WO2024092563A1

WO2024092563A1 - Modified polyester thin film, preparation method, composite current collector, electrode sheet and use thereof

Info

Publication number: WO2024092563A1
Application number: PCT/CN2022/129315
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: 2022-11-02
Filing date: 2022-11-02
Publication date: 2024-05-10

Abstract

The present application relates to a modified polyester thin film. The modified polyester thin film comprises the following raw materials in percentage by mass: 94.0%-99.2% of polyester, 0.5%-3.0% of a bridging agent, and 0.3%-3.0% of an aid, wherein the bridging agent comprises one or more of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol, and decaglycerol.

Description

Modified polyester film, preparation method, composite current collector, electrode sheet and use thereof

Technical Field

The present application relates to the technical field of polymer material manufacturing, and in particular to a modified polyester film, a preparation method, a composite current collector, an electrode sheet and uses thereof.

Background technique

Composite current collectors usually use polymer films as base films, and a layer of metal is plated on the surface of the base film by physical vapor deposition or electroplating to form a metal layer. Compared with traditional current collectors, composite current collectors can further improve the safety performance and energy density of batteries, so they have broad application prospects in the fields of electric vehicles, mobile electronic devices, etc. The tensile strength of traditional polyester films is usually less than 250MPa. If a metal layer is deposited on the surface of the film by physical vapor deposition, due to the large tension of the winding system in the physical vapor deposition system environment, the bombardment of metal atoms and the increase in the surface temperature of the film, the traditional polyester film is prone to film breakage during the deposition of the metal layer, and the composite current collector prepared with traditional polyester film as the base film has a high defect rate.

Summary of the invention

According to various embodiments of the present application, a modified polyester film, a preparation method, a composite current collector, an electrode sheet and uses thereof are provided.

The technical solution of this application is as follows:

The present application provides a modified polyester film, comprising the following raw materials in percentage by weight: 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent and 0.3% to 3.0% auxiliary agent;

The bridging agent includes one or more of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.

In some embodiments, the polyester includes one or more of polybutylene adipate terephthalate, polybutylene 2,5-furandicarboxylate, polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene 2,6-naphthalate, poly-1,4-cyclohexanedimethanol terephthalate, poly-butylene 2,6-naphthalate, polyethylene terephthalate, polyarylate, polybutylene terephthalate, poly-2,6-naphthalate, polytrimethylene terephthalate, and derivatives thereof;

Optionally, the intrinsic viscosity of the polyester is 0.600 dL/g to 0.800 dL/g;

Optionally, the molecular weight distribution index of the polyester is 1.9 to 2.3.

In some embodiments, the auxiliary agent includes one or more of a slip agent, an antioxidant, a nucleating agent, and an antistatic agent.

In some embodiments, the auxiliary agent includes one or more of a slip agent, an antioxidant, a nucleating agent and an antistatic agent, and the slip agent includes one or more of titanium dioxide, acrylate, calcium carbonate, talc, silicon dioxide, diatomaceous earth, siloxane and kaolin.

In some embodiments, the auxiliary agent includes one or more of a slip agent, an antioxidant, a nucleating agent, and an antistatic agent, and the antioxidant includes one or more of a phosphonate and bisphenol A phosphite.

In some embodiments, the auxiliary agent includes one or more of a lubricant, an antioxidant, a nucleating agent and an antistatic agent, and the nucleating agent includes one or more of zinc oxide, benzophenone, aluminum oxide, sodium benzoate, polycaprolactone, sodium carbonate, barium sulfate, triphenyl phosphate, magnesium oxide, magnesium stearate and copper oxide.

In some embodiments, the auxiliary agent includes one or more of a slip agent, an antioxidant, a nucleating agent, and an antistatic agent, and the antistatic agent includes one or more of glycerol, polyether ester, carbon black, graphite, and conductive fiber.

In some embodiments, the modified polyester film has a thickness of 1 μm to 20 μm.

The present application also provides a method for preparing the modified polyester film, comprising the following steps:

preparing polyester chips;

The polyester slices are made into films and then irradiated with electron beams to obtain modified polyester films;

The polyester chips are made of 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent and 0.3% to 3.0% auxiliary agent in terms of mass percentage. The bridging agent includes one or more of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.

In some embodiments, the process conditions of the electron beam irradiation treatment include: the electron beam energy is 0.5 MeV to 10 MeV, and the irradiation treatment time is 10 s to 60 s.

