Air composite copper current collector and preparation method thereof

Abstract

The invention relates to the technical field of air-composite copper current collectors, and discloses an air-composite copper current collector and a preparation method thereof. The component structure is a polymer film, a bonding transition layer, a metal copper layer and an anti-oxidation layer from the inside to the outside. The polymer film is located in the middle of the composite copper current collector, the bonding transition layer is formed on both sides of the polymer film, the metal copper layer is formed on both sides of the bonding transition layer, and the anti-oxidation layer is formed on both sides of the metal copper layer. The preparation steps include: magnetically controlling a layer of metal material on the upper and lower sides of the polymer film to obtain the bonding transition layer; simultaneously vapor-depositing metal aluminum and metal copper on the surfaces of the upper and lower bonding transition layers, immersing in a 10wt% sodium hydroxide solution after the vapor-depositing, dissolving the metal aluminum, and obtaining the metal copper layer; performing anti-oxidation treatment on the surfaces of the upper and lower metal copper layers to obtain the air-composite copper current collector.

Description

Technical Field

[0001] The present invention relates to the technical field of air-composite copper current collectors, in particular to an air-composite copper current collector and a preparation method thereof. Background Art

[0002] The technology used in traditional copper composite current collectors on the market is mainly to magnetron sputter a layer of copper on the upper and lower surfaces of the polymer film, and then thicken the copper layer through water plating technology; this makes the surface roughness of the copper layer low and the specific surface area small, resulting in poor bonding between copper and the negative electrode active material. At the same time, the interface resistance between the copper layer and the negative electrode is large, generating more heat, affecting battery performance.

[0003] Therefore, it is of great significance to invent an air composite copper current collector. Summary of the Invention

[0004] The object of the present invention is to provide an air-composite copper current collector and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] An air composite copper current collector comprises a polymer film, an adhesive transition layer, a metal copper layer and an anti-oxidation layer; the adhesive transition layer, the metal copper layer and the anti-oxidation layer are symmetrically arranged in sequence on both sides of the polymer film.

[0007] Furthermore, the total thickness of the air composite current collector is 2-20 μm; the puncture strength is ≥50 gf, the tensile strength MD is ≥50 MPa, TD is ≥50 MPa, the elongation MD is ≥1%, TD is ≥1%; and the upper and lower surface roughness Rz is greater than 1 μm.

[0008] Furthermore, the polymer film includes any one of a polyethylene film, a polypropylene film, a polyethylene terephthalate film, and a polyimide film; and has a thickness of 1-19 μm.

[0009] Furthermore, the metal material of the bonding transition layer includes any one of nickel-chromium alloy, inorganic metal oxide, and ternary metal material; and the thickness is 0.5-100 nm.

[0010] Furthermore, the thickness of the metal copper layer is 0.1-2 μm, and the porosity is greater than 0.1%.

[0011] Furthermore, the anti-oxidation layer is any one of a chromium layer, a zinc-nickel layer, and a copper nanowire-graphene composite layer; and has a thickness of 1-100 nm.

[0012] A method for preparing an air-composite copper current collector comprises the following steps:

[0013] S1: Magnetically control a layer of metal material on the upper and lower surfaces of the polymer film to obtain a bonding transition layer;

[0014] S2: Simultaneously evaporating aluminum and copper on the surfaces of the upper and lower bonding transition layers to obtain a copper-aluminum composite layer. After the evaporation is completed, the layer is immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer.

[0015] S3: Anti-oxidation treatment is performed on the surfaces of the upper and lower metal copper layers to obtain an air composite copper current collector.

[0016] Furthermore, the antioxidant treatment comprises the following steps:

[0017] The product containing the metallic copper layer in step S2 is immersed in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15-20 minutes, washed, dried, and then placed in an argon environment and heated to 180-185°C for reaction for 2-2.5 hours, and then placed in a 10% hydrogen environment and heated to 265-270°C for reaction for 3.5-4 hours to obtain a copper nanowire intermediate; the nitrogen-doped modified graphene mixed suspension is evenly dripped onto the surface of the copper nanowire intermediate, the solvent is evaporated at 60-65°C, and the same dripping and drying process is repeated to control the thickness of the anti-oxidation layer.

