A multilayer current collector, its preparation method and application

Abstract

The application specifically discloses a multilayer current collector, a preparation method and application thereof. The multilayer current collector comprises a substrate layer and a composite metal layer arranged on at least one side surface of the substrate layer in sequence, wherein the composite metal layer comprises a current collecting layer and an aluminum layer arranged in sequence, and the current collecting layer is located between the substrate layer and the aluminum layer; the resistivity p of the composite metal layer on any side surface of the multilayer current collector satisfies 2.7 Ω·m < p ≤ 3.1 Ω·m. The application has the advantages of reducing structural defects of the multilayer current collector and improving the bending resistance of the multilayer current collector.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current collectors, in particular to a multilayer current collector and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of new energy and advanced manufacturing industry, the key performances of battery such as cycle life, safety performance and energy density need to be improved. The current collector is a key component in the battery, which plays a role in collecting current, and the performance of the current collector will directly affect the cycle life, energy density, safety and other technical indicators of the battery.

[0003] At present, the positive and negative current collectors commonly used 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, and its performance in battery safety and bending resistance is often unsatisfactory. With the continuous development of the current collector technology field, the multilayer current collector gradually replaces the pure metal current collector in the battery field due to its advantages in safety, energy density and cost control.

[0004] The multilayer current collector generally includes two metal layers and a substrate interposed between the two metal layers. The known setting method of the metal layer includes electroplating, evaporation (physical vapor deposition), chemical deposition, magnetron sputtering, adhesion, coating and compounding; however, since the substrate in the multilayer current collector is mostly a high molecular polymer film, this will increase the internal resistance of the battery to some extent, in addition, the adhesion between the metal layer and the substrate in the multilayer current collector is poor, and there may also be interlayer structure defects in the plating process, which is not conducive to the improvement of the mechanical properties and bending resistance of the multilayer current collector. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a multilayer current collector and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a multilayer current collector, which adopts the following technical solution:

[0007] A multilayer current collector, comprising a substrate layer and a composite metal layer provided on at least one side surface of the substrate layer, the composite metal layer comprising a current collecting layer and an aluminum layer stacked, the current collecting layer being located between the substrate layer and the aluminum layer.

[0008] The resistivity p of the composite metal layer on any one side surface of the multilayer current collector satisfies 2.7Ω·m

[0009] The present application selects a composite metal layer with the above-mentioned resistivity value, the grains in the composite metal layer are more refined, the pores or defects are fewer, and the compactness is higher, and the inventors have found that the composite metal layer with the above-mentioned resistivity value range is more conducive to improving the bending resistance of the current collector when matched with the substrate layer, which may be due to the fact that the compact structure in the composite metal layer can make the material inside more uniform, and is not prone to fracture due to defect expansion during bending, and the compact structure in the composite metal layer can better resist external stress, thereby improving the bending resistance of the current collector, so that the lowest number of times of light transmission after n times of bending is >100 times, and the cycle life of the battery is further improved.

[0010] Preferably, the relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer is 30%-60%.

[0011]

[0012] represents the experimental diffraction intensity of the <200> crystal plane of the aluminum layer;

[0013] represents the standard diffraction intensity of the <200> crystal plane of the aluminum layer;

[0014] I hkl represents the experimental diffraction intensity of any crystal plane of the aluminum layer in the XRD spectrum;

[0015] represents the standard diffraction intensity of any crystal plane of the aluminum layer;

[0016] represents the sum of the ratio of the experimental diffraction intensity to the standard diffraction intensity of all crystal planes of the aluminum layer.

[0017] The inventors have found that by controlling the relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer, the bending resistance of the multilayer current collector can be further improved; this is because by adjusting the resistivity of the composite metal layer and the relative texture coefficient of the <200> crystal plane of the aluminum layer, the microstructure and stress distribution of the material can be optimized simultaneously; on the one hand, the optimized crystal orientation makes the stress distribution more uniform, and the optimized microstructure reduces the number of defects in the aluminum layer, and the two work together to make the aluminum layer better withstand stress during bending; on the other hand, the two work together to affect the movement and deformation mechanism of dislocations, so that the aluminum layer can realize plastic deformation through dislocation movement and resist further deformation through strain hardening during bending; in addition, the regulation of the crystal orientation enhances the interface stability between the layers, and the regulation of the resistivity optimizes the overall microstructure, so that the aluminum layer has good interface bonding strength and optimized microstructure during bending, thereby further improving the overall bending resistance of the multilayer current collector.

