A preparation method of a flexible alloy negative electrode with an embedded structure

Abstract

The application relates to the technical field of new energy materials, and relates to a flexible alloy negative electrode with an embedded structure and a preparation method. A polyvinylidene fluoride (PVDF) film layer with a certain thickness is coated on a surface layer of a polyimide (PI) film, then array grooves are carved on the PI film through femtosecond laser, then a certain thickness of Cu and Al metal layers are co-deposited on the film surface through a magnetron sputtering device, then the film is immersed in dilute hydrochloric acid for a certain time and is washed and dried, then a certain thickness of Mg and Gd alloy is co-deposited through the magnetron sputtering device, then a certain thickness of C is deposited, finally, the electrode is immersed in acetone, ultrasonic cleaning and drying are carried out, and the final alloy negative electrode material is prepared. The application can effectively inhibit the growth of lithium dendrites, avoid short circuit risks, and has high safety. The electrode material preparation method is simple, and industrialized scale production can be realized.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to a method for preparing a flexible alloy anode with an embedded structure. Background Technology

[0002] Currently, commercial lithium-ion batteries still use graphite anode materials. Limited by its theoretical specific capacity of 372 mAh / g, traditional lithium-ion batteries are approaching a bottleneck in improving energy density. To address this issue, researchers have studied various alloy electrode materials, including Si-based materials, transition metal oxides, metal alloys, and layered metal sulfides, aiming to replace graphite anode materials and meet the demands of next-generation high-energy-density batteries. Among these candidate materials, magnesium has attracted significant attention due to its high specific capacity (3,350 mAh / g, up to 3,832 mAh / cm³), low reaction voltage (lithiation voltage approximately 18 mV, delithiation voltage approximately 50 mV), and minimal structural changes during the reaction with lithium (alleviating charge / discharge voltage hysteresis). Furthermore, magnesium is an environmentally friendly and resource-rich material. Despite its attractiveness as an anode material, magnesium's slow lithium intercalation kinetics severely hinder its electrochemical reaction. Coupled with a relatively low lithium intercalation plateau, this makes the process more difficult and even more prone to lithium plating. Studies have shown that magnesium and lithium cannot alloy at current densities above 10 mA / g. Nanostructure design is considered an effective strategy to address this issue. However, to ensure the integrity and electronic conductivity of nanoporous electrodes, large amounts of binders and conductive additives are often required, and these inactive components significantly reduce the electrode's energy density. Furthermore, the volume expansion problem during cycling of alloyed anodes also limits their development. Therefore, the development of high-capacity, high-rate, long-cycle, and highly safe magnesium anodes still faces significant challenges. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned technical problems by providing a flexible alloy anode with an embedded structure and its preparation method. The aim is to fabricate a flexible alloy electrode with a directional array of holes and a three-dimensional framework structure through a simple and controllable technical method, thereby improving the reaction kinetics of magnesium and alleviating the internal stress caused by lithium insertion / extraction in the alloy. The electrode prepared using this technical solution exhibits high volumetric energy density and excellent rate performance, cycle performance, and safety performance. This electrode has significant engineering application prospects.

[0004] The technical solution of this invention is:

[0005] A method for preparing a flexible alloy negative electrode with an embedded structure is provided, comprising the following steps:

[0006] Step 1: Prepare PVDF acetone solution. PVDF acetone solution is a viscous adhesive. Apply PVDF solution to the surface of PI substrate film by spin coating and dry to obtain PI substrate film with PVDF protective layer.

[0007] Step 2: The PI substrate film is cut into electrode shapes according to the stacked lithium battery by machining to obtain cut sheets;

[0008] Step 3: Etch the side of the cut piece with the PVDF layer to etch parallel grooves into the PI substrate film. The grooves are separated by a parallel PVDF protective layer. The etching process is femtosecond laser etching.

[0009] Step 4: Deposit Cu-Al alloy on the etched side using magnetron sputtering, so that the Cu-Al alloy fills the etched trenches;

[0010] Step 5: Soak the cut slice in dilute hydrochloric acid to remove metallic Al. After soaking, wash and dry to make the groove a porous Cu structure.

