Preparation method of flexible alloy negative electrode with embedded structure

Abstract

The invention relates to the technical field of new energy materials, in particular to a flexible alloy negative electrode with an embedded structure and a preparation method thereof.The surface layer of a polyimide (PI) film is coated with a polyvinylidene fluoride (PVDF) film layer with a certain thickness, then array grooves are carved in the PI film through femtosecond laser, then a magnetron sputtering device is adopted, and the flexible alloy negative electrode with the embedded structure is prepared. The preparation method comprises the following steps: co-depositing a Cu and Al metal layer with a certain thickness on the surface of a film, then immersing into diluted hydrochloric acid, carrying out ultrasonic treatment for a certain time, washing and drying, then co-depositing Mg and Gdh alloy with a certain thickness through a magnetron sputtering device, then depositing C with a certain thickness, finally immersing an electrode into acetone, carrying out ultrasonic cleaning and drying, and thus obtaining the final alloy negative electrode material. Growth of lithium dendrites can be effectively inhibited, the risk of short circuit is avoided, and high safety is achieved. The preparation method of the electrode material is simple, and industrial large-scale production can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to a method for preparing a flexible alloy negative electrode with an embedded structure. Background Art

[0002] Currently, commercial lithium-ion batteries still use graphite as anode material. Limited by its theoretical specific capacity of 372 mAh / g, conventional lithium-ion batteries are approaching a bottleneck in increasing their energy density. To address this issue, researchers have investigated various alloy-based electrode materials, including Si-based materials, transition metal oxides, metal alloys, and layered metal sulfides, as alternatives to graphite anode materials to meet the needs of next-generation high-energy-density batteries. Among these candidate materials, magnesium has attracted considerable attention due to its high specific capacity (3,350 mAh / g, based on a theoretical value of 3,832 mAh / cm³), low reaction voltage (lithiation voltage approximately 18 mV, delithiation voltage approximately 50 mV), and minimal structural change upon reaction with lithium, which mitigates charge-discharge voltage hysteresis. Furthermore, magnesium metal is environmentally friendly and abundant in resources. Despite its attractiveness as an anode material, magnesium's slow lithium insertion kinetics severely hinder its electrochemical reactions. This, coupled with a low lithium insertion platform, complicates the lithium insertion process and even increases the risk of lithium plating. Studies have shown that magnesium and lithium cannot undergo alloying reactions at current densities above 10 mA / g. Nanostructure design is considered to be an effective strategy to solve the above problems. However, in order to ensure the integrity and electronic conductivity of nanoporous electrodes, a large amount of binders and conductive additives are often required. These inactive components will significantly reduce the energy density of the electrode. In addition, the volume expansion problem of alloy negative electrodes during cycling also limits its development. Therefore, the development of high-capacity, high-rate, long-cycle, and high-safety magnesium negative electrodes still faces severe challenges. Summary of the Invention

[0003] The present invention addresses the aforementioned technical challenges and provides a flexible alloy anode with an embedded structure and a method for its preparation. This method utilizes a simple, controllable technique to produce a flexible alloy electrode with a directional array of pores and a three-dimensional skeleton structure, thereby enhancing the reaction kinetics of magnesium and alleviating the internal stress generated by lithium intercalation and deintercalation. The electrode produced using this technical solution exhibits a high volume-to-mass energy density and excellent rate capability, cycling performance, and safety. This electrode has great potential for engineering applications.

[0004] The technical solution of the present 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 a PVDF acetone solution. The PVDF acetone solution is a viscous glue. Apply the PVDF solution on the surface of the PI basement membrane by spin coating and dry it to obtain a PI basement membrane with a PVDF protective layer.

[0007] Step 2: Cut the PI base film into the shape of the pole piece of the laminated lithium battery by machining to obtain a cut piece;

[0008] Step 3: Etching the side of the cut piece with the PVDF layer to form parallel grooves on the PI base film, with parallel PVDF protective layers between the grooves. The etching process is femtosecond laser etching.

