Polyester base film, method for preparing the same and use thereof, electrode tab, and lithium single battery

Abstract

The present disclosure provides a polyester-based film, a method for preparing the same and uses thereof, an electrode tab, and a lithium primary battery. The material of this polyester-based film contains a polyester derivative, which is a derivative obtained by replacing a part of the original diol monomer in the corresponding polyester with a diol monomer containing a polar group, and the polar group contains one or more of an amide group and an amine group. This polyester derivative is used as a material for preparing a polyester-based film, can increase the polar group content of the polyester-based film, improve the surface tension of the polyester-based film, and the surface tension of the polyester-based film can be stabilized over a long period, effectively promoting a strong bond between the polyester-based film and the surface metal layer.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a polyester-based film, a preparation method and use thereof, an electrode tab, and a lithium single battery.

Background Art

[0002] Currently, composite current collectors based on polymer thin films have been widely noted and applied in the new energy industry. Compared with conventional current collectors, composite current collectors made of polymer thin films have characteristics such as low cost, light weight, and good internal insulation. Due to these characteristics, when applied to batteries, composite current collectors made of polymer thin films can reduce the cost of the batteries and improve the energy density and safety of the batteries.

[0003] The preparation process of the composite current collector usually includes depositing a layer of metal material on the polymer thin film by physical vapor deposition, and the composite current collector is a thin film with a metallized surface that has a certain conductivity. The polymer thin film applied to the composite current collector needs to precisely control the thermal shrinkage rate, reduce the thermal influence on the base film material when physically vapor depositing the metal material, and avoid the occurrence of quality problems such as wrinkles in the product due to thermal shrinkage.

[0004] However, in the actual preparation process of the composite current collector, the phenomenon that the bonding between the polymer thin film and the surface metal layer is not strong easily occurs, which is a problem that needs to be urgently solved in the preparation process of the composite current collector.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Based on this, the present invention provides a polyester-based film, a preparation method and use thereof, an electrode tab, and a lithium single battery, and the composite current collector prepared based on the polyester-based film can improve the bonding force between the base film and the surface metal layer.

Means for Solving the Problems

[0006] In Embodiment 1 of the present invention, the material of the polyester-based film includes a polyester derivative, and the polyester derivative includes a first polyester derivative which is one or more of a polyethylene terephthalate derivative, a polybutylene terephthalate derivative, and a polyethylene naphthalate derivative. The first polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing a nitrogen-containing polar group, and the nitrogen-containing polar group includes one or more of an amide group and an amine group. A polyester-based film is provided.

[0007] In some embodiments, the molar ratio of the diol-based monomer containing a nitrogen-containing polar group to the original diol-based monomer not replaced in the first polyester derivative is (0.1 to 4):1.

[0008] In some embodiments, the number of nitrogen-containing polar groups in the diol-based monomer containing a nitrogen-containing polar group is n, and 1 ≤ n ≤ 3.

[0009] In some embodiments, the diol-based monomer containing a nitrogen-containing polar group is one of a chain shape, a saturated cyclic shape, and an unsaturated cyclic shape, and the unsaturated cyclic shape includes one of a benzene ring and a heterocyclic ring.

[0010] In some embodiments, the diol-based monomer containing a nitrogen-containing polar group includes one or more of diethanolamine, 3-hydroxy-N-(2-hydroxyethyl)propionamide, 4-amino-1,2-butanediol, 3-dimethylamine-1,2-propanediol, and 3-amino-1,2-propanediol.

[0011] In some embodiments, the polyester derivative further comprises a second polyester derivative including one or more of polyethylene terephthalate derivatives, polybutylene terephthalate derivatives, and polyethylene naphthalate derivatives, and the second polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing one or more polar groups selected from an etheroxy group, a carboxyl group, and a phenolic hydroxyl group.

[0012] In some embodiments, the second polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing one or more polar groups selected from diethylene glycol and 3-(2-hydroxyethyl) phenylethyl alcohol.

[0013] In some embodiments, the weight average molecular weight of the polyester derivative is 20,000 to 80,000, and / or the intrinsic viscosity is 0.5 to 1.2 dL / g.

[0014] In some embodiments, the polyester derivative is one or more of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer.

[0015] In some embodiments, the polyester derivative is an alternating copolymer, or a mixture of an alternating copolymer and one or more of a random copolymer, a block copolymer, and a graft copolymer.

[0016] In some of these embodiments, the mass of the polyester derivative in the polyester base film is 10 wt% to 100 wt% of the polyester base film.

[0017] In some embodiments, the polyester-based film further comprises a polyester, and the polyester comprises one or more of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0018] In some of these embodiments, the weight ratio of the polyester derivative to the polyester is (1 / 9 to 9):1.