[0011] Step 6: Mg-Gd alloy is deposited on the etched side using magnetron sputtering, so that the Mg-Gd alloy fills the voids of the removed metal Al and fills the etched trenches to form a Mg-Gd alloy layer.

[0012] Step 7: Deposit carbon element on the etched side using magnetron sputtering process to fill the trench with carbon element;

[0013] Step 8: Soak the cut slices in acetone solution, then ultrasonically wash and dry them to peel off the PVDF layer, thus obtaining a flexible alloy anode material with an embedded structure.

[0014] Step two involves die-cutting the substrate into a specific shape and size, which is suitable for the design and fabrication of various types of stacked batteries.

[0015] Step three uses femtosecond laser engraving technology to remove a portion of the material at a predetermined threshold, processing the surface into a specific high-precision three-dimensional structure.

[0016] In step four, an alloy material of a certain thickness is deposited on one side of the engraved surface. Through Cu and Al co-deposition, the two types of atoms are fully mixed and bonded, resulting in a three-phase alloy material containing Cu, CuAl2, and Al. The three-phase material is intricately distributed, providing conditions for the next step of in-situ generation of a Cu framework structure with micropores.

[0017] In step five, the material is immersed in dilute hydrochloric acid of a certain concentration for a certain period of time to selectively dissolve Al and CuAl2 phase compounds, thus obtaining a pure Cu framework structure with micropores in situ.

[0018] In step six, a certain amount of active alloy material is deposited on one side of the engraved surface. Through the co-deposition of Mg and Gd, the two elements are uniformly blended at the atomic level, and finally, Gd-doped Mg active alloy particles are embedded in situ within the Cu framework.

[0019] Furthermore, in step one, the PVDF solution concentration is 5–10 wt%, the coating machine rotation speed is 500–1000 rpm, and the coating time is 30–120 s. By optimizing the parameters, a PVDF film of a certain thickness is coated on the PI substrate as a sacrificial layer, so that it can play a protective role in the previous process and can be easily removed in the final process.

[0020] Furthermore, in step three, the trench width is 1–5 μm, and the trench depth is 15–25 μm. The laser energy density is 2.5–3.0 J / cm². 2 The scanning speed is 500–1000 mm / s. By optimizing the laser process parameters, the width and depth of the trench are precisely controlled to adjust the active material loading and current density of the electrode.

[0021] Furthermore, the physical deposition equipment described in step four is a three-target high-vacuum magnetron sputtering system. The vacuum level after the sample is placed in the working chamber is 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1 The working pressure was ~1 Pa, and the power supply was an RF power source. The working power of the Cu target was 100-200 W, and the working power of the Al target was 100-200 W, with a co-deposition time of 1-10 h. By controlling the deposition rate of the two targets and adjusting the atomic ratio of the two elements, a framework structure of a certain size could be prepared. RF sputtering was used to ensure that the metal atoms to be deposited had sufficiently high energy, allowing them to penetrate into the PI matrix to a certain extent and improve the bonding force at the heterogeneous interface.

[0022] Furthermore, in step five, the hydrochloric acid concentration is 0.05–2 M, the hydrochloric acid temperature is 30–60 °C, and the soaking time is 10–60 min. By optimizing the parameters, selective dissolution of the Al and CuAl2 phases is achieved, allowing the Cu framework to be fully exposed. This results in the in-situ preparation of a three-dimensional conductive structure with micropores, which receives the physical deposition of Mg and Gd in subsequent steps, thereby improving the rate capability and cycle performance of the electrode.

[0023] Furthermore, the physical deposition equipment described in step six is ​​a three-target magnetron sputtering device. The vacuum level after the sample is placed in the working chamber is 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1~1Pa, operating power is RF power. Mg target operating power is 100~200 W, Gd target operating power is 100~200 W, co-deposition time is 1~10h.

