Copper-zinc alloy-based three-dimensional hierarchical porous current collector for inhibiting lithium dendrites and preparation method of copper-zinc alloy-based three-dimensional hierarchical porous current collector

Abstract

The invention discloses a copper-zinc alloy-based three-dimensional hierarchical porous current collector for inhibiting lithium dendrites and a preparation method thereof, and belongs to the technical field of lithium metal battery negative electrode materials, and the method comprises the following steps: mixing copper-zinc alloy powder with a pore-forming agent and a binder, dispersing with an organic solvent, coating and drying, calcining at high temperature, and forming pores by etching to construct a porous conductive skeleton; and the lithium affinity of the material is further improved through surface vulcanization modification, so that the three-dimensional hierarchical porous current collector is formed. According to the structure, by reducing the current density, increasing the lithium containing space and reducing the lithium nucleation barrier, the growth of lithium dendrites is synergistically inhibited, and the volume change in the lithium deposition-stripping process is relieved. Experiments show that the current collector can stably circulate for 400-2000 hours under the conditions of 0.5-5 mA cm <-2 > and 1-10 mAh cm <-2 >, and has excellent electrochemical performance and industrial application potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium metal battery negative electrode materials, and specifically relates to a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites and a preparation method thereof. Background Art

[0002] With the rapid development of new energy electric vehicles, aerospace equipment, and portable electronic devices, the inherent theoretical capacity limitations (372mAh / g) of traditional lithium-ion batteries using graphite negative electrodes have become difficult to meet the growing demand for high-performance energy storage systems. In this context, the development of new negative electrode materials with high specific capacity and high energy density has become a key path to breaking through the bottlenecks of existing technologies. Lithium metal has shown significant advantages due to its excellent energy storage properties: it not only has an ultra-high theoretical specific capacity of 3860mAh / g (about 10.4 times that of graphite materials), but also has an extremely low redox potential of -3.040V vs. SHE standard hydrogen electrode. More importantly, its mass energy density can reach more than 6 times that of traditional graphite negative electrode systems. These characteristics make lithium metal the most promising negative electrode material choice for building a new generation of high-energy-density energy storage systems, and it is recognized by the international academic community as a strategic direction for breaking through the bottlenecks of existing lithium battery technology.

[0003] As representatives of high-energy-density battery systems, lithium-oxygen (Li-O2) and lithium-sulfur (Li-S) batteries both use metallic lithium as the anode material. However, their practical application still faces three major technical bottlenecks that urgently need to be overcome: the first is the volume expansion of the anode: the volume expansion coefficient of metallic lithium approaches infinity during the deposition / stripping process. This drastic deformation causes repeated fractures of the solid electrolyte interface (SEI) and the continuous generation of inactive "dead lithium," leading to irreversible capacity decay. Second, lithium dendrite growth is difficult to suppress: the uneven electric field distribution on the electrode surface induces the directional growth of lithium dendrites, and the tip effect causes the risk of separator puncture, posing a thermal runaway safety hazard. Furthermore, the high chemical activity of metallic lithium leads to poor interfacial stability: its continuous side reaction with the organic electrolyte forms a loose and porous SEI film structure, significantly increasing the interfacial impedance and exacerbating the imbalance in lithium deposition kinetics, forming an autocatalytic vicious cycle. These intrinsic defects severely restrict the cycle life and safety performance of metallic lithium batteries, becoming a key obstacle to their commercial application.

