Preparation method of multi-layer current collector

Abstract

The invention discloses a preparation method of a multi-layer current collector, which comprises the following steps of: forming a metal layer on at least one surface of a macromolecular base film by a magnetron sputtering method to obtain the multi-layer current collector; when the metal layer is formed through the magnetron sputtering method, the macromolecule base film is wound on a main drum of a magnetron sputtering device, a baffle is arranged between a target material of the magnetron sputtering device and the main drum, and inclined holes for metal atoms to pass through are formed in the baffle. According to the preparation method, metal atoms can grow directionally to form a metal layer on the surface of the macromolecular base film, so that the tensile strength and the elongation at break of the multi-layer current collector can be greatly improved, and the processing performance of the multi-layer current collector at a battery end is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of current collectors, and in particular to a method for preparing a multilayer current collector. Background Art

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

[0003] At present, the common current collectors in the battery industry are mostly made of copper foil and aluminum foil. The current collectors made of pure metal have high cost and quality. At the same time, the performance of battery safety is often unsatisfactory. 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. With the continuous development of the lithium-ion battery industry, people are increasingly pursuing high energy density and lightweight batteries. As an important component of the battery, reducing the quality of the current collector is an effective method, and multilayer current collectors came into being. At present, the preparation method of multilayer current collectors is generally prepared by evaporation coating, but the tensile strength of the prepared multilayer current collectors is low, resulting in poor processing performance and poor pass rate of the multilayer current collectors in the battery manufacturing process.

[0004] Therefore, it is urgent to develop a new method for preparing a multilayer current collector to solve the problem of poor processing performance of the existing multilayer current collector at the battery end. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a multilayer current collector in view of the deficiencies in the prior art, so as to enhance the tensile strength and elongation at break of the multilayer current collector, thereby improving the processing performance of the multilayer current collector at the battery end.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing a multilayer current collector comprises the following steps: forming a metal layer on at least one surface of a polymer base film by magnetron sputtering to obtain a multilayer current collector;

[0008] When the metal layer is formed by magnetron sputtering, the polymer base film is wound on the main drum of the magnetron sputtering device. A baffle is provided between the target material and the main drum of the magnetron sputtering device, and the baffle is provided with inclined holes for metal atoms to pass through.

[0009] The present invention sets a baffle between the main drum and the target material, and the baffle is provided with an oblique hole, so that the metal atoms can be guided to sputter on the polymer base film in a specific direction through the oblique hole, and other metal atoms deviating from the sputtering direction are blocked by the baffle, thereby realizing the directional sputtering of metal atoms on the polymer base film. In this way, the metal atoms can grow along the main (111) crystal direction and (200) crystal direction on the surface of the polymer base film, and reduce the proportion of crystal directions such as (220) crystal direction and (300) crystal direction, so that the metal atoms grow in a directional manner to form a metal layer, which is beneficial to greatly improve the tensile strength and elongation at break of the multilayer current collector, thereby improving the processing performance of the multilayer current collector at the battery end.

[0010] It should be noted that during magnetron sputtering, the main drum generally rotates at a constant speed. Of course, in practical applications, the main drum can also be stationary or rotated intermittently to obtain a multi-layer current collector with patterns or levels.

[0011] As a preferred embodiment, in the present invention, the distance between the baffle and the main drum is 5-10 mm, and the distance between the target and the main drum is 100-150 mm.

[0012] This spacing range can prevent the baffle from being too close to the main drum, thereby avoiding damage to the polymer base film during sputtering; it can also prevent the baffle from being too close to the target material and affecting the deposition efficiency of metal atoms.

[0013] As a preferred embodiment, in the present invention, the position where the metal atoms pass through the oblique hole and hit the polymer base film on the surface of the main drum is taken as the incident point, and the angle between the incident ray of the metal atoms at the incident point and the tangent line corresponding to the incident point is 0° to 45°. In this incident angle range, the metal atoms emitted by the target material can be firmly and evenly deposited on the surface of the polymer base film, and it is helpful to control the force of the metal atoms when they are incident to avoid damaging the polymer base film.

[0014] As a preferred embodiment, in the present invention, the target material is a copper target material or an aluminum target material, the sputtering power is 5 to 50 kW, the inert gas is any one of argon, argon, neon, krypton and xenon, the flow rate of the inert gas is 30 to 300 sccm, and the coating vacuum is ≤5.0×10 -2 Pa, the winding speed is 5 to 20 m / min, and the cooling temperature of the main drum is -25 to -5°C.

