Composite current collector and preparation method thereof, electrode plate, battery and power utilization device

Abstract

The invention relates to the technical field of composite current collectors, in particular to a composite current collector and a preparation method thereof, an electrode plate, a battery and an electric device, and the composite current collector comprises a polyester matrix layer and a conductive layer arranged on at least one surface of the polyester matrix layer; the polyester matrix layer is prepared from the following components in parts by mass: 40 to 65 parts of polyester, 20 to 50 parts of metal material, 5 to 15 parts of filler, 3 to 8 parts of compatilizer, 0.5 to 3 parts of hydrolysis stabilizer and 0.1 to 1 part of antioxidant; the hydrolysis stabilizer comprises an oligomer containing an epoxy group and an oligomer containing a carbodiimide group. According to the composite current collector provided by the invention, the binding force between the base material and the conductive layer is improved, the hydrolytic degradation process of the polyester matrix layer in an electrolyte environment is inhibited, and the mechanical property of the composite current collector is improved.

Description

Technical Field

[0001] This application relates to the field of composite current collector technology, and in particular to composite current collectors and their preparation methods, electrode sheets, batteries and electrical devices. Background Technology

[0002] Current collectors are a crucial component of batteries, responsible for collecting and transmitting current. Traditional current collectors include metal foil and composite current collectors. Composite current collectors have a multi-layered structure with a polyester film as the substrate and metal layers plated on both sides. Although composite current collectors have advantages over traditional metal foils, such as lighter weight, higher mechanical strength, stronger heat resistance, and better internal insulation, the polyester film contains ester bonds, which makes it prone to hydrolytic degradation during long-term battery use, especially in high-temperature electrolyte environments containing trace amounts of moisture. This leads to a sharp decline in the mechanical properties of the substrate, causing composite current collector failure and posing a battery safety hazard. Furthermore, the bonding force between the polyester film and the metal layers is relatively weak, making them prone to interlayer delamination during long-term battery cycling, especially under electrolyte immersion, resulting in increased internal resistance or even battery failure. Summary of the Invention

[0003] Based on this, this application provides a composite current collector and its preparation method, electrode sheet, battery and power device, which improves the bonding force between the substrate and the conductive layer, inhibits the hydrolytic degradation process of the polyester matrix layer in the electrolyte environment, and improves the mechanical properties of the composite current collector.

[0004] The first aspect of this application provides a composite current collector, comprising a polyester matrix layer and a conductive layer disposed on at least one surface of the polyester matrix layer; the polyester matrix layer comprises the following components in parts by weight: 40 to 65 parts of polyester, 20 to 50 parts of metal material, 5 to 15 parts of filler, 3 to 8 parts of compatibilizer, 0.5 to 3 parts of hydrolysis stabilizer, and 0.1 to 1 part of antioxidant; the hydrolysis stabilizer comprises oligomers containing epoxy groups and oligomers containing carbodiimide groups.

[0005] In some embodiments, the metal material satisfies at least one of the following conditions: (1) the metal material includes at least one of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy; (2) the metal material is in the form of flakes or dendrites; (3) the particle size D50 of the metal material is 1 μm to 15 μm.

[0006] In some embodiments, the filler satisfies at least one of the following conditions: (1) the filler includes at least one of mica, boron nitride, talc, boehmite, zirconium oxide, alumina and magnesium oxide; (2) the filler is in the form of flakes; (3) the particle size D50 of the filler is 0.5 μm to 5 μm; (4) the oil absorption value of the filler is 20 mL / 100g to 80 mL / 100g.

[0007] In some embodiments, the compatibilizer satisfies at least one of the following conditions: (1) the compatibilizer is a copolymer of an olefin monomer, an acrylate monomer and glycidyl methacrylate; (2) the epoxy equivalent of the compatibilizer is 400 g / mol to 600 g / mol; (3) the melt index of the compatibilizer is 5 g / 10 min to 15 g / 10 min; (4) the glass transition temperature of the compatibilizer is -5 °C to 5 °C; (5) the glycidyl methacrylate content of the compatibilizer is 6 wt% to 10 wt%; (6) the melting point of the compatibilizer is 60 °C to 80 °C.

[0008] In some embodiments, the hydrolytic stabilizer satisfies at least one of the following conditions: (1) the mass ratio of the oligomer containing epoxy groups to the oligomer containing carbodiimide groups is (1~3):1; (2) the epoxy equivalent of the oligomer containing epoxy groups is 400 g / mol~600 g / mol; (3) the molecular weight of the oligomer containing carbodiimide groups is 2000 g / mol~5000 g / mol.

