Composite current collector and preparation method thereof, electrode plate and battery

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 and a battery. The composite current collector comprises a modified non-woven fabric layer which comprises a non-woven fabric base material, a porous conductive material and a binder, and the porous conductive material and the binder are arranged on the surfaces of the two sides of the non-woven fabric base material and in pores; the metal layers are arranged on the surfaces of the two sides of the modified non-woven fabric layer; wherein conductive metal is filled in pores of the porous conductive material. Porous conductive materials are arranged on the surfaces of the two sides and in pores of the non-woven fabric base material in the modified non-woven fabric layer, and conductive metal is filled in the porous conductive materials, so that the conductivity, the mechanical strength and the interface bonding strength of the composite current collector are improved, the thermal runaway risk and the failure probability of a battery prepared from the composite current collector are reduced, and the service life of the battery is prolonged. The industrial application is facilitated.

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, and batteries. Background Technology

[0002] Composite current collectors have advantages such as high safety, light weight, high energy density and low cost.

[0003] Reports have shown the use of polymer films as the substrate for composite current collectors, forming a sandwich structure of "metal layer-polymer layer-metal layer". However, the polymer layer, acting as an insulating layer, hinders the electron transport path between the metal layers on both sides of the polymer layer. Simultaneously, the ultra-thin metal coating further restricts the conductive volume, resulting in a significant decrease in bulk conductivity and consequently an increase in the resistance of the electrode and the overall battery. When this structure is applied to high-power batteries, the high internal resistance can trigger a significant Joule heating effect, leading to accelerated temperature rise during charging and discharging, posing a potential thermal safety risk.

[0004] Unlike the aforementioned polymer films, there are also reports of using nonwoven fabrics with abundant fiber channels as the substrate for composite current collectors, which is beneficial for achieving forward and reverse conductivity of the metal layer.

[0005] However, composite current collectors based on nonwoven fabrics suffer from insufficient mechanical strength and poor bonding strength with the metal layer. Summary of the Invention

[0006] Based on this, this application provides a composite current collector and its preparation method, electrode sheet, and battery, which can simultaneously improve the conductivity, mechanical strength, and interfacial bonding strength of the nonwoven composite current collector.

[0007] A first aspect of this application provides a composite current collector, comprising: a modified nonwoven fabric layer including a nonwoven fabric substrate, a porous conductive material, and an adhesive, wherein the porous conductive material and the adhesive are disposed on both sides of the nonwoven fabric substrate and within its pores; and a metal layer disposed on both sides of the modified nonwoven fabric layer; wherein the pores of the porous conductive material are filled with conductive metal.

[0008] In some embodiments, the porous conductive material includes: a carbon material; a porous conductive polymer material coated on the surface of the carbon material; and a hydrophilic polymer material disposed within the pores of the porous conductive polymer material; wherein a conductive metal fills the pores of the porous conductive polymer material.

[0009] Optionally, the carbon material includes one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphene oxide, reduced graphene oxide, carbon fiber, and conductive carbon black.

[0010] Alternatively, the hydrophilic polymer material includes hydrophilic polylactic acid.

[0011] In some embodiments, the porous conductive polymer material completely coats the surface of the carbon material, and the porous conductive polymer material has a positive temperature coefficient effect.

[0012] Alternatively, the porous conductive polymer material includes one or more of poly(3-dodecylthiophene), poly(3-octylthiophene), and poly(3-butylthiophene).

[0013] Optionally, the thickness of the porous conductive polymer material is 0.5μm-2.5μm.

[0014] In some embodiments, the composite current collector satisfies at least one of the following conditions: (1) the pore depth of the porous conductive polymer material is 0.1 μm-1 μm. (2) the mass ratio of the porous conductive polymer material to the hydrophilic polymer material is 2%-5%. (3) the pore depth of the porous conductive material is 20 nm-300 nm.

[0015] In some embodiments, at least one metal layer includes: a metal underlayer disposed on the surface of the modified nonwoven fabric layer; and a metal thickening layer disposed on the side of the metal underlayer away from the modified nonwoven fabric layer.

[0016] Optionally, the thickness of the metal underlayer is 30nm~100nm.

[0017] Optionally, the thickness of the metal thickening layer is 0.5 μm to 2 μm.

[0018] In some embodiments, the composite current collector satisfies at least one of the following conditions: (1) the material of the nonwoven substrate includes one or more of polypropylene, polyethylene terephthalate, polyphenylene sulfide, polyimide and liquid crystal polymer; (2) the binder includes one or more of polyacrylic acid, polyurethane, epoxy resin and polyvinylidene fluoride; (3) the mass ratio of porous conductive material to binder is (5~10):1.

[0019] A second aspect of this application provides a method for preparing a composite current collector, the method comprising the following steps: immersing a nonwoven fabric substrate in a mixture containing a porous conductive material and a binder, followed by drying, so that the porous conductive material and the binder are formed on both sides of the nonwoven fabric substrate and within its pores, thereby preparing a modified nonwoven fabric layer; preparing a metal layer on both sides of the modified nonwoven fabric layer; and filling the pores of the porous conductive material with conductive metal.

[0020] In some embodiments, the porous conductive material is prepared by the following steps: coating a porous conductive polymer material onto the surface of a carbon material; and grafting a hydrophilic polymer material into the pores of the porous conductive polymer material.

[0021] In some embodiments, a porous conductive polymer material is coated onto the surface of a carbon material, specifically including the following steps: mixing the carbon material, the monomer of the conductive polymer material and an initiator, reacting them to prepare a carbon material coated with the conductive polymer material; and etching the carbon material coated with the conductive polymer material to prepare a carbon material coated with a porous conductive polymer material.

[0022] Optionally, the mass ratio of the monomers of the carbon material and the conductive polymer material is (0.5~2):(5-10).

[0023] Optionally, the monomers of the conductive polymer include at least one of 3-dodecylthiophene, 3-octylthiophene, and 3-butylthiophene.

[0024] Optionally, the initiator includes at least one of anhydrous ferric chloride, cerium oxide, and manganese oxide.

[0025] Optionally, the etchant used in the etching process is selected from at least one of hydrogen peroxide and sodium hypochlorite aqueous solution.

[0026] In some embodiments, metal layers are prepared on both sides of the modified nonwoven fabric layer, specifically including: preparing a metal underlayer on at least one side of the modified nonwoven fabric layer; and preparing a metal thickening layer on the side of the metal underlayer away from the modified nonwoven fabric layer.

[0027] Optionally, a metal underlayer can be prepared using magnetron sputtering.

[0028] Alternatively, the metal thickening layer can be prepared using an electroplating process.

[0029] In some embodiments, a magnetron sputtering process and / or an electroplating process is used to fill the pores of the porous conductive material with conductive metal.

