Composite current collector, and preparation method therefor and use thereof

Abstract

The present application provides a composite current collector, and a preparation method therefor and the use thereof. The composite current collector comprises: a polymer supporting layer; a transition layer, which is provided on the surface of at least one side of the polymer supporting layer, wherein the material of the transition layer comprises a nano metal material modified with a silane coupling agent, the nano metal material comprising a nano metal simple substance and / or a nano metal oxide; and a conductive layer, which is provided on the surface of the transition layer along a direction away from the polymer supporting layer. In the present application, introducing the nano metal material modified with a silane coupling agent as a transition layer can tightly combine the organic and inorganic interfaces, and improve the bonding force between the polymer supporting layer and the transition layer; in addition, the particle aggregation degree can be reduced by means of the modification of the silane coupling agent, such that the particles are evenly distributed in the transition layer, thereby improving the bonding force between the conductive layer and the transition layer. The composite current collector has excellent bonding force and stability; and the safety performance and high-temperature cycle performance of a battery prepared on this basis are significantly improved.

Description

A composite current collector, its preparation method and application Technical Field

[0001] This application belongs to the field of battery materials technology, specifically relating to a composite current collector, its preparation method, and its application. Background Technology

[0002] Currently, composite current collectors based on polymer films are receiving widespread attention and application in the new energy industry. These composite current collectors are typically prepared by depositing a metal layer onto a polymer film (such as polyester or polyolefin films) using physical vapor deposition (PVD), thus creating a composite current collector with good conductivity. Compared to traditional current collectors, polymer film-based composite current collectors offer advantages such as low cost, light weight, and good internal insulation. These characteristics enable composite current collectors to reduce battery costs and improve battery energy density and safety when used in batteries.

[0003] However, the intermediate polymer layer in the composite current collector has weak surface polarity, resulting in poor adhesion to the metal layer. Even with a base layer of transition metals such as nickel and chromium or their compounds, the improvement in adhesion is limited, and the poor adhesion is often particularly noticeable after high-temperature cycling. This not only causes battery capacity loss but also makes the battery more susceptible to detachment, posing a safety hazard. This significantly impacts the electrochemical and safety performance of batteries using electrodes made with this composite current collector.

[0004] Therefore, how to solve the problem of declining battery electrochemical and safety performance due to weak bonding force of composite current collectors is the focus of current research.

[0005] Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] To address the shortcomings of existing technologies, this application aims to provide a composite current collector, its preparation method, and its applications. This application introduces a nanomaterial modified with a silane coupling agent as a transition layer between a polymer support layer and a conductive layer. The silane coupling agent tightly bonds the organic and inorganic interfaces, improving the adhesion between the polymer support layer and the transition layer. Simultaneously, surface modification of the nanomaterial with the silane coupling agent reduces particle agglomeration, allowing for more uniform distribution within the transition layer and reducing roughness, thereby enhancing the adhesion between the conductive and transition layers. Furthermore, this transition layer increases the contact area between the polymer and the nanomaterial, and its binding energy falls between that of the polymer support layer and the conductive layer, resolving the issue of poor adhesion caused by the large difference in binding energy between the organic and inorganic layers. This composite current collector exhibits excellent adhesion and stability, resulting in significantly improved safety and high-temperature cycling performance of batteries prepared based on it.

[0008] To achieve this objective, the present application adopts the following technical solution:

[0009] In a first aspect, this application provides a composite current collector, the composite current collector comprising:

[0010] Polymer support layer;

[0011] A transition layer is disposed on at least one side of the surface of the polymer support layer, wherein the material of the transition layer comprises a silane coupling agent modified nano-metal material, wherein the nano-metal material comprises nano-metal element and / or nano-metal oxide;

[0012] A conductive layer is disposed on the surface of the transition layer in a direction away from the polymer support layer.

[0013] This application introduces a silane coupling agent-modified nanomaterial as a transition layer between a polymer support layer and a conductive layer. The silane coupling agent tightly bonds the organic and inorganic interfaces, improving the adhesion between the polymer support layer and the transition layer. Simultaneously, surface modification of the nanomaterial with the silane coupling agent reduces particle agglomeration, allowing for more uniform distribution within the transition layer and reducing roughness, thereby enhancing the adhesion between the conductive and transition layers. Furthermore, this transition layer increases the contact area between the polymer and the nanomaterial, and its binding energy falls between that of the polymer support layer and the conductive layer, resolving the issue of poor adhesion caused by the large difference in binding energy between the organic and inorganic layers. This composite current collector exhibits excellent adhesion and stability, significantly improving the safety performance and high-temperature cycling performance of batteries prepared based on it.

[0014] It should be noted that the organic groups in the silane coupling agent can react with the polymer, and the organic groups can also react with each other. Therefore, the silane coupling agent can tightly bond the polymer support layer and the transition layer, improving adhesion. In addition, due to the high bond energy of the Si-O bond (363 kJ / mol), it is relatively stable and has high heat resistance and high temperature resistance. Therefore, the presence of the thermally stable transition layer can protect the polymer support layer when subjected to high temperatures and localized heat, thereby improving the stability and high-temperature cycle performance of the battery based on this composite current collector.