[0024] In step seven, the deposition equipment is a three-target magnetron sputtering device, and the operating vacuum level is 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1 The operating pressure was ~1 Pa, and the power supply was an RF power source; the C target operating frequency was 100-200 W, and the deposition time was 1-30 min. The deposition rate of different targets was adjusted to control the proportion of deposition elements. Gd doping effectively improved the mechanical toughness of Mg, reduced the internal stress caused by lithium insertion / extraction, and suppressed pulverization. Simultaneously, it created a "rare earth texture" on the alloy surface, homogenizing the lithium-ion flow and suppressing lithium dendrite formation. Furthermore, a C protective layer of a certain thickness was prepared, enabling the in-situ generation of a high-quality SEI film during subsequent charge / discharge processes.

[0025] Furthermore, in step eight, the cut slices are immersed in acetone solution for 1–5 hours and sonicated for 10–30 minutes. This ensures that the PVDF film layer and the metal deposits attached to it are fully peeled off, resulting in an embedded structural material that guarantees the overall flatness and flexibility of the electrode sheet.

[0026] The advantages and beneficial effects of this invention are:

[0027] (1) The preparation method is simple and eliminates the complex process steps such as slurry preparation and coating in traditional porous electrode technology, making it suitable for large-scale production. It has the characteristics of flexibility, high capacity, high rate capability and high safety, and is applicable to various lithium battery systems such as traditional liquid batteries, solid batteries and semi-solid batteries.

[0028] (2) Laser sintering has the characteristics of concentrated energy and small heat-affected zone. Through threshold removal, it can achieve high-precision processing of two-dimensional and three-dimensional structures. The PI array "backbone" separates the active materials at equal intervals. From the perspective of the entire electrode, it constructs a directional microporous structure, reduces the tortuosity in the electrode, shortens the lithium ion transport distance, and improves the reaction kinetics of the active materials.

[0029] (3) Through in-situ reaction of Cu and Al and selective solution of acid solution, a highly conductive three-dimensional framework structure with nanopores was constructed in situ, in which the active material was embedded. On the one hand, the conductivity of the active material was improved, the local current density was reduced, and the rate performance of the electrode was enhanced; on the other hand, the framework structure restricted the volume deformation caused by lithium insertion and extraction of the active material, suppressed the crushing of the active material, and improved the cycle performance of the electrode.

[0030] (4) During the co-deposition process, Mg and Gd form an in-situ Mg-Gd alloy active material. Due to the mismatch at the heterogeneous interface, the generated active material is in the form of nanoparticles with nanopores between the particles, exhibiting high reactivity. The doping of Gd gives the alloy high toughness, which can alleviate the internal stress caused by lithium insertion / extraction and suppress particle fragmentation. At the same time, the generated "rare earth texture" can homogenize the lithium ion flow, improve the electrochemical stability of the electrode, and suppress the formation of lithium dendrites.

[0031] (5) An amorphous carbon layer with a thickness of nanometers is constructed on the surface of the active material. During the first charge and discharge process, lithium ions form a stable and high-quality SEI film with the carbon layer, which can both homogenize the lithium ion flow and act as a physical barrier, thereby effectively suppressing the generation of lithium dendrites and improving the safety performance of the electrode. Attached Figure Description

[0032] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0033] The disclosed examples will be described more fully with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described, and these examples should not be construed as limited to those set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0034] Example 1

[0035] The steps of using the method described in this invention are as follows:

[0036] Step 1: Prepare a 5 wt.% PVDF acetone solution, and apply a certain thickness of the PVDF solution to the surface of the PI substrate film using a spin-coating method, then dry it. The coating machine rotation speed is 800 rpm, and the coating time is 60 seconds.

[0037] Step 2: Cut the above material into electrode sheets of 43*56mm size using a metal die-cutting machine.

[0038] Step 3: With the PVDF film-coated side facing up, an array of trenches with specific spacing and depth is etched using a femtosecond laser. The trench width is 1 μm, and the trench depth is 15 μm. The laser energy density is 2.5 J / cm². 2 The scanning speed is 500 mm / s.

[0039] Step 4: Place the sample, etched side up, on the sample tray of the magnetron sputtering apparatus to co-deposit a certain thickness of Cu-Al alloy. The vacuum level of the sample after it is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas, 10-1 Pa, the operating power supply is an RF power supply. The operating power of the Cu target is 150 W, the operating power of the Al target is 100 W, and the total deposition time is 5 hours.

