Functional current collector, preparation method thereof and lithium ion battery

Abstract

The invention provides a functional current collector, a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: performing magnetron sputtering on two side surfaces of a base film to form a conductive seed layer respectively to obtain a composite film material; and placing the composite membrane material in a modified aluminum-based ion electroplating solution for electroplating so as to form a thickening layer on the surface of the conductive seed layer, thereby obtaining the functional current collector, wherein the conductive seed layer and the thickening layer are the same in type, the components in the modified aluminum-based ion electroplating liquid comprise an aluminum-based ion liquid and a modifier, and the modifier comprises light aromatic naphtha. The production defects can be reduced, the process window can be improved, the grain size of the aluminum film of the functional current collector can be refined, the porosity of the aluminum film is reduced, the internal stress of the aluminum film is avoided, the adhesive force of the aluminum film is improved, the mechanical performance of the functional current collector is comprehensively improved, and the practicability is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a functional current collector, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] With the rapid development of new energy and advanced manufacturing industries, the key performance of batteries such as cycle life, safety performance, and energy density urgently needs to be improved. The current collector is a key component in the battery, which plays a role in collecting current. At the same time, the quality of the current collector directly affects technical indicators such as the cycle life, energy density, and safety of the battery.

[0003] Currently, the common positive and negative current collectors in the battery industry are mostly made of copper foil and aluminum foil. The current collector made of pure metal has high cost and quality. At the same time, its performance in battery safety is often not satisfactory. In addition, the pure metal current collector also has a high "dead weight", which is not conducive to improving the energy density of the battery. The traditional production process of composite aluminum foil is generally obtained by evaporating aluminum vapor onto a polymer material in a vacuum environment. This method has a simple process and is easy for industrial production. However, when using the evaporation coating process, the temperature of aluminum vapor is relatively high, often reaching thousands of degrees Celsius, and the process window is small. Often, multiple evaporation coatings are required to obtain a film layer with excellent performance. Moreover, there are some inevitable defects in the aluminum foil produced by the traditional evaporation coating process, such as missing plating, film surface scalding, and pinholes. Therefore, it is necessary to develop a new production process to reduce production defects and expand the process window.

[0004] Electroplating is a surface treatment technology that uses the principle of electrolysis to deposit a metal coating on the surface of a metal or other conductive material. It can solve the defects and problems that occur in the production process of the above traditional evaporation coating process. However, since the precipitation potential of aluminum is lower than the hydrogen evolution potential, the electroplating method in an aqueous solution is not suitable for the production of aluminum current collectors.

[0005] Therefore, it is urgent to design a method for preparing an aluminum current collector by ionic liquid electroplating, so as to reduce production defects, expand the process window, refine the aluminum grain size, and effectively improve the comprehensive mechanical properties of the product. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a functional current collector, a preparation method thereof, and a lithium-ion battery. The present invention combines the method of magnetron sputtering a conductive seed layer and electroplating with an aluminum-based ionic electroplating solution, and at the same time introduces a modifier including light aromatic naphtha to modify the ionic electroplating solution. This means can not only reduce production defects and improve the process window, but also refine the grain size of the aluminum film of the functional current collector, reduce the porosity of the aluminum film, avoid the internal stress of the aluminum film, improve the adhesion of the aluminum film, comprehensively improve the mechanical properties of the functional current collector, and has strong practicability.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted in the present invention:

[0008] In the first aspect, the present invention provides a preparation method of a functional current collector, and the preparation method includes the following steps:

[0009] Magnetron sputter a conductive seed layer on both side surfaces of a base film to obtain a composite film material.

[0010] Place the composite film material in a modified aluminum-based ionic electroplating solution for electroplating, so as to form a thickening layer on the surface of the conductive seed layer, and obtain the functional current collector.

[0011] Among them, the conductive seed layer and the thickening layer are of the same type, and the components in the modified aluminum-based ionic electroplating solution include an aluminum-based ionic liquid and a modifier, and the modifier includes light aromatic naphtha.

[0012] The present invention combines the method of magnetron sputtering a conductive seed layer and electroplating with an aluminum-based ionic electroplating solution, and at the same time introduces a modifier including light aromatic naphtha to modify the ionic electroplating solution. This means can not only reduce production defects and improve the process window, but also refine the grain size of the aluminum film of the functional current collector, reduce the porosity of the aluminum film, avoid the internal stress of the aluminum film, improve the adhesion of the aluminum film, comprehensively improve the mechanical properties of the functional current collector, and has strong practicability.

