Anti-fatigue gradient Ag multilayer structure metal thin film and preparation method and application thereof

Abstract

The application discloses an anti-fatigue gradient Ag multilayer structure metal film and a preparation method and application thereof, and belongs to the technical field of battery current collectors. The anti-fatigue gradient Ag multilayer structure metal film is made of a substrate and two gradient Ag films, the two gradient Ag films are symmetrically deposited on two sides of the substrate, each gradient Ag film is composed of a plurality of Ag layers with the same thickness, the Ag layers are stacked, and in each Ag layer, the grain orientation is from the substrate to the surface, and the (111) texture intensity presents gradient decrease, gradient increase or first gradient decrease and then gradient increase. The anti-fatigue gradient Ag multilayer structure metal film is characterized in that: the thickness of each Ag layer is consistent, and the deposition air pressure in the preparation process is designed to follow a specific gradient change mode, the grain orientation of different Ag layers is changed by controlling the deposition air pressure, the crack initiation and propagation are inhibited, the fatigue performance is optimized, and the fatigue life is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of battery current collector technology, specifically relating to a fatigue-resistant gradient Ag multilayer metal thin film, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, due to their superior performance such as high energy density, long cycle life, and environmental friendliness, have been widely used in new energy vehicles, electronic devices, and energy storage systems. Current collectors are a crucial component of lithium-ion batteries, serving as a conductive framework and mechanical support, collecting electrode current, transmitting electrons, and supporting the active material coating. However, traditional current collectors are often metal foils, and this single-metal structure has significant shortcomings: metal foils account for 15% to 20% of the battery's non-active components, hindering breakthroughs in energy density; simultaneously, during charge-discharge cycles, lithium dendrites can puncture the separator, and traditional current collectors, as continuous conductors, cannot block short-circuit currents, becoming a weak point in a thermal runaway chain reaction.

[0003] The flexible substrate-flexible metal thin film system possesses both excellent mechanical flexibility and superior conductivity. Composite current collectors with a "metal-polymer-metal" sandwich structure prepared using this system are lightweight due to the use of a lower-density polymer instead of a metal substrate. Simultaneously, the intermediate insulating layer actively intercepts lithium dendrites; even if one side of the metal is punctured, the polymer barrier layer can still cut off the electron pathway, fundamentally suppressing internal short circuits. Compared to traditional current collectors, composite current collectors offer advantages such as high energy density, low cost, and high safety.

[0004] In practical applications, during the charging and discharging process of lithium-ion batteries, the diffusion of lithium ions within the active material creates an internal concentration gradient, leading to non-uniform volume deformation of the active material. Since the active material layer is tightly coated onto the current collector surface, the current collector is further subjected to stress loading. As charge-discharge cycles continue, the current collector will experience fatigue failure under these cyclic loads, resulting in a sharp decline in electrical performance and even device failure. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention proposes a fatigue-resistant gradient Ag multilayer metal thin film, its preparation method, and its application. The fatigue-resistant gradient Ag multilayer metal thin film of this invention is made of a substrate and two gradient Ag films. The two gradient Ag films are symmetrically deposited on both sides of the substrate. Each gradient Ag film consists of several Ag layers of the same thickness, stacked together. In each Ag layer, the grain orientation extends from the substrate to the surface, and the texture intensity exhibits a gradient decrease, gradient increase, or a gradient decrease followed by a gradient increase. The orientation gradient structure effectively delays the initiation of fatigue cracks and inhibits their subsequent propagation, significantly improving the fatigue performance of the fatigue-resistant gradient Ag multilayer metal thin film and extending the fatigue life of the composite current collector.

[0006] Based on the above-mentioned technical objectives, the present invention is achieved through the following technical solution:

[0007] This invention protects a fatigue-resistant gradient Ag multilayer metal thin film, which is made of a substrate and two gradient Ag films, which are symmetrically deposited on both sides of the substrate.

[0008] The fatigue-resistant gradient Ag multilayer metal thin film is composed of several Ag layers of the same thickness. The same layer thickness is designed to avoid variables caused by different layer thicknesses. Each Ag layer is stacked. In each Ag layer, the grain orientation is from the substrate to the surface. (111) The texture intensity shows a gradient decrease, gradient increase, or first gradient decrease and then gradient increase, so as to realize the difference of Schmid factor between different layers. The embodiment of the present invention uses 5 layers to reflect the changes between each layer, and can also design other layers.