[0030] Optionally, the electroplating solution in the hydroplating process includes a dispersant.

[0031] A third aspect of this application provides an electrode sheet comprising the composite current collector provided in the first aspect above, or a composite current collector prepared by the method for preparing the composite current collector provided in the second aspect above.

[0032] A fourth aspect of this application provides a battery comprising the electrode plates provided in the third aspect above.

[0033] Compared with traditional technologies, this application has at least the following beneficial effects:

[0034] The composite current collector provided in this application embodiment has porous conductive material on both sides and within the pores of the nonwoven fabric substrate in the modified nonwoven fabric layer, and conductive metal is filled in the pores of the porous conductive material. On the one hand, the porous conductive material facilitates the forward and reverse conduction of the metal layers on both sides of the modified nonwoven fabric layer, improves the bulk conductivity of the composite current collector, reduces the internal resistance of the battery prepared thereby, suppresses the Joule heating effect, and improves the safety performance of the battery. On the other hand, the porous conductive material, disposed within the pores of the nonwoven fabric substrate, plays a filling and supporting role, enhances the toughness and processability of the modified nonwoven fabric layer, and thus improves the mechanical strength of the composite current collector. At the same time, the porous conductive material itself has a porous structure, providing space for the filling of conductive metal, allowing the conductive metal to fill the pores of the porous conductive material, improving the interfacial bonding strength between the modified nonwoven fabric layer and the metal layer, and reducing the probability of battery failure.

[0035] In summary, the aforementioned composite current collector, by setting porous conductive materials on both sides and within the pores of the nonwoven substrate in the modified nonwoven layer, and filling the pores of the porous conductive materials with conductive metal, simultaneously improves the conductivity, mechanical strength, and interfacial bonding strength of the composite current collector, thereby reducing the risk of thermal runaway and the probability of failure of the battery prepared thereby, which is beneficial for industrial applications. Attached Figure Description

[0036] 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.

[0037] Figure 1 This is a schematic diagram of the composite current collector in one embodiment of this application.

[0038] Figure 2 This is a schematic diagram of the structure of the modified material in one embodiment of this application.

[0039] Figure 3 This is a schematic flowchart of a method for preparing a composite current collector according to one embodiment of this application.

[0040] 1. Composite current collector; 10. Modified nonwoven fabric layer; 20. Metal layer; 21. Metal underlayer; 22. Metal thickening layer; 100. Porous conductive material; 101. Carbon material; 102. Porous conductive polymer material; 103. Hydrophilic polymer material. Detailed Implementation

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] 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.

[0049] 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.

[0050] In this article, "non-woven fabric" refers to a fabric formed directly by bonding fibers without the need for spinning and weaving processes.

[0051] In this document, "porous conductive polymer material" refers to a conductive polymer material with a porous structure. In some embodiments of this application, the porous structure of the porous conductive polymer can be prepared by treating the molecular chains on the surface of the conductive polymer with an etchant to break some of the molecular chains.

[0052] In this article, the "positive temperature coefficient effect" (PTC) refers to the characteristic that the resistance of a material increases with increasing temperature.

[0053] In this article, "dyne value" refers to the surface tension value of a liquid spreading on a solid surface, and its unit is dyne / cm or millinewton / m.

[0054] In this article, "soluble polymer" refers to polymer materials that can be dissolved in a specific solvent.

[0055] Composite current collectors have advantages such as high safety, light weight, high energy density and low cost.

[0056] Reports have shown the use of polymer films as the substrate for composite current collectors, forming a sandwich structure of "metal layer-polymer layer-metal layer". However, the polymer layer, acting as an insulating layer, hinders the electron transport path between the metal layers on either side of the polymer layer. Simultaneously, the ultra-thin metal coating further restricts the conductive volume, resulting in a significant decrease in bulk conductivity and consequently, an increase in the resistance of the electrode and the overall battery. When this structure is applied to high-power batteries, the high internal resistance can trigger a significant Joule heating effect, leading to accelerated temperature rise during charging and discharging, posing a potential thermal safety risk.

[0057] Unlike the aforementioned polymer films, there are also reports of using nonwoven fabrics with abundant fiber channels as the substrate for composite current collectors, which is beneficial for achieving forward and reverse conductivity of the metal layer.

[0058] The wet process of nonwoven fabric originates from the papermaking process, which uses water as a medium to evenly disperse short-cut fibers (polyester, aramid, viscose, etc.) into a pulp, and then filters, dehydrates and dries them to produce a web-like material.

[0059] However, nonwoven fabric fibers only have hydrogen bonds and mechanical entanglement, resulting in a fragile structure and insufficient mechanical strength. When nonwoven fabric is used as a substrate for composite current collectors, the thickness of the composite current collector needs to be reduced to meet requirements, further decreasing the mechanical strength of the composite current collector based on the nonwoven fabric substrate.

[0060] The inventors of this application have discovered that during the processing of forming a metal layer on nonwoven fabric (such as copper plating), the fibrous network structure of the nonwoven fabric is easily damaged under tension, resulting in a continued significant decrease in mechanical strength. Simultaneously, due to the lack of supporting structure in the pore fibers of the nonwoven fabric, the bonding strength between the nonwoven fabric and the metal layer is poor, making the resulting battery prone to failure.

[0061] In addition, it is still necessary to properly control the pores of the nonwoven fabric layer to ensure that the metal in the pores can fully play its role in positive and negative conduction bridging.

[0062] To solve the aforementioned technical problems, the first aspect of this application, in conjunction with... Figure 1 and Figure 2 As shown, a composite current collector 1 is provided, comprising a modified nonwoven fabric layer 10 and a metal layer 20. The modified nonwoven fabric layer 10 comprises a nonwoven fabric substrate, a porous conductive material 100, and an adhesive, wherein the porous conductive material 100 and the adhesive are disposed on both sides of the nonwoven fabric substrate and within its pores. The metal layer 20 is disposed on both sides of the modified nonwoven fabric layer 10. The pores of the porous conductive material 100 are filled with conductive metal.

[0063] The composite current collector 1 provided in this application embodiment has a porous conductive material 100 disposed on both sides and within the pores of the nonwoven fabric substrate in the modified nonwoven fabric layer 10, and conductive metal is filled in the pores of the porous conductive material 100. On the one hand, the porous conductive material 100 facilitates the forward and reverse conduction of the metal layers 20 on both sides of the modified nonwoven fabric layer 10, improves the bulk conductivity of the composite current collector 1, reduces the internal resistance of the battery prepared thereby, suppresses the Joule heating effect, and improves the safety performance of the battery. On the other hand, the porous conductive material 100 is disposed within the pores of the nonwoven fabric substrate, playing a filling and supporting role, enhancing the toughness and processability of the modified nonwoven fabric layer 10, thereby improving the mechanical strength of the composite current collector 1. At the same time, the porous conductive material 100 itself has a porous structure, providing space for the filling of conductive metal, allowing the conductive metal to fill the pores of the porous conductive material 100, improving the interfacial bonding strength between the modified nonwoven fabric layer 10 and the metal layer 20, and reducing the probability of battery failure.