[0015] In one embodiment, the polymer support layer is made of at least one of polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), and polyimide (PI).

[0016] As an optional technical solution of this application, the general structural formula of the silane coupling agent is (R1O)3-Si-R2-R3, wherein R1 includes substituted or unsubstituted C1-C4 alkyl groups, R2 includes straight-chain or branched alkyl groups having substituted or unsubstituted C1-C18, straight-chain or branched alkenyl groups having substituted or unsubstituted C2-C18 and having at least one double bond, straight-chain or branched alkynyl groups having substituted or unsubstituted C2-C18 and having at least one triple bond, saturated or at least partially unsaturated cycloalkyl groups having substituted or unsubstituted C3-C18, and at least one containing -NH-, and R3 includes at least one of -OH, -NH2, vinyl, acrylate groups, epoxy groups, halogen groups, and alkali metal groups.

[0017] It should be noted that silane coupling agents are preferably selected that contain functional groups that can react with at least one of the polymer, nanomaterials in the transition layer, and conductive layer, thereby making the bonding between the inorganic interface and the organic interface tighter.

[0018] In one embodiment, the silane coupling agent comprises at least one of vinyl, amino, mercapto, and epoxy groups.

[0019] In one embodiment, the silane coupling agent includes vinyltrimethoxysilane (A-171). At least one of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH-792), 3-aminopropyltrimethoxysilane (APTMS), 3-mercaptopropyltrimethoxysilane (MPS), bis(triethoxysilylpropyl)tetrasulfide (TESPT), 3-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and 3-(methacryloyloxy)propyltrimethoxysilane (KH-570), preferably at least two of vinyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane.

[0020] As an optional technical solution of this application, the nano-metallic element includes at least one of aluminum, copper, gold, silver, nickel, zinc, chromium, cobalt, lead, tin, niobium, titanium and tantalum, and may further be at least one of aluminum, copper and zinc.

[0021] In one embodiment, the nano-metal oxide includes at least one of aluminum oxide, copper oxide, gold oxide, silver oxide, nickel oxide, zinc oxide, chromium oxide, cobalt oxide, lead oxide, tin oxide, niobium oxide, titanium oxide, and tantalum oxide, and may further be at least one of aluminum oxide, copper oxide, titanium oxide, and zinc oxide.

[0022] In one embodiment, the particle size D50 of the nano-metal oxide is 1-100nm, for example, it can be 1nm, 5nm, 10nm, 30nm, 50nm, 70nm or 90nm, and can be further selected as 5-80nm.

[0023] As an optional technical solution of this application, the molar ratio of the nano-metal material and the silane coupling agent is 1:(0.1-0.5), for example, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4 or 1:0.5, and can be further selected as 1:(0.1-0.4).

[0024] In this application, if the molar ratio of nanomaterials to silane coupling agent is too small, i.e., the amount of silane coupling agent used is too large, the excess silane coupling agent will entangle with each other, affecting subsequent use; if the molar ratio of nanomaterials to silane coupling agent is too large, i.e., the amount of silane coupling agent used is too small, the modification will be insufficient and the effect will not be obvious.

[0025] In one embodiment, the thickness of the transition layer is ≥5nm, for example, it can be 5nm, 50nm, 100nm, 150nm, 200nm or 300nm, etc., and can be selected as 10-100nm, and further selected as 20-50nm.

[0026] In this application, if the thickness of the transition layer is too thin, it cannot effectively improve the adhesion of the composite current collector and does not significantly improve the high-temperature cycling performance of the battery; if the thickness of the transition layer is too thick, it will not further improve the adhesion and high-temperature cycling performance of the battery.

[0027] As an optional technical solution of this application, the thickness of the polymer support layer is 1-10μm, for example, it can be 1μm, 3μm, 5μm, 7μm or 9μm, etc.

[0028] In this application, considering the application requirements of composite current collectors, and taking into account the difficulty and cost of the preparation process, the thickness of the polymer base film can be selected as 1-10 μm.

[0029] In one embodiment, the material of the conductive layer includes at least one selected from aluminum, copper, gold, silver, nickel, zinc, and their alloys.

[0030] It should be noted that "and its alloys" refers to alloys composed of at least one of aluminum, copper, gold, silver, nickel and zinc, such as aluminum alloys, copper-aluminum alloys, copper-gold alloys or copper-nickel alloys.

[0031] In one embodiment, the thickness of the conductive layer is 400-2000 nm, for example, it can be 400 nm, 500 nm, 1000 nm, 1500 nm or 2000 nm, and can be further selected as 800-1200 nm.

[0032] In this application, if the conductive layer is too thin, the conductivity of the composite current collector will be poor; if the conductive layer is too thick, the composite current collector will be too heavy, which is not conducive to improving the energy density of the battery. Considering both conductivity and energy density improvement, a thickness of 800-1200 nm can be selected.

[0033] It should be noted that the metal elements in the transition layer and the metal elements in the conductive layer have similar physical properties, which can enhance the adhesion between the transition layer and the conductive layer.

