A surface-modified composite current collector, preparation method and battery

Abstract

An embodiment of the present invention provides a surface-modified composite current collector, a preparation method and a battery. The method includes: preparing a sputtered metal layer on the surface of a polyimide film by magnetron sputtering; obtaining a composite film with template particles on the surface through spraying and low-temperature drying; electroplating an electroplated metal layer on the surface of the composite film by electroplating; using an etching method to remove the template particles from the composite film to obtain a surface-modified composite current collector; wherein, the surface of the surface-modified composite current collector has spherical segment-shaped metal cavities; thus, the contact angle between the surface of the composite current collector and the slurry can be reduced, the infiltration of the slurry on the surface of the composite current collector can be promoted, which is beneficial to improving the electrochemical performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery current collectors, and particularly relates to a surface-modified composite current collector, a preparation method and a battery. Background Art

[0002] The current collector is one of the indispensable components of a battery, and has the important functions of carrying active materials and collecting microcurrents. Traditional metal current collectors such as aluminum foil current collectors and copper foil current collectors have a large mass density, which limits the improvement of the energy density of the battery. If the thickness of the traditional metal current collector is further reduced to reduce the mass, it will lead to a decrease in the strength of the current collector and an increase in cost. Compared with traditional current collectors, composite current collectors based on polymers such as polyethylene terephthalate (PET) and polyimide (PI) have significant advantages in reducing costs, increasing the energy density of the battery and enhancing the safety of the battery due to their light weight and softness, and have received increasing attention in recent years.

[0003] The structure of the composite current collector itself is "metal layer - polymer film - metal layer". Compared with traditional current collectors, the metal layer of the composite current collector itself is too thin, and the polymer substrate has a much smaller hardness than the metal, which makes the surface of the composite current collector more likely to produce micro-deformations compared to the surface of traditional current collectors. Such micro-deformations will cause the electrode slurry and the composite current collector to not form a completely stable interface during the coating process of electrode preparation, resulting in the active materials falling off from the surface of the composite current collector or poor contact between the active materials and the composite current collector during the operation of the battery, hindering the electrochemical performance of the battery. Therefore, it is necessary to perform surface modification on the composite current collector to improve its performance. Since in the existing electrode slurry systems, the commonly used dispersion media are mainly deionized water or N-methylpyrrolidone (NMP), it is necessary to improve the wettability of water and NMP on the surface of the composite current collector to form a more stable active material - composite current collector interface. Summary of the Invention

[0004] In view of this, the present invention provides a surface-modified composite current collector, a preparation method and a battery. By preparing a metal layer with a specific structure on the surface of the composite current collector, the contact angle between the surface of the composite current collector and the slurry is reduced, the infiltration of the slurry on the surface of the composite current collector is promoted, and the electrochemical performance of the battery is improved.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a preparation method of a surface-modified composite current collector, the method comprising:

[0007] Preparing a sputtered metal layer on the surface of a polyimide film by magnetron sputtering;

[0008] A composite film with template particles on its surface is obtained by spray method and low-temperature drying;

[0009] An electroplated metal layer is prepared on the surface of the composite film by electroplating method;

[0010] The template particles of the composite film are removed by etching method to obtain a surface-modified composite current collector; wherein, the surface of the surface-modified composite current collector has a spherical segment-shaped metal cavity.

[0011] Preferably, the distance from the center point of the bottom of the spherical segment-shaped metal cavity to the edge position of the spherical segment is the opening radius L, and the included angle between the opening radius and the line segment connecting the edge of the spherical segment and the vertex of the spherical segment is the opening angle θ; wherein, the range of the opening radius is 0.5 - 2.5 μm, and the range of the opening angle is 15 - 40°.

[0012] Preferably, the opening radius is:

[0013]

[0014] wherein, the diameter of the template particle is D, and the thickness of the electroplated metal layer is H.

[0015] Preferably, the opening angle is:

[0016]

[0017] wherein, the diameter of the template particle is D, and the thickness of the electroplated metal layer is H.

[0018] Preferably, the thickness range of the sputtered metal layer is 0.1 - 0.3 μm.

[0019] Preferably, the template particle is a silica particle with a diameter of 2 - 5 μm.