[0009] Step 4: depositing Cu-Al alloy on the etched side by magnetron sputtering process, so that the Cu-Al alloy fills the etched grooves;

[0010] Step 5: Soaking the cut piece in dilute hydrochloric acid to remove the metal Al, washing and drying after soaking, so that the grooves are a Cu porous structure;

[0011] Step 6: Depositing Mg-Gd alloy on the etched side by magnetron sputtering process, so that the Mg-Gd alloy fills the gaps removed by the metal Al and fills the etched grooves to form a Mg-Gd alloy layer;

[0012] Step 7: depositing element C on the etched side by a magnetron sputtering process, so that the element C fills the groove;

[0013] Step 8: Soak the cut pieces in an acetone solution, and then ultrasonically clean and dry them to peel off the PVDF layer, thereby obtaining a flexible alloy negative electrode material with an embedded structure.

[0014] Through step 2, the substrate is die-cut into a certain shape and size, which is suitable for the design and preparation of various types of laminated batteries.

[0015] Through step three femtosecond laser engraving technology, part of the material is removed at a certain threshold and the surface is processed into a specific high-precision three-dimensional structure.

[0016] In step four, a predetermined thickness of alloy material is deposited on one side of the engraved surface. Through the co-deposition of Cu and Al, the two types of atoms are thoroughly mixed and bonded, resulting in a three-phase alloy material consisting of Cu, CuAl2, and Al. The three-phase material is distributed in an intricate, cross-linked pattern, paving the way for the in-situ generation of a microporous Cu skeleton structure.

[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, and a pure Cu skeleton structure with micropores is prepared in situ.

[0018] A certain amount of active alloy material is deposited on one side of the engraved surface in step 6. By co-depositing Mg and Gd, a uniform blend of the two elements at the atomic level is achieved, and finally Gd-doped Mg active alloy particles are in-situ embedded in the Cu skeleton.

[0019] Furthermore, the PVDF solution concentration in step 1 is 5-10 wt%, the coating apparatus rotation speed is 500-1000 rpm, and the coating time is 30-120 seconds. By optimizing these parameters, a PVDF film of a certain thickness is coated on the PI substrate, acting as a sacrificial layer. This provides protection in the initial steps while being easily removed in the final step.

[0020] Furthermore, the groove width in step 3 is 1-5 μm, the groove depth is 15-25 μm, and the laser energy density is 2.5-3.0 J / cm 2 The scanning speed is 500-1000 mm / s. By optimizing the laser process parameters, the groove width and depth are precisely controlled to adjust the active material loading and current density of the electrode.

[0021] Furthermore, the physical deposition equipment in step 4 is a three-target high vacuum magnetron sputtering instrument. The vacuum degree of the sample after being placed in the working chamber is 10 -4 ~10 -3 Pa, the pressure after filling with argon is 10 -1 The target pressure is 100-200W for the Cu target and 100-200W for the Al target, with a co-deposition time of 1-10 hours. By controlling the deposition rates of the two targets and adjusting the atomic ratio of the two elements, a skeleton structure of a specific size can be prepared. Using radio frequency sputtering, the deposited metal atoms possess sufficient energy to penetrate the PI matrix to a certain extent, thereby improving the bonding strength of the heterophase interface.

[0022] Furthermore, in step five, the hydrochloric acid concentration is 0.05-2M, the hydrochloric acid temperature is 30-60°C, and the immersion time is 10-60 minutes. By optimizing the parameters, the selective dissolution of Al and CuAl2 phases is achieved, the Cu skeleton is fully exposed, and a three-dimensional conductive structure with micropores is prepared in situ, which can receive the physical deposition of Mg and Gd in subsequent steps, thereby improving the rate and cycle performance of the electrode.

[0023] Furthermore, the physical deposition equipment in step 6 is a three-target magnetron sputtering device. The vacuum degree of the sample after being placed in the working chamber is 10 -4 ~10 -3 Pa, the pressure after filling with argon is 10 -1~1Pa, the working power is a radio frequency power supply. The working power of the Mg target is 100~200W, the working power of the Gd target is 100~200W, and the co-deposition time is 1~10h. The working frequency of the C target is 100~200W, and the deposition time is 1~30min. By regulating the deposition rate of different target materials, the proportion of deposited elements is regulated. Through the doping of Gd, the mechanical toughness of Mg is effectively improved, the internal stress generated by the material's lithium insertion and extraction is reduced, and the pulverization phenomenon is suppressed. At the same time, a "rare earth texture" is generated on the surface of the alloy, which homogenizes the lithium ion flow and suppresses the generation of lithium dendrites. In addition, the preparation of a C protective layer with a certain thickness is achieved, and a high-quality SEI film is generated in situ during the subsequent charge and discharge process.