The present application also provides a composite current collector, comprising a modified polyester film and a metal layer located on at least one side of the modified polyester film, wherein the modified polyester film is the modified polyester film described above or a modified polyester film prepared by the preparation method described above.

In some embodiments, the thickness of the metal layer is 500 nm to 2000 nm.

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

In some embodiments, a protective layer is disposed on the surface of the metal layer.

In some embodiments, a protective layer is disposed on the surface of the metal layer, and the thickness of the protective layer is 10 nm to 150 nm.

In some embodiments, a protective layer is provided on the surface of the metal layer, and the material of the protective layer includes 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.

The present application also provides an electrode sheet, comprising the above-mentioned composite current collector, and an active material layer attached to at least one surface of the composite current collector.

The present application also provides a battery, comprising the above-mentioned electrode sheet.

The details of one or more embodiments of the present application are set forth in the description below. Other features, objects, and advantages of the present application will become apparent from the description and claims.

Detailed ways

The technical solution of the present application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "one or more" used herein includes any and all combinations of one or more of the related listed items.

One embodiment of the present application provides a modified polyester film, comprising the following raw materials in percentage by weight: 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent, and 0.3% to 3.0% auxiliary agent;

The modified polyester film is subjected to electron beam irradiation during the preparation process. For example, when preparing the modified polyester film, the raw material can be first made into polyester slices, and after the polyester slices are made into a film, the modified polyester film is subjected to electron beam irradiation. Since the ends of the polyester contain hydroxyl groups and the bridging agent also contains hydroxyl groups, when the electron beam irradiation treatment is carried out, part of the hydroxyl groups in the polyester can be induced to condense with part of the hydroxyl groups in the bridging agent, thereby increasing the molecular weight and crosslinking degree of the polyester and improving the mechanical properties of the modified polyester film. Applying the modified polyester film to the composite current collector can reduce the defective rate caused by film breakage and improve the mechanical properties of the composite current collector. It can be understood that, in terms of mass percentage, the modified polyester film can, for example, include 94.0% polyester, 3.0% bridging agent and 3.0% auxiliary agent, or include 94.5% polyester, 2.5% bridging agent and 3.0% auxiliary agent, or include 95.5% polyester, 1.5% bridging agent and 3% auxiliary agent, or include 96% polyester, 2% bridging agent and 2% auxiliary agent, or include 97.5% polyester, 2.2% bridging agent and 0.3% auxiliary agent, or include 99.2% polyester, 0.5% bridging agent and 0.3% auxiliary agent, or include 96% polyester, 3% bridging agent and 1% auxiliary agent. It is understandable that the bridging agent may include any one of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol, or may include a mixture of multiple compositions of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.

In some embodiments, the polyester includes one or more of polybutylene adipate terephthalate, polybutylene 2,5-furandicarboxylate, polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene 2,6-naphthalate, poly-1,4-cyclohexanedimethanol terephthalate, poly-2,6-naphthalate, polyethylene terephthalate, polyarylate, polybutylene terephthalate, poly-2,6-naphthalate, polytrimethylene terephthalate, and derivatives thereof.

In some embodiments, the intrinsic viscosity of the polyester is 0.600 dL/g to 0.800 dL/g. It should be noted that when the intrinsic viscosity of the polyester is too low, the average molecular weight of the prepared modified polyester film is low and the mechanical properties are poor; when the intrinsic viscosity of the polyester is too high, the average molecular weight of the prepared modified polyester film is high, resulting in poor film-forming properties of the modified polyester film and easy film breakage. It can be understood that the intrinsic viscosity of the polyester can be any value between 0.600 dL/g and 0.800 dL/g, for example, it can be 0.600 dL/g, 0.611 dL/g, 0.615 dL/g, 0.624 dL/g, 0.636 dL/g, 0.658 dL/g, 0.672 dL/g, 0.693 dL/g, 0.703 dL/g, 0.722 dL/g, 0.745 dL/g, 0.763 dL/g, 0.788 dL/g, 0.792 dL/g or 0.800 dL/g, etc.