[0013] It should be noted that light aromatic naphtha can dilute the aluminum-based ionic liquid to a certain extent, thereby enhancing the conductivity of the aluminum-based ionic liquid. At the same time, light aromatic naphtha can also form a complex with Al 3+ to reduce the deposition potential of aluminum in the electroplating process of the aluminum-based ionic liquid, facilitate the deposition of the thickening layer, improve the quality of the thickening layer, and refine the grain size of the aluminum film. For heavy aromatic naphtha, it mainly contains aromatic substances with more carbon atoms, focusing on aromatic substances with 10 or more carbon atoms, such as polycyclic aromatic hydrocarbons like naphthalene, anthracene, and phenanthrene, as well as some aromatic compounds with long side chains. These aromatics have large molecular weights, high boiling points, and relatively complex structures, and have a weak impact on the deposition process of aluminum in the ionic liquid and cannot achieve a modification effect.

[0014] In the present invention, magnetron sputtering is used to prepare a conductive seed layer, which can deposit a uniform and dense film on the surface of the base film, thereby providing an ideal crystallization core and growth basis for the subsequent electroplating deposition of the thickening layer, enabling the thickening layer to firmly adhere to the substrate and improving the structural stability of the functional current collector.

[0015] Preferably, the base film is a polymer base film. Exemplarily, the material of the polymer base film is polypropylene (PP), etc.

[0016] Preferably, in the modified aluminum-based ionic electroplating solution, the concentration of the modifier is 0.03 - 0.04 mol / L, for example, it can be 0.03 mol / L, 0.032 mol / L, 0.034 mol / L, 0.036 mol / L, 0.038 mol / L or 0.04 mol / L, etc.

[0017] In the present invention, a suitable concentration of the modifier in the modified aluminum-based ionic electroplating solution not only helps to reduce the deposition potential of aluminum in the electroplating process and improve the conductivity of the ionic liquid, but also can improve the quality of the aluminum layer and refine the grain size of the aluminum film.

[0018] Preferably, the components in the light aromatic naphtha include small molecule organic compounds.

[0019] It should be noted that light aromatic naphtha is a type of mixture, which contains various small molecule organic compounds. The small molecule organic compounds mentioned in the present invention refer to organic compounds with a relative molecular mass between 72 - 200 and a carbon number between 5 - 9.

[0020] Preferably, the small molecule organic compounds include at least one of straight-chain alkanes, monocyclic alkanes, bicyclic alkanes, alkylbenzenes, benzene, indane and tetralin with carbon numbers from C5 to C9. Exemplarily, the straight-chain alkanes with carbon numbers from C5 to C9 can be n-hexane and / or n-pentane, etc., the monocyclic alkanes with carbon numbers from C5 to C9 can be cyclohexane, etc., the bicyclic alkanes with carbon numbers from C5 to C9 can be bicycloheptane, etc., and the alkylbenzenes with carbon numbers from C5 to C9 can be ethylbenzene, etc.

[0021] In the small molecule organic compounds provided by the present invention, the benzene ring structure mainly affects the deposition process of aluminum in the ionic liquid.

[0022] Preferably, the light aromatic naphtha, by mass percentage, comprises: 50-60% (such as 50%, 52%, 54%, 56%, 58% or 60%, etc.) of linear alkanes, 25-35% (such as 25%, 27%, 30%, 32% or 35%, etc.) of monocyclic alkanes, 2-3% (such as 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%, etc.) of bicyclic alkanes, 10-15% (such as 10%, 11%, 12%, 13%, 14% or 15%, etc.) of alkylbenzenes, 0.05-0.15% (such as 0.05%, 0.1% or 0.15%, etc.) of benzene, and 0.05-0.15% (such as 0.05%, 0.1% or 0.15%, etc.) of indane and / or tetralin.

[0023] In the present invention, by using the light aromatic naphtha with the above component contents to modify the aluminum-based ionic liquid, the viscosity of the ionic liquid can be better reduced, and at the same time, the conductivity of the ionic liquid can be improved.

[0024] Preferably, before use, the light aromatic naphtha is first subjected to distillation treatment.

[0025] In the present invention, the purpose of distilling the light aromatic naphtha is to obtain small molecule organic compounds with relatively lower molecular weights, such as n-hexane, benzene, ethylbenzene, etc.

[0026] Preferably, the steps of the distillation treatment include:

[0027] The light aromatic naphtha is heated to a first temperature at a first heating rate for distillation, and then heated to a second temperature at a second heating rate.

[0028] The two-stage heating adopted in the present invention helps to fully distill and prevent the mixing of organic compounds with relatively larger molecular weights and higher boiling points.

[0029] Preferably, the first heating rate is less than or equal to 2 °C / h, such as 2 °C / h, 1.5 °C / h or 1 °C / h, etc.

[0030] In the present invention, heating to the first temperature at the above slow heating rate helps to precisely control the heating rate.

