Negative current collector and preparation method thereof

Abstract

The invention discloses a negative electrode current collector and a preparation method thereof, the negative electrode current collector comprises a film substrate layer and aluminum oxide layers arranged on the upper and lower sides of the film substrate layer, and the outer side of each aluminum oxide layer is provided with a copper metal layer; the film base material layer comprises a PET (Polyethylene Terephthalate) base film layer and PP (Polypropylene) film layers positioned on two sides of the PET base film layer. By adopting the negative current collector structure provided by the invention, the production cost of the negative current collector can be reduced, and the binding force between the layer structures on the negative current collector can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative electrode current collector and a preparation method thereof. Background Art

[0002] Composite current collector is a new type of battery current collector structure that optimizes battery performance by combining different materials (such as metals and polymer materials) into a multilayer or composite structure.

[0003] The current composite current collectors include negative composite current collectors and positive composite current collectors, and the structures of the negative composite current collectors and the positive composite current collectors are both provided with metal layers on both sides of the film. The negative composite current collector film uses PP film in the industry, while the positive composite current collector film uses PET film in the industry. The reason is that although the bonding strength of PP film with the metal layer is not as good as that of PET film, PP film will not swell at the negative electrode of the battery, while PET film will swell at the negative electrode.

[0004] In order to make the metal layer and the PP film have better bonding, the industry will add some additives to the PP film. However, for the composite current collector manufacturers, it is necessary to develop a new production line to develop the corresponding film or require the film supplier to develop a new film, which will undoubtedly increase the cost of producing the composite current collector. Higher costs will push up the selling price of the composite current collector, causing the composite current collector to lose its price advantage compared to the traditional current collector, affecting the sales of the composite current collector. It is also common in the industry to coat the composite current collector with a material containing an adhesive in the hope of increasing the bonding strength between the metal layer and the film on the composite current collector. Similarly, this approach will greatly increase costs, affect final sales, and also reduce the energy density of the battery; both of the above two approaches are not desirable. The bonding strength and square resistance of the negative electrode current collector obtained by directly forming a metal layer on the PP film cannot meet the requirements.

[0005] Therefore the prior art still needs to be improved and enhanced. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a negative electrode current collector and a preparation method thereof, so as to solve the problem of poor binding force of the existing negative electrode current collector in the background technology.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A negative electrode current collector comprises: a thin film substrate layer and an aluminum oxide layer arranged on the upper and lower sides of the thin film substrate layer, wherein a copper metal layer is arranged on the outer side of the aluminum oxide layer; the thin film substrate layer comprises a PET base film layer and PP film layers located on both sides of the PET base film layer.

[0009] The thickness of the film substrate layer is 3um-10um.

[0010] The thickness of the aluminum oxide layer is 10nm-60nm, and the thickness of the copper metal layer is 100nm-1um.

[0011] The thickness of the PP film layer is 10nm-1um, and the thickness of the PET base film layer is 1um-9um.

[0012] Based on the total weight of the film substrate layer, the weight of the PET base film layer accounts for 80%-90%, and the weight of the PP film layer accounts for 10%-20%.

[0013] Conductive particles are arranged in both the PET base film layer and the PP film layer.

[0014] The weight proportion of the conductive particles in the PET base film layer is less than that in the PP film layer; based on the total weight of the PET base film layer, the weight proportion of the conductive particles in the PET base film layer is 20%-30%; based on the total weight of the PP film layer, the weight proportion of the conductive particles in the PP film layer is 50%-60%.

[0015] The conductive particles are made of metal or non-metal material.

[0016] A method for preparing a negative electrode current collector, comprising:

[0017] The PP film layer is bonded to both sides of the PET base film layer through a hot pressing composite process;

[0018] An aluminum oxide layer is coated on the outside of the PP film layer by vacuum coating;

[0019] A copper metal layer is plated on the outer side of the aluminum oxide layer by magnetron sputtering.

[0020] Before the step of coating the aluminum oxide layer on the outer side of the PP film layer by vacuum coating, the method further includes: treating the surface of the PP film layer by plasma equipment.