[0004] In response to the above technical bottlenecks, the field of materials engineering has formed a multi-dimensional solution system. The current technical paths mainly include: optimization of electrolyte components, construction of metal lithium interface protection layer, development of lithium alloy negative electrode and design of three-dimensional current collector structure. Among them, the design of three-dimensional current collector based on Sand's time theory has made significant breakthroughs in recent years. This theory points out that the local current density distribution on the electrode surface directly regulates the lithium deposition behavior, and when the current density is lower than the critical threshold, it can effectively inhibit the growth of dendrites. By constructing a three-dimensional porous framework structure, its optimized conductive network can reduce the apparent current density by 2-3 orders of magnitude. At the same time, by designing gradient lithium-affinity sites, the lithium metal nucleation overpotential is reduced from more than 150mV in the conventional system to less than 50mV, achieving uniform deposition of lithium ions on the micron scale. More importantly, this type of structural engineering strategy exhibits dual regulatory advantages: first, the mechanical support of the three-dimensional skeleton can absorb up to 300% of the volume strain during the cycle, controlling the deformation of the electrode structure within 5%; second, its internally connected ion channels can maintain stable Li + Flux distribution reduces the stress concentration factor of the SEI film by 80%. These breakthroughs make three-dimensional current collector technology the most promising solution for achieving high-safety and long-cycle lithium metal batteries. Summary of the Invention

[0005] To address the aforementioned deficiencies in the prior art, the present invention provides a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites and a method for preparing the same. This method involves mixing copper-zinc alloy powder with a pore-forming agent and a binder, dispersing the powder with an organic solvent, coating and drying, calcining it at high temperature, and etching to create pores, thereby constructing a porous conductive framework. Surface sulfurization is then performed to enhance the material's lithium affinity, resulting in a three-dimensional hierarchical porous current collector. The present invention features a simple preparation process and is suitable for large-scale production.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites comprises the following steps:

[0008] Step 1: Mix copper-zinc alloy powder, pore-forming agent and binder in a mass ratio of 1:1:0.01-20:1:0.1, add organic solvent A, stir at 200-800 rpm for 20-30 minutes, and form a uniform slurry by ultrasonic treatment;

[0009] Step 2: Apply the slurry to the surface of the substrate, dry it, and then calcine it at high temperature in an inert gas atmosphere to form a porous conductive skeleton;

[0010] Step 3: Use deionized water to repeatedly wash to remove the pore-forming agent, ultrasonicate for 10-20 minutes, and then vacuum dry;

[0011] Step 4: placing the skeleton in a sulfurizing agent environment and performing sulfurization to obtain a three-dimensional lithium-philic hierarchical porous current collector.

[0012] Furthermore, in step 1, the copper-zinc alloy powder is spherical brass powder, flaky brass powder or copper nanowires with a zinc mass ratio of 10-70%, which is placed in a vacuum drying oven and dried at 50-70° C. for 4-8 hours to remove surface adsorbed moisture.

[0013] Furthermore, in step 1, the pore-forming agent is selected from at least one of sodium chloride, potassium hydroxide, polyurethane, urea, talc or ammonium bicarbonate;

[0014] The organic solvent A is at least one of acetone, isopropanol, n-hexane or N-methylpyrrolidone, and the total amount of the solvent is 1-5 times the mass of the mixed solid;

[0015] The binder is at least one of PVDF, PVA, PTFE, CMC, SBR, PP or PE.

[0016] Furthermore, in step 1, the ultrasonic conditions are: 60-100W, 10-20 minutes, to obtain a uniform slurry with a concentration of 5-20 mg / mL.

[0017] Furthermore, in step 2, an aluminum foil or copper foil with a thickness of 5-10 μm is selected as the substrate, and ultrasonically cleaned with acetone, ethanol, and deionized water for 10-20 minutes each, and vacuum dried at 60-80° C. for later use;

[0018] Use a doctor blade coater to evenly apply the slurry to the substrate surface with a wet film thickness of 0.5-2mm;

[0019] After coating, the substrate is transferred to an oven and dried at 50-70° C. for 2-6 hours to obtain a preliminarily formed current collector precursor.

[0020] Furthermore, in step 2, the inert atmosphere is at least one of argon, nitrogen, and helium, and the flow rate is 10-100 mL / min.

[0021] Furthermore, in step 2, the calcination temperature is 400-800° C., and the calcination time is 1-3 hours;

[0022] The heating rate during the calcination process is 5-10° C. / min, and after calcination, the skeleton porosity is 60-85%, and the pore diameter is 10 nm-100 μm.

[0023] Furthermore, in step three, the vacuum drying temperature is 50-70° C., and the drying time is 6-10 h.