[0009] Preferably, the thickness of the fatigue-resistant gradient Ag multilayer metal thin film is 500nm~2000nm.

[0010] Preferably, the matrix is ​​selected from a flexible polymer matrix.

[0011] This invention also protects a method for preparing fatigue-resistant gradient Ag multilayer metal thin films, characterized by comprising the following steps:

[0012] In an argon atmosphere, a DC magnetron sputtering process is used to co-sputter and deposit different Ag layers on a substrate according to the requirements for Ag grain size in different Ag layers. By adjusting the deposition gas pressure, different Ag layers are deposited sequentially. After deposition, the substrate is cooled to room temperature to obtain a fatigue-resistant gradient Ag multilayer metal film. This invention utilizes magnetron sputtering deposition technology to control the Ag grain orientation by changing the deposition gas pressure, thereby constructing a fatigue-resistant gradient Ag multilayer metal film with texture variations from the substrate to the surface.

[0013] Among them, (111) the texture intensity shows a gradient decrease, while the deposition gas pressure gradient increases.

[0014] (111) If the texture intensity shows a gradient increase, then the deposition gas pressure gradient decreases.

[0015] (111) If the texture intensity decreases first and then increases, the deposition gas pressure increases first and then decreases.

[0016] Preferably, (111) the depositional gas pressure with a gradient decrease in texture intensity is 0.1 Pa to 2 Pa; (111) the depositional gas pressure with a gradient increase in texture intensity is 2 Pa to 0.1 Pa; (111) the depositional gas pressure with a gradient decrease in texture intensity followed by a gradient increase is: first from 0.1 Pa to 2 Pa, and then from 2 Pa to 0.1 Pa.

[0017] Preferably, (111) the depositional gas pressure with a gradient decrease in texture intensity is 0.3 Pa to 1.3 Pa; (111) the depositional gas pressure with a gradient increase in texture intensity is 1.3 Pa to 0.3 Pa; (111) the depositional gas pressure with a gradient decrease in texture intensity followed by a gradient increase is: first from 0.3 Pa to 1.3 Pa, then from 1.3 Pa to 0.3 Pa.

[0018] Preferably, the DC magnetron sputtering method is as follows: at room temperature, under the conditions of deposition power of 50W~300W, rotation speed of 10r / min~30r / min, and argon flow rate of 20sccm-60sccm, different Ag layers are deposited on the substrate.

[0019] This invention also protects the application of fatigue-resistant gradient Ag multilayer metal thin films in the preparation of current collectors.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The fatigue-resistant gradient Ag multilayer metal thin film proposed in this invention, during its fabrication, increases the density of argon gas in the chamber as the deposition gas pressure increases, generating more argon ions after ionization. These argon ions collide with the Ag target, exciting more sputtered particles, which then deposit onto the substrate surface. During their journey to the substrate surface, these sputtered particles frequently collide with gas molecules in the high-density argon environment, resulting in energy loss and a significant reduction in energy. Consequently, these sputtered particles lack sufficient kinetic energy for effective surface migration upon reaching the substrate surface. Therefore, with increasing deposition gas pressure, the Ag grain size decreases, and the Ag grain orientation tends to become disordered. In the fabrication process of the fatigue-resistant gradient Ag multilayer metal thin film, the changing deposition gas pressure of different Ag layers causes a gradient change in the orientation of Ag grains from the surface to the substrate.