[0034] As an optional technical solution of this application, the composite current collector further includes a protective layer, which is disposed on the surface of the conductive layer away from the polymer support layer.

[0035] In this application, the purpose of providing a protective layer is to prevent the conductive layer from being chemically corroded or physically damaged.

[0036] It should be noted that when protective layers are provided on both sides of the composite current collector, the materials of the protective layers on both sides may be the same or different, and the thickness may be the same or different.

[0037] In one embodiment, the material of the protective layer includes at least one of nickel, chromium, nickel-chromium alloy, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, carbon nanotubes, carbon nanofibers, graphene, and graphene oxide.

[0038] In one embodiment, the thickness of the protective layer is 10-100nm, for example, it can be 10nm, 30nm, 50nm, 70nm, 90nm or 100nm, and may be further selected as 20-80nm.

[0039] Secondly, this application provides a method for preparing the composite current collector as described in the first aspect, the method comprising the following steps:

[0040] The composite current collector is obtained by sequentially depositing a transition layer and a conductive layer on at least one side surface of the polymer support layer.

[0041] The preparation method provided in this application is simple and has good prospects for industrialization.

[0042] As an optional technical solution of this application, the preparation method of the polymer support layer includes melt-extrusion-biaxial stretching method.

[0043] As an optional technical solution in this application, the preparation steps of the transition layer include:

[0044] (1) Preparation of silane coupling agent modified metal solution:

[0045] A silane coupling agent, nanomaterials, and solvent are mixed and reacted to obtain a silane coupling agent-modified metal solution.

[0046] (2) The metal solution modified by the silane coupling agent is coated on at least one side surface of the polymer support layer and dried to obtain the transition layer.

[0047] In one embodiment, the reaction temperature of the reaction in step (1) is room temperature to 100°C, such as 40°C, 60°C, 80°C or 100°C, and the reaction time is 0.5-4h, such as 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.

[0048] It should be noted that this application does not limit the room temperature. For example, room temperature refers to 25±5℃, such as 20℃, 25℃ or 30℃.

[0049] In one embodiment, during the mixing process described in step (1), an organic base is added to adjust the pH so that the pH value of the mixed solution is 7-9, for example, it can be 7, 7.5, 8, 8.5 or 9.

[0050] It should be noted that when the silane coupling agent is weakly acidic, the above-mentioned organic base needs to be added for adjustment; when the silane coupling agent is neutral or alkaline, no organic base needs to be added.

[0051] In one embodiment, the organic base comprises tetramethylammonium hydroxide (TMAH).

[0052] In one embodiment, the solid content of the silane coupling agent modified metal solution in step (1) is 0.5-60 mg / mL, for example, it can be 0.5 mg / mL, 1 mg / mL, 5 mg / mL, 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL or 60 mg / mL, and can be further selected as 5-30 mg / mL.

[0053] In this application, if the solid content of the metal solution modified with silane coupling agent is too low, the deposition amount will be insufficient; if the solid content of the metal solution modified with silane coupling agent is too high, it will easily lead to solid precipitation. Therefore, a further selectable range is 5-30 mg / mL.

[0054] As an optional technical solution of this application, the method for preparing the conductive layer includes at least one of vapor deposition, magnetron sputtering, chemical plating, electroplating and CVD, and may further be electroplating or magnetron sputtering.

[0055] In one embodiment, the specific process conditions for preparing the conductive layer in the electroplating method include: a current intensity of 20,000-50,000 A and a current density of 5,000-10,000 A / m. 2 The concentration of copper ions in the electroplating solution is 65-100 g / L, and the concentration of acid in the electroplating solution is 90-110 g / L.

[0056] In one embodiment, the electroplating method uses a high-purity metal (purity ≥ 99.9%) as the anode and a titanium plate as the cathode.

[0057] In one embodiment, the specific process conditions for preparing the conductive layer in the magnetron sputtering method include: a power of 2-20kW (e.g., 2kW, 5kW, 10kW, 15kW, or 20kW), a vacuum degree ≤0.1Pa, a gas source flow rate of 20-500mL / min (e.g., 20mL / min, 50mL / min, 100mL / min, 200mL / min, 300mL / min, 400mL / min, or 500mL / min), and a coating time of 0.1-120s.

[0058] In one embodiment, the magnetron sputtering method uses a high-purity aluminum target (purity ≥ 99.9%) and a DC power supply.

[0059] In one embodiment, a protective layer is further disposed on the surface of the conductive layer away from the polymer support layer, and the protective layer is prepared by at least one of physical vapor deposition, chemical vapor deposition, in-situ molding, and coating.

[0060] As an optional technical solution of this application, the preparation method includes the following steps:

[0061] (1) Preparation of silane coupling agent modified metal solution:

[0062] The silane coupling agent and the nano-metal material were dispersed in ethanol and stirred at room temperature to 100°C for 0.5-4 hours until the reaction was complete. After centrifugation and washing, the mixture was ultrasonically dispersed in ethanol, and an organic base was added to adjust the pH to 7-9 to obtain a silane coupling agent modified metal solution with a solid content of 0.5-60 mg / mL.