[0021] Compared with the prior art, the present invention provides a negative electrode current collector and a preparation method thereof, wherein the negative electrode current collector comprises: a thin film substrate layer and an aluminum oxide layer disposed on the upper and lower sides of the thin film substrate layer, and a copper metal layer is disposed on the outer side of the aluminum oxide layer; the thin film substrate layer comprises a PET base film layer and a PP film layer located on both sides of the PET base film layer. The negative electrode current collector structure in the present application can reduce the production cost of the negative electrode current collector and improve the bonding strength between the various layers of the negative electrode current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1This is a schematic diagram of the structure of the negative electrode current collector provided by the present invention.

[0023] Figure 2 A schematic flow chart of a method for preparing a negative electrode current collector provided by the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. 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.

[0025] It should be noted that when a component is referred to as being "mounted on", "fixed on" or "disposed on" another component, it may be directly on the other component or there may be a central component at the same time. When a component is referred to as being "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time.

[0026] It should also be noted that the directional terms such as left, right, up, and down in the embodiments of the present invention are merely relative concepts or are based on the normal use status of the product and should not be considered as restrictive.

[0027] Composite current collector is a new type of battery current collector structure that optimizes battery performance by combining different materials (such as metals and polymer materials) into a multilayer or composite structure.

[0028] The current composite current collectors include negative composite current collectors and positive composite current collectors, and the structures of the negative composite current collectors and the positive composite current collectors are both provided with metal layers on both sides of the film. The negative composite current collector film uses PP film in the industry, while the positive composite current collector film uses PET film in the industry. The reason is that although the bonding strength of PP film with the metal layer is not as good as that of PET film, PP film will not swell at the negative electrode of the battery, while PET film will swell at the negative electrode.

[0029] In order to make the metal layer and the PP film have better bonding, the industry will add some additives to the PP film. However, for the composite current collector manufacturers, it is necessary to develop a new production line to develop the corresponding film or require the film supplier to develop a new film, which will undoubtedly increase the cost of producing the composite current collector. Higher costs will push up the selling price of the composite current collector, causing the composite current collector to lose its price advantage compared to the traditional current collector, affecting the sales of the composite current collector. It is also common in the industry to coat the composite current collector with a material containing an adhesive in the hope of increasing the bonding strength between the metal layer and the film on the composite current collector. Similarly, this approach will greatly increase costs, affect final sales, and also reduce the energy density of the battery; both of the above two approaches are not desirable. The bonding strength and square resistance of the negative electrode current collector obtained by directly forming a metal layer on the PP film cannot meet the requirements.

[0030] This application provides a negative electrode current collector, please refer to Figure 1 , including: a thin film substrate layer 1 and an aluminum oxide layer 2 arranged on the upper and lower sides of the thin film substrate layer 1, and a copper metal layer 3 is arranged on the outer side of the aluminum oxide layer 2; the thin film substrate layer 1 includes a PET base film layer 11 and a PP film layer 12 located on both sides of the PET base film layer 11. The negative electrode current collector structure in the present application can reduce the production cost of the negative electrode current collector and improve the bonding force between the various layers of the negative electrode current collector. In addition, because the PET base film layer 11 is light and flexible, the composite structure of the PET base film layer 11 and the PP film layer 12 is used as the thin film substrate layer 1, which is beneficial to reduce the weight of the negative electrode current collector and improve the flexibility of the structure; the PP film layer 12 on both sides of the PET base film layer 11 further enhances the stability of the overall structure. The aluminum oxide layer 2 has good insulation and stability, and plays an insulating role on the copper metal layer 3, reducing the occurrence of side reactions; the aluminum oxide layer 2, as a transition layer between the copper metal layer 3 and the thin film substrate layer 1, not only improves the bonding force between the layers and prevents the metal layer from falling off, but also effectively protects the internal thin film substrate layer 1 from mechanical damage due to its high hardness and wear resistance, which is conducive to enhancing the service life of the negative electrode current collector. The drawings in this application do not limit the thickness of each film layer, but only show the structure of the negative electrode current collector.