[0018] Furthermore, the preparation method of the nitrogen-doped modified graphene mixed suspension comprises the following steps:

[0019] Polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide were added to acetonitrile and stirred uniformly to obtain solution A; nitrogen-doped modified graphene powder was added to acetonitrile and ultrasonically dispersed to obtain suspension B; solution A was added to suspension B and stirred to obtain nitrogen-doped modified graphene mixed suspension;

[0020] Furthermore, the molar ratio of ethylene oxide to lithium bis(trifluoromethanesulfonyl)imide is 4:1; and the concentration of the suspension B is 4-4.5 wt %.

[0021] Furthermore, the preparation method of the nitrogen-doped modified graphene powder comprises the following steps:

[0022] Adding a graphene oxide aqueous solution and polyvinyl pyrrolidone to a 92% v / v ethanol solution, adding a 25% v / v ammonia aqueous solution and tetraethyl silicate, reacting at 30-35° C. for 6-6.5 hours, filtering, washing, and then dispersing into deionized water to obtain a dispersion C; adding the dispersion C to a 30% v / v ethanol solution and stirring evenly, adding resorcinol, formaldehyde, ethylenediamine, and tetraethyl silicate, and reacting at 40-45° C. for 24 hours to obtain a product D; placing the product D in a nitrogen environment at a high temperature of 700-900° C. for 6-24 hours, and treating it with a 10% v / v hydrofluoric acid aqueous solution to obtain a nitrogen-doped modified graphene powder;

[0023] Furthermore, in the dispersion C, the mass ratio of graphene oxide aqueous solution: polyvinyl pyrrolidone: ammonia solution: tetraethyl silicate is 10: (0.6-0.8): 12: 6; the concentration of the graphene oxide aqueous solution is 6-7 mg / mL;

[0024] Furthermore, in the product D, the mass ratio of dispersion C: resorcinol: formaldehyde: ethylenediamine: tetraethyl silicate is (10-12): 0.4: 0.6: 0.6: 1.2.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention forms a metal copper layer by evaporating metal aluminum and dissolving metal copper. On the one hand, the surface roughness of the copper layer is improved, the specific surface area of ​​the surface is increased, the bonding force between the negative electrode active material and the current collector surface is enhanced, and the interface resistance between the copper layer and the negative electrode is reduced. On the other hand, the porosity of the metal layer is increased, the surface density is reduced, and the energy density of the battery is increased.

[0027] The present invention uses sodium hydroxide and ammonium persulfate to further perform surface chemical modification on the metal copper layer, forming a three-dimensional copper hydroxide nanowire structure on the surface of the metal copper layer, and then preparing a surface copper nanowire structure intermediate through heat treatment, forming a richer pore structure on the surface of the metal copper layer, which has the effects of increasing specific surface area, reducing mass and volume ratio, enhancing lithium affinity, reducing local current density, inducing uniform deposition and nucleation of lithium in the three-dimensional porous structure, stabilizing the SEI (solid electrolyte interface) layer, preventing dendrite growth, and improving the electrochemical performance of the battery.

[0028] The present invention prepares a nitrogen-doped modified graphene mixed suspension by mixing polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide and nitrogen-doped modified graphene powder, and forms an ultra-thin coating on the surface of a three-dimensional nano-copper wire by drop coating. On the one hand, it can provide an antioxidant effect; on the other hand, it can solve the problem of a porous structure (metallic copper layer and three-dimensional copper nanowire structure) with an excessively large specific surface area, which causes electrolyte decomposition, battery CE (Coulomb efficiency) and capacity decay when the battery operates at high surface capacity due to the excessive contact area between the electrolyte and lithium. The invention can effectively inhibit electrolyte decomposition, ensure the rapid movement of lithium ions, and improve the electrochemical performance of the battery.

