Multilayer aluminum current collector and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a multilayer aluminum current collector and a preparation method thereof. According to the invention, metal sputtering, rewinding oxidation and vacuum evaporation of a metal layer are carried out on the surface of a high-molecular base film through a magnetron sputtering process to obtain a finished product. The prepared finished current collector is stable in performance and high in reliability, and the problem that a metal coating is prone to falling off from the surface of a base material in an existing electrolyte environment can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, in particular to a multilayer aluminum current collector and a preparation method thereof. Background Art

[0002] In the application of lithium-ion batteries, the current collector is a key component, which mainly carries the electrode material and conducts electrons. Reasonable selection of the current collector is a prerequisite for the successful operation of lithium-ion batteries. At present, the positive electrode current collector uses a multilayer current collector with a "metal-polymer material-metal" structure to replace the traditional aluminum foil current collector. The polymer multilayer metal current collector is a new type of composite material made of a polymer material such as PET / PP as a base film, and a nano-scale metal is formed on the surface of the polymer base film by vacuum evaporation, magnetron sputtering, etc. It has obvious advantages in improving the safety of lithium-ion batteries and increasing the energy density of batteries.

[0003] The multilayer current collector material itself has advantages, but it still faces some problems, mainly due to the immaturity of equipment and process. Specific problems include the poor adhesion between the polymer substrate and the metal coating in the multilayer aluminum current collector product, which causes the metal coating to easily fall off the surface of the substrate in the electrolyte environment, seriously affecting the long-term stability of the current collector in the battery. In order to solve the problem of delamination of the multilayer current collector in the electrolyte, a method of introducing an intermediate layer such as aluminum oxide / silicon oxide between the substrate and the metal layer is usually adopted. This intermediate layer can utilize the bonding effect of the polymer on the surface of amorphous aluminum oxide / silicon oxide, thereby improving the bonding force between the substrate and the metal coating. However, the preparation of multilayer aluminum current collectors currently mostly uses vacuum evaporation coating to prepare a primer layer on a polymer film. Compared with the magnetron sputtering method, this deposition method is a rapid stacking of a large number of metal atoms, resulting in relatively poor adhesion and density of the prepared film. This poor adhesion and density further leads to poor adhesion between the primer layer and the polymer substrate and the metal coating, thereby causing problems such as cracking, discontinuity, unevenness or local dealumination of the metal layer. These problems significantly reduce the conductivity of the electrode material, increase the internal resistance of the battery, and thus cause battery safety issues. Therefore, it is necessary to develop new technologies to improve the bonding strength between the polymer base film and the metal coating.

[0004] In order to overcome the defects of the prior art, the present invention provides a multilayer aluminum current collector and a preparation method thereof. Summary of the invention

[0005] The object of the present invention is to provide a multilayer aluminum current collector and a preparation method thereof to solve the problems in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A multi-layer aluminum current collector comprises, from bottom to top, a polymer base film, a primer layer and a metal layer; the primer layer is any one of aluminum oxide and silicon oxide.

[0008] More optimally, the thickness of the base layer is 1-50 nm; the polymer base film is any one of PET, PE, PP, PEN, PPTA, PI, PC, PEEK, POM, PPS, PPO, PVC, PA, and PTFE.

[0009] More optimally, the base layer is aluminum oxide; the thickness of the base layer is 2-10 nm; and the polymer base film is PET.

[0010] Preferably, the thickness of the multi-layer aluminum current collector is 3-13 μm.

[0011] More optimally, the base layer is prepared by magnetron sputtering metal and then rewinding oxidation. The rewinding oxidation forms a gradient change in the degree of oxidation from the inside to the outside of the film layer, specifically: the internal part in contact with the polymer base film has a lower oxygen content, forming relatively large grains, and the outside is in full contact with the air to quickly form a dense oxide film, resulting in a gradient film layer state with large grains inside and small grains outside.