[0064] In summary, the aforementioned composite current collector 1, by providing porous conductive material 100 on both sides and within the pores of the nonwoven substrate in the modified nonwoven layer 10, and filling the pores of the porous conductive material 100 with conductive metal, simultaneously improves the conductivity, mechanical strength, and interfacial bonding strength of the composite current collector, thereby reducing the risk of thermal runaway and the probability of failure of the battery prepared thereby, which is beneficial for industrial applications.

[0065] In some implementations, such as Figure 2 As shown, the porous conductive material 100 includes a carbon material 101, a porous conductive polymer material 102, and a hydrophilic polymer material 103. The porous conductive polymer material is coated on the surface of the carbon material 101. The hydrophilic polymer material 103 is disposed within the pores of the porous conductive polymer material 102. A conductive metal fills the pores of the porous conductive polymer material 102.

[0066] In some embodiments, the carbon material 101 includes one or more of single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (DWNTs), graphene, graphene oxide (GO), reduced graphene oxide (r-GO), carbon fibers (CNTs), and conductive carbon black (SP).

[0067] In some embodiments, the hydrophilic polymer material 103 includes hydrophilic polylactic acid.

[0068] Furthermore, the hydrophilic polylactic acid is starch-modified polylactic acid or cellulose-modified polylactic acid. This is a conventional modification, and the specific modification method is not specifically limited.

[0069] In some embodiments, the porous conductive polymer material 102 completely coats the surface of the carbon material 101, and the porous conductive polymer material 102 exhibits a positive temperature coefficient effect. By selecting a porous conductive polymer material 102 with a positive temperature coefficient effect, the porous conductive polymer material 102 exhibits a low-resistance conductive state when the battery is at normal operating temperature; when the battery temperature rises sharply, the resistance of the porous conductive polymer material 102 also rises sharply, changing from a conductor to an insulator, interrupting the current path, reducing the continuous generation of heat, and thus improving the battery's safety performance. The complete coating of the porous conductive polymer material 102 on the surface of the carbon material 101 ensures that the porous conductive polymer material 102 with a positive temperature coefficient effect can effectively interrupt the current path at high temperatures.

[0070] In some embodiments, the porous conductive polymer material 102 includes one or more of poly(3-dodecylthiophene) (P3DDT), poly(3-octylthiophene) (P3OT), and poly(3-butylthiophene) (P3BT). Choosing these materials as the porous conductive polymer material 102 is advantageous because their molecular structure contains a π-conjugated system, resulting in high electron mobility at room temperature and exhibiting good conductivity and charge transport capabilities. Simultaneously, since the porous conductive polymer material 102 is a polar molecule, its pores are also polar, enhancing compatibility and bonding with the metal layer 20 and reducing the risk of delamination. Furthermore, the porous conductive polymer material 102 exhibits a PTC effect, which can interrupt the current path when the battery temperature rises sharply, reducing continuous heat generation and improving battery safety performance.

[0071] In some embodiments, the thickness D of the porous conductive polymer material 102 is 0.5 μm to 2.5 μm. For example, the thickness D of the porous conductive polymer material includes, but is not limited to, 0.5 μm, 0.7 μm, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, and 2.5 μm.

[0072] In some embodiments, the pore depth d1 of the porous conductive polymer material 102 is 0.1 μm to 1 μm. For example, the pore depth d1 of the porous conductive polymer material 102 can be, but is not limited to, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, or 1 μm.

[0073] It should be noted that the pore depth d1 of the porous conductive polymer material 102 is less than the thickness D of the porous conductive polymer material 102, so that the porous conductive polymer material can completely encapsulate the carbon material.

[0074] In some embodiments, the pore depth d2 of the porous conductive material is 20nm-300nm. For example, the pore depth d2 of the porous conductive material can be 20nm, 50nm, 80nm, 100nm, 130nm, 150nm, 180nm, 200nm, 230nm, 250nm, 280nm, or 300nm.

[0075] It should be noted that the pore depth of the porous conductive material here refers to the pore depth of the porous conductive polymer material after grafting with the hydrophilic polymer.

[0076] In some embodiments, the mass ratio of the hydrophilic polymer material 103 to the porous conductive polymer material 102 is 2% to 5%. For example, the mass ratio of the hydrophilic polymer material 103 to the porous conductive polymer material 102 can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0077] In some embodiments, the nonwoven substrate material includes one or more of polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyimide (PI), and liquid crystal polymer.

[0078] In some embodiments, the thickness of the nonwoven fabric substrate is 4μm to 20μm. Exemplarily, the thickness of the nonwoven fabric substrate can be, but is not limited to, 4μm, 8μm, 10μm, 12μm, 15μm, 18μm, or 20μm.

[0079] In some embodiments, the average pore size of the nonwoven fabric substrate is 50 μm-150 μm. Exemplarily, the average pore size of the nonwoven fabric substrate includes, but is not limited to, 50 μm, 70 μm, 90 μm, 110 μm, 130 μm, and 150 μm.

[0080] In some embodiments, the adhesive includes one or more of polyacrylic acid, polyurethane, epoxy resin and polyvinylidene fluoride.

[0081] In some embodiments, at least one metal layer 20 includes a metal underlayment 21 and a metal thickening layer 22. The metal underlayment 21 is disposed on the surface of the modified nonwoven fabric layer 10. The metal thickening layer 22 is disposed on the surface of the metal underlayment 21 away from the modified nonwoven fabric layer 10.

[0082] In some embodiments, the materials of the metal underlayer 21, the metal thickening layer 22, and the conductive metal are each independently selected from one or more of copper, aluminum, nickel, titanium, silver, or their alloys or metal oxides.

[0083] Furthermore, the metal thickening layer 22 is made of the same material as the conductive metal.

[0084] In some embodiments, the thickness of the metal substrate 21 is 30nm to 100nm. For example, the thickness of the metal substrate 21 can be, but is not limited to, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm.

[0085] In some embodiments, the thickness of the metal thickening layer 22 is 0.5 μm to 2 μm. For example, the thickness of the metal thickening layer 22 can be, but is not limited to, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, or 2 μm.

[0086] In some embodiments, the mass ratio of the porous conductive material 100 to the binder is (5~10):1. Exemplarily, the mass ratio of the porous conductive material 100 to the binder can be, but is not limited to, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.