[0029] High-temperature sintering treatment can transform the nitrogen-doped graphene's nitrogen-doping type from pyrrolic nitrogen to pyridinic nitrogen. Pyridinic nitrogen has better lithium affinity, reduces the nucleation overpotential of lithium ions on the surface, can guide the uniform deposition of lithium, inhibit the growth of lithium dendrites, and has a synergistic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 This is the structure diagram of the air composite copper current collector;

[0032] Among them, there are a polymer film 1, an adhesive transition layer 2, a metal copper layer 3 and an anti-oxidation layer 4. DETAILED DESCRIPTION

[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0034] It should be noted that the purchase manufacturers of all raw materials involved in the present invention are not particularly restricted and illustratively include: polypropylene model RF401, purchased from Dongguan Chuangshi Plastic Raw Materials Co., Ltd.; polyethylene oxide specification: molecular weight: 400,000; graphene oxide purchased from Tokyo Chemical Industry Development Co., Ltd. (Shanghai); lithium bis(trifluoromethanesulfonyl)imide CAS: 90076-65-6, and the remaining raw materials are commercially available.

[0035] Example 1: A method for preparing an air-composite copper current collector: S1: magnetically control a 50nm nickel-chromium metal layer on the upper and lower surfaces of a 4.0μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0036] S2: Simultaneously depositing aluminum and copper on the surfaces of the upper and lower bonding transition layers to obtain a 1 μm copper-aluminum composite layer, which is then immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer 3;

[0037] S3: Performing chromium plating anti-oxidation treatment on the surfaces of the upper and lower metal copper layers with a thickness of 10 nm to obtain an air composite copper current collector.

[0038] Example 2: A method for preparing an air-composite copper current collector: S1: magnetically control a 50 nm nickel-chromium metal layer on both the upper and lower surfaces of a 4.0 μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0039] S2: Simultaneously depositing aluminum and copper on the upper and lower bonding transition layers to obtain a 1 μm copper-aluminum composite layer, which is then immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer 3;

[0040] S3: 10 g of 6 mg / mL graphene oxide aqueous solution and 0.6 g of polyvinyl pyrrolidone were added to 250 mL of 92% v / v ethanol solution, and 12 g of 25% v / v ammonia aqueous solution and 6 g of tetraethyl silicate were added and reacted at 30°C for 6 h. The mixture was filtered, washed, and dispersed into 60 mL of deionized water to obtain dispersion C. 12 g of dispersion C was added to 200 mL of 30% v / v ethanol solution and stirred evenly. 0.4 g of resorcinol, 0.6 g of formaldehyde, 0.6 g of ethylenediamine, and 1.2 g of tetraethyl silicate were added and reacted at 40°C for 24 h to obtain product D. Product D was placed in a nitrogen environment for 80 The nitrogen-doped modified graphene powder was obtained by sintering at high temperature at 0°C for 24h and treating with 10% v / v hydrofluoric acid aqueous solution; 1g of polyethylene oxide and 1.625g of lithium bis(trifluoromethanesulfonylimide) were added to 50mL of acetonitrile and stirred evenly to obtain solution A; the nitrogen-doped modified graphene powder was added to 50mL of acetonitrile and ultrasonically dispersed to obtain a 4wt% suspension B; solution A was added to suspension B and stirred to obtain a nitrogen-doped modified graphene mixed suspension.

[0041] S4: Immerse the product containing the metallic copper layer in step S2 in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15 minutes, wash, dry, and place in an argon environment, heat to 180°C for reaction for 2 hours, and then place in a 10% hydrogen environment, heat to 265°C for reaction for 3.5 hours to obtain a copper nanowire intermediate; uniformly add the nitrogen-doped modified graphene mixed suspension dropwise on the surface of the copper nanowire intermediate, place at 60°C to evaporate the solvent, repeat the same dropping and drying process to control the thickness of the anti-oxidation layer to 10 nm, and obtain an air-composite copper current collector.

[0042] Example 3: A method for preparing an air-composite copper current collector: S1: magnetically controlling a 50 nm nickel-chromium metal layer on both the upper and lower surfaces of a 4.0 μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0043] S2: Simultaneously depositing aluminum and copper on the upper and lower bonding transition layers to obtain a 1 μm copper-aluminum composite layer, which is then immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer 3;