[0018] Preferably, the aluminum layer comprises a first element, the first element comprising at least one of magnesium, calcium, chlorine, nickel, and the mass percentage of the first element in the aluminum layer is 0.1%-1%.

[0019] By adding the first element in the aluminum layer, the tensile strength of the composite metal layer can be further improved, and the cracking of the multilayer current collector during the bending process can be avoided.

[0020] Preferably, the aluminum layer comprises a first sub-aluminum layer, a second sub-aluminum layer and a third sub-aluminum layer arranged in a stack, the first sub-aluminum layer is close to the current collecting layer;

[0021] Preferably, the resistivity of the first sub-aluminum layer and the resistivity of the third sub-aluminum layer are both greater than the resistivity of the second sub-aluminum layer.

[0022] The thickness of the aluminum layer x 10%≤ the thickness of the second sub-aluminum layer < the thickness of the first sub-aluminum layer.

[0023] The thickness of the aluminum layer x 10%≤ the thickness of the second sub-aluminum layer < the thickness of the third sub-aluminum layer.

[0024] The present application can absorb and disperse most of the stress during the bending process by setting the outer metal layer to have a lower density but a thicker thickness, while the second sub-aluminum layer has a high density and a thin thickness, which can provide high-strength support; during the bending process, the second sub-aluminum layer can act as a "buffer layer" to prevent micro-cracks in the outermost metal layer (third sub-aluminum layer) from expanding to the inner layer (first sub-aluminum layer), ultimately improving the overall structure's bending resistance; in addition, the interface of the multilayer structure can disperse stress and reduce the propagation path of cracks, which can significantly improve the crack resistance and ductility of the multilayer current collector.

[0025] Preferably, the thickness of the aluminum layer is 0.2-5μm; preferably, the thickness of the aluminum layer is 0.8-2μm.

[0026] Preferably, the thickness of the current collecting layer is 1%-10% of the thickness of the aluminum layer; the material of the current collecting layer comprises at least one of aluminum, aluminum alloy, nickel, nickel alloy, chromium, chromium alloy, silver, silver alloy, titanium, titanium alloy.

[0027] Preferably, the material of the substrate layer comprises at least one of polyethylene terephthalate PET, polyethylene PE, polypropylene PP, polyethylene naphthalate PEN, poly-p-phenylene terephthalamide PPTA, polyimide PI, polycarbonate PC, polyether ether ketone PEEK, polyoxymethylene POM, polyphenylene sulfide PPS, polyphenylene oxide PPO, polyvinyl chloride PVC, polyamide PA, polytetrafluoroethylene PTFE; the thickness of the substrate layer is 1-10μm.

[0028] In a second aspect, the application provides a method for preparing a multilayer current collector, which comprises the following technical solutions:

[0029] A method for preparing a multilayer current collector, comprising the following steps:

[0030] S1, generating the current collecting layer on the surface of the base layer by a magnetron sputtering process to obtain a pretreated base layer;

[0031] S2, generating the aluminum layer on the surface of the pretreated base layer by a molten salt electroplating method.

[0032] Preferably, the process parameters in the magnetron sputtering process satisfy: the sputtering power is 6-20 kW, the base vacuum degree is 3×10 -3 -5×10 -3 Pa, the argon flow rate is 60-300 sccm, the sputtering main roller cooling temperature is -35℃ to 0℃, and the winding speed is 5-8 m / s.

[0033] Preferably, the molten salt electroplating method comprises the following steps:

[0034] A1, mixing AlCl3, NaCl and KCl to obtain a ternary inorganic salt, heating the ternary inorganic salt, and then performing dehydration and electrolysis impurity removal treatment to obtain an inorganic molten salt;

[0035] A2, electroplating the pretreated base layer in the inorganic molten salt to generate the aluminum layer on the surface of the pretreated base layer.

[0036] Preferably, in A1, the mass ratio of AlCl3, NaCl and KCl in the ternary inorganic salt is (6-10):(1-2):(1-2); the heating temperature of the ternary inorganic salt is 100-300℃; dry HCl gas is used for dehydration treatment; and the current density in the electrolysis impurity removal process is 4-30 mA·cm -2 .