[0063] (2) The metal solution modified by the silane coupling agent is coated on at least one side surface of the polymer support layer and dried to obtain the transition layer;

[0064] (3) A conductive layer with a thickness of 400-2000 nm is prepared on the surface of the transition layer away from the polymer support layer by electroplating or magnetron sputtering.

[0065] (4) A protective layer is prepared on the surface of the conductive layer away from the polymer support layer. The method for preparing the protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ molding and coating.

[0066] Thirdly, this application provides a lithium-ion battery, wherein the electrodes of the lithium-ion battery include a composite current collector as described in the first aspect.

[0067] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0068] Compared with the prior art, this application has the following advantages:

[0069] (1) This application introduces a nano-metal material modified with a silane coupling agent as a transition layer between the polymer support layer and the conductive layer. The silane coupling agent tightly binds the organic and inorganic interfaces, improving the adhesion between the polymer support layer and the transition layer. Simultaneously, surface modification of the nano-metal material with the silane coupling agent reduces particle agglomeration, allowing for more uniform distribution within the transition layer and reducing roughness, thereby enhancing the adhesion between the conductive layer and the transition layer. Furthermore, this transition layer increases the contact area between the polymer and the nano-metal material, and its binding energy is between that of the polymer support layer and the conductive layer, solving the problem of poor adhesion caused by the large difference in binding energy between the organic and inorganic layers. Finally, due to the high bond energy of the Si-O bond (363 kJ / mol), the heat resistance and high-temperature performance of the transition layer are improved, protecting the polymer support layer when subjected to high temperatures and localized heat. Therefore, this composite current collector exhibits excellent adhesion and stability, significantly improving the safety performance and high-temperature cycling performance of the battery prepared based on it.

[0070] (2) The preparation method provided in this application is simple and conducive to promoting the application of composite current collectors.

[0071] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0072] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0073] Figure 1 is a schematic diagram of the composite current collector prepared in Example 1 of this application.

[0074] Among them, 1-polymer support layer; 2-transition layer; 3-conductive layer; 4-protective layer. Detailed Implementation

[0075] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0076] Example 1

[0077] This embodiment provides a composite current collector, the structural schematic of which is shown in Figure 1. The composite current collector includes:

[0078] Polymer support layer 1, which is made of PET and has a thickness of 6μm;

[0079] A transition layer 2 is disposed on both sides of the polymer support layer 1. The material of the transition layer 2 includes a nano-metal oxide modified with a silane coupling agent, wherein the silane coupling agent is A-171, the nano-metal oxide is zinc oxide, the particle size D50 of the zinc oxide is 50 nm, the molar ratio of the nano-metal oxide to the silane coupling agent is 1:0.3, and the thickness of the single-sided transition layer 2 is 20 nm.

[0080] The conductive layer 3 is disposed on the surface of the transition layer 2 along a direction away from the polymer support layer 1, and its material is aluminum. The thickness of the single-sided conductive layer 3 is 850 nm.

[0081] The protective layer 4 is disposed on the surface of the conductive layer 3 along a direction away from the polymer support layer 1. The material of the protective layer 4 is chromium, and the thickness of each side of the protective layer 4 is 20 nm.

[0082] This embodiment also provides a method for preparing the above-mentioned composite current collector, the method comprising the following steps:

[0083] (1) After ultrasonically dispersing zinc oxide particles in ethanol, A-171 was added, followed by organic base (TMAH) ethanol solution. The molar ratio of the three was 1:0.3:0.15. The pH of the resulting mixture was 8. The mixture was then heated to 80°C and stirred for 0.5 h. The reaction was then stopped, cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain an A-171 modified ZnO ethanol solution with a solid content of 15 mg / mL.

[0084] (2) The ZnO ethanol solution modified by A-171 is ultrasonically coated on both sides of the PET film and dried to obtain a PET composite film with a double-sided transition layer 2.

[0085] (3) Preparation of conductive layer 3:

[0086] The PET composite film with double-sided transition layer 2 is placed in a magnetron sputtering machine, and an aluminum layer is deposited on each side of the composite film. The specific process conditions include: aluminum target (purity: 99.99%) as the target material, power of 2.8kW, argon flow rate of 70mL / min, coating vacuum degree of 0.1Pa, coating time of 100s, and cooling temperature of the main roller during the coating process of 0℃, to obtain a PET composite film with transition layer 2 and conductive layer 3.

[0087] (4) Preparation of protective layer 4:

[0088] The PET composite film having transition layer 2 and conductive layer 3 is immersed in a 0.5 g / L chromic anhydride aqueous solution (25°C) for 20 seconds. After treatment, it is washed in a pure water bath. After washing, it is dried in a 60°C oven to form protective layer 4, thus obtaining the composite current collector.

[0089] Example 2

[0090] The difference between this embodiment and Embodiment 1 is that the silane coupling agent is changed to KH-792.

[0091] The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] Example 3

[0093] The difference between this embodiment and Embodiment 1 is that the silane coupling agent is changed to APTMS.