[0031] Furthermore, the thickness of the PP film layer 12 is 10nm-1um, and the thickness of the PET base film layer 11 is 1um-9um. Such thickness distribution further optimizes the performance of the film substrate layer 1. The PP film layer 12 is relatively thin but can play its role in protecting the PET base film layer 11 and assisting in enhancing stability, while not increasing the weight too much; the PET base film layer 11 is the main supporting layer, and the appropriate thickness ensures sufficient mechanical strength and flexibility. In the embodiment of the present application, the middle of the film substrate layer 1 is the PET base film layer 11, and the upper and lower surfaces of the PET base film layer 11 are provided with the PP film layer 12. Compared with the existing negative electrode current collector using pure PP film as the film substrate layer 1, the present application uses the PET base film layer 11 as the base film, and the two sides are the PP film layer 12. Since the PET film is cheaper than the PP film, this structure can reduce the cost. The melting point of the PP film layer 12 is about 160°C, while the melting point of the PET base film layer 11 is above 260°C. Therefore, when the copper metal layer 3 is plated, the metal copper particles are less likely to burn through the film substrate layer 1 into pinholes, which is beneficial to reduce holes.

[0032] Furthermore, the thickness of the film substrate layer 1 is 3um-10um. In the embodiment of the present application, if the thickness of the film substrate layer 1 is too large, the production cost will be increased, the weight of the negative electrode current collector will be increased, and more importantly, the surface tension will be smaller, which will affect the bonding force between the film substrate layer 1 and the aluminum oxide layer 2. By limiting the thickness of the film substrate layer 1, it is ensured that the negative electrode current collector has good flexibility and a certain mechanical strength, and will not increase too much weight due to excessive thickness, affecting the battery energy density; nor will it be too thin, resulting in insufficient mechanical properties, and causing problems such as breakage during battery manufacturing and use.

[0033] Furthermore, the thickness of the aluminum oxide layer 2 is 10nm-60nm, and the thickness of the copper metal layer 3 is 100nm-1um. In the embodiment of the present application, if the thickness of the aluminum oxide layer 2 is too large, the cost will increase on the one hand, and the weight of the negative electrode current collector will increase on the other hand. More importantly, the thickness of the aluminum oxide layer 2 within the limited range can improve the surface tension of the PP film layer 12. The thickness of the PP film layer 12 combined with the thickness of the aluminum oxide layer 2 can greatly improve the binding force of the copper metal layer 3 on the aluminum oxide layer 2. In addition, the insulation performance and chemical stability of the aluminum oxide layer 2 within this thickness range can be better exerted, effectively isolating and protecting the copper metal layer 3; the copper metal layer 3 within this range ensures good conductivity, meets the conductivity requirements of the negative electrode current collector, and does not increase weight due to excessive thickness.

[0034] Further, based on the total weight of the film substrate, the weight of the PET base film layer 11 accounts for 80%-90%, and the weight of the PP film layer 12 accounts for 10%-20%. In the embodiment of the present application, due to the good heat resistance of the PET film, the relative weight of the PET base film layer 11 and the PP film layer 12 in the film substrate is limited to reduce defects such as line wrinkles during the coating process. In addition, the weight ratio of the PET base film layer 11 and the PP film layer 12 is set, on the one hand, to reduce the production cost of the negative electrode current collector, and on the other hand, the negative electrode current collector achieves a good balance between weight, flexibility and mechanical stability. The higher proportion of the PET base film layer 11 ensures the lightness and flexibility of the negative electrode current collector, while the appropriate amount of the PP film layer 12 enhances the stability of the overall structure.

[0035] Furthermore, conductive particles are provided in the PET base film layer 11 and the PP film layer 12; the traditional PET film is a polyethylene terephthalate film, and the traditional PP film is a polypropylene film. In this application, conductive particles are added to the traditional film layer. On the one hand, the resistivity of the film substrate layer 1 can be reduced. When used in the battery current collector, it can effectively reduce the energy loss during the battery charging and discharging process and improve the battery charging and discharging efficiency. On the other hand, it allows electrons to be quickly conducted in the current collector, improving the high-rate charging and discharging performance of the battery. In addition, the conductive particles can also improve the mechanical properties of the film layer, enhance the toughness of the film layer, increase the hardness and roughness of the film layer surface, and thus improve the stability and reliability of the negative electrode current collector.