[0044] S3: 10 g of 6 mg / mL graphene oxide aqueous solution and 0.6 g of polyvinyl pyrrolidone were added to 250 mL of 92% v / v ethanol solution, and 12 g of 25% v / v ammonia aqueous solution and 6 g of tetraethyl silicate were added and reacted at 30°C for 6 h. The mixture was filtered, washed, and dispersed in 60 mL of deionized water to obtain dispersion C. 12 g of dispersion C was added to 200 mL of 30% v / v ethanol solution and stirred evenly. 0.4 g of resorcinol, 0.6 g of formaldehyde, 0.6 g of ethylenediamine, and 1.2 g of tetraethyl silicate were added and reacted at 40°C for 24 h to obtain product D. Product D was placed in a nitrogen environment for 800 ℃ for 24h and treated with 10% v / v hydrofluoric acid aqueous solution to obtain nitrogen-doped modified graphene powder; 1g of polyethylene oxide and 1.625g of lithium bis(trifluoromethanesulfonylimide) were added to 50mL of acetonitrile and stirred evenly to obtain solution A; the nitrogen-doped modified graphene powder was added to 50mL of acetonitrile and ultrasonically dispersed to obtain a 4.5wt% suspension B; solution A was added to suspension B and stirred to obtain a nitrogen-doped modified graphene mixed suspension.

[0045] S4: Immerse the product containing the metallic copper layer in step S2 in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15 minutes, wash, dry, and place in an argon environment, heat to 180°C for reaction for 2 hours, and then place in a 10% hydrogen environment, heat to 265°C for reaction for 3.5 hours to obtain a copper nanowire intermediate; uniformly add the nitrogen-doped modified graphene mixed suspension dropwise on the surface of the copper nanowire intermediate, place at 60°C to evaporate the solvent, repeat the same dropping and drying process to control the thickness of the anti-oxidation layer to 10 nm, and obtain an air-composite copper current collector.

[0046] Comparative Example 1: A method for preparing an air-composite copper current collector: S1: a 50nm nickel-chromium metal layer is magnetically controlled on both the upper and lower surfaces of a 4.0μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0047] S2: Copper is simultaneously deposited on the upper and lower bonding transition layers to obtain a 20 nm copper layer 3, which is then immersed in a copper sulfate solution to electroplate the upper and lower copper layers to a thickness of 1 μm.

[0048] S3: Performing chromium plating anti-oxidation treatment on the surfaces of the upper and lower metal copper layers with a thickness of 10 nm to obtain an air composite copper current collector.

[0049] Comparative Example 2: A method for preparing an air-composite copper current collector: S1: a 50nm nickel-chromium metal layer is magnetically controlled on both the upper and lower surfaces of a 4.0μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0050] S2: Simultaneously depositing aluminum and copper on the upper and lower bonding transition layers to obtain a 1 μm copper-aluminum composite layer, which is then immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer 3;

[0051] S3: 10 g of 6 mg / mL graphene oxide aqueous solution and 0.6 g of polyvinyl pyrrolidone were added to 250 mL of 92% v / v ethanol solution, and 12 g of 25% v / v ammonia solution and 6 g of tetraethyl silicate were added to react at 30 ° C for 6 h, filtered, washed and dispersed into 60 mL of deionized water to obtain dispersion C; 12 g of dispersion C was added to 200 mL of 30% v / v ethanol solution and stirred evenly, and 0.4 g of resorcinol, 0.6 g of formaldehyde, 0.6 g of ethylenediamine and 1.2 g of tetraethyl silicate were added to the mixture. The reaction was carried out at 40°C for 24 hours to obtain product D; product D was placed in a nitrogen environment and sintered at 800°C for 24 hours, and treated with a 10% v / v hydrofluoric acid aqueous solution to obtain nitrogen-doped modified graphene powder; 1g of polyethylene oxide and 1.625g of lithium bis(trifluoromethanesulfonylimide) were added to 50mL of acetonitrile and stirred uniformly to obtain solution A; the nitrogen-doped modified graphene powder was added to 50mL of acetonitrile and ultrasonically dispersed to obtain a 1wt% suspension B; solution A was added to suspension B and stirred to obtain a nitrogen-doped modified graphene mixed suspension;

[0052] S4: Immerse the product containing the metallic copper layer in step S2 in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15 minutes, wash, dry, and place in an argon environment, heat to 180°C for reaction for 2 hours, and then place in a 10% hydrogen environment, heat to 265°C for reaction for 3.5 hours to obtain a copper nanowire intermediate; uniformly add the nitrogen-doped modified graphene mixed suspension dropwise on the surface of the copper nanowire intermediate, place at 60°C to evaporate the solvent, repeat the same dropping and drying process to control the thickness of the anti-oxidation layer to 10 nm, and obtain an air-composite copper current collector.

