Composite current collectors and their preparation methods, lithium batteries, and electrical devices

Abstract

This application relates to the field of lithium battery technology, specifically a composite current collector, its preparation method, and lithium batteries and electrical devices. It addresses the problem in related technologies where the polymer film and metal layer of composite current collectors easily separate, hindering their normal use. A composite current collector includes: a substrate layer comprising a first surface and a second surface disposed opposite to each other along its thickness direction, the substrate layer being made of a polymer material; a first modified layer disposed on the first surface of the substrate layer, the first modified layer being made of one or more of silicon dioxide, titanium dioxide, and aluminum dioxide nanomaterials; and a first metal layer disposed on the surface of the first modified layer away from the substrate layer. This application is used for the preparation of lithium batteries.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a composite current collector and its preparation method, as well as lithium batteries and electrical devices. Background Technology

[0002] Currently, lithium batteries are increasingly developing towards higher energy density, higher volume utilization, and higher safety.

[0003] Compared to traditional pure metal current collectors, composite current collectors, with their high-molecular polymer films, offer advantages such as high tensile strength, softness, thin coating, light weight, and good internal insulation. Firstly, composite current collectors are less prone to burrs, and even if burrs do appear, their softness and thin coating minimize the likelihood of them puncturing the separator, effectively preventing internal short circuits and improving battery safety. Secondly, composite current collectors exhibit higher energy density per unit weight for the same thickness. Furthermore, the thickness of composite current collectors can be reduced, thereby achieving higher volumetric energy density.

[0004] However, the differences in surface structure and chemical environment between the polymer film and the metal layer used in current composite current collectors result in weak adhesion after they are combined. This leads to the easy separation of the polymer film and the metal layer during use, affecting the normal use of the composite current collector.

[0005] Therefore, it is necessary to develop a composite current collector that can effectively improve the adhesion performance between polymer films and metal layers. Summary of the Invention

[0006] Based on this, this application provides a composite current collector, its preparation method, a lithium battery, and an electrical device, to solve the problem that the polymer film and metal layer of the composite current collector are prone to separation in related technologies, which is not conducive to the normal use of the composite current collector.

[0007] Firstly, a composite current collector is provided, comprising:

[0008] The substrate layer includes a first surface and a second surface disposed opposite to each other along its thickness direction, and the material of the substrate layer includes a polymer material.

[0009] A first modified layer is disposed on the first surface of the substrate layer, and the material of the first modified layer includes one or more of silicon oxycarbonate, titanium oxycarbonate and aluminum oxycarbonate nanomaterials.

[0010] The first metal layer is disposed on the surface of the first modified layer away from the substrate layer.

[0011] In one possible implementation of the first aspect, the crystal lattice structure of the crystal near the surface of the first modified layer is doped with metal atoms contained in the first metal layer.

[0012] In one possible implementation of the first aspect, atoms of the first modified layer near the surface of the base layer are covalently bonded to the base layer.

[0013] In one possible implementation of the first aspect, the molar content of oxygen atoms on the surface of the first modified layer away from the substrate layer is 10% to 50%.

[0014] In one possible implementation of the first aspect, the average size of the grains on the surface of the first modified layer away from the substrate layer is 50–88 nm.

[0015] In one possible implementation of the first aspect, the surface tension of the surface of the first modified layer away from the substrate layer is 42–57 mN / m.

[0016] In one possible implementation of the first aspect, the surface roughness of the surface of the first modified layer away from the substrate layer is 75–125 nm.

[0017] In one possible implementation of the first aspect, the thickness of the first modified layer is 100–200 nm.

[0018] In one possible implementation of the first aspect, the thickness of the substrate layer is 2–20 μm.

[0019] In one possible implementation of the first aspect, the polymer material includes one or more of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, and polyamide.

[0020] In one possible implementation of the first aspect, it further includes: a second metal layer and a second modified layer;

[0021] The second modified layer is disposed on the second surface of the substrate layer, and the second metal layer is disposed on the surface of the second modified layer away from the substrate layer. The material and / or surface structure of the second modified layer are the same as those of the first modified layer.

[0022] In one possible implementation of the first aspect, it further includes: a first protective layer and / or a second protective layer;

[0023] The first protective layer is disposed on the surface of the first metal layer away from the substrate layer, and the second protective layer is disposed on the surface of the second metal layer away from the substrate layer.

[0024] In one possible implementation of the first aspect, the thickness of the first protective layer does not exceed 1 / 10 of the thickness of the first metal layer; the thickness of the second protective layer does not exceed 1 / 10 of the thickness of the second metal layer.

[0025] In one possible implementation of the first aspect, the thickness of the first protective layer and the second protective layer may be the same or different, and each may be independently 10 to 150 nm.

[0026] In one possible implementation of the first aspect, the thickness of the first metal layer is 500–2000 nm.

[0027] Secondly, a lithium battery is provided, comprising:

[0028] It is a composite current collector as described in the first aspect.

[0029] Thirdly, an electrical device is provided, comprising a lithium battery as described in the second aspect.

[0030] Fourthly, a method for preparing a composite current collector is provided, comprising:

[0031] A base layer is provided, the material of which includes polymer materials;

[0032] A first modified layer is formed on a first surface of the substrate layer along its thickness direction, wherein the material of the first modified layer includes one or more of silicon oxycarbonate, titanium oxycarbonate, and aluminum oxycarbonate nanomaterials.

[0033] A first metal layer is formed on the surface of the first modified layer away from the base layer.

[0034] In one possible implementation of the fourth aspect, a first modified layer is formed on a first surface of the substrate layer along its thickness direction using plasma-assisted chemical vapor deposition.

[0035] In one possible implementation of the fourth aspect, the radio frequency generator used in the plasma-assisted chemical vapor deposition method has a frequency of 10-15 MHz and a power of 100-300 W.

[0036] In one possible implementation of the fourth aspect, the reaction gases used in the plasma-assisted chemical vapor deposition method include: an oxygen gas source, a carbon gas source, and an X gas source, wherein X includes one or more of silicon, titanium, and aluminum, and the carbon gas source is a small molecule alkane such as methane, ethane, propane, etc.

[0037] In one possible implementation of the fourth aspect, during the reaction process, a plasma gas source is first introduced into the plasma-assisted chemical vapor deposition apparatus, and then a reaction gas is introduced into the plasma-assisted chemical vapor deposition apparatus.

[0038] The plasma gas supply rate results in a pressure of 10–30 mTorr within the plasma-assisted chemical vapor deposition apparatus, and the reaction gas supply rate results in a pressure of 35–50 mTorr within the plasma-assisted chemical vapor deposition apparatus. The flow rate ratios of the oxygen, carbon, and X element gas sources satisfy the following: the ratio of the total molar amount of oxygen and carbon contained in the oxygen and carbon gas sources to the total molar amount of X element is 2:1, and the molar ratio of oxygen to carbon is 3:17–3:1.

[0039] In one possible implementation of the fourth aspect, the reaction time is 2 to 20 minutes.

[0040] Compared with the prior art, this application has the following beneficial effects:

[0041] By setting a first modified layer on the first surface of the substrate layer, and since the material of the first modified layer includes one or more of silicon carbide, titanium carbide, and aluminum carbide nanomaterials, compared with the related technologies where the substrate layer and the first metal layer are prone to separation due to differences in surface structure and chemical environment, the first modified layer can form covalent bonds with the polymer material in the substrate layer. For example, silicon carbide nanomaterials can form CO-Si bonds with polymer materials, which can improve the bonding strength between the first modified layer and the substrate layer. On the other hand, the surface of the first modified layer away from the substrate layer can be connected to the first metal layer through physical and / or chemical means, thereby improving the bonding strength between the first metal layer and the substrate layer. This solves the problem in the related technologies where the substrate layer and the first metal layer are prone to separation, which is not conducive to the normal use of the composite current collector.