[0037] Preferably, in A2, the pretreated base layer is placed in the inorganic molten salt in the electroplating process, the temperature in the electroplating process is 100-200℃, and the current density in the electroplating process is 10 mA·cm -2 -150 mA·cm -2 .

[0038] In the application, the resistivity of the aluminum layer is adjusted by adjusting the concentration of aluminum ions in the inorganic molten salt system and the current density in the electroplating process. When the concentration of aluminum ions in the inorganic molten salt system is high and the current density in the electroplating process is low, it is helpful to prepare an aluminum layer with low resistivity.

[0039] In a third aspect, the present application provides a pole piece, which adopts the technical scheme as follows:

[0040] A pole piece, comprising the multilayer current collector and an electrode active material located on the multilayer current collector. DETAILED DESCRIPTION

[0041] For better understanding and implementation, the technical scheme of the present application will be described clearly and completely in combination with examples below. Obviously, the described examples are only a part of the embodiments of the present application, but not all the embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as approximations as the exact properties are not critical to the present application. Hence, unless otherwise indicated, the numerical parameters set forth in the specification and claims are approximations that can vary depending on the requirements of the intended application.

[0044] As used herein, "and / or" means one or all of the listed items.

[0045] As used herein "comprises" and "comprising" are inclusive or open-ended and specify the presence of stated features, integers, steps, or components but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0046] All percentages in the present application are weight percentages, unless otherwise indicated.

[0047] As used in the description of the application, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. For example, the term "a component" is intended to mean one or more components, and thus, a plurality of components is contemplated and can be employed or used in the practice of the application.

[0048] Example 1

[0049] A multilayer current collector, comprising a substrate layer and a composite metal layer arranged on both surfaces of the substrate layer, the composite metal layer comprising a current collecting layer and an aluminum layer arranged in a stack, the current collecting layer being located between the substrate layer and the aluminum layer;

[0050] The material of the substrate layer is polyimide, and the thickness of the substrate layer is 8 μm.

[0051] The material of the current collecting layer is aluminum, and the thickness of the current collecting layer is 120 nm.

[0052] The thickness of the aluminum layer is 1 μm;

[0053] The relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer is 27%;

[0054] The resistivity of the composite metal layer is ρ = 2.8 Ω·m.

[0055] The present embodiment provides a preparation method of the above-mentioned current collector, which comprises the following steps:

[0056] S1, avoiding magnetron sputtering treatment on the base layer (the parameters in the magnetron sputtering process are controlled as follows: the sputtering power is 10 kW, the base vacuum degree is 4 × 10 -3 Pa, the argon flow is 130 sccm, the sputtering main roller cooling temperature is -25℃, and the winding speed is 7 m / min), to generate a current collecting layer, thereby obtaining a pretreated base layer;

[0057] S2, drying NaCl and KCl at 300℃ for 5h, mixing AlCl3, NaCl and KCl according to the mass ratio of 10:1:1, heating at 130℃, and dehydrating by introducing dry HCl gas, and then electrolyzing at a current density of 5 mA·cm -2 to remove impurities, thereby obtaining an inorganic molten salt;

[0058] S3, placing the above-mentioned pretreated base layer in the above-mentioned inorganic molten salt, controlling the electroplating temperature to be 150℃, and controlling the current density to be 10 mA·cm -2 , to obtain an aluminum layer with a thickness of 1 μm, i.e. a multilayer current collector.

[0059] Example 2

[0060] The difference between the present embodiment and Example 1 is that the resistivity of the composite metal layer is ρ = 2.9, and in the preparation method of the current collector, AlCl3, NaCl and KCl are mixed according to the mass ratio of 8:1:1 in step S2, and the current density is 20 A·cm -2 in step S3, and the other steps and parameter settings are consistent with those of Example 1.

[0061] Example 3

[0062] The difference between the present embodiment and Example 1 is that the resistivity of the composite metal layer is ρ = 3.1, and in the preparation method of the current collector, AlCl3, NaCl and KCl are mixed according to the mass ratio of 6:1:1 in step S2, and the current density is 40 A·cm -2 in step S3, and the other steps and parameter settings are consistent with those of Example 1.

