A method for preparing a lithium metal negative electrode with a multi-dimensional skeleton structure

Abstract

This invention relates to the field of new energy materials technology, specifically a method for preparing a lithium metal anode with a multidimensional framework structure. The method involves heat-treating a foamed brass material of a certain thickness under a specific atmosphere for a certain time, followed by cooling. Then, the sample is calcined in air for a certain time and cooled. Next, Sn is magnetron sputtered onto the sample for a certain time. The sample is then immersed in a polydopamine aqueous solution of a certain concentration for a certain time, removed, and dried. Finally, it is calcined in a hydrogen-argon mixture for a certain time and cooled. Finally, a Li-Ga molten solution of a certain composition is poured in and cooled to obtain the final lithium metal anode material. This invention offers high safety performance, effectively suppressing lithium dendrite growth and mitigating short-circuit risks. The electrode material preparation method is simple and can be industrialized on a large scale.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to a method for preparing a lithium metal anode with a multidimensional framework structure. Background Technology

[0002] With the rapid development of smart devices such as portable electronic devices, electric vehicles, and smart grids, higher demands are being placed on the energy density of lithium-ion batteries. Lithium metal anodes have attracted significant attention due to their ultra-high theoretical specific capacity (~3860 mAh / g) and extremely low reaction potential (-3.04 V vs. standard hydrogen electrode), and are considered the "holy grail" of anode materials. However, during prolonged charge-discharge cycles, lithium anodes exhibit lithium dendrite growth, causing rapid capacity decay and even safety hazards, severely limiting their practical applications. According to Sand theory, the higher the operating current, the more pronounced the lithium dendrite growth phenomenon. However, many applications require lithium batteries to operate at 5 mA / cm². 2 The above current densities are required for operation. Therefore, exploring strategies to suppress lithium dendrite growth at high current densities is crucial and relates to the application and development of lithium metal anodes.

[0003] To address these issues, researchers have conducted extensive research. Among these efforts, 3D structure design is one of the most effective strategies. Generally, 3D structures possess a larger specific surface area and abundant porosity, significantly reducing the actual current density at the interface. Simultaneously, they provide sufficient space to accommodate lithium deposition and mitigate volume expansion. Conductive framework materials are mainly divided into carbon materials (such as graphene and carbon fibers) and metallic materials (such as copper foam and nickel foam). However, these substrate materials often exhibit poor lithiophilicity, creating high nucleation barriers. Lithium is likely to deposit directly on the porous electrode surface rather than within the pores, leading to severe battery failure. Therefore, researchers have further modified the electrodes with lithiophilic materials (such as Al, Sn, and Mg) to enhance the affinity of the framework material interface for lithium metal.

[0004] Although the above strategies significantly improve electrode rate performance by reducing local current intensity, the modified interface exhibits low electronic or ionic conductivity, resulting in low porosity utilization efficiency in the three-dimensional structure. Furthermore, methods for lithium-affinity modification of the electrode surface are both complex and expensive. More importantly, these alloy coatings readily react with lithium to form lithium alloys. During cycling, repeated alloying / dealloying reactions cause the coating volume to expand / contract repeatedly, generating significant internal stress that causes it to peel off from the substrate material, ultimately leading to the loss of the interface modification effect. For these reasons, no studies have yet reported on the application of lithium alloys at high current densities (e.g., >5 mA / cm²). 2 and moderately high areal capacity (e.g., >3 mAh / cm²) 2Lithium metal anodes that can cycle stably at high rates, especially in commercial carbonate electrolytes, are particularly challenging to develop. Therefore, fabricating lithium metal electrodes capable of stable cycling at high rates using simple and efficient strategies is extremely challenging. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned technical problems by providing a lithium metal anode with a multidimensional framework structure and its preparation method. The aim is to obtain a lithium metal anode with a high specific surface area, high lithium affinity, and high conductivity through a simple and controllable technical method. The electrode prepared using this technical solution exhibits high specific energy and excellent rate performance, cycle performance, and safety performance. This electrode has significant engineering application prospects.