[0019] In Aspect 2 of the present invention, there is provided a method for preparing the polyester-based film according to Aspect 1 of the present invention, which includes melt-extruding the material and then biaxially stretching to produce a polyester-based film. A method for preparing a polyester-based film is provided.

[0020] In Aspect 3 of the present invention, there is provided the use of the polyester-based film according to Aspect 1 of the present invention in the preparation of a composite current collector.

[0021] In Aspect 4 of the present invention, there is provided a pole piece including the polyester-based film according to Aspect 1 of the present invention and an electrode active material located on the polyester-based film. A pole piece is provided.

[0022] In Aspect 5 of the present invention, there is provided a lithium single battery including the pole piece according to Aspect 4 of the present invention. A lithium single battery is provided.

[0023] In Aspect 6 of the present invention, there is provided a battery pack including the lithium single battery according to Aspect 5 of the present invention. A battery pack is provided.

[0024] In Aspect 7 of the present invention, there is provided an electrical device including the lithium single battery according to Aspect 5 of the present invention or the battery pack according to Aspect 6 of the present invention. An electrical device is provided.

Advantages of the Invention

[0025] In the polyester-based film, its preparation method and use, the electrode tab, and the lithium single battery according to the present invention, the material of the polyester-based film contains a polyester derivative, and the polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing a nitrogen-containing polar group. Moreover, the nitrogen-containing polar group contains one or more of an amide group and an amine group. Using the polyester derivative as the material for preparing the polyester-based film can increase the polar group content of the polyester-based film, improve the surface tension of the polyester-based film, and enable the surface tension of the polyester-based film to be stabilized over a long period, effectively promoting a strong bond between the polyester-based film and the surface metal layer.

Embodiments for Carrying Out the Invention

[0026] For the convenience of understanding the present invention, the present invention will be described more comprehensively below. Preferred embodiments of the present invention are shown below. However, the present invention can be realized in many different forms and is not limited to the embodiments described in this specification. On the contrary, these embodiments are provided to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0027] Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art. In this specification, the terms used in the description of the present invention are only for explaining specific embodiments and are not for limiting the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0028] In the present invention, the open-endedly described technical features include a closed technical solution consisting of the listed features and an open technical solution including the listed features.

[0029] In the present invention, "one or more combinations" means any one or two or more combinations of the listed items.

[0030] In the present invention, regarding numerical ranges, unless otherwise specified, within the above numerical ranges, it is considered continuous and includes the minimum value and the maximum value of the range, and each value between such minimum value and maximum value. Further, when the range refers to an integer, it includes each integer between the minimum value and the maximum value of the range. Also, when providing a plurality of ranges to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this specification should be understood to include any and all sub-ranges contained therein.

[0031] For the unit of the data range according to this specification, if the unit is attached only after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 0.5~1.2 dL / g means that the units of both the left endpoint "0.5" and the right endpoint "1.2" are dL / g.

[0032] The preferred ranges of "and / or", "or / and", and "and / or" used in this specification include any one of two or more related listed items, and also include any and all combinations of the related listed items, and the above any and all combinations include combinations of any two related listed items, any more related listed items, or all related listed items.

[0033] Currently, composite current collectors made of polymer thin films are widely noted and applied in the new energy industry. Compared with conventional current collectors, composite current collectors made of polymer thin films have characteristics such as low cost, light weight, and good internal insulation. Due to these characteristics, when applied to batteries, composite current collectors made of polymer thin films can reduce the cost of the batteries and improve the energy density and safety of the batteries.

[0034] The preparation process of the composite current collector using a polymer thin film usually involves depositing a layer of metal (such as aluminum, copper, etc.) material on the polymer thin film (such as polypropylene, polyethylene, polyester-based, etc.) by physical vapor deposition, including that the prepared thin film with a metallized surface having a certain conductivity ability is the composite current collector.

[0035] However, in the actual preparation process of the composite current collector, the phenomenon that the bond between the polymer thin film and the surface metal layer is not strong is likely to occur.

[0036] As a result of research, the applicant found that the reason for this problem is that commonly used polymer thin films such as polypropylene, polyethylene, and polyester have weak polarity of the material itself, so the surface tension of the material is low, and the affinity between the polymer thin film with low surface tension and the metal material with high surface tension is poor, and the adhesion between the interfaces of the two is reduced, resulting in a weak bond.

[0037] To solve this problem, usually, the method of corona treatment on the surface of the polymer thin film is adopted to improve the surface tension of the thin film and improve the bond strength between the polymer thin film and the metal material. However, this method has the following deficiencies. (1) On the premise of ensuring that the mechanical properties of the polymer thin film do not change significantly, the surface tension of the PET (polyethylene terephthalate) polymer thin film after corona treatment is generally between 50 and 70 mN / m, and the increase range is limited compared with the surface tension of the polymer thin film before treatment (25 - 45 mN / m), and there is still a large difference from the surface tension of the metal material (greater than 100 mN / m), and the bonding effect between the two is not ideal. When peeled off after pasting with tape, large-area shedding of the metal layer can be seen. (2) The surface tension of the polymer thin film after corona treatment is unstable. After storage for a while, the surface tension decreases and finally approaches the surface tension of the polymer thin film before treatment, that is, there is a problem of unstable storage.

