Negative current collector

Abstract

The utility model discloses a cathode current collector which comprises a film substrate layer and aluminum oxide layers arranged on the upper side and the lower side of the film substrate layer, and copper metal layers are arranged on the outer sides of the aluminum oxide layers. 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 utility model relates to battery technology field especially relates to a negative electrode current collector. BACKGROUND

[0002] The composite current collector is a new type of battery current collector structure, which is combined with different materials (such as metal and polymer material) into a multilayer or composite structure to optimize the battery performance.

[0003] The current composite current collector includes a negative electrode composite current collector and a positive electrode composite current collector, and the negative electrode composite current collector and the positive electrode composite current collector are both provided with a metal layer on both sides of a film. The film of the negative electrode composite current collector is all PP film in the industry, and the film of the positive electrode composite current collector is all PET film in the industry, because the bonding force of the PP film with the metal layer is not as good as that of the PET film, but the PP film will not swell at the negative electrode of the battery, while the PET film will swell at the negative electrode.

[0004] In order to make the metal layer and the PP film have better bonding force, some additives are added to the PP film in the industry, but this requires a new production line to develop a corresponding film or requires a film supplier to develop a new film for the composite current collector manufacturer, which undoubtedly increases the cost of producing the composite current collector. Higher cost will increase the selling price of the composite current collector, resulting in that the composite current collector loses the price advantage compared with the traditional current collector, affecting the sales of the composite current collector. It is also common in the industry to coat a material containing an adhesive on the composite current collector in order to increase the bonding force of the metal layer and the film on the composite current collector. Similarly, this method greatly increases the cost, affects the final sales, and also reduces the energy density of the battery. Both of the above methods are not desirable. The negative electrode current collector formed by directly forming a metal layer on the PP film cannot meet the requirements in terms of bonding force and sheet resistance.

[0005] Therefore, the prior art still needs to be improved and improved. UTILITY MODEL CONTENT

[0006] In view of the above shortcomings of the prior art, the purpose of the utility model is to provide a negative electrode current collector to solve the problem of poor bonding force of the existing negative electrode current collector in the background art.

[0007] In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0008] A negative electrode current collector comprises a film base material layer and aluminum oxide layers arranged on the upper and lower sides of the film base material layer, and a copper metal layer is arranged on the outer side of the aluminum oxide layer; the film base material 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 thin 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 thin film substrate layer, the weight percentage of the PET base film layer is 80%-90%, and the weight percentage of the PP film layer is 10%-20%.

[0013] The PET base film layer and the PP film layer are both provided with conductive particles.

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

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

[0016] The average particle size of the conductive particles is larger than that of the copper metal particles in the copper metal layer.

[0017] The outer surface of the PP film layer is treated by a plasma device, and the roughness of the outer surface of the PP film layer is 0.1um-1um.

[0018] Compared with the prior art, the negative current collector provided by the utility model comprises a thin film substrate layer and aluminum oxide layers arranged on the upper and lower sides of the thin film substrate layer, and the outer side of the aluminum oxide layer is provided with a copper metal layer; the thin film substrate layer comprises a PET base film layer and PP film layers arranged on the two sides of the PET base film layer. The negative current collector structure in the application can reduce the production cost of the negative current collector and improve the bonding force between the layers of the negative current collector. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The utility model provides a structure schematic view of the negative current collector.

[0020] Figure 2 The utility model provides a preparation method flow chart schematic view of the negative current collector. DETAILED DESCRIPTION

[0021] To make the purpose, technical scheme and effect of the utility model more clear and definite, the utility model will be further explained in detail below with reference to the drawings and examples.

[0022] It should be noted that when a component is referred to as being "mounted on", "fixed on" or "disposed on" another component, it can be directly on the other component or a middle component can be present at the same time.

[0023] It should also be noted that the terms left, right, up, down and the like in the embodiments of the utility model are merely relative concepts or are referenced to the normal use state of the product, and should not be considered as limiting.

[0024] The composite current collector is a new type of battery current collector structure, which combines different materials (such as metal and polymer materials) into a multi-layer or composite structure to optimize battery performance.