[0031] Preferably, the first temperature is 75-85 °C, such as 75 °C, 80 °C or 85 °C, etc.

[0032] Preferably, the second heating rate is 1-3 °C / min, such as 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min or 3 °C / min, etc.

[0033] Preferably, the second temperature is less than or equal to 120 °C, for example, it can be 110 °C, 115 °C or 120 °C, etc., and preferably it is 110-120 °C.

[0034] The present invention limits the second temperature not to exceed 120 °C to avoid the mixing of high-boiling components.

[0035] Preferably, the aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride (BMIMCl) and aluminum chloride (AlCl3).

[0036] Preferably, the molar ratio of the 1-butyl-3-methylimidazolium chloride to the aluminum chloride is 1:(1-3), for example, it can be 1:1, 1:1.5, 1:2 or 1:3, etc.

[0037] Preferably, the conductive seed layer is an aluminum seed layer, and the thickness of the aluminum seed layer is 50-100 nm, for example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, etc.

[0038] Preferably, the parameters in the magnetron sputtering method include:

[0039] The target is an aluminum target, the sputtering power is 8-12 KW (for example, it can be 8 KW, 9 KW, 10 KW or 12 KW, etc.), the gas flow rate is 100-150 sccm (for example, it can be 100 sccm, 110 sccm, 120 scmm, 130 sccm, 140 sccm or 150 sccm, etc.), the vacuum degree is 3×10 -3 ~5×10 -3 Pa (for example, it can be 3×10 -3 Pa, 4×10 -3 Pa or 5×10 -3 Pa, etc.), the cooling temperature of the sputtering main roller is -35 to 0 °C (for example, it can be -35 °C, -25 °C, -15 °C, -5 °C or 0 °C, etc.), and the winding speed is 5-8 m / min (for example, it can be 5 m / min, 6 m / min, 7 m / min or 8 m / min, etc.).

[0040] In the present invention, the winding speed refers to the moving speed of the base film passing through the magnetron sputtering coating area when using the magnetron sputtering technology to coat the base film. An appropriate winding speed helps to obtain a conductive seed layer with uniform thickness and is beneficial to improving the adhesion between the thickening layer and the base film.

[0041] Preferably, the electroplating process is carried out in a protective atmosphere.

[0042] Preferably, the gas in the protective atmosphere includes nitrogen.

[0043] Preferably, during the electroplating process, the temperature is 20 - 30°C, for example, it can be 20°C, 25°C, 30°C, etc.

[0044] Preferably, the linear speed of the electroplating is 2 - 5 m / min, for example, it can be 2 m / min, 2.5 m / min, 3 m / min, 3.5 m / min, 4 m / min, 4.5 m / min, or 5 m / min, etc.

[0045] It should be noted that in the present invention, the linear speed of electroplating generally refers to the moving speed of the composite film material in the modified aluminum-based electroplating solution. The speed of the linear speed has a crucial impact on the thickness uniformity of the aluminum film on the surface of the composite film material. An appropriate linear speed can enable each part of the composite film material to have a relatively balanced residence time in the modified aluminum-based electroplating solution, which helps to obtain a thickening layer with uniform thickness. The electroplating process is relatively stable, and electroplating ions can be deposited on the surface of the composite film material with appropriate energy and manner, and fully combine with the conductive seed layer on the surface of the composite film material, so that the formed thickening layer firmly adheres to the base film.

[0046] Preferably, during the electroplating process, the value range of the current density is 0 - 50 mA / cm 2 , for example, it can be 1 mA / cm 2 , 5 mA / cm 2 , 10 mA / cm 2 , 20 mA / cm 2 , 30 mA / cm 2 , 40 mA / cm 2 or 50 mA / cm 2 etc.

[0047] Preferably, during the electroplating process, the current density changes in a gradient increasing manner. The current density increases from 0 - 5 mA / cm 2 (for example, it can be 1 mA / cm 2 , 2 mA / cm 2 , 3 mA / cm 2 , 4 mA / cm 2 or 5 mA / cm 2 etc.) to 45 - 50 mA / cm 2 (for example, it can be 45 mA / cm 2 , 46 mA / cm 2 , 47 mA / cm 2 , 48 mA / cm 2 , 49 mA / cm 2 or 50 mA / cm 2 etc.).

[0048] In the present invention, electroplating is carried out in the above-mentioned manner of increasing the current density gradient, which helps to obtain a higher-quality coating at a low current density and quickly obtain a coating with an ideal thickness at a high current density.

[0049] Preferably, the increment of the gradient increase of the current density is 0-10 mA / cm 2 , for example, it can be 2 mA / cm 2 , 4 mA / cm 2 , 6 mA / cm 2 , 8 mA / cm 2 or 10 mA / cm 2 etc., and preferably 5 mA / cm 2 .