[0038] To solve the problems of the technology, the present invention provides a polyester-based film, the material of which may include a polyester derivative. The polyester derivative includes a first polyester derivative, and the first polyester derivative includes one or more of a polyethylene terephthalate derivative, a polybutylene terephthalate derivative, and a polyethylene naphthalate derivative. The first polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing a nitrogen-containing polar group, and the nitrogen-containing polar group includes one or more of an amide group and an amine group.

[0039] Note that the original diol-based monomer means the diol-based monomer contained in the polyester corresponding to the polyester derivative. For example, when the polyester derivative is a polyethylene terephthalate derivative and / or a polyethylene naphthalate derivative, the original diol-based monomer means ethylene glycol. When the polyester derivative is a polybutylene terephthalate derivative, the original diol-based monomer means butanediol. When the polyester derivative is a polyethylene terephthalate derivative and a polybutylene terephthalate derivative, or when the polyester derivative is a polybutylene terephthalate derivative and a polyethylene naphthalate derivative, or when the polyester derivative is a polyester derivative including a polyethylene terephthalate derivative, a polybutylene terephthalate derivative, and a polyethylene naphthalate derivative, the original diol-based monomer means butanediol and ethylene glycol.

[0040] The polyester-based film according to the present invention has a material containing a polyester derivative, the polyester derivative contains a first polyester derivative, and the first polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing a nitrogen-containing polar group, and the nitrogen-containing polar group contains one or more of an amide group and an amine group. Using a polyester derivative as a material for preparing the polyester-based film can increase the polar group content of the polyester-based film, improve the surface tension of the polyester-based film, and enable the surface tension of the polyester-based film to be stabilized over a long period, effectively promoting a strong bond between the polyester-based film and the surface metal layer. It is advantageous to use the nitrogen-containing polar group to coordinate with the metal by the lone pair of electrons of the N atom to promote a strong bond between the polyester-based film and the surface metal layer. In addition, the amino group has a slightly weaker hydrogen bonding force than the hydroxy group, and can effectively prevent adhesion between films when the polyester-based film is wound.

[0041] In some embodiments, the nitrogen-containing polar group may be located in the main chain of the diol-based monomer or in the side chain of the diol-based monomer.

[0042] In some embodiments, the polyester derivative further contains a second polyester derivative, the second polyester derivative contains one or more of a polyethylene terephthalate derivative, a polybutylene terephthalate derivative, and a polyethylene naphthalate derivative, and the second polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing one or more polar groups selected from an etheroxy group, a carboxyl group, and a phenolic hydroxyl group.

[0043] In some of these embodiments, the mass content percentage of the polyester derivative in the polyester-based film is 10 wt% to 100 wt%, for example, it may be 10%, 33.33%, 50%, 66.67%, 75%, 80%, 83.33%, 85.71%, 87.50, 88.89, 90% or 100%, etc., and is not specifically limited. When the mass content percentage of the polyester derivative is less than this range, the number of polar groups is small, and the polarity of the finally produced polyester-based film is poor, so the surface tension of the polyester-based film decreases.

[0044] In some embodiments, the thickness of the polyester-based film may be 2 μm to 20 μm, for example, it may be 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm or 20 μm, etc., and is not specifically limited.

[0045] In some embodiments, the MD (longitudinal direction) tensile strength of the polyester-based film can reach 120 Mpa to 400 Mpa, the TD (transverse direction) tensile strength can reach 100 Mpa to 350 Mpa, and the elongation at break in the MD and TD directions can reach 50% to 150%.

[0046] In some embodiments, the surface tension of the polyester-based film can reach 40 to 100 mN / m, and after being stored for 3 months, the surface tension can reach 30 to 80 mN / m, that is, after being stored for a long time, the change in the surface tension of the polyester-based film is not large and can be stabilized over a long period.

[0047] In some embodiments, the surface roughness of the polyester-based film can reach 5 nm to 150 nm. In the comparative experiment of sticking and peeling with tape, the detachment area of the polyester-based film with respect to the metal layer ≦ 0.2% indicates that the polyester-based film can be firmly bonded to the surface metal layer.