[0025] The current composite current collector includes a negative composite current collector and a positive composite current collector, and the negative composite current collector and the positive composite current collector are both provided with a metal layer on both sides of a film. The film of the negative composite current collector is a PP film in the industry, and the film of the positive composite current collector is a PET film in the industry. The reason is that although the bonding force of the PP film with the metal layer is not as good as that of the PET film, the PP film will not swell at the negative electrode of the battery, while the PET film will swell at the negative electrode.

[0026] In order to make the metal layer and the PP film have better bonding force, some additives are added to the PP film in the industry, but this requires a new production line to develop a corresponding film or requires a film supplier to develop a new film for the composite current collector manufacturer, which undoubtedly increases the cost of producing the composite current collector. Higher cost will increase the selling price of the composite current collector, resulting in that the composite current collector loses the price advantage compared with the traditional current collector, affecting the sales of the composite current collector. It is also common in the industry to coat a material containing an adhesive on the composite current collector in order to increase the bonding force of the metal layer and the film on the composite current collector. Similarly, this method will greatly increase the cost, affect the final sales, and also reduce the energy density of the battery. Both of the above methods are not desirable. The negative current collector obtained by directly forming a metal layer on the PP film cannot meet the requirements in terms of bonding force and sheet resistance.

[0027] The application provides a negative current collector, which refers to Figure 1The negative electrode current collector structure comprises a film base material layer 1 and aluminum oxide layers 2 arranged on the upper and lower sides of the film base material layer 1, and the outer side of the aluminum oxide layer 2 is provided with a copper metal layer 3; the film base material layer 1 comprises a PET base film layer 11 and PP film layers 12 arranged on the two sides of the PET base film layer 11. The negative electrode current collector structure can reduce the production cost of the negative electrode current collector, improve the bonding force between the layers of the negative electrode current collector. In addition, the PET base film layer 11 is light in weight and good in flexibility, and the composite structure of the PET base film layer 11 and the PP film layer 12 as the film base material layer 1 is beneficial to reduce the weight of the negative electrode current collector and improve the flexibility of the structure; the PP film layers 12 on the two sides of the PET base film layer 11 further enhance the stability of the overall structure. The aluminum oxide layer 2 has good insulation and stability, and plays a role in isolating the copper metal layer 3, thereby reducing the occurrence of side reactions; the aluminum oxide layer 2 as a transition layer between the copper metal layer 3 and the film base material 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 film base material layer 1 from mechanical damage due to its high hardness and wear resistance, which is beneficial to enhance the service life of the negative electrode current collector. The drawings in the application do not limit the thickness of each film layer, but only show the structure of the negative electrode current collector.

[0028] Further, 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 base material layer 1. The PP film layer 12 is relatively thin but can play a role in protecting and assisting the stability of the PET base film layer 11, and at the same time will not increase the weight too much; the PET base film layer 11 as the main support layer has a suitable thickness to ensure sufficient mechanical strength and flexibility. In the embodiment of the application, the middle of the film base material 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 base material layer 1, the application uses the PET base film layer 11 as the base film and the PP film layer 12 on both sides. 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℃, and the melting point of the PET base film layer 11 is above 260℃. Therefore, when the copper metal layer 3 is plated, the copper particles are not easy to burn through the film base material layer 1 into pinholes, which is beneficial to reduce the holes.

[0029] Further, the thickness of the thin film substrate layer 1 is 3um-10um. In the embodiment of the present application, the thickness of the thin film substrate layer 1 is too large to increase the production cost and the weight of the negative electrode current collector, and more importantly, the surface tension is smaller, which affects the binding force of the thin film substrate layer 1 and the aluminum oxide layer 2. By limiting the thickness of the thin film substrate layer 1, it is ensured that the negative electrode current collector has good flexibility and certain mechanical strength, and will not increase too much weight due to too thick, affecting the battery energy density; also will not cause mechanical performance deficiency, resulting in damage and other problems in the process of battery manufacturing and use.

[0030] Further, 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, on the one hand, the cost increases, on the other hand, the weight of the negative electrode current collector increases, and 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, and the thickness of the PP film layer 12 and 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 aluminum oxide layer 2 within the thickness range has good insulation performance and chemical stability, which can effectively isolate and protect the copper metal layer 3; the copper metal layer 3 within the range ensures good electrical conductivity, meets the electrical conductivity requirements of the negative electrode current collector, and also will not cause weight increase due to too thick.