[0087] A second aspect of this application provides a method for preparing a composite current collector, the method comprising the following steps: immersing a nonwoven fabric substrate in a mixture containing a porous conductive material and a binder, followed by drying, so that the porous conductive material and the binder are formed on both sides of the nonwoven fabric substrate and within its pores, thereby preparing a modified nonwoven fabric layer; preparing a metal layer on both sides of the modified nonwoven fabric layer; and filling the pores of the porous conductive material with conductive metal.

[0088] In some embodiments, the porous conductive material is prepared using the following steps:

[0089] S01. Coating the surface of a carbon material with a porous conductive polymer material.

[0090] S02. Grafting a hydrophilic polymer material into the pores of a porous conductive polymer material.

[0091] In this embodiment, in step S01, coating the surface of the carbon material with a porous conductive polymer material can achieve a high ion mobility. When the porous conductive polymer material is selected to have a PTC effect and is completely coated on the surface of the carbon material, it can play a role in cutting off the conductive channel. In step S02, a hydrophilic polymer material is grafted into the pores of the porous conductive polymer material to improve the hydrophilicity inside the pores. This facilitates the introduction of the electroplating solution into the pores during the subsequent electroplating process, thereby filling the conductive metal. At the same time, by adjusting the amount of hydrophilic polymer material filling the pores, the size of the space in the pores that can be used to fill the conductive metal can be controlled, thereby adjusting the amount of conductive metal filling.

[0092] In some embodiments, a metal layer is prepared on both sides of the modified nonwoven fabric layer, specifically including the following steps:

[0093] S011. Mix the monomers of carbon materials and conductive polymer materials with an initiator, react them, and prepare carbon materials coated with conductive polymer materials.

[0094] S012. The carbon material coated with conductive polymer material is etched and reacted to prepare a porous carbon material coated with conductive polymer material.

[0095] In this embodiment, step S011 involves directly polymerizing the monomers of the conductive polymer to coat the carbon material surface in situ, resulting in a uniform coating effect. In step S012, an etchant is used to etch the outer side of the conductive polymer, causing some molecular chain segments of the conductive polymer to break and form a porous structure, providing space for subsequent filling with conductive metal.

[0096] In some embodiments, in step S11, the mass ratio of the monomers of the carbon material and the conductive polymer material is (0.5~2):(5-10). Exemplarily, the mass ratio of the monomers of the carbon material and the conductive polymer material can be, but is not limited to, 1:10, 1:16, 1:20, 2:5, 1:4, or 1:5.

[0097] In some embodiments, in step S11, the polymer monomer of the conductive polymer includes at least one of 3-dodecylthiophene, 3-octylthiophene, and 3-butylthiophene.

[0098] In some embodiments, in step S11, the initiator includes at least one of anhydrous ferric chloride, cerium oxide, and manganese oxide.

[0099] In some specific embodiments, in step S12, the etchant is selected from at least one of hydrogen peroxide and sodium hypochlorite aqueous solution.

[0100] In some embodiments, the preparation method further includes the step of purifying the carbon material before immersing the nonwoven substrate in a mixture containing a porous conductive material and a binder.

[0101] In this embodiment, the carbon material is purified to remove impurities (amorphous carbon impurities, metallic impurities) from the carbon material, thereby reducing the risk of thermal runaway.

[0102] In some embodiments, before immersing the nonwoven substrate in a mixture containing a porous conductive material and an adhesive, the preparation method further includes the steps of drying the nonwoven substrate and / or plasma surface activation treatment.

[0103] In this embodiment, drying the nonwoven fabric substrate helps remove moisture adsorbed on the surface and pores of the nonwoven fibers, facilitating the subsequent filling of modified materials. Plasma surface activation treatment of the nonwoven fabric substrate can introduce oxygen-containing polar functional groups (such as -OH, -COOH) without damaging the substrate itself, thereby improving the wettability of the nonwoven fabric substrate.

[0104] In some specific embodiments, after the nonwoven fabric substrate is subjected to plasma surface activation treatment, the dyne value of both sides of the nonwoven fabric substrate is greater than or equal to 32 mN / m.

[0105] In some embodiments, metal layers are prepared on both sides of the modified nonwoven fabric layer, specifically including the following steps: depositing a metal underlayer on at least one side of the modified nonwoven fabric layer; and preparing a metal thickening layer on the side of the metal underlayer away from the modified nonwoven fabric layer.

[0106] In some implementations, a magnetron sputtering process is used to prepare the metal underlayer.

[0107] In this embodiment, during magnetron sputtering, orthogonal electromagnetic fields cause the polar molecules of porous conductive polymers in the porous conductive material to polarize and form dipoles, which then align under the drive of the electric field, promoting the ordering of molecular chains and ultimately forming a porous core-shell structure with gradient changes. This structure not only improves the uniformity of metal deposition, but also enhances the compatibility with the metal layer due to its polar interface characteristics, allowing the metal underlayer to be embedded into the three-dimensional network of the nonwoven substrate, forming mechanical interlocking and further strengthening the interface bonding.

[0108] In some implementations, an electroplating process is used to prepare the metal thickening layer.

[0109] Furthermore, a metal underlayer is prepared using magnetron sputtering, and a metal thickening layer is prepared using electroplating. The magnetron sputtering process provides the electrodes for the subsequent electroplating process.

[0110] In some embodiments, a magnetron sputtering process and / or an electroplating process is used to fill the pores of the porous conductive material with conductive metal.

[0111] In traditional techniques, the electroplating solution in the electroplating process has difficulty penetrating into the pores of the three-dimensional network structure of the nonwoven fabric, thus failing to effectively achieve the conduction of the metal layers on both sides of the nonwoven fabric layer.

[0112] In this embodiment, the metal layers on both sides of the nonwoven fabric layer are made conductive by filling the pores of the three-dimensional network structure of the nonwoven fabric substrate with porous conductive material. At the same time, the porous structure of the porous conductive material significantly increases the specific surface area of ​​the porous conductive material. First, metal is filled into the pores of the porous conductive material on the surface of the modified nonwoven fabric layer by magnetron sputtering. Furthermore, in the presence of hydrophilic polymer material, the electroplating solution of the water electroplating process can smoothly enter into more pores of the porous conductive material inside the modified nonwoven fabric layer and fill the conductive metal, thereby reducing the resistance of the composite current collector and further improving the interfacial bonding performance.

[0113] Furthermore, while preparing the metal underlayer using magnetron sputtering, conductive metal is filled into the pores of the porous conductive material.

[0114] Furthermore, while preparing the metal thickening layer using an electroplating process, conductive metal is filled into the pores of the porous conductive material.