[0022] Gradient structures induce strength and hardening due to heterogeneous deformation. This strengthening helps reduce the plastic strain amplitude of the surface layer, decreases plastic strain accumulation, and delays fatigue crack initiation. Gradient structures also provide a "graded yielding" mechanism. Due to different Schmid factors, different Ag layers (orientation layers) have different yield strengths. Under cyclic loading, not all Ag layers simultaneously achieve significant plastic deformation. The "softer" layers (Ag layers with larger Schmid factors are "softer" and more prone to slip) first undergo plastic deformation to absorb energy, while the "harder" layers (Ag layers with smaller Schmid factors are "harder" and less prone to slip) provide support, achieving good fatigue resistance through different plastic deformation capabilities. This continuous, hierarchical plastic deformation capability helps disperse cyclic plastic strain, suppressing its severe concentration at a single location (such as the surface or specific grain boundaries), thereby delaying crack initiation. Furthermore, gradient structures alter the stress / strain field at the crack tip, causing fatigue crack deflection, increasing the crack propagation path, and improving propagation resistance. Attached Figure Description

[0023] To clearly illustrate the technical details of the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below. It should be understood that the following drawings only illustrate some embodiments of the present invention and should not be considered as limiting its scope of protection. For those skilled in the art, other related drawings can be derived from these drawings without any inventive effort.

[0024] Figure 1 In the figure, (a) is the XRD pattern of the fatigue-resistant gradient Ag multilayer metal thin film of Examples 1 to 3, and (b) is the XRD pattern of the Ag metal thin film of Comparative Examples 1 to 5.

[0025] Figure 2 In the figures, (a) to (c) are schematic diagrams of the fatigue-resistant gradient Ag multilayer metal thin films of Examples 1 to 3, respectively, and (d) to (f) are schematic diagrams of the Ag metal thin films of Comparative Examples 1, 3 and 5, respectively.

[0026] Figure 3 In the figure, (a), (c) and (e) are TEM images of Ag metal thin films of Comparative Example 1, Comparative Example 3 and Comparative Example 5, respectively, and (b), (d) and (f) are grain size distribution diagrams of Ag metal thin films of Comparative Example 1, Comparative Example 3 and Comparative Example 5, respectively.

[0027] Figure 4In the figure, (a), (c) and (e) are TKD cross-sectional photographs of the fatigue-resistant gradient Ag multilayer structure metal thin films of Examples 1, 3 and 5, respectively, and (b), (d) and (f) are statistical diagrams of the layered (111) texture strength of the fatigue-resistant gradient Ag multilayer structure metal thin films of Examples 1, 3 and 5, respectively.

[0028] Figure 5 The graphs show the resistance of the fatigue-resistant gradient Ag multilayer metal films of Examples 1 and 3, and the Ag metal films of Comparative Examples 1, 3, and 5 as a function of fatigue cycles. Detailed Implementation

[0029] To clearly illustrate the objectives, technical solutions, and advantages of the embodiments of the present invention, the technical solutions in this embodiment will be comprehensively and thoroughly described below with reference to the accompanying illustrations. It should be noted that the embodiments shown and described represent only a portion of the embodiments of the present invention, and not all of them. Generally, the layout and design of the components in the illustrations of the embodiments of the present invention can be adjusted according to various different configurations.

[0030] This invention provides a fatigue-resistant gradient Ag multilayer metal thin film for composite current collectors, with a thickness of 1000 nm. It consists of different Ag layers prepared by different DC magnetron sputtering deposition gas pressures, and successfully prepares gradient Ag multilayer metal thin films with different grain orientations.

[0031] In some embodiments, the thickness of each Ag layer in the fatigue-resistant gradient Ag multilayer metal thin film is the same, each being 200 nm, with a total of five layers and a total thickness of 1000 nm; the deposition gas pressure of each Ag layer increases gradually from the substrate to the surface.

[0032] In some embodiments, the thickness of each Ag layer in the fatigue-resistant gradient Ag multilayer structure metal thin film is the same, each being 200 nm, with a total of five layers and a total thickness of 1000 nm; the deposition gas pressure of each Ag layer changes from the substrate to the surface in a manner that first increases and then decreases.

[0033] In some embodiments, the thickness of each Ag layer in the fatigue-resistant gradient Ag multilayer metal thin film is the same, each being 200 nm, with a total of five layers and a total thickness of 1000 nm; the deposition pressure of each Ag layer decreases gradually from the substrate to the surface.

[0034] This fatigue-resistant gradient Ag multilayer metal film, under a fatigue strain amplitude of 1%, after 1×10⁻⁶ days... 5 After repeated pull-pull cycles, the resistance change is at least within 4%.