[0040] Step 5: Immerse the above sample in a dilute hydrochloric acid solution of a certain concentration for a certain period of time, and then wash and dry it. The hydrochloric acid concentration is 0.05M, the hydrochloric acid temperature is 60℃, and the immersion time is 30 minutes.

[0041] Step Six: Place the sample, etched side up, on the sample tray of the magnetron sputtering apparatus. The vacuum level after the sample is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas, 10 -1 The operating power supply is an RF power supply. The Mg target operating power is 150 W, the Gd target operating power is 100 W, and the total deposition time is 5 hours. The C target operating frequency is 100 W, and the deposition time is 1 minute.

[0042] Step 7: Immerse the prepared diced material in acetone solution for 5 hours and sonicate for 10 minutes to obtain the final flexible alloy anode material with embedded structure.

[0043] Example 2

[0044] The steps of using the method described in this invention are as follows:

[0045] Step 1: Prepare a 10 wt.% PVDF acetone solution, and apply a certain thickness of the PVDF solution to the surface of the PI substrate film using a spin-coating method, then dry it. The coating machine rotation speed is 500 rpm, and the coating time is 30 seconds.

[0046] Step 2: Cut the above material into electrode sheets of 43*56mm size using a metal die-cutting machine.

[0047] Step 3: With the PVDF film-coated side facing up, an array of trenches with specific spacing and depth is etched using a femtosecond laser. The trench width is 1 μm, and the trench depth is 20 μm. The laser energy density is 2.6 J / cm². 2 The scanning speed is 500 mm / s.

[0048] Step 4: Place the sample, etched side up, on the sample tray of the magnetron sputtering apparatus to co-deposit a certain thickness of Cu-Al alloy. The vacuum level of the sample after it is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas, 10 -1 Pa, the operating power supply is an RF power supply. The operating power of the Cu target is 150 W, the operating power of the Al target is 100 W, and the total deposition time is 8 hours.

[0049] Step 5: Immerse the above sample in a dilute hydrochloric acid solution of a certain concentration for a certain period of time, and then wash and dry it. The hydrochloric acid concentration is 1M, the hydrochloric acid temperature is 60℃, and the immersion time is 20 minutes.

[0050] Step Six: Place the sample on the sample tray of the magnetron sputtering apparatus with the etched surface facing upwards. First, co-deposit a Mg-Gd alloy of a certain thickness, then deposit a carbon layer of a certain thickness. The vacuum level after the sample is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas, 10 -1 The operating power supply is an RF power supply. The Mg target operating power is 150 W, the Gd target operating power is 100 W, and the total deposition time is 8 hours. The C target operating frequency is 100 W, and the deposition time is 1 minute.

[0051] Step 7: Immerse the above material in acetone solution for a period of time, then ultrasonically wash it, remove it, and dry it to obtain the final flexible alloy anode material with an embedded structure. Immerse the prepared diced material in acetone solution for 5 hours and ultrasonically wash it for 10 minutes.

[0052] Example 3

[0053] The steps for preparing a flexible alloy negative electrode with an embedded structure using the method described in this invention are as follows:

[0054] Step 1: Prepare an 8 wt.% PVDF acetone solution, and apply a certain thickness of the PVDF solution to the surface of the PI substrate film using a spin-coating method, then dry it. The coating machine rotation speed is 1000 rpm, and the coating time is 60 seconds.

[0055] Step 2: Cut the above material into electrode sheets of 43*56mm size using a metal die-cutting machine.

[0056] Step 3: With the PVDF film-coated side facing up, an array of trenches with specific spacing and depth is etched using a femtosecond laser. The trench width is 1 μm, and the trench depth is 15 μm. The laser energy density is 2.6 J / cm². 2 The scanning speed is 800 mm / s.

[0057] Step 4: Place the sample, etched side up, on the sample tray of the magnetron sputtering apparatus to co-deposit a certain thickness of Cu-Al alloy. The vacuum level of the sample after it is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas, 10 -1 Pa, the operating power supply is an RF power supply. The operating power of the Cu target is 160 W, the operating power of the Al target is 110 W, and the total deposition time is 4 hours.