[0020] Preferably, the thickness range of the electroplated metal layer is 0.5 - 2 μm.

[0021] Preferably, the method used in the process of removing the template particles is the etching method, the etching agent used is hydrofluoric acid solution, and the concentration of the hydrofluoric acid solution is 50%.

[0022] In a second aspect, an embodiment of the present invention provides a surface-modified composite current collector, which is prepared by the preparation method of the surface-modified composite current collector according to any embodiment of the present invention.

[0023] In a third aspect, an embodiment of the present invention provides a battery, which includes the surface-modified composite current collector according to any embodiment of the present invention.

[0024] An embodiment of the present invention provides a surface-modified composite current collector, a preparation method thereof, and a battery. A sputtered metal layer is prepared on the surface of a polyimide film by a magnetron sputtering method; a composite film with template particles on the surface is obtained by a spraying method and low-temperature drying; an electroplated metal layer is prepared on the surface of the composite film by an electroplating method; an etching method is used to remove the template particles from the composite film to obtain a surface-modified composite current collector; wherein, the surface of the surface-modified composite current collector has a spherical segment-shaped metal cavity; thus, the contact angle between the surface of the composite current collector and the slurry can be reduced, the infiltration of the slurry on the surface of the composite current collector can be promoted, and it is beneficial to improve the electrochemical performance of the battery.

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

[0026] (1) In this technical solution, a spherical segment-shaped metal structure with a specific opening angle is prepared on the surface of the composite current collector through template particles, which can enhance the wettability of the electrode slurry on the surface of the current collector, form a more stable and ion-transport-favorable interface between the active material layer and the composite current collector, and improve the battery cycle performance;

[0027] (2) Compared with traditional copper foils and conventional composite copper foils, the spherical segment-shaped metal structure on the surface of the surface-modified composite current collector provided by this technical solution reduces the mass of a part of the metal layer without affecting the conductive effect of the composite current collector, thereby reducing the overall mass of the composite current collector, and can improve the energy density of the battery to a certain extent;

[0028] (3) The preparation process of the composite film prepared by this technical solution avoids factors such as high temperature, strong acid, and strong alkali that may affect the structure of the composite current collector itself. Compared with conventional surface modification methods, the preparation method provided by this technical solution is more suitable for composite current collectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a cross-sectional schematic diagram of a surface-modified composite current collector provided by Embodiment 1 of the present invention.

[0030] Wherein, 1. Polyimide film; 2. Sputtered metal layer; 3. Electroplated metal layer; 4. Radius of template particles; 5. Opening radius; 6. Opening angle; 7. Sphere corresponding to template particles. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Please refer to Figure 1 , an embodiment of the present invention provides a preparation method of a surface-modified composite current collector, and the method includes:

[0033] A sputtering metal layer is prepared on the surface of a polyimide film by magnetron sputtering method;

[0034] A composite film with template particles on the surface is obtained by spraying method and low-temperature drying;

[0035] An electroplated metal layer is prepared on the surface of the composite film by electroplating method;

[0036] The template particles on the composite film are removed by etching method to obtain a surface-modified composite current collector; wherein, the surface of the surface-modified composite current collector has a spherical segment-shaped metal cavity.

[0037] Through the above embodiments, thus, the contact angle between the surface of the composite current collector and the slurry can be reduced, the infiltration of the slurry on the surface of the current collector can be promoted, which is beneficial to improving the electrochemical performance of the battery.

[0038] In one embodiment, the distance between the center point at the bottom of the spherical segment-shaped metal cavity and the position of the spherical segment edge is the opening radius L, and the included angle between the opening radius and the line segment connecting the spherical segment edge and the spherical segment vertex is the opening angle θ; wherein, the range of the opening radius is 0.5 - 2.5 μm, and the range of the opening angle is 15 - 40°.

[0039] The opening radius is:

[0040]

[0041] Wherein, the diameter of the template particles is D, and the thickness of the electroplated metal layer is H.

[0042] The opening angle is:

[0043]

[0044] Wherein, the diameter of the template particles is D, and the thickness of the electroplated metal layer is H.

[0045] In one embodiment, the thickness range of the sputtering metal layer is 0.1 - 0.3 μm.