[0006] The technical solution of this invention is:

[0007] A method for preparing a lithium metal anode with a multidimensional framework structure is provided, comprising the following steps:

[0008] Step 1: Place a copper mesh of a certain thickness in a CVD furnace for chemical vapor deposition and cool it to room temperature under hydrogen protection to grow graphene on its surface; the copper mesh is made of copper-zinc alloy.

[0009] Step 2: The deposited copper mesh is calcined in the air, allowing the Zn element in the copper mesh to react with oxygen in the air, generating ZnO nanowires in situ. After calcination, it is naturally cooled to obtain a multidimensional framework with a mixed distribution of micron-pores and nanopores.

[0010] Step 3: Magnetron sputtering is performed on the multidimensional framework with Sn as the target material to obtain lithophilic modification on the surface of the copper / graphene framework and ZnO nanowires.

[0011] Step 4: Immerse the lithiophilic modified multidimensional framework in a polydopamine aqueous solution to fully coat the multidimensional framework, and then remove and dry it.

[0012] Step 5: Calcine the multidimensional framework in a hydrogen-argon mixture to fully carbonize the polydopamine and form a stable, highly conductive protective layer; this causes Zn to vaporize and be discharged, while Sn remains in the highly conductive protective layer as nano-modified particles, and then the mixture is cooled.

[0013] Step 6: Prepare a Li-Ga alloy molten liquid, pour the molten liquid into the multidimensional framework obtained in Step 5 and cool it to obtain a lithium metal anode.

[0014] In step four, polydopamine serves as a carbon source, and carbon-coated materials can be obtained through subsequent high-temperature carbonization.

[0015] In step five, the internal Zn and Sn melt. Due to the large difference in their boiling points, Zn will form vapor and be released, while Sn will remain in the carbon layer in the form of nano-modified particles.

[0016] In step six, the Li-Ga alloy exhibits a high lithium-ion diffusion coefficient, which can induce Li... + It penetrates the alloy and deposits within the framework, thereby suppressing the growth of lithium dendrites.

[0017] Furthermore, in step one, the copper mesh thickness is 100–500 μm, the pore size is 20–50 μm, and the mass ratio of Zn to Cu in the copper-zinc alloy is 0.05–0.1:1. The working atmosphere in the CVD furnace is a mixture of hydrogen and methane, with a total pressure of 50–80 Pa, a hydrogen flow rate of 30–50 sccm, and a methane flow rate of 5–15 sccm. The CVD calcination temperature is 350–500 °C, and the calcination time is 10–30 h. During cooling, the hydrogen flow rate is 30–50 sccm. By selecting the composition and structure of the copper-zinc alloy, the pore size and arrangement in the multidimensional structure are controlled. By optimizing the heat treatment process parameters, thin-layer, low-defect graphene can be prepared and coated.

[0018] Furthermore, in step two, the calcination temperature is 350–500℃, and the calcination time is 10–30 h. Graphene and ZnO have a low lattice mismatch, and by adjusting the temperature, ZnO is catalyzed to grow in a direction perpendicular to the graphene sheet into one-dimensional ZnO nanowires.

[0019] Furthermore, before calcination in step two, two flat plates are placed on the top and bottom of the copper mesh. Pressure is applied to the two plates to prevent the nanowires from growing along the thickness direction, thus limiting the use of electrode materials.

[0020] Furthermore, in step three, the vacuum level after the multidimensional skeleton is placed into the working chamber is 10. -4 ~10 -3 Pa, the pressure after filling with argon gas is 10. -1 The pressure is ~1 Pa, and the working power supply is DC. The working power of the Sn target is 20~40W, and the deposition time is 10~60min. Sn has high lithiophilicity, and by optimizing the process parameters, a uniform lithiophilic layer of a certain thickness can be constructed on the surface of multidimensional materials.

[0021] Furthermore, in step four, the polydopamine concentration is 0.05 wt.%–0.15 wt.%, and the immersion time is 10–60 min. By controlling the solution concentration and sample immersion time, complete and uniform coating of the carbon source is ensured, and the final carbon coating thickness is controlled.