[0012] A method for preparing a multilayer aluminum current collector comprises the following steps:

[0013] Step 1: Use magnetron sputtering process to sputter metal on the surface of polymer base film, and then rewind and oxidize to obtain the base layer;

[0014] Step 2: Prepare a metal layer on the surface of the base layer using a vacuum evaporation process to obtain a finished product.

[0015] More optimally, in step 1, the speed of the rewinding and oxidation of the base layer is 1-20 m / min; and the rewinding and oxidation is completed in an oxygen-containing environment.

[0016] More optimally, in step 1, the speed of rewinding and oxidizing the base layer is 2-15 m / min.

[0017] More optimally, in step 1, the magnetron sputtering process parameters are: argon gas flow rate is 500-900sccm, and power is 12-26kW.

[0018] More optimally, in step 2, the vacuum evaporation process parameters are: wire feeding rate is 350-400 mm / min, and winding speed is 13-15 m / min.

[0019] Beneficial effects of the present invention:

[0020] The present invention sputters metal on the surface of the polymer base film through a magnetron sputtering process, rewinds and oxidizes, and vacuum evaporates the metal layer to obtain a finished product. The present invention provides a method for preparing a multilayer aluminum current collector, which can effectively improve the bonding force between the base layer and the polymer base film and the metal coating, as follows:

[0021] 1. Compared with vacuum evaporation, the base film prepared by magnetron sputtering in the present invention has higher adhesion and density. Magnetron sputtering is to bombard the target material with high-energy particles, so that the target atoms are sputtered out and deposited on the substrate. After being deposited on the substrate, these high-energy particles still have a certain amount of energy, can migrate on the surface of the substrate and combine with other atoms. In comparison, vacuum evaporation coating is more difficult. In addition, magnetron sputtering is more likely to form O-AL bonds between the polymer base film and the base film, thereby forming a stronger bond between the polymer base film and the film layer. This bonding significantly improves the bonding force between the base film and the polymer substrate, and increases the adhesion and density of the base film.

[0022] 2. The present invention provides a method for preparing a multilayer aluminum current collector, which first performs magnetron sputtering of an aluminum layer, and then performs a post-rewinding oxidation treatment in the air, so that the film layer undergoes a slow oxidation process. This treatment method can refine the grains inside the film layer, increase the density of the film layer, and form a gradient change in the degree of oxidation from the inside to the outside of the film layer. Specifically, the oxygen content of the part in contact with the polymer base film is relatively low, and the grains formed are relatively large; the outside is fully in contact with the air, and a dense oxide film is quickly formed, which hinders the further reaction of oxygen and aluminum, forming a film layer state with large grains inside and small grains outside. The distribution of small grains fills the defects such as holes that appear in the large-grain film layer, further increasing the density of the film layer. This method not only improves the bonding force between the base layer and the polymer substrate and the metal coating, solves the problem that the metal coating is easy to fall off from the surface of the substrate in the existing electrolyte environment, but also makes the prepared multilayer aluminum current collector stable in performance and high in reliability. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1: Step 1: A 5 nm thick PET base film is sputtered with a magnetron sputtering process, and then rewound and oxidized to obtain a base layer; magnetron sputtering process parameters: argon gas flow rate is 800 sccm, power is 15 kW; the speed of rewinding and oxidizing the base layer is 10 m / min; the base layer is aluminum oxide;

[0025] Step 2: A metal aluminum layer is prepared on the surface of the base layer by a vacuum evaporation process to obtain a finished product; the wire feeding rate is 350 mm / min, and the winding speed is 13 m / min; the thickness of the multilayer aluminum current collector is 8 μm.

[0026] Example 2: It is basically the same as Example 1, except that the thickness of the magnetron sputtered aluminum layer is 10 nm, the parameters of the magnetron sputtering are an argon gas flow rate of 500 sccm, and a power of 26 kW.