[0063] Example 4

[0064] The embodiment differs from embodiment 1 in that the relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer is 30%, and sodium polydithiobispropane sulfonate (SPS) is added to the electroplating solution at a concentration of 1.5 mg / L; other steps and parameter settings remain consistent with embodiment 1.

[0065] Embodiment 5

[0066] The embodiment differs from embodiment 1 in that the relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer is 40%, and sodium polydithiobispropane sulfonate (SPS) is added to the electroplating solution at a concentration of 2 mg / L; other steps and parameter settings remain consistent with embodiment 1.

[0067] Embodiment 6

[0068] The embodiment differs from embodiment 1 in that the relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer is 60%, and sodium polydithiobispropane sulfonate (SPS) is added to the electroplating solution at a concentration of 3.5 mg / L; other steps and parameter settings remain consistent with embodiment 1.

[0069] Embodiment 7

[0070] The comparative example differs from embodiment 1 in that the relative texture coefficient (RTC) of the <200> crystal plane of the aluminum layer is 70%, and sodium polydithiobispropane sulfonate (SPS) is added to the electroplating solution at a concentration of 4 mg / L; other steps and parameter settings remain consistent with embodiment 1.

[0071] Embodiment 8

[0072] The embodiment differs from embodiment 1 in that the aluminum layer includes a first sub-aluminum layer with a thickness of 333 nm, a second sub-aluminum layer with a thickness of 333 nm, and a third sub-aluminum layer with a thickness of 333 nm, the resistivity of the first, second, and third sub-aluminum layers is the same, all being 2.8 Ω·m; other steps and parameter settings remain consistent with embodiment 1.

[0073] Embodiment 9

[0074] The embodiment differs from embodiment 8 in that the aluminum layer includes a first sub-aluminum layer with a thickness of 333 nm, a second sub-aluminum layer with a thickness of 333 nm, and a third sub-aluminum layer with a thickness of 333 nm, the resistivity of the first, second, and third sub-aluminum layers is different, the resistivity of the first sub-aluminum layer is 2.8 Ω·m, the resistivity of the second sub-aluminum layer is 2.9 Ω·m, and the resistivity of the third sub-aluminum layer is 3.0 Ω·m; other steps and parameter settings remain consistent with embodiment 8.

[0075] Embodiment 10

[0076] The embodiment differs from example 9 in that the aluminum layer comprises a first sub-aluminum layer with a thickness of 333 nm, a second sub-aluminum layer with a thickness of 333 nm, and a third sub-aluminum layer with a thickness of 333 nm, the first sub-aluminum layer has a resistivity of 3.0 Ω·m, the second sub-aluminum layer has a resistivity of 2.9 Ω·m, and the third sub-aluminum layer has a resistivity of 2.8 Ω·m; other steps and parameter settings remain the same as in example 9.

[0077] Example 11

[0078] The embodiment differs from example 9 in that the aluminum layer comprises a first sub-aluminum layer with a thickness of 333 nm, a second sub-aluminum layer with a thickness of 333 nm, and a third sub-aluminum layer with a thickness of 333 nm, the first sub-aluminum layer has a resistivity of 2.9 Ω·m, the second sub-aluminum layer has a resistivity of 2.8 Ω·m, and the third sub-aluminum layer has a resistivity of 3.0 Ω·m; other steps and parameter settings remain the same as in example 9.

[0079] Example 12

[0080] The embodiment differs from example 11 in that the aluminum layer comprises a first sub-aluminum layer with a thickness of 400 nm, a second sub-aluminum layer with a thickness of 200 nm, and a third sub-aluminum layer with a thickness of 400 nm; other steps and parameter settings remain the same as in example 11.

[0081] Example 13

[0082] The embodiment differs from example 1 in that magnesium chloride is added to the electroplating solution, and the mass percentage of magnesium in the aluminum layer is 0.5%; other steps and parameter settings remain the same as in example 1.

[0083] Example 14

[0084] The comparative example differs from example 1 in that nickel chloride is added to the electroplating solution, and the mass percentage of nickel in the aluminum layer is 1%; other steps and parameter settings remain the same as in example 1.

[0085] Example 15

[0086] The comparative example differs from example 1 in that lanthanum chloride is added to the electroplating solution, and the mass percentage of lanthanum in the aluminum layer is 0.1%; other steps and parameter settings remain the same as in example 1.