[0053] Comparative Example 3: A method for preparing an air-composite copper current collector: S1: a 50nm nickel-chromium metal layer is magnetically controlled on both the upper and lower surfaces of a 4.0μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0054] S2: Simultaneously depositing aluminum and copper on the upper and lower bonding transition layers to obtain a 1 μm copper-aluminum composite layer, which is then immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer 3;

[0055] S3: 10 g of 6 mg / mL graphene oxide aqueous solution and 0.6 g of polyvinyl pyrrolidone were added to 250 mL of 92% v / v ethanol solution, and 12 g of 25% v / v ammonia solution and 6 g of tetraethyl silicate were added to react at 30 ° C for 6 h, filtered, washed and dispersed into 60 mL of deionized water to obtain dispersion C; 12 g of dispersion C was added to 200 mL of 30% v / v ethanol solution and stirred evenly, and 0.4 g of resorcinol, 0.6 g of formaldehyde, 0.6 g of ethylenediamine and 1.2 g of tetraethyl silicate were added to the mixture. The reaction was carried out at 40°C for 24 hours to obtain product D; product D was placed in a nitrogen environment and sintered at 800°C for 24 hours, and treated with a 10% v / v hydrofluoric acid aqueous solution to obtain nitrogen-doped modified graphene powder; 1g of polyethylene oxide and 1.625g of lithium bis(trifluoromethanesulfonylimide) were added to 50mL of acetonitrile and stirred uniformly to obtain solution A; the nitrogen-doped modified graphene powder was added to 50mL of acetonitrile and ultrasonically dispersed to obtain a 10wt% suspension B; solution A was added to suspension B and stirred to obtain a nitrogen-doped modified graphene mixed suspension;

[0056] S4: Immerse the product containing the metallic copper layer in step S2 in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15 minutes, wash, dry, and place in an argon environment, heat to 180°C for reaction for 2 hours, and then place in a 10% hydrogen environment, heat to 265°C for reaction for 3.5 hours to obtain a copper nanowire intermediate; uniformly add the nitrogen-doped modified graphene mixed suspension dropwise on the surface of the copper nanowire intermediate, place at 60°C to evaporate the solvent, repeat the same dropping and drying process to control the thickness of the anti-oxidation layer to 10 nm, and obtain an air-composite copper current collector.

[0057] Comparative Example 4: A method for preparing an air-composite copper current collector: S1: a 50 nm nickel-chromium metal layer is magnetically controlled on both the upper and lower surfaces of a 4.0 μm polypropylene film 1 to obtain an adhesive transition layer 2;

[0058] S2: Simultaneously depositing aluminum and copper on the upper and lower bonding transition layers to obtain a 1 μm copper-aluminum composite layer, which is then immersed in a 10 wt% sodium hydroxide solution to dissolve the aluminum to obtain a copper layer 3;

[0059] S3: 1 g of polyethylene oxide and 1.625 g of lithium bis(trifluoromethanesulfonyl)imide were added to 50 mL of acetonitrile and stirred to obtain solution A; graphene powder was added to 50 mL of acetonitrile and ultrasonically dispersed to obtain a 4 wt% suspension B; solution A was added to suspension B and stirred to obtain a nitrogen-doped modified graphene mixed suspension;

[0060] S4: Immerse the product containing the metallic copper layer in step S2 in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15 minutes, wash, dry, and place in an argon environment, heat to 180°C for reaction for 2 hours, and then place in a 10% hydrogen environment, heat to 265°C for reaction for 3.5 hours to obtain a copper nanowire intermediate; uniformly add the nitrogen-doped modified graphene mixed suspension dropwise on the surface of the copper nanowire intermediate, place at 60°C to evaporate the solvent, repeat the same dropping and drying process to control the thickness of the anti-oxidation layer to 10 nm, and obtain an air-composite copper current collector.

[0061] Test: Tensile strength: The tensile strength was tested in accordance with the national standard GB / T 1040.3-2006.