[0048] In some embodiments, the molar ratio of the diol monomer containing a polar group in the first polyester derivative or the second polyester derivative to the original diol monomer that has not been replaced may each independently be (0.1 to 4):1. For example, it may be 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, etc., and is not specifically limited. When the molar ratio of the diol monomer containing a polar group in the polyester derivative to the original diol monomer that has not been replaced is less than this range, the surface tension of the produced polyester base film cannot be effectively improved. On the other hand, when the molar ratio is greater than this range, since there are too many polar groups, it affects the mechanical properties of the produced polyester base film. When the molar ratio of the diol monomer containing a polar group in the first polyester derivative or the second polyester derivative to the original diol monomer that has not been replaced is (0.1 to 4):1, it is advantageous for further improving the surface tension of the produced polyester base film and does not affect the mechanical properties of the polyester base film.

[0049] In some embodiments, in the diol monomer containing a polar group in the first polyester derivative or the second polyester derivative, the number of polar groups is n, and 1 ≤ n ≤ 3. For example, the number of polar groups contained may be 1, 2, or 3, and is not specifically limited. Here, the polar group is a nitrogen-containing polar group and may contain one or more of an amide group and an amine group. When the number of polar groups in the diol monomer containing a polar group is 1 ≤ n ≤ 3, the steric hindrance of the diol monomer is small, facilitating the polymerization reaction with the carboxylic acid monomer and effectively increasing the content of the polar units in the produced polyester base film, thereby improving the surface tension of the polyester base film.

[0050] In some embodiments, the diol monomer containing the nitrogen-containing polar group may be one of a chain shape, a saturated cyclic shape, and an unsaturated cyclic shape, and the unsaturated cyclic shape includes one of a benzene ring and a heterocyclic ring.

[0051] In some embodiments, the diol monomer containing the nitrogen-containing polar group may include one or more of diethanolamine, 3-hydroxy-N-(2-hydroxyethyl) propionamide, 4-amino-1,2-butanediol, 3-dimethylamine-1,2-propanediol, and 3-amino-1,2-propanediol.

[0052] In some embodiments, the weight average molecular weight of the polyester derivative may be 20,000 to 80,000, for example, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, or 80,000, etc., and is not specifically limited.

[0053] In some embodiments, the intrinsic viscosity of the polyester derivative may be 0.5 to 1.2 dL / g, for example, 0.5 dL / g, 0.6 dL / g, 0.7 dL / g, 0.8 dL / g, 0.9 dL / g, 1.0 dL / g, 1.1 dL / g, or 1.2 dL / g, etc., and is not specifically limited.

[0054] In some embodiments, the polyester derivative may be one or more of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer.

[0055] In some embodiments, the polyester derivative may be an alternating copolymer, or a mixture of an alternating copolymer and any one or more of a random copolymer, a block copolymer, and a graft copolymer. When the polyester derivative is an alternating copolymer, the distribution of the functional groups can be made more uniform, which is further advantageous for promoting a strong bond between the polyester-based film and the surface metal layer.

[0056] In some embodiments, the material further includes polyester, and the polyester includes one or more of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. That is, it can be a material for preparing a polyester base film by blending at least one polyester derivative and at least one polyester. In addition, when using a material prepared by blending one polyester derivative and one polyester to prepare a polyester base film, the polyester derivative and the polyester do not have to correspond. For example, when the adopted polyester derivative is a polyethylene terephthalate derivative, the adopted polyester may be a polyester including any one of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0057] In some embodiments, the weight ratio of the polyester derivative to the polyester may be (1 / 9 to 9):1. For example, it may be 1 / 9:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1, etc., and is not specifically limited. In some embodiments, when using a mixture of a polyester derivative and a polyester with a weight ratio of (1 / 9 to 9):1 to prepare a polyester base film, it is advantageous to further improve the surface tension of the polyester base film and does not affect the mechanical properties of the polyester base film.

[0058] The present invention further provides a method for preparing the above-mentioned polyester base film, which includes melt-extruding the material and then biaxially stretching to prepare the polyester base film.

[0059] Note that melt extrusion and biaxial stretching are, that is, the melt extrusion method and the biaxial stretching method commonly used in this field.

[0060] In the present invention, when preparing a polyester-based film using a polyester derivative or a mixture of a polyester derivative and a polyester, the stretching ratio in the MD (machine direction) can reach 1:(3 - 8), the stretching ratio in the TD (transverse direction) can reach 1:(3 - 8), the stretching speed in the MD (machine direction) can reach 30 - 80 times / minute, and the stretching speed in the TD (transverse direction) can reach 50 - 200 times / minute.

[0061] When preparing a polyester-based film using a polyester derivative or a mixture of a polyester derivative and a polyester, it is not necessary to perform post-treatment of polarization of the thin film, which is simple to perform and easy to produce industrially.