[0015] For example, when the target material is copper, the sputtering power is 35 kW, the inert gas is argon, the inert gas flow rate is 180 sccm, and the coating vacuum is ≤5.0×10 -2Pa, the winding speed is 20m / min, and the main drum cooling temperature is -20℃. When the target material is aluminum target, the sputtering power is 10kW, the inert gas is argon, the inert gas flow rate is 200sccm, and the coating vacuum is ≤5.0×10 -2 Pa, the winding speed is 15 m / min, and the main drum cooling temperature is -15°C. When the preparation method of the present invention is used to prepare the aluminum multilayer current collector for the positive electrode, an aluminum target is used, and when the preparation method of the present invention is used to prepare the copper multilayer current collector for the negative electrode, a copper target is used.

[0016] As a preferred embodiment, in the present invention, a first metal layer is formed on at least one surface of the polymer base film by magnetron sputtering, and then a second metal layer is formed on the surface of the first metal layer by electroplating to obtain a multilayer current collector;

[0017] When the second metal layer is formed by electroplating, a polymer base film having a first metal layer is used as a cathode belt, and the electroplating device includes an anode plate arranged at a relative interval to the cathode belt. A plurality of anode plates are evenly spaced along the belt-traveling direction of the cathode belt, and during the belt-traveling process of the cathode belt, the plurality of anode plates swing periodically and synchronously, and the swing of the anode plate is based on the central axis, and the two ends of the anode plate move closer to or away from the cathode belt.

[0018] During the electroplating process, there is a stable electric field between the anode plate and the cathode strip, and the direction of the electric field points from the anode plate to the cathode strip. The direction and strength of the electric field can be adjusted according to demand. The present invention realizes the regular change of the direction of the electric field by controlling the periodic swing of the anode plate to form a directional potential field, so as to control the metal atoms of the second metal layer to grow along the main (111) crystal direction and (200) crystal direction on the basis of the first metal layer. Based on this, the setting of the directional potential field can make the metal atoms deposited on the first metal layer in a directional manner during the electroplating process, so that the directional potential field cooperates with the directional magnetron sputtering, so that the tensile strength and elongation at break of the metal layer are further improved.

[0019] As a preferred embodiment, in the present invention, the spacing between two adjacent anode plates is 20 to 100 cm, and the swing angle of the anode plate is -30° to 30° based on being parallel to the cathode belt. The walking speed of the cathode belt is 2 to 30 m / min, and the time it takes for the cathode belt to complete the spacing between the corresponding positions of two adjacent anode plates is the time it takes for the anode plate to swing for one cycle.

[0020] As a preferred embodiment, in the present invention, ultrasonic oscillation is performed throughout the entire process of forming the second metal layer by electroplating, an ultrasonic transmitter is set close to the cathode belt, the frequency of ultrasonic oscillation is 25-30kHz, the power of the ultrasonic transmitter is 100-500W, and one ultrasonic transmitter is distributed every 2m along the direction of the cathode belt, and the total length of the ultrasonic area can be 10-30m. Ultrasonic treatment of the cathode belt area during the electroplating process is conducive to guiding the uniform deposition of metal atoms, thereby further improving the tensile strength and elongation at break of the metal layer.

[0021] As a preferred embodiment, in the present invention, electroplating is carried out in a molten salt electroplating system, and the molten salt electroplating system includes AlCl 3 , NaCl, KCl;

[0022] Alternatively, the electroplating is carried out in a water plating solution, which includes the following raw materials: additives 0.04-0.15 g / L, copper sulfate 80-140 g / L, sulfuric acid 90-150 g / L, chloride ions 40-70 ppm, copper plating aid 1-10 ml / L, and the rest is water; wherein the additives include malachite green 0.01-0.07 g / L, and ethylenediamine 0.03-0.08 g / L.

[0023] For example, when the preparation method of the present invention is used to prepare an aluminum multilayer current collector, the electroplating is carried out in a molten salt electroplating system. The molten salt electroplating method includes the following steps: 3 , NaCl and KCl in a mass ratio of 6-10:1-2:1-2 and then dried to obtain a ternary inorganic salt, the ternary inorganic salt is heated, and then dehydrated and electrolytically removed impurities to obtain an inorganic molten salt; the polymer base film having a first metal layer is placed in the inorganic molten salt for electroplating to generate a second metal layer on the surface of the first metal layer.

[0024] When the preparation method of the present invention is used to prepare a copper multilayer current collector, electroplating is carried out in a water plating solution, and the copper plating additives in the water plating solution include 2-5 ml / L of Jie Ruimei copper plating additive 200A and 1-5 ml / L of Jie Ruimei copper plating additive 200B.