In some embodiments, the molecular weight distribution index of the polyester is 1.9 to 2.3. It should be noted that the molecular weight distribution index refers to the ratio of the weight average molecular weight to the number average molecular weight. When the molecular weight distribution index of the polyester is too low, the film-forming properties of the modified polyester film deteriorate; when the molecular weight distribution index of the polyester is too high, the stability of the modified polyester film deteriorates. It can be understood that the molecular weight distribution index of the polyester can be any value between 1.9 and 2.3, for example, it can be 1.9, 1.93, 1.95, 2.02, 2.06, 2.1, 2.15, 2.18, 2.2, 2.24, 2.27 or 2.3.

In some embodiments, the auxiliary agent includes one or more of a lubricant, an antioxidant, a nucleating agent, and an antistatic agent. For example, the auxiliary agent may include any one of a lubricant, an antioxidant, a nucleating agent, and an antistatic agent, or may include a mixture of multiple lubricants, antioxidants, nucleating agents, and antistatic agents in any proportion.

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

Specifically, the antioxidant includes one or more of phosphonate (such as antioxidant 1222, antioxidant 300) and bisphenol A phosphite.

Specifically, the nucleating agent includes one or more of zinc oxide, benzophenone, aluminum oxide, sodium benzoate, polycaprolactone, sodium carbonate, barium sulfate, triphenyl phosphate, magnesium oxide, magnesium stearate, and copper oxide.

Specifically, the antistatic agent includes one or more of glycerol, polyether ester, carbon black, graphite and conductive fiber.

In some embodiments, the thickness of the modified polyester film is 1 μm to 20 μm. It is understood that the thickness of the modified polyester film can be, for example, 1 μm, 1.3 μm, 1.5 μm, 1.57 μm, 1.9 μm, 2 μm, 2.2 μm, 2.4 μm, 3 μm, 3.5 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, 17 μm or 20 μm, and the thickness of the modified polyester film can also be other values between 1 μm and 20 μm.

Another embodiment of the present application provides a method for preparing the modified polyester film, comprising the following steps:

preparing polyester chips;

Calculated by mass percentage, the polyester chips are made of 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent and 0.3% to 3.0% auxiliary agent, and the bridging agent includes one or more of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.

Electron beam irradiation treatment can induce condensation of some hydroxyl groups in polyester with some hydroxyl groups in bridging agent, thereby increasing the molecular weight and crosslinking degree of polyester and improving the mechanical properties of polyester film. It can be understood that, by mass percentage, the modified polyester film can include, for example, 94.0% polyester, 3.0% bridging agent and 3.0% auxiliary agent, or 94.5% polyester, 2.5% bridging agent and 3.0% auxiliary agent, or 95.5% polyester, 1.5% bridging agent and 3% auxiliary agent, or 96% polyester, 2% bridging agent and 2% auxiliary agent, or 97.5% polyester, 2.2% bridging agent and 0.3% auxiliary agent, or 99.2% polyester, 0.5% bridging agent and 0.3% auxiliary agent, or 96% polyester, 3% bridging agent and 1% auxiliary agent.

In some embodiments, the process conditions of the electron beam irradiation treatment include: the electron beam energy is 0.5MeV to 10MeV, and the irradiation treatment time is 10s to 60s. It is understood that the electron beam energy can be any value between 0.5MeV and 10MeV, for example, it can be 0.5MeV, 1MeV, 1.5MeV, 2MeV, 2.5MeV, 3MeV, 4MeV, 5MeV, 6MeV, 7MeV, 8MeV, 9MeV or 10MeV, etc.; the irradiation treatment time can be any value between 10s and 60s, for example, it can be 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s, etc.

In some embodiments, the polyester chips are prepared from 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent and 0.3% to 3.0% auxiliary agent by sequentially heating, melting, mixing, extruding and forming chips.

The present application also provides a composite current collector, comprising a modified polyester film and a metal layer located on at least one side of the modified polyester film, wherein the modified polyester film is the above-mentioned modified polyester film or a modified polyester film prepared by the above-mentioned preparation method.

It can be understood that applying the above-mentioned modified polyester film to the composite current collector can reduce the defect rate caused by film breakage, thereby improving the mechanical properties of the composite current collector.

In some embodiments, the thickness of the metal layer is 500nm to 2000nm. It is understood that the thickness of the metal layer can be any value between 500nm and 2000nm, for example: 500nm, 520nm, 540nm, 560nm, 580nm, 600nm, 610nm, 630nm, 650nm, 670nm, 690nm, 700nm, 720nm, 750nm, 770nm, 800nm, 830nm, 850nm, 900nm, 1200nm, 1500nm, 1800nm, or 2000nm.