[0062] The present invention further provides the use of the above polyester-based film in the preparation of a composite current collector. Using the polyester-based film according to the present invention as a substrate to prepare a composite current collector can effectively solve the problem that the bonding between the polymer thin film and the surface metal layer in the composite current collector is not strong, and can improve the stability of the composite current collector.

[0063] In some embodiments, the following method can be adopted to prepare a composite current collector.

[0064] Composite negative current collector: First, for the preparation of the metal conductive layer, place the polyester-based film in a vacuum evaporation chamber, melt and evaporate high-purity copper wire (purity greater than 99.99%) in the metal evaporation chamber at a high temperature of 1400 - 2000 °C. After evaporation, the metal atoms pass through the cooling system in the vacuum film-forming chamber and are deposited on both surfaces of the polyester-based film to form a copper metal conductive layer with a thickness of 1 μm. Next, for the preparation of the protective layer, 1 g of graphene is uniformly dispersed in 999 g of N-methylpyrrolidone (NMP) solution by ultrasonic dispersion method, and formulated into a coating solution with a solid content of 0.1 wt.%. Then, through the die coating process, the coating solution is uniformly coated on the surface of the metal conductive layer. Here, the coating amount is controlled to 80 μm, and finally dried at 100 °C.

[0065] The present invention further provides a pole piece including the above polyester-based film and an electrode active material located on the polyester-based film.

[0066] The present invention further provides a lithium single cell including the above pole piece.

[0067] The present invention further provides a battery pack including the above lithium single cell.

[0068] The present invention further provides an electric device including the above lithium single cell or battery pack.

[0069] Hereinafter, the polyester-based film according to the present invention, its preparation method and use will be described in detail with reference to specific examples.

[0070] Note that in the following examples, PET refers to polyethylene terephthalate, PBT refers to polybutylene terephthalate, and PEN refers to polyethylene naphthalate.

Examples

[0071] (1) Preparation of a polyester-based film of a composite current collector with high peel strength

[0072] Resin selection: In parts by weight, 2 parts of a PET resin having an intrinsic viscosity of 0.60 dL / g and 8 parts of a PET derivative having an intrinsic viscosity of 0.70 dL / g were selected for blending the materials. Here, the used PET derivative is a random copolymer, and a part of ethylene glycol in the PET derivative is replaced with diethylene glycol, and the molar ratio of diethylene glycol to ethylene glycol is 3:7.

[0073] A polyester-based film was prepared by adopting a process of biaxial stretching after melt extrusion. Stretching process: The stretching ratio in the MD direction was 1:4, and the stretching ratio in the TD direction was 1:6. A biaxially stretched polyester thin film with a final thickness of 8 μm was produced. The stretching strength of the thin film in the MD direction was 200 Mpa, the stretching strength in the TD direction was 180 Mpa, and the elongation at break in both directions was 80% or more.

[0074] (2) A composite current collector was prepared by adopting the preparation method of the composite current collector described above.

Example

[0075] (1) Preparation of a polyester-based film for a composite current collector with high peel strength

[0076] Resin selection: By weight, 9 parts of PBT resin with an intrinsic viscosity of 0.9 dL / g and 1 part of PET derivative with an intrinsic viscosity of 0.55 dL / g were selected for blending the materials. Here, the PET derivative used was a graft copolymer, and a part of ethylene glycol in the PET derivative was replaced with diethanolamine, and the molar ratio of diethanolamine to ethylene glycol was 1:1.

[0077] A polyester-based film was prepared by adopting a process of biaxial stretching after melt extrusion. Stretching process: The stretching ratio in the MD direction was 1:4, and the stretching ratio in the TD direction was 1:6. A biaxially stretched polyester thin film with a final thickness of 8 μm was produced. The stretching strength of the thin film in the MD direction was 300 Mpa, the stretching strength in the TD direction was 280 Mpa, and the elongation at break in both directions was 120% or more.

[0078] (2) A composite current collector was prepared by adopting the preparation method of the composite current collector described above.

Example

[0079] (1) Preparation of a polyester-based film for a composite current collector with high peel strength

[0080] Resin selection: By weight, 1 part of PEN resin with an intrinsic viscosity of 0.7 dL / g, 5 parts of PEN derivative with an intrinsic viscosity of 0.5 dL / g, and 4 parts of PBT derivative with an intrinsic viscosity of 0.9 dL / g were selected for blending the materials. Here, the PEN derivative used was an alternating copolymer, and a part of ethylene glycol in the PEN derivative was replaced with 3-hydroxy-N-(2-hydroxyethyl)propionamide, and the molar ratio of 3-hydroxy-N-(2-hydroxyethyl)propionamide to ethylene glycol was 2:1. The PBT derivative used was a block copolymer, and a part of butanediol in the PBT derivative was replaced with 3-(2-hydroxyethyl)phenyl ethyl alcohol, and the molar ratio of 3-(2-hydroxyethyl)phenyl ethyl alcohol to butanediol was 3:1.