[0025] As a preferred embodiment, in the present invention, when electroplating is carried out in a molten salt electroplating system, the current density is 2 to 65 mA / cm 2 , the electroplating temperature is 100~220℃;

[0026] When electroplating in water bath, the current density is 5-40 mA / cm 2 , the electroplating temperature is 20~50℃.

[0027] As a preferred embodiment, in the present invention, the total thickness of the metal layer on one surface of the polymer base film is 0.63-2.1 μm, the thickness of the first metal layer is 25-100 nm, and the thickness of the second metal layer is 0.6-2.0 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a front view of the magnetron sputtering device of the present invention;

[0029] Figure 2 It is a schematic diagram of the magnetron sputtering device of the present invention.

[0030] Reference numerals:

[0031] 1. Baffle; 2. Main drum; 3. Oblique hole. DETAILED DESCRIPTION

[0032] For better understanding and implementation, the technical solution of the present application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] Unless otherwise indicated, all numerical values ​​expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties desired to be obtained.

[0035] As used herein, "and / or" means one or all of the mentioned elements.

[0036] As used herein, “including” and “comprising” encompasses the case where only the stated elements are present as well as the case where there are other elements other than the stated elements.

[0037] All percentages in this application are by weight unless otherwise stated.

[0038] Unless otherwise indicated, "a", "an", "an" and "the" used in this specification are intended to include "at least one" or "one or more". For example, "a component" means one or more components, so more than one component may be considered and may be employed or used in the implementation of the embodiment.

[0039] The present invention provides a method for preparing a multilayer current collector, which can be used to prepare an aluminum multilayer current collector for a positive electrode or a copper multilayer current collector for a negative electrode. A first metal layer can be formed on at least one surface of a polymer base film by magnetron sputtering, and then a second metal layer is formed on the surface of the first metal layer by point breaking. The process parameters of magnetron sputtering and electroplating are adjusted according to actual production requirements to obtain a corresponding multilayer current collector. The technical solution of the present invention is described in detail below by taking the preparation of an aluminum multilayer current collector for a positive electrode as an example.

[0040] Example 1

[0041] A method for preparing an aluminum multilayer current collector comprises the following steps:

[0042] S1, forming a first metal layer with a thickness of 80 nm on two opposite surfaces of a 6 μm thick polymer base film PI film by magnetron sputtering with a power of 10 kW and an argon gas flow rate of 200 sccm;

[0043] When the first metal layer is formed by magnetron sputtering, the PI film is wound on the main drum 2 of the magnetron sputtering device. A baffle 1 is provided between the aluminum target material of the magnetron sputtering device and the main drum 2. The baffle 1 is provided with an inclined hole 3 for metal atoms to pass through. The inclined hole 3 extends along the axial direction of the baffle 1, and a plurality of inclined holes 3 are provided at intervals along the radial outer periphery of the baffle 1. The spacing between the baffle 1 and the main drum 2 is 7 mm, and the spacing between the target material and the main drum 2 is 120 mm. The position where the metal atoms pass through the inclined hole 3 and hit the PI on the surface of the main drum 2 is the incident point, and the angle between the incident ray of the metal atoms at the incident point and the tangent corresponding to the incident point is 30°.

[0044] The vacuum degree of coating is ≤5.0×10 -2 Pa, winding speed is 15m / min, main drum cooling temperature is -15℃;

[0045] S2, forming a second metal layer with a thickness of 920 nm on the surface of the first metal layer by electroplating to obtain an aluminum multilayer current collector with a total thickness of 1 μm for the single-sided metal layer;

[0046] When the second metal layer is formed by electroplating, the PI film with the first metal layer is used as the cathode belt, and the electroplating device includes an anode plate arranged at intervals relative to the cathode belt, and a plurality of anode plates are evenly arranged at intervals along the belt running direction of the cathode belt, and during the belt running of the cathode belt, the plurality of anode plates swing synchronously and periodically, and the swing of the anode plate is based on the central axis, and the two ends of the anode plate move close to or away from the cathode belt;

[0047] The distance between two adjacent anode plates is 50 cm. The swing angle of the anode plate is -30° to 30°, with the cathode belt as the reference. The cathode belt travel speed is 18 m / min. The time it takes for the cathode belt to travel the distance between two adjacent anode plates is the time it takes for the anode plate to swing for one cycle.

[0048] Ultrasonic oscillation is performed throughout the entire process of forming the second metal layer by electroplating. The ultrasonic transmitter is set close to the cathode belt. The frequency of ultrasonic oscillation is 28kHz, the power of the ultrasonic transmitter is 300W, and one ultrasonic transmitter is distributed every 2m. The total length of the ultrasonic area can be 20m.