In some embodiments, the material of the metal layer includes one or more of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy and copper. It should be noted that when both layers of the modified polymer film are provided with metal layers, the materials of the two metal layers need to be consistent.

Specifically, the preparation method of the metal layer includes, but is not limited to, a resistance heating vacuum evaporation method, an electron beam heating vacuum evaporation method, a laser heating vacuum evaporation method, or a magnetron sputtering method.

Specifically, the thickness of the protective layer is 10nm to 150nm. For example: 10nm, 10.1nm, 10.2nm, 10.3nm, 10.4nm, 10.5nm, 10.6nm, 10.7nm, 10.8nm, 10.9nm, 11nm, 11.2nm, 11.5nm, 12nm, 15nm, 20nm, 23nm, 33nm, 43nm, 45nm, 50nm, 55nm, 60nm, 62nm, 67nm, 72nm, 77nm, 80nm, 83nm, 88nm, 90nm, 100nm, 120nm or 150nm. It should be noted that the thickness of the protective layer does not exceed one tenth of the thickness of the metal layer.

Specifically, the material of the protective layer includes 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. It should be noted that the purpose of providing the protective layer is to prevent the metal layer from being chemically corroded or physically damaged. When the metal layer is provided on both sides of the modified polymer film, the materials of the protective layers on the surfaces of the two metal layers may be consistent or inconsistent.

It should be noted that the electrode sheet includes a positive electrode sheet and a negative electrode sheet, and the above-mentioned composite current collector can be used as a positive electrode current collector or a negative electrode current collector in a positive electrode sheet or a negative electrode sheet. When the above-mentioned composite current collector is used as a positive electrode current collector, the preparation method of the active material layer can be, for example, as follows: a slurry formed by mixing a positive electrode material, a binder, a conductive agent and a solvent is coated on the surface of the composite current collector and dried to form an active material layer; when the above-mentioned composite current collector is used as a negative electrode current collector, the preparation method of the active material layer can be, for example, as follows: a slurry formed by mixing a negative electrode material, a binder, a conductive agent and a solvent is coated on the surface of the composite current collector and dried to form an active material layer; the present application has no particular restrictions on the positive electrode material, the negative electrode material, the binder, the conductive agent, and the preparation method of the active material layer, and the materials or preparation methods commonly used in the technical field are all within the scope of the active material layer of the present application.

The battery may include, for example, a positive electrode sheet, a separator and a negative electrode sheet, and one or more of the positive electrode sheet and the negative electrode sheet may use the electrode sheet.

The present application also provides an electrical device, comprising the above-mentioned battery.

It should be noted that the above-mentioned battery can be used in electrical devices, including but not limited to electric toys, wearable devices, tablets, mobile phones, computers, electric vehicles or energy storage devices.

In order to further understand the present application, the modified polyester film and the preparation method of the modified polyester film provided by the present application are specifically described below in conjunction with embodiments.

Unless otherwise specified, various raw materials of the present application can be purchased commercially or prepared according to conventional methods in the art.

Example 1

The raw materials selected in this embodiment are: the polyester is polyethylene terephthalate (PET), whose intrinsic viscosity is 0.675 dL/g and whose molecular weight distribution index is 2.2; the auxiliary agents are antioxidant 300 and aluminum oxide (average particle size is 0.2 μm); and the bridging agent is diethylene glycol.

The above drugs were all analytically pure.

The modified polyester film was prepared as follows:

(1) adding 99.2% PET, 0.15% antioxidant 300, 0.15% alumina and 0.5% diethylene glycol into a twin-screw extruder according to the mass percentage, and preparing polyester chips by heating, melting, mixing, extruding, molding and slicing in sequence;

(2) conveying the polyester chips obtained in step (1) to a crystallizer and a drying tower in sequence for treatment, wherein the polyester chips are treated at 150° C. for 40 min in the crystallizer and dried at 155° C. for 140 min in the drying tower;

(3) heating the polyester chips obtained in step (2) to 270° C. in a twin-screw extruder to melt the polyester chips, and extruding the resulting molten material through a die;

(4) The molten material extruded in step (3) is cast onto a casting roll, and is formed by cooling the casting roll and water cooling to form a casting sheet having a thickness of 54 μm;