[0042] In addition, one or more of silicon dioxide, titanium dioxide, and aluminum dioxide nanomaterials are used as the first modified layer. The first modified layer is conductive. When the first metal layer is formed on its surface, it can also prevent the generation of static electricity on the surface of the first modified layer and the formation of pore defects in the composite current collector (such as the first metal layer, the first modified layer, and the base layer), thereby improving the product yield. Furthermore, the reduction of pore defects can further improve the density of the first metal layer, thereby improving the bonding strength between the first metal layer and the first modified layer. Attached Figure Description

[0043] Figure 1 A cross-sectional structural schematic diagram of a composite current collector provided in an embodiment of this application;

[0044] Figure 2 Cross-sectional infrared spectra of the polymer film and modified layer of Example 1 and Comparative Example 1 provided for embodiments of this application;

[0045] Figure 3 A schematic flowchart illustrating a method for preparing a composite current collector according to an embodiment of this application;

[0046] Figure 4 XPS spectra of cross sections of the polymer films of Example 1 and Comparative Example 1 provided for embodiments of this application;

[0047] Figure 5 EDS test diagram of the cross section of the composite current collector of Embodiment 1 provided in this application. Detailed Implementation

[0048] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] Based on the above technical problems, some embodiments of this application provide a composite current collector 10, such as... Figure 1 As shown, it includes: a substrate layer 1, a first metal layer 2, and a first modified layer 3. The substrate layer 1 includes a first surface 11 and a second surface 12 disposed opposite to each other along its thickness direction, and the material of the substrate layer 1 includes a polymer material. The first metal layer 2 is disposed on the first surface 11 of the substrate layer 1. The first modified layer 3 is disposed on the first surface of the substrate layer 1, and the material of the first modified layer 3 includes one or more of silicon oxycarbonate, titanium oxycarbonate, and aluminum oxycarbonate nanomaterials; the first metal layer 2 is disposed on the surface of the first modified layer 3 away from the substrate layer 1.

[0051] In some embodiments, such as Figure 1As shown, the composite current collector 10 further includes a second metal layer 4 and a second modified layer 5. The second modified layer 5 is disposed on the second surface 12 of the substrate layer 1, and the second metal layer 4 is disposed on the surface of the second modified layer 5 away from the substrate layer 1. The material and / or surface structure of the second modified layer 5 are the same as those of the first modified layer 3. Thus, the same material and / or surface structure as the first modified layer 3 can be obtained. For example, in some embodiments, the materials of the first modified layer 3 and the second modified layer 5 both include one or more of silicon oxycarbide, titanium oxycarbide, and aluminum oxycarbide nanomaterials, and the average grain size and surface roughness of the surfaces of the first modified layer 3 and the second modified layer 5 away from the substrate layer 1 are the same. The first modified layer 3 and the second modified layer 5 can be prepared by the same process conditions. In the following embodiments, the first metal layer 2 and the first modified layer 3 will be used as examples to describe this application in detail. The description of the second metal layer 4 can be referred to the following description of the first metal layer 2.

[0052] The aforementioned silicon dioxide nanomaterials, titanium dioxide nanomaterials, and aluminum dioxide nanomaterials all refer to silicon dioxide, titanium dioxide, and aluminum dioxide compounds with dimensions on the nanometer scale. Therefore, on the one hand, the first modified layer 3, containing silicon dioxide nanomaterials, titanium dioxide nanomaterials, and aluminum dioxide nanomaterials, can bond well with the polymer material because the atoms (such as oxygen atoms) in the first modified layer 3 can form covalent bonds with the polymer material, thereby improving the bonding strength between the first modified layer 3 and the substrate layer 1. On the other hand, the first modified layer 3 can be a nanofilm, with its surface away from the substrate layer 1 composed of nanoparticles (or grains), possessing a certain roughness. By adjusting the size of the nanoparticles, the surface roughness of the first modified layer 3 can be adjusted, thereby adjusting the bonding strength between the first modified layer 3 and the first metal layer 2. On the other hand, when the crystal lattice structure of the crystal on the surface of the first modified layer 3 away from the substrate layer 1 is similar to the metal lattice structure of the first metal layer 2, such as the silicon dioxide lattice structure and the metal lattice structure being both face-centered cubic lattice structures, it is beneficial for the metal lattice of the first metal layer 2 to be embedded in the lattice of the first modified layer 3 away from the substrate layer 1, thereby further improving the bonding strength between the first modified layer 3 and the first metal layer, and thus improving the adhesion between the first metal layer 2 and the substrate layer 1. On the other hand, for silicon dioxide nanomaterials, titanium dioxide nanomaterials, and aluminum dioxide nanomaterials, by controlling the number of oxygen atoms on the surface of the first modified layer 3 away from the base layer 1, the surface tension of the surface of the first modified layer 3 away from the base layer 1 can be adjusted, and the metal atoms and the oxygen atoms on the surface of the first modified layer 3 can generate interaction forces, such as forming metal-O bonds, thereby improving the adhesion between the first modified layer 3 and the first metal layer 2, and further improving the adhesion between the first metal layer 2 and the base layer 1, ultimately improving the bonding strength between the first metal layer 2 and the base layer 1.

[0053] In summary, by using a first modified layer 3 on the first surface of the substrate layer 1, and since the material of the first modified layer 3 includes one or more of silicon dioxide, titanium dioxide, and aluminum dioxide nanomaterials, compared with related technologies where the differences in surface structure and chemical environment between the substrate layer 1 and the first metal layer 2 make them prone to separation, the first modified layer 3 allows atoms to form covalent bonds with the polymer material in the substrate layer 1. For example, silicon dioxide nanomaterials can form CO-Si bonds with polymer materials, which can improve the bonding strength between the first modified layer 3 and the substrate layer 1. Furthermore, the surface of the first modified layer 3 away from the substrate layer 1 can be connected to the first metal layer 2 through physical and / or chemical means, thereby improving the bonding strength between the first metal layer 2 and the substrate layer 1. This solves the problem in related technologies where the substrate layer 1 and the first metal layer 2 are prone to separation, which is detrimental to the normal use of the composite current collector.

[0054] In addition, one or more of silicon dioxide, titanium dioxide, and aluminum dioxide nanomaterials are used as the first modified layer 3. The first modified layer 3 is conductive. When the first metal layer 2 is formed on its surface, it can also prevent the generation of static electricity on the surface of the first modified layer 3 and the formation of pore defects in the composite current collector (such as the first metal layer, the first modified layer, and the base layer), thereby improving the product yield. Furthermore, the reduction of pore defects can further improve the density of the first metal layer 2, thereby improving the bonding strength between the first metal layer 2 and the first modified layer 3.

[0055] In some embodiments, the crystal lattice structure of the first modified layer 3 near the surface of the first metal layer 2 is doped with metal atoms contained in the first metal layer 2.

[0056] In these embodiments, the material of the first modified layer 3 may include silicon carbide nanomaterials. The crystal structure of the silicon carbide nanomaterials may be a face-centered cubic crystal structure. The crystal structures of metals such as aluminum and copper used in the first metal layer 2 are also face-centered cubic structures. Therefore, the crystal structure of the crystals on the surface of the first modified layer 3 away from the substrate layer 1 and the crystal structure of the first metal layer 2 are easily interlocked. This results in the crystal structure of the crystals on the surface of the first modified layer 3 near the surface of the first metal layer 2 being doped with metal atoms contained in the first metal layer 2. The above features can be characterized by performing metal element line scanning on the cross sections of the first modified layer 3 and the first metal layer 2 using EDS (Energy Dispersive Spectrometer).

[0057] In some embodiments, silicon dioxide nanomaterials can be SiO2. x C y , x+y=2, 3:17≤x:y≤3:1.