[0049] The electroplating is carried out in a molten salt electroplating system, comprising the following steps: AlCl 3 , NaCl, and KCl were mixed in a mass ratio of 10:1:1 and dried at 300 °C for 5 h. After heating at 130 °C, dry HCl gas was introduced for dehydration. 2 Perform electrolytic de-doping to obtain an inorganic molten salt; heat the inorganic molten salt at 180°C, place the PI film with the first metal layer in the inorganic molten salt for electroplating, and control the current density to 10 mA / cm 2 A second metal layer is generated on the surface of the first metal layer, thereby obtaining an aluminum multilayer current collector.

[0050] Example 2

[0051] The difference between this embodiment and the embodiment 1 is that in step S1, the magnetron sputtering device is a common device, and the baffle plate 1 and the inclined hole 3 on the baffle plate 1 are not provided between the main drum 2 and the target material.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that in step S2, no directional potential field is set during the electroplating process, that is, the anode plate is fixedly set and does not oscillate periodically.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that in step S1, the magnetron sputtering device is a common device, and the baffle 1 and the inclined hole 3 on the baffle 1 are not arranged between the main drum 2 and the target material; in step S2, no directional potential field is arranged during the electroplating process, that is, the anode plate is fixedly arranged and does not oscillate periodically.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that the aluminum multilayer current collector is prepared by an evaporation process, and the steps are as follows: evacuating the evaporation chamber of the vacuum evaporation equipment until the vacuum degree of the evaporation chamber is less than <1×10 -2, a PI film with a thickness of 6μm was placed in the evaporation chamber as the evaporation base film. High-purity aluminum with a purity of 99.9% was placed in the evaporation boat and evaporated at 1000℃. During the vacuum evaporation process, the aluminum vapor concentration was maintained at 75mol / L and the evaporation rate was 50m / min. The aluminum vapor crystallized into aluminum metal particles and continuously deposited on the two surfaces of the PI film to form an aluminum metal layer, in which the thickness of the aluminum metal layer on one side was 1μm respectively. It was rolled up under a tension of 5N to obtain an aluminum multilayer current collector with a thickness of 8μm.

[0058] Test Method

[0059] The aluminum multilayer current collectors prepared in Examples 1-3 and Comparative Examples 1-2 were tested for tensile strength and elongation at break using a tensile testing machine with reference to GB-13022-91, a tensile speed of 100 mm / min, a gauge length of 100 mm, a width of 15 mm, and the values ​​when the metal layer was broken were used as the standard.

[0060] The tensile strength and elongation at break test results of the aluminum multilayer current collectors of Examples 1-3 and Comparative Examples 1-2 are recorded in Table 1.

[0061] Table 1

[0062]

[0063] As can be seen from Table 1, the tensile strength and elongation at break of the aluminum multilayer current collectors prepared in Examples 1-3 are significantly improved compared to Comparative Examples 1 and 2, and the tensile strength and elongation at break of the aluminum multilayer current collector prepared in Example 1 are better than those in Example 2 and Example 3. The reason is that:

[0064] The preparation methods of Comparative Examples 1 and 2 cause aluminum atoms to grow randomly on the surface of the PI film, and the ratio of the (111) crystal orientation to the (200) crystal orientation is low, so the tensile strength and elongation at break are low.

[0065] Example 3 adopts a directional magnetron sputtering process. During the magnetron sputtering process, the inclined holes 2 on the baffle 1 are used to guide the aluminum atoms to sputter on the PI film in a specific direction, while other aluminum atoms that deviate from the sputtering direction are blocked by the baffle 1, thereby realizing the directional sputtering of aluminum atoms on the PI film. In this way, aluminum atoms can grow along the main (111) crystal direction and (200) crystal direction on the surface of the PI film, reducing the proportion of crystal directions such as (220) crystal direction and (300) crystal direction. Example 2 adopts a directional potential field electroplating process. During the electroplating process, the periodic oscillating structure of the anode plate realizes the regular change of the electric field direction to form a directional potential field, so as to control the aluminum atoms of the second metal layer to grow along the main (111) crystal direction and (200) crystal direction on the basis of the first metal layer, thereby utilizing the directional potential field to make the aluminum atoms directionally deposited on the first metal layer during the electroplating process. Based on this, the aluminum multilayer current collectors prepared in Examples 2 and 3 both have a metal layer with directional growth of aluminum atoms, which is beneficial to improving the tensile strength and elongation at break of the aluminum metal layer.

[0066] In Example 1, a directional potential field is combined with directional magnetron sputtering, and the aluminum atoms in the metal layer of the prepared aluminum multilayer current collector grow in a directional manner, so that the tensile strength and elongation at break of the aluminum metal layer are significantly improved.