[0022] Furthermore, in step five, the volume ratio of the hydrogen-argon mixture is H2:Ar = 0.05–0.1:1, the calcination temperature is 600–1000℃, and the holding time is 1–10 h. By optimizing the process parameters, on the one hand, the polydopamine is fully carbonized to generate amorphous carbon as a protective and conductive layer; on the other hand, the low-boiling-point Zn in the one-dimensional structure is completely separated and Sn is melted and recrystallized, ultimately constructing a Sn@C one-dimensional material.

[0023] Furthermore, in step six, a Li-Ga alloy molten liquid is prepared using pure lithium rods and pure Ga, and heat-treated at 300–600℃ for 0.5–2 hours. Optimizing process parameters ensures complete melting and reaction of the Li-Ga alloy, constructing a Li-Ga filler material with high ionic conductivity. Additionally, during the melting process, Ga is initially oxidized, generating a non-lithophile material, Ga₂O₃, which floats to the electrode surface as a protective layer, suppressing side reactions between lithium metal and the electrolyte and improving the electrode coulombic efficiency.

[0024] The advantages and beneficial effects of this invention are:

[0025] (1) The lithium metal anode prepared by the invention has the characteristics of high capacity, high rate, high cycle life, and high safety, and is suitable for various lithium battery systems such as traditional liquid batteries, solid batteries, and flexible batteries. At the same time, the preparation method is simple, pollution-free, and low-cost, making it suitable for large-scale production.

[0026] (2) Utilizing the mechanism by which copper catalyzes graphene growth, a complete graphene coating is achieved on the surface of a copper framework. The low lattice mismatch between graphene and ZnO induces a reaction between Zn and oxygen, generating ZnO nanowires. Due to the detachment of Zn, nanopores appear in the Cu framework. This results in the in-situ construction of a high specific surface area framework structure with a two-dimensional structure interlaced within the three-dimensional pores, exhibiting a mixed distribution of micron and nanopores. As an electrode, this significantly reduces the current density and improves rate performance.

[0027] (3) Uniform Sn coating is achieved on the surface of multidimensional complex structures using magnetron sputtering, giving the material high lithium affinity. Combined with the high electronic conductivity of graphene and amorphous carbon, this dual-induced Lithium-based coating... + By depositing lithium dendrites through the Li-Ga alloy and within the multidimensional structure rather than on the electrode surface, the growth of lithium dendrites is limited, resulting in high electrode safety and improved cycle stability.

[0028] (4) Carbon source coating is performed on the multidimensional structure by utilizing the wettability of the carbon source solution. After carbonization, an amorphous carbon functional layer is generated in situ. On the one hand, this increases the electronic conductivity of the entire multidimensional framework. On the other hand, its hollow structure reserves space for volume expansion during the Sn lithium intercalation process. As a protective layer, it prevents the lithium-loving metal Sn from peeling off from the framework, thus ensuring that its "induction" effect persists for a long time.

[0029] (5) Li-Ga alloys have a high lithium-ion diffusion coefficient, and the binding energy between Li and Sn is higher than that between Li and Ga, which comprehensively induces Li + Lithium is deposited within the framework of the alloy. The deposited lithium is encapsulated by a highly ductile Li-Ga alloy shell, thereby suppressing the growth of lithium dendrites. Furthermore, during the melting process, Ga is first oxidized to form a non-lithophile material, Ga₂O₃, which floats to the electrode surface as a protective layer, suppressing side reactions between lithium metal and the electrolyte and improving the electrode's coulombic efficiency. Detailed Implementation

[0030] In fact, many different examples can 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.

[0031] Example 1

[0032] The steps for preparing a lithium metal anode with a multidimensional framework structure using the method described in this invention are as follows:

[0033] Step 1: Place a 200µm thick brass mesh (Zn:Cu = 0.05:1) in a CVD furnace for heat treatment. During the process, control the total pressure of the mixed gas at 60 Pa, with a hydrogen flow rate of 40 sccm and a methane flow rate of 10 sccm. The heat treatment temperature is 450℃, and the holding time is 20 hours. During cooling, the hydrogen flow rate is 40 sccm.