[0024] Furthermore, in step 4, the vulcanizing agent is one of thiourea, sodium thiosulfate, dibenzyl disulfide, hydrogen sulfide, and carbon disulfide;

[0025] The vulcanization temperature is 100-400° C. and the vulcanization time is 10-120 minutes.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] The present invention discloses a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites and a preparation method thereof. The high conductivity of the copper-zinc alloy and the lithium affinity of the sulfide layer synergistically improve the electrochemical performance. The hierarchical porous structure (porosity 60-85%, pore size 10nm-100μm) increases the lithium storage space and adapts to the volume changes of lithium deposition / stripping. The preparation process is simple and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0029] Figure 1 is an SEM image of the three-dimensional current collector in Example 1, showing a uniform porous structure and a sulfide layer distribution;

[0030] Figure 2 is an SEM image of the current collector after lithium deposition in Example 1, showing that lithium is uniformly deposited and has no dendrites;

[0031] Figure 3 This is the EDS spectrum in Example 2, confirming the uniform distribution of copper, zinc, and sulfur elements;

[0032] Figure 4 The value of 1 mA cm in Example 2 is -2 and 1mAh cm -2 Under the conditions of , the voltage-time curve comparison of S / HPCu-Zn@Li and Cu@Li assembled into symmetrical batteries;

[0033] Figure 5 The results of Example 2 and Comparative Example 1 at 1 mA cm -2 and 1mAh cm -2 Comparison of the voltage-time curves of HPCu-Zn@Li and S / HPCu-Zn@Li assembled into symmetrical batteries under the conditions of . DETAILED DESCRIPTION

[0034] In order to clearly and completely describe the technical solution and specific working process of the present invention, the specific implementation methods of the present invention are as follows in conjunction with the accompanying drawings:

[0035] Example 1

[0036] This embodiment provides a method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites, which specifically includes the following steps:

[0037] Step 1: Slurry preparation:

[0038] Spherical brass powder (Zn content: 30% by mass, particle size: 100 nm) was placed in a vacuum drying oven and dried at 70°C for 8 hours to remove surface adsorbed moisture and set aside.

[0039] The above-mentioned spherical brass powder, sodium chloride (particle size 2 μm) and binder were mixed in a mass ratio of 20:1:0.5, and N-methylpyrrolidone solvent was added. The total amount of N-methylpyrrolidone solvent was 5 times the mass of the mixed solid. The mixture was mechanically stirred at 800 rpm for 30 minutes, then transferred to an ultrasonic instrument and ultrasonically treated at 100 W power for 20 minutes, repeated 3 times, and then placed in a mortar and ground for 60 minutes to obtain a uniform slurry with a concentration of 20 mg / mL.

[0040] Step 2: Select aluminum foil with a thickness of 10μm as the substrate, ultrasonically clean it with acetone, ethanol, and deionized water for 20 minutes each, and vacuum dry it at 80℃ for later use; use a scraper coater to evenly apply the slurry to the surface of the copper foil, and control the wet film thickness to 2mm. Use a scraper coater to evenly apply the slurry to the surface of the copper foil, and control the wet film thickness to 2mm. Place the dried current collector precursor in a tube furnace, introduce inert gas (flow rate 100mL / min), heat it to 900℃ at 10℃ / min, and keep it warm for 2h to complete the sintering of the alloy skeleton and the thermal decomposition of the binder.

[0041] Step 3: The calcined material was immersed in deionized water and ultrasonically treated (100W) for 20 minutes. The pore-forming agent was removed by repeated immersion and washing until the washing solution was neutral. The washed material was transferred to a vacuum oven and dried at 70°C for 10 hours to form a porous conductive skeleton.

[0042] Step 4: Place the porous framework in a sealed tube furnace, add the sulfurizing agent thiourea (sulfurizing agent to brass powder mass ratio of 1:10), and introduce inert gas to expel air. Raise the temperature to 300°C at a rate of 10°C / min, hold for 90 minutes, and cool naturally to room temperature to obtain a surface-sulfurized, three-dimensional, lithium-philic, hierarchical porous current collector.