[0094] The remaining preparation methods and parameters are consistent with those in Example 1.

[0095] Example 4

[0096] The difference between this embodiment and Example 1 is that the silane coupling agent is changed to MPS.

[0097] The remaining preparation methods and parameters are consistent with those in Example 1.

[0098] Example 5

[0099] The difference between this embodiment and Example 1 is that the silane coupling agent is changed to TESPT.

[0100] The remaining preparation methods and parameters are consistent with those in Example 1.

[0101] Example 6

[0102] The difference between this embodiment and Embodiment 1 is that the silane coupling agent is changed to KH-560.

[0103] The remaining preparation methods and parameters are consistent with those in Example 1.

[0104] Example 7

[0105] The difference between this embodiment and Embodiment 1 is that the silane coupling agent is changed to KH-570.

[0106] The remaining preparation methods and parameters are consistent with those in Example 1.

[0107] Example 8

[0108] The difference between this embodiment and Embodiment 2 is that the silane coupling agent is adjusted to a mixture of KH-792 and MPS, that is, step (1) is adjusted to:

[0109] Zinc oxide particles were ultrasonically dispersed in ethanol, KH-792 was added first, followed by an organic base (TMAH) ethanol solution. The mixture was then heated to 80°C and stirred for 0.5 h. MPS was then added. The molar ratio of zinc oxide, KH-792, MPS and TMAH was 1:0.15:0.15:0.15. The mixture was stirred again for 0.5 h, and the reaction was stopped. The mixture was cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain a silane coupling agent modified ZnO ethanol solution.

[0110] The remaining preparation methods and parameters are consistent with those in Example 2.

[0111] Example 9

[0112] The difference between this embodiment and Embodiment 8 is that zinc oxide particles are replaced with titanium dioxide particles.

[0113] The remaining preparation methods and parameters are consistent with those in Example 8.

[0114] Example 10

[0115] The difference between this embodiment and Embodiment 2 is that the silane coupling agent is adjusted to a mixture of KH-792 and TESPT, that is, step (1) is adjusted to:

[0116] Zinc oxide particles were ultrasonically dispersed in ethanol, KH-792 was added first, followed by an organic base (TMAH) ethanol solution. The mixture was then heated to 80°C and stirred for 0.5 h. TESPT was then added. The molar ratio of zinc oxide, KH-792, TESPT and TMAH was 1:0.15:0.15:0.15. The mixture was stirred again for 0.5 h, and the reaction was stopped. The mixture was cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain a silane coupling agent modified ZnO ethanol solution.

[0117] The remaining preparation methods and parameters are consistent with those in Example 2.

[0118] Example 11

[0119] The difference between this embodiment and Embodiment 2 is that the silane coupling agent is adjusted to a mixture of KH-792 and KH-560, that is, step (1) is adjusted to:

[0120] Zinc oxide particles were ultrasonically dispersed in ethanol, KH-792 was added first, followed by an organic base (TMAH) ethanol solution. The mixture was then heated to 80°C and stirred for 0.5 h. KH-560, which had been pre-ring-opened with BF3, was then added. The molar ratio of zinc oxide, KH-792, KH-560, and TMAH was 1:0.15:0.15:0.15. The mixture was stirred again for 0.5 h, and the reaction was stopped. The mixture was cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain a silane coupling agent modified ZnO ethanol solution.

[0121] The remaining preparation methods and parameters are consistent with those in Example 2.

[0122] Example 12

[0123] The difference between this embodiment and Embodiment 2 is that the silane coupling agent is adjusted to a mixture of KH-792 and KH-570, that is, step (1) is adjusted to:

[0124] Zinc oxide particles were ultrasonically dispersed in ethanol, KH-792 was added first, followed by an organic base (TMAH) ethanol solution. The mixture was then heated to 80°C and stirred for 0.5 h. KH-570, which had been pre-activated by EDC, was then added. The molar ratio of zinc oxide, KH-792, KH-570 and TMAH was 1:0.15:0.15:0.15. The mixture was stirred again for 0.5 h, and the reaction was stopped. The mixture was cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain a silane coupling agent modified ZnO ethanol solution.

[0125] The remaining preparation methods and parameters are consistent with those in Example 2.

[0126] Example 13

[0127] The difference between this embodiment and Example 4 is that the silane coupling agent is adjusted to a mixture of MPS and KH-560, that is, step (1) is adjusted to:

[0128] Zinc oxide particles were ultrasonically dispersed in ethanol, MPS was added first, followed by an organic base (TMAH) ethanol solution. The mixture was then heated to 80°C and stirred for 0.5 h. KH-560, which had been pre-ring-opened by BF3, was then added. The molar ratio of zinc oxide, MPS, KH-560, and TMAH was 1:0.15:0.15:0.15. The mixture was stirred again for 0.5 h, and the reaction was stopped. The mixture was cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain a silane coupling agent modified ZnO ethanol solution.

[0129] The remaining preparation methods and parameters are consistent with those in Example 4.