[0009] The second aspect of this application provides a method for preparing a composite current collector as provided in the first aspect of this application, comprising the following steps: mixing polyester, metal material, filler, compatibilizer, hydrolytic stabilizer and antioxidant to prepare a mixture; melting and kneading the mixture under a protective atmosphere, extruding it, and then performing a film-forming treatment to prepare a polyester matrix layer; placing a conductive layer on at least one surface of the polyester matrix layer and performing a pressing treatment to prepare a composite current collector.

[0010] In some embodiments, the composite current collector satisfies at least one of the following conditions: (1) the moisture content of the polyester and the filler is independently less than 0.02%; (2) the melt mixing temperature is 260°C to 290°C.

[0011] The third aspect of this application provides an electrode sheet, including the composite current collector provided in the first aspect of this application or the composite current collector prepared by the preparation method provided in the second aspect of this application.

[0012] A fourth aspect of this application provides a battery including the electrode plates provided in the third aspect of this application.

[0013] The fifth aspect of this application provides an electrical device, including the battery provided in the fourth aspect of this application.

[0014] Compared with traditional technologies, this application has the following advantages:

[0015] This application constructs a synergistic system composed of hydrolysis stabilizers, fillers, and compatibilizers in the polyester matrix layer. This system works synergistically from three levels: chemical inhibition of hydrolysis, physical barrier to penetration, and interfacial reinforcement, ensuring that the composite current collector maintains excellent mechanical strength, stable interfacial structure, and long service life even under long-term electrolyte immersion.

[0016] The synergistic effect is as follows: By introducing a hydrolysis stabilizer into the polyester matrix layer, and further through the synergistic effect of oligomers containing epoxy groups and oligomers containing carbodiimide groups, active groups generated by trace moisture intrusion can be actively captured and neutralized. This chemically inhibits the hydrolytic breakage of polyester molecular chains, thereby suppressing the hydrolytic degradation process of polyester in the electrolyte environment, improving the mechanical strength of the polyester matrix layer, and extending the service life of the composite current collector. Furthermore, by introducing fillers into the polyester matrix layer, a physical barrier network is constructed within the polyester matrix, effectively blocking the penetration and diffusion paths of the electrolyte, improving the electrolyte corrosion resistance of the composite current collector, and providing a longer time and a more favorable internal environment for the hydrolysis stabilizer to function. Furthermore, by introducing a compatibilizer into the polyester matrix layer, the highly reactive compatibilizer undergoes an efficient ring-opening reaction with the polyester end groups (-COOH or -OH) to form strong covalent bonds, enhancing the interfacial bonding between the polyester matrix and the conductive layer and reducing the risk of interlayer delamination under electrolyte wetting. At the same time, the high reactivity helps to quickly form a stable interface during processing, improving product durability. Meanwhile, the stable interfacial bonding protects the edges of the matrix layer, reducing the possibility of electrolyte intrusion from weak points in the interface. This, combined with the hydrolysis inhibition and physical barrier effects inside the matrix, jointly improves the overall durability of the composite current collector. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the composite current collector in one embodiment of this application.

[0019] Figure 2 This is a flowchart of the preparation method of the composite current collector in one embodiment of this application.

[0020] Figure 3 This is a SEM image of the sheet-like boron nitride filler in one embodiment of this application.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Composite current collector; 10. Conductive layer; 20. Polyester matrix layer. Detailed Implementation

[0023] A detailed reference is now provided to embodiments of this application, one or more of which are described below. Each embodiment is provided for explanation and not for limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0024] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0025] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0026] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] In this article, when referring to units of data ranges, if a unit is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0028] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0029] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0030] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0031] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0032] In order to overcome the technical problems of traditional metal foil current collectors being heavy and prone to internal short circuits during battery thermal runaway, multilayer composite current collectors have emerged. Specifically, a polyester layer is used as the substrate, and metal layers are plated on both sides of it. However, although this multilayer composite current collector reduces weight and has a certain short-circuit resistance, it still has the following problems: (1) Weak interfacial bonding: The bonding force between the polyester layer and the conductive layer is insufficient. During long-term battery cycling, especially under electrolyte immersion, interlayer delamination is prone to occur, leading to increased battery internal resistance or even failure. (2) Poor high temperature / high humidity / electrolyte resistance: The polyester substrate layer is prone to swelling and hydrolysis in high-temperature electrolyte environment, resulting in a decrease in the mechanical properties of the composite current collector and dimensional instability. (3) Complex process: Usually, it is necessary to prepare the polyester substrate layer first, and then carry out multiple processes such as magnetron sputtering and electroplating, which is costly and inefficient.

