution with a solid content of 0.1 wt %. The coating solution was uniformly applied to the surface of the metal layer using a die coating process, and then dried at 100 °C to obtain a composite positive electrode current collector, where the coating amount was limited to 80 μm.

[0095] A composite negative electrode current collector is manufactured according to the following method.

[0096] (1) Manufacturing of the metal layer After cleaning the surface of the composite polyester film, it was placed in a vacuum deposition chamber. High-purity copper wire (purity exceeding 99.99%) in the metal evaporation chamber was melted and evaporated at high temperatures of 1400-2000°C. The evaporated metal atoms passed through the cooling system in the vacuum deposition chamber and were deposited on the two surfaces of the composite polyester film, forming a copper metal layer 1 μm thick.

[0097] (2) Manufacturing the protective layer Using ultrasonic dispersion, 1 g of carbon nanotubes was uniformly dispersed in 999 g of N-methylpyrrolidone (NMP) solution to prepare a coating solution with a solid content of 0.1 wt %. The coating solution was uniformly applied to the surface of the metal layer using a die coating process, and then dried at 100 °C to obtain a composite negative electrode current collector, where the coating amount was limited to 80 μm.

[0098] Example 2 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 50 mol / t.

[0099] Example 3 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 60 mol / t.

[0100] Example 4 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 70 mol / t.

[0101] Example 5 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 80 mol / t.

[0102] Example 6 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 90 mol / t.

[0103] Example 7 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 100 mol / t.

[0104] Example 8 This was basically the same as Example 7, except that the content of terminal carboxyl groups in the PET in the second polyester layer was 5 mol / t.

[0105] Example 9 The present example is basically the same as Example 7, except that the content of terminal carboxyl groups in the PET in the second polyester layer is 10 mol / t.

[0106] Example 10 This was basically the same as Example 7, except that the content of terminal carboxyl groups in the PET in the second polyester layer was 25 mol / t.

[0107] Example 11 This was basically the same as Example 7, except that the content of terminal carboxyl groups in the PET in the second polyester layer was 30 mol / t.

[0108] Example 12 This example is basically the same as Example 7, except that PBT was used as the polyester material for the first polyester layer, the second polyester layer, and the third polyester layer.

[0109] Example 13 The present embodiment is basically the same as Example 7, except that PEN was used as the polyester material for the first polyester layer, the second polyester layer, and the third polyester layer.

[0110] Example 14 In step S1, polyester chip 1, polyester chip 2, and polyester chip 3 were basically the same as in Example 1, except that, in terms of mass%, they were each independently produced by heating, melting, mixing, extruding, molding, and slicing 97.0% PET, 1.5% antioxidant 300, and 1.5% aluminum oxide.

[0111] Example 15 In step S1, polyester chip 1, polyester chip 2, and polyester chip 3 were basically the same as in Example 1, except that they were each independently produced by heating, melting, mixing, extruding, molding, and slicing 99.0% PET, 0.5% antioxidant 300, and 0.5% aluminum oxide in terms of mass %.

[0112] Example 16 In step S1, polyester chip 1, polyester chip 2, and polyester chip 3 were basically the same as in Example 1, except that they were each independently produced by heating, melting, mixing, extruding, molding, and slicing 99.8% PET, 0.1% antioxidant 300, and 0.1% aluminum oxide in terms of mass %.

[0113] Example 17 In step S1, polyester chip 1, polyester chip 2, and polyester chip 3 were basically the same as in Example 1, except that they were each independently produced by heating, melting, mixing, extruding, molding, and slicing 99.9% PET, 0.05% antioxidant 300, and 0.05% aluminum oxide in terms of mass %.

[0114] Comparative Example 1 This example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 35 mol / t.

[0115] Comparative Example 2 The terminal carboxyl group content of the PET in the first polyester layer and the third polyester layer is 20 mol / t, and the first polyester layer and the third polyester layer in the composite polyester film are treated by a corona method. did Except for this, the present example is basically the same as Example 1. Specifically, the corona method includes the steps of placing the produced composite polyester film in a roll-to-roll corona treatment device, and modifying the surfaces of the first polyester layer and the third polyester layer at a corona power of 10 kW, a current of 6 A, and a linear speed of 50 m / min.