[0036] The weight proportion of the conductive particles in the PET base film layer 11 is less than that in the PP film layer; based on the total weight of the PET base film layer 11, the total weight proportion of the conductive particles in the PET base film layer 11 is 20%-30%; based on the total weight of the PP film layer 12, the weight proportion of the conductive particles in the PP film layer 12 is 50%-60%. When welding the tabs, the internal resistance at the tab welding point can be reduced; at the same time, since there are fewer conductive particles in PET, the thermal conductivity of the current collector can be improved and the cost can be reduced.

[0037] Furthermore, a metal oxide with a certain hardness is provided in the PET base film layer 11, and its function is: hydrogen fluoride will appear during the operation of the lithium battery, and hydrogen fluoride will penetrate into the PET base film layer 11. At this time, the metal oxide in the PET base film layer 11 will react with hydrogen fluoride to reduce the corrosion of hydrogen fluoride on the PET base film layer 11; the metal oxide has a certain hardness, which improves the puncture resistance of the current collector. The specific metal oxide can be selected from aluminum oxide or others, which can be selected according to actual conditions, and this application is not limited here. Based on the weight of the PET base film layer 11, the weight proportion of the metal oxide in the PET base film layer 11 is 10%-15%. Based on the weight of the PP film layer 12, the PP film layer 12 is provided with a desiccant with a weight proportion of 1%-5%, so that the water generated by the reaction of the metal oxide in the PET base film layer 11 and hydrogen fluoride will be absorbed by the desiccant in the PP film layer 12 to ensure the stability of the battery operation. The desiccant can be selected from molecular sieves or other materials, and this application does not limit the specific selection of the desiccant.

[0038] In the embodiment of the present application, the average particle size of the conductive particles is larger than the average particle size of the copper metal particles in the copper metal layer 3, so that the copper metal particles can be prevented from burning through the film substrate layer 1 to form pinholes when forming the copper metal layer 3.

[0039] Furthermore, the conductive particles are made of metal or non-metal. In the embodiment of the present application, the conductive particles can be made of metal such as copper, aluminum, titanium, nickel, etc., or can be made of carbon or other non-metal materials with similar or identical properties. The present application does not limit the specific material of the conductive particles, and can be adaptively selected according to actual conditions.

[0040] The present application also provides a method for preparing a negative electrode current collector, please refer to Figure 1 and Figure 2 ,include:

[0041] S1, combining the PP film layer 12 on both sides of the PET base film layer 11 through a hot pressing composite process;

[0042] S2, coating an aluminum oxide layer 2 on the outer side of the PP film layer 12 by vacuum coating;

[0043] S3, plating a copper metal layer 3 on the outer side of the aluminum oxide layer 2 by magnetron sputtering.

[0044] Among them, the PP film layer 12 is tightly bonded to both sides of the PET base film layer 11 through a hot pressing composite process, including: the PP film layer 12 and the PET base film layer 11 are composited by heating and pressurizing to form a three-layer structure, so that the PP film layer 12 is located on both sides of the PET base film layer 11, wherein the temperature for heating the PET base film layer 11 can be selected between 60°C and 150°C, the time for pressurizing the PP film layer 12 can be selected between 1 minute and 2 minutes, and the pressure range of pressurization is between 0.5Mpa and 2Mpa. First, an aluminum oxide layer 2 is plated on the outside of the PP film layer 12 using a vacuum evaporation device, and then a copper metal layer 3 is plated on the outside of the aluminum oxide layer 2 using a magnetron sputtering device. The advantage is that the energy generated by magnetron sputtering is high and the force is large. On the one hand, it is conducive to the copper metal layer 3 to be combined with the aluminum oxide layer 2, and on the other hand, the aluminum oxide layer 2 is firmly hit on the PP film layer 12 during the magnetron sputtering process, further improving the bonding force between the aluminum oxide layer 2 and the film substrate layer 1.