(5) preheating the 54 μm thick casting sheet obtained in step (4) at 90° C., and then longitudinally stretching the film at a temperature of 110° C. and a longitudinal stretching ratio of 3:1, and heat-setting the film obtained by longitudinal stretching at 170° C. and cooling it at 40° C.;

(6) preheating the film obtained in step (5) at 90° C., and then performing a transverse stretching treatment, the transverse stretching temperature is 120° C., the transverse stretching ratio is 3:1, and the film obtained by the transverse stretching is heat-set at 170° C., and cooled at 110° C. to form a film with a thickness of 6 μm;

(7) rolling up the film obtained in step (6);

(8) The film wound up in step (7) is placed in the unwinding system of a roll-to-roll irradiation treatment device, and then the unwinding film is pulled into the irradiation treatment system. The irradiation treatment system consists of an electron gun, a radio frequency linear accelerator, an emission channel and an emission window. The electron beam is emitted by the electron gun, accelerated by the radio frequency linear accelerator, passes through the emission channel, enters the emission window, and irradiates the film. The distance between the emission window and the film is 50 cm, the energy of the irradiated electron beam is 0.5 MeV, and the irradiation treatment time is 10 s. The irradiated film enters the winding system for winding, thereby obtaining a modified polyester film.

Example 2

The preparation method is the same as that of Example 1, except that the energy of the irradiated electron beam in step (8) is 4.0 MeV.

Example 3

The preparation method is the same as that of Example 1, except that the energy of the irradiated electron beam in step (8) is 8.0 MeV.

Example 4

The preparation method is the same as that of Example 1, except that the energy of the irradiated electron beam in step (8) is 10.0 MeV.

Example 5

The preparation method is the same as that of Example 1, except that the energy of the irradiated electron beam in step (8) is 0.3 MeV.

Example 6

The preparation method is the same as that of Example 1, except that the energy of the irradiated electron beam in step (8) is 10.2 MeV.

Example 7

The preparation method is the same as that of Example 3, except that the irradiation treatment time in step (8) is 25 seconds.

Example 8

The preparation method is the same as that of Example 3, except that the irradiation treatment time in step (8) is 40 seconds.

Example 9

The preparation method is the same as that of Example 3, except that the irradiation treatment time in step (8) is 60 seconds.

Example 10

The preparation method is the same as that of Example 3, except that the irradiation treatment time in step (8) is 8 s.

Embodiment 11

The preparation method is the same as that of Example 3, except that the irradiation treatment time in step (8) is 62 s.

Example 12

The preparation method is the same as that of Example 8, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 2.0%, and the mass percentages of PET, antioxidant 300, and aluminum oxide are 97.7%, 0.15%, and 0.15%, respectively.

Embodiment 13

The preparation method is the same as that of Example 8, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 3.0%, and the mass percentages of PET, antioxidant 300, and aluminum oxide are 96.7%, 0.15%, and 0.15%, respectively.

Embodiment 14

The preparation method is the same as that of Example 13, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 3.0%, and the mass percentages of PET, antioxidant 300, and aluminum oxide are 94.0%, 1.50%, and 1.50%, respectively.

Embodiment 15

The preparation method is the same as that of Example 13, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 3.0%, and the mass percentages of PET, antioxidant 300, and aluminum oxide are 95.0%, 1.0%, and 1.0%, respectively.

Example 16

The preparation method is the same as that of Example 1, except that in the polyester chips of step (1), diethylene glycol is replaced by polyethylene glycol 400, and polyethylene terephthalate (PET) is replaced by poly (2,6-naphthalate) trimethylene glycol.

Embodiment 17

The preparation method is the same as that of Example 1, except that: in the polyester chips of step (1), diethylene glycol is replaced by diglycerol, and polyethylene terephthalate (PET) is replaced by polybutylene adipate terephthalate.

Embodiment 18

The preparation method is the same as that of Example 1, except that in the polyester chips of step (1), diethylene glycol is replaced by tetraglycerol, and polyethylene terephthalate (PET) is replaced by polyethylene 2,6-naphthalate.

Embodiment 19

The preparation method is the same as that of Example 1, except that in the polyester chips of step (1), diethylene glycol is replaced by hexaglycerol, and the antioxidant 300 and alumina are replaced by sodium benzoate and talc.