[0033] To address the aforementioned technical problems, a first aspect of this application provides a composite current collector, comprising a polyester matrix layer and a conductive layer disposed on at least one surface of the polyester matrix layer. The polyester matrix layer comprises the following components in parts by weight: 40 to 65 parts polyester, 20 to 50 parts metallic material, 5 to 15 parts filler, 3 to 8 parts compatibilizer, 0.5 to 3 parts hydrolytic stabilizer, and 0.1 to 1 part antioxidant; the hydrolytic stabilizer includes oligomers containing epoxy groups and oligomers containing carbodiimide groups.

[0034] In this application, polyester refers to polyethylene terephthalate (PET).

[0035] This application constructs a synergistic system composed of hydrolysis stabilizers, fillers, and compatibilizers in the polyester matrix layer. This system works synergistically from three levels: chemical inhibition of hydrolysis, physical barrier to penetration, and interfacial reinforcement, ensuring that the composite current collector maintains excellent mechanical strength, stable interfacial structure, and long service life even under long-term electrolyte immersion.

[0036] The synergistic effect is as follows: By introducing a hydrolysis stabilizer into the polyester matrix layer, and further through the synergistic effect of oligomers containing epoxy groups and oligomers containing carbodiimide groups, active groups generated by trace moisture intrusion can be actively captured and neutralized. This chemically inhibits the hydrolytic breakage of polyester molecular chains, thereby suppressing the hydrolytic degradation process of polyester in the electrolyte environment, improving the mechanical strength of the polyester matrix layer, and extending the service life of the composite current collector. Furthermore, by introducing fillers into the polyester matrix layer, a physical barrier network is constructed within the polyester matrix, effectively blocking the penetration and diffusion paths of the electrolyte, improving the electrolyte corrosion resistance of the composite current collector, and providing a longer time and a more favorable internal environment for the hydrolysis stabilizer to function. Furthermore, by introducing a compatibilizer into the polyester matrix layer, the highly reactive compatibilizer undergoes an efficient ring-opening reaction with the polyester end groups (-COOH or -OH) to form strong covalent bonds, enhancing the interfacial bonding between the polyester matrix and the conductive layer and reducing the risk of interlayer delamination under electrolyte wetting. At the same time, the high reactivity helps to quickly form a stable interface during processing, improving product durability. Meanwhile, the stable interfacial bonding protects the edges of the matrix layer, reducing the possibility of electrolyte intrusion from weak points in the interface. This, combined with the hydrolysis inhibition and physical barrier effects inside the matrix, jointly improves the overall durability of the composite current collector.

[0037] The synergistic effect of oligomers containing epoxy groups and oligomers containing carbodiimide groups in hydrolysis stabilizers is as follows: Oligomers containing carbodiimide groups can rapidly neutralize the carboxylic acid (the carboxylic acid terminal groups generated after the self-hydrolysis of PET polymer chains) that initiates autocatalysis. They can efficiently remove carboxylic acid in the early and middle stages of hydrolysis, prevent the continuous breakage of polyester molecular chains, and maintain the initial strength and modulus of polyester materials. Their carbodiimide groups (-N=C=N-) react rapidly with the carboxylic acid generated by polyester hydrolysis to generate acylurea, which terminates the chain reaction of polyester autocatalytic hydrolysis. However, when oligomers containing carbodiimide groups are used alone as hydrolysis stabilizers, their protective effect rapidly decreases once they are depleted. Therefore, introducing oligomers containing epoxy groups repairs broken molecular chains and capsulates active groups. The epoxy groups react with the carboxylic acids and hydroxyl groups produced by hydrolysis, reconnecting the broken molecular chains (chain extension) and capping them, preventing further hydrolysis. This provides continuous protection throughout the entire lifespan, preventing and repairing some of the damage to the molecular chains. Through chain extension, it partially restores the molecular weight lost due to hydrolysis, significantly improving the material's toughness retention rate (such as elongation at break). However, if oligomers containing epoxy groups are used alone as hydrolysis stabilizers, their ability to rapidly neutralize the large amounts of carboxylic acids produced is weak. Therefore, this application achieves a multi-layered protective effect through the synergistic effect of the combination of both, covering the entire lifespan from processing and storage to long-term use. This allows the composite current collector to maintain its strength and flexibility even after undergoing severe aging, avoiding brittle fracture and improving cyclic mechanical stability and interfacial stability.