[0058] In some embodiments, metal-oxide bonds are further formed between the first metal layer 2 and the first modified layer 3. This can further improve the bonding strength between the first metal layer 2 and the first modified layer 3. This feature can be characterized using XPS (X-ray photoelectron spectroscopy).

[0059] In some embodiments, the molar content of oxygen atoms on the surface of the first modified layer 3 away from the base layer 1 is 10% to 50%. The molar content of oxygen atoms is also the percentage of oxygen atoms in the total number of atoms.

[0060] In these embodiments, by controlling the molar content of oxygen atoms within the above-mentioned range, on the one hand, a suitable surface tension can be given to the surface of the first modified layer 3 away from the base layer 1, and on the other hand, a certain number of metal-oxygen bonds can be formed between oxygen atoms and the metal atoms contained in the first metal layer 2, thereby maximizing the bonding strength between the first metal layer 2 and the first modified layer 3.

[0061] It should be noted that the molar content of oxygen atoms can be characterized by XPS (X-ray photoelectron spectroscopy). During the test, X-rays are excited on the surface of the first modified layer 3, and the kinetic energy of the electrons emitted from the surface of the first modified layer 3 within a thickness range of 30 nm is measured to obtain the XPS spectrum.

[0062] In some embodiments, atoms of the first modified layer 3 near the surface of the base layer 1 are covalently bonded to the base layer 1.

[0063] In these embodiments, the bonding strength between the first modified layer 3 and the base layer 1 can be improved, thereby improving the bonding strength between the first metal layer 2 and the base layer 1.

[0064] This feature can be obtained by infrared spectroscopy characterization of the cross section of the modified substrate 1 (such as the first modified layer 3 and substrate 1).

[0065] For example, with the substrate layer 1 being a PP (Polypropylene) film, the first modified layer 3 and the PP film are bonded together via CO-Si bonds, and the infrared spectrum is shown below. Figure 2 As shown.

[0066] The above describes the situation where the surface of the first modified layer 3 away from the substrate layer 1 is bonded to the first metal layer 2 via chemical bonds. Those skilled in the art will understand that the bonding strength between the surface of the first modified layer 3 away from the substrate layer 1 and the first metal layer 2 is also related to the physical properties of the surface of the first modified layer 3 away from the substrate layer 1, such as surface tension and surface roughness. Therefore, in some embodiments, the surface tension of the surface of the first modified layer 3 away from the substrate layer 1 is 42–57 mN / m.

[0067] In these embodiments, by controlling the surface tension of the surface of the first modified layer 3 away from the base layer 1 within the range of 42 to 57 mN / m, the bonding strength between the first metal layer 2 and the first modified layer 3 can be maximized.

[0068] In some embodiments, the average size of the grains of the nanomaterial on the surface of the first modified layer 3 away from the substrate layer 1 is 50-88 nm, and the surface roughness of the surface of the first modified layer 3 away from the substrate layer 1 is 75-125 nm.

[0069] In these embodiments, the bonding strength between the first modified layer 3 and the first metal layer 2 can be maximized.

[0070] Based on the above, it should also be noted that the function of the first modified layer 3 is to improve the surface structure and properties of the base layer 1. Increasing the thickness of the first modified layer 3 under the condition of uniform modification cannot further improve the bonding strength between the first modified layer 3 and the first metal layer 2, and will also increase the raw material cost.

[0071] Based on this, in some embodiments, the thickness of the first modified layer 3 is 100-200 nm.

[0072] In these embodiments, by controlling the thickness of the first modified layer 3 within the above-mentioned range, the base layer 1 can be regarded as the result of silicon oxide surface modification treatment on the surface of the polymer film, which can improve the bonding strength between the polymer film and the metal layer without affecting the flexibility of the base layer 1.

[0073] In some embodiments, the elastic modulus of the modified substrate 1 is less than or equal to 3660 MPa.

[0074] In these embodiments, the flexibility of the composite current collector can be maintained to the greatest extent.

[0075] In some embodiments, the thickness of the substrate 1 is 2 to 20 μm.

[0076] The role of the substrate layer 1 is to promote the improvement of the energy density of the composite current collector. Experiments have shown that although the thinner the substrate layer 1 is, the better it is not necessarily true that the substrate layer 1 is thinner. This is because the substrate layer 1 also acts as a carrier, supporting the first metal layer 2 and the first modified layer 3 during the preparation of the composite current collector. Therefore, it is most suitable to control the thickness of the substrate layer 1 in the range of 2 to 20 μm.

[0077] The selection of the polymer material for the base layer 1 is not specifically limited. As long as the polymer material can promote the improvement of the energy density of the composite current collector and has good flexibility, it is acceptable.

[0078] In some embodiments, the polymer material includes one or more of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, and polyamide.

[0079] Polypropylene (PP) is a semi-crystalline thermoplastic with high impact resistance, strong mechanical properties, and resistance to various organic solvents and acid / alkali corrosion. Polyethylene (PE) is a thermoplastic resin obtained by polymerizing ethylene. It is odorless, non-toxic, has excellent low-temperature resistance, good chemical stability, resistance to most acids and alkalis, low water absorption, and excellent electrical insulation properties. Polyethylene terephthalate (PET) exhibits excellent physical and mechanical properties over a wide temperature range, with a long-term service temperature up to 120℃. It has excellent electrical insulation properties, maintaining good electrical performance even at high temperatures and high frequencies. Furthermore, it demonstrates good creep resistance, fatigue resistance, abrasion resistance, and dimensional stability. Polybutylene terephthalate (PBT) is a translucent or opaque, crystalline thermoplastic polyester resin produced by the condensation of 1,4-butanediol with terephthalic acid or terephthalate esters and a compounding process. It possesses excellent molding and processing properties, high cost-effectiveness, and comprehensive performance. Polyethylene naphthalate two-formic acid glycol ester (PEN) has a similar chemical structure to PET, but the difference lies in the molecular chain: PEN uses a more rigid naphthalene ring instead of the benzene ring found in PET. This naphthalene ring structure gives PEN higher physical and mechanical properties, gas barrier properties, chemical stability, and resistance to heat, ultraviolet radiation, and radiation compared to PET. Polyimide (PI) refers to a class of polymers containing an imide ring (-CO-NR-CO-) in its main chain and is one of the organic polymer materials with the best overall performance. Polypropylene (PPE) is a composite material made by blending other thermoplastic materials such as PS (styrene) and PA (polyamide, commonly known as nylon) into PPE. After processing and molding, it exhibits good geometric stability, chemical stability, electrical insulation, and a low coefficient of thermal expansion. Polyvinyl chloride (PVC) has good mechanical properties and excellent dielectric properties. Polyvinylidene fluoride (PVDF) has excellent properties such as anti-aging, chemical resistance, weather resistance, and UV radiation resistance. Polytetrafluoroethylene (PTFE) has excellent chemical stability, corrosion resistance, sealing properties, high lubricity and non-stickiness, electrical insulation, and good anti-aging ability. Polyphenylene sulfide (PPS) is a new type of high-performance thermoplastic resin with advantages such as high mechanical strength, high temperature resistance, chemical resistance, flame retardancy, good thermal stability, and excellent electrical properties.Polyphenylene oxide (PPO) is transparent, has a low relative density, and possesses excellent mechanical strength, resistance to stress relaxation, creep resistance, heat resistance, water resistance, water vapor resistance, and dimensional stability. Polystyrene (PS) products have extremely high transparency, with light transmittance exceeding 90%, good electrical insulation properties, are easy to color, have good processing flowability, good rigidity, and good chemical corrosion resistance. Polyamide (PA) has excellent comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance, and self-lubricating properties. It also has a low coefficient of friction, some flame retardancy, is easy to process, and is suitable for reinforcement and modification with glass fiber and other fillers, which can improve its performance and expand its application range.