[0031] Further, based on the total weight of the thin film substrate, the weight ratio of the PET film layer 11 is 80%-90%, and the weight ratio of the PP film layer 12 is 10%-20%. In the embodiment of the present application, because the heat resistance of the PET film is good, by limiting the relative weight of the PET film layer 11 and the PP film layer 12 in the thin film substrate, the defects such as line wrinkles in the film plating process are reduced. In addition, the weight ratio of the PET film layer 11 and the PP film layer 12 is set, on the one hand, the production cost of the negative electrode current collector is reduced, and on the other hand, the weight, flexibility and mechanical stability of the negative electrode current collector are balanced. A higher proportion of the PET film layer 11 ensures the lightness and flexibility of the negative electrode current collector, and an appropriate amount of the PP film layer 12 enhances the stability of the overall structure.

[0032] Further, the PET base film layer 11 and the PP film layer 12 are both provided with conductive particles; the traditional PET film is a polyethylene terephthalate film, and the traditional PP film is a polypropylene film. In the present application, conductive particles are added to the traditional film layer. On the one hand, the resistivity of the thin film base material layer 1 can be reduced, and when the thin film base material layer 1 is applied to the battery current collector, the capacity loss during the charging and discharging process of the battery can be effectively reduced, the charging and discharging efficiency of the battery is improved, and on the other hand, the electron conduction in the current collector is fast, and the high-rate charging and discharging performance of the battery is improved. 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 surface of the film layer, and thus improve the stability and reliability of the negative electrode current collector.

[0033] The weight percentage of the conductive particles in the PET base film layer 11 is less than the weight percentage of the conductive particles in the PP film layer. The total weight percentage of the conductive particles in the PET base film layer 11 is 20%-30% based on the total weight of the PET base film layer 11. The weight percentage of the conductive particles in the PP film layer 12 is 50%-60% based on the total weight of the PP film layer 12. When the tab is welded, the internal resistance at the tab welding position can be reduced. At the same time, the heat conduction performance of the current collector can be improved and the cost can be reduced due to the smaller amount of conductive particles in the PET.

[0034] Further, the PET base film layer 11 is provided with metal oxides with a certain hardness. The metal oxides in the PET base film layer 11 will react with hydrogen fluoride to reduce the corrosion of the PET base film layer 11 by hydrogen fluoride when hydrogen fluoride penetrates into the PET base film layer 11 during the working process of the lithium battery. The metal oxides have a certain hardness, which improves the puncture resistance of the current collector. The specific metal oxides can be alumina or other materials, which can be selected according to the actual situation, and the present application does not limit it. The weight percentage of the metal oxides in the PET base film layer 11 is 10%-15% based on the weight of the PET base film layer 11. The PP film layer 12 is provided with a desiccant with a weight percentage of 1%-5% based on the weight of the PP film layer 12. The water produced by the reaction of the metal oxides in the PET base film layer 11 with hydrogen fluoride can be absorbed by the desiccant in the PP film layer 12, which ensures the stability of the battery.

[0035] In the present application, the average particle size of the conductive particles is greater than the average particle size of the copper metal particles in the copper metal layer 3, which can reduce the burning of the thin film base material layer 1 to form a pinhole when the copper metal layer 3 is formed.

[0036] Further, the conductive particles are metallic or non-metallic. In the embodiments of the present application, the conductive particles can be metallic copper, aluminum, titanium, nickel, etc., or carbon or other non-metallic materials with similar or identical properties. The specific material of the conductive particles is not limited in the present application, and can be selected as appropriate according to actual conditions.

[0037] The present application also provides a preparation method of the negative electrode current collector, please refer to Figure 1 and Figure 2 , comprising:

[0038] S1, combining the PP film layer 12 on both sides of the PET base film layer 11 by hot pressing composite process;

[0039] S2, plating an aluminum oxide layer 2 on the outside of the PP film layer 12 by vacuum plating;

[0040] S3, plating a copper metal layer 3 on the outside of the aluminum oxide layer 2 by magnetron sputtering.