[0038] Furthermore, this application also obtains a composite current collector with excellent comprehensive performance by using the components within the above-mentioned specific mass range, as follows: 1) The polyester used in this system within the above-mentioned mass range provides the necessary mechanical strength and molding ability while ensuring the conductivity and functionality of the composite current collector. Less than 40 parts by mass of polyester cannot completely encapsulate the copper powder and filler, resulting in poor film formation and failing to meet the basic requirements of the composite current collector for the mechanical properties of the substrate; if the amount of polyester is higher than 65 parts by mass, it may lead to a reduction in the amount of metal material added in the system, thereby resulting in insufficient conductivity of the composite current collector; at the same time, the content of filler will also be limited, affecting the electrolyte resistance performance. 2) The lower limit of the amount of the metal material mentioned above in this application is the minimum requirement for the composite current collector to achieve current collection and transmission. Less than 20 parts by mass of metal material will prevent the formation of a continuous conductive path in the base film; more than 50 parts by mass of metal material may result in too little polyester matrix, and the base film will tend to have the rigidity of metal, making the composite base film brittle and hard, with a significant decrease in elongation at break, making it easy to break when the battery is bent or impacted. At the same time, excessive metal content will also increase cost and weight. Therefore, the use of metal material within the above mass range in this system can make the base film have a very dense conductive network, while maintaining the good flexibility and processability of the base film. 3) In this application, fillers in the polyester matrix layer of less than 5 parts by weight will prevent the base film from forming a continuous and tortuous permeation barrier, allowing small electrolyte molecules to penetrate relatively directly. Fillers in more than 15 parts by weight will first cause a sharp increase in melt viscosity, resulting in poor processing fluidity and difficulty in casting into a film. Secondly, excessive fillers will disrupt the continuity of the polymer matrix, becoming stress concentration points, leading to material embrittlement and decreased mechanical properties. They may also introduce defects due to filler agglomeration. 4) Compatibilizers have the function of enhancing interfacial bonding, improving dispersibility, and optimizing processing fluidity. Their epoxy groups react with PET end groups to form covalent bonds, significantly improving the adhesion between the metal layer and the base film, and promoting the uniform dispersion of metal materials and fillers in the matrix, avoiding agglomeration. Fillers in less than 3 parts by weight are prone to insufficient interfacial bonding, while fillers in more than 3 parts by weight may lead to excessive cross-linking and increased brittleness of the base film.

[0039] The composite current collector provided in this application can effectively suppress dendrite growth and reduce the risk of battery thermal runaway.

[0040] In one specific implementation, such as Figure 1 As shown, the composite current collector 1 includes a polyester matrix layer 20 and a conductive layer 10 disposed on one side surface of the polyester matrix layer 20.

[0041] In some embodiments, the intrinsic viscosity of the polyester is 0.75 dL / g to 0.85 dL / g. Polyesters within this intrinsic viscosity range have sufficient molecular weight, high tensile strength, modulus and toughness, and can withstand mechanical stresses such as rolling and cutting during battery manufacturing. At the same time, they can play a better buffering role in maintaining performance in environments that are prone to hydrolysis and degradation.

[0042] In some embodiments, the metallic material includes at least one selected from copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Further, the metallic material is copper or aluminum.

[0043] In some embodiments, the metal material is in the form of sheets or dendrites. Using sheet-like or dendritic metal materials promotes the formation of a conductive network and enhances the anchoring effect at the metal-polyester interface, preventing the metal material from detaching.

[0044] It should be noted that, in this application, "dendritic" refers to a shape in which branches of a certain aspect ratio extend from a main structure with a certain aspect ratio in different directions. These branches can be linear extensions or structures that bend midway; they can be first-level branches or multi-level branches, for example, a branch is a second-level branch obtained by further extending a secondary branch from a first-level branch.

[0045] In some embodiments, the particle size D50 of the metallic material is 1μm to 15μm, including but not limited to 1μm, 3μm, 5μm, 7μm, 10μm, 12μm, and 15μm.

[0046] It should be noted that in this application, "particle size" refers to the equivalent sphere diameter, that is, the diameter of a sphere with the same volume as the given material; "particle size D50" refers to the volume-based median particle size.

[0047] In some embodiments, the filler includes at least one of mica, boron nitride, talc, boehmite (γ-AlOOH), zirconium oxide, alumina (e.g., α-alumina), and magnesium oxide. Further, the filler includes at least one of mica, boron nitride, and talc.