[0046] In one embodiment, the template particles are silica particles with a diameter of 2 - 5 μm.

[0047] In one embodiment, the thickness range of the electroplated metal layer is 0.5 - 2 μm.

[0048] In one embodiment, the method used in the process of removing the template particles is etching method, the etching agent used is hydrofluoric acid solution, and the concentration of the hydrofluoric acid solution is 50%.

[0049] The following further describes the specific implementation manners of the present invention in conjunction with embodiments, and the present invention is not limited to the scope of the described embodiments accordingly.

[0050] Embodiment 1

[0051] A surface-modified composite current collector prepared according to an embodiment of the present invention is as follows:

[0052] (1) The magnetron sputtering system is evacuated, and when the vacuum degree is measured to be 10 -2 Pa, the polyimide film is placed in the vacuum chamber, and then argon gas at 1 Pa is introduced into the vacuum chamber. The system vacuum degree is maintained between 0.5 - 1 Pa, and then the cathode voltage is adjusted to 1 kV. A polyimide film with a sputtered metal layer having a thickness of 0.2 μm on the surface is prepared by the action of a radio frequency voltage with a DC negative high voltage.

[0053] (2) The composite film is placed on a flat tabletop, and a mixed solution containing silicon dioxide particles is used to uniformly spray silicon dioxide particles with a diameter of 5 μm on the sputtered metal surface of the composite film by moving the spray at a constant speed. After the spraying process is completed, the film with silicon dioxide particles on the surface is dried at a low temperature to obtain a composite film with a certain proportion of template particles attached to the surface.

[0054] (3) The composite film with attached template particles is placed in an electroplating solution, and the solution temperature is adjusted to 50 °C. Using the method of single-sided electroplating, first electroplate for 1 min with a current density of 1 A / dm 2 , and then electroplate for 0.5 min with a current density of 3 A / dm 2 . After the electroplating process is completed, the composite film is taken out of the electroplating solution and washed with pure water, and after drying, a composite film with a sputtered / plated composite metal layer is obtained.

[0055] (4) The electroplated composite film is immersed in a hydrofluoric acid solution with a concentration of 50% to remove the silicon dioxide particles. After no more bubbles appear in the hydrofluoric acid solution, the composite film is taken out and washed. The washed composite film is subjected to another process of removing silicon dioxide particles. After the second removal process is completed, it is washed and dried. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having an electroplated metal layer thickness of 0.45 - 0.50 μm, an opening radius of 1.50 - 1.62 μm, and an opening angle of 18.4 - 19.2° is obtained, and its contact angle with water is 58.2 - 59.4°, and its contact angle with NMP is 13.9 - 14.1°.

[0056] Embodiment 2

[0057] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, and only the diameter of the template particles is adjusted from 5 μm to 2 μm in the "template particle attachment" step for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having an electroplated metal layer thickness of 0.45 - 0.50 μm, an opening radius of 0.86 - 0.92 μm, and an opening angle of 30.1 - 31.1° is obtained, and its contact angle with water is 69.5 - 70.8°, and the contact angle with NMP is 16.7 - 17.1°.

[0058] Example Three

[0059] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, and only the diameter of the template particles is adjusted from 5 μm to 3 μm in the "template particle attachment" step for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having an electroplated metal layer thickness of 0.45 - 0.50 μm, an opening radius of 1.12 - 1.18 μm, and an opening angle of 24.0 - 24.8° is obtained, and its contact angle with water is 61.2 - 62.4°, and the contact angle with NMP is 14.7 - 14.9°.

[0060] Example Four

[0061] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, and only the diameter of the template particles is adjusted from 5 μm to 4 μm in the "template particle attachment" step for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having an electroplated metal layer thickness of 0.45 - 0.50 μm, an opening radius of 1.32 - 1.40 μm, and an opening angle of 20.8 - 22.3° is obtained, and its contact angle with water is 59.5 - 60.3°, and the contact angle with NMP is 14.3 - 14.6°.

[0062] Example Five

[0063] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, and only the first electroplating time is adjusted from 1 min to 3 min in the "electroplating to prepare the metal layer" step for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having an electroplated metal layer thickness of 0.82 - 0.90 μm, an opening radius of 1.92 - 2.01 μm, and an opening angle of 25.1 - 26.4° is obtained, and its contact angle with water is 63.3 - 64.2°, and the contact angle with NMP is 15.2 - 15.4°.

