Composite copper-based current collector and preparation method therefor, and lithium ion battery

Abstract

A composite copper-based current collector and a preparation method therefor, and a lithium ion battery, relating to the technical field of battery materials. The composite copper-based current collector comprises: a polymer substrate film; and a modified copper layer arranged on at least one surface of the polymer substrate film, wherein the modified copper layer comprises a C-Cu heterogeneous microstructure with dispersed carbon quantum dots. Carbon quantum dots are introduced, and the carbon quantum dots are uniformly dispersed in copper grains and at copper grain boundaries, thereby forming the C-Cu heterogeneous microstructure with dispersed carbon quantum dots; the presence of the carbon quantum dots can exert resistance to grain coarsening, thereby inhibiting grain coarsening and promoting grain refinement, improving the tensile strength of the composite copper-based current collector; the C-Cu heterogeneous microstructure can enhance dislocation storage capacity and strengthen strain hardening, thereby improving the elongation at break of the composite copper-based current collector; and improvements of the tensile strength and the elongation at break jointly enhance mechanical properties of the current collector, and improve the stability of the current collector in the battery.

Description

Composite copper-based current collector, preparation method thereof, and lithium-ion battery Technical Field

[0001] The present application relates to the field of battery material technology, for example, a composite copper-based current collector and a preparation method thereof, and a lithium-ion battery. Background Art

[0002] At present, composite copper current collectors based on polymer films have received widespread attention and application in the new energy industry. The preparation of this composite copper current collector usually adopts the method of physical vapor deposition (PVD) to deposit a layer of copper metal on a polymer film (such as polyester, polyolefin, etc.), thereby preparing a composite copper current collector with good conductivity. Compared with traditional copper current collectors, composite copper current collectors based on polymer films have the characteristics of low cost, light weight, and good internal insulation. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and safety of the battery when used in the battery.

[0003] However, traditional composite copper current collectors have poor mechanical properties, namely low tensile strength and yield strength, which makes them prone to deformation and defects during the electrode preparation process, causing their conductivity to deteriorate, and ultimately causing the battery's charge and discharge cycle performance to decay.

[0004] Therefore, in order to further improve the mechanical properties of the composite copper current collector, it is necessary to develop a new composite copper current collector to promote the application and promotion of the composite copper current collector in batteries.

[0005] Summary of the Invention

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

[0007] The present application provides a composite copper-based current collector, a preparation method thereof, and a lithium-ion battery. This application introduces carbon quantum dots into a modified copper layer, uniformly dispersing the carbon quantum dots within the copper grains and grain boundaries, thereby forming a C-Cu heterogeneous microstructure in which the carbon quantum dots are dispersed. On the one hand, the presence of the carbon quantum dots can exert resistance to grain coarsening, inhibiting grain coarsening and promoting grain refinement, thereby improving the tensile strength of the composite copper-based current collector. On the other hand, the C-Cu heterogeneous microstructure can increase dislocation storage capacity and strengthen strain hardening, thereby improving the elongation at break of the composite copper-based current collector. Together, these two factors improve the mechanical properties of the composite copper-based current collector and promote its stability during battery processing and cycling.

[0008] In a first aspect, the present application provides a composite copper-based current collector, comprising:

[0009] polymer-based films;

[0010] A modified copper layer disposed on at least one surface of the polymer base film;

[0011] The modified copper layer includes a C-Cu heterogeneous microstructure in which carbon quantum dots are dispersed.

[0012] The present application introduces carbon quantum dots into the modified copper layer so that the carbon quantum dots are uniformly dispersed in the copper grains and copper grain boundaries, thereby forming a C-Cu heterogeneous microstructure with dispersed carbon quantum dots. On the one hand, the presence of carbon quantum dots can exert resistance to grain coarsening, inhibit grain coarsening, and promote grain refinement, thereby improving the tensile strength of the composite copper-based current collector. On the other hand, the C-Cu heterogeneous microstructure can increase the dislocation storage capacity and strengthen strain hardening, thereby improving the elongation at break of the composite copper-based current collector. The two together improve the mechanical properties of the composite copper-based current collector and promote its stability during battery processing and cycling.