[0087] Example 16

[0088] The comparative example differs from example 1 in that magnesium chloride is added to the electroplating solution, and the mass percentage of magnesium in the aluminum layer is 2%; other steps and parameter settings remain the same as in example 1.

[0089] Example 17

[0090] The difference between this example and Example 5 is that the aluminum layer comprises a first sub-aluminum layer with a thickness of 400 nm, a second sub-aluminum layer with a thickness of 200 nm, and a third sub-aluminum layer with a thickness of 400 nm, the resistivity of the first sub-aluminum layer is 2.9 Ω.m, the resistivity of the second sub-aluminum layer is 2.8 Ω.m, and the resistivity of the third sub-aluminum layer is 3.0 Ω.m; other steps and parameter settings remain consistent with Example 5.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that the resistivity p of the composite metal layer is 4.2; in the preparation method of the current collector, in step S2, AlCl3, NaCl, and KCl are in a mass ratio of 4:1:1, and in step S3, the current density is 150 A.cm -2 ; other steps and parameter settings remain consistent with Example 1.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is that the aluminum layer is prepared by vacuum evaporation, the raw material used in the vacuum evaporation process is high-purity aluminum wire (purity of 99.93%), the heating temperature is 1200°C, and the vacuum degree of the vacuum chamber is 0.1 Pa; other steps and parameter settings remain consistent with Example 1.

[0095] Test method

[0096] Sheet resistance test: The multilayer current collector prepared in the above examples and comparative examples is placed on a sample stage, and a four-probe sheet resistance meter is used to test the sheet resistance of the sample.

[0097] Elongation test: The test is carried out according to the standard GB / T 1040.3-2006.

[0098] Resistivity test: The resistivity of the composite metal layer in the multilayer current collector prepared in the above examples and comparative examples is tested according to the method specified in GB / T 22638.6-2016 "Aluminum Foil Test Methods Part 6: Determination of Direct Current Resistance".

[0099] Bending test: The sample is fixed on a bending test device, the bending angle is set to 180°, and the bending test is started. After each bending, pause, and place the sample on a transmittance tester to measure the transmittance. When the number of transmittance points within 2 cm exceeds 10 or a length of more than 3 mm transmittance appears, record the number of transmittance points less than 10 or the length of the transmittance point less than 3 mm when the corresponding bending number is the maximum bending number.

[0100] Table 1

[0101]

[0102]

[0103] In combination with Examples 1-3, Comparative Example 1 and Table 1, it can be seen that when the resistivity of the composite metal layer does not meet the limit (Comparative Example 1), the sheet resistance of the multilayer current collector increases significantly and the number of bending times decreases significantly, which is due to the fact that at this time the grains in the composite metal layer are large, the number of pores and defects increases, resulting in a decrease in the density of the composite metal layer and a decrease in the ability of the composite metal layer to resist external stress. At this time, the multilayer current collector formed by the composite metal layer in cooperation with the base layer has a significantly increased sheet resistance, a decreased bending resistance, and is not conducive to optimizing the battery performance.

[0104] In combination with Example 1, Comparative Example 2 and Table 1, it can be seen that by using a molten salt electroplating method to generate an aluminum layer on the surface of the current collecting layer, compared with the operation of using vacuum evaporation to prepare an aluminum layer in Comparative Example 2, the adhesion stability between the composite metal layer and the base layer can be significantly improved, and the sheet resistance, resistivity and roughness of the current collector can be reduced, and the bending resistance can be improved.

[0105] In combination with Examples 1, 4-7 and Table 1, it can be seen that by controlling the relative texture coefficient of the <200> crystal plane of the aluminum layer to be within the range of 30%-60%, the sheet resistance of the multilayer current collector can be further reduced and the bending resistance can be further improved; this is because by controlling the relative texture coefficient of the <200> crystal plane of the aluminum layer, the stress distribution uniformity in the aluminum layer can be further optimized and the number of defects in the aluminum layer can be reduced, thereby affecting the ability of the aluminum layer to resist deformation during bending and enhancing the interface stability between the layers.