[0116] Comparative Example 3 The present example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the first polyester layer and the third polyester layer is 105 mol / t.

[0117] Comparative Example 4 In step S1, polyester chip 1, polyester chip 2 and polyester chip 3 were basically the same as in Example 1, except that they were each independently produced by heating, melting and mixing PET, extruding, and molding and slicing.

[0118] Comparative Example 5 In step S1, polyester chip 1, polyester chip 2, and polyester chip 3 were basically the same as in Example 1, except that, in terms of mass%, they were each independently produced by heating, melting, mixing, extruding, molding, and slicing 96.0% PET, 2.0% antioxidant 300, and 2.0% aluminum oxide.

[0119] Comparative Example 6 The second polyester layer was basically the same as Example 1, except that the content of terminal carboxyl groups in the PET was 4 mol / t.

[0120] Comparative Example 7 This example is basically the same as Example 1, except that the content of terminal carboxyl groups in the PET in the second polyester layer is 31 mol / t.

[0121] Test Example 1: Performance measurement of composite polyester film and composite current collector

[0122] The measurement results of surface tension, adhesive strength, defect rate and elastic modulus are shown in Table 1. In Table 1, MD indicates the machine direction of the composite polyester film, and TD indicates the cross direction of the composite polyester film, the machine direction being the direction in which the side length of the composite polyester film is longer, and the cross direction being the direction in which the side length of the composite polyester film is shorter, and the two directions MD and TD are perpendicular to each other. [Table 1]

[0123] As can be seen from Table 1, as the content of terminal carboxyl groups in the PET in the first and third polyester layers in Examples 1 to 7 gradually increased, the initial surface tension of the composite polyester film gradually improved, as did the adhesive strength between the composite polyester film and the aluminum metal layer and the adhesive strength between the composite polyester film and the copper metal layer. Looking at Examples 8 to 11, it was found that increasing the content of terminal carboxyl groups in the PET in the second polyester layer did not affect the initial surface tension of the composite polyester film.

[0124] Compared with Comparative Examples 1-2 and 4-5, the composite polyester film produced in Example 1 had a higher initial surface tension and showed little change in surface tension after 3 months of storage. The adhesive strength between the corresponding composite polyester film and the aluminum metal layer and copper metal layer was also strong. This indicates that adjusting the raw materials for the first, second, and third polyester layers of the composite polyester film and the content of their terminal carboxyl groups effectively solves the problems of low surface tension, unstable surface tension, and weak bonding with the surface metal layer. Compared with Example 1, the composite polyester film produced in Comparative Example 3 had an improved surface tension and stable surface tension after 3 months of storage. However, the high content of terminal carboxyl groups in the PET resulted in a high reject rate during film formation.

[0125] The surface tension of the composite polyester films produced in Comparative Examples 6 and 7, and the adhesive strength between the composite polyester films and the aluminum metal layer and the copper metal layer, were not significantly different from those in Example 1. However, the composite polyester films produced in Comparative Examples 6 and 7 had significantly lower elastic moduli in the MD and TD directions, which resulted in poor mechanical properties of the composite polyester films produced in Comparative Examples 6 and 7.

[0126] 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 combinations of these technical features should be considered to fall within the scope described in this specification unless there is a contradiction.

[0127] The above examples are merely illustrative of some embodiments of the present application, and although the descriptions are more specific and detailed, they should not be understood as limiting the scope of the claims. Those skilled in the art may make minor modifications and improvements without departing from the spirit of the present application, and all such modifications and improvements should fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent is governed by the appended claims.

Claims

1. A composite polyester film comprising a first polyester layer, a second polyester layer, and a third polyester layer, the first polyester layer and the third polyester layer are respectively located on opposite surfaces of the second polyester layer; the first polyester layer, the second polyester layer, and the third polyester layer each independently contain, by mass %, 97.0% to 99.9% of a polyester material and 0.1% to 3.0% of an additive; the content of terminal carboxyl groups in the polyester material of each of the first polyester layer and the third polyester layer is 40 to 100 mol / t, and the content of terminal carboxyl groups in the polyester material of the second polyester layer is 5 to 30 mol / t; A composite polyester film is provided.