[0115] In some specific implementations, such as Figure 3 As shown, the preparation method of this composite current collector includes the following steps:

[0116] S1. The nonwoven fabric substrate is immersed in a mixture containing a porous conductive material and a binder, and then dried to form the porous conductive material and binder on both sides of the nonwoven fabric substrate and in the pores, thus preparing a modified nonwoven fabric layer; wherein, the porous conductive material includes carbon material, porous conductive polymer material and hydrophilic polymer material, the porous conductive polymer material is coated on the surface of the carbon material, and the hydrophilic polymer material is disposed in the pores of the porous conductive polymer material.

[0117] S2. A metal underlayer is deposited on at least one side of the modified nonwoven fabric layer using a magnetron sputtering process, and the pores of the porous conductive polymer material are filled with conductive metal.

[0118] S3. Using an electroplating process, a metal thickening layer is prepared on the side of the metal base layer away from the modified nonwoven fabric layer, and conductive metal is filled into the pores of the porous conductive polymer material.

[0119] Furthermore, the electroplating solution in the electroplating process includes a dispersant. The dispersant can further improve the wettability of the electroplating solution, allowing it to enter the pores of the porous conductive material more smoothly, filling the conductive metal, thereby reducing the resistance of the composite current collector and improving the interfacial bonding performance.

[0120] Furthermore, the dispersant is polyvinyl alcohol.

[0121] A third aspect of this application provides an electrode sheet comprising the composite current collector provided in the first aspect above, or a composite current collector prepared by the method for preparing the composite current collector provided in the second aspect above.

[0122] A fourth aspect of this application provides a battery comprising the electrode plates provided in the third aspect above.

[0123] The battery includes a positive electrode and a negative electrode. At least one of the positive and negative electrode sheets is the electrode sheet provided in the third aspect above. The metal layer of the composite current collector in the positive electrode sheet can be made of aluminum. The positive electrode material can be a ternary positive electrode material or a lithium iron phosphate positive electrode material. The metal layer of the composite current collector in the negative electrode material can be made of copper. The negative electrode material can be at least one of artificial graphite, natural graphite, silicon carbide, hard carbon, and lithium titanate.

[0124] A fifth aspect of this application provides an electrical device that includes the battery provided in the fourth aspect above.

[0125] The electrical device used in this application is not particularly limited and can be any electrical device known in the prior art. For example, the electrical device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors.

[0126] The present application will now be described in detail with reference to specific embodiments and comparative examples.

[0127] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0128] Example 1

[0129] This embodiment provides a method for preparing a composite current collector.

[0130] (1) The PET nonwoven fabric substrate (width 1350 mm, thickness 10 μm, average pore size 150 μm) was vacuum dried at a vacuum degree of 100 Pa and 65℃; then plasma surface activation treatment was performed (the process gas was argon and oxygen with a volume ratio of 3:1, the power was 150W, the gas flow rate was 200 sccm, and the treatment time was 20s). After treatment, the double-sided dyne value of the nonwoven fabric substrate was not less than 32 mN / m.

[0131] (2) Under an air atmosphere, single-walled carbon nanotubes (SWNTs) with a diameter of 2 nm and a length of 25 μm were heat-treated at 300 °C for 1 h to remove amorphous carbon impurities. Then, 1 part of the SWNTs with amorphous carbon impurities removed was weighed and dissolved in 1000 parts of concentrated hydrochloric acid (mass fraction of 37%) and stirred at 25 °C for 8 h at a stirring speed of 2000 rpm to obtain a suspension. The above suspension was filtered using a polytetrafluoroethylene (PTFE) microfiltration membrane with an average pore size of 100 nm and washed with deionized water with a conductivity of 10 μs / cm for 5 min. Then, it was vacuum dried at a vacuum degree of 100 Pa and 120 °C to obtain purified SWNTs.

[0132] (3) Take 5 parts by mass of anhydrous ferric chloride with a purity >99% as an initiator and add 100 parts by mass of chloroform to prepare a suspension. Stir at 2000 rpm for 15 min. After adjusting the pH to 3, slowly add 4 parts by mass of 3-octylthiophene with a purity >95% and 1 part by mass of purified SWNTs to the above suspension. Stir at 25°C for 8 h at a stirring speed of 2000 rpm to carry out the core-shell structure reaction. Then wash with deionized water with a conductivity of 10 μs / cm for 15 min to ensure that the Fe ion content in the washing solution is less than 20 ppm. Finally, vacuum dry at 100 Pa and 100°C to prepare SWNTs@P3OT material with poly(3-octylthiophene) (P3OT) as the shell and SWNTs as the core (average molecular weight of 1000 kDa, domain regularity of 80%). The thickness of the P3OT shell is 0.5 μm.

[0133] (4) Add 20 parts of the above-prepared SWNTs@P3OT and 0.5 parts of Triton X-100 to 50 parts of 0.5% hydrogen peroxide and adjust the pH to 4.5. First, stir and react at 35°C for 1 hour, then at 120°C for 1 hour, with a stirring speed of 2000 rpm to obtain a porous P3OT layer completely coated with SWNTs. At this time, the pore depth of the porous P3OT layer is 0.1 μm, and a suspension is prepared. After adjusting the pH of the above suspension to neutral, add starch-modified hydrophilic polymer. Lactic acid was mixed with starch-modified hydrophilic polylactic acid (molecular weight 100 kDa) at a mass ratio of 0.5% to suspension and reacted at 60°C for 8 hours with a stirring speed of 2000 rpm. Starch-modified hydrophilic polylactic acid was grafted into the pores of the porous P3OT layer to obtain a porous conductive material. The mass ratio of starch-modified hydrophilic polylactic acid to the porous P3OT layer in the obtained porous conductive material was 2%, and the pore depth of the porous conductive material (i.e., the pores of the porous P3OT layer after grafting hydrophilic polylactic acid) was 20 nm.

[0134] (5) A porous conductive material, deionized water with a conductivity of 10 μs / cm and polyurethane (molecular weight of 300 kDa) are mixed in a mass ratio of 8:1:1 to form an emulsion. The mixture is first stirred at 2000 rpm in an impregnation tank, and then impregnated at 5 m / min in an impregnation tank with a width of 1400 mm. Finally, the mixture is treated with an infrared dryer at 80°C to obtain a modified nonwoven fabric layer.

[0135] (6) A 30nm copper underlayer was deposited on both sides of the modified nonwoven fabric layer using a roll-to-roll double-sided magnetron sputtering equipment. The specific steps are as follows: A high-purity copper target (99.99% purity) was used as the sputtering target material. The equipment was equipped with 20 sets of targets, with 10 sets corresponding to each side of the base film. After loading the base film into the equipment, one side was deposited on the target material first. The process parameters were set as follows: working vacuum degree was 0.3 Pa, argon flow rate in argon atmosphere was 150 sccm, target power was 7kW, main roller temperature was maintained at -20℃, base film conveyor belt speed was 10m / min, and winding and unwinding tension was controlled at 100 N.