[0048] In some embodiments, the filler is sheet-like. By introducing sheet-like fillers into the polyester matrix layer 20, the sheet-like fillers are arranged in parallel within the matrix layer, forming multiple physical barriers. Small electrolyte molecules (such as solvents, ions, or trace amounts of water) must bypass these multiple physical barriers to penetrate into the interior of the polyester matrix layer 20. The penetration path is tortuous and long, effectively blocking the penetration of the electrolyte. Figure 3 The image shown is a SEM image of the plate-shaped boron nitride filler.

[0049] In some embodiments, the particle size D50 of the filler is 0.5μm to 5μm, including but not limited to 0.5μm, 1μm, 2μm, 3μm, 4μm, and 5μm.

[0050] In some embodiments, the oil absorption value of the filler is 20mL / 100g to 80mL / 100g, including but not limited to 20mL / 100g, 40mL / 100g, 60mL / 100g, and 80mL / 100g.

[0051] This application uses fillers within the aforementioned particle size and oil absorption value ranges. The fillers have good fluidity, which improves the electrolyte corrosion resistance of the polyester matrix layer 20 while ensuring process feasibility (processing performance) and reducing raw material costs.

[0052] In some embodiments, the compatibilizer is a copolymer of olefin monomers, acrylate monomers, and glycidyl methacrylate. The epoxy functional groups in the compatibilizer react with the end groups in the polyester material to form a strong interfacial bonding effect.

[0053] Among them, olefin monomers include at least one of ethylene, propylene, butene, octene, styrene, and methylstyrene.

[0054] Acrylic ester monomers include at least one of methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, allyl methacrylate, allyl acrylate, 2-hydroxybutyl acrylate, and 2-hydroxybutyl methacrylate.

[0055] In some embodiments, the epoxy equivalent (EEW, grams required per mole of epoxy group) of the compatibilizer is 400 g / mol to 600 g / mol, including but not limited to 400 g / mol, 500 g / mol, and 600 g / mol. By selecting a compatibilizer within this epoxy equivalent range, the compatibilizer can provide more reaction sites at the same dosage, undergoing an efficient ring-opening reaction with the end groups (-COOH or -OH) of the polyester material to form strong covalent bonds, enhancing the interfacial bonding between the polyester matrix and the conductive layer 10, and reducing the risk of interlayer delamination under electrolyte wetting; at the same time, high reactivity helps to quickly form a stable interface during processing, improving product durability.

[0056] In some embodiments, the melt flow index (MFI) of the compatibilizer is 5 g / 10 min to 15 g / 10 min, including but not limited to 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, and 15 g / 10 min. By selecting a compatibilizer within this melt flow index range, excellent flowability and dispersibility are ensured during extrusion and film formation. An excessively low MFI can lead to uneven dispersion and affect interfacial bonding; an excessively high MFI may cause migration to the surface, reducing overall performance. At the same time, a compatibilizer within this melt flow index range can uniformly coat the metal material and filler to form a continuous phase, improving the mechanical strength and conductive network stability of the polyester matrix layer 20.

[0057] In some embodiments, the compatibilizer has a glass transition temperature (Tg) of -5°C to 5°C, including but not limited to -5°C, 0°C, 2°C, and 5°C. By selecting a compatibilizer within this Tg range, the polyester matrix layer 20 remains flexible within the battery operating temperature range, absorbs stress changes during charging and discharging, reduces the risk of brittle fracture, and improves the toughness and dimensional stability of the composite current collector 1. In particular, it avoids interfacial failure caused by thermal cycling in high-temperature electrolyte environments.

[0058] In some embodiments, the compatibilizer contains 6 wt% to 10 wt% glycidyl methacrylate (GMA), including but not limited to 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%. Selecting a compatibilizer with GMA content within this range not only provides sufficient reactivity for crosslinking with polyester end groups, but also avoids processing difficulties or matrix embrittlement caused by excessive crosslinking, thereby improving interfacial adhesion and molding stability.

[0059] In some embodiments, the melting point of the compatibilizer is 60°C to 80°C, including but not limited to 60°C, 70°C, and 80°C. By selecting a compatibilizer within the above melting point range, the melting point of the compatibilizer is lower than the processing temperature of the polyester material, ensuring that the compatibilizer can flow and react sufficiently during melt blending.

[0060] In some embodiments, the compatibilizer includes at least one of Lotader® AX8900, Lotader® AX8840, and Dow / DuPont’s Elvaloy® PTW.

[0061] In some embodiments, the mass ratio of the epoxy-containing oligomer to the carbodiimide-containing oligomer in the hydrolytic stabilizer is (1~3):1, including but not limited to 1:1, 2:1, and 3:1. By setting the mass ratio of the epoxy-containing oligomer to the carbodiimide-containing oligomer within the above range, a seamless connection between the two mechanisms of carboxylic acid removal and molecular chain repair is ensured, thus constructing full life-cycle protection from material processing to the end of its service life. Simultaneously, the most effective concentration of the hydrolytic stabilizer can be maintained at different stages of the aging process, avoiding the poor protective effect caused by using a single hydrolytic stabilizer.