[0050] In the present invention, an appropriate increment of the current density helps to improve the coating quality and reduce coating defects.

[0051] Preferably, the preparation method includes the following steps:

[0052] (1) Using magnetron sputtering, a layer of aluminum seed layer with a thickness of 50-100 nm is deposited on both surfaces of the polymer-based film to obtain a composite film material. The specific parameters include:

[0053] The target is an aluminum target, the sputtering power is 8-12 KW, the gas flow rate is 100-150 sccm, the vacuum degree is 3×10 -3 -5×10 -3 Pa, the cooling temperature of the sputtering main roller is -35-0 °C, and the winding speed is 5-8 m / min.

[0054] (2) The composite film material is placed in a modified aluminum-based ion electroplating solution, and electroplating is carried out in an inert atmosphere with gradient current densities of 0-5 mA / cm 2 , 5-10 mA / cm 2 , 10-15 mA / cm 2 , 15-20 mA / cm 2 , 20-25 mA / cm 2 , 25-30 mA / cm 2 , 30-35 mA / cm 2 , 35-40 mA / cm 2 , 40-45 mA / cm 2 and 45-50 mA / cm 2 . After the electroplating treatment, a thickened layer is formed on the surface of the aluminum seed layer to obtain the functional current collector.

[0055] Among them, the components in the modified aluminum-based ion electroplating solution include an aluminum-based ionic liquid and a modifier, and the modifier includes light aromatic naphtha; the components in the light aromatic naphtha include small molecule organic compounds, and the small molecule organic compounds include at least one of straight-chain alkanes, monocyclic alkanes, bicyclic alkanes, alkylbenzenes, benzene, indane, and tetralin with 5 to 9 carbon atoms; the aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride and aluminum chloride with a molar ratio of 1:(1 to 3).

[0056] In a second aspect, the present invention provides a functional current collector, and the functional current collector is prepared by using the preparation method described in the first aspect.

[0057] The functional current collector includes a base film and aluminum films provided on both surface sides of the base film, and the aluminum films are composed of a conductive seed layer and a thickening layer, and the conductive seed layer is located between the base film and the thickening layer.

[0058] Preferably, the thickness of the aluminum film is 0.8 to 1.2 μm, and for example, it can be 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, or 1.2 μm, etc.

[0059] Preferably, the grain size of the aluminum film is 70 to 90 nm, and for example, it can be 70 nm, 75 nm, 80 nm, 85 nm, or 90 nm, etc.

[0060] In the present invention, the refined grain size of the aluminum film helps to reduce the porosity of the aluminum film, avoid the internal stress of the aluminum film, improve the adhesion of the aluminum film, and comprehensively improve the mechanical properties of the functional current collector.

[0061] In a third aspect, the present invention provides a lithium-ion battery, and the positive electrode of the lithium-ion battery includes the functional current collector described in the second aspect.

[0062] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] The present invention combines the method of electroplating with a conductive seed layer and an aluminum-based ion electroplating solution, and at the same time introduces a modifier including light aromatic naphtha to modify the ion electroplating solution. This means can not only reduce production defects and improve the process window, but also refine the grain size of the aluminum film of the functional current collector, reduce the porosity of the aluminum film, avoid the internal stress of the aluminum film, improve the adhesion of the aluminum film, comprehensively improve the mechanical properties of the functional current collector, and has strong practicability. Detailed Embodiments

[0065] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0066] Example 1

[0067] This embodiment provides a preparation method of a functional current collector, and the preparation method includes the following steps:

[0068] (1) By using the magnetron sputtering method, a polymer-based film (made of PP) is placed in a double-drum magnetron sputtering device, and an aluminum seed layer with a thickness of 75 nm is deposited on both surfaces of the polymer-based film to obtain a composite film material. The specific parameters include:

[0069] The target is an aluminum target with a purity of 99.99%, the sputtering power is 10 KW, the gas flow rate is 125 sccm, the background vacuum degree is 4×10 -3 Pa, the cooling temperature of the sputtering main roller is -15°C, and the winding speed is 6 m / min.

[0070] (2) Provide a closed ten-tank winding electroplating line, and the same component of modified aluminum-based ion electroplating solution is placed in each tank. During the electroplating process, the composite film material is controlled to pass through the first tank to the tenth tank in sequence at a linear speed of 2 m / min. The current densities of the first tank to the tenth tank are controlled to be 1 mA / cm 2 , 6 mA / cm 2 , 11 mA / cm 2 , 16 mA / cm 2 , 21 mA / cm 2 , 26 mA / cm 2 , 31 mA / cm 2 , 36 mA / cm 2 , 41 mA / cm 2 , and 46 mA / cm 2 respectively. The electroplating process is carried out in a nitrogen atmosphere, the electroplating temperature is 20°C, and a thickening layer is formed on the surface of the aluminum seed layer after the electroplating treatment to obtain the functional current collector.