[0067] In summary, the application of the preparation method of the present invention can enhance the tensile strength and elongation at break of the multilayer current collector, thereby improving the processing performance of the multilayer current collector at the battery end.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a multilayer current collector, characterized in that: The following steps are involved: Forming a metal layer on at least one surface of the polymer base film by magnetron sputtering to obtain the multilayer current collector; When the metal layer is formed by the magnetron sputtering method, the polymer base film is wound on the main drum of the magnetron sputtering device, a baffle is arranged between the target material of the magnetron sputtering device and the main drum, and the baffle is provided with oblique holes for metal atoms to pass through.

2. The method for preparing a multilayer current collector according to claim 1, characterized in that: The distance between the baffle and the main drum is 5-10 mm, and the distance between the target and the main drum is 100-150 mm.

3. The method for preparing a multilayer current collector according to claim 1, characterized in that: The position where the metal atom passes through the inclined hole and hits the polymer base film on the surface of the main drum is taken as the incident point, and the angle between the incident ray of the metal atom at the incident point and the tangent line corresponding to the incident point is 0° to 45°.

4. The method for preparing a multilayer current collector according to claim 1, characterized in that: The target material is a copper target material or an aluminum target material, the sputtering power is 5-50 kW, the inert gas is any one of argon, argon, neon, krypton and xenon, the flow rate of the inert gas is 30-300 sccm, and the coating vacuum is ≤5.0×10 -2 Pa, the winding speed is 5 to 20 m / min, and the cooling temperature of the main drum is -25 to -5°C.

5. The method for preparing a multilayer current collector according to any one of claims 1 to 4, characterized in that: Forming a first metal layer on at least one surface of the polymer base film by magnetron sputtering, and then forming a second metal layer on the surface of the first metal layer by electroplating to obtain the multilayer current collector; When the second metal layer is formed by the electroplating method, the polymer base film having the first metal layer is used as a cathode belt, and the electroplating device includes an anode plate arranged relative to the cathode belt, and a plurality of anode plates are evenly spaced along the belt-traveling direction of the cathode belt. During the belt-traveling process of the cathode belt, the plurality of anode plates swing periodically and synchronously, and the swing of the anode plate is based on the central axis, and the two ends of the anode plate move closer to or away from the cathode belt.

6. The method for preparing a multilayer current collector according to claim 5, characterized in that: The spacing between two adjacent anode plates is 20 to 100 cm. Taking parallel to the cathode belt as the reference, the swing angle of the anode plate is -30° to 30°, the belt speed of the cathode belt is 2 to 30 m / min, and the time it takes for the cathode belt to complete the spacing between the corresponding positions of two adjacent anode plates is the time it takes for the anode plate to swing for one cycle.

7. The method for preparing a multilayer current collector according to claim 5, characterized in that: Ultrasonic oscillation is performed throughout the entire process of forming the second metal layer by the electroplating method. An ultrasonic transmitter is set close to the cathode belt. The frequency of the ultrasonic oscillation is 25 to 30 kHz. The power of the ultrasonic transmitter is 100 to 500 W. One ultrasonic transmitter is distributed every 2 m along the running direction of the cathode belt. The total length of the ultrasonic area can be 10 to 30 m.

8. The method for preparing a multilayer current collector according to claim 5, characterized in that: The electroplating is carried out in a molten salt electroplating system, wherein the molten salt electroplating system includes AlCl3, NaCl, and KCl in a mass ratio of 6-10:1-2:1-2; Alternatively, the electroplating is carried out in a water plating solution, the water plating solution comprising the following raw materials: Additives 0.04-0.15 g / L, copper sulfate 80-140 g / L, sulfuric acid 90-150 g / L, chloride ions 40-70 ppm, copper plating auxiliary agent 1-10 ml / L, and the rest is water; wherein the additives include malachite green 0.01-0.07 g / L and ethylenediamine 0.03-0.08 g / L.

9. The method for preparing a multilayer current collector according to claim 8, characterized in that: When electroplating in a molten salt electroplating system, the current density is 2 to 65 mA / cm 2 , the electroplating temperature is 100~220℃; When electroplating in water bath, the current density is 5-40 mA / cm 2 , the electroplating temperature is 20 ~ 50 ℃.

10. The method for preparing a multilayer current collector according to claim 5, characterized in that: The total thickness of the metal layer on one surface of the polymer base film is 0.63-2.1 μm, the thickness of the first metal layer is 25-100 nm, and the thickness of the second metal layer is 0.6-2.0 μm.

Images