[0081] A polyester-based film was prepared by adopting a process of biaxially stretching after melt extrusion. Stretching process: The stretching ratio in the MD direction was 1:4.5, and the stretching ratio in the TD direction was 1:5. A biaxially stretched polyester thin film with a final thickness of 7.5 μm was produced. The stretching strength in the MD direction of the thin film was 190 Mpa, the stretching strength in the TD direction was 160 Mpa, and the elongation at break in both directions was more than 80%.

[0082] (2) A composite current collector was prepared by adopting the preparation method of the composite current collector described above.

Example

[0083] (1) Preparation of the polyester-based film of the composite current collector with high peel strength

[0084] Resin selection: By weight, 3 parts of a PET derivative with an intrinsic viscosity of 0.8 dL / g, 3 parts of a PEN derivative with an intrinsic viscosity of 0.6 dL / g, and 4 parts of a PBT derivative with an intrinsic viscosity of 1.2 dL / g were selected for blending the materials. Here, the PET derivative used is a random copolymer, a part of ethylene glycol in the PET derivative is replaced by diethylene glycol, and the molar ratio of diethylene glycol to ethylene glycol in the PET derivative is 0.1:1. The PEN derivative used is a graft copolymer, a part of ethylene glycol in the PEN derivative is replaced by diethanolamine, and the molar ratio of diethanolamine to ethylene glycol is 4:1. The PBT derivative used is a block copolymer, a part of butanediol in the PBT derivative is replaced by 3-(2-hydroxyethyl)phenyl ethyl alcohol, and the molar ratio of 3-(2-hydroxyethyl)phenyl ethyl alcohol to butanediol is 2.5:1.

[0085] A polyester-based film was prepared by adopting a process of biaxially stretching after melt extrusion. Stretching process: The stretching ratio in the MD direction was 1:4.5, and the stretching ratio in the TD direction was 1:5. A biaxially stretched polyester thin film with a final thickness of 6 μm was produced. The stretching strength in the MD direction of the thin film was 210 Mpa, the stretching strength in the TD direction was 180 Mpa, and the elongation at break in both directions was 80% or more.

[0086] (2) A composite current collector was prepared by adopting the preparation method of the composite current collector described above.

Example

[0087] (1) Preparation of the polyester-based film of the composite current collector with high peel strength

[0088] Resin selection: In parts by weight, 5 parts of a PET derivative with an intrinsic viscosity of 0.85 dL / g and 5 parts of a PEN derivative with an intrinsic viscosity of 0.85 dL / g were selected for blending the materials. Here, the PET derivative used was a random copolymer, a part of ethylene glycol in the PET derivative was replaced with diethylene glycol, and the molar ratio of diethylene glycol to ethylene glycol in the PET derivative was 0.5:1. The PEN derivative used was a block copolymer, a part of ethylene glycol in the PEN derivative was replaced with diethanolamine, and the molar ratio of diethanolamine to ethylene glycol was 3.5:1.

[0089] A process of biaxial stretching after melt extrusion was adopted to prepare a polyester-based film. Stretching process: The stretching ratio in the MD direction was 1:4.5, and the stretching ratio in the TD direction was 1:5. A biaxially stretched polyester thin film with a final thickness of 5.5 μm was prepared. The stretching strength in the MD direction of the thin film was 250 Mpa, the stretching strength in the TD direction was 220 Mpa, and the elongation at break in both directions was 100% or more.

[0090] (2) A composite current collector was prepared by adopting the preparation method of the composite current collector described above.

Example

[0091] The difference between Example 6 and Example 1 was only that a polyester-based film was prepared using only 10 parts by weight of a PET derivative with an intrinsic viscosity of 0.70 dL / g, and the rest were all the same. The stretching strength in the thin MD direction of the obtained film was 160 Mpa, the stretching strength in the TD direction was 120 Mpa, and the elongation at break in both directions was 100% or more. Comparative Example 1

[0092] The difference between Comparative Example 1 and Example 1 was only that a polyester-based film was prepared using only 10 parts by weight of a PET resin with an intrinsic viscosity of 0.60 dL / g, and the rest were all the same. The stretching strength in the thin MD direction of the obtained film was 200 Mpa, the stretching strength in the TD direction was 180 Mpa, and the elongation at break in both directions was 100% or more. Comparative Example 2

[0093] The difference between Comparative Example 2 and Example 1 lies in that a polyester base film was prepared using only 10 parts by weight of a PET resin with an intrinsic viscosity of 0.60 dL / g, and the polyester base film was prepared by the corona method. The obtained film had a thin MD-direction stretching strength of 200 Mpa, a TD-direction stretching strength of 180 Mpa, and elongation at break in both directions of 100% or more. Comparative Example 3