[0071] Among them, the components in the modified aluminum-based ion electroplating solution include an aluminum-based ionic liquid and a modifier with a concentration of 0.036 mol / L. The modifier is light aromatic naphtha (purchased from Henan Tianyu Hongyuan Chemical Co., Ltd.); the components in the light aromatic naphtha include small molecule organic compounds. By mass percentage, the small molecule organic compounds include: 55% n-hexane, 30% cyclohexane, 2.5% bicycloheptane, 12.3% ethylbenzene, 0.1% benzene, 0.05% indane, and 0.05% tetralin; the aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride and aluminum chloride with a molar ratio of 1:1.5.

[0072] This embodiment also provides a functional current collector prepared by the above preparation method. The functional current collector includes a polymer-based film, and aluminum films provided on both surface sides of the polymer-based film. The aluminum films are composed of a conductive seed layer and a thickening layer, and the conductive seed layer is located between the base film and the thickening layer; the thickness of the aluminum film is 1 μm.

[0073] Example 2

[0074] This embodiment provides a preparation method of a functional current collector. The preparation method includes the following steps:

[0075] (1) Using the magnetron sputtering method, place a polymer-based film (made of PP) in a double-drum magnetron sputtering device, and deposit an aluminum seed layer with a thickness of 50 nm on both surface sides of the polymer-based film to obtain a composite film material. The specific parameters include:

[0076] The target is an aluminum target with a purity of 99.99%. The sputtering power is 8 KW, the gas flow rate is 100 sccm, the background vacuum degree is 4×10 -3 Pa, the cooling temperature of the sputtering main roller is -25 °C, and the winding speed is 8 m / min.

[0077] (2) Provide a closed ten-tank winding electroplating line. The same-component modified aluminum-based ion electroplating solution is placed in each tank. During the electroplating process, control the composite film material to pass through the first tank to the tenth tank in sequence at a linear speed of 4 m / min. The current densities of the first tank to the tenth tank are controlled to be 3 mA / cm 2 , 8 mA / cm 2 , 13 mA / cm 2 , 18 mA / cm 2 , 23 mA / cm 2 , 28 mA / cm 2 , 33 mA / cm 2 , 38 mA / cm 2 , 43 mA / cm 2 , and 48 mA / cm 2, the electroplating process is carried out in a nitrogen atmosphere, the electroplating temperature is 25 °C, and a thickening layer is formed on the surface of the aluminum seed layer after the electroplating treatment to obtain the functional current collector.

[0078] Among them, the components of the modified aluminum-based ion electroplating solution include an aluminum-based ionic liquid and a modifier with a concentration of 0.03 mol / L. The modifier is light aromatic naphtha; the components of the light aromatic naphtha include small molecule organic compounds. By mass percentage, the small molecule organic compounds include: 50% n-hexane, 35% cyclohexane, 3% bicycloheptane, 11.9% ethylbenzene, 0.05% benzene, 0.025% indane, and 0.025% tetralin; the aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride and aluminum chloride with a molar ratio of 1:1.5.

[0079] This embodiment also provides a functional current collector prepared by the above preparation method. The functional current collector includes a polymer-based film and aluminum films provided on both side surfaces of the polymer-based film. The aluminum film is composed of a conductive seed layer and a thickening layer, and the conductive seed layer is located between the base film and the thickening layer; the thickness of the aluminum film is 0.8 μm.

[0080] Example 3

[0081] This embodiment provides a preparation method of a functional current collector. The preparation method includes the following steps:

[0082] (1) Using the magnetron sputtering method, place a polymer-based film (made of PP) in a double-drum magnetron sputtering device, and deposit an aluminum seed layer with a thickness of 100 nm on both side surfaces of the polymer-based film to obtain a composite film material. The specific parameters include:

[0083] The target is an aluminum target with a purity of 99.99%, the sputtering power is 12 KW, the gas flow rate is 150 sccm, the background vacuum degree is 4×10 -3 Pa, the cooling temperature of the sputtering main roller is -35 °C, and the winding speed is 5 m / min.