[0064] Example Six

[0065] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, except that in the step of "electroplating to prepare a metal layer", the current density of the first electroplating is changed from 1 A / dm 2 to 2 A / dm 2 for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having a thickness of the electroplated metal layer of 0.65 - 0.74 μm, an opening radius of 1.73 - 1.82 μm, and an opening angle of 22.0 - 23.4° is obtained. The contact angle between it and water is 59.1 - 60.3°, and the contact angle between it and NMP is 14.2 - 14.6°.

[0066] Example Seven

[0067] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, except that in the step of "electroplating to prepare a metal layer", the second electroplating time is changed from 0.5 min to 1.5 min for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having a thickness of the electroplated metal layer of 1.02 - 1.14 μm, an opening radius of 2.07 - 2.16 μm, and an opening angle of 28.0 - 29.2° is obtained. The contact angle between it and water is 64.1 - 65.5°, and the contact angle between it and NMP is 15.4 - 15.7°.

[0068] Example Eight

[0069] A surface-modified composite current collector prepared according to an embodiment of the present invention, the specific implementation manner is the same as that of Embodiment 1, except that in the step of "electroplating to prepare a metal layer", the current density of the second electroplating is changed from 3 A / dm 2 to 4 A / dm 2 for experiments. Finally, a surface-modified composite current collector with a spherical segment-shaped cavity metal structure having a thickness of the electroplated metal layer of 0.52 - 0.62 μm, an opening radius of 1.62 - 1.74 μm, and an opening angle of 20.3 - 21.1° is obtained. The contact angle between it and water is 59.5 - 60.8°, and the contact angle between it and NMP is 14.3 - 14.5°.

[0070] Comparative Example One

[0071] A surface-modified composite current collector prepared in the comparative example of the present invention, the specific implementation manner is the same as that of Embodiment 1, except that in the step of "electroplating to prepare a metal layer", the current density during the two electroplating processes is uniformly adjusted to 3 A / dm 2 , and the overall electroplating time is adjusted to 5 min for experiments.

[0072] The thickness of the electroplated metal layer on the composite current collector prepared in this experiment exceeds the radius of the template particles. The values of the opening radius and opening angle of the prepared cavity structure are outside the calculation formula provided by the present invention, and its contact angle with water is 102.3 - 104.6°, and the contact angle with NMP is 52.1 - 53.4°.

[0073] Comparative Example 2

[0074] A surface-modified composite current collector prepared in the comparative example of the present invention has the same specific implementation as that of Example 1, except that in the "template particle attachment" step, the diameter of the template particles is adjusted from 5 μm to 0.5 μm for the experiment.

[0075] The thickness of the electroplated metal layer on the composite current collector prepared in this experiment exceeds the radius of the template particles. The values of the opening radius and opening angle of the prepared cavity structure are outside the calculation formula provided by the present invention, and its contact angle with water is 136.8 - 142.1°, and the contact angle with NMP is 65.9 - 68.1°.

[0076] Comparative Example 3

[0077] A surface-modified composite current collector prepared in the comparative example of the present invention, on the basis of Example 1, removes the "template particle attachment" step and directly performs the "electroplating to prepare the metal layer" step after the "sputtering to prepare the metal layer" step for the experiment.

[0078] The composite current collector prepared in this experiment does not have a spherical segment-shaped cavity structure, and its contact angle with water is 82.1 - 83.2°, and the contact angle with NMP is 18.6 - 19.4°.

[0079] See Table 1 for a comparative summary of the effects of the diameter of silica particles and the thickness of the electroplated metal layer on the opening radius, cavity opening angle, water contact angle, and NMP contact angle in the examples of the present invention. It can be seen from the table that:

[0080] (1) In Example 1, the diameter of the silica particles is 5 μm, the first electroplating current density is 1 A / dm 2 , the first electroplating time is 1 min, the second electroplating current density is 3 A / dm 2 , the second electroplating time is 0.5 min. The prepared surface-modified composite current collector is the composite current collector with the best parameters. Its opening radius is 1.50 - 1.62 μm, the cavity opening angle is 18.4 - 19.2°, the contact angle between the composite current collector and water is 58.2 - 59.4°, and the contact angle with NMP is 13.9 - 14.1°.