[0136] (7) A water electroplating process is used to thicken the copper layer on the surface of the copper base layer by water electroplating to obtain a conductive copper layer. At the same time, copper metal fills the pores of the porous P3OT material, so that the overall thickness of the metal layers on both sides is 1μm, thus obtaining a composite current collector. Among them, the water electroplating adopts a side clamp type winding structure, the water plating winding speed is 5 m / min, and the water electroplating winding tension is 65N; the copper sulfate concentration of the copper plating solution is 130 g / L, the sulfuric acid concentration is 90 g / L, and the chloride ion mass ratio is 50 ppm; the brightener is sodium polydisulfide dipropane sulfonate 0.4 mL / L, the carrier agent is polyethylene glycol 3 mL / L, and the dispersant is polyvinyl alcohol 3 mL / L.

[0137] Example 2

[0138] The preparation method of the composite current collector in this embodiment is basically the same as that in Example 1, except that:

[0139] In step (1), the PET nonwoven fabric is replaced with PI nonwoven fabric (width 1350mm, thickness 16μm, average pore size 50μm).

[0140] In step (2), SWNTs are replaced with DWNTs (single diameter 3nm, length 25μm).

[0141] Example 3

[0142] The preparation method of the composite current collector in this embodiment is basically the same as that in Example 1, except that:

[0143] In step (3), the 3-octylthiophene monomer is replaced with 3-butylthiophene, and poly(3-butylthiophene) (P3BT) shell is formed by in-situ polymerization under the action of an initiator.

[0144] Example 4

[0145] The preparation method of the composite current collector in this embodiment is basically the same as that in Example 1, except that:

[0146] In step (3), 3-octylthiophene is 10 parts by mass and the P3OT shell thickness is 1.5 μm.

[0147] In step (4), hydrogen peroxide is 70 parts by mass, so the pore depth of the porous P3OT material is 0.4 μm; the mass ratio of hydrophilic polymer material to suspension is 0.8%; the mass ratio of starch-modified hydrophilic polylactic acid to porous P3OT layer is 3.2%; the pores of porous conductive material, i.e. the pores of porous P3OT layer after grafting hydrophilic polylactic acid, have a pore depth of 100 nm.

[0148] In step (5), the mass ratio of porous conductive material to polyurethane is 5:1.

[0149] In step (6), a 60nm copper underlayer is deposited on both sides of the modified nonwoven fabric layer using a roll-to-roll double-sided magnetron sputtering device.

[0150] In step (7), an electroplating process is used to electroplat a thickened copper layer on the surface of the copper base layer to obtain a conductive copper layer, so that the overall thickness of the metal layers on both sides is 1.5 μm respectively.

[0151] Example 5

[0152] The preparation method of the composite current collector in this embodiment is basically the same as that in Example 1, except that:

[0153] In step (3), 20 parts by mass of 3-octylthiophene are used, and the thickness of the P3OT shell is 2.5 μm.

[0154] In step (4), hydrogen peroxide is 100 parts by mass, so the pore depth of the porous P3OT material is 1 μm; the mass ratio of hydrophilic polymer material to suspension is 1.25%; the mass ratio of starch-modified hydrophilic polylactic acid to porous P3OT layer is 5%; the pores of porous conductive material, i.e. the pores of the grafted porous P3OT layer, have a pore depth of 300 nm.

[0155] In step (5), the mass ratio of porous conductive material to polyurethane is 10:1.

[0156] In step (6), a 100nm copper underlayer is deposited on both sides of the modified nonwoven fabric layer using a roll-up double-sided magnetron sputtering device.

[0157] In step (7), an electroplating process is used to electroplat a thickened copper layer on the surface of the copper base layer to obtain a conductive copper layer, so that the overall thickness of the metal layers on both sides is 2μm respectively.

[0158] Example 6

[0159] The preparation method of the composite current collector in this embodiment is basically the same as that in Example 1, except that:

[0160] In step (7), the electroplating solution does not contain a dispersant.

[0161] Comparative Example 1

[0162] This comparative example provides a method for preparing a composite current collector.

[0163] Compared to Example 1, the composite current collector provided in Comparative Example 1 was obtained by copper plating on an unmodified nonwoven fabric substrate, and the specific preparation is as follows:

[0164] (1) The PET nonwoven fabric substrate (width 1350 mm, thickness 10 μm, average pore size 150 μm) was vacuum dried at a vacuum degree of 100 Pa and 65℃; then plasma surface activation treatment was performed (the process gas was argon and oxygen with a volume ratio of 3:1, the power was 150W, the gas flow rate was 200 sccm, and the treatment time was 20s). After treatment, the double-sided dyne value of the nonwoven fabric substrate was not less than 32 mN / m.

[0165] (2) A 30nm copper underlayer was deposited on both sides of the nonwoven substrate using a roll-to-roll double-sided magnetron sputtering equipment. The specific steps are as follows: A high-purity copper target (99.99% purity) was used as the sputtering target material. The equipment was equipped with 20 sets of targets, with 10 sets corresponding to each side of the base film. After loading the base film into the equipment, one side was deposited on the target material first. The process parameters were set as follows: working vacuum degree was 0.3 Pa, argon flow rate in argon atmosphere was 150 sccm, target power was 7kW, main roller temperature was maintained at -20℃, base film conveyor belt speed was 10m / min, and winding and unwinding tension was controlled at 100 N.

[0166] (3) A conductive copper layer is obtained by electroplating a thickened copper layer on the surface of the copper base layer, so that the overall thickness of the metal layers on both sides is 1 μm, thus obtaining a composite current collector. Among them, the electroplating adopts a side clamp type winding structure, the water plating winding speed is 5 m / min, and the water plating winding tension is 65 N; the copper sulfate concentration of the copper plating solution is 130 g / L, the sulfuric acid concentration is 90 g / L, and the chloride ion mass percentage is 50 ppm; the brightener is sodium polydisulfide dipropane sulfonate 0.4 mL / L, the carrier agent is polyethylene glycol 3 mL / L, and the dispersant is polyvinyl alcohol 3 mL / L.

[0167] Comparative Example 2

[0168] This comparative example provides a method for preparing a composite current collector. The difference between this method and Example 1 is that no hydrophilic polymer material was added during the preparation of the porous conductive material in Comparative Example 2, and no dispersant was added to the electroplating solution.