[0084] (2) Provide a closed ten-tank winding electroplating line. Each tank is filled with a modified aluminum-based ion electroplating solution with the same components. During the electroplating process, control the composite film material to pass through the first tank to the tenth tank in sequence at a linear speed of 5 m / min. The current densities of the first tank to the tenth tank are controlled to be 5 mA / cm 2 、10 mA / cm 2 、15 mA / cm 2 、20 mA / cm 2 、25 mA / cm 2 、30 mA / cm 2 、35 mA / cm2 、 40 mA / cm 2 、 45 mA / cm 2 and 50 mA / cm 2 The electroplating process is carried out in a nitrogen atmosphere at a temperature of 30 °C. After the electroplating treatment, a thickening layer is formed on the surface of the aluminum seed layer to obtain the functional current collector.

[0085] Among them, the components of the modified aluminum-based ion electroplating solution include an aluminum-based ionic liquid and a modifier with a concentration of 0.04 mol / L. The modifier is light aromatic naphtha; the components of the light aromatic naphtha include small molecule organic compounds. By mass percentage, the small molecule organic compounds include: 60% n-hexane, 25% cyclohexane, 2% bicycloheptane, 12.7% ethylbenzene, 0.15% benzene, 0.075% indane, and 0.075% tetralin; the aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride and aluminum chloride with a molar ratio of 1:1.5.

[0086] This embodiment also provides a functional current collector prepared by the above preparation method. The functional current collector includes a polymer-based film and aluminum films provided on both surface sides of the polymer-based film. The aluminum film is composed of a conductive seed layer and a thickening layer. The conductive seed layer is located between the base film and the thickening layer; the thickness of the aluminum film is 1.2 μm.

[0087] Example 4

[0088] The difference between this embodiment and Example 1 is that in the modified aluminum-based ion electroplating solution, the concentration of light aromatic naphtha is 0.012 mol / L.

[0089] The remaining preparation methods and parameters are the same as those in Example 1.

[0090] Example 5

[0091] The difference between this embodiment and Example 1 is that in the modified aluminum-based ion electroplating solution, the concentration of light aromatic naphtha is 0.024 mol / L.

[0092] The remaining preparation methods and parameters are the same as those in Example 1.

[0093] Example 6

[0094] The difference between this embodiment and Example 1 is that in the modified aluminum-based ion electroplating solution, the concentration of light aromatic naphtha is 0.048 mol / L.

[0095] The remaining preparation methods and parameters are the same as those in Example 1.

[0096] Example 7

[0097] The difference between this embodiment and Embodiment 1 is that in the modified aluminum-based ion electroplating solution, the concentration of light aromatic naphtha is 0.06 mol / L.

[0098] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0099] Embodiment 8

[0100] The difference between this embodiment and Embodiment 1 is that the electroplating process is carried out in only one tank, and the current density of this tank is controlled to increase sequentially from 1 mA / cm 2 to 6 mA / cm 2 , 11 mA / cm 2 , 16 mA / cm 2 , 21 mA / cm 2 , 26 mA / cm 2 , 31 mA / cm 2 , 36 mA / cm 2 , 41 mA / cm 2 and 46 mA / cm 2 to achieve electroplating.

[0101] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0102] Embodiment 9

[0103] The difference between this embodiment and Embodiment 1 is that during the electroplating process, the current densities of the first tank to the tenth tank are the same, all being 25 mA / cm 2 .

[0104] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0105] Embodiment 10

[0106] The difference between this embodiment and Embodiment 1 is that before the light aromatic naphtha is used, it is first subjected to distillation treatment, and the steps of the distillation treatment include:

[0107] The light aromatic naphtha is heated to 80 °C at a first heating rate of 2 °C / h for distillation, and then heated to 120 °C at a heating rate of 2 °C / min.

[0108] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0109] Comparative Example 1

[0110] This comparative example provides a preparation method of a functional current collector, and the preparation method includes the following steps:

[0111] The polymer-based film made of PP is coated by vacuum evaporation method, so as to form aluminum films with a thickness of 1μm on both surfaces of the polymer-based film. The specific parameters include:

[0112] Place the polymer-based film in the chamber of vacuum evaporation. Melt and evaporate the high-purity aluminum wire (purity greater than 99.99%) in the metal evaporation chamber at a temperature of 1200°C. The moving speed of the polymer-based film is 30m / min. The evaporated aluminum atoms pass through the cooling system in the vacuum coating chamber and are deposited on the two opposite surfaces of the polymer-based film, forming an aluminum film with a single-sided thickness of 1μm.

[0113] Comparative Example 2

[0114] The difference between this comparative example and Example 1 is that in the modified aluminum-based ion electroplating solution, the concentration of light aromatic naphtha is 0mol / L.

[0115] The remaining preparation methods and parameters are the same as those in Example 1.