[0081] (2) By comparing Examples 1, 2, 3, and 4, it can be concluded that the diameter of silica particles has the greatest influence on the contact angles between the surface-modified composite current collector and water and NMP. If the diameter of silica particles is too small, it will affect the wetting effect of water and NMP on the composite current collector.

[0082] (3) By comparing Examples 1, 5, 6, 7, and 8, it can be concluded that the thickness of the electroplated metal layer has little influence on the water contact angle and NMP contact angle of the surface-modified composite current collector. By comparing the contact angles between the composite current collector and water and NMP, it can be concluded that the parameters in Example 1 are the best.

[0083] (4) By comparing Example 1 with Comparative Examples 1 and 2, it can be concluded that when the electroplated metal layer is too thick or the diameter of silica particles is too small, a metal cavity structure exceeding the semi-circular height will be formed, and the opening radius and opening angle it has will exceed the range of the calculation formula in this application, and it will increase the contact angles between the composite current collector and water and NMP, hindering the wetting of the aqueous slurry and oil-based slurry on the composite current collector.

[0084] (5) By comparing Example 1 with Comparative Example 3, it can be seen that when the composite current collector does not have the spherical segment-shaped metal cavity structure in this application, its contact angle with water is 82.1 - 83.2°, and its contact angle with NMP is 18.6 - 19.4°. Compared with the composite current collector in Example 1, it shows a poor wetting effect with aqueous slurry and oil-based slurry.

[0085]

[0086]

[0087] Table 1

[0088] In summary, the present invention discloses a surface-modified composite current collector, a preparation method, and a battery. The steps include: preparing a sputtered metal layer on the surface of a polyimide film by magnetron sputtering; obtaining a composite film with template particles on the surface through spraying and low-temperature drying; electroplating an electroplated metal layer on the surface of the composite film by electroplating; using an etching method to remove the template particles from the composite film to obtain a surface-modified composite current collector; wherein, the surface of the surface-modified composite current collector has a spherical segment-shaped metal cavity; thus, the contact angle between the surface of the composite current collector and the slurry can be reduced, promoting the wetting of the slurry on the surface of the current collector, which is beneficial to improving the electrochemical performance of the battery.

[0089] The above is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, and improvements made within the scope of the present invention are included in the protection scope of the present invention.

Claims

1. A preparation method of a surface-modified composite current collector, characterized in that, The method includes: Preparing a sputtered metal layer on the surface of a polyimide film by magnetron sputtering; Obtaining a composite film with template particles on the surface by spraying and low-temperature drying; Preparing an electroplated metal layer on the surface of the composite film by electroplating; Removing the template particles from the composite film by etching to obtain a surface-modified composite current collector; wherein, the surface of the surface-modified composite current collector has a spherical segment-shaped metal cavity; The distance from the edge position of the spherical segment perpendicular to the straight line connecting the bottom center point and the center of the spherical segment-shaped metal cavity is the opening radius L, and the angle between the opening radius and the line segment connecting the edge of the spherical segment and the vertex of the spherical segment is the opening angle θ; wherein, the range of the opening radius is 0.5 - 2.5 μm, and the range of the opening angle is 15 - 40°.

2. The preparation method of a surface-modified composite current collector according to claim 1, characterized in that, The opening radius is: The opening angle is: Wherein, the diameter of the template particles is D, and the thickness of the electroplated metal layer is H.

3. The preparation method of a surface-modified composite current collector according to claim 1, characterized in that, The thickness range of the sputtered metal layer is 0.1 - 0.3 μm.

4. The preparation method of a surface-modified composite current collector according to claim 1, characterized in that, The template particles are silica particles with a diameter of 2 - 5 μm.

5. The preparation method of a surface-modified composite current collector according to claim 1, characterized in that, The thickness range of the electroplated metal layer is 0.5 - 2 μm.

6. A surface-modified composite current collector, characterized in that, It is prepared by using the preparation method of the surface-modified composite current collector described in any one of claims 1 - 5.

7. A battery, characterized in that, It includes the surface-modified composite current collector described in claim 6.

Images