[0169] (1) The PET nonwoven fabric substrate (width 1350 mm, thickness 10 μm, average pore size 150 μm) was vacuum dried at a vacuum degree of 100 Pa and 65℃; then plasma surface activation treatment was performed (the process gas was argon and oxygen with a volume ratio of 3:1, the power was 150W, the gas flow rate was 200 sccm, and the treatment time was 20s). After treatment, the double-sided dyne value of the nonwoven fabric substrate was not less than 32 mN / m.

[0170] (2) Under an air atmosphere, single-walled carbon nanotubes (SWNTs) with a diameter of 2 nm and a length of 25 μm were heat-treated at 300 °C for 1 h to remove amorphous carbon impurities. Then, 1 part of the SWNTs with amorphous carbon impurities removed was weighed and dissolved in 1000 parts of concentrated hydrochloric acid (mass fraction of 37%) and stirred at 25 °C for 8 h at a stirring speed of 2000 rpm to obtain a suspension. The above suspension was filtered using a polytetrafluoroethylene (PTFE) microfiltration membrane with an average pore size of 100 nm and washed with deionized water with a conductivity of 10 μs / cm for 5 min. Then, it was vacuum dried at a vacuum degree of 100 Pa and 120 °C to obtain purified SWNTs.

[0171] (3) Take 5 parts by weight of anhydrous ferric chloride with a purity >99% as an initiator and add 100 parts by weight of chloroform to prepare a suspension. Stir at 2000 rpm for 15 min. After adjusting the pH to 3, slowly add 4 parts by weight of 3-octylthiophene with a purity >95% and 1 part by weight of purified SWNTs to the above suspension. Stir at 25°C for 8 h at a stirring speed of 2000 rpm to carry out the core-shell structure reaction. Then wash with deionized water with a conductivity of 10 μs / cm for 15 min to ensure that the Fe ion content in the washing solution is less than 20 ppm. Finally, vacuum dry at 100 Pa and 100°C to prepare SWNTs@P3OT material with poly(3-octylthiophene) (P3OT) as the shell and SWNTs as the core (average molecular weight of 1000 kDa, regioregularity of 80%).

[0172] (4) Add 20 parts of the above-prepared SWNTs@P3OT and 0.5 parts of Triton X-100 to 50 parts of hydrogen peroxide with a mass fraction of 0.5%, and adjust the pH to 4.5. First, stir and react at 35°C for 1 hour, and then react at 120°C for 1 hour. The stirring speed is 2000 rpm to obtain a porous P3OT material completely coated with SWNTs. The pore depth of the porous P3OT material is 0.1 μm, and a porous conductive material is obtained.

[0173] (5) A porous conductive material, deionized water with a conductivity of 10 μs / cm and polyurethane (molecular weight of 300 kDa) are mixed in a mass ratio of 8:1:1 to form an emulsion. The mixture is first stirred at 2000 rpm in an impregnation tank, and then impregnated at 5 m / min in an impregnation tank with a width of 1400 mm. Finally, the mixture is treated with an infrared dryer at 80°C to obtain a modified nonwoven fabric layer.

[0174] (6) A 30nm copper underlayer was deposited on both sides of the modified nonwoven fabric layer using a roll-to-roll double-sided magnetron sputtering equipment. The specific steps are as follows: A high-purity copper target (99.99% purity) was used as the sputtering target material. The equipment was equipped with 20 sets of targets, with 10 sets corresponding to each side of the base film. After loading the base film into the equipment, one side was deposited on the target material first. The process parameters were set as follows: working vacuum degree was 0.3 Pa, argon flow rate in argon atmosphere was 150 sccm, target power was 7kW, main roller temperature was maintained at -20℃, base film conveyor belt speed was 10m / min, and winding and unwinding tension was controlled at 100 N.

[0175] (7) A water electroplating process is used to thicken the copper layer on the surface of the copper base layer to obtain a conductive copper layer, so that the overall thickness of the metal layers on both sides is 1μm, thus obtaining a composite current collector. Among them, the water electroplating adopts a side clamp type winding structure, the water plating winding speed is 5 m / min, and the water electroplating winding tension is 65N; the copper sulfate concentration of the copper plating solution is 130 g / L, the sulfuric acid concentration is 90 g / L, and the chloride ion mass percentage is 50 ppm; the brightener is sodium polydisulfide dipropane sulfonate 0.4 mL / L, and the carrier agent is polyethylene glycol 3 mL / L.

[0176] Test case

[0177] (1) Mechanical property testing

[0178] Tensile strength tests were conducted on the substrates and composite current collectors of the above embodiments and comparative examples. A 20mm×100mm sample was cut, mounted on a fixture, and a suitable speed (100mm / min) was set. The test was repeated 5 times.

[0179] The substrate in Examples 1-6 and Comparative Example 2 is the modified nonwoven fabric layer prepared in step (4); the substrate in Comparative Example 1 is PET nonwoven fabric.

[0180] (2) Shear resistance test

[0181] Sheet resistance tests were performed on the composite current collectors of the above embodiments and comparative examples. Specifically: the composite current collector was cut into a square size, and then placed under the two test probes of the electrode resistance meter. The two probes were connected to the resistance meter through two terminals. The handle of the testing device was rotated, and the probes were subjected to stable pressure to squeeze the current collector. The pressure was controlled by a pressure gauge. After reaching a certain pressure, the resistance data of the resistance meter was read. This data is the sheet resistance value.

[0182] (3) Chemical bonding strength test

[0183] The chemical adhesion of the composite current collectors in the above examples and comparative examples was tested by immersion in an electrolyte solution. A carbonate-based electrolyte with a molar concentration of 1 mol / L was used for evaluation. Three 30 mm × 30 mm samples were cut, ensuring the samples were free of burrs, notches, wrinkles, and obvious mechanical damage. In a glove box (with oxygen and moisture content controlled to ≤1 ppm), the samples were placed into pre-dried test bottles, and 10.8 ± 0.5 g of electrolyte was added to completely immerse the samples. After tightening the test bottles, they were removed and placed in an oven at 65°C for static treatment. The maximum corrosion detachment area of ​​the composite copper-aluminum foil after 5 days of immersion was compared.

[0184] The composite current collectors prepared in the above embodiments and comparative examples were each assembled into batteries. The specific steps are as follows:

[0185] Step 1: Using a Kejingzhida EI-300 coating machine, calender aluminum foil and composite current collector are coated to prepare positive and negative electrode sheets respectively. The material formula of the positive electrode sheet is: 95wt% ternary NCM (911 system), 3wt% polyvinylidene fluoride, and 2wt% conductive carbon black; the material formula of the negative electrode sheet is: 96wt% graphite, 2wt% conductive carbon black, and 2wt% carboxymethyl cellulose.