[0062] In some embodiments, the epoxy equivalent of the oligomer containing epoxy groups is 400 g / mol to 600 g / mol, including but not limited to 400 g / mol, 500 g / mol, and 600 g / mol. This epoxy equivalent range ensures good compatibility and low migration in polyester materials.

[0063] In some embodiments, the oligomer containing epoxy groups includes at least one of Clariant CESA-nord, Clariant CESA-extend, Arkema Biostrength®, BASF Joncryl® ADR-4368, and BADGE type epoxy resin (bisphenol A diglycidyl ether).

[0064] In some embodiments, the oligomers containing carbodiimide groups have a molecular weight of 2000 g / mol to 5000 g / mol, including but not limited to 2000 g / mol, 3000 g / mol, 4000 g / mol, and 5000 g / mol. Oligomers containing carbodiimide groups at this molecular weight ensure good compatibility and durability in polyester materials, and are less prone to precipitation or volatilization during processing and use, thus achieving long-term protection.

[0065] In some embodiments, the oligomer containing carbodiimide groups includes at least one of Stabaxol P, Stabaxol P-100, Stabaxol KE, Addocat 503, and Carbodilite LA-1.

[0066] In some embodiments, the antioxidant includes at least one of Irganox 1010, Irganox 1076, Irganox 1330, Irgafos 168, and Irgafos 126.

[0067] In some embodiments, the polyester matrix layer 20 further includes 0.5 to 2 parts of additives. The type of additive is not particularly limited in this application. Any known additive suitable for the polyester matrix layer 20 can be used in this application without departing from the overall inventive concept. The following is merely an example: the polyester matrix layer 20 also includes a lubricating dispersant, such as ethylene bis-stearamide (EBS).

[0068] like Figure 2 As shown, the second aspect of this application provides a method for preparing the composite current collector 1 as provided in the first aspect of this application, comprising the following steps:

[0069] S1. Mix polyester, metal materials, fillers, compatibilizers, hydrolytic stabilizers and antioxidants to prepare a mixture.

[0070] S2. Under a protective atmosphere, the mixture is melt-blended, extruded, and then film-formed to prepare the polyester matrix layer 20.

[0071] S3. The conductive layer 10 is placed on at least one side surface of the polyester matrix layer 20 and pressed to prepare the composite current collector 1.

[0072] In some embodiments, the step S1 above is further included: vacuum drying the polyester and filler to make the moisture content of the polyester and filler each independently below 0.02%.

[0073] Furthermore, the vacuum drying temperature is 120℃~140℃, including but not limited to 120℃, 130℃, and 140℃.

[0074] The vacuum drying time is 4h to 6h, including but not limited to 4h, 5h, and 6h.

[0075] In some embodiments, the melt-blending temperature is 260°C to 290°C, including but not limited to 260°C, 270°C, 280°C, and 290°C. Further, the temperature is 270°C to 285°C.

[0076] In one specific embodiment, S2 is as follows: under a nitrogen atmosphere, the mixture is melt-blended at 260°C to 290°C using a twin-screw extruder, and then cast into a film using a T-die or calendered into a film using a calender to prepare a polyester matrix layer 20.

[0077] In some embodiments, in S3 above, a hot press roller is used for pressing.

[0078] In some implementations, a winding step is included after S3.

[0079] This application overcomes the problems of easy hydrolysis of polyester during high-temperature processing and easy oxidation of metal materials through the above-mentioned material formulation and preparation process, and achieves stable production.

[0080] The third aspect of this application provides an electrode sheet, including the composite current collector 1 provided in the first aspect of this application or the composite current collector 1 prepared by the preparation method provided in the second aspect of this application.

[0081] A fourth aspect of this application provides a battery including the electrode plates provided in the third aspect of this application.

[0082] The fifth aspect of this application provides an electrical device, including the battery provided in the fourth aspect of this application.

[0083] Furthermore, this application provides the following specific embodiments and comparative examples to further illustrate the specific implementation of this application and its advantages.

[0084] Unless otherwise specified, the raw materials used in the following specific embodiments and comparative examples are all commercially available products; the instruments used are all commercially available products; and the processes used are all conventionally selected by those skilled in the art unless otherwise specified.