[0043] like Figure 1As shown in the figure, a microscopic image of a three-dimensional lithium-philic hierarchical porous current collector was prepared by surface sulfurization modification using copper-zinc alloy as a framework. It can be seen from the figure that the sulfur element is evenly modified on the copper-zinc alloy skeleton; the skeleton is rich in hierarchical porous structure, which increases the specific surface area of ​​the three-dimensional lithium-philic hierarchical porous current collector.

[0044] The current collector was cut into 12mm diameter pole pieces and assembled with lithium sheets into a symmetrical battery for lithium deposition. The electrolyte was 1M LiPF6 / EC:DEC (volume ratio 1:1). The electron microscope image after lithium deposition was observed using a scanning electron microscope, as shown in the figure below. Figure 2 As shown in the figure, it can be seen that lithium metal is uniformly deposited in the three-dimensional lithium-philic hierarchical porous current collector, effectively inhibiting the growth of lithium dendrites.

[0045] Example 2

[0046] The difference from Example 1 is that spherical brass powder with a Zn mass ratio of 30% is used, the vulcanizing agent is changed to sodium thiosulfate; the calcination temperature is increased to 700° C., and the vulcanization time is extended to 120 minutes;

[0047] Example 3

[0048] The difference from Example 1 is that flaky brass powder with a Zn mass ratio of 30% is used, the vulcanizing agent is still thiourea; the calcination temperature is 400°C, the heating rate is maintained at 10°C / min, and the vulcanization time is extended to 120 minutes.

[0049] Example 4

[0050] The difference from Example 1 is that spherical brass powder with a Zn mass ratio of 15% is used, the vulcanizing agent is still thiourea; the calcination temperature is 400°C, the heating rate is maintained at 10°C / min, and the vulcanization time is extended to 120 minutes.

[0051] Example 5

[0052] The difference from Example 1 is that spherical brass powder with a Zn mass ratio of 15% is used, the vulcanizing agent is changed to sodium thiosulfate; the calcination temperature is increased to 700°C, the heating rate is maintained at 10°C / min, and the vulcanization time is shortened to 30 minutes.

[0053] Example 5

[0054] The difference from Example 1 is that spherical brass powder with a Zn mass ratio of 30% is used, the vulcanizing agent is changed to sodium thiosulfate; the calcination temperature is increased to 700°C, the heating rate is maintained at 10°C / min, and the vulcanization time is shortened to 30 minutes.

[0055] Example 6

[0056] The difference from Example 1 is that flaky brass powder with a Zn mass ratio of 30% is used, the vulcanizing agent is changed to sodium thiosulfate; the calcination temperature is increased to 700°C, the heating rate is maintained at 10°C / min, and the vulcanization time is shortened to 30 minutes.

[0057] Example 7

[0058] The difference from Example 1 is that flaky brass powder with a Zn mass ratio of 30% is used, the vulcanizing agent is changed to benzyl disulfide; the calcination temperature is increased to 700°C, the heating rate is maintained at 10°C / min, and the vulcanization time is shortened to 30 minutes.

[0059] pass Figure 3 From the EDS graph, it can be seen that copper, zinc and sulfur elements are evenly distributed, which can effectively reduce the current density and increase the lithium capacity space; zinc nanoparticles modified on the main skeleton composed of brass powder can guide the uniform deposition of lithium metal.

[0060] from Figure 4 It can be seen that at 1mA / cm 2 and 1mAh / cm 2 Under the conditions of , the three-dimensional lithium-philic hierarchical porous current collector can be stably cycled for 600 h.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that there is no sulfurization modification process; due to the lack of sulfurization, the lithium-philic sites in the current collector are insufficient, the lithium nucleation overpotential is too high, resulting in an increase in local current density, which hinders the uniform deposition of lithium metal. In Example 1 and Example 2, the sulfurization modification method is adopted to convert pure metal into metal sulfide. The metal sulfide has good lithium affinity and can reduce the nucleation overpotential during the lithium metal deposition process, so that the lithium metal is uniformly deposited on the current collector. Therefore, the current collector that is not sulfurized has dendrites after 500 hours of circulation ( Figure 4 );