[0080] In some embodiments, the materials of the first metal layer 2 and the second metal layer 4 can be any metal with conductivity. For example, the materials of the first metal layer 2 and the second metal layer 4 can be selected from one or more elements of copper, aluminum, nickel, titanium, and silver, or an alloy of multiple elements.

[0081] Among metallic materials, copper and aluminum foil have the best electrical conductivity and are inexpensive. Furthermore, for wound batteries, the electrodes used in their fabrication need a certain degree of flexibility to prevent brittle breakage during winding, and copper and aluminum foil are relatively soft metallic materials. Moreover, copper and aluminum foil are relatively stable in air. Aluminum readily reacts with oxygen in the air to form a dense aluminum oxide film on its surface, preventing further reactions. This thin aluminum oxide film also provides some protection for the aluminum in the electrolyte. Copper itself is relatively stable in air and undergoes virtually no chemical reaction in dry air.

[0082] For lithium batteries, the positive electrode potential is high, and copper foil is easily oxidized at high potential. Aluminum has a high oxidation potential, and the aluminum foil surface has a dense oxide foil, which has a good protective effect on the internal aluminum. Therefore, in some embodiments, when the composite current collector is the positive electrode current collector, the first metal layer 2 and the second metal layer 4 can both be aluminum or aluminum alloy. When the composite current collector is the negative electrode current collector, the first metal layer 2 and the second metal layer 4 can both be copper or copper alloy.

[0083] In some embodiments, such as Figure 1 As shown, the composite current collector 10 further includes a first protective layer 6 and / or a second protective layer 7. The first protective layer 6 is disposed on the surface of the first metal layer 2 away from the substrate layer 1, and the second protective layer 7 is disposed on the surface of the second metal layer 4 away from the substrate layer 1.

[0084] In these embodiments, by providing a first protective layer 6 and a second protective layer 7, the first metal layer 2 and the second metal layer 4 can be protected, preventing the first metal layer 2 and the second metal layer 4 from being exposed to the outside and being chemically corroded or physically damaged.

[0085] The materials of the first protective layer 6 and the second protective layer 7 may be the same or different, and their thicknesses may be the same or different. No specific limitations are made here, as long as the first protective layer 6 and the second protective layer 7 can protect the first metal layer 2 and the second metal layer 4.

[0086] In some embodiments, the materials of the first protective layer 6 and the second protective layer 7 are both selected from antioxidant materials.

[0087] The antioxidant material can be a metallic or non-metallic material.

[0088] Examples of metallic materials include those that do not readily oxidize in air, such as nickel, chromium, nickel-based alloys, and copper-based alloys. Examples of non-metallic materials include metal oxides and non-metallic elements.

[0089] Examples of metal oxide materials may include one or more of copper oxide, aluminum oxide, nickel oxide, chromium oxide, and cobalt oxide, while examples of non-metallic elements may include one or more of graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon nanofibers, and graphene.

[0090] In some embodiments, the thickness of the first protective layer 6 does not exceed 1 / 10 of the thickness of the first metal layer, and the thickness of the second protective layer 7 does not exceed 1 / 10 of the thickness of the second metal layer 4.

[0091] In these embodiments, by ensuring that the thickness of the first protective layer 6 does not exceed 1 / 10 of the thickness of the first metal layer and the thickness of the second protective layer 7 does not exceed 1 / 10 of the thickness of the second metal layer 4, the problem of increased resistivity of the composite current collector caused by excessive thickness of the first protective layer 6 and the second protective layer 7, which would lead to poor conductivity of the composite current collector, can be prevented.

[0092] In some embodiments, the thickness of the first protective layer 6 and the second protective layer 7 may be the same or different, and are independently 10 to 150 nm.

[0093] In these embodiments, by controlling the thickness of the first protective layer 6 and the second protective layer 7 within the range of 10 to 150 nm, it is possible to minimize the thickness of the first protective layer 6 and the second protective layer 7 while ensuring good protection of the first metal layer 6 and the second metal layer 7, thereby improving the energy density of the composite current collector.

[0094] Optionally, the thickness of both the first protective layer 6 and the second protective layer 7 can be 20–100 nm.

[0095] In some embodiments, the thickness of the first metal layer 2 is 500–2000 nm.

[0096] In these embodiments, by controlling the thickness of the first metal layer 2 within the range of 500 to 2000 nm, it is possible to ensure the high conductivity of the first metal layer 2 while preventing the problem of material waste caused by the first metal layer 2 being too thick.

[0097] Optionally, the thickness of the first metal layer 2 is 700–1200 nm.

[0098] Some embodiments of this application provide a lithium battery comprising the composite current collector as described above.

[0099] In some embodiments, the lithium battery described above may include a positive electrode and a negative electrode. The positive electrode may include a positive current collector and a positive active material, and the negative electrode may include a negative current collector and a negative active material.

[0100] In some embodiments, the positive current collector and / or the negative current collector may be the composite current collector described above.

[0101] When the positive electrode current collector is the composite current collector described above, the first metal layer and the second metal layer included in the composite current collector can both be aluminum foil. In this case, the lithium battery also includes a positive electrode active material formed on at least one surface of the composite current collector (such as two opposing surfaces of the composite current collector along its thickness direction). When the negative electrode current collector is the composite current collector described above, the first metal layer and the second metal layer included in the composite current collector can both be copper foil. In this case, the lithium battery also includes a negative electrode active material formed on at least one surface of the composite current collector.

[0102] Taking lithium-ion batteries as an example, the positive electrode active material can be a lithium alloy metal oxide material, and the negative electrode active material can be a carbon material, a silicon-based material, a titanium oxide material, a tin-based composite material, etc. Unlike lithium-ion batteries, in the case of lithium metal batteries, the negative electrode active material can be metallic lithium or its alloy metals.

[0103] Of course, in some embodiments, when the lithium battery is a lithium-ion battery, the positive electrode active material can also be a sodium alloy metal oxide material; in this case, the lithium-ion battery can also be called a sodium-ion battery. When the lithium battery is a lithium metal battery, the negative electrode active material can be metallic sodium or its alloy metal; in this case, the lithium metal battery can also be called a sodium metal battery. In other embodiments, when the lithium battery is a lithium metal battery, the negative electrode active material can be prepared as a slurry and coated onto the negative electrode current collector, or a negative electrode material layer (such as a lithium metal layer) can be formed on the negative electrode current collector by electroplating.

[0104] Some embodiments of this application provide an electrical device that includes a lithium battery as described above.

[0105] In some embodiments, examples of electrical devices may be electric vehicles, mobile phones, tablets, laptops, or digital cameras.

[0106] Some embodiments of this application provide a method for preparing a composite current collector, such as... Figure 3 As shown, it includes:

[0107] S31. A substrate layer 1 is provided, wherein the material of the substrate layer 1 includes a polymer material.

[0108] The base layer 1 can be obtained commercially or made in-house.

[0109] In some embodiments, the base layer 1 may be prepared from a polymer material through a preparation process of melting, extrusion, and stretching.

[0110] The aforementioned stretching can be unidirectional or bidirectional.

[0111] S32. A first modified layer 3 is formed on the first surface of the base layer 1 along its thickness direction. The material of the first modified layer 3 includes one or more of silicon oxide nanomaterials and titanium oxide nanomaterials.

[0112] Plasma-assisted chemical vapor deposition can be used to form a first modified layer 3 on the first surface 11 of the base layer 1 along its thickness direction.

[0113] Plasma is the fourth state of matter, a macroscopic system in an unbound state composed of equal amounts of free electrons and charged ions.

[0114] Chemical vapor deposition (CVD) is a process that uses gaseous substances to undergo chemical reactions on a solid surface to generate solid deposits.