[0024] Furthermore, in step seven, the electrode is immersed in an acetone solution for 1 to 5 hours and ultrasonicated for 10 to 30 minutes to ensure that the PVDF film layer and the metal deposit attached thereto are fully peeled off to obtain the embedded structural material and ensure the overall flatness and flexibility of the electrode.

[0025] The advantages and beneficial effects of the present invention are:

[0026] (1) This preparation method is simple, eliminating the complex process steps of slurry preparation and coating in traditional porous electrode technology solutions, and is suitable for large-scale production. It has the characteristics of flexibility, high capacity, high rate, and high safety, and is suitable for various lithium battery systems such as traditional liquid batteries, solid-state batteries, and semi-solid batteries.

[0027] (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 distances. From the perspective of the entire electrode, it constructs a directional microporous structure, reduces the tortuosity within the electrode, shortens the transmission distance of lithium ions, and improves the reaction kinetics of the active materials.

[0028] (3) Through the in-situ reaction of Cu and Al and the selective dissolution of acid solution, a highly conductive three-dimensional framework with nanopores is constructed in situ, into which the active material is embedded. On the one hand, the conductivity of the active material is improved, the local current density is reduced, and the rate performance of the electrode is enhanced; on the other hand, the framework structure limits the volume deformation of the active material caused by lithium insertion and extraction, inhibits the crushing of the active material, and improves the cycle performance of the electrode.

[0029] (4) During the co-deposition process, Mg and Gd form an in-situ Mg-Gd alloy active material. Due to the mismatch of the heterogeneous interface, the generated active material is nanoparticle-like with nanopores between the particles, and has high reactivity. The doping of Gd gives the alloy high toughness, which can relieve the internal stress generated by lithium insertion and extraction and inhibit particle fragmentation. The "rare earth texture" generated at the same time can homogenize the lithium ion flow, improve the electrochemical stability of the electrode, and inhibit the formation of lithium dendrites.

[0030] (5) Constructing an amorphous carbon layer of nanometer thickness on the surface of the active material. During the first charge and discharge process, lithium ions and the carbon layer form a stable, high-quality SEI film with a high elastic modulus, which can not only uniformize the lithium ion flow but also act as a physical barrier, thereby effectively inhibiting the formation of lithium dendrites and improving the safety performance of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0032] 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 can be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0033] Example 1

[0034] The steps of adopting the method of the present invention are as follows:

[0035] Step 1: Prepare a 5 wt.% PVDF acetone solution, apply a certain thickness of the PVDF solution to the surface of the PI substrate by spin coating, and dry it. The coating machine rotates at 800 rpm and the coating time is 60 seconds.

[0036] Step 2: Use a metal die-cutting machine to cut the above materials into 43*56mm electrodes.

[0037] Step 3: With the PVDF film facing up, a femtosecond laser was used to etch an array of grooves with a certain spacing and depth. The groove width was 1 μm and the groove depth was 15 μm. The laser energy density was 2.5 J / cm 2 , the scanning speed is 500mm / s.

[0038] Step 4: Place the etched surface upward on the sample plate of the magnetron sputtering device to co-deposit a certain thickness of Cu-Al alloy. The vacuum degree of the sample after being placed in the working chamber is 10 -4 Pa, the pressure after filling with argon is 10 -1 Pa, the working power is RF power. The working power of Cu target is 150W, the working power of Al target is 100W, and the co-deposition time is 5h.

[0039] Step 5: Immerse the sample in a certain concentration of dilute hydrochloric acid for a certain period of time, then wash and dry. The hydrochloric acid concentration is 0.05M, the hydrochloric acid temperature is 60°C, and the immersion time is 30 minutes.