[0130] Example 14

[0131] The difference between this embodiment and Embodiment 6 is that the silane coupling agent is adjusted to a mixture of KH-560 and KH-570, that is, step (1) is adjusted to:

[0132] Zinc oxide particles were ultrasonically dispersed in ethanol, KH-560 was added first, followed by an organic base (TMAH) ethanol solution. The mixture was then heated to 80°C and stirred for 0.5 h. KH-570 was then added. The molar ratio of zinc oxide, KH-560, KH-570 and TMAH was 1:0.15:0.15:0.15. The mixture was stirred again for 0.5 h, and the reaction was stopped. The mixture was cooled to room temperature (25°C), and the solvent was removed by centrifugation. The mixture was then ultrasonically dispersed in ethanol again to obtain a silane coupling agent modified ZnO ethanol solution.

[0133] The remaining preparation methods and parameters are consistent with those in Example 6.

[0134] Example 15

[0135] The difference between this embodiment and Embodiment 10 is that the thickness of the transition layer is 10 nm.

[0136] The remaining preparation methods and parameters are consistent with those in Example 10.

[0137] Example 16

[0138] The difference between this embodiment and Embodiment 10 is that the thickness of the transition layer is 50 nm.

[0139] The remaining preparation methods and parameters are consistent with those in Example 10.

[0140] Example 17

[0141] The difference between this embodiment and Embodiment 10 is that the thickness of the transition layer is 100 nm.

[0142] The remaining preparation methods and parameters are consistent with those in Example 10.

[0143] Example 18

[0144] The difference between this embodiment and Embodiment 11 is that the molar ratio of zinc oxide, KH-792, KH-560 and TMAH is 1:0.15:0.05:0.05.

[0145] The remaining preparation methods and parameters are consistent with those in Example 11.

[0146] Example 19

[0147] The difference between this embodiment and Example 11 is that the molar ratio of zinc oxide, KH-792, KH-560 and TMAH is 1:0.15:0.1:0.1.

[0148] The remaining preparation methods and parameters are consistent with those in Example 11.

[0149] Example 20

[0150] The difference between this embodiment and Embodiment 11 is that the molar ratio of zinc oxide, KH-792, KH-560 and TMAH is 1:0.15:0.2:0.2.

[0151] The remaining preparation methods and parameters are consistent with those in Example 11.

[0152] Example 21

[0153] The difference between this embodiment and Example 1 is that the molar ratio of nano-metal oxide and silane coupling agent is 1:0.05.

[0154] The remaining preparation methods and parameters are consistent with those in Example 1.

[0155] Example 22

[0156] The difference between this embodiment and Example 1 is that the molar ratio of nano-metal oxide and silane coupling agent is 1:1.

[0157] The remaining preparation methods and parameters are consistent with those in Example 1.

[0158] Comparative Example 1

[0159] The difference between this comparative example and Example 1 is that no transition layer is provided.

[0160] The remaining preparation methods and parameters are consistent with those in Example 1.

[0161] Comparative Example 2

[0162] The difference between this comparative example and Example 1 is that the transition layer is a nickel-chromium alloy layer with a thickness of 20 nm, and the specific process conditions are as follows:

[0163] The target material was a nickel-chromium target (purity: 99.99%), the power was 4.0KW, the argon flow rate was 50mL / min, the coating vacuum degree was 0.1Pa, the coating time was 5s, and the temperature of the main roller during the coating process was 20℃.

[0164] The remaining preparation methods and parameters are consistent with those in Example 1.

[0165] Comparative Example 3

[0166] The difference between this comparative example and Example 1 is that the transition layer is a pure zinc oxide layer with a thickness of 20 nm, and the specific process conditions are as follows:

[0167] The target material was zinc oxide (purity: 99.99%), the power was 5.7kW, the argon flow rate was 50mL / min, the coating vacuum degree was 0.1Pa, the coating time was 5s, and the temperature of the main roller during the coating process was 20℃.

[0168] The remaining preparation methods and parameters are consistent with those in Example 1.

[0169] Performance testing

[0170] The composite current collectors prepared in the above embodiments and comparative examples were subjected to adhesion force tests, and then assembled into batteries. The cycle performance and safety performance of the batteries were tested. The specific test methods are as follows:

[0171] 1) Adhesion test:

[0172] Cut a sample of the composite current collector with a width of 24 mm and a length of 300 mm. Fold one end of the cut sample together with adhesive to form a folded layer of about 12 mm in length. Attach the other end of the sample to one end of a steel plate and roll it twice with an adhesive tape roller at a speed of 600 mm / min. Place the sample in an electronic peel tester, set the test speed to 300 mm / min, and the sample width to 24 mm. The equipment automatically records the force value during the peeling process and reports the peel strength of the sample accordingly.