[0115] Plasma can be generated by electrical breakdown, radio frequency discharge, microwave excitation, shock waves, high-energy particle streams, high-temperature heating, and other methods.

[0116] Plasma-assisted chemical vapor deposition (PCVD) is a solid-state deposition method that uses plasma generated by glow discharge to control the reaction pressure, gas flow rate, substrate (referring to the base layer) material temperature, and deposition time during low-pressure chemical vapor deposition, thereby controlling the nucleation and crystallization processes of the nanomaterials in the first modified layer 3.

[0117] The microscopic processes in this plasma-assisted chemical vapor deposition process are as follows:

[0118] Gas molecules collide with electrons in the plasma, producing active groups and ions. Active groups can diffuse directly to the substrate 1, or they can interact with other gas molecules or active groups to form chemical groups required for deposition. These chemical groups diffuse to the surface of the substrate 1. Gas molecules can also diffuse directly to the vicinity of the substrate 1 without undergoing the above activation process. Various chemical groups that reach the surface of the substrate undergo various deposition reactions and release reaction products. The reaction products are discharged from the system under the influence of unreacted gas molecules.

[0119] In some embodiments, the reactive gases used in the plasma-assisted chemical vapor deposition described above may include: an oxygen source, a carbon source, and an X source, wherein X includes one or more of silicon, titanium, and aluminum. Examples of carbon sources include short-chain alkanes such as methane, ethane, and propane.

[0120] In this process, an inert gas is used as the plasma gas source, and the reactant gas is the aforementioned gas molecules. By causing the gas molecules to collide with electrons in the plasma, active groups containing one or more silicon atoms, titanium atoms, and aluminum atoms, as well as oxygen atoms, are generated. These active groups containing one or more silicon atoms, titanium atoms, and aluminum atoms, as well as oxygen atoms, diffuse into the substrate 1, thereby forming a nanomaterial thin film on the substrate 1.

[0121] In this process, by controlling the flow rates of plasma gas source, oxygen and reaction gas, the nucleation process of nanomaterials in the first modified layer 3 can be controlled, thereby controlling the grain size and oxygen atom molar content (hereinafter referred to as: oxygen atom content) of nanomaterials in the first modified layer 3. Furthermore, the grain size, oxygen atom content, surface roughness and surface tension of the surface of the first modified layer 3 away from the substrate can be controlled, which prepares for improving the adhesion between the first modified layer 3 and the first metal layer 2.

[0122] In some embodiments, before the reaction begins, the pressure in the plasma-assisted chemical vapor deposition (PCVD) apparatus is reduced to below 10 mTorr by vacuuming. During the reaction, a plasma gas source is first introduced into the PCVD apparatus, followed by a reaction gas. The plasma gas flow rate is such that the pressure inside the PCVD apparatus is 10–30 mTorr, and the total flow rate of the reaction gas is such that the pressure inside the PCVD apparatus is 35–50 mTorr. The flow rate ratios of the oxygen, carbon, and X element gas sources satisfy the following: the ratio of the total molar amount of oxygen and carbon in the oxygen and carbon gas sources to the total molar amount of X element is 2:1, and the molar ratio of oxygen to carbon is 3:17–3:1.

[0123] In these embodiments, by first introducing a plasma gas source, which generates plasma under the action of glow discharge power generation, and then introducing a reactive gas, the plasma can be used to activate the reactive gas, causing the two to react and deposit one or more of silicon atoms, titanium atoms, and aluminum atoms, as well as oxygen atoms, on the surface of the substrate layer 1, thereby forming the first modified layer 3.

[0124] During this process, by controlling the pressure of the plasma gas source, the pressure of the reactant gas, and the flow ratio of the oxygen, carbon, and X element gas sources, the surface structure and properties of the first modified layer 3 can be adjusted. This ensures that the grain size, surface tension, surface roughness, and sheet resistance of the surface of the first modified layer 3 away from the substrate layer 1 meet application requirements. Furthermore, excessively high or low oxygen molar content is detrimental to the uniformity of oxygen atom distribution on the surface of the first modified layer 3, thus hindering the subsequent bonding between the first metal layer and the first modified layer 3. Conversely, excessively low carbon molar content hinders the improvement of surface conductivity of the first modified layer 3, thus impeding the reduction of surface porosity defects. Conversely, excessively high carbon molar content and excessively low oxygen content hinder the improvement of the bonding strength between the first metal layer and the first modified layer 3.

[0125] In some embodiments, the plasma gas source may include one or more of argon, helium, and neon. The silicon gas source may be an alkoxysilane, which may be selected from one or more of hexamethyloxydisiloxane, tetraethoxysilane, dimethyldiethoxysilane, ethyltriethoxysilane, and vinyltriethoxysilane.

[0126] The titanium element gas source can be a titanate ester, which can be selected from one or more of isopropyl titanate, n-propyl titanate, ethyl titanate, and methyl titanate.

[0127] The aluminum gas source can be alkyl aluminum, which can be selected from one or more of trimethylaluminum, triethylaluminum, and triisobutylaluminum.

[0128] The carbon source is a short-chain alkane, which can be one or more of methane, ethane, and propane.

[0129] The oxygen source can be oxygen gas.

[0130] In some embodiments, plasma-assisted chemical vapor deposition can employ a radio frequency generator to generate plasma, enabling low-temperature deposition. In this case, the frequency of the radio frequency generator can be 10–15 MHz, and the power can be 100–300 W.

[0131] By limiting the frequency and power of the RF generator within the aforementioned range, the deposition yield and the uniformity of oxygen atom distribution in the first modified layer 3 can be improved. Insufficient power results in poor deposition, while excessive power leads to uneven oxygen atom distribution in the first modified layer.

[0132] In some embodiments, the reaction time can be 2 to 20 minutes.

[0133] In these embodiments, the thickness and surface properties of the first modified layer 3 can be well controlled. If the reaction time is too short, the first modified layer 3 will not form completely, and the desired effect will not be achieved. If the time is too long, the thickness of the first modified layer 3 will increase cumulatively, which is not conducive to the control of raw material costs.

[0134] It should be noted that the aforementioned plasma-assisted chemical vapor deposition (PECVD) apparatus can be a roll-to-roll type, equipped with a winding roller, allowing PECVD to be performed on both sides of the polymer film. Specifically, a first modified layer 3 is formed on the first surface of the substrate 1, and a second modified layer 5 is formed on the second surface of the substrate 1. The parameters for the formation of the second modified layer 5 have the same value range as those for the formation of the first modified layer 3, and can be found in the description of each parameter above; further details are omitted here.

[0135] S33. A first metal layer 2 is formed on the surface of the first modified layer 3 away from the base layer 1.

[0136] The first metal layer 2 can be formed on the surface of the first modified layer 3 away from the substrate layer 1 by one or more of the following methods: physical vapor deposition (such as resistance heating vacuum evaporation, electron beam heating vacuum evaporation, laser heating vacuum evaporation, magnetron sputtering, etc.), electroplating, and chemical plating.

[0137] Similar to the second modified layer 5 described above, the preparation method of the second metal layer 4 can be the same as the preparation method of the first metal layer 2, and will not be repeated here.

[0138] S34. A first protective layer 6 is formed on the surface of the first metal layer 2 away from the base layer 1.

[0139] The first protective layer 6 can be formed on the surface of the first metal layer 2 away from the substrate layer 1 by one or more of the following methods: physical vapor deposition, chemical vapor deposition, in-situ molding, and coating.

[0140] Among them, vapor deposition can include one or more of vacuum evaporation and magnetron sputtering; chemical vapor deposition can include one or more of atmospheric pressure chemical vapor deposition and plasma-assisted chemical vapor deposition; in-situ forming can be a method of forming metal oxides (such as one or more of copper oxide, aluminum oxide, nickel oxide, chromium oxide, and cobalt oxide as described above) in situ on the surface of the first metal layer 2, thereby obtaining the first protective layer 6 containing metal oxides; coating method can include one or more of die coating, blade coating, and extrusion coating.