[0013] As an optional technical solution of the present application, along the direction away from the polymer base film, the modified copper layer includes a seed layer and a thickening layer.

[0014] In this application, the role of the seed layer is to provide a certain degree of conductivity and to provide a basis for the preparation of the thickening layer.

[0015] In this application, the role of the thickened layer is to provide the main conductivity for the composite current collector.

[0016] In one embodiment, the material of the seed layer includes metallic copper and / or copper alloy, and can be metallic copper.

[0017] In one embodiment, the material of the thickening layer includes copper material and carbon quantum dots.

[0018] In the present application, carbon quantum dots are introduced into the thickening layer so that the carbon quantum dots are uniformly dispersed in the copper grains and copper grain boundaries, thereby forming a C-Cu heterogeneous microstructure in which the carbon quantum dots are dispersed. On the one hand, the presence of carbon quantum dots can exert resistance to grain coarsening, inhibit grain coarsening, and promote grain refinement, thereby improving the tensile strength of the composite copper-based current collector; on the other hand, the formed C-Cu heterogeneous microstructure can increase the dislocation storage capacity and strengthen strain hardening, thereby improving the elongation at break of the composite copper-based current collector. The two together improve the mechanical properties of the composite copper-based current collector.

[0019] In one embodiment, based on the mass of the modified copper layer, the mass fraction of the carbon quantum dots is ≤1% and is not 0, for example, it can be 1%, 0.8%, 0.5%, 0.3%, 0.1%, 0.08%, 0.05% or 0.01%, etc., and can be optionally 0.05-1%.

[0020] In the present application, if the mass fraction of carbon quantum dots is too high, the mechanical properties of the composite copper-based current collector will not be significantly improved, and the conductive properties of the composite copper current collector will be affected.

[0021] As an optional technical solution of the present application, the average particle size of the carbon quantum dots is ≤20 nm, for example, it can be 20 nm, 15 nm, 10 nm, 5 nm or 1 nm, etc., and can be optionally 2-10 nm.

[0022] In the present application, if the average particle size of the carbon quantum dots is too large, it is difficult for the carbon quantum dots to be evenly dispersed in the copper grains, resulting in a decrease in their ability to inhibit grain coarsening, and a decrease in the dislocation storage capacity of the formed C-Cu heterogeneous microstructure, thereby failing to effectively improve the mechanical properties of the composite copper-based current collector.

[0023] As an optional technical solution of the present application, the carbon quantum dots contain doping elements, and the doping elements include any one of nitrogen, silicon or sulfur, or a combination of at least two of them.

[0024] In the present application, doping carbon quantum dots helps to improve the compatibility of carbon quantum dots with copper atoms, promote their strengthening effect on copper grain refinement and strain hardening, and thus improve the mechanical properties of the prepared composite copper current collector.

[0025] In one embodiment, based on the mass of the carbon quantum dots, the content of the doping element is 0-20%, for example, 0%, 5%, 10%, 15% or 20%.

[0026] In the present application, if the content of the doping element in the carbon quantum dots is too high, the conductivity of the carbon quantum dots is poor, resulting in poor conductivity of the prepared composite copper current collector.

[0027] As an optional technical solution of the present application, the thickness of the seed layer is 40-100 nm, for example, it can be 40 nm, 60 nm, 80 nm or 100 nm.

[0028] In this application, if the thickness of the seed layer is too low, the conductivity is too poor and the stable preparation of the thickened layer cannot be guaranteed; if the thickness of the seed layer is too high, the stable preparation of the thickened layer cannot be further promoted, and the energy consumption during the preparation process is high, which will affect the mechanical properties of the composite copper-based current collector.

[0029] In one embodiment, the thickness of the thickened layer is 500-2000 nm, for example, 500 nm, 1000 nm, 1500 nm or 2000 nm, etc., and can be optionally 800-1200 nm.