[0173] Battery assembly: For the positive electrode, the positive electrode current collector is the composite current collector prepared in the above examples and comparative examples, and the positive electrode material is LiNi. 0.6 Mn 0.2 Co 0.2 O2 (NCM622); For the negative electrode: the negative electrode current collector uses traditional copper foil (6μm thick), and the negative electrode material uses artificial graphite; For the separator, an alumina ceramic-coated polyethylene separator (25μm thick) is used. μm For the electrolyte, use 1 mol·L⁻¹ -1 A carbonate solution of LiPF6 is prepared using a mixture of propylene carbonate, ethylene carbonate, and ethyl methyl carbonate in a mass ratio of 1:1:1. A lithium-ion battery is assembled using the above materials.

[0174] 2) Cyclic performance test:

[0175] The test steps include: ① Discharge the battery cell I1 (1-hour discharge current) to the discharge termination voltage at 45℃, and let it stand for 30 minutes; ② Charge the battery cell with a constant current of I1 to the charging termination voltage, then switch to constant voltage charging, and stop charging when the charging termination current drops to 0.05 times I1, and let it stand for 30 minutes after charging; ③ Discharge the battery cell with I1 to the discharge termination voltage; ④ Repeat steps ①-③ for 500 cycles, record the battery capacity at the first cycle and the 500th cycle, and calculate the battery capacity retention rate, which is the battery capacity at the 500th cycle / the battery capacity at the first cycle × 100%.

[0176] The test results are shown in Table 1.

[0177] Table 1

[0178] analyze:

[0179] As shown in the table above, this application introduces a nanomaterial modified with a silane coupling agent as a transition layer between the polymer support layer and the conductive layer. This improves the adhesion between the polymer support layer and the transition layer, while also enhancing the adhesion between the conductive layer and the transition layer. Furthermore, due to the high bond energy of the Si-O bond (363 kJ / mol), the heat resistance and high-temperature performance of the transition layer are improved, protecting the polymer support layer under high temperature and localized heat. Therefore, this composite current collector exhibits excellent adhesion and stability, significantly improving the safety performance and high-temperature cycling performance of the battery prepared based on it.

[0180] As can be seen from Examples 1 and 2-7, adjusting the type of silane coupling agent shows that various silane coupling agents can achieve similar beneficial effects.

[0181] As can be seen from Examples 2 and 8, and Examples 10-12, adjusting the silane coupling agent to a combination of multiple coupling agents can better improve the adhesion of the composite current collector and the cycle performance of the battery.

[0182] As can be seen from Examples 8 and 9, replacing zinc oxide particles with titanium dioxide particles has a similar effect on improving the adhesion of the composite current collector and the cycle performance of the battery.

[0183] As can be seen from Examples 1 and 21-22, if the molar ratio of nano-metal material to silane coupling agent is too large, that is, the amount of silane coupling agent is too small, the modification is insufficient, and the adhesion of the composite current collector and the cycle performance of the battery are poor. If the molar ratio of nano-metal material to silane coupling agent is too small, that is, the amount of silane coupling agent is too large, the excess silane coupling agent will entangle with each other, affecting subsequent use, and the adhesion of the composite current collector and the cycle performance of the battery will deteriorate.

[0184] As can be seen from Example 1 and Comparative Example 1, if a transition layer is not provided, the adhesion between the support layer and the conductive layer is difficult to improve, resulting in battery capacity loss and potential safety hazards due to detachment. This has a significant impact on the electrochemical and safety performance of the battery with the electrode made of this composite current collector.

[0185] As can be seen from Example 1 and Comparative Example 2, if the transition layer is a nickel-chromium alloy layer, the improvement on adhesion is very limited, and the poor adhesion is often particularly noticeable after high-temperature cycling.

[0186] As can be seen from Example 1 and Comparative Example 3, if the transition layer is a pure zinc oxide layer, the improvement on adhesion is very limited, and the poor adhesion is often particularly noticeable after high-temperature cycling. This not only causes battery capacity loss, but also makes it easier to cause safety hazards due to detachment. This has a great impact on the electrochemical performance and safety performance of the battery with the electrode made of this composite current collector.

[0187] The applicant declares that this application illustrates the process method through the above embodiments, but this application is not limited to the above process steps, that is, it does not mean that this application must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent substitutions of the raw materials used in this application, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of this application.

Claims

1. A composite current collector, comprising: Polymer support layer; A transition layer is disposed on at least one side of the surface of the polymer support layer, wherein the material of the transition layer comprises a silane coupling agent modified nano-metal material, wherein the nano-metal material comprises nano-metal element and / or nano-metal oxide; A conductive layer is disposed on the surface of the transition layer in a direction away from the polymer support layer.

2. The composite current collector according to claim 1, wherein, The general structural formula of the silane coupling agent is (R1O)3-Si-R2-R3, wherein R1 includes substituted or unsubstituted C1-C4 alkyl groups, R2 includes straight-chain or branched alkyl groups having substituted or unsubstituted C1-C18, straight-chain or branched alkenyl groups having substituted or unsubstituted C2-C18 and at least one double bond, straight-chain or branched alkynyl groups having substituted or unsubstituted C2-C18 and at least one triple bond, saturated or at least partially unsaturated cycloalkyl groups having substituted or unsubstituted C3-C18, and at least one containing -NH-, and R3 includes at least one of -OH, -NH2, vinyl, acrylate groups, epoxy groups, halogen groups, and alkali metal groups; Optionally, the groups of the silane coupling agent include at least one of vinyl, amino, mercapto, and epoxy groups; Optionally, the silane coupling agent comprises at least one of vinyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane, preferably at least two of vinyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane.