[0106] In combination with Examples 1, 8-12 and Table 1, it can be seen that by adjusting the aluminum layer to include a first sub-aluminum layer, a second sub-aluminum layer and a third sub-aluminum layer, and adjusting the resistivity of the first sub-aluminum layer, the second sub-aluminum layer and the third sub-aluminum layer to be 2.9 Ω·m, 2.8 Ω·m and 3.0 Ω·m, respectively, and the thickness of the first sub-aluminum layer, the second sub-aluminum layer and the third sub-aluminum layer to be 400 nm, 200 nm and 400 nm, respectively, the bending resistance of the multilayer current collector is significantly improved; this is because the layered aluminum layer structure at this time can absorb and disperse most of the stress during bending and can provide high-strength support to prevent the propagation of micro-cracks.

[0107] In combination with Embodiments 1, 13-17 and Table 1, it can be seen that by providing the first element in the aluminum layer and controlling the mass percentage of the first element in the aluminum layer to satisfy 0.1%-1%, the bending resistance of the multilayer current collector can be significantly improved; especially in Embodiment 17, when the aluminum layer is provided with layering and the first element is provided in the aluminum layer at the same time, the elongation and bending times of the multilayer current collector are both significantly increased.

[0108] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that the technical solutions of the present application can be modified or replaced equivalently, and these modifications or replacements are all within the protection scope of the present application.

Claims

1. A multilayer current collector, characterized in that: The system includes a substrate layer and a composite metal layer disposed on at least one side surface of the substrate layer, the composite metal layer including a current collector layer and an aluminum layer stacked together, the current collector layer being located between the substrate layer and the aluminum layer; The resistivity ρ of the composite metal layer on any side surface of the multilayer current collector satisfies 2.7Ω·m<ρ≤3.1Ω·m; The aluminum layer <200> The relative texture factor of the crystal planes is 30%-60%.

2. The multilayer current collector according to claim 1, characterized in that: The aluminum layer includes a first element, which includes at least one of magnesium, calcium, chlorine, and nickel, and the mass percentage of the first element in the aluminum layer is 0.1%-1%.

3. The multilayer current collector according to claim 1, characterized in that: The aluminum layer includes a first sub-aluminum layer, a second sub-aluminum layer, and a third sub-aluminum layer stacked together, with the first sub-aluminum layer close to the current collector layer; wherein the resistivity of the first sub-aluminum layer and the resistivity of the third sub-aluminum layer are both greater than the resistivity of the second aluminum layer; The thickness of the aluminum layer × 10% ≤ the thickness of the second sub-aluminum layer < the thickness of the first sub-aluminum layer; The thickness of the aluminum layer × 10% ≤ the thickness of the second sub-aluminum layer < the thickness of the third sub-aluminum layer.

4. The multilayer current collector according to claim 1, characterized in that: The thickness of the aluminum layer is 0.2-5 μm.

5. The multilayer current collector according to claim 1, characterized in that: The thickness of the current collector layer is 1%-10% of the thickness of the aluminum layer; the material of the current collector layer includes at least one of aluminum, aluminum alloy, nickel, nickel alloy, chromium, chromium alloy, silver, silver alloy, titanium, and titanium alloy.

6. The method for preparing a multilayer current collector according to any one of claims 1-5, characterized in that: Includes the following steps: S1, the current collector layer is generated on the surface of the substrate layer by magnetron sputtering process to obtain a pretreated substrate layer; S2, the aluminum layer is generated on the surface of the pretreated substrate layer using molten salt electroplating.

7. The method for preparing a multilayer current collector according to claim 6, characterized in that: The process parameters in the magnetron sputtering process meet the following requirements: sputtering power of 6-20kW, and background vacuum of 3×10⁻⁶. -3 -5×10 -3 Pa, argon flow rate of 60-300 sccm, sputtering main roller cooling temperature of -35℃ to 0℃, and winding speed of 5-8 m / s.

8. The method for preparing a multilayer current collector according to claim 6, characterized in that: The molten salt electroplating method includes the following steps: A1, AlCl3, NaCl and KCl are mixed to obtain a ternary inorganic salt, the ternary inorganic salt is heated, and then dehydrated and electrolytically purified to obtain an inorganic molten salt; A2, the pretreated substrate layer is placed in the inorganic molten salt for electroplating, and the aluminum layer is generated on the surface of the pretreated substrate layer.

9. An electrode sheet, characterized in that: It includes the multilayer current collector as described in any one of claims 1-5 and the electrode active material located on the multilayer current collector.

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