[0030] In this application, if the thickness of the thickening layer is too low, the conductivity is poor; if the thickness of the thickening layer is too high, the prepared composite current collector is too thick and heavy, which is not conducive to improving the energy density of the battery. Therefore, considering both conductivity and energy density, the thickness of the selected layer is 800-1200nm.

[0031] As an optional technical solution of the present application, the thickness of the polymer base film is 1-10 μm, for example, it can be 1 μm, 3 μm, 5 μm, 7 μm or 9 μm.

[0032] In this application, considering the application requirements of the composite copper-based current collector and the difficulty and cost of the preparation process, the thickness of the optional polymer base film is 1-10 μm.

[0033] In one embodiment, the material of the polymer base film includes any one or a combination of at least two 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) or polyimide (PI).

[0034] In one embodiment, an adhesive layer is provided between the polymer-based film and the modified copper layer.

[0035] In one embodiment, the material of the bonding layer includes any one or a combination of at least two of aluminum oxide, silicon oxide, titanium oxide, nickel, chromium, titanium, nickel-chromium alloy, nickel-chromium-copper alloy, silicon-aluminum alloy, polyacrylic acid, polyacrylate, polyacrylamide or polyurethane.

[0036] In one embodiment, the thickness of the bonding layer is 1-100 nm, for example, 1 nm, 10 nm, 30 nm, 50 nm, 75 nm or 100 nm.

[0037] In the present application, if the thickness of the bonding layer is too low, the bonding strength to the composite copper-based current collector is not significantly improved; if the thickness of the bonding layer is too high, the bonding strength cannot be further improved and the production efficiency is affected.

[0038] In one embodiment, a protective layer is further provided on the surface of the modified copper layer along a side away from the polymer-based film.

[0039] In one embodiment, the material of the protective layer includes any one of nickel, chromium, nickel-chromium alloy, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers, graphene or graphene oxide, or a combination of at least two thereof.

[0040] In one embodiment, the thickness of the protective layer is 5-100 nm, for example, 5 nm, 10 nm, 30 nm, 50 nm, 70 nm or 90 nm, etc., and can be optionally 20-80 nm.

[0041] In one embodiment, the thickness of the protective layer is less than or equal to one tenth of the thickness of the modified copper layer.

[0042] In a second aspect, the present application provides a method for preparing the composite copper-based current collector as described in the first aspect, the preparation method comprising the following steps:

[0043] A modified copper layer is prepared on at least one surface of a polymer-based film, wherein the modified copper layer comprises a C-Cu heterogeneous microstructure in which carbon quantum dots are dispersed.

[0044] The preparation method provided in this application is simple and easy to implement, and can be easily scaled up for production.

[0045] It should be noted that the present application does not limit the preparation method of the polymer base film. For example, it can be a melt-extrusion-biaxial stretching method.

[0046] As an optional technical solution of the present application, the modified copper layer includes a seed layer and a thickening layer.

[0047] In one embodiment, the preparation method of the seed layer includes any one of physical vapor deposition, electroless plating or chemical vapor deposition, or a combination of at least two thereof.

[0048] In one embodiment, the physical vapor deposition method includes magnetron sputtering and / or evaporation.

[0049] In one embodiment, the preparation method of the thickened layer includes electroplating.

[0050] In one embodiment, in the electroplating method, components of the electroplating solution include copper sulfate, sulfuric acid, hydrochloric acid, a brightener, a leveler, a wetting agent, and carbon quantum dots.

[0051] In one embodiment, the concentration of the copper sulfate is 70-130 g / L, for example, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L or 130 g / L, the concentration of the sulfuric acid is 70-160 g / L, for example, 70 g / L, 80 g / L, 100 g / L, 120 g / L, 140 g / L or 160 g / L, and the concentration of the hydrochloric acid is 20-80 mg / L, for example, 20 mg / L, 40 mg / L or 50 mg / L. g / L, 60 mg / L or 80 mg / L, etc., the concentration of the brightener is 0.5-20 ppm, for example, it can be 0.5 ppm, 5 ppm, 10 ppm, 15 ppm or 20 ppm, etc., the concentration of the leveler is 0.5-5 ppm, for example, it can be 0.5 ppm, 1 ppm, 3 ppm or 5 ppm, etc., the concentration of the wetting agent is 20-200 ppm, for example, it can be 20 ppm, 50 ppm, 100 ppm, 150 ppm or 200 ppm, etc.