[0141] In some embodiments, the method further includes: Figure 3 As shown, a second protective layer 7 is formed on the surface of the second metal layer 4 away from the base layer 1.

[0142] The preparation method of the second protective layer 7 can be the same as that of the first protective layer 6, and will not be described in detail here.

[0143] The specific implementation methods of this application have been described above. In order to objectively illustrate the technical effects produced by this application, the following examples and comparative examples will be used to describe them.

[0144] In the following examples and comparative examples, all raw materials were commercially available, and to maintain the reliability of the experiments, the raw materials used in the following examples and comparative examples had the same physical and chemical parameters or underwent the same treatment.

[0145] Example 1

[0146] Preparation of surface-modified polymer films (i.e., forming a first modified layer and a second modified layer on the upper and lower surfaces of the polymer film):

[0147] A 6μm thick biaxially oriented polypropylene (PP) film, purchased commercially, was placed in a plasma-assisted chemical vapor deposition (PECVD) apparatus. The PECVD apparatus's radio frequency generator was set to 13.45MHz and the power to 100W. A vacuum pump was used to evacuate the chamber to a pressure of 10mTorr. Then, the argon gas line control valve was opened, and argon gas was slowly introduced into the PECVD apparatus. The argon gas flow rate was adjusted to maintain the pressure inside the PECVD apparatus at 20mTorr. Subsequently, the oxygen, ethane, and hexamethyldisiloxane (HMD) lines were opened, and oxygen, ethane, and HMD were slowly introduced into the chamber. The total flow rate of oxygen and ethane was 2:1 to that of HMD, and the flow rate of oxygen was 3:17. The total flow rate of the three substances was adjusted to maintain the pressure inside the chamber at 40mTorr. After processing for 2 minutes, the gas supply was stopped, the vacuum pump was turned off, and the pressure was released. After the pressure was released, the polymer film was removed, yielding the surface-modified PP film.

[0148] Preparation of composite current collectors:

[0149] Preparation of metal layers (preparation of the first metal layer and the second metal layer): The surface-modified PP film prepared above is placed in a vacuum evaporation chamber, and the high-purity copper wire (purity greater than 99.99%) in the metal evaporation chamber is melted and evaporated at a high temperature of 1400-2000℃. The evaporated metal atoms are cooled by the cooling system in the vacuum coating chamber and deposited on the two surfaces of the surface-modified polymer film to form a copper metal layer with a thickness of 1μm.

[0150] Preparation of protective layers (preparation of the first and second protective layers): 1g of graphene was uniformly dispersed in 999g of N-methylpyrrolidone (NMP) solution by ultrasonic dispersion to prepare a coating solution with a solid content of 0.1wt%. The coating solution was uniformly coated onto the surface of the metal layer by a die coating process, wherein the coating thickness was controlled at 80μm. The coating was dried at 80℃ to obtain the protective layer.

[0151] Example 2

[0152] It is basically the same as Example 1, except that the power of the radio frequency generator is 200W.

[0153] Example 3

[0154] It is basically the same as Example 1, except that the power of the radio frequency generator is 300W.

[0155] Example 4

[0156] It is basically the same as Example 1, except that the flow ratio of oxygen to ethane is 1:1.

[0157] Example 5

[0158] It is basically the same as Example 1, except that the flow ratio of oxygen to ethane is 3:1.

[0159] Example 6

[0160] It is basically the same as Example 1, except that the modification treatment time is 5 minutes.

[0161] Example 7

[0162] It is basically the same as Example 1, except that the modification treatment time is 10 minutes.

[0163] Example 8

[0164] It is basically the same as Example 1, except that the modification treatment time is 15 minutes.

[0165] Example 9

[0166] It is basically the same as Example 1, except that the modification treatment time is 20 minutes.

[0167] Example 10

[0168] It is basically the same as Example 1, except that the polymer film is a PET film.

[0169] Comparative Example 1

[0170] It is basically the same as Example 1, except that the power of the radio frequency generator is 95W.

[0171] Comparative Example 2

[0172] It is basically the same as Example 1, except that the power of the radio frequency generator is 305W.

[0173] Comparative Example 3

[0174] It is basically the same as Example 1, except that the flow ratio of oxygen to ethane is 3:18.

[0175] Comparative Example 4

[0176] It is basically the same as Example 1, except that the flow ratio of oxygen to ethane is 4:1.

[0177] Comparative Example 5

[0178] It is basically the same as Example 1, except that the modification treatment time is 1 minute.

[0179] Comparative Example 6

[0180] It is basically the same as Example 1, except that the modification treatment time is 21 min.

[0181] Comparative Example 7

[0182] It is basically the same as Example 1, except that the polymer film is not subjected to surface modification treatment.

[0183] Test Evaluation:

[0184] As mentioned earlier, the modified layer (i.e., the first and second modified layers described above) has a CO-Si covalent bond with the polymer film, thereby improving the bonding strength between the polymer film and the modified layer; the modified layer has a metal-O chemical bond with the metal layer, which, along with the surface structure and properties of the modified layer, promotes the adhesion between the modified layer and the metal layer. To verify this, infrared spectroscopy was performed on the cross-sections of the polymer film and modified layer of Example 1 and Comparative Example 1, XPS scanning was performed near the interface between the modified layer and the metal layer of Example 1 and Comparative Example 1, and EDS line scanning was performed near the interface between the modified layer and the metal layer of Example 1. The specific test methods and results are as follows:

[0185] 1. Infrared Spectroscopy Characterization: The modified polymer film prepared in Example 1 was cross-sectionally prepared using an argon ion polisher (Fischione 1061). The cross-sectional sample was then placed in a Fourier transform attenuated total reflectance infrared spectrometer (Thermo Nicolet 6700) for infrared spectral scanning, resulting in the infrared spectrum shown below. Figure 2 As shown. The polymer film provided in Comparative Example 1 was prepared using the same cross-sectional sample preparation method as in Example 1, and the above operations were repeated for infrared spectroscopy scanning, resulting in the infrared spectrum shown below. Figure 2 As shown.

[0186] Depend on Figure 2 It can be seen that, compared with the unmodified PP film, the modified PP film has an additional 1250 cm⁻¹ in its infrared spectrum. -1 1199cm -1 1077cm -1 956cm -1 783cm -1 The characteristic absorption peaks at these positions correspond to the characteristic absorption peaks of the symmetric stretching vibrations of CO-Si, C-Si, Si-O-Si, the bending stretching vibrations of CO-Si, and the asymmetric stretching vibrations of Si-O-Si, respectively. This indicates the formation of the modified layer and the formation of covalent bonds between the modified layer and the PP base film.

[0187] 2. XPS Characterization: The surface of the prepared composite current collector was polished using an argon ion polisher (Fischione 1061) to remove the protective layer and the oxidized metal layer. Then, a cross-sectional sample was prepared. After sample preparation, the prepared cross-sectional sample was placed in an XPS (PHI Versaprobe 4) to scan the sample cross-section, thus obtaining the XPS spectrum as shown below. Figure 4 As shown. The polymer film provided in Comparative Example 1 was prepared using the same cross-sectional sample preparation method as in Example 1, and the above operations were repeated for infrared spectroscopy scanning, resulting in the XPS spectrum shown below. Figure 4 As shown.

[0188] Depend on Figure 4 It can be seen that, compared with the composite current collector prepared with unmodified PP film as the base film, the XPS spectrum of the cross section of the composite current collector prepared with modified PP film as the base film showed characteristic peaks of Cu(Ⅰ) and Cu(Ⅱ), which proved that Cu-O chemical bonds were generated between the modified PP film and the metal layer. Among them, Cu(Ⅰ) represents monovalent copper ions and Cu(Ⅱ) represents divalent copper ions.