[0116] Comparative Example 3

[0117] The difference between this comparative example and Example 1 is that the deposition method of the conductive seed layer is thermal evaporation method. The specific parameters include: Place the polymer-based film in the chamber of vacuum evaporation. Melt and evaporate the high-purity aluminum wire (purity greater than 99.99%) in the metal evaporation chamber at a high temperature of 1200°C. The moving speed of the polymer-based film is 40m / min. The evaporated aluminum atoms pass through the cooling system in the vacuum coating chamber and are deposited on the two opposite surfaces of the polymer-based film, forming an aluminum seed layer with a thickness of 75nm.

[0118] The remaining preparation methods and parameters are the same as those in Example 1.

[0119] Comparative Example 4

[0120] The difference between this comparative example and Example 1 is that light aromatic naphtha is replaced by heavy aromatic naphtha.

[0121] The remaining preparation methods and parameters are the same as those in Example 1.

[0122] Performance Test

[0123] I. Use an X-ray diffractometer to perform surface analysis on the functional current collectors provided in the above examples and comparative examples to obtain the grain size of the aluminum film.

[0124] II. Test the adhesion of the functional current collectors provided in the above examples and comparative examples.

[0125] The specific test method includes: cutting a specimen of 20×150 mm, pasting one side of the specimen to the movable sample stage with double-sided tape, also pasting the other side of the specimen with double-sided tape, clamping one side of the double-sided tape with a fixture, and then starting the test at a test rate of 100 mm / min.

[0126] The above analysis and test results are shown in Table 1.

[0127] Table 1

[0128]

[0129] Analysis:

[0130] The present invention combines the electroplating method using a conductive seed layer and an aluminum-based ion electroplating solution, and at the same time introduces a modifier including light aromatic naphtha to modify the ion electroplating solution. This method can not only reduce production defects and improve the process window, but also refine the grain size of the aluminum film of the functional current collector, reduce the porosity of the aluminum film, avoid the internal stress of the aluminum film, improve the adhesion of the aluminum film, comprehensively improve the mechanical properties of the functional current collector, and has strong practicability.

[0131] It can be seen from Example 1 and Examples 4-7 that as the concentration of light aromatic naphtha increases, the conductivity of the ionic liquid increases and the deposition rate of the aluminum film increases. If the concentration of light aromatic naphtha is too low, it is not conducive to quickly increasing the thickness of the aluminum film, and the change in grain size is not obvious and the tensile strength is not high; if the concentration of light aromatic naphtha is too high, it is not conducive to improving the mechanical properties of the aluminum film.

[0132] It can be seen from Example 1 and Example 8 that if the electroplating process is carried out only in one tank and the current density gradient increases with the progress of the electroplating process, it is not conducive to refining the grain size of the aluminum layer and is not conducive to the tensile strength.

[0133] It can be seen from Example 1 and Example 9 that if the current density is the same from the first tank to the tenth tank during the electroplating process, it is not conducive to refining the grain size of the aluminum layer.

[0134] It can be seen from Example 1 and Example 10 that if light aromatic naphtha is distilled before use, it is conducive to refining the grain size of the aluminum layer.

[0135] It can be seen from Example 1 and Comparative Example 1 that if only the vacuum evaporation method is used to prepare the aluminum film, compared with the technical solution of the present application, the grain size is significantly increased and the mechanical properties of the aluminum film are significantly decreased.

[0136] It can be seen from Example 1 and Comparative Example 2 that if the aluminum-based ion electroplating solution is not modified, the grain size of the obtained aluminum layer is significantly increased and the refining effect cannot be achieved.

[0137] As can be seen from Example 1 and Comparative Example 3, if the deposition method of the conductive seed layer is the thermal evaporation method, it is not conducive to the subsequent preparation of the thickening layer by the electroplating method, resulting in a relatively large grain size of the aluminum film and poor mechanical properties.

[0138] As can be seen from Example 1 and Comparative Example 4, if light aromatic naphtha is replaced by heavy aromatic naphtha, the influence on the deposition process of aluminum in the ionic liquid is weak, and the modification effect cannot be achieved, resulting in a relatively large grain size of the aluminum film and extremely poor adhesion.

[0139] The applicant declares that the process method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a functional set fluid, characterized in that, The preparation method includes the following steps: Magnetron sputter a conductive seed layer on both side surfaces of a base film to obtain a composite film material; Place the composite film material in a modified aluminum-based ion electroplating solution for electroplating, so as to form a thickening layer on the surface of the conductive seed layer to obtain the functional current collector; Wherein, the conductive seed layer and the thickening layer are of the same type, the components in the modified aluminum-based ion electroplating solution include an aluminum-based ionic liquid and a modifier, and the modifier includes light aromatic naphtha.

2. The preparation method of the functional current collector according to claim 1, wherein In the modified aluminum-based ion electroplating solution, the concentration of the modifier is 0.03 - 0.04 mol / L.