[0052] In one embodiment, the content of the carbon quantum dots is 10-600 ppm, for example, 10 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm or 600 ppm.

[0053] In one embodiment, the brightener includes any one of sodium polydisulfide propane sulfonate, sodium 3-mercapto-1-propane sulfonate, or sodium N,N-dimethyldithiocarboxamide propane sulfonate, or a combination of at least two thereof.

[0054] In one embodiment, the leveler includes any one of N,N-diethylthiourea, 2-mercaptopyridine, or Janus Green, or a combination of at least two thereof.

[0055] In one embodiment, the wetting agent includes any one of polyethylene glycol, polypropylene glycol, or polyoxyethylene ether, or a combination of at least two thereof.

[0056] In one embodiment, the specific process parameters of the electroplating method include:

[0057] The average cathode current density is 0.5-5A / dm 2 , for example, it can be 0.5A / dm 2 , 1A / dm 2 , 2A / dm 2 、3A / dm 2 , 4A / dm 2 or 5A / dm 2The plating solution temperature is 15-35°C, for example, 15°C, 20°C, 25°C, 30°C or 35°C, and the electroplating time is 1-20min, for example, 1min, 5min, 10min, 15min or 20min.

[0058] As an optional technical solution of the present application, an adhesive layer is provided between the polymer base film and the modified copper layer, and a preparation method of the adhesive layer includes physical vapor deposition and / or coating method.

[0059] In one embodiment, a protective layer is further prepared on the surface of the modified copper layer along the side away from the polymer base film, and the preparation method of the protective layer includes any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating methods or a combination of at least two thereof.

[0060] In a third aspect, the present application provides a negative electrode plate, which includes the composite copper-based current collector as described in the first aspect.

[0061] In a fourth aspect, the present application provides a lithium-ion battery, comprising the negative electrode sheet as described in the third aspect.

[0062] 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 simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0063] Compared with the related art, this application has the following beneficial effects:

[0064] (1) The present application introduces carbon quantum dots into the modified copper layer so that the carbon quantum dots are uniformly dispersed in the copper grains and copper grain boundaries, thereby forming a C-Cu heterogeneous microstructure in which the carbon quantum dots are dispersed. On the one hand, the presence of the carbon quantum dots can exert resistance to grain coarsening, inhibit grain coarsening, and promote grain refinement, thereby improving the tensile strength of the composite copper-based current collector. On the other hand, the C-Cu heterogeneous microstructure can increase the dislocation storage capacity and strengthen strain hardening, thereby improving the elongation at break of the composite copper-based current collector. The two together improve the mechanical properties of the composite copper-based current collector and promote its stability during battery processing and cycling.

[0065] (2) The preparation method provided in this application is simple and easy to implement, and can be easily scaled up for production.

[0066] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0067] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0068] Example 1

[0069] This embodiment provides a composite copper-based current collector, comprising:

[0070] Polymer base film, thickness 4.5μm, material is PET;

[0071] The adhesive layers provided on both surfaces of the polymer base film include a first adhesive layer and a second adhesive layer, each having a thickness of 5 nm and made of nickel-chromium alloy;

[0072] A modified copper layer is provided on a surface of the bonding layer on a side relatively far from the polymer base film, comprising a first modified copper layer and a second modified copper layer; the modified copper layer comprises a C-Cu heterogeneous microstructure in which carbon quantum dots are dispersed;

[0073] The modified copper layer is further provided with a protective layer on a surface away from the polymer base film, including a first protective layer and a second protective layer, with a single-side thickness of 10 nm;

[0074] The modified copper layer includes a seed layer with a thickness of 50 nm and a thickening layer with a thickness of 1000 nm. The material of the seed layer is metallic copper, and the material of the thickening layer includes metallic copper and carbon quantum dots. Based on the mass of the modified copper layer, the mass fraction of the carbon quantum dots is 0.05%, the average particle size of the carbon quantum dots is 2 nm, and the content of the doping element is 0.