[0189] 3. EDS (Energy Dispersive Spectrometer) Characterization: The prepared composite current collector was cross-sectionally prepared using an argon ion polishing instrument (Fischione 1061). The prepared cross-sectional sample was then placed in an X-ray energy dispersive spectrometer (Bruker Quanta X EDS). 7) X-ray scanning is performed on the vicinity of the interface between the modified layer and the metal layer (with the interface as the origin, extending 30 nm vertically) using an EDS (energy dispersive spectroscopy) instrument, and the resulting EDS test image is shown below. Figure 5 As shown.

[0190] like Figure 5 As shown, the origin of the coordinate system is the interface between the modified layer and the metal layer. The negative coordinate represents the position on the metal layer side, and the positive coordinate represents the position on the modified layer side. It can be seen that the presence of Cu metal was detected from the interface to a depth of 30 nm inside the modified layer and even deeper. This indicates that the copper crystal is embedded in the modified layer. This is because the surface temperature of the modified layer is high during the formation of the metal layer, and the crystals in the modified layer rearrange and move. The generated Cu crystal and the silicon carbide crystal in the modified layer both have a face-centered cubic lattice structure, which is similar to the structure. Therefore, the copper crystal and the silicon carbide crystal are intercalated.

[0191] As mentioned earlier, one purpose of preparing the surface-modified polymer film is to improve the bonding performance between the polymer film and the metal layer, thereby solving the problem of weak adhesion between the base film and the metal layer of the composite current collector prepared with the polymer film as the base film. The bonding performance between the polymer film and the metal layer depends on the structure and properties of its surface. Here, the polymer film is subjected to silicon oxide surface modification treatment, and the average grain size, surface oxygen atom content, surface tension, and surface roughness of the surface-modified polymer film provided in this application and the unmodified polymer film in related technologies, as well as the adhesion between the polymer film and the metal layer, are tested to characterize the influence of the surface structure and properties of the polymer films in the embodiments and comparative examples provided in this application on the bonding performance between the polymer film and the metal layer. Another purpose of preparing the surface-modified polymer film is to improve the surface conductivity of the prepared polymer film, thereby reducing the number of pore defects caused by electrostatics during physical vapor deposition. Here, the sheet resistance of the prepared surface-modified polymer film and the number of pores on the surface of the prepared composite current collector film are characterized. In addition, to objectively evaluate the modification effect of the embodiments of this application, the thickness of the modified layer (i.e., the silicon dioxide layer) was characterized, and the elastic modulus of the polymer films with modified layers of different thicknesses was also characterized, so as to objectively evaluate the flexibility of the polymer film after modification. Specific test methods and results are as follows:

[0192] 1. Test of average surface grain size: The polymer films prepared in Examples 1-16 and Comparative Example 1 were placed in a field emission scanning electron microscope for surface morphology testing. The average surface grain size of Examples 1-16 and Comparative Example 1 was analyzed using image processing software. The specific test results are shown in Table 1 below.

[0193] 2. Surface oxygen atom content test: X-ray photoelectron spectroscopy (XPS) was used to characterize the surface elements of the polymer film and analyze the relative content of surface oxygen atoms of the polymer films corresponding to Examples 1-16 and Comparative Example 1. The specific test results are shown in Table 1 below.

[0194] 3. Surface tension test: The test was conducted in accordance with the national standard GB / T 14216-2008. The specific test results are shown in Table 1 below.

[0195] 4. Surface roughness test: The test was conducted in accordance with the national standard GB / T 31227-2014. The specific test results are shown in Table 1 below.

[0196] 5. Adhesion between the polymer film and the metal layer: A layer of Permacel P-94 double-sided adhesive is bonded to a 1mm thick aluminum foil. A composite current collector is then bonded on top of the double-sided adhesive. A layer of ethylene-acrylic acid copolymer film (DuPont Nurcel 0903, 50μm thick) is then placed on top of the composite current collector. Finally, a bonding strength of 1.3×10⁵ N / m is applied. 2 The sample was hot-pressed at 120℃ for 10 seconds, cooled to room temperature, and cut into strips of 150mm × 15mm. The ethylene-acrylic acid copolymer film of each strip was then fixed to the upper clamp of a tensile testing machine, while the remaining portion was fixed to the lower clamp. After fixing, the upper and lower clamps moved at a speed of 100mm / min at 180-degree angles to peel the polymer film and metal layer. The tensile force applied during the peeling process was tested, thus obtaining the adhesion between the polymer film and the metal layer. The specific test results are shown in Table 1 below.

[0197] 6. Modified layer thickness: The modified polymer film sample prepared above was placed in an argon ion polisher (Fischione 1061) and cut using an argon ion beam (1 mm in diameter). After cutting, the sample was sputter-coated with gold to prepare a cross-sectional sample. The prepared cross-sectional sample was placed in a field emission scanning electron microscope (Zeiss Gemini Sigma 300VP SEM) at 50,000x magnification to observe the cross-sectional morphology. The thickness of the modified layer in the cross-sectional morphology was marked using the measurement software built into the electron microscope, thus obtaining the thickness of the modified layer.

[0198] 7. Elastic modulus of modified polymer film: Refer to national standard GB / T 1040.3-2006.

[0199] 8. Sheet resistance: The prepared surface-modified polymer film is placed on the sample stage, and the sheet resistance of the sample is tested using a four-probe sheet resistance meter.

[0200] 9. Holes: The composite current collector is placed in a surface quality inspection system (micro-vision charge-coupled device CCD) to scan the surface. The light signal is then converted into an electrical signal and transmitted to a computer to count the number of surface pores with a diameter of less than 100μm per unit area (per square meter) of the composite aluminum current collector (generally, the finished product should not have pores larger than 100μm).

[0201] Table 1

[0202]

[0203] As shown in Table 1, the adhesion between the surface-modified polymer film and the metal layer was effectively improved, and the surface pore defects of the prepared composite current collector were effectively controlled. In particular, by controlling the power of the radio frequency generator within the range of 100-300W, the flow ratio of oxygen to ethane within the range of 3:17-3:1, and the reaction time within the range of 2-20min, the adhesion between the surface-modified polymer film and the metal layer can reach more than 1.0N / cm. The surface of the prepared composite current collector is free of pore defects, which can significantly improve the adhesion between the polymer film and the metal layer, and at the same time significantly reduce the surface defects of the prepared composite current collector.

[0204] Comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that as the power of the RF generator increases, the average size and surface roughness of the silicon dioxide nanocrystals on the modified polymer film gradually increase, while the surface oxygen atom content and surface tension remain unchanged. These changes in surface structure and properties lead to an initial increase followed by a decrease in the adhesion between the polymer film and the metal layer. Furthermore, as the power of the RF generator increases, the deposition efficiency improves, resulting in a gradual increase in the thickness of the modified layer. This increase in thickness leads to a decrease in surface sheet resistance and a slight increase in elastic modulus. However, as the thickness gradually increases, the elastic modulus remains within an acceptable range and does not significantly affect the flexibility of the composite current collector. Therefore, it can be concluded that when the power of the RF generator is controlled within the range of 100-300W, the surface structure and properties of the obtained polymer film are optimal, maximizing the adhesion between the polymer film and the metal layer.