[0034] Step 2: Place two plates on the top and bottom of the sample, and calcine it in a muffle furnace under air atmosphere. The calcine temperature is 400℃, and the calcine time is 10 hours. Then air cool to room temperature.

[0035] Step 3: Place the sample obtained above into a high-vacuum magnetron sputtering instrument. The vacuum level after the sample is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas is 10. -1 Pa, the working power supply is DC power. The Sn target working power is 30W, and the deposition time is 10min.

[0036] Step 4: Immerse the sample obtained above in an aqueous solution containing 0.10 wt.% polydopamine for 20 minutes, and then remove and dry it.

[0037] Step 5: Place the sample obtained above into a CVD furnace, fill the reaction chamber with a hydrogen-argon mixture, calcine at 950℃ for 5 hours, and then cool. The volume ratio of the hydrogen-argon mixture is H2:Ar = 0.05:1.

[0038] Step 6: Place 1gLi and 100gGa in a crucible, heat to 400℃ and keep warm for 1 hour. Then pour the molten liquid into the above multidimensional framework and cool to obtain the final anode material.

[0039] Example 2

[0040] The steps for preparing a lithium metal anode with a multidimensional framework structure using the method described in this invention are as follows:

[0041] Step 1: Place a 200µm thick brass mesh (Zn:Cu = 0.06:1) in a CVD furnace for heat treatment. During the process, control the total pressure of the mixed gas at 60Pa, with a hydrogen flow rate of 45sccm and a methane flow rate of 15sccm. The heat treatment temperature is 400℃, and the holding time is 20 hours. During cooling, the hydrogen flow rate is 40sccm.

[0042] Step 2: Place two plates on the top and bottom of the sample, and calcine it in a muffle furnace under air atmosphere. The calcine temperature is 400℃, and the calcine time is 10 hours. Then air cool to room temperature.

[0043] Step 3: Place the sample obtained above into a high-vacuum magnetron sputtering instrument. The vacuum level after the sample is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas is 10. -1 Pa, the working power supply is DC power. The Sn target working power is 35W, and the deposition time is 30min.

[0044] Step 4: Immerse the sample obtained above in an aqueous solution containing 0.06 wt.% polydopamine for 20 minutes, and then remove and dry it.

[0045] Step 5: Place the sample obtained above into a CVD furnace, fill the reaction chamber with a hydrogen-argon mixture, calcine at 980℃ for 3 hours, and then cool. The volume ratio of the hydrogen-argon mixture is H2:Ar = 0.05:1.

[0046] Step 6: Place 2gLi and 100gGa in a crucible, heat to 420℃ and keep warm for 1 hour. Then pour the molten liquid into the above multidimensional framework and cool to obtain the final anode material.

[0047] Example 3

[0048] The steps for preparing a lithium metal anode with a multidimensional framework structure using the method described in this invention are as follows:

[0049] Step 1: Place a 200µm thick brass mesh (Zn:Cu = 0.08:1) in a CVD furnace for heat treatment. During the process, control the total pressure of the mixed gas at 60Pa, with a hydrogen flow rate of 30 sccm and a methane flow rate of 5 sccm. The heat treatment temperature is 450℃, and the holding time is 20 hours. During cooling, the hydrogen flow rate is 40 sccm.

[0050] Step 2: Place two plates on the top and bottom of the sample, and calcine it in a muffle furnace under air atmosphere. The calcine temperature is 400℃, and the calcine time is 10 hours. Then air cool to room temperature.

[0051] Step 3: Place the sample obtained above into a high-vacuum magnetron sputtering instrument. The vacuum level after the sample is placed in the working chamber is 10. -4 Pa, the pressure after filling with argon gas is 10. -1 Pa, the working power supply is DC power. The Sn target working power is 35W, and the deposition time is 20min.