3. The composite current collector according to claim 1 or 2, wherein, The nano-metallic element includes at least one of aluminum, copper, gold, silver, nickel, zinc, chromium, cobalt, lead, tin, niobium, titanium, and tantalum, and may further be at least one of aluminum, copper, and zinc; Optionally, the nano-metal oxide includes at least one of aluminum oxide, copper oxide, gold oxide, silver oxide, nickel oxide, zinc oxide, chromium oxide, cobalt oxide, lead oxide, tin oxide, niobium oxide, titanium oxide, and tantalum oxide, and may further be at least one of aluminum oxide, copper oxide, titanium oxide, and zinc oxide. Optionally, the particle size D50 of the nano-metal oxide is 1-100 nm, and more preferably 5-80 nm.

4. The composite current collector according to any one of claims 1-3, wherein, The molar ratio of the nano-metal material to the silane coupling agent is 1:(0.1-0.5), preferably 1:(0.1-0.4); Optionally, the thickness of the transition layer is ≥5nm, optionally 10-100nm, and further optionally 20-50nm; Optionally, the thickness of the polymer support layer is 1-10 μm; Optionally, the material of the conductive layer includes at least one of aluminum, copper, gold, silver, nickel, zinc, and their alloys; Optionally, the thickness of the conductive layer is 400-2000 nm, and more preferably 800-1200 nm.

5. The composite current collector according to any one of claims 1-4, wherein, The composite current collector also includes a protective layer, which is disposed on the surface of the conductive layer away from the polymer support layer. Optionally, the material of the protective layer includes at least one of nickel, chromium, nickel-chromium alloy, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, carbon nanotubes, carbon nanofibers, graphene, and graphene oxide. Optionally, the thickness of the protective layer is 10-100 nm, and more preferably 20-80 nm.

6. A method for preparing a composite current collector as described in any one of claims 1-5, comprising the following steps: The composite current collector is obtained by sequentially depositing a transition layer and a conductive layer on at least one side surface of the polymer support layer.

7. The preparation method according to claim 6, wherein, The preparation steps of the transition layer include: (1) Preparation of silane coupling agent modified metal solution: A silane coupling agent, nanomaterials, and solvent are mixed and reacted to obtain a silane coupling agent-modified metal solution. (2) The metal solution modified by the silane coupling agent is coated on at least one side surface of the polymer support layer and dried to obtain the transition layer; Optionally, the reaction temperature in step (1) is room temperature to 100°C, and the reaction time is 0.5 to 4 hours. Optionally, during the mixing process described in step (1), an organic base is added to adjust the pH so that the pH of the resulting solution is 7-9. Optionally, the solid content of the silane coupling agent modified metal solution in step (1) is 0.5-60 mg / mL, preferably 5-30 mg / mL.

8. The preparation method according to claim 6 or 7, wherein, The method for preparing the conductive layer includes at least one of vapor deposition, magnetron sputtering, chemical plating, electroplating, and CVD, preferably electroplating or magnetron sputtering. Optionally, in the electroplating method, the specific process conditions for preparing the conductive layer include: a current intensity of 20,000-50,000 A and a current density of 5,000-10,000 A / m. 2 The concentration of copper ions in the electroplating solution is 65-100 g / L, and the concentration of acid in the electroplating solution is 90-110 g / L. Optionally, in the magnetron sputtering method, the specific process conditions for preparing the conductive layer include: power of 2-20kW, vacuum degree ≤0.1Pa, gas source flow rate of 20-500mL / min, and coating time of 0.1-120s; Optionally, a protective layer is further provided on the surface of the conductive layer away from the polymer support layer. The preparation method of the protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ molding, and coating.

9. The preparation method according to any one of claims 6-8, wherein, The preparation method includes the following steps: (1) Preparation of silane coupling agent modified metal solution: The silane coupling agent and the nano-metal material were dispersed in ethanol and stirred at room temperature to 100°C for 0.5-4 hours until the reaction was complete. After centrifugation and washing, the mixture was ultrasonically dispersed in ethanol, and an organic base was added to adjust the pH to 7-9 to obtain a silane coupling agent modified metal solution with a solid content of 0.5-60 mg / mL. (2) The metal solution modified by the silane coupling agent is coated on at least one side surface of the polymer support layer and dried to obtain the transition layer; (3) A conductive layer with a thickness of 400-2000 nm is prepared on the surface of the transition layer away from the polymer support layer by electroplating or magnetron sputtering. (4) A protective layer is prepared on the surface of the conductive layer away from the polymer support layer. The method for preparing the protective layer includes at least one of physical vapor deposition, chemical vapor deposition, in-situ molding and coating.

10. A lithium-ion battery comprising the composite current collector as described in any one of claims 1-5 and the composite current collector prepared by the preparation method as described in any one of claims 6-9.

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