Embodiment 20

The preparation method is the same as that of Example 1, except that: in the polyester chips of step (1), diethylene glycol is replaced by decaglycerol, and the antioxidant 300 and alumina are replaced by propylene glycol and siloxane.

Comparative Example 1

The preparation method is the same as that of Example 1, except that in the polyester chips of step (1), the mass percentages of PET, antioxidant 300 and aluminum oxide are 99.7%, 0.15% and 0.15% respectively, and step (8) is not performed.

Comparative Example 2

The preparation method is the same as that of Example 8, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 0.3%, and the mass percentages of PET, antioxidant 300, and aluminum oxide are 99.4%, 0.15%, and 0.15%, respectively.

Comparative Example 3

The preparation method is the same as that of Example 8, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 3.2%, and the corresponding mass percentages of PET, antioxidant 300, and aluminum oxide are 96.5%, 0.15%, and 0.15%, respectively.

Comparative Example 4

The preparation method is the same as that of Example 8, except that: in the polyester chips of step (1), the mass percentage of diethylene glycol is 1.0%, and the mass percentages of PET, antioxidant 300, and aluminum oxide are 93%, 3.0%, and 3.0%, respectively.

Comparative Example 5

The preparation method is the same as that of Example 1, except that in the polyester chips of step (1), the mass percentages of PET, antioxidant 300 and aluminum oxide are 99.7%, 0.15% and 0.15% respectively.

Comparative Example 6

The preparation method is the same as that of Example 1, except that step (8) is not performed.

Preparation of composite current collector

The surfaces of the modified polyester films prepared in Examples 1 to 20 and Comparative Examples 1 to 6 were cleaned respectively, and high-purity aluminum wire with a purity greater than 99.99% was heated to 1500°C to melt and evaporate it, and the melted and evaporated aluminum atoms were deposited on the two surfaces of the modified polyester film to form an aluminum metal conductive layer with a thickness of 1 μm; graphene and nitrogen methyl pyrrolidone were evenly mixed to prepare a coating liquid with a solid content of 0.1wt.%, and then evenly coated on the surface of the aluminum metal conductive layer according to a coating amount of 80 μm, and then dried (drying temperature is 100°C) to obtain a composite current collector.

Elastic modulus, tensile strength and elongation at break tests

With reference to the national standard GB/T 1040.3-2006, the elastic modulus, tensile strength and elongation at break of the modified polyester films in the MD direction and the composite current collector prepared in Examples 1 to 20 and Comparative Examples 1 to 6 were tested respectively, and the defective rate of the composite current collector was tested, and the results are shown in Table 1. The MD direction of the modified polyester film refers to the mechanical direction, length direction or longitudinal direction of the modified polyester film, and the MD direction of the composite current collector refers to the mechanical direction, length direction or longitudinal direction of the composite current collector.

Defective rate test

The ratio of the number of unqualified products caused by film breakage in the process of preparing the composite current collector to the total number of products. Since the width of the composite current collector is the same, the number of unqualified products is calculated based on the length. The results are shown in Table 1.

Table 1

From Table 1, we can see that:

Compared with Comparative Example 1, Comparative Example 5 and Comparative Example 6, the elongation at break of the modified polyester film and the composite current collector in the MD direction of Example 1 changes less, and the elastic modulus and tensile strength of the modified polyester film and the composite current collector in the MD direction of Example 1 are significantly improved, and the defective rate of the composite current collector is significantly reduced.

Compared with Comparative Example 4, the defective rate of the composite current collector of Example 8 is significantly reduced, and the elastic modulus and tensile strength in the MD direction of the modified polyester film and the MD direction of the composite current collector are greatly improved.

From Example 8, Examples 12 to 13 and Comparative Examples 2 to 3, it can be seen that when the percentage of diethylene glycol is 0.5% to 3.0%, increasing the percentage of diethylene glycol, the mechanical properties of the modified polyester film in the MD direction and the composite current collector in the MD direction first increase and then slightly decrease.

From Examples 1 to 6, it can be seen that: when the energy of the irradiated electron beam is 0.5MeV to 10MeV when modifying the polyester film, increasing the energy of the irradiated electron beam, the elastic modulus of the modified polyester film in the MD direction and the tensile strength in the MD direction, as well as the elastic modulus and the tensile strength in the MD direction of the composite current collector first increase and then slightly decrease, and the defective rate in the preparation process of the composite current collector is significantly reduced, while being able to take into account the elongation at break in the MD direction of the modified polyester film and the MD direction of the composite current collector.