[0062] Elongation: Elongation at break is tested according to the national standard GB / T 1040.3-2006.

[0063] Surface roughness: The instrument's stylus contacts the surface being measured and gently traverses it to measure surface roughness. A sharp stylus is placed vertically on the surface being measured and moved laterally. Due to the roughness of the working surface, the stylus will fluctuate vertically, following the contour of the surface being measured. This minute displacement is converted into an electrical signal by an electrical circuit, amplified, and processed to obtain the surface roughness parameter value. Alternatively, a surface profile can be plotted using a recorder, and the data processed to determine the surface roughness parameter value. The specific test method is to calculate the difference between the average height of the five largest profile peaks and the average depth of the five largest profile valleys within a sampling length (10 cm).

[0064] Energy density: 88 wt% of graphene, 7 wt% of superconductive acetylene black, 2 wt% of carboxymethyl cellulose and 3 wt% of styrene-butadiene rubber were mixed and the mixture was dispersed in N-methyl-2-pyrrolidone to prepare a composition for the negative electrode active material layer. Next, the above composition was coated on a copper foil, dried and compressed to make the negative electrode. 90 wt% of LiCoO2, 5 wt% of polyvinylidene fluoride and 5 wt% of superconductive acetylene black were mixed in N-methylpyrrolidone to prepare a composition for the positive electrode active material layer. The above composition was then coated on a 6-micron aluminum current collector, dried and compressed to prepare the positive electrode. Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:3:4, and LiPF6 was dissolved therein at a concentration of 1.15M to prepare an electrolyte. Finally, the positive electrode, composite separator, and negative electrode are assembled, and then the tabs of all the positive electrode sheets of the laminated battery cell are ultrasonically welded, and the tabs of all the negative electrode sheets are ultrasonically welded, and finally the electrolyte is filled to make the battery.

[0065] The lithium-ion battery was left at room temperature for 30 minutes, charged to 4.4V (nominal voltage) at a constant current of 0.05C, and then the electrochemical device was discharged to 3.0V at a rate of 0.05C at a certain voltage. The above charge and discharge steps were repeated for 3 cycles to complete the formation of the electrochemical device to be tested. After the electrochemical device was formed, it was charged to 4.4V at a constant current of 2C, and then discharged to 3.0V at a discharge rate of 2C. The discharge capacity was recorded, and then the energy density at 0.1C discharge was calculated:

[0066] Energy density (Wh / L) = discharge capacity (Wh) / lithium-ion battery volume (L)

[0067] Interface resistance: The AC impedance system in the electrochemical workstation can be used to measure resistance and test the interface resistance of the battery.

[0068] The composite diaphragm includes a base film and a polymer coating coated on the surface of the film. In this embodiment, the base film is a PP / PE / PP ordinary diaphragm. The polymer coating is opposite to the copper foil. The polymer coating includes a polyoxyethylene compound and titanium dioxide nanoparticles. The coating thickness in this embodiment is 200 μm, but is not limited to this. In this embodiment, the molecular weight of the polyoxyethylene compound is 100,000, and the mass ratio of titanium dioxide nanoparticles in the polymer coating is 5%.

[0069] Table 1 Composite copper current collector data

[0070]

[0071]

[0072] Conclusion: The composite copper current collectors prepared in Examples 1-3 exhibit excellent mechanical and electrochemical properties. In Comparative Example 2, the nitrogen-doped modified graphene mixed suspension contained too little nitrogen-doped modified graphene, resulting in incomplete surface coverage and the formation of tri-color solid polymer electrolyte spots. In Comparative Example 3, the nitrogen-doped modified graphene mixed suspension contained too much nitrogen-doped modified graphene, leading to over-coverage and reduced lithium ion transport. In Comparative Example 4, the use of conventional graphene oxide weakened lithium ion transport, reduced stability, and decreased ability to inhibit lithium dendrite crystallization.