[0052] Step 4: Immerse the sample obtained above in an aqueous solution containing 0.08 wt.% polydopamine for 20 minutes, and then remove and dry it.

[0053] Step 5: Place the sample obtained above into a CVD furnace, fill the reaction chamber with a hydrogen-argon mixture, calcine at 960℃ for 5 hours, and then cool. The volume ratio of the hydrogen-argon mixture is H2:Ar = 0.05:1.

[0054] Step 6: Place 3gLi and 100gGa in a crucible, heat to 450℃ and keep warm for 1 hour. Then pour the molten liquid into the above multidimensional framework and cool to obtain the final anode material.

[0055] 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 lithium metal anode with a multidimensional framework structure, characterized in that: Includes the following steps: Step 1: Place a copper mesh of a certain thickness in a CVD furnace for chemical vapor deposition and cool it to room temperature under hydrogen protection to grow graphene on its surface; the copper mesh is made of copper-zinc alloy. Step 2: The deposited copper mesh is calcined in the air, allowing the Zn element in the copper mesh to react with oxygen in the air, generating ZnO nanowires in situ. After calcination, it is naturally cooled to obtain a multidimensional framework with a mixed distribution of micron-pores and nanopores. Step 3: Magnetron sputtering is performed on the multidimensional framework with Sn as the target material to obtain lithophilic modification on the surface of the copper / graphene framework and ZnO nanowires. Step 4: Immerse the lithiophilic modified multidimensional framework in a polydopamine aqueous solution to fully coat the multidimensional framework, and then remove and dry it. Step 5: Calcine the multidimensional framework in a hydrogen-argon mixture to fully carbonize the polydopamine and form a stable, highly conductive protective layer; this causes Zn to vaporize and be discharged, while Sn remains in the highly conductive protective layer as nano-modified particles, and then the mixture is cooled. Step 6: Prepare a Li-Ga alloy molten liquid, pour the molten liquid into the multidimensional framework obtained in Step 5 and cool it to obtain a lithium metal anode.

2. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: In step one, the copper mesh thickness is 100–500 μm, the aperture is 20–50 μm, the mass ratio of Zn to Cu in the copper-zinc alloy is 0.05–0.1:1, the working atmosphere in the CVD furnace is a mixture of hydrogen and methane, the total pressure is 50–80 Pa, the hydrogen flow rate is 30–50 sccm, and the methane flow rate is 5–15 sccm; the calcination temperature of CVD is 350–500 °C, and the calcination time is 10–30 h; during cooling, the hydrogen flow rate is 30–50 sccm.

3. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: In step two, the calcination temperature is 350–500℃ and the calcination time is 10–30 h. Graphene and ZnO have a low lattice mismatch. By adjusting the temperature, ZnO is catalyzed to grow in a direction perpendicular to the graphene sheet into one-dimensional ZnO nanowires.

4. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: Before calcination in step two, two flat plates are placed on the top and bottom of the copper mesh, and pressure is applied to the two plates to prevent the nanowires from growing along the thickness direction and to limit the use of electrode materials.

5. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: The vacuum degree of the multi-dimensional skeleton in step three is 10 -4 ~ 10 -3 Pa, the pressure after filling argon is 10 -1 ~ 1 Pa, the working power source is a direct current power source, the working power of the Sn target is 20 ~ 40 W, and the deposition time is 10 ~ 60 min.

6. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: In step four, the polydopamine concentration is 0.05 wt.% to 0.15 wt.%, and the immersion time is 10 to 60 minutes. By controlling the solution concentration and sample immersion time, complete and uniform coating of the carbon source is ensured, and the final carbon coating thickness is controlled.

7. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: In step five, the volume ratio of hydrogen to argon mixture is H2:Ar = 0.05–0.1:1, the calcination temperature is 600–1000℃, and the holding time is 1–10 h.

8. The method for preparing a lithium metal anode with a multidimensional framework structure according to claim 1, characterized in that: In step six, a Li-Ga alloy molten liquid is prepared using pure lithium rods and pure Ga, and the heat treatment temperature is 300–600℃, with a holding time of 0.5–2h.