[0058] Step 5: Immerse the above sample in a dilute hydrochloric acid solution of a certain concentration for a certain period of time, and then wash and dry it. The hydrochloric acid concentration is 1M, the hydrochloric acid temperature is 60℃, and the immersion time is 10 minutes.

[0059] Step Six: Place the sample on the sample tray of the magnetron sputtering apparatus with the etched surface facing upwards. First, co-deposit a Mg-Gd alloy of a certain thickness, then deposit a carbon layer of a certain thickness. The vacuum level after the sample is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas, 10 -1 The operating power supply is an RF power supply. The Mg target operating power is 160 W, the Gd target operating power is 110 W, and the total deposition time is 4 hours. The C target operating frequency is 100 W, and the deposition time is 1 minute.

[0060] Step 7: Immerse the above material in acetone solution for a period of time, then ultrasonically wash it, remove it, and dry it to obtain the final flexible alloy anode material with an embedded structure. Immerse the prepared diced material in acetone solution for 3 hours and ultrasonically wash it for 20 minutes.

[0061] Descriptions of various advantageous arrangements have been shown for illustrative and descriptive purposes, but such descriptions are not intended to be exclusive or limited to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different advantageous examples may describe different advantages compared to other advantageous examples. One or more examples have been selected and described in order to best illustrate the principles and practical application of the examples, and to enable those skilled in the art to understand that this disclosure contains various examples with various modifications suitable for the particular intended use.

Claims

1. A method for preparing a flexible alloy negative electrode with an embedded structure, characterized in that: Includes the following steps: Step 1: Prepare PVDF acetone solution. PVDF acetone solution is a viscous adhesive. Apply PVDF solution to the surface of PI substrate film by spin coating and dry to obtain PI substrate film with PVDF protective layer. Step 2: The PI substrate film is cut into electrode shapes according to the stacked lithium battery by machining to obtain cut sheets; Step 3: Etch the side of the cut piece with the PVDF layer to etch parallel grooves into the PI substrate film. The grooves are separated by a parallel PVDF protective layer. The etching process is femtosecond laser etching. Step 4: Deposit Cu-Al alloy on the etched side using magnetron sputtering, so that the Cu-Al alloy fills the etched trenches; Step 5: Soak the cut slice in hydrochloric acid to remove metallic Al. After soaking, wash and dry to make the groove a porous Cu structure. Step 6: Mg-Gd alloy is deposited on the etched side using magnetron sputtering, so that the Mg-Gd alloy fills the voids of the removed Al metal and fills the etched trenches to form a Mg-Gd alloy surface layer. Step 7: Deposit carbon element on the etched side using magnetron sputtering process to fill the trench with carbon element; Step 8: Soak the cut slices in acetone solution, then ultrasonically wash and dry them to peel off the PVDF layer, thus obtaining a flexible alloy anode material with an embedded structure.

2. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step one, the PVDF solution concentration is 5–10 wt%, the coating machine rotation speed is 500–1000 rpm, and the coating time is 30–120 s.

3. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step three, the trench width is 1–5 μm, the trench depth is 15–25 μm, and the laser energy density is 2.5–3.0 J / cm². 2 The scanning speed is 500-1000 mm / s.

4. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step four, the deposition equipment is a three-target high-vacuum magnetron sputtering system, operating at a vacuum level of 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1 ~1Pa, the working power supply is radio frequency power supply; the working power of Cu target is 100~200 W, the working power of Al target is 100~200 W, and the co-deposition time is 1~10h.

5. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step five, the hydrochloric acid concentration is 0.05–2M, the hydrochloric acid temperature is 30–60℃, and the soaking time is 10–60 minutes.

6. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step six, the deposition equipment is a three-target magnetron sputtering device, and the operating vacuum level is 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1 ~1Pa, the working power supply is radio frequency power supply; the working power of Mg target is 100~200 W, the working power of Gd target is 100~200 W, and the co-deposition time is 1~10h.

7. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step eight, the cut slices are immersed in acetone solution for 1–5 hours and sonicated for 10–30 minutes.

8. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step seven, the deposition equipment is a three-target magnetron sputtering device, and the operating vacuum level is 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1 ~1Pa, the working power supply is radio frequency power supply; the working power of C target is 100~200W, and the deposition time is 1~30min.

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