[0075] This embodiment also provides a method for preparing the composite copper-based current collector, which comprises the following steps:

[0076] (1) PET film was prepared by melt-extrusion-biaxial stretching method;

[0077] (2) placing the PET film in a magnetron sputtering machine, and depositing a bonding layer on each side of the PET film. The specific process conditions are: using a nickel-chromium target (purity: 99.99%) as the target material, a target power of 5.0 kW, an argon flow rate of 50 mL / min, a coating vacuum of 0.08 Pa, a coating time of 1 s, and a main roller temperature of 0° C. during the coating process, to obtain a PET composite film having a bonding layer on the surface;

[0078] (3) Preparation of modified copper layer:

[0079] ① The PET composite film with an adhesive layer on the surface was placed in a magnetron sputtering machine, and a copper target (purity: 99.99%) was used as the target material to prepare a seed layer on each side of the PET composite film. The specific process conditions were: target power of 12 kW, argon flow rate of 50 mL / min, coating vacuum of 0.08 Pa, coating time of 5 s, and the temperature of the main roller during the coating process was 2°C;

[0080] ② A thickening layer was prepared on the surface of the seed layer by electroplating. The specific process conditions were as follows: the electroplating solution components included 100 g / L copper sulfate, 120 g / L sulfuric acid, 60 mg / L hydrochloric acid, 2.5 ppm sodium polydisulfide dipropane sulfonate, 1.2 ppm Janus green, 60 ppm polyethylene glycol (average molecular weight 8000) and 30 ppm carbon quantum dots, and the average cathode current density was 2.0 A / dm 2 , the plating solution temperature is 25℃, and the plating time is 250s;

[0081] (4) Preparation of a protective layer: The composite film having a modified copper layer on the surface prepared above is placed in a coating device and coated with a 0.10 wt.% graphene solution (nitromethylpyrrolidone (NMP) as a solvent). After coating, the composite film is placed in an oven at 80°C for drying to obtain the composite copper-based current collector.

[0082] Example 2

[0083] The difference between this embodiment and embodiment 1 is that the content of carbon quantum dots in the electroplating solution in step (3) is 60 ppm, so that the content of carbon quantum dots in the prepared modified copper layer is 0.1%.

[0084] The rest of the preparation methods and parameters remained the same as in Example 1.

[0085] Example 3

[0086] The difference between this embodiment and embodiment 1 is that the content of carbon quantum dots in the electroplating solution in step (3) is 180 ppm, so that the content of carbon quantum dots in the prepared modified copper layer is 0.3%.

[0087] The rest of the preparation methods and parameters remained the same as in Example 1.

[0088] Example 4

[0089] The difference between this embodiment and embodiment 1 is that the content of carbon quantum dots in the electroplating solution in step (3) is 420 ppm, so that the content of carbon quantum dots in the prepared modified copper layer is 0.7%.

[0090] The rest of the preparation methods and parameters remained the same as in Example 1.

[0091] Example 5

[0092] The difference between this embodiment and embodiment 1 is that the content of carbon quantum dots in the electroplating solution in step (3) is 600 ppm, so that the content of carbon quantum dots in the prepared modified copper layer is 1%.

[0093] The rest of the preparation methods and parameters remained the same as in Example 1.

[0094] Example 6

[0095] The difference between this embodiment and embodiment 1 is that the average particle size of the carbon quantum dots is 5 nm.

[0096] The rest of the preparation methods and parameters remained the same as in Example 1.

[0097] Example 7

[0098] The difference between this embodiment and embodiment 1 is that the average particle size of the carbon quantum dots is 10 nm.

[0099] The rest of the preparation methods and parameters remained the same as in Example 1.

[0100] Example 8

[0101] The difference between this embodiment and embodiment 1 is that the average particle size of the carbon quantum dots is 20 nm.

[0102] The rest of the preparation methods and parameters remained the same as in Example 1.