[0035] Correspondingly, the present invention also provides a method for preparing fatigue-resistant gradient Ag multilayer metal thin films, comprising the following steps:

[0036] In a vacuum environment, a DC magnetron sputtering process is used to sequentially deposit Ag layers on a substrate. The deposition time for each Ag layer is the same, but the deposition gas pressure is determined according to the setting. After reaching the set number of layers, the substrate is cooled to room temperature to obtain a fatigue-resistant gradient Ag multilayer metal thin film.

[0037] In the preparation process, the substrate is first cleaned and dried, then etched, and then the target is pre-sputtered to remove the adsorbed substances on the target surface. Finally, DC magnetron sputtering is performed on the etched and cleaned substrate to deposit a gradient multilayer Ag layer.

[0038] In some embodiments, the substrate etching and pre-sputtering methods are as follows:

[0039] The cleaned polyimide substrate was fixed onto the base plate and placed into the coating chamber. Then, the back vacuum of the chamber was evacuated to 4.0 × 10⁻⁶. -4 Below Pa, using Ar + Ions are used for etching and cleaning to further remove impurities from the substrate surface. The etching power is 100W~300W, the argon gas pressure is 0.3Pa~1Pa, and the etching time is 3min~8min.

[0040] Then, pre-sputtering is performed. Before pre-sputtering, argon gas is introduced for 30 seconds at a flow rate of 40 sccm. Then, pre-sputtering is performed for 30 seconds to remove adsorbed substances from the surface of the target material.

[0041] This invention employs magnetron sputtering technology to prepare gradient multilayer Ag thin films under specific gas pressure. This preparation method is not only simple to operate and cost-effective, but also possesses good scalability, making it suitable for large-scale industrial production. This invention introduces a high-performance composite current collector innovation solution to the battery industry, aiming to effectively solve the problem of insufficient fatigue resistance in current composite current collectors, thereby promoting the continuous advancement of composite current collectors and their widespread practical applications.

[0042] Example 1

[0043] A method for preparing a fatigue-resistant gradient Ag multilayer metal thin film includes the following steps:

[0044] Step 1: Place the polyimide matrix in anhydrous ethanol and ultrasonically clean it for 15 minutes, then quickly dry it to ensure that the surface of the polyimide matrix is ​​clean and free of impurities.

[0045] Step 2: Fix the cleaned polyimide substrate onto the base plate and place it into the coating chamber. Then, evacuate the back vacuum to 4.0 × 10⁻⁶. -4Etching begins at a pressure below Pa to remove impurities from the surface of the polyimide substrate. The etching power is 200W, the etching pressure is 0.5Pa, and the time is 5min, resulting in an etched polyimide substrate.

[0046] Step 3: Prepare a gradient Ag film on an etched polyimide substrate using DC magnetron sputtering.

[0047] Argon gas was first introduced for 30 seconds to reach the working pressure, and the target was pre-sputtered for 30 seconds. Then, a high-purity Ag target (purity of 99.995 wt.%) was used to deposit an Ag layer on the etched polyimide substrate. The deposition power was 120 W, the disk rotation speed was 15 r / min, the argon flow rate was 40 sccm, and the deposition was carried out at room temperature. A total of five Ag layers were deposited, each with a thickness of 200 nm. The deposition pressure increased gradually from the etched polyimide substrate to the surface. The deposition pressures of the Ag layers from the etched polyimide substrate to the surface were 0.3 Pa, 0.5 Pa, 0.8 Pa, 1.0 Pa, and 1.3 Pa, respectively.

[0048] The sputtering rate of the Ag target was 0.36 nm / s, and the sputtering time of each Ag layer was 556 s. After each Ag layer was deposited, there was a 30 s interval before the next layer was deposited. The total sputtering time was 2900 s. After sputtering, the film was naturally cooled to room temperature in the vacuum coating chamber for 1 h before being taken out, resulting in a gradient Ag film with a thickness of 1000 nm.

[0049] S4. After the deposition on one side of the cleaned polyimide substrate is completed, the cleaned polyimide substrate is flipped over, and the operations of steps 2 and 3 are repeated on the other side of the cleaned polyimide substrate to symmetrically deposit gradient Ag films on both sides of the cleaned polyimide substrate and obtain fatigue-resistant gradient Ag multilayer metal thin films.