3. The preparation method of the functionalized fluid collector according to claim 1 or 2, characterized in that, The components in the light aromatic naphtha include small molecule organic substances; Preferably, the small molecule organic substances include at least one of straight-chain alkanes, monocyclic alkanes, bicyclic alkanes, alkylbenzenes, benzene, indane, and tetralin with 5 to 9 carbon atoms; Preferably, the light aromatic naphtha, by mass percentage, includes: 50 - 60% straight-chain alkanes, 25 - 35% monocyclic alkanes, 2 - 3% bicyclic alkanes, 10 - 15% alkylbenzenes, 0.05 - 0.15% benzene, 0.05 - 0.15% indane and / or tetralin; Preferably, before use, the light aromatic naphtha is first subjected to distillation treatment.

4. The preparation method of the functional current collector according to any one of claims 1-3, characterized in that, The aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride and aluminum chloride; Preferably, the molar ratio of 1-butyl-3-methylimidazolium chloride to aluminum chloride is 1:(1 - 3).

5. The preparation method of the functional current collector according to any one of claims 1-4, characterized in that The conductive seed layer is an aluminum seed layer, and the thickness of the aluminum seed layer is 50 - 100 nm; Preferably, the parameters in the magnetron sputtering method include: The target is an aluminum target, the sputtering power is 8 - 12 KW, the gas flow rate is 100 - 150 sccm, the vacuum degree is 3×10 -3 ~5×10 -3 Pa, the cooling temperature of the sputtering main roller is -35 - 0 °C, and the winding speed is 5 - 8 m / min.

6. The preparation method of the functional current collector according to any one of claims 1-5, characterized in that, The electroplating process is carried out in a protective atmosphere; Preferably, the gas in the protective atmosphere includes nitrogen; Preferably, during the electroplating process, the temperature is 20 - 30 °C; Preferably, the electroplating linear speed is 2 - 5 m / min.

7. The preparation method of the functional current collector according to any one of claims 1-6, characterized in that, During the electroplating process, the value range of the current density is 0 - 50 mA / cm 2 ; Preferably, during the electroplating process, the current density changes in a gradient increasing manner, and the current density increases from 0 to 5 mA / cm 2 to 45 to 50 mA / cm 2 ; Preferably, the increment of the gradient increase of the current density is 0 to 10 mA / cm 2 .

8. The preparation method of the functional current collector according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) Using the magnetron sputtering method, deposit an aluminum seed layer with a thickness of 50 - 100 nm on both side surfaces of a polymer base film to obtain a composite film material, and the specific parameters include: The target is an aluminum target, the sputtering power is 8 - 12 KW, the gas flow rate is 100 - 150 sccm, the vacuum degree is 3×10 -3 ~5×10 -3 Pa, the cooling temperature of the sputtering main roller is -35 - 0°C, and the winding speed is 5 - 8 m / min; (2) Place the composite film material in a modified aluminum-based ion electroplating solution, and in an inert atmosphere, electroplate it successively with gradient current densities of 0 - 5 mA / cm 2 , 5 - 10 mA / cm 2 , 10 - 15 mA / cm 2 , 15 - 20 mA / cm 2 , 20 - 25 mA / cm 2 , 25 - 30 mA / cm 2 , 30 - 35 mA / cm 2 , 35 - 40 mA / cm 2 , 40 - 45 mA / cm 2 , and 45 - 50 mA / cm 2 . The electroplating temperature is 20 - 30 °C, the linear velocity is 2 - 5 m / min. After the electroplating treatment, a thickening layer is formed on the surface of the aluminum seed layer to obtain the functional current collector; Wherein, the components in the modified aluminum-based ion electroplating solution include an aluminum-based ionic liquid and a modifier, and the modifier includes light aromatic naphtha; the components in the light aromatic naphtha include small molecule organic substances, and the small molecule organic substances include at least one of straight-chain alkanes, monocyclic alkanes, bicyclic alkanes, alkylbenzenes, benzene, indane, and tetralin with 5 to 9 carbon atoms; the aluminum-based ionic liquid includes 1-butyl-3-methylimidazolium chloride and aluminum chloride with a molar ratio of 1:(1 - 3).

9. A functional set fluid, characterized in that, The functional current collector is prepared by using the preparation method of the functional current collector according to any one of claims 1 - 8; The functional current collector includes a base film, and aluminum films provided on both side surfaces of the base film, and the aluminum films are composed of a conductive seed layer and a thickening layer, and the conductive seed layer is located between the base film and the thickening layer; Preferably, the thickness of the aluminum film is 0.8 - 1.2 μm; Preferably, the grain size of the aluminum film is 70 - 90 nm.

10. A lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery includes the functional current collector according to claim 9.

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