2. In terms of mass %, the raw materials for manufacturing the first polyester layer, the second polyester layer, and the third polyester layer each independently comprise 99.0% to 99.8% polyester material and 0.2% to 1.0% additive; 2. The composite polyester film according to claim 1.

3. the content of terminal carboxyl groups in the polyester material of each of the first polyester layer and the third polyester layer is 50 to 100 mol / t, and the content of terminal carboxyl groups in the polyester material of the second polyester layer is 10 to 25 mol / t; The composite polyester film according to any one of claims 1 to 2.

4. The polyester material comprises one or more of polyethylene-2,6-naphthalenedicarboxylate, polyethylene terephthalate-1,4-cyclohexanedimethylene terephthalate, polyethylene terephthalate, polycyclohexane 1,4-dimethylene terephthalate, polypropylene-2,6-naphthalenedicarboxylate, polybutylene terephthalate, polytrimethylene terephthalate, polybutylene adipate terephthalate, polybutylene-2,6-naphthalenedicarboxylate, polybutylene-2,5-furanoate, polyarylate, and derivatives thereof; The composite polyester film according to any one of claims 1 to 3.

5. the additives include one or more of a nucleating agent, an antioxidant, a lubricant, and an antistatic agent; Preferably, the nucleating agent comprises one or more of sodium carbonate, triphenyl phosphate, polycaprolactone, benzophenone, aluminum oxide, copper oxide, magnesium oxide, zinc oxide, barium sulfate, magnesium stearate, and sodium benzoate; Preferably, the antioxidant comprises one or more of bisphenol A phosphite and phosphonate esters; Preferably, the lubricant comprises one or more of titanium dioxide, silica, siloxane, calcium carbonate, diatomaceous earth, talc powder, kaolin, and acrylic esters; Preferably, the antistatic agent comprises one or more of polyethylene glycol, glycerin, polyglycerin, polyether ester, carbon black, graphite and conductive fibers. The composite polyester film according to any one of claims 1 to 4.

6. A method for producing the composite polyester film according to any one of claims 1 to 5, Step S1, in which polyester chips 1, 2, and 3 are produced, respectively, by mass%, of polyester chips 1, 2, and 3, each of which is independently produced from 97.0% to 99.9% polyester material and 0.1% to 3% additive, wherein the content of terminal carboxyl groups of the polyester material in polyester chips 1 and 3 is 40 to 100 mol / t, and the content of terminal carboxyl groups of the polyester material in polyester chip 2 is 5 to 30 mol / t; Step S2 of producing a molten polyester material having a first polyester layer, a second polyester layer and a third polyester layer, wherein the first polyester layer, the second polyester layer and the third polyester layer are produced by the polyester chip 1, the polyester chip 2 and the polyester chip 3 in order, and the first polyester layer and the third polyester layer are respectively located on both sides of the second polyester layer; and step S3 of subjecting the molten polyester material to a molding treatment and a heat treatment in that order.

7. A substrate layer comprising the composite polyester film according to any one of claims 1 to 5 or the composite polyester film produced by the production method according to claim 6, and a metal layer provided on at least one surface of the substrate layer.

1. A metallized polyester film comprising:

8. The thickness of the metal layer is 20 to 2000 nm.

8. The metallized polyester film of claim 7.

9. the material of the metal layer comprises one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium and silver; 9. The metallized polyester film according to claim 7.

10. The metallized polyester film according to any one of claims 7 to 9, A composite current collector characterized by:

11. The composite current collector further includes a protective layer provided on the surface of the metal layer of the metallized polyester film.

11. The composite current collector of claim 10.

12. The thickness of the protective layer is 10 to 150 nm.

12. The composite current collector of claim 11.

13. the material of the protective layer comprises one or more of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, acetylene black, ketjen black, carbon nano quantum dots, carbon nanotubes, carbon nanofibers, and graphene; 13. The composite current collector according to claim 11, wherein the current collector is a composite current collector.

14. A composite current collector comprising the composite current collector according to any one of claims 10 to 13. An electrode piece characterized by:

15. The electrode strip according to claim 14, Electrochemical device characterized by:

16. 16. The electrochemical device of claim 15, 1. A power consuming device comprising:

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