From Example 3 and Examples 7 to 11, it can be seen that: when the irradiation treatment time is 10s to 60s, as the irradiation treatment time is increased, the elastic modulus and tensile strength of the modified polyester film in the MD direction and the composite current collector in the MD direction first increase and then slightly decrease, and the elongation at break in the MD direction of the modified polyester film and the composite current collector in the MD direction does not change significantly.

The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, 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, they should be considered to be within the scope of this specification.

The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

A modified polyester film, characterized in that it comprises the following raw materials in percentage by weight: 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent and 0.3% to 3.0% auxiliary agent;

The bridging agent includes one or more of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.
The modified polyester film according to claim 1, characterized in that the polyester comprises one or more of polybutylene adipate terephthalate, polybutylene 2,5-furandicarboxylate, polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene 2,6-naphthalate, poly-1,4-cyclohexanedimethanol terephthalate, poly-butylene 2,6-naphthalate, polyethylene terephthalate, polyarylate, polybutylene terephthalate, poly-2,6-naphthalate trimethylene, polytrimethylene terephthalate and derivatives thereof;

Optionally, the intrinsic viscosity of the polyester is 0.600 dL/g to 0.800 dL/g;

Optionally, the molecular weight distribution index of the polyester is 1.9 to 2.3.
The modified polyester film according to any one of claims 1 to 2 is characterized in that the auxiliary agent includes one or more of a lubricant, an antioxidant, a nucleating agent and an antistatic agent.
The modified polyester film according to claim 3, characterized in that the lubricant comprises one or more of titanium dioxide, acrylate, calcium carbonate, talc, silicon dioxide, diatomaceous earth, siloxane and kaolin.
The modified polyester film according to any one of claims 3 to 4, characterized in that the antioxidant comprises one or more of phosphonates and bisphenol A phosphite.
The modified polyester film according to any one of claims 3 to 5, characterized in that the nucleating agent includes one or more of zinc oxide, benzophenone, aluminum oxide, sodium benzoate, polycaprolactone, sodium carbonate, barium sulfate, triphenyl phosphate, magnesium oxide, magnesium stearate and copper oxide.
The modified polyester film according to any one of claims 3 to 6, characterized in that the antistatic agent comprises one or more of glycerol, polyether ester, carbon black, graphite and conductive fiber.
The modified polyester film according to any one of claims 1 to 7, characterized in that the thickness of the modified polyester film is 1 μm to 20 μm.
The method for preparing the modified polyester film according to any one of claims 1 to 8, characterized in that it comprises the following steps:

preparing polyester chips;

The polyester slices are made into films and then irradiated with electron beams to obtain modified polyester films;

The polyester chips are made of 94.0% to 99.2% polyester, 0.5% to 3.0% bridging agent and 0.3% to 3.0% auxiliary agent in terms of mass percentage, wherein the bridging agent comprises one or more of diethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol.
The preparation method according to claim 9 is characterized in that the process conditions of the electron beam irradiation treatment include: the electron beam energy is 0.5MeV to 10MeV, and the irradiation treatment time is 10s to 60s.
A composite current collector, characterized in that it comprises a modified polyester film and a metal layer located on at least one side of the modified polyester film, wherein the modified polyester film is the modified polyester film described in any one of claims 1 to 8 or the modified polyester film prepared by the preparation method described in any one of claims 9 to 10.
The composite current collector according to claim 11, characterized in that it comprises at least one of the following features (1) to (5):

(1) The thickness of the metal layer is 500nm to 2000nm;

(2) The material of the metal layer includes one or more of titanium, silver, aluminum alloy, aluminum, nickel alloy, nickel, copper alloy and copper;

(3) A protective layer is provided on the surface of the metal layer;

(4) A protective layer is provided on the surface of the metal layer, and the thickness of the protective layer is 10 nm to 150 nm;

(5) A protective layer is provided on the surface of the metal layer, and the material of the protective layer includes 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.
An electrode sheet, characterized in that it comprises the composite current collector according to any one of claims 11 to 12, and an active material layer attached to at least one surface of the composite current collector.
A battery, characterized by comprising the electrode sheet according to claim 13.
An electrical device, characterized by comprising the battery according to claim 14.