[0094] The difference between Comparative Example 3 and Example 1 was only that a part of the ethylene glycol in the PET derivative was replaced with diethylene glycol, and the molar ratio of diethylene glycol to ethylene glycol was 0.05:1, and the rest was the same. The obtained film had a thin MD-direction stretching strength of 250 Mpa, a TD-direction stretching strength of 220 Mpa, and elongation at break in both directions of 100% or more. Comparative Example 4

[0095] The difference between Comparative Example 4 and Example 1 was only that a part of the ethylene glycol in the PET derivative was replaced with diethylene glycol, and the molar ratio of diethylene glycol to ethylene glycol was 5:1, and the rest was the same. The obtained film had a thin MD-direction stretching strength of 100 Mpa, a TD-direction stretching strength of 90 Mpa, and elongation at break in both directions of 150% or more, and the mechanical strength was too weak to meet the requirements of the next current collector preparation process.

[0096] Performance Test Surface tension and surface roughness tests were performed on the polyester base films prepared in Examples 1 to 6 and Comparative Examples 1 to 4 using an atomic force microscope, and the results are as shown in Table 1.

[0097]

Table 1

[0098] The adhesion performance of the composite current collectors prepared in Examples 1 to 6 and Comparative Examples 1 to 3 was evaluated. The evaluation method was to attach a 3M Scotch tape (type 600 or 610) with a length of 200 mm and a width of 15 mm to the metal layer on the surface of the composite current collector, and use a roller to roll-press the sample back and forth twice at a speed of 10 mm / s. Then, the tape was peeled off at a speed of 100 mm / min and an angle of 60 degrees. Finally, the area occupancy rate of the metal peeled off by the tape was statistically analyzed. The results are as shown in Table 2.

[0099]

Table 2

[0100] As can be seen from the results in Table 1 and Table 2, the surface tension and surface roughness of the polyester-based films prepared in Examples 1 to 6 were significantly improved, and the storage was stabilized. The adhesion performance between the polyester-based film and the metal layer was significantly improved, and it was more suitable for preparing a composite current collector by vapor-depositing metal on the surface. When a polyester-based film was prepared using at least one kind of polyester derivative, or a mixture of a polyester derivative and a polyester with a weight ratio of (1 / 9 to 9):1 was used to prepare a polyester-based film, and the molar ratio of the original diol monomer not replaced by the diol monomer containing a polar group in the polyester derivative was (0.1 to 4):1, the surface tension and surface roughness of the polyester-based films manufactured by adopting different stretching process parameters were both significantly improved, and the surface tension of the polyester-based film could be stabilized over a long period of time, effectively promoting a strong bond between the polyester-based film and the surface metal layer, and it was clearly shown that it was suitable for the preparation of a composite current collector.

[0101] As can be seen from the results in Tables 1 and 2, in Examples 2 to 5, the raw materials for preparing the polyester-based film include at least one polyester derivative, which is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer having a nitrogen-containing polar group. Therefore, even if the polyester derivative in the polyester-based film is 10% by mass, the prepared polyester-based film can have good surface tension and surface roughness, and the storage is stabilized.

[0102] As can be seen from the results of Examples 1 to 2, Example 6, and Examples 3 to 5, when at least two polyester derivatives are included in the raw materials for preparing the polyester-based film, both the surface tension and surface roughness of the prepared polyester-based film are superior to those of the polyester-based film prepared when one polyester derivative is included in the raw materials. Moreover, the surface tension and surface roughness of the polyester-based film prepared when the raw material is a mixture of one polyester derivative and at least one polyester are superior to those of the polyester-based film prepared when the raw material is only one polyester derivative.

[0103] As can be seen from the results of Example 1, Example 6, and Comparative Examples 1 to 2, when a polyester-based film was prepared using only polyester, both the surface tension and surface roughness of the prepared polyester-based film were poor. Even when a polyester-based film was prepared using polyester as the material in the corona process, the improvement in the surface tension and surface roughness of the prepared polyester-based film was limited, and the surface tension of the polyester-based film could not be stabilized over a long period, and the adhesion performance between the polyester-based film and the metal layer was poor. It was revealed that by using a polyester derivative in which a part of the original diol-based monomer was replaced with a diol-based monomer containing a polar group as the material for preparing the polyester-based film, increasing the polar group content of the polyester-based film, improving the surface tension of the polyester-based film, and enabling the surface tension of the polyester-based film to be stabilized over a long period, a strong bond between the polyester-based film and the surface metal layer could be effectively promoted.