[0040] Step 6: Place the etched surface upward on the sample plate of the magnetron sputtering device. The vacuum degree of the sample after being placed in the working chamber is 10 -4 Pa, the pressure after filling with argon is 10 -1 Pa, the working power is RF power. The Mg target working power is 150W, the Gd target working power is 100W, and the co-deposition time is 5 hours. The C target working frequency is 100W, and the deposition time is 1 minute.

[0041] Step 7: Immerse the above-prepared electrode in an acetone solution for 5 hours and ultrasonicate for 10 minutes to obtain the final flexible alloy negative electrode material with an embedded structure.

[0042] Example 2

[0043] The steps of adopting the method of the present invention are as follows:

[0044] Step 1: Prepare a 10 wt.% PVDF acetone solution, apply a certain thickness of the PVDF solution to the surface of the PI substrate by spin coating, and dry it. The coating machine rotates at 500 rpm and the coating time is 30 seconds.

[0045] Step 2: Use a metal die-cutting machine to cut the above materials into 43*56mm electrodes.

[0046] Step 3: With the PVDF film facing up, a femtosecond laser was used to etch an array of grooves with a certain spacing and depth. The groove width was 1 μm and the groove depth was 20 μm. The laser energy density was 2.6 J / cm 2 , the scanning speed is 500mm / s.

[0047] Step 4: Place the etched surface upward on the sample plate of the magnetron sputtering device to co-deposit a certain thickness of Cu-Al alloy. The vacuum degree of the sample after being placed in the working chamber is 10 -4 Pa, the pressure after filling with argon is 10 -1 Pa, the working power is RF power. The working power of Cu target is 150W, the working power of Al target is 100W, and the co-deposition time is 8h.

[0048] Step 5: Immerse the sample in a certain concentration of dilute hydrochloric acid for a certain period of time, then wash and dry. The hydrochloric acid concentration is 1M, the hydrochloric acid temperature is 60°C, and the immersion time is 20 minutes.

[0049] Step 6: Place the etched surface upward on the sample plate of the magnetron sputtering device, first co-deposit a certain thickness of Mg-Gd alloy, and then deposit a certain thickness of carbon layer. The vacuum degree of the sample after being placed in the working chamber is 10 -4 Pa, the pressure after filling with argon is 10 -1Pa, the working power is RF power. The Mg target working power is 150W, the Gd target working power is 100W, and the co-deposition time is 8 hours. The C target working frequency is 100W, and the deposition time is 1 minute.

[0050] Step 7: Soak the above material in acetone solution for a period of time, then ultrasonically clean it, remove it, and dry it to obtain the final flexible alloy negative electrode material with an embedded structure. Soak the above prepared electrode in acetone solution for 5 hours and ultrasonically clean it for 10 minutes.

[0051] Example 3

[0052] The steps of preparing a flexible alloy negative electrode with an embedded structure using the method of the present invention are as follows:

[0053] Step 1: Prepare an 8 wt.% PVDF acetone solution, apply a certain thickness of the PVDF solution to the surface of the PI substrate by spin coating, and dry it. The coating machine rotates at 1000 rpm and the coating time is 60 seconds.

[0054] Step 2: Use a metal die-cutting machine to cut the above materials into 43*56mm electrodes.

[0055] Step 3: With the PVDF film facing up, a femtosecond laser was used to etch an array of grooves with a certain spacing and depth. The groove width was 1 μm and the groove depth was 15 μm. The laser energy density was 2.6 J / cm 2 , the scanning speed is 800mm / s.

[0056] Step 4: Place the etched surface upward on the sample plate of the magnetron sputtering device to co-deposit a certain thickness of Cu-Al alloy. The vacuum degree of the sample after being placed in the working chamber is 10 -4 Pa, the pressure after filling with argon is 10 -1 Pa, the working power is RF power. The working power of Cu target is 160W, the working power of Al target is 110W, and the co-deposition time is 4h.

[0057] Step 5: Immerse the sample in a certain concentration of dilute hydrochloric acid for a certain period of time, then wash and dry. The hydrochloric acid concentration is 1M, the hydrochloric acid temperature is 60°C, and the immersion time is 10 minutes.