[0205] Comparing Examples 1, 4, and 5 with Comparative Examples 3-4, it can be concluded that as the flow ratio of oxygen to ethane increases, the grain size and surface roughness of the silicon dioxide on the polymer film remain essentially unchanged, while the surface oxygen atom content and surface tension increase. These changes in surface structure and properties lead to an increasing trend in the adhesion between the polymer film and the metal layer. Furthermore, as the flow ratio of oxygen to ethane increases, the thickness of the modified layer remains essentially unchanged, but due to the increasing flow ratio, the carbon content of the modified layer decreases, resulting in reduced conductivity and increased sheet resistance. When the ratio is too high, the surface sheet resistance is too low, leading to poor conductivity and resulting in pore defects on the surface of the prepared composite current collector film. When the ratio is too low, the surface oxygen content is low, resulting in low surface tension, which in turn leads to low adhesion between the base film and the metal layer of the prepared composite current collector. Therefore, when the flow ratio of oxygen to ethane is in the range of 3:17 to 3:1, the adhesion between the polymer film and the metal layer can be maximized, and the prepared composite current collector film can be free of pore defects, thus meeting the requirements for pore defects in battery applications.

[0206] Comparing Examples 1, 6-9, and Comparative Examples 5-6, it can be concluded that as the processing time increases, the average size and surface roughness of the silica nanocrystals on the polymer film surface gradually increase, while the surface oxygen atom content and surface tension remain unchanged. These changes in surface structure and properties lead to an initial increase followed by a decrease in the adhesion between the polymer film and the metal layer. Furthermore, as the processing time increases, the modified layer thickness increases, the sheet resistance decreases, and the elastic modulus slightly increases, but the elastic modulus remains within an acceptable range and does not significantly affect the flexibility of the composite current collector. This indicates that longer processing times are detrimental to improving the subsequent adhesion between the polymer film and the metal layer. Controlling the processing time within the range of 2-20 minutes can maximize the adhesion between the polymer film and the metal layer.

[0207] Comparing Examples 1 and 10, it can be concluded that under the same modification conditions, the modification effects of PP film and PET film are similar.

[0208] Comparing Examples 1-9 with Comparative Example 7, it can be seen that compared with the unmodified PP film, the adhesion between the base film and the metal layer of the composite current collector prepared with the modified PP film as the base film is significantly improved and the surface pore defects are significantly reduced.

[0209] In summary, by forming a first modified layer and a second modified layer on the upper and lower surfaces of the polymer film, and by controlling the process conditions for forming these layers, the microstructure and properties of the surfaces of the first and second modified layers furthest from the polymer film can be adjusted. This results in a polymer film that effectively improves the bonding strength between the metal layer and the polymer film during metal deposition. Experiments have shown that higher values ​​for the parameters in the process conditions for forming the first and second modified layers are not necessarily better; rather, they are related to the microstructure and properties of the surfaces of the first and second modified layers furthest from the polymer film. This reveals the interaction between the microstructure and properties of the surfaces of the first and second modified layers furthest from the polymer film and the adhesion between the polymer film and the metal layer, providing a research basis for understanding the influence of the surface structure and properties of the polymer film on the bonding strength between the polymer film and the metal layer.

[0210] 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.

[0211] The embodiments described above are merely illustrative of 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 composite current collector comprises: a substrate layer comprising a first surface and a second surface oppositely arranged along the thickness direction thereof, the material of the substrate layer comprising a polymer material; a first modification layer arranged on the first surface of the substrate layer, the material of the first modification layer comprising one or more of silicon oxide, titanium oxide and aluminum oxide nanomaterials; a first metal layer arranged on the surface of the first modification layer away from the substrate layer; the atoms on the surface of the first modification layer close to the substrate layer are covalently bonded to the substrate layer, and a metal-oxygen chemical bond is formed between the first metal layer and the first modification layer.

2. The composite current collector according to claim 1, wherein the crystal lattice structure of the crystal on the surface of the first modification layer close to the first metal layer is doped with metal atoms contained in the first metal layer.

3. The composite current collector according to claim 1, wherein the material of the first modification layer at least comprises silicon oxide.

4. The composite current collector according to claim 1, wherein the molar content of oxygen atoms on the surface of the first modification layer away from the substrate layer is 10% to 50%.

5. The composite current collector according to claim 1, wherein the average size of the crystal grains on the surface of the first modification layer away from the substrate layer is 50 to 88 nm.

6. The composite current collector according to claim 1, wherein the surface tension of the surface of the first modification layer away from the substrate layer is 42 to 57 mN / m.

7. The composite current collector according to claim 1, wherein the surface roughness of the surface of the first modification layer away from the substrate layer is 75 to 125 nm.

8. The composite current collector according to claim 1, wherein the thickness of the first modification layer is 100 to 200 nm.

9. The composite current collector according to any one of claims 1 to 8, wherein the thickness of the substrate layer is 2 to 20 μm.

10. The composite current collector according to any one of claims 1 to 8, wherein the polymer material comprises one or more of polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene and polyamide.

11. The composite current collector of any one of claims 1-8, wherein, Further comprising: a second metal layer and a second modification layer; the second modification layer is arranged on the second surface of the substrate layer, and the second metal layer is arranged on the surface of the second modification layer away from the substrate layer, the material and / or surface structure of the second modification layer are the same as those of the first modification layer.

12. The composite current collector of claim 11, wherein, Further comprising: a first protective layer and / or a second protective layer; the first protective layer is arranged on the surface of the first metal layer away from the substrate layer, and the second protective layer is arranged on the surface of the second metal layer away from the substrate layer.

13. The composite current collector according to claim 12, wherein the thickness of the first protective layer is not more than 1 / 10 of the thickness of the first metal layer. The thickness of the second protective layer is not more than 1 / 10 of the thickness of the second metal layer.

14. The composite current collector according to claim 12 or 13, wherein, The thickness of the first protective layer and the second protective layer is the same or different, and each is independently 10-150 nm.

15. The composite current collector according to any one of claims 1-8, wherein, The thickness of the first metal layer is 500-2000 nm.

16. A lithium battery, characterized by The composite current collector according to any one of claims 1-15. The lithium battery according to claim 16.

17. An electrical device, comprising: The lithium battery according to claim 16. A substrate layer is provided, and the material of the substrate layer comprises a polymer material; 18. A method of making a composite current collector, characterized by, A first modification layer is formed on a first surface of the substrate layer along the thickness direction of the substrate layer, and the material of the first modification layer comprises one or more of silicon oxide carbon, titanium oxide carbon, and aluminum oxide carbon nanomaterials; A first metal layer is formed on the surface of the first modification layer away from the substrate layer; The atoms on the surface of the first modification layer close to the substrate layer are covalently bonded to the substrate layer, and a metal-oxygen chemical bond is formed between the first metal layer and the first modification layer.

19. The method according to claim 18, wherein, The first modification layer is formed on the first surface of the substrate layer along the thickness direction of the substrate layer by a plasma-assisted chemical vapor deposition method.

20. The method according to claim 19, wherein, The frequency of the radio frequency generator used in the plasma-assisted chemical vapor deposition method is 10-15 MHz, and the power is 100-300 W.

21. The method according to claim 19, wherein, The reaction gas used in the plasma-assisted chemical vapor deposition method comprises an oxygen element gas source, a carbon element gas source, and an X element gas source, wherein X comprises one or more of silicon, titanium, and aluminum.

22. The method according to claim 21, wherein, During the reaction, a plasma gas source is first introduced into the plasma-assisted chemical vapor deposition device, and then the reaction gas is introduced into the plasma-assisted chemical vapor deposition device; The amount of the plasma gas source introduced is such that the pressure in the plasma-assisted chemical vapor deposition device is 10-30 mTorr, the amount of the reaction gas introduced is such that the pressure in the plasma-assisted chemical vapor deposition device is 35-50 mTorr, and the flow ratio of the oxygen element gas source, the carbon element gas source, and the X element gas source satisfies: the ratio of the total moles of oxygen elements and carbon elements contained in the oxygen element gas source and the carbon element gas source to the total moles of X elements is 2:1, and the ratio of the moles of the oxygen elements to the moles of the carbon elements is 3:17-3:

1.

23. The method according to claim 22, wherein, The reaction time is 2-20 min. ​ ​

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