[0104] As can be seen from the results of Example 1, Comparative Example 3, and Comparative Example 4, when the molar ratio of diethylene glycol to ethylene glycol in the PET derivative was 3:7, both the surface tension and surface roughness of the prepared polyester-based film were superior to those of the polyester-based film prepared when the molar ratio of diethylene glycol to ethylene glycol in the PET derivative was 0.05:1. Moreover, the polyester-based film prepared when the molar ratio of diethylene glycol to ethylene glycol in the PET derivative was 5:1 could not further meet the requirements for preparing a current collector, that is, it affected the mechanical performance of the prepared polyester-based film. It was revealed that when the molar ratio of the diol-based monomer containing a polar group to the original diol-based monomer not replaced in the polyester derivative was (0.1 to 4):1, it was advantageous for further improving the surface tension of the prepared polyester-based film and did not affect the mechanical performance of the polyester-based film.

[0105] Each of the technical features of the above-described embodiments can be arbitrarily combined. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should all be considered within the scope described in this specification.

[0106] The above-described embodiments only show some embodiments of the present invention, and their descriptions are relatively specific and detailed. However, it should not be understood that this limits the patent scope of the invention. It should be pointed out that those skilled in the art can also make some modifications and improvements on the premise of not departing from the idea of the present invention, and all of these should be regarded as belonging to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should conform to the scope of the appended claims.

Claims

1. The material of the polyester base film contains a polyester derivative, and the polyester derivative contains a first polyester derivative including one or more of polyethylene terephthalate derivative, polybutylene terephthalate derivative, and polyethylene naphthalate derivative. The first polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing a nitrogen-containing polar group, and the nitrogen-containing polar group contains one or more of an amide group and an amine group. A polyester base film.

2. The molar ratio of the original diol-based monomer not replaced by the diol-based monomer containing a nitrogen-containing polar group in the first polyester derivative is (0.1 to 4):

1. The polyester base film according to Claim 1, characterized in that.

3. The number of nitrogen-containing polar groups in the diol-based monomer containing a nitrogen-containing polar group is n, and 1 ≤ n ≤ 3. The polyester base film according to Claim 1, characterized in that.

4. The diol-based monomer containing a nitrogen-containing polar group is one of a chain shape, a saturated cyclic shape, and an unsaturated cyclic shape, and the unsaturated cyclic shape contains one of a benzene ring and a heterocyclic ring. The polyester base film according to Claim 1, characterized in that.

5. The diol-based monomer containing a nitrogen-containing polar group contains one or more of diethanolamine, 3-hydroxy-N-(2-hydroxyethyl)propionamide, 4-amino-1,2-butanediol, 3-dimethylamine-1,2-propanediol, and 3-amino-1,2-propanediol. The polyester base film according to any one of Claims 1 to 4, characterized in that.

6. The weight average molecular weight of the polyester derivative is 20,000 to 80,000, and / or the intrinsic viscosity is 0.5 to 1.2 dL / g. The polyester base film according to Claim 1, characterized in that.

7. The polyester derivative is one or more of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer. Preferably, the polyester derivative is an alternating copolymer, or a mixture of an alternating copolymer and one or more of a random copolymer, a block copolymer, and a graft copolymer. The polyester-based film according to claim 1, characterized in that...

8. The polyester derivative further includes a second polyester derivative containing one or more of polyethylene terephthalate derivative, polybutylene terephthalate derivative, and polyethylene naphthalate derivative, The second polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing one or more polar groups selected from an etheroxy group, a carboxyl group, and a phenolic hydroxyl group. The polyester-based film according to claim 1, characterized in that...

9. The second polyester derivative is a derivative obtained by replacing a part of the original diol-based monomer in the corresponding polyester with a diol-based monomer containing one or more polar groups selected from diethylene glycol and 3-(2-hydroxyethyl)phenyl ethyl alcohol. The polyester-based film according to claim 8, characterized in that...

10. The mass of the polyester derivative in the polyester-based film is 10 wt% to 100 wt% of the polyester-based film, The polyester-based film according to any one of claims 1 to 9, characterized in that...

11. The material of the polyester-based film further includes polyester, and the polyester includes one or more of polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. The polyester-based film according to any one of claims 1 to 9, characterized in that...

12. The weight ratio of the polyester derivative to the polyester is (1 / 9 to 9):

1. The polyester-based film according to claim 11, characterized in that...

13. A method for preparing a polyester-based film according to any one of claims 1 to 12, which includes melt-extruding the material and then biaxially stretching to produce a polyester-based film. A method for preparing a polyester-based film.

14. Use of the polyester-based film according to any one of claims 1 to 12 in the preparation of a composite current collector.

15. A polyester base film according to any one of claims 1 to 12, and an electrode active material located on the polyester base film, characterized by a pole piece.

16. Including the pole piece according to claim 15, characterized by a lithium single cell.

17. Including the lithium single cell according to claim 16, characterized by a battery pack.

18. Including the lithium single cell according to claim 17 or the battery pack according to claim 17, characterized by an electrical device.

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