[0058] Step 6: Place the etched surface upward on the sample plate of the magnetron sputtering device, first co-deposit a certain thickness of Mg-Gd alloy, and then deposit a certain thickness of carbon layer. The vacuum degree of the sample after being placed in the working chamber is 10 -4 Pa, the pressure after filling with argon is 10 -1Pa, RF power supply. Mg target operating power 160W, Gd target operating power 110W, co-deposition time 4h. C target operating frequency 100W, deposition time 1min.

[0059] Step 7: Soak the above material in acetone solution for a period of time, then ultrasonically clean it, remove it, and dry it to obtain the final flexible alloy negative electrode material with an embedded structure. Soak the above prepared electrode in acetone solution for 3 hours and ultrasonically clean it for 20 minutes.

[0060] The description of various advantageous arrangements has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the examples disclosed. Many modifications and variations will be apparent to those skilled in the art. In addition, different advantageous examples may describe different advantages compared to other advantageous examples. The selected example or examples are chosen and described to best illustrate the principles of the examples, their practical application, and to enable those skilled in the art to understand the disclosure with various examples with various modifications suitable for the particular use contemplated.

Claims

1. A method for preparing a flexible alloy negative electrode with an embedded structure, characterized in that: The steps include: Step 1: Prepare a PVDF acetone solution. The PVDF acetone solution is a viscous glue. Apply the PVDF solution on the surface of the PI basement membrane by spin coating and dry it to obtain a PI basement membrane with a PVDF protective layer. Step 2: Cut the PI base film into the shape of the pole piece of the laminated lithium battery by machining to obtain a cut piece; Step 3: Etching the side of the cut piece with the PVDF layer to form parallel grooves on the PI base film, with parallel PVDF protective layers between the grooves. The etching process is femtosecond laser etching. Step 4: depositing Cu-Al alloy on the etched side by magnetron sputtering process, so that the Cu-Al alloy fills the etched grooves; Step 5: Soaking the cut piece in hydrochloric acid to remove the metal Al, washing and drying it after soaking, so that the grooves are a Cu porous structure; Step 6: Depositing Mg-Gd alloy on the etched side by magnetron sputtering process, so that the Mg-Gd alloy fills the gaps removed by the metal Al and fills the etched grooves to form a Mg-Gd alloy surface layer; Step 7: depositing element C on the etched side by a magnetron sputtering process, so that the element C fills the groove; Step 8: Soak the cut pieces in an acetone solution, and then ultrasonically clean and dry them to peel off the PVDF layer, thereby obtaining a flexible alloy negative electrode 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: The concentration of the PVDF solution in step 1 is 5-10 wt %, the rotation speed of the coating apparatus 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: The groove width in step 3 is 1-5 μm, the groove depth is 15-25 μm, and the laser energy density is 2.5-3.0 J / cm 2 , the scanning speed is 500~1000mm / s.

4. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step 4, the deposition equipment is a three-target high vacuum magnetron sputtering instrument, and the working vacuum degree is 10 －4 ~10 －3 Pa, the pressure after filling with argon is 10 －1 ~1Pa, the working power is a radio frequency power supply; the working power of the Cu target is 100~200W, the working power of the Al target is 100~200W, 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: The concentration of hydrochloric acid in step five is 0.05-2M, the temperature of the hydrochloric acid is 30-60° C., and the soaking time is 10-60 min.

6. The method for preparing a flexible alloy negative electrode with an embedded structure according to claim 1, characterized in that: In step 6, the deposition equipment is a three-target magnetron sputtering device, and the working vacuum degree is 10 －4 ~10 －3 Pa, the pressure after filling with argon is 10 －1 ~1Pa, the working power is a radio frequency power supply; the working power of the Mg target is 100~200W, the working power of the Gd target is 100~200W, 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 electrode is immersed in the acetone solution for 1 to 5 hours, and the ultrasonic time is 10 to 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 7, the deposition equipment is a three-target magnetron sputtering device, and the working vacuum degree is 10 －4 ~10 －3 Pa, the pressure after filling with argon is 10 －1 ~1Pa, the working power supply is RF power supply; the working frequency of C target is 100~200W, and the deposition time is 1~30min.

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