[0027] Step 1: sputtering 10nm of metal aluminum on the surface of a PET base film with a thickness of 6μm by a magnetron sputtering process, and then rewinding and oxidizing to obtain a base layer; magnetron sputtering process parameters: argon gas flow rate of 500sccm, power of 26kW; the speed of rewinding and oxidizing the base layer is 10m / min; the base layer is aluminum oxide;

[0028] Step 2: A metal aluminum layer is prepared on the surface of the base layer by a vacuum evaporation process to obtain a finished product; the wire feeding rate is 350 mm / min, and the winding speed is 13 m / min; the thickness of the multilayer aluminum current collector is 8 μm.

[0029] Example 3: It is basically the same as Example 1, except that the speed of the bottom layer rewinding oxidation is 5m / min

[0030] Step 1: sputtering 5nm of metal aluminum on the surface of a PET base film with a thickness of 6μm by a magnetron sputtering process, and then rewinding and oxidizing to obtain a base layer; magnetron sputtering process parameters: argon gas flow rate of 800sccm, power of 15kW; the speed of rewinding and oxidizing the base layer is 5m / min; the base layer is aluminum oxide;

[0031] Step 2: A metal aluminum layer is prepared on the surface of the base layer by a vacuum evaporation process to obtain a finished product; the wire feeding rate is 350 mm / min, and the winding speed is 13 m / min; the thickness of the multilayer aluminum current collector is 8 μm.

[0032] Example 4: It is basically the same as Example 1, except that the speed of the bottom layer rewinding oxidation is 15m / min

[0033] Step 1: sputtering 5nm of metal aluminum on the surface of a PET base film with a thickness of 6μm by a magnetron sputtering process, and then rewinding and oxidizing to obtain a base layer; magnetron sputtering process parameters: argon gas flow rate of 800sccm, power of 15kW; the speed of rewinding and oxidizing the base layer is 15m / min; the base layer is aluminum oxide;

[0034] Step 2: A metal aluminum layer is prepared on the surface of the base layer by a vacuum evaporation process to obtain a finished product; the wire feeding rate is 350 mm / min, and the winding speed is 13 m / min; the thickness of the multilayer aluminum current collector is 8 μm.

[0035] Example 5: It is basically the same as Example 1, except that the thickness of the magnetron sputtered aluminum layer is 2 nm, the parameters of the magnetron sputtering are argon gas flow rate of 900 sccm, and power of 12 kW.

[0036] Step 1: sputtering 2nm of metal aluminum on the surface of a PET base film with a thickness of 6μm by a magnetron sputtering process, and then rewinding and oxidizing to obtain a base layer; magnetron sputtering process parameters: argon gas flow rate of 900sccm, power of 12kW; the speed of rewinding and oxidizing the base layer is 10m / min; the base layer is aluminum oxide;

[0037] Step 2: A metal aluminum layer is prepared on the surface of the base layer by a vacuum evaporation process to obtain a finished product; the wire feeding rate is 350 mm / min, and the winding speed is 13 m / min; the thickness of the multilayer aluminum current collector is 8 μm.

[0038] Example 6: basically the same as Example 1, except that the PET base film is replaced by a PP base film

[0039] Step 1: sputtering 5nm of metal aluminum on the surface of a 6μm thick PP base film by magnetron sputtering process, and then rewinding and oxidizing to obtain a base layer; magnetron sputtering process parameters: argon gas flow rate of 800sccm, power of 15kW; the speed of rewinding and oxidizing the base layer is 10m / min; the base layer is aluminum oxide;

[0040] Step 2: A metal aluminum layer is prepared on the surface of the base layer by a vacuum evaporation process to obtain a finished product; the wire feeding rate is 350 mm / min, and the winding speed is 13 m / min; the thickness of the multilayer aluminum current collector is 8 μm.