[0063] from Figure 5 It can be seen that at 1mA / cm 2 and 1mAh / cm 2 Under the conditions of , the sulfide three-dimensional lithiophilic hierarchical porous current collector prepared in Example 2 can stably cycle for 600 hours, while the three-dimensional lithiophilic hierarchical porous current collector prepared in Comparative Example 1 has excessive addition of pore-forming agent (the ratio of brass powder to sodium chloride particles is greater than 20:1, and the ratio of brass powder to sodium chloride particles used in Comparative Example 1 is 20:5). This is because excessive addition of pore-forming agent results in a porosity greater than 85%, which reduces the mechanical strength of the current collector and causes structural collapse. In contrast, adding an appropriate amount of pore-forming agent (20:1) in the embodiment can construct a uniformly distributed hierarchical porous structure, which facilitates the uniform diffusion of lithium ions without affecting the original mechanical strength of the material.

[0064] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0065] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0066] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites, characterized in that: The specific steps include: Step 1: Mix copper-zinc alloy powder, pore-forming agent and binder in a mass ratio of 1:1:0.01-20:1:0.1, add organic solvent A, stir at 200-800 rpm for 20-30 minutes, and form a uniform slurry by ultrasonic treatment; Step 2: Apply the slurry to the surface of the substrate, dry it, and then calcine it at high temperature in an inert gas atmosphere to form a porous conductive skeleton; Step 3: Use deionized water to repeatedly wash to remove the pore-forming agent, ultrasonicate for 10-20 minutes, and then vacuum dry; Step 4: placing the skeleton in a sulfurizing agent environment and performing sulfurization to obtain a three-dimensional lithium-philic hierarchical porous current collector.

2. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 1, the copper-zinc alloy powder is spherical brass powder, flaky brass powder or copper nanowires with a zinc mass ratio of 10-70%, which is placed in a vacuum drying oven and dried at 50-70° C. for 4-8 hours to remove surface adsorbed moisture.

3. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 1, the pore-forming agent is selected from at least one of sodium chloride, potassium hydroxide, polyurethane, urea, talc or ammonium bicarbonate; The organic solvent A is at least one of acetone, isopropanol, n-hexane or N-methylpyrrolidone, and the total amount of the solvent is 1-5 times the mass of the mixed solid; The binder is at least one of PVDF, PVA, PTFE, CMC, SBR, PP or PE.

4. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 1, the ultrasonic conditions are: 60-100W, 10-20 minutes, to obtain a uniform slurry with a concentration of 5-20 mg / mL.

5. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 2, aluminum foil or copper foil with a thickness of 5-10 μm is selected as the substrate, and ultrasonically cleaned with acetone, ethanol, and deionized water for 10-20 minutes each, and vacuum dried at 60-80°C for later use; Use a doctor blade coater to evenly apply the slurry to the substrate surface with a wet film thickness of 0.5-2mm; After coating, the substrate is transferred to an oven and dried at 50-70° C. for 2-6 hours to obtain a preliminarily formed current collector precursor.

6. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 2, the inert atmosphere is at least one of argon, nitrogen, and helium, and the flow rate is 10-100 mL / min.

7. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, characterized in that: In step 2, the calcination temperature is 400-800° C. and the calcination time is 1-3 hours; The heating rate during the calcination process is 5-10° C. / min, and after calcination, the skeleton porosity is 60-85%, and the pore diameter is 10 nm-100 μm.

8. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 3, the vacuum drying temperature is 50-70° C., and the drying time is 6-10 h.

9. The method for preparing a copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites according to claim 1, wherein: In step 4, the vulcanizing agent is one of thiourea, sodium thiosulfate, dibenzyl disulfide, hydrogen sulfide, and carbon disulfide; The vulcanization temperature is 100-400° C. and the vulcanization time is 10-120 minutes.

10. A copper-zinc alloy-based three-dimensional hierarchical porous current collector for suppressing lithium dendrites, characterized in that: The method is prepared by any one of claims 1 to 9.

Images