[0045] After the PP film layer 12 is tightly bonded to both sides of the PET base film layer 11 by a hot pressing composite process and before the aluminum oxide layer 2 is plated on the outside of the PP film layer 12 by vacuum coating, the outer surface of the composite PP film layer 12 is treated by a plasma treatment device to have a surface roughness of 0.1um-1um, so as to enhance the adhesion of the aluminum oxide layer 2 on the PP film layer 12.

[0046] In the method for preparing the negative electrode current collector, a vacuum evaporation device for coating the aluminum oxide layer 2 on the outer side of the PP film layer 12 by vacuum coating and a plasma treatment device for treating the outer surface of the composite PP film layer 12 can be set in one device, which is conducive to improving the preparation efficiency of the negative electrode current collector. Similarly, a vacuum evaporation device for coating the aluminum oxide layer 2 on the outer side of the PP film layer 12 by vacuum coating and a magnetron sputtering device for coating the copper metal layer 3 on the outer side of the aluminum oxide layer 2 by magnetron sputtering can be set in one device, which is also conducive to improving the preparation efficiency of the negative electrode current collector.

[0047] In summary, the present invention provides a negative electrode current collector and a preparation method thereof, wherein the negative electrode current collector comprises: a thin film substrate layer and an aluminum oxide layer disposed on the upper and lower sides of the thin film substrate layer, and a copper metal layer is disposed on the outer side of the aluminum oxide layer; the thin film substrate layer comprises a PET base film layer and a PP film layer located on both sides of the PET base film layer. The negative electrode current collector structure in the present application can reduce the production cost of the negative electrode current collector and improve the bonding strength between the various layers of the negative electrode current collector.

[0048] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. A negative electrode current collector, characterized in that: include: A film substrate layer and an aluminum oxide layer arranged on the upper and lower sides of the film substrate layer, wherein a copper metal layer is arranged on the outer side of the aluminum oxide layer; the film substrate layer comprises a PET base film layer and a PP film layer located on both sides of the PET base film layer.

2. The negative electrode current collector according to claim 1, characterized in that: The thickness of the film substrate layer is 3um-10um.

3. The negative electrode current collector according to claim 2, characterized in that: The thickness of the aluminum oxide layer is 10nm-60nm, and the thickness of the copper metal layer is 100nm-1um.

4. The negative electrode current collector according to claim 3, characterized in that: The thickness of the PP film layer is 10nm-1um, and the thickness of the PET base film layer is 1um-9um.

5. The negative electrode current collector according to claim 1, characterized in that: Based on the total weight of the film substrate layer, the weight of the PET base film layer accounts for 80%-90%, and the weight of the PP film layer accounts for 10%-20%.

6. The negative electrode current collector according to claim 5, characterized in that: Conductive particles are arranged in both the PET base film layer and the PP film layer.

7. The negative electrode current collector according to claim 6, characterized in that: The weight proportion of the conductive particles in the PET base film layer is less than that in the PP film layer; based on the total weight of the PET base film layer, the weight proportion of the conductive particles in the PET base film layer is 20%-30%; based on the total weight of the PP film layer, the weight proportion of the conductive particles in the PP film layer is 50%-60%.

8. The negative electrode current collector according to claim 7, characterized in that: The conductive particles are made of metal or non-metal material.

9. A method for preparing a negative electrode current collector according to any one of claims 1 to 8, characterized in that: include: The PP film layer is bonded to both sides of the PET base film layer through a hot pressing composite process; An aluminum oxide layer is coated on the outside of the PP film layer by vacuum coating; A copper metal layer is plated on the outer side of the aluminum oxide layer by magnetron sputtering.

10. The method for preparing a negative electrode current collector according to claim 9, characterized in that: Before the step of coating the aluminum oxide layer on the outer side of the PP film layer by vacuum coating, the method further includes: treating the surface of the PP film layer by plasma equipment.

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