[0041] Comparative Example 1: The magnetron sputtering process in step 1 is replaced by a vacuum evaporation process, and the rewinding oxidation process is removed. The rest is the same as Example 1, and the specific steps are as follows: Step 1: A 5 nm aluminum oxide layer is evaporated on the surface of a PET base film with a thickness of 6 μm by a vacuum evaporation process to obtain a base layer; vacuum evaporation process parameters: oxygen flow rate is 1500 sccm, wire feeding amount is 100 mm / min, and winding speed is 200 m / min;

[0042] Step 2: Prepare a metal aluminum layer on the surface of the base layer using a vacuum evaporation process to obtain a finished multilayer aluminum current collector with a thickness of 8 μm; vacuum evaporation process parameters: wire feeding rate is 350 mm / min, and winding speed is 13 m / min.

[0043] Detection test:

[0044] Density test: refer to GB / T3850-2015, that is, the volume and mass of the base film are tested before the base layer and the metal aluminum coating, and then the volume and mass of the finished product are tested, so as to calculate the density data of the base layer and the metal aluminum layer.

[0045] Tensile strength test: Use a vertical tensile testing machine to test, and the final breaking value shall prevail.

[0046] Plating peeling force test: Cut a 120×50mm sample, stick the sample on a steel plate with 3M double-sided tape, roll it, and then stick 3M transparent tape on the sample. After rolling again, place the sample on the fixture of the electronic peeling force tester, and test to get the sample coating peeling force value. The results are as follows:

[0047]

[0048] Conclusion: The present invention creatively adopts magnetron sputtering and rewinding oxidation to prepare the base layer, which can effectively improve the bonding force between the base layer and the polymer base film and the metal coating, increase the adhesion and density of the base layer film, but has no obvious effect on the tensile strength.

[0049] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process method article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process method article or device.

[0050] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multilayer aluminum current collector, characterized in that: From bottom to top, there are polymer base film, primer layer and metal layer; the primer layer is any one of aluminum oxide and silicon oxide.

2. A multilayer aluminum current collector according to claim 1, characterized in that: The thickness of the base layer is 1-50nm; the polymer base film is any one of PET, PE, PP, PEN, PPTA, PI, PC, PEEK, POM, PPS, PPO, PVC, PA, and PTFE.

3. A multilayer aluminum current collector according to claim 2, characterized in that: The bottom layer is aluminum oxide; the thickness of the bottom layer is 2-10 nm; and the polymer base film is PET.

4. A multilayer aluminum current collector according to claim 1, characterized in that: The thickness of the multi-layer aluminum current collector is 3-13 μm.

5. The multi-layer aluminum current collector according to claim 1, characterized in that: The base layer is prepared by magnetron sputtering metal and then rewinding oxidation. The rewinding oxidation forms a gradient change in the degree of oxidation from the inside to the outside of the film layer, specifically: the internal part in contact with the polymer base film has a lower oxygen content, forming relatively large grains, and the external part is in full contact with the air to quickly form a dense oxide film, thereby obtaining a gradient film layer state with large grains inside and small grains outside.

6. A method for preparing a multilayer aluminum current collector, characterized in that: The following steps are involved: Step 1: Use magnetron sputtering process to sputter metal on the surface of polymer base film, and then rewind and oxidize to obtain the base layer; Step 2: Prepare a metal layer on the surface of the base layer using a vacuum evaporation process to obtain a finished product.

7. The method for preparing a multilayer aluminum current collector according to claim 6, characterized in that: In step 1, the speed of the rewinding and oxidation of the base layer is 1-20 m / min; and the rewinding and oxidation is completed in an oxygen-containing environment.

8. The method for preparing a multilayer aluminum current collector according to claim 7, characterized in that: In step 1, the speed of rewinding and oxidizing the base layer is 2-15 m / min.

9. The method for preparing a multilayer aluminum current collector according to claim 6, characterized in that: In step 1, the magnetron sputtering process parameters are: argon gas flow rate is 500-900sccm, and power is 12-26kW.

10. The method for preparing a multi-layer aluminum current collector according to claim 6, characterized in that: In step 2, the vacuum evaporation process parameters are: wire feeding rate is 350-400 mm / min, and winding speed is 13-15 m / min.

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