[0103] Example 9

[0104] The difference between this embodiment and embodiment 1 is that the carbon quantum dots are doped with nitrogen, and the doping amount is 20%.

[0105] The rest of the preparation methods and parameters remained the same as in Example 1.

[0106] Example 10

[0107] The difference between this embodiment and embodiment 1 is that the carbon quantum dots are doped with silicon and sulfur in a mass ratio of 1:1, and the total doping amount is 20%.

[0108] The rest of the preparation methods and parameters remained the same as in Example 1.

[0109] Example 11

[0110] The difference between this embodiment and embodiment 1 is that the content of carbon quantum dots in the electroplating solution in step (3) is 720 ppm, so that the content of carbon quantum dots in the prepared modified copper layer is 1.2%.

[0111] The rest of the preparation methods and parameters remained the same as in Example 1.

[0112] Example 12

[0113] The difference between this embodiment and embodiment 1 is that the average particle size of the carbon quantum dots is 22 nm.

[0114] The rest of the preparation methods and parameters remained the same as in Example 1.

[0115] Example 13

[0116] The difference between this embodiment and embodiment 9 is that the doping amount of nitrogen is 22%.

[0117] The remaining preparation methods and parameters remained the same as in Example 9.

[0118] Comparative Example 1

[0119] The difference between this embodiment and embodiment 1 is that the modified copper layer does not contain C-Cu heterogeneous microstructure in which carbon quantum dots are dispersed, that is, the electroplating solution in step (3) does not contain carbon quantum dots.

[0120] The rest of the preparation methods and parameters remained the same as in Example 1.

[0121] Performance Testing

[0122] The composite copper-based current collectors prepared in the above examples and comparative examples were tested for tensile strength, elongation at break, and square resistance.

[0123] Tensile strength and elongation at break test:

[0124] Samples were taken along the longitudinal direction of the composite copper-based current collector, and then the tensile strength and elongation at break were tested according to the national standard GB / T 1040.3-2006.

[0125] Square resistance test:

[0126] The flat composite copper-based current collector product is placed on the sample table, and the square resistance of the product is tested using a four-probe square resistance meter.

[0127] The above test results are shown in Table 1.

[0128] Table 1

[0129] analyze:

[0130] It can be seen from Examples 1-10 and Comparative Example 1 that compared with traditional composite copper current collectors, the composite copper-based current collector prepared in the present application has an increasing trend in tensile strength and elongation at break without changing the square resistance (conductive performance), that is, the mechanical properties are improved.

[0131] It can be seen from Examples 1-5 and Example 11 that with the increase of the carbon quantum dot content in the modified copper layer, the tensile strength and elongation at break of the prepared composite copper-based current collector show an increasing trend. This is because with the increase of the carbon quantum dot content, the ability of carbon quantum dots to inhibit grain coarsening is improved and the dislocation storage capacity of the C-Cu heterogeneous microstructure is improved. The two jointly promote the improvement of the tensile strength and elongation at break of the composite copper-based current collector. However, when the content is too high (i.e., more than 1%), the tensile strength and elongation at break are not significantly improved, and the square resistance becomes larger, that is, the conductive performance deteriorates.

[0132] It can be seen from Examples 1, 6-8 and 12 that as the average particle size of the carbon quantum dots in the modified copper layer increases, the tensile strength and elongation at break of the prepared composite copper-based current collector show a decreasing trend. This is because as the particle size increases, the ability of the carbon quantum dots to be evenly dispersed in the copper grains becomes worse, resulting in a decrease in its ability to inhibit grain coarsening and a decrease in the dislocation storage capacity of the formed C-Cu heterogeneous microstructure. These two factors together lead to a decrease in the tensile strength and elongation at break of the composite copper-based current collector.

[0133] It can be seen from Examples 1, 9 and 10 that, compared with carbon quantum dots, nitrogen-doped carbon quantum dots and silicon-sulfur co-doped carbon quantum dots can better improve the tensile strength and elongation at break of the composite copper-based current collector.