[0050] The microstructure of the gradient Ag film on one side of the fatigue-resistant gradient Ag multilayer metal thin film prepared in Example 1 was characterized. The grain orientation was from the etched polyimide matrix to the surface, and the texture intensity (111) showed a decreasing trend.

[0051] Example 2

[0052] A method for preparing a fatigue-resistant gradient Ag multilayer metal thin film includes the following steps:

[0053] Step 1: Place the polyimide matrix in anhydrous ethanol and ultrasonically clean it for 15 minutes, then quickly dry it to ensure that the surface of the polyimide matrix is ​​clean and free of impurities.

[0054] Step 2: Fix the cleaned polyimide substrate onto the base plate and place it into the coating chamber. Then, evacuate the back vacuum to 4.0 × 10⁻⁶. -4Etching begins at a pressure below Pa to remove impurities from the surface of the polyimide substrate. The etching power is 200W, the etching pressure is 0.5Pa, and the time is 5min, resulting in an etched polyimide substrate.

[0055] Step 3: Prepare a gradient Ag film on an etched polyimide substrate using DC magnetron sputtering.

[0056] Argon gas was first introduced for 30 seconds to reach the working pressure, and the target was pre-sputtered for 30 seconds. Then, a high-purity Ag target (purity 99.995 wt.%) was used to deposit an Ag layer on the etched polyimide substrate. The deposition power was 120 W, the disk rotation speed was 15 r / min, the argon flow rate was 40 sccm, and the deposition was carried out at room temperature. A total of five Ag layers were deposited, each with a thickness of 200 nm. The deposition pressure increased first and then decreased from the etched polyimide substrate to the surface. The deposition pressures of the Ag layers from the etched polyimide substrate to the surface were 0.3 Pa, 0.8 Pa, 1.3 Pa, 0.8 Pa, and 0.3 Pa, respectively.

[0057] The sputtering rate of the Ag target was 0.36 nm / s, and the sputtering time of each Ag layer was 556 s. After each Ag layer was deposited, there was a 30 s interval before the next layer was deposited. The total sputtering time was 2900 s. After sputtering, the film was naturally cooled to room temperature in the vacuum coating chamber for 1 h before being taken out, resulting in a gradient Ag film with a thickness of 1000 nm, which is a fatigue-resistant gradient Ag multilayer metal thin film.

[0058] S4. After the deposition on one side of the cleaned polyimide substrate is completed, the cleaned polyimide substrate is flipped over, and the operations of steps 2 and 3 are repeated on the other side of the cleaned polyimide substrate to symmetrically deposit gradient Ag films on both sides of the cleaned polyimide substrate and obtain fatigue-resistant gradient Ag multilayer metal thin films.

[0059] Example 3

[0060] A method for preparing a fatigue-resistant gradient Ag multilayer metal thin film includes the following steps:

[0061] Step 1: Place the polyimide matrix in anhydrous ethanol and ultrasonically clean it for 15 minutes, then quickly dry it to ensure that the surface of the polyimide matrix is ​​clean and free of impurities.

[0062] Step 2: Fix the cleaned polyimide substrate onto the base plate and place it into the coating chamber. Then, evacuate the back vacuum to 4.0 × 10⁻⁶. -4 Etching begins at a pressure below Pa to remove impurities from the surface of the polyimide substrate. The etching power is 200W, the etching pressure is 0.5Pa, and the time is 5min, resulting in an etched polyimide substrate.

[0063] Step 3: Prepare a gradient Ag film on an etched polyimide substrate using DC magnetron sputtering.

[0064] Argon gas was first introduced for 30 seconds to reach the working pressure, and the target was pre-sputtered for 30 seconds. Then, a high-purity Ag target (purity of 99.995 wt.%) was used to deposit an Ag layer on the etched polyimide substrate. The deposition power was 120 W, the disk rotation speed was 15 r / min, the argon flow rate was 40 sccm, and the deposition was carried out at room temperature. A total of five Ag layers were deposited, each with a thickness of 200 nm. The deposition pressure decreased gradually from the polyimide substrate to the surface. The deposition pressures of the Ag layers from the etched polyimide substrate to the surface were 1.3 Pa, 1.0 Pa, 0.8 Pa, 0.5 Pa, and 0.3 Pa, respectively.