[0085] Example 1

[0086] Raw material preparation: 50 parts polyester, 35 parts flake copper (D50 of 6μm), 8 parts flake boron nitride (D50 of 5μm), 5 parts Lotader® AX8900, 1.5 parts hydrolytic stabilizer (bisphenol A diglycidyl ether and Stabaxol P in a mass ratio of 2:1) and 0.5 parts Irganox 1010.

[0087] The polyester and sheet boron nitride were vacuum dried at 130°C for 5 hours.

[0088] The above raw materials are mixed in a high-speed mixer for 15 minutes to prepare a mixture; under a nitrogen atmosphere, the mixture is melt-mixed and extruded through a twin-screw extruder at 270°C, and cast into a film to prepare a polyester matrix layer 20; before cooling and shaping, the two sides of the polyester matrix layer 20 are respectively bonded to 1μm thick electrolytic copper foil through hot press rollers (pressure 5MPa, temperature 100°C), cooled and wound up to obtain a composite current collector 1.

[0089] Example 2

[0090] The preparation methods of Example 2 and Example 1 are basically the same. The main difference is in the preparation of raw materials in this example: 40 parts of polyester, 38 parts of dendritic copper (D50 is 1 μm), 15 parts of flaky mica (D50 is 2 μm), 3 parts of Lotader® AX8900, 3 parts of hydrolytic stabilizer (the mass ratio of bisphenol A diglycidyl ether and Stabaxol P is 2:1) and 1 part of Irganox 1010.

[0091] Example 3

[0092] The preparation methods of this embodiment are basically the same as those of Example 1. The main difference is in the preparation of raw materials in this embodiment: 65 parts of polyester, 20 parts of flake copper (D50 is 15 μm), 6.4 parts of flake boron nitride (D50 is 5 μm), 8 parts of Lotader® AX8900, 0.5 parts of hydrolytic stabilizer (the mass ratio of bisphenol A diglycidyl ether and Stabaxol P is 2:1) and 0.1 parts of Irganox 1010.

[0093] Example 4

[0094] The preparation methods of this embodiment are basically the same as those of Example 1. The main difference is that the mass ratio of bisphenol A diglycidyl ether and Stabaxol P in this embodiment is 1:1.

[0095] Example 5

[0096] The preparation methods of this embodiment are basically the same as those of Example 1. The main difference is that the mass ratio of bisphenol A diglycidyl ether to Stabaxol P in this embodiment is 3:1.

[0097] Example 6

[0098] The preparation methods of this embodiment are basically the same as those of Example 1. The main difference is that the mass ratio of bisphenol A diglycidyl ether and Stabaxol P in this embodiment is 1:2.

[0099] Example 7

[0100] The preparation methods of this embodiment are basically the same as those of Example 1. The main difference is that the mass ratio of bisphenol A diglycidyl ether to Stabaxol P in this embodiment is 4:1.

[0101] Example 8

[0102] The preparation method of this embodiment is basically the same as that of Example 1. The main difference is that this embodiment also includes 1 part of the lubricating dispersant ethylene bis-stearamide and 49 parts by weight of polyester.

[0103] Example 9

[0104] The preparation methods of this embodiment are basically the same as those of Example 1. The main difference is that the compatibilizer in Example 1 is replaced with maleic anhydride-grafted polypropylene (PP-g-MAH, BONDINE® LX 4110) in this embodiment.

[0105] Comparative Example 1

[0106] The preparation method of this comparative example is basically the same as that of Example 1. The main difference is that no hydrolytic stabilizer was added in this comparative example, and the polyester content was 51.5 parts by weight.

[0107] Comparative Example 2

[0108] The preparation method of this comparative example is basically the same as that of Example 1. The main difference is that the hydrolysis stabilizer in this comparative example is 1.5 parts of bisphenol A diglycidyl ether.

[0109] Comparative Example 3

[0110] The preparation method of this comparative example is basically the same as that of Example 1, the main difference being that the hydrolysis stabilizer in this comparative example is 1.5 parts of Stabaxol P.

[0111] Test case

[0112] (1) The initial elongation at break (%) (elongation at break before hydrolysis aging test) of the composite current collector 1 prepared in the above examples and comparative examples was measured in accordance with GB / T 5230-2020. The results are shown in Table 1 below.

[0113] (2) The composite current collector 1 prepared in the above examples and comparative examples was aged at 85℃ / 85%RH for 500h. The elongation at break after hydrolysis aging was measured (%) (tested according to GB / T 5230-2020), and the elongation at break retention rate (%) was calculated as (elongation at break after aging test / initial elongation at break) × 100%. The results are shown in Table 1 below.