[0134] It can be seen from Examples 9 and 13 that if the doping amount of nitrogen in the carbon quantum dots is too much, the conductivity of the prepared composite copper current collector deteriorates. This is because the doping amount of nitrogen is too much and the conductivity of the carbon quantum dots is poor. Further increasing the doping amount of nitrogen in the carbon quantum dots cannot further significantly improve the performance of the prepared composite copper current collector.

[0135] The applicant declares that while the above-mentioned embodiments are used to illustrate the technical solutions of this application, this application is not limited to these embodiments, and does not imply that this application must rely on these embodiments in order to be implemented. Persons skilled in the art should understand that any improvements to this application, equivalent replacements for the raw materials of the products of this application, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of this application.

Claims

1. A composite copper-based current collector comprising: polymer-based films; A modified copper layer disposed on at least one surface of the polymer base film; The modified copper layer includes a C-Cu heterogeneous microstructure in which carbon quantum dots are dispersed.

2. The composite copper-based current collector according to claim 1, wherein: Along the direction away from the polymer base film, the modified copper layer includes a seed layer and a thickening layer; The material of the seed layer includes metallic copper and / or copper alloy; The material of the thickening layer includes copper material and carbon quantum dots; Based on the mass of the modified copper layer, the mass fraction of the carbon quantum dots is ≤1% and is not 0.

3. The composite copper-based current collector according to claim 1, wherein: The average particle size of the carbon quantum dots is ≤20 nm.

4. The composite copper-based current collector according to claim 1, wherein: The carbon quantum dots contain doping elements, and the doping elements include any one or a combination of at least two of nitrogen, silicon or sulfur; Based on the mass of the carbon quantum dots, the content of the doping element is 0-20%.

5. The composite copper-based current collector according to claim 2, wherein: The thickness of the seed layer is 40-100 nm; The thickness of the thickened layer is 500-2000 nm.

6. The composite copper-based current collector according to claim 1, wherein: The thickness of the polymer base film is 1-10 μm; An adhesive layer is provided between the polymer base film and the modified copper layer; The material of the bonding layer includes any one or a combination of at least two of aluminum oxide, silicon oxide, titanium oxide, nickel, chromium, titanium, nickel-chromium alloy, nickel-chromium-copper alloy, silicon-aluminum alloy, polyacrylic acid, polyacrylate, polyacrylamide or polyurethane; The thickness of the bonding layer is 1-100 nm; The modified copper layer is further provided with a protective layer on a surface along a side away from the polymer base film; The material of the protective layer includes any one or a combination of at least two of nickel, chromium, nickel-chromium alloy, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers, graphene or graphene oxide; The thickness of the protective layer is 5-100 nm.

7. A method for preparing the composite copper-based current collector according to any one of claims 1 to 6, comprising the following steps: A modified copper layer is prepared on at least one surface of a polymer-based film, wherein the modified copper layer comprises a C-Cu heterogeneous microstructure in which carbon quantum dots are dispersed.

8. The preparation method according to claim 7, wherein The modified copper layer includes a seed layer and a thickening layer; The preparation method of the seed layer includes any one of physical vapor deposition, electroless plating or chemical vapor deposition, or a combination of at least two thereof; The preparation method of the thickened layer includes electroplating; In the electroplating method, the components of the electroplating solution include copper sulfate, sulfuric acid, hydrochloric acid, brightener, leveler, wetting agent and carbon quantum dots; The content of the carbon quantum dots is 10-600ppm; The specific process parameters of the electroplating method include: The average cathode current density is 0.5-5A / dm 2 , the plating solution temperature is 15-35℃, and the plating time is 1-20min; An adhesive layer is provided between the polymer base film and the modified copper layer, and a preparation method of the adhesive layer includes physical vapor deposition and / or coating method; The modified copper layer is also provided with a protective layer along the surface of the side away from the polymer base film. The preparation method of the protective layer includes any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating methods, or a combination of at least two of them.

9. A negative electrode sheet, wherein: The negative electrode plate includes the composite copper-based current collector according to any one of claims 1 to 6.

10. A lithium-ion battery, wherein: The lithium-ion battery comprises the negative electrode sheet according to claim 9.

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