[0073] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an air-composite copper current collector, characterized in that: The following steps are involved: S1: magnetically controlling a layer of metal material on the upper and lower surfaces of the polymer film (1) to obtain a bonding transition layer (2); S2: simultaneously evaporating metal aluminum and metal copper on the surfaces of the upper and lower bonding transition layers, and immersing them in a 10 wt % sodium hydroxide solution after the evaporation is completed to dissolve the metal aluminum to obtain a metal copper layer (3); S3: performing an anti-oxidation treatment on the surfaces of the upper and lower metal copper layers to obtain an anti-oxidation layer (4) and an air composite copper current collector; The anti-oxidation layer (4) is any one of a chromium layer, a zinc-nickel layer, and a copper nanowire graphene composite layer; and has a thickness of 1-100 nm; The method for preparing the copper nanowire-graphene composite layer comprises the following steps: The product containing the metallic copper layer in step S2 is immersed in a mixed solution of 2 mol / L sodium hydroxide and 0.1 mol / L ammonium persulfate for 15-20 minutes, washed, dried, placed in an argon environment, heated to 180-185°C for reaction for 2-2.5 hours, and then placed in a 10% hydrogen environment, heated to 265-270°C for reaction for 3.5-4 hours to obtain a copper nanowire intermediate; the nitrogen-doped modified graphene mixed suspension is uniformly dripped on the surface of the copper nanowire intermediate, the solvent is evaporated at 60-65°C, and the same dripping and drying process is repeated to control the thickness of the anti-oxidation layer.

2. The method for preparing an air-composite copper current collector according to claim 1, characterized in that: The preparation method of the nitrogen-doped modified graphene mixed suspension comprises the following steps: Add polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide into acetonitrile and stir evenly to obtain solution A; add nitrogen-doped modified graphene powder into acetonitrile and ultrasonically disperse to obtain suspension B; add solution A into suspension B and stir to obtain nitrogen-doped modified graphene mixed suspension; The molar ratio of ethylene oxide to lithium bis(trifluoromethanesulfonyl)imide is 4:1; and the concentration of the suspension B is 4-4.5 wt %.

3. The method for preparing an air-composite copper current collector according to claim 2, characterized in that: The method for preparing the nitrogen-doped modified graphene powder comprises the following steps: Adding graphene oxide aqueous solution and polyvinyl pyrrolidone to 92% v / v ethanol solution, adding 25% v / v ammonia aqueous solution and tetraethyl silicate to react at 30-35°C for 6-6.5h, filtering, washing and dispersing in deionized water to obtain dispersion C; adding dispersion C to 30% v / v ethanol solution and stirring evenly, adding resorcinol, formaldehyde, ethylenediamine and tetraethyl silicate to react at 40-45°C for 24h to obtain product D; placing product D in a nitrogen environment at 700-900°C for high temperature sintering for 6-24h, and treating with 10% v / v hydrofluoric acid aqueous solution to obtain nitrogen-doped modified graphene powder; In dispersion C, the mass ratio of graphene oxide aqueous solution: polyvinyl pyrrolidone: ammonia solution: tetraethyl silicate is 10: (0.6-0.8): 12: 6; the concentration of graphene oxide aqueous solution is 6-7 mg / mL; In product D, the mass ratio of dispersion C: resorcinol: formaldehyde: ethylenediamine: tetraethyl silicate is (10-12): 0.4: 0.6: 0.6: 1.

2.

4. The air-composite copper current collector prepared by the method for preparing an air-composite copper current collector according to any one of claims 1 to 3 is characterized in that: The air composite copper current collector comprises a polymer film (1), an adhesive transition layer (2), a metal copper layer (3) and an anti-oxidation layer (4); the adhesive transition layer (2), the metal copper layer (3) and the anti-oxidation layer (4) are symmetrically arranged in sequence on both sides of the polymer film (1).

5. The air-composite copper current collector according to claim 4, characterized in that: The total thickness of the air composite current collector is 2-20 μm.

6. The air-composite copper current collector according to claim 4, characterized in that: The polymer film (1) comprises any one of a polyethylene film, a polypropylene film, a polyethylene terephthalate film and a polyimide film; and has a thickness of 1-19 μm.

7. The air-composite copper current collector according to claim 4, characterized in that: The metal material of the bonding transition layer (2) includes any one of a nickel-chromium alloy and a ternary metal material; and the thickness is 0.5-100 nm.

8. The air-composite copper current collector according to claim 4, characterized in that: The thickness of the metal copper layer (3) is 0.1-2 μm.

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