[0114] (3) The composite current collector 1 prepared in the above examples and comparative examples was immersed in an electrolyte at 65°C for 10 days. The copper layer peeling phenomenon was observed and the peel strength (KN / m) after immersion in the electrolyte was measured (tested according to GB / T 2792-2014). The results are shown in Table 2 below.

[0115] The electrolyte comprises 30% EC, 50% EMC, 4.5% VC, 15% LiPF6, and 0.5% water by mass.

[0116] Table 1

[0117]

[0118] Table 2

[0119]

[0120] As can be seen from the comparison between Example 1 and Comparative Examples 1-3, compared with material formulations that do not introduce hydrolytic stabilizers or only introduce a single stabilizer, the hydrolytic stabilizer of the compound system provided in this application significantly improves the elongation at break retention rate of the prepared composite current collector 1 in the aging test at 85℃ / 85%RH for 500 hours, and significantly improves the interfacial stability between the polyester matrix layer 20 and the conductive layer 10. This is because the polyester material is protected by the compound hydrolytic stabilizer, making the bonding interface between the polyester matrix layer 20 and the conductive layer 10 more stable. At the same time, as can be seen from Table 2, the composite current collector 1 provided in this application still has interlayer peel strength after being immersed in electrolyte under strict conditions.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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 be considered to be within the scope of this specification.

[0122] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A composite current collector, characterized in that, It includes a polyester matrix layer and a conductive layer disposed on at least one surface of the polyester matrix layer; The polyester matrix layer comprises the following components in parts by weight: 40 to 65 parts polyester, 20 to 50 parts metal material, 5 to 15 parts filler, 3 to 8 parts compatibilizer, 0.5 to 3 parts hydrolytic stabilizer, and 0.1 to 1 part antioxidant. The hydrolysis stabilizer includes oligomers containing epoxy groups and oligomers containing carbodiimide groups.

2. The composite current collector according to claim 1, characterized in that, The metallic material satisfies at least one of the following conditions: (1) The metallic material includes at least one of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy; (2) The metal material is in the form of sheets or dendrites; (3) The particle size D50 of the metal material is 1μm~15μm.

3. The composite current collector according to claim 1, characterized in that, The packing material satisfies at least one of the following conditions: (1) The filler includes at least one of mica, boron nitride, talc, boehmite, zirconium oxide, alumina and magnesium oxide; (2) The filler is in the form of flakes; (3) The particle size D50 of the filler is 0.5μm~5μm; (4) The oil absorption value of the filler is 20mL / 100g~80mL / 100g.

4. The composite current collector according to claim 1, characterized in that, The compatibilizer satisfies at least one of the following conditions: (1) The compatibilizer is a copolymer of olefin monomers, acrylate monomers and glycidyl methacrylate; (2) The epoxy equivalent of the compatibilizer is 400 g / mol to 600 g / mol; (3) The melt index of the compatibilizer is 5 g / 10 min to 15 g / 10 min; (4) The glass transition temperature of the compatibilizer is -5℃ to 5℃; (5) The compatibilizer contains 6wt% to 10wt% glycidyl methacrylate. (6) The melting point of the compatibilizer is 60℃~80℃.

5. The composite current collector according to any one of claims 1 to 4, characterized in that, The hydrolysis stabilizer satisfies at least one of the following conditions: (1) The mass ratio of the oligomer containing epoxy groups to the oligomer containing carbodiimide groups is (1~3):1; (2) The epoxy equivalent of the oligomer containing epoxy groups is 400 g / mol to 600 g / mol; (3) The molecular weight of the oligomer containing carbodiimide group is 2000 g / mol to 5000 g / mol.

6. A method for preparing a composite current collector as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Polyester, metallic materials, fillers, compatibilizers, hydrolytic stabilizers, and antioxidants are mixed to prepare a mixture; Under a protective atmosphere, the mixture is melt-blended, extruded, and then film-formed to prepare a polyester matrix layer; The conductive layer is placed on at least one surface of the polyester matrix layer and pressed to prepare the composite current collector.

7. The method for preparing the composite current collector according to claim 6, characterized in that, At least one of the following conditions must be met: (1) The moisture content of the polyester and the filler is independently less than 0.02%; (2) The melting and mixing temperature is 260℃~290℃.

8. An electrode sheet, characterized in that, The composite current collector includes the composite current collector described in any one of claims 1 to 5 or the composite current collector prepared by the preparation method described in any one of claims 6 to 7.

9. A battery, characterized in that, Includes the electrode sheet as described in claim 8.

10. An electrical device, characterized in that, Includes the battery as described in claim 9.

Images