[0065] The sputtering rate of the Ag target was 0.36 nm / s, and the sputtering time of each Ag layer was 556 s. After each Ag layer was deposited, there was a 30 s interval before the next layer was deposited. The total sputtering time was 2900 s. After sputtering, the film was naturally cooled to room temperature in the vacuum coating chamber for 1 h before being taken out, resulting in a gradient Ag film with a thickness of 1000 nm.

[0066] S4. After the deposition on one side of the cleaned polyimide substrate is completed, the cleaned polyimide substrate is flipped over, and the operations of steps 2 and 3 are repeated on the other side of the cleaned polyimide substrate to symmetrically deposit gradient Ag films on both sides of the cleaned polyimide substrate and obtain fatigue-resistant gradient Ag multilayer metal thin films.

[0067] The microstructure of the gradient Ag film on one side of the fatigue-resistant gradient Ag multilayer metal film prepared in Example 3 was characterized. The grain orientation was from the etched polyimide matrix to the surface, and the texture intensity (111) showed an increasing trend.

[0068] Example 4

[0069] A method for preparing a fatigue-resistant gradient Ag multilayer metal thin film includes the following steps:

[0070] Step 1: Place the polyimide matrix in anhydrous ethanol and ultrasonically clean it for 15 minutes, then quickly dry it to ensure that the surface of the polyimide matrix is ​​clean and free of impurities.

[0071] Step 2: Fix the cleaned polyimide substrate onto the base plate and place it into the coating chamber. Then, evacuate the back vacuum to 4.0 × 10⁻⁶. -4 Etching begins below Pa to remove impurities from the surface of the polyimide substrate. The etching power is 100W, the etching pressure is 1Pa, and the time is 3min, resulting in an etched polyimide substrate.

[0072] Step 3: Prepare a gradient Ag film on an etched polyimide substrate using DC magnetron sputtering.

[0073] Argon gas was first introduced for 30 seconds to reach the working pressure, and the target was pre-sputtered for 30 seconds. Then, a high-purity Ag target (purity 99.995 wt.%) was used to deposit an Ag layer on an etched polyimide substrate. The deposition power was 50 W, the disk rotation speed was 10 r / min, the argon flow rate was 20 sccm, and the deposition was carried out at room temperature. The deposition pressure decreased gradually from the polyimide substrate to the surface. The deposition pressures of each Ag layer from the etched polyimide substrate to the surface were 0.1 Pa, 0.3 Pa, 0.5 Pa, 0.8 Pa, 1 Pa, 1.1 Pa, 1.3 Pa, 1.5 Pa, 1.8 Pa, and 2 Pa, respectively, to obtain a gradient Ag film with a thickness of 500 nm.

[0074] S4. After the deposition on one side of the cleaned polyimide substrate is completed, the cleaned polyimide substrate is flipped over, and the operations of steps 2 and 3 are repeated on the other side of the cleaned polyimide substrate to symmetrically deposit gradient Ag films on both sides of the cleaned polyimide substrate and obtain fatigue-resistant gradient Ag multilayer metal thin films.

[0075] Example 5

[0076] A method for preparing a fatigue-resistant gradient Ag multilayer metal thin film includes the following steps:

[0077] Step 1: Place the polyimide matrix in anhydrous ethanol and ultrasonically clean it for 15 minutes, then quickly dry it to ensure that the surface of the polyimide matrix is ​​clean and free of impurities.

[0078] Step 2: Fix the cleaned polyimide substrate onto the base plate and place it into the coating chamber. Then, evacuate the back vacuum to 4.0 × 10⁻⁶. -4 Etching begins below Pa to remove impurities from the surface of the polyimide substrate. The etching power is 300W, the etching pressure is 0.3Pa, and the time is 8min, resulting in an etched polyimide substrate.

[0079] Step 3: Prepare a gradient Ag film on an etched polyimide substrate using DC magnetron sputtering.