[0041] In the present application, the PP film layer 12 is tightly combined on both sides of the PET base film layer 11 by hot pressing composite process, which comprises: combining the PP film layer 12 and the PET base film layer 11 by heating and pressing 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 heating temperature of the PET base film layer 11 can be selected between 60℃-150℃, the pressing time of the PP film layer 12 can be selected between 1 minute-2 minutes, and the pressing pressure range is between 0.5Mpa-2Mpa. First, the aluminum oxide layer 2 is plated on the outside of the PP film layer 12 by vacuum evaporation device, and then the copper metal layer 3 is plated on the outside of the aluminum oxide layer 2 by magnetron sputtering device. The advantage is that the energy generated by magnetron sputtering plating film is high and strong, which is beneficial to the combination of the copper metal layer 3 on the aluminum oxide layer 2, and on the other hand, the aluminum oxide layer 2 is firmly fixed on the PP film layer 12 during the magnetron sputtering process, further improving the bonding force between the aluminum oxide layer 2 and the thin film base layer 1.

[0042] After the PP film layer 12 is tightly combined on both sides of the PET base film layer 11 by hot pressing composite process, and before the aluminum oxide layer 2 is plated on the outside of the PP film layer 12 by vacuum plating, the outer surface of the combined 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.

[0043] In the preparation method of the negative current collector, the vacuum evaporation device for plating the aluminum oxide layer 2 on the outer side of the PP film layer 12 by vacuum plating and the plasma treatment device for treating the outer surface of the composite PP film layer 12 can be arranged in one equipment, which is beneficial to improve the preparation efficiency of the negative current collector. Similarly, the vacuum evaporation device for plating the aluminum oxide layer 2 on the outer side of the PP film layer 12 by vacuum plating and the magnetron sputtering device for plating the copper metal layer 3 on the outer side of the aluminum oxide layer 2 by magnetron sputtering can be arranged in one equipment, which is also beneficial to improve the preparation efficiency of the negative current collector.

[0044] In conclusion, the negative current collector provided by the utility model comprises a film base material layer and aluminum oxide layers arranged on the upper and lower sides of the film base material layer, and a copper metal layer is arranged on the outer side of the aluminum oxide layer; the film base material layer comprises a PET base film layer and PP film layers located on the two sides of the PET base film layer. The negative current collector structure in the application can reduce the production cost of the negative current collector and improve the bonding force between the layers of the negative current collector.

[0045] It can be understood that, for those skilled in the art, equivalent replacement or change can be made according to the technical scheme and the utility model concept of the utility model, and all these changes or replacements shall belong to the protection scope of the claims attached to the utility model.

Claims

1. A negative electrode current collector, characterized by, The application relates to a thin film substrate layer and aluminum oxide layers arranged on the upper and lower sides of the thin film substrate layer, and a copper metal layer arranged on the outer side of the aluminum oxide layer. The thickness of the thin film substrate layer is 3-10 um.

2. The negative current collector according to claim 1, wherein The thickness of the aluminum oxide layer is 10-60 nm, and the thickness of the copper metal layer is 100 nm-1 um.

3. The negative current collector according to claim 2, wherein The thickness of the PP film layer is 10 nm-1 um, and the thickness of the PET base film layer is 1-9 um.

4. The negative current collector according to claim 3, wherein The weight percentage of the PET base film layer is 80-90% based on the total weight of the thin film substrate layer, and the weight percentage of the PP film layer is 10-20%.

5. The negative current collector according to claim 1, wherein The PET base film layer and the PP film layer are both provided with conductive particles.

6. The negative current collector according to any one of claims 1 to 5, wherein The weight percentage of the conductive particles in the PET base film layer is less than that in the PP film layer; the weight percentage of the conductive particles in the PET base film layer is 20-30% based on the total weight of the PET base film layer; and the weight percentage of the conductive particles in the PP film layer is 50-60% based on the total weight of the PP film layer.

7. The negative current collector according to claim 6, wherein The conductive particles are metallic or non-metallic.

8. The negative current collector according to claim 7, wherein The average particle size of the conductive particles is larger than that of the copper metal particles in the copper metal layer.

9. The negative current collector according to claim 7, wherein The outer surface of the PP film layer is treated by a plasma device, and the roughness of the outer surface of the PP film layer is 0.1-1 um.

10. The negative current collector according to claim 1, wherein ​

Images