[0186] Step 2: After baking, rolling, die-cutting, roll welding, stacking, spot welding, plastic film forming, electrolyte injection, formation, and capacity testing, the above-mentioned electrode sheets are used to prepare a 50AH soft-pack battery. The die-cut positive and negative electrode sheets are 126mm*162mm for the positive electrode and 128mm*164mm for the negative electrode; the number of stacked layers is 60 layers for the positive electrode and 61 layers for the negative electrode. The prepared battery is charged and discharged at 25℃ at 1C, 3C, and 5C.

[0187] (4) Temperature rise test

[0188] The batteries prepared by the composite current collectors of the above examples and comparative examples were placed in a chamber at a constant temperature of 25°C and subjected to 50 cycles of 5C charge-discharge, and the temperature of the batteries was tested.

[0189] (5) Needle prick test

[0190] The batteries prepared by the composite current collectors in the above examples and comparative examples are charged to full capacity. Then, a high-temperature resistant steel needle with a diameter of 5 mm is used to penetrate the battery from a direction perpendicular to the large surface of the battery at a speed of 25±5 mm / s. The penetration position is close to the geometric center of the pierced surface. The steel needle remains in the battery and is observed for 1 hour. If no fire or explosion occurs during this process, it is considered OK; otherwise, it is considered NG.

[0191] The test results are shown in Table 1.

[0192] Table 1

[0193]

[0194] As shown in Table 1, comparing Examples 1-6 and Comparative Examples 1-2, it can be seen that the composite current collector provided in this application can simultaneously improve conductivity, mechanical strength and interfacial bonding strength, thereby reducing the risk of thermal runaway and failure probability of the battery prepared therefrom.

[0195] 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.

[0196] 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 by, The application relates to a modified non-woven fabric, which comprises a non-woven fabric substrate, a porous conductive material and a binder, wherein the porous conductive material and the binder are arranged on both sides of the non-woven fabric substrate and in the pores of the non-woven fabric substrate; and a metal layer arranged on both sides of the modified non-woven fabric layer; wherein the pores of the porous conductive material are filled with conductive metal. The porous conductive material comprises a carbon material, a porous conductive polymer material arranged on the surface of the carbon material, and a hydrophilic polymer material arranged in the pores of the porous conductive polymer material; wherein the conductive metal is filled in the pores of the porous conductive polymer material. Optionally, the carbon material comprises one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, graphene oxide, reduced graphene oxide, carbon fibers and conductive carbon black. Optionally, the hydrophilic polymer material comprises hydrophilic polylactic acid. The porous conductive polymer material completely covers the surface of the carbon material, and the porous conductive polymer material has a positive temperature coefficient effect.

2. The composite current collector of claim 1, wherein Optionally, the porous conductive polymer material comprises one or more of poly (3-dodecyl thiophene), poly (3-octyl thiophene) and poly (3-butyl thiophene). Optionally, the thickness of the porous conductive polymer material is 0.5-2.5 micrometers. At least one of the metal layers comprises a metal primer layer arranged on the surface of the modified non-woven fabric layer, and a metal thickening layer arranged on the side of the metal primer layer away from the modified non-woven fabric layer. Optionally, the thickness of the metal primer layer is 30-100 nanometers. Optionally, the thickness of the metal thickening layer is 0.5-2 micrometers. Optionally, the material of the non-woven fabric substrate comprises one or more of polypropylene, polyethylene terephthalate, polyphenylene sulfide, polyimide and liquid crystal polymer. Optionally, the binder comprises one or more of polyacrylic acid, polyurethane, epoxy resin and polyvinylidene fluoride.

3. The composite current collector of claim 2, wherein, Optionally, the mass ratio of the porous conductive material to the binder is (5-10):

1. The application also discloses a preparation method of the modified non-woven fabric, which comprises the following steps: impregnating a non-woven fabric substrate in a mixed solution containing a porous conductive material and a binder, and then drying to form the porous conductive material and the binder on both sides of the non-woven fabric substrate and in the pores of the non-woven fabric substrate, thereby preparing a modified non-woven fabric layer; preparing a metal layer on both sides of the modified non-woven fabric layer; and filling the pores of the porous conductive material with conductive metal. The porous conductive material is prepared by the following steps: coating a porous conductive polymer material on the surface of a carbon material; and grafting a hydrophilic polymer material in the pores of the porous conductive polymer material.

4. The composite current collector of claim 3, wherein ​ ​ ​ ​ 5. The composite current collector according to any one of claims 1 to 4, wherein ​ ​ ​ ​ ​ 6. The composite current collector of any one of claims 1-4, wherein, ​ ​ ​ ​ 7. A method of making a composite current collector, characterized by, ​ ​ ​ ​ 8. The method of making a composite current collector of claim 7, wherein, ​ ​ ​ 9. The method of making a composite current collector of claim 8, wherein, Coating a porous conductive polymer material on a surface of a carbon material, specifically comprising the following steps: Mixing a carbon material, monomers of the conductive polymer material and an initiator, and reacting to prepare a carbon material coated with a conductive polymer material; Performing etching treatment on the carbon material coated with the conductive polymer material to prepare a carbon material coated with a porous conductive polymer material; Optionally, the mass ratio of the carbon material and the monomers of the conductive polymer material is (0.5-2):(5-10); Optionally, the polymerized monomers of the conductive polymer include at least one of 3-dodecyl thiophene, 3-octyl thiophene and 3-butyl thiophene; Optionally, the initiator includes at least one of anhydrous ferric chloride, cerium oxide and manganese oxide; Optionally, the etchant of the etching treatment is selected from at least one of hydrogen peroxide and sodium hypochlorite aqueous solution.

10. The method of claim 7, 8 or 9, wherein the composite current collector is prepared by a method comprising: Preparation of a metal layer on both sides of the modified non-woven fabric layer, specifically comprising the following steps: Preparation of a metal primer layer on at least one side of the modified non-woven fabric layer; Preparation of a metal thickening layer on a side of the metal primer layer away from the modified non-woven fabric layer; Optionally, the metal primer layer is prepared by a magnetron sputtering process; Optionally, the metal thickening layer is prepared by a water electroplating process.

11. The method of making a composite current collector of any of claims 7-9, wherein, Filling of a conductive metal in the pores of the porous conductive material by a magnetron sputtering process and / or a water electroplating process; Optionally, the electroplating solution of the water electroplating process includes a dispersing agent.

12. An electrode, characterized by A composite current collector comprising the composite current collector as claimed in any one of claims 1-6, or a composite current collector prepared by the preparation method as claimed in any one of claims 7-11.

13. A battery, characterized by An electrode tab comprising the electrode tab as claimed in claim 12.

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