[0080] Argon gas was first introduced for 30 seconds to reach the working pressure, and the target was pre-sputtered for 30 seconds. Then, a high-purity Ag target (purity of 99.995 wt.%) was used to deposit an Ag layer on an etched polyimide substrate. The deposition power was 300 W, the disk rotation speed was 30 r / min, the argon flow rate was 60 sccm, and the deposition was carried out at room temperature. The deposition pressure decreased gradually from the polyimide substrate to the surface. The deposition pressures of each Ag layer from the etched polyimide substrate to the surface were 2 Pa, 1.8 Pa, 1.5 Pa, 1.3 Pa, 1.1 Pa, 1 Pa, 0.8 Pa, 0.5 Pa, 0.3 Pa, and 0.1 Pa, respectively, resulting in a gradient Ag film with a thickness of 2000 nm.

[0081] S4. After the deposition on one side of the cleaned polyimide substrate is completed, the cleaned polyimide substrate is flipped over, and the operations of steps 2 and 3 are repeated on the other side of the cleaned polyimide substrate to symmetrically deposit gradient Ag films on both sides of the cleaned polyimide substrate and obtain fatigue-resistant gradient Ag multilayer metal thin films.

[0082] Comparative Example 1

[0083] A method for preparing an Ag metal thin film is the same as the preparation steps in Examples 1 to 3, except that there is no change in the deposition gas pressure and no interval during the deposition process. It is a common single-layer Ag metal thin film. The deposition rate of the Ag metal thin film is 0.36 nm / s, the deposition gas pressure is 0.3 Pa, the deposition time is 2778 s, and the thickness of the obtained Ag metal thin film is 1000 nm.

[0084] Comparative Example 2

[0085] A method for preparing an Ag metal thin film is the same as the preparation steps in Examples 1 to 3, except that there is no change in the deposition gas pressure and no interval during the deposition process. It is a common single-layer Ag metal thin film. The deposition rate of the Ag metal thin film is 0.36 nm / s, the deposition gas pressure is 0.5 Pa, the deposition time is 2778 s, and the thickness of the obtained Ag metal thin film is 1000 nm.

[0086] Comparative Example 3

[0087] A method for preparing an Ag metal thin film is the same as the preparation steps in Examples 1 to 3, except that there is no change in the deposition gas pressure and no interval during the deposition process. It is a common single-layer Ag metal thin film. The deposition rate of the Ag metal thin film is 0.36 nm / s, the deposition gas pressure is 0.8 Pa, the deposition time is 2778 s, and the thickness of the obtained Ag metal thin film is 1000 nm.

[0088] Comparative Example 4

[0089] A method for preparing an Ag metal thin film is the same as the preparation steps in Examples 1 to 3, except that there is no change in the deposition gas pressure and no interval during the deposition process. It is a common single-layer Ag metal thin film. The deposition rate of the Ag metal thin film is 0.36 nm / s, the deposition gas pressure is 1.0 Pa, the deposition time is 2778 s, and the thickness of the obtained Ag metal thin film is 1000 nm.

[0090] Comparative Example 5

[0091] A method for preparing an Ag metal thin film is the same as the preparation steps in Examples 1 to 3, except that there is no change in the deposition gas pressure and no interval during the deposition process. It is a common single-layer Ag metal thin film. The deposition rate of the Ag metal thin film is 0.36 nm / s, the deposition gas pressure is 1.3 Pa, the deposition time is 2778 s, and the thickness of the obtained Ag metal thin film is 1000 nm.

[0092] Figure 1 The XRD patterns of fatigue-resistant gradient Ag multilayer metal thin films of Examples 1-3 and Comparative Examples 1-5 are shown. Figure 2 The diagrams show the fatigue-resistant gradient Ag multilayer metal thin films of Examples 1 to 3, as well as the Ag metal thin films of Comparative Examples 1, 3, and 5. Figure 3 Planar TEM images and grain size distribution diagrams of Ag metal thin films in Comparative Examples 1, 3, and 5 are shown. Figure 4 Cross-sectional TKD photographs and layered (111) texture intensity statistics of fatigue-resistant gradient Ag multilayer metal films of Examples 1 and 3 and the Ag metal film of Comparative Example 1, prepared by DC magnetron sputtering deposition technology, are shown. The samples in the examples are gradient samples, and planar transmission samples could not be prepared (it was impossible to determine which specific layer), so [fatigue-resistant gradient sputtering deposition was performed on the samples]. Figure 4 Characterization of cross-sectional samples. Figure 1 , Figure 3 and Figure 4 The microstructure characteristics of different thin films were revealed, demonstrating that different layers in the fatigue-resistant gradient Ag multilayer metal thin film of the embodiment have different (111) texture strengths. By designing different grain orientations, the Schmid factors between different layers are different, which inhibits the initiation and propagation of cracks, thereby achieving excellent fatigue performance.

[0093] Figure 5Fatigue-resistance curves of fatigue-resistant gradient Ag multilayer metal films and Ag metal films were shown. The fatigue loading strain amplitude was 1%, the loading method was tensile fatigue test, and the loading frequency was 1 Hz. The test results show that the fatigue-resistant gradient Ag multilayer metal films exhibit excellent electrical stability and outstanding fatigue performance under cyclic loading.

[0094] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A fatigue-resistant gradient Ag multilayered structure metal thin film, characterized in that, The fatigue-resistant gradient Ag multilayer structure metal thin film is made of a substrate and two gradient Ag films, which are symmetrically deposited on both sides of the substrate. Each gradient Ag film consists of several Ag layers of the same thickness, with each Ag layer stacked on top of the others. In each Ag layer, the grain orientation is from the substrate to the surface. (111) The texture intensity exhibits a gradient decrease, a gradient increase, or a gradient decrease followed by a gradient increase.

2. The fatigue-resistant gradient Ag multilayer metal thin film according to claim 1, characterized in that, The thickness of the gradient Ag film is 500nm~2000nm.

3. The fatigue-resistant gradient Ag multilayer metal thin film according to claim 1, characterized in that, The matrix is ​​selected from flexible polymer matrices.

4. A method for preparing a fatigue-resistant gradient Ag multilayer metal thin film according to any one of claims 1 to 3, characterized in that, Includes the following steps: In an argon atmosphere, DC magnetron sputtering was used at room temperature and a deposition power of 50W~300W to sequentially co-sputter and deposit different Ag layers on the substrate by adjusting the deposition gas pressure. After deposition, the substrate was cooled to room temperature to obtain a fatigue-resistant gradient Ag multilayer metal film. From the matrix to the surface, the (111) texture intensity decreases gradually, while the deposition pressure gradient increases. From the matrix to the surface, the (111) texture intensity increases in a gradient, while the deposition pressure gradient decreases. From the matrix to the surface, (111) the texture intensity first decreases and then increases, so the deposition gas pressure first increases and then decreases. (111) The depositional gas pressure with a gradient decrease in texture intensity is 0.1 Pa to 2 Pa; (111) The depositional gas pressure with a gradient increase in texture intensity is 2 Pa to 0.1 Pa; (111) The depositional gas pressure with a gradient decrease in texture intensity followed by a gradient increase is: first from 0.1 Pa to 2 Pa, and then from 2 Pa to 0.1 Pa.

5. The method for preparing fatigue-resistant gradient Ag multilayer metal thin films according to claim 4, characterized in that, (111) The depositional gas pressure with a gradient decrease in texture intensity is 0.3 Pa to 1.3 Pa; (111) The depositional gas pressure with a gradient increase in texture intensity is 1.3 Pa to 0.3 Pa; (111) The depositional gas pressure with a gradient decrease followed by a gradient increase in texture intensity is: first from 0.3 Pa to 1.3 Pa, and then from 1.3 Pa to 0.3 Pa.

6. The method for preparing fatigue-resistant gradient Ag multilayer metal thin films according to claim 4, characterized in that, The DC magnetron sputtering method involves depositing different Ag layers on a substrate under conditions of a rotation speed of 10 r / min to 30 r / min and an argon flow rate of 20 sccm to 60 sccm.

7. The application of the fatigue-resistant gradient Ag multilayer structure metal thin film